OxyScholar Copyright (c) 2013 Occidental College All rights reserved. http://scholar.oxy.edu Recent documents in OxyScholar en-us Tue, 21 May 2013 01:32:57 PDT 3600 Death and All Its Friends: The Role of Programmed Death-1 in T-cell Exhaustion During Chronic Viral Infection http://scholar.oxy.edu/biochem_student/1 http://scholar.oxy.edu/biochem_student/1 Mon, 20 May 2013 10:12:50 PDT Programmed Death-1 (PD-1) is a CD-28 family inhibitory immune receptor that is located on Tc cells, particularly during chronic infection. Its role in regulating the immune response is crucial because it ensures a middle ground between preventing self-immunity and ensuring immune efficacy. My topic focuses on T-cell exhaustion during chronic viral infection. Numerous studies have found that as the infection progresses, virus-specific T-cells increasingly show signs of exhaustion (lowered cytokine secretion and replicative ability and increased apoptosis). In infections such as HIV and hepatitis C, these signs are directly correlated to the increased expression of PD-1, which interacts with its ligands on antigen presenting cells: PD-L1 and PD-L2. The binding of the ligands to PD-1 has immune suppressant effects on the Tc cells by inhibiting the PI3k/Akt pathway.

The three papers that I focus on address the role of PD-1 in increasing cell exhaustion during viral infection. All three also explore the role of additional receptors (CD 57 and CTLA-4) as co-factors with PD-1. The third paper, in particular, explores the role of HIV infection in upregulating PD-1 ligand expression on antigen-presenting cells, and the role of the PI3K/Akt pathway in this regard. This research has tremendous potential to combat HIV and other viruses, complementing anti-retroviral therapy. This possible medication, that blockades PD-1 and its co-receptors, could prevent the weakening of the immune system and help to slow viral replication by utilizing the body’s immune system to help fight disease progression.

]]> Utsav Patwardhan Substantive Progress or Neoliberalism in Disguise? An Analysis of the World Bank’s Discourse on Corruption since 1995 http://scholar.oxy.edu/dwa_student/9 http://scholar.oxy.edu/dwa_student/9 Sat, 18 May 2013 11:00:20 PDT I undertake a discourse analysis of World Bank documents from 1995 to the present to explore scholarly debates surrounding the question, “To what extent are the World Bank’s efforts to combat corruption evidence of its attempts to further the neoliberal agenda, characterized by the original Washington Consensus?” Since the late 1990’s, the World Bank has been a leader in the fight against corruption, integrating anti-corruption into its operations worldwide and making it a major issue addressed in World Development Reports, Presidential speeches, and specific anti-corruption strategies. While some scholars see this as an evolutionary move away from neoliberalism, others see the focus on corruption as a way for the Bank to continue to advance and expand the neoliberal agenda after the failure of structural adjustment programs. I argue that while the World Bank’s anti-corruption strategy featured distinctly neoliberal ideals in its early years, over time it has moved away from a focus on liberalization and competition to a more holistic focus on transparency and civic participation as pillars of good governance.

]]> Megan Lang Dispersion of Ions in the Drift Dark Matter Detector http://scholar.oxy.edu/urc_student/1240 http://scholar.oxy.edu/urc_student/1240 Thu, 16 May 2013 18:22:31 PDT This summer I worked on measuring the drift velocity and dispersion of ions in a miniature version of the DRIFT (Directional Recoil Identification from Tracks) detector. To do so I focused a flash lamp on a thin aluminum plate in the back of a vacuum vessel. Via the photoelectric effect, electrons are released from the metal sheet. These free electrons then attach to the electronegative gas within the system. By implementing an electric field it is then possible to direct the ions toward the detection plane of wires. By analyzing this data through the statistical program R I was able to calculate the drift velocity and longitudinal diffusion in the z direction plane. Furthermore, by scanning the UV light source across multiple wires I was able to calculate the lateral diffusion in the x direction plane of the ions through space. Understanding the drift velocity and the dispersion in the x-plane and z-plane is crucial to the understanding of events within the DRIFT detector.

]]> Nicole Chen Simulation and analysis of regular and chaotic particle dynamics in asymmetry-induced transport http://scholar.oxy.edu/urc_student/1239 http://scholar.oxy.edu/urc_student/1239 Thu, 16 May 2013 18:22:27 PDT Asymmetry-induced transport of a non-neutral plasma within a coaxial Malmberg-Penning trap is analyzed using a single-particle simulation with collisional effects. Simulations of the case with standing wave asymmetry and periodic boundary conditions were studied. The relationship between the periods of oscillation for regular motion and the scaled radius matched between computer simulation and analysis of the scaled equations of motion: r vs t: Vz vs t: where A and B are constants. Poincaré sections were also used to gain more general knowledge regarding the boundary between regular and chaotic motion. It was discovered that particles can transition between the two states of motion, meaning they can become both trapped and untrapped over the duration of one simulation. The Poincaré sections also revealed that large radial excursions are possible over a greater number of velocity values, but axial trapping is what is truly required for regular motion.

]]> Jacob Coleman Investigating Insect Interactions on Pentaclethra macroloba http://scholar.oxy.edu/urc_student/1238 http://scholar.oxy.edu/urc_student/1238 Thu, 16 May 2013 18:22:23 PDT Pentaclethra macroloba is a dominant canopy tree found in humid tropical forests from Honduras to Brazil, comprising 30-40% of all basal area at La Selva Biological Station, Costa Rica. To understand the full role that Pentaclethra macroloba plays in its surrounding environment I took a closer look into the interactions of the insects most abundant on P. macroloba; which include caterpillars, ants, and treehoppers. For a period of 2 months in La Selva Biological Station in Heredia, Costa Rica I observed and collected insects from P. macroloba saplings. To see what time the ants are most active on the plant as well as to see what species are most prevalent on P. macroloba, I looked at 38 saplings and conducted a census for ants at 4 times during the day: one in the early morning, one in the late morning/ afternoon, one at dusk, and one in the evening. The results clearly indicate that Crematogaster was the dominant ant species and were most active at 4:00pm when the sun was setting. In the treehopper experiment I visited a total of 5 stems that once had both treehoppers and ants and recorded the number of ants, number of treehoppers and recorded their behavior. The ants were often next to or on top of the treehoppers and the numbers of the treehoppers dwindled as the time passed, indicating that the treehoppers spent a period of time without moving from the particular P. macroloba stem and then dispersed. Lastly to study the herbivores of this canopy tree I collected a total of 31 caterpillars, 30 different species, found eating P. macroloba and reared them to adulthood to be identified. The information that I collected will be added to a database of known herbivores of P. macroloba. There are now six pinned specimens of the adults and one parasitoid in the insect collection. . The information collected gives insight into the variety of insects supported by this dominant canopy tree.

]]> Arlin Alger The Effects of Aspect Ratio on Onset Pattern Formation in Simulated Rayleigh-Benard Convection http://scholar.oxy.edu/urc_student/1237 http://scholar.oxy.edu/urc_student/1237 Thu, 16 May 2013 18:22:19 PDT This talk will discuss onset patterns in Rayleigh-Benard Convection. Rayleigh-Benard Convection refers to a fluid-filled cell which is heated from the bottom and cooled at the top. At a large enough temperature difference between the bottom and top plate, the hot fluid rises while simultaneously the cool fluid sinks, driving a convective motion. Just above this critical temperature difference, a distinct and stable pattern appears. The aspect ratio, which is defined as the diameter to depth ratio of the cylindrical cell, affects the pattern that is formed. This presentation will focus on the transition from purely modal patterns found in smaller aspect ratios to patterns of straight parallel rolls found in moderate to large aspect ratios. We used the spectral element code Nek5000 to create numerical simulations of such systems for a range of aspect ratios with either insulating or conducting sidewall boundary conditions. The vertical temperature difference at which convection begins is characterized by the dimensionless parameter known as the critical Rayleigh number, which is proportional to the change in temperature. This talk will describe how the critical Rayleigh number is related to the aspect ratio. The critical Rayleigh numbers for aspect ratio 1 through 9 are estimated and compared with the results of previous work. This talk will also discuss the effects of the kinematic viscosity and thermal diffusivity of the fluid, which is described by the dimensionless Prandtl number, on onset pattern formation and critical Rayleigh number.

]]> Mary Flagstad Glucose and Fructose Ingestion following High Intensity Exercise does not Affect Subsequent Exercise Capacity http://scholar.oxy.edu/urc_student/1236 http://scholar.oxy.edu/urc_student/1236 Thu, 16 May 2013 18:22:16 PDT Previous studies have suggested that ingestion of glucose+fructose prior to and during long duration endurance exercise may benefit performance more than ingestion of glucose alone. The purpose of this study was to investigate the effects of glucose+fructose ingestion on short duration high intensity exercise capacity. Eight trained malecollege athletes performed three randomized experimental trials consisting of a 20 minute run at 90% VO2 max, a 5 minute recovery period, and a time-to-exhaustion (TTE) run at 90% VO2 max. During the recovery period, subjects ingested a beverage containing glucose + fructose (G+F), glucose only (GLU), or placebo (PLA) matched for taste and electrolyte content. Carbohydrate (CHO) beverages each contained ~20g of carbohydrate. Subjects’ blood glucose was measured immediately before and after each run period. Heart rate (HR) and Rating of Perceived Exertion (RPE) was recorded every 2 minutes during TTE. Blood glucose levels standardized to baseline values were significantly greater in the G+F trial both prior to and after TTE relative to PLA (P<0.05). However, there was no significant difference in HR, RPE, and TTE performance (G+F: 22.15±5.88min, GLU: 18.27±4.18min, PLA: 17.75±3.26min) between trials (P>0.05). Results from this study suggest that ingestion of glucose and fructose following high intensity exercise lasting 20 min does not enhance subsequent performance capacity more than glucose alone or placebo. Future studies are needed to determine if a stronger reliance on endogenous versus exogenous CHO in the early stages of high intensity exercise can account for the lack of performance benefits seen in this study.

]]> Adam Gutierrez Stress-Induced Alcohol Preferences: A Novel Test in Selectively Bred Rats http://scholar.oxy.edu/urc_student/1235 http://scholar.oxy.edu/urc_student/1235 Thu, 16 May 2013 18:22:11 PDT This summer research is a novel test that examines stress-induced alcohol preferences in selectively bred high versus low saccharin-consuming rats. Susceptibility to alcohol abuse is dependent on various environmental and biological factors. Many studies have hypothesized that stress is one cause of alcohol abuse. In laboratory models, then, stress might be expected to increase alcohol intake. However, there have been contradictory results. Findings show that depending on the stressor and its severity, stress can either decrease or increase alcohol intake. The variety of results of stress effects in alcohol motivated behavior suggests that the answer to this phenomenon is not simple. Multiple variables influence the alcohol preferences, some of which increase and some of which decrease alcohol motivation. The present study used two acute stressors, footshocks and food deprivation, to determine whether acute stress would increase alcohol preference in high (HiS) and low (LoS) saccharin-consuming male rats. Rats selectively bred on this taste phenotype show different behaviors in emotionality, preference for alcohol and alcohol-paired flavors, and susceptibility to stress. The rats were conditioned with plain and 4% ethanol Kool-Aid solutions for ten days before being given two stress tests. Stressed rats should show behavioral shifts in drinking. Therefore, we expected that both lines would have greater preferences for the alcohol-paired flavor after stress; we also expected that LoS rats would show a greater increase in alcohol preferences after stress. However, stressed rats did not show a significant increase in the alcohol-paired flavor compared to the control group after both stress tests. These results indicate that acute stress is not effective at modifying expression of flavor preferences in HiS and LoS rats, at least under the test conditions utilize

]]> Chardonnay Madkins Locomotion and Anxiety After Caffeine Intake in HiS and LoS Rats http://scholar.oxy.edu/urc_student/1234 http://scholar.oxy.edu/urc_student/1234 Thu, 16 May 2013 18:22:07 PDT Caffeine is a widely consumed psychoactive substance, present in many types of comestibles. As a stimulant, caffeine is positively correlated with increased alertness and energy. Caffeine’s arousing effect stems from the blockage of adenosine receptors in the brain, which when blocked, increase neuron firing in the brain and adrenaline production. Caffeine also induces anxiety. During prolonged exposure to caffeine, tolerance develops as an adaptive response; however, removal of the drug may result in a state of emergency.

The present research investigated the behavioral effects of caffeine intake and withdrawal with regards to locomotor activity and anxiety in an “open field” apparatus. High-Saccharin- (HiS) and Low-Saccharin-preferring (LoS) rats were used to examine drug effects; their differential consumption of saccharin may influence drug-related behaviors. They have been shown to differ in emotionality, with LoS rats typically displaying more anxiety than HiS rats.

Results indicate that on day 1, movement in the center of the open field was lower among caffeine-treated rats. In addition, latency to enter the center was longer in caffeine-treated rats; this effect arose primarily from the test conducted after caffeine was removed, suggesting withdrawal effects. There was no significant difference in total locomotion between the “caffeine” and “control” groups, pointing to anxiety rather than reduced activity in the drug effects. Relative to HiS rats, LoS rats had shorter latencies to enter the center of the open field and were more active in the center, but the lines responded similarly to caffeine. Future research could examine whether dosage or intake method has an effect on behavior.

]]> Jennifer Wang Groundbreaking Strides without Transformational Change: The Integration of Gender Perspectives into US Department of State Peacebuilding Strategy Under Secretary Clinton http://scholar.oxy.edu/dwa_student/8 http://scholar.oxy.edu/dwa_student/8 Thu, 16 May 2013 17:30:16 PDT Although peacebuilding aims to address root causes of conflict, while constructing stable institutions and social relations, conventional peacebuilding’s negligence of gender in post-conflict societies and peace processes has restricted its potential. Most actors that contribute to peacebuilding efforts have participated in this ignorance, causing an outburst of feminist literature highlighting the severe need to integrate gender perspectives into peacebuilding. However, existing literature provides few specific recommendations and insufficiently examines mechanisms for integrating gender into state-led peacebuilding. Major actors, such as the United States, have recently embarked on attempts to incorporate gender perspectives into peacebuilding, creating large scopes of policy in need of analysis. This paper investigates the integration of gender perspectives into US Department of State peacebuilding strategies under Secretary of State Hillary Rodham Clinton, who significantly elevated the importance of women’s rights and brought attention to gender considerations in US foreign policy. Through the review of policy changes and the study of US peacebuilding in Afghanistan, this paper concludes that the integration of gender perspectives in Department of State peacebuilding efforts is incomplete, leaving policy altered, but not transformed, and inhibiting hopes for gender equality and inclusive, sustainable peace.

]]> Jessie M. Durrett The Road to Hell is Paved With Good Intentions: The Construction of Femininity Within and Through the Human Security Paradigm http://scholar.oxy.edu/dwa_student/7 http://scholar.oxy.edu/dwa_student/7 Mon, 13 May 2013 22:40:29 PDT This paper uses a particular form of postmodern feminism to analyze the construction of femininity within and through the human security paradigm. It explores the ways in which human security has been implicated in the power-knowledge system of patriarchy. It does so in order to investigate the human security discourse that has shaped the subject position of the individual suffering from insecurity. It establishes and interrogates the following questions: How is the power-knowledge system of patriarchy implicated in human security? Has the insecure individual’s subject position in the human security paradigm negatively affected the way that the paradigm addresses agency? This paper argues that human security is feminized and denigrated in relation to national security. Further, human security’s epistemological foundations remain in the power-knowledge system of patriarchy. These bases of power-knowledge are implicated in the feminization of human security as a concept, as well as the feminization of insecure individuals. The paper is organized into three main sections. First, it provides an overview of how traditional national security and human security are gendered concepts. Second, it analyzes the feminization of the insecure individual to demonstrate how this political action marginalizes individual agency as it paradoxically attempts to “protect” people from insecurities. Drawing upon a case study of United States anti-trafficking efforts, it examines how pre-existing humanitarian gender motifs have influenced human security, preventing effective policy from emerging in a contemporary form. Third, it outlines how a postmodern feminist approach can create a site for, and insert individual agency into the center of socio-political scholarship.

]]> Chelsea Moore Species of Demersal Zooplankton Inhabiting a Kelp Forest Ecosystem off Santa Catalina Island, California http://scholar.oxy.edu/scas/vol78/iss3/7 http://scholar.oxy.edu/scas/vol78/iss3/7 Wed, 08 May 2013 15:50:27 PDT Demersal zooplankton are those animals that migrate at various times between the benthic and pelagic environments. Previous studies have concentrated on coral reef habitats (e.g. Emery, 1968; Porter, 1974; Alldredge and King, 1977; Porter and Porter, 1977; Porter et al., 1977; Hobson and Chess, 1979; Ohlhorst and Hutchinson, 1979). Inverted funnel traps were used by Thomas and Jelley (1972) to study demersal zooplankton in an estuarine ecosystem. King and All- dredge (1978) reported on the emergence patterns of demersal zooplankton from a subtidal sand-flat. Diel changes in zooplankton composition over an intertidal eelgrass flat were monitored by Robertson and Howard (1978).

]]> Richard M. Hammer et al. Range Extension and Notes on the Habitat of the Isopod Munna halei Menzies http://scholar.oxy.edu/scas/vol78/iss3/6 http://scholar.oxy.edu/scas/vol78/iss3/6 Wed, 08 May 2013 15:50:26 PDT The small asellote isopod Munna halei Menzies, 1952, was described from Tomales Point, Marin County, California, from under stones and in kelp (Macrocystis) holdfasts in the lowest intertidal zone (Menzies, 1952). It remained unknown elsewhere until Iverson (1974) reported it at El Capitan Beach, San Luis Obispo County, California, from among the spines of the purple sea urchin Strongylocentrotus purpuratus (Stimpson) from mid-intertidal rocks.

]]> Rebekah Harty Observations of a Gray Whale Birth http://scholar.oxy.edu/scas/vol78/iss3/5 http://scholar.oxy.edu/scas/vol78/iss3/5 Wed, 08 May 2013 15:50:25 PDT Observations of births of gray whales (Eschrichtius robustus) have been made by Balcomb (1974), Leatherwood and Beach (1975) and Storro-Patterson and Kipping (1977). We report a fourth observation of a gray whale birth; this from Estero de la Soledad in the Bahia Magdalena complex, Baja California Sur, Mex- ico (Fig. 1). We learned from Storro-Patterson that both his (1977) and Balcomb's (1974) observations were also made in this area; Storro-Patterson' s at a location near the cannery at Puerto Adolfo Lopez Mateos, and Balcomb's nearby to the north (per. coram.). Leatherwood 's observations were made in the open sea off Mission Bay, San Diego.

]]> James G. Mills et al. The Salt Marsh and Transitional Vegetation of Bahia de San Quintin http://scholar.oxy.edu/scas/vol78/iss3/3 http://scholar.oxy.edu/scas/vol78/iss3/3 Wed, 08 May 2013 15:50:24 PDT This study describes a relatively pristine salt marsh and ecotones that could serve as a comparison for understanding disturbed West Coast marshes. The salt marsh and terrestrial transitional vegetation of Bahia de San Quintin is composed of a low number of species with only a few dominants, and it is similar to southern California marshes. Species react to minor elevational differ- ences to create vegetation patterns or gradients, with each species reaching its highest frequency in the higher drier portions in a particular part of the marsh. Salicornia virginica has the broadest amplitude of occurrence. Plant cover increases with elevation which corresponds to decreases in tidal inundation, saturated soils, and salinity. Frequencies of species were low and variable in the marsh-upland transitions, but were high and consistent in the marsh proper. The presence of capillary extensions of tidal waters appears to be a critical factor in controlling the distribution of species in the ecotone areas. The establishment of submerged Zostera marina beds blocks the open body of water and initiates successive development that may culminate in terrestrial vegetation by contributing to its stabilization and sedimentation. Piles of detached Zostera mat down the emergent vegetation which results in open pockets that are eventually revegetated.

]]> Leon F. Neuenschwander et al. Gametogenesis and Embryonic Development in the Calcareous Sponges Clathrina coriacea and C. blanca from Santa Catalina Island, California http://scholar.oxy.edu/scas/vol78/iss3/4 http://scholar.oxy.edu/scas/vol78/iss3/4 Wed, 08 May 2013 15:50:24 PDT Gametogenesis and embryonic development of Clathrina coriacea and C. blanca, two closely related calcareous sponges from Santa Catalina Island, California, are described. Oogenesis is asynchronous in both species. Spermato- genesis was not observed. Cleavage is total and equal, resulting in the formation of a blastula larva. The larva of C. coriacea contains one large posterior granular cell, whereas two posterior granular cells are present in the larva of C. blanca. Migration of the larval blastomeres into the blastocoel begins while the larva is in the tube of the parent sponge.

]]> Marion Fischel Johnson Seventieth Anniversary of Academy Excavations at Rancho La Brea http://scholar.oxy.edu/scas/vol78/iss3/2 http://scholar.oxy.edu/scas/vol78/iss3/2 Wed, 08 May 2013 15:50:23 PDT The Southern California Academy of Sciences was one of the early organizations permitted to collect fossil material from the Pleistocene beds at Rancho La Brea in Los Angeles, California. The Academy work began in June, 1909, though the first recognition of the importance of the fossils had come 34 years before. In 1875 William Denton visited Major Henry Hancock at the rancho, collected a few fossil bones and, two years later, published a description of them in the Proceedings of the Boston Society of Natural History. The article apparently created no appreciable notice and was soon forgotten (Stock, 1956).

]]> Gretchen Sibley Cover http://scholar.oxy.edu/scas/vol78/iss3/1 http://scholar.oxy.edu/scas/vol78/iss3/1 Wed, 08 May 2013 15:50:21 PDT The Calcanea of Members of the Hyaenidae http://scholar.oxy.edu/scas/vol78/iss2/9 http://scholar.oxy.edu/scas/vol78/iss2/9 Wed, 08 May 2013 15:45:22 PDT The calcanea of all currently recognized species of living members of the Hyaenidae were examined. These are the calcanea of Crocuta crocuta (15 specimens), Hyaena brunnea (2 specimens, 1 malformed), H. hyaena (5 specimens), and Proteles cristatus (4 specimens). All calcanea of hyaenas have the same articular surfaces: posterior (PAS), medial (MAS), anterior (AAS), and cuboid (CAS) (Fig. 1); the proximal end of the medial articular surface folds over the proximal end of the sustentaculum astragali (SA); and the outline of the outer surface lacks a distinct trochlear process (TP) and tends to dip inward near the cuboid facet (Fig. 1). See Stains (1959, 1962, 1973) or Robinette and Stains (1970) for terminology.

]]> Howard J. Stains Post-larval Polychaetes in Sandy Beaches of Tomales Bay, California http://scholar.oxy.edu/scas/vol78/iss2/8 http://scholar.oxy.edu/scas/vol78/iss2/8 Wed, 08 May 2013 15:45:20 PDT Although many macrobenthic organisms spend part of their lives as transient members of the meiofauna (Thorson, 1966), relatively little quantitative data are available on their interactions in the meiobenthos. For example, Muus (1973) presents data on macrobenthic larval settling and mortality rates, and the duration of their stay in this habitat.

]]> Jerry D. Kudenov