4,384 research outputs found

    Designing and Operating Safe and Secure Transit Systems: Assessing Current Practices in the United States and Abroad, MTI Report 04-05

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    Public transit systems around the world have for decades served as a principal venue for terrorist acts. Today, transit security is widely viewed as an important public policy issue and is a high priority at most large transit systems and at smaller systems operating in large metropolitan areas. Research on transit security in the United States has mushroomed since 9/11; this study is part of that new wave of research. This study contributes to our understanding of transit security by (1) reviewing and synthesizing nearly all previously published research on transit terrorism; (2) conducting detailed case studies of transit systems in London, Madrid, New York, Paris, Tokyo, and Washington, D.C.; (3) interviewing federal officials here in the United States responsible for overseeing transit security and transit industry representatives both here and abroad to learn about efforts to coordinate and finance transit security planning; and (4) surveying 113 of the largest transit operators in the United States. Our major findings include: (1) the threat of transit terrorism is probably not universal—most major attacks in the developed world have been on the largest systems in the largest cities; (2) this asymmetry of risk does not square with fiscal politics that seek to spread security funding among many jurisdictions; (3) transit managers are struggling to balance the costs and (uncertain) benefits of increased security against the costs and (certain) benefits of attracting passengers; (4) coordination and cooperation between security and transit agencies is improving, but far from complete; (5) enlisting passengers in surveillance has benefits, but fearful passengers may stop using public transit; (6) the role of crime prevention through environmental design in security planning is waxing; and (7) given the uncertain effectiveness of antitransit terrorism efforts, the most tangible benefits of increased attention to and spending on transit security may be a reduction in transit-related person and property crimes

    Spatial dependency between task positive and task negative networks

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    Functional neuroimaging reveals both relative increases (task-positive) and decreases (task-negative) in neural activation with many tasks. There are strong spatial similarities between many frequently reported task-negative brain networks, which are often termed the default mode network. The default mode network is typically assumed to be a spatially-fixed network; however, when defined by task-induced deactivation, its spatial distribution it varies depending on what specific task is being performed. Many studies have revealed a strong temporal relationship between task-positive and task-negative networks that are important for efficient cognitive functioning and here. Here, using data from four different cognitive tasks taken from two independent datasets, we test the hypothesis that there is also a fundamental spatial relationship between them. Specifically, it is hypothesized that the distance between task positive and negative-voxels is preserved despite different spatial patterns of activation and deactivation being evoked by different cognitive tasks. Here, we show that there is lower variability in the distance between task-positive and task-negative voxels across four different sensory, motor and cognitive tasks than would be expected by chance - implying that deactivation patterns are spatially dependent on activation patterns (and vice versa) and that both are modulated by specific task demands. We propose that this spatial relationship may be the macroscopic analogue of microscopic neuronal organization reported in sensory cortical systems, and we speculate why this spatial organization may be important for efficient sensorimotor and cognitive functioning.Comment: 16 pages, 4 figure

    Examining the impact of coaching for independence in adventure sports

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    This study of adventure sports learners expands on earlier work on adventure sports coaching. We examine learners’ perceptions of their coaching and its effect on their self-efficacy and independence as adventure sports performers. We utilise a convergent mixed approach that deploys the Outdoor Recreation Self-Efficacy Scale, pre- and post-coaching, and a reflexive thematic analysis of semi-structured interviews. The findings indicate improved self-efficacy and greater independence as a result of the coach’s practice, supporting our initial conjecture that the adventure sports coaches in this study developed independence as a definable outcome of their coaching practice

    Evidence for a very slow X-ray pulsar in 2S0114+650 from RXTE All-Sky Monitor Observations

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    Rossi X-ray Timing Explorer (RXTE) All-Sky Monitor (ASM) observations of the X-ray binary 2S0114+650 show modulations at periods close to both the optically derived orbital period (11.591 days) and proposed pulse period (~ 2.7 hr). The pulse period shows frequency and intensity variability during the more than 2 years of ASM observations analyzed. The pulse properties are consistent with this arising from accretion onto a rotating neutron star and this would be the slowest such period known. The shape of the orbital light curve shows modulation over the course of the entire orbit and a comparison is made with the orbital light curve of Vela X-1. However, the expected phase of eclipse, based on an extrapolation of the optical ephemeris, does not correspond with the observed orbital minimum. The orbital period derived from the ASM light curve is also slightly longer than the optical period.Comment: To be published in the Astrophysical Journal, 1999, volume 511. 9 figure

    Mixed valency in cerium oxide crystallographic phases: Determination of valence of the different cerium sites by the bond valence method

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    We have applied the bond valence method to cerium oxides to determine the oxidation states of the Ce ion at the various site symmetries of the crystals. The crystals studied include cerium dioxide and the two sesquioxides along with some selected intermediate phases which are crystallographically well characterized. Our results indicate that cerium dioxide has a mixed-valence ground state with an f-electron population on the Ce site of 0.27 while both the A- and C-sesquioxides have a nearly pure f^1 configuration. The Ce sites in most of the intermediate oxides have non-integral valences. Furthermore, many of these valences are different from the values predicted from a naive consideration of the stoichiometric valence of the compound

    Precise Measurement of the b-Quark Fragmentation Function in Z0 Boson Decays

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    We have developed a new technique for inclusive reconstruction of the energy of B hadrons. The excellent efficiency and resolution of this technique allow us to make the most precise determination of the b-quark fragmentation function, using e[superscript +]e[superscript -]→Z[superscript 0] decays recorded in the SLAC Large Detector experiment. We compared our measurement with the predictions of a number of fragmentation models. We excluded several of these models and measured the average scaled energy of weakly decaying B hadrons to be 〈x[subscript B]〉 = 0.714±0.005(stat)±0.007(syst)±0.002 (model dependence).Istituto Nazionale di Fisica Nucleare of ItalyJapan-U.S. Cooperative Research Project on High Energy PhysicsDepartment of EnergyU.K. Particle Physics and Astronomy Research CouncilKorea Science and Engineering Foundatio

    The analysis of rapidly developing fog at the Kennedy Space Center

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    This report documents fog precursors and fog climatology at Kennedy Space Center (KSC) Florida from 1986 to 1990. The major emphasis of this report focuses on rapidly developing fog events that would affect the less than 7-statute mile visibility rule for End-Of-Mission (EOM) Shuttle landing at KSC (Rule 4-64(A)). The Applied Meteorology Unit's (AMU's) work is to: develop a data base for study of fog associated weather conditions relating to violations of this landing constraint; develop forecast techniques or rules-of-thumb to determine whether or not current conditions are likely to result in an acceptable condition at landing; validate the forecast techniques; and transition techniques to operational use. As part of the analysis the fog events were categorized as either advection, pre-frontal or radiation. As a result of these analyses, the AMU developed a fog climatological data base, identified fog precursors and developed forecaster tools and decision trees. The fog climatological analysis indicates that during the fog season (October to April) there is a higher risk for a visibility violation at KSC during the early morning hours (0700 to 1200 UTC), while 95 percent of all fog events have dissipated by 1600 UTC. A high number of fog events are characterized by a westerly component to the surface wind at KSC (92 percent) and 83 percent of the fog events had fog develop west of KSC first (up to 2 hours). The AMU developed fog decision trees and forecaster tools that would help the forecaster identify fog precursors up to 12 hours in advance. Using the decision trees as process tools ensures the important meteorological data are not overlooked in the forecast process. With these tools and a better understanding of fog formation in the local KSC area, the Shuttle weather support forecaster should be able to give the Launch and Flight Directors a better KSC fog forecast with more confidence
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