FACULTY PUBLICATIONS

Williams College’s Hopkins Observatory:
The Oldest Extant Observatory in the United States

Pasachoff, Jay M., 1998

Journal of Astronomical History and Heritage, 1, (1), 61-78

A description of the history of astronomy at Williams and of its historic observatory.

Halley and his Maps of the Total Eclipses of 1715 and 1724

Pasachoff, Jay M., 1999

Astronomy & Geophysics (Royal Astronomical Society), 40, 18-22, April

Describes the pioneering work of Halley about predictions of the paths of the 1715 and 1724 total solar eclipses that crossed England, and relates to the total solar eclipse of August 11, 1999.

Halley as an Eclipse Pioneer: his Maps and Observations of the Total Solar Eclipses of 1715 and 1724

Pasachoff, Jay M., 1999

Journal of Astronomical History and Heritage, 2 (1), 39-54, June

In addition to the eclipse maps of Halley, describes the observations he made himself and those he collected about the 1715 eclipse, and relates them to the modern determinations of the size of the Sun.

Halley et Ses Cartes d’Eclipses Totales de 1715 et 1724

Pasachoff, Jay M., 1999

Ciel et Terre, 115, mars-avril, 51-56

Describes the Halley eclipse maps for a French-speaking audience, in advance of the August 11, 1999, total solar eclipse that will cross France.

Physics for Scientists and Engineers

Wolfson, Richard, and Pasachoff, Jay

Addison Wesley Longman, 3^rd edition

Physics for Scientists and Engineers (Extended with Modern Physics)

Wolfson, Richard, and Pasachoff, Jay

Addison Wesley Longman, 3^rd edition

Astronomy

Pasachoff, Jay

Addison-Wesley Longman, 1999 middle-school level

Sound and Light

Pasachoff, Jay

Addison-Wesley Longman, 1999 middle-school level

Morphology and Composition of the Helix Nebula

Henry, R. B. C., Kwitter, K. B., and Dufour, R. J.

Astrophysical Journal, June 1, 1999

We present new narrow-band filter imagery in H-alpha and [N II] »6584 along with UV and optical spectrophotometry measurements from 1200 A to 9600 A of NGC 7293, the Helix Nebula, a nearby, photogenic planetary nebula of large diameter and low surface brightness. Detailed models of the observable ionized nebula support the recent claim that the Helix is actually a flattened disk whose thickness is roughly one-third its diameter with an inner region containing hot, highly ionized gas which is generally invisible in narrow-band images. The outer visible ring structure is of lower ionization and temperature and is brighter because of thickening in the disk. We also confirm a central star effective temperature and luminosity of 120,000 K and 100 L₀ and we estimate a lower limit to the nebular mass to be 0.30 M₀. Abundance measurements indicate the following values: He/H=0.12 (±0.017), O/H=4.60x10^-4(±0.18), C/O=0.87(±0.12), N/O=0.54(±0.14), Ne/O=0.33(±0.04), S/O=3.22x10^-3(±0.26), and Ar/O=6.74x10^-3(±0.76). Our carbon abundance measurements represent the first of their kind for the Helix Nebula. The S/O ratio which we derive is low; such values are found only in a few other planetary nebulae. The central star properties, the super-solar values of He/H and N/O, and a solar level of C/O are consistent with a 6.5M₀ progenitor which underwent three phases of dredge-up and hot bottom burning before forming the planetary nebula.

Atmosphere & Weather

Kwitter, K. B., and Souza, S. P.

J. Weston Walch, Publisher, 1998

This book and the two below are hands-on activity books for middle school students.

Force & Motion

Souza, S. P. and Kwitter, K. B.

J. Weston Walch, Publisher, 1999 middle-school level

The Solar System

Souza, S. P., and Kwitter, K. B.

J. Weston Walch, Publisher, 1999 middle-school level

PGAM-M Expression is Regulated Pre-Translationally in Hindlimb
Muscles and under Altered Loading Conditions

R. Kell ‘97, H. Pierce ‘97 and Steven J. Swoap, Assistant Professor of Biology

J. Appl. Physiol., 86, 236-242(1999)

Enzymatic activity from the muscle-specific isoform of phosphoglycerate mutase (PGAM-M) is higher within glycolytic skeletal muscles than in oxidative muscles. The hypothesis that PGAM-M is regulated pre-translationally among muscles of the hindlimb was tested using enzymatic assays, western blots, and northern blots. We further investigated the regulatory level(s) at which PGAM-M gene expression is controlled during hindlimb unweighting. PGAM-M mRNA and immunoreactive protein levels were 4 fold lower in the rat soleus than in the tibialis anterior (TA), plantaris, and extensor digitorum longus muscles. Four weeks of unweighting induced a 2.5 fold increase in PGAM enzymatic activity within the soleus; a 1.8 fold increase in PGAM-M immunoreactivity; and a 3.5 fold increase in PGAM-M mRNA. To examine potential transcriptional regulatory mechanisms, the proximal 400 base pairs of the rat PGAM-M promoter were linked to a firefly luciferase and injected into normal and unweighted TA and soleus muscles. Firefly luciferase activity was elevated 2-3 fold in both the TA and the unweighted soleus over the normal soleus. These data suggest that PGAM-M expression is pre-translationally regulated among muscle types and within unweighted slow muscle. Further, the proximal 400 bp of the PGAM-M promoter contains cis-acting sequences to allow both muscle type specific expression of a reporter gene and responsiveness to soleus muscle unweighting.

An E-box within the MHC IIB Gene is Bound by MyoD and is Required for
Gene Expression in Fast Muscle

M. Wheeler ‘98, E.C. Snyder ‘99, M. Patterson, and S. Swoap, Assistant Professor of Biology

Am. J. Physiol, 276, C1069-C1078 (1999)

The myosin heavy chain IIB (MHC IIB) gene is selectively expressed in skeletal muscles, imparting fast contractile kinetics. Why the MHC IIB gene product is expressed in muscles like the tibialis anterior (TA) and not expressed in muscles like the soleus is currently unclear. It is shown here that the mutation of an E-box within the MHC IIB promoter decreased reporter gene activity in the fast-twitch TA muscle 90-fold as compared to the wild type promoter. Reporter gene expression within the TA required this E-box for activation of a heterologous construct containing upstream regulatory regions of the MHC IIB promoter linked to the basal Hsp-70 TATA promoter. Electrophoretic mobility shift assays demonstrated that mutation of the E-box prevented the binding of both MyoD and myogenin to this element. In co-transfected C2C12 myotubes and HepG2 cells, MyoD preferentially activated the MHC IIB promoter in an E-box dependent manner, whereas myogenin activated the MHC IIB promoter to a lesser extent, and in an E-box independent manner. A time course analysis of hindlimb suspension demonstrated that the unweighted soleus muscle activated expression of MyoD mRNA prior to the de novo expression of MHC IIB mRNA. These data suggest a possible causative role for MyoD in the observed upregulation of MHC IIB in the unweighted soleus muscle.

Changes in Adult Zebra Finch Song Require a Forebrain Nucleus That Is Not
Necessary for Song Production

Heather Williams, Associate Professor of Biology, Heil Mehta ‘95

J. Neurobiol., 39, 14-28 (1999)

Male zebra finches normally crystallize song at approximately 90 days and do not show vocal plasticity as adults. However, changes to adult song do occur after unilateral tracheosyringeal (ts) nerve injury, which denervates one side of the vocal organ. We examined the effect of placing bilateral lesions in LMAN (a nucleus required for song development but not for song maintenance in adults) upon the song plasticity that is induced by ts nerve injury in adults. The songs of birds that received bilateral lesions within LMAN followed by right ts nerve injury silenced, on average, 0.25 syllables, and added 0.125 syllables (for an average turnover of 0.375 syllables), and changed neither the frequency with which individual syllables occurred within songs nor the motif types they used most often. In contrast, the songs of birds that received sham lesions followed by ts nerve injury lost, on average, 1.625 syllables, silenced .125 syllables, and added .75 syllables - turning over an average of 2.5 syllables. They also significantly changed both the frequency with which individual syllables were included in songs and the motif variants used. Thus song plasticity induced in adult zebra finches with crystallized songs requires the presence of LMAN, a nucleus which had been thought to play a role in vocal production only during song learning. Although the changes to adult songs induced by nerve transection are more limited than those that arise during song development, the same circuitry appears to underlie both types of plasticity.

Decrease in Occurrence of Fast Startle Responses after Selective
Mauthner Cell Ablation in Goldfish (Carassius auratus)

Steven J. Zottoli, Professor of Biology, B. Newman ‘95, H. Reiff ‘95 and C. Winters ‘95

J. Comp. Physiol A, 184, 207-218 (1999)

A single action potential in one of a pair of reticulospinal neurons, the Mauthner cells, precedes a short-latency electromyographic response of the trunk and tail musculature on the opposite side of the body and a fast startle response in goldfish. It has been postulated that not only the Mauthner cell, but also an array of neurons can trigger or participate in fast startle responses (Eaton et al 1991). We have selectively ablated the Mauthner cells in goldfish to study how neurons of the brainstem fast startle response network interact. The probability of eliciting a fast startle response was significantly less in fish with double Mauthner cell ablations, as compared to the responsiveness of control fish. The finding that there is a significant decrease in the occurrence of fast startle responses in animals with no Mauthner cells, implies that the Mauthner cell may play a role in triggering the involvement of the other network elements in fast startle responses. We hypothesize that Mauthner cell activation may be important in bringing those reticulospinal neurons that are “primed” by the behavioral context to threshold and provides the basis for studies focused on the interactive nature of the brainstem startle response network.

Adiabatic Ionization Potential and Electron Affinity of Formaldehyde

Joseph S. Francisco, Sterling Brown Visiting Professor of Chemistry, and
John W. Thoman, Jr., Associate Professor of Chemistry

Chemical Physics Letters, 300, 553-560, 1999.

The adiabatic ionization potential and electron affinity for CH₂O have been calculated using high levels of ab initio molecular orbital theory. Harmonic vibrational frequencies and zero-point energies have also been predicted. At the CCSD(T)/6-311++G(3df,3pd) level of theory, the adiabatic ionization potential is calculated as 10.82 eV as compared to the experimental literature value of 10.8887 ± 0.0030 eV. The electron affinity is calculated to be – 0.96 eV, compared to the experimental literature value of – 0.65 eV.

An FTIR Study of the Adsorption of SO₂ on n-Hexane and Soot from -130° to -40°C

Birgit G. Koehler, Assistant Professor of Chemistry, Victoria T. Nicholson ‘98, Henry G. Roe ‘97, and Erin S. Whitney ‘96

Geophys. Res.-Atmos., 104, 5507-5514, 1999.

This paper focuses on the uptake of SO₂ on soot at temperatures below room temperature. Oxidation on soot may provide a mechanism for the oxidation of atmospheric SO₂ under conditions when the standard gas-phase and aqueous-phase mechanisms cannot explain the rapid rate of H₂SO₄ production. An understanding of the uptake of SO₂ under dry conditions provides a useful step toward understanding the uptake and oxidation of SO₂ on soot under wet conditions. We find that rapid, reversible SO₂ adsorption on soot occurs within a few seconds, presumably by adsorption on the outer surfaces of the spherical soot particles. Subsequently, uptake continues slowly for over an hour, presumably by diffusion into micropores within the soot particles. We focused only on the rapid adsorption. An isothermal analysis of rapid SO₂ uptake revealed that a small fraction (<1%) of adsorption sites have a strong binding affinity (”H_des= 42±4 kJ/mol), while the majority of adsorption sites bind SO₂ more weakly (26±4 kJ/mol). The lower-limit saturation coverage of SO₂ on soot is 0.3 monolayer, but the more likely value is 0.7 monolayer. The uptake coefficient is 0.002 (plus or minus factor of 2) at low coverages.

Infrared Carbonyl Frequencies of Heterocyclic Lactones

J. Hodge Markgraf, Professor of Chemistry emeritus

Heterocycles, 47, 559-624, 1998.

Infrared carbonyl frequencies of 756 heterocyclic lactones are tabulated on the basis of ring size, number and position of heteroatoms, substituents, unsaturation, and solvent effects.

Kinetic Isotope Effects in the Chromium (VI) Oxidation of Bicyclic Alcohols

J. Hodge Markgraf, Professor of Chemistry emeritus, Jordan S. Dubow ‘99,

Jessica A. Charland ‘98, and Elliott H. Sohn ‘98

Journal of Chemical Research (Synopsis), 146-147, 1999.

Pseudo first-order rate constants were determined for the oxidation of a series of secondary alcohols and their monodeuterated analogues by ammonium chromate in aqueous acidic solution at several temperatures. The relative rates and activation parameters were consistent with a cyclic, symmetrical transition state.

Oxidation of Benzyl Ethers via Phase Transfer Catalysis

J. Hodge Markgraf, Professor of Chemistry emeritus, and Bo Yoon Choi ‘98

Synthetic Communications, 29, 2405-2411, 1999.

A convenient procedure for the oxidation of benzyl ethers to benzoate esters was reported for nine compounds. Potassium permanganate in dichloromethane with phase transfer catalysis by triethylbenzylammonium chloride afforded products regiospecifically in fair to excellent yields.

Oxidation of Benzyl Ethers via Phase Transfer Catalysis

J. Hodge Markgraf, Professor of Chemistry emeritus, and Bo Yoon Choi ‘98

Synthetic Communications, 29, 2405-2411, 1999.

A convenient procedure for the oxidation of benzyl ethers to benzoate esters was reported for nine compounds. Potassium permanganate in dichloromethane with phase transfer catalysis by triethylbenzylammonium chloride afforded products regiospecifically in fair to excellent yields.

A Statically Safe Alternative to Virtual Types

Kim B. Bruce, Professor of Computer Science, Philip Wadler, Bell Laboratories, and
Martin Odersky, University of South Australia

Proceedings of ECOOP ‘98 (European Conference on Object-Oriented Programming), LNCS 1445, pp. 523-549.

Recent years have seen the development of several foundational models for statically typed object-oriented programming, but despite their intuitive similarity, differences in the technical machinery used to formulate the various proposals have made them difficult to compare. Parametric types and virtual types have recently been proposed as extensions to Java to support genericity. In this paper we investigate the strengths and weaknesses of each. We suggest a variant of virtual types that has similar expressiveness, but supports safe static type checking. This results in a language in which both parametric types and virtual types are well integrated, and which is statically type-safe.

Formal Semantics and Interpreters in a Principles of Programming Languages Course

Kim B. Bruce, Professor of Computer Science

Proceedings of SIGCSE ‘99 (Computer Science Education), pp. 331-335.

Most junior-senior level programming languages courses approach the subject either from the point-of-view of principles (concepts) of programming languages or from the perspective of understanding languages through writing progressively more complex interpreters. In this paper we show how to use formal semantics in a series of interpreter assignments in a principles or concepts-based course. The interpreter assignments make the semantics more concrete for students while providing a deeper understanding of concepts.

Predicting the Future: AI Approaches to Time-Series Problems

Andrea Danyluk, Assistant Professor of Computer Science

Tom Fawcett and Foster Provost, Bell Atlantic Science and Technology

American Association for Artificial Intelligence Technical Report WS-98-07, 92 pp. (1998)

This volume contains a compilation of edited papers presented at the workshop on Time-Series Analysis held in Madison, Wisconsin in July 1998.

Predicting the Future: AI Approaches to Time-Series Problems
(A Report on the 1998 Workshop)

Andrea Danyluk, Assistant Professor of Computer Science

Tom Fawcett and Foster Provost, Bell Atlantic Science and Technology

AI Magazine, 20(1), 124 (1999)

The Workshop on AI Approaches to Time-Series Problems, jointly sponsored by the Fifteenth National Conference on Artificial Intelligence (AAAI-98) and the International Conference on Machine Learning (ICML-98), was held in Madison, Wisconsin, on 27 July 1998. The organizing committee consisted of Andrea Danyluk of Williams College, and Tom Fawcett and Foster Provost, both of Bell Atlantic Science and Technology. There were approximately 30 attendees.

The goal of the workshop was to bring together AI researchers who study time-series problems along with practitioners and researchers from related fields. These problems are of particular interest because of the large number of high-profile applications today that include historical time series (for example, prediction of market trends, crisis monitoring). The focus was primarily on machine-learning and data-mining approaches, but perspectives on statistical time-series analysis and state-space analysis (for example, work on hidden Markov models) were also included.

Oxygen Isotope Fractionation between Diatomaceous Silica and Water

Mark E. Brandriss, Research Associate, et al.

Geochimica et Cosmochimica Acta, 62 (7), 1119-1125 (1998)

The temperature dependence of the oxygen isotope fractionation between diatomaceous silica and water was determined by analyzing frustules of freshwater diatoms cultured in the laboratory at temperatures ranging from 3.6 to 20.0^oC. Within the limits of experimental reproducibility, measured oxygen isotope fractionations were independent of species and of the isotopic composition of the water. The fractionation varied regularly with temperature according to the equation 10001n±_{(silica-water)} = 15.56 (10³T^-1) – 20.92. This relation corresponds to a temperature coefficient of roughly 0.2‰ per ^oC, significantly lower than published coefficients estimated from analyses of fossil diatoms from sediments and from extrapolation of experimentally determined quartz-water fractionations to low temperatures. The magnitude of the fractionation at a given temperature was 3-8‰ lower than previously published fractionations that were determined from analyses of fossil diatoms and from experimental data for quartz. The discrepancies between the new results and those of previous studies are attributed mainly to intrinsic differences in the oxygen isotope characteristics of fresh and fossil diatoms. Fresh diatomaceous silica appears to have an isotopically anomalous surficial layer containing large amounts of readily exchangeable, relatively low-¹⁸O oxygen, including abundant oxygen in hydroxyl groups, with the result that partial dissolution or diagenesis may systematically shift the ´¹⁸O values of fossil diatom frustules to higher values by removing this relatively unstable surficial material. If the effects of partial dissolution and diagenesis are regular or predictable, then the temperature information recorded during diatom growth may prove useful for paleoclimate studies.

Dynamics of Marine Transgression onto a Non-Linear Shoreline:
The Middle Cambrian Flathead Sandstone, Clarks Fork Valley, Wyoming

Robin A. Beebee ‘97
Rónadh Cox, Assistant Professor of Geosciences

The Mountain Geologist, 35, 55-64 (1998)

The Flathead Sandstone of northwestern Wyoming and Montana is a quartz-rich sheet sandstone overlying the Archean igneous and metamorphic basement rocks of the area. It represents the first cycle of deposition as the Cambrian Sea transgressed over the craton, and is Middle Cambrian in age. Little detailed work has been done on the Flathead Sandstone, and its provenance and environment of deposition are poorly understood.

Petrographic analysis and stratigraphic evidence are used to distinguish the various marine and continental environments present during deposition of the formation in the Clarks Fork area. Point-count data indicate a craton interior provenance with some evidence for basement uplift. The composition of the sandstone is consistent with derivation from the underlying granitic rocks. However, a portion of the samples contains grains of chert and metamorphic quartz, suggesting contribution from an older sedimentary and/or metamorphic source.

Internal structures, textures, and mineralogic composition point to both marine and fluvial facies in the Flathead Sandstone. Fluvial facies are distinguished by pebble lag deposits, submature textures, and feldspathic composition. Structures evident within the fluvial facies are trough cross-stratification, cut-and-fill structures, and thin horizontal bedding. Marine facies are on average medium-grained, texturally mature quartz arenites, some of which display horizontal feeding traces or vertical burrows. Sedimentary structures include thick horizontal bedding, low-angle planar and trough cross-bedding, and hummocky cross-stratification.

The interlayering of marine and terrigenous deposits in the Clarks Fork area indicates that on a local scale many factors cause departures from the ideal transgressive sequence. Sediment flux resulting from tropical storms and aggravated by the unvegetated nature of the Paleozoic craton, as well as relief on the nonconformity, contributed to a complex and dynamic shelf and shoreline during the Middle Cambrian.

Sedimentology, Geochronology and Provenance of the Proterozoic Itremo Group,
Central Madagascar, and Implications for Pre-Gondwana Paleogeography

Rónadh Cox, Assistant Professor of Geosciences
Richard A. Armstrong, Australian National University
Lewis D. Ashwal, Rand Afrikaans University

Journal of the Geological Society of London, 155, 1009-1024 (1998)

Proterozoic metasediments of the Itremo Group in central Madagascar probably represent a passive margin sequence predating Gondwana assembly. The quartzites are well-sorted quartz arenites that contain flat lamination, wave ripples, current ripple cross-lamination, and dune cross bedding. The carbonate rocks preserve abundant stromatolites and algal laminates. A continental source is indicated by mudrock major and trace element chemistry. The combination of lithologic association, sediment architecture, and mudrock chemistry indicates that the sequence was deposited on a continental shelf or platform.

SHRIMP data from detrital zircons indicate that the source area included early Proterozoic and late Archean rocks with ages between 1.85 and 2.69 Ga, and that the depositional age of the Itremo Group must be less than 1855 ± 11 Ma. The sequence has been deformed into a series of large-scale folds separated by ductile shear zones. SHRIMP data indicate both massive lead loss from detrital zircons and new zircon growth in the metasediments at 833 ± 112 Ma, which we interpret as the age of metamorphism of the sequence. Comparison of detrital grain ages with basement ages in East Africa and in India indicates that the source area for the Itremo Group probably lay on the present African mainland.

A Diagenetic Origin for Quartz-Cobble Conglomerates

Rónadh Cox, Assistant Professor of Geosciences
Ethan D. Gutmann ‘99

Geological Society of America Abstracts with Programs, 30, A194 (1998)

Quartz-cobble conglomerates, in which essentially all clasts consist of vein quartz, chert or quartzite, are common in the geologic record. They are generally explained by either intense chemical weathering or mechanical abrasion or recycling of older conglomerates. We propose that in some cases, quartz cobble conglomerates may result from diagenetic removal of less-resistant lithologies. It is well known that sandstones can be heavily modified in the subsurface, and that many quartz arenites are diagenetic in origin. Observations of Precambrian conglomerates in the southwestern United States suggests that the anomalously high percentages of resistant lithic types in quartz cobble conglomerates may have a similar origin in some instances.

Conglomerates of the Proterozoic Deadman Quartzite and Del Rio Quartzite in Arizona show several features suggestive of extensive diagenetic modification. There is extensive development of phyllosilicate pseudomatrix indicating diagenetic breakdown of labile detrital components. Whole-rock chemical analyses show that the matrix contains significant amounts of the relatively insoluble oxides Al2O3, Fe2O3, and TiO2. In contrast, the soluble oxides are depleted: K2O is minor or absent, and CaO and Na2O are generally not present in measurable amounts. There is abundant petrographic evidence for pressure solution, and in some cases there are well-developed stylolites. All of these lines of evidence indicate that these rocks have experienced large-scale diagenetic mass-transfer of material.

Evolution of Mudrock Chemistry and its Relationship to the
Development of Continental Crust

Rónadh Cox, Assistant Professor of Geosciences
Eliza Nemser ‘98

Geological Society of America Abstracts with Programs, 30, A345 (1998)

Compilation from the literature of trace element data for mudrocks indicates that average Th/Sc and La/Sc values increased and Eu/Eu* values decreased progressively through the Archean and post-Archean, with no sharp compositional shifts at the Archean-Proterozoic boundary. Archean mudrocks from quartzite-pelite stratigraphic sequences (continental settings) have similar average trace-element compositions to those from greenstone sequences (non-cratonic settings). However, compositions of mudrocks from cratonic and non-cratonic settings evolve differently through time. Eu/Eu* values decline for both continental and active margin mudrocks, but the rate of change is significantly greater for mudrocks from active margin settings. In addition, average Th/Sc and La/Sc values increase in younger continental mudrocks, but there is no statistically significant change in these ratios for active margin mudrocks.

The increasing differences between the compositions of mudrocks from differing tectonic settings may be explained by increasing proportions of evolved granitic continental crust relative to juvenile crust exposed at the surface and by growth or amalgamation of large continental masses with stable interiors effectively isolated from their active edges.

The evolution of trace element ratios is non-linear. The rate of change of composition is greater for Archean and Early Proterozoic mudrocks, and decreases for younger rocks. Polynomial regression reveals that rates change in Mid Proterozoic to Late Proterozoic time. The major inflection point in the curve is in the 1.5-1.0 Ga time interval for all of the ratios examined, and seems to be close to 1.25 Ga in most cases. The rate change may reflect changes in the balance of tectonic processes, possibly indicating the onset of more effective sediment recycling in the Mid Proterozoic.

Quartzites of the Proterozoic Mazatzal Group, Arizona, Were Deposited as
Immature Sediments in a Tectonically Active Setting

Rónadh Cox, Assistant Professor of Geosciences
Jana Comstock ‘99

Geological Society of America Abstracts with Programs, 30, A291 (1998)

Proterozoic sediments of the Mazatzal Group in central Arizona stratigraphically overlie the 1.7 Ga Red Rock Rhyolite and postdate the major continental accretion events in the southwestern U.S. The sediments include quartzitic sandstones, conglomerates, and mudrocks with intercalated rhyolites. The volume of contemporaneous volcanic rocks indicates a tectonically active depositional setting, but the quartzites are petrologically mature, with framework grain populations overwhelmingly dominated by quartz. The quartz-rich compositions have generally been interpreted to reflect protracted reworking and/or derivation from quartz-rich source rocks including older Precambrian sediments and banded iron formations. The paradox of mature quartz arenite deposition synchronous with active volcanism has posed problems for tectonic interpretations. Recent work indicates that the Mazatzal Group quartzites are in fact diagenetic quartz arenites, and that their present-day framework grain populations are not representative of the composition of the sediment when it was deposited. Previous studies have reported that the Mazatzal Group quartzites contain substantial amounts of pseudomatrix material, but its provenance significance has not been addressed. Diagenetic pseudomatrix ranges from 2% to over 50% by volume, and averages 20%. These high values indicate that the sediments when they were deposited were not petrologically mature and that their current quartz-rich framework populations reflect diagenetic breakdown of the more labile detrital components. Chemical analyses show that the pseudomatrix is highly aluminous and also contains Fe2O3, K2O, and in some cases CaO and Na2O. Normative compositions, integrating petrography and chemistry, fall in the recycled orogen field on a Dickinson QFL plot. The restored compositions of the Mazatzal Group quartzites show that the original sediments contained substantial lithic and feldspathic material. The immature nature of the restored compositions and the association with coarse conglomerates indicate that the sediment was derived locally from uplifted regions. The Mazatzal Group may represent either syntectonic or post-orogenic molasse sedimentation associated with mid-Proterozoic continental accretion in the southwestern United States.

Geology of the Mazatzal Mountains, Central Arizona

Rónadh Cox, Assistant Professor of Geosciences
Clint Cowan, Carleton College
Paul Karabinos, Professor of Geosciences

Keck Research Symposium in Geology Proceedings, 12, 216-218 (1999)

The Arizona project was based in the Mazatzal Mountains and surrounding area. Field sites were in the Mazatzal Mountains, at Tonto Natural Bridge, and on the alluvial fan sediments between the Mazatzal Mountains and the Sierra Ancha. The area has a long and diverse geologic history that fueled a diverse set of junior projects. The Mazatzal Group is a series of quartzites, pelites, and associated rhyolitic flows and tuffs that were deposited in the waning stages of a major amalgamation of terranes and juvenile crustal material that formed the real estate of the southwestern United States, about between 1.7 and 1.65 Ga ago (Karlstrom and Bowring, 1991). These supracrustal rocks were deformed into a series of thrust sheets during the Mazatzal Orogeny at about 1.65 Ga. The Mazatzal Mountains as a physiographic feature were uplifted in the Tertiary and are surrounded by an apron of alluvial fan deposits that were produced in Pliocene and Pleistocene time, when the range-bounding faults were active.

Some students in the Arizona Project undertook sedimentologic and structural analysis of the Mazatzal Group to address questions about the tectonic setting in which the sediments were deposited; others looked at the young alluvial fan sediments in order to understand the unroofing history of the Proterozoic basement.

Latest Pleistocene Emergence and Repopulation History at Three Sites in the
Northern Puget Lowland, Washington

David P. Dethier, Professor of Geosciences
Taylor Schildgen ‘99

Geological Society of America Abstracts with Programs, 30, A386 (1998)

Sediment and organic remains at several sites in the northern Puget Lowland, Washington, record transitions from glaciomarine to shallow marine to terrestrial deposition and organic colonization as glacioisostatic rebound lifted the area above sea level between 13.5 and 12.3 14C years before present (ka). Pebbly glaciomarine diamict containing sparse shells (Clinocardium, Hiatella, and Balanus ) gives ages of about 13.5 ka in the eastern part of the area, between 13.2 and 12.9 ka in the San Juan Islands and about 12.7 ka to the north near Bellingham, charting retreat of individual ice lobes to the NW and NE. Sandy, shallow subtidal deposits containing locally abundant Saxidomus record widespread shallowing of marine water by 12.4± 0.2 ka at sites having present elevations as high as 30 m. One site indicates and several sites suggest that shallowing waters deepened at about 12.6 ka. Before 12.1 ka non-marine genera replaced marine molluscs, and deposition of fibrous peat began as several of these sites became coastal wetlands.

Organic remains are particularly abundant at a site (elev. 30 m) on San Juan Island >70 km from the nearest unglaciated area. Macrofossil remains in silty sand containing root casts include abundant non-marine molluscs (Gyraulus, Lymnaea, Planorbus) dated at 12.3 ka, as well as fragments of Mytilus and marine molluscs, suggesting that colonization of this coastal wetland occurred within a few centuries of its emergence from the sea. Oribatid mites, sparse beetle fragments (Haliplus leechi; indeterminate Carabidae, Chrysomelidae & Curculionidae) fish spines and vertebrae, seeds of wetland vegetation (Chara, Carex, Potamogeton) and ostracodes typical of a salt-marsh environment (R. Forester, pers. comm., 1998) are also present. Overlying fibrous peat is rich in seeds (Chara, Carex, Potamogeton, Zannichelia palustris, Scirpus) and contains sparse beetle fragments (Carabidae, Helophorus sp., Rhantus sp., Plateumaris sp., Curculionidae: two spp.). The distribution of radiocarbon ages, elevations, and depth relationships demonstrates that the record of emergence is complex and may include a sudden rise in local sea level. Colonization of the emerging postglacial landscape occurred rapidly between 48° and 49° N.

Diversification of Rocky-Shore Biotas through Geologic Time

Markes E. Johnson, Professor of Geosciences
B. Gudveig Baarli, Research Associate

Geobios, 32, 257-273 (1999)

Changes in biodiversity of rocky-shore ecosystems from the early Precambrian (3,500 Ma) to the last interglacial epoch (125 Ka) are summarized on the basis of the fossil record associated with geological unconformities that reflect coastal paleotopography. This analysis is derived from data reported in 130 published papers culled and updated from previous bibliographic reviews. Minimum total diversity of fossil and extant species treated herein is 655 species. The highest biodiversity from any single locality is a mollusk-dominated biota of 62 species from San Nicolas Island on the Pacific coast of North America dating from the last interglacial epoch. Diversification was affected by mass extinctions, as rocky-shore ecosystems expanded and contracted through a combination of species attributed to Archaic, Paleozoic, Mesozoic, and/or Modern biotas. Stromatolites dominated Precambrian rocky shores, but continued as the principal Archaic biota through to the Miocene. The Paleozoic rocky-shore biota is characterized by encrusting inarticulate brachiopods, tabulate corals, and polyplacophorans, as well as ichnofossils representative of boring sipunculid worms (ichnogenus Trypanites) and acrothoracican barnacles (ichnogenus Zapfella). Boring bivalves (ichnogenus Gastrochaenolites), encrusting bivalves (including oysters and rudists), scleractinian corals, and coralline red algae, as well as terebratulid brachiopods, are typical of an enhanced Mesozoic rocky-shore biota. The much expanded biodiversity of the Modern rocky-shore biota is demonstrated by clinging but mobile gastropods, fixed bivalves that adopted byssate and wedging habits, and by balanomorph barnacles.

Adaptive innovations played critical roles in the long-term colonization of rocky-shore substrates, but the primary force behind the expansion of rocky-shore ecosystems through geologic time was selective biotic displacement from offshore low-energy to onshore high-energy settings. Rocky coastlines subjected to strong and persistent wave shock are effective “safe places” where species living in the intertidal zone often find refuge from predators and other competitors. This thesis is tested by checking the offshore origins of successful rocky-shore groups including barnacles, bivalves, corals, and coralline red algae. Concepts of keystone species and ecological locking in ancient rocky-shore ecosystems are explored. Latitudinal gradients and other geographic relationships among Pleistocene rocky-shore groups are commensurate with the Recent record, but only vaguely apparent for groups dating from earlier periods such as the Cretaceous. Time intervals for which even the most rudimentary data on rocky-shore biotas are most sparse include the Paleocene, Triassic, and the Devonian.

Enigmatic Fossil Encrusting an Upper Ordovician Rocky Shore on Hudson Bay, Canada

Markes E. Johnson, Professor of Geosciences
Mu Xi-Nan, Nanjing Institute of Geology and Palaeontology
Rong Jia-Yu, Nanjing Institute of Geology and Palaeontology

Journal of Paleontology, 72, 927-932 (1998)

Storeacolumnella Hudsonensis is described as a new genus and species of encrusting, colonial organism that lived in an intertidal, rocky-shore environment. The fossil was discovered in the basal beds of the Upper Ordovician Port Nelson Formation at a coastal outcrop on Hudson Bay near Churchill, Manitoba. Showing some possible characteristics of sponges and other possible characteristics of calcaerous green algae, this matlike organism is considered nonetheless to have uncertain taxonomic affinities. It consists of cylinder-shaped columns, each with an internal system of star-shaped filaments or spicules as viewed in transverse section. The cylinders stand vertical in longitudinal section and are densely packed together to form a mat. The hard substrate to which the mat is attached consists of a boulder eroded from the Precambrian Churchill Quartzite. Maximum colony size observed in a single example exhibits a diameter of not less than 80 mm and maximum thickness of 5.85 mm.

Tectonic and Stratigraphic Development of the Connecticut Valley Trough in the
New England Appalachians

Paul Karabinos, Professor of Geosciences

Geological Society of America Abstracts with Programs, 30, A-191 (1998)

The Connecticut Valley Trough (CVT) is filled with a thick succession of Silurian and Devonian metasediments and minor metavolcanics. Hatch (1991) used graded beds to infer that rocks along the margins are younger than rocks in the core of the trough and that the boundaries are Acadian faults in contrast with the traditional interpretation of the belt as a synclinorium bounded by unconformities. Hepburn (1991) presented geochemical evidence from mafic volcanics indicating that the CVT formed as a rift basin. Karabinos et al. (1998) further suggested that the CVT formed as a back-arc basin between the Bronson Hill and Shelburne Falls arcs during the Silurian and Early Devonian. Many of the apparently conflicting stratigraphic and structural relationships in the CVT are readily explained by a new model in which deposition occurred at the same time as rifting. According to this model, the oldest rocks are in the core of the trough and preserved as the Waits River Formation and the coeval lower part of the Gile Mountain Formation, which is dominated by quartz-rich schist and quartzite. The carbonate rich beds of the Waits River Formation were derived from the craton to the west whereas the Gile Mountain Formation sediments were derived from the Bronson Hill arc to the east. The Standing Pond Volcanics commonly occur at or near the contact between these two lithologies but are also found within both. The middle part of the Gile Mountain Formation consists of interbedded quartzite and pelitic schist. It overlies the lower part of the Gile Mountain Formation and the Waits River Formation. Pelitic schist of the Northfield Formation and Meetinghouse Member of the Gile Mountain Formation form the upper part of this sedimentary sequence which formed as water depth increased. Syn-depositional faulting along the western border of the trough resulted in an unconformity where the youngest sediments are in contact with the underlying Cambrian and Ordovician rocks and a low-angle normal fault where older basin rocks are present along the contact. Dikes found in the Missisquoi Formation west of the CVT are geochemically identical to some flows of the Standing Pond Volcanics and were probably feeder dikes to the volcanics, now displaced by low-angle normal faulting.

Taconian Orogeny in the New England Appalachians:
Collision between Laurentia and the Shelburne Falls Arc: Reply

Paul Karabinos, Professor of Geosciences
Scott D. Samson, Syracuse University
J. Christopher Hepburn, Boston College
Heather M. Stoll, Universidad de Oviedo

Geology, 27 (4), 382 (1999)

Ratcliffe and others raise two issues central to the tectonics of the Taconian orogeny: the location and age of arc-related igneous rocks and the time of impact between Laurentia and the colliding arc. We presented evidence for arc-related igneous activity in western Massachusetts and southern Vermont ranging from 485 to 470 Ma, not 485 to 447 Ma as stated by Ratcliffe and others. The 447 + 3 Ma age cited by us is for a post-Taconian, within-plate granitic pluton that we used to constrain the age of Taconian deformation in western Massachusetts (Karabinos and Williamson, 1994). We contrasted our results with the younger ages of arc-related rocks (454 to 442 Ma) presented by Tucker and Robinson (1990) from central Massachusetts and southern New Hampshire directly across strike from our study area. We then went on to suggest that the older rocks formed above an east-dipping subduction zone preceding the Taconian orogeny (Shelburne Falls arc) and that the younger rocks formed above a west-dipping subduction zone after the orogeny (Bronson Hill arc). Space limitations prevented us from discussing all of the age data bearing on our model, leading Ratcliffe and others to express some concerns about regions north and south of our study area.

Our tectonic model explains existing data better than the model advocated by Ratcliffe and others in which one very long-lived arc formed continuously above an east-dipping subduction zone for 60 million years (496 to 436 Ma) i.e., before, during, and after the Taconian orogeny. Deformation and metamorphism of the Laurentian margin began by ca. 470 Ma, leading us to conclude that the oceanic lithosphere separating Laurentia and the colliding arc was completely subducted at this time. The Taconian orogeny reflects crustal convergence between Laurentia and this arc, which we identified as the Shelburne Falls arc. Renewed subduction of oceanic lithosphere is needed, however, to account for arc magmas formed from ca. 455 to 440 Ma. We maintain that the most straightforward way to explain the younger arc-related rocks is to propose a west-dipping subduction zone beneath the Laurentian margin, then buttressed by the newly accreted arc terrane. Such a subduction zone could have produced the Late Ordovician magmas in the Bronson Hill arc (coeval with cooling of metamorphic rocks to the west) and accommodated post-orogenic plate convergence between Laurentia and Iapetus. This proposed subduction zone is also consistent with evidence for Silurian back-arc rifting in the Connecticut Valley trough (Hepburn, 1991) and models of the Acadian orogeny (e.g. Bradley, 1983).

Proterozoic Geology of the Arkansas River Canyon, Colorado

Reinhard A. Wobus, Professor of Geosciences
Kate Wearn ‘98, and others

Geological Society of America Abstracts with Programs, 30 (7), A96 (1998)

Mapping, structural analysis, and geochemical sampling of Proterozoic rocks from north of Howard to east of Texas Creek in the Arkansas River canyon established similar geologic histories between the 1.7 Ga Salida and Wet Mountain terranes and were unable to locate evidence of a distinct boundary between these terranes. Rocks north of Howard at the western end of the canyon are low-amphibolite grade metabasalt, metatuff, and metasediments. The lack of deformation or partial melting is similar to Salida terrane rocks. Geochemistry of the metabasalts correlates well with Salida and southern Front Range amphibolites and supports an arc or back-arc setting. Magma-mingling occurs on a local scale. Further east, near Texas Creek, the rocks are extensively deformed, partially melted, and perforated by granitic plutons. However, the rocks show similar lithogies including amphibolite-grade bimodal volcanics and metasedimentary gneisses such as sillimanite-muscovite-biotite gneiss and cordierite schist. The latter unit contains large cordierite porphyroblasts which appear to have overgrown original bedding which was crenulated. An early penetrative deformation involved isoclinal folding and transposition. Foliation and axial surfaces strike E-W to SE-NW with N to NE dips. Locally, high-grade shear zones truncate these rocks and record oblique-slip displacement. Open folding about NE axes warped the regional foliation, possibly during the emplacement of 1.4 Ga plutons. Growth of randomly oriented minerals is interpreted to have accompanied this plutonism. Geochemical studies of the felsic metavolcanics revealed two groups of volcanics interlayered throughout the region from Howard to the northern Wet Mountains. Similar studies of metabasalt showed immature arc signatures nearly indistinguishable from Salida and Wet Mountain rocks. Thus, no distinct lithologies or structural zones were found to separate these terranes.

Late Silurian Volcanism in Coastal Maine: The Cranberry Island Series

Reinhard A. Wobus, Professor of Geosciences, et al.

Geological Society of America Bulletin, 111, 686-708 (1999)

The Cranberry Island series is a Silurian (424 ± 1 Ma) volcanic succession that crops out on three islands along the southeastern coast of Maine. It is part of the coastal Maine magmatic province and represents bimodal magmatism that occurred on a composite crustal block before or during accretion to Laurentia. The series consists of ~1.8 km of felsic pyroclastic rocks and felsic lava flows overlain by ~0.8 km of basaltic tuffs and basaltic lava flows. The lower and upper members of the Cranberry Island series are interpreted, respectively, as (1) felsic pyroclastic rocks and lavas erupted from a mingled felsic and mafic magma reservoir and (2) phreatomagmatic basaltic rocks overlain by effusive basaltic flows. Some of the basaltic inclusions hosted by the felsic pyroclastic rocks may be chilled magmatic enclaves, suggesting that droplets of basaltic magma were entrained by felsic magma prior to eruption. The compositionally layered plutons of the Cadillac Mountain intrusive complex to the north are likely candidates, in both age and composition, for the magma bodies from which the Cranberry Island series erupted. Mafic rocks of the Cranberry Island series do not show the enrichment in large ion lithophile elements and the depletion in high field strength elements diagnostic of subduction-related magmas. The bimodal character of magmatism, the lack of strong arc geochemical signature, and the rarity of andesites in the Cranberry Island series and throughout the coastal Maine volcanic belt argue against an origin in a compressional setting. Alternative settings for magmatism include (1) backarc extension, (2) crustal extension associated with large-scale transcurrent faulting, and (3) extension-related magmatism associated with rifting of the coastal Maine volcanic belt from another continental margin.

Igneous and Metamorphic Geology of Vinalhaven Island, Maine

Reinhard A. Wobus, Professor of Geosciences
David P. Hawkins, Colorado College
Robert A. Wiebe, Franklin and Marshall College

Keck Research Symposium in Geology, Proceedings, 12, 75-77 (1999)

The coastal plutonic rocks of Maine were originally named and described by Chapman (1962, 1968) as the Bays-of-Maine igneous complex. He recognized the bimodal character of the complex, the widespread evidence for mixing between highly contrasted magmas, and described the mafic plutons as large, sheet-like masses with overlying granitic material that collected beneath a country rock roof. Some of these mafic bodies are well layered and fractionated. Granitic bodies occur both as sheet-like masses and as subequant plutons with steep contacts. These plutonic rocks intrude a wide range of metasedimentary and metavolcanic rocks that belong to different fault-bounded, northeast-trending terranes with different stratigraphies and structural and metamorphic histories (Williams and Hatcher, 1982). The field relations of these plutons suggest that they post-date the main assembly of these lithotectonic terranes (Ludman, 1986). Hogan and Sinha (1989) emphasized the bimodal character of these plutons and suggested that at least some of the magmatism was related to rifting within a region of transtension in a transcurrent fault system.

This project examined the geology of Vinalhaven Island (Gastes, in press). The igneous 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. Two previous Keck projects in Maine have studied similar systems along the Maine coast (Cadillac Mountain and Gouldsboro complexes) and led to the publication of several papers.

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. Huge inclusions of metamorphosed country rock also occur near the base of the plutons. Two main varieties of granite, both with mafic enclaves, are widely exposed and were easily sampled in coastal sections, vast quarries, and glaciated exposures inland. The highest levels of the intrusion cut into fresh, weakly deformed basaltic and rhyolitic volcanics that may be co-genetic with the plutonic rocks.

The northwestern part of Vinalhaven is underlain by a remarkably well preserved sequence of Siluro-Devonian (?) volcanic, subvolcanic, and volcaniclastic rocks ranging in composition from basalt to rhyolite. The entire sequence has been gently folded into a basin-like structure, but regional metamorphic and other deformational effects are minimal so that primary structures and textures are still obvious.

Writing Natural History for Survival - 1820-1856:
The Case of Sarah Bowdich, Later Sarah Lee

Donald deB. Beaver

Archives of Natural History, 25:1 (1999): 19-31.

One of the more remarkable women in natural history in early nineteenth century Britain is Sarah Bowdich, later Mrs R. Lee. Mrs. Bowdich, among the earliest European women to visit tropical West Africa, was the first woman systematically to discover new species and genera of plants, and new species of fish. She published 20 books, many of them on natural history, among them the rare and beautiful Fresh Water Fishes of Great Britain, (1828-1838), and Taxidermy. For her contributions in natural history, she received a Civil List pension late in life. Although her entry in the Dictionary of National Biography shows her to have been well known to her contemporaries, today Mrs. Bowdich is all but invisible. Alternately traveler, collector, natural historian, illustrator, novelist, biographer, children’s author, mother, and wife, it seems that her achievements may have been too diffuse and widely spread, her identities too multiple, for history to grasp her memorable character. Of the many fascinating aspects of her life and career, this paper concentrates on how Mrs. Bowdich used her knowledge of natural history and of Africa to help maintain her family and standard of living.

Maximal Cusps, Collars and Systoles for Hyperbolic Surfaces

Colin Adams, Professor of Mathematics

Indiana University Mathematics Journal, 47, 2, 419-437, (1998)

It is proved that a maximal cusp in any orientable hyperbolic surface has area at least 4, with the lower bound of four realized only for a cusp in the three-punctured sphere. For a maximal cusp in any other hyperbolic surface with p punctures, it is shown that it has area at most 6|Ç (S) | - (P-1), and that there is a metric that realize this upper bound. Moreover, over all possible hyperbolic metrics, the area a of the maximal cusp takes on all values such that 4 < A 6|Ç (S) | - (P-1).

If S is a punctured orientable hyperbolic surface other than the thrice-punctured sphere, and if S is endowed with any complete hyperbolic metric, then it is proved that there exists a choice of a maximal set of cusps in the hyperbolic surface with total area greater than 5p/2 if p is even and 5p/2 + 3/2 if p is odd. These universal lower bounds lower bounds are best possible. Applications of these results to collars and systoles are included.

The Newest Inductee in the Number Hall of Fame

Colin Adams, Professor of Mathematics

Mathematics Magazine, 71, 5, 341-349, (1998)

The wards ceremony to induct the Gieseking Constant (the volume of an ideal regular hyperbolic tetrahedron) in the Number Hall of Fame, including basic background on hyperbolic geometry.

Simple Geodesics in Hyperbolic 3-Manifolds

Colin Adams, Professor of Mathematics

J. Hass, University of California, Davis

P. Scott, University of Michigan

Bulletin of the London Mathematical Society, 31, 81-86, (1999)

Among orientable hyperbolic 2-manifolds, the thrice-punctured sphere is the only example that contains no simple closed geodesics. We are interested in determining which hyperbolic 3-manifolds do and do not contain simple closed geodesics. We prove that the Fushsian group corresponding to the thrice-punctured sphere again generates the only example of a complete non-elementary hyperbolic 3-manifold such that it does not contain a simple geodesic. Moreover, we will prove that a hyperbolic 3-orbifold that is not obtained from a particular set of Fushsian groups will always contain a simple geodesic.

Isoperimetric Curves on Hyperbolic Surfaces

Colin Adams, Professor of Mathematics

Frank Morgan, Professor of Mathematics

Proceedings of the American Mathematical Society, 127, 5, 1347-1356, (1999)

Least-perimeter enclosures of prescribed area on hyperbolic surfaces are characterized.

Minimal Edge Piecewise Linear Knots

Jorge Calvo, Visiting Assistant Professor of Mathematics

Kenneth C. Millett, University of California, Santa Barbara

Ideal Knots, (Andrzej Stasiak, Vaevolod Katrich, and Louis Kauffman, eds.)

Series on Knots and Everything, 19, World Scientific, Singapore, 107-128, (1999)

Immiscible Fluid Clusters in R² and R³

Frank Morgan, Dennis Meenan (‘54) Centennial Professor of Mathematics

Mich. Math. J., 45, 441-450, (1998)

We prove that an energy-minimizing planar cluster of immiscible fluids consists of finitely many circular arcs meeting at finitely many points, as long as the interfacial energies satisfy strict triangle inequalities. For R³, we generalize soap bubble cluster regularity.

Math Chat

Frank Morgan, Dennis Meenan (‘54) Centennial Professor of Mathematics

MAA Web Page (www.maa.org) (first and third Thursday of each month, 1998)

Biweekly column with questions, answers, and prizes.

Wulff Clusters in R²

Frank Morgan, Dennis Meenan (‘54) Centennial Professor of Mathematics

Christopher French ‘95, Scott Greenleaf

J. Geom. Anal. 7, 593-611, (1999)

The first existence and regularity results on the cheapest way to enclose and separate planar regions of prescribed areas, where cost is given by a general norm Φ, thus generalizing the Wulff shape for enclosing a single region.

The Hexagonal Honeycomb Conjecture

Frank Morgan, Dennis Meenan (‘54) Centennial Professor of Mathematics

Trans. AMS, 351, 1753-1763, (1999)

Contrary to popular belief, it remains conjectural that the planar hexagonal honeycomb provides the least-perimeter way to enclose and separate infinitely many regions of unit area. We prove existence for two formulations of the problem. Many questions remain.

The Isoperimetric Problem on Surfaces

Frank Morgan, Dennis Meenan (‘54) Centennial Professor of Mathematics

Hugh Howards ‘92, Michael Hutchings

Amer. Math. Monthly, 106, 430-439, (1999)

A survey of old and new results, including a proof that horizontal circles provide the least-perimeter way to enclose given area in a paraboloid of revolution.

A Power Weakly Mixing Infinite Transformations

Cesar Silva, Professor of Mathematics

S. L. Day, B. R. Grivna, and E. P. McCartney ‘99

New York J. of Math, 5, 17-24, (1999)

This work constructs a transformation T on the infinite real line that preserves the usual Lebesgue measure such that it satisfies the following dynamical property: for all nonzero integers k₁,...k₂,...,k_r, the transformation T k₁, x . . . x T k_r is ergodic.

Effects of Confinement on Carrier Dynamics in InGaAs Heterostructures

Sarah Bolton, Assistant Professor of Physics, Gregg Sucha, Daniel Chemla,
D.L. Sivco and A.Y. Cho

Physical Review B 58, 16326 (1998)

To study the effects of confinement by quantum-well potential discontinuities on ultrafast carrier dynamics, we performed pump-broadband probe studies of a series of InGaAs quantum wells excited 30 meV above the band edge. Our measurements show that the rate of carrier thermalization is well width independent, however, the rate of carrier cooling to the band edge is strongly influenced by confinement. This influence has two separate physical origins. First, the dimensionality dependence of the density of states results in a larger proportion of thermalized electrons that can emit LO phonons in three dimensions than in two. Second, modification of the phonon density of states by the ionic mass discontinuity at the well boundaries may reduce the electron-LO-phonon coupling.

Effects of Cavity Topology on the Nonlinear Dynamics of
Additive-Pulse Mode-Locked Lasers:

G. Sucha, D.S. Chemla, and S.R. Bolton, Assistant Professor of Physics

Journal of the Optical Society of America, B 15, 2847 (1998)

We study the effect of cavity topology on the nonlinear dynamics of additive-pulse mode-locked (APM) lasers configured in the Fabry-Perot and Michelson geometries. In experiments the Fabry-Perot laser often exhibits such behaviors as period doubling and quasiperiodicity as the nonlinearity is increased, whereas the Michelson APM (M-APM) exhibits none of these effects. Numerical studies confirm that the M-APM appears to be more resistant to such behavior, and thus is more tolerant of excessive nonlinearity in the control cavity. Using the concepts of intensity- and phase-dependent two-beam and multiple-beam interference, we obtain a general empirical rule connecting cavity topology to pulse train instabilities for fast saturable absorber mode-locked lasers employing coupled cavities.

Pulse Resolved Measurements of Subharmonic Oscillations in a Kerr-lens
Mode-Locked Ti:Sapphire Laser

S.R. Bolton, Assistant Professor of Physics, R.A. Jenks ‘98, C.N. Elkinton ‘98, and Gregg Sucha

Journal of the Optical Society of America, B 16, 339 (1999)

We made pulse resolved observations of subharmonic oscillations in the pulse train of a Kerr lens model locked Ti:Sapphire laser. Pulse-resolved beam profiles demonstrate that these oscillations, which include period doubling as well as P3, P4, and quasi periodicity, are accompanied by spatial modulation of the beam. A pulse resolved autocorrelation technique, believed to be novel, is used to show that temporal pulse reshaping does not accompany these dynamics. The power dependence of subharmonic oscillation frequencies exhibits the frequency locking characteristic of nonlinear dynamics in systems of coupled oscillators.

Distribution Functions for Reversibly Self-assembling Spherocylinders

Eric M. Kramer and Judith Herzfeld

Physical Review E, 58, 5934-5947 (1998)

Avoidance Model for Soft Particles.
I: Charged Spheres and Rods in the Dilute Limit

Eric M. Kramer and Judith Herzfeld

Journal of Chemical Physics, 110, 8825-8834 (1999)

Measurement of the Electric Quadrupole Amplitude Within the 1283 nm 6P1/2 – 6P3/2
Transition in Atomic Thallium

P.K. Majumder and Leo L. Tsai ‘98

Physics Review A, 60, (to appear July 1999)

We have measured the ratio of the electric quadrupole (E2) to magnetic dipole (M1) transition amplitude within the 6P1/2 – 6P3/2 transition in atomic thallium. We find that c E2/M1 = 0.2387 (10) (38), where the first error is statistical and the second represents a combined systematic error. In addition to providing a stringent test of theoretical wavefunction calculations in thallium, accurate knowledge of this amplitude ratio is essential for existing and future measurements of parity nonconserving optical rotation on this same 1283 nm line in thallium.

Quantum Entanglement as a Quantifiable Resource

William K. Wootters, Professor of Physics

Phil. Trans. R. Soc. London A, 356, 1717-1731 (1998)

Quantum mechanical objects can exhibit correlations with one another that are fundamentally at odds with the paradigm of classical physics; one says that the objects are “entangled.” In the past few years, entanglement has come to be studied not only as a marvel of nature but also as a potential resource, particularly as a resource for certain unusual kinds of communication. This paper reviews two such uses of entanglement, called “teleportation” and “dense coding.” Teleportation is the direct, though not instantaneous, transfer of a quantum state from one object to another over a distance. Dense coding is the effective doubling of the information-carrying capacity of a quantum particle through prior entanglement with a particle at the receiving end. The final section of the paper presents various quantitative measures of entanglement and considers novel features that arise when entanglement is shared among three objects.

Quantum Nonlocality without Entanglement

William K. Wootters, Professor of Physics, et al.

Physical Review A, 59, 1070-1091 (1999)

We exhibit an orthogonal set of product states of two three-state particles that nevertheless cannot be reliably distinguished by a pair of separated observers ignorant of which of the states has been presented to them, even if the observers are allowed any sequence of local operations and classical communication. It is proved that there is a finite gap between the mutual information obtainable by a joint measurement on these states and a measurement in which only local actions are permitted. This result implies the existence of separable superoperators that cannot be implemented locally. A set of states is found involving three two-state particles that also appear to be nonmeasurable locally. These and other multipartite states are classified according to the entropy and entanglement costs of preparing and measuring them by local operations.

Defensiveness and Defense Mechanisms

Phebe Cramer

Journal of Personality, 66, 879-894 (1998)

This introduction to the Journal of Personality’s special issue on the topic defense mechanisms raises the question of why defenses have been largely overlooked in personality research. Although defenses were originally discussed in the context of psychopathology, for the past 60 years psychodynamically oriented psychologists have understood that defenses play an important part in normal psychological development. Recently, psychologists outside the field of personality have incorporated the ideas of unconscious mental process and of defenses into their research programs. In this issue, personality researchers discuss their ideas about defense mechanisms, organized around three topical areas: current conceptualizations of defense, the measurement of defense mechanisms, and the integration of defense mechanisms into personality research. The issue concludes with a commentary on these articles and provides suggestions for future work.

Coping and Defense Mechanisms: What’s the Difference?

Phebe Cramer

Journal of Personality, 66, 919-946 (1998)

Defense mechanisms and coping strategies are discussed as two different types of adaptational processes. They may be clearly differentiated on the basis of the psychological processes involved, but not on the basis of their relation to outcome measures. Criteria that critically differentiate between defense and coping processes include the conscious/unconscious status and the intentional /non-intentional nature of the processes. Criteria based on the dispositional or situational status of the process, and on the conceptualization of the processes as hierarchical, are found to be more a matter of emphasis than of critical difference. A criterion that attempts to differentiate between defense and coping processes on the basis of their relation to psychological or physical health is found to be without support once the bias in self-report outcome measures is recognized.

Future Directions for the Thematic Apperception Test

Phebe Cramer

Journal of Personality Assessment, 72, 74-92 (1999)

Emphasis on the narrative mode of thought offers new ideas about the interpretation of the Thematic Apperception Test (TAT). I discuss two new approaches to the TAT, based on psychodynamic concepts and sensitive to the narrative features of TAT stories. Research supporting these coding systems– assessing the level of object relations and assessing the use of defense mechanisms – has shown these measures to be reliable and valid. I discuss considerations of reliability and validity, as they apply to the TAT.

Stories Are Telling

Phebe Cramer

SPA Exchange, 8, 5-7 (1999)

The survival of an assessment method, such as the TAT, will depend on its demonstrated usefulness. It is up to us to decide, useful for what? If we let that decision be made by insurance companies, the TAT will likely fall into increasing disuse. If, however, we believe that our interests lie in understanding the complexities of human personality, the interwoven motives, goals, aspirations, and modes of self-deception, along with the internal representations of significant others and self, we may turn increasingly to the TAT as a source of valuable information.

Automatic Activation of Stereotypes: The Role of Self-Image

Threat Spencer, S. J., Fein, S., Wolfe, C. T., Fong, C., & Dunn, M. A.

Personality and Social Psychology Bulletin, 24, 1139-1152 (1998)

Does self-image threatening feedback make perceivers more likely to activate stereotypes when confronted by members of a minority groups? Participants in Study 1 saw an Asian-American or European-American woman for several minutes, and participants in Studies 2 and 3 were exposed to drawings of an African-American or European-American male face for fractions of a second. These experiments found no evidence of automatic stereotype activation when perceivers were cognitively busy and when they had not received negative feedback. When perceivers had received negative feedback, however, evidence of stereotype activation emerged even when perceivers were cognitively busy. The theoretical implications of these results for stereotype activation and the relationship of motivation, affect, and cognition are discussed.

To Stereotype or Not to Stereotype: Motivation and Stereotype Activation,
Application, and Inhibition

Fein, S., von Hippel, W. H., & Spencer, S. J.

Psychological Inquiry, 10, 49-54 (1999)

Clearly ‘tis nobler to harness one’s slings and arrows and refrain from taking arms against a sea of others through the use of negative stereotypes. That is not the question here. What is an important question is what role motivation can play in determining whether stereotypes are likely to be activated and applied. Just as Hamlet was on the brink of choosing whether to continue to be, or not to be, are we all faced frequently with the choice, often unknowingly, of whether we want to perceive others in stereotypic ways, and, in so doing, act upon that choice? Do our goals and needs moderate stereotype activation, application, and inhibition? We address these questions in the present article. We review converging evidence that suggests not only that people’s motivations can strongly influence these processes, but also that begin to suggest conditions in which motivation cannot overwhelm the influence of cognitive processes. At the very least, this research demonstrates that using motivational accounts as a heuristic in designing social-cognitive research can be fruitful. If some might argue that it is madness to try to find unambiguous evidence supporting the role of motivation in social cognition, we think that the present research shows that there is method in it.

Reduced Primary Antibody Responses in a Genetic Animal Model of Depression

Elliot Friedman, Kelly Becker ‘99

and D. Overstreet, University of North Carolina School of Medicine

Neuroimmunomodulation, 6,219 (1999)

The Flinders Sensitive Line (FSL) rat is a genetic animal model of human depression that has been shown to have a number of immunological abnormalities reminiscent of those reported in depressed patients. Recently, clinically depressed human subjects were shown to mount a diminished virus-specific cellular immune response to immunization against varicella zoster virus (Irwin et al., 1998). The aim of the present study was to determine whether the in vivo antibody response to primary immunization would be similarly impaired in FSL rats. FSL (n = 10) and control FRL (n = 8) rats were immunized intraperitoneally with keyhole limpet hemocyanin (KLH; 300 μg/kg), and blood samples were drawn from tail veins before and 3, 5, 7, 11, and 14 days after immunization. Serum samples were then analyzed for KLH-specific IgM and IgG antibody levels by enzyme-linked immunosorbent assay (ELISA). Statistical analyses showed that the FSL rats had significantly lower IgM responses than the FRL rats overall [F(1,16) = 5.17, p<.05) and that the differences between the strains were particularly marked after day 3 [F(5,80) = 4.48, p<.01]. In contrast, IgG responses were similar between the two strains at all time points. A second set of experiments focused on the IgG response. Since previous research suggested that processing of KLH may involve the IgG2a subtype more than the IgG1 subtype of IgG, we hypothesized that IgG2a levels specifically would be reduced in the FSL rats compared with control FRL animals. Samples from the above experiments were analyzed by ELISA for KLH-specific IgG1 and IgG2a levels. Statistical analyses showed a trend (p = 0.1) toward reduced IgG2a levels in the FSL rats and no differences in IgG1 levels between the two strains. Collectively, these data suggest that the FSL rats may be spontaneously less responsive to primary immunization than control animals; these results parallel clinical observations of impaired responses to immunization in depressed patients. Moreover, there is some suggestion from these data that specific populations of T cells involved in the primary antibody response (e.g. T-helper type-1 cells) may be altered in these animals.

Assessing Individual Family Members’ Constructions of Family Problems

Laurie Heatherington, Benjamin Johnson, Brown University
Linda E. Burke, Children’s Health Council Palo Alto, CA
Myrna L. Friedlander, SUNY at Albany, Rebecca M. Buchanan, University of Maryland
Deirdre M. Shaw, Allen Press

Family Process, 37, 167-187 (1998)

Much contemporary family therapy theory and practice takes into account clients’ cognitive constructions of their family problems. Recent calls for therapists to elicit and work with clients’ causal explanations and narratives parallel accumulating evidence in the social-clinical literature about the predictive importance of attributions in family relationships. In this article, we introduce the Constructions of Problems Scale (CPS), provide preliminary evidence of its reliability and validity, and suggest ways in which it can be used clinically to reveal new areas for questioning and to generate new ideas. The CPS is a brief questionnaire that can be used to create a profile of each individual family member’s private constructions. To complete the CPS, each family member writes a free-form narrative of the presenting problems and then rates his or her perceptions of the contributing causes. The CPS profiles can be used to compare the perspectives of different family members and to assess cognitive constructions at different points in treatment. We discuss its potential for these and other clinical uses.

When Another Stumbles: Gender and Self-Presentation to Vulnerable Others

Laurie Heatherington, Andrea B. Burns ‘98, and Timothy B. Gustafson ‘98

Sex Roles, 38, 889-899 (1998)

Pursuing answers to the twin questions of when and why women engage in “modest” self-presentation, this study examined the self-presentation of academic achievement in a college setting. Gender of the participants, gender of the partners, and vulnerability (concern over his/her low grades or not) of the partner were completely crossed. participants were 85 first-year students drawn from a college population that was 6% African-American, 9% Asian, 79% Euro-American, and 5% Latinola. They heard information about a partner’s academic record, and then were induced to predict their own grade point average, in a context in which they anticipated interacting closely with the partner on a joint task. Women’s grade point average predictions were lower than men’s, and particularly, so when the partner was vulnerable. Vulnerable male partners were particularly salient for women in both the grade point average predictions and self-report data; the nonvulnerable male partners were particularly salient for men. Results are discussed with reference to self-in-relation and social comparison theories.

Assessing Clients’ Constructions of Their Problems in Family Therapy Discourse

Myrna L. Friedlander, SUNY at Albany and Laurie Heatherington

Journal of Marital and Family Therapy, 24, 289-303 (1998)

To study family members’ narrative descriptions of their difficulties, we developed an observational coding system, the Cognitive Constructions Coding System (CCCS). In this system, 4 dimensions of clients’ problem descriptions (intrapersonal-interpersonal) and causal explanations (internal-external, responsible-not responsible, linear-circular) are coded in the context of a Problem Elaboration Episode, a segment of psychotherapy discourse. In Studies 1 and 2 the reliability of the CCCS was assessed using transcripts from family therapy texts and interviews provided by 7 constructivist theorists. Across studies, mean interjudge agreements ranged from 56% to 98%; the mean reliability estimates ere, however, more modest and variable (range .46 to .94). In Study 3, trained judges coded videotapes in which volunteers described personal problems that corresponded to specific CCCS codes. Results of this experiment showed that, on every dimension, the coding was more accurate than chance, all ps<.005. In Study 4, the CCCS successfully discriminated 6 of 8 family intake sessions in which the parents’ descriptions of the presenting problem either did or did not shift from intrapersonal to interpersonal over the course of the interview. Directions for future research with the coding system are suggested, along with a discussion of its relevance for practice.

Men, Women, and the Self-Presentation of Achievement

Laura B. Brown, Lisa Uebelacker, Laurie Heatherington

Sex Roles, 38, 253-264 (1998)

This study examined men’s and women’s self-presentation of academic achievement in an interactional context. First-year college students are led to expect an interaction with a peer to discuss academic achievement. However, the peer was actually a confederate who portrayed his or her achievement in a boastful, moderate, or self-deprecating manner. Prior to the anticipated interaction, subjects were induced to describe their own academic achievement and make predictions about their first-semester grade point averages (GPAs) to be shared with the peer. Men’s GPA predictions were highest in the boastful condition (and higher than their actual GPAs), next highest in the moderate condition, and lowest (and lower than their actual GPAs) in the self-deprecating condition. Women’s predicted GPAs, unexpectedly, did not vary by condition. Women were less comfortable in predicting their GPAs than men, and there was a tendency for men to be more comfortable than women while observing the boastful peer and women to be more comfortable than men while observing the self-deprecating peer. Results are discussed with regard to past research and self-in-relation theory.

I’m Innocent!: Effects Of Training On Judgments Of Truth And Deception
In The Interrogation Room.

Saul M. Kassin, Christina M. Fong 98’

Law and Human Behavior, 23, 499-516 (1999)

The present research examined the extent to which people can distinguish true and false denials made in a criminal interrogation and tested the hypothesis that training in the use of verbal and nonverbal cues increases the accuracy of these judgments. In Phase One, 16 participants committed one of four mock crimes (breaking and entering, vandalism, shoplifting, a computer break-in) or a related but innocent act. Given incentives to deny involvement rather than confess, these suspects were then interrogated. In Phase Two, 40 observers were either trained in the analysis of verbal and nonverbal deception cues or not trained before viewing the videotaped interrogations and making their judgments. As in past studies conducted in non-forensic settings, observers were generally unable to distinguish between truthful and deceptive suspects. In addition, those who underwent training were less accurate than naive controls-though they were more confident and cited more reasons for their judgments. The implications of these findings are discussed in light of what is known about police interrogations, false confessions, and the wrongful conviction of innocent suspects.

Eyewitness Identification Procedures: The Fifth Rule

Saul Kassin

Law and Human Behavior, 22, 649-653 (1998)

Wells and others (1998) recently proposed four guidelines for improving the collection of eyewitness identification evidence. Their recommendations for double-blind lineup testing, nonbiased instructions, the matching of distractors to the witness’s description, and the immediate assessment of confidence will minimize many potential problems. However, an additional fifth rule is proposed in this article, that all lineups be videotaped. This rule is necessary for two reasons: (1) to maintain an objective record of all procedures that were followed, independent of police self_report, and (2) to provide judges, juries, and attorneys with diagnostic behavioral information concerning the witness’s decision and the context in which that decision was made.

Inadmissible Testimony, Instructions to Disregard, and the Jury:
Substantive versus Procedural Considerations

Saul Kassin and Samuel R. Sommers,’97’

Personality and Social Psychology Bulletin, 23, 1046-1054 (1997).

The present study tested the hypothesis that jurors comply selectively with instructions to disregard inadmissible evidence. Eighty-one mock jurors read a murder trial summary in which a wiretap was ruled admissible, inadmissible because it was not reliable, or inadmissible because it was illegally obtained (there was also a no-wiretap control group). As predicted, participants were more likely to vote guilty and interpret subsequent evidence as more incriminating in the admissible and inadmissible-due process conditions than in the admissible-unreliable and control groups. These results suggest that jurors are influenced not by the judge’s ruling per se, but by the causal basis for that ruling. Conceptual and practical implications are discussed.

On the Power of Confession Evidence:
An Experimental Test of the ‘Fundamental Difference’ Hypothesis.

Saul Kassin and Karen Neumann, 96’.

Law and Human Behavior, 21, 469-484 (1997

In Arizona v. Fulminante (1991), a U.S. Supreme Court majority stated that confessions are similar to, not fundamentally different from, other types of evidence. To evaluate this claim, three mock juror studies compared the impact of confessions to other common forms of evidence. In Experiment 1, participants read summaries of four criminal trials (murder, rape, assault, theft), each of which contained a confession, an eyewitness identification, character testimony, or none of the above. Significantly, the confessions produced the highest conviction rates. In Experiments 2 and 3, participants read a murder or assault trial containing all three types of evidence and made a series of midtrial judgments. Results indicated that the confession was seen as the most incriminating, followed by the eyewitness and character testimony. Although the comparisons we made are limited in certain respects, our findings suggest that confessions are uniquely potent.

Heroin Addicts have Higher Discount Rates for Delayed Rewards than
Non-drug-using Controls

Kris N. Kirby, Nancy M. Petry and Warren K. Bickel

Experimental Psychology: General, 128, 78-87 (1999)

Fifty-six heroin addicts and 60 age-matched controls were offered choices between monetary rewards ($11 to $80) available immediately and larger rewards ($25 to $85) available after delays ranging from 1 week to 6 months. Participants had a 1-in-6 chance of winning a reward that they chose on one randomly selected trail. Delay-discounting rates were estimated from the pattern of participants’ choices. The discounting model of impulsiveness (Ainslie, 1975) implies that delay-discounting rates will be positively correlated with impulsiveness. On average, heroin addicts’ discount rates were twice those of controls’ (p=.004), and discount rates were positively correlated with impulsivity as measured by self-report questionnaires (p<.05). The results lend external validity to the delay-discounting rate as a measure of impulsiveness, a characteristic associated with substance abuse.

Superstition and the Regression Effect

J. Kruger, Kenneth Savitsky, and T. Gilovich

Skeptical Inquirer, 23, 24-29 (1999)

Whenever two variables are imperfectly correlated, an extreme value on one is likely to be matched by a less extreme value on the other. People’s misunderstanding of this statistical fact results in a variety of superstitious beliefs, from the benign to the pernicious.

The Illusion of Transparency: Biased Assessments of Others’ Ability to Read Our
Emotional States

T. Gilovich, Kenneth Savitsky, and V.H. Medvec

Journal of Personality and Social Psychology, 75, 332-346 (1998)

We present evidence for an illusion of transparency, or a tendency for people to overestimate the extent to which others can discern their internal states. People often mistakenly believe that others can “see right through them,” or that their internal states “leak out” more than they really do. We suggest that this bias stems from a tendency for people to adjust insufficiently from the “anchor” of their own phenomenological experience when attempting to take the perspective of another. In a series of investigations, we document the illusion by showing that liars overestimate the detectability of their lies (Studies 1a, 1b, and 1c) and that people believe their feelings of disgust are more apparent than they actually are (Studies 2a and 2b). In a final pair of experiments (Studies 3a and 3b), we explore the implications of the illusion of transparency for people’s reluctance to intervene in emergencies. All three sets of studies also provide evidence consistent with the proposed anchoring and adjustment interpretation.

Prenatal Experience and Postnatal Stress Modulate the Adult
Neurosteroid and Catecholaminergic Stress Responses

Betty Zimmerberg and Rachel C. Brown ‘94

International Journal of Developmental Neuroscience, 16, 217-228 (1998)

Allopregnanolone (3±-hydroxy-5±-pregnan-20-one) is a neuroactive steroid recently shown to be involved in the neurochemical stress response via its positive modulation of the GABA_A receptor complex. This experiment investigated the effects of postnatal stress (daily maternal separation during the first week of life) on the subsequent adult response to a stressor (10 min. forced swim) in Long-Evans rats from one of three prenatal treatment groups (alcohol, pair-fed and control). Indices of stress response were allopregnanolone concentrations in plasma, cortex and hippocampus, and dopamine and norepinephrine concentrations in prefrontal cortex, nucleus accumbens and striatum. Females had higher levels of allopregnanolone than males in both plasma and brain. Prenatal alcohol exposure combined with early maternal separation stress resulted in an increase in the endogenous levels of allopregnanolone in the prefrontal cortex and hippocampus of adult offspring in response to a stressor compared to subjects without a prior history of postnatal stress; this effect was greater in females. This increased allopregnanolone was also associated with decreased dopamine and norepinephrine levels in prefrontal cortex. In the prenatal alcohol-exposed offspring, postnatal maternal separation blunted the increase in dopamine levels in the striatum seen in both control groups. Postnatal maternal separation increased norepinephrine levels in the nucleus accumbens regardless of prenatal experience, while in the prefrontal cortex only prenatal diet condition (pair-feeding and alcohol) resulted in lower norepinephrine levels. The results of this experiment suggest that experience, both pre- and postnatal, can have long-term consequences for the developing neurochemical responses to stressors.

Context is Everything: The Nature of Memory

Susan Engel

WH Freeman, April 1999.

This book describes how the context of recollection affects the memory process. It is written for the lay person as well as the research psychologist and explores how the place, company, purpose, and situation profoundly affect the essence and experience of a memory.

Looking Backwards: Representations of Childhood in Literary Work

Susan Engel

Journal of Aesthetic Education, 33, (1999)