15,407 research outputs found

    Application of Risk Informed Decision Making to Highly Reliable Three Dimensionally Woven Thermal Protection System for Mars Sample Return

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    The NASA Risk Informed Decision Making process is used to assess a trade space of three dimensionally woven thermal protection systems for application to the Mars Sample Return Earth Entry Vehicle. Candidate architectures are assessed based on mission assurance, technical development, cost, and schedule risk. Assessment methodology differed between the architectures, utilizing a four-point quantitative scale for mission assurance and technical development and highly tailored PERT techniques for cost and schedule. Risk results are presented, in addition to a review of RIDM effectiveness for this application

    The properties of kaonic nuclei in relativistic mean-field theory

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    The static properties of some possible light and moderate kaonic nuclei, from C to Ti, are studied in the relativistic mean-field theory. The 1s and 1p state binding energies of KK^- are in the range of 739673\sim 96 MeV and 226322\sim 63 MeV, respectively. The binding energies of 1p states increase monotonically with the nucleon number A. The upper limit of the widths are about 42±1442\pm 14 MeV for the 1s states, and about 71±1071\pm 10 MeV for the 1p states. The lower limit of the widths are about 12±412\pm 4 MeV for the 1s states, and 21±321\pm 3 MeV for the 1p states. If V030V_{0}\leq 30 MeV, the discrete KK^- bound states should be identified in experiment. The shrinkage effect is found in the possible kaonic nuclei. The interior nuclear density increases obviously, the densest center density is about 2.1ρ02.1\rho_{0}.Comment: 9 pages, 2 tables and 1 figure, widths are considered, changes a lo

    Applications of Trajectory Data From the Perspective of a Road Transportation Agency: Literature Review and Maryland Case Study

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    Transportation agencies have an opportunity to leverage increasingly-available trajectory datasets to improve their analyses and decision-making processes. However, this data is typically purchased from vendors, which means agencies must understand its potential benefits beforehand in order to properly assess its value relative to the cost of acquisition. While the literature concerned with trajectory data is rich, it is naturally fragmented and focused on technical contributions in niche areas, which makes it difficult for government agencies to assess its value across different transportation domains. To overcome this issue, the current paper explores trajectory data from the perspective of a road transportation agency interested in acquiring trajectories to enhance its analyses. The paper provides a literature review illustrating applications of trajectory data in six areas of road transportation systems analysis: demand estimation, modeling human behavior, designing public transit, traffic performance measurement and prediction, environment and safety. In addition, it visually explores 20 million GPS traces in Maryland, illustrating existing and suggesting new applications of trajectory data

    Do-it-yourself: construction of a custom cDNA macroarray platform with high sensitivity and linear range

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    Background: Research involving gene expression profiling and clinical applications, such as diagnostics and prognostics, often require a DNA array platform that is flexibly customisable and cost-effective, but at the same time is highly sensitive and capable of accurately and reproducibly quantifying the transcriptional expression of a vast number of genes over the whole transcriptome dynamic range using low amounts of RNA sample. Hereto, a set of easy-to-implement practical optimisations to the design of cDNA-based nylon macroarrays as well as sample (33)P-labeling, hybridisation protocols and phosphor screen image processing were analysed for macroarray performance. Results: The here proposed custom macroarray platform had an absolute sensitivity as low as 50,000 transcripts and a linear range of over 5 log-orders. Its quality of identifying differentially expressed genes was at least comparable to commercially available microchips. Interestingly, the quantitative accuracy was found to correlate significantly with corresponding reversed transcriptase - quantitative PCR values, the gold standard gene expression measure (Pearson's correlation test p < 0.0001). Furthermore, the assay has low cost and input RNA requirements (0.5 mu g and less) and has a sound reproducibility. Conclusions: Results presented here, demonstrate for the first time that self-made cDNA-based nylon macroarrays can produce highly reliable gene expression data with high sensitivity and covering the entire mammalian dynamic range of mRNA abundances. Starting off from minimal amounts of unamplified total RNA per sample, a reasonable amount of samples can be assayed simultaneously for the quantitative expression of hundreds of genes in an easily customisable and cost-effective manner

    Angular Dependence in Proton-Proton Correlation Functions in Central 40Ca+40Ca^{40}Ca+^{40}Ca and 48Ca+48Ca^{48}Ca+^{48}Ca Reactions

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    The angular dependence of proton-proton correlation functions is studied in central 40Ca+40Ca^{40}Ca+^{40}Ca and 48Ca+48Ca^{48}Ca+^{48}Ca nuclear reactions at E=80 MeV/A. Measurements were performed with the HiRA detector complemented by the 4π\pi Array at NSCL. A striking angular dependence in the laboratory frame is found within p-p correlation functions for both systems that greatly exceeds the measured and expected isospin dependent difference between the neutron-rich and neutron-deficient systems. Sources measured at backward angles reflect the participant zone of the reaction, while much larger sources observed at forward angles reflect the expanding, fragmenting and evaporating projectile remnants. The decrease of the size of the source with increasing momentum is observed at backward angles while a weaker trend in the opposite direction is observed at forward angles. The results are compared to the theoretical calculations using the BUU transport model.Comment: 8 pages, 3 figures, submitted to PR

    Interplay of initial deformation and Coulomb proximity on nuclear decay

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    Alpha particles emitted from an excited projectile-like fragment (PLF*) formed in a peripheral collision of two intermediate-energy heavy ions exhibit a strong preference for emission towards the target-like fragment (TLF). The interplay of the initial deformation of the PLF* caused by the reaction, Coulomb proximity, and the rotation of the PLF* results in the observed anisotropic angular distribution. Changes in the shape of the angular distribution with excitation energy are interpreted as being the result of forming more elongated initial geometries in the more peripheral collisions.Comment: 4 figure

    "Freshwater killer whales": beaching behavior of an alien fish to hunt land birds

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    The behavioral strategies developed by predators to capture and kill their prey are fascinating, notably for predators that forage for prey at, or beyond, the boundaries of their ecosystem. We report here the occurrence of a beaching behavior used by an alien and large-bodied freshwater predatory fish (Silurus glanis) to capture birds on land (i.e. pigeons, Columbia livia). Among a total of 45 beaching behaviors observed and filmed, 28% were successful in bird capture. Stable isotope analyses (δ¹³C and δ¹⁵N) of predators and their putative prey revealed a highly variable dietary contribution of land birds among individuals. Since this extreme behavior has not been reported in the native range of the species, our results suggest that some individuals in introduced predator populations may adapt their behavior to forage on novel prey in new environments, leading to behavioral and trophic specialization to actively cross the water-land interface
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