Center for Interdisciplinary Studies
Abstracts from the Department of Biology
DNA microarrays are becoming increasingly prevalent because this technology provides investigators the opportunity to explore simultaneously the interactions among all genes in an organism’s genome. Our group effectively designed a microarray and printed teaching chips for a genomics laboratory course. Teaching chips provide students with a thorough understanding of microarray methodology but do not necessitate the use of expensive RNA samples or genomic DNA. Rather than traditional RNA hybridization, the probes we used are oligonucleotides that are detected with Genisphere's 3DNA kit. This method is advantageous because students have the opportunity to learn through the active creation and analysis of microarrays while the cost of reagents is minimized. This poster describes our experimental methods and discusses the merits of incorporating similar investigative experiments into undergraduate curriculum. We explored many of the intricate steps necessary to produce good results and met course goals as we practiced communicating complex procedures through oral and written formats. We also optimized a printing protocol to make similar experiments more accessible for future students. Integrating comprehensive genomic research opportunities into undergraduate education will facilitate advancement of the field of genomics, thus broadening the potential medical applications of microarray technology.
BLACK, CARRIE, KEVIN SAUNDERS, AMANDA ALDRIDGE, SARAH HOLMBERG, AND KAREN HALES. Department of Biology. Immunoblotting to test antibody specificity for nmd gene product in Drosophila melanogaster.
We investigated the specificity of an anti-Nmd rabbit polyclonal antibody (pAb), which will be used to immunolocalize the no mitochondrial derivative (nmd) gene product in Drosophila melanogaster. To elucidate the specificity of the anti-Nmd antibody, immunoblotting under various conditions was performed. Primary and secondary antibody concentrations, as well as protein concentration, were changed to find the best resolution for immunoblotting with the anti-Nmd pAb. A dot blot was performed to determine the appropriate primary and secondary antibody concentrations to use in immunoblotting. Dot blots determined that a 1 in 100 dilution of primary antibody and a 1 in 10,000 dilution of secondary antibody produce clear fluorographs. The resolution of the immunoblots was optimized by increasing wash times and preparing antibody solutions with 7% non-fat dry milk. Variables such as membrane type (PVDF and Nitrocellulose), exposure time, transfer voltage, antibody solution volume, wash buffer volume and volume of protein loaded were also optimized to enhance resolution. In addition, an anti-Actin rabbit pAb was used as a positive control for the immunoblotting technique. Future immunoblotting will determine the specificity of the anti-Nmd pAb. Depending on future results, either affinity purification or immunolocalization will directly ensue.
BUDISCHAK, SARAH A., JOY M. HESTER, MICHAEL E. DORCAS, AND STEVEN J. PRICE. Biology Dept. The natural history of box turtles (Terrapene carolina) in an urbanized landscape.
Globally, many turtle species are experiencing population declines due to anthropogenic causes. Eastern box turtles (Terrapene carolina) are important components of the biota of eastern forests and in developing areas. In 1999 we initiated a long-term mark-recapture study of eastern box turtles in the vicinity of Davidson College, Davidson, NC. We used data from this study to describe the natural history characteristics of this box turtle population and to examine potential effects of urbanization. Specifically, we examined meristic characteristics, turtle condition, activity patterns, population structure, and growth rates in conjunction with the amount of anthropogenically modified habitat near each turtle’s collection location. Males and females exhibited different, seasonal patterns of activity and body condition, measured using the residual of a mass/carapace length ratio. Growth rates decreased with age and varied between developed and forested habitats. Proportionally, the oldest turtles were found in areas with the most extensive forest cover. Condition did not vary by amount of forest cover for males or females. Natural history studies, like this one, which describe basic characteristics and how those characteristics are affected by urbanization, form the first critical step in developing sound conservation strategies for box turtles in the eastern US.
BUDISCHAK, SARAH A1, PATRICIA A. PERONI1, AND JONATHAN G. RIPPERTON2. 1Davidson College Biology Dept., 2UNC-Asheville. The effects of seed age on seed viability, seedling performance, and sex ratios in white campion (Silene latfolia).
In order for seed banks to be an effective evolutionary strategy, seeds must not only remain viable, but also be able to germinate, grow, and compete against conspecifics and other competitors after years of burial. Using white campion (Silene latifolia), a dioecious perennial that maintains a dormant seed bank, as a model species, we examined how age affects the viability and germination rate of seeds and the performance of seedlings. Seeds were collected annually from four southwestern Virginia populations over a 5-10 yr period and then stored under dry, laboratory conditions. Some seeds remained viable after 11 years, but percent viability varied among populations. Increasing seed age was associated with significant decreases and delays in germination. Second, we planted germinated seeds in the greenhouse to assess seedling performance. Seedlings that originated from younger seeds emerged and produced true leaves significantly earlier than seedlings from older seeds. Seedlings from older seeds also tended to have significantly smaller leaves and higher survival rates than those from younger seeds. Sex ratios of seedlings did not deviate significantly from 50:50. The decreased and delayed initial growth of seedlings from older seeds may put them at a competitive disadvantage to those from younger seeds.
CECALA, KRISTEN K., STEVEN J. PRICE, PIERSON HILL, BILL JOHNSON, CLINT MCCOY, BETSY FAILEY, LAUREN WATSON, LEIGH ANNE HARDEN, SHANNON PITTMAN, AND MICHAEL E. DORCAS. Dept. of Biology. The effects of urbanization on stream salamanders: Initiation of a landscape-level experiment.
The Charlotte, NC metropolitan area contains one of the nation’s fastest growing human populations and urban sprawl is quickly expanding into the Piedmont forested lands. Amphibians are particularly vulnerable to landscape-scale habitat destruction, especially when roads, neighborhoods, and shopping centers dissect previously intact habitat. Previous research showed that stream salamander abundance was negatively correlated to the percentage of disturbed (e.g., urban) land within watersheds of first-order streams; however the proximate mechanisms resulting in this reduced abundance were unknown. Therefore, we are performing a multi-year, landscape-scale experiment in the Charlotte metro area to: 1) investigate how the relative abundance of stream salamanders change as stream watersheds undergo urbanization, 2) examine the ability of adult salamanders to persist in disturbed stream habitats and, 3) explore other sub-lethal stressors that impact salamanders in urbanized watersheds. Currently, we have captured over 1,500 salamanders of 6 different species, including Desmognathus fuscus, Eurycea cirrigera, Eurycea guttolineata, Gyrinophilus porphyriticus, Pseudotriton montanus, and Pseudotriton ruber. To provide data on adult persistence, we have used visible fluorescent implant elasomers to uniquely mark 198 salamanders. Furthermore, we have found several salamanders heavily infested with mites, which may be an important sub-lethal stressor on Piedmont salamander populations.
CHRISAWN, CHARLIE, BEN KITTINGER, AND CHRIS PARADISE. Davidson College Biology Department. The effects of Toxorhynchites rutilus on natural treeholes.
Natural treeholes, small aquatic habitats, are useful for studying top down control in communities. The top predator in treeholes, Toxorhynchites rutilus, is a ferocious mosquito that is only a predator in the larval state. Our study focuses on seven full censuses that spanned ten months and investigated twenty-eight different natural treeholes in three different locations in Davidson, North Carolina. Our objective was to find the effects of T. rutilus on the treehole community. After examining the data, we can conclude that T. rutilus, widely assumed to be generalist predator, has differential effects on species in the community. Toxorhynchites rutilus had no effect on scirtid beetle density (Helodes pulchella) while it has large negative effects on density of the midge Culicoides guttipennis. Effects on mosquitoes and species richness were equivocal, but the predator may have some seasonal negative effects on mosquito density and positive effects on richness. Generalizations about the effects of predators in treeholes and top-down control in communities will be discussed.
COBAIN, ERIN F., WILLIAM C. HAAS AND MICHAEL E. DORCAS. Dept. of Biology. An Investigation of Physiological and Behavioral Thermoregulation during Heating and Cooling in Charina bottae.
We investigated the ability of rubber boas (Charina bottae) to physiologically and behaviorally adjust rates of heating and cooling. In this investigation, temperature sensitive PIT tags were implanted into the bodies of ten captive rubber boas. The snakes were subjected randomly to four heating and cooling treatments over a 5-33°C temperature range: 1) heating in a constrained position, 2) cooling in a constrained position, 3) heating in an unconstrained position and 4) cooling in an unconstrained position. A thermal time constant was calculated for each snake in all treatments. Preliminary results have yielded three general conclusions: 1) larger snakes had greater thermal time constants than smaller snakes in all treatments, 2) rubber boas generally heated faster than they cooled and 3) rubber boas that were constrained had a faster rate of temperature change for both heating and cooling treatments than unconstrained rubber boas. Our results suggest that some small reptiles may possess both physiological and behavioral mechanisms by which they can alter rates of heating and cooling.
DAVIS, SARAH N., BARBARA LOM. Dept. of Biology. Zebrafish embryos are most severely affected by earlier and longer exposures to sub-lethal concentrations of malathion.
Pesticides contaminating water can have teratogenic effects on non-target organisms, such as amphibian and fish embryos. Malathion, used to reduce mosquitoes, is an organophosphorus pesticide that inhibits acetylcholinesterase (AChE). Previous studies have shown that zebrafish exposed to malathion have fewer hepatic cells, abnormal ovaries, skeletal deformities, decreased lengths, reduced eyes, and pericardial edemas. This study 1) examined if zebrafish had sensitive periods to malathion during the first 96 hours of development and 2) visualized AChE activity in pesticide-treated embryos. Recently fertilized zebrafish embryos were exposed to a sub-lethal malathion concentration for various 24- or 48-hour windows, or for the entire 96-hour period following fertilization. Embryos were morphologically analyzed at 96 hours and stained to evaluate AChE activity. Exposure to sub-lethal doses of malathion for 96 hours had the most significant effects on zebrafish development, altering abdominal morphology and stunting overall growth, while malathion exposure during the first 48 hours had similar significant, though less drastic developmental consequences, and 24-hour exposure did not visibly alter zebrafish embryogenesis. These results correlated with the extent of AChE inhibition observed by various staining techniques. Thus zebrafish embryos do experience windows of development in which they are differentially sensitive to malathion’s teratogenic effects.
GOOCH, MICHELLE M., AUBREY M. HEUPEL, STEVEN J. PRICE, MICHAEL E. DORCAS. Dept. of Biology. The effects of survey protocol on detection probabilities and site occupancy estimates of summer-breeding anurans.
Recent declines in amphibian populations have created an urgent need for monitoring efforts and many anuran monitoring programs have been established that utilize calling surveys. Calling surveys can be effective monitoring tools; however, differences among survey protocols often bias survey results. Failure to take into account detection probabilities when monitoring anurans can lead to inaccurate inferences about site occupancy, since non-detections in survey data do not necessarily mean that a species is absent unless the probability of detection is 1. We used the likelihood-based computer program PRESENCE to estimate detection probabilities and site occupancy rates for summer-breeding anurans. Using detection data from calling-surveys, we evaluated how detectability and site occupancy for 5 anuran species were influenced by 1) time spent listening at each site, 2) number of surveys per site, and 3) sample- and site-specific covariates. We found that detectability varied more with sampling occasion than with survey duration for each species; longer surveys did not significantly increase detectability for any species. Covariates had differing effects on occupancy and detectability among individual species. Multiple surveys per site within a season are necessary to eliminate biased detection probabilities, but we found that 3- or 5-minute surveys are adequate for detecting all species.
HARSHAW, LAUREN, STELLA KENYI, AND CHRIS PARADISE. Davidson College Biology Department. Effects of scirtid beetles and leaf-litter resources on mosquito performance in a processing chain interaction.
Treeholes are aquatic habitats that contain sediment, leaf litter, and various organisms including bacteria and insects. Treehole mesocosms made out of PVC pipe were used to study the growth and survival of one cohort of mosquitoes under varying conditions. Out of 40 mesocosms there were five replicates of each type of treatment: low leaf litter with low and medium scirtid densities, medium leaf litter with low, medium, and high scirtid densities, and high leaf litter with low, medium, and high scirtid densities. Scirtids were allowed to process leaf litter over the winter and twenty first instar mosquito larvae were added to each mesocosm in February 2005. In a previous study, scirtid densities of 25/L were found to produce larger female mosquitoes, but density was not controlled in this experiment. Leaf litter density has also been shown to have positive effects on mosquitoes, because they browse directly on it, and it can increase growth of microbes, upon which mosquitoes feed. We assumed all mosquitoes added were Ochlerotatus triseriatus. However, we document here a new invasive species, Oc. japonicus in Mecklenburg County. We will present results showing effects of scirtids and leaf litter on survival and growth of both species.
HESTER, JOY M., STEVEN J. PRICE, MICHAEL E. DORCAS. Dept. of Biology – Effects of relocation on movements and home ranges of eastern box turtles (Terrapene carolina).
Eastern box turtle (Terrapene carolina) populations are threatened by expanding urbanization, the resulting loss of habitat, and the introduction of threats such as roads, railroads, and pets. Individual box turtles are often captured relocated substantial distances from their capture location by scientists, wildlife rehabilitators, and well-meaning community members. Previous studies examining the effects of relocation on box turtles are limited. Thus, we compared the home ranges, movement patterns, and mortality of resident and relocated box turtles. We radio tracked ten relocated and ten resident female box turtles on the Davidson College Ecological Preserve, in Davidson, NC, twice weekly during the active season beginning in May 2004. Geographic coordinates were recorded during each tracking session. Results suggest that relocated box turtles have larger home ranges and move longer distances per day than resident box turtles. Additionally, relocated turtles had higher mortality and disappearance rates than resident turtles. Our preliminary results indicate that relocated box turtles do not quickly reestablish home ranges in a new habitat, and may attempt to leave their relocation site, thus, raising questions about the success of relocation as a conservation strategy for eastern box turtles.
HILL, E. PIERSON, WILLIAM J. JOHNSON, AND MICHAEL E. DORCAS. Department of Biology. Habitat selection of Eastern Ratsnakes (Elaphe alleghaniensis) in the western Piedmont of North Carolina.
Habitat fragmentation is a well-documented cause for species decline and extinction, especially in reptiles. However, some species may benefit from moderate anthropogenic disturbances to habitats that create high edge to interior ratios. The Eastern Ratsnake (Elaphe alleghaniensis) can be found throughout areas of human development as well as undisturbed forest habitats in the Piedmont of North Carolina. To examine how ratsnakes use macrohabitats in a fragmented landscape, we radiotracked 14 snakes over a three-year period on the Davidson College Ecological Preserve in Mecklenburg and Iredell Counties, NC. Snakes were found to use kudzu patches more than expected by their availability and avoided planted pine forests (p<0.001). We found considerable inter-individual differences among snakes in their preferred habitats with some individuals selecting habitat types others avoided. All snakes had a strong preference for edge habitats, defined either at 10-m and 20-m distance intervals (p<0.001). Overall, moderate fragmentation due to anthropogenic modification of the landscape appears to result in habitats favored by Eastern Ratsnakes.
HOEKSTRA, JENNIFER A.,
SARAH N. DAVIS, JAMES S. BARNES, BARBARA LOM. Department of Biology. Malathion
decreases heart rate and alters cardiac morphology in embryonic zebrafish
Malathion, an organophosphorous pesticide commonly used to control mosquitoes, can inadvertently affect non-target species in aquatic systems. Zebrafish are a model organism for developmental toxicology. These fresh water fish produce large numbers of offspring that are sensitive to environmental changes. The transparency of the zebrafish embryo allows for the careful study of cardiac form and function. We investigated malathion’s effects upon heart rate in zebrafish by rearing embryos in individual wells for the 72 hours following fertilization in three treatments: tank water, 0.03% acetone (vehicle control), and 2.5 mg/L malathion. At 72 hours, heart beats were counted for 15-second intervals using light microscopy. Kruskal Wallis non-parametric statistical analysis revealed that malathion-treated fish had significantly lower heart rates than both controls (p<0.0001). To determine if malathion affects cardiac morphology, we reared embryos for 24, 36, 48, and 72 hours in malathion or control solutions. We immunostained embryos with a myosin antibody (MF20) and used confocal microscopy to visualize cardiac morphology. Preliminary observations suggest that malathion-treated hearts do not have the characteristic bending pattern of control hearts, nor do they have proper chamber formation. Thus it is likely that the pesticide malathion adversely affects cardiac form and function in embryonic zebrafish
JOHNSON, WILLIAM J., E. PIERSON HILL, MICHAEL E. DORCAS. Dept of Biology. Home-range size and site fidelity of Eastern Rat Snakes (Elaphe alleghaniensis) in the western Piedmont of North Carolina.
Understanding an animal’s spatial ecology is a necessary component of conservation, particularly where urban development alters habitat. Many species show repeated use of specific locales within their environment and could be imperiled if those frequented areas are disturbed or eliminated, forcing the animal to move elsewhere. We examined the spatial ecology of the eastern rat snake (Elaphe alleghaniensis) by radiotracking 13 snakes over a three-year period on the Davidson College Ecological Preserve in Mecklenburg County, NC. Snakes had an average active-season home-range size of 8.7 ha (measured as 95 % kernel). Many of our snakes showed repeated use of particular areas within their home ranges over the duration of the study; with 17% of core areas and 35 % of successive years’ home ranges common to both years, with no difference between sexes. Conservation lessons learned from common species such as the rat snake can be applied to more imperiled species.
KEGAN, BEN, LESLIE SMITH, JOHN BURKHART, CHRIS PARADISE. Department of Biology. Dynamics of processor and resource densities on treehole community structure.
Treeholes are water filled cavities that support a variety of aquatic invertebrates. Scirtid beetles, common inhabitants of treeholes, shred leaf litter and may increase resources for microbes and other insects affecting the treehole community structure. We utilized a mesocosm approach with a two factor design of leaf litter (1g/L, 5g/L, 10g/L) and scirtids (0/L, 25/L, 100/L), with 4 replicates of each treatment combination. The mesocosms were employed in October 2003, a week later leaf litter and water were added. Two weeks later, scirtid beetles (Helodes pulchella) were added in randomly selected mesocosms and the mesocosms were covered. In March 2004, mesocosms were opened for colonization and in July 2004 the scirtid beetles were restocked. Our objective in this analysis is to track changes in the community structure of treeholes through the two years of this experiment, specifically comparing the first year, when scirtids were present and densities were kept near nominal levels, and the second year, after scirtids had either died or pupated. We have found evidence to suggest that scirtid beetles and leaf litter affected treehole communities during the first year. There has been no significant evidence, however, of a continued effect on treehole communities into the second year.
KIRLIN, MICHELLE S., MICHELLE M. GOOCH, STEVEN J. PRICE, MICHAEL E. DORCAS. Dept. of Biology. The effects of habitat and weather variables on the detectability and site occupancy estimates of spring-breeding anurans.
Recent global amphibian population
declines have created an urgent need for monitoring efforts, many of which
have been established to utilize calling surveys. Habitat and weather variables
influence when and where anurans breed and need to be considered when establishing
monitoring efforts. We investigated the effects of habitat and weather variables
on the detection probabilities and site occupancy estimates of spring breeding
anurans in the Western Piedmont of North Carolina. We conducted calling surveys
at 27 ponds in Mecklenburg County, NC, over a 6-week period in early spring.
Using the program PRESENCE, we evaluated how anuran detectability and site
occupancy estimates were influenced by habitat type (a 200 m buffer surrounding
each pond) and weather variables that were recorded during each survey. We
determined the best-fit model for each of the three species we observed that
took these variables into account. Pseudacris feriarum was most associated
with distance to nearest road and air temperature, Pseudacris crucifer
was most associated with weather, and Rana utricularia was most associated
with day of the year. We conclude that habitat and weather variables have
differing effects on occupancy and detectability among individual species
of spring-breeding anurans and must be considered when developing monitoring
KORNILEV, YURII V., STEVEN J. PRICE, AND MICHAEL E. DORCAS. Dept. of Biology. Responses of eastern box turtles (Terrapene carolina) when trapped between railroad tracks.
To investigate the potential negative impacts of railroads on box turtles, we recorded the number of climbing attempts, the distance moved, the overall speed of travel, and the exit behavior of 12 adult animals experimentally trapped for 1 hr between railroad tracks. Only one individual escaped by climbing over a rail. The total distance moved by the majority of tested turtles was less than 100 m. When presented with the option to leave at a railroad crossing, 3 turtles stayed between the tracks, 4 exited and headed towards an adjacent parallel road, and 5 headed in the opposite direction towards a vegetated field. The mean distance between railroad crossings in our study area is 379 m; more than 50% of the crossings are more than 200 m. Thus, at least two hours would be necessary for a turtle consistently moving in its original direction to get from one railroad crossing to another. However, on a mild day (air temperature = 24 C) the core temperatures of turtles trapped on railroads may reach lethal temperatures within this time. Railroads, like other human infrastructures, serve as sources of direct mortality and barriers to turtle dispersal, leading to population declines and fragmentation.
MCDONALD, MEGAN E. Dept. of Biology, and Dept. of Physics. Examining the physical properties of DNA in DNA microarrays using optical tweezers.
DNA microarrays are an important method in the growing field of genomics, and are used to determine gene expression levels in an organism. While this system is widely used, little is known about the molecular level interactions that make up the technique. One way to better understand the method at a molecular level is to examine the interactions of the DNA on the glass slide. To accomplish this goal, DNA undergoes the typical microarray process of spotting, UV-crosslinking, and boiling (creating single stranded DNA) in order to obtain an accurate representation of the microarray process. 1um aldehyde-modified polystyrene beads are then attached to the exposed bases in the single stranded DNA. A bead is trapped by the optical tweezers and held in place while the slide is moved at a constant velocity. Bead displacement from the center of the trap is measured from the refracted light using a four-quadrant photodetector. This data is then used to calculate the force constant of single stranded DNA.
NAKAISHI, LINDSAY A., AMANDA L. ALDRIDGE, KAREN G. HALES. Dept. of Biology. Ethylmethanesulfonate (EMS) mutagenesis screen for a new allele of the no mitochondrial derivative (nmd) gene in the fruit fly Drosophila melanogaster.
We conducted an EMS screen on Drosophila fruit flies to generate a new allele of the no mitochondrial derivative (nmd) gene that is associated with sterility in male flies. Characterizing different alleles of the nmd gene will to help to better understand the mitochondria function during spermatogenesis. nmd mutant flies have mitochondria that do not align properly during meiosis and instead are dispersed around the meiotic spindle, which results in abnormal mitochondria function during the spermatogenesis and ultimately sterility. We exposed 250 yw;?/Cyo males to 9.0 µL (0.35 % solution) of EMS for 18 hours. EMS exposure was followed by two crosses to create independent mutant strains from the mutagenized founder males. We tested 682 individual male lines and discovered one male line that tested positive for sterility. A complementation test was conducted on the possible new mutation fly line in order to determine the mutations are in nmd. The testes of males with the possible new mutation were dissected and examined under the microscope to detect the failure of mitochondrial aggregation and abnormal mitochondria in the cells of the testes.
NEWTON, KIMBERLY*, ANDREW PICKENS* and KAREN BERND. Dept. of Biology. Novel organic compounds DRR 3 and DRR 5 affect growth rate differentially in model bacteria Escherichia coli, Salmonella typhimurium, and Staphylococcus simulans.
The synthesis of new compounds
is vital in the search for better and more effective drugs. Purine-derived
and purine-analog drugs are at the forefront of these new synthesizing processes.
Using our existing library of purine-analogs, we tested compound 1-DRR-5 (DRR-5)
and 1-DRR-3 (DRR-3) and its starting materials for biological activity in
three microbial species: Escherichia coli (E.coli), Salmonella
typhimurium (Salmonella), and Staphylococcus simulans
(Staphylococcus). Using these three species, we were able to look
at how structure (chemical properties) and function (biological properties)
are related. Results show that DRR-5 has the capability to increase in the
growth rate of E.coli while DRR-3 decreased the growth rate of all
three bacterial species. These results show that these novel organic compounds
can have either a trophic or toxic effect on bacterial growth depending on
the side chain or amount of branching.
*K.N. and A.P. made equal contributions to this project.
SMITH, LESLIE M., PETER J. MEYERS, KARA M. KOEHRN, CHARLOTTE A. HINDLSEY. Department of Biology. The effects of NC-3000, a non-chloride chemical anti-icer, on the germination of lettuce seeds (Lactuca sativa L.).
We investigated whether NC-3000, a chemical anti-icer, has any effect on the fraction germination of lettuce seeds (Lactuca sativa L.) and whether these effects are reversible. Five different concentrations (100%, 50%, 33%, 25%, 20% solutions of NC-3000) were applied to five replicates of each treatment (50 seeds/dish) with one distilled water control. For each dish, fraction germination was recorded over a ten day trial. NC-3000 inhibited germination at each of the five concentrations (p<0.0001). We conducted a follow-up experiment to examine the reversibility of the inhibiting effects of NC-3000. Seeds from the previous experiment were washed with a 5% Clorox solution and rinsed with distilled water. Our two most dilute concentrations had significantly lower fraction germination (p<0.0001) than the other four concentrations. The 50% and 33% solutions also differed significantly from the control (p<0.0001). The difference in mean fraction germination of the more dilute concentrations could be attributed to the infestation of mold. We found a strong negative correlation between mold coverage and fraction germination (p<0.0001). Future studies should be conducted to compare the effects of NC-3000 and NaCl on seed germination and the effects of NC-3000 on seed germination in soil.
WESSNER, DAVID R., EMILY B. WILSON, ANNA M. HARGER. Dept. of Biology. HIV/AIDS and popular culture: A new web-based educational tool.
To address the need for improved HIV/AIDS education, we developed a website to disseminate information about HIV/AIDS through art, music, television and film (www.bio.davidson.edu/projects/aidspopculture). Additionally, information about the major scientific advancements for each period is provided. We investigated the effectiveness of this multi-media website as a teaching tool for HIV/AIDS education by assessing its impact on a group of 103 first year college students. An anonymous questionnaire addressing HIV/AIDS knowledge and awareness was given to each participant. Some participants saw the site prior to answering the questionnaire; other participants simply answered the questionnaire. We calculated the fraction of correct answers for each objective question and compared the results of the two groups using a Mann-Whitney U statistical test. We found that the group who was exposed to the website prior to answering the questionnaire answered a significantly higher fraction of questions correctly as compared to those students who did not receive the website (p<0.0001). With this multi-media website that examines popular culture references to HIV/AIDS, then, we have developed an effective HIV/AIDS educational tool. Ideally, this site will be useful both in academic environments and as an information source for the general public.
WHELESS, LEE, JAMES BARNES, AND BARBARA LOM. Dept. of Biology. Retinal ganglion cell branching and growth cone extension are influenced by fibroblast growth factor in vitro.
Fibroblast growth factor (FGF) is a peptide expressed in the retina and along the optic pathway that retinal ganglion cell (RGC) axons navigate to wire the eye to the brain. To determine if RGCs respond to FGF stimulation, we compared Xenopus laevis RGC growth cone extension rates before and after FGF2-treatment. Stage 28 eyebuds were cultured for 24 or 48 hours and then time-lapse imaged for 30 minutes to determine growth cone advancement rates. FGF-2 (20 ng/mL) was then applied and growth cones imaged for another 30 minutes. We found that FGF-2 significantly increased RGC growth cone extension rates (128% of control, n=45, p<0.05), suggesting that FGF along the optic pathway may promote RGC axon growth. To determine if FGF plays a role in neurite branching, we compared the branching patterns of RGCs treated with the FGF receptor inhibitor DMBI (50 mM). Stage 28 eyebuds were dissociated and cultured for 48 hours, then immunostained to identify RGCs. When FGFRs were inhibited RGC branching (136% of control, n=59, p<0.05) and overall lengths increased (167% of control, n=59, p<0.05). These results indicate that FGFR signaling may also influence RGC morphological development.
WHIGHAM, BEN, MONICA SIEGENTHALER1, AMANDA ALDRIDGE1, R. STEVE STOWERS2, KAREN HALES1. 1) Department of Biology, Davidson College, Davidson, NC; 2) Department of Molecular and Cellular Biology, UC Berkeley, Berkeley, CA. Milton functions in mitochondrial elongation during Drosophila spermatogenesis.
milton is necessary for mitochondrial transport in Drosophila neurons and encodes an adaptor protein that links mitochondria with kinesin (Stowers et al., 2002, Neuron 36: 1063). We analyzed Milton’s function in Drosophila spermatogenesis, a process that involves several distinct stages of mitochondrial morphogenesis. The milton mutation is recessive lethal and therefore prevents the creation of a homozygous milton stock whose testes can be analyzed. In order to observe the milton phenotype in spermatogenesis, we used the FLP-FRT recombinant system to induce mitotic recombination in the testes of a heterozygous milton stock. Mitotic recombination in primary spermatocytes produced milton-afflicted spermatids. A transheterozygous copy of GFP allowed us to confirm whether individual spermatids had descended from recombinant primary spermatocytes. The milton spermatids showed abnormal mitochondrial elongation as the spermatid matured. Our observations suggest that Milton functions during the elongation stage in spermatogenesis.
Ruthenium(II) complexes containing the 8-aminoquinoline ligand undergo polymerization when oxidized. The polymerization reaction is thought to proceed via radical coupling at sites around the quinoline ring. The purpose of this project was to synthesize an 8-aminoquinoline ligand containing methyl substituents positioned to deter polymerization. 2,4,5,7-Tetramethylquinoline was synthesized by coupling 3,5-dimethylaniline and 2,4-pentanedione followed by acid-catalyzed cyclization and aromatization. This resulting tetramethylquinoline was nitrated, yielding a mixture of 6- and 8-nitroquinolines. Reduction of this mixture with tin afforded the corresponding 8-aminoquinoline while the 6-nitroquinoline was unaffected. The desired 2,4,5,7-tetramethyl-8-aminoquinoline was isolated by column chromatography on silica gel and characterized.
Palatinus, Joseph A., David N. Blauch, and Felix A. Carroll. Department of Chemistry. A Mathcad worksheet to predict alkane boiling point from molecular structure.
Cao et al. (J. Chem. Inf. Comp. Sci. 1999, 39, 1105) have reported a method for predicting the boiling point of a branched alkane based on the inner molecular polarizability index (IMPI) of the compound. The IMPI is used to calculate NC(eff), the “quasi-length” of the branched alkane, which in turn is used to predict the boiling point. The calculation of the IMPI for larger structures involves many steps, which makes implementation of the method difficult and which increases the probability of introducing errors when the IMPI is calculated manually. We report here a computational procedure to calculate boiling points of branched alkanes using MDL ISIS/Draw and Mathcad. The branched alkane is first constructed in ISIS/Draw, and the resulting structure file is then used in a Mathcad worksheet. This method allows for the rapid, accurate prediction of the boiling point of a branched alkane directly from its structure.
PALATINUS, JOSEPH A, RUTH F. BEESTON, MICHAEL TOUMAZOU. Dept. of Chemistry. Soil phosphate mapping of the sanctuary excavation at Malloura, Cyprus.
Soil samples were removed from the active archaeological excavation of a sanctuary believed to have been built around 700 B.C. at the ancient site of Malloura just outside of Athienou, Cyprus. The phosphate concentrations of samples originating from stratigraphic layers corresponding to the sanctuary floor were determined using spectrophotometric techniques. The analysis involved extraction of phosphate with hydrochloric acid and treatment of the extract with ammonium molybdate and ascorbic acid to produce a dark blue complex. Phosphate levels were mapped using a variety of computational methods. As of August, 2004, the altar of this sanctuary had not been located. Because the altar would have been associated with ritual activities such as burning, the proximal phosphate concentration would be expected to be higher than other areas of the sanctuary. The phosphate map produced in this study will serve as a guide to the field archeologists by directing them to archeologically active unexcavated areas.
TRAPPEY III, ALFRED F., KATE WILLIAMS, CINDY DEFOREST HAUSER. Dept. of Chemistry. Quantification of oxidant concentration and the determination of reactive intermediates in the ozonolysis of hexadecene aerosols.
Attempts to quantify ozone concentrations for use in stoichiometric calculations of its reactions with hexadecane aerosols have been carried out using both IR and UV techniques. Varying the rate of N2(g) flow through the ozone trap, reaction apparatus, and IR cell generates a linear relationship between ozone peak area at 1050 cm-1 and flow rate. Using a UV cell for pre-mix ozone quantification has generated a logarithmic relationship between O3(g) flow and V/V0. The thermal degradation of ozone in the post-reaction heating stages has shown that no ozone signal is detectable when the bulk flow is heated past 500°C. However, an unidentifiable peak has been detected whose area varies with temperature, suggesting a thermal degradation byproduct.
WILLIAMS, KATE M., FRANCOIS TRAPPEY III, CINDY DEFOREST HAUSER. Dept. of Chemistry. Applications of FT-IR spectroscopy to the study of aerosol heterogeneous chemistry.
Aerosols play an important role in many atmospheric processes and have been implicated in adverse health effects. Although aerosol scientists are gaining ground in determining the composition of atmospheric particles, much work remains in evaluating their chemical processing, which affects the gas-phase chemistry of the troposphere as well as the composition of the particulate fraction. In the work presented here, heterogeneous chemical reactions of organic aerosols are being studied by reacting ozone with aerosol particle components in a flow cell, followed by analysis using Fourier transform infrared (FT-IR) spectroscopy.
I investigated the possible applications of chaotic dynamical systems in the area of cryptography. Chaotic systems are popularly misunderstood as being random—in fact, they are not random but rather appear random. The power of an encryption scheme based on this type of system is that its behavior is both deterministic and reproducible yet apparently random. The key to the polyalphabetic substitution cipher that I developed provides the initial state of the system; such information proves exceeding difficult to obtain from a brute force attack. A discussion of Lyapunov exponents is provided as a means to gauge the degree of sensitivity to initial conditions, the hallmark of chaotic systems, and therefore decide on a choice for the dynamical map to be used. The conclusion of my analysis is that chaotic dynamics may be utilized to secure data, however any such scheme will inherit statistical tendencies that may provide clues to opponents attempting unauthorized access to the data. However, in attempting to utilize such information, the sensitivity of the system to its initial state reduces the usefulness of this information.
REID, AUSTIN, Dept. of Math. Dimension Theory, fractals, and chaos.
Although it is rather abstract, there actually exist numerous methods for measuring the dimension of a given object. In objects we encounter on a daily basis, these dimensional measures appear to agree. It is not surprising, then, that these constructs are not used to describe “everyday” objects. They are much better suited for use with objects that defy normal classification. These objects tend to be fractal in nature, whether they are true fractals, “statistical” fractals, or are chaotic orbits with a strange attractor. Some examples were created with Java. We looked at Lebesgue Covering, Hausdorff-Besicovich, and Minkowski-Bouligand dimensions, along with information, correlation, and Lyapunov dimension, with a special focus on dimensional changes when attractors are present, as well as a brief foray into the dimensionality of specific fractal curves.
This experiment examined the process of spatial filtering by masking a portion of a diffraction pattern during the image formation process. To begin, I explored the basic principals of Fraunhofer diffraction using a HeNe laser as the source. Placing a lens between a single slit and a screen creates a diffraction pattern at the focal length of the lens and a two dimensional image of the single slit at the screen. In mathematical terms this 2-d image is the Fourier transform of the diffraction pattern which is in turn the Fourier transform of the source. We masked various parts of the diffraction pattern and observed the mask’s effect on the 2-d image of the slit focused on the screen.
CORRELL, ROBERT W. Dept. of Physics. Qualitative simulation of classical waves originating from a point source using the Open-Source Physics Library.
I investigated the evolution of a wave front in an elliptical reflective container. The program uses the approximation of geometrical optics; i.e. the simulation represents the limit as ??0. The simulation allows the user to set the coordinates of the point source, as well as the lengths of the semi-major and semi-minor axes of the ellipse. One animation displays the motion of the wave front over time and traces its evolution; another display represents the energy distribution of the system with a continuously-emitting point source. The model assumes that partial absorption takes place at each reflection, and only models the evolution of one pulse. In addition to the ellipse, a brief analysis is also performed of rectangles. Comparisons to known solutions, such as a point source located at a focus of an ellipse, confirm the validity of the algorithm. The results extend Kaplan’s findings of partial focusing of light in circular cavities to the more general case of an ellipse. Further research is required to more fully explain the origin of the distinctive patterns produced by the waves.
CUNDARI, AUDREY. Dept. of Physics. Wilberforce Pendulum
The Wilberforce Pendulum is a coupled oscillator that can be used to model physical structures, such as complex molecules, that have multiple degrees of freedom. An initial translational displacement or angular rotation sets the Wilberforce Pendulum into motion, causing it to alternate between translational and rotational modes of oscillation. How quickly and the extent to which the pendulum switches between modes depends on spring, damping, and coupling constants, as well as the addition of a driving frequency. Plots of position and energy vs. time under different initial conditions allow the user to visualize the pendulum’s energy transfer, resonance frequencies, and normal modes of oscillation.
FULTON, MARY F. Dept. of Physics. Observing the hyperfine structure of Rubidium (Rb) by using saturated absorption laser spectroscopy to eliminate the Doppler Effect.
I investigated the hyperfine structure of Rb by shining a tunable diode laser through a cell containing gaseous Rb. The Doppler Effect was eliminated by splitting the input laser beam and causing the beams to overlap and propagate in opposite directions through the Rb cell. This technique eliminates Doppler broadening of the signal and allows fine and hyperfine structure to be resolved.
GILLESPIE, COLLEEN G. Dept. of Physics. The effect of concentration and annealing conditions on 5D3 ? 7FJ emission in terbium-doped sol-gel glasses.
Sol-gel glasses have optical properties similar to those of traditional melt glasses, but are appealing because they can hold a higher concentration of dopants due to their lower processing temperatures. In silicate sol-gel doped with trivalent terbium, the intensity of fluorescence from the 5D3 level to the 7FJ (J = 0…6) ground state manifold levels is highly dependent on both terbium concentration and annealing conditions. 5D3 emission is observed in glasses annealed at 750?C and increases in intensity with increasing annealing time and with higher annealing temperature. The relative intensity of emission from the 5D3 state decreases with increasing Tb3+ concentration. A cross-relaxation process involving two nearby Tb3+ ions depopulates the 5D3 level and causes this concentration quenching.
JENKS, MICHAEL. Physics. Applications of statistical mechanics in astrophysics.
The states and properties of white dwarf and neutron stars can be explained through application of statistical mechanics to these systems. White dwarf and neutron stars both experience various processes in reaching that state. This study involves descriptions of stellar evolution, development of postulates of statistical mechanics and their application to the existence of stellar bodies. Specifically, the size-mass relationships of white dwarf and neutron stars are explained through statistical mechanics and particle degeneracies. The statistical mechanical state of black holes is also considered; it is shown that the expansionary force of particle degeneracy cannot overcome the collapsing gravitational force in black holes.
KAUFMAN, MICHAEL. Department of Physics. Exploring Chaos in Diodes and Mechanical Oscillators
Chaos appears in many systems and it results can be intriguing. In this project, I explored the chaotic properties of a periodically driven Van der Pole Oscillator with a double-well potential function through the use of a Poincaré section and FFT’s. I also used these same two tools to explore the behavior or an inductor-diode circuit (mimicking an LRC circuit). Poincaré sections help us understand the growth of the phase space at specific points based on the driver. FFT’s will help explain the make up of the chaotic motion and help demonstrate the period doubling path to chaos.
KAUFMAN, MICHAEL. Physics. The solar neutrino problem.
Over fifty years of research have been conducted on neutrinos, and a great deal of information has been learned. Recently, there have been numerous experiments aimed at determining the mass and type of neutrinos ejected from the sun, yet still we are left with holes in our theories. This paper looks at the solar neutrino problem, and how the recent discovery of neutrino mass, coupled with the possibility of neutrino oscillations has opened up a path towards a solution.
MCDONALD, MEGAN E. Dept. of Biology, and Dept. of Physics. Examining the physical properties of DNA in DNA microarrays using optical tweezers.
DNA microarrays are an important
method in the growing field of genomics, and are used to determine gene expression
levels in an organism. While this system is widely used, little is known about
the molecular level interactions that make up the technique. One way to better
understand the method at a molecular level is to examine the interactions
of the DNA on the glass slide. To accomplish this goal, DNA undergoes the
typical microarray process of spotting, UV-crosslinking, and boiling (creating
single stranded DNA) in order to obtain an accurate representation of the
microarray process. 1um aldehyde-modified polystyrene beads are then attached
to the exposed bases in the single stranded DNA. A bead is trapped by the
optical tweezers and held in place while the slide is moved at a constant
velocity. Bead displacement from the center of the trap is measured from the
refracted light using a four-quadrant photodetector. This data is then used
to calculate the force constant of single stranded DNA.
Poster displayed in Biology Section (1st floor Watson).
ORTIZ, CARLOS P. Department of Physics. Magnetic Pendulums And The Rise of Chaos
It’s not surprising that magnetic pendulums are popular gifts to offer scientists and engineers. Instead of a metal ball in the end, magnetic pendulums swing a strong permanent magnet. Below the pendulum, there is a plane with other magnets arranged in a particular pattern. The magnets are arranged such that every magnet on the plane attracts the swinging magnets. Once released, the swinging magnet appears to behave “randomly” and “erratically.” However, the orbit of the swinging magnet can be predicted quite accurately because the equations of motion of the magnet are deterministic, assuming we knew the initial position with sufficient accuracy. However, based on the initial position, we may not predict what magnet is the swinging magnet going to settle over. The inability to predict the final outcome of a trial stems from what’s known as sensitivity of initial conditions, which this particular physical map exhibits. By showing that the map exhibits sensitivity of initial conditions and by showing that there exists a strange attractor dominating the behavior of the system, then we may conclude the system behaves “chaotically.” The computational process of measuring chaotic behavior can be done through a number of techniques: plotting the bifurcation diagram of the system, finding the basins of attraction of the map, applying Markov transition matrix theory to compute the number of periodic orbits at every iteration, etc. I chose to find the basin of attraction of the system by looking at Poincaré sections (projections onto a 2D plane) of the phase space of the system (multidimensional structure representing all the possible states of the system).
PARK III, G. BARRATT. Dept. of Math. Models for Periodic Behavior and Chaos in the Belouzov-Zhabotinsky Reaction.
The Belouzov-Zhabotinsky (BZ) reaction is a cerium-catalyzed oxidation and bromination of an organic substrate, usually malonic acid. When carried out in a continuous-flow stirred tank reactor, it represents the best studied of a wide assortment of chemical reactions displaying nonlinear dynamics leading to periodicity and chemical chaos. The famous Oregonator model, proposed by Field, Körös, and Noyes, is presented along with an analysis that demonstrates the appearance of periodic behavior that arises through successive Hopf bifurcations. However, this model fails to predict chaos. Next, the Györgyi-Field model is presented. The results of numerical analyses show strong evidence for the existence of chaos. This model is compared with the experimental results of Györgyi and coworkers. Although it is in good qualitative agreement, quantitative agreement is poor. A likely reason for the lack of quantitative agreement may be the use of inaccurate kinetics rate constants.
PARK III, G. BARRATT, W. SEAN MCGIVERN, JEFFREY A. MANION, WING TSANG. Dept. of Chemistry. Shock Tube Studies of 1,4-pentadiene Isomerization and Decomposition.
The thermal unimolecular isomerization and decomposition reactions of 1,4-pentadiene were studied in a single-pulse shock tube at temperatures ranging from 1000-1300 K. Reactions were carried out in argon bath gas at pressures of 1-3 atm. The reaction mixture contained about 0.5% 1,4-pentadiene and conversion rates were about 2% during the 500 ?s heating pulse. Product analysis was performed using gas chromatography with flame ionization detection. Three major reaction pathways were determined to be important: biradical pathways activated by ?-bond cleavage, radical pathways activated by ?-bond cleavage, and concerted retroene pathways. These pathways had overall kinetics governed by frequency factors of (1.68±0.06) x 1011, (6.98±0.08) x 1011, and (3.29±0.04) x 1013 s-1, respectively, and activation energies of 214±8, 252±16, and 296±12 kJ mol-1, repectively. Uncertainties represent only random statistical deviation. We estimate that Arrhenius parameters may contain systematic error of up to 20%. The major product of the dominant reaction pathway is cyclopentene. Since pyrolysis reactions of unsaturated hydrocarbons are important in combustion reactors, this has important implications for the environment since cyclopentene is a known polycyclic aromatic hydrocarbon (PAH) precursor.
PENEV, TODOR. Physics. Radiative torques in interstellar grains.
Interstellar grains play an important role in star formation, as they facilitate the synthesis of H2 molecules and have an important function in heating the interstellar medium through photoelectric radiation. Understanding dust-grain dynamics is key to analyzing both optical and infra-red observations of stars, as well as measuring the Cosmic Microwave Background. Rotating dust particles are aligned in the local magnetic field through radiative forces due to starlight and magnetic relaxation via the Galactic magnetic field. Due to irregularities in the dust particle geometries, radiative torques play a major role in grain rotation and provide for rapid particle alignment in star-forming regions. This project aims at studying the general dynamics and equations of motion due to radiative torques on the interstellar grains.
REID, AUSTIN. Dept. of Physics. Using Cellular Automata to Model Turbulent Fluid Flow
First developed in the 1940’s, Cellular Automata are exceedingly useful tools for modeling the complex interactions of the physical world. A cellular automaton (CA) is a lattice of points, where each point has a finite number of states. These states are changed by “looking” at neighboring sites and then applying a set of discrete rules. This simple concept allows the creation of surprisingly complex behavior, such as fractal growth and fluid flow. A java application built by Kip Barros utilizing the Open Source Physics (OSP) library was expanded to analyze turbulence in the flow of a two dimensional CA fluid. Laminar (smooth) flow of a fluid is characterized by the zero curl of its velocity vector field, thus a non-zero curl implies turbulent flow. Using a continuously updating plot of the fluid’s curl, the critical Reynolds number was obtained, which was compared to literature values. Further exploration of the cellular automaton’s accuracy included verification of the code with Bernoulli’s equation. Finally, even though the Reynolds number was calculated with a disk, flow around other shapes is explored as well.
REYNOLDS, BLAIR. Physics. Lagrangian methods in classical mechanics and quantum field theory.
I plan on showing how two different uses of Lagrangian methods (classical mechanics and quantum field theory) are similarly related. I will use the Lagrangian equation, L = T - U to bridge between the classical and quantum field theory methods.
ROTHENBACH, CHRISTIAN A. Physics. Quantum-mechanical perturbations.
I seek to explore the behavior and understanding of the quantum-mechanical perturbation theory, mainly the time-independent perturbation theory and how it relates to atomic physics and the energy levels of atoms. Beginning with the infinite square well, we can chose to add perturbations to the potential energy function and see how these perturbations change energies and wave equations. As David Griffiths defines it, “Perturbation theory is a systematic procedure for obtaining approximate solutions to the perturbed problem, by building on the known exact solutions to the unperturbed case.” Both numeric answers as well as graphical representations will be obtained by using Java simulations. Furthermore, this can be achieved by studying techniques like the variational principle, for example, for Helium.
ROTHENBACH, CHRISTIAN A. Dept. of Physics. Coupled Oscillatory Systems
I studied the behavior of systems of coupled oscillators. As the energy or position of one of the masses is changed, we can see how this change affects the other masses and how the energy is redistributed in the system. This involved solving multiple differential equations using ODE solvers and observing the positions and energies of these masses to further study the motion by presenting examples of coupled systems and their solutions. Such systems can be found in Physics and Biology, like mechanical systems, electrical circuits, colonies of ants and of flies, and the connection of the thalamus and cerebral cortex, among others.
SCHAMPER, CHRISTOPHER. Physics. Solar system formation: Models and problems.
The goal of this project is to explore current models of solar system formation in the context of physical mechanisms. There are several outstanding problems involving our understanding of the solar system including the distribution of angular momentum throughout the solar system. Open Source Physics (OSP) will be used to visualize these models and related physical measurements.
SHEIBLEY, DAVID L. Dept. of Physics. Investigation of test mass motion around Lagrange points in a planet-star system.
I simulated the motion of test masses under the influence of a planet-star system. The purpose was to investigate the stable points of the satellite’s orbit, known as Lagrange points. This is a form of the restricted n-body problem. Specifically, my project focuses mostly on the L4 point. The star is assumed to be stationary, the planet moves under influence of the star, and the test mass moves under influence of the star and planet. A control panel allows users to adjust initial parameters of the problem. Displays show the system from a stationary reference frame with respect to the sun and from a reference frame rotating with the planet. By simulating multiple particles around L4, I studied the stability and sensitivity of test mass motion near that Lagrange point.
SIMOV, KIRIL R. Physics. Look down a black hole.
Dr. Einstein suggested that space is curved by gravity around massive objects, such as black holes. Even though photons have no mass and should not be affected by gravity, light would follow the shortest path in space to minimize the time of travel according to Fermat’s principle. This theory helped Dr. Einstein become famous in 1919 after Sir Arthur Eddington verified the phenomena of curving light and ever since, this phenomenon has been referred to as Einstein Rings. The purpose of this project is to create a computer algorithm to reproduce Einstein Rings in an interactive program that will allow the user to specify the mass of the black hole, the distance from the black hole to the object and the observer. The final goal of the project is to have the option to upload a picture with a pre-set size and see how the observed image would change if placed close to a black hole.
SIMOV, KIRIL R., DR. WOLFGANG CHRISTIAN, Modeling Optical Phenomena Using Open Source Physics (OSP)
The project aims at creating a suite of Java programs to help in teaching optical theory. The development of new computational algorithms and visualization techniques allows the user to interact with optical tools and learn the theory before entering the lab. In turn, this ensures correct and thorough understanding before the students perform the same experiments in real life. The phenomena researched in this project are: polarization, 1D diffraction, 2D diffraction, and Fabry-Perot Interferometry. The programs are based on the OSP library, which can be found at http://www.opensourcephysics.org
SIMOV, PETER R. Dept. of Physics. Modeling a plate oscillating about a non-vertical axis using quaternion coordinates.
I investigated the properties of a plate which oscillates around an axis of rotation. This is known as Feynmann wobbling plate problem. He noticed that a plate set in the dining hall in Cornell did two wobbles by the time it rotated once. The basic algorithms included objects from Java OSP library such as quaternion rotations, 3D objects, simulation control and RK45 numerical method. The first part of the project included a plate which rotates around a vertical shaft, which keeps the ? (angular velocity) constant. It was determined that the angular momentum must change and consequently there should be applied a torque to this system. The torque had its direction along the xy plane. The torque did two oscillations by the time the shaft rotated once. This was extended to model of a plate, whose axis of rotation will not be around the z-axis and which would experience no external torque while rotating. It showed the same 2-1 ratio, this time the ? made two rotations by the time the plate rotated once. In conclusion, this 2-1 ratio seems to derive from the motion. The behavior of the plates is further described in this project.
SONNI, SEAN S. Physics. Zero point energy: Something from nothing.
The zero point energy is one of the most unintuitive results of quantum mechanics. The energy calculations lead to a completely different view of the “empty” vacuum; one filled with the constant creation and annihilation of virtual particles. These virtual particles are responsible for the Casimir force and Hawking radiation and have been a possible candidate for the illusive dark energy. This paper introduces several basic quantum-mechanical principles that underlie virtual particles, gives a qualitative description of several of the effects caused by these particles, and then presents an example calculation of the Casimir force using the Riemann regularization procedure.
WELLS, JAMES E. Dept. of Physics. Using the Open-Source Physics Library to model a classical hydrogen atom in a magnetic field in three dimensions.
The problem of a classical hydrogen atom in an external magnetic field is fundamental, with applications to many areas of science. It also holds theoretical significance; other theories build on it, such as the study of heavy atoms’ structure built on knowledge of the structure of the hydrogen atom. While the study of this system has been extensive, our understanding of this system has only truly arisen in the last 20 years. While much research has been done, little has been done in the field of computational physics on this system, and little at the level that can be easily grasped by an undergraduate. The purpose of this exercise is to model the system of a classical hydrogen atom in a magnetic field using computational methods. In order to accomplish this, an electron in a crossed magnetic and electric field was simulated in both two and three dimensions. The results matched published results and theoretical predictions. This was used as the basis for the model of the hydrogen atom in an external field in both two and three dimensions. More research will be needed to better quantitatively compare these results with published results.
Perceiving anger on the face of a Black male is related to an individual’s implicit prejudice regarding black people (Hugenberg & Bodenhausen, 2003). The current experiment examined whether this interaction between implicit prejudice and race extends to the stereotype of Asians being more passive (Oyserman & Sakamato, 1997). Twenty-seven Davidson college students took an Implicit Association Test (IAT) and identified facial changes in a facial detection task. IAT scores did not have a significant effect on participant’s judgment of White or Asian facial expressions of emotion. These findings do not support earlier research that suggests implicit prejudice affects the way people perceive facial expression of emotion. Further studies need to more thoroughly investigate this phenomenon.
CHAPIN, EVELYN A., RUTH L. AULT. Dept. of Psychology. Interviewing preschoolers: Using observational learning to improve response accuracy.
This study assessed a practical pre-interview intervention aimed at teaching children a response strategy to increase their accuracy. Children (N = 24; age range = 3.5 – 5 years) randomly watched 1 of 2 videos. A 6-year-old boy modeled saying “I don’t know” 4 times, for the experimental group, or never, for the control group. Afterwards, participants answered questions regarding a story they created. Control and experimental groups did not differ in their frequency of “I don’t know” responses, z = -0.954, p = .340. On open-misleading questions, children watching the experimental video were more likely than controls to say “I don’t know,” p = .034, Fisher’s exact test. Overcoming procedural and sample size limitations would provide a stronger test of the effectiveness of video modeling.
COHEN, MARIKA B. and STUART R. TOMKO. Dept. of Psychology. Effects
of flunitrazepam and GHB on motor performance in rats.
Date rape and sexual assault are becoming an increasingly common problem in society. In addition, these actions often occur in conjunction with drug use. The benzodiazepine flunitrazepam and gammahydroxybutyrate (GHB) are two drugs that have been implicated alone and in combination in instances of sexual assault. This experiment examined the effects of flunitrazepam and GHB in an animal model of motor performance. Using a rotorod apparatus, rats were given cumulative doses of flunitrazepam alone in combination with various doses of GHB. Motor performance was significantly impaired by both drugs when administered alone. Importantly, GHB pretreatment increased the effects of flunitrazepam in an additive manner. These results highlight the dangers of these drugs both alone and in combination to potential sexual assault victims.
FASSBENDER, JANELLE M. Dept. of Psychology. Progressive unilateral entorhinal cortex lesions accelerate crossed-temporodentate synapse capacity for long-term potentiation.
If LTP is responsible for recovery of working memory after a one-stage unilateral entorhinal cortex (EC) lesion, it should be present in the sprouted crossed-temporodentate pathway at the time behavior changes, around six days post-lesion. High-frequency stimulation was used (eight trains of eight pulses at 400 Hz each with trains separated by 10 s) to elicit LTP in CTD synapses six days after one-stage and progressive unilateral EC lesions. At six days post-lesion, four one-stage animals showed no consistent signs of potentiation at any level of stimulation (100% stimulation: M = 95.1% baseline slope (mV/ms); 90%: M = 92.3%; 50%: M = 88.7%; 25%: M = 99.2%). Six progressive animals maintained potentiation above the baseline slope (M > 100% baseline slope for all levels of stimulation). Values from progressive animals (90% stimulation: M = 103.7% baseline slope; 25%: M = 107.7%) parallel previous conclusions that one-stage animals show capacity for LTP 8-10 days post-lesion (Reeves & Steward, 1986). However, LTP probably does not account for recovery of working memory in rats because it is not elicited along the same time course as behavioral recovery after unilateral EC lesions.
HAMAMOTO, MAYUMI. Dept. of Psychology. Musicians, intermediate musicians, and nonmusicians’ perception of bitonality: Non-directed, preferential, and learning tasks.
Bitonal music is characterized by a dissonant "crunch" sound that had been believed to be clearly audible by everyone (Wolpert, 2000). However, Wolpert found that nonmusicians did not identify bitonality in a free response task. The present study replicated Wolpert’s findings, but also had participants rate song clips for preference, correctness and pleasantness. Monotonal music was rated higher on all dimensions independent of the individual’s level of musical training. In addition, following a brief training session, nonmusicians (less than 1 year of musical training) identified the tonality of the final clips at equivalently high rates as the intermediate (mean 2.4 years) and expert (mean 9.2 years) musician groups.
LLOYD, TRAVIS G., MARGARET P. MUNGER. Dept. of Psychology. Emotional expression in percussion performance.
The psychological study of music has generated several remarkable theories as to how listeners perceive and interpret music. Recent experimental research isolating the musical property of rhythm supports these theories and offers insight into both the processes of listening and performing. Research has also revealed that specific emotions can be conveyed to listeners via expressive musical performance. The present study isolated the musical characteristics of tempo, dynamic level, and rhythmic pattern of solo percussion music in an attempt to investigate their contributions to listeners’ perceptions of emotion. The results indicated that these musical characteristics differentially affect perceptions of emotion.
LYLE, MEGAN A. Dept. of Psychology. Effects of chronic exercise on sensitivity to mu opioids in female rats.
Chronic exercise, which leads to a sustained release of beta-endorphin, is associated with decreased sensitivity to the antinociceptive effects of mu opioids, which may reflect the development of cross tolerance between beta-endorphin and exogenous opioids. The purpose of the present study was to examine the effects of chronic exercise on sensitivity to the effects of mu opioids in female rats and to determine if these changes in sensitivity are correlated with exercise output. The antinociceptive effects of morphine, levorphanol, buprenorphine, and butorphanol were examined in the warm-water, tail-withdrawal procedure in eight female rats under initial sedentary, exercise, and subsequent sedentary conditions. Under sedentary conditions, all four opioids increased tail-withdrawal latencies. Sensitivity decreased under exercise conditions, leading to decreases in the potency or effectiveness of each drug. When rats were returned to sedentary conditions, sensitivity increased to levels observed prior to the exercise condition. Changes in sensitivity were positively correlated with exercise output in individual rats. Despite higher running rates in females, changes in sensitivity were similar to those observed previously in males. Thus, exercise may have a ceiling effect on opioid receptor sensitivity and/or female gonadal hormones may attenuate the compensatory responses of the opioid receptor system during chronic exercise.
MAH, NICOLE A., ROSE FEOR, TUTI PENEV. Dept. of Psychology, Dept. of Mathematics, Instructional Technology Group. A web-based simulation and wet-laboratory website using the 6-OHDA Parkinson’s disease model.
The rat 6-hydroxydopamine (6-OHDA) unilateral lesion model of Parkinson’s disease (PD) offers easily quantifiable behavior and a short time course for neurodegeneration, making it useful for testing drugs that act on dopamine (DA) and DA receptors. We performed a meta-analysis on published 6-OHDA studies and created a mathematical model predicting the direction and extent of rotation observed with various amounts of nigrostriatal DA denervation, measured by striatal tyrosine hydroxylase immunoreactive (TH+) neurons. Based on this model, we created a web-based simulation of a typical 6-OHDA experiment. The website complements a wet-laboratory website which describes and illustrates the behavioral, surgical, and histological procedures for a 6-OHDA experiment. Student assessments of the websites demonstrate that both sites are effective and practical teaching tools.
OTVOS, JUDIT, and KRISTI S. MULTHAUP. Dept. of Psychology. The effects of verbalization on eyewitness memory for same and different race culprits.
Sixty White Davidson College students participated in an experiment investigating the effects of verbal descriptions preceding eyewitness identification for both same-race and other-race perpetrators. The purpose of this study was to extend the finding that the cross-race effect is eliminated when preceded by verbal descriptions. Participants viewed a crime on a computer screen and then identified the perpetrator from a line-up that showed not only the face, but the whole body. It was found that identification in the other-race condition was identical for verbalization or no verbalization conditions. In the same-race condition, verbalization decreased accuracy. No significant differences were found due to lack of statistical power, however the pattern of data is consistent with what was hypothesized.
PERKINS, JESSICA, KRISTI S. MULTHAUP, H. WESLEY PERKINS, COLE BARTON. Dept. of Psychology. Efficacy expectations, participation in physical and social activity, and emotional well-being among older adults in Spain and the United States.
We explored Bandura’s (1997) efficacy expectation theory as applied to participation in physical and social activity, and how such participation and physical health affected emotional well-being. Older adults in Spain (n = 53) and the United States (n = 55) completed a questionnaire regarding self-efficacy, outcome expectancy, participation in physical and social activities, and health. Self-efficacy significantly predicted both physical and social activity; outcome expectancy did not. Social activity significantly predicted emotional well-being in the United States sample and the Spanish sample with more than six years of education; physical activity did not. Regardless of cultural context, self-efficacy appears to explain participation and social activity appears to be the primary influence on emotional well-being for older adults with more than minimal education.
PERKINS, JESSICA, MEGGIE PATTERSON, MARIE JAGUSZTYN, BRENDA WEIGAND, SIU PING CHIN FEMAN, KRISTI S. MULTHAUP, & MARK E. FAUST. Dept. of Psychology. Aging, end effects, & most of life effects in quality of life ratings.
Diener, Wirtz, and Oishi (2001) reported that the valence (i.e., positive or negative nature) of the end of life is weighted heavily when judging the quality of a life. This study examined factors that would modulate this end effect. We assessed how different combinations of positive and negative main life portions and life endings (Pp, Pn, Np, Nn), rater’s age, and a hypothetical character’s age at time of death influenced quality of life ratings. Seventy-eight undergraduates, 64 middle-aged adults, and 65 older adults read the four life descriptions and rated the desirability of each life. Results yielded a rater age group (young, middle-aged, older) x hypothetical character age (30, 80) x main life portion (Positive, Negative) x end of life (positive, negative) interaction. For young adults, there was a larger end effect for positive than negative lives for the character who died at age 30, but not for the character who died at age 80. The opposite was true for older adults. No interaction existed for the middle-aged group. Both most of life and end of life effects influenced the quality of life rating. End effects, however, were five times greater than most of life effects.
SALTER, PHIA & KRISTI S. MULTHAUP. Dept. of Psychology. Ethnic self-identification in the African American community: The role of aging in label preferences.
Self-identification is the ethnic label that one uses to describe oneself (Phinney, 1990). Historically, African Americans have used different labels to express their collective identity. Evolving from Colored, to Negro, to Black, and shifting towards African American, each label evokes different connotations. This study surveyed 85 participants, investigating whether the dominant label used during the years that define a generation (ages 17-25) determined preferred self-identification labels of African Americans. Although not statistically significant (low power), trends suggest that labels used during the formative years influence self-identification of African Americans: African American adults 18-41 (n = 38) preferred the label African American more than the adults 56-66; African American adults 56-66 (n = 12) preferred Black more than the adults 18-41.
SASANFAR, JAMIE. Dept. of Psychology. Attractive female faces: additional dimensions reflecting race and participant gender.
The present study investigated the relationship between thinness and attractive female facial caricatures. Sixteen male and female upper-level psychology students viewed nine faces that represented three ethnicities (White, Black, and Asian), and three degrees of thinness (thin, regular, and heavy), then judged attractiveness, thinness, and gender using a 5-point Likert scale. Regular faces were significantly more attractive than thin and heavy faces F(2, 13) = 5.17, p = .02. Black and Asian faces received higher attractiveness scores compared to White faces F(2, 13) = 18.06, p < .01. Females perceived all the caricatures as significantly more attractive than males F(1, 14) = 6.07, p = .03. The impact of race and participant gender on attractiveness ratings suggests additional dimensions of attractive female faces.
STUTTS, LAUREN A., RUTH L. AULT. Dept. of Psychology. Effects of chronic illness on elementary school children’s and adults’ understanding of psychogenic bodily reactions.
We investigated the effects of chronic illness on elementary school children’s and adults’ understanding of psychogenic bodily reactions (i.e., physical responses with psychological origins). Children between 7 and 12 years old (23 healthy; 20 with chronic illnesses) and adults (19 healthy; 16 with chronic illnesses) answered questions about the possibility of psychogenic reactions, their psychogenic experiences, and their beliefs about alternative treatments. Participants answered 20 questions probing for the possibility of psychogenic reactions. Each of 5 scenarios (nervousness and throwing up; worried and tummy ache; scared and goosebumps; frustrated and headache; shyness and face getting red) included 4 possible causes: physical, psychological, psychogenic, and (for control) moral transgression. Adults reported that psychogenic reactions were possible significantly more than did children, F(1, 74) = 8.16, p < .006. However, experience with illness did not significantly affect psychogenic understanding, perhaps because there was too much variability in the types of chronic illnesses to show that illness experience affects psychogenic understanding. Children and adults believe in psychogenic treatments, asserting that psychological activities can positively influence physical illness. This implies that the medical profession consider treating their patients more holistically.
TOMKO, STUART R., ELIZABETH L. BOOKS, COLE BARTON. Dept. of Psychology. The use of physiological measures to determine emotional valence in a clinical setting.
Whether or not specific physiological profiles exist for each emotion has been a hotly debated topic in the literature for decades. This study takes the position that emotional specificity does exist, and posits that these distinct physiological profiles can be used to differentiate emotions in a laboratory setting. Participants were divided into low and high self-efficacy groups based on Global Self Efficacy score and then asked to engage in a task designed to elicit frustration while heart rate, breathing rate, and electrodermal activity (EDA) were monitored. The participants’ reactions to the task were then coded across four 30 s intervals from videotaped facial expressions of Positive, Negative, or Neutral emotions. Preliminary analyses indicated that mean EDA as well as the standard deviation of EDA are associated with type of emotion. Further, in one of the coding epochs, the standard deviation of breathing rate as well as mean of the absolute values of the second differences of the normalized breathing rate were significant predictors. There were no significant differences between participants based on self-efficacy. These results indicate that EDA and perhaps breathing rate can be useful in predicting emotion in laboratory paradigms.
TOMKO, STUART R., MARI B. COHEN, MARK A. SMITH. Dept. of Psychology. Effects of the low-efficacy opioid agonist (–)-metazocine when coadministered with cocaine on locomotor activity in rats.
Low-efficacy, mixed-action opioid agonists may have potential as a pharmacological treatment of cocaine addiction. Evidence suggests, however, that this class of drugs may increase some of cocaine’s effects. The current study examines the effects of cocaine when given alone and in combination with the low-efficacy opioid agonist (–)-metazocine on locomotor activity in rats. Cocaine dose-dependently increased locomotor activity and (–)-metazocine increased this effect in a synergistic manner. (–)-Metazocine alone also increased locomotor activity, a result which conflicts with previous research. The results of the current study suggest that more research be directed at the interaction between low-efficacy agonists and cocaine before the use of opioids in the treatment of cocaine addiction becomes widespread.
VOYLES, RACHAEL AND COLE BARTON. Dept. of Psychology. Significant predictors of student alcohol consumption attitudes and student opinions of college alcohol policy: A study of a private liberal arts college.
A148-item questionnaire collected information about student alcohol consumption attitudes and opinions of the Alcohol Policy at a small, private, liberal arts college. The item categories were demographics, family history, personality characteristics, campus living, alcohol behaviors, attitudes about alcohol, beliefs about alcohol health risks, perceptions of the Davidson College Alcohol Policy, and alcohol violations. Electronic administration of the questionnaire to a random sample of 800 students yielded 369 completed questionnaires. A data reduction technique using a principal components factor analysis established 13 factors. Multiple regressions identified the most significant predictors of Personal Alcohol Consumption Attitudes as Eating House (Greek-like organization) Influence, Living Pattern, Organization/Commitment, and Good Samaritan Rule. The most significant predictors of Opinion of the Alcohol Policy are Class Rank and Gender with high opinions of the Policy held by female underclassmen.
WOODS, KIMBERLY D., KELLY SCHMIDT, KRISTI S. MULTHAUP, SCOTT TONIDANDEL. Dept. of Psychology. Physician-patient relationships: What do older adults expect?
Physician-patient relationships can influence patients’ medical experiences. We assessed older adults’ expectations in physician-patient relationships and compared them to those of physicians. 223 older adults (ages 60-99) and 142 physicians completed questionnaires that posed questions based on their expectations of communication, personal support, and active role in physician-patient relationships. For some of the questions, age was related to older adults’ responses so older adults were subdivided by age. Physicians tended to think they should provide more personal support than older adults expected. Physicians and older adults agreed on some aspects of communication and active role, but disagreed on other aspects. From this study, physicians can learn what older adults expect in order to form more effective relationships with them.
Through independent and collaborative undertakings, I explored the depths and intricacies of today’s drug industry. Key individuals and noteworthy events helped the pharmaceutical industry evolve into what it is today. Investigated was the long, arduous road of transforming a molecular idea into a successfully marketable product. Various perspectives through which the industry was studied include ethnobotany, stereochemistry, green and environmental chemistry, cosmeceuticals and nutraceuticals, drug polymorphism, drug pricing and price regulation, and generic pharmaceutical roles. To witness first-hand how the aforementioned topics are integrated in the drug industry, my professor and I visited, toured, and conducted on-site interviews at three local pharmaceutical companies: small firm, active pharmaceutical intermediates (Pharmacore), generic drug company (Alpharma), and large, research-based firm (GlaxoSmithKline). Furthermore, I weekly monitored and ventured to justify the stock quotes of five pharmaceutical companies listed on the New York Stock Exchange. The course served as a medium through which I gleaned a broader and deeper understanding of the inner workings of the modern pharmaceutical industry.
The Office of the Vice President for Academic Affairs generously provided funds for the 2005 Science and Math Student Research Symposium. Dr. Patricia Peroni organized the event. Special thanks to Mrs. Fern Duncan and Dr. Mark Smith for their helpful advice on coordination of this event.