Natural Science Seminar - Abstracts Fall 2006

Sarah De Leiris
February 12, 2007

Coyote (Canis latrans) scat analysis in the Narragansett Bay region of Rhode Island
Mentor: Dr. Lou Weber.

Abstract: Coyote (Canis latrans) populations are growing in numbers throughout Rhode Island and New England.  Previous studies indicate that humans influence diet, but the extent to which they affect game species and household pets has not been determined.  My objective was to determine the composition of coyote diets in the island populations of Rhode Island.  Scat samples were collected from Aquidneck and Conanicut Islands.  The sample contents were separated into categories of Hair; Bone; Plant; Insect; Feather; Other, and volume percentages were calculated.  The Hair category had the highest volume percentage (52.6%), the Plant category had the next highest volume percentage (26.0%), and all the other categories were below 10.0% volume.  Deer hair was present in 31.4% of the samples, and cat hair was found in 10.0% of the samples.  The data indicate that the influence on coyote diets by the close proximity of humans is minor.  There is not enough evidence to show that a change in human behavior will affect the coyote population size.  Rhode Island residents should be aware of the presence and habits of coyotes when allowing their pets outside on their own.

Marie Williamson
February 19, 2007
Urinary ergot alkaloid excretion by beef heifers and cows grazing endophyte-infected (Neotyphodium coenphialum) tall fescue (Festuca arundinacea) pastures and hay.
Mentor: Dr. Victoria Collins

Abstract: Fescue (festuca arundinacea) is the predominant grass in pastures at Warren Wilson College farm.   Fescue has a symbiotic relationship with a fungal endophyte (Neotyphodium coenphialum) that lives within leaf sheath cells and produces alkaloids.  Ergot alkoloids are responsible for fescue toxicosis, the symptoms that cattle experience grazing endophyte-infected (E+) fescue.  Symptoms include vasoconstriction, decreased conception rates, and decreased lactation.    Measuring total ergot alkaloid content in urine is being developed as a diagnostic tool for fescue toxicosis.  Urinary analysis is useful because it provides a reliable snapshot of current alkaloid consumption by cattle.   The objective of this study was to compare urinary ergot alkaloid levels from cows and heifers grazing E+ pasture.  A second objective was to compare urinary ergot alkaloid levels from cows and heifers grazing E+ pasture to cows and heifers consuming fescue hay. Samples were obtained from cows and heifers grazing E+ fescue in Dogwood, Charlie’s, and Daisy Hill pastures in September 2006.  Samples were also obtained from cows and heifers consuming fescue hay.  A competitive ELISA test kit, manufactured by Agrinostics Ltd., was used to determine ergot alkaloid levels. No significant difference ( p= 0.4048) of alkaloid excretion was measured between cows and heifers, allowing the data for all cattle to be pooled.  There was no significant difference (p=: 0.8567) in alkaloid excretion in Dogwood, Charlie’s, and Daisy Hill pastures or when cattle consumed hay.  The average alkaloid excretion by cattle grazing E+ pastures was 18.21 ng alkaloid/ mg creatinine.  Alkaloid excretion in the fall corresponds to low fescue toxicity levels in published data.

Betsy Kain
February 19, 2007
Coloration and Courtship Behavior in Male Guppies Treated with Estrogen
Mentors: Dr. Jeff Holmes and Dr. Robert Eckstein.

Abstract: Fish species around the world are being identified as intersex, which is the presence of both male and female gonadal features in one individual.  One explanation for the presence of intersex fish is endocrine disrupting chemicals (EDCs) in our aquatic ecosystems.  Steroidal estrogens such as 17-a-Ethynylestradiol (EE2), which is derived from contraceptive pills, are designed to be extremely potent and have the greatest endocrine-disrupting capability of all EDCs.  This study was designed to assess the effect of EE2 on the development of male coloration and the expression of male mating behaviors in guppies, a fish in which both are well characterized.  Groups of male guppies were exposed to approximately 10, 50, or 200 ng/L of EE2 over the course of 78 days.  Then, individual males were paired with females and the following four courtship behaviors were observed:  sigmoid display, gonopodial swing, gonopodial thrust, and biting cloaca.  The average number of total behaviors per fish per day for each treatment group was statistically analyzed using ANOVA.  The highest dose group had significantly fewer behaviors than the control group, with a P value of 0.007.  Color intensity was rated for all males by eight different observers.  Four out of the seven fish in the control tank were ranked as most intensely colored compared to the fish in the other tanks.    These results suggest that exposure to EE2 may result in reduced male coloration and behavioral changes that might be expected to have a negative effect on the reproductive fitness of males exposed to this environmental contaminant.

Neal Maker
February 26, 2007
Basal area and form class relationship for small diameter Loblolly pine (Pinus taeda) in the North Carolina piedmont
Mentor: Dr. Amy Boyd

Abstract:  Demand for value added forest products and an abundance of unused small-diameter timber have created interest in structural uses for small diameter timber.  Research on structural roundwood is focused on the western United States because of thinning occurring there for fire reduction, but small-diameter timber is also left unused in the southeastern United States after pre-commercial thinning.  Several factors determine the usefulness of timber for small-diameter structural applications, including timber taper.  This study was an attempt to determine if a relationship exists between tree taper in a stand in the southeast and the stand’s density. A relationship would help landowners manage for taper of standing, small-diameter timber.  Basal area (a measure of stand density) and average Girard’s form class (a measure of tree taper) were measured on thirty-five plots of 12 to 18 year old loblolly pine in the Duke Forest on the North Carolina piedmont using a Spiegel-Relaskop.  No significant correlation was found between basal area and form class (r2=0.070).  This is surprising because a correlation does exist for mature Loblolly pine.  One possible explanation is that variation in taper due to early dominance development in loblolly is overshadowing the density-taper relationship.

Todd Steven Boera
March 5, 2007
Agricultural Lime as a Control Method for Leaf Cutter Ants (Atta sp.).

Abstract: Leafcutter ants (Atta sp.) represent a problem to farmers throughout Central America. It is not uncommon for Atta to destroy an entire citrus or cassava plot in just one evening of work. Atta is considered to be the dominant herbivore in the tropics, with the amount of vegetable matter being cut estimated at 12-17 percent of annual leaf production. The current and most common control method employed throughout Central America is the use of a chemical insecticide known as lorsban. Farmers complain about the expense of this product as well as the human and environmental health problems with which it is associated. Organic farmers in San Pedro Columbia, Belize often experiment with alternative methods to control Atta populations. The focus of this study was to determine if agricultural lime as a treatment would produce a significant difference in activity amongst three different hives. Results showed that there was a significant difference (p-value=.00004) from the treatments. However, the significant difference was due to one hive (p-value= .0000003) which caused the large difference amongst all data. The implementation of agricultural lime as a control method is recommended for Central American farmers to decrease Atta activity.

Laura Foulke
March 5, 2007
Ground Water Analysis of Formaldehyde at the Edges of Cemeteries in Buncombe County, NC.
Mentor: Dr. Victoria Collins

Abstract: Embalming of human remains is necessary when burial or refrigeration is not performed within 24 hours. Embalming currently uses about five liters of a 14-17 % formaldehyde solution and is common practice in the United States for aesthetics. EPA classifies formaldehyde as a hazardous substance, hazardous waste, and a possible human carcinogen, yet approximately 1,325,000 liters (350,000 gallons) are legally buried by the funeral industry each year. No evidence of prior research on formaldehyde concentrations in and or around cemeteries was found, but some articles noted concern that formaldehyde might migrate in groundwater due to its high water solubility. The objective of this study was to determine the formaldehyde concentrations in ground water at the edge of three cemeteries from soil and water samples. Both types of samples were collected from each cemetery twice between November 2006 and February 2007 and analyzed using EPA method number 8315 A, which uses High Performance Liquid Chromatography to detect a 2,4 dinitrophenylhydrazone derivative of formaldehyde at 360 nm wavelength. The determined detection limit was 25mM in soil and 0.5mM in water. Formaldehyde was detected in the water at the two with streams and in soil samples at all three.  Formaldehyde concentration was higher in soil than in water and was not related to depth, rainfall, or age of the cemetery. The data suggests that formaldehyde is persistent in soil, but not in water. Future research of other cemetery contaminants such as lead and arsenic and of microbial activity in cemetery soil are recommended.

Rebecca DaVanon
March 12, 2007
The Response of Native Grasses to Controlled Burning and Herbicide Application on a Native Grass Restoration Site
Mentor: Dr. Amy Boyd

Abstract: Grassland communities are threatened by the encroachment and establishment of woody broadleaf shrubs.  Frequent burning has traditional maintained grass dominance, but a decrease in fire size and frequency in the last 150 years has resulted in an increase in shrub size and density.  Frequent controlled burning has been shown to decrease broadleaf cover as long as shrubs have not already become established.  Selective herbicide application has been shown to suppress broadleaf competition.  The Christmas Tree Hill Restoration site grass community has experienced competition with invasive species since it was established.  The objective of this study was to evaluate controlled burning and herbicide application as management techniques for species cover of native grasses at the Christmas Tree Hill Restoration site.  Plots on site received treatments of either controlled burn, herbicide application, herbicide/burn, or control.   Fifty-two plots were analyzed for presence and dominance of study group species (broomsedge, Indiangrass, total species) and percent species cover was determined.  The dominance of broomsedge was significantly higher (p=0.0292) for herbicide/burn plots than for control plots.  Treatment type was insignificant for presence and dominance in all other study groups.  Broomsedge accounted for half of the presence of native grasses on site (28% presence broomsedge/56% total species presence).  The Indiangrass presence (p=0.0530), with more replication, may indicate a difference between treatment type received.  A positive response for broomsedge to fire and to herbicide application on broadleaf species corresponds to published data. Further study is needed to determine broomsedge’s effect on the site’s native grass community.

Sage Brodersen
March 12, 2007
Managed Native Grasses and Oldfield Insect Communities
Mentor: Dr. Amy Boyd

Abstract: Currently the grassland biome is being threatened by introduced invasive plant species. It is unknown how these introduced plant species will affect the wildlife associated with grasslands. This is a particularly important issue for oldfield insects because they are the most abundant form of wildlife in the grassland ecosystem. The objective of this study was to determine the effects of managed native grasses on the diversity and composition of oldfield insect communities. Three different sampling areas were used with 30 insect samples and 15 plant biomass samples taken in each. Insects were identified to the order and family level. The three sampling areas consisted of one that is managed for native grasses, one that was cut and then left unmanaged, and one that is managed for turf forming grasses. This method of sampling is pseudoreplication because I only had one replicate for each type of sampling area. Analysis was done to determine order and family richness, and a Simpson’s diversity index was used to determine order and family diversity. Discriminant analysis was used to find the differences in the insect orders across the three treatment areas. The native grass area showed the highest richness and diversity. In addition more predatory and parasitic insects were found in the native grass area while more pest type species were found in the unmanaged testing area. If multiple sampling areas were used yielding the same results that I found here, this study would have major implications.  These implications are that in losing the biodiversity of the grasslands plants we are also losing biodiversity in the insect communities associated with them.  In addition, the presence of the parasitic and predatory insects in the native grass area suggests that borders of native grassland plants could be a helpful tool in agricultural systems.

Will Lyons
March 26, 2007
The effect of efficient microbes (EM)ä on compost

Abstract: Compost builds soil quality by increasing organic matter, providing plant nutrients and hormones, and serving as an innoculum of beneficial organisms.  The successful production of high quality compost requires careful management of physical, chemical, and biological characteristics of the pile: moisture, temperature, aeration, C: N ratio, and microbial community structure.  While many compost systems simply use available material some use inoculants for starting or accelerating the decomposition process.  A Japanese professor, Teruo Higa, invented one such product known as Effective Microorganisms.  My objective was to determine whether inoculation with Effective Microorganisms during pile construction significantly altered any physical, chemical, or biological processes during the first 75 days of composting.  All piles were constructed from dairy manure and straw.  Two piles were inoculated with Efficient Microbes™ (EM).  All piles were aerated weekly over the study period from November 1, 2006 through January 15, 2007.  Temperature was monitored three times a week.  Samples for moisture, pH, and C:N ratio were taken weekly.  Microbial community structure was examined using phospholipid fatty acid (PLFA) analysis to measure the % bacterial fatty acids and % fungal fatty acids present in the piles.  The use of EM™ did not affect any of the measured parameters.  The project received funding from the North Carolina Academy of Sciences through a Yarborough grant. 

Aaron Malenke
April 6, 2007
Metalloestrogen concentrations in the blood of American alligators, Alligator mississippiensis, in two Florida lakes.

Metalloestrogens are inorganic xenoestrogens that bind to and activate estrogen receptors.  An increase of estrogenic activity in American alligators has been linked to reproductive disorders and can override temperature-dependent sex determination. The objective of this study was to determine if metalloestrogen blood concentrations differ between American alligators living in two Florida lakes: Lake Woodruff and Cape Canaveral.  Lake Woodruff is a national wildlife preserve, while Cape Canaveral borders the Kennedy Space Center, a possible heavy metal contamination source.  Blood samples were dissolved with 70% nitric acid and 30% hydrochloric acid, and analyzed for aluminum, antimony, cadmium, chromium, copper, lead, nickel, tin, and vanadium using an inductively coupled plasma emission spectrophotometer.  Aluminum and vanadium standards were not testable due to possible contamination.  Antimony, copper, and nickel concentrations were below detectable range of 10 ppb, 50,000 ppb, and 20,000 ppb respectively.  Using a standard t-test analysis, cadmium, chromium, lead, and tin concentrations were not significantly different (p < .05 considered significant) between the two lakes.  Further studies can treat alligator eggs with metalloestrogen concentrations similar to those found in blood from Cape Canaveral alligators. These studies could determine the effects of heavy metals on alligators at Cape Canaveral

Michael Hutchison
Weed Seedbank Assessment in Four Farm Fields
April 2, 2007

Abstract: Weeds have been interacting with humans since the advent of agriculture, and have evolved and adapted to many disturbance regimes (Buhler, 1999).  However, weeds also provide beneficial habitat, and provide important soil forming processes (Altieri, 1981; Liebman, 1981).  A crucial component of weed- crop interactions is the pool of dormant seeds existing in the soil, called the weed seed bank (Roberts, 1981).  The objective of this observational study was to quantify the density, composition and diversity of the germinable fraction of the weed seed bank in four crop fields at Warren Wilson College.  Four different treatments in the crop rotation were used to control disturbance.  Soil texture was controlled for with three treatments in Iotla and one treatment in Dillard series.  A randomized transect sampling method was used, based on the Hayashi species-volume curve (Hayashi and Numata, 1975).  Fifty five 0.5 cm samples were taken at each location, and bulked.  Samples were spread on potting soil and placed in conditions conducive to germination according to Gross et al (1990).  Seedling were counted and removed upon identification to species.  Twenty two species were identified.  Estimated weed seed per hectare ranged from 3.14 x 109 in Ballfield, to 7.8 x 107 seed/ha in Northups.  It was determined that primary tillage is most important seed bank forming factor.  While a simple preliminary study, seed bank analysis is an important aspect of crop monitoring. 

Travis Briggs
Cold Tolerance and Range Expansion of Upside-down Jellyfish (Cassiopea xamachana)
April 9, 2007

Abstract: Upside-down Jellyfish (Cassiopea xamachana), once limited to waters off the Florida Bay, recently began a northward expansion.  Presently, Cassiopea populations have become numerous as far north as Sarasota Bay, inhabiting shallow mangrove bays and lagoons with mud and sand bottoms.  The objective of this project was to determine why Cassiopea are currently expanding northerly along the gulf coast of Florida.  Initial cold tolerance tests were conducted to establish that Cassiopea’s pulse rate is affected by water temperature. Pulsation in Cassiopea allows for effective exchange of dissolved oxygen, the ability to clear tentacles of sediment, and the means for locomotion.  Further cold tolerance tests showed that when Cassiopea reached a critical temperature (12-14°C) pulsation stops. A second set of cold tolerance tests found that Cassiopea could survive a 22-24 hour exposure to critical temperatures.  An extended exposure to critical temperatures, beyond 22-24 hours, resulted in 100% mortality.  In 1994, The Mote Marine Laboratory (MML) began recording water temperature data from New Pass in Sarasota, FL.  The results from the cold tolerance tests were compared to historical temperature records collected by the MML to determine that there was no apparent correlation between changes in local water temperatures and the presence of Cassiopea.

John Andrew Wagner
April 9th, 2007
Effects of Imidacloprid on Eastern Hemlocks Infested by the Hemlock Wooly Adelgid

Abstract: The hemlock wooly adelgid is currently devastating the hemlock forests of the eastern U.S., and much research has involved finding information about the pest and possible means of control.  Chemical therapy is the only currently effective method for adelgid control, and biological control is not working.  Imidacloprid is the most widely accepted chemical treatment due to its relatively low toxicity to vertebrate species, but there is no reliable information regarding the effects of Imidacloprid to plants.  Monoterpene composition is shown in many studies to vary in the presence of environmental stresses such as predation and drought.  The objective of this research was to use monoterpenes to study possible effects of Imidacloprid therapy in relation to natural defenses in eastern hemlock.  In December, thirty six composite needle samples were collected from eastern hemlocks in the Berea stand at Warren Wilson College.  All trees used in this study were infested by hemlock wooly adelgid.  These samples were extracted, and the extracts were analyzed by gas chromatography to measure the composition of the terpene components.  Peak enhancement was simultaneously performed to identify nine of the terpene components in the mixture.  Mood’s non-parametric test was performed on the percent composition of 18 compounds from the terpene extract.  One unidentified compound was the only component with a statistically different percent composition in treated versus non-treated trees.  Because the only affected component in the terpene extract was unidentified, no judgments can be made as to if the effect is deleterious or beneficial to hemlock health.  However, there is presently no apparent effect of Imidacloprid on the immune health of eastern hemlock.

Daniel Dayton
April 16, 2007
Comparison of the Microbial Composition of the Three Compost Systems at Warren Wilson College Using Phospholipid Fatty Acid Analysis
Mentor: Dr. Vicki Collins

Abstract: A critical part of a healthy soil community is a diverse microbial population.  Soil microbes include bacterial and fungal populations. ( These organisms perform numerous beneficial activities that help to stimulate healthy plant growth. These activities include immobilization of nutrients with in the biomass, production of compounds that increase soil aggregation, active competition with disease-causing organisms, and increased nutrient and water uptake for plants through mutualistic relationships)omit.  Compost is used in many sustainable agricultural settings as a means to promote healthy soil microbial populations.  Compost refers to the aerobic decomposition of organic matter by microorganisms under controlled conditions.  There are many influencing factors in the production of compost including: carbon to nitrogen ratio, temperature of decomposition, pH, moisture and scale.  At Warren Wilson College, there are three main composting systems in place.  Two of the three, Farm and Garden, are passive windrow systems that use passive aeration and long curing time to finish the compost.  The third, Recycling compost, is an in-vessel, agitated aeration system that uses a large rotating drum to constantly aerate the compost greatly speeding the initial decomposition to 3-5 days.  This compost is then aged approximately 6-8 months before it is incorporated into the soil.  The objective of this project was to conduct an initial study of the microbial composition of the finished compost produced by each of these three composting systems.  The microbial composition was compared by calculating the fungal: bacterial ratio for all three treatments.  A second(sub-)objective was to observe if a correlation existed between temperature and fungal: bacterial ratio.  Phospholipid fatty acid analysis (PFLA) was used to observe the microbial makeup of the compost.  PFLA is a process of extracting the membrane lipids from the compost, hydrolyzing the phospholipids to fatty acids and quantifying the products, in this case with a Gas Chromatograph using Flame (no caps) Ionization Detection.  The results produced) no significant differences were found between treatments for between any individual fatty acid or the total fungal: bacterial ratio after comparison using non-parametric tests.  The effect of temperature on microbial composition was also inconclusive with a correlation value R2 of 0.2671.  The fatty acid profiles for all three composting systems were highly variable.  This indicated that the composting process is highly complex and highly variable within each pile. 

Kathryn Kuehl
April 16th, 2007
Olfactory stimulation by lavender (Lavendula angustifolia) essential oil and behavior of kenneled dogs (Canis familiaris).
Mentor: Dr. Robert Eckstein

Abstract: A common trait of the domestic dog is a keen sense of smell.  Studies on different mammals have shown that olfactory stimulation is connected with behavior, emotions, and health.  In particular, lavender scent has been shown to have a sedative effect.  This study was designed to compare the behaviors of dogs confined in a boarding kennel with behaviors while exposed to olfactory stimulation of diffused lavender essential oil.  Behaviors for each dog were recorded at five minute sampling intervals using a scan- sample technique.  Behaviors were recorded for two hours, the olfactory stimulation was introduced, and then after 30 minutes, behaviors were recorded again for two hours.  For each sample point, a dog’s posture was recorded as sitting, standing, jumping, resting or sleeping, and its behavior was also recorded as either vocalizing or not vocalizing.  For each dog, the proportion of sampling intervals performing a behavior during the control period was compared to the proportion during the scent treatment using either a paired t-test or a Wilcoxon matched-pairs signed-ranks test.  A significant difference of proportions was shown for all behaviors (p< 0.0003), with sitting, standing, jumping, and vocalizing being reduced, and resting and sleeping increasing with olfactory stimulation.  These results suggest that olfactory stimulation does affect the behaviors of kenneled dogs.  This information could be used to look at the use of olfactory stimulation with other scents, for treatment of dogs with specific behavioral issues, or in other settings, such as shelters or veterinary clinics.

Dietrich J. Blum
April 23, 2007
Effect of Citrate on the Phytoremediation of Pb by Barley (Hordeum vulgare L.)

Mentor: Dr Victoria Collins

Abstract: Phytoremediation, the use of plants to remove, degrade, or control the movement of toxins in soil or water systems, is an emerging technology in the area of environmental clean up and protection. This study focuses on the use of barley (Hordeum vulgare L.), a high biomass hyperaccumulator, to remove lead (Pb) from contaminated soil with the amendment of citrate. Citrate is a naturally occurring low molecular weight organic acid. The objective of this experiment was to determine the effect of citrate on the uptake and translocation of lead to the harvestable portion of barley. Concerns over the mobility of lead into the water table were addressed by analysis of the soil leachate. Total Pb concentration in the soils was determined by nitric acid extraction. Mobile Pb in the soils was determined with an acetic acid extraction buffered to pH 5.5. There were 10 replicate pots with 11 barley plants per pot grown in the greenhouse for each of the four experimental conditions. Treatments included the presence / absence of Pb contaminated soil and the presence / absence of an amendment of 0.0225 moles of citric acid per pot. Pb concentration in barley shoots from plants grown in contaminated soil was found to average 191.6 ppm with the citrate amendment compared to 3.4 ppm without the amendment, a significant difference (p= 1.56 E-06).  Plants grown in citrate amended, Pb contaminated soil produced roots with an average Pb concentration of 129.4 ppm, a significant difference (p= 0.016), when compared to the shoots grown in the same soil with the citrate amendment. It was found that citrate mobilized Pb into the leachate of amended contaminated soil with and average of 18.0 ppm compared to 0.0 ppm  in leachate from contaminated soil without the citrate amendment, a significant difference (p= 6.0 E -4). Citrate was found to be an effective chelator moving Pb both into barley plants and within the barley plant from the root into the shoot. Citrate was found to move Pb into soil leachate. Citrate while useful for enhancing Pb uptake and translocation may cause unwanted movement of Pb within the soil profile and into the water table.  

James Blair
April 23, 2007
Agricultural Labor Issues and Market Potential Of Latino-owned Businesses in Western North Carolina

Mentors: Dr. Laura Lengnick and Laura Kirby

Abstract: In Western North Carolina (WNC) the overall population has grown 17% from 1990 to 2000.  One noticeable trend is the growing Latino population, within the same period it has grown over 520%.  An assessment of WNC regional food system suggests that the Latino community has an important role.  Latinos overlap with the food system as a growing percentage of new farmers and are the largest source of farm labor in the region.  In addition the potential exists of new and growing markets for local foods within Latino-owned restaurants and tiendas.  The objective of this study is to determine market potential of locally grown food in Latino-owned businesses and to identify barriers and labor issues among Latino farmers and farm workers. In order to meet this objective seven Coalicion de Organizaciones Latino-Americanas member organizations that work closely with the Latino community were surveyed about potential markets and labor concerns.  The most significant labor concerns focused on lack of training/protective equipment and pesticide exposure and workers undocumented status.  Latino farmers also faced lack of agricultural resource support and difficulties due to lack of community support and available markets.   Although results estimated that over 50 tiendas and 75 restaurants are operating in the seven counties surveyed there appeared to be no interest of local sourcing.  With the appropriate outreach the growing number of Latino-owned businesses could be a viable market for farmers.  In conclusion this study suggests the need for a more inclusive and supportive environment for Latino farmers and farm workers as their influence on the farming in the region continues to grow.

George Keel
April 30, 2007
Observation and analysis of light curves of eclipsing cataclysmic variable IP Pegasi

Mentor: Dr. Donald Collins

Abstract: IP Pegasi, an eclipsing cataclysmic variable star, consists of a white dwarf and a red dwarf in binary orbit.  The high-density white dwarf accretes matter from the red dwarf by means of an accretion disk.  The red dwarf eclipses the white dwarf every 3.8 hours causing a large decrease in luminosity every cycle.  Occasionally the system goes into outburst due to accretion disk instabilities resulting in an overall luminosity increase.  Data was obtained from the American Association of Variable Star Observers (AAVSO) during outbursts. Data was also obtained through an 8-inch aperture Schmidt Cassegrain Telescope with a Meade DSI-Pro CCD camera at Warren Wilson College.  The light curve during the outburst displays a high luminosity midway between narrow eclipses.  In the quiescent state the peak intensity occurs just before the eclipse begins, and the eclipse is no longer symmetrical.  It is believed that during outburst the brightest region lies in the center of the accretion disk.  As the outburst progresses the bright region disperses throughout the accretion disk.  During the quiescent state the brightest regions of the system are the red dwarf, the white dwarf, and the hot spot on the perimeter of the accretion disk. During quiescence the hot spot contributes a much larger proportion of the luminosity of the system.

Edwin Self
April 30, 2007
Nitrate leaching from manure compost and its effects on groundwater quality

Mentor: Dr. Mark Brenner

Abstract: Management strategies for controlling waste are important to minimize the amount of nitrogenous compounds lost to the groundwater.  One of these methods is composting of manures.  WWC farm composts all of the waste collected from the winter feeding of cattle and the hog and chicken operations.  The purpose of this study was to determine if the composting of manure solids on the Warren Wilson College Farm was contributing excess nitrates (>10mg/L) to the groundwater.  Groundwater monitoring wells were constructed and placed up gradient and down gradient of the composting windrows.  Wells were sampled weekly for six weeks and analyzed for NO3- using methods found in the HACH spectrophotometer manual.  Four out of five wells had mean nitrate concentrations less than the maximum containment level (MCL) for drinking water (10 mg/L nitrate-N).  Down gradient wells showed a slight increase in nitrate concentration but still under the MCL for drinking water.  The well placed furthest away up gradient from the composting windrows showed a mean concentration of 29.9 mg/L NO3- -N three times higher than the MCL for drinking water.  The wells in close proximity to the compost were shown not to be contributing excess nitrate to the groundwater. 

Kylie Krauss
May 7, 2007
Homovanillic Acid as an Indicator of Neuronal Dopamine Levels In Mountain Bikers and Non-Mountain Bikers

Mentor: Dr. Victoria Collins

Abstract: Gravity specific mountain biking includes the high-risk events of downhill and dual-slalom, where crashes are high-speed, severe, and frequent.  Psychologists have defined a personality trait of Thrill and Adventure Seeking to describe a person’s willingness and desire to take risks and participate in high-risk sports.  The neurotransmitter dopamine has been shown to be linked to the tendency towards risky behavior.  In certain people, the experience of risk may produce an intense, pleasurable response, due to high levels of dopamine release.  Dopamine can be measured peripherally by measuring its main metabolite, homovanillic acid, in easily accessible body fluids.  This study looked at measured homovanillic acid levels in urine as an indicator of dopamine levels in competitive, gravity-specific mountain bikers and non-mountain bikers.  The study population consisted of two groups of eighteen white, college-aged (18-25 years old) males: bikers and non-bikers.  With informed consent, urine samples were collected from each group, with sample collection beginning at the NCCA Collegiate National Championships in October, 2006.  The urine was analyzed for homovanillic acid (HVA) using a Shimadzu LC-10ATvp reversed-phase High Performance Liquid Chromatograph (HPLC) with electrochemical detection.  Hydration levels of each sample were accounted for by measuring the creatinine concentration using the Jaffe Reaction of alkaline picrate and taking the absorbance.  Data for each sample was recorded as a ratio of HVA to creatinine, and the mean ratios were compared using a two-sided t-test with a Welch correction. There was a significant difference (p=0.0428) between the HVA:creatinine levels in mountain bikers and in non-mountain bikers, with mountain bikers having a higher mean ratio.  While this study is merely correlational and limitations exist based on the peripheral nature of psychopharmacological studies and neurotransmitter measurements in humans, it does support trends shown in previous studies, suggesting a direct relationship between dopamine levels and activity and risk-taking behavior.

Tina Milne
May 14, 2007

Arsenic and Cadmium Biosorption by the fungus Cunninghamella echinulata

Mentors: Dr. Mark Brenner and Dr. John Brock

Abstract: As arsenic and cadmium continue to be released into the biota, presenting a variety of problems, the need for development of waste treatment technology increases. Mycoremediation, an organic, in-situ method of metal remediation involving degradation or sequestration of metal ions by fungi, is garnering attention. The metal ions are sequestered via biosorption, a reversible, metabolism-independent metal uptake mechanism that involves interaction of metal ions with metal binding biomolecules located on cell walls. The objective of this study is to establish whether the biomass of the filamentous fungi C. echinulata (var. elegans) is capable of biosorbtion of cadmium or arsenic ions from a solution, and if so, how biosorption efficiency is affected by initial concentration. A culture was obtained, subcultured, and the fungal pellets were harvested, dried to a constant weight, and pulverized. Metal solutions were prepared and analyzed for their initial concentrations using an ICP-OES, after which the fungal biomass was allowed to interact with the solutions. The biomass was filtered out and the final metal concentrations were analyzed. The greatest average arsenic uptake (277 µg/g) occurred in the 75 ppb As treatment.  The largest average percent reduction in arsenic concentration was 22%, observed in the 25 ppb As treatment. The greatest average cadmium uptake, 13.3 µg/g, occurred in the 25 ppb Cd treatment.  The largest average percent reduction in cadmium concentration (22%) was observed in the 25 ppb Cd treatment. Thus, this fungus is a candidate for mycoremediation applications; however, further research of metal uptake mechanisms and influencing factors is necessary.