585 research outputs found

    Direct optical observations of surface thermal motions at sub-shot noise levels

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    We measure spectral properties of surface thermal fluctuations of liquids, solids, complex fluids and biological matter using light scattering methods. The random thermal fluctuations are delineated from random noise at sub-shot noise levels. The principle behind this extraction, which is quite general and is not limited to surface measurements, is explained. An optical lever is used to measure the spectrum of fluctuations in the inclinations of surfaces down to 1017rad2/Hz\sim 10^{-17}\rm rad^2/Hz at 110μ1\sim10 \muW optical intensity, corresponding to 1029m2/Hz\sim 10^{-29} \rm m^2/\rm Hz in the vertical displacement, in the frequency range 1kHz10MHz1{\rm}\rm kHz\sim10 MHz. The dynamical evolution of the surface properties is also investigated. The measurement requires only a short amount of time and is essentially passive, so that it can be applied to a wide variety of surfaces.Comment: 5pp, 5 figure

    Do Foreign Exchange Markets Still Trend?

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    Is it possible to profitably trade trends in foreign currencies? We examine the major currency futures contracts which have been trading since the 1970s as well as more recent contracts on exotic currencies that have only begun to trade in the past few years. The main conclusion is that the era of easy profits from simple trend following strategies in major foreign currencies is over. The markets have adapted to the extent that profits from these simple trading strategies have vanished.Presumably, trending may be a feature confined to currencies in the early years of a floating rate regime. When we look at some newly trading currencies, we see more attractive profit opportunities. Newly trading currency futures prices, like their counterparts thirty years ago, appear susceptible to trend following trading strategies

    Nonlinear Dynamics of Capacitive Charging and Desalination by Porous Electrodes

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    The rapid and efficient exchange of ions between porous electrodes and aqueous solutions is important in many applications, such as electrical energy storage by super-capacitors, water desalination and purification by capacitive deionization (or desalination), and capacitive extraction of renewable energy from a salinity difference. Here, we present a unified mean-field theory for capacitive charging and desalination by ideally polarizable porous electrodes (without Faradaic reactions or specific adsorption of ions) in the limit of thin double layers (compared to typical pore dimensions). We illustrate the theory in the case of a dilute, symmetric, binary electrolyte using the Gouy-Chapman-Stern (GCS) model of the double layer, for which simple formulae are available for salt adsorption and capacitive charging of the diffuse part of the double layer. We solve the full GCS mean-field theory numerically for realistic parameters in capacitive deionization, and we derive reduced models for two limiting regimes with different time scales: (i) In the "super-capacitor regime" of small voltages and/or early times where the porous electrode acts like a transmission line, governed by a linear diffusion equation for the electrostatic potential, scaled to the RC time of a single pore. (ii) In the "desalination regime" of large voltages and long times, the porous electrode slowly adsorbs neutral salt, governed by coupled, nonlinear diffusion equations for the pore-averaged potential and salt concentration

    Large Scale Structures a Gradient Lines: the case of the Trkal Flow

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    A specific asymptotic expansion at large Reynolds numbers (R)for the long wavelength perturbation of a non stationary anisotropic helical solution of the force less Navier-Stokes equations (Trkal solutions) is effectively constructed of the Beltrami type terms through multi scaling analysis. The asymptotic procedure is proved to be valid for one specific value of the scaling parameter,namely for the square root of the Reynolds number (R).As a result large scale structures arise as gradient lines of the energy determined by the initial conditions for two anisotropic Beltrami flows of the same helicity.The same intitial conditions determine the boundaries of the vortex-velocity tubes, containing both streamlines and vortex linesComment: 27 pages, 2 figure

    Quantum Kinetic Theory of Condensate Growth---Comparison of Experiment and Theory

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    In a major extension of our previous model (C.W. Gardiner, P. Zoller, R.J. Ballagh and M.J. Davis, Phys. Rev. Lett. 79, 1793 (1997)) of condensate growth, we take account of the evolution of the occupations of lower trap levels, and of the full Bose-Einstein formula for the occupations of higher trap levels. We find good agreement with experiment, especially at higher temperatures. We also confirm the picture of the ``kinetic'' region of evolution, introduced by Kagan et al, for the time up to the initiation of the condensate. The behavior after initiation essentially follows our original growth equation, but with a substantially increased rate coefficient W^{+}.Comment: RevTeX, 4 pages and 4 eps figure

    Statics and Dynamics of an Interface in a Temperature Gradient

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    The response and nonconserved dynamics of a two-phase interface in the presence of a temperature gradient oriented normally to the interface are considered. Two types of boundary conditions on the order parameter are considered, and the structure of the effective free energy and the Langevin equation for the collective coordinate specifying the interface position are analyzed.Comment: 15 pages, Revtex 3.0, 5 figures available upon reques

    The profile of a narrow line after single scattering by Maxwellian electrons: relativistic corrections to the kernel of the integral kinetic equation

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    The frequency distribution of photons in frequency that results from single Compton scattering of monochromatic radiation on thermal electrons is derived in the mildly relativistic limit. Algebraic expressions are given for (1) the photon redistribution function, K(nu,Omega -> nu',Omega'), and (2) the spectrum produced in the case of isotropic incident radiation, P(nu -> nu'). The former is a good approximation for electron temperatures kT_e < 25 keV and photon energies hnu < 50 keV, and the latter is applicable when hnu(hnu/m_ec^2) < kT_e < 25 keV, hnu < 50 keV. Both formulae can be used for describing the profiles of X-ray and low-frequency lines upon scattering in hot, optically thin plasmas, such as present in clusters of galaxies, in the coronae of accretion disks in X-ray binaries and AGNs, during supernova explosions, etc. Both formulae can also be employed as the kernels of the corresponding integral kinetic equations (direction-dependent and isotropic) in the general problem of Comptonization on thermal electrons. The K(nu,Omega -> nu',Omega') kernel, in particular, is applicable to the problem of induced Compton interaction of anisotropic low-frequency radiation of high brightness temperature with free electrons in the vicinity of powerful radiosources and masers. Fokker-Planck-type expansion (up to fourth order) of the integral kinetic equation with the P(nu -> nu') kernel derived here leads to a generalization of the Kompaneets equation. We further present (1) a simpler kernel that is necessary and sufficient to derive the Kompaneets equation and (2) an expression for the angular function for Compton scattering in a hot plasma, which includes temperature and photon energy corrections to the Rayleigh angular function.Comment: 29 pages, 17 figures, accepted for publication in ApJ, uses emulateapj.sty, corrects misprints in previous astro-ph versio

    ПОБІЧНІ РЕАКЦІЇ У ХВОРИХ НА НЕЕФЕКТИВНО ЛІКОВАНИЙ ВПЕРШЕ ДІАГНОСТОВАНИЙ ТУБЕРКУЛЬОЗ

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    SUMMARY. The aim of the study was to establish structure of adverse reactions (AR) and peculiarities of tuberculosis in patients with newly diagnosed treatment failure tuberculosis, which had adverse reactions to antituberculosis drugs of first group. To achieve the aim we analyzed 60 cases of patients. Patients were divided into 2 groups: AR (I group) – 34 patients without AR (second group), that included 26 patients. We determined the statistical significance of differences between groups using the criterion of "χ-squared", while the number of cases, that used was less than 20 we additional used Yates' correction for continuity. For quantitative – using the Student t-test. The duration of the intensive phase of treatment (including treatment for categories 1 and 2 together) in patients who have AR was more: (188.6±9.5) doses in I group in comparison with (166.2±6.1) doses in group II (p&lt;0.05), due to its extension due to lack of conversion of sputum smear or negative radiological dynamics. 32.4 % of patients had adverse reactions with clinical manifestations, that caused the abolition of anti-tuberculosis drugs and did not disappear after administration of corrective therapy. All these led to increase of terms of treatment in the intensive phase at (22.4±3.4) doses р&lt;0.05.РЕЗЮМЕ. Метою дослідження стало встановлення структури побічних реакцій (ПР) та особливостей перебігу туберкульозу у хворих на вперше діагностований неефективно лікований туберкульоз, у яких виникли побічні реакції на протитуберкульозні препарати першого ряду. Проаналізовано 60 історій хвороб пацієнтів. Хворих було поділено на 2 групи: з ПР (І група) – 34 пацієнти, без ПР (ІІ група) – 26 хворих. Визначали статистичну значимість відмінностей між групами за допомогою критерію χ-квадрат, при кількості випадків менше 20 додатково користувалися правкою Єтса. Для аналізу кількісних показників використовували t-критерій Стьюдента. Тривалість інтенсивної фази лікування (з урахуванням терапії за 1 і 2 категоріями разом) у хворих, які мали ПР, була більшою: (188,6±9,5) доз проти (166,2±6,1) доз пацієнтів ІІ групи (р&lt;0,05), за рахунок її подовження через відсутність конверсії мазка мокротиння або негативну рентгенологічну динаміку. У 32,4 % хворих побічні реакції мали клінічні прояви, вимагали відміни протитуберкульозних засобів і не зникали після призначення коригуючої терапії, що призводило до збільшення термінів лікування в інтенсивній фазі на (22,4±3,4) доз, р&lt;0,05.
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