5,729 research outputs found

    Probing light WIMPs with directional detection experiments

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    The CoGeNT and CRESST WIMP direct detection experiments have recently observed excesses of nuclear recoil events, while the DAMA/LIBRA experiment has a long standing annual modulation signal. It has been suggested that these excesses may be due to light mass, m_chi ~ 5-10 GeV, WIMPs. The Earth's motion with respect to the Galactic rest frame leads to a directional dependence in the WIMP scattering rate, providing a powerful signal of the Galactic origin of any recoil excess. We investigate whether direct detection experiments with directional sensitivity have the potential to observe this anisotropic scattering rate with the elastically scattering light WIMPs proposed to explain the observed excesses. We find that the number of recoils required to detect an anisotropic signal from light WIMPs at 5 sigma significance varies from 7 to more than 190 over the set of target nuclei and energy thresholds expected for directional detectors. Smaller numbers arise from configurations where the detector is only sensitive to recoils from the highest speed, and hence most anisotropic, WIMPs. However, the event rate above threshold is very small in these cases, leading to the need for large experimental exposures to accumulate even a small number of events. To account for this sensitivity to the tail of the WIMP velocity distribution, whose shape is not well known, we consider two exemplar halo models spanning the range of possibilities. We also note that for an accurate calculation the Earth's orbital speed must be averaged over. We find that the exposures required to detect 10 GeV WIMPs at a WIMP-proton cross-section of 10^-4 pb are of order 10^3 kg day for a 20 keV energy threshold, within reach of planned directional detectors. Lower WIMP masses require higher exposures and/or lower energy thresholds for detection.Comment: 9 pages, 6 figures, v2: version to appear in Phys. Rev. D with additional discussio

    Directional Statistics for WIMP direct detection II: 2-d read-out

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    The direction dependence of the WIMP direct detection rate provides a powerful tool for distinguishing a WIMP signal from possible backgrounds. We study the the number of events required to discriminate a WIMP signal from an isotropic background for a detector with 2-d read-out using non-parametric circular statistics. We also examine the number of events needed to i) detect a deviation from rotational symmetry, due to flattening of the Milky Way halo and ii) detect a deviation in the mean direction due to a tidal stream. If the senses of the recoils are measured then of order 20-70 events (depending on the plane of the 2-d read out) will be sufficient to reject isotropy of the raw recoil angles at 90% confidence. If the senses can not be measured these number increase by roughly two orders of magnitude (compared with an increase of one order of magnitude for the case of full 3-d read-out). The distributions of the reduced angles, with the (time dependent) direction of solar motion subtracted, are far more anisotropic, however, and if the isotropy tests are applied to these angles then the numbers of events required are similar to the case of 3-d read-out. A deviation from rotational symmetry will only be detectable if the Milky Way halo is significantly flattened. The deviation in the mean direction due to a tidal stream is potentially detectable, however, depending on the density and direction of the stream.Comment: 11 pages, 4 figures, version to appear in Phys. Rev. D, added consideration of other detector locations and discussion of optimal plane for maximum anisotropy in signal, conclusions unchange

    Computational Tools and Experimental Methods for the Development of Passive Prosthetic Feet

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    Modern prosthetic foot designs are incredibly diverse in comparison to what was o↵ered to amputees at the turn of the millennium. Powered ankles can supply natural levels of joint torque, whilst passive feet continue to optimise for kinematic goals. However, most passive feet still do not solve the issue of unhealthy loads, and an argument can be made that optimisation methods have neglected the less active and elderly amputee. This thesis creates a framework for a novel approach to prosthetic foot optimisation by focusing on the transitionary motor tasks of gait initiation and termination.An advanced FEA model has been created in ANSYS® using boundary con-ditions derived from an ISO testing standard that replicates stance phase loading. This model can output standard results found in the literature and goes beyond by parameterising the roll-over shape within the software using custom APDL code. Extensive contact exploration and an experimental study have ensured the robustness of the model. Subject force and kinematic data can be used for specific boundary conditions, which would allow for easy adaptation to the transitionary motor tasks.This FEA model has been used in the development of prosthetic experiment tool, which can exchange helical springs to assess e↵ects of small changes in sti↵-ness on gait metrics. A rigorous design methodology was employed for all compo-nents, including parametric design studies, response surface optimisation, and ISO level calculations. The design has been manufactured into a working prototype and is ready for clinical trials to determine its efficacy.The conclusion of this framework is in the development of an experimental method to collect subject data for use in the models. A pilot study uncovered reliable protocols, which were then verified with ANOVA statistics. Proportional ratios were defined as additions to metric peak analyses already found in the liter-ature. These tools are ready for deployment in full clinical trials with amputees, so that a new prosthetic optimisation pathway can be discovered for the benefit of less active or elderly amputees

    Intensive Cultural Resources Survey for the Proposed Buena Vista Road Improvements

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    The Federal Highway Administration (FHWA) Central Federal Lands Highway Division (CFLHD) is proposing to improve Buena Vista Road, a two-lane, paved roadway accessing the Laguna Atascosa National Wildlife Refuge (NWR) in Cameron County, Texas. While the project is located within the Laguna Atascosa NWR, the roadway falls under the jurisdiction of Cameron County. The proposed project includes pavement reconstruction and widening by pulverizing and overlaying Buena Vista Road along a 2.7-mile (4.35 kilometer [km]) segment from the intersection of General Brant Road to the north entrance of the Laguna Atascosa NWR (Figure 1-1). The improvements will also include the installation of roadside ditches, signage, and speed humps. The survey corridor will comprise the approximately 65-feet (ft) wide (32.5 ft on either side of the centerline) existing road Right-of-Way (ROW), and areas adjacent to the Laguna Atascosa NWR will extend an additional two ft beyond the existing ROW fence line. The survey will extend 100 ft past road/driveway intersections, where the survey corridor will also be limited to the existing ROW (65 ft in width). The maximum depth of impacts for the proposed project is 3.5 ft (1.1 meters [m]) below surface in order to replace the existing culverts. As a county road, the proposed project is required to be in compliance with Chapter 191 of the Texas Natural Resources Code, also known as the Antiquities Code of Texas (13 Texas Administrative Code [TAC] 26.12). The purpose of the cultural resources investigation is to conduct an inventory to determine the presence/absence of cultural resources (36 Code of Federal Regulations [CFR] 800.4) and to evaluate identified resources for their eligibility for inclusion in the National Register of Historic Places (NRHP), as per Section 106 (36 CFR 800) of the National Historic Preservation Act of 1966, as amended, or as a designated State Antiquities Landmark (SAL) under the Antiquities Code of Texas (13 TAC 26.12). Archaeology fieldwork was completed by Principal Investigator Ben Fullerton and Archaeology Field Technicians Katie Alexander and Corinne Harvey on July 2–7, 2017. This survey was conducted under Texas Antiquities Permit Number 8089. The fieldwork for historic resources was conducted by HDR architectural historian Kristin Morgan on July 5–6, 2017. During the course of the archaeological field survey, the APE was subjected to pedestrian survey, shovel testing, and photo-documentation. The survey resulted in a 100 percent pedestrian walkover and a staggered 100-m shovel test transect for the entire length of the APE. A total of 44 shovel tests were excavated, none of which yielded cultural materials. All shovel tests were terminated prior to reaching 80 cmbs (32 inbs) due to encounter with subsoil or disturbance. A scatter of seven oyster shell fragments was identified on the ground surface within the eastern ROW at the intersection of Buena Vista Road and Ocelot Road. The location of the scatter is approximately 150 m (492 feet) east of Site 41CF115, which consists of a campsite yielding bone, as well as shell. Pedestrian survey and shovel testing near the scatter encountered disturbed soils and no cultural material. Due to the lack of associated cultural material and distance of the scatter from 41CF115, it is unclear if the shell fragments are archaeological or modern deposits. Overall, no definitive cultural materials were identified during the intensive survey. During the course of the field survey for historic resources, six resources built prior to 1972 were identified within the APE: Buena Vista Road, two vehicular access gates onto unpaved refuge roads, and three culverts. Two of the culverts span Buena Vista Road, and the other spans an unpaved access road for the refuge. None of the culverts have any visible marks to designate construction date or under whose authority it was installed. None of the six historic resources are recommended eligible for NRHP listing due to lack of significance. In accordance with and 13 TAC 26.12, no further cultural resources investigations are recommended for the presently-defined APE, and the proposed Buena Vista Road improvements project may proceed. However, in the event that any archaeological deposits are encountered during construction, work should cease and the Texas Historical Commission (THC) should be notified. All records and materials generated by this project will be permanently curated at the Center for Archaeological Studies at Texas State University in San Marcos, Texas

    Sleaze: we have the data, we have the outcry, but it is still unclear whether these will result in institutional change

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    Ben Worthy and Cat Morgan offer some thoughts on the role of data in the second jobs scandal and the potential for change in the light of recent developments

    Using Groupware in a Classroom Environment

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    As the use of project teams and work groups continues to grow, employers are beginning to value and to recruit those students who understand how to perform well in groups. This interest creates the logical opportunity to introduce both the concepts and practical applications of groupware (Group Supports Systems (GSS), Group Decision Support Systems (GDSS) and Electronic Meeting Systems (EMS)) into business school courses. This introduction provides students with the conceptual understanding, basic skills and fundamental knowledge about working and being productive in teams. This article describes several tips on how to use groupware in a classroom to help meet this demand for team-oriented education