Ab-initio effective potentials in crystal Hartree-Fock theory

Ab initio effective potential technique of Ewiget al is applicable directly to crystal Hartree-Fock formalism provided the effective potentials are suitably defined. Corresponding to every atom or every molecule by constructing a crystal one can assign a unit species configuration. The effective potentials in the crystal can be expressed as functions of lattice parameters in terms of integrals over the orbitals of this unit species. These expressions are in a more exact form than those usually employed in molecular calculations.     

Genetic contribution to high neonatally lethal malformation rate in the United Arab Emirates

OBJECTIVES: We examined the contribution of genetic disorders to congenital anomalies (CA) causing neonatal deaths in the Al Ain Medical District (AMD) in the United Arab Emirates (UAE) because of the high consanguineous marriage rate in the community. METHODS: Charts of all neonatal deaths in the three perinatal units, which accounted for 99% of all births in AMD (1992-2000), were studied. Data regarding pregnancy, a family history including the level of parental consanguinity, the results of genetic evaluations and neonatal outcomes were recorded as part of an ongoing malformation surveillance system. Causes of death were based on clinical, laboratory and imaging findings. RESULTS: Of the 508 neonates who died, 212 (42%) had CA, which were the leading cause of death. Forty-four percent of the CA were due to definite genetic disorders and 75% of these were single gene defects. Multisystem malformations were the commonest congenital malformations. Parental consanguinity was associated with a 2-fold increased risk of non-chromosomal multisystem malformations. CONCLUSIONS: Lethal malformations were the leading cause of neonatal deaths, and parental consanguinity was associated with an increased risk of autosomal recessive disorders. The results underscore the importance of genetic screening and counseling in strategies for further significant reductions in the neonatal mortality rate in the UAE.     

Cavitation bubble-driven cell and particle behavior in an ultrasound standing wave

The self- and mutual radiation impedances and the farfield directional response of rectangular pistons conformal to a rigid elliptic cylindrical baffle are formulated. The pistons are assumed to vibrate with uniform normal velocity and the solution for the acoustic pressure is expressed in terms of a modal series representation in Mathieu functions. The Mathieu functions are obtained using computer programs that have been recently developed to provide accurate values of the functions at high frequencies. Results for the normalized self- and mutual radiation resistance and reactance and the directional response of acoustic radiation are presented over a wide frequency range for different piston sizes and elliptic cylinder cross section shapes.     

Quantum chaos in the Yang-Mills-Higgs system at finite temperature

Quantum chaos in the finite-temperature Yang-Mills-Higgs system is studied. The energy spectrum of a spatially homogeneous SU(2) Yang-Mills-Higgs system is calculated within thermofield dynamics. Level statistics of the spectra is studied by plotting nearest-level spacing distribution histograms. It is found that finite-temperature effects lead to a strengthening of chaotic effects, i.e. a spectrum which has the Poissonian distribution at zero temperature has the Gaussian distribution at finite temperature.Received: 18 August 2004, Revised: 23 March 2005, Published online: 22 June 2005PACS: 05.45.-a,11.10.Wx, 11.15.-q     

Wavelength division multiplexed loop buffer memory based optical packet switch

Photonic all-optical switching is widely considered as one of the technique to utilize the enormous optical bandwidth. Optical packet switching provides high speed, data rate transparency, data format transparency, efficient use of bandwidth and flexibility. To resolve the conflict during contention, packets are needed to be buffered. Due to the lack of optical RAM, fiber delay lines (FDLs) are the most suited option to buffer the packets. This paper proposes new optical packet switch architecture alongwith feedback shared buffer utilizing the advantage of WDM loop buffer memory. The loop buffer module used in this switch architecture is a new approach towards WDM buffering of packets. The mathematical modeling is done to validate the results obtained from simulation.     

Real-time determination of the slippage length in autophobic polymer dewetting

We investigated the kinetics of autophobic dewetting, caused by differences in entropy, of a polymer melt slipping on a monolayer of end-grafted identical molecules (polymer brush). From simultaneous measures of the dewetted distance and the width of the resulting rim, we obtained in real time and quantitatively the slippage length and the contact angle, a measure of the "incompatibility" between identical molecules. Furthermore, we could directly relate a decrease in the slippage length in the course of the experiments at elevated temperatures to temporal or permanent attachment of polymers from the melt to the brush.     

Generating Relations of the Hypergeometric Functions by the Lie Group-Theoretic Method

In this paper, the generating relations for a set of hypergeometric functions _,,,m (x) are obtained by using the representation of the Lie group SL(2,C) giving a suitable interpretation to the index m in order to derive the elements of Lie algebra. The principle interest in our results lies in the fact that a number of special cases would inevitably yield too many new and known results of the theory of special functions, namely the Laguerre, even and odd generalized Hermite, Meixner, Gottlieb, and Krawtchouk polynomials.     

Photoluminescence of ion-implanted phosphors

Ion-implanted phosphors were prepared by implanting Sb in CaS at 25 keV with concentration ranging from 0.05 to 0.2% by weight. Samples of similar concentration were also prepared using the conventional technique. The spectral response under UV excitation of both types of samples is compared.     

X-Ray K-absorption edges of cobalt in two recently prepared chelates

K-absorption edges of cobalt in two chelates,viz., Co (II) bis S-ethyl 1-amidino 2-thiourea and Co (III) isonitroso acetylacetonate have been recorded photographically. The results have been discussed in the light of available magnetic measurements and favour a tetragonal structure for the first and an octahedral one for the second chelate.