20,044 research outputs found

    Angular correlations in single-top-quark and Wjj production at next-to-leading order

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    I demonstrate that the correlated angular distributions of final-state particles in both single-top-quark production and the dominant Wjj backgrounds can be reliably predicted. Using these fully-correlated angular distributions, I propose a set of cuts that can improve the single-top-quark discovery significance by 25%, and the signal to background ratio by a factor of 3 with very little theoretical uncertainty. Up to a subtlety in t-channel single-top-quark production, leading-order matrix elements are shown to be sufficient to reproduce the next-to-leading order correlated distributions.Comment: 22 pages, 23 figs, RevTex4, fixed typos, to appear in Phys. Rev.

    Google Earth Visualizations: Preview and Delivery of Hydrographic and Other Marine Datasets

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    Existing hydrographic data analysis and visualization tools are very powerful, but lack easy access to web data management tools. Virtual globe software provides a gateway to a host of important data products in formats usable by specialized tools such as CARIS, Fledermaus, and Arc/Info. With virtual globe interfaces, users see complimentary and consistent geographic representations of available data in an easy-tonavigate format. We present a preview of visualizations that build upon virtual globe software. These examples are viewed in Google Earth, but could also be implemented in a number of alternative programs (e.g. NASA World Wind, Dapple, OSSIM Planet). We have assembled Google Earth visualizations from three datasets to illustrate each of the four primary types of data (handle point, line, area, and time data). The USCG Marine Information for Safety and Law Enforcement (MISLE) database of ship incidents illustrates point data. A short sample of the USCG National Automatic Identification System logs (N-AIS) demonstrates rendering of line data. Area data is exemplified in the United Nations Convention f the Law of the Sea (UNCLOS) multibeam bathymetry. Point, line and area data are combined to present a preview of S57 chart information. Finally, the MISLE database uses time to show maritime incidents that occurred in US waterways. The visualizations for our initial work were created with hand coding and small scripts. However, tools such as Fledermaus and RockWare have added Google Earth export functionality that makes authoring Google Earth resources easy to construct. For large dataset that require additional processing and analyses, Google Earth visualizations can offer users a range of download formats and suggest what software to use. We believe that this virtual globe-based-approach can make geospatial data sets more widely accessible via the world-wide-web

    Correlation of free-flight turbulent heat-transfer data from axisymmetric bodies with compressible flat-plate relationships

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    Correlation of free flight turbulent heat transfer data from axisymmetric bodies with compressible flat plate relationship

    Standard model explanation of a CDF dijet excess in Wjj

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    We demonstrate the recent observation of a peak in the dijet invariant mass of the Wjj signal observed by the CDF Collaboration can be explained as the same upward fluctuation observed by CDF in single-top-quark production. In general, both t-channel and s-channel single-top-quark production produce kinematically induced peaks in the dijet spectrum. Since CDF used a Monte Carlo simulation to subtract the single-top backgrounds instead of data, a peak in the dijet spectrum is expected. The D0 Collaboration has a small upward fluctuation in their published t-channel data; and hence we predict they would see at most a small peak in the dijet invariant mass spectrum of Wjj if they follow the same procedure as CDF.Comment: 3 pg., 2 figs, revtex, minor clarifications, to appear in Phys. Rev.

    Implicit Encoding Explored Through the Flankers Task

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    The problem we examined involves the process of selective attention and its relationship with implicit and explicit memory encoding. One task that has been used previously to examine selective attention is the flankers task, which consists of three items with the center item being the item that requires a response - the target. The two items on either side of the target are the “irrelevant” flankers. The correlated flanker effect is the difference in reaction time between the trials in which the flankers that are correlated with the correct response are present (congruent) and trials in which the flankers correlated with the opposite response are present (incongruent). Participants are about 30ms faster to respond on congruent trials than incongruent trials (Miller, 1987). The current study sought to further understand the mechanisms behind this selective attention task by asking, is incidental (implicit) learning of irrelevant information encoded in memory differently than intentional (explicit) learning? Participants completed a correlated flankers task. Half the participants were told to expect a memory task for the flankers and half were not given warning. Participants also completed an implicit memory task and an explicit memory questionnaire. Response times (RT) on congruent correlation trials and on incongruent correlation trials were measured. In the implicit memory task, participants’ responding to neutral targets surrounded by previously shown flankers was measured. We hypothesized that the greater recall of the irrelevant information in the implicit task over the explicit task. Results demonstrated no presence of the flanker effect yet participants were significantly more accurate than chance on the implicit task but not the explicit task

    Individual Control of Risk: Seat Belt Use, Subjective Norms and the Theory of Reasoned Action

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    When faced with a risk for which an inexpensive solution is available, individuals often choose the risk rather than the solution. Protection from certain kinds of risks, e.g., using seat belts or condoms or insulating against radon, is largely under personal control, but individuals often choose not to comply with behaviors which would reduce the risk. The Theory of Reasoned Action (TRA) has been used to predict when individuals will comply. The authors attempted to validate aspects of the TRA by the use of scenarios. Factor analysis of their data supports the theory that intention is a major determinate of behavior but fails to establish the influence of scenarios on subjects\u27 intention to wear seat belts

    Evaluation of MOSTAS computer code for predicting dynamic loads in two bladed wind turbines

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    Calculated dynamic blade loads were compared with measured loads over a range of yaw stiffnesses of the DOE/NASA Mod-O wind turbine to evaluate the performance of two versions of the MOSTAS computer code. The first version uses a time-averaged coefficient approximation in conjunction with a multi-blade coordinate transformation for two bladed rotors to solve the equations of motion by standard eigenanalysis. The second version accounts for periodic coefficients while solving the equations by a time history integration. A hypothetical three-degree of freedom dynamic model was investigated. The exact equations of motion of this model were solved using the Floquet-Lipunov method. The equations with time-averaged coefficients were solved by standard eigenanalysis

    An Information NEXUS: The NASA Global Hawk Link Module

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    The Link Module described in this paper was first developed for the NASA Global Hawk Pacific Mission (GloPAC), four flights of 30 hour duration, supporting the Aura Validation Experiment (AVE). Its second use was during the Genesis and Rapid Intensification Processes (GRIP) experiment, a NASA Earth Science field experiment to better understand how tropical storms form and develop into major hurricanes. In these missions, the Link module negotiated all communication over the high bandwidth Ku satellite link, archived al the science data from onboard experiments in a spatially enable database, routed command and control of the instruments from the Global Hawk Operations Center, and retransmitted select data sets directly to experimenters control and analysis systems. The availability of aggregated information from collections of sensors, and remote control capabilities, in real-time, is revolutionizing the way Airborne Science is being conducted. Also described is the next generation Link Module now being designed and tested to support the NASA Earth Venture missions, the Hurricane and Severe Storm Sentinel (HS3) mission, and Airborne Tropical Tropopause Experiment (ATTREX) mission. Advanced data fusion technologies being developed will further advance the Scientific productivity, flexibility and robustness of these systems. Historically, the Link module evolved from the instrument and communication interface controller used by NASA's Pathfinder and Pathfinder plus solar powered UAS's in the late 1990's. It later was expanded for use in the AIRDAS four channel scanner flown on the NASA Altus UAS, and then again to a module in the AMS twelve channel multispectral scanner flying on the NASA (Predator-b) Ikhana UAS. The current system is the next step in the evolution, a multi board system packaged in a Curtiss Wright MIL-spec, flight qualified enclosure

    Can cluster environment modify the dynamical evolution of spiral galaxies?

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    Over the past decade many effects of the cluster environment on member galaxies have been established. These effects are manifest in the amount and distribution of gas in cluster spirals, the luminosity and light distributions within galaxies, and the segregation of morphological types. All these effects could indicate a specific dynamical evolution for galaxies in clusters. Nevertheless, a more direct evidence, such as a different mass distribution for spiral galaxies in clusters and in the field, is not yet clearly established. Indeed, Rubin, Whitmore, and Ford (1988) and Whitmore, Forbes, and Rubin (1988) (referred to as RWF) presented evidence that inner cluster spirals have falling rotation curves, unlike those of outer cluster spirals or the great majority of field spirals. If falling rotation curves exist in centers of clusters, as argued by RWF, it would suggest that dark matter halos were absent from cluster spirals, either because the halos had become stripped by interactions with other galaxies or with an intracluster medium, or because the halos had never formed in the first place. Even if they didn't disagree with RWF, other researchers pointed out that the behaviour of the slope of the rotation curves of spiral galaxies (in Virgo) is not so clear. Amram, using a different sample of spiral galaxies in clusters, found only 10% of declining rotation curves (2 declining vs 17 flat or rising) in opposition to RWF who find about 40% of declining rotation curves in their sample (6 declining vs 10 flat or rising), we will hereafter briefly discuss the Amram data paper and compare it to the results of RWF. We have measured the rotation curves for a sample of 21 spiral galaxies in 5 nearby clusters. These rotation curves have been constructed from detailed two-dimensional maps of each galaxy's velocity field as traced by emission from the Ha line. This complete mapping, combined with the sensitivity of our CFHT 3.60 m. + Perot-Fabry + CCD observations, allows the construction of high-quality rotation curves. Details concerning the acquisition and reduction procedures of the data are given in Amram. We present and discuss our preliminary analysis and compare them with RWF's results
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