FACULTY PUBLICATIONS

ASTRONOMY

History of the Cosmological Constant
M. Demianski

Ann. Phys. (Leipzig), 9, 3-5, 278-287, (2000)

General review of history of the cosmological constant problem is presented. Some theoretical ideas suggesting that Λ = 0 are mentioned and recent observational results are discussed.

Abundances of Sulfur, Chlorine, and Argon in Planetary Nebulae. I: Observations and Abundances in a Northern Sample
Kwitter, K.B., and Henry, R.B.C.

Astrophysical Journal, Vol. 562, p. 804, (2001)

This paper is the first of a series specifically studying the abundances of sulfur, chlorine, and argon in type II planetary nebulae (PNe) in the Galactic disk. Ratios of S/O, C1/O, and Ar/O constitute important tests of differential nucleosynthesis of these elements and serve as strict constraints on massive star yield predictions. We present new ground-based optical spectra extending from 3600-9600 Å for a sample of 19 northern type II PNe. This range includes the strong near-infrared lines of [S II] at 9069 Å and 9532 Å, which allows us to test extensively their effectiveness as sulfur abundances indicators. We also introduce a new model-tests ionization corrections factor for sulfur. For the present sample, we find average values of S/O=1.2±0.71 x 10^-2, C1/O=3.3±1.6 x 10^-4, and Ar/O=5.0±1.9 x 10^-3.

Abundances of Sulfur, Chlorine, and Argon in Planetary Nebulae. IIA: Observations of a Southern Sample
Milingo, J.B., Kwitter, K.B., Henry, R.B.C., and Cohen, R.A.*

*(KNAC Summer Fellow, Wesleyan ‘03)

Astrophysical Journal Supplement, Vol. 138, p. 279, (2002)

In this paper we present fully reduced and dereddened emission-line strengths for a sample of 45 southern type II planetary nebulae (PNe). The spectrophotometry for these PNe covers an extended optical-near-infrared ranged from 3600-9600 Å. This PN study and subsequent analysis (presented in a companion paper), together with a similar treatment for a northern PN sample, is aimed at addressing the lack of homogeneous, consistently observed, reduced, and analyzed data sets that include the near-infrared [S III] lines at 9069 Å and 9532 Å. The use of type II objects only is intended to select disk nebulae that are uncontaminated by nucleosynthesis products of the progenitor star. Extending spectra redward to include the strong [S III] lines enables us to look for consistency between S⁺² abundances inferred from these lines and from the more accessible, albeit weaker, [S II] line at 6312 Å.

Abundances of Sulfur, Chlorine, and Argon in Planetary Nebulae. IIB: Abundances in a Southern Sample
Milingo, J.B., Henry, R.B.C., and Kwitter, K.B.

Astrophysical Journal Supplement, Vol. 138, p. 285, (2002)

We have undertaken a large spectroscopic survey of over 80 planetary nebulae (PNe) with the goal of providing a homogeneous spectroscopic database between 3600 and 9600 Å, as well as a set of consistently determined abundances, especially for oxygen, sulfur, chlorine, and argon. In the current paper we calculate and report the S/O, C1/O, and Ar/O abundance ratios for 45 southern PNe (predominantly type II), using our own recently observed line strengths published in a companion paper. One of the salient features of our work is the use of the near-infrared lines of [S III] at 9069 Å and 9532 Å coupled with the [S III] temperature, to determine the S⁺² ionic abundance. We find the following average abundances for these objects: S/O=0.011±0.0064, C1/O=0.00031±0.00012, and Ar/O=0.0051±0.0020.

Moon Struck: Artists Rediscover Nature and Observe
Olson, R.J.M., and Jay M. Pasachoff

Earth, Moon and Planets, 85/86, 303-341, 2001

Deuterium Near and Far in the Milky Way
Lubowich, D.A., Jay M. Pasachoff, and J. Ostenson

Cosmic Evolution, E. Vangioni-Flam, R. Ferlet, and M. Lemoine, eds., World Scientific, pp. 63-64 (2001)

Menzel and Eclipses
Pasachoff, Jay M.

Journal for the History of Astronomy, 33(2), No. 111, 139-156, 2002

Short-Period Waves That Heat the Corona Detected at the 1999 Eclipse
Jay M. Pasachoff, B.A. Babcock, K.D. Russell and D.B. Seaton

Solar Physics, 207, 241–257, 2002

What Should College Students Learn? Phases and Seasons? Is Less More or Is Less Less?
Pasachoff, Jay M.

Astronomy Education Review, 1, 2002

What Should Students Learn?
Pasachoff’s Points, letter
Pasachoff, Jay M.

The Physics Teacher, 39, September 18-19 (2001)

The Physics Teacher, 40, April 196-198 (2002)

Gloria on the Subway
Pasachoff, Jay M., and Eloise Pasachoff

American Journal of Physics, September (2001)

Public Education in Developing Countries on the Occasions of Eclipses
Pasachoff, Jay M.

Astronomical Society of the Pacific, Alan H. Batten, ed. pp. 101-106, ISBN 1-58381-067-6; additional comments on pp. 139-140, 338-339 (2001)

Eclipse/SOHO Joint Observations of Solar Eclipses
Jay M. Pasachoff, Kevin Russell, Daniel B. Seaton, Bryce A. Babcock, and Stephan Martin

American Geophysical Union, Boston; AGU Abstract #SH-41B-25, p. 91, (2001)

Donald H. Menzel: Scientist, Educator, Builder
Jay M. Pasachoff, O. Gingerich, D. Layzer, R.W. Noyes, W.H. Parkinson, and B. Welther

American Geophysical Union, Boston, AGU Abstract #SH-41B-26, p. 91 (2001)

TRACE Observations of the 15 November 1999 Transit of Mercury
Schneider, G., Jay M. Pasachoff, and L. Golub

Bull. Am. Astron. Soc., 33, #3, 1037 (2001)

Coronal Heating, Mapping, and Polarization: The Williams College Expedition
Pasachoff, Jay M.

Observations et Travaux, Karine Bocchialini and Serge Koutchmy, eds., Vol. 53, pp. 42-44 (2002)

The Working Group on Eclipses of the IAU
Pasachoff, Jay M.

Observations et Travaux, Karine Bocchialini and Serge Koutchmy, eds., Vol. 53, pp. 56, (2002)

Galileo
Pasachoff, Jay M.

Space Sciences (Planetary Science and Astronomy), Macmillan Reference USA (2002)

Spectra
Pasachoff, Jay M.

World Book (2001)

BIOLOGY

Infant Deaths in Developing Countries
Banta, L, Visiting Associate Professor of Biology, J. Beetham, D.Draper, N. Hartwig, M. Klein and G. Marquis

In Life Science Ethics (G. Comstock, ed.) Iowa State Press

FQR1, A Novel Primary Auxin-Response Gene, Encodes a Flavin Mononucleotide-Binding Quinone Reductase
Marta Laskowski, Assistant Professor of Biology

Plant Physiol. 128(2), 578-590 (2002)

Ant-Dependent Oviposition in the Membracid Publilia concava
M.A. Morales, Assistant Professor of Biology

Ecological Entomol. 27, 247-250 (2002)

Variation in Timing and Abundance of Flowering by Delphinium barbeyi Huth (Ranumcuaceae): The Roles of Snow pack, Frost, and La Νiña, in the context of Climate Change
Inouye, D.W., M.A. Morales, Assistant Professor of Biology, and G.J. Dodge

Oecologia 130, 543-550 (2002)

Delphinium barbeyi is a common herbaceous wildflower in montane meadows at 2,900 m near the Rocky Mountain Biological Laboratory, and its flowers are important nectar resources for bumblebees and hummingbirds. During the period 1977-1999 flowering was highly variable in both timing (date of first flower ranged from 5 July to 6 August, mean=17 July) and abundance (maximum open flowers per 2x2-m plot ranged from 11.3 to 197.9, mean=82). Time and abundance of flowering are highly correlated with the previous winter's snow pack, as measured by the amount of snow remaining on the ground on 15 May (range 0-185 cm, mean=67.1). We used structural equation modeling to investigate relationships among snow pack, first date of bare ground, first date of flowering, number of inflorescences produced, and peak number of flowers, all of which are significantly correlated with each other. Snow pack depth on 15 May is a significant predictor of the first date of bare ground (R²=0.872), which in turn is a significant predictor of the first date of flowering (R²=0.858); snow pack depth is also significantly correlated with number of inflorescences produced (R²=0.713). Both the number of inflorescences and mean date of first flowering are significant predictors of flowers produced (but with no residual effect of snow pack). Part of the effect of snow pack on flowering may be mediated through an increased probability of frost damage in years with lower snow pack – the frequency of early-season “frost events” explained a significant proportion of the variance in the number of flowers per stem. There is significant reduction of flower production in La Niña episodes. The variation in number of flowers we have observed is likely to affect the pollination, mating system, and demography of the species. Through its effect on snow pack, frost events, and their interaction, climate change may influence all of these variables.

Incidental Nest Predation in Songbirds: Using Behavioral Indicators to Determine Ecological Processes and Scales
K.A. Schmidt, Visiting Assistant Professor of Biology, J.R. Goheen, and R. Naumann

Ecology 82, 2937-2947 (2001)

We examined the effects of separate removal experiments of two generalist consumers, the white-footed mouse (Peromyscus leucopus), and the eastern chipmunk (Tamias striatus), on nest predation rates of forest songbirds. Mice are numerically dominant at our study sites and were shown to be strong predators in other predator-prey interactions, such as those involving gypsy moths. Therefore, we hypothesized that removal of mice would result in decreased levels of nest predation relative to control treatments with a complete predator assemblage, but that the removal of chipmunks would not result in decreased nest predation. Both hypotheses were supported. Mice depredated > 60% of artificial nests in control plots (mouse populations intact), whereas chipmunks depredated ~ 20%. Daily nest mortality rates were more than halved in mouse removal treatments relative to controls, but were virtually identical between chipmunk removal and control treatments. Nonetheless, when we examined predation rates across plots in which the density of mice varied naturally, total daily mortality rates declined as the density of mice increased. This pattern occurred because mortality from non-mouse predators decreased as the density of mice increased and overwhelmed increasing mortality from mice to drive the overall dynamics of the system. Analysis of the relationships between the density of mice and predation rates by mice as a function of the abundance of natural food in their environment revealed probable reasons for these conflicting results. We suggest that high local densities of mice deplete resources for larger, non-mouse predators, which preferentially occupy areas of few mice and high local food abundance. In these areas, songbirds may be faced with higher overall nest predation dominated by non-mouse predators. Mice thus influence nest predation rates through both direct and indirect pathways.

Experimental Removals of Strong and Weak Predators: Mice and Chipmunks Preying on Songbird nests
K.A. Schmidt, Visiting Assistant Professor of Biology, J. Goheen, R. Naumann, R.S. Ostfeld, E.M. Schauber, and A. Berkowitz

Ecology 82, 2927-2936 (2001)

Incidental predation occurs when secondary prey items are encountered and subsequently consumed not through directed search for such prey but through their consequential encounter by a predator engaged in search for primary prey. We developed a mathematical model that examines the relationships between the abundance of primary prey, patch exploitation (i.e., quitting harvest rates), and the rate of incidental predation on secondary prey items. The model's predictions are dependent upon the spatial scale over which a forager integrates foraging costs and thus determines its quitting harvest rate (QHR). At local (i.e., foraging) spatial scales, we predicted incidental predation should increase with local food abundance. Also at the foraging scale, local food abundance should not influence QHRs, but local predation risk (from higher trophic levels) should increase QHRs. Therefore, we predicted incidental predation rates should be negatively correlated with QHRs. Greater food abundance or predation risk experience over large (i.e., landscape) spatial scales increases QHRs, and we predicted predation rates should vary inversely with QHR through two complementary mechanisms: foragers use a greater proportion of space and spend more time foraging as quitting harvest rates decrease.

We experimentally tested the qualitative predictions of the theory in the field using artificial veery (Catharus fuscescens) nests depredated by white-footed mice, Peromyscus leucopus, across three spatial scales. We used the technique of giving-up densities to measure QHRs and determine the scale at which mice integrate different foraging costs. In accord with our predictions, at the foraging scale nest predation was positively influenced by the local abundance of food. Also at the foraging scale, local predation risk to mice and perhaps interference competition from chipmunks resulted in higher giving-up densities and lower nest predation. At the landscape scale, there was an inverse relationship between giving-up densities and nest predation, which was likely the result of large scale differences in resource abundance between plots. Our study demonstrates how linking theoretical development to the use of empirical behavioral indicators can help determine the relevant ecological scales and processes necessary for understanding predator-prey interactions.

Site Fidelity in Habitats with Contrasting levels of Next Predation and Brood Parasitism
K.A. Schmidt, Visiting Assistant Professor of Biology

Evol. Ecol. Res. 3, 633-648

The phenomenon of site fidelity (i.e., remaining faithful to sites where an individual has bred successfully in the past) has been documented for many taxa, especially birds. These studies suggest that individuals may use a simple rule of thumb: stay (or return) if breeding was successful, or switch to a new site if breeding was unsuccessful (win-stay:lose-switch; WSLS). Using simulations, I examined the evolutionary dynamics of the WSLS strategy in competition with two alternative strategies: stay-always (SA; total site fidelity) and two forms of an ideal free settling strategy (IFS; site indifferent). I considered two habitats identical in all respects except that one habitat (low quality) had a higher level of nest predation than the other. Between breeding seasons, females either: (1) remained in a habitat if they successfully bred or otherwise dispersed to the alternative habitat (WSLS); (2) remained in the habitat regardless of their breeding success (SA); or (3) settled within habitats such that the quality of the highest ranking unoccupied territory was equalized, when possible, across habitats (IFS). The WSLS strategy invades and replaces either of the alternative strategies. I then examined the consequences of the WSLS strategy on population density and mean fecundity across two habitats that had contrasting levels of nest predation or brood parasitism. Unlike contrasting predation rates between habitats, higher levels of brood parasitism in the low quality habitat rapidly drain away individuals from the better habitat. This result, however, depended both qualitatively and quantitatively on differences (or the lack thereof) in predation between the two habitats. A second invasibility analysis conducted on populations experiencing contrasting brood parasitism between habitats indicated that the WSLS resists invasion by the SA strategy but not the IFS strategy. IFS resists invasions by either alternative. Thus cowbird brood parasitism may rapidly drain individuals away from high quality habitat because birds cannot discriminate between low and high quality habitats. Parasitism furthermore alters the evolutionary dynamics of competing site fidelity strategies.

Altered Leptin Signaling Is Sufficient, but not Required, for the Hypotension Associated with Caloric Restriction
SJ Swoap, Assistant Professor of Biology

Amer. J. Physiol. 281(6), H2473-H2479 (2001)

Inhibition of Leptin Signaling Pathways Reduces Hypotensive Response to Caloric Restriction
Jennifer L. Barone ’03, Jason I. Pack ’02, Graham B. Garber ’97, Steven J. Swoap, Assistant Professor of Biology

FASEB Journal, 16(5), A485 (2001)

Remodeling of Gene Expression in the Reloaded Soleus Muscle
Graham B. Garber ’97, Heather S. Thompson, Steven T. Rettke ’02, Brigitte D. Teissedre ’03, David S. Lewis ’03, Stylianos P. Scordilis, Steven J. Swoap, Assistant Professor of Biology

FASEB Journal, 16(5), A760 (2002)

Effect of Torpor on Ucp Expression in Mouse Tissues
Steven J. Swoap, Assistant Professor of Biology, Natalie A. Stephens ’03, Graham B. Garber ’97, Joyce Sun, James Stoppani, P. Darrell Neufer

FASEB Journal, 16(5) A42 (2002)

Diaphragm Contractile Dysfunction in MyoD Gene Inactivated Mice
JL Staib, SK Powers, SJ Swoap, Assistant Professor of Biology, MA Rudnicki

FASEB Journal, 16(5) A767 (2002)

Choreography of Song, Dance, and Beak Movements in the Zebra Finch (Taeniopygia guttata)
Heather Williams, Professor of Biology

J. Exp. Biol. 204 3497-3506 (2001)

As do many songbirds, zebra finches sing their learned songs while performing a courtship display that includes movements of the body, head and beak. The coordination of these display components was assessed by analyzing video recordings of courting males. All birds changed beak aperture frequently within a single song, and each individual’s pattern of beak movements was consistent from song to song. Birds that copied their fathers’ songs reproduced many of the changes in beak aperture associated with particular syllables. The acoustic consequences of opening the beak were increases in amplitude and peak frequency, but not in fundamental frequency. The change in peak frequency is consistent with the hypothesis that an open beak results in a shortened vocal tract and so a higher resonance frequency. Dance movements (hops and changes in body or head position) were less frequent, and the distribution of dance movements within the song was not as strongly patterned as for changes in beak aperture, nor were the peaks in the distribution as strongly marked. However, the correlation between the positioning of dance movements within fathers’ and sons’ songs was striking, suggesting that the choreography of dance patterns is transmitted from tutor to pupil along with the song.

http://jeb.biologists.org/cgi/reprint/204/20/3497.pdf (for pdf of paper)

http://jeb.biologists.org/cgi/content/full/204/20/3497/DC1 (for associated video clip)

CHEMISTRY

ESR Analysis at Treugol’naya Cave, Russia: Dating Lower Paleolithic Occupations in the Northern Caucasus
Bonnie A. B. Blackwell, Research Scientist, Natalie L. Rosenwasser, Sergey V. Mass, Joel I. B. Blickstein, Anne R. Skinner, Senior Lecturer of Chemistry

Proceedings of the 32^nd International Archaeometry Symposium (2001)

At 1510 m elevation, Treugol’naya Cave is the highest cave showing evidence for human usage in the Northern Caucasus, Russia. It also contains the oldest archaeological deposits in Europe east of the Carpathian Mountains, which include numerous tools made from various raw materials assigned to three different Lower Paleolithic flake tool industries and a pebble tool industry. These occur with abundant faunal remains, including several extinct Middle Pleistocene species.

Electron spin resonance (ESR) can date tooth enamel from 10 ka to 5 Ma in age. Five cervid teeth associated with the Lower Paleolithic archaeological layers have been dated using standard and isochron ESR analysis. Using a volumetrically averaged external dose rate measured for the sediment, and assuming linear uptake (LU), two teeth from Layer 4β gave a preliminary age of 338 ± 17 ka, while two teeth from Layer 4B yielded an age of 381 ± 16 ka, which agrees with the isochron age for one of those teeth. Using a time-averaged external dose rate derived from the isochron analysis, six independent analyses for a tooth from layer 5b averaged 406 ± 16 ka, assuming LU. The two isochron analyses indicate that neither tooth experienced any significant U leaching or secondary uptake, and that LU provides a reasonable model for the uptake. Therefore ESR, paleomagnetic, palynological and paleontological analyses all suggest that Layer 5b correlates best with the Oxygen Isotope Stage (OIS) 11, while Layer 4B correlates with late OIS 11 or early OIS 10, and Layer 4β probably with OIS 9. ESR dating using tooth enamel can yield valuable data for Treugol’naya Cave, but more dates and sedimentary analyses are necessary to test the ages for other units in the deposits and to check for reworked teeth in all units.

Illustrating Chemical Concepts with Coin Flipping
Raymond Chang, Professor of Chemistry, and John W. Thoman, Jr., Professor of Chemistry

The Chemical Educator, 6, 360-361 (2001)

Three classroom demonstrations, which involve the participation of students flipping coins, are described. The half-life of a first-order chemical reaction is illustrated by standing students sitting down when they flip a “tails.” Dynamic chemical equilibrium is illustrated by students standing or sitting depending on the outcome of coin-flips. In a third demonstration, the motion of gas molecules from one bulb to another is governed by the flip of a coin, showing the improbability of all the molecules gathering in just one bulb.

The Bacillus subtilis Competence Transcription Factor, ComK, Overrides LexA-imposed Transcriptional Inhibition without Physically Displacing LexA
Leendert W. Hamoen, Bertjan Haijema, Jetta J. Bijlsma, Gerard
Venema, and Charles M. Lovett, Professor of Chemistry

J. Biol. Chem., 276(46), 42901-42907 (2001)

During the development of competence in Bacillus subtilis the recA gene is activated by the competence transcription factor, ComK, which is presumably required to alleviate the transcriptional repression of recA by LexA. To investigate the mechanism by which ComK activates recA transcription we examined the binding of ComK and LexA to the recA promoter in vitro. Using hydroxyl radical protection analyses to establish the location of ComK dimer-binding sites within the recA promoter, we identified four AT-boxes in a configuration unique for ComK-regulated promoters. Gel mobility shift experiments showed that all four ComK dimer-binding sites were occupied at ComK concentrations in the physiological range. In addition, occupation of all ComK-binding sites did not prevent LexA from binding to the recA promoter, despite the fact that the ComK and LexA recognition motifs partially overlap. Although ComK did not replace LexA from the recA promoter, in vitro transcription analyses indicated that the presence of ComK is sufficient to alleviate LexA repression of recA.

Transformation and Recombination
Dubnau, D. and Lovett, C.M.

In Bacillus subtilis and Its Relatives: From Genes to Cells, Sonenshein, Losick, and Hoch (eds.)

ASM Press, Washington, D.C., 2002.

Translocation within the Acceptor Helix of a Major tRNA Identity Determinant
Martha A. Lovato, Joseph W. Chihade, Assistant Professor of Chemistry, and Paul Schimmel

EMBO Journal, 20, 4846-4853 (2001)

The genetic code is defined by the specific aminoacylations of tRNAs by aminoacyl-tRNA synthetases. Specificity is achieved through recognition of tRNA identity elements by the synthetases. Although the synthetases are widely conserved through evolution, aminoacylation of a given tRNA is often system-specific, that is, a synthetase from one source will not acylate its cognate tRNA from another. This system specificity is commonly due to variations in the sequence of a critical tRNA identity element that is compensated by a sequence change in the synthetase contact residue(s). In bacteria and the cytoplasm of eukaryotes throughout evolution, an acceptor stem G3:U70 base pair marks a tRNA for aminoacylation with alanine. In contrast, D. melanogaster (Dm) mitochondrial (mt) tRNA^Alahas a G2:U71 base pair but not a G3:U70 pair. Here we show that this translocated G:U and the adjacent G3:C70 are major determinants for recognition by Dm mt alanyl-tRNA synthetase. In addition, G:U at the 3:70 position serves as an antideterminant for Dm mt AlaRS. As a consequence, the mitochondrial enzyme cannot charge a substrate with the major identity element from cytoplasmic tRNA^Ala. Most or all insect mitochondrial alanyl-tRNA synthetases appear to have split apart recognition of mitochondrial from cytoplasmic tRNA^Ala by translocation of G:U. This splitting apart may be essential for preventing the introduction of ambiguous states into the genetic code.

Carnot Cycle Revisited
Enrique Peacock-López, Professor of Chemistry

The Chemical Educator, 7, 127-131 (2002)

Sadi Carnot stated that the efficiency of a reversible Carnot cycle is independent of the properties of the material used to run the cycle. Using this statement, all textbook discussions of the Carnot cycle use an ideal gas. Here, in contrast, we consider, in the spirit of the Caratheodory approach, a general analysis centered on the existence of an integrating factor that transforms an inexact differential into an exact differential. Also we derive a general relation between temperature and volume along an adiabatic path. Using these two results, we obtain the efficiency of the Carnot cycle η = 1 - T_C / T_H, for any equation of state.

ESR Dating at the Burnham Site, Oklahoma
Anne R. Skinner, Senior Lecturer of Chemistry, A. B. Blackwell, Research Scientist, Henry P. Schwarcz, and Donald G. Wycoff

Proceedings of the 32^nd International Archaeometry Symposium (2001)

The Burnham Site occurs in a short-lived pond deposit. The pond formed in a gulley eroded into a soil dated at 34-36 +/- 2-4 kyr BP by AMS radiocarbon. Snails living during the pond’s deposition were dated at 31-36 +/- 2-9 kyr BP. Fossils from species now either extinct or extirpated from North America were found associated with what appear to be resharpening flakes from scrapers and knives. ESR (electron spin resonance) dating uses the radiation-sensitive signal occurring in fossil tooth enamel. ESR was used to independently date six subsamples from one Equus tooth closely associated with the artifacts. The tooth’s standard ESR ages averaged 37 +/- >4 ka (assuming early uptake of uranium into the tooth), and 68 +/- 7 ka (assuming linear uptake). Isochron analysis is consistent with these ages. These ages are consistent with the radiocarbon results.

Solid Phase Organic Synthesis and Combinatorial Chemistry: A Laboratory Preparation of Oligopeptides
George A. Truran, Karelle S. Aiken ’00, Thomas R. Fleming ’00, Peter J. Webb ’02, and J. Hodge Markgraf, Professor of Chemistry emeritus

Journal of Chemical Education, 79, 85-86 (2002)

The principles and practice of solid phase organic synthesis and combinatorial chemistry are utilized in a laboratory preparation of oligopeptides. A parallel synthesis scheme is used to generate a series of tripeptides. A divergent synthesis scheme is used to prepare two pentapeptides, one of which is leucine enkephalin, a neurotransmitter known to be a naturally-occurring analgesic agent in the brain.

COMPUTER SCIENCE

Foundations of Object-Oriented Languages: Types and Semantics
Kim B. Bruce

MIT Press, 2002.

Abstract: In recent years, object-oriented programming has emerged as the dominant computer programming style, and object-oriented languages such as C++ and Java enjoy wide use in academia and industry. This text explores the formal underpinnings of object-oriented languages to help the reader understand the fundamental concepts of these languages and the design decisions behind them.

The text begins by analyzing existing object-oriented languages, paying special attention to their type systems and impediments to expressiveness. It then examines two key features: subtypes and subclasses. After a brief introduction to the lambda calculus, it presents a prototypical object-oriented language, SOOL, with a simple type system similar to those of class-based object-oriented languages in common use. The text offers proof that the type system is sound by showing that the semantics preserves typing information. It concludes with a discussion of desirable features, such as parametric polymorphism and a MyType construct, that are not yet included in most statically typed object-oriented languages.

Fifth Workshop on Foundations of Object-Oriented Programming
Kim B. Bruce and Didier Remy, eds.

Information and Computation, 172 (2002), no. 1

Abstract: This issue contains papers selected from the fifth Workshop on the Foundations of Object-Oriented Languages (FOOL), held in San Diego, California on January 17 and 18, 1998, in conjunction with the 25th ACM Symposium on Principles of Programming Languages (POPL ’98). The workshop consisted of three invited lectures, and 12 contributed papers selected by the program committee. The three papers in this issue were selected from those presented at the workshop.

Teaching Breadth-first Depth-first
Thomas Murtagh, Professor of Computer Science

ItiCSE Proceedings, pp. 37 – 40 (2001)

This paper argues that current approaches to teaching the introductory course for the CS major fail to provide students with an accurate sense of the nature of our field. We propose that an introductory course focused on a single sub-field of our discipline could better prepare potential majors by using that sub-field as a vehicle to present an overview of the techniques and principles fundamental to computer science. We discuss our experience with such a course based on the field of computer networks.

Architecting Dynamic Systems Using Containment
Barbara Lerner, Assistant Professor of Computer Science, Leon J. Osterweil, Jamieson M. Cobleigh, Lori A. Clarke

Units Working Conference on Complex and Dynamic System Architectures, Brisbane, Australia, December 2001

Dynamic Octree Load Balancing Using Space-Filling Curves
James D. Teresco, Assistant Professor of Computer Science and
Paul C. Campbell, Joseph E. Flaherty, Luis G. Gervasio, Karen D. Devine

Journal of Parallel and Distributed Computing (2002)

The Zoltan dynamic load balancing library provides applications with a reusable object oriented interface to a range of load balancing methods, including coordinate bisection, octree/space filling curve methods, and multilevel graph partitioners. We describe enhancements to Zoltan's octree load balancing procedure and the distributed octree structures used therein. These include improved performance of the space filling curve (SFC) procedures that exploit similarities between octree and SFC construction, and a new distributed octree that maintains the tree structure between successive repartitionings. The new SFC implementation includes efficient Morton, Gray code, and Hilbert orderings. Maintaining the tree avoids the cost of rebuilding at each rebalancing step and enhances performance and scalability with dynamic adaptive computations. We present the results of a number of scalability and partition quality studies utilizing the new octree structures and orderings.

GEOSCIENCES

Undergraduate Research Projects Provide a 30-Year Record of Change in a Fringing Reef Complex at Mary Creek, Virgin Islands National Park
Rónadh Cox, Assistant Professor of Geosciences

Geological Society of America Abstracts with Programs, 33, A166 (2001)

Decline in the diversity and abundance of hard corals in reef environments worldwide is a current focus of substantial research and conservation effort. Understanding the changes requires long-term records of reef environments, but relatively few such records exist. The Mary Creek fringing reef complex (MCRC), in the Virgin Islands National Park on St. John, has been the site of several undergraduate research projects over the last thirty years, including an Amherst College field research seminar in 1968, Williams College senior thesis projects in the late 80s and early 90s, and a Williams field research course in 1998. Since creation of the National Park in 1956, the reefs have been subject to increasing tourist visitation and infrastructure construction, as well as hurricanes and climate change, but the net effects are unknown because continuous reef-monitoring programs in the park began only in 1989. The undergraduate projects were not undertaken with the intent of reef monitoring, but the accumulated data track large-scale changes in the MCRC between 1968 and 1998. To the best of our knowledge, the MCRC is the only reef in the area for which a 30-year record exists, making this site an excellent candidate for a continued reef-monitoring study.

Substantial changes in the MCRC over the last thirty years include severe loss of living coral cover, and infilling of the back-reef lagoon. In 1968, the reef crest zone was dominated by dense stands of Acropora palmata, with subordinate but prominent colonies of A. cervicornis. By 1986, however, A. palmata occurred in less than 5% of surveyed quadrants, and the 1998 survey encountered only two living colonies. In 1968, a prominent western reef lobe was populated with A. cervicornis, but in 1986 it was recorded in less than 2% of quadrants surveyed. The 1998 map indicates that the A. cervicornis lobe no longer exists as a resistant structure and is probably represented by an extended rubble zone at the western edge of the MRCR. In 1968, depths in the lagoon averaged 1.5 m and in places were in excess of 2 m. In 1998, in contrast, the average depth was approximately 0.4 m, and the deepest high-tide water level recorded in the back-reef was 0.6 m. This corresponds to a net sediment accumulation rate of approximately 3.6 cm/year.

A Newly-Recognized Late Neoproterozoic Metasedimentary Sequence in Central Madagascar Suggests Terrane Juxtaposition at 560±7 Ma During Gondwana Assembly
Rónadh Cox, Assistant Professor of Geosciences
Drew S. Coleman, Univ. North Carolina
Joseph L. Wooden, U.S. Geological Survey
Stephen B. DeOreo ’01

Geological Society of America Abstracts with Programs, 33, A436 (2001)

Two distinct Proterozoic metasedimentary packages (Itremo Group and newly-recognized Molo sequence) are preserved in central Madagascar. The units are lithologically similar and are tectonically interleaved. Consequently, they are distinguishable only on the basis of their detrital zircon populations. Zircon populations in the younger Molo sequence and associated granitoid rocks are significant because they suggest that rocks exposed in central Madagascar represent two distinct crustal blocks, which were deformed and metamorphosed together at 560±7 Ma.

Detrital zircon populations define mutually exclusive age brackets for the two sequences. The Itremo Group, of probable Mesoproterozoic age, was deposited some time after 1722±40 Ma (youngest concordant detrital age) and before 795±8 Ma (age of oldest dated intrusive rocks). The Molo sequence contains detrital grains equivalent in age to the granites that intrude the older Itremo Group, and was therefore deposited in the Neoproterozoic, after 647±29 (youngest concordant detrital age), and before regional metamorphism at 560±7 Ma. In addition to their different ages, the two units have dramatically different provenance signatures. The Itremo Group has five distinct detrital zircon populations between 1875 and 2690 Ma in age (n = 271). In contrast, concordant detrital ages in the Molo Sequence range from 741 to 1075 Ma (n = 79), indicating a period of uplift and sedimentation post-dating Itremo Group deposition and intrusion.

The Molo sequence detrital grains resolve into four age populations with averages at approximately 640±20 Ma (10% of grains analyzed), 830±10 Ma (45%), 950±10 Ma (35%) and 1065±15 Ma (10%). The presence of grains in the 1000-1100 Ma (Kibaran) range is highly significant, because no crystalline rocks of that age have been found in Madagascar although Kibaran-aged rocks are common in most Rodinia fragments. Possible basement to the Molo sequence is represented by associated 800 Ma granitoids that also have Kibaran inheritance, suggesting that these rocks together may represent a fundamentally different terrane than that which underlies the Itremo Group and most of central/northern Madagascar. We interpret the 560±7 Ma metamorphism to record the amalgamation of the two crustal blocks.

Diagenetic Origin for Quartz-Pebble Conglomerates
Rónadh Cox, Assistant Professor of Geosciences
Ethan D. Gutmann ’99 and Patricia G. Hines ’00

Geology, 30, 323-326 (2002)

The occurrence of quartz-pebble conglomerates (QPC) in the rock record increases backward through time from the Tertiary through the Precambrian. The positive correlation between QPC abundance and age is valid both for numbers of reported QPC and for QPC as a percentage of all conglomerate, and at both the era and the period level. QPC are usually interpreted as due to intense chemical weathering, protracted transport, or sediment recycling, but none of these can account for the age distribution of QPC, which is the opposite of the global mass-age distribution for sedimentary rocks. Precambrian and Tertiary conglomerates with similar sources and sedimentology have vastly different clast populations, with non-quartzose clasts much more abundant in the younger rocks. Comparison of the petrology of QPC and polymict conglomerates shows that QPC have consistently higher proportions of diagenetic secondary matrix and pressure-solved grain contacts. We conclude that diagenetic factors play an important role in QPC formation by preferentially destroying less durable clasts.

Quartz-Pebble Conglomerates: Do They Form During Diagenesis?
Rónadh Cox, Assistant Professor of Geosciences
Ethan D. Gutmann ’99 and Patricia G. Hines ’00

Geological Society of America Abstracts with Programs, 34, A62-63 (2002)

In quartz-pebble conglomerates (QPC) more than 90% of the clasts consist of vein quartz, chert, and quartzite. Thick, laterally extensive QPC are well-known in the rock record, but no such deposits are forming in modern environments. QPC occurrence, as measured by records in the AGI GeoRef database, increases backward through time from the Tertiary through the Precambrian. The inverse relationship between QPC abundance and stratigraphic age is seen both in numbers of reported QPC and in QPC as a percentage of all conglomerate records. This is in direct contrast to the record for sedimentary rocks as a whole, which show a well-documented decrease in preserved volume with increasing geologic age.

We propose that progressive diagenesis, whereby labile clasts have a greater probability of selective destruction over time, provides the best explanation for this distribution. Evidence in support of this hypothesis comes from petrologic comparison of polymict and quartz-pebble conglomerates. Precambrian and Tertiary conglomerates with similar sources and sedimentology have vastly different clast populations, with non-quartzose clasts much more abundant in the younger rocks. In addition, petrologic comparison of similar-aged QPC and polymict conglomerates shows that QPC have consistently higher proportions of diagenetic secondary matrix and pressure-solved grain contacts. We do not propose that all QPC originate diagenetically, and acknowledge that protracted transport, intense chemical weathering, and sediment recycling may all produce QPC. We conclude, however, that diagenetic factors can play an important role in QPC formation by preferentially destroying less durable clasts, and that this may provide the best explanation in cases where independent evidence for an alternative mechanism is lacking and appropriate petrologic indicators are present.

Pleistocene Incision Rates in the Western United States Calibrated Using Lava Creek B Tephra
David P. Dethier, Professor of Geosciences

Geology, 29 (9), 783-786 (2001)

The Lava Creek B ash bed, erupted from the Yellowstone caldera ca. 0.64 Ma, provides a datum for measuring long-term fluvial incision west of the Mississippi River. The ash is widely preserved due to its substantial volume, broad initial dispersal, and the aggrading environment into which the ash fell. Drainages incised soon after Lava Creek B deposition, isolating the ash from fluvial erosion and preserving it in fill terraces. Calculated rates of incision since ca. 0.60 Ma range from 2 to 30 cm k.y^.-1. Rates are high in most areas near the Rocky Mountains and downstream along rivers draining mountainous terrain, and are lowest east of the High Plains and along the Snake River. Incision rates along many rivers decrease downstream. Rates of downcutting increased in the late Pleistocene along several major rivers, indicating that climate change altered sediment budgets. Regional and temporal data suggest that fluvial incision records increased middle and late Pleistocene runoff from the southern Rocky Mountains, rather than epeirogenic uplift, but regional rock uplift cannot be excluded as a significant factor.

Cosmogenic Analysis of the Rocky Flats Alluvium Near Boulder, Colorado
David P. Dethier, Professor of Geosciences
Taylor Schildgen ’00
Paul Bierman ’85, Univ. of Vermont
Marc Caffee, Lawrence Livermore Laboratory

Geological Society of America Abstracts with Programs, 33 (6), A312-313 (2001)

Analysis of a 4 m deep cosmogenic isotope profile from Rocky Flats Alluvium near Boulder, Colorado shows that nuclide abundance decreases with depth, consistent with a variety of interpretive models. The Rocky Flats is the most extensively exposed older piedmont alluvium in the vicinity of Denver. Correlative alluvial deposits and remnant erosional surfaces extend regionally along the Front Range and tens of km east into the High Plains ca. 100 m above modern channels. Stratigraphic and geomorphic relations demonstrate that Rocky Flats Alluvium is younger than middle Pliocene and older than ca. 0.6 Ma. Regional paleontologic evidence and ages inferred from soil carbonate accumulation imply that deposits are early Pleistocene. Most workers suggest that the Rocky Flats and younger alluvial sequences correlate with glaciation in the Front Range, but alluvium in the type area was deposited by streams that drain unglaciated catchments.

We collected a 9-sample sequence from the surface to –4.2 m in oxidized, clast to matrix-supported gravel exposed temporarily during realignment of an irrigation canal. ¹⁰Be activity in quartz grains from the sand fraction ranges from 3.12 *10⁶ atoms/gram in a strongly developed Bt horizon buried 0.25 m below the surface to 0.77 *10⁶ at a depth of 3.7 m. Several scenarios constrained by muon production <2% and SL, >60o ¹⁰Be production of 5.17 atoms g^-1 y^-1 fit the nuclide data equally well. A simple, steady erosion model (3.7 m My^-1) and time since deposition of 2 My require high inheritance (2.1 *10⁶ atoms g^-1), equivalent to source basin erosion of 9.4 m My^-1. A no-erosion, exposure model implies deposition of alluvium at 0.2 Ma with inheritance (9*10⁵ atoms g^-1 ¹⁰Be), equivalent to a source basin erosion rate of 22 m My^-1. Multi-stage models (fan surface is stable, then episodically eroded 1 to 4 m, then stable again) fit the data equally well and are supported by geologic and pedologic evidence. The fit of such models is optimized by original deposition at ca. 1.5 Ma, stripping between 0.1 and 0.2 Ma, and inheritance of ca. 10⁶ atoms g^-1 ¹⁰Be. In all models, high density (2.4 g cm³) and significant inheritance (>10⁶ atoms g^-1) are key to good fits.

Episodic Pliocene and Pleistocene Drainage Integration along the Rio Grande Through New Mexico
James C. Cole, Byron D. Stone, R. R. Shroba, U.S. Geological Survey
David P. Dethier, Professor of Geosciences

Geological Society of America Abstracts with Programs, 33 (6), A-357 (2001)

Drainage through the Rio Grande tectonic rift zone has evolved over the last several million years from multiple closed basins, to interconnected basin systems, to a fully integrated system that drains from Colorado to the Gulf of Mexico. The evolution has been affected to variable degrees by tectonic subsidence/uplift, by episodic dams formed by basalt and ash-flow eruptions, and by sediment-supply factors along different segments of the rift zone. We compare the sedimentation/incision history of the Santa Fe-Socorro reach of the Rio Grande with the Socorro-El Paso reach, and with the headwaters-Taos reach, to show that each drainage segment evolved independently until a through-flowing connection was established between pairs of them. The Santa Fe-Socorro reach was a closed-basin system through the middle Pliocene, when it connected southward after about 3.4 Ma (Mack and others, 1993). Sedimentation in the lower, closed basins of the Socorro-El Paso reach (Lake Cabeza de Vaca of Gile and others, 1981) was fed by material incised from the Miocene-lower Pliocene closed-basin deposits along the Santa Fe-Socorro reach. Shortly before about 750 ka (Bishop ash), the integrated Santa Fe-El Paso reach was captured by drainage that connected to the Gulf of Mexico (Gile and others, 1981; Mack and others, 1993). The headwaters-Taos reach remained isolated from the Rio Grande until erosion cut through the basalt dam of the Taos volcanic plateau after about 690 ka (Wells and others, 1987). We interpret the sedimentologic and chronologic record of the last 5 million years to indicate that progressive change toward cooler, wetter climate has been more significant that tectonics in driving drainage integration for the region.

Continental Island from the Upper Silurian (Ludfornian Stage) of Inner Mongolia: Implications for Eustasy and Paleogeography
Markes E. Johnson, Professor of Geosciences
J. Rong, C. Wang, and P. Wang, Nanjing Inst. Of Geology and Palaeontology

Geology, 29, 955-958 (2001)

An unconformity between the Silurian Xibiehe Formation and Ordovician igneous rocks marks the perimeter of a small paleoisland near Bater Obo in north-central Inner Mongolia, 180 km northwest of the provincial capital of Hohhot. The stratigraphic position of the lower part of the Xibiehe Formation is correlated by means of conodonts with the upper part of the Ancoradella ploeckensis Zone in the basal Ludfordian Stage (corresponds to mid-Ludlovian Epoch, ca. 421 Ma). Elongate in plan (610 m x 200 m), the exhumed diorite core rises 30 m above the lowest elevations of surrounding Silurian strata. Paleoshores along the principal axis of the inlier delineate contrasting facies. Robust stromatoporoids are in growth position within silty limestones, some directly encrusting the unconformity surface of the sheltered southeast margin. A basal conglomerate of diorite cobbles and boulders characterizes the high-energy northwest margin. The depositional constraints and timing of transgressive facies associated with this continental paleoisland have implications for the eustatic and paleogeographic history of the parent Sino-Korean plate. Burial of the island corresponds to the beginning of a global rise in sea level that peaked in late Ludlovian time. Our interpretation of windward and leeward facies requires an approximate 90º clockwise rotation of the parent plate to accommodate the dominant pattern of low-latitude trade winds and storms.

Miocene-Pleistocene Tectono-Sedimentary Evolution of Bahía Concepción Region, Baja California Sur (Mexico)
Markes E. Johnson, Professor of Geosciences
J. Ledesma-Vázquez, Univ. Autonoma de Baja California

Sedimentary Geology, 144, 83-96 (2001)

Bahía Concepción is one of the largest fault-bound bays in the Gulf of California. It is one of the area’s best examples of an extensional basin, and an accommodation zone related to the Late Miocene extension in the Gulf of California region. Extensional tectonics in the Gulf region initiated from middle to early Late Miocene, in a simple east-west manner. The units within the Comondú Group are tilted between 14 and 45o in opposite directions (E/W), as a direct result of a single main extensional episode. This event produced subsidence that created the depocenters for nearshore marine basins. The oldest sedimentary units present in the region are assigned to the Late Miocene-early Pliocene Tirabuzón Formation. Up-faulted granodiorite basement occurs on the Peninsula Concepción and at Punta San Antonio as a direct result of the Late Miocene extensional episode. Extension on the Bahía Concepción zone was responsible for development of a divided half-graben structure first flooded in Late Pliocene time.

The tectono-sedimentary evolution of Bahía Concepción is recorded by three stratigraphic stages: (1) pre-rift strata represented by the Comondú Group, (2) a syn-rift unconformity, and (3) post-rift strata represented by the Late Miocene to Pliocene flat laying sedimentary units. This triad of stratigraphic stages clearly varies from other basins along the margin of the Gulf of California.

Upper Pleistocene terrace deposits generally conform to the 6-12 m elevation regionally associated with substage 5e. Their uniformity in elevation inside and outside Bahía Concepción indicates that tectonic uplift was locked in step throughout the immediate region at least since that time.

Discovering the Geology of Baja California – Six Hikes on the Southern Gulf Coast
Markes E. Johnson, Professor of Geosciences

The University of Arizona Press, 240 p. (2002)

Baja California: wild, desolate, and a treasure-house of geological wonders. Along its ancient shorelines, careful observers can learn much about how the Gulf of California came into existence and what the future of the Baja California peninsula might be.

For those who wish to unlock the mysteries of Baja California, geologist Markes Johnson offers the key. He has taken a body of technical research on the geology and paleontology of the region and made it accessible in plain language for anyone who visits the peninsula, whether for study or recreation. His book teaches general concepts in coastal geomorphology and tectonics, as well as the basic geological and natural history of the Gulf of California, in a conversive, intellectually stimulating fashion.

Johnson’s guide takes the form of six day-long hikes in the area of Punta Chivato on the east coast of the southern Baja California peninsula. Punta Chivato is represented as a microcosm of the entire region; it can enable visitors to better understand major themes in the natural history of the Gulf of California and its geological past. All of the hikes begin at the southeast corner of the Punta Chivato promontory and loop out in different directions. Each circuit is designed to minimize overlap with adjacent hikes and to maximize the visitor’s exposure to instructive variations in the landscape.

Discovering the Geology of Baja California invites visitors to these shores to explore not only rocks and fossils but also the continuum of past ecosystems with the ecology of the present. It offers both an unparalleled guide to a remote area and a new understanding of life caught in an endless cycle of change.

Geochronology and Geochemistry of the Shelburne Falls Arc: The Taconic Orogeny in Western New England
Paul Karabinos, Professor of Geosciences
J. C. Hepburn, Boston College

Guidebook for Geological Field Trips in New England, H1-H20 (2001)

The Ordovician Taconic orogeny in western New England was typically ascribed to a collision between the Laurentian margin and a magmatic arc identified as the Bronson Hill arc. However, in central Massachusetts and southern New Hampshire, rocks in the Bronson Hill arc are 454 to 442 Ma (Tucker and Robinson, 1990) and, therefore, younger than the onset of Taconic metamorphism in western New England and Quebec, which began by approximately 470 to 460 Ma (Laird and others, 1984; Castonguay and others, 1997). Karabinos and others (1998) used U-Pb zircon ages and geochemistry to document the presence of an older magmatic arc, the Shelburne Falls arc, which formed west of the Bronson Hill arc by approximately 485 to 470 Ma above an east-dipping subduction zone. The Taconic orogeny was the result of the collision between Laurentia and the Shelburne Falls arc beginning at approximately 470 Ma. The younger Bronson Hill arc formed above a west-dipping subduction zone that developed along the eastern edge of the newly accreted terrane after the Taconic orogeny. The Taconic orogeny ended when plate convergence between Laurentia and Iapetus was accommodated by the newly developed west-dipping subduction zone instead of by crustal shortening in the Taconian thrust belt.

How Do Orogenies End? An Example from the Taconic Orogeny in the Northern Appalachians
Paul Karabinos, Professor of Geosciences

Geological Society of America Abstracts with Programs, 33, A-260 (2001)

A viable tectonic model must not only explain the architecture of an orogenic belt in terms of plate interactions, but also account for how the orogeny ended. The Taconic orogeny is commonly attributed to collision of Laurentia with an arc that formed above an east-dipping subduction zone. The end of the Taconic orogeny must be related to a reconfiguration of plate boundaries that transferred convergence from the orogen to a new subduction zone. Accurately determining the time span of the Taconic orogeny in western New England and Quebec is critical to this problem. Currently the orogeny is constrained by the oldest metamorphic cooling ages of Laurentian rocks (ca. 470 Ma; Laird et al., 1984, Castonguay et al; 2001) and deposition of the youngest syn-orogenic flysch in the Taconic thrust belt (ca. 452 Ma, Bradley, 1989, using the timescale of Tucker and McKerrow, 1995). Karabinos et al. (1998) argued that the Shelburne Falls arc (485 to 470 Ma) collided with Laurentia rather than the Bronson Hill arc (454 to 442 Ma; Tucker and Robinson, 1990). Because a continent-arc collision stops the continuous supply of oceanic lithosphere to the subduction zone, Karabinos et al. (1998) also hypothesized that the Bronson Hill arc formed above a new west-dipping subduction zone near the Laurentian margin, after a flip in subduction polarity. Although it is possible that the Bronson Hill arc formed above an east-dipping subduction zone far from the Laurentian margin (e.g. Van Staal et al., 1998), the spatial overlap of older and younger arc-related rocks in Connecticut and New Hampshire suggests that the Bronson Hill arc formed near Laurentia. Because the Bronson Hill arc began to form at approximately the same time that the Taconic orogeny ended, it is likely that initiation of the new west-dipping subduction zone was instrumental in bringing the orogeny to a close. Prevalent 40Ar/39Ar cooling ages in western New England in the range of 450 to 440 Ma probably record orogenic collapse and rapid exhumation of rocks in the Taconic thrust belt following polarity reversal, analogous to the present situation in Taiwan.

Geology of the City of Rocks National Reserve: New Insights from Keck Geology Consortium Undergraduate Research
Kevin Pague, Whitman College
Paul Karabinos, Professor of Geosciences, et al.

Geological Society of America Abstracts with Programs, 33 (6), A-123 (2001)

The City of Rocks National Reserve encompasses a scenic landscape of fins, spires, and domes eroded from the Oligocene Almo Pluton and the Archean Green Creek Complex in the core of the Albion Range metamorphic core complex. The “Silent” City of Rocks was a landmark on the California Trail that was often mentioned in the diaries of the forty-niners. Recent human history has been the focus of most of the interpretive resources of the National Reserve in spite of its fascinating geologic history. In the summer of 2000, a Keck Undergraduate Research Project was conducted in an effort to better understand the processes and geologic controls that created the spectacular landscape and to communicate these concepts to park staff. Individual student projects addressed geologic problems that are often the source of visitors’ questions. The results of the projects were made available to park staff, and a route for a geologic interpretive trail was laid out.

The primary results of the student projects can be summarized as follows: Joint sets in the City of Rocks are the most important factor in controlling the spacing, shape, and distribution of rock outcrops. Individual joint sets can be tied to discrete tectonic events. For example, a north-striking joint set related to Oligocene extension hosts hydrothermal alteration and mineralization and is responsible for the formation of the major “avenues” of the City of Rocks. Panholes have played a very important role in shaping and lowering the surfaces of rock outcrops; their shape and size evolves through time in a predictable manner. Flare structures along the bases of outcrops are not randomly distributed but can be related to parameters such as aspect, slope, and soil moisture. The Circle Creek Basin which contains the City of Rocks appears to have developed through discrete stages of relative stability separated by periods when the erosion of deeply weathered granite was accelerated as a result of climatic changes, tectonic uplift, or both.

Extension Tectonics of the Acadian Orogeny
Paul Karabinos, Professor of Geosciences
Matthew Student ’01

Geological Society of America Abstracts with Programs, 34, A-28 (2002)

Tectonic models for the Devonian Acadian orogeny in the New England Appalachians typically invoke two major periods of crustal shortening: an early phase of recumbent folding followed by an upright doming event. In the western part of the Acadian orogen, Devonian deformation overprinted the Ordovician Taconic thrust belt. An alternative interpretation of the numerous domes in the western part of the Acadian orogen is that they record large-scale ductile extension. Evidence for extension includes dramatic tectonic thinning of Paleozoic units and synmetamorphic exhumation of foot-wall rocks. The best evidence for normal faulting is in the Chester dome in southeastern Vermont. There stratigraphic separation diagrams clearly show that Cambrian and Ordovician units have been excised by faulting; locally Middle Proterozoic basement rocks are separated from Silurian units by less than 0.5 km! Acadian extension occurred during garnet-grade metamorphism on low-angle, nearly-planar normal faults. Kinematic indicators reveal that hanging wall rocks were displaced to the southwest. The Chester dome is defined by a folded mylonitic foliation. During dome-stage folding, the mylonitic foliation and the tops-to-the-southwest kinematic indicators, such as C-S fabrics and rotated porphyroclasts, were complexly overprinted by simple shear into different patterns on the east and west sides of the dome. Acadian extension was most likely the result of gravitational collapse following surface uplift and thermal weakening of the lower crust.

Potential and Limitations of Paleoproxies from Sr/Ca Ratios in Coccolith Carbonate
Heather Stoll, Assistant Professor of Geosciences, et. al.

Eos Trans. AGU, 82 (47), Fall Meeting Supplement, Abstract PP12A-0471 (2001)

Climate Proxies from Sr/Ca of Coccolith Calcite: Calibrations from Continuous Culture of Emiliania huxleyi
Heather Stoll, Assistant Professor of Geosciences
Yair Rosenthal, Paul Falkowski, Rutgers Univ.

Geochimica et Cosmochimica Acta, 66, 927-936 (2002)

Continuous culture of coccolithophorid Emiliania huxleyi demonstrates that coccolith Sr/Ca ratios depend not only on calcification rate but also on temperature. At constant temperature of 18° C and variable illumination, coccolith Sr/Ca ratios increase nearly 15% as growth rate increases from 0.1 to 1.5 divisions per day and calcification rate increases from 1.5 to 50 pg calcite/cell/day. When temperature increases from 7° to 26° C, Sr/Ca ratios increase by more than 25%, although the range in growth and calcification rates was the same as for experiments at constant temperature. The steep positive correlation of coccolith Sr/Ca with temperature contrasts with field studies in the Equatorial Pacific where Sr/Ca ratios are highest at the locus of maximum upwelling and productivity despite depressed temperatures. This may reflect different calcification rate effects between E. huxleyi and the other species dominating assemblages in the Equatorial Pacific sediments, which may be resolved by new techniques for separation of monospecific coccolith samples from sediments. Despite the dual influence of temperature and growth rate on coccolith Sr/Ca, coccolith Sr/Ca correlates with "b", the slope of the dependence of carbon isotope fractionation in biomarkers, (εp) on CO2 (aq), at a range of growth rates and temperatures. Consequently, using coccolith Sr/Ca in combination with alkenone ep may improve paleo-CO2 determinations. Models of crystal growth indicate that kinetic effects on Sr partitioning in calcite due to surface enrichment could explain the Sr/Ca variations observed in constant temperature experiments. However, the increase in Sr/Ca with temperature is likely due to temperature dependence of the effective equilibrium partitioning of Sr in calcite.

Potential and Limitations of Sr/Ca Ratios in Coccolith Carbonate: New Perspectives from Cultures and Monospecific Samples from Sediments
Heather Stoll, Assistant Professor of Geosciences, et. al.

Philosophical Transactions Royal Society of London A, 360, 719-747 (2002)

The Sr/Ca ratio of coccoliths was recently proposed as a potential indicator of past growth rates of coccolithophorids, marine algae which play key roles in both the global carbonate and carbon cycles. We synthesize calibrations of this proxy through laboratory culture studies and analysis of monospecific coccolith assemblages from surface sediments. Cultures of coccolithophorids Helicosphaera carteri, Syracosphaera pulchra, and Algirospira robusta confirm a 1-2% increase in Sr/Ca per ^oC previously identified in Emiliania huxleyi and Gephyrocapsa oceanica. This effect is not due merely to increases in growth rate with temperature and must be considered in paleoceanographic studies. In light-limited cultures of E. huxleyi, Calcidiscus leptoporus, and G. oceanica at constant temperature, coccolith Sr/Ca ratios vary by 10% across the range of possible growth and calcification rates for a given species. Among different species under similar culture conditions, Sr/Ca ratios vary by 30%. Although the highest ratios are in the cells with highest calcification and organic C fixation rates, at lower rates there is much scatter indicating that different mechanisms control interspecific and intraspecific coccolith Sr/Ca variations. In field studies in the equatorial Pacific and Somalia coastal region, coccolith Sr/Ca correlates with upwelling intensity and productivity. A more dynamic response is observed in larger coccoliths like C. leptoporus (23 -55% variation in Sr/Ca) than smaller coccoliths of G. oceanica or Florisphaera profunda (6-15% variation in Sr/Ca). This response suggests that despite temperature effects, coccolith Sr/Ca has potential as an indicator of coccolithophorid productivity. If the variable Sr/Ca response of different species accurately reflects their variable productivity response to upwelling (and not different slopes of Sr/Ca with productivity), coccolith Sr/Ca could provide useful data on past changes in coccolith ecology. The mechanism of coccolith Sr/Ca variations remains poorly understood but is probably more closely tied to biochemical cycles during carbon acquisition than to chemical kinetic effects on Sr incorporation in the calcite coccolith crystals.

Geochemistry and Tectonic Setting of Paleoproterozoic Metavolcanic Rocks of the Southern Front Range, Lower Arkansas River Canyon and Northern Wet Mountains, Central Colorado
Reinhard A. Wobus, Professor of Geosciences
Martha Folley ’97, Katherine Wearn ’98,
Jeffrey B. Noblett, Colorado College

Rocky Mountain Geology, 36 (2), 99-118 (2001)

Across a 5000 km2 area of central Colorado, previously unstudied Paleoproterozoic metabasalts (amphibolites) and metarhyolites (felsic gneisses) comprise a bimodal metavolcanic association within a dominantly metasedimentary terrain. Extending southward from about 39º N latitude in the southern Front Range to about 38º 15' N latitude in the Wet Mountains, and from the mountain front westward to the Wet Mountain Valley and Pleasant Valley fault system, this area includes the exceptional exposures within the lower Arkansas River Canyon from Howard downstream to Canon City. Regional metamorphism from garnet to sillimanite grade, pervasive deformation, and intrusion by three generations of Proterozoic plutons have largely obscured original stratigraphic relationships and primary structures within these metamorphic basement rocks, although a few pyroclastic features persist locally within the felsic members. These metavolcanic rocks are compositionally similar to the much better preserved bimodal section in the Salida area, dated at 1728 ± 6 Ma by Bickford (1986), which emerges from beneath Paleozoic cover rocks about 15 km beyond the western edge of the area of this report.

Geochemical studies of 45 samples (30 amphibolites and 15 felsic gneisses) delineate two groups of metavolcanic rocks ranging in silica content from 45 to 55% and from 65 to almost 80% in the other. Along a 100 km transect from north to south, metavolcanic rocks of the lower silica group (amphibolites) show an increase in total alkalies (from 2% to 5–6%) and large ion lithophile trace elements as well as an increase in degree of enrichment in light rare earth elements (from LaN/LuN < 2 to LaN/LuN ~5). Rocks with higher silica content (felsic metavolcanic rocks) occur mostly in the Arkansas Canyon area and contain 6–8% total alkalies; they show strong fractionation between light and heavy rare earth elements, with moderate to pronounced negative europium anomalies.

Tectonic discriminant diagrams using relatively immobile high-field-strength elements indicate volcanic arc settings for both mafic and felsic populations. Metavolcanic rocks from the northern Wet Mountains and Arkansas Canyon suggest a mature arc environment, possibly on an expanding continental margin. The isolated metabasalts to the north in the southern Front Range, where no felsic metavolcanic rocks have been identified, are more primitive island-arc tholeiites; they may represent pyroclastic rocks with a source beyond the study area.

These new dates from a wide area of central Colorado reinforce results from the well-studied Paleoproterozoic bimodal arc assemblages to the west near Salida and Gunnison. They also allow the extension across a wider geographic area of previous tectonic models for the Paleoproterozoic evolution of the Colorado province (as defined by Bickford et al., 1986). These models (Condie, 1986; Reed et al., 1987; Karlstrom et al., 1987) portray the rapid addition of juvenile crust to the southern margin of the Wyoming province by accretion of individual volcanic arcs or larger, previously amalgamated arc terranes, resulting in the southward expansion of the craton by about 1300 km from 1800–1650 Ma.

Intermediate Volcanics in a Bimodal Setting: Silurian Andesites of the Fox Islands, ME
Nathan C. Cardoos ’02
R. A. Wobus, Professor of Geosciences

Geological Society of America Abstracts with Programs, 34 (7), A-67 (2002)

Silurian volcanic rocks occur in the northern part of Vinalhaven Island and along the south shore of North Haven Island (the Fox Islands) in Penobscot Bay, Maine. They overlie the fossiliferous Lower (?) Silurian Ames Knob Formation and are intruded by the Vinalhaven granite pluton (420 ± 1 Ma: David Hawkins, pers. comm.), one of several plutons of the Coastal Maine Magmatic Province produced by the repeated injection of mafic magma into a silicic chamber at a shallow crustal level. The younger members of the volcanic pile - the Vinalhaven Rhyolite (Newton, J.L., 1999) and underlying Vinalhaven Diabase (Klemetti, E.W., 1999) - resemble the rocks of the pluton in their apparently bimodal character, though the “diabase” is geochemically a basaltic andesite to andesite and has petrographic features suggesting it is a hybrid. Older volcanics in the Silurian sequence are the felsic tuffs in the Polly Cove Formation (named by Ollie Gates, 2001, and the stratigraphic equivalent of the Ames Knob), the overlying Thorofare Andesite, and the tuffs and tuff breccias of the lower part of the Seal Cove Formation (Gates, O., 2001; Szramek, L., 2002). The Thorofare forms a 750-meter-thick pile of gray to reddish-brown intermediate lava flows and breccias on either side of the Thorofare strait and on small islands within it. The fragmental rocks are dominated by laharic breccias but also consist of autobreccias, bedded tuff breccias, and rare airfall tuffs. Breccia clasts are mainly andesite and mudstone, with locally abundant felsic volcanic fragments that may be the equivalent of volcanics in the Upper Cambrian Castine and Ellsworth formations to the north. Lower greenschist metamorphism and local hydrothermal alteration have largely obscured the primary mineralogy of the flow units in the Thorofare. The least altered samples from it preserve an intergranular fabric of mostly andesine and clinopyroxene, on a Winchester and Floyd (1977) classification diagram using immobile trace elements they plot mostly as andesites with overlap into the fields of basaltic andesite and dacite. Most flow samples are in the AT (island arc tholeiite) field of a Mullen-type (1983) tectonic discrimination diagram, suggesting that they formed before consolidation of the pen-Avalonian arc systems with the Laurentian mainland.

Correlation and Stratigraphy of Exotic Blocks in the Vinalhaven Pluton, Maine, to the Seal Cove Formation
Lindsay Szramek, Bowdoin College
Rachel Beane (’93), Bowdoin College
R. A. Wobus, Professor of Geosciences

Geological Society of America Abstracts with Programs, 34 (1), A-666 (2002)

Vinalhaven Island, located in lower Penobscot Bay, Maine, is a bimodal pluton rimmed by stratified sedimentary and volcanic rocks. The island is ideal for exploring questions related to magma chamber dynamics, because its coastal exposures and granite quarries offer a nearly complete cross section from the bottom of the chamber in the south to the top of the chamber in the north. To better define the chamber dynamics, exotic blocks in the pluton were examined and compared to the stratified rocks that rim the island. Blocks of metamorphosed bedded tuffs in the pluton correlate well with the Seal Cove Formation exposed on the north-central coast of Vinalhaven. The exposed Seal Cove Formation is composed primarily of 0.1-2.0 meter thick layers of quartzite and calc-silicate, and also includes a garnet-rich rock (80% garnet) and tuff breccia. The exposure is cut by a granitic sill. Blocks of the Seal Cove Formation, sized from a few meters to tens of meters, are located at Round Neck, on the south-central coast, and on Greens Island, southwest of Vinalhaven. Similar to the in-place exposure, these blocks contain 0.1 to 1.7 meter thick layers of quartzite and calc-silicates, and are locally intruded by granite from the surrounding pluton. Both the blocks and the exposed Seal Cove Formation show evidence of contact metamorphism. Garnet compositions with a high andradite component (and 45-68, gro41-18) provide supporting evidence to suggest that the protolithic tuff was calcic, possibly andesitic in nature, and underwent metasomatism resulting from thermal metamorphism related to the emplacement of the Vinalhaven pluton. The position and attitudes of the exotic blocks seem to support suggestions that the magma chamber underwent convection; however, the large, coherent nature of the blocks provides convincing evidence that the magma in the chamber was not turbid.

Geology of Vinalhaven Island, Maine
R. A. Wiebe, Franklin & Marshall College
David Hawkins, Denison University
R. A. Wobus, Professor of Geosciences

15^th Annual Undergraduate Research Symposium, Keck Geology Consortium, 15, 94 (2002)

This project examined the geology of Vinalhaven Island (Fig. 1). The plutonic rocks on Vinalhaven belong to the Coastal Maine Magmatic Province (Hogan and Sinha, 1989), and represent the roots of a Silurian bimodal volcanic system that apparently developed in an extensional tectonic setting, possibly in a back-arc environment. Three previous Keck projects in Maine have studied similar systems along the Maine coast (Cadillac Mountain and Gouldsboro complexes in 1993 and 1994, and Vinalhaven in 1998) and led to the publication of several papers (Wiebe et al., 1997a, 1997b; Weibe and Adams, 1997). The Vinalhaven plutonic complex appears to be perhaps the best exposed of these bimodal intrusions. The coastal outcrops are superb and show complex commingling and mixing relations between gabbroic, dioritic and granitic rocks near the base of the intrusion. Extensive areas of large contact-metamorphosed blocks of country rock also occur in the lower portions of the pluton. Two varieties of granite, along with tonalite, and gabbro are widely exposed and easily sampled in coastal sections, numerous quarries, and glaciated inland exposures.

To the northwest, the Vinalhaven pluton has intruded a remarkably well preserved sequence of interlayered Silurian volcanic and sedimentary rocks which have been gently folded into a basin-like structure. Even the oldest of these units on the island, the Polly Cove formation, contains felsic pyroclastic rocks which retain primary fabrics and show little evidence of regional metamorphism. It is overlain by more than 750 m of intermediate flows and breccias of the Thorofare andesite, followed by tuff-breccias and distinctive sedimentary rocks of the lower Seal Cove formation. Above this weakly deformed basaltic and rhyolitic volcanics may be cogenetic with the plutonic rocks. Large stoped blocks of the lower Seal Cove occur near the base of the pluton at the southern edge of Vinalhaven and on Greens Island to the west. All of the aforementioned layered units have been studied by this year’s Keck group for the first time, building on the work of two students in the previous Vinalhaven project on the bimodal volcanics at the tip of the Silurian sequence (the Vinalhaven diabase, Perry Creek formation, and the Vinalhaven rhyolite).

HISTORY OF SCIENCE

Reflections on Scientific Collaboration (and Its Study): Past, Present, and Future
Donald deB. Beaver

Scientometrics, 52:3, 365-377 (2001)

Also printed in Proceedings of the Second Berlin Workshop on Scientometrics and Informetrics, Collaboration in Science and Technology, September 1-3, 2000 at Free University Berlin, Frank Havemann, et al, eds, 29-40

Personal observations and reflections on scientific collaboration and its study, past, present, and future, containing new material on motives for collaboration, and on some of its salient features. Continuing methodological problems are singled out, together with suggestions for future research.

Age Structures of Scientific Collaboration in Chinese Computer Science
Liming Liang, Hildrun Kretschmer, Yongzheng Guo, Donald deB Beaver

Scientometrics 52:3 471-486, (2001)

This paper is a scientometric study of the age structure of scientific collaboration in Chinese computer science. Analysis reveals some special age structures in scientific collaboration in Chinese computer science. Most collaborations are composed of scientists younger than thirty-six (Younger) or older than fifty (Elder). For two-dimensional collaboration formed by first and second authors, Younger-elder and Younger-Younger are the predominant age structures. For three-dimensional collaboration formed by first, second and third authors, Younger-Younger-Elder and Younger-Younger-Younger are the most important age structures. Collaboration between two authors older than 38 amounts to only 6.4 percent of all two-person collaborations. Collaboration between two middle-aged scientists is seldom seen.

Why do such types of age structure in Chinese computer science exist? We suggest a tentative explanation based on analyses of the age composition of all authors, the age distributions of the authors in different ranks, and the name-ordering of authors in articles written by professors and their students.

MATHEMATICS

Waist Size for Cusps in Hyperbolic 3-Manifolds
Colin C. Adams, Mark Hopkins Professor of Mathematics

Topology, 41, No. 2, 257-270 (2002)

The waist size of a cusp in an orientable hyperbolic 3-manifold is the length of the shortest nontrivial curve in the maximal cusp boundary generated by a parabolic isometry. A variety of results on waist size are proved. In particular, it is shown that the smallest possible waist size, which is 1, is realized only by the cusp in the figure-eight knot complement.

Alternating Knots in S x I
Colin C. Adams, Mark Hopkins Professor of Mathematics
T. Fleming, M. Levin, and A. Turner

Pacific Journal of Mathematics, 203, No. 1, 1-22 (2002)

One of the Tait conjectures, which was stated 100 years ago and proved in the 1980's, said that reduced alternating projections of alternating knots have the minimal number of crossings. We prove a generalization of this for knots in S x I, where S is a surface. We use a combination of geometric and polynomial techniques.

The Shape of the Universe: Ten Possibilities
Colin C. Adams, Mark Hopkins Professor of Mathematics
J. Shapiro

American Scientist, 89, 443-453 (2001)

Recent observations suggest the global geometry of the spatial universe may be Euclidean. Mathematicians have proved that a Euclidean universe must be one of 18 possibilities. Eight of these are unlikely for physical reasons. The remaining ten are described in this paper.

A Deprogrammer’s Tale
Colin C. Adams, Mark Hopkins Professor of Mathematics

Mathematical Intelligencer, 23, No. 3, 13-14 (2001)

What to do when your child gets hooked on mathematics.

Why Knot: Knots, Molecules and Stick Numbers
Colin C. Adams, Mark Hopkins Professor of Mathematics

Plus Magazine, on-line science magazine, 15 (2001)

An exposition of the ideas behind knot theory, stick number of knots and its implications for chemistry.

Hiring Season
Colin C. Adams, Mark Hopkins Professor of Mathematics

Mathematical Intelligencer, 23, No. 3, 21-22 (2001)

The difficulties in hiring in a math department.

Fields Medalist Stripped
Colin C. Adams, Mark Hopkins Professor of Mathematics

Mathematical Intelligencer, 24, No. 1, 36 (2002)

What happens when a mathematician takes drugs to enhance his abilities.

Homotopy on the Range
Colin C. Adams, Mark Hopkins Professor of Mathematics

Mathematical Intelligencer, 24, No. 2, 19 (2002)

Algebraic topology meets a cattle drive.

Diophantine Inequalities and Irrationality Measures for Certain Transcendental Numbers
Edward B. Burger, Professor of Mathematics

The Indian Journal of Pure and Applied Mathematics, 32 1591-1599 (2001)

Here we construct U-numbers having pre-subscribed diophantine structure for which effective measures of irrationality are computed.

“Math Forum”—I Couldn’t Keep My Distance: A Mathematical Seduction
Edward B. Burger (as Drew Aderburg), Professor of Mathematics

The Mathematical Association of America Math Horizons, 12-15 (February 2002)

Here in a humor style, we give an introduction to p-adic numbers and construct infinite series that possess incredible convergence properties.

“On a Quantitative Refinement of the Lagrange Spectrum
Edward B. Burger, Professor of Mathematics
Amanda Folsom, Alexander Pekker, Rungporn Roengpitya ’01, Julia Snyder ’02

Acta Arithmetica, 102, 55-82 (2002)

Here we answer a question posed by Davenport in 1947 regarding diophantine inequalities exhibiting only finitely many solutions. As a consequence of the results introduced here, a quantitative version of the classical Lagrange spectrum is found.

Data Mining et Statistique: Discussion de l’article de Besse et al
Richard D. De Veaux, Professor of Mathematics

Journal de la Societe Francaise de Statistique, 142, No. 1 (2001)

Data Mining: A View from Down in the Pit
Richard D. De Veaux, Professor of Mathematics

Stats Magazine, 34, 3-9 (2002)

All the Mathematics You Missed [But Need to Know for Graduate School]
Thomas Garrity, Professor of Mathematics

Cambridge University Press (2001)

Beginning graduate students in mathematics and other quantitative subjects are expected to have a daunting breadth of mathematical knowledge, but few have such a background. This book will help students see the broad outline of mathematics and to fill in the gaps in that knowledge.

President Garfield and the Pythagorean theorem
Victor E. Hill IV, Thomas T. Read Professor of Mathematics

Math Horizons, 9-11,15 (February 2002)

When James A. Garfield was in the House of Representatives in 1876, he produced a new proof of the Pythagorean Theorem on right triangles. This article is concerned with his background and interests in mathematics as well as his experiences as a student at Williams 1854-56.

Generic Formal Fibers of Polynomial Rings
Susan Loepp, Associate Professor of Mathematics

Journal of Pure and Applied Algebra, 163, 93-106 (2001)

In this paper, we construct an excellent regular local ring A whose generic formal fiber is local and we show that the generic formal fiber of the polynomial ring over A in finitely many variables can also be controlled.

Some Results on Tight Closure and Completion
Susan Loepp, Associate Professor of Mathematics
C. Rotthaus

Journal of Algebra, 246, 859-880 (2001)

In this paper, we construct examples of nonexcellent local domains for which tight closure and completion do not commute. In addition, we construct an example of a complete local normal Gorenstein domain which is not F-regular but is the completion of an F-regular local ring.

Proof of the Double Bubble Conjecture
Frank Morgan, Dennis Meenan (’54) Centennial Professor of Mathematics
Michael Hutchings, Manuel Ritore, and Antonio Ros

Ann. Math., 155, 459-489 (2002)

We prove that the standard double bubble provides the least-area way to enclose and separate two regions of prescribed volume in R³.

Isoperimetric Regions in Cones
Frank Morgan, Dennis Meenan (’54) Centennial Professor of Mathematics
Manuel Ritore

Trans. AMS, 354, 2327-2339 (2002)

We consider cones C over Mⁿ and prove that if the Ricci curvature of M is at least n−1, then geodesic balls about the vertex minimize perimeter for given volume.

Math Chat
Frank Morgan, Dennis Meenan (’54) Centennial Professor of Mathematics

MAA Web Page, Semi-Monthly (1998)

Column with questions, answers, and prizes. Available at the Mathematical Association of America web page at www.maa.org.

An Isoperimetric Comparison Theorem for Schwarzschild Space and Other Manifolds
Frank Morgan, Dennis Meenan (’54) Centennial Professor of Mathematics
Hubert Bray

Proc. AMS, 130, 1467-1472 (2002)

We give a very general isoperimetric comparison theorem, which implies for example that geodesic spheres in the Schwarzschild space minimize area for given volume, which in turn has applications to the Penrose Inequality in general relativity.

Hexagonal Economic Regions Solve the Location Problem
Frank Morgan, Dennis Meenan (’54) Centennial Professor of Mathematics

Amer. Math. Monthly, 109, 165-172 (2002)

We show in a certain mathematical sense that congruent regular hexagons solve the location problem, i.e. provide optimal market regions about centers of production.

Small Perimeter-Minimizing Double Bubbles in Compact Surfaces Are Standard
Frank Morgan, Dennis Meenan (’54) Centennial Professor of Mathematics

Electronic Proceedings of the 78^th Annual Meeting of the Louisiana/Mississippi Section of the MAA, Univ. of Miss. (2001)

We prove that in a smooth, compact, two-dimensional submanifold of R^N, the least-perimeter way to enclose and separate two regions of small prescribed areas is a standard double bubble, consisting of three constant-curvature curves meeting in threes at 120 degrees. This paper is largely superseded by the next one, which proves that small stable double bubbles are standard.

The Standard Double Bubble Is the Unique Stable Double Bubble in R²
Frank Morgan, Dennis Meenan (’54) Centennial Professor of Mathematics
Wacharin Wichiramala

Proc. AMS, 130, 2745-2751 (2002)

We prove that the only equilibrium double bubble in R² which is stable for fixed areas is the standard double bubble. This uniqueness result also holds for small stable double bubbles in surfaces, where it is new even for perimeter-minimizing double bubbles.

The Perfect Shape for a Rotating Rigid Body
Frank Morgan, Dennis Meenan (’54) Centennial Professor of Mathematics

Mathematics Magazine, 75, 30-32 (2002)

The energy-minimizing shape for a rotating rigid body is not an oblate spheroid but a stationary ball with a small, distant planet.

Whad’Ya Know
Frank Morgan, Dennis Meenan (’54) Centennial Professor of Mathematics
Joseph Corneli, Paul Holt, Nicholas Leger, and Eric Schoenfeld

MAA Focus (2001)

An humorous account of the appearance of Morgan, his Geometry Group, and other mathematicians on the popular program on Public Radio International, in Madison, Wisconsin during the MathFest.

Rank-One Power Weakly Mixing Non-Singular Transformations
Cesar E. Silva, Professor of Mathematics
T. Adams and N. Friedman

Ergodic Theory Dynamical Systems, 21, No. 5, 1321-1332 (2001)

We show that Chacon's nonsingular type IIIλ transformation T, for λ between 0 and 1, is power weakly mixing, i.e., for all sequences of nonzero integers k_1, ..., k_r the transformation T^k_1 x ... x T^k_r is ergodic. We then show that in infinite measure, this condition is not implied by infinite ergodic index (having all finite Cartesian products ergodic), and that infinite ergodic index does not imply 2-recurrence.

Double Ergodicity of Nonsingular Transformations and Infinite Measure-Preserving Staircase Transformations
Cesar E. Silva, Professor of Mathematics
A. Bowels, L. Fidkowski, and A. Marinello

Illinois J. Math, 45, No. 3, 999-1019 (2001)

A nonsingular transformation is said to be doubly ergodic if for all sets A and B of positive measure there exists an integer n > 0 such that the measure of the intersection o T^-n (A) with each of the sets A and B is positive. While double ergodicity is equivalent to weak mixing for finite measure preserving transformations, we show that this is not the case for infinite measure preserving transformations. We show that all measure preserving tower staircase rank one constructions are doubly ergodic, but that there exist tower staircase transformations with non-ergodic Cartesian square. We also show that double ergodicity implies weak mixing but that there are weakly mixing skyscraper constructions that are not doubly ergodic, and also study some properties of double ergodicity.

Sharp Estimate for the Weighted Hilbert Transform via Bellman Functions
Janine Wittwer, Assistant Professor of Mathematics
S. Petermichl

Michigan Mathematics Journal, 50, No. 1, 71-88 (2002)

In this paper, we find the best possible upper bound of the Hilbert transform (an operator important in harmonic analysis and the theory of differential equations), as an operator in weighted L² space on the disk.

A Sharp Estimate on the Norm of the Continuous Square Function
Janine Wittwer, Assistant Professor of Mathematics

Proceedings of the AMS, 130, 2335-2342 (2002)

In this paper, we show that the continuous square function has a nice bound in weighted L² space.

PHYSICS

Dynamics of Photoinduced Collisions of Cold Atoms Probed with Picosecond Laser Pulses
Kevin Jones, Professor of Physics, and others

The Physical Review A, 64, 033421 (2001)

Pump-probe experiments are performed in which cold colliding Na atoms are photoassociated to form Na₂ molecules, and subsequently ionized. The experiments are performed in a regime where the pulsed photoassociation to an intermediate potential takes place at long range, and to several electronic, vibrational, and rotational states. A probe pulse then produces an ionization signal by further exciting these molecules to autoionizing doubly excited states. The time dependence of the ion signal shows a dramatic flux-enhancement effect on a nanosecond time scale due to the motion on the intermediate potentials. This time dependence can be viewed as monitoring the inward motion and dephasing of a population wave packet formed at long range.

Photoassociation of Sodium in a Bose-Einstein Condensate
Kevin Jones, Professor of Physics, and others

Physical Review Letters, 88, 120403 (2002)

We form ultracold Na₂ molecules by single-photon photoassociation of a Bose-Einstein condensate, measuring the photoassociation rate, linewidth, and light shift of the J = 1, v = 135 vibrational level of the A ¹∑⁺_u molecular state. The photoassociation rate constant increases linearly with intensity, even where it is predicted that many-body effects might limit the rate. Our observations are in good agreement with a two-body theory having no free parameters.

Entanglement Sharing among Quantum Particles with More Than Two Orthogonal States
Kenneth A. Dennison ’01 and William K. Wootters, Professor of Physics

Physical Review A, 65, 010301 (2001)

Consider a system consisting of n d-dimensional quantum particles (qudits), and suppose that we want to optimize the entanglement between each pair. One can ask the following basic question regarding the sharing of entanglement: what is the largest possible value E_max(n,d) of the minimum entanglement between any two particles in the system? (Here we take the entanglement of formation as our measure of entanglement). For n=3 and d=2, that is, for a system of three qubits, the answer is known: E_max(3,2)=0.550. In this paper we consider first a system of d qudits and show that E_max(d,d) ≥ 1. We then consider a system of three particles, with three different values of d. Our results for the three-particle case suggest that as the dimension d increases, the particles can share a greater fraction of their entanglement capacity.

PSYCHOLOGY

Identification and Its Relation to Identity Development
Phebe Cramer, Professor of Psychology

Journal of Personality, 69, 667-687 (2001)

Two meanings of identification – as a developmental process and as a mechanism of defense – were investigated as they relate to identity status. Identification with parents were assessed by comparing participants’ “ideal self” Adjective-Q-sort (Block, 1978) with the same Q-sort done for either mother or father. Defense identification was assessed from TAT stories using Cramer’s (1991a) Defense Mechanism Manual. Marcia’s (1996, 1980) categories of identity status were determined from Mallory’s (1989) prototypes based on the California Adult Q-sort (Block, 1961/1978). The results indicated that the four identity statuses are differentially predicted by parent identification, by defense identification, and by an interaction between the two types of identification. Further, the nature of these relations differs by gender. Caution should be used in applying these findings to other populations.

The Unconscious Status of Defense Mechanisms
Phebe Cramer, Professor of Psychology

American Psychologist, 56, 762-763 (2001)

Responds to L. S. Newman’s and M. H. Erdelyi’s comments (see records 2001-18061-011 and 2001-18061-012, respectively) on the P. Cramer article (see record 2000-15774-007). The author maintains that to consciously and intentionally modify one’s thinking, affect, or behavior (i.e., to cope) so as to manage a stressful situation is an inherently different process than the unintentional cognitive distortion that occurs on an unconscious level when a defense mechanism is used. Furthermore, it is argued that the features of being unconscious and unintentional are critical for defining the defense mechanism and for differentiating this process from other methods of adaptation.

Defense Mechanisms, Behavior and Affect in Young Adulthood
Phebe Cramer, Professor of Psychology

Journal of Personality, 70, 103-126 (2002)

The relationship between defense mechanism use, observed behavior, and affect was investigated in a sample of 91 young adults. Defense mechanisms were assessed using Cramer’s (1991a) Defense Mechanism Manual for TAT stories; behavior was based on observer Q-sort ratings (Block, 1978). The findings show that men and women who rely on the immature defense of denial at age 23 show multiple signs of behavioral immaturity, as well as anxiety. In contrast, extensive use of projection was related to a suspicious, hyperalert personality style, including anxiety and depression, in men, but to a sociable, nonwary, nondepressed style in women. The use of the mature defense of identification, by women, was related to behavior characterized by maturity, social competence, and the absence of depressive symptoms.

Defense Mechanisms
Phebe Cramer, Professor of Psychology

The Freud Encyclopedia: Theory, Therapy, and Culture, 139-141 (2002)

Denial
Phebe Cramer, Professor of Psychology

The Freud Encyclopedia: Theory, Therapy, and Culture, 141-143 (2002)

Projection
Phebe Cramer, Professor of Psychology

The Freud Encyclopedia: Theory, Therapy, and Culture, 426-427 (2002)

The Study of Defense Mechanisms: Gender Implications
Phebe Cramer, Professor of Psychology

In The Psychodynamics of Gender and Gender Role.(2002)

Maintaining One's Self-Image vis-à-vis Others: The Role of Self-Affirmation in the Social Evaluation of the Self
Steven J. Spencer, Steven Fein, & Christine D. Lomore

Motivation and Emotion, 25: 41-65 (2001)

Three studies examined how people maintain their self-images when they face threat to interpersonal aspects of the self. In Studies 1 and 2, the authors found evidence that low self-esteem people lower their estimates of their performance when they expect immediate feedback in order to protect themselves from the interpersonal threat inherent in such feedback, and that self-affirmation reduces this tendency among low self-esteem people. In Study 3, the authors found that when people are self-affirmed they are more likely to engage in upward social comparisons and less likely to engage in downward social comparisons. Together these findings suggest that people can cope with threats to interpersonal aspects of the self by affirming other important aspects of the self.

Reduced Primary Antibody Responses in a Genetic Animal Model of Depression.
E.M. Friedman, Assistant Professor of Psychology, K.A. Becker, D.H. Overstreet, & D.A. Lawrence

Psychosomatic Medicine, 64: 267-273 (2002)

Objective: Clinical depression is associated with multiple abnormalities of immune function including reduced virus-specific responses. This study tested the hypothesis that the Flinders Sensitive Line (FSL) rat, a promising genetic animal model of depression, would exhibit reductions in antigen-specific primary antibody responses to immunization. Methods: FSL (n = 13) and control Flinders Resistant Line (FRL; n = 14) rats were immunized with the protein antigen keyhole limpet hemocyanin (KLH; 300 mg/ml), and KLH-specific IgM, IgG, IgG1, and IgG2a responses were measured before and 3, 5, 7, 11, and 14 days after immunization. In separate experiments, production of interferon-g (IFN-g) by cells from naïve and KLH-immunized animals was measured in vitro in order to determine whether strain differences in antibody production might be associated with differential production of this regulatory cytokine. Results: KLH-specific production of IgM (p<.01) and IgG2a (p<.05) were significantly reduced in the FSL rats compared to the FRL controls. There were no strain differences in IgG or IgG1 production. While IFN-g production between the two strains was similar in naïve animals, cells from KLH-immunized FSL rats produced significantly less IFN-g when stimulated with KLH in vitro than cells from KLH-immunized FRL controls (p=.01). Conclusions: This study extends previous reports of altered immune function in the FSL rats to include reduced in vivo antigen-specific antibody responses. Moreover, diminished production of IFN-g by KLH-primed lymphocytes may contribute to lower antibody production in these animals. Collectively, these data suggest deficiencies in type 1 T helper cell-mediated immunity in the FSL rats.

Environmental Stress Mediates Changes in Neuroimmunological Interactions
Elliot M. Friedman, Assistant Professor of Psychology & David A. Lawrence

Toxicological Sciences, 67: 4-10 (2002)

Combinations of environmental stress coordinately increase toxicological assaults on health, dependent on the genetics of the exposed organism. Multiple gene variances between individuals influence the risks associated with environmental exposures, and environmental stress presents in multiple forms including chemical, physical, and psychological stresses. Combined chemical, physical, and psychological stresses are suggested as exacerbating the initiation and/or duration of illnesses, and many of the detrimental outcomes on health are posited to relate to changes in neuroendocrine immune circuitry. However, most human epidemiological or experimental animal studies have not considered the combination of chemical, physical, and psychological stress on health status. Current consideration is being given to “real world” exposures for assessment of health risk, but this mainly relates to evaluation of chemical mixtures. In addition to concomitant chemical exposures having agonistic and/or antagonistic interactions, the physical and psychological status of the individual can influence exposure outcomes. An individual’s psychosocial environment is likely to be important in epidemiological investigations. Neuroimmunology is a burgeoning discipline, and neurotoxicology and immunotoxicology studies should consider the bidirectional regulatory mechanisms between these organ systems and the potential long-term influences of psychological stress. This mini-review discusses some intriguing data from animal and human studies, which address the regulatory pathways between the neural, endocrine, and immune systems, with emphasis on psychological stress.

Observing Couples’ Interaction: Integrative Analysis of Interpersonal Control, Cognitive Constructions, and Emotional Impact
Valentin Escudero, Laurie Heatherington, Professor of Psychology, Myrna L. Friedlander

Metodologia de las Ciencias del Comportamiento, 3, 247-265 [2001]

This paper presents a methodology, and a single case study as illustration, for the observational study of couple interaction from an integrative, multi-systemic perspective. From a systemic perspective, couple interaction is a complex system of behavioral, affective, and cognitive components working simultaneously as stimuli and reactions in an evolving interpersonal system. For example, interpersonal behavior always has an emotional component because it implies reactions to others’ behavior; interpersonal behavior is also closely connected with cognitive constructions, as partners frequently have an “explanation” of their behavior and their partner’s behavior that influences their affect and their subsequent behavior. We present observational coding systems and a data analytic strategy for studying these three dimensions –behavioral, cognitive, and affective- over time, in relation to each other, and in relation to each other over time. An intensive study of one couple’s interaction over four time periods, drawn from a larger on-going study using data archived from the Denver Family Development Study is included as in illustration of the kinds of research questions that can be addressed using this strategy of observational research.

Eyewitness Researchers as Experts in Court: Responsive to Change in a Dynamic and Rational Process
Saul M. Kassin, Professor of Psychology, V.A. Tubb, H.M. Hosch, & A. Memon

American Psychologist, 57, 378-379 (2002)

Responds to the comments by M. L. McCullough (see record 2002-12932-018) on the original article (see record 2001-17140-001) which discussed eyewitness testimony. The current author states that McCullough's commentary rests on a foundation of assumptions that were both naive and erroneous.

Caregiver-Child Social Pretend Play: What Transpires?
Robert D. Kavanaugh, Professor of Psychology

In Pretending and Imagination in Animals and Children, R. W. Mitchell (ed.), (2002)

You Don’t Know Me, But I Know You: Asymmetric Assessment of Insight into Self and Other
E. Pronin, J. Kruger, Kenneth Savitsky, Assistant Professor of Psychology, and L. Ross

Journal of Personality and Social Psychology, 81, 639-656 (2001)

It is hypothesized that people show an asymmetry in assessing their own interpersonal and intrapersonal knowledge relative to that of their peers. Six studies suggested that people perceive their knowledge of their peers to surpass their peers’ knowledge of them. Several of the studies explored sources of this perceived asymmetry, especially the conviction that while observable behaviors (e.g., interpersonal revelations or idiosyncratic word completions) are more revealing of others than self, private thoughts and feelings are more revealing of self than others. Study 2 also found that college roommates believe they know themselves better than their peers know themselves. Study 6 showed that group members display a similar bias—they believe their groups know and understand relevant out-groups better than vice versa. The relevance of such illusions of asymmetric insight for interpersonal interaction and our understanding of “naïve realism” is discussed.

Brain Activation and Sexual Arousal in Healthy, Heterosexual Males
Bruce A. Arnow, John E. Desmond, Linda L. Banner, Gary H. Glover, Ari Solomon, Assistant Professor of Psychology, Mary Lake Polan, Tom F. Lue, and Scott W. Atlas

Brain, 125, 1014-1023 (2002)

Despite the brain’s central role in sexual function, little is known about relationships between brain activation and sexual response. In this study, we employed functional MRI (fMRI) to examine relationships between brain activation and sexual arousal in a group of young, healthy, heterosexual males. Each subject was exposed to two sequences of video material consisting of explicitly erotic (E), relaxing ® and sports (S) segments in an unpredictable order. Data on penile turgidity was collected using a custom-built pneumatic pressure cuff. Both traditional block analyses using contrasts between sexually arousing and non-arousing video clips and a regression using penile turgidity as the covariate of interest were performed. In both types of analyses, contrast images were computed for each subject and these images were subsequently used in a random effects analysis. Strong activations specifically associated with penile turgidity were observed in the right subinsular region including the claustrum, left caudate and putamen, right middle occipital/ middle temporal gyri, bilateral cingulate gyrus and right sensorimotor and pre-motor regions. Smaller, but significant activation was observed in the right hypothalamus. Few significant activations were found in the block analyses. Implications of the findings are discussed. Our study demonstrates the feasibility of examining brain activation/sexual response relationships in an fMRI environment and reveals a number of brain structures whose activation is time-locked to sexual arousal.

Social Isolation Stress During the Third Week of Life Has Age-Dependent Effects on Spacial Learning in Rats
Deborah F. Frisone‘00, Cheryl A Frye, Betty Zimmerberg, Professor of Psychology

Behavioural Brain Research, 128, 153-160 (2002)

Despite extensive research on the relationship between acute stress and hippocampal function in adults, little is known about the short- and long-term effects of prolonged juvenile stress on learning, memory, and other hippocampal function. This experiment investigated whether spatial learning would be altered in juvenile and adult rats previously exposed to a chronic stressor: 6h of social isolation (SI) daily at 15-21 days of age. SI was found to increase circulating plasma levels of corticosterone (CORT) and allopregnanolone (3-alpha, 5alphs-pregnan-20-one;3,5-THP) at 1 h after separation on the fourth day, indicating that the isolation was an effective stressor. When tested as juveniles (post-natal (PN) 22-24), spatial learning was impaired on the Morris water maze in the previously isolated subjects compared to non-isolated controls. However, when tested as adults (PN 92-94), subjects previously exposed to SI during the third week of life demonstrated more rapid learning of the task than controls. These results are discussed in light of research on the effects of CORT on the developing hippocampus.