3,017 research outputs found

    Prepotentials for local mirror symmetry via Calabi-Yau fourfolds

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    In this paper, we first derive an intrinsic definition of classical triple intersection numbers of K_S, where S is a complex toric surface, and use this to compute the extended Picard-Fuchs system of K_S of our previous paper, without making use of the instanton expansion. We then extend this formalism to local fourfolds K_X, where X is a complex 3-fold. As a result, we are able to fix the prepotential of local Calabi-Yau threefolds K_S up to polynomial terms of degree 2. We then outline methods of extending the procedure to non canonical bundle cases.Comment: 42 pages, 7 figures. Expanded, reorganized, and added a theoretical background for the calculation

    Interferometric Studies of the extreme binary, ϵ\epsilon Aurigae: Pre-eclipse Observations

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    We report new and archival K-band interferometric uniform disk diameters obtained with the Palomar Testbed Interferometer for the eclipsing binary star ϵ\epsilon Aurigae, in advance of the start of its eclipse in 2009. The observations were inteded to test whether low amplitude variations in the system are connected with the F supergiant star (primary), or with the intersystem material connecting the star with the enormous dark disk (secondary) inferred to cause the eclipses. Cepheid-like radial pulsations of the F star are not detected, nor do we find evidence for proposed 6% per decade shrinkage of the F star. The measured 2.27 +/- 0.11 milli-arcsecond K band diameter is consistent with a 300 times solar radius F supergiant star at the Hipparcos distance of 625 pc. These results provide an improved context for observations during the 2009-2011 eclipse.Comment: Accepted for Ap.J. Letters, Oct. 200

    Female Reproductive Traits in Selected Arkansas Snakes

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    Female reproductive characteristics of 17 genera of Arkansas snakes (27 species and subspecies) were examined. Most of the snakes (n= 495) were collected over a 10-year span (1984-1993). Methods used to estimate clutch and/or litter size were as follows: 1) counts of previtellogenic ovarian follicles,2) counts of vitellogenic ovarian follicles,3) counts of oviductal eggs or embryos, 4) counts of corpora luteal scars, and 5) counts of neonates from egg clutches or litters. In several species, Method 1 tended to overestimate clutch size as determined by Method 2 by as much as 100% (e.g., in Diadophis punctatus, Elaphe obsoleta, and Lampropeltis getula), whereas these methods produced similar counts in Virginia striatula and Thamnophis proximus. The largest clutch size as estimated by Method 1 was 79 ova in a 744 mm in snout-vent length (SVL) individual of Thamnophis sirtalis; the smallest clutch size as recorded by this method was in Carphophis vermis (2 ova; 182 mm in SVL). Method 2 reduces the total egg count by one third over Method 1 in most species, and this count was very similar to the estimates obtained by Method 3, the most reliable way to estimate clutch or litter size (without actually having counts from egg clutches or litters). The presence of atretic ovarian follicles accounts for discrepancies found between clutch size estimates using Methods 1 and 2 as compared to Method 3. Comparisons of clutch sizes in Arkansas specimens to those recorded for snake species in neighboring states revealed similar sizes in 13 species; counts were larger in 8 species from Arkansas and smaller in only one species

    Shocked Quartz in Polymict Impact Breccia from the Upper Cretaceous Yallalie Impact Structure in Western Australia

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    Yallalie is a ~12 km diameter circular structure located ~200 km north of Perth, Australia. Previous studies have proposed that the buried structure is a complex impact crater based on geophysical data. Allochthonous breccia exposed near the structure has previously been interpreted as proximal impact ejecta; however, no diagnostic indicators of shock metamorphism have been found. Here we report multiple (27) shocked quartz grains containing planar fractures (PFs) and planar deformation features (PDFs) in the breccia. The PFs occur in up to five sets per grain, while the PDFs occur in up to four sets per grain. Universal stage measurements of all 27 shocked quartz grains confirms that the planar microstructures occur in known crystallographic orientations in quartz corresponding to shock compression from 5 to 20 GPa. Proximity to the buried structure (~4 km) and occurrence of shocked quartz indicates that the breccia represents either primary or reworked ejecta. Ejecta distribution simulated using iSALE hydrocode predicts the same distribution of shock levels at the site as those found in the breccia, which supports a primary ejecta interpretation, although local reworking cannot be excluded. The Yallalie impact event is stratigraphically constrained to have occurred in the interval from 89.8 to 83.6 Ma based on the occurrence of Coniacian clasts in the breccia and undisturbed overlying Santonian to Campanian sedimentary rocks. Yallalie is thus the first confirmed Upper Cretaceous impact structure in Australia

    Reproductive Phenophases and Clutch Characteristics of Selected Arkansas Amphibians

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    Seasonal reproductive phenomena in 13 species of salamanders and 16 species of anurans from Arkansas were investigated. Most specimens were collected during a span of 6 years (1985-1990). Clutch characteristics, including mensural and meristic data, were determined from gravid females. In some species, the size of egg masses was also documented. Among the plethodontid salamanders, average clutch size (in parentheses) was greatest in Eurycea lucifuga (77.7) and smallest in Plethodon serratus (7.0). One of 2 ambystomatid salamanders (Ambystoma texanum) averaged 545.4 eggs per clutch; the other species (Ambystoma tigrinum) averaged 1 30.5. Siren intermedia nettingi (one of 3 large salamanders examined) had the greatest mean clutch size (851.3). Among anurans, Rana catesbeiana had the largest clutch size and mass (43,073 eggs and 55.9 g), whereas clutches of Acris crepitans blanchardi averaged the smallest (264.1 eggs and 0.1382 g). Multiple clutch production may be the rule in some amphibians (e.g., Desmognathus brimleyorum, A. c. blanchardi, Pseudacris triseriata feriarum, and P. streckeri streckeri); however, partial clutch deposition remains a possibility in these species. By knowing the synchrony between male and female reproductive cycles, a clarification of the onset, timing, and duration of reproductive phenophases (e.g., courtship, breeding, egg laying, etc.) was documented in many species

    Microarray analysis of Foxa2 mutant mouse embryos reveals novel gene expression and inductive roles for the gastrula organizer and its derivatives

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    <p>Abstract</p> <p>Background</p> <p>The Spemann/Mangold organizer is a transient tissue critical for patterning the gastrula stage vertebrate embryo and formation of the three germ layers. Despite its important role during development, there are still relatively few genes with specific expression in the organizer and its derivatives. Foxa2 is a forkhead transcription factor that is absolutely required for formation of the mammalian equivalent of the organizer, the node, the axial mesoderm and the definitive endoderm (DE). However, the targets of Foxa2 during embryogenesis, and the molecular impact of organizer loss on the gastrula embryo, have not been well defined.</p> <p>Results</p> <p>To identify genes specific to the Spemann/Mangold organizer, we performed a microarray-based screen that compared wild-type and <it>Foxa2 </it>mutant embryos at late gastrulation stage (E7.5). We could detect genes that were consistently down-regulated in replicate pools of mutant embryos versus wild-type, and these included a number of known node and DE markers. We selected 314 genes without previously published data at E7.5 and screened for expression by whole mount <it>in situ </it>hybridization. We identified 10 novel expression patterns in the node and 5 in the definitive endoderm. We also found significant reduction of markers expressed in secondary tissues that require interaction with the organizer and its derivatives, such as cardiac mesoderm, vasculature, primitive streak, and anterior neuroectoderm.</p> <p>Conclusion</p> <p>The genes identified in this screen represent novel Spemann/Mangold organizer genes as well as potential Foxa2 targets. Further investigation will be needed to define these genes as novel developmental regulatory factors involved in organizer formation and function. We have placed these genes in a Foxa2-dependent genetic regulatory network and we hypothesize how Foxa2 may regulate a molecular program of Spemann/Mangold organizer development. We have also shown how early loss of the organizer and its inductive properties in an otherwise normal embryo, impacts on the molecular profile of surrounding tissues.</p

    Investigation of immune cell markers in feline oral squamous cell carcinoma

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    Squamous cell carcinoma is the most common oral cancer in the cat and presents as a locally aggressive lesion for which an effective therapeutic protocol remains elusive. Feline oral squamous cell carcinoma (OSCC) shares many clinical characteristics with human head and neck squamous cell carcinoma (HNSCC). Accordingly, present studies were conducted to determine similarities for immune markers shared by feline OSCC and human HNSCC. Biopsies harvested from a feline patient cohort-1 (n = 12) were analyzed for lymphoid cell infiltrates by immunohistochemistry (IHC). Results revealed unique patterns of T cell infiltration involving both neoplastic epithelium and stroma that were detected in most patient tumor biopsies (92%) examined by IHC staining for CD3. Intratumoral B cell infiltrates were detected within tumor stroma only, based on IHC staining for CD79a and CD20 for all patients within the same cohort-1. Infiltration of tumors by a regulatory CD4 T cell subset (Tregs) defined by expression of the forkhead transcription factor FoxP3, was also detected in biopsies from 57% of patients and involved infiltration of neoplastic epithelium and stroma. Patient biopsies were also examined for expression of immunomodulator cyclooxygenase (COX)-2 and revealed positive but weak staining of neoplastic epithelium in a significant proportion of cases (75%). Interestingly, COX-2 expression was detected in both neoplastic epithelium and stroma. Blood collected from a second cohort of feline OSCC patients (n = 9) revealed an increased frequency of circulating CD4+FoxP3+ T cells when compared to healthy adult controls (n = 7) (P = 0.045), although frequencies of CD4+CD25+FoxP3+ T cells were comparable between patients and healthy pet cat controls. Lastly, biopsies from feline OSCC patients were characterized for histologic subtype using a classification scheme previously described for human HNSCC. This analysis revealed the conventional subtype as the predominant variant (75%) with conventional subtypes split evenly between well differentiated and moderately differentiated carcinomas. Two cases were classified as papillary and one case as basaloid subtypes. Correlations between subtype, immune marker scores or circulating Treg frequencies and clinical characteristics or outcome were not detected, most likely due to small patient numbers within patient cohorts. However, findings from these studies provide a preliminary step in the characterization of immune and histologic markers that will be critical to defining prognostic immune markers for feline OSCC and potential targets for testing of immunotherapeutics also relevant to human HNSCC in future studies

    The Grizzly, December 10, 2015

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    Museum Studies Minor Coming in Spring 2016 • Students Demand Diversity • BEAR Pitch Competition Crowns Winners • International Perspective: Differences in Cultural Cleaning Routines • Flapjacks for Finals • Artists\u27 Tribute to Chadwick • Bringing Safety to the Students • Opinions: Protests Prompt Hate on Yik Yak; Why Syrian Refugees Don\u27t Pose a Threat • Outrunning the Competition • Men\u27s Basketball Set to Take on Division I Pennhttps://digitalcommons.ursinus.edu/grizzlynews/1679/thumbnail.jp

    Stress Free Temperature Testing and Calculations on Out-of-Autoclave Composites

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    Future launch vehicles will require the incorporation of large composite parts that will make up primary and secondary components of the vehicle. NASA has explored the feasibility of manufacturing these large components using Out-of-Autoclave impregnated carbon fiber composite systems through many composites development projects. Most recently, the Composites for Exploration Project has been looking at the development of a 10 meter diameter fairing structure, similar in size to what will be required for a heavy launch vehicle. The development of new material systems requires the investigation of the material properties and the stress in the parts. Residual stress is an important factor to incorporate when modeling the stresses that a part is undergoing. Testing was performed to verify the stress free temperature with two-ply asymmetric panels. A comparison was done between three newly developed out of autoclave IM7/Bismaleimide (BMI) systems. This paper presents the testing results and the analysis performed to determine the stress free temperature of the material
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