1,549 research outputs found

    Force-insensitive optical cavity

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    We describe a rigidly-mounted optical cavity which is insensitive to inertial forces acting in any direction and to the compressive force used to constrain it. The design is based on a cubic geometry with four supports placed symmetrically about the optical axis in a tetrahedral configuration. To measure the inertial force sensitivity, a laser is locked to the cavity while it is inverted about three orthogonal axes. The maximum acceleration sensitivity is 2.5\times10^-11/g (where g=9.81 ms^-2), the lowest passive sensitivity to be reported for an optical cavity.Comment: 3 pages, 3 figures, journa

    How Cities Can Combat Illegal Guns and Gun Violence

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    Though gun violence peaked in American cities in the early 1990s, firearms are still used in more than 30 homicides per day in the U.S.One major challenge is how to stanch the flow of guns to criminals. Researchers from the School's Center for Gun Policy and Research have recently zeroed in on illegal sales by licensed dealers (the dominant means of diverting guns into illegal markets). These sales include unrecorded, "off the books" transactions and "straw purchases" in which a person unable to pass a federal background check relies on another individual for the purchase.Daniel Webster, MPH, ScD '91, Center co-director, wants to increase the accountability of gun dealers. This report outlines how to reduce illegal gun trafficking, reduce illegal gun carrying, and use technology to prevent gun violence

    Improved Monte Carlo Simulations of Massive Quarks

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    Motivated by the interest in top and bottom quark production processes at the LHC, we study the simulation of heavy quarks in the Herwig 7 Monte Carlo event generator. We first present a much improved treatment of heavy quarks in the dipole shower in Herwig 7 and extend the shower to handle decays of massive coloured particles. Taking advantage of these developments, we perform an in-depth study of the simulation of top quark pair production at the LHC, paying particular attention to the parton shower and matching uncertainties involved. Next we implement an algorithm in the dipole shower to include spin correlation effects. Using this algorithm we can produce accurate predictions of the angular distributions of top quark decay products in top pair production at the LHC. Following this we describe a modified version of the veto algorithm used in parton showers that enables the incorporation of weights. We show that the algorithm can be used to significantly reduce the CPU time required to evaluate the effects of scale variations in parton showers. Finally, we investigate the description of gluon splittings to heavy quark pairs in the angular-ordered and dipole parton showers in Herwig 7. While both parton showers correctly reproduce the leading-logarithmic term in the description of these splittings, we find that the effects of subleading contributions are significant

    Sexually-Transmitted Diseases Robert C.Noble1979Medical Examination Publishing Co., IncGarden City, New York166$8

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    Strategic Planning in Human Service Agencies

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    Recent public policy initiatives including deinstitutionalization, deregulation, decentralization, and privatization have resulted in: (a) rapid growth in the number of private not-for-profit organizations; and, (b) competitive environments. These conditions have forced agencies to examine their planning processes to determine if agency goals are appropriate for meeting market demands. An exploratory study of 154 human service agencies examined if and how strategic planning was used to respond to these conditions. The Chief Executive Officers for those agencies reported that strategic planning was replacing incremental planning as a preferred planning model. However, the choice resulted because of pressure from outside influentials not because of a perception of increased competition. Despite this, agencies choosing a strategic planning model were generally rigorous in its application. One-half of the sample reported a major change outcome for the agency as a result of the planning process but broad participation by stakeholders impeded substantial change. Questions are raised about using strategic planning when major change is not sought and/or broad participation by stakeholders is important
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