1,760 research outputs found

    Method and apparatus for receiving and tracking phase modulated signals

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    An apparatus and technique are described for receiving and tracking analog or digital phase modulated signals from 0 deg to 360 deg phase shift. In order to track a signal with many phases, a detector discerns the phase modulation of the incoming signal and a phase shifter generates a negative phase shift opposite in angle to the detected phase angle. This produces a converted series sideband component barrier signal. The residual carrier signal and the converted series sideband component carrier are added together to produce a tracking carrier signal. The tracking carrier signal is multiplied with the output from a voltage controlled oscillator in the tracking loop to obtain an error signal which drives the voltage controlled oscillator and tracks the incoming signal frequency. The technique is less susceptible to carrier interference which may degrade tracking and tracking may be performed at lower signal to noise ratios and for lower input signal power levels

    Brownian motion meets Riemann curvature

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    The general covariance of the diffusion equation is exploited in order to explore the curvature effects appearing on brownian motion over a d-dimensional curved manifold. We use the local frame defined by the so called Riemann normal coordinates to derive a general formula for the mean-square geodesic distance (MSD) at the short-time regime. This formula is written in terms of O(d)O(d) invariants that depend on the Riemann curvature tensor. We study the n-dimensional sphere case to validate these results. We also show that the diffusion for positive constant curvature is slower than the diffusion in a plane space, while the diffusion for negative constant curvature turns out to be faster. Finally the two-dimensional case is emphasized, as it is relevant for the single particle diffusion on biomembranes.Comment: 16 pages and 3 figure

    Photo-ionization of planetary winds: case study HD209458b

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    Close-in hot Jupiters are exposed to a tremendous photon flux that ionizes the neutral escaping material from the planet leaving an observable imprint that makes them an interesting laboratory for testing theoretical models. In this work we present 3D hydrodynamic simulations with radiation transfer calculations of a close-in exoplanet in a blow-off state. We calculate the Ly-α\alpha absorption and compare it with observations of HD 209458b an previous simplified model results.Our results show that the hydrodynamic interaction together with a proper calculation of the photoionization proccess are able to reproduce the main features of the observed Ly-α\alpha absorption, in particular at the blue-shifted wings of the line. We found that the ionizing stellar flux produce an almost linear effect on the amount of absorption in the wake. Varying the planetary mass loss rate and the radiation flux, we were able to reproduce the 10%10\% absorption observed at 100 km s1-100~\mathrm{km~s^{-1}}.Comment: 9 pages, 6 figure

    An Empirical Examination of Symptom Substitution Associated with Behavior Therapy for Tourette\u27s Disorder

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    Over the past six decades, behavior therapy has been a major contributor to the development of evidence-based psychotherapy treatments. However, a long-standing concern with behavior therapy among many nonbehavioral clinicians has been the potential risk for symptom substitution. Few studies have been conducted to evaluate symptom substitution in response to behavioral treatments, largely due to measurement and definitional challenges associated with treated psychiatric symptoms. Given the overt motor and vocal tics associated with Tourette’s disorder, it presents an excellent opportunity to empirically evaluate the potential risk for symptom substitution associated with behavior therapy. The present study examined the possible presence of symptom substitution using four methods: (a) the onset of new tic symptoms, (b) the occurrence of adverse events, (c) change in tic medications, and (d) worsening of co-occurring psychiatric symptoms. Two hundred twenty-eight participants with Tourette’s disorder or persistent motor or vocal tic disorders were randomly assigned to receive behavioral therapy or supportive therapy for tics. Both therapies consisted of eight sessions over 10 weeks. Results indicated that participants treated with behavior therapy were not more likely to have an onset of new tic symptoms, experience adverse events, increase tic medications, or have an exacerbation in co-occurring psychiatric symptoms relative to participants treated with supportive therapy. Further analysis suggested that the emergence of new tics was attributed with the normal waxing and waning nature of Tourette’s disorder. Findings provide empirical support to counter the long-standing concern of symptom substitution in response to behavior therapy for individuals with Tourette\u27s disorder

    The Genes and Enzymes of Phosphonate Metabolism by Bacteria, and Their Distribution in the Marine Environment

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    Phosphonates are compounds that contain the chemically stable carbon–phosphorus (C–P) bond. They are widely distributed amongst more primitive life forms including many marine invertebrates and constitute a significant component of the dissolved organic phosphorus reservoir in the oceans. Virtually all biogenic C–P compounds are synthesized by a pathway in which the key step is the intramolecular rearrangement of phosphoenolpyruvate to phosphonopyruvate. However C–P bond cleavage by degradative microorganisms is catalyzed by a number of enzymes – C–P lyases, C–P hydrolases, and others of as-yet-uncharacterized mechanism. Expression of some of the pathways of phosphonate catabolism is controlled by ambient levels of inorganic P (Pi) but for others it is Pi-independent. In this report we review the enzymology of C–P bond metabolism in bacteria, and also present the results of an in silico investigation of the distribution of the genes that encode the pathways responsible, in both bacterial genomes and in marine metagenomic libraries, and their likely modes of regulation. Interrogation of currently available whole-genome bacterial sequences indicates that some 10% contain genes encoding putative pathways of phosphonate biosynthesis while ∼40% encode one or more pathways of phosphonate catabolism. Analysis of metagenomic data from the global ocean survey suggests that some 10 and 30%, respectively, of bacterial genomes across the sites sampled encode these pathways. Catabolic routes involving phosphonoacetate hydrolase, C–P lyase(s), and an uncharacterized 2-aminoethylphosphonate degradative sequence were predominant, and it is likely that both substrate-inducible and Pi-repressible mechanisms are involved in their regulation. The data we present indicate the likely importance of phosphonate-P in global biogeochemical P cycling, and by extension its role in marine productivity and in carbon and nitrogen dynamics in the oceans

    Casimir-like tunneling-induced electronic forces

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    We study the quantum forces that act between two nearby conductors due to electronic tunneling. We derive an expression for these forces by calculating the flux of momentum arising from the overlap of evanescent electronic fields. Our result is written in terms of the electronic reflection amplitudes of the conductors and it has the same structure as Lifshitz's formula for the electromagnetically mediated Casimir forces. We evaluate the tunneling force between two semiinfinite conductors and between two thin films separated by an insulating gap. We discuss some applications of our results.Comment: 8 pages, 3 figs, submitted to Proc. of QFEXT'05, to be published in J. Phys.

    Los recursos creativos utilizados por Rosa Beltrán en La corte de los ilusos

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    Tesis (Maestría en Letras Españolas) U.A.N.L.UANLhttp://www.uanl.mx

    Suicide ideation, planning, and attempts: the case of the Latinx LGB youth

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    Background: Guided by an ecological systems theory (EST) framework, the purpose of the present study was to investigate how multiple micro, mezzo, and macro factors influence the suicidality continuum from suicidal ideation to suicide attempt among Latinx LGB (lesbian, gay, and bisexual) youth living in the United States. Methods: Data for this cross sectional-study included 451 participants who self-identified as Latinx LGB on the 2017-National Youth Risk Behavioral Survey. The analysis explored micro, mezzo, and macro-level factors’ association with three suicidality outcomes (ideation, planning, and attempt) at the bivariate and multivariate level. Since the outcome variables were dichotomized, univariate logistic regressions and backward elimination logistic regressions were used. Results: The most commonly reported suicidal behavior was ideation (n = 173; 40%), followed by planning (n = 150; 34%), and then attempt (n = 64; 21%). Findings from the backward elimination logistic regression on suicidal ideation suggest the best set of independent variables are being bullied at school (odds ratio [OR] = 2.81; CI: 1.61–4.89), experiencing sexual assault (OR = 2.32; CI: 1.32–4.07), experiencing depressive symptoms (OR = 1.99; CI: 1.07– 3.69), being cannabis use (OR = 1.76; CI: 1.08–2.89), and being female (OR = 1.72; CI: 1.01–2.93). For suicide planning the model suggested, experiencing depressive symptoms (OR = 3.21; CI: 1.74–5.91), cannabis use (OR = 2.46; CI: 1.49–4.07), being bullied at school (OR = 2.04; CI: 1.17–3.58), and experiencing sexual assault (OR = 1.88; CI: 1.07–3.31) exhibited the strongest relationships. Suicide attempt was significantly associated with cannabis use (OR = 3.12; CI: 1.60–6.08), experiencing depression (OR= 2.89; CI: 1.30–6.43), experiencing sexual assault (OR = 2.77; CI: 1.34–5.71), and being bullied at school (OR = 2.34; CI: 1.12–4.91). Conclusion: Given the findings of this study, it is essential that tailored suicide prevention efforts be established that uniquely address the intersections of race/ethnicity and sexual orientation and how this intersection influences micro, mezzo, and macro factors associated with suicide ideation, planning, and attempt among Latinx LGB adolescents

    Strange matter in rotating compact stars

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    We have constructed equations of state involving various exotic forms of matter with large strangeness fraction such as hyperon matter, Bose-Einstein condensates of antikaons and strange quark matter. First order phase transitions from hadronic to antikaon condensed and quark matter are considered here. The hadronic phase is described by the relativistic field theoretical model. Later those equations of state are exploited to investigate models of uniformly rotating compact stars. The effect of rotation on the third family branch for the equation of state involving only antikaon condensates is investigated. We also discuss the back bending phenomenon due to a first order phase transition from KK^- condensed to quark matter.Comment: 8 pages, 4 figures; Plenary talk delivered at Strangeness in Quark Matter (SQM) 2004 held in Cape Town, South Africa from 15-20 September; Accepted for publication in the proceedings in Journal of Physics
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