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FACULTY PUBLICATIONS

ASTRONOMY

The Structure of Pluto’s Atmosphere from the 2002 August 21 Stellar Occultation
Pasachoff, Jay M., Steven P. Souza, Bryce A. Babcock, David R. Ticehurst (Williams College); James L. Elliot, M. J. Person, and Kelly B. Clancy (MIT); Lewis C. Roberts, Jr., and Doyle T. Hall (Boeing Co., Maui); and David J. Tholen (U. Hawaii)
Astron. J., 129, 1718-1723 [2005]
We have observed the 2002 August 21 occultation by Pluto of the R=15.7 mag star P131.1, using 0.5 s cadence observations in integrated white light with the Williams College frame-transfer, rapid-readout CCD at the 2.24 m University of Hawaii telescope. We detected an occultation that lasted 5 minutes, 9.1+/-0.7 s between half-light points. The “kinks” in the ingress and egress parts of the curve that were apparent in 1988 had become much less pronounced by the time of the two 2002 occultations that were observed, indicating a major change in the structure of Pluto’s atmosphere. Analysis of our light curves shows that the pressure in Pluto’s atmosphere has increased at all the altitudes that we probed. Essentially, the entire pressure scale has moved up in altitude, increasing by a factor of 2 since 1988. Spikes in our light curve reveal vertical structure in Pluto’s atmosphere at unprecedented high resolution. We have confirmation of our spikes at lower time resolution as part of observations of the emersion made at 1.4 s and 2.4 s cadence with the 3.67 m AEOS telescope on Maui.
The Black Drop Effect Explained in Transits of Venus:
New Views of the Solar System and Galaxy
Pasachoff, Jay M., Glenn Schneider, and Leon Golub
IAU Colloquium No. 196 (U.K., 2004), D. W. Kurtz and G. E. Bromage, eds., 242-253 [2005]
We summarize the history of observations of the black-drop effect at transits of Venus and how it affected measurements of the size and scale of the solar system, concluding with a discussion of our own observations.
Satellite and Ground-Based Observations of the Transit of Venus
Pasachoff, J. M., G. Schneider (Steward Obs., U AZ), B. A. Babcock (Sci. Ctr., Williams Col.), D. L. Butts, J. W. Gangestad, O. W. Westbrook, and A. R. Cordova (Astr. Dept., Williams Col.), K. Gaydosh (Bryn Mawr Col./KNAC), and J. H. Seiradakis (U. Thessaloniki),
Bull. Am. Astron. Soc. 36 (4), 1161 delivered at the American Astronomical Society/Division of Planetary Sciences, Louisville, KY [2004]
We report on a coordinated program of CCD observations of the transit of Venus of 8 June 2004 made with NASA’s Transition Region and Coronal Explorer (TRACE) spacecraft and with ground-based observations from Greece (including the first two contacts) and the U.S. (the last two contacts). We observed in white light, with special attention to imaging Venus’s atmosphere at ingress and egress and to the presence and formation of the black-drop effect at second and third contacts. We analyze the data in terms of the telescope’s point-spread function, the solar limb darkening (which we previously showed to have a role in the black-drop effect for a transit of Mercury), and seeing effects from the terrestrial atmosphere. Our TRACE data have a 7-s cadence at uncompressed data transmission and higher for compressed data, both over the 20-min ingress and egress phases. Our expedition was supported by a grant from the Committee for Research and Exploration of the National Geographic Society. We thank Sigma Xi for additional student support.
Fascinating Pluto
Pasachoff, Jay M., and James L. Elliot
The Physics Teacher, 57 (9), letter, September, 18 [2004]
Pluto shares in the planetary diversity described in a special issue of the journal. Our observations of an occultation showed that its atmosphere had expanded. The New Horizons mission to Pluto may or may not arrive before the expansion is reversed.
The Effect of the Transit of Venus on ACRIM’s Total Solar Irradiance Measurements
Pasachoff, J. M., G. Schneider, and R. C. Willson
Bull. Am. Astron. Soc., 36, #5, 1566, for the January American Astronomical Society meeting in San Diego, CA, 135.11 [2005]
We used 131-s-cadence observations made with ACRIM3 on ACRIMsat on 8 June 2004 to follow the effect of the transit of Venus, which lasted about 6 hours, on the total solar irradiance (TSI). Venus’s angular diameter, in transit, is approximately 1/30 the solar diameter, so it covered approximately 0.1% of the sun’s surface. With our ACRIM3 data, we measure temporal changes in TSI with a one-sigma per sample (unbinned) certainty of approximately 100 milliwatts per square meter (0.007%). We found a diminution in TSI of approximately 1.4 watts per square meter (approximately 0.1%, closely corresponding to the geometrically occulted area of the photosphere) at mid-transit compared with a mean pre/post transit TSI of 1365.9 watts per square meter. The measured light curve is complex because of the parallactic motion of Venus induced by the satellite’s polar orbit, but exhibits the characteristic signature of photospheric limb-darkening when orbit-driven variations are accounted for. Analysis of the limb darkening can reveal temporal structure with height in the photosphere and asymmetries can, in principle, be attributable to planetary atmospheres. Similar observations will increasingly be detected from exoplanet transits, so detailed analysis of the transit within our solar system will provide a useful analogue for interpreting the many more such transits expected to be discovered within the next decade. JMP’s and GS’s transit of Venus observations were supported by a grant from the Committee for Research and Exploration of the National Geographic Society. NASA provides support for RCW at Columbia University under contract NNG04HZ42C.
Deuterium Nucleosynthesis in AGN: Is D Cosmological?
Lubowich, D. A., N. Kuno (Nobeyama Radio Observatory), H. Roberts (U. Ohio), T. J. Millar (U. Manchester), C. Henkel (Max-Planck-Institut fur Radioastronomie), J. M. Pasachoff, and R. Mauersberger (IRAM, Spain)
Bull. Am. Astron. Soc., 36, #5, 1546 [2005], January American Astronomical Society meeting in San Diego, CA 118.07
Although deuterium is predicted to be primarily cosmological, D can also be produced by cosmic-ray or gamma –ray spallation reactions – possibly between high energy jets and the surrounding gas in AGN. We used the Nobeyama Millimeter Array with a 3” resolution (220 pc) in April 2003 to search for any enhanced D from the DCN J = 2-1 line in the Seyfert galaxy NGC 1068. NGC 1068 is an optimal target because it has jets, starburst activity, a circumnuclear molecular ring and disk, dense optically thick concentrations of HCN, and a low-energy X-ray flux of 1042 erg/s (the highest X-ray flux of any galaxy in which HCN has been detected and the flux required to produce high D abundances). We did not detect DCN (which is detected in all other molecular clouds with optically thick HCN in the Galaxy or LMC) and we obtained an upper limit of S=15 mJy/beam = 48.5 mK in the circumnuclear region and a DCN/HCN ratio of 0.0046. Using our 5300 reaction chemical network we estimate D/H=1.5x10-5 as compared to the local Galactic ISM D/H = 1.4x10-5. Thus there is no significant D production in the nuclear region of NGC 1068 and NGC 1068 has probably not had a recent period of activity with a gamma –ray or cosmic-ray luminosity > 1042 erg/s. If jet-cloud nucleosynthesis produces significant amounts of D, then the D is produced outside of the nuclear region where the subsequent infall may be one way to continuously supply galactic nuclei with D. However, any enhanced D produced via spallation reactions would have been destroyed via astration due to the faster star formation rate. Our results are additional evidence that D is primarily cosmological and that AGN do not produce D.
Photon-counting Spicules, Mass Transfer, Oscillations, and the Heating of the Corona
Pasachoff, Jay M., Kamen A. Kozarev, David L. Butts III, and Joseph W. Gangestad (Williams College), Daniel B. Seaton (UNH), Bart De Pontieu (Lockheed Martin Solar and Astrophysics Laboratory), Leon Golub and Edward DeLuca (Smithsonian Astrophysical Observatory), Klaus Wilhelm (MPI Sonnensystemforschung),
and Ingolf Dammasch (Mullard SSL/University College London)
EOS Trans. American Geophysical Union, 86(18), Joint Assembly Suppl., Abstract SH13C-02, American Astronomical Society Solar Physics Division/American Geophysical Union meeting, New Orleans, May 2005
The mass moving in chromospheric spicules is enough to replace the corona in a brief time, so understanding the dynamics of spicules is important for understanding the support and heating of the solar corona. We have undertaken a program involving simultaneous high-resolution observations in various chromospheric visible lines (H-alpha, Ca II H, and G-band, as well as Dopplergrams) using the Swedish Solar Telescope on La Palma, ultraviolet chromospheric, transition-region, and coronal lines (Fe IX/X 171 A, Lyman-alpha 1216 A, and continuum/C I/C IV 1600 A) using NASA’s TRACE, and ultraviolet chromospheric and transition-region lines (Si II 1533, C IV 1548, and Ne VIII 770) using SUMER (Solar Ultraviolet Measurements of Emitted Radiation) on the NASA/ESA Solar and Heliospheric Observatory (SOHO). Our first coordinated observing run, in May 2004, yielded a variety of images that are under study, especially for the morphological statistics and dynamics of spicules. The energy transfer through the chromosphere is relevant to the overlapping investigation of coronal heating through rapid (1 Hz range) oscillations of coronal loops as observed at total eclipses by Williams College expeditions. This research is supported by NASA grant number NNG04GK44G to Williams College. TRACE analysis at SAO is supported by a contract from Lockheed Martin. SOHO is a project of international cooperation between ESA and NASA.
Transit Research in the 21st Century
Pasachoff, Jay M.
Sky & Telescope 108, #5, 82
The story of Pasachoff’s involvement in observations of the black-drop effect using NASA’s Transition Region and Coronal Explorer spacecraft.
The Open Cluster h Per as Seen by Chandra
N. S. Bizunok, N. R. Evans, S. J. Wolk, B. Spitzbart, F. D. Seward, S. J. Kenyon (Harvard-Smithsonian Center for Astrophysics), T. G. Barnes (University of Texas), and J. M. Pasachoff (Williams College)
Bull. Am. Astron. Soc., 37, #2, 488, for the May-June AAS meeting in Minneapolis, MN, 36.04 [2005]
In December 2004, we observed the open star cluster h Per with Chandra ACIS for 40 ksec. We have identified more than 200 X-ray sources on the image and found optical counterparts for many of them. The ANCHORS pipeline, which we used to process the data, provides homogeneous output products for this and many other star forming regions. Among the outputs are fits to the instrumental low resolution spectra for cool pre-main sequence stars in h Per that yield flux, temperature and absorption for these sources. Funding for this investigation has been provided by Chandra contract NAS8-39073 and NASA Grant G05-6007A.
Think Tank: Astronomy
Pasachoff, J. M.
Discover 26, No. 6, June 2005, 70
The first of a series for Discover magazine by different authors commenting on the most important topics for the next 25 years. This contribution deals with solar research.
Holt Earth Science
Allison, Ease A., Arthur T. DeGaetano, and Jay M. Pasachoff
Holt Earth Science, Holt, Rinehart, and Winston [2006]
Middle-school science textbook (published 11/04).

BIOLOGY

In the Belly of the Beast: Microbial Dangers and Regulatory Debacles
Banta, L.M., Visiting Associate Professor
Gastronomica, 4, 106-110. (2004)
Botany: A Record-Breaking Pollen Catapult
Edwards, J., Professor of Biology, Whitaker, D., Klionsky, S. ’04, Laskowski, MJ
Nature, 435, 7039 (2005)
Analyzing Axon guidance in the Zebrafish Retinotectal System
Hutson, L.D., Assistant Professor, Campbell, D.S., Chien, C.B.
Methods Cell Biology, 76, 13-35 (2004)
The developing visual system has been the subject of intensive study in many model organisms except C. elegans, which unfortunately lacks eyes. There are several reasons for its popularity. It is experimentally accessible, its normal anatomy is understood extremely well, and its function is understood equally well. Thus one can observe how the visual system develops, use perturbations to test the mechanisms of its development, and link alterations in development to changes in mature anatomy and, ultimately, to visual behavior. Here we describe the strategies that have been used to observe and to perturb retinotectal development in the zebrafish.
Robo2 Is Required for Establishment of a Precise Glomerular Map in the Zebrafish Olfactory System
Miyasaka, N., Sato, Y, Yeo, S.Y., Hutson, L.D., Assistant Professor, Chien, C.B., Okamoto, H., Yoshihara, Y
Development, 132(6), 1283-93 (2005)
Olfactory sensory neurons (OSNs) expressing a given odorant receptor project their axons to specific glomeruli, creating a topographic odor map in the olfactory bulb (OB). The mechanisms underlying axonal pathfinding of OSNs to their precise targets are not fully understood. Here, we demonstrate that Robo2/Slit signaling functions to guide nascent olfactory axons to the OB primordium in zebrafish. Robo2 is transiently expressed in the olfactory placode during the initial phase of olfactory axon pathfinding. In the robo2 mutant, astray (ast), early growing olfactory axons misroute ventromedially or posteriorly, and often penetrate into the diencephalon without reaching the OB primordium. Four zebrafish Slit homologs are expressed in regions adjacent to the olfactory axon trajectory, consistent with their role as repulsive ligands for Robo2. Masking of endogenous Slit gradients by ubiquitous misexpression of Slit2 in transgenic fish causes posterior pathfinding errors that resemble the ast phenotype. We also found that the spatial arrangement of glomeruli in OB is perturbed in ast adults, suggesting an essential role for the initial olfactory axon scaffold in determining a topographic glomerular map. These data provide functional evidence for Robo2/Slit signaling in the establishment of olfactory neural circuitry in zebrafish.
Arabidopsis thaliana Sphingosine Kinase and the Effects of Phytosphingosine-I-phosphate on Stomatal Aperture
Coursel, S., H. Le Stunff, D.V. Lynch, Professor of Biology, S Gilroy, S.M. Assman, and S. Spiegel
Plant Physiology, 137, 724-737 (2005)
A Phenological Mid-domain Effect in Flowering Diversity
Morales, M.A., Assistant Professor, Dodge, G.J., Inouye, D.W.
Oecologia, 142(1), 83-89 (2005)
Effect of Ambient Temperature on Cardiovascular Parameters in Rats and Mice:
A Comparative Approach
Swoap, S.J., Associate Professor, Overton, J.M., Garber, G ’97
Am J. Physiol. Regul. Integr. Comp. Physiol., 287, R391-R396 (2004)
Ambient air temperatures (Ta) of less than 6°C or greater than 29°C have been shown to induce large changes in arterial blood pressure and heart rate in homeotherms. The present study was designed to investigate whether small incremental changes in Ta, such as those found in typical laboratory settings, would have an impact on blood pressure and other cardiovascular parameters in mice and rats. We predicted that small decreases in Ta would impact the cardiovascular parameters of mice more than rats due to the increased thermogenic demands resulting from a greater surface area/volume ratio in mice relative to rats. Cardiovascular parameters were measured with radiotelemetry in mice and rats that were housed in temperature-controlled environments. The animals were exposed to different Ta every 72 hours, beginning at 30°C and incrementally decreasing by 4°C at each time interval to 18°C and then incrementally increasing back up to 30°C. As Ta decreased, mean blood pressure, heart rate, and pulse pressure increased significantly for both mice (1.6 mmHg /°C, 14.4 bpm /°C, and 0.8 mmHg /°C, respectively) and rats (1.2 mmHg /°C, 8.1 bpm /°C, and 0.8 mmHg /°C, respectively). Thus, small changes in Ta significantly impact the cardiovascular parameters of both rats and mice, with mice demonstrating a greater sensitivity to these Ta changes.
Cancer Cachexia Is Regulated by Selective Targeting of Skeletal Muscle Gene Products
Acharyya, S., K.J. Ladner, L.L. Nelsen, J. Damrauer, P.J. Reiser, S.J. Swoap, Associate Professor, D.C. Gutridge
J. Slin. Invest., 113, 370-378 (2004)
Cachexia is a syndrome characterized by wasting of skeletal muscle and contributes to nearly one-third of all cancer deaths. Cytokines and tumor factors mediate wasting by suppressing muscle gene products, but exactly which products are targeted by these cachectic factors is not well understood. Because of their functional relevance to muscle architecture, such targets are presumed to represent myofibrillar proteins, but whether these proteins are regulated in a general or a selective manner is also unclear. Here we demonstrate, using in vitro and in vivo models of muscle wasting, that cachectic factors are remarkably selective in targeting myosin heavy chain. In myotubes and mouse muscles, TNF-alpha plus IFN-gamma strongly reduced myosin expression through an RNA-dependent mechanism. Likewise, colon-26 tumors in mice caused the selective reduction of this myofibrillar protein, and this reduction correlated with wasting. Under these conditions, however, loss of myosin was associated with the ubiquitin-dependent proteasome pathway, which suggests that mechanisms used to regulate the expression of muscle proteins may be cachectic factor specific. These results shed new light on cancer cachexia by revealing that wasting does not result from a general downregulation of muscle proteins but rather is highly selective as to which proteins are targeted during the wasting state.
Hypotension and Bradycardia during Caloric Restriction in Mice Are Independent of Salt Balance and Do Not Require the ANP Receptor
Hunt, L.M. ’03, E.W. Hogeland ’04, M.K. Henry ’05, S.J. Swoap, Associate Professor
Amer. J. Physiol.: Heart, 287(4), H1446-51 (2004)
We hypothesized that caloric restriction (CR)-induced hypotension would correlate with increased sodium excretion through an atrial natriuretic peptide (ANP) dependent mechanism. To test this hypothesis, cardiovascular parameters of c57/Bl mice were measured with radiotelemetry while collecting urine. 24 hour mean BP dropped from 108.6 ± 1.8 to 92.7 ± 2.4 mmHg and 24 hour HR dropped from 624 ± 5 to 426 ± 13 bpm over 7 days of CR at 29°C. Contrary to our hypothesis, urine sodium excretion decreased by 55% by day 7 of CR. Consistent with decreased sodium excretion was the drop in plasma ANP (from 82.4 ± 4.3 to 68.0 ± 5.8 pg/ml). To explore the possibility that CR lowers BP through an ANP receptor-dependent mechanism that is independent of its effect on sodium retention, we measured the cardiovascular parameters of mice deficient in the ANP receptor (NPR1 -/-) or the ANP clearance receptor (NPR3 -/-). Mean BP fell from 117.1 ± 3.9 to 108.0 ± 4.7 mmHg in the NPR1 -/- mice, and from 87.0 ± 2.4 to 78.4 ± 1.7 mmHg in the NPR3 -/- mice during CR. These data indicate that the hypotension induced by CR does not depend on increased sodium excretion. Rather, it appears that the mouse responds to the low blood pressure induced by CR with an increase in sodium reabsorption. Further, circulating ANP levels and data from NPR1-/- and NPR3-/- mice suggest that the ANP pathway may not be involved in the cardiovascular response to caloric restriction.
Cardiovascular Risk Factors Emerge from Artificial Selection for Low Aerobic Capacity in Rats
Wisløff. U., S.M. Najjar, Ø. Elingsen, P.M., Steven J. Swoap, Associate Professor, Q. Al-Share, M. Fernström, K. Rezaei, S.J. Lee, L.G. Koch, S.L. Britton
Science, 307, 418-420 (2005)
In humans, the strong statistical association between fitness and survival suggests a link between impaired oxygen metabolism and disease. We hypothesized that artificial selection of rats based on low and high intrinsic exercise capacity would yield models that also contrast for disease risk. After 11 generations, rats with low aerobic capacity scored high on cardiovascular risk factors that constitute the metabolic syndrome. The decrease in aerobic capacity was associated with decreases in the amounts of transcription factors required for mitochondrial biogenesis and in the amounts of oxidative enzymes in skeletal muscle. Impairment of mitochondrial function may link reduced fitness to cardiovascular and metabolic disease.
Perinatal MSG Treatment Attenuates Fasting-Induced Bradycardia and Metabolic Suppression
M.M. Messina, S.A. Evans, S.J. Swoap, Associate Professor, J.M. Overton
Appetite, 42(3) (2004)
We studied the effect of arcuate nucleus (ARC) lesions induced pharmacologically by the perinatal treatment of monosodium L-glutamate (MSG) on the cardiovascular, metabolic, and behavioral responses to fasting. Saline and MSG-treated male Sprague-Dawley rats were instrumented with telemetry devices for measurement of mean arterial pressure (MAP) and heart rate (HR) and housed in room calorimeters at an ambient temperature (Ta) of 23°C for assessment of oxygen consumption (VO2). At baseline, controls and MSG-treated rats had similar MAP (control= 95 ± 4; MSG= 91 ± 2 mmHg), HR (control= 323 ± 4; MSG= 324 ± 2 bpm), and VO2 (control= 8.7 ± 0.3; MSG =8.6 ± 0.2 ml/min). There were no differences in fasting-induced reductions in body weight or in food intake upon refeeding. MSG-treatment significantly attenuated fasting-induced reductions in HR and VO2. This effect was specific to reduced caloric availability, as MSG-treated rats exhibited intact capacity to both increase and decrease HR and VO2 in response to cold (Ta=15°C) and to thermoneutrality (Ta=30°C). Additional studies were performed in saline- and MSG-treated rats chronically treated with β1-adrenergic receptor blockade (atenolol) prior to and during fasting. In controls, the cardiovascular responses to fasting during β1-blockade were blunted and generally mimicked the effects of MSG-treatment, while β1-blockade had no additional effect on MSG-treated rats. The results are consistent with the hypothesis that ARC neuronal signaling is requisite for intact homeostatic responses to fasting and may participate in fasting-induced withdrawal of cardiac sympathetic activity.
Risk Factors for Complex Diseases Diverge in Rats Selectively Bred for Low and High Aerobic Running Capacity
Lauren Gerard Koch, Joseph Hornyak, Ulrik Wisloff, Øyving Ellingsen, Per Magnus Haram, Sonia M. Najjar, Steven Swoap, Associate Professor, and Steve L. Britton
FASEB Journal, 19(4), A198 (2005)
Current approaches to generate animal models of complex diseases such as chemical, transgenic, and mutagenic are insufficient because they fail to emulate mechanistically the progression of diseases. The strong association of low aerobic exercise capacity with high mortality suggests a mechanistic link of oxygen metabolism with disease. We hypothesized that artificial selection for low and high aerobic treadmill running capacity in rats would yield models that contrast for disease risks. Eleven generations of selection produced lines that differed by 347% in running capacity. The High Capacity Runners (HCR) measured higher for VO2max, economy of running, response to training, five measures of heart function, nitric oxide-mediated vasodilation, and abundance of 6 proteins from a type 1 skeletal muscle (soleus) that are integral for energy transfer (PGC-1±, PPARG, UQCRC2, COXI, UCP2, and F1-ATP synthase). The Low Capacity Runners (LCR) measured higher for blood pressure, body weight, visceral adiposity, and plasma glucose, insulin, free fatty acids, and triglycerides. From a broad view, the tight linkage of oxygen metabolism with complex diseases and the evolution of biologic complexity were both predictive that artificial selection for low and high aerobic running capacity would yield models that contrast for risks associated with disease.
Torpor in Mice Is Regulated by Peripheral Sympathetic Nervous System Activity
Ross Osborne Smith’05, David Weinshenker, Steve John Swoap, Associate Professor
FASEB Journal, 19(4), A673 (2005)
Torpor is a hypometabolic response to stressful environmental conditions, found in many small mammals, marsupials, and birds. Torpor, in contrast to hypothermia, is composed of a controlled rapid drop in body temperature (Tb). In mice, torpor is initiated by caloric restriction at low ambient temperature (18°C). We examined the role of the sympathetic nervous system (SNS) in mediating the torpor response to fasting by telemetrically monitoring the Tb of dopamine beta hydroxylase (dbh -/-) mice which lack the ability to produce the SNS transmitters, norepinephrine (NE) or epinephrine (E). Littermate controls (dbh +/-) entered torpor upon fasting (max rate of Tb decline -0.16 ± 0.01°C /min, n=6 ), while none of the dbh -/- mice entered torpor (max rate of Tb decline -0.05 ± 0.01°C /min, n=6). Dbh -/- mice that were treated with DOPS, which allows for restoration of NE and E, regained the ability to enter torpor (max rate of Tb decline -0.09 ± 0.01°C /min, n=6), suggesting that a developmental defect does not prevent dbh -/- mice from entering torpor. Further, with the use of benserazide, a peripheral blocker of DOPS conversion to NE and E, we have shown that the DOPS rescue of the torpor phenotype is peripherally-mediated (max rate of Tb decline -0.04 ± 0.01°C /min, n=6). These data strongly support a critical role of peripheral SNS activity in the torpor response to limited energy availability and cold ambient temperature.
Ghrelin Acts through the Arcuate Nucleus to Modulate Torpor in Mice
Elizabeth Francesca Gluck ’05, Steven John Swoap, Associate Professor
FASEB Journal, 19(4), A210 (2005)
Torpor is a hypo-metabolic response to low ambient temperature and food scarcity in mice and other small rodents. This research analyzes the roles of ghrelin and the hypothalamic arcuate nucleus (ARC) in torpor. Body temperature of mice was measured telemetrically. The ARC was ablated by perinatal treatment of monosodium glutamate (MSG), while littermate controls received perinatal vehicle. Upon fasting at 16°C, all of the control mice entered torpor (min. Tb: 21.7 ± 2.1) whereas none of the MSG-treated animals entered torpor (min. Tb: 31.5 ± 0.6), indicating the requirement of the ARC in mediating the onset of torpor. Fasted control mice had a torpor bout that was deeper (min. Tb: 19.7 ± 0.6) when acutely injected with ghrelin. However, ghrelin did not induce torpor in MSG-treated mice (min. Tb: 31.8 ± 0.8), suggesting that the effect of ghrelin on torpor is mediated through the ARC. One of the primary signaling pathways within the ARC is the melanocortin signaling pathway. To determine if ghrelin functions through this pathway, Agouti mice, which are constitutively blocked in this pathway, were fasted and injected with saline or ghrelin. Twenty-five percent of saline injected Agouti mice entered torpor whereas 83% of ghrelin-injected mice entered torpor. Interestingly, ghrelin injected mice all entered torpor at approximately the same time, 31.2 ± 2.7 minutes after injection. Collectively, these data show that the ARC nucleus is required for both torpor and ghrelin‚s influence on torpor. Further, ghrelin‚s actions through the ARC are independent of the melanocortin signaling pathway.
Cold-Induced Tachycardia in Mice is Not Dependent on Sympathetic Nervous System Activation
FASEB Journal, 19(4), A203 (2005)
Regulation of heart rate is highly sensitive to ambient temperature (Ta) changes, with decreases in environmental temperatures correlating to tachycardia. We hypothesize that cold-induced increases in heart rate are caused by a combination of both sympathetic nervous system activation and parasympathetic nervous system withdrawal. To test this hypothesis, we telemetrically measured the heart rates, body temperatures (Tb), and activity levels of dbh -/- mice, which cannot produce epinephrine or norepinephrine, and their littermate controls. The mice were exposed to two day incremental decreases in Ta from 30°C to 18°C. The increase in heart rate for dbh -/- mice (dark cycle: 12.2 ±1.5 bpm/°C; light cycle: 13.1 ± 1.5 bpm/°C) did not differ from that for control mice (dark cycle: 9.2 ± 1.7 bpm/°C; light cycle: 14.9 ± 1.5 bpm/°C) from 30°C to 22°C. In addition, Tb did not significantly change for either group in response to decreasing Ta. At 18°C, drastic decreases in Tb of dbh -/- were observed, as the animals began experiencing hypothermia. The similarity in cardiovascular responses to decreasing Ta from 30°C to 22°C suggests that parasympathetic nervous system withdrawal is primarily responsible for cold-induced increases in heart rate in mice. However, below 22°C, sympathetic nervous system activation may be necessary for temperature homeostasis and cardiovascular control.
Genome Diversification in Marine Cyanobacteria: Implication for Photosynthetic Physiology and Environmental Stress Response Mechanisms
Claire S. Ting, Assistant Professor, Elizabeth Westly ’04, and Emily Russell-Roy ’06
Photosynthesis: Fundamental Aspects to Global Perspectives, 2, 614-616 (A. van der Est., D. Bruce, eds.) (2005)
Non-Beta receptor Mediated Cardiovascular and Metabolic Responses to Negative Energy Homeostasis and Thermoneutrality
J. M. Overton, S.J. Swoap, Associate Professor, A.D. Parsons and T.D. Williams
FASEB Journal, 19(4), A1133 (2005)
Mice lacking beta-1,2 and 3 adrenergic receptors (betaless) and wild-type (WT) controls were instrumented with telemetry devices for continuous measurement of mean arterial pressure (MAP) and heart rate (HR) and housed in room calorimeters at standard ambient temperature (Ta=23°C) for assessment of oxygen consumption (VO2) in response to acute exposure to fasting and thermoneutrality (TMN; Ta=32°C). At 23°C, mice had similar body weight and MAP (WT=109±2; betaless=109±3 mmHg), but lower HR (WT=579±12; betaless=474±20 bpm) and VO2 (WT=2.0±0.0; betaless=1.6±0.1 ml/min). Betaless mice exhibited a 50% attenuation in fasting-induced bradycardia (WT= -126±34; betaless= -68±10 bpm), but similar reductions in VO2 (WT= -0.2 ± 0.07; betaless= -0.3±0.06 ml/min). Similarly, beta-less mice exhibited an attenuated reduction in TMN-induced bradycardia (WT= -234±14; betaless= -148±8 bpm). but similar reductions in VO2 (WT= -0.92 ± 0.04; betaless= -0.74±0.04 ml/min). In spite of the attenuated responses to fasting and TMN, the results reveal substantial, non-beta-receptor mediated regulation of cardiovascular and metabolic responses to thermal and energetic challenges. We conclude that energetic signals such as food availability and Ta modulate non-sympathetic regulation of HR and metabolism.

CHEMISTRY

Directed Assembly of Discrete Gold Nanoparticle Groupings Using Branched DNA Scaffolds
Sarah L. Goh, Assistant Professor of Chemistry, Shelly A. Claridge, Jean M. J. Fréchet, Shara C. Williams,
Christine M. Micheel, and A. Paul Alivisatos
Chemistry of Materials, 17, 1628-1635 (2005)
The concept of self-assembled dendrimers is explored for the creation of discrete nanoparticle assemblies. Hybridization of branched DNA trimers and nanoparticle-DNA conjugates results in the synthesis of nanoparticle trimer and tetramer complexes. Multiple tetramer architectures are investigated, utilizing Au-DNA conjugates with varying secondary structural motifs. Hybridization products are analyzed by gel electrophoresis, and discrete bands are observed corresponding to structures with increasing numbers of hybridization events. Samples extracted from each band are analyzed by transmission electron microscopy, and statistics compiled from micrographs are used to compare assembly characteristics for each architecture. Asymmetric structures are also produced in which both 5 and 10-nm Au particles are assembled on branched scaffolds.
An Introduction to Turing Patterns in Nonlinera Chemical Kinetics
Enrique Peacock-López, Professor of Chemistry, and Edward A. McGehee ’05
The Chemical Educator, 10, 84-94 (2005)
Although Turing determined the general conditions for the formation of spatial patterns in 1952, it was not until 1990 that De Kepper and co-workers were able to obtain patterns in a chemical system. Since then, spatial patterns in chemical systems have been an active area of research. In this paper we use an algebraically workable model, the Templator, to introduce students to the field of pattern formation in chemical systems. The Templator model is simple enough that numerical analysis with available software packages is accessible to advanced students of Physical Chemistry. Additionally, this paper provides a general background on Turing patterns and then shows how Mathematica can be used to reproduce these patterns.
Turing Patterns in a Modified Lotka-Volterra Model
Enrique Peacock-López, Professor of Chemistry, and Edward A. McGehee ’05
Physics Letters, A342, 90-98 (2005)
In this letter we consider a modified Lotka-Volterra model widely known as the Bazykin model, which is a MacArthur-Rosenzweig (MR) model that includes a prey dependent response function and is modified with the inclusion of intraspecies interactions. We show that the inclusion of a quadratic intra-prey interaction term, which is the most realistic nonlinearity, yields sufficient conditions for Turing patterns. For the Bazykin model we find the Turing region in parameter space and Turing patterns in one dimension.
Complex Dynamics in a Three-Level Trophic System with Intraspecies Interaction
Enrique Peacock-López, Professor of Chemistry, Alison B. Peet ’03, and Peter A. Deutsch ’04
Journal of Theoretical Biology, 232, 491-503 (2005)
In this paper, we present a three-level trophic food chain, including intraspecies interaction. In contrast with other analyses, we consider the effect on the third trophic level by the first level parameters. The model shows complex, as well as, chaotic oscillations. Bifurcation diagrams show period doubling route to chaos and crises. Also from the forward and backwards sections of the bifurcation diagrams, we find hysteresis. This result implies the coexistence of attractors for the same parameter values. In particular, we consider the coexistence of a chaotic and a P1 attractors. Our results show that the regulation in the food chain is not exclusive to either a food-prey or prey-predator interaction, but to a more subtle food-prey-predator interaction, where, for some parameter values, a food-prey or a prey-predator regulation may dominate the system's dynamics. Finally, we consider the impact of the intraspecies interaction in the overall dynamics of the food chain.
ESR Dating at Mezmaiskaya Cave, Russia
Anne R. Skinner, Senior Lecturer, Bonnie A. B. Blackwell, Sara Martin ’05, A. Ortega, Joel I.B. Blickstein,
Lubov V. Golovanova, and Vladimir B. Doronichev
Applied Radiation and Isotopes, 62, 219-224 (2005)
Mezmaiskaya Cave has yielded more than 10,000 artifacts, thousands of very well preserved faunal remains, and hominid remains, found in seven Middle Paleolithic (Mousterian) and three Upper Paleolithic levels. A complete Neanderthal infant skeleton was preserved in anatomical juxtaposition lying on a large limestone block, overlain by the earliest Mousterian layer, Layer 3. Twenty-four skull fragments from a 1-2 year-old Neanderthal infant, showing post-mortem deformation, occurred in a pit originating in the Mousterian Layer 2 and penetrating into underlying layers 2A and 2B(1). Bone from Layer 2A was dated by AMS 14C at 35.8-36.3 0.5 kyr BP. Direct dating of Neanderthal bone from Layer 3 gave an age of 29 kyr, but that is now considered to be due to contamination by modern carbon. Fourteen large mammal teeth from Layers 2 through 3 have been dated by standard ESR Low U concentrations in both the enamel and dentine ensure that ESR ages do not depend significantly on the U uptake model, but do depend strongly on the sedimentary dose rates. Assuming a sedimentary water concentration equal to 20 wt%, ESR ages for the Mousterian layers range from 36.2 to 73.0 5.0 ka.
ESR at Treugol'naya Cave, Northern Caucasus Mt., Russia: Dating Russia's Oldest Archaeological Site and Paleoclimatic Change in Oxygen Isotope Stage 11
Anne R. Skinner, Senior Lecturer, Bonnie A. B. Blackwell, Sisi Liang, Lubov V. Golovanova,
Vladimir B. Doronichev, and Joel I.B. Blickstein
Applied Radiation and Isotopes, 62, 237-245 (2005)
At 1510 m asl, Treugol'naya Cave, Russia, is the highest cave showing evidence for human occupation in eastern Europe. Layers 4-7 in the 4.5-m-thick sequence yielded many artifacts representing Lower Paleolithic pebble and flake tool industries. Abundant faunal remains include extinct Middle Pleistocene species. Palynological, paleomagnetic, and microsedimentological analyses indicate that several climatic changes of different magnitudes occurred in the sequence.
To determine absolute ages for Treugol'naya, 32 independent subsamples from nine ungulate teeth collected from the Lower Paleolithic layers were dated by standard and isochron electron spin resonance (ESR) analyses. Isochron analyses indicate that the teeth experienced no significant U leaching or secondary uptake, and that linear uptake (LU) provides accurate ages. Layers 4B through 5B dated to 365 ± 12 ka to 406 ± 15 ka. Therefore, hominids visited the site periodically throughout OIS 11, indicating that they utilized resources at elevations > 1000 m at least seasonally by 400 ka. ESR, paleomagnetic, palynological and paleontological analyses all indicate that the Lower Paleolithic Layers 4-5 correlate with Oxygen Isotope Stage (OIS) 11. The thickness of Layers 4-5 (more than 1.5 m) makes this one of the thickest OIS 11 terrestrial deposits known.
Fossilization Effects on U Uptake by Tooth Enamel: Insights into an ESR Dating Problem
Q-Band ESR Spectra as Indicators of Fossilization in Tooth Enamel
Anne R. Skinner, Senior Lecturer, N. D. Chasteen, J. L. Shao, G. A. Goodfriend, and Bonnie A.B. Blackwell
Quaternary International, 135, 13-20 (2005)
Electron spin resonance (ESR) dating of the hydroxyapatite (HAP) in tooth enamel uses an ESR signal that remains stable for approximately 1019 y at 25oC, and is particularly useful in the time range between the maximum 14C and the minimum 39Ar/40Ar age limits. Because the ESR dating signal results from radiation damage to samples during burial, the ESR age depends on the radioisotope concentrations, within both the sample and its surrounding sediment. Since teeth are not closed systems with respect to U uptake, however, ESR dates must measure an U uptake model by coupled 230Th/234U-ESR dating, or assume one based on paleoclimatic and geological factors. Experiments to find criteria that might be used to determine the model in teeth too old for 230Th/234U dating began using samples whose abnormal HAP ESR spectra in the X band hinted that fossil diagenesis might be the culprit.
Unlike X band, Q band ESR spectroscopy resolves spectral peaks better, by separating signals with very similar g values for individual study. When examining abnormal enamel spectra from well fossilized Early Pleistocene and Pliocene teeth in the Q band, the problematic signal can be resolved as two signals, both with g ~2.002, but one considerably broader than the other. How much broader, however, appears to be a function of age. ESR theory suggests that the broader signal results from crystal distortion, as might be expected in fossilized samples. 
To test this, modern tooth enamel was artificially fossilized by prolonged heating in a buffered aqueous solution. To test if the teeth had developed characteristics typical in naturally fossilized teeth, the samples were analyzed by HPLC and GC to determine their amino acid racemization (AAR) ratios. Although the Q band spectra from artificially fossilized teeth did not entirely mimic those from natural fossilization, similar ESR signal broadening occurred and correlated with the aIle/Ile ratios from the AAR analyses. Therefore, fossil diagenesis appears to cause distorted HAP crystals, which would make teeth more likely to absorb U through microcracks in the enamel. This suggests that samples exhibiting a broad peak might have absorbed much of their U relatively recently, and that accurate ESR dating requires a recent uptake model.
CH-Stretching Overtone Spectroscopy of 1,1,1,2-Tetrafuoroethane
John W. Thoman, Jr., Professor of Chemistry, Brian G. Saar ’05, Adam H. Steeves ’02,
Daryl L. Howard, Daniel P. Schofield, and Henrik G. Kjaergaard
Journal of Physical Chemistry, 104, 5323-5331 (2005)
We have recorded the vibrational absorption spectrum of 1,1,1,2-tetrafluoroethane (HFC-134a) in the fundamental and first five CH-stretching overtone regions with the use of Fourier transform infrared, dispersive long-path, intracavity laser photoacoustic, and cavity ringdown spectroscopies. We compare our measured total oscillator strengths in each region with intensities calculated using an anharmonic oscillator local mode model. We calculate intensities with 1D, 2D, and 3D Hamiltonians, including one or two CH stretches and two CH stretches with the HCH bending mode, respectively. The dipole moment function is calculated ab initio with self-consistent-field Hartree-Fock and density functional theories combined with double- and triple-zeta-quality basis sets. We find that the basis set choice affects the total intensity more than the choice of the Hamiltonian dimension. We achieve agreement between the calculated and measured total intensities of approximately a factor of 2 or better for the fundamental and first five overtones.

COMPUTER SCIENCE

Controversy on How to Teach CS 1: A Discussion on the SIGCSE-members Mailing List
Kim B. Bruce
Inroads (ACM SIGCSE Bulletin), 29-34, (2004)
A discussion took place on the SIGCSE mailing list in late March of 2004 that raised important issues on how to teach introductory courses using Java. This article attempts to summarize several of the important points raised during this discussion, among them whether or how objects should be taught early or late in a CS 1 course, or indeed whether object-oriented languages should be postponed until a second course.
Why Structural Recursion Should Be Taught before Arrays in CS 1
Kim B. Bruce, Andrea P. Danyluk, and Thomas Murtagh
Electronic Notes in Theoretical Computer Science, 82(8), 2003
SIGCSE Proceedings, 246-250, (2005)
URL: http://www.elsevier.nl/locate/entcs/volume82.html.
The approach to teaching recursion in introductory programming courses has changed little during the transition from procedural to object-oriented languages. It is still common to present recursion late in the course and to focus on traditional, procedural examples such as calculating factorials or solving the Towers of Hanoi puzzle. In this paper, we propose that the shift to object-oriented programming techniques calls for a significant shift in our approach to teaching recursion. First, we argue that in the context of object-oriented programming students should be introduced to examples of simple recursive structures such as linked lists and methods that process them, before being introduced to traditional procedural examples. Second, we believe that this material should be presented before students are introduced to structures such as arrays. In our experience, the early presentation of recursive structures provides the opportunity to reinforce the fundamentals of defining and using classes and better prepares students to appreciate the reasons to use classes to encapsulate access to other data structures when they are presented.
Exploiting Purity for Atomicity
Stephen N. Freund, Cormac Flanagan, and Shaz Qadeer
IEEE Transactions on Software Engineering, 31(4), 275-291, (2005)
This paper investigates ways in which atomicity analysis can better handle irreducible blocks that cause spurious warnings.
Modular Verification of Multithreaded Programs
Stephen N. Freund, Cormac Flanagan, Shaz Qadeer, and Sanjit Seshia
Theoretical Computer Science, 338(1-3), 153-183, (2005)
This paper presents a scalable and expressive static checker for multithreaded programs based on automatic theorem proving.
Type Inference for Atomicity
Stephen N. Freund, Cormac Flanagan, and Marina Lifshin `05
Proceedings of the ACM Workshop on Types in Language Design and Implementation, 47-58, (2005)
Type Inference against Races
Stephen N. Freund and Cormac Flanagan
Proceedings of the Static Analysis Symposium, 116-132, (2004)
Exploiting Purity for Atomicity
Stephen N. Freund, Cormac Flanagan, and Shaz Qadeer
Proceedings of the ACM International Symposium on Software Testing and Analysis, 221-231, (2004)
Resource-Aware Scientific Computation on a Heterogeneous Cluster
James D. Teresco, Jamal Faik, and Joseph E. Flaherty
Computing in Science & Engineering, 7, Number 2, 40-50 (2005)
The popularity of clusters has opened a new platform for software originally designed for tightly-coupled supercomputers. This includes a large base of portable software, such as solvers for systems of partial differential equations using finite element and related methods. However, design decisions and optimizations are based on the platform for which the software is first developed. Moving from a tightly-coupled supercomputer to a cluster, or even from one cluster to another may reduce efficiency. We describe experiences using the "Bullpen Cluster" at Williams College to run parallel adaptive finite element software. The cluster added complications including nonuniform processor speeds, a mixture of 1, 2, and 4-processor nodes, and a slower network relative to processing speed than previous platforms. We describe two application-independent tools that we have developed to support computing on heterogeneous and hierarchical clusters: the Dynamic Resource Utilization Model (DRUM), and a Hierarchical Partitioning and Dynamic Load Balancing system.
New Challenges in Dynamic Load Balancing
James D. Teresco, Karen D. Devine, Erik G. Boman, Robert T. Heaphy, Bruce A. Hendrickson, Jamal Faik,
Joseph E. Flaherty, and Luis G. Gervasio
Applied Numerical Mathematics, 52, Issues 2-3, 133-152 (2005)
Data partitioning and load balancing are important components of parallel computations. Many different partitioning strategies have been developed, with great effectiveness in parallel applications. But the load-balancing problem is not yet solved completely; new applications and architectures require new partitioning features. Existing algorithms must be enhanced to support more complex applications. New models are needed for non-square, non-symmetric, and highly connected systems arising from applications in biology, circuits, and materials simulations. Increased use of heterogeneous computing architectures requires partitioners that account for non-uniform computing, network, and memory resources. And, for greatest impact, these new capabilities must be delivered in toolkits that are robust, easy-to-use, and applicable to a wide range of applications. In this paper, we discuss our approaches to addressing these issues within the Zoltan Parallel Data Services toolkit.
Partitioning and Dynamic Load Balancing for the Numerical Solution of Partial Differential Equations
James D. Teresco, Karen D. Devine, and Joseph E. Flaherty
Chapter in Numerical Solution of Partial Differential Equations on Parallel Computers, Are Magnus Bruaset, Petter Bjørstad, Aslak Tveito, editors, Springer-Verlag (2005)
In parallel simulations, partitioning and load-balancing algorithms compute the distribution of application data and work to processors. The effectiveness of this distribution greatly influences the performance of a parallel simulation. Decompositions that balance processor loads while keeping the application's communication costs low are preferred. Although a wide variety of partitioning and load-balancing algorithms have been developed, their effectiveness depends on the characteristics of the application using them. In this chapter, we review several partitioning algorithms, along with their strengths and weaknesses for various PDE applications. We also discuss current efforts toward improving partitioning algorithms for future applications and architectures.
Toward a Framework for Dynamically Reconfigurable Scientific Computing
James D. Teresco, Kauotar El Maghraoui, Travis Desell, Boleslaw K. Szymanski, and
Carlos A.Varela
Chapter in Grid Computing: New Frontiers of High Performance Computing, L. Grandinetti, editor, Elsevier (2005)
Computational grids are appealing platforms for the execution of large scale applications among the scientific and engineering communities. However, designing new applications and deploying existing ones with the capability of exploiting this potential still remains a challenge. Computational grids are characterized by their dynamic, non-dedicated, and heterogeneous nature. Novel application-level and middleware-level techniques are needed to allow applications to reconfigure themselves and adapt automatically to their underlying execution environments. In this paper, we introduce a new software framework that enhances the performance of Message Passing Interface (MPI) applications through an adaptive middleware for load balancing that includes process checkpointing and migration. Fields as diverse as fluid dynamics, materials science, biomechanics, and ecology make use of parallel adaptive computation. Target architectures have traditionally been supercomputers and tightly coupled clusters. This framework is a first step in allowing these computations to use computational grids efficiently.
Hierarchical Partitioning and Dynamic Load Balancing for Scientific Computation
James D. Teresco, Jamal Faik, and Joseph E. Flaherty
Proceedings of PARA'04 Workshop on State-Of-The-Art in Scientific, 2005
Cluster and grid computing has made hierarchical and heterogeneous computing systems increasingly common as target environments for large-scale scientific computation. A cluster may consist of a network of multiprocessors. A grid computation may involve communication across slow interfaces. Modern supercomputers are often large clusters with hierarchical network structures. For maximum efficiency, software must adapt to the computing environment. We focus on partitioning and dynamic load balancing, in particular on hierarchical procedures implemented within the Zoltan Toolkit, guided by DRUM, the Dynamic Resource Utilization Model. Here, different balancing procedures are used in different parts of the domain. Preliminary results show benefits to using hierarchical partitionings on hierarchical systems.
Resource-Aware Parallel Adaptive Computation for Clusters
James D. Teresco, Laura Effinger-Dean ’06, and Arjun Sharma ’07
Proceedings of the 5th International Conference on Computational Science (ICCS’05), Part II, 3515 of Lecture Notes in Computer Science, Vaidy S. Sunderam, Geert Dick van Albada, Peter M. A. Sloot, et al. editors, 107-115. Springer (2005)
Smaller institutions can now maintain local cluster computing environments to support research and teaching in high-performance scientific computation. Researchers can develop, test, and run software on the local cluster and move later to larger clusters and supercomputers at an appropriate time. This presents challenges in the development of software that can be run efficiently on a range of computing environments from the (often heterogeneous) local clusters to the larger clusters and supercomputers. Meanwhile, the clusters are also valuable teaching resources. We describe the use of a heterogeneous cluster at Williams College and its role in the development of software to support scientific computation in such environments, including two summer research projects completed by Williams undergraduates.

GEOSCIENCES

Mary Creek Fringing Reef and Lagoon, Virgin Islands National Park
Rónadh Cox, Associate Professor of Geosciences and Emily Clinch ’04
Geological Society of America Abstracts with Programs, 36(5), 228 (2004)
Data spanning 40 years reveal shifting changes in the Mary Creek reef complex (MCRC). Our study included bathymetric and substrate data from 1968, 1998, and 2004 and GIS analysis of air photos taken in 1965, 1983, 1993, and 1999. The MCRC consists of three fringing reef lobes: two Acropora palmata-dominated lobes, and a small rubbly remnant of a former A. cervicornis lobe. The coral framework structures are separated from the shoreline by a back-reef lagoon about 120 m wide by 0.5 m deep. Bathymetric data show progressive lagoon shallowing. Both time intervals (1968-1998 and 1998-2004) have the same average sedimentation rate, 3.2 cm/year. This suggests consistent infilling, probably related to periodic storm transport of sediment over the reef crest. The reef lobes have changed in size, but not progressively. Between 1965 and 1983 the A. palmata-dominated eastern and central lobes increased in total area (by 7% and 21% respectively), whereas the A. cervicornis-dominated western lobe decreased by 53% in the same time period. From 1983 to 1996, all reef lobes experienced size decline: 7% and 5% for the two A. palmata lobes, and a further 26% for the A. cervicornis lobe. The onset of decline in the A. palmata lobes coincides with disease-related death of the constituent corals in the 1980s, and is interpreted to represent subsequent mechanical erosion of the dead coral framework. The consistent decrease in size of the A. cervicornis lobe, predating the disease outbreaks of the 1980s, may reflect the marginal nature of the very shallow lagoonal habitat for this deeper-water species. A. palmata colonies have recently begun to repopulate the MCRC. There was little regeneration after the 1980s die-off, and in January 1998 only 5 colonies, all less than 0.5 m in diameter and 0.3 m high, were observed on the MCRC. In January 2004, however, we documented about 90 healthy A. palmata colonies in the 70% of the MCRC surveyed, of which 20 were more than 1 m in diameter, and 50 were more than 0.3 m high. If recolonization continues, we anticipate that the size decrease of the A. palmata-dominated lobes will reverse. In contrast, only two A. cervicornis colonies were observed, and neither was healthy. We believe that the westernmost lobe will therefore continue to decline, and that the MCRC is now essentially a two-lobed rather than a three-lobed reef complex.
Geological versus Human Controls on Lavaka Formation and Extreme Erosion in Madagascar
Rónadh Cox, Associate Professor of Geosciences, A.F. Michel Rakotondrazafy, and Hery Tiana Rakotondramazava
Geological Society of America Abstracts with Programs, 36(5), 171 (2004)
Extreme erosion characterizes Madagascar's central highlands. The country has a “world-record erosion rate” according to the World Bank, and the widespread hillslope gullies called lavaka have been described as “cat claw-marks” on the landscape and are featured in tourist guidebooks as examples of catastrophic denudation of the country’s landscape. Lavakas are caused mainly by groundwater sapping. They initiate suddenly and grow rapidly, shedding sediment volumes on the order of 8000 m3 in a few months. They cause substantial infrastructural problems because they undermine roads and bridges, and because the debris flows that issue from them swamp agricultural land. They are widely cited as being largely or entirely anthropogenic in origin, and the major source of high sediment loads in Madagascar's rivers. The connection between human influence and lavaka formation is not simple, however. Lavakas form exclusively on lateritised Precambrian gneisses, and initial results of field and GIS analysis of lavakas in the Miarinarivo area of central Madagascar suggest that their formation is partially controlled by the relationship between the structural grain of the saprolitised bedrock and the orientation and geometry of the hillslope. Lavakas do not appear to form in dip slopes, and form most readily when gneissic foliation dips at a moderate angle into a steep hillside. We infer that infiltrated water is transferred deep into the saprolite along the inward-dipping foliation planes. This geometry also facilitates long-term within-hill water storage, promoting dissolution and clay formation, and contributing to eventual cohesion loss. There is clear anthropogenic influence on lavaka formation: they often initiate downslope of cart and cattle tracks, and upslope of roadcuts. But in spite of published assertions that they are caused entirely by humans, there is strong evidence that they were a feature of the Malagasy landscape before the arrival of people. The deeply lateritised highlands of Madagascar are very steep, with convex hillslopes commonly greater than 50°. The laterites and saprolites are unconsolidated and mechanically incompetent. We interpret lavakas as a primary response of the unstable landscape to recent tectonic over-steepening, with initiation accelerated by anthropogenic factors.
Evidence That Chaos Terrain on Jupiter’s Moon Europa Is Formed by Crust-Penetrating Impacts
Rónadh Cox, Associate Professor of Geosciences, Lissa Ong ’04, and Masahiko Arakawa, Hokkaido Univ.
Geological Society of America Abstracts with Programs, 36(5), 144 (2004)
Analysis of Galileo images and experiment results suggest that chaos terrain on Europa’s surface may be formed by high-energy impactors that penetrate thin brittle crust and bury themselves in a ductile or liquid subsurface. Chaos consists of rough-textured frozen matrix, often encasing rafts or blocks of broken but undeformed pre-existing crust. The matrix:block ratio varies from about 0.6-1. Many chaos areas have circular or equant shapes and escarpment boundaries, consistent with penetration. The matrix may be updomed, and some chaos areas show overflow or extrusion of matrix material onto the surrounding topography, suggestive of resurgence. Some large chaos areas, notably Murias Chaos and Thrace Macula, are associated with clusters of small (<1 km diameter) craters, interpreted as secondary craters. Some chaos areas are surrounded by blobs of matrix material and sometimes small blocks, which may represent splash ejecta. We tested whether impacts could produce chaos-like features by launching ice projectiles at high velocity (117-405 m/sec) into layered targets consisting of ice over water and ice over slush. Impacts at lower energy or into thicker ice produced classic craters. Impacts at higher energy or into thicker ice, however, penetrated the ice layer completely and reproduced the features of chaos terrain in the shattered ice. Penetration features ranged from circular holes filled with slushy matrix (matrix:block =1) and surrounded by splash ejecta to complete fragmentation of the ice plate, producing rafts of ice floating level or tilted in a matrix of slush (matrix:block ≈0.6). For constant ice thickness, simple holes formed at lower impact energies than did complete fragmentation features; and for a constant impact energy, circular holes formed in thick ice and complete fragmentation in thin. The destruction-diameter:bolide ratio ranged from 1-5 for simple holes, but exceeded 20 for complete fragmentation. Chaos areas on Europa include analogues for both simple holes and complete fragmentation. The strong resemblance between the mapped features on Europa and those produced during experimental simulations supports our hypothesis that chaos terrain can be formed by bolide impact.
Is Chaos on Europa Caused by Crust-Penetrating Impacts?
Rónadh Cox, Associate Professor of Geosciences, Lissa Ong ’04, and M. Arakawa, Hokkaido Univ.
Japanese Society for Planetary Sciences Annual Meeting Abstracts, 7 (2004)
Impact breaching of Europa’s solid ice surface is not only possible, but probable. Estimates of crustal thickness range from a few 10s of km down to a few km or even a few hundred m in places [1-3], and numerical simulations demonstrate that an ice shell 4-7 km thick or less is likely to be breached by 1 km diameter comets impacting at average speed [4, 5]. In addition, the larger impact structures Tyre, Callanish, and Mananàn produced by bolides of about 1-2 km diameter, based on equations in Zahnle et al. [6] have all been interpreted to represent partial breaching of the ice crust and leakage of fluid material from below [2, 7-9]. If 1-2 km diameter bolides split the crust, and 2 km is only the median diameter for impactors at Jupiter [6], larger bolides must produce full crustal penetration. Many chaos areas (equidimensional and sharply-bounded) may be a hitherto unrecognized record of full-crustal penetrations by bolides.
Craters and Chaos Structures on Europa
Rónadh Cox, Associate Professor of Geosciences, Lissa Ong ’04, and M. Arakawa , Hokkaido Univ.
Japanese Society for Planetary Sciences Annual Meeting Abstracts, 7, (2004)
Chaos structure found on Europa was experimentally reproduced by the impact experiments. Two-layer model composed of water layer covered with thin ice plate was used for the target on the cratering experiments by ice projectile colliding at the velocity from 140 to 400 m/s. We have found three types of impact structures according to the impact conditions, which were simple crater, penetrated hole, and chaos failure. The shock stress propagation in ice and water could be a key process to understand the mechanism creating these different structures.
Subglacial Environment Inferred from Bedrock-Coating Siltskins, Mendenhall Glacier, Alaska, U.S.A.
David P. Dethier, Professor of Geosciences, Carissa Carter ’01, and Robert Newton, Smith College
Journal of Glaciology, 49(167), 568-576 (2003)
Retreat of Mendenhall Glacier near Juneau, Alaska, U.S.A., has exposed a bedrock ridge spotted with “siltskins,” patchy coatings of calcite-cemented clay- to sand-sized lithic grains. Coatings 0.5-20 mm thick occur in two distinct morphologies. Thin, striated siltskins coat mainly stoss faces. Thicker, corrugated siltskins on lee faces consist of parallel micro-ridges elongated downslope. Thin-section analysis shows that siltskins consist of a basal, calcite-rich layer overlain by microlaminated layers of calcite-cemented lithic grains. Scanning electron microscope (SEM) energy-dispersive spectrometer (EDS) analysis of laminae and surfaces shows laterally persistent Ca/Si differences. Isotopic values for δΟ18 and δΟ13 ranged from –19.52% to –12.74% and –6.18% to –3.44%, respectively, consistent with deposition from subglacial waters of varying isotopic composition and with derivation of carbon from inorganic sources. Corrugated siltskins are complex depositional features modified by erosional processes. Parallel micro-ridges spaced 1-10 mm apparently formed as sediment-rich water dripped down lee-slope rock faces. Ice-rock separation, flow energy and the transported sediment controlled the layering and depositional forms. Siltskins probably formed when a subglacial cavity system was active on the rock ridge and provide clues about how microscale hydrologic processes interact with larger-scale subglacial systems.
Geomorphic Analysis of Regolith Thickness in the Boulder Creek Catchment, Front Range, Colorado
David P. Dethier, Professor of Geosciences, Eli Lazarus ’04, M.C. Jungers ’03, and K.C. Remsen ’03
Geological Society of America Abstracts with Programs, 36(5), 283 (2004)
Regolith thickness represents a balance between weathering and erosion and should reflect the influence of lithology, proximity to channels, and local slope. We assembled a GIS dataset and mapped bedrock weathering and regolith thickness in six adjacent 7.5' quadrangles using drillers' logs from 1872 wells, a digital geologic map of Colorado (Green, 1992), a high-resolution DEM, and field measurements from the Boulder Creek catchment. We measured outcrop weathering using the scheme of Clayton et al. (1979), which categorizes the decomposition of fresh granitic rocks to grus. Weathered profiles consisting of saprolite and grus are thickest beyond the area eroded by Pleistocene valley glaciers. Precambrian granitic rocks are most deeply weathered. Metasedimentary rocks are pervasively jointed and oxidized, but neither fresh nor deeply weathered material is common. Tertiary intrusive rocks show only minor evidence of chemical weathering but are extensively jointed. Rock units within the Colorado Mineral Belt are highly altered, but oxidation does not decrease with depth below the surface. Where highly weathered rocks are exposed in roadcuts or noted in drillers' logs, profiles are 1 to 7 m thick. Outcrops show variable weathering patterns that laterally juxtapose deeply weathered material against oxidized but otherwise unaltered rock. Outcrops near the Continental Divide are mainly unweathered (Clayton 1 and 2), whereas areas beyond the glacial limit give Clayton values as high as 6 and 7 (denoting grus). Density values range from 1.4 to 2.2 g cm-3. Boulder Creek granodiorite tends to weather to saprolite (1.9 g cm-3) and grus (1.7 g cm-3) overlying or surrounding denser core stones (2.5 g cm-3). Geochemical analyses of weathering profiles record expansion in the weathered substrate and progressive loss of Si and Ca. Spatial interpolations of regolith thickness show no simple correlation between lithology and depth of weathering, but suggest complex relationships among several variables. Multiple-regression analyses using local slope, proximity to channels and glacial limit, and lithology help explain the distribution of weathering depths and styles within the Boulder Creek catchment and provide a context for erosion models.
Digital Analysis of Surficial Materials, Colorado Front Range Using Field, GIS and Aster Techniques
David P. Dethier, Professor of Geosciences and Robert Hahn ’05
Geological Society of America Abstracts with Programs, 37(1), 57-58 (2005)
We report data from a GIS-based map of surficial deposits in the Boulder Creek catchment (294 km2) based on field measurements and an image-to-image comparison using a 14-band, high-resolution Aster image collected by the Earth Observing System's satellite, Terra. The catchment heads in the glaciated, alpine Indian Peaks area and extends past the late Pleistocene glacial limit to the lightly forested zone at an elevation of about 2800 m. Surficial deposits reflect local bedrock geology, weathering, and erosion and transport by glaciers, mass movements and other surface processes. Calculations of long-term weathering and erosion rates for the Front Range require measurements for area and thickness of these surface deposits.
The digitized map is dominated by weathered bedrock and colluvium covered with forest (~54%), mainly east of the glacial limit. Till covers 18% of the mapped area and extends in tongues from the larger alpine catchments down U-shaped valleys between about 3400 and 2700 m. This elevation range separates glaciated valleys from weathered bedrock, talus, and periglacial deposits preserved above late Pleistocene glacial limits. Bedrock and talus comprise 14% of the map area and crop out on steep flanks of the valleys and upper basins, whereas alpine colluvium (8% of mapped area) and patterned ground (1.75%) are common on gently sloping ridges at elevations as high as 3900 m. Nearly 78% of the measured bedrock area is near the basin head; bedrock also crops out along steep canyon walls and tors east of the glacial limit. Alpine colluvial deposits and patterned ground occur exclusively above 3000 m.
From an imaging perspective, spectral distinctions between some surficial materials are not clearly defined because classifications cannot separate patterns easily perceived by the human eye. Therefore, we also used DEM-based slope and aspect measurements. Using a decision-tree method in conjunction with DEM data, for instance, enables classification of north and south-facing slopes separately because the former has insufficient spectral signature. Most surficial units are best defined using band ratioing. Overall, the classified Aster image suggests that in this environment, field-based mapping helps improve classification of surficial deposits over satellite imagery alone.
Paleogeographic Orientation of the Sino-Korean Plate Based on Evidence for a Prevailing Silurian Wind Field
Markes E. Johnson, Professor of Geosciences, J.-Y Rong, and W.-B Su
Journal of Geology, 112, 671-684 (2004)
The regional geology of southern Inner Mongolia records relationships between an Upper Silurian coastline and a small island on what was formerly the continental shelf of the Sino-Korean Plate (North China Block). In both cases, rocky shorelines are defined by unconformities between strata of Ludlow age in the Xibiehe Formation and underlying igneous rocks of Ordovician age. The paleoisland occurs near Bater Obo about 50 km south of the Chinese-Mongolian border. The diorite core of this geological inlier is oriented on an axis N55Eº. A simple dichotomy of exposed windward versus sheltered leeward environments accounts for contrasting carbonate facies on the flanks of the paleoisland. Wider corroboration of a prevailing Silurian wind field is supported by evidence from other unconformities about 30 km to the southwest, where a linear paleoshore extends for 15 km on an average bearing of N60Eº. Siliciclastic sandstone derived from a granodiorite source in the Gushan area now sits in close proximity to basaltic bedrock in the Baoerhantu area. Local transport of sand is the result of long-shore currents driven by winds that were consistent in direction with the facies pattern around the paleoisland.
Global-scale interpretations of Silurian paleogeography typically place the Sino-Korean Plate in low latitudes north of the paleoequator, where it would receive trade winds out of the northeast. In terms of present geography, however, the Silurian winds of Inner Mongolia are aligned with a source out of the northwest. None of the published scenarios of Sino-Korean paleogeography accommodates the physical data from the Bater Obo, Baoerhantu, and Gushan areas of Inner Mongolia. Based on these relationships, the Sino-Korean Plate must be rotated 90º clockwise from its present orientation in order to approximate its original Silurian orientation under a prevailing atmospheric system associated with northeasterly trade winds.
Transpression, Orogen-Parallel Extrusion, and the Formation of Mantled Gneiss Domes
Paul Karabinos, Professor of Geosciences
Geological Society of America, Abstracts with Programs, 36, 91 (2004)
There are two north-south trending sets of gneiss domes in the New England Appalachians. The western belt contains thirteen domes that expose either Laurentian basement rocks or 475 Ma rocks of the Shelburne Falls arc (SFA). The eastern belt contains twenty-one gneiss domes cored by either Avalonian (?) crust or 450 Ma rocks of the Bronson Hill arc (BHA). The dome belts are flanked by Silurian to Early Devonian basins that formed just before the Acadian orogeny, the Connecticut Valley trough (CVT) and the Central Maine terrane (CMT). During the Acadian, km-scale nappes from the CVT and CMT were transported westward over the regions now occupied by the gneiss domes. The domes are elongated north-south and surrounded by high-strain zones (HSZ) that separate the core gneisses from the mantling units. The nappes were refolded during doming and units were dramatically thinned or omitted in the HSZ. In the Chester dome in Vermont sense of shear indicators suggest that rocks above the high-strain zone were displaced southwest relative to rocks below it. P-T paths of rocks from below the HSZ in the Chester dome indicate decompression of several kbars during metamorphism, whereas rocks above the HSZ record nearly isobaric conditions. This pattern is consistent with normal-sense displacement between the core of the dome and its mantling sequence during Acadian metamorphism.
The domes occur in a region where the Acadian orogen is atypically narrow. Mechanical decoupling along the HSZ occurred between the quartz-feldspar-rich core gneisses of the domes and the overlying nappes of mica-rich metasediments. Pressure estimates of approximately 10 kbar indicate significant tectonic loading in the core of the Chester dome, presumably during the westward transport of nappes from the CVT. East-west shortening and vertical thickening of the quartz-feldspar-rich gneisses below the nappes would have required enormous work against gravity. It was energetically more favorable for the gneisses to be extruded northward where the orogen was wider and not as dramatically thickened. During extrusion, the core gneisses cut upsection into the nappes of Silurian rocks and the thickness of the Lower Paleozoic section was dramatically reduced. The New England gneiss domes owe their north-south elongation and streamlined shapes to this flow pattern.
Thrusting in the Berkshire Massif, Western New England
Paul Karabinos, Professor of Geosciences and Ryan Gordon ’05
Geological Society of America, Abstracts with Programs, 37, 71-73 (2005)
The Berkshire Massif in western Massachusetts and Connecticut is composed of Middle Proterozoic rocks that were thrust over Cambrian to Ordovician continental shelf deposits. It is widely accepted that westward-directed thrusting occurred during the Ordovician Taconic orogeny, yet the kinematics and age of deformation have not been well constrained. Ratcliffe and Harwood (1975) described zones of cataclasis and recrystallization in “blastomylonitic seams” along the western edge of the massif, but sense of shear indicators and microstructures have not been described in these rocks since their work. Furthermore, it may be possible to date fabric development and deformation with monazite.
We collected samples of deformed basement and cover rocks near thrust faults in the southwestern part of the massif. Rocks within a few meters of faults are mylonites with a strong, recrystallized, planar foliation. Strain decreases dramatically within tens of meters of faults, based on the appearance of deformation fabrics. Basement rocks approximately 20 m away from faults generally preserve their Proterozoic gneissic fabric, which is crosscut by distinct mica-rich shear bands with recrystallized feldspar and quartz. Biotite seams, quartz ribbons, and regions of fine-grained recrystallized feldspar define a sub-planar fabric that wraps around feldspar porphyroclasts. Porphyroclasts have short tails and theta- or sigma-type shapes, suggesting that recrystallization was very rapid compared to the strain rate. Asymmetric porphyroclasts, S-C fabrics, and extensional shear bands locally show east over west displacement. Elongate quartz ribbons are composed of equant subgrains that are commonly recovered and strain-free, whereas the interiors of most feldspar porphyroclasts preserve evidence of deformation by grain-size reduction. Such grains are highly strained and show undulose extinction, suggesting that deformation was controlled by dislocation creep at temperatures above 500 degrees C. No evidence for cataclasis or other brittle mechanisms is preserved in these rocks.
It may be possible to identify monazite grains that grew during the development of thrust-related mylonitic fabrics and thereby date the age of thrusting and constrain the timing of the Taconic orogeny in this part of the northern Appalachians.
Limited Range of Interspecific Vital Effects in Coccolith Stable Isotopic Records during the Paleocene-Eocene Thermal Maximum
Heather Stoll, Assistant Professor of Geosciences
Paleoceanography, (2005)
Small but significant differences exist among stable carbon and oxygen isotopic excursions measured in coccolith-dominated bulk carbonate and planktic foraminifera during the Paleocene-Eocene Thermal Maximum (PETM). One hypothesis suggests that the bulk carbonate isotopic record is compromised by changing nannofossil assemblages, since modern nannofossils show a large (5 permil) range of interspecific vital effects. New techniques are employed here to separate different size fractions of coccoliths from PETM sediments at ODP Site 690 for isotopic analysis, removing a major portion of the variation in nannofossil assemblages. Isotopic compositions of coarse and fine coccolith fractions dominated by coccoliths of genus Chiasmolithus and Toweius, respectively, differ by less than 0.5 permil for both oxygen and carbon. The near-monogeneric Toweius record closely parallels the main trends in the bulk carbonate isotope records, including multiple steps in the negative carbon isotopic excursion, suggesting that the trends in the bulk carbonate record are not artifacts of changing species assemblages. Because both coccolithophorids and symbiont-bearing foraminifera like Acarinina must inhabit the photic zone, it is unlikely that the 103 year lags in isotope event onset between coccoliths and Acarinina reflect true time-transgressive invasion of isotopically depleted CO2 into the water column. The small range of vital effects among Paleocene coccoliths is unlikely to result from diagenetic homogenization, and instead may reflect more similar carbon acquisition strategies of Paleocene coccolithophorid algae due to larger and/or more similar cell sizes and higher atmospheric carbon dioxide. The small range of vital effects suggests that bulk carbonate records are likely reliable for other early-and pre-Cenozoic sediments where foraminifera are often scarce.
Can Cave Deposits in Northern Spain Reconstruct the North Atlantic Oscillation?
Heather Stoll, Assistant Professor of Geosciences, Tyler Auer ’07, Robert Hahn ’05, Ashleigh Theberge ’06, and Montse Jimenez
Geological Society of America Abstracts with Programs, 37(1), (2005)
Speleothems deposits offer a potential high resolution terrestrial record that might allow us to reconstruct rainfall and past behavior of the North Atlantic Oscillation (NAO). We will analyze cave hydrology and consider stalagmite geochemistry to explore potential relationships between trace elements and North Atlantic climate variability. We have 48 hour discrete drip water samples from Pindal Cave in Northern Spain (43.0º N, 4.5º W) from December 2003 through present. Analysis of drip water chemistry revealed strong correlations between the drip rate and Ca, Mg/Ca, and Sr/Ca (r2 values of 0.52, 0.48, and 0.56 respectively). The relationship between Pindal Cave's drip rate and local meteoric precipitation is less clear on a weekly time scale due to temporary storage in intermediate reservoirs.
Analysis of a cross-section of a recent actively growing stalagmite reveals an average growth rate of 0.6 mm/yr based on counting inferred annual layers. Mg/Ca and Sr/Ca ratios of estimated 57-year record show some coherent variation, which may be related to precipitation. We will compare this record to local historical precipitation data as well as NAO data. We will also use a fossil stalagmite to search for longer amplitude changes in Sr/Ca and Mg/Ca.
Monsoon-Induced Changes in Coccolithophorid Primary Productivity in the Bay of Bengal
Heather Stoll, Assistant Professor of Geosciences, Alicia Arevalos ’05, Andrea Burke ’06,
Seth Zeren ’05 and Patrizia Ziveri
Geological Society of America Abstracts with Programs, 37(1), (2005)
The Bay of Bengal represents and ideal location to test marine productivity changes in response to monsoon-driven fluctuations in riverine nutrient input. The productivity of marine primary producers may represent an important feedback in the climate system. Using the new productivity indicator, the Sr/Ca ratio of coccolith calcite, we tested recent sediment from the Bay of Bengal collected in traps over a one-year period and monsoon cycle (1994-1995). Data from sediment trap site NBBT-N8 (N 17.5 E 89.5; trap depth 684m) shows the flux of total coccolith carbonate more than doubles between the months of April and September, and has a smaller later surge in early November. Preliminary species separation and microscope observation suggest that this change is due mostly to an increase in F. profunda and G. oceanica during the monsoon months. Sr/Ca analysis shows an increase in productivity of all species beginning in March. All species reach an initial productivity peak in mid-April. F. profunda peaks for a second time in mid-July. All species have a final productivity surge between September and December, but F. profunda and G. oceanica peak in late October while Calcidiscus and Helicosphera peak later, in late November/early December. Between December and March, productivity is low for all species. NBBT-N8 data suggests that monsoon-induced nutrient fluxes do increase coccolith productivity during monsoon months. However, the monsoon cycle does not explain the later productivity surge. We will compare more distal traps from locations NBBT-S8 (N 15.5 E 89.2; trap depth 731 m) and SBBT-08 (05.5 N; 86.75E; trap depth 1919m) to see if response at the locations mirrors that of NBBT-N8 or if the coccolith productivity response varies with distance from the river delta. In Quaternary sediments from the Bay of Bengal, variations in clay mineralogy are interpreted to indicate fluctuations in continental weathering intensity during monsoon cycles (Colin et al., 1999). Using relationships from the sediment trap calibration, and data on coccolith assemblages and Sr/Ca changes over the last 200,000 years, we will evaluate whether monsoon-induced increases in continental weathering affected nutrient supply and productivity.
Tropical Atlantic Coccolith Sr/Ca Productivity Records from the Paleocene-Eocene Thermal Maximum
Heather Stoll, Assistant Professor of Geosciences, Nora Matell ’06, Ashleigh Theberge ’06, and Nobumich Shimuzu
Geological Society of America Abstracts with Programs, 37(1), (2005)
One hypothesis explaining the rapid recovery of temperature and atmospheric carbon following the PETM involves increased primary marine productivity and subsequent carbon burial in deep ocean sediments. The tropics, which contain the majority of the world's oceanic surface area, are of particular importance in evaluating the geographic extent of this proposed feedback. Previous research is limited to sites in the Antarctic (ODP site 690) and the mid-latitude Pacific (ODP site 1209). Here we present Sr/Ca of coccoliths as a proxy for productivity changes at ODP site 1258 Demerara Rise in the tropical Atlantic. Sr/Ca incorporation in coccoliths has been shown to be positively correlated with productivity. We measured Sr/Ca in bulk samples of two different size sediment fractions (5-8 µm and 8-12 µm) via Atomic Absorption Spectroscopy, and in individually picked coccoliths of several genera using Secondary Ion Mass Spectrometry ion probe. This allows us to isolate the productivity responses of specific genera. Sample depths ranged from 176.0 mbsf to 171.75 mbsf, providing data points encompassing the PETM and the surrounding time period. Toweius showed a large decrease in productivity during the PETM, eventually recovering to near pre-PETM levels. In contrast, Coccolithus pelagicus showed an increase in productivity during the event. Bulk data for the 5-8 µm and 8-12 µm sediment fractions showed similar trends to Toweius and C. pelagicus, respectively. The presence of additional genera in the bulk samples accounts for minor deviations from the genus specific data. The difference in the productivity response of these two genera is likely due to varied modification of their respective ecological niches produced by the conditions of the PETM. Combined with previous research from OPD sites 690 and 1209, the data indicate that there was no unified coccolithophorid response to the PETM. In the tropics and mid-latitudes, there are examples of both productivity increases and decreases among different genera, whereas in the high latitudes all studied genera appear have increased or constant productivity.
Coccolithophorid Productivity Response to Paleocene-Eocene Thermal Maximum
Heather Stoll, Assistant Professor of Geosciences, N. Shimizu, Alicia Arevalos ’05, and Susanna Theroux ’05
EOS, Trans. American Geophysical Union, 85(47) (2004)
The response of marine plankton to the Paleocene-Eocene Thermal Maximum may have influenced the rate of uptake of greenhouse gases and recovery of the climate but indicators of marine productivity in the open ocean are sparse and have yielded conflicting results at some sites. Here we report on the productivity response of coccolithophorids during the PETM at sites from the Southern Ocean, Tropical Pacific, and Tropical Atlantic. A novel technique for picking individual coccoliths for analysis using secondary ion mass spectrometry (SIMS) allows us to apply the coccolith Sr/Ca productivity proxy to individual genera and avoid biases from changing species assemblages and noncoccolith carbonate in sediments. In the Southern Ocean site, Chiasmolithus experiences a brief surge in productivity in the first thousand years following the event onset, Zygrhablithus experiences an increase in productivity beginning about 20,000 years following the event onset and lasting about 50,000 years. Toweius, the dominant genera, experiences increased productivity beginning about 20,000 years following the event onset and lasting about 100,000 years and likely contributing to the high carbonate accumulation rates at this site during the carbon isotope recovery. Discoaster shows a slight decrease in productivity. In the Equatorial Pacific Site, Toweius experiences a dramatic decline in productivity after the event onset, and recovery to pre-event levels about 50,000 years later. Discoaster shows a slight increase in productivity during the PETM. In the Equatorial Atlantic site, Toweius shows a slight decrease in productivity during the PETM whereas Coccolithus is unaffected. Consequently, while published Os isotopic data are inferred to indicate increased global average weathering rates, the largest effect of such an increase may have been in higher latitude areas which were previously weathering-limited. Hence, the effect of nutrient fertilization may have been confined to these regions.
Unraveling Nutrient, Growth Rate, Calcification, and Diagenesis Effects on the Chemistry of Coccolith Calcite
Heather Stoll, Assistant Professor of Geosciences, Alicia Arevalos ’05, Andrea Burke ’06,
Susanna Theroux ’05, N. Shimizu, and P. Ziveri
Geochimica et Cosmochimica Acta, 69(10), A127 (2005)
Coccoliths are the dominant biogenic carbonate in many deep sea sediment cores, and recent work to constrain the influence of vital effects on coccolith stable isotopic measurements, and to exploit vital effects on Sr/Ca ratios in coccoliths, have renewed interest in proxies from coccolith chemistry. Coccolith Sr/Ca ratios are correlated with productivity across upwelling gradients and in some transient blooms. To assess whether this response is triggered by cell growth and calcification or nutrient availability, and whether different responses among different genera reflect different ecological responses to these environmental gradients, we analyze Sr/Ca ratios of different coccolith fractions from a series of sediment traps in the northern and southern Bay of Bengal. In the northern trap series close to major river deltas, maximum coccolith fluxes occur during the southwest summer monsoon when productivity is highest, and correspond to elevated Sr/Ca ratios in several species. In some species, Sr/Ca ratios are more correlated to total productivity than to the export flux of coccoliths from that species, suggesting a link to an environmental variable like nutrients, or export response truncated by grazing. We further evaluate the nutrient influence on Sr/Ca with analysis of coccolith chemistry in N-limited and P-limited chemostat cultures of coccolithophorid Emiliania huxleyi.
New ion probe techniques for Sr/Ca measurements on individually picked coccoliths isolate the Sr/Ca variations in single species of fossil coccoliths from sediments. This approach reveals a large heterogeneity of Sr/Ca ratios among different genera of coccoliths. Such heterogeneity suggests that diagenesis has not homogenized the Sr/Ca ratios of coccoliths in many older (in this case Paleocene) sediments, an asset for paleoreconstructions. However, it indicates that the elemental variations in bulk carbonate may be influenced by changing nannofossil assemblages.
Keck Consortium Field Projects on the Maine Coast
R. A. Wobus, Professor of Geosciences, R. A. Wiebe, and D. P. Hawkins
Geological Society of America Abstracts with Programs, 36(5), 418 (2004)
The Keck Geology Consortium, with help from NSF, supported four summer research projects on Silurian bimodal plutonic-volcanic complexes on the Maine coast between 1993 and 2002. These projects involved the authors as project leaders and a total of 32 undergraduates from 13 different liberal arts colleges. During each four-week project the students completed fieldwork, cut rocks for thin sections and wrote research proposals. Nearly all students completed a formal senior thesis over the following academic year.
The field areas proved ideal for a wide range of interconnected process-oriented field problems. After preliminary reading and 2-3 days of field trips, the group identified a list of key problems, and students chose projects from the list. Fieldwork was supported by about 20 visiting geologists from the students’ home institutions, research institutions, and the Maine Geological Survey. Each student completed careful fieldwork, acquired petrographic and geochemical data and then described and analyzed those results in a senior thesis. The year-long projects culminated in late Spring at a symposium where all students presented the results of their research. Extended abstracts were published in a proceedings volume.
A case has often been made that these types of programs provide valuable experience for faculty at small colleges and for undergraduates, especially those who pursue graduate studies or become professional geologists. However, we think these programs can also provide rich opportunities for high quality research. Although student projects only rarely reached a level ready for publication, the resulting set of observations and analytical databases were later integrated into powerful data sets that addressed a complex set of inter-related magmatic processes. The observations and data from these four Keck projects resulted in numerous abstracts, 13 journal articles involving 12 different students as coauthors, and led to three field trips (GSA, NEIGC, Hutton) and a GSA Field Forum. In addition, the projects chosen by students, supported by the involvement of faculty from other institutions, broadened the research topics far beyond the expertise of the project leaders. As a result we recognized and pursued many promising research topics that we might never have identified.
The Elusive Intrusive: A Petrologic, Structural, and Geochemical Analysis of a Basaltic Body in an Abandoned Rift, Vatnsdalsfjall, Northern Iceland
R. A. Wobus, Professor of Geosciences and Paige McClanahan ’04
EOS, Trans. American Geophysical Union, 85(47) (2004)
The Hjallin Lens is a thick, lenticular basaltic unit in Vatnsdalsfjall near the southern end of the Skagi Peninsula, northern Iceland. The lens was named and first studied by Annells (1968), who interpreted it as a shallow laccolith. However, recent field observations followed by extensive petrographic, geochemical, and geochronologic analyses support an alternate interpretation: that the lens is actually an extrusive feature formed by the ponding of a thick basalt flow in a topographic low developed above a monoclinal flexure (Ackerly, 2004). The lens extends approximately 3000 meters NNW-SSE and 800 meters ENE-WNW. It reaches its greatest thickness (over 150 meters) near its southern end; its upper contact, however, is not exposed along the ridge crest. The lithology of the lens is virtually uniform throughout: a very hard, fine-grained aphyric basalt that has cooled in well developed columns. It is underlain by a rhyolitic ash flow tuff (previously interpreted as a chilled margin) along a sharply defined lower contact. At the southern end of the lens, the ash flow tuff overlies a poorly lithified sediment with well preserved fragments of carbonized and silicified wood. The presence of these relatively undisturbed surficial units immediately beneath the lens is one line of evidence supporting the extrusive origin of its basalt. Geochemically the basalt of the lens is a tholeiite enriched in incompatible elements and with Zr/Nb values less than 10, indicating a plume overprint of N-MORB composition. The striking textural, mineralogical, and geochemical homogeneity of the lens basalt suggests that the entire body must have cooled very rapidly, without the internal differentiation that would likely have accompanied a slower-cooling intrusive basalt of this thickness. New argon-argon dating provided an age of 6.98±-0.18 Ma for the lens basalt, indicating that it formed during the waning stages of volcanic activity in the Snaefellsnes Rift, which was an active spreading center from about 15-7 Ma.
Petrology and Evolution of a Monoclinally-Folded Paleo-Rift Lava Sequence, Vatnsdalsfjall, Northern Iceland
R. A. Wobus, Professor of Geosciences and Katherine Ackerly ’04
EOS, Trans. American Geophysical Union, 85(47) (2004)
The Hvammur-Breidin area of southern Vatnsdalsfjall in northern Iceland lies 15 km east of the axis of the abandoned Snaefellsnes rift zone that was an active spreading center from 15–7 Ma. It contains an unusual and exceptionally well exposed monoclinal flexure that deforms a thick volcanic sequence produced during the waning stages of rift-related volcanic activity. A sequence of thin basalt flows thickens dramatically into the trough of the monocline, leading upwards to a 150-meter thick basaltic unit called the Hjallin Lens, mapped originally as an intrusion but recently reinterpreted as extrusive (McClanahan, 2004). Flows that are part of the monocline and flows that overlie the monocline can be distinguished petrologically and geochemically, although there is no evidence of erosion or soil development between the two sequences. The monocline sequence contains several silicic pyroclastic units interlayered with basalts of varying textures, whereas the overlying sequence contains only fine-grained intergranular basalts. In plots of major and trace element ratios, the monocline basalts display a high degree of compositional variation, which is absent in the overlying sequence. In Harker-type variation diagrams, the two sequences show two distinct trends. Both sequences show consistent Zr/Nb ratios less than 10, signifying a plume-influenced MORB source. Enrichment in these and other light incompatible elements increases upwards, but a substantial gap in Zr and Nb concentration occurs at the contact between the two sequences. Two new argon-argon dates, one from the top of the monocline sequence (7.62±-0.32 Ma) and one from the overlying Hjallin Lens (6.98±-0.18 Ma; McClanahan, 2004) bracket a period of 0.60 Ma (average) that encompasses both the formation of the monocline and the eruption of the intervening undeformed thin basalts that thicken into its trough. This interval also constrains the age of displacement along a normal fault running just east of the monocline axis. The monocline is interpreted as a shallow structure that formed incrementally during the eruption of the overlying thin basalt flows above an upward-propagating normal fault that ultimately displaced the entire sequence. The flexure is likely the result of local subsidence caused by a change in spreading rates and/or contemporaneous crustal loading due to renewed magmatism, which culminated in the eruption and ponding of the thick basalt flow of the Hjallin Lens.

MATHEMATICS

Brunnian Clothes: Not for the Bashful
Colin C. Adams, Francis C. Oakley Third Century Professor of Mathematics, T. Fleming and C. Koegel
American Mathematical Monthly, 111, No. 9, 741-748 (2004)
Brunnian links are links such that the removal of any one component trivializes the link. Can you make Brunnian clothes? This paper discusses the consequences.
Integers Causing Bipolar Orientation Reversal of Appendage Motion
Colin C. Adams, Francis C. Oakley Third Century Professor of Mathematics
Math Horizons, XII, Issue 3, 10-11, 24 (2005)
Try to draw a six in the air as you move your foot in a counterclockwise direction. This paper is an investigation of the positive integers that cause orientation reversal upon air depiction.
A Proof of God
Colin C. Adams, Francis C. Oakley Third Century Professor of Mathematics
Mathematical Intelligencer, 26, No. 3, 13-15 (2004)
What if someone claimed a proof of God? And what if it was right?
Mangum, P.I.
Colin C. Adams, Francis C. Oakley Third Century Professor of Mathematics
Mathematical Intelligencer, 26, No. 4, 22-24 (2004)
The adventures of a principal investigator on an NSF grant.
Trial and Error
Colin C. Adams, Francis C. Oakley Third Century Professor of Mathematics
Mathematical Intelligencer, 27, No. 1, 37-40 (2005)
What happens if the courts get involved in grading.
The Mathematical Ethicist
Colin C. Adams, Francis C. Oakley Third Century Professor of Mathematics
Mathematical Intelligencer, 27, No. 2, 24-25 (2005)
A sample of the column to which ethically challenged mathematicians turn.
Continuous Foldability of Polygonal Paper
Satyan Devadoss, Assistant Professor of Mathematics, Erik Demaine, Joe Mitchell and Joe O’Rourke
Proceedings of the 16th CCCG Conference, 64-67 (2004)
We prove that any given well-behaved folded state of a piece of paper can be reached via a continuous folding process starting from the unfolded paper and ending with the folded state. The argument is an extension of that originally presented in Demaine-Mitchell.
Intro Stats
Richard D. Deveaux, Associate Professor of Statistics, Paul Velleman and David Bock
Addison-Wesley, Boston, 2nd Edition (2005)
Bagging and Boosting
Richard D. Deveaux, Associate Professor of Statistics
Encyclopedia of Biostatistics, Wiley, New York, 2nd Edition (2004)
Definitions and examples of two popular methods for combining models.
Resizing Triathlons for Fairness
Richard D. Deveaux, Associate Professor of Statistics, with H. Wainer
J.H. Albert, J. Bennett, J.J. Cochran, Editors
Anthology of Statistics in Sports, Society for Industrial and Applied Mathematics (2005)
In this paper, we argue that by standardizing the performances across the three sports, it is clear that swimmers are disadvantaged in standard triathlons. A “fair” triathlon is proposed.
Reducing Junk Mail Using Data Mining Techniques
Richard D. Deveaux, Associate Professor of Statistics with Herb Edelstein R. Peck, Editor
Statistics, A Guide to the Unknown, Thomson, Brooks/Cole, 307-322 (2005)
An overview of data mining techniques for the lay person using junk mail as the motivating example.
Comparison of Tree Based Methods on Mammography Data
Richard D. Deveaux, Associate Professor of Statistics with Thu Hoang, Tu Boa Ho, David Cheung, Huan Liu, Editors
Advances in Knowledge Discovery and Data Mining, Springer, 186-191 (2005)
We find that by combining tree models using bagging, we are able to improve on the radiologists’ reading of mammograms in terms of both false positive and false negative rates. This finding has potential for financial and health impacts for much of the developing world.
Recommended Resources in Algebraic and Differential Geometry
Thomas Garrity, Professor of Mathematics, Kristine Fowler, Editor
Using the Mathematical Literature, Marcel Dekker (2004)
Surveys of the basic literature in algebraic and differential geometry are given.
Review of John Adam’s Mathematics in Nature
Thomas Garrity, Professor of Mathematics
Mathematical Intelligencer, 27, No. 2, 81-82 (2005)
A review of a book by John Adam’s on how powerful mathematics is in describing the real world.
Optimality of Stasis and Small Switching Cycles in Planar Systems with Two-Valued Controls
Stewart Johnson, Professor of Mathematics
SIAM J. Control and Optimization, 43, No. 6, 1987-1999 (2005)
This paper investigates cyclic non-probabilistic approximations to fixed points under probabilistic control. It is shown that generically, in two dimensions, every such fixed point can be approximated by a cycle and every cycle contains a fixed point. A normal form is established where it is shown that performance depends smoothly on the parameterized approximations. The paper concludes with an application to previously established optimal control of locomotive engines.
Semilocal Generic Formal Fibers
Susan Loepp, Associate Professor of Mathematics, Philippa Charters ’03
Journal of Algebra, 278, 370-382 (2004)
In this paper, we give necessary and sufficient conditions for a complete local ring to be the completion of an integral domain with a semilocal generic formal fiber.
A Round Ball Uniquely Minimizes Gravitational Potential Energy
Frank Morgan, Webster Atwell Class of 1921 Professor of Mathematics
Amer. Math. Soc., 133, 2733-2735 (2005)
We prove that among measurable bodies in R3 of mass m0 and density at most 1, a round ball of unit density uniquely minimizes gravitational potential energy.
Streams of Cylindrical Water
Frank Morgan, Webster Atwell Class of 1921 Professor of Mathematics
Math. Intelligencer, 26, 70-72 (2004)
Just as isotropic surface energy produces round water droplets and unstable undulating streams, crystalline energy produces cylindrical droplets and crystalline unduloids.
Cylindrical Surfaces of Delaunay
Frank Morgan, Webster Atwell Class of 1921 Professor of Mathematics
Rend. Circ. Mat. Palermo, 53, 469-477 (2004)
For the cylindrical norm on R3, for which the isoperimetric shape is a cylinder rather than a round ball, there are analogs of the classical Delaunay surfaces of revolution of constant mean curvature.
Planar Wulff Shape Is Unique Equilibrium
Frank Morgan, Webster Atwell Class of 1921 Professor of Mathematics
Proc. Amer. Math. Soc., 133, 809-813 (2005)
In R2, for any norm, an immersed closed rectifiable curve in equilibrium for fixed area must be the Wulff shape (possibly with multiplicity).
Planar Clusters and Perimeter Bounds
Frank Morgan, Webster Atwell Class of 1921 Professor of Mathematics, Aladar Heppes
Phil. Mag., 85, 1333-1345 (2005)
We provide upper and lower bounds on the least-perimeter way to enclose and separate n regions of equal area in the plane. Along the way, inside the hexagonal honeycomb, we provide minimizers for each n.
A Note on Cross-Profile Morphology for Glacial Valleys
Frank Morgan, Webster Atwell Class of 1921 Professor of Mathematics
Short Communications, Earth Surface Processes and Landforms, 30, 513-514 (2005)
We provide an improvement to the Hirano-Aniya catenary model for the cross-profile morphology of a glacial valley.
Proof of the Double Bubble Conjecture
Frank Morgan, Webster Atwell Class of 1921 Professor of Mathematics, Robert Hardt, Editor
Six Themes on Variation, Amer. Math. Soc., 59-77 (2004)
Reprint of a American Mathematical Monthly article on our 2002 proof of the Double Bubble Conjecture.
Fractals and Geometric Measure Theory: Friends and Foes
Frank Morgan, Webster Atwell Class of 1921 Professor of Mathematics, Michael L. Lapidus and
Michiel van Frankenhuijsen, Editors
Fractal Geometry and Applications: A Jubilee of Benoit Mandelbrot, Proc. Symp. Pure Mathematics, 72, 93-96 (2004)
Mandelbrot’s fractals, like good friends, inspire more general and realistic geometries. But later, like foes, they thwart efforts to prove that solutions to geometric problems are well behaved.
Kepler’s Conjecture and Hales’s Proof
Frank Morgan, Webster Atwell Class of 1921 Professor of Mathematics
Notices Amer. Math. Soc., 52, 44-47 (2005)
A review of G. Szpiro’s book on Kepler’s Conjecture and a discussion of Hales’s recent proof.
Quadratic Reciprocity via Theta Functions
Allison Pacelli, Assistant Professor of Mathematics, Ram Murty
Ramanujan Mathematical Society Lecture Notes Series, 1, 107-116 (2005)
In 1801, Gauss first discovered the Law of Quadratic Reciprocity, which he referred to as the Golden Theorem. Today, over 200 proofs are known, and use a variety of mathematical techniques. One such proof, outlined by Hecke, uses theta-functions, and has the advantage of natural generalizations in higher dimensional contexts. In this paper, we fill in and simplify the details of Hecke's proof.
Measurable Dynamics of Simple p-adic Polynomials
Cesar Silva, Professor of Mathematics
American Mathematical Monthly, 112, No. 3, 212-232 (2005)
Many simple polynomials defined on the p-adic numbers are minimal invertible isometries on balls or spheres of Qp. Minimal invertible isometries defined on compact open subsets of Qp are permutations on balls of Qp, and while they are uniquely ergodic, hence ergodic for Lebesgue measure, they are never totally ergodic. The transformations we consider are translations, multiplications, and monomial mappings. To study their measurable and topological dynamics we start with a review of the p-adic numbers, including their topology and the relevant measures on them, and then define the basic notions from dynamics that we require. We also present a short proof of the known fact that for invertible isometries on compact open subsets of the p-adics, the properties of minimality, ergodicity, and unique ergodicity are equivalent.
Nonnegatively and Positively Curved Invariant Metrics on Circle Bundles
Kristopher Tapp, Assistant Professor of Mathematics
Proc. Amer. Math. Soc., 133, 2449-2459 (2005)
We derive and study necessary and sufficient conditions for an S1-bundle to admit an invariant metric of positive or nonnegative sectional curvature. In case the total space has an invariant metric of nonnegative curvature and the base space is odd dimensional, we prove that the total space contains a flat totally geodesic immersed cylinder. We provide several examples, including a connection metric of nonnegative curvature on a trivial bundle that is not a product metric.

PHYSICS

Asymmetry in RNA Pseudoknots
Nathan O. Hodas ’04 and Daniel P. Aalberts
Nucleic Acids Res. 33, 2210 (2005)
RNA can fold into a topological structure called a pseudoknot, composed of non-nested double-stranded stems connected by single-stranded loops. Our examination of the PseudoBase database of pseudoknotted RNA structures reveals asymmetries in the stem and loop lengths and provocative composition differences between the loops. By taking into account differences between major and minor grooves of the RNA double helix, we explain much of the asymmetry with a simple polymer physics model and statistical mechanical theory, with only one adjustable parameter.
Efficient Computation of Optimal Oligo-RNA Binding
Nathan O. Hodas ’04 and Daniel P. Aalberts
Nucleic Acids Res. 32, 6636 (2004)
We present an algorithm that calculates the optimal binding conformation and free energy of two RNA molecules, one or both oligomeric. This algorithm has applications to modeling DNA microarrays, RNA splice-site recognitions, and other anti-sense problems. While other recent algorithms perform the same calculation in time proportional to the sum of the lengths cubed, O(N1+N2)3), our oligomer binding algorithm, called BINDIGO scales as the product of the sequence lengths, O(N1N2). The algorithm performs well in practice with the aid of a heuristic for large asymmetric loops. To demonstrate its speed and utility, we use BINDIGO to investigate the binding proclivities of U1 snRNA to mRNA donor splice sites.
Quantifying Optical Accuracy of Local Primary Sequence Bioinformatics Methods
Daniel P. Aalberts, Eric G. Daub ’04 and Jesse W. Dill ’04
Bioinformatics (2005) in press
Traditional bioinformatics methods scan primary sequences for local patterns. It is important to assess how accurate local primary sequence methods can be. We study the problem of donor pre-mRNA splice site recognition, where the sequence overlaps between real and decoy data sets can be quantified, exposing the intrinsic limitations of the performance of local primary sequence methods. We assess the accuracy of primary sequence methods generally by studying how they scale with dataset size and demonstrate that our new Primary Sequence Ranking methods have superior performance.
Measurement and Modeling of Hyperfine- and Rotation-induced State Mixing in Large Weakly Bound Sodium Dimers
Kevin Jones and others
Physical Review A, 71, 052703 (2005)
We present high-precision trap loss spectroscopy of excited Na2 molecules obtained by the photoassociation of ultracold sodium atoms. Near the 3 2S + 3 2P3/2 dissociation limit, hyperfine and rotational (Coriolis type) interactions cause significant mixing of states of different nominal Hund’s case (c) symmetry resulting in a complex pattern of spectral lines. We construct a theoretical model of the large, slowly-rotating molecule starting from a long-range, atomic viewpoint. Interaction potentials are derived from the known long-range resonant dipole and van der Waals forces between atoms, supplemented at short-range by the results of ab initio electronic structure calculations. Spin-dependent interactions coupling the various angular momenta – nuclear spin, electron spin, electron orbit and the mechanical rotation of the molecule as a whole – are derived from known atomic parameters. We avoid imposing approximate symmetries or coupling schemes and consequently include all non-adiabatic mixing of different degrees of freedom. Quantitative agreement between experiment and theory for both line positions and intensities is found. Specifically we observe and calculate mixing of levels of 0g-, 0u+ and 1 symmetry bound by <50 GHz below the 3 2S + 3 2P3/2 asymptote.
Warped Supersymmetric Unification with Non-Unified Superparticle Spectrum
David Tucker-Smith
Physical Review, D71 075004 (2005)
We present a new supersymmetric extension of the standard model. The model is constructed in warped space, with a unified bulk symmetry broken by boundary conditions on both the Planck and TeV branes. In the supersymmetric limit, the massless spectrum contains exotic colored particles along with the particle content of the minimal supersymmetric standard model (MSSM). Nevertheless, the model still reproduces the MSSM prediction for gauge coupling unification and does not suffer from a proton decay problem. The exotic states acquire masses from supersymmetry breaking, making the model completely viable, but there is still the possibility that these states will be detected at the LHC. The lightest of these states is most likely A_5^XY, the fifth component of the gauge field associated with the broken unified symmetry. Because supersymmetry is broken on the SU(5)-violating TeV brane, the gaugino masses generated at the TeV scale are completely independent of one another. We explore some of the unusual features that the superparticle spectrum might have as a consequence.
Matter Unification in Warped Supersymmetric SO(10)
Yasunori Nomura and David Tucker-Smith
Nucl. Phys., B698, 92-110 (2004)
We construct models of warped unification with a bulk SO(10) gauge symmetry and boundary conditions that preserve the SU(4)_C x SU(2)_L x SU(2)_R Pati-Salam gauge group (422). In the dual 4D description, these models are 422 gauge theories in which the apparent unification of gauge couplings in the minimal supersymmetric standard model is explained as a consequence of strong coupling in the ultraviolet. The weakness of the gauge couplings at low energies is ensured in this 4D picture by asymptotically non-free contributions from the conformal sector, which are universal due to an approximate SO(10) global symmetry. The 422 gauge symmetry is broken to the standard model group by a simple set of Higgs fields. An advantage of this setup relative to SU(5) models of warped unification is that matter is automatically required to fill out representations of 422, providing an elegant understanding of the quantum numbers of the standard-model quarks and leptons. The models also naturally incorporate the see-saw mechanism for neutrino masses and bottom-tau unification. Finally, they predict a rich spectrum of exotic particles near the TeV scale, including states with different quantum numbers than those that appear in SU(5) models.
Discrete Phase Space Based on Finite Fields
Kathleen S. Gibbons ’03, Matthew J. Hoffman ’04, and William K. Wootters
Physical Review A, 70, 062101 (2004)
The original Wigner function provides a way of representing in phase space the quantum states of systems with continuous degrees of freedom. Wigner functions have also been developed for discrete quantum systems, one popular version being defined on a 2N x 2N discrete phase space for a system with N orthogonal states. Here we investigate an alternative class of discrete Wigner functions, in which the field of real numbers that labels the axes of continuous phase space is replaced by a finite field having N elements. There exists such a field if and only if NB is a power of a prime; so our formulation can be applied directly only to systems for which the state-space dimension takes such a value. Though this condition may seem limiting, we note that any quantum computer based on qubits meets the condition and can thus be accommodated within our scheme. The geometry of our N x N phase space also leads naturally to a method of constructing a complete set of N+1 mutually unbiased bases for the state space.

PSYCHOLOGY

Storytelling, Narrative, and the Thematic Apperception Test
Phebe Cramer, Professor of Psychology
New York: Guilford Press (Paperback Edition 2004)
The Thematic Apperception Test (TAT) is a systematic approach to storytelling that offers insight into the unique psychological reality of each individual. This book integrates a variety of interpretive approaches to the TAT to illuminate the meaning of narratives and explore their clinical implications. Informed by psychodynamic theory and empirical research, the book addresses such topics as the ways narratives reveal different personality organizations; how stories change over the course of therapy; the influence of age, gender, and defense mechanisms on narratives; and the use of the TAT in clinical studies. A new preface to the paperback edition situates the book within the contemporary landscape of personality research.
Stress, Autonomic Nervous System Reactivity, and Defense Mechanisms
Phebe Cramer, Professor of Psychology
Defense Mechanisms: Theoretical, Research and Clinical Perspectives, Advances in Psychology, 136, 325-349,
U. Hentschel, G. Smith, J.G. Draguns, and W. Ehlers, editors, (2004)
Another “Lens” for Understanding Therapeutic Change:
The Interaction of IQ with Defense Mechanisms
Phebe Cramer, Professor of Psychology
Relatedness, Self-Definition and Mental Representation: Essays in Honor of Sidney J. Blatt, 120-133, J.S. Auerbach, K.N. Levy, and C.E. Schaffer, editors, New York: Routledge (2005)
What Children’s Stories Tell Us About Children’s Experience
Susan Engel, Senior Lecturer
Studies of Children’s Experience, D. Hogan, S. Greene, editors, London, England, Elsevier Press (2004)
The author argues that narratives provide a valuable window into children's experience. She describes methods by which researchers can elicit and analyze children's stories in order to learn about their every day lives.
Arousal and Stereotype Threat
T. Ben-Zeev, Steven Fein, Professor of Psychology, and M. Inzlicht
Journal of Experimental Social Psychology, 41, 174-181 (2005)
Seemingly insignificant features of the context can undermine the quantitative performance of skilled females—an effect attributed to stereotype threat. The present studies tested the hypotheses that stereotype threat triggers arousal, and that attributions about that arousal could moderate the effects of stereotype threat on performance. To examine whether arousal is triggered by stereotype threat, we conducted two experiments in which female participants were asked to take a math test under conditions of stereotype threat or not. In Study 1, women under stereotype threat performed better on an easy threat-irrelevant task, but worse on a difficult threat-irrelevant task than women not under threat. In Study 2, threatened women underperformed on a math test, but this underperformance was attenuated for women directed to misattribute their arousal. These results suggest that arousal—and how arousal is attributed—may play an important role in the debilitating effects of stereotype threat.
“Math Is Hard!” (Barbie™, 1994): Responses of Threat versus Challenge Mediated Arousal to Stereotypes Alleging Intellectual Inferiority
T. Ben-Zeev, C.M. Carrasquillo, A.M.L. Ching, T.J. Kliengklom, K.L. McDonald, D.C. Newhall, G.E. Patton, T.D. Stewart, T. Stoddard, M. Inzlicht, and Steven Fein, Professor of Psychology
Gender Differences in Mathematics, A. Gallagher, J.C. Kaufman, editors, Cambridge, MA: Cambridge University Press (2005)
The Role of Motivation in the Unconscious: How Our Motives Control the Activation of Our Thoughts and Shape Our Actions
S.J. Spencer, Steven Fein, Professor of Psychology, E.J. Strahan, and M.P. Zanna
Social Motivation: Conscious and Unconscious Processes, 113-129, J.P. Forgas, K.D. Williams, W. von Hippel, editors, NY: Psychology Press (2005)
Readings in Social Psychology: The Art and Science of Research (3rd edition)
Steven Fein and Saul M. Kassin, Professors of Psychology
Boston, MA: Houghton Mifflin (2005)
A reader containing 16 original articles, each with a brief introduction and questions to stimulate critical thinking about social psychology in practice. The articles represent some of the most creative and accessible research in the field, both classic and contemporary, that interests students.
Spin and (Pitch) Doctors: Campaign Strategies in Televised Political Debates
Michael I. Norton and George R. Goethals, Professor of Psychology
Political Behavior, 26, 227-247 (2004)
Political campaigns frequently set low expectations (using a “low pitch”) in televised political debates to make the later claim that their candidates have done better than expected. The limited credibility of campaign aides, coupled with the fact that perception often confirms expectations, makes this strategy psychologically problematic. In Study 1, when no post-debate information was provided, lowering expectations for a candidate led to lower ratings of performance. In Study 2, when positive feedback (a post-debate “spin”) was provided after a low pitch, participants did rate performance positively, but only when the spin was supplied by a credible media source. The same strategy when used by campaign strategists adversely impacted candidates, leading to lower ratings of debate performance and network coverage.
The Psychodynamics of Leadership: Freud’s Insights and Their Vicissitudes
George R. Goethals, Professor of Psychology
The Psychology of Leadership: New Perspectives and Research, 97-112, D.M. Messick, R. Kramer, editors, Hillsdale, NJ: Erlbaum (2005)
A discussion of Freud's theory of leadership and a consideration of ways that Freud anticipated issues that have been researched by later scholars. Freud deserves more credit for identifying crucial dimensions of leadership.
Nonverbal Behavior and Political Leadership
George R. Goethals, Professor of Psychology
Applications of Nonverbal Communication, 95-115, R.E. Riggio, R.S. Feldman, editors, Mahwah, NJ: Erlbaum (2005)
A discussion of the ways that nonverbal behavior affects our responses to leadership. We particularly explore how people from different ethnic groups respond to the nonverbal behavior of ingroup and outgroup leaders.
Presidential Leadership
George R. Goethals, Professor of Psychology
Annual Review of Psychology, 56, 545-570 (2005)
This chapter reviews psychological theories of leadership and selected literature on the American presidency to highlight key psychological principles of presidential leadership. Psychological theories, framed by the principles of leadership outlined by Freud (1921), include those of Burns (1978, 2003) on transformational leadership, Bass (1997) and House & Shamir (1993) on charismatic and transformational leadership, Gardner (1995) on stories of identity, Hogg (2001, 2003) on social identity, and Tyler & Lind (1992) on procedural justice. The discussion of presidential scholarship considers work by Barber (1992) on presidential character, Simonton (1986, 1987) on presidential personality and success, Skowronek (1997) on reconstructive politics, and winter (1987) on presidential motive profiles. These studies suggest that followers have high expectations for presidents and that successful presidential leadership depends on opportunity, high levels of activity, intelligence, optimistic resilience, and flexibility.
Research in Couple and Family Therapy: Methodological Challenges and Opportunities
Laurie Heatherington, Professor of Psychology, Myrna L. Friedlander and Leslie Greenberg
Journal of Family Psychology, 19, 18-27 (2005)
In our field, the study of therapeutic change processes lags behind the study of treatment efficacy. Nonetheless, in the past 10 years major strides have been made in delineating change process mechanisms in couple and family therapy. To focus the efforts of future change process researchers, the authors discuss 5 critical needs: (a) more well-articulated, midrange theory about systemic change processes; (b) more attention to client change processes; (c) more attention to covert intrapersonal processes (emotion, cognition, and clients’ experience of the alliance); (d) better articulation of strategies for analyzing data from multiple participants; and (e) more focus on the degree to which various change processes work similarly (or not) for diverse couples and families.
Couple Interaction during Problem Discussions: Toward an Integrative Methodology
Laurie Heatherington, Professor of Psychology, Valentín Escudero, and Myrna L. Friedlander
Journal of Family Communication, 5, 191-207 (2005)
This study demonstrates and illustrates an integrative, systemic methodology for studying couples’ interactions. We investigated the problem discussions of 58 engaged couples who participated in the Denver Family Development Study (e.g., Markman, Floyd, Stanley, & Storaassli, 1988). Sequential analyses were used to analyze the relational control behavior, covert affective impact, and verbal expressions of cognitive constructions. Results indicated a predominance of positive affect and relational complementarity and a lack of blaming constructions, which were consistent with participants’ status as engaged couples and their moderately high satisfaction levels. Relational control behavior and causal explanations for the conflicts under discussion were related to the partners’ affect. Interestingly, female partners’ “domineering” control moves were more likely to be met with male partners’ “submissive” moves in the more satisfied couples. Suggestions and caveats are discussed for using contingency methods in systemic research on marital and family interaction in both clinic and community samples.
The Psychology of Confession Evidence: A Review of the Literature and Issues
Saul Kassin, Professor of Psychology and G. Gudjonsson
Psychological Science in the Public Interest, 5, 35-69 (2004)
Recently, in a number of high-profile cases, defendants who were prosecuted, convicted, and sentenced on the basis of false confessions have been exonerated through DNA evidence. As a historical matter, confession has played a prominent role in religion, in psychotherapy, and in criminal law—where it is a prosecutor’s most potent weapon. In recent years, psychologists from the clinical, personality, developmental, cognitive, and social areas have brought their theories and research methods to bear on an analysis of confession evidence, how it is obtained, and what impact it has on judges, juries, and other people. Drawing on individual case studies, archival reports, correlational studies, and laboratory and field experiments, this monograph scrutinizes the following sequence of events during which confessions may be obtained from criminal suspects and used as evidence: the pre-interrogation interview, the Miranda warning and waiver, the modern police interrogation, the confession itself, and the consequences of confession evidence as evaluated by police and prosecutors, followed by judges and juries in court. Finally, we address the role of psychologists as expert witnesses and suggest a number of possible safeguards. In particular, we argue that there is a need to reform interrogation practices that increase the risk of false confessions and recommend a policy of mandatory videotaping of all interviews and interrogations.
On the Psychology of Confessions: Does Innocence Put Innocents at Risk?
Saul Kassin, Professor of Psychology
American Psychologist 60, 215-228 (2005)
The Central Park jogger case, and other recent exonerations, highlights the problem of wrongful convictions, 15 to 25 percent of which contained confessions in evidence. Recent research suggests that actual innocence does not protect people across a sequence of pivotal decision: (1) In pre-interrogation interviews, investigators commit false positive errors, presuming innocent suspects guilty; (2) naively believing in the transparency of their innocence, innocent suspects waive their rights; (3) despite or because of their denials, innocent suspects elicit highly confrontational interrogations; (4) certain commonly used techniques lead suspects to confess to crimes they did not commit; and (5) police and others cannot distinguish between uncorroborated true and false confessions. It appears that innocence puts innocents at risk, that consideration should be given to reforming current practices, and that a policy of videotaping interrogations is a necessary means of protection.
“I’d Know a False Confession If I Saw One”:
A Comparative Study of College Students and Police Investigators
Saul Kassin, Professor of Psychology and Rebecca Norwick ’00
Law and Human Behavior, 29, 211-227 (2005)
College students and police investigators watched or listened to ten prison inmates confessing to crimes. Half the confessions were true accounts; half were false—concocted for the study. Consistent with much recent research, students were generally more accurate than police, and accuracy rates were higher among those presented with audiotaped than videotaped confessions. In addition, investigators were significantly more confident in their judgments and also prone to judge confessors guilty. To determine if police accuracy would increase if this guilty response bias were neutralized, participants in a second experiment were specifically informed that half the confessions were true and half were false. This manipulation eliminated the investigator response bias, but it did not increase accuracy or lower confidence. These findings are discussed for what they imply about the post-interrogation risks to innocent suspects who confess.
Investigating True and False Confessions within a Novel Experimental Paradigm
M. B. Russano, C. A. Meissner, F. M. Narchet, and Saul M. Kassin, Professor of Psychology
Psychological Science, 16, 481-486 (2005)
The primary goal of the current study was to develop a novel experimental paradigm with which to study the influence of psychologically-based interrogation techniques on the likelihood of true and false confessions. The paradigm involves guilty and innocent participants being accused of intentionally breaking an experimental rule, or “cheating.” In the first demonstration of this paradigm we explored the influence of two common police interrogation tactics: minimization and an explicit offer of leniency, or a “deal.” Results indicated that guilty persons were more likely to confess than innocent persons, and that the use of minimization and the offer of a deal increased the rate of both true and false confessions. Taken together, police investigators are encouraged to avoid interrogation techniques that imply or directly promise leniency, as they appear to reduce the diagnostic value of any confession that is elicited.
Readings from the American Psychological Society: Current Directions in Psychology
Saul Kassin, Professor of Psychology and Kathleen H. Briggs
Upper Saddle River, NJ: Prentice Hall (2005)
The American Psychological Society has published a series of readers using articles from leading researchers that appeared in the APS journal Current Directions in Psychological Science. This reader is divided into sections on psychology as scientific process of discovery, the biological aspects of human nature, the cognitive processes that occur ‘inside the head,’ motivations and emotions, human development across the life span, social and cultural influences on human behavior, and psychological disorders such as depression, anxiety, and schizophrenia.
Social Psychology 6/e
Sharon Brehm, Saul Kassin, Professor of Psychology and Steven Fein, Professor of Psychology
Boston, MA: Houghton Mifflin (2005)
This text introduces key concepts through balanced coverage of classic studies, contemporary research, and current social issues. The authors bring vivid examples to reflect social psychology concepts in real life. The use of current events, social issues, and evocative photographs makes the text more compelling to students by helping them relate concepts to their own lives and to see the world through the eyes of a social psychologist.
Psychology in Modules
Saul Kassin, Professor of Psychology
Upper Saddle River, NJ: Prentice Hall (2006)
Psychology in Modules challenges students to discover, experience, and debate the methods and findings of psychological research, and actively learn how to think like psychologists. With 50 short, specific, free-standing modules-each of which can be covered in a single class and read in a single sitting-this text engages students and allows them to have a better grasp of the topics at hand.
Impatience and Grades: Delay-Discount Rates Correlate Negatively with College GPA
Kris N. Kirby, Professor of Psychology, Gordon Winston, Professor of Economics, and M. Santiesteban, ’97
Learning and Individual Differences, 15, 213-222 (2005)
Because the rewards of academic performance in college are often delayed, the delay-discounting model of impulsiveness (Ainslie, 1975) predicts that academic performance should tend to decrease as people place less weight on future outcomes. To test this hypothesis, we estimated (hyperbolic) discount rates for real delayed monetary rewards ($10 to $20) using second-price auction procedures with 247 undergraduates at two liberal arts colleges. College GPA was reliably correlated with discount rates, r = –.19 (p = .003), and remained reliable after partialling out SAT scores. The results add to the external validity of the discounting model of impulsiveness, and point to a possible contributor to academic performance of interest in the study of higher education.
Heroin and Cocaine Abusers Have Higher Discount Rates for Delayed Rewards
than Alcoholics or Non-Drug-Using Controls
Kris N. Kirby, Professor of Psychology, and N. M. Petry
Addiction, 99, 461-471 (2004)
Aims: To test a prediction of the discounting model of impulsiveness that discount rates would be positively associated with addiction. The delay-discount rate refers to the rate of reduction in the present value of a future reward as the delay to that reward increases. Design and measurements: We estimated participants’ discount rates on the basis of their pattern of choices between smaller immediate rewards ($11–80) and larger, delayed rewards ($25–85; at delays from 1 week to 6 months) in a questionnaire format. Participants had a one-in-six chance of winning a reward that they chose on one randomly selected trial. Participants and setting: Heroin (n = 27), cocaine (n = 41) and alcohol (n = 33) abusers and non-drug-using controls (n = 44) were recruited from advertisements. They were tested in a drug abuse research clinic at a medical school. Findings: On average, the cocaine and heroin groups had higher rates than controls (both P < 0.001), but alcoholics did not (P = 0.44). Abstinence was associated with lower rates for heroin abusers (P = 0.03), but not for cocaine or alcohol abusers (both P > 0.50). Conclusions: These data suggest that discount rates vary with the preferred drug of abuse, and that high discount rates should be considered in the development of substance abuse prevention and treatment efforts.
Sex Differences in the Long-Term Effect of Preweanling Isolation Stress on Memory Retention
Noah J. Sandstrom, Assistant Professor of Psychology
Hormones and Behavior, 47, 556-562 (2005)
Social experiences during development can powerfully modulate later neuroendocrine and behavioral system. In the present study, male and female rat pups experienced daily bouts of social isolation for six hrs per day or control conditions during the third postnatal week. Performance on a 12-arm radial maze with 8 arms consistently baited with food reward was examined in adulthood. During the social isolation, both male and female pups exhibited a significant increase in plasma corticosterone levels. When tested on the radial arm maze as adults, the performance of female rats that had experienced social isolation during development was not affected; however, male rats in the isolation condition initially exhibited impairments in working memory but not reference memory. Despite achieving comparable asymptotic levels of performance on the maze, male rats that experienced social isolation during the third week demonstrated a disruption in working memory retention when radial arm maze trials were interrupted after the fourth arm choice. Thus, while male rats that experience social isolation during the third week of life eventually perform comparably to controls on the standard radial arm maze task, their ability to retain information over a delay remains impaired. These findings highlight an important sex difference in the long-term effects of stress during this period of late preweanling development.
The Role of Symmetry in the Recognition of Faces at Novel Orientations
T. A. Busey and Safa R. Zaki, Assistant Professor of Psychology
Memory and Cognition, 32, 916-931 (2004)
In three experiments, we examine the recognition of faces at novel orientations. While performance tends to decay as difference between the study and test angles increases, an orientation that is symmetric with respect to the study orientation shows strong performance, in many cases better than the frontal view. We investigate the properties of this particular facility in perception and memory tasks. Symmetrized faces show surprisingly different patterns of behavior than unsymmetrized faces, despite the fact that many faces are already fairly symmetric. In memory experiments, subjects show robust symmetric orientation effects, and can differentiate between the original study views and the symmetric orientation. In a third experiment, we demonstrate that smooth motion improves performance at the symmetric orientation, while two control motions do not. Together the three experiments support the view that multiple representations are at work during the recognition of faces at the symmetric orientation, and that during memory tasks subjects tend to rely on representations that are more robust against texture asymmetries and that may include limited depth information.
Is Categorization Really Intact in Amnesia? A Meta-Analysis
Safa R. Zaki, Assistant Professor of Psychology
Psychonomic Bulletin and Review, 11, 1048-1054 (2004)
Most published studies of category learning in amnesia report intact categorization performance. These results have been used to challenge single-system accounts of categorization and recognition in which a single representational system mediates performance in these two tasks. Many of the published studies, however, show a numerical advantage for controls over amnesics and often have low statistical power. A meta-analysis was conducted to assess whether this numerical advantage is significant when the data are pooled across studies. This analysis indicates that amnesic subjects do in fact show deficits in categorization tasks, which is consistent with single-system exemplar model predictions.
False-Prototype Enhancement Effects in Dot-Pattern Categorization
Safa R. Zaki, Assistant Professor of Psychology and R. M. Nosofsky
Memory and Cognition, 32, 390-398 (2004)
Results from the classic dot-pattern distortion paradigm have sometimes yielded prototype enhancement effects that could not be accounted for by exemplar models of categorization. However, in these experiments, the status of the prototype was confounded with certain stimulus-specific properties, as well as with the frequency of presentation of the prototype during testing. In two mock-subliminal experiments, participants made categorization judgments to patterns that were generated as prototypes, low-level distortions, or high-level distortions. Participants rated the prototypes as being more likely to be members of a category, although no patterns were presented during training, and there was no objective category structure. In two other experiments, greater prototype enhancement effects were observed when the prototype and low-level distortions were presented with greater frequency during transfer. These results suggest that classic prototype enhancement effects may not be due to the abstraction of a prototype at time of original learning, but rather to other factors not formalized in extant models.
Sexually Dimorphic Effects of Postnatal Allopregnanolone on the Development of Anxiety Behavior after Early Deprivation
Betty Zimmerberg, Professor of Psychology and Elizabeth W. Kajunski ’98
Pharmacology, Biochemistry and Behavior, 78, 465-471 (2004)
Stress early in life exerts persistent detrimental effects on brain development. In this experiment, a rodent model of child neglect, early deprivation (ED), was used to investigate the role of the neurosteroid allopregnanolone [AlloP; 3α-hydroxy-5α-pregnan-20-one (3α,5α-THP)] in the development of anxiety behavior. Subjects were either undisturbed controls or ED: separated individually for 6 h per day from postnatal day (PN) 2 to 6. Control and ED subjects were also either noninjected, vehicle-injected or injected with 5 mg/kg AlloP prior to the isolation. At PN 7, responses to 2.5 or 5 μg icv injections of AlloP were determined for separation-induced ultrasonic vocalizations (USVs). Tolerance to the USV-reducing effect of daily AlloP was seen in control but not ED pups, and daily AlloP reversed the expected ED suppression of USVs. As adults, controls treated with postnatal AlloP were less anxious than all other groups on the elevated plus maze. ED counteracted this effect. Male controls showed a reversal of the typical sex difference. There were no effects on open-field activity. These results suggest that the neonatal brain is responsive to alterations in AlloP levels, and that neuroactive progesterone metabolites may play a role in mediating the development of stress-related sex differences.
Differences in Affective Behaviors and Hippocampal Allopregnanolone Levels
in Adult Rats of Lines Selectively Bred for Infantile Vocalizations
Betty Zimmerberg, Professor of Psychology, Susan A. Brunelli, Alyssa J. Fluty ’05, and Cheryl E. Frye
Behavioural Brain Research, 159, 301-311 (2005)
Allopregnanolone, 3α-hydroxy-5α-pregnan-20-one (3α,5α-THP), a progesterone metabolite, is an endogenous neurosteroid mediating affective behaviors via its positive modulation of GABAA receptors. In order to better understand the role of this neurosteroid in individual differences in affective behavior, we used an animal model based on selective breeding for an infantile affective trait, ultrasonic vocalizations (USV). Adult male and female (in either proestrus or diestrus) rats that had been bred for low (low line) or high (high line) rates of USV after maternal separation were tested in a series of affective behavioral tests: open field, emergence, social interaction, defensive freezing, and the Porsolt forced swim task. Concentrations of allopregnanolone in combined hippocampus and amygdala tissue were then measured. Low line subjects showed significantly lower anxiety and depression responses in the emergence, open field, and Porsolt forced swim tasks than did high line subjects. Proestrus females exhibited less affective behaviors than diestrus females or males. Allopregnanolone levels in hippocampus/amygdala were significantly higher in low line subjects compared to high line subjects, and in proestrus females compared to diestrus females and males. These data indicate that: (1) affective behaviors in lines selectively bred for an infantile anxiety trait exhibit selection persistence into adulthood; and (2) levels of allopregnanolone in the limbic system parallel selected disparities in affective behavior, suggesting a selection for alterations in the neurosteroid/GABAA receptor system in these lines.