37,679 research outputs found

    Results of the AFRSI Detailed-Environment Test of the 0.035-Scale SSV Pressure-Loads Model 84-0 in the Ames 11X11 Ft. TWT and the Lewis 8X6 Ft. and 10X10 Ft. SWT (OA-310A, B, C), Volume 2

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    In order to support analysis of the STS-6 advanced flexible reusable surface insulation (AFRSI) anomaly, data were obtained for aerodynamic and aeroacoustic environments in affected areas of the orbiter. Data are presented in tabular form

    Laser phase noise to intensity noise conversion by lowest-order group-velocity dispersion in optical fiber: exact theory

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    An exact result for the spectral density of intensity variations that occur after propagation of ergodic light in a medium having lowest-order-only group-velocity dispersion is obtained and applied to the problem of semiconductor laser phase noise to intensity noise conversion in a single-mode optical fiber. It is shown that the intensity spectrum after propagation formally approaches, for a large laser linewidth or a long (or high-dispersion) fiber, the intensity spectrum of a thermal source having the same line shape as the laser

    Inverse Medea as a Novel Gene Drive System for Local Population Replacement: A Theoretical Analysis

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    One strategy to control mosquito-borne diseases, such as malaria and dengue fever, on a regional scale is to use gene drive systems to spread disease-refractory genes into wild mosquito populations. The development of a synthetic Medea element that has been shown to drive population replacement in laboratory Drosophila populations has provided encouragement for this strategy but has also been greeted with caution over the concern that transgenes may spread into countries without their consent. Here, we propose a novel gene drive system, inverse Medea, which is strong enough to bring about local population replacement but is unable to establish itself beyond an isolated release site. The system consists of 2 genetic components—a zygotic toxin and maternal antidote—which render heterozygous offspring of wild-type mothers unviable. Through population genetic analysis, we show that inverse Medea will only spread when it represents a majority of the alleles in a population. The element is best located on an autosome and will spread to fixation provided any associated fitness costs are dominant and to very high frequency otherwise. We suggest molecular tools that could be used to build the inverse Medea system and discuss its utility for a confined release of transgenic mosquitoes

    The Role of Neurocognitive Tests in the Assessment of Adult Attention-Deficit/Hyperactivity Disorder

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    Despite widespread recognition that attention-deficit/hyperactivity disorder (ADHD) is a lifelong neurodevelopmental disorder, optimal methods of diagnosis among adults remain elusive. Substantial overlap between ADHD symptoms and cognitive symptoms of other mental health conditions, such as depression and anxiety, and concerns about validity in symptom reporting have made the use of neuropsychological tests in ADHD diagnostic assessment appealing. However, past work exploring the potential diagnostic utility of neuropsychological tests among adults has often relied on a relatively small subset of tests, has failed to include symptom and performance validity measures, and often does not include comparison groups of participants with commonly comorbid disorders, such as depression. The current study examined the utility of an extensive neuropsychological measure battery for diagnosing ADHD among adults. Two hundred forty-six participants (109 ADHD, 52 depressed, 85 nondisordered controls) completed a multistage screening and assessment process, which included a clinical interview, self, and informant report on behavior rating scales, performance and symptom validity measures, and an extensive neuropsychological testing battery. Results indicated that measures of working memory, sustained attention, response speed, and variability best discriminated ADHD and non-ADHD participants. While single test measures provided performed poorly in identifying ADHD participants, analyses revealed that a combined approach using self and informant symptom ratings, positive family history of ADHD, and a reaction time (RT) variability measure correctly classified 87% of cases. Findings suggest that neuropsychological test measures used in conjunction with other clinical assessments may enhance prediction of adult ADHD diagnoses

    Lower bounds for polynomials using geometric programming

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    We make use of a result of Hurwitz and Reznick, and a consequence of this result due to Fidalgo and Kovacec, to determine a new sufficient condition for a polynomial fR[X1,...,Xn]f\in\mathbb{R}[X_1,...,X_n] of even degree to be a sum of squares. This result generalizes a result of Lasserre and a result of Fidalgo and Kovacec, and it also generalizes the improvements of these results given in [6]. We apply this result to obtain a new lower bound fgpf_{gp} for ff, and we explain how fgpf_{gp} can be computed using geometric programming. The lower bound fgpf_{gp} is generally not as good as the lower bound fsosf_{sos} introduced by Lasserre and Parrilo and Sturmfels, which is computed using semidefinite programming, but a run time comparison shows that, in practice, the computation of fgpf_{gp} is much faster. The computation is simplest when the highest degree term of ff has the form i=1naiXi2d\sum_{i=1}^n a_iX_i^{2d}, ai>0a_i>0, i=1,...,ni=1,...,n. The lower bounds for ff established in [6] are obtained by evaluating the objective function of the geometric program at the appropriate feasible points

    Numerical Studies of the Compressible Ising Spin Glass

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    We study a two-dimensional compressible Ising spin glass at constant volume. The spin interactions are coupled to the distance between neighboring particles in the Edwards-Anderson model with +/- J interactions. We find that the energy of a given spin configuration is shifted from its incompressible value, E_0, by an amount quadratic in E_0 and proportional to the coupling strength. We then construct a simple model expressed only in terms of spin variables that predicts the existence of a critical value of the coupling above which the spin-glass transition disappears.Comment: REVTeX, 4 pages, 4 figures. Submitted to Phys. Rev. Let

    Fourier transform spectroscopy of a spin-orbit coupled Bose gas

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    We describe a Fourier transform spectroscopy technique for directly measuring band structures, and apply it to a spin-1 spin-orbit coupled Bose-Einstein condensate. In our technique, we suddenly change the Hamiltonian of the system by adding a spin-orbit coupling interaction and measure populations in different spin states during the subsequent unitary evolution. We then reconstruct the spin and momentum resolved spectrum from the peak frequencies of the Fourier transformed populations. In addition, by periodically modulating the Hamiltonian, we tune the spin-orbit coupling strength and use our spectroscopy technique to probe the resulting dispersion relation. The frequency resolution of our method is limited only by the coherent evolution timescale of the Hamiltonian and can otherwise be applied to any system, for example, to measure the band structure of atoms in optical lattice potentials

    CP nonconservation in the leptonic sector

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    In this paper we use an exact method to impose unitarity on moduli of neutrino PMNS matrix recently determined, and show how one could obtain information on CP nonconservation from a limited experimental information. One suggests a novel type of global fit by expressing all theoretical quantities in terms of convention independent parameters: the Jarlskog invariant JJ and the moduli Uαi|U_{\alpha i}|, able to resolve the positivity problem of Ue3|U_{e 3}|. In this way the fit will directly provide a value for JJ, and if it is different from zero it will prove the existence of CP violation in the available experimental data. If the best fit result, Ue32<0|U_{e3}|^2<0, from M. Maltoni {\em et al}, [New J.Phys. {\bf 6} (2004) 122] is confirmed, it will imply a new physics in the leptonic sector
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