28th Hayes Graduate Research Forum (February, 2014)

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1st place: Yin, Yanfei
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2nd place: Wilson, Geoffrey
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3rd place: Alonso, Orlay
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Biological Sciences
1st place: Lakshmanan, Aparna
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2nd place: Davidson, Reshma
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3rd place: Hesp, Zoe
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1st place: Lee, Hyojin
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2nd place: Summers, Chris
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3rd place: Daniel, Jamie Levine
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Education and Human Ecology
1st place: Hooper, Emma
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2nd place: Sanders, Margaret
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3rd place: Mountain, Travis
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1st place: Li, Likai
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2nd place: Caruthers, Elena
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3rd place: Mazumder, Ria
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1st place: Teegarden, Matthew
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2nd place: Pempek, Jessica
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3rd place: Petrella, Dominic
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1st place: Winans, Adrienne
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2nd place: Barajas, Jennifer
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3rd place: Lopez, Delano
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Math and Physical Sciences
1st place: Mauk, Rachel
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2nd place: Wrzesien, Melissa
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3rd place: Anandakrishnan, Archana
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Professional Biological Sciences
1st place: Frakes, Ashley
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2nd place: Likhite, Shibi
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3rd place: Tazi, Mia

Social and Behavioral Sciences
1st place: Belding, Jennifer
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2nd place: Durso, Geoffrey
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3rd place: Dailey, Phokeng
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Poster Division: Arts, Humanities, and Social Sciences
1st place: Berger, Laura
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2nd place: Grammon, Devin
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3rd place: Long, Leroy III

Poster Division: Biological Sciences
1st place: Cooper, Grace
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2nd place: Pitarresi, Jason
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3rd place: McKim, Daniel
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Poster Division: Engineering, Math, and Physical Sciences
1st place: Ghosh, Arijit
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2nd place: Grieshop, Sara
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3rd place: Pritchard, Joshua
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Recent Submissions

Now showing 1 - 20 of 37
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    Art1-Arrestin in cytokinesis
    (2014-02) Davidson, Reshma
    Background: Cytokinesis partitions a mother cell into two daughter cells and is essential for cell proliferation and cell differentiation. Septins, a family of conserved GTPases, are essential for cytokinesis in budding yeast and some animal cells. However, septin deletion mutants are viable in the fission yeast S. pombe, indicating the presence of a parallel pathway for maintenance of cell integrity during cytokinesis. A synthetic lethal screen with septin deficient strain identified the arrestin Art1 as a component of this parallel pathway. Arrestins are known to regulate cellular signaling in higher eukaryotes. However, their functions in S. pombe are unknown. Findings: I found that art1∆ (deletion) cells lysed during cell-cell separation after mitosis. Electron microscopy showed that they had a septal-wall defect that mimicked Rho GEF rgf3 mutants. Both Rho1 and Rgf3 are essential in S. pombe and have homologs in mammalian cells . Art1 and Rgf3 both accumulate at the division site during cytokinesis. IP and yeast 2 hybrid assays show that Art1 binds to Rgf3 at a region adjacent to its catalytically active GEF domain. Protein quantification revealed that loss of Art1 caused a decrease in cellular Rgf3 levels and adversely affected its contractile-ring localization. Conversely, Art1 overexpression led to an increase in cellular and contractile ring levels of Rgf3. Upon mislocalizing Art1 in the cell, Rgf3 was found to mislocalize to Art1’s location. Together, these data suggest that Art1 is involved in Rgf3 stability and its recruitment to the contractile ring. To determine the role of Art1 in Rgf3 function, we compared GTP-Rho1 localization and levels using a Rho1 biosensor and found that art1∆ cells had lower levels of active GTP-Rho1 at the division site during septum formation. Conclusion and significance: The findings suggest that the arrestin Art1 is involved in cytokinesis by regulating Rgf3 protein stability and recruiting it to the division site. Thus art1 loss leads to lower GTP-Rho1 levels at the division site during septum formation. Art1 is the first known S. pombe arrestin characterized to have a role in cytokinesis. The results obtained imply a novel, previously unknown role for arrestins.
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    Therapeutic AAV9-mediated Suppression of Mutant SOD1 Slows Disease Progression and Extends Survival in Models of Inherited ALS
    (Nature- Molecular Therapy, 2014-02) Likhite, Shibi; Kaspar, Brian
    Mutations in superoxide dismutase 1 (SOD1) are linked to familial amyotrophic lateral sclerosis (ALS) resulting in progressive motor neuron death through one or more acquired toxicities. Involvement of wild-type SOD1 has been linked to sporadic ALS, as misfolded SOD1 has been reported in affected tissues of sporadic patients and toxicity of astrocytes derived from sporadic ALS patients to motor neurons has been reported to be reduced by lowering the synthesis of SOD1. We now report slowed disease onset and progression in two mouse models following therapeutic delivery using a single peripheral injection of an adeno-associated virus serotype 9 (AAV9) encoding an shRNA to reduce the synthesis of ALS-causing human SOD1 mutants. Delivery to young mice that develop aggressive, fatal paralysis extended survival by delaying both disease onset and slowing progression. In a later-onset model, AAV9 delivery after onset markedly slowed disease progression and significantly extended survival. Moreover, AAV9 delivered intrathecally to nonhuman primates is demonstrated to yield robust SOD1 suppression in motor neurons and glia throughout the spinal cord and therefore, setting the stage for AAV9-mediated therapy in human clinical trials.
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    The In/visibility of Race: Mixed-race Chinese Americans during the Exclusion Era
    (2014-02) Winans, Adrienne; Wu, Judy Tzu-Chun
    “The In/visibility of Race: Mixed-Race Chinese Americans during the Exclusion Era” interrogates the experiences of mixed-race Chinese American families during the years of Chinese exclusion, 1875-1943. Drawing on a piece of my dissertation, “Race, Space, and Gender: Re-mapping a Chinese American from the Margins, 1975-1943,” I read through the archives left by the anti-Chinese measures of the U.S. gate-keeping state. In this presentation, I use the history of Charlie Stewart Cue as a case study of intimate interraciality in small town America at the turn of century and as an example of the erasure of not only these spaces but also of biraciality from the narrative of Chinese America.
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    The Illuminated Scores & The Architectural Design of Musical Form
    (2014-02) Alonso, Orlay
    The Illuminated Scores are designed as scholarly editions for performing artists and educators, to portray the form and structure of a musical composition. They incorporate semiotic tools into the study of musical language intended to make the architectural design visible in a coherent format. The purpose of the study is to develop a method of representing music graphically that differs from the established score layout, reorganizing content in a manner that allows one to overcome the constraints under which musical skills are developed in the current model of publishing music. The motivation for such a study grew out of the need to enable students to experience an immediate representation of the overall formal design of a musical composition. It is the author’s hypothesis that this new perspective will impact the ways we learn and teach musical form and its structure. The goal is to portray music notation in a format similar to that of poetic verse, rather than that of continuous prose, where one measure follows another in no relevant way; phrase lengths, melodic relationships, harmonic structure, and the number of measures in a system will play a significant role in the visual layout of the work. Initially thought of as overlaying a Schenkerian analytical sketch over the published work horizontally aligned, the project has developed into a new publishing format containing the researcher’s analysis of examples of works by Bach, Mozart, Schubert and Schoenberg. In addition, diagrams and color-coding illustrate how mathematics and music are combined to explain the concept of balance in musical form, thereby revealing the inherent beauty of a composer’s cohesive thought process. The author points out mathematical concepts of Mersenne Primes, numerical sequences and other patterns in Bach, the Fibonacci sequence and the Golden Proportion in sonata form movements of Mozart and in Schubert impromptus. The current stage of this research is that of a scholarly work aiming to develop the representational method, using new engraving software programs capable of digitizing scores in a new format. Once this has been done we can implement the appropriate curriculum materials on a larger scale and measure its effect on students achievement through individual lessons and piano labs. Through this project, the author hopes to show the intrinsic beauty of form with the objective of impacting performance and music pedagogy. The objective of the Illuminated Scores is to present a practical holistic method that leaves students excited about the possibility of exploring the fascinating tools employed by the most brilliant minds in the world of music.
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    Lysine Methylation is an Endogenous Post-Translational Modification of Tau Protein in Human Brain and a Modulator of Aggregation Propensity
    (2014-02) Cooper, Grace; Kuret, Jeff
    Alzheimer’s Disease (AD) is the most common form of dementia, affecting 13% of Americans aged at least 65 years and 43% of Americans aged at least 85 years. It is a major driver of long-term care costs in the U.S., and there is currently no cure or preventative treatment. AD is defined by the appearance of two hallmark lesions: extracellular plaques composed of the beta-amyloid peptide and intracellular neurofibrillary tangles (NFTs) composed of the microtubule-binding protein tau. The accumulation of these proteins in aggregated forms is believed to contribute to the pathogenesis of AD. However, the accumulation of NFTs better correlates with disease and symtom progression, and the quantity and distribution of NFTs, not plaques, are used to definitvely diagnose AD post mortem. For these reasons, the biology of normal tau protein, and how it malfunctions in disease, is being investigated for clues to the mechanisms underlying AD pathogenesis. Normal tau protein functions in monomeric form to stabilize microtubules and promote their assembly. In AD, however, tau aggregates into long fibrils that eventually grow to fill the neuronal cytoplasm. Candidate triggers for this conformational change include post translational modifications (PTMs). Previous work identified phosphorylation of Ser and Thr residues as major physiological PTMs capable of triggering tau aggregation. More recent work conducted in model systems has revealed that PTMs of Lys residues can also serve to modulate tau aggregation propensity. But to date, Lys modifications have not been demonstrated at single residue resolution in authentic human brain specimens. To test the hypothesis that tau is normally modified on Lys residues, tau was isolated from normal human brain (n = 4; all cases 55 yr old) and subjected to a “bottom up” proteomic characterization. In this approach, purified human tau protein was digested with the proteolytic enzyme trypsin, and the resulting peptides characterized by mass spectroscopy methods. The resulting structural characterization revealed methylation as a novel tau PTM on Lys residues. The modification clustered perdominantly in the C-terminal region of the tau molecule known to mediate pathological self association. To characterize the effects of Lys methylation on tau function, purified recombinant tau was subjected to chemical methylation to generate a library of modified tau species that varied with respect to methylation stoichiometry. The methylated samples were then tested for their ability to promote microtubule assembly (i.e., normal tau function), as well as their ability to aggregate (i.e., pathological malfunction). To test the effect of methylation on tau’s microtubule assembly promoting activity, methyl tau was incubated with tubulin and an absorbance reading was taken every two minutes over the course of an hour to monitor the formation of microtubules. This experiment revealed that at lower, physiological levels, methylation did not inhibit tau’s ability to promote microtubule assembly. In contrast, a transmission electron microscope study examining aggregate formation of methyl tau showed that even low, physiological levels of methylation were able to inhibit tau aggregation. To characterize the mechanism of inhibition, the effects of Lys methylation on tau aggregation propensity was examined as function of time and tau protein concentration. These studies revealed that methylation inhibited aggregation by increasing the amount of protein needed to form aggregates. It did so by increasing tau’s dissociation rate from fibrils, and decreasing the fibril extension rate. In addition, methylation slowed aggregation rate by depressing filament nucleation, the rate limiting step in tau filament formation. Together these data show that low-occupancy methylation is a normal human tau PTM that does not affect tau’s normal function, but that does depress tau aggregation propensity. The experimental findings point to methylation being a potential regulatory PTM of tau. We postulate that methylation may decrease in AD compared to normal brain, and that maintaining or increasing methylation of tau could be a therapeutic approach for slowing the rate and extent of neurofibrillary lesion formation in AD.
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    Microglia induce motor neuron death via the classical NF-κB pathway in amyotrophic lateral sclerosis
    (Cell Press, Neuron, 2014-02) Frakes, Ashley; Kaspar, Brian
    Neuroinflammation is one of the most striking hallmarks of amyotrophic lateral sclerosis (ALS). Nuclear Factor-kappa B (NF-κB), a master regulator of inflammation, is upregulated in spinal cords of ALS patients and SOD1-G93A mice. In this study, we show that selective NF-κB inhibition in ALS astrocytes is not sufficient to rescue motor neuron (MN) death. However, the localization of NF-κB activity and subsequent deletion of NF-κB signaling in microglia led to rescued MNs from microglial-mediated death in vitro and extended survival in ALS mice by impairing pro-inflammatory microglial activation. Conversely, constitutive activation of NF-κB selectively in WT microglia induced gliosis and MN death in vitro and in vivo. Taken together, these data provide a mechanism by which microglia induce MN death in ALS, and suggest a novel therapeutic target that can be modulated to slow the progression of ALS and possibly other neurodegenerative diseases by which microglial activation plays a role.
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    What Price Postmodernism?
    (2014-02) Lopez, Delano; Conn, Steve
    A case study of the funding of an intellectual movement- Postmodernism- and its effect on the political claims of that movement.
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    Validation of a 10-Item Questionnaire Measuring Fruit and Vegetable Consumption in 9-11 year old Children Living in Low Income Households
    (2014-02) Berger, Laura; Zubieta, Ana Claudia; Gunther, Carolyn
    Background: Many U.S. children do not meet the recommended daily requirement for fruit and vegetable intake; this is particularly true among low-income populations. In order to determine the effectiveness of nutrition education programs aimed at improving children’s food choices and eating behaviors, cost-effective and easily administered validated assessment tools are needed. Unfortunately, to date, few such survey tools exist. Purpose: The purpose of this pilot study was to test the criterion (concurrent) validity of a 10-item fruit and vegetable questionnaire (FVQ) in preadolescent children (ages 9 to 11 years), previously validated for face and content validity. The 24-hr dietary recall was selected as the ‘gold standard’ reference tool. Methods: Children enrolled in the 3rd and 4th grade classrooms of the University District Freedom School Summer Literacy Program were invited to participate in the study. Trained nutritionists administered the 10-item FVQ followed by the 24-hour dietary recall to study participants on the same day. Frequency of fruit and vegetable intake was calculated for the 24-hour dietary recall (mean=5.06, SD=2.49) and a frequency score for the 10-item questionnaire (mean=33.06, SD=6.92). Spearman correlation was used to measure level of agreement between questionnaires. Results: Low-income child participants (n=17), ages 9 to 11 years, completed the study. The means of fruit and vegetable intake frequency from the 10-item FVQ was significantly correlated with the 24-hour dietary recall (r=0.77, p<0.001). Conclusions and Implications of Findings: Results from this pilot test demonstrate the potential validity of this easily administered and cost-effective 10-item FVQ. Future studies encompassing test-re-test reliability, sensitivity, construct, and further examination of criterion validity with a larger sample size should be conducted to establish full validity of this screening tool.
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    When grammar meets politics: Uses of stigmatized language on a political talk show
    (2014-02) Grammon, Devin; Babel, Anna
    In this study, we trace the use of stigmatized Spanish grammatical variants on a Venezuelan political talk show, Aló Presidente, with the aim of better understanding how non-standard grammar associated with poor and uneducated speakers can be taken up as ideological resources in high-stakes political interactions. These stigmatized grammatical forms, conjugations of the presentational verb haber displaying non-standard plural agreement, are widely held to be indexical of the primary political constituency of the show’s host: the controversial former Venezuelan president Hugo Chavez. Hypothesizing that the use of these variants will be predicted in both colorful stylistic uses of language and interpersonal dialogue, we submit 500 observations of speakers’ uses of haber spanning 13 years of broadcast and 72 speakers to statistical modeling using R. Variables previously found to predict this variation (e.g. animacy, syntactic position of NP, speaker gender) are coded along with a measure of a speaker’s regularity on the show, the gender of one’s interlocutor, and the intended audience of a given utterance (general audience, individual, group). Our results show that a speaker’s relationship to Chávez and the show is the most important predictor of non-standard agreement on Aló Presidente. Non-regular guests and especially women are the most likely to produce these stigmatized forms while Chávez does so very infrequently. In fact, we find this variable to be extremely uncharacteristic of Chávez’s lively tirades and colorful speech styles directed at his general audience. When he does make use of them, these variants emerge primarily in interpersonal dialogues between Chávez and these same non-regular guests. More telling, however, is the finding that they are never used during conversations between Chávez and the regular guests on the show: his inner political circle and close friends. We interpret these findings as indicative of the political nature of grammar and assert that in order to comprehend the variation of linguistic forms we must simultaneously understand the emergence and distribution of power among speakers.
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    Housing system may affect behavior and performance of Jersey heifer calves
    (2014-02) Pempek, Jessica; Eastridge, Maurice
    There is increasing social pressure to adopt alternative housing and management practices that allow farm animals more opportunity to exercise and demonstrate social behavior. The present study investigated the effect of paired housing on the behavior and performance of Jersey heifer calves. Forty female Jersey calves were allocated to individual or pair housing at birth and monitored for 9 wk. Calves were provided with a single hutch, and those allocated to the paired housing treatment were provided a pen enclosure twice the size of individually housed calves and only one hutch was provided per pair. All calves were fed milk replacer via bucket twice per day (1.9 L/feeding first 7 d; 2.27 L/feeding until weaned) and had ad libitum access to calf starter and water. Gradual weaning commenced on day 49 by reducing the calves’ milk allowance to one feeding per day and weaning occurred on day 56. Grain consumption was monitored daily and calves were weighed weekly. Direct behavioral observations were conducted twice per week. Calves housed in pairs tended to have greater average daily gain (ADG) compared with calves housed individually (0.63 ± 0.02 versus 0.59 ± 0.02 kg/d; respectively). Pair housing also increased final body weight (BW) compared with individual housing (64.9 ± 0.76 versus 61.7 ± 0.81 kg, respectively). During observation periods, calves housed individually spent more time engaging in nonnutritive sucking than calves housed in pairs (21.5 versus 8.15%). Calves housed in pairs were observed cross-sucking 13.2% of the time during observational periods. In conclusion, although housing Jersey calves in pairs may increase measures of performance, future research should aim to reduce cross-sucking behavior within the Jersey breed through alternative feeding systems or environmental enrichment.
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    Mission-Based Objectives, Market-Based Funding: The Relationship between Nonprofit Enterprise and Service Delivery
    (2014-02) Levine Daniel, Jamie; Moulton, Stephanie
    This paper addresses the relationship between earned revenue activities and core service delivery in nonprofit organizations. Two key assumptions drive this study: (1) organizations are resource-dependent and (2) nonprofit organizations are mission-driven. Past studies have examined earned revenue as aggregate measures, i.e.: the sum of all market-driven income activities, or the sum of revenue from program/service related activities. Some of these studies argue earned revenue complements service delivery because organizations can use this financial resource to invest in the organizational technologies and acquire the resources needed to deliver their core services. Other studies have considered the potential negative effects because the pursuit of this type of income can crowd out income from other sources, in effect becoming a substitute for service activities. However, not all market-based activities may affect service volume and access in the same way. This study uses fixed effects regression to analyze data from 2115 arts and culture organizations over a period of four years in order to to assess the embeddedness (use of the same organizational technologies, targeting the same markets) of the market-driven activity relative to the core mission activity. Findings show that activities that are fully embedded are positively related to increases in service volume, but earned revenue activities that are not fully embedded – that is, that share some but not all organizational inputs or target markets – are negatively related to both service volume and service access. These findings may help nonprofit organizations considering the pursuit of earned revenue to determine the best strategy to complement service delivery.
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    Repeated social defeat decreased neurogenesis and impaired working memory in mice
    (2014-02) McKim, Daniel; Godbout, Jonathan
    Recent studies demonstrate that microglia activation and inflammatory cytokines are potent regulators of cognition and neuroplasticity. Moreover, repeated social defeat (RSD) in mice causes microglia activation and increased production inflammatory cytokines in the brain. The present examined the association between hippocampal cytokine expression, learning & memory, and hippocampal neurogenesis. We show that RSD increased production of hippocampal cytokines (i.e., IL-1b, IL-6, and TNFa) without reducing common neurogenic growth factors (e.g., VEGF, NGF, IGF1, and BDNF). Increased hippocampal cytokine expression was not associated with reduced proliferation or survival of hippocampal neural progenitor cells (NPCs) but was associated with reduced NPC differentiation into NeuN expressing neurons (BrdU+/NeuN+). Moreover, corresponding with increased hippocampal cytokines, impaired spatial memory recall was observed in the Morris water maze and Barnes maze that was independent of increased anxiety-like behaviors (i.e., thigmotaxis). Taken together, RSD-induced hippocampal cytokine expression was associated with impaired spatial memory recall and impaired NPC differentiation.
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    Ets-2 in Pancreatic Cancer Associated Fibroblasts Promotes Tumor Initiation and Development.
    (2014-02) Pitarresi, Jason; Ostrowski, Michael
    Pancreatic cancer remains an overwhelmingly fatal disease with less than 5% of patients surviving beyond 5 years, largely due to our lack of understanding of the complexity of the disease. Many recent reports have begun to highlight the potential role that stromal cells—fibroblasts in particular—may have on pancreatic tumor cell biology and this report provides data that supports the theory of tumor-stroma co-evolution in pancreatic cancer. Here we use a novel mouse model to show that Ets-2 in the tumor-associated stroma promotes pancreatic tumor initiation and development. We observed a decrease in tumorigenesis events such as acinar-to-ductal metaplasia (ADM) and pancreatic intraepithelial neoplasia (PanIN) lesions when Ets-2 is conditionally deleted in pancreatic cancer associated fibroblasts (CAFs). To determine how Ets-2 in fibroblasts is able to effect tumor progression, we harvested pancreatic CAFs from Ets-2 deleted and Ets-2 intact tumor bearing mice and performed microarray gene expression analysis. We found that Ets-2 deleted CAFs had a significantly altered secretome that crucially lacked tumor necrosis factor alpha (TNF-α), a known pro-tumor ligand in pancreatic carcinogenesis. Furthermore, ChIP analysis showed that Ets-2 binds the proximal promoter of TNF-α to directly regulate its expression. Thus, Ets-2 ablation in pancreatic fibroblasts delays pancreatic tumor initiation by decreasing the pro-tumor ligand TNF-α. This report shows for the first time that deleting a gene in pancreatic fibroblasts causes a change in tumor-stroma co-evolution and that Ets-2 is able to act as a novel oncogene in cancer associated fibroblasts to promote pancreatic carcinogenesis.
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    Assessing the Impact of Financial Disclosure Forms on the Mortgage Selection Process
    (2014-02) Mountain, Travis
    The recent housing crisis has raised the important question of whether consumers are making appropriate decisions when it comes to various mortgage options. Specifically, do consumers know when to choose an adjustable rate mortgage versus a fixed rate mortgage? Further, does additional mortgage disclosure help consumers make the correct decision? This study uses unique data in a 2x2 experimental design in which some participants were randomly assigned to receive a Federal Reserve Board document containing information explaining the difference between these two major mortgage types. Participants were then given two distinct scenarios, one where an adjustable and one where a fixed rate mortgage is more appropriate. Path analysis is used to determine the probability of consumers making the correct decision in both scenarios. The results suggest that receiving a mortgage information disclosure document does indeed make a difference in consumers selecting the most appropriate mortgage type. 23% of those who did not receive mortgage information correctly chose the most appropriate mortgage for both scenarios while 36% correctly answered both after receiving the mortgage education information, a 57% increase. Factors such as overall financial knowledge and Truth in Lending Act comprehension are also important predictors of choosing the correct mortgage type. Not all consumers who were exposed to financial information made the correct decision which supports the continued use of mortgage counselors and or educational programs to further assist consumers in selection the best mortgage type for their situation.
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    Fabrication and Analysis of Thermally Invariant Smart Composites via Ultrasonic Additive Manufacturing
    (2014-02) Pritchard, Joshua; Dapino, Marcelo
    Ultrasonic additive manufacturing (UAM), a form of 3D printing based on ultrasonic metal welding, is a fabrication technique that is rapidly altering the development of new components within the research and commercial industries. Through the use of piezoelectric boosters, vibrating at 20 kHz, and the application of normal forces in excess of 5000 Newtons, thin metal foils can be welded in a fusionless, low-temperature process to produce bulk structures. Because of its low-temperature, UAM provides the opportunity to embed thermally sensitive materials, such as nickel-titanium (NiTi), a shape memory alloy. NiTi exhibits a shape change as it undergoes thermally-induced crystallographic phase transformation between martensite, the low-temperature phase, and austenite, the high-temperature phase. During phase transformations, NiTi can recover up to 8% elastic strain and have a change in elastic modulus of 100%. When embedded, the strain recovery of NiTi can be used to counteract the thermal expansion of the matrix material—specifically aluminum in this study—for the purpose of producing components with low coefficients of thermal expansion (CTE) while keeping the weight at a minimal level. The work herein covers the design, fabrication, and characterization of Al-NiTi composites to aid in the development of a composite that has a coefficient of thermal expansion at, or below, 5 µє/°C. A composite is produced that has a CTE of 13.83 µє/°C; a 40.4% decrease as compared to Al alone. In addition, electrical resistivity measurements in the longitudinal direction and thermal diffusivity measurements in the out-of-plane directions are presented.
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    Comparison of the Corrosion Behavior of High Strength Aluminum Alloys after Exposure to ASTM B117 Environment
    (2014-02) Grieshop, Sara; Buchheit, Rudy
    In recent years, design requirements for new aircraft have required materials engineers to develop a stronger yet lighter aluminum alloy than the traditional AA7075 and AA2024 type alloys used previously. The aluminum-lithium alloy system is attractive to the aerospace industry due to the its lower density, increased elastic modulus, increased fatigue crack growth resistance, formation of strengthening phases, and increased corrosion resistance when compared to AA7075 and AA2024. Third generation aluminum-lithium alloys have proven to be a viable replacement for incumbent alloys AA7075 and AA2024 in aircraft structures. A key interest in these alloys is increased corrosion resistance and much research has been done to understand the corrosion mechanisms present in 3rd generation aluminum-lithium. Despite this, no direct comparison of the bulk corrosion behavior observed in AA7075 to that observed in a 3rd generation aluminum-lithium alloy, like AA2099, has been reported. To this end, B117 salt fog exposure tests were performed on AA7075, AA7050, AA2099, and AA2024 plate samples, in the longitudinal (L), short transverse (ST), and longitudinal transverse (LT) directions, to compare their corrosion behavior. AA2524 sheet alloy was also compared in the longitudinal direction. Three tests were performed, an interrupted test of 72 hours, 120 hours, and a longer duration 168 hours test, with analysis of the results performed by optical microscopy, optical profilometry, and scanning electron microscopy. Optical microscopy of the AA7075, AA7050, and AA2024 samples generally showed localized shallow pitting with trenching around some secondary phase particles as well as areas of localized corrosion on the ST and LT directions. In contrast, AA2099 samples featured small pits across the sample surface with no evidence of trenching due to the alloys lack of secondary particles. Localized corrosion was not observed in the AA2099 samples at all exposure conditions. Analysis of the interrupted test samples by optical profilometry reveals that for a lower limit threshold of 20.0 microns and an upper limit threshold of 1500 microns, AA7075 and AA2024 featured more pits than the longitudinal, short-transverse, and longitudinal-transverse directions of AA2099. AA7075, AA7050, AA2524, and AA2024 samples were revealed to contain a larger number of pits that were slightly larger in size in all three directions. Further examination of the microstructure and texture of both non-corroded and corroded samples via scanning electron microscopy will be presented, with careful examination of the role of secondary phases in influencing pitting potential.
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    Determination of Biologically Relevant Vitamin D Metabolites in a Mouse Model of Non Melanoma Skin Cancer
    (2014-02) Teegarden, Matthew; Schwartz, Steven
    Background: Vitamin D has received recent attention as a nutrient in which a large portion of Americans may be deficient. Vitamin D is a unique “essential” nutrient in that it can be produced endogenously in the skin via UVB irradiation of 7-dehydrocholesterol, or taken in from the diet. Although it is well established that vitamin D plays a role in bone health, a growing body of evidence suggests that it may also have a role in chronic diseases, including several types of cancer. Vitamin D is not naturally present in many foods although some foods including dairy products and ready to eat cereals are fortified. Some researchers recommend that individuals receive approximately 5 to 15 minutes of unprotected sun exposure several times a week in order to produce sufficient amounts of vitamin D, yet unprotected sun exposure is also a risk factor for skin cancer. Cell studies have demonstrated that 1,25-dihydroxyvitamin D, the active metabolite of vitamin D, has an inhibitory effect on skin cancer initiation, but cancerous cells lose sensitivity to the growth regulating properties of the compound. These recent reports indicate an important biological role of vitamin D metabolites in skin cancer development, but there have been no studies on the disease measuring these compounds in skin. This is primarily due to the challenging nature of this analysis and need for highly sensitive and sophisticated analytical instrumentation. Purpose/Rationale: Since vitamin D may have a role in the prevention of skin cancer, and the UVB exposure needed for endogenous synthesis of the vitamin is a risk factor for the disease, the effects of dietary vitamin D on the development of skin cancer is a critical area of investigation. However, before results can be translated to humans, appropriate animal models of skin cancer need to be investigated. The purpose of this research is to measure the levels of biologically relevant vitamin D metabolites in the skin and serum of mice fed escalating doses of vitamin D. Research Methods: To evaluate the effects of dietary vitamin D on non-melanoma skin cancer (NMSC), 150 Skh-1 hairless, but immunocompetent, mice were placed on diets with escalating doses of the vitamin for 29 weeks. The Skh-1 mouse is a well-recognized model of NMSC. Equal numbers of male and female mice were assigned to each dietary level of vitamin D (25, 150, 1000 IU). Within each dietary level, n=15 mice were exposed to UVB light three times per week for the last 25 weeks of the study, and n=10 mice were abstained from the treatment. The UVB exposure given to the mice was one minimal erythemic dose, which is equivalent to a light sunburn. Vitamin D metabolite levels will be measured in the serum and skin of the mice using high performance liquid chromatography with tandem mass spectrometry (HPLC-MS/MS), a sensitive and advanced analytical technique. The estimated levels of these compounds in the skin are quite low, thus extracts from skin samples will be derivatized with 4-phenyl-1,2,4-triazoline-3,5-dione (PTAD), allowing more efficient and sensitive analysis of the vitamin D metabolites. Predicted Findings: We expect to see increased vitamin D metabolites in samples from mice supplemented with the nutrient. A dose-dependent increase in specific metabolites is also expected. Implications: The levels of vitamin D-related compounds in the tissues and serum of mice from this study will be correlated with previously evaluated cancer outcomes. This will be the first study of its kind to measure vitamin D metabolites in murine skin using HPLC-MS/MS in an effort to elucidate the influence of dietary vitamin D on NMSC.
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    Degenerate Gaugino Mass Region and Mono-Boson Collider Signatures
    (2014-02) Anandakrishnan, Archana; Raby, Stuart
    We propose here a program of searches for degenerate electro-weakinos in various final state search topologies. In particular we emphasize the usefulness of searching for mass degenerate charginos and neutralinos in the mono-Z search channel. We demonstrate that the mono-Z search supersedes the mono-jet and mono-photon search topologies and present arguments using effective operators to explain why mono Z searches can succeed where mono-jet and mono-photon searches have failed.
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    War Bugs: Street Art as Performed Discourse in Bogotá
    (2014-02) Wilson, Geoffrey; Puga, Ana
    Historically, the embodied practice of making stencil or graffiti art has been uniquely heightened because of the fact that the artist is in danger of arrest during the creation of the work. This has led to anti-authoritarian posturing and interpretation by the artists and spectators. However, new commercial opportunities for urban artists and increasing acceptance of their art as art has led to the establishment of legal spaces for street art in some cities, including Bogotá. Theorists such as Jean Boudrillard, Dwight Conquergood, and others who have contributed to the theorization of graffiti have generally conceived of graffiti as textual, that is, they discuss graffiti in terms employed for the analysis of stable texts or artifacts. Graffiti artists acknowledge that their work is not stable; rather it is subject to amendment or deletion by other artists, by property owners, or by the authorities. For this reason, my analysis follows Diana Taylor’s distinction between the archive, or forms of documentation which are usually stable such as books, recordings, etc., and the repertoire, or systems of memory making which are temporal, embodied, and fluid. My project is to shift the theoretical perspective on graffiti away from the text/statement frame toward a performance/discourse frame. The visual landscape in public urban spaces is predominantly controlled by government or religious interests and corporate branding. Street art repertoires seek to interrupt this visual field, contesting the narratives of powerful interests and re-writing, or rather, over-writing the urban geography. If graffiti and stencil art implicitly critique the dominance of the visual landscape by corporate and government interests, is this criticism undermined when urban artists become commercially successful? How does that affect the political efficacy of the art? These are a few of the questions I begin to address in my ongoing research. In a country whose government is, even as I write, attempting to negotiate a peaceful resolution to decades-long conflict in which tens of thousands of lives have been lost, it is critical to examine the politically engaged cultural production of artists like Dj Lu, whose work contests dominant narratives and underscores links between corporate consumerism, the weapons which are supplied and disseminated in the support of neoliberal ideology, and the traumatized Earth violated by pollution and exploitation.
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    Waveguide Magnetic Resonance Elastography in a Pressure-Varying Porcine Model
    (2014-02) Mazumder, Ria; Clymer, Bradley; Kolipaka, Arunark
    Purpose: To determine anisotropic myocardial stiffness using waveguide cardiac magnetic resonance elastography (CMRE) in an ex-vivo porcine model with varying left ventricular pressure simulating heart failure with preserved ejection fraction and compare the results against isotropic myocardial stiffness. Methods: Diffusion tensor imaging (DTI) and CMRE was implemented on three ex-vivo porcine hearts inflated with two different pressure values on a 3T MRI scanner to obtain fiber orientation and displacement information respectively. An orthotropic inversion was performed on the displacement data to estimate the anisotropic stiffness coefficients (compressional and shear) in the heart for both the inflation pressures and the results were compared against isotropic stiffness estimates. Paired student’s t-test was performed to determine the significant difference in stiffness values between the two inflation pressures with the two different inversion techniques. Results: Our results show that anisotropic stiffness estimates demonstrated a significant difference between the two inflation pressures both in the compressional (P-Value=0.0053) and shear (P-Value=0.0015) measurements. On the other hand, the isotopic stiffness measurements showed a minute slight increase in stiffness as a function of pressure with no significant difference (P-value=0.75). Conclusion: From the results we can conclude that it is feasible to estimate anisotropic stiffness in the myocardium and anisotropic myocardial stiffness provides superior information as compared to isotropic myocardial stiffness.