Deuteron spin-lattice relaxation times in undercooled aqueous potassium- and cesium halide solutions

Abstract Aqueous emulsions of potassium-and cesium halides in cycloalkane mixtures can be undercooled at a pressure of 225 MPa to temperatures around 170K. In these emulsions deuterium spin-lattice relaxation times T1 have been determined as function of salt concentration, temperature and pressure at magnetic fields of 2.4 Tesla and 7.0 Tesla. The frequency and temperature dependence of the relaxation time curves is described quantitatively within a motional model which is consistent with known local structural features in these solutions. Model parameters deduced are compared with those obtained in related studies of the other alkali-halides, and conclusions are drawn regarding the influence of structure and composition on molecular motions. </jats:p

Parallel-tempering cluster algorithm for computer simulations of critical phenomena

In finite-size scaling analyses of Monte Carlo simulations of second-order phase transitions one often needs an extended temperature range around the critical point. By combining the parallel tempering algorithm with cluster updates and an adaptive routine to find the temperature window of interest, we introduce a flexible and powerful method for systematic investigations of critical phenomena. As a result, we gain one to two orders of magnitude in the performance for 2D and 3D Ising models in comparison with the recently proposed Wang-Landau recursion for cluster algorithms based on the multibondic algorithm, which is already a great improvement over the standard multicanonical variant.Comment: pages, 5 figures, and 2 table

Electromagnetic meson form factor from a relativistic coupled-channel approach

Point-form relativistic quantum mechanics is used to derive an expression for the electromagnetic form factor of a pseudoscalar meson for space-like momentum transfers. The elastic scattering of an electron by a confined quark-antiquark pair is treated as a relativistic two-channel problem for the $q\bar{q}e$ and $q\bar{q}e\gamma$ states. With the approximation that the total velocity of the $q\bar{q}e$ system is conserved at (electromagnetic) interaction vertices this simplifies to an eigenvalue problem for a Bakamjian-Thomas type mass operator. After elimination of the $q\bar{q}e\gamma$ channel the electromagnetic meson current and form factor can be directly read off from the one-photon-exchange optical potential. By choosing the invariant mass of the electron-meson system large enough, cluster separability violations become negligible. An equivalence with the usual front-form expression, resulting from a spectator current in the $q^+=0$ reference frame, is established. The generalization of this multichannel approach to electroweak form factors for an arbitrary bound few-body system is quite obvious. By an appropriate extension of the Hilbert space this approach is also able to accommodate exchange-current effects.Comment: 30 pages, 5 figure

Study of the Activity of Phospholipase A2 in Venom of the Transcaucasian Macrovipera Lebetina Obtusa

The activity of phospholipase A2 in the venom of the Transcaucasian Macrovipera lebetina obtusa, collected from viperas inhabiting in different regions of Azerbaijan in terms of pollution, was studied. The lowest (30,2 IU / mg) was detected in the venom of Viperas collected in Sabirabad district, Karatuga village and the highest was detected in the venom of Viperas collected in Baku, s. Bina (38,5IU / mg). As a result of experimental studies it follows that the activity of phospholipase in the venom collected in the vicinity of the Sabirabad district Karatuga village and Agsu district Garagoyunlu village, Gobustan district Childag village, Bina and Sumgait is 30.2 ± 1.1 IU / mg, 32.6 ± 0.9 IU / mg, 34.5 ± 0.8 IU / mg, 38.5 ± 0.2 IU / mg and 36.1 ± 0 , 8 IU / mg, respectively. Thus, the activity of phospholipase A2 in the venom of the Transcaucasian Viperas Macrovipera lebetina obtusa collected from snakes inhabiting different in the degree of contamination of the regions of Azerbaijan was studied. The results of the experimental data can be used to determine the biological activity of the venom samples, including, for identification and standardization of the venom of the vipera

Phase transition in the one-dimensional Kondo lattice model with attractive electron-electron interaction

The one-dimensional Kondo lattice model with attractive interaction among the conduction electrons is analyzed in the case of half-filling. It is shown that there are three distinct phases depending on the coupling constants of the model. Two phases have a spin and charge gap. While one shows a clear separation of the spin and charge excitation spectrum the other phase may be characterized as a band insulator type where both excitations are due to two-particle states. The third phase is gapless in both channels and has quasi long-range order in the spin and charge density wave correlation. In this phase the spin and charge excitations have again a clearly separated spectrum. For the analysis we discuss first two limiting cases. Then a density matrix renormalization group calculation on finite systems is applied to determine the phase diagram and the correlation functions in the gapped and gapless phase for general couplding constants.Comment: 9 pages, 7 Postscript figures, REVTe