618 research outputs found

    Return-to-launch-site three degree of freedom analysis, constant inertial attitude during the fuel dissipation phase

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    Results are presented of a study to show the effect of selecting a constant inertial attitude during the fuel dissipation phase of a return-to-launch-site abort. Results are also presented which show that the selection of the constant inertial attitude will affect the arrival point on the range-velocity target line. An alternate selection of the inertial attitude will provide control over the trajectory shape

    Swipe, Tap, and Read: Research on E-book Tools, Features, and Student Engagement

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    This study explores the digital tools and features that students had access to and interacted with while reading e-books on Raz-Kids. The goal was to use this information to understand how e-book reading impacted student motivation and engagement. This study was conducted for five weeks, and implemented three days per week with two first grade classes during Daily 5 or Reading Centers. I collected qualitative data by conducting a student survey, documenting the e-books that the student participants read and the digital tools and features that they used, recording field note observations, and conducting audio-recorded interviews with the student participants. Findings were derived from the research. The findings were a) the impact of Raz-Kids on reading engagement; b) first graders’ knowledge of e-book tools and features using Raz-Kids; and c) first graders’ access to and interaction with e-books outside of the classroom. Conclusions of this research study include that a) student reading experience is influenced by the Raz-Kids star system; b) the quantity of e-book tools lead to exploration; and c) the quality of e-book features impact student reading engagement

    GPGPU microbenchmarking for irregular application optimization

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    Irregular applications, such as unstructured mesh operations, do not easily map onto the typical GPU programming paradigms endorsed by GPU manufacturers, which mostly focus on maximizing concurrency for latency hiding. In this work, we show how alternative techniques focused on latency amortization can be used to control overall latency while requiring less concurrency. We used a custom-built microbenchmarking framework to test several GPU kernels and show how the GPU behaves under relevant workloads. We demonstrate that coalescing is not required for efficacious performance; an uncoalesced access pattern can achieve high bandwidth - even over 80% of the theoretical global memory bandwidth in certain circumstances. We also make other further observations on specific relevant behaviors of GPUs. We hope that this study opens the door for further investigation into techniques that can exploit latency amortization when latency hiding does not achieve sufficient performance

    Letters between R. M. Winans and W. J. Kerr

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    Letters concerning a position in the dairy department at Utah Agricultural College

    Generation of Thymidine Kinase-Deficient Mutants of Infectious Laryngotracheitis Virus

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    AbstractCurrent vaccines for the avian respiratory disease infectious laryngotracheitis consist of naturally attenuated strains of the causative agent—the herpesvirus infectious laryngotracheitis virus (ILTV). Due to the dissemination of these viruses from vaccinated chickens as well as their possible reversion to more pathogenic forms, the use of genetically engineered viral vaccines lacking virulence factors while retaining antigenicity is being considered. Since the thymidine kinase (TK) activity of herpesviruses has been associated with virulence, inactivation of the encoding gene in the ILTV genome should attenuate the virus. Moreover, by analogy to other TK- herpesviruses, the ability of such ILTV mutants to induce a protective response in chickens should not be compromised. Therefore, the deliberate genetic alteration of ILTV was attempted. In order to prevent reversion and also to enable identification of the modified virus, a "marker" transcriptional unit (Escherichia coli lacZ gene fused to a SV-40 3′-polyadenylation signal sequence and regulated by the pseudorabies virus gX gene promoter) was inserted via homologous recombination at one of two loci within the ILTV TK gene. Recombinant viruses were identified and plaque-purified on the basis of their ability to produce β-galactosidase. Retention of the foreign DNA at the predicted sites in the genomes of the recombinant ILTV was verified by Southern hybridization. Since their replication was unaffected by the thymine analog 1-(2-fluoro-2-deoxy-β-d-arabinofuranosyl)-5-methyluracil, the recombinants appeared to have a TK- phenotype. Despite this apparent deficiency, prior inoculation of either recombinant virus into chickens afforded the birds protection against a lethal challenge of virulent ILTV. Moreover, the degree of respiratory distress in the chickens vaccinated with the recombinants was relatively mild compared to the severe reaction in birds receiving the parental virus. Thus, ILTV can be genetically attenuated without an accompanying loss of immunogenicity

    Response of selected microorganisms to experimental planetary environments

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    Experiments indicate that hardy organisms will likely grow in the Martian environment if moisture is available, and that these organisms definitely present a threat to contamination of the biopackage if they are transported to the surface of Mars

    Efferent connections of dorsal and ventral agranular insular cortex in the hamster, Mesocricetus auratus

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    The anterior portion of rodent agranular insular cortex consists of a ventral periallocortical region (AIv) and a dorsal proisocortical region (AId). Each of these two cortical areas has distinct efferent connections, but in certain brain areas their projection fields are partially or wholly overlapping. Bilateral projections to layers I, III and VI of medial frontal cortex originate in the dorsal agranular insular cortex and terminate in the prelimbic, anterior cingulate and medial precentral areas; those originating in ventral agranular insular cortex terminate in the medial orbital, infralimbic and prelimbic areas. The dorsal and ventral regions of the agranular insular cortex project topographically to the ipsilateral cortex bordering the rhinal fissure, which includes the posterior primary olfactory, posterior agranular insular, perirhinal and lateral entorhinal areas. Fibers to these lateral cortical areas were found to travel in a cell-free zone, between cortical layer VI and the claustrum, which corresponds to the extreme capsule. The dorsal and ventral regions send commissural projections to layer I, lamina dissecans and outer layer V, and layer VI of the contralateral homotopical cortex, via the corpus callosum. Projections from the ventral and dorsal regions of the agranular insular cortex to the caudatoputamen are topographically arranged and terminate in finger-like patches. The ventral, but not the dorsal region, projects to the ventral striatum and ventral pallidum. The thalamic projections of the ventral and dorsal regions are largely overlapping, with projections from both to the ipsilateral reticular nucleus and bilaterally to the rhomboid, mediodorsal, gelatinosus and ventromedial nuclei. The heaviest projection is that to the full anteroposterior extent of the medial segment of the mediodorsal nucleus. Brainstem areas receiving projections from the ventral and dorsal regions include the lateral hypothalamus, substantia nigra pars compacta, ventral tegmental area and dorsal raphe nucleus. In addition, the ventral region projects to the periaqueductal gray and the dorsal region projects to the parabrachial and ventral pontine nuclei.These efferent connections largely reciprocate the afferent connections of the ventral and dorsal agranular insular cortex, and provide further support for the concept that these regions are portions of an outer ring of limbic cortex which plays a critical role in the expression of motivated, species-typical behaviors.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/23826/1/0000065.pd

    Mating activates androgen receptor-containing neurons in chemosensory pathways of the male Syrian hamster brain

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    Fos-immunoreactivity is induced during mating in the male Syrian hamster in limbic areas that relay chemosensory information and contain receptors for gonadal steroid hormones. The induction of Fos is an index of neuronal activation. After mating, c-fos expression is greatest in subnuclei of the medial amygdaloid nucleus (Me), bed nucleus of the stria terminalis (BNST), and medial preoptic area (MPOA). The present study determined if individual neurons in these activated subnuclei contain androgen receptors. We aim to understand how essential chemosensory and hormonal signals are integrated to control copulation Adult male hamster (n = 6) were allowed to mate with a sexually receptive female for 30 min. They were perfused 1 h later with 4% paraformaldehyde and 40 [mu]m frozen sections were processed for immunocytochemistry using antisera against Fos (Cambridge Research Biochemicals) and the androgen receptor (G.S. Prins). The brains of three non-mated males were also processed for Fos immunocytochemistry. Mating significantly increased the number of Fos-immunoreactive neurons within subnuclei of Me, BNST, and MPOA relative to non-mated males (P < 0.05). These nuclei contained abundant androgen receptors. In the corticomedial amygdala, 20-40% of Fos-immunoreactive neurons in mated hamsters expressed androgen receptors. Although few androgen receptors are found in the anteromedial and postero-intermediate subdivisions of the BNST, these areas exhibited 26% and 47% co-localization, respectively. In posteromedial BNST, which contains large numbers of steroid receptor-containing neurons, androgen receptors were identified in 48% of Fos-immunoreactive neurons. In the MPOA, 54% of Fos-immunoreactive neurons expressed the androgen receptor throughout the rostrocaudal extent of the medial preoptic nucleus (MPN). The largest percentage of co-localized Fos neurons (70%) was found in the magnocellular subdivision of MPN. These results provide the first direct evidence that androgen receptor neurons are activated by mating behavior, suggesting that such neurons may be incorporated in the neural circuitry underlying copulation. Further, they show that mating selectively and differentially activates androgen receptor cells.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/30740/1/0000389.pd
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