995 research outputs found

    2006 Status of the Momentum eXchange Electrodynamic Re-Boost (MXER) Tether Development

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    The MXER Tether technology development is a high-payoff/high-risk investment area within the NASA In-Space Propulsion Technology (ISPT) Program. The ISPT program is managed by the NASA Headquarters Science Mission Directorate and implemented by the Marshall Space Flight Center in Huntsville, Alabama. The MXER concept was identified and competitively ranked within NASA's comprehensive Integrated In-Space Transportation Plan (IISTP); an agency-wide technology assessment activity. The objective of the MXER tether project within ISPT is to advance the technological maturation level for the MXER system, and its subsystems, as well as other space and terrestrial tether applications. Recent hardware efforts have focused on the manufacturability of space-survivable high-strength tether material and coatings, high-current electrodynamic tether, lightweight catch mechanism, high-accuracy propagator/predictor code, and efficient electron collection/current generation. Significant technical progress has been achieved with modest ISPT funding to the extent that MXER has evolved to a well-characterized system with greater capability as the design has been matured. Synergistic efforts in high-current electrodynamic tethers and efficient electron collection/current generation have been made possible through SBIR and STTR support. The entire development endeavor was orchestrated as a collaborative team effort across multiple individual contracts and has established a solid technology resource base, which permits a wide variety of future space cable/tether applications to be realized

    Elliptic flow fluctuations in Au+Au collisions at sNN=200\sqrt{s_{NN}}=200 GeV

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    Please note that after these results were reported at Quark Matter 2006 and posted on the preprint server it was found that what is reported here as \textit{elliptic flow fluctuations}, should rather be taken as an upper limit on the fluctuations. Further analysis has shown that fitting the multiplicity dependence of the q-distribution does not enable one to disentangle non-flow and fluctuations. The data from the q-vector distrubution does not, therefore, exclude the case of zero fluctuations. The remainder of these proceedings we leave as they were originally reported.Comment: Statements regarding disentangling non-flow and fluctuations by examining the multiplicity dependence of the q-vector distributions are retracted: data presented here on elliptic flow fluctuations should be taken as an upper limit on the fluctuation

    Increases in ROPS Pricing from 2006-2012 and the Impact on ROPS Demand

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    In 2006, a social marketing campaign was developed to increase the installation of rollover protective structures (ROPS) on unprotected New York tractors. Using data gathered from the program\u27s hotline, the impact of price increases on farmers\u27 interest in ROPS is examined. Pricing data were obtained for all rigid ROPS kits commercially available in the U.S. since 2006. These data were stratified into two groups of ROPS suppliers: (1) tractor manufacturers that sell ROPS for their own tractors, referred to in this study as original equipment manufacturers (OEMs), and (2) aftermarket (AM) ROPS suppliers. The trend in price increases was contrasted with the change in the consumer price index (CPI), the probability of retrofitting within quintiles of cost was estimated, and the increase in ROPS prices over time was plotted The average price increase for a ROPS kit (excluding shipping and installation) over the six years of the study was 23.3% for OEM versus 60.5% for AM (p \u3c 0.0001). Out-of-pocket expenses held steady for OEM versus a six-year increase of $203 for AM (p = 0.098). The probability of a farmer retrofitting dropped monotonically from 66.9% in the lowest ROPS cost quintile to 23% in the highest. If these trends continue, the proportion of inquiries resulting in a ROPS retrofit will fall below 20% by 2020 for AM ROPS. Based on other trends identified in the literature, it is reasonable to assume that decreases in ROPS installation are likely to affect the tractor owners who are most likely to need these safety devices

    Symmetric Grothendieck polynomials, skew Cauchy identities, and dual filtered Young graphs

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    Symmetric Grothendieck polynomials are analogues of Schur polynomials in the K-theory of Grassmannians. We build dual families of symmetric Grothendieck polynomials using Schur operators. With this approach we prove skew Cauchy identity and then derive various applications: skew Pieri rules, dual filtrations of Young's lattice, generating series and enumerative identities. We also give a new explanation of the finite expansion property for products of Grothendieck polynomials

    A Gaussian Theory of Superfluid--Bose-Glass Phase Transition

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    We show that gaussian quantum fluctuations, even if infinitesimal, are sufficient to destroy the superfluidity of a disordered boson system in 1D and 2D. The critical disorder is thus finite no matter how small the repulsion is between particles. Within the gaussian approximation, we study the nature of the elementary excitations, including their density of states and mobility edge transition. We give the gaussian exponent η\eta at criticality in 1D and show that its ratio to η\eta of the pure system is universal.Comment: Revtex 3.0, 11 pages (4 figures will be sent through airmail upon request

    Human small cell lung cancer NYH cells resistant to the bisdioxopiperazine ICRF-187 exhibit a functional dominant Tyr165Ser mutation in the Walker A ATP binding site of topoisomerase IIα

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    AbstractBisdioxopiperazine anti-cancer agents are catalytic inhibitors of topoisomerase II which by unknown means lock the enzyme in a closed clamp form and inhibit its ATPase activity. In order to demarcate a putative pharmacophore, we here describe a novel Tyr165Ser mutation in the enzyme’s Walker A ATP binding site leading to specific bisdioxopiperazine resistance when transformed into a temperature-conditional yeast system. The Tyr165Ser mutation differed from a previously described Arg162Gln by being heterozygous and by purified Tyr165Ser enzyme being drug-resistant in a kinetoplast DNA decatenation enzymatic assay. This suggested dominant nature of Tyr165Ser was supported by co-transformation studies in yeast of plasmids carrying wild type and mutant genes. These results enable a model of the bisdioxopiperazine pharmacophore using the proposed asymmetric ATP hydrolysis of the enzyme

    Site-dependent nuclear dynamics in core-excited butadiene

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    Symmetry breaking and competition between electronic decay and nuclear dynamics are major factors determining whether the memory of the initial core-hole localisation in a molecule is retained long enough to affect fragmentation. We investigate the fate of core holes localised at different sites in the free 1,3 trans butadiene molecule by using synchrotron radiation to selectively excite core electrons from different C 1s sites to π* orbitals. Fragmentation involving bonds localised at the site of the core hole provides clear evidence for preferential bond breaking for a core hole located at the terminal carbon site, while the signature of localisation is weak for a vacancy on the central carbon site. The origin of this difference is attributed to out-of-plane vibrations, and statistical evaporation of protons for vacancies located at the central carbon sites
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