Delay times for symmetrized and antisymmetrized quantum tunneling configurations

The quartic confining potential has emerged as a key ingredient to obtain fast rotating vortices in BEC as well as observation of quantum phase transitions in optical lattices. We calculate the critical temperature T_c of bosons at which normal to BEC transition occurs for the quartic confining potential. Further more, we evaluate the effect of finite particle number on T_c and find that ΔT_c/T_c is larger in quartic potential as compared to quadratic potential for number of particles <10⁵. Interestingly, the situation is reversed if the number of particles is 10⁵.     

Polarization enhancement of anti-Stokes emission in a para-H2 Raman laser

The effect of polarization can influence the frequency conversion and enhance the anti-Stokes emission in a rotational para-H₂ Raman laser. Stokes (16 μm) and anti-Stokes (7 μm) radiations were obtained from a line tunable CO₂ laser at 10 μm.     

Effective interactions between colloidal particles suspended in a bath of swimming cells

The dynamics of passive colloidal tracers in a bath of self-propelled particles is receiving a lot of attention in the context of nonequilibrium statistical mechanics. Here we demonstrate that active baths are also capable of mediating effective interactions between suspended bodies. In particular we observe that a bath of swimming bacteria gives rise to a short range attraction similar to depletion forces in equilibrium colloidal suspensions. Using numerical simulations and experiments we show how the features of this interaction arise from the combination of nonequilibrium dynamics (peculiar of bacterial baths) and excluded volume effects.     

The influence of model parameters and of the thermomechanical coupling on the behavior of shape memory devices

Shape memory materials (SMM) are receiving increasing attention for their use in applications that exploit their dynamic behavior. A thermomechanical model for devices with pseudoelastic behavior has been proposed in previous works [11] (Bernardini and Pence, 2005) [15] (Bernardini and Rega, 2005). The model takes into account several aspects of SMM behavior by means of seven model parameters.In this paper the effect of each parameter on the non-isothermal rate-dependent behavior of the device is studied, by paying particular attention to the effect of the thermomechanical coupling. Some overall synthetic indicators of the behavior of the shape memory device are defined in terms of the model parameters. By evaluating such indicators, a lot of information about the mechanical, thermal and thermomechanical effects on the device behavior can be gained before computing explicitly the response of the shape memory oscillator.The present work may provide a guide for the proper utilization of the model for the investigation of the dynamic response.     

Second-order corrections to neutrino two-flavor oscillation parameters in the wave packet approach

We report about an analytic study involving the intermediate wave packet formalism for quantifying the physically relevant information which appears in the neutrino two-flavor conversion formula and helping us to obtain more precise limits and ranges for neutrino flavor oscillation. By following the sequence of analytic approximations where we assume a strictly peaked momentum distribution and consider the second-order corrections in a power series expansion of the energy, we point out a residual time-dependent phase which, coupled with the spreading/slippage effects, can subtly modify the neutrino-oscillation parameters and limits. Such second-order effects are usually ignored in the relativistic wave packet treatment, but they present an evident dependence on the propagation regime so that some small modifications to the oscillation pattern, even in the ultra-relativistic limit, can be quantified. These modifications are implemented in the confrontation with the neutrino-oscillation parameter range (mass-squared difference Δm² and the mixing angle θ) where we assume the same wave packet parameters previously noticed in the literature in a kind of toy model for some reactor experiments. Generically speaking, our analysis parallels the recent experimental purposes which are concerned with higher precision parameter measurements. To summarize, we show that the effectiveness of a more accurate determination of Δm² and θ depends on the wave packet width a and on the averaged propagating energy flux Ē which still correspond to open variables for some classes of experiments. PACS 02.30.Mv; 03.65.Pm; 14.60.Pq     

PHYSICAL AND PHOTOCHEMICAL PROPERTIES OF A FLUORESCENT CHLOROPHYLL COLLOID

Abstract— A fluorescent colloid of chlorophyll a , of which some qualitative properties were noted by Krasnovsky and Brin⁽¹¹⁾, has been quantitatively characterized. The colloid is formed in neutral PO₄ buffer containing 0 1 to 8.0% Tween 20, and is stable in darkness. The extinction coefficient is 7.8 × 10⁴ 1. mole cm^-1 at the red absorption peak (668 mμ), the yield of fluorescence is ˜ 0.25, and the yield of photoautooxidative bleaching is ˜ 2 times 10^-4. The colloid sensitizes the autooxidation of paratoluenediamine with a yield of ˜0.01 to ˜0.3 depending on light intensity and substrate concentration. The yield is independent of detergent and chlorophyll concentrations. In all respects—except the dependence of yield on illumination—the colloid appears to be physically and photochemically equivalent to dissolved chlorophyll, as known in dilute solutions in organic solvents. The light dependence—the yield is inversely proportional to the cube root of absorbed intensity—could be due to a bimolecular back reaction of a chlorophyll or substrate derivative.     

The time-like electromagnetic form factors of the charged pseudoscalar mesons from 1.44 to 9.0 GeV2

The study of 620 hadron pairs produced in the s-range (1.44?9.0) GeV², has yielded 110 collinear hadronic events. Their identification in terms of π and K mesons allows the determination of the time-like electromagnetic from factors of these pseudoscalar mesons in the above time-like range. The total number of (e⁺e^?) events observed in the same experimental conditions is 18 048.     

Accuracy of the multipole expansion applied to a sphere in a creeping flow parallel to a wall

An example system is studied to discuss precision of the multipoleexpansion, applied to determine forces exerted on particlesby a viscous low-Reynolds-number fluid flow. A single spherein an ambient flow (pure shear, quadratic, and modulated shear)parallel to a close plane wall is considered. Forces and torquesexerted by the ambient flow on a motionless sphere are evaluated.Their precision is determined and related to a multipole orderof the truncation. Similar analysis is performed for a movingsphere with no ambient flow and for a freely moving sphere.Relative motion of the sphere with respect to the wall givesrise to strong lubrication interactions. It is analysed howthese interactions affect accuracy of the pure multipole expansion,and what are the smallest distances where it becomes insufficient.An alternative precise method is applied, in which lubricationexpressions are subtracted from the hydrodynamic forces andtorques, and the residue is evaluated as a fast-convergent seriesof inverse powers of the distance between the sphere centreand the wall. The accuracy of this procedure is carefully analysed.