Inelastic Scattering Of Light From Magnetoplasma Excitations In Solids

Raman scattering by magnetoplasma excitations in doped semiconductors for arbitrary experimental geometry is considered. A theory, based on the generalized Landau quasiparticle picture, is developed in order to obtain the scattering cross section. We consider an application to the case of a nondegenerate plasma in parabolicband semiconductors. The geometry-dependent mixing between the hybrid-plasma first cyclotron mode and the first Bernstein mode is studied. We also discuss field-dependent attenuation effects. © 1976 The American Physical Society.1483532353

Ultrafast Transient Transport In Nonequilibrium Semiconductors

A study of ultrafast transient transport in nonequilibrium direct-gap polar semiconductors under high levels of excitation is presented. The dynamic equation for the drift velocity is derived. A numerical application, appropriate for the case of photoexcited carriers distributed in the zone-center valleys of GaAs, is done. The time evolution of the momentum relaxation time and drift velocity is discussed, and it is shown that, depending on experimental conditions, a velocity overshoot may result. © 1983 The American Physical Society.2763874387

Coupled Electron-hole Plasma-phonon System In Far-from-equilibrium Semiconductors

Zubarev's nonequilibrium statistical thermodynamic method is applied to the study of the time evolution of a coupled carrier-LO-phonon system in polar direct-gap semiconductors. The carrier system is composed of a photoexcited electron-hole plasma, strongly departed from thermal equilibrium, generated by a pulse of laser light. The macroscopic description is done in terms of time-dependent quasitemperatures for the carriers and for the different phonon modes. These quasitemperatures can be determined by means of ultrafast optical spectroscopy; a calculation of the expected time-resolved Raman spectrum with numerical applications for the case of GaAs is presented. © 1980 The American Physical Society.22126355636

Microscopic Approach To Irreversible Thermodynamics. I. General Theory

In this paper we show how an extension of the nonequilibrium-statistical- operator method, relying upon the maximum-entropy principle set up by Jaynes [Am. J. Phys. 33, 391 (1965)], may be used to describe the time evolution of an arbitrary many-body system. The Gibbs space of the observables describing the macrostates of the system is extended to include not only the conserved variables, but additional ones whose origin is directly related to the microscopic nature of the system manifested in its Hamiltonian. This allows us to go beyond linear irreversible thermodynamics and enter into the domain of what is now known as extended irreversible thermodynamics (EIT). Transport equations for the extended basic set of macrovariables are derived, showing that the Maxwell-Cattaneo-Vernotte equations of EIT are obtained. The relaxation times and transport coefficients contained therein can be calculated from the microscopic dynamics of the system averaged over an appropriate nonequilibrium coarse-grained probability density. Other outstanding features of the methods are emphasized and related to already-established results for nonequilibrium systems. © 1991 The American Physical Society.43126622663

Transient Analysis Of Thermal Distortion In A Silicon Substrate On Incidence Of A Single Soft X-ray Fel Pulse

We discuss the dynamics of a silicon surface after incidence of a short, high energy pulse in the soft X-ray range. We focus on time-delays long enough after pulse incidence, so that the absorbed energy can be seen as a nonuniform time-dependent heat distribution in the solid. A model is developed using techniques of non-equilibrium hydro-thermodynamics, considering just the longitudinal and transverse acoustic phonon systems in the excited solid. The general theory leads to Maxwell-Cattaneo partial differential equations for the material medium n(r,t) and the energy h(r,t) volume densities; these reduce to the diffusion equation for the temperature T(r,t) and the usual thermo-mechanical elastic equation for the strain u(r,t) on further simplification. Here we solve the Maxwell-Cattaneo equation for T(r,t) and compare to previous results where the diffusion equation was used instead; the Maxwell-Cattaneo equation predicts faster cooling at short (dozens of fs, say) time delays. Previously obtained results for the strain field are briefly recalled. © 2011 SPIE.8077De Castro, A.R.B., Vasconcellos, A.R., Luzzi, R., Thermo-elastic analysis of a silicon surface under X-ray free-electron-laser irradiation (2010) Rev. Sci. Instrum., 81. , art 073102de Castro A. R. B., Vasconcellos A. R. and Luzzi R., "Erratum: Thermo-elastic analysis of a silicon surface under X-ray freeelectron-laser irradiation (Rev. Sci. Instrum., 81, art 073102 (2010))", Rev. Sci. Instrum., submitted (2011)Luzzi, R., Vasconcellos, A.R., Ramos, J.G., (2002) Predictive Statistical Mechanics: A Non-equilibrium Ensemble Formalism, , Kluwer Academic, DorbrechtBoguliubov, N.N., (1962) Studies in Statistical Mechanics i, , North Holland, AmsterdamLandau, L.M., Lifschitz, E.M., (1986) Theory of Elasticity, , Pergamon, OxfordMorse, P.M., Feshbach, H., (1953) Methods of Theoretical Physics, , McGraw-Hill Book Company, N YorkDe Castro, A.R.B., Möller, T., Time-dependent strain analysis of mirrors illuminated with intense femtosecond pulses in the soft X-ray spectral range (2005) Rev. Sci. Instrum., 76. , art 06310

Level of physical activity, stress and health of bank clerks

The purpose of this study was to investigate the relationship among level of physical activity, stress and health in male and female bank clerks. Two hundred eighty three bank clerks answered the Questionnaire of Habitual Physical Activities (Pate et al., 1995), the Perceived Stress Scale (Cohen, Karmack, & Mermelsteinm, 1983), and two scales of self-evaluated health (Andrade, 2001). More active bank clerks showed themselves as less stressed (F = 4.87, p = .008), significant results only for women (F = 4.11, p = .019). More active bank clerks also perceived themselves as healthier (p = .000, gamma = .56) and fell ill less frequently (p = .02, gamma = −.34), significant results only for men (p = .001, gamma = .60 e p = .033, gamma = −.33, respectively). Bank clerks with better perceived health showed significantly lower stress (F = 13.45, p = .000), significant results for both men (F = 9.75, p = .000) and women (F = 7.88, p = .000), as well as those getting sick less frequently (F = 5.40, p = .001), significant results only for women (F = 4.60, p = .004). Findings indicated a relationship among all the variables investigated and differing relationships for men and women

Thermodynamic Variables In The Context Of A Nonequilibrium Statistical Ensemble Approach

We consider the question of the definition of thermodynamic-like variables in the context of a statistical thermodynamics, which is a large generalization of Gibbs statistical thermostatics and linear and local-equilibrium classical irreversible thermodynamics. It is based on a nonequilibrium ensemble approach known as the nonequilibrium statistical operator method. Some of these quasithermodynamic variables are characteristic of the nonequilibrium state and go to zero in the limit of local or global equilibrium, but others go over the thermodynamic variables that are present in such a limit. We consider in particular temperature-like variables for the different subsystems of the sample. For illustration we apply the theory to the study of optical properties of highly photoexcited plasma in semiconductors, following a good agreement between theory and experimental data. It is shown that high-resolution spectroscopy provides an excellent experimental testing ground for corroboration of the theoretical concepts, and a quite appropriate way for characterizing and measuring nonequilibrium thermodynamic-like variables. © 1997 American Institute of Physics.1071873837396Tisza, L., (1991) Thermodynamics: History and Philosophy, pp. 515-522. , edited by K. Martinas, L. Ropolyi, and P. Szegedi World Scientific, SingaporeGarcia-Colin, L.S., Vasconcellos, A.R., Luzzi, R., (1994) J. Non-Equilib. Thermodyn., 19, p. 24Luzzi, R., Vasconcellos, A.R., (1997) Physica A, 241, p. 677Nettleton, R.E., Sobolev, S.L., (1995) J. Non-Equilib. Thermodyn., 20, p. 205Sieniutycz, S., Solomon, P., (1990) Nonequilibrium Theory and Extremum Principles, , Taylor and Francis, New YorkVansconcellos, A.R., Luzzi, R., Garcia-Colin, L.S., (1991) Phys. Rev. A, 43, p. 6622(1991) Phys. Rev. A, 43, p. 6633(1995) J. Non-Equilib. Thermodyn., 20, p. 103(1995) J. Non-Equilib. 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Measuring Nonequilibrium Temperature of Forced Oscillators

The meaning of temperature in nonequilibrium thermodynamics is considered by using a forced harmonic oscillator in a heat bath, where we have two effective temperatures for the position and the momentum, respectively. We invent a concrete model of a thermometer to testify the validity of these different temperatures from the operational point of view. It is found that the measured temperature depends on a specific form of interaction between the system and a thermometer, which means the zeroth law of thermodynamics cannot be immediately extended to nonequilibrium cases.Comment: 8 page

An optimization principle for deriving nonequilibrium statistical models of Hamiltonian dynamics

A general method for deriving closed reduced models of Hamiltonian dynamical systems is developed using techniques from optimization and statistical estimation. As in standard projection operator methods, a set of resolved variables is selected to capture the slow, macroscopic behavior of the system, and the family of quasi-equilibrium probability densities on phase space corresponding to these resolved variables is employed as a statistical model. The macroscopic dynamics of the mean resolved variables is determined by optimizing over paths of these probability densities. Specifically, a cost function is introduced that quantifies the lack-of-fit of such paths to the underlying microscopic dynamics; it is an ensemble-averaged, squared-norm of the residual that results from submitting a path of trial densities to the Liouville equation. The evolution of the macrostate is estimated by minimizing the time integral of the cost function. The value function for this optimization satisfies the associated Hamilton-Jacobi equation, and it determines the optimal relation between the statistical parameters and the irreversible fluxes of the resolved variables, thereby closing the reduced dynamics. The resulting equations for the macroscopic variables have the generic form of governing equations for nonequilibrium thermodynamics, and they furnish a rational extension of the classical equations of linear irreversible thermodynamics beyond the near-equilibrium regime. In particular, the value function is a thermodynamic potential that extends the classical dissipation function and supplies the nonlinear relation between thermodynamics forces and fluxes