Acceptance Dependence of Fluctuation in Particle Multiplicity

The effect of limiting the acceptance in rapidity on event-by-event multiplicity fluctuations in nucleus-nucleus collisions has been investigated. Our analysis shows that the multiplicity fluctuations decrease when the rapidity acceptance is decreased. We explain this trend by assuming that the probability distribution of the particles in the smaller acceptance window follows binomial distribution. Following a simple statistical analysis we conclude that the event-by-event multiplicity fluctuations for full acceptance are likely to be larger than those observed in the experiments, since the experiments usually have detectors with limited acceptance. We discuss the application of our model to simulated data generated using VENUS, a widely used event generator in heavy-ion collisions. We also discuss the results from our calculations in presence of dynamical fluctuations and possible observation of these in the actual data.Comment: To appear in Int. J. Mod. Phys.

Low-temperature UV photoluminescence of ion beam synthesized Si nanoclusters embedded in Si

Ultraviolet (UV) photoluminescence (PL) data taken on a double Au implanted Si matrix are reported. This has been studied over a wide temperature range of 28-220 K. At low temperature, the spectrum shows four peaks corresponding to a zero-phonon line (ZP

Inelastic effects in electron transport studied with wave packet propagation

A time-dependent approach is used to explore inelastic effects during electron transport through few-level systems. We study a tight-binding chain with one and two sites connected to vibrations. This simple but transparent model gives insight about inelastic effects, their meaning and the approximations currently used to treat them. Our time-dependent approach allows us to trace back the time sequence of vibrational excitation and electronic interference, the ibrationally introduced time delay and the electronic phase shift. We explore a full range of parameters going from weak to strong electron-vibration coupling, from tunneling to contact, from one-vibration description to the need of including all vibrations for a correct description of inelastic effects in transport. We explore the validity of single-site resonant models as well as its extension to more sites via molecular orbitals and the conditions under which multi-orbital, multi-vibrational descriptions cannot be simplified. We explain the physical meaning of the spectral features in the second derivative of the electron current with respect to the bias voltage. This permits us to nuance the meaning of the energy value of dips and peaks. Finally, we show that finite-band effects lead to electron back-scattering off the molecular vibrations in the regime of high-conductance, although the drop in conductance at the vibrational threshold is rather due to the rapid variation of the vibronic density of states.Comment: 38 pages, 14 figure

Effect of textile softeners on BTCA treated cotton fabric

96-101The effect of two softeners (Sapamine® OC and Ultratex® ASG) on physical properties of BTCA finished cotton fabric has been studied. Bleached cotton fabrics are treated with 1, 2, 3, 4-butane tetracarboxylic acid (BTCA) followed by finishing with a cationic and a silicone softener by conventional pad-dry-cure method. Properties, such as crease recovery angle, absorbency, whiteness index, tensile strength, moisture regain, surface morphology and crystallinity of the finished fabrics, have been evaluated. The crease recovery angle of the finished fabrics increases from 154° to 257° after treatment with BTCA and further increases to 266° after BTCA+silicone softener based finishing. The absorbency of cationic softener finished fabric is found to be higher than that of silicone softener finished fabrics. Tensile strength reduces after BTCA finishing by more than 50%, and about 17% softeners is recovered. Scanning electron microscope images show smooth ridges and surface characteristics of cotton fibres in BTCA treated samples as well as deposition of softener on the fibre surface in cationic and silicone softener finished fabrics