15,020 research outputs found

    The Minimum-Mass Extrasolar Nebula: In-Situ Formation of Close-In Super-Earths

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    Close-in super-Earths, with radii R = 2-5 R_Earth and orbital periods P < 100 days, orbit more than half, and perhaps nearly all Sun-like stars in the universe. We use this omnipresent population to construct the minimum-mass extrasolar nebula (MMEN), the circumstellar disk of solar-composition solids and gas from which such planets formed, if they formed near their current locations and did not migrate. In a series of back-of-the-envelope calculations, we demonstrate how in-situ formation in the MMEN is fast, efficient, and can reproduce many of the observed properties of close-in super-Earths, including their gas-to-rock fractions. Testable predictions are discussed.Comment: Accepted to MNRAS 2013 March

    Modern CACSD using the Robust-Control Toolbox

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    The Robust-Control Toolbox is a collection of 40 M-files which extend the capability of PC/PRO-MATLAB to do modern multivariable robust control system design. Included are robust analysis tools like singular values and structured singular values, robust synthesis tools like continuous/discrete H(exp 2)/H infinity synthesis and Linear Quadratic Gaussian Loop Transfer Recovery methods and a variety of robust model reduction tools such as Hankel approximation, balanced truncation and balanced stochastic truncation, etc. The capabilities of the toolbox are described and illustated with examples to show how easily they can be used in practice. Examples include structured singular value analysis, H infinity loop-shaping and large space structure model reduction

    Phase-sensitive quantum effects in Andreev conductance of the SNS system of metals with macroscopic phase breaking length

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    The dissipative component of electron transport through the doubly connected SNS Andreev interferometer indium (S)-aluminium (N)-indium (S) has been studied. Within helium temperature range, the conductance of the individual sections of the interferometer exhibits phase-sensitive oscillations of quantum-interference nature. In the non-domain (normal) state of indium narrowing adjacent to NS interface, the nonresonance oscillations have been observed, with the period inversely proportional to the area of the interferometer orifice. In the domain intermediate state of the narrowing, the magneto-temperature resistive oscillations appeared, with the period determined by the coherence length in the magnetic field equal to the critical one. The oscillating component of resonance form has been observed in the conductance of the macroscopic N-aluminium part of the system. The phase of the oscillations appears to be shifted by π\pi compared to that of nonresonance oscillations. We offer an explanation in terms of the contribution into Josephson current from the coherent quasiparticles with energies of order of the Thouless energy. The behavior of dissipative transport with temperature has been studied in a clean normal metal in the vicinity of a single point NS contact.Comment: 9 pages, 7 figures, to be published in Low Temp. Phys., v. 29, No. 12, 200

    Extremal black holes in D=4 Gauss-Bonnet gravity

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    We show that four-dimensional Einstein-Maxwell-Dilaton-Gauss-Bonnet gravity admits asymptotically flat black hole solutions with a degenerate event horizon of the Reissner-Nordstr\"om type AdS2×S2AdS_2\times S^2. Such black holes exist for the dilaton coupling constant within the interval 0≤a2<acr20\leq a^2<a^2_{\rm cr}. Black holes must be endowed with an electric charge and (possibly) with magnetic charge (dyons) but they can not be purely magnetic. Purely electric solutions are constructed numerically and the critical dilaton coupling is determined acr≃0.488219703a_{\rm cr}\simeq 0.488219703. For each value of the dilaton coupling aa within this interval and for a fixed value of the Gauss--Bonnet coupling α\alpha we have a family of black holes parameterized by their electric charge. Relation between the mass, the electric charge and the dilaton charge at both ends of the allowed interval of aa is reminiscent of the BPS condition for dilaton black holes in the Einstein-Maxwell-Dilaton theory. The entropy of the DGB extremal black holes is twice the Bekenstein-Hawking entropy.Comment: New material and references added, errors corrected including higher decimals in a_cr, figures improve

    Role of aggressivity on reactivity and craving before and after cue exposure in recently detoxified alcoholics: Results from an experimental study

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    The role of aggressivity and cue exposure in induction of craving were investigated in a clinical setting. Thirty abstinent alcoholic patients were divided into a low and a high aggressive group based on scores on the physical aggression subscale of the Buss-Durkee Hostility Inventory and exposed to alcohol cues. Craving was measured by means of the Alcohol Craving Questionnaire (ACQ) and Visual Analogue Scales (VAS). Important findings are: (1) main effects of aggressivity on `emotionality', `purposefulness' and `expectancy' of ACQ were very significant; (2) on `drinking intention' and `craving for alcohol' of VAS, aggressivity and cue exposure showed a significant interaction; (3) the main effect of cue exposure on heart rate also reached a significance level of 0.007. The results were discussed in the context of the Classical, Operant Conditioning Theory, the Cognitive Craving Theory of Tiffany, Gilbert's STAR Model, and the Self-Medication Hypothesis Copyright (C) 2001 S. Karger AG, Basel

    Effects of irritability on craving before and after cue exposure in abstinent alcoholic inpatients: Experimental data on subjective response and heart rate

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    Objective: Irritability is often linked with problem drinking. The aim of this study is to examine the possible influence of irritability on craving induced by a cue-exposure paradigm. Methods: 30 male abstinent alcoholic inpatients of the Psychiatric Hospital of Munich University, Germany gave answers to a series of personality questionnaires. Results of this study concerning the impact of aggressivity on craving for alcohol has recently been published. In this study, the subjects were subdivided into a low- and a high-irritable group based on their scores on the irritability subscale of the Buss-Durkee Hostility Inventory and were exposed to alcohol cues. Craving was measured by means of the Alcohol Craving Questionnaire (ACQ) and Visual Analogue Scales (VAS). The heart rate was also assessed throughout the whole process. ANCOVA for repeated measurement was employed to evaluate the data - irritability disposition as the between-subject factor and the experimental manipulation (absence vs. presence of alcohol cues) as the within-subject factor. Results: Major findings are: (1) main effects of irritability on `emotionality', `purposefulness', and `expectancy' of the ACQ as well as on `craving for alcohol' of the VAS were significant; (2) cue exposure also exerted a significant main effect on I craving for alcohol' of the VAS and on the heart rate after the presentation of alcohol cues; (3) on `compulsivity' of the ACQ and `intention to alcohol intake' of the VAS; there was a significant interaction between irritability and cue exposure. The high-irritable alcoholics, compared with their statements in the baseline, tended to report a higher control over alcohol intake and a lower intention to alcohol use after cue exposure. However, after confrontation with alcohol stimuli, their low-irritable counterparts reported a much lower control and a slightly higher intention than they did in the baseline. Conclusions: The results of this study indicate that induced craving in hospitalized alcohol addicts probably varies with the magnitude of their irritability; it might make patients more aware of their vulnerability to alcohol, help them develop more differential coping strategies and improve medical therapy against alcohol craving. Copyright (C) 2002 S. Karger AG, Basel

    The Family SU(2)_l x SU(2)_h x U(1) Model

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    We consider extension of the standard model SU(2)l×SU(2)h×U(1)SU(2)_l \times SU(2)_h \times U(1) where the first two families of quarks and leptons transform according to the SU(2)lSU(2)_l group and the third family according to the SU(2)hSU(2)_h group. In this approach, the largeness of top-quark mass is associated with the large vacuum expectation value of the corresponding Higgs field. The model predicts almost degenerate heavy W′W' and Z′Z' bosons with non-universal couplings, and extra Higgs bosons. We present in detail the symmetry breaking mechanism, and carry out the subsequent phenomenology of the gauge sector. We compare the model with electroweak precision data, and conclude that the extra gauge bosons and the Higgs bosons whose masses lie in the TeV range, can be discovered at the LHC.Comment: Latex 18 pages. No figure. Some references added. Version appeared in PR

    Algorithms for computing the multivariable stability margin

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    Stability margin for multiloop flight control systems has become a critical issue, especially in highly maneuverable aircraft designs where there are inherent strong cross-couplings between the various feedback control loops. To cope with this issue, we have developed computer algorithms based on non-differentiable optimization theory. These algorithms have been developed for computing the Multivariable Stability Margin (MSM). The MSM of a dynamical system is the size of the smallest structured perturbation in component dynamics that will destabilize the system. These algorithms have been coded and appear to be reliable. As illustrated by examples, they provide the basis for evaluating the robustness and performance of flight control systems
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