On use of ghost-less beam splitter in reversal shear interferometer for measurement of spatial coherence of large cross-section laser beam

A configuration of reversal shear interferometer suitable for measurement of spatial coherence of high average power, large cross-section laser beam has been discussed. Ghost-less beam splitters in which unwanted multiple reflections from the surfaces have been suppressed by total internal reflection are used for beam splitting and re-combination. Advantages and drawbacks of this configuration have been discussed.     

Effects of screening on quark-antiquark cross sections in quark-gluon plasma

Lowest-order cross sections for qq? production and annihilation can be approximately corrected for higher-order QCD effects by using a corrective K-factor. For energies where quark masses cannot be ignored, the K-factor is dominated by the wave function distortion arising from the initialor final-state interaction between the quark and the antiquark. We evaluate this K-factor for qq? production and annihilation in a quark-gluon plasma by taking into account the effects of Debye screening through a color-Yukawa potential. We present the corrective K-factor as a function of dimensionless parameters which may find applications in other systems involving attractive or repulsive Yukawa interactions. Prominent peaks of the K-factor occur for an attractive q-q? color-Yukawa interaction with Debye screening lengths of 0.835 and 3.23 times the Bohr radius, corresponding to two lowest s-wave qq? bound states moving into the continuum to become qq? resonances as the Debye screening length decreases. These resonances, especially the cc? and the bb? resonances, may be utilized to study the quark-gluon plasma by examining the systematics of the temperature dependence of heavy-quark pair production just above the threshold.     

Proton NMR in CeNiInH0.53 down to liquid helium temperature

The NMR probe and the matching network has been designed for the¹H NMR study in CeNiInH_0.53 down to liquid helium temperature using Bruker MSL 100 spectrometer. NMR line-shape measurement shows the absence of any signature of proton pairing in CeNiInH_0.53 down to 3.86 K, as it was observed for high hydrogen concentration. The measurement of the spin-lattice relaxation time in the temperature range 300–20K reveals that the relaxation rate is mainly governed by the Korringa-type relaxation mechanism.     

Study of copolymer–copolymer interactions and formation of intermacromolecular complexes

Interpolymer complex formation has been studied between methacrylic acid-methacrylamide copolymer and acrylic acid–acrylamide copolymer. The respective co-monomer units of the two copolymers enter into complex formation through H-bonding and ion dipole interactions. The unreacted units in the copolymer complex also interact with homopolymers such as PEO and PVP to form ternary complex. Formation of complexes and replacement reactions could be shown through several experimental techniques, e.g., viscometry, conductometry, and potentiometry.     

Effect of radiation on the Peierls transition

The effect of radiation on the Peierls transition in a one-dimensional metal is investigated. It is pointed out that an external radiation field satisfying appropriate frequency conditions reduces the width of the Peierls gap.     

Influence of electrolytic hydrogen on the etch pit density of iron (110) surfaces

Etch pit densities on iron (110) surfaces in sulphuric acid grow linearly with the interfacial hydrogen activity in excess of a critical activity. The hydrogen activity is approximately proportional to the square root of the cathodic current density. At constant cathodic current density the etch pit density increases with temperature and decreases with external stress. Dislocations at which the excess etch pits form penetrate into the iron at a rate proportional to the hydrogen activity and the square root of time. Effects of prior hydrogen deposition on the shape of etch pits are seen at depths greater than the penetration depth of hydrogen generated dislocations. Changes of etch pit shape similar to those produced by hydrogen are also found when external stress is applied.The results are compared to Prussin's theory in which the assumption is made that stresses accompanying diffusion of an impurity are fully relieved by plastic deformation and formation of dislocations for stresses exceeding a critical stress. While some of the predictions of the theory are met by the experiments, the dislocations penetrate into the iron much slower than diffusion of hydrogen, since dislocations cannot move fast enough, i.e. stresses are not fully relieved.