12,018 research outputs found

    Forage Feeding Systems for Dairy Cattle

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    Fabrication process of a high temperature polymer matrix engine duct

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    The process that was used in the molding of an advanced composite outer by-pass duct planned for the F404 engine is discussed. This duct was developed as a potential replacement for the existing titanium duct in order to reduce both the weight and cost of the duct. The composite duct is now going into the manufacturing technology portion of the program. The duct is fabricated using graphite cloth impregnated with the PMR-15 matrix system

    Hydration and mobility of HO-(aq)

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    The hydroxide anion plays an essential role in many chemical and biochemical reactions. But a molecular-scale description of its hydration state, and hence also its transport, in water is currently controversial. The statistical mechanical quasi-chemical theory of solutions suggests that HO[H2O]3- is the predominant species in the aqueous phase under standard conditions. This result is in close agreement with recent spectroscopic studies on hydroxide water clusters, and with the available thermodynamic hydration free energies. In contrast, a recent ab initio molecular dynamics simulation has suggested that HO[H_2O]4- is the only dominant aqueous solution species. We apply adiabatic ab initio molecular dynamics simulations, and find good agreement with both the quasi-chemical theoretical predictions and experimental results. The present results suggest a picture that is simpler, more traditional, but with additional subtlety. These coordination structures are labile but the tri-coordinate species is the prominent case. This conclusion is unaltered with changes in the electronic density functional. No evidence is found for rate-determining activated inter-conversion of a HO[H2O]4- trap structure to HO[H2O]3-, mediating hydroxide transport. The view of HO- diffusion as the hopping of a proton hole has substantial validity, the rate depending largely on the dynamic disorder of the water hydrogen-bond network.Comment: 7 pages, 5 figures, additional results include

    Tsunamis, Viscosity and the HBT Puzzle

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    The equation of state and bulk and shear viscosities are shown to be able to affect the transverse dynamics of a central heavy ion collision. The net entropy, along with the femtoscopic radii are shown to be affected at the 10-20% level by both shear and bulk viscosity. The degree to which these effects help build a tsunami-like pulse is also discussed.Comment: Contribution to SQM 2007 in Levoca, Slovaki

    Towards the 3D-Imaging of Sources

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    Geometric details of a nuclear reaction zone, at the time of particle emission, can be restored from low relative-velocity particle-correlations, following imaging. Some of the source details get erased and are a potential cause of problems in the imaging, in the form of instabilities. These can be coped with by following the method of discretized optimization for the restored sources. So far it has been possible to produce 1-dimensional emission source images, corresponding to the reactions averaged over all possible spatial directions. Currently, efforts are in progress to restore angular details.Comment: Talk given at the Int. Workshop on Hot and Dense Matter in Relativistic Heavy Ion Collisions, March 24-27, 2004, Budapest; 10 pages, 6 figure

    Hydrogen Dissociation and Diffusion on Ni and Ti -doped Mg(0001) Surfaces

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    It is well known, both theoretically and experimentally, that alloying MgH2_2 with transition elements can significantly improve the thermodynamic and kinetic properties for H2_2 desorption, as well as the H2_2 intake by Mg bulk. Here we present a density functional theory investigation of hydrogen dissociation and surface diffusion over Ni-doped surface, and compare the findings to previously investigated Ti-doped Mg(0001) and pure Mg(0001) surfaces. Our results show that the energy barrier for hydrogen dissociation on the pure Mg(0001) surface is high, while it is small/null when Ni/Ti are added to the surface as dopants. We find that the binding energy of the two H atoms near the dissociation site is high on Ti, effectively impeding diffusion away from the Ti site. By contrast, we find that on Ni the energy barrier for diffusion is much reduced. Therefore, although both Ti and Ni promote H2_2 dissociation, only Ni appears to be a good catalyst for Mg hydrogenation, allowing diffusion away from the catalytic sites. Experimental results corroborate these theoretical findings, i.e. faster hydrogenation of the Ni doped Mg sample as opposed to the reference Mg or Ti doped Mg.Comment: 17 pages, 15 figures, to appear in Journal of Chemical Physic

    Final state interactions in two-particle interferometry

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    We reconsider the influence of two-particle final state interactions (FSI) on two-particle Bose-Einstein interferometry. We concentrate in particular on the problem of particle emission at different times. Assuming chaoticity of the source, we derive a new general expression for the symmetrized two-particle cross section. We discuss the approximations needed to derive from the general result the Koonin-Pratt formula. Introducing a less stringent version of the so-called smoothness approximation we also derive a more accurate formula. It can be implemented into classical event generators and allows to calculate FSI corrected two-particle correlation functions via modified Bose-Einstein "weights".Comment: 12 pages RevTeX, 2 ps-figures included, submitted to Phys. Rev.

    Introducing First Year Medical Students to Personalized Medicine Concepts in a Small Group Activity

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    Presented as a Poster Presentation at 2020 IUSM Education Day.An individuals’ genetic profile is becomingly an increasingly important parameter in healthcare decisions. This small group activity was developed to introduce first year medical students in the Molecules to Cells and Tissues course to the concept and significance of Pharmacogenomics and personalized medicine. Additionally, this activity provided students with an opportunity to work with a large dataset and use the information to impact clinical decision making. This activity has two cases, takes student groups approximately 2 hours to complete, and requires internet access. Case materials are available through the learning management system Canvas, and include open-ended questions to guide students through the cases. In these cases students explore the functional significance of different alleles of a panel of cytochrome P450 genes. The group activity has the students examine a large data set of cytochrome P450 genes and cognate alleles to determine their prevalence in the local population and calculate the individuals’ gene scores. The students are then asked to explain the impact of the genotype (or gene score) on the resulting patient phenotype (i.e. the functional significance of the genotype). The first case involves a breast cancer survivor support group in which patients taking Taxol discuss lack of adequate pain relief from opioids and the potential impact of concomitant use of natural compounds/supplements on drug metabolism. The second case involves a patient presenting with recurrent stroke-like symptoms despite being on the anticoagulant medication clopidogrel. The patient is initially suspected to be non-compliant, but is later determined to be a poor metabolizer of the anticoagulant clopidogrelto its active form thus decreasing its efficacy. The expertise of the IUSM Medical Genetics research faculty was leveraged to provide a large data set of cytochrome P450 genes and cognate alleles. The selection of cytochrome P450 was based upon delivering content focused on the biochemistry of the enzyme system and provided an opportunity to highlight the drug interaction database available through IUSM Clinical Pharmacology (The FlockhartTable™ ; https://drug-interactions.medicine.iu.edu/). The addition of natural compounds was to draw students’ attention to the Natural Medicines database, which is the recommended source for evidence-based data on complementary and alternative medicine. Natural Medicines is available through the Ruth Lilly Medical Library and can be searched by substance or condition. It provides both a summary of the literature available on substances as well as the level of evidence or quality of studies done on the substance
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