Generalized Boltzmann equation for a trapped Bose-condensed gas using the Kadanoff-Baym formalism

Using the Kadanoff-Baym non-equilibrium Green's function formalism, we derive kinetic equations for the non-condensate atoms at finite temperatures which include the effect of binary collisions between atoms. The effect of collisions is included using the second-order self-energy given by the Beliaev (gapless) approximation. We limit our discussion to finite temperatures where we can use the single-particle Hartree-Fock spectrum for the excited atoms. In this limit, we can neglect the off-diagonal propagators ($\tilde{g}_{12}$ and $\tilde{g}_{21}$). As expected, this leads to the kinetic equations and collision integrals used in recent work by Zaremba, Nikuni, and Griffin (ZNG) [1]. We also derive a consistent equation of motion for the condensate wavefunction, involving a finite-temperature generalization of the well-known Gross-Pitaevskii equation which includes a dissipative term, as well as the mean field of the non-condensate.Comment: Given at the workshop on ``Kadanoff-Baym Equations'', Rostock, Sept. 20-24, 1999. To be published in the proceedings by World Scientifi

Characterizing RecA-Independent Induction of Shiga toxin2-encoding Phages by EDTA Treatment

The bacteriophage life cycle has an important role in Shiga toxin (Stx) expression. The induction of Shiga toxin-encoding phages (Stx phages) increases toxin production as a result of replication of the phage genome, and phage lysis of the host cell also provides a means of Stx toxin to exit the cell. Previous studies suggested that prophage induction might also occur in the absence of SOS response, independently of RecA

A novel and widely accessible HPLC method for determination content of homosalate in sunscreen products on the market

Introduction: Considering that the research has shown that homosalate act as endocrine-active substance, it is very important to develop quick and sensitive method for tracking its concentrations in sunscreen products. The aim of this paper is to develop and validate the method for determining homosalate in sunscreen preparations and controlling the content of the products found on the market of Bosnia and Herzegovina. Methods: A high pressure liquid chromatography (HPLC) method for determination homosalate in sunscreen products has been developed and validated. Samples of six different manufacturers have been analyzed. HPLC method is method of choice for this type of investigation. Results: According to the calibration curve it has been found that the proposed analytical method in a given range of concentration is linear and that the correlation coefficient is R2=0.9998. Accuracy of the method is in range 94.26% -121.53%.The results have shown that the homosalate concentration in the tested samples did not exceed the maximally permissible concentration (10%). In the sample AV50 homosalate was not declared as an active ingredient, but it was identified and quantified at a concentration of 0.143%. Conclusion: Results of investigation of cosmetic products that are widely present on the market show the need of developing a sufficiently sensitive, easily accessible, analytical method for controlling the content of organic UV filters since the exceeding of the maximally permissible concentration can have a harmful effect on people who use these kinds of products. The results show that developed method meets conditions and is suitable for wide application

Analytical approach to relaxation dynamics of condensed Bose gases

The temporal evolution of a perturbation of the equilibrium distribution of a condensed Bose gas is investigated using the kinetic equation which describes collision between condensate and noncondensate atoms. The dynamics is studied in the low momentum limit where an analytical treatment is feasible. Explicit results are given for the behavior at large times in different temperature regimes.Comment: 25 pages, 3 figures. Typos corrected. Final version to appear in Annals of Physic

Finite-temperature simulations of the scissors mode in Bose-Einstein condensed gases

The dynamics of a trapped Bose-condensed gas at finite temperatures is described by a generalized Gross-Pitaevskii equation for the condensate order parameter and a semi-classical kinetic equation for the thermal cloud, solved using $N$-body simulations. The two components are coupled by mean fields as well as collisional processes that transfer atoms between the two. We use this scheme to investigate scissors modes in anisotropic traps as a function of temperature. Frequency shifts and damping rates of the condensate mode are extracted, and are found to be in good agreement with recent experiments.Comment: 4 pages, 3 figure

Landau-Khalatnikov two-fluid hydrodynamics of a trapped Bose gas

Starting from the quantum kinetic equation for the non-condensate atoms and the generalized Gross-Pitaevskii equation for the condensate, we derive the two-fluid hydrodynamic equations of a trapped Bose gas at finite temperatures. We follow the standard Chapman-Enskog procedure, starting from a solution of the kinetic equation corresponding to the complete local equilibrium between the condensate and the non-condensate components. Our hydrodynamic equations are shown to reduce to a form identical to the well-known Landau-Khalatnikov two-fluid equations, with hydrodynamic damping due to the deviation from local equilibrium. The deviation from local equilibrium within the thermal cloud gives rise to dissipation associated with shear viscosity and thermal conduction. In addition, we show that effects due to the deviation from the diffusive local equilibrium between the condensate and the non-condensate (recently considered by Zaremba, Nikuni and Griffin) can be described by four frequency-dependent second viscosity transport coefficients. We also derive explicit formulas for all the transport coefficients. These results are used to introduce two new characteristic relaxation times associated with hydrodynamic damping. These relaxation times give the rate at which local equilibrium is reached and hence determine whether one is in the two-fluid hydrodynamic region.Comment: 26 pages, 3 postscript figures, submitted to PR