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ABSTRACTS OF STUDENT THESES


ASTRONOMY

Aspects of Astronomy Education in U.S. High Schools: History, Context, and Materials

Jason R. Lorentz

This thesis is not a typical one. Rather than attempting to prove a specific point about its subject, it is instead a collection of three inquiries concerning astronomy education in American high schools, past and present. These inquiries are designed to characterize the nature of astronomy teaching for myself and the reader, and they consider it within the larger context of the major movements in science education itself. Specifically, the study consists of an examination of the history of astronomy education in the U.S. since colonial times, a history and analysis of recently established national standards for science education, and finally, a survey and analysis of the astronomy currently being taught in high school earth science textbooks. As someone interested in pursuing a career in secondary school science education, such a study, allowing for a broader look at astronomy's role in high schools, is ideal. It is my hope that the reader may find it interesting and useful as well.

BIOLOGY

Mapping of the Macronuclear Genome in Tetrahymena thermophila

Janet R. Alter

Tetrahymena thermophila is a ciliated freshwater protozoan whose genetic material is organized in two different ways: the germ line genome is stored in the micronucleus and the transcriptionally-active somatic genome is contained in the macronucleus. In order to create a more detailed physical map of the macronuclear genome, vectors for fragmentation mapping and yeast artificial chromosome cloning were designed in this project. DNA inserted into a fragmentation vector undergoes homologous recombination within the macronucleus to create truncated macronuclear chromosome. The size of this shortened chromosome, as determined by southern hybridization, is indicative of the physical location of the cloned DNA in the original macronuclear chromosome. The TYAC (Tetrahymena-yeast artificial chromosome) vector is a modified form of the fragmentation vectors which contains all the elements necessary for stable replication in a yeast host. Recombination at the site of the cloned DNA yields a construct containing all of the macronuclear sequences distal to the cloned DNA linked to the [caron]YAC vector. This TYAC can then be shuttled into yeast for further study. Production of these vectors was unsuccessful, however, and further modifications to the construction protocol must be made in order to generate these tools for mapping the macronuclear genome of T. thermophila.

Drought Suppression of Hybrids in an Intrograding Natural Population of Willows,
Salix sericea, S. eriocephala, and their Hybrid

Daniel Bolnick

Environmental control of hybrid growth and fitness may influence introgression between Salix sericea and S. eriocephala. We tested a hypothesis of drought suppression of hybrid performance relative to parental performance on a greenhouse population of these North American willows. A chronic drought experiment tested the interaction between different levels of stress and taxon on plant growth and water relations over a 48-day period. In an acute drought experiment, we tested the ability of these species to tolerate drydown. Leaf growth and water relations were monitored regularly to determine response rates in the three taxa. We surveyed the spatial distribution of the three taxa with respect to plant distance from a stream, to test whether plant responses in greenhouse might explain the structure of a natural population. Hybrid water relations (water potential and relative water content) were not significantly different from the parents, yet hybrids experienced more pronounced suppression of leaf production, stem growth, and increased senescence in response to drought. This pattern suggests a lower hybrid tolerance of tissue water deficit, rather than lower hybrid ability to maintain water relations. S. sericea maintained leaf growth, soil moisture, and water relations longer than S. eriocephala or the hybrid, indicating greater drought resistance. This effect may explain S. sericea's higher frequency away from the stream in the natural population, suggesting that greenhouse responses do reflect plant water relations in the field. Despite hybrid suppression of growth rates, stressed hybrids maintained a higher gross size (total stem length, numbers of leaves, numbers of stems) than the parents. Heterosis, in which hybrid performance exceeds that of parental taxa, was maintained throughout all levels of stress due to rapid compensating growth after high-stress events. The impacts of compensation on carbohydrate storage, herbivory, and growth form may reduce hybrid's capacity for over-winter survival, and ability to compete for light.

Diagnosing Dementia in Primary Care: A Useful Cognitive Screening Battery
Sensitive to Alzheimer's Disease

Michael Brush

The recognition and diagnosis of dementia, specifically Alzheimer's Disease (AD), in the primary care practice is an uncommon event. As such, there is a need in primary care for a cognitive screening battery that is sensitive to AD. In order to be used in primary care, this battery must be short, simple to administer and score, use only basic materials, and be both sensitive and specific. The two most commonly used mental status exams in primary care, the Mini-Mental Status Exam (MMSE) and the Blessed Information-Memory-Concentration Test (BIMC), are both simple and short. However they have been shown to have poor sensitivity in the detection of early AD, the stage most likely to be seen in primary care. Solomon et al. (1996) developed a screening battery for AD that met the necessary guidelines and was shown to be extremely sensitive to a prescreened population of age and education matched patients. The goal of this study was to extend their research by putting the battery to use in a primary care practice. Subjects were 137 consecutive patients over the age of 60 of Dr. Daniel Sullivan, a primary practitioner at the Williamstown Medical Associates in Williamstown, MA. This represented an estimated 90% of the eligible population. All subjects were administered the screening battery. Using a logistic regression formula derived in Solomon et al. (1996), all subjects were classified as either High or Low Probability of Dementia (HPD or LPD) using a cutoff of 0.6. Of the 137 subjects, 123 were classified as LPD and 14 as HPD. Full neuropsychological evaluations indicated that the battery correctly classified 9 or 10 HPDs (90%) and 26 of 27 randomly selected LPDs (96.3%). These results indicated that the battery can be a useful diagnostic tool for AD in a primary care practice.

Historical Land-Use Effects on Northern Hardwood Forest Vegetation

Jonathan C. Cluett

Historical changes in human activity and the ways in which humans interact with the landscape have modified the forest communities of New England. Land throughout New England has been deforested, farmed in diverse ways, and subsequently reforested. The purpose of this study is to evaluate the importance of different human impacts on the land and to show how previous patterns of land-use structure the present day ecosystem.

In a 240 acre area of northern hardwood forest (the Birch Brook Research Area of Hopkins Memorial Forest) the pattern of human land-use can be best explained by the slope (percent grade) of the landscape. Farming practices within this research area reflect prevailing social and economic conditions for the region. In the mid 1800s, this land was cultivated (36%), pastured (32%), and used as woodlot (30%). The reforestation process which followed was characterized by unique vegetation communities determined by the type of land-use. Rates of succession were affected by the type of land-use, and the stage of succession was determined by the time since agricultural abandonment of the land.

The Effects of Neuronal Stimulus on NPY mRNA Levels in PC-12 Cells

Warren Eng

An amazing aspect of the nervous system is it capacity to remember external stimuli. At the cellular level, this phenomenon of plasticity is manifested by long-term changes in neuronal function. For example, repeated stimulation of a neuron may result in permanent physiological changes in the neuron: it may develop more dendrites (Purves et al., 1986), may increase its membrane permeability to certain ions through the development of additional ion channels (McMorris et al., 1976) and/or turn on or off certain genes (Sheng and Greenberg, 1990).

Ni++ Affinity Chromatography Purification of 10-Histidine Vaccinia dUTPase

Bryan R. Greenhouse

Deoxyuridine triphosphate pyrophosphates (dUTPase, EC 3.6.1.23) is an enzyme involved in DNA metabolism and found in a wide variety of organisms, including viruses. It has been proven to be required for replication in both prokaryotic and eukaryotic systems, and is therefore a potential target for anti-viral and anti-cancer chemotherapeutic agents. Alignment of dUTPase amino-acid sequences from various organisms reveals five evolutionary conserved motifs. In order to study the function of the last of these regions, motif 5, a truncated gene missing motif 5 was created. Previous methods for purifying dUTPase have relied upon the nucleotide binding capability of the enzyme. As this and other mutations may reduce or destroy this capability, a new protocol for purifying the enzyme was developed. The procedure involved cloning the gene into the bacterial overexpression plasmid pET16b, which attached a 10-histidine tag to the amino terminus upon translation. Since histidine binds divalent cations, a Ni++-coated resin was used to purify the overexpressed protein from the crude extract of induced E. coli containing the plasmid. The protocol was quick and easy, and returned about 50% of the overexpressed full-length gene construct at approximately 90% purity. The purified enzyme retained activity, but kinetic studies remain to be performed in order to confirm the equivalence of this construct to wild-type vaccinia dUTPase. After these studies are performed, this protocol may be used to purify future mutants of the enzyme. The truncated gene product was purified as well, and preliminary data indicate that this protein, like the wild-type enzyme, exists as a homotrimeric species. Thus motif 5 may have a non-structural function, perhaps a role in substrate binding or in the active site of the enzyme.

Isolation and Characterization of the S. cerevisiae Gene EXM2

Michelle L. Gonzales

The eukaryotic cell cycle, defined as the cyclic procession through phases of growth, DNA replication, and division, is monitored and controlled at several checkpoints. Some checkpoint genes inhibit cell-cycle progression in response to damage induced by environmental agents, such as ultraviolet light or chemical mutagens. Other checkpoints are believed to monitor the progression of routine cell-cycle events, such as DNA replication, spindle assembly, or chromosome segregation, and to inhibit cell cycle progression until those events have been completed. One such gene, EXM2 (exit from mitosis), has been implicated in a checkpoint controlling completion of telophase in the single-celled eukaryote Saccharomyces cerevisiae. To facilitate further study of the function of EXM2, the open reading frame, or coding sequence, of the gene was isolated through a combination of molecular biological and genetic techniques.

Based on the nucleotide sequence of a fragment of yeast DNA known to be essential for EXM2, the physical location of the gene was determined to be on the left arm of chromosome IV, in close proximity to the previously characterized gene ASM4 (Giot et al., 1995). Comparison of the restriction map of the ASM4 region and that of the EXM2 region confirmed that the two regions are indeed identical. To evaluate whether EXM2 and ASM4 are the same gene, a 1.8 kb fragment of DNA immediately adjacent to (but not including any part of) the open reading frame of ASM4 was subcloned into the high-copy shuttle vector RS315 (Sikorski and Hieter, 1989). When transformed into a temperature-sensitive exm2-1 mutant strain, this plasmid fully retained the ability to complement the temperature-sensitive defect caused by the exm2-1 mutation, indicating that ASM4 and EXM2 are two different genes.

Through communication with colleagues participating in the Yeast Genome Systematic Sequencing Project, the complete sequence of the 1.8kb fragment of yeast DNA containing EXM2 was obtained. Sequence analysis of this fragment revealed a 786 bp open reading frame, encoding a putative protein product of 262 amino acids, estimated molecular weight 28 kD. Preliminary analyses of the peptide sequence suggest that EXM2 may a have a homolog in C. elegans. In addition, several short domains in the center of the protein showed similarity to the yeast proteins SMC1 and RAD50, both of which are involved in chromosomal metabolism during mitosis or meiosis. Finally, short regions of similarity were found between EXM2 and the microtubule-associated motor proteins CIN8, dynein, and USO1, and between EXM2 and the actin-associated motor protein myosin S2. However, as the homology was not within the highly conserved regions that characterize these proteins, no immediate inferences can be made about the roles of these short domains or the overall function of EXM2.

Environmental Mechanisms Through Which Past Land-Use Influences Spring
Ephemeral Wildflower Distribution Patterns in the Hopkins Memorial Forest

Emilie B. Grossman

The spring ephemerals of New England have limited distributions within the forested land, probably primarily due to the effects of past land use. Much of New England's forests today are secondary growth which has covered abandoned agricultural land. The mechanisms through which past land use limits wildflower populations is not defined, however. The mound and pit microtopography of the forest floor (or lack thereof in the secondary forests) may influence wildflower survival band diversity by providing microscale variations in the forest floor. These mounds and pits may have been eradicated by past agricultural use. Since many spring ephemerals are myrmecochorous (depend upon ants as their dispersal vectors), ant population levels may also influence wildflower populations indirectly through the changes it initiates in the ant populations. If any population are limited, or fundamentally changed within once-cleared land, then this may provide an additional barrier to the dispersal of the spring wildflowers into the once-cleared land. This issue may be especially important, because the myrmecochores depend on other aspects of their interactions with ants besides simply dispersal for their survival, and health. Ant populations in turn, might be influenced by those wildflower populations, if they depend heavily on the wildflowers as an early spring source of food. Ant populations may also be influenced by past land use in the forest as well as the wildflower populations. The composition of the canopy, may also influence wildflower distribution. The presence of Acer saccharum may positively influence the spring richwood herbs, while Fagus grandifolia, and Quercus rubrum, when they dominate the canopy, may negatively influence spring herb populations. Competition from other herbs may also influence spring ephemerals. The combination of Maianthemum canadense, Trientalis borealis, Lycopodium complanatum, and L. obscurum in the ground cover may competitively exclude other herbs from invading old pastures.

Two Roads Diverged in a Goldfish Brain: Pathway Selection
of the Mauthner Cell Following CNS Damage

Cynthia Huang

The Mauthner cells are a pair of identifiable CNS neurons in fish and amphibians which are involved in the fast startle response known as the C-start. Because fish are capable of functional recovery following damage to the CNS, they are ideal models for studies in regeneration.

Previous studies have shown that following a spinal cord crush at the spinal medullary level (SML), neurons normally constructed to the CNS often exit the spinal cord at the first ventral root (PNS) (Bentley and Zottoli, 1994). A crush at this level not only damages CNS neurons, but also the motoneuron pool (PNS) which normally extends axons out the first ventral root. Since PNS injury has long been known to attract regenerating CNS neurons, it was hypothesized that if the damage to the motoneuron pool was decreased, then sprouts would be less likely to take the incorrect pathway during regeneration (out the ventral root) and continue correctly down the spinal cord. In order to address this question, two treatments of fish were created. The first group had a spinal cord crush at the SML (which causes extensive damage to the motoneuron pool) (SMLCP) and a second group had a spinal cord crush just caudal to the ventral roots (which minimizes the damage to the motoneuron pool) (VRLCP).

Following a SML crush, more sprouts were attracted by the ventral root than following a crush just caudal to the ventral roots (supporting the hypothesis that damaged PNS attracts regenerating CNS neurons). The majority of reversals in the VRLCP fish occurred to the wound, contrary to previous studies which state that the wound site in non-mammals is not a barrier to regenerative elongation (Lurie and Selzer, 1991). Furthermore, the majority of sprouts in both surgeries initially choose to elongate in the appropriate caudal and ipsilateral direction, indicating that directional cues are locally available. Because sprouts were not restricted from rostral elongation and because they extend more laterally than control axons, it is unlikely that systematic guidance mechanism exists to guide regenerating axons back to their developmentally correct targets.

Biotic and Abiotic Determinants of Herbivorous Insect Population Dynamics
on the Black Mustard, Brassica nigra

David W. Long

While several studies of the cultivated crucifer Brassica oleracea are well documented, virtually no published study has involved the investigation of Brassica nigra a wild crucifer which grows in disturbed habitats. The purpose of this study was to elucidate on the biotic and abiotic factors which may influence the plant-insect interactions of the B. nigra community.

This study examined B. nigra at two sites featuring human disturbance and two sites featuring river disturbance. Insects found on B. nigra at four sites were identified and censured over eight weeks in the summer of 1995. Insect diversity, species richness, and species equitability were measured for each census date. A fifth site featured a census of the insects on B. oleracea for comparative purposes. Plant morphological measurements were made including foliar nitrogen, biomass, leaf area, density, and ground cover. Soil, the abiotic factor investigated, was examined for organic content, pH, exchangeable cations, and soil texture.

A significant increase over time in the number of insects per square meter of leaf material was found. A highly significant increase in the population of Phyllotreta cruciferae, a major herbivore of Brassicas pp. was also discovered. Other herbivores such as Phyllotreta striolata, Lygus lineolaris, and Brevicryne brassicae displayed similar significant increases over the course of the summer. P. cruciferae was especially prevalent at the human disturbed sites and, not surprisingly, was overwhelmingly dominant at the farm site. While insect counts significantly increased over the summer, diversity, species richness, and species equitability all declined for all B. nigra sites-the dominance of a few species could be responsible for these effects.

Some of the biotic factors examined may have had some influence on the insect population dynamics. Foliar nitrogen levels significantly dropped over the course of the summer. Leaf area, leaf biomass, and B. nigra density all significantly declined over the span of the study as well while ground cover increased (due to neighboring plant species). These findings are suggestive of conditions which may allow the main herbivores, such P. cruciferae, to become dominant. No plant or soil measure, with the exception of potassium cations in the soil, was clearly characteristic of either a human or river disturbed habitat. More research is necessary to help explain these distinct differences in the abundance's of certain insects between the two types of site disturbances.

The Effect of Long Chain Bases on the Oxido-Reductase in Plant Plasma Membranes

Rebecca Marin

The activity of the plasma membrane electron transport chain in plant cells has been implicated as an important player in many cellular processes. This present study has demonstrated that sphingoid long chain bases are able to mediate the actin of the oxido-reductase in this plasma membrane redox system. By working in vitro with corn microsomes and in vivo with the apical root tips of corn, it has been possible to further characterize the influence of sphingoid long chain bases on the oxido-reductase activity. In vitro, when the effects of high concentrations of sphingosine and phytosphingosine (100 uM to 200 uM) on the oxido-reductase activity were assayed, it was discovered that these bases interacted with the corn microsomes in such a way that the initial and final absorbency levels were increased, ultimately resulting in an inhibition of enzymatic activity. At lower concentrations of sphingoid base (20 uM - 50 uM), while the enzymatic activity was also inhibited, it persisted for an extended period of time. Non-natural long chain bases (stearylamine and threo-sphingosine), when added to the in vitro assay, had the same effect on the oxido-reductase, suggesting that the long chain bases were not involved in a specific biochemical interaction with the redox enzymes, but instead were interacting with other components of the redox chain in a non-specific way. In vivo, when sphingosine, phytosphingosine, stearylamine and threo-sphingosine were assayed, it was discovered that each of these bases caused the rate of oxido-reductase activity to decrease while persisting for an extended period of time. In addition, when an endogenous supply of sphingoid bases was created through treatment with fumonisin, the same inhibition of oxido-reductase activity was noted. These results support the in vitro findings of a non-specific interaction between the long chain bases and the redox system that influences the redox activity, thereby confirming the significance of the sphingoid long chain bases in the regulation of the oxido-reductase activity and their potential role in the control of related cellular processes.

Effects of Collagen and Polyethylenimine on Morphogenesis
in Neuronally Differentiated PC12 Cells

Magdalene Moran

To perform calcium imagine experiments on neuronally differentiated rat pheochromocytoma cells (PC12) we had to use a substrate that adhered to glass. We chose to employ the synthetic substrate, polyethylenimine (PEI). Before conducting experiments, we felt that it was critical to determine if cells grown on PEI and cells grown on collagen, since substrate/cell interactions can have a profound effect on cell phenotype. We found that PC12 cells grown on two concentrations of PEI had significantly longer neurites than their collagen counterparts. Differences in neurite morphology were also characterized. Collagen treated cells tended to have much straighter neurites than PEI-treated cells, which had wandering neurites.

KC1 Depolarization in PC12 Cells

Jennifer C. Nicholson

Neurons are the messenger cells of the body, dedicated in structure and function to receiving, organizing, and transmitting information. The organization of the nervous system enables an organism to coordinate its responses and behaviors, while the plasticity of the nervous system allows the organism to change its behavior in response to stimuli and adapt to different environmental conditions. To understand how the network of the nervous system functions and responds to change, it is necessary to study neurons and neuronal synapses at the individual level. Neurons are stimulated to fire by depolarizations that are propagated along the axon to the nerve terminal, where they stimulate an influx of calcium which in turn leads to neurotransmitter release. These chemical messengers, the neurotransmitters, interact with receptors on the post-synaptic cell, which may lead to depolarization or other responses.

The Effect of Cold Stress and Food Deprivation on Maximal Oxygen Consumption
and Body Temperature in the Black-Capped Chickadee (Parus atricapillus)

Jessica S. Racusin

The oxygen consumption (VO2) of black-capped chickadees (Parus atricapillus), captured from Hopkins Memorial Forest, was studied in the laboratory to test the effects of anesthesia, thermocouple implantation, and nutrient stress on maximal metabolic rate (VO2 max) during cold stress in a helium-oxygen (helox) gas mixture. Body temperature was also measured during cold stress in birds implanted with thermocouples, and ventilatory frequency was measured non-invasive in all birds. Six birds were anesthetized prior to cold stress; three were anesthetized and implanted with a wire thermocouple; four birds were fasted for approximately six hours prior to thermocouple implantation and cold stress; and six birds acted as controls, with no treatment prior to cold stress. In all birds, VO2 increased with decreasing ambient temperature, and ventilatory frequency was positively correlated with VO2. VO2 max values for individual birds ranged from 2.95 to 4.37 ml O2/min, and were attained at temperatures in helox ranging from 5.4 to -14.3[currency]C. There were no statistically significant effects of anesthesia, thermocouple implantation, or nutrient stress on cold-induced VO2 max. In implanted birds, both temperature decreased with decreasing ambient temperature under cold stress. Mean body temperature at VO2 max averaged 36.9[currency]C and did not differ significantly between nutrient stressed and non-stressed birds.

The Characterization and Cloning of an Extragenic Suppressor of cdc14

Alvaro Sagasti

CDC14, an essential Saccharomyces cerevisiae gene involved in controlling exit from mitosis, has been cloned, sequenced, and mapped (Wan et al., 1991). Sequence analysis has revealed that it contains a region homologous to the active site of a tyrosine-specific protein phosphates, but the mechanisms by which CDC14 is regulated and performs its function are not understood. In order to elucidate the precise role of CDC14 in the yeast cell cycle, several extragenic suppressors of cdc14-7, a temperature-sensitive mutant which arrests in late anaphase, have been isolated (Schilling, 1995). These mutants sort into four or five complementation groups, and genetic tests have confirmed that a single, recessive locus, unlinked to cdc14, is responsible for the suppression of each group (Schilling, 1995). The allele-specificity's of two of these suppressors, sup 9-13 and sup 1-15, have been tested in this study. Both of these suppressors, in addition to suppressing cdc14-7, are able to suppress some alleles of cdc14 weakly, but are completely unable to suppress at least one other allele. These results suggest that these genes are neither bypass suppressors nor canonical interactional suppressors. Although these suppressors are not strictly allele-specific, genetic tests with several alleles of cdc15 suggest that they are probably gene-specific. The cellular morphologies and cell cycle distributions of sup 9-13 cells and sup 9-13/cdc14-7 double-mutants were examined microscopically. sup 9-13 cells accumulate as unbudded cells at both their restrictive and permissive temperatures, in contrast to cdc14 mutants which accumulate as large-budded cells. sup9-13/cdc14-7 cells have a strikingly unusual morphology at cdc14's restrictive temperature, forming large, irregular agglomerations. This observation indicates that sup 9-13 does not suppress by simply restoring Cdc14p's function to its normal state. Two attempts were made at cloning SUP9-13 from a YCp50 plasmid library of genomic S. cerevisiae DNA. Although no clones were found in the first experiment, three strong candidate clones were isolated the second time this experiment was performed. The cloning of sup9-13 makes possible powerful molecular techniques for the further characterization of this gene.

Further Characterization of sup 1-15, A Suppressor of cdc 14

Tanis M. Shaw

In order for successful cellular reproduction to occur, a cell must integrate stage-specific events, such as the initiation of chromosomal DNA replication, with continuous processes such as metabolism, maintenance, and growth (Pringle and Hartwell, 1981). Although the potential for lethal errors exists at every stage of the cell cycle, cells rarely fail to accurately replicate each gene, package every chromosome, disjoin sister chromatids, and distribute nuclei and organelles to daughter cells (Hartwell, 1978). Through the genetic analysis of mutant strains of cells that are unable to replicate successfully, many aspects of cell cycle regulation and control have been elucidated.

This study focuses on one such mutant, the cell division cycle mutant cdc14 of the budding yeast Saccharomyces cerevisiae. At nonpermissive temperatures, cdc14 cells arrest during late nuclear division, in anaphase. While this phenotype suggests that wild-type CDC14 is essential for successful completion of mitosis, the functional role of wild-type CDC14 and its gene product is not well understood. Furthermore, the interactions between CDC14 and other genes and gene products have yet to be elucidated.

The goal of this study is to further characterize CDC14 and it interactions with other genes. If two proteins physically interact, a mutation in the gene encoding one protein may be suppressed by a compensating mutation in the gene encoding the interacting protein. Suppressor proteins that physically interact with the gene product of cdc14 must function in the same pathway as wild-type CDC14. Identifying and characterizing such suppressors would provide a way to elucidate the mechanisms at work in one of the pathways that regulates the cell's exit from mitosis.

This project seeks to further characterize a recessive cold-sensitive suppressor of cdc14, which has been designated sup1-15. Another goal of this project is to clone, partially sequence and identify wild-type SUP1-15.

Cultural Evolution in House Finch Song

Adam R. Smith

Variability in a dialect of the house finch (Carpodacus mexicanus) was examined in recordings made from 1990-1996. Several types of acoustic variation were observed. New song elements were introduced through mutation and foreign introduction. These combines with each other and existing song elements in novel combinations and blends. Acoustic variation sometimes corresponded with syntactic variation. Song syntax often varied independently of the song elements' acoustic properties. Only a small percentage of the recorded variants were incorporated into the dialect. This process of selection drove the cultural evolution seen from 1990-1996. A speculative model focusing on the characteristics of the singing birds (rather than their songs) is presented.

Hydroxylation of Sphinganine in Corn Shoot Tips

Jonathan Snow

One step in the biosynthesis of sphingolipids that is poorly understood is the formation of hydroxysphinganine, or phytosphingosine. Its synthesis is thought to be through the hydroxylation of sphinganine.

This study has shown by a number of means that sphinganine is hydroxylated in vivo in corn shoot tips. The accumulation of sphinganine in tissue, by exogenously supplying the long-chain base or as a consequence of fumonisin treatment, produced an increase in the levels of phytosphingosine. The addition of ß-chloroalanine, an inhibitor of sphinganine synthesis, brought sphinganine and phytosphingosine to sub-control levels. These experiments demonstrated that in the absence of de novo synthesis of sphinganine, phytosphingosine levels do not increase.

A radioactive tracer experiment was used as a final means of demonstrating the activity in vivo. When [14C]-serine was added in conjunction with fumonisin, the radioactivity in phytosphingosine rose more than 3-fold over the control and increased more than the radioactivity in sphinganine, which rose 2-fold above the control, not treated with fumonisin.

We found that conductivity rose appreciable with addition of fumonisin, increasing 5-fold over controls at 50 hrs. The groups treated with 20 uM phytosphingosine or 20 uM sphinganine behaved similarly. Increases in sphinganine and phytosphingosine were temporally compared with electrolyte leakage, and it was found that conductivity began to rise as LCB concentrations reached maximum levels.

Efforts to demonstrate the activity of a "sphinganine hydroxylase" in vitro were not wholly successful. Although one assay did seem to show hydroxylase activity, this result was not repeatable in subsequent assays.

The Role of Nectar Amino Acids in the Fitness and Fecundity of the White Cabbage Butterfly Pieris rapae (Lepidoptera: Pieridae) and in the Fitness of its Offspring

Brian Spitzer

The role of nectar amino acids in the nutrition of nectar-feeding insects is an unresolved question. Circumstantial evidence suggests that the amino acids found in floral nectar contribute to the fecundity of pollinators, but no conclusive, direct evidence for this has been published. The series of experiments reported here investigated the role of nectar amino acids in the longevity and fecundity of the white cabbage butterfly Pieris rapae (Lepidoptera: Pieridae) and their effect on the fitness of its offspring, an effect which has not previously been studied. Butterflies feeding on a nectar mimic containing amino acids laid more eggs than did those feeding on a nectar mimic without amino acids, especially late in the lifespan. However, if females were caged with males, male nutrient donation during mating could apparently compensate for the lack of nitrogen in the nectar. Amino acids in the nectar consumed by the butterflies had little or no discernible effect on offspring which were raised in highly controlled conditions. In the field, offspring of nitrogen-deprived parents were attacked marginally more often by parasitoids, an effect which may be caused indirectly by maternal provisioning; however, this effect was statistically insignificant. In short, nectar amino acids allowed female P. rapae to lay more eggs if males were not present to compensate for a nitrogen deficit, but did not have any strong effect on the performance of offspring either in the laboratory or in the field.

The Effect of Long-Chain Bases on Pyrophosphatase-Driven Proton Transport
in Plant Tonoplast Membranes

Garth Swanson

The effect of long-chain bases on pyrophosphatase driven proton transport was studied in tonoplast membranes. Based on measurements of change in absorbency of acridine orange in a microsomal membrane fraction (Bille, Weiser, and Bentrup, 1992), the dihydroxy long-chain base sphingosine, the predominant long-chain base in animals, was shown to increase PPase proton transport. The addition of 80 uM sphingosine (d18:1), the acridine orange assay showed a smaller increase of PPase activity, 2.9%, compared to sphingosine. The addition of another dihydroxy long chain base, sphinganine (d18:0), showed a slightly larger, 5.9%, increase in PPase activity in the microsomal fraction. It was therefore the dihydroxy long-chain bases that were more effective of modulation of PPase activity. Psychosine, containing a glucosyl sugar head group did not effect PPase activity, suggesting that a free long-chain bases prevalent in plant tissues, long-chain bases were extracted and isolated from wheat glucosylceramide. Characterization of the purified free long-chain bases by high performance liquid chromatography was performed following conversion to o-pthalaldehyde derivatives (Merrill et al., 1988). The elution profile of wheat glucosylceramide revealed the presence of two predominant long-chain bases 4,8-sphingadiene (d18:2) and 4-hydroxy-8-sphingenine (t18:1). The long-chain bases derived from wheat glucosylceramide showed the greatest increase in proton pumping across the membrane, a 70.6% increase over control. Attempts to separate and recover the two long-chain bases through HPLC for individual study in the acridine orange assay were not successful. However, from previous results, it may be hypothesized that the dihydroxy long-chain base from the wheat germ, 4,8-sphingadienine (d18:2), will have the greatest effect on increasing proton transport via the PPase in the tonoplast. These results support a role for the breakdown products of sphingolipids in regulatory cell processes in plant tissues, especially membrane transport and communication.

The Effects of Prenatal Alcohol Exposure on the Developing Sympathetic
Nervous System in the Rat

Grace J. Wang

Prenatal alcohol exposure has been shown to impair the ability to activate the sympathetic nervous system for thermogenesis. The present research investigated the effects of prenatal alcohol exposure on the developing sympathetic nervous system by several factors in Brown Adipose Tissue (BAT) thermogenesis: activation of cholinergic receptors on the sympathetic postganglionic neuron to indirectly cause the release of noradrenergic junction, the binding of norepinephrine to beta-adrenergic receptors, and the functional responsiveness of BAT following sympathetic activation via assays for 3,5,3'-triiodothyronine hormone, or T3. Pregnant females were randomly assigned to one of three types of diets: a control diet, which consisted of lab chow and water, an ethanol liquid diet, where 35% of its calories were derived from ethanol, and a liquid diet, where 0% of its calories were derived from ethanol to control for nutritional effects of liquid administration. When the offspring were 20 days of age, the subjects were randomly assigned to one of five treatment groups: control (no injection), saline (0.9% NaCl), isoproterenol hydrochloride (50, 100, 200 or 400 ug/kg), d-amphetamine hydrochloride (0.5, 1.0, 2.0, or 4.0 mg/kg), or nicotine (0.05, 0.1, 0.2, 0.4, or 0.8 mg/kg). A tissue implantable thermistor was inserted into a guide cannula implanted and following injections, BAT temperatures were recorded for twenty minutes at two minute intervals. The results for animals that were not injected indicated that alcohol-exposed animals have lower BAT temperatures compared to both control groups, demonstrating an inability to produce thermogenesis. The nicotine results indicate that prenatal alcohol-exposed animals have a greater density of or have more sensitive cholinergic receptors on their sympathetic postganglionic neurons compared to both control groups. The cholinergic receptors thus may be more easily desensitized by lower concentrations of ACh. This may lead to deactivation of the norepinephrine neuron in the event of an activational stimulus. Alcohol-exposed rats also exhibit an impairment in the release of norepinephrine from the noradrenergic terminal, as shown by the amphetamine results. This impairment can be overcome with a high degree of sympathomimetic stimulation, because the alcohol-exposed rats actually experience a greater thermogenic response to high doses of amphetamine compared to both control groups. The alcohol-exposed rats also have a greater density of beta-adrenergic receptors compared to rats from both control groups, as shown by the isoproterenol results, demonstrating the phenomena of deregulation due to the lack of norepinephrine that is released from the norepinephrine neuron. BAT excisions and subsequent T3 assays demonstrated that prenatal treatment did not affect levels of T3 in brown adipose. This correlated with earlier studies which showed that UCP levels did not differ according to prenatal treatment group. However, further studies of whether the UCP is properly embedded in the mitochondrial membrane need to be investigated before drawing conclusions about the functional capabilities of BAT itself. Prenatal alcohol exposure evidently alters many of the steps in the sympathetic nervous system which are enacted to cause thermogenesis.

The Path Less Traveled by the Mauthner Cell: The Effect of Ventral Root Cuts
on the Pathway of the Regenerating Mauthner Axon

Michael Wong

The central nervous system (CNS) of higher vertebrates cannot regenerate, but the peripheral nervous system (PNS) can regenerate and recover function. Damaged CNS neurons prefer the PNS micro environment and can be grown in the PNS either by placing the damaged CNS neuron on PNS tissue in vitro (Varboneto et al., 1978), or by allowing it to regrow into a PNS graft in vivo (David, Aguayo, 1985, Richardson et al., 1980, Smith, Kodama, 1991). The PNS can induce regrowth of damaged CNS axons and lure CNS neurons into the PNS, making an inappropriate pathway choice (i.e., intrinsic CNS neurons into the PNS). Despite the regrowth of the CNS, unless the correct pathway choice is made, functional recovery is unlikely.

In this study, these requirements for spinal cord repair were explored using the goldfish spinalcord as a model for spinal cord injury using the Mauthner cells as a model for intrinsic, descending CNS neurons. The purpose of this study was to perform two surgeries to explore the following question by observing the pathway choice of the M-cells: what is the influence of the PNS on the pathway choice of damaged CNS neurons? Two surgeries were reformed; 1) Selective Axotomy at the Spinal Medullary Level Pathway (SASMLF), and 2) Selective Axotomy at the Spinal Medullary Level and Ventral Root Cut Pathway (SASMLVRCP). The SASMLP fish will have no PNS damage, while the SASMLVRCP fish will have damaged PNS motoneuron pools as described by Bentley and Zottoli (1993).

The hypothesis was that the Mauthner axons of the SASMLVRCP fish will be drawn into the first ventral root by the contact with the damaged PNS neurons whereas the SASMLP Mauthner axons will take the appropriate pathway down the spinal cord.

The results disproved the hypothesis. The pathway choice of the regenerating Mauthner axons with and without PNS damage did not show significant differences. The PNS damage did not seem to influence the outgrowth or pathway choice of the regenerating Mauthner cells. This line of research suggests further studies to elucidate pathway mechanisms and hopefully bring about a medical application that may aid in spinal cord repair.

Shifting Syllable Clusters: Characterizing Changes
in Untutored Zebra Finch (Taenopygia guttata) Song

Justin P. Wright

Juvenile male zebra finches (Taenopygia guttata) were removed from their natal cages at day 18 and were placed with either hearing or deaf females to examine the role of female selection in song development. Songs of related and unrelated birds were compared in an attempt to determine the existence and function of an innate auditory template which might guide song development. All comparisons between songs were based on a new method for characterizing individual bird's songs. This method calculated the "song space" of a bird by enclosing the space around the cluster of all of the syllables produced by the subject. The area of this cluster provides a measure of the variety within a bird's repertoire, and the overlap between two birds' song space indicates how similar the two songs are.

The song space of birds raised with hearing females decreased at a steady rate as the birds aged, indicating that the variety of their song was decreasing - a pattern one sees in normal song development. The song space of birds raised with deaf females did not undergo a similar reduction until after they were placed in an aviary with normally raised adult make and female zebra finches. Related birds showed a greater degree of overlap with each other than with unrelated birds, indicating that despite the fact that they had never been placed in contact with each other, siblings tended to sing similar songs. These results shed further light on the existence, function, and mechanisms of an innate auditory template which guides song development.

CHEMISTRY

Low Temperature Quenching of Nitric Oxide [A2[Sigma]+, v'= 0]
Laser-Induced Fluorescence

Laralyn A. Bergstedt

Laser light in the 225-227 nm range is used to effect single-photon excitation [A2[Sigma]+, v'= 0 <- X2[Pi], v''= 0] of nitric oxide at temperatures between 217 and 298 K. Analysis of the subsequent fluorescence emission [A2[Sigma]+, v'= 0 <- X2[Pi], v''= 3] yields a quenching cross-section describing the energy transfer between nitric oxide and its collision partner. Cross-sections for NO self-quenching at 217 K are studied as a function of rotational state and the temperature dependence of quenching by dimethyl ether is determined.

Nitric oxide self-quenching measurements at 217 +/- 2 K indicate insignificant quenching dependence on rotational state. Over the rotational spectrum, cross-sections varied by 6% from 41.09 +/- 1.06 Å2 to 43.76 +/- 2.63 Å2 at K'=3 and K'=17, respectively. Difficulties encountered in calibrating the laser wavelength preclude a definitive conclusion about the relationship between rotational state and energy transfer, but the small range in cross-section values indicates that if dependence does exist, it is minimal. Systematic error in quenching measurements results in a 10% cross-section variation between different research groups. Thus, a 6% variation caused by possible rotational state effects is comparatively insignificant.

Quenching cross-sections for dimethyl ether between 217 and 298 K illustrate increased quenching efficiency with decreasing temperature. Cross-sections were 60.96 +/- 0.58 Å2, 72.95 +/- 0.74 Å2, 76.27 +/- 0.69 Å2, and 80.66 +/- 0.75 Å2 for temperatures of 273.1 +/- 0.2 K, 236.8 +/- 0.1 K, and 214.3 +/- 0.2 K, respectively. Analysis of cross-section dependence on temperature with the Parmenter attractive force model yields a dimethyl ether-nitric oxide potential well depth of 205 cm-1. Indicative of fairly strong temperature dependence, this well depth is consistent with the predicted dominance of collision complex formation at low temperatures.

The Structural Characterization of
Southeast Asian Dart Poison Components

Christine A. Carter

Southeast Asian dart poisons from the Antiaris toxicaria tree often contain biologically active materials. Used by indigenous people in these areas as their main source for hunting game, the active components of these A. Toxicaria-derived poisons are believed to be cardiac glycosides. Chemical research has shown that the biochemical mechanism of these compounds involves the inhibition of the essential cell enzyme Na+/K+-ATPase. Previous research has also shown that A. toxicaria-derived poison samples have some inhibitory effect on this enzyme. However, no definitive studies correlating the bioactivity of the individual A. toxicaria components with their structure have been performed. The goal of this research was to make such comparisons.

Utilizing preparative scale HPLC analysis, 13.6 mg of one of the individual components was isolated. The structure of this component was pieced together using various NMR techniques. In comparison to a- and [beta]-antiarin, two previously isolated A. toxicaria components, these studies showed that the antiarigenin steroid nucleus was conserved in this compound. The glycoside portion proved to be different from the antiarins in that it contained a methoxy group in the C-2' position of the six-member ring.

Structure/Function Studies of HIV-1 Reverse Transcriptase:
The Characterization of Site 1 Mutants

Justin M. Cole

Photoaffinity labeling studies employing the nucleotide analogs 5-N3-dUTP, 8-N3-ATP, and 8-N3-dATP have identified two distinct sites of binding on the p66 subunit of RT. These have been deemed site 1, a lower affinity site, and site 2, a higher affinity site. Site directed mutagenesis through the method of unique site elimination has been utilized to introduce mutations into site 1 of the protein. The mutant proteins generated were W24H, I37Q, and K30M. Site 1 comprises the highly conserved amino acid residues from Val21 to Ile37 on RT. The high level of conservation in this region of the protein, our ability to crosslink nucleotide analogs there, and past mutagenic work in the vicinity of site 1 all support the hypothesis that site 1 has an important biological function. It now appears that this function is as an allosteric ATP binding site that modulates active site nucleotide binding.

Mutations introduced at amino acid residues Trp24 and Ile37 do not lead to significant alterations in the steady-state kinetics of the resulting mutant proteins. Each of these mutations gives rise to a protein with near WT Kms using all three primer/templates studied. The kcat of both proteins is actually elevated for prC-dG12-18 and prA-dT15. Using pdC-dG12-18, kcat is either slightly depressed or else unaffected. For I37Q it is 65% that of WT, while for W24H it is 104% of WT.

The mutant protein K30M retains between 30-60% of WT activity depending on primer/template, yet shows a dramatic increase in Km for RNA/DNA primer/templates. The Km of K30M using prA-dT15 is 19 fold higher than WT, and that using prC-dG12-18 is 9 fold higher than WT. On the contrary, the Km for K30M using pdC-dG12-18 is only elevated 1.5 fold. This indicates that Lys30 might selectively interact with RNA/DNA hybrid primer/templates. The fact that site 1 may be involved in primer/template binding is suggested in a low resolution crystal structure of RT complexed with a short segment of double stranded DNA. Filter-binding assays have been attempted in order to determine the role of site 1 in primer/binding, but have thus far been unsuccessful due to technical difficulties with the assay.

In the presence of complimentary primer/template, 5-N3-dUTP labels RT at two distinct sites. The Kd of these two sites is not altered in K30M or I37Q. This fact, along with mutagenic work performed in site 2 by Seddon Thomas `96, has led to the proposed model that two overlapping nucleotide binding sites are created near site 2 in the presence of primer/template. One of these is the active site, while the other may be the site of substrate inhibition. The fact that K30M retains the same level of substrate inhibition as WT provides indirect support for this model. However, ATP has been demonstrated to greatly increase the binding affinity for 5-N3-dUTP at these sites. This modulatory effect is greatly attenuate in K30M. This suggests that site 1 may be involved in low affinity ATP binding for the purpose of modulating nucleotide binding at the active site of RT. When functioning in this role, ATP is known to have a Kd of 870 micromolar for WT. Future experiments should be performed both to demonstrate that this value is elevated for K30M, as well as that the Kd for 8-N3-ATP at p66 site 1 increases from the WT value of 148-164 micromolar.

Light, Night and Heat: The Synthesis and Characterization of Liquid Crystals
through Cross-Polarizing Light Microscopy and Calorimetry

Susan Gillmor

This year we embarked on a project to synthesize and characterize a family of zirconium based liquid crystals. In the effort to make the metal complex, we have completed the synthetic pathways to three different pyrrole based ligands with a common basis of their connection to p-alkoxyphenyl rings through ester linkages. Our preliminary characterization through microscopy and DSC indicates that these ligands show promising liquid crystalline properties. We have concentrated on the even length carbon chains in an effort to see a wide range of each series and to find the limits of the liquid crystalline behavior in each family of ligands. Future plans include completing each of the ligand series with the odd number chains to follow up on our initial studies of the even length alkoxy chains, using X-ray diffraction to complete the characterization of the ligands and also finishing the synthesis of the zirconium complex.

An Investigation of the Chemical Defense of Willow Species;
Isolation and Characterization of Major Phenolic Glycosides

Edith C. Glazer

Willow species are known to produce phenolic glycosides as secondary metabolites used in the plant's natural defense system. The chemical extracts from leaf tissues of two different taxa, Salix sericea and Salix eriocephala, along with that of the hybrid offspring of the two species, were screened for phenolic glycosides.

The focus of this study was to compare the chemical constituents of the different taxa and the hybrid. To achieve this goal, it was necessary to refine methods of extraction and isolation of the phenolic compounds present in the plant systems, and to characterize the compounds obtained. The chemical content of the plant extracts was analyzed by gas chromatography / mass spectroscopy (GC/MS) and high pressure liquid chromatography (HPLC). Through a process of flash column chromatography and preparative high pressure chromatography, a number of compounds were isolated. Subsequent proton and carbon nuclear magnetic resonance spectroscopy (NMR) confirmed the classification of the compounds due to the characteristic carbohydrate and phenolic glycoside signal patterns. A compound isolated from the S. sericea plant extract, as well as one isolated from the hybrid plant extract, was characterized as salicortin. In addition, a novel compound present in the hybrid, but not indicated in either parental strain, was isolated and determined to be tremuloidin.

Synthesis of Ruthenium-Polypyridine Complexes and the Attempted Formation
of Mono- and Bi-dentate Anthraquinone-Polypyridine Ligands

Joshua M. Hubbard

The goal of this research has been the synthesis of a series of charged polypyridine ligands and the formation of ruthenium complexes with these novel ligands. The 1-(2'-(1'methyl-pyridinium))-2-(2"-pyridine)aminomethane, Pre-IDP+, ligand has been synthesized and a possible dehydrogenation preparation of the imine ligand, IDP+, by Pd/C worked out. However, the IDP+ ligand appears to be unstable to water. The Pre-IDP+ ligand was then complexed to both Ru(II)(bpy)2 and (Ru(II)(NH3)4, and the shift in UV absorbance of these complexes measured. Due to changes in the UV absorbance, it is hypothesized that excitation of an electron into the Pre-IDP+ ligand occurs without formation of the imine linkage. The formation of a charged pyridinium ligand containing an anthraquinone moiety was attempted, and while not fully purified, the synthesis seems to have been successful. To expand upon this synthesis, the formation of a mono-dentate ligand containing an anthraquinone and a bipyridine was attempted. Unfortunately, this reaction seems to have been unsuccessful under a variety of conditions.

Synthetic Routes to Azapentahelicenes

Chia-Yu Hwu

Azapentahelicenes are polycyclic, ortho-fused, nitrogen-containing aromatic rings. Carbocyclic helicenes have been synthesized and studied as interesting chiral molecules for their physical properties and structure. The present work focused on the preparation of aza analogs of the five-ring system. The lone pair of electrons on the nitrogen atom provided a means by which chemical and physical properties could be assessed. The first synthesis of 1-azapentahelicene was accomplished in three steps in 3.2% overall yield. The initial step was oxidation of 7-methylquinoline to the aldehyde, the second step was a Wittig reaction, and the final step was a photocyclodehydrogenation. An alternate route to 1-azapentahelicene via the Skraup reaction was explored. A pathway to 2,13-diazapentahelicene, a potentially interesting bidentate chiral ligand, was patterned after the same synthetic strategy.

Diels-Alder Routes to Carbolines

Matthew G. Jarvis

Attempts to develop general routes to [beta]- and [gamma]-carbolines utilizing intermolecular hetero Diels-Alder reactions were unsuccessful. Isocanthine was prepared by a novel three-step synthesis, the key step of which was an intramolecular hetero Diels-Alder reaction. This step was performed on (4-pentynyl)-1H-indole-3-carboxaldehyde O-methyloxime, which was synthesized using traditional reactions from indole-3-carboxaldehyde.

The unmaximized yield of this synthesis represents a more than two-fold improvement over that recently reported for an eight-step synthesis. All Diels-Alder reactions were attempted in refluxing sulfolane, without success. The successful intramolecular reaction was performed in sealed ampules under various conditions.

Protein-DNA Interactions between the Bacillus subtilis SOS Repressor DinR and din Operators: Implications for Competence Development

Michael C. Miller

DinR is the 23kD autocatalytic transcriptional repressor of the Bacillus subtilis SOS DNA repair regulatory network, including the recA gene. It is apparent from previous studies that there are two distinct mechanisms for removing DinR from the recA operator during the SOS response and competence development; the former dependent on RecA-mediated autocatalysis and the latter not. This study investigates the binding of DinR to din operators in order to explicate the depression mechanism used during competence development. dinR was amplified from chromosomal B. subtilis DNA and cloned into a E. coli overexpression vector. DinR protein was then purified to homogeneity by affinity and cation-exchange chromatography. DNase and hydroxyl radical footprinting showed that the DinR dimer makes contact with six short stretches of the dinC DNA backbone primarily on the same side of the helix as the consensus bases in the major groove. When mapped on to the recA sequence, these data suggest that there is some overlap between the DinR-protected bases and those protected by ComK, the competence transcription factor (Leendert Hamoen, personal communication). This suggests that DinR must be displaced from the DNA before ComK can bind immediately upstream of the -35 site.

Preliminary studies suggest improved conditions for large scale, high yield purification of DinR for structure determination by NMR. NMR appears feasible, but difficulties with solubility and aggregation must still be overcome.

The Synthesis and Characterization of Precursors to Zirconium-based Liquid Crystals

Amy L. Prieto

We have made significant progress in the synthesis and purification of families of alkoxy phenol, alkoxy phenolate, and pyrrole ligands with alkyl chains ranging from 6 to 18 carbons in length (even numbers). Preliminary characterization using differential scanning calorimetry (DSC) on members of these series is reported here. Within the alkoxy phenolate and pyrrole families a birefringent phase between the room temperature solid phase and the isotropic liquid phase has been observed. DSC data appears to indicate that this intermediate phase may be another solid phase, rather than a true liquid crystalline phase.

High pH Autodigestion of DinR, the B. subtilis SOS Repressor

Joshua B. Resnick

The B. subtilis SOS system is made up a group of approximately 20 genes coding for 3 major DNA repair mechanism which are all constitutively repressed by DinR in the absence of a DNA damage signal. The system is activated through the cleavage of the repressor. In vivo, the cleavage is presumably mediated by RecA, which recognizes and is activated for DinR cleavage by the ssDNA signal.

In fact, DinR, along with the E. coli SOS repressor, LexA, is part of a class of enzymes capable of intramolecularly catalyzing their own cleavage. The model for the autodigestion has a deprotonated amine on a lysine residue acting as a general base in order to increase the nucleophilicity of the oxygen of a serine reside, which then cleaves the enzyme by attacking the carbonyl of a peptide bond. This autodigestion can be induced in vitro by raising the pH of the environment high enough to deprotonate the Lys residue. I have found that this autodigestion has a pH of 10.0 (10.1). The rate of the reaction is highly dependent on pH, with the kmax of 0.81/hour occurring at a pH of 10.5.

The rate of digestion is also highly temperature dependent. At pH 9.67, an increase in the temperature of 10[ring]C leads to a 4-fold increase in the rate constant. At pH 10.16, a like increase in temperature leads to a 3.5-fold rate constant increase.

The energy of activation (Ea) of the autodigestion was found to be 105 kJ/mol at pH 10.16 and 113 kJ/mol at pH 9.67.

Synthesis and Reactivity of a Novel Benzene-Ruthenium (II) Lewis Acid

Steven W. Singer

The goal of this project was to synthesize a reactive organometallic Lewis acid that would form stable complexes with weak Lewis bases. Synthetic routes to novel complexes, [([eta]6-C6H6)Ru(PPh3)2I]+ X- (X=SbF6-, PF6-) were developed, and the iodide was abstracted to form the Lewis acid [([eta]6-C6H6)Ru(PPh3)2]2+ [X-]2. Attempts to coordinate acetone to the dicationic Lewis acid were complicated by irreversible counter-ion coordination in the SbF6 complex, and hydrolysis of the counter-ion by coordinated acetone in the PF6 complex. Acetonitrile was successfully coordinated to the SbF6 analog of the Lewis acid to form [([eta]6-C6H6)Ru(PPh3)2(NCCH3)]2+

[SbF6-]2. The acetonitrile complex was characterized, and its spectroscopic features compared to reported acetonitrile complexes.

Structure/Function Studies of HIV-1 Reverse Transcriptase:
Characterization of Motif E Mutants

Seddon Y. Thomas

HIV-1 Reverse Transcriptase (RT) is a unique enzyme used by the HIV-1 retrovirus to transcribe its diploid single-stranded RNA genome into double-stranded DNA for incorporation into the host cell. This enzyme has been the focus of research because it is a vital step in the viral pathway and does not have a human analog. Since several inhibitors have been designed to work against this enzyme (AZT, ddI, and ddC), further research correlating structural elements of RT with enzymatic function should provide information in designing more specific inhibitors and in understanding how the enzyme works in the cell.

The focus of this study has been to understand the relationship between structure and function in a highly conserved region of RT known as Motif E. Motif E is composed of two antiparallel [beta] sheets 12-13 located between amino acids 227-237 in the p66 subunit of RT (Jacob-Molina et al. 1993). To study Motif E, tryptophan-229 was substituted with valine (W229V) or histidine (W229H) and methionine-230 was substituted with alanine (M230A) or leucine (M230L) by site-directed mutagenesis. This project continued previous work and involved the further characterization of W229V, M230A, and M230L RT mutants and the generation of a fourth mutant, W229H. We report an increase of Km and a decrease in kcat for dTTP and dGTP with both RNA and DNA templates for the non-conservative RT mutants (W229V and M230A). In addition, substrate inhibition for dTTP with an RNA template was abolished in these mutants. Cross linking studies with [[gamma]32P]5-N3-dUTP in the presence of complementary primer-template indicate a loss of binding affinity (Kd) for a high and low affinity site in the p66 subunit and a loss of specificity for complementary protecting nucleotides in W229V and M230A. To explain this data, a model of overlapping sites was proposed for RT with a productive, high affinity active site and a non-productive, low affinity substrate inhibition site.

Heterogeneous Atmospheric Chemistry: Design, Construction, and Preliminary Results of an Apparatus for a Kinetic Study of the Adsorption of Perfluorooctyl Bromide onto Soot

Erin S. Whitney

Heterogeneous reactions are those in which the reactants are of different physical phases. As applied to atmospheric chemistry, the study of atmospheric heterogeneous reactions has developed primarily in the last ten to twenty years as researchers have realized roles of these reactions in key atmospheric processes.

Our research aims to understand the interactions of tropospheric trace gases with atmospheric particulates. We started a kinetic investigation of the uptake of perfluorooctyl bromide (PFOB), a possible blood substitute, onto soot. Once emitted in the troposphere, PFOB(g) could diffuse into the stratosphere to liberate the bromine radical, an even more efficient scavenger of ozone than chlorine. The interaction between PFOB(g) and tropospheric soot provides a possible removal mechanism for PFOB(g).

I designed, built, debugged, calibrated, and obtained preliminary results from a custom vacuum chamber equipped with temperature and pressure controls which simulate tropospheric conditions. Using a Fourier-transform infrared (FT-IR) spectrophotometer, I monitored the thickness and growth rate of ice and PFOB(s) films on silicon and soot substrates as a function of temperature and pressure. I found a trend of increasing density and possible phase changes in PFOB(s) films from -165[ring]C to -90[ring]C, and I calculated sticking coefficients for PFOB(s) (0.085 to 0.027 from -165[ring]C to -90[ring]C) and ice (0.80 and 0.41 at -165[ring]C and -100[ring]C, respectively) on silicon substrates. Our experimental sticking coefficients for ice agreed reasonably well with literature values and served as a calibration of the apparatus. For both PFOB(s) and ice multilayers, the identity of the substrate (soot or silicon) did not drastically change the sticking coefficients.

Confirmation of the PFOB(s) density trend will allow us to plot temperature-programmed evaporation profiles for PFOB(s) in order to obtain kinetic parameters which are essential to general climatic models. Our kinetic investigation also provides a template for the future study of other heterogeneous atmospheric reactions with our versatile apparatus.

COMPUTER SCIENCE

A Debugger-Friendly Distributed Tuple Space

Alice J. Bernheim

Many of the performance features of parallel programs, including massive concurrence and nondeterminism, make debugging difficult. To study this issue, we have continued to extend Linder, a public domain programming environment supporting Gelernter's tuple space programming model.

The first section of this thesis develops protocols to support effective distribution of tuples among disparate processes. This distribution has potential performance advantages, but also complicates the coordination of processes.

In the second section, we present protocols that support centralized debugging of tuple space programs. The Linder Tuple Space Debugger (LDB) is a textually-based interactive debugging environment. LDB allows users to set breakpoints on tuples, query the tuple space, and examine the communication history of the system. With its unique mixture of history information and interactive control, we believe novice users will find LDB a conducive debugging environment.

An Algorithm for Finding Hamiltonian Cycles in Grid Graphs Without Holes

Christopher M. Umans

The Hamiltonian cycle problem for general grid graphs is NP-complete. However, it is conjectured that an efficient algorithm to solve the Hamiltonian cycle problem exists for a subclass of general grid graphs known as grid graphs without holes. This thesis contains a number of results concerning the structure of this subclass of graphs which are then used to give a correct polynomial time algorithm for finding Hamiltonian cycles in grid graphs without holes.

A module System for Loom

Leaf E. Petersen

A strong module system is a very important language tool for developing software systems. Classes alone do not allow for sufficient levels of abstraction and separate compilation. Modules can be very helpful in organizing codes, providing abstraction, and supporting separate compilation. Abstraction makes it difficult to share types between modules, but transparent types can propagate too much information to allow separate compilation. The use of partially abstract types and manifest types can help to avoid these problems.

Earlier work by Robert van Gent and Angela Schuett under the direction of Professor Kim Bruce resulted in the design and implementation of the language PolyTOIL, a type safe object-oriented language with strong polymorphic features. LOOM is a direct descendant of PolyTOIL which omits subtyping in favor of a more flexible version of matching, including matching-based subsumption. We give an overview of LOOM and of a prototype interpreter for the language. Proofs of the complexity of the matching algorithm and the decidability of type checking are presented. We describe the design and implementation of a module system for LOOM, and present an in-depth discussion of the issues that motivated and affected the design process. Formal type checking and semantic rules are given, and the prototype implementation is described. The module system is evaluated, and proposals are made for further work.

Exploring Aperiodic Tilings With Inflation

Forrest P. Trepte

We develop a data structure for representing dual graphs of aperiodic tilings generated by inflation rules. An index sequence identifies a tiling about a point by locating the point within an infinite hierarchy of self-similar tilings known as inflations. We use finite-length index sequences as an addressing system and an n-digit address identifies a tile within n inflations of some prototile. An algorithm is constructed to find the addresses neighboring any given tile. Appending digits to an address extends the currently represented region, placing it within a larger patch to simulate the exploration of an infinite expanse of tiles. The information maintained grows as needed and the number of tiles in the patches represented is exponential in the number of digits stored. Our system could be used to investigate very large quasiperiodic structures and the principles behind the data structures illuminate many beautiful properties of aperiodic tilings.

GEOLOGY

The Geochemistry and Petrogenesis of Volcanic Rocks Near Keno, Oregon,
in the Southern Cascade Range

Myra J. Hill

Volcanism in the northwestern United States is the result of both subduction-related and extensional tectonic processes. The overlap of these tectonic regimes occurs on the eastern margin of the High Cascades. Geochemical changes across this border can be marked, with calc-alkaline Cascade arc volcanics being overprinted by relatively younger extensional lavas. Within an eight square mile area mapped in the vicinity of Keno, Oregon, in the southern Cascades, both types of volcanism can be seen to be responsible for the lavas erupted.

Within this area six eruptive units were determined, five of which contain lava flows. These units were identified in hand sample; four were categorized as basaltic andesites and one as a basalt. The basaltic andesites are generally light gray and porphyritic, while the basalt has a characteristic diktytaxitic texture. Faulting is usually expressed as ridges trending NW-SE, the general trend of Basin and Range faulting in the region. Sources for the basaltic andesites are believed to be vents to the south and northwest, but a source for the basalt has not been definitively determined. Small pyroclastic cones are also present here.

A petrographic study of 29 samples representing the entire 8 mi2 map area supports the classification of the units as basalts and basaltic andesites. All units contain plagioclase, clinopyroxene, and olivine, with accessory magnetite and Cr-spinel. All units also have large zoned plagioclase phenocrysts which are more frequent in the basaltic andesite samples. The basaltic andesites are generally intergranular with some large euhedral olivine phenocrysts, and the basalt samples are diktytaxitic and ophitic.

Geochemical analysis was done by XRF and INAA on these 29 samples. A clear separation of the basalt and basaltic andesite units is seen on an AFM triangle plot; the basalt is tholeiitic, and the basaltic andesites are calc-alkaline. Variation diagrams and REE plots support a model of crystal fractionation within the basaltic andesites, as suggested in the petrography by the presence of the zoned plagioclase and large olivine phenocrysts. The basaltic andesites are also more enriched in lighter elements typically from continental crust.

The calc-alkaline samples thus all seem to be derived from subduction and probably share a common parental magma. The tholeiitic basalt, however, remains geochemically distinct from the other units in this area and is related to extensional tectonics in the Basin and Range.

Inside a Latest Pleistocene Ice-Contact Submarine Fan,
Northern Puget Lowland, Washington

Mary Ann Hirshfeld

Mapping of surficial deposits, well logs, and marine seismic reflection studies demonstrate that Cattle Point, the south tip of San Juan Island, and adjacent submerged Salmon Bank represent a series of latest Pleistocene (Fraser glaciation) ice-contact deposits. San Juan Island lies in northwest Washington in an extensive trough that was filled with Cordilleran ice during the Fraser glaciation. Since deglaciation, erosion resulting from glacioisostatic rebound and eustatic sea level rise has reshaped some glacial depositional and erosional features. During deglaciation of northwest Washington after about 14.0 14C yrs B.P. (14.0 ka), the Puget and San Juan Lobes of the Cordilleran ice sheet calved back rapidly, pausing periodically on topographic highs. Retreating ice probably grounded near Cattle Point before about 13.2 ka. The > 2 km wide, 100 m thick deposit of sand and gravel, named the Cattle Point moraine by J Harlen Bretz, is interpreted as an ice-contact submarine fan. Mapping of sea cliffs along the margins of Cattle Point shows that 700 m long west- and south-dipping beds of interbedded sands and medium gravels rest on bedded medium sand. Channels eroded > 10 m into the sand contain boulders up to 35 cm in diameter. Paleocurrent measurements based on pebble imbrication indicate flow distributed symmetrically within 50o of 180o. Two 500 m wide channels filled with glaciomarine diamict were eroded into the fan, presumably as the ice lobe retreated north from Cattle Point. Seismic reflection profiling of Salmon Bank shows that > 60 m of flat lying or gently dipping sediment overlies bedrock or glacial till, implying that this adjacent, 6 km-long feature is genetically related to the ice-contact submarine fan at Cattle Point. A hummocky bedrock ramp underlying Salmon Bank and Cattle Point provided a series of minor pinning points, slowing ice retreat, and allowing the accumulation of glaciomarine sediment. Ultimately the ice margin grounded at Cattle Point, and extended stability allowed the growth of an extensive ice-contact submarine fan. The glaciomarine complex of Salmon Bank and Cattle Point could have been deposited in several tens of years. Seismic reflection profiles of Griffin Bay reveal a hummocky, bedrock floor with only minor sediment filling channels in bedrock. The Friday Harbor Sand and Gravel Pit represents the next location of extended terminus stability, allowing the growth of an ice-contact delta. Stratigraphic relationships, sedimentary structures, and paleoflow directions provide information about the depositional processes of these glaciomarine structures and allow a better understanding of the retreating Cordilleran ice.

Terrestrial and Marine Evidence for Changing Ice Regime During Latest Pleistocene Ice Recession, Northern Puget Lowland

Willard S. Morgan

Deposits and landforms on the south end of Lopez Is. and beneath adjacent marine water in the Puget Lowland, Washington, record retreat of Cordilleran ice, glaciomarine and marine deposition between 13.2 and 12.4 14C yrs B.P. (ka), and rapid isostatic rebound. We mapped terrestrial landforms, measured ice flow direction, compiled well-logs and collected 16 km of shallow seismic reflection lines over Lawson Reef, an arcuate submarine bank 4.5 km long and 45-80 m thick, located SE of Lopez Is. The extensive exposures of glaciomarine fans and diamicts on Lopez, throughout the San Juan Is., and on the sea floor, imply widespread sedimentation from grounding line tidewater margins during ice retreat. Striae, grooves and troughs oriented from 165o to 250o record reorientation of flow as ice thinned and evolved a lobate margin.

Marine seismic surveys of Lawson Reef demonstrate that it is a morainal embankment composed mainly of submarine outwash. Crossbedding and features record paleoflow to the south and southwest. The morphology and composition of Lawson Reef and regional relations suggest that it formed at the margin of a lobe of Cordilleran ice during a brief stillstand. Submarine fan deposits on southeast Lopez Island suggest a contiguous margin from Mackaye Harbor to the east limb of Lawson Reef where active ice and abundant meltwater constructed ice margin deposits.

On S. Lopez Is., glacioisostatic rebound has raised shallow subtidal sediment containing in situ Saxidomis gigantea > 130 m, probably soon after about 12.5 ka. The terrestrial and marine evidence suggests that retreat of Cordilleran ice from NW Washington and Laurentide ice from coastal Maine were similar in chronology, styles of sedimentation and magnitude of glacioisostatic rebound.

Paleoenvironmental Reconstruction of the Cyclic Lithologies
at Monte dei Corvi, Ancona, Italy

Bryan D. Stanley

Monte dei Corvi is situated along the eastern coast of Italy. These seaside cliffs are located on the Conero Riviera about ten miles south of the port-city of Ancona in the Umbria-Marche region. The cliffs contain excellent exposure of upper Miocene-aged lithologies with remarkable amounts of bioturbation. The lithologies also contain vast amounts of foraminifera. Lithologies are limestones, marly limestones, marls, and shales. The different lithologies represent pelagic cyclic to pseudo-cyclic deposition dependent on changes in environmental parameters. The abundance of bioturbation and foraminifera provided the opportunity to examine the ethologic succession of organisms in an ever- changing environment. Eight meters of Serravallian-aged lithologies were examined in the field between June 26, 1995, and July 10, 1995, by Jack Denman `96 of Colorado College and Bryan Stanley `96 of Williams College. In the field, the beginnings of an ichnologic analysis were performed in order to reconstruct the paleoenvironment at the time of deposition and to discern the cause for the cyclic lithologies. In the United States, each partner received four meters of rock to examine in order to reconstruct the paleoenvironment using the principles of ichnology to refine environmental settings . Micropaleontology was used strictly to look at ethologic changes through time.

Trace fossil and resulting trace-maker behavior were studied in order to identify the Monte dei Corvi trace fossils according to an ichnotaxonomic system. The traces, Thalassonoides, Planolites, Chondrites and Zoophycos were found in the outcrop. This placed the trace fossils in the Zoophycos Ichnofacies, which has the interpretation of being a benthic off-shore deep-water environment below the storm-wave base. Ichnofabric analysis resulted in distinct ethologic characteristics which revealed varying environmental parameters. Cross-cutting relationships, abundances, and location in bed revealed that the Monte dei Corvi trace fossils had preferences towards the lithologies that they would choose to inhabit. Identification of Chondrites and Zoophycos revealed that changes in lithologies were related to changes in oxygen levels in the water. Both environment and organism responded to large changes in oxygen. Even, planktonic foraminifera, like Orbulina or Globigerina, responded to changes in oxygen indicating stress throughout the water column.

Oxygenation variation was responsible for the paleoenvironment stresses on organisms and for the deposition of particular lithologies. Limestone represented periods of oxia; marl represented disoxic periods; and shales represented almost complete anoxia. Trace-maker behavior declined during the deposition of the shales, but trace fossils became extremely abundant upon the return to a more oxic period. Foram behavior often appeared inverse to trace-maker behavior. Forams would be more abundant in the oxic periods while conditions in the water column oxidized all dead organic material contributing to the lack of food in the benthic situations. The result was that trace fossils, like Chondrites, Zoophycos and Planolites, became less abundant except for Thalassonoides which prefers a well-oxygenated environment. In the anoxic shales nothing survived until the return of minimal amounts of oxygen. The first trace to be seen after anoxia was Planolites.

The cause of oxygen-deprivation was debatable, but previous examination by Kruge et al., (1994) and Montanari et al. (1995) reveal high amounts of algal material in the shales. Algal blooms most likely caused the anoxic episodes by systematically robbing the entire water column of oxygen and killing everything off. Siliclastic input from the nearby Alpine and Apennine orogenies was most likely responsible for inducing periods of disoxia by clouding the waters and killing off foram carbonate production. Siliclastic influxes created a similar yet not as strong situation as algal blooms and perhaps allowed for the algal blooms to initiate.

The reasons why algal blooms and siliclastic input might vary is questionable. Climatic changes could induce high siliclastic input or algal blooms by creating a wet/dry oscillation. This may be tied into Milankovitch cycles; however, results have given varying cycle durations. Increased tectonic activity could be responsible by producing more uplift and perhaps more denudation which might start disoxia and lead to anoxia. A modern analog to this might currently lie off the coast of Italy in the Adriatic Sea.

Metamorphic History of Archean Ultramafic Rocks of the Tobacco Root Mountains, Southwestern Montana

Rebecca B. Thomas

The Archean units of the Tobacco Root Mountains, southwestern Montana, have been divided into three metamorphic suites and have been a puzzle to the many researchers that have studied in the area. Two years ago, a group of senior geology majors did their senior thesis research in these mountains, sponsored by the W. M. Keck Foundation. In this project they discovered that there were potentially two periods of metamorphism and they learned something about the geochemistry of the rocks of two of the three metamorphic suites. In the summer of 1995, another Keck project went back to the Tobacco Root Mountains to continue what was started by the first researchers. This second project was interested in learning more about the geochemistry of the rocks that comprise the Archean units of the Tobacco Root Mountains and more about the geochemistry of the rocks that compose the three metamorphic suites, the structural relationships of the contacts between the suites, and two rock units that are found in all three metamorphic suites. This project focuses on the ultramafic pods, which are one of the types that are common to all three metamorphic suites.

Physically, the ultramafic pods look different. The outcrops are found in different environments; some are found in the walls of glacial cirques and on mountain ridges, others form knobs in the lowlands. They weather differently; some stand out as massive walls, others blend in with the soil. The textures of the rocks are different as well. Some are massive and greenish-brown, others have orthopyroxene knobs sticking out of them, and some have elongate amphibole crystals tracking all over them.

Mineralogically, however, the samples that were not completely altered look very similar. The common mineral assemblages are olivine, orthopyroxene, magnesio-hornblende, tremolite, anthophyllite, and spinel. At thin section scale, some of the samples contain only amphibole and others contain a variety of minerals; some are fine grained, and some have large orthopyroxene or olivine porphyroblasts.

Mineral chemistry was performed on a scanning electron microscope with an energy dispersive spectrometer attached. Using these two tools it was possible to see microtextures and to obtain the chemical formula of the minerals. Among the many textures seen, it was found that some of the amphiboles are zoned, with a magnesio-hornblende core and an anthophyllite rim. Olivine was found to engulf both orthopyroxene and anthophyllite, and amphiboles overgrew everything. The silica content in amphiboles is dependent upon metamorphic grade. In one part of the outcrop, two generations of magnesio-hornblende were found. The second generation had the lower silica content, suggesting that there was a temperature spike that caused the second metamorphic event.

It was determined that despite some physical differences, these pods are all related and had the same metamorphic history, reaching upper-amphibolite grade metamorphism. Those pods that were studied in detail were the largest, zoned, and least altered pods that were found. These pods provided the most complete history, starting with high-pressure prograde metamorphism and ending with low pressure retrograde metamorphism. The pods located in other regions tended to show only the low-pressure retrograde metamorphism part of the pressure-temperature path.

MATHEMATICS

Probabilistic Enumerative Geometry: How Many Inflection Points are Real

Daniel H. Ebert

Classically, enumerative, or counting, questions have been answered in complex projective space where the answers are precise. In this project, we ask these enumerative questions in real afghan space; in real space, the answers may no longer be precise. For instance, changing the coefficients of an nth degree polynomial gives different numbers of real roots. So, we must answer these enumerative questions in real projective space probabilistically, finding the expected, not exact, value. After examining Edelman and Kostlan's exposition and expansion on Kacs formula for the expected number of real roots of a random polynomial, the thesis focuses on trying to find the number of real inflection points of an nth degree polynomial. Interestingly, through Mathematica calculations, the expected number of real inflection points for a quartic and quintic is a little less than twice that of the expected number of real roots for an mth degree polynomial where m is the degree of the resultant of the Hessian curve with the original quartic or quintic polynomial curve.

Analysis of Trend: The Chemistry of Rainfall in Hopkins Forest

Teon E. Edwards

Recent concerns about the environment have led to numerous studies over long periods of time. In this thesis, the chemistry of three types of precipitation collected in Hopkins Memorial Forest is examined. The data are analyzed using a number of methods for trend detection: linear model, nonlinear model, Mann-Kendall Test for Trend, Seasonal Kendall Test for Trend, and autocorrelation. By considering the advantages and disadvantages of these methods and comparing the results from simulated data and the Hopkins Forest precipitation data, the concept trend is explored. Trend is a vague concept; no analytic definition of trend is possible. Various aspects of trend and methods of trend detection are considered throughout this thesis.

Examining Continuity Along Tubular Neighborhoods

Daniel G. Kim

We use concepts of geometric continuity to develop a relationship between manifolds and tubular neighborhoods. Specifically, we examine a pair of Ck manifolds of dimension r whose intersection lies along a Ck manifold of dimension r - 1; if the r-manifolds meet with Gk continuity, then the boundaries of their corresponding tubular neighborhoods intersect with Gk-1 continuity. We also discuss possible ways to extend the scope of this research.

Constructing a Moduli Space of Quadrilaterals up to Similarity

Alexander M. Meadows

A method for constructing a space of quadrilaterals modulo similarity is provided. We begin with several methods of constructing a space of triangles up to similarity. Then we construct the moduli space of quadrilaterals up to similarity using both algebraic and geometric methods.

On Some Problems in Diophantine Analysis

Jonathan M. Todd

In this thesis we consider four areas in Diophantine analysis. First, we look at new representations of numbers, and prove a generalized Zeckendorf theorem. We then closely analyze the structure of convergents to quadratic irrationals, presenting an important theorem on recurrences which is not widely known. We next consider the Betti sequence, and present our own proof of the Three Gap Theorem. The final section concerns approximation in the project and p-adic cases.

On Ergodic Nonsingular Actions of Z2

Michael P. Touloumtzis

We consider nonsingular actions of the group Z2 on the unit interval and on the real numbers. In particular, we present background material for the discussion of Z2-actions, then discuss two examples in detail. The first is an action of type II
*
; that is, it admits an equivalent, infinite measure for which the action is invariant -- we construct this measure directly. The second example is of type IIIl, and has the property that the two Z-actions which describe it are both ergodic (that is, the action has "ergodic directions"). We present a direct proof of this as well.

Wavelet Analysis in Dense-Target Signal Processing

Takeshi Yokoo

The main goal in radar is to find out the location and the velocity of the object of interest. For a dense-target environment, in particular, we are interested in recovering the density distribution of elementary targets, defined on the position-velocity plane. Using wavelets as the outgoing radar signal, it is possible to reconstruct the density function by taking a wavelet-transform of the returning echo. In this work, which is an extension of Harold Naparst's 1991 paper "Dense Target Signal Processing", we investigate a wavelet-based implementation for dense-target radar and its robustness in noisy situations.

PHYSICS

Construction of an Optical System for Use in Precise Measurement of Thallium Atomic Structure

Paul F. Boerner

Precise measurements of weak force parity nonconservation have been made by studying optical rotation by a thallium vapor. These measurements can be used to check the Standard Model of the electroweak interaction. However, their usefulness is limited by the accuracy of theoretical models of thallium's atomic structure. This thesis describes the construction of an optical system that will be used to make precise measurements of thallium atomic structure in order to facilitate calculation of those theoretical models. In the process of assembling the optical system, a number of subsidiary concerns arose, and these are dealt with in the thesis. Using the optical system described herein and the oven and vapor interaction region described in the thesis of Kyle Downey, measurements soon will be made on the 1283 nm M1/E2 transition. Future work will include tests of the 378 nm E1 transition, and the construction of an atomic beam apparatus.

Modifications Made on an Er-Yb Fiber Laser and a Background Free Autocorrelator

Matthew F. DeCamp

This is a report on the progress made over the past year in the fiber optics laser lab at Williams College. This is a continuing project started last year by Todd Stievater `95 and Kira Maginnis `95. Improvements have been made in the design of an erbium-ytterbium co-doped fiber laser, designed and built by Todd Stievater. In the past year there has been an improvement by a factor of 100 in the duration of pulses generated from the Er-Yb doped fiber laser. The pulses generated from the optical fiber laser are on order of 5ns in duration. A measuring device for picosecond pulses of light, called an autocorrelator, has been fully stabilized and is fully functional. It is hoped that in the near future both of these devices will meet the design specifications, namely the production and measurement of picosecond pulses.

An Atom-Laser Interaction Region and Electromagnetic Structure Measurements in Atomic Thallium

Kyle F. Downey

In order to compare measurements of the weak force in a complex atom such as thallium with the predictions of the Standard Model, one must understand the electronic structure of the atom itself. Without the wave functions, the predictions cannot be compared to the experimental results. This thesis will describe the first wave function measurement experiment, a measurement of the E2 transition at 1283 nm, with particular emphasis on the design of the oven in which the lasers will interact with the thallium vapor. We will follow this measurement with a similar one of the E1 transition at 378 nm that uses many of the same techniques; the end of this thesis will go into future experiments.

Temperature Dependence of Stress Induced Birefringence in Single Mode Optical Fiber

Benjamin K. Evans

This thesis reports an investigation into the temperature dependence of stress induced birefringence in single mode optical fiber. A computer controlled experimental system to simultaneously measure birefringence and temperature has been constructed, and theoretical principles of the effect have been qualitatively identified. Initial results indicate that the effect is significantly greater than previously observed, however insufficient data has been collected to fully characterize the relationship between fiber stress and birefringence. Several possible improvements in the experimental procedure have been proposed and subjects in need of further theoretical understanding have been identified, in order that this work may be continued in the future.

Realizing Generalized Quantum Measurements on the Polarization of Photons

Joshua Grossman

While quantum measurements are traditionally thought of as having orthogonal outcomes, generalized quantum measurements need not be orthogonal. Such measurements may be either complete or incomplete. This thesis addresses the problem of realizing generalized quantum measurements on the polarization of photons. Two methods of realizing any generalized complete measurement and certain incomplete measurements on the polarization of a single photon by using only linear optical elements are described. A method of realizing any generalized measurement on the polarization of a single photon by using nonlinear elements is also described, and some of the issues involved in performing measurements on the polarizations of two photons are discussed.

PSYCHOLOGY

Effects of Item Relevance and Group Status on Group Polarization

D. Scott Allan

The effects of evaluative minority status and item relevance on group polarization were investigated. Subjects were randomly categorized into evaluative minority and non minority status conditions. Group polarization was assessed by comparing mean shifts from pre-test to post-test scores on a choice-dilemma questionnaire. This choice dilemma questionnaire contained four items, two of which were designed to be relevant to the status categorization manipulation, and two of which were designed to be irrelevant to that manipulation. In addition, group discussions were analyzed for content, and the effects of evaluative minority status and item relevance on group polarization on differences in the relative use of statements indicative of normative influence and informational influence were investigated. No significant effects were obtained for either of the independent variables. Analysis of a modified Collective Self-Esteem Scale, used as a manipulation check, indicated that subjects did not find the status categorization manipulation credible. Design flaws which may have contributed to the failure of the independent variables to produce significant results are discussed.

Reversing the Behavioral Outcome of Prenatal Stress with the Endogenous
Neurosteroid Allopregnanolone

Lisa Blaskey

This study examined the effects of exposure to prenatal stress in rats, and whether the concomitant administration of an anxiolytic neurosteroid, allopregnanolone, could ameliorate some of the behavioral outcomes associated with this stress exposure. Pregnant dams were assigned to one of five treatment groups on gestational day 14. These groups were exposed to either: 1) restraint stress for 45 minutes, three times daily; 2) a 5 mg/kg injection of allopregnanolone twice daily; 3) a vehicle injection twice daily; 4) restraint stress with allopregnanolone injections; or 5) were unhandled. Assays for serum allopregnanolone concentrations indicated that levels of allopregnanolone were much higher in the pregnant darns and their pups during gestation in the allopregnanolone-alone treatment group. Support for the assertion that allopregnanolone was acting on the brains of these animals was, therefore, obtained. Offspring of all pregnant dams were tested for anxiety behavior based upon performance on plus maze and ultrasonic vocalization (USV) tests, while activity levels were examined through tests of open field activity. Results suggest that co-administration of allopregnanolone with stress may modulate affective behaviors, as seen through the normalization of the combined stress and allopregnanolone animals in the USV and Plus maze tests. Locomotor activity, however, appeared to remain unaffected. Results also unexpectedly revealed that the group treated with allopregnanolone alone behaved more similarly to the stress treated animals than to controls. This result suggests that the doses of allopregnanolone administered in this study may have created a sedative effect in pregnant dams causing an anxiogenic rather than anxiolytic effect. If such was the case, the possibility exists that the findings of this study were actually the result of a prenatal stress that was more severe in the combined stress and allopregnanolone group. These findings are discussed and suggestions made for future experimentation by which this response may be more clearly elucidated.

The Effects of Negative Political Campaigning on Perceptions of Political Candidates

Amy L. Bradfield

This research examined the effects of political attacks on perceptions of political candidates. A study was conducted over electronic mail in which 122 Williams College undergraduates received messages constructed to simulate newspaper articles that might appear in an actual campaign. Participants received a new piece of information each day for four consecutive days: information about the campaign and candidates, a character or competence attack, an ignore or rebut response from the target and an apology or repeat from the sponsor of the attack. Ratings of overall impressions, likeability and competence were taken each day. The results indicated that the sponsor's ratings dropped more dramatically than the target's and remained significantly below their initial measure while the target's ratings eventually recovered. Relevant political science and social psychological research are outlined. Implications for candidate behavior in actual political campaigns and future research directions are discussed.

Diagnosing Dementia in Primary Care: A Useful Cognitive Screening Battery Sensitive to Alzheimer's Disease

Michael D. Brush

The recognition and diagnosis of dementia, specifically Alzheimer's Disease (AD), in the primary care practice is an uncommon event. As such, there is a need in primary care for a cognitive screening battery that is sensitive to AD. In order to be used in primary care, this battery must be short, simple to administer and score, use only basic materials, and be both sensitive and specific. The two most commonly used mental status exams in primary care, the Mini-Mental Status Exam (MMSE) and the Blessed Information-Memory Concentration Test (BIMC), are both simple and short. However they have been shown to have poor sensitivity in the detection of early AD, the stage most likely to be seen in primary care. Solomon et al. (1996) developed a screening battery for AD that met the necessary guidelines and was shown to be extremely sensitive to a prescreened population of age and education matched patients. The goal of this study was to extend their research by putting the battery to use in a primary care practice. Subjects were 137 consecutive patients over the age of 60 of Dr. Daniel Sullivan, a primary practitioner at the Williamstown Medical Associates in North Adams, MA. This represented an estimated 90% of the eligible population. All subjects were administered the screening battery. Using a logistic regression formula derived in Solomon et al. (1996), all subjects were classified as either High or Low Probability of Dementia (HPD or LPD) using a cutoff of 0.6. Of the 137 subjects, 123 were classified as LPD and 14 as HPD. Full neuropsychological evaluations indicated that the battery correctly classified 9 of 10 HPDs (90%) and 26 of 27 randomly selected LPDs (96.3%). These results indicated that the battery can be a useful diagnostic tool for AD in a primary care practice.

The Implementation of Dementia Screening in a Primary Care Setting: A Brief Screening Battery Sensitive to Alzheimer's Disease

Vivian L. Calvo

Due to the prevalence of Alzheimer's disease (AD) and the advent of effective pharmacological treatment, there is an urgency for early diagnosis of the disease. Screening for the disease in primary care practice, would facilitate this early diagnosis. However, with current trends in medical care this screen would have to be short, easy to administer, as well as cost effective. The goal of this research was to test such a screening tool in a primary care practice. The battery was developed by Hirschoff (1994) and tests the four areas of cognitive function which are impaired in AD, memory, visuospatial function, language, and cognitive function. Scores were weighted in a formula derived by Solomon et al. (1996) thereby generating a probability between 0 and 1.0. Subjects with a probability of 0.6 or greater was determined to be a high probability of dementia (HPD) while probabilities less than 0.6 were low probabilities of dementia (LPD). In order to assess the accuracy of the screening battery, full neuropsychological evaluations were conducted.

The subjects were 142 consecutive admissions to the practice of Dr. Daniel Sullivan at Williamstown Medical Associates in North Adams, Massachusetts. Of these 142, 7 were discontinued for various reasons, 13 were determined to be HPDs, and 121 were LPDs. To date, 10 of the 13 LPDs have agreed to be retested. The battery classified 9 of these 10 patients correctly and thus was 90% sensitive. The battery correctly classified 26 of the 27 LPDs correctly and thus was 96.3% specific. On average, the time of administration for all subjects was 7.3 minutes. Assessment of the battery's test-retest reliability determined that the test was reliable over a 1 to 2 month time interval as well as across different evaluators. Furthermore, the results of this study show that the Hirschoff battery is more accurate than other common short mental status examinations such as the Mini Mental Status Exam and the Blessed Information Memory Concentration Test. This study therefore suggests that this test is an accurate screening instrument sensitive to AD in an undiagnosed population such as that in a primary care setting. The diagnostic accuracy of the battery could more thoroughly be assessed by determining its sensitivity to other primary degenerative dementias and depression.

International Students: Identity and Well-Being in Cross-Cultural Transitions

Yulia Chentsova

The research examined cultural identification in relation to psychological adjustment among international students of Williams College. It also compared self-rated changes in personal identity and psychological adjustment of international and American students. The theories of culture shock, U-curve adjustment and cultural identification were tested. The results revealed that identification with home country and with the US were stable. The affective component of identification with home country correlated with self-esteem, and the affective component of identification with the US correlated with depression in international students. International students did not differ from American students in self-rated changes in personal identity and in psychological adjustment. The data showed no evidence of U-curve adjustment among international students. The reasons for lack of evidence of culture shock and U-curve of adjustment are discussed.

The Effects of the Neurosteroid Allopregnanolone on the Sexual Behavior of the Male Rat

Eric W. Fish

Male sexual behavior is mediated, in part, by activity of the postsynaptic receptor for the neurotransmitter GABA in specific areas of the brain. In addition to GABA, this receptor's activity is affected by a variety of endogenous neuromodulators. This thesis investigated the effects of the most potent of these neuromodulators, the neurosteroid allopregnanolone, a positive modulator of the GABAa receptor, on the sexual motivation and sexual performance of male rats. Sexually experienced adult male rats in control, vehicle (20% beta-cyclodextrin), 1.25 mg/kg, 2.5 mg/kg, and 5.0 mg/kg allopregnanolone conditions were tested in a T-maze to determine preference for an estrous female. Sexual performance, ultrasonic vocalizations in the presence of estrous bedding, and the post ejaculatory song were not affected by allopregnanolone. This neurosteroid, however, prolong the post-ejaculatory refractory period at 1.25 mg/kg and 2.5 mg/kg. There was a dose-dependent reduction of grooming behavior in the T-maze by allopregnanolone. These results suggest that neuroactive steroids may modulate both sexual motivation and the refractory period in ma]e rats. Further investigation into the effects of allopregnanolone on male sexual behavior may prove useful for the treatment of sexual disorders and sexual dysfunction as well as increasing our understanding of the basic neural mechanisms underlying this behavior.

Personality Perception and Expression in Computer-Mediated Communication

Lisa R. Matus

Computer-mediated communication's (CMC) ability to support personality perception and its effects on personality expression were studied. The cues available in CMC for personality perception were also studied. 120 Williams College students were recruited as members of 60 dyads that had CMC-based conversations from different rooms. An additional 45 participants observed these conversations in a third room on another computer monitor. The conversations were limited to a list of five non-threatening topics to be discussed for the purpose of "trying to get to know" each other. All volunteers who participated directly in the conversations completed the Goldberg adjective scales inventory, a Big Five personality dimensions instrument (Goldberg, 1992). Members of the dyads used the Goldberg adjective scales (Goldberg, 1992) to describe their view of themselves in general, their view of themselves in the CMC context, and their view of their partners. Observers also filled out Goldberg adjective scales (Goldberg, 1992) for both members of the conversations dyad whom they observed. All participants completed a questionnaire devised by the experimenter to assess the personality cues that informed their ratings specific to each of the Big Five personality dimensions.

Participants' ratings of themselves in general were similar to their ratings of themselves in the CMC context, but significantly less similar than is typically observed when participants describe themselves twice in the same context. This finding suggests that CMC users do express their personalities differently in the CMC context from other contexts. Accuracy of conversation participants' ratings of themselves in the CMC context and ratings of them by their partners were significant for the Big Five dimensions of Agreeableness and Openness. It appears that personality perception is possible in CMC for some of the Big Five dimensions. A MANOVA revealed significant interactions between participants' perspectives, (as raters of themselves in general and themselves in the CMC context, and as targets for their partners' ratings), the Big Five personality dimensions and how they were perceived. The interaction between perspective and personality dimension suggests that there is some sort of effect of the medium on users' perceptions of various targets. Exploratory coding of participants' reported cues for each of the Big Five dimensions revealed seven cue categories, each of which was differentially associated with particular personality dimensions. These results provide evidence that CMC can support personality cues, and that CMC users attribute these cues to specific Big Five personality dimensions.

Confession Evidence and the Jury:
An Experimental Test of the "Fundamental Difference" Hypothesis

Katharine Neumann

The present research evaluated the U.S. Supreme Court opinion in Arizona v. Fulminate (1991) that confessions are equivalent to other forms of trial evidence in their impact on the jury. Three mock jury studies compared the effects of confessions to eyewitness identifications and character testimony. Experiment 1 showed that when presented with four criminal trials, each including one form of evidence, subjects voted to convict more often in the presence of a confession than the other types of evidence. In Experiments 2 and 3, subjects read a summary of one trial (murder or assault), in which all three types of evidence were presented and made a series of on-line judgments of the defendant's guilt. Results indicated that subjects found the defendant most guilty after being presented with a confession, followed by the eyewitness identification and character testimony. Taken together, these findings suggest that the Supreme Court was incorrect in its assertion that confessions are like all other types of evidence. The policy implications of these findings are discussed.

Cognitive Improvement in the Healthy Elderly:
An Evaluation of Over-the-Counter Memory Enhancers

Amanda L. Silver

Age associated memory impairment is a well documented phenomenon. The degree of memory loss incurred in normal aging is thought to correlate in part with a decline in acetylcholine (ACh) levels in the brain, and thus it has been suggested that memory may be improved by increasing ACh brain levels. Ginseng also has been proposed to enhance cognitive functioning. A number of commercial compounds are available which purport to augment neurotransmitter levels, including ACh, and enhance memory. Because these compounds are not considered drugs, they are not required by the FDA to undergo controlled clinical trials to demonstrate efficacy. This study evaluated the effectiveness of two over-the counter purported memory enhancers, Choline Cooler (Durk Pearson and Sandy Shaw Designer FoodsTM) and Ginsana®, in a double-blind, placebo-controlled, six-week protocol using a healthy, normal elderly population. Subjects underwent comprehensive neuropsychological testing both before and after taking either compound or a placebo. No significant differences were found in learning and memory or attention and concentration. Subjects tended to improve between testing, which can be attributed to the practice or saving effect, but there were no improvements due to either compound. It appears that over-the-counter memory enhancers do not significantly improve memory in the elderly.


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