(e, 3e) test on e-e correlations in helium

The angular variations of the five-fold differential cross section obtained by using different wave functions of helium are compared with experimental data. It is found that in the coplanar geometry two kinematical arrangements, (i) equal energy sharing between the two ejected electrons with one of them ejected along the momentum transfer direction and the other along varying direction and (ii) the Bethe ridge condition with fixed sum of ejected electron energies and varying angle between them, are very sensitive to e-e correlations contained in the target wave function. This comparison has been used to show that open-shell class of wave functions better incorporate e-e correlations than the closed-shell class.     

PMD-compensation techniques

PMD has become a serious limitation for the advent of 40G optical transmission systems. Commercial operators still avoid the utilization of optical PMD compensators since crucial questions such as expected performance and reliability are still subject to research and are not yet satisfactory answered for all relevant cases. The common solutions of tackling PMD, e.g., limiting transmission distance or selecting low-PMD fibers, does not necessarily apply for optical OTDM systems with bit rates beyond 160 Gbit/s. This article describes current approaches for PMD compensators with special focus on the requirements of optical OTDM systems.     

Theory of sheath in a collisional multi-component plasma

The aim of this brief report is to study the behaviour of sheath structure in a multi-component plasma with dust-neutral collisions. The plasma consists of electrons, ions, micron size negatively charged dust particles and neutrals. The sheath-edge potential and sheath width are calculated for collisionally dominated sheath. Comparison of collisionless and collisionally dominated sheath are made.     

Fast iterative methods for symmetric sinc-Galerkin systems

The symmetric sinc-Galerkin method developed by Lund, when appliedto the second-order self-adjoint boundary value problem, givesrise to a symmetric coefficient matrix has a special structureso that it can be advantageously used in solving the discretesystem. In this paper, we employ the preconditioned conjugategradient method with banded matrices as preconditioners. Weprove that the condition number of the preconditioned matrixis uniformly bounded by a constant independent of the size ofthe matrix. In particular, we show that the solution of an n-by-ndiscrete symmetric sinc-Galerkin system can be obtained in O(nlog n) operations. We also extend our method to the self-adjointelliptic partial differential equation. Numerical results aregiven to illustrate the effectiveness of our fast iterativesolvers.     

(e, 3e) Differential cross section of He (21 S) and He (23 S)

The angular distribution of the five-fold differential cross section for the electron impact double ionization of He (2¹ S) and He (2³ S) has been studied. The kinematical conditions for maxima/minima in the angular distribution for the two cases have been compared. The two-step process for the double ionization is found to contribute very little in the triplet case.     

Pseudo-bistable self-actuated domes for morphing applications

We present a new concept of morphing bistable structure which relies on viscoelastic effects. We show how a careful choice of geometrical and material parameters for an isotropic spherical dome can result in a pseudo-bistable structure which, once actuated, can return to its original state without further actuation. A numerical model is used to investigate the effect of various parameters on the nature of the pseudo-bistability, and a global geometrical parameter is found to govern the characteristic response of the structure. Experimental results demonstrate this phenomenon in a real dome.     

Microwave absorption studies of MgB2 superconductor

Microwave absorption studies have been carried out on MgB₂ superconductor using a standard X-band EPR spectrometer. The modulated low-field microwave absorption signals recorded for polycrystalline (grain size ∼ 10 μm) samples suggested the absence of weak-link character. The field dependent direct microwave absorption has been found to obey a ✓H dependence with two different slopes, which indicated a transition from strongly pinned lattice to flux flow regime.     

Catalytic contributions of key residues in the adenine glycosylase MutY revealed by pH-dependent kinetics and cellular repair assays

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Highlights? Asp 138 must be deprotonated to stabilize the transition state for maximal activity ? Consequences of altering catalytic amino acids in MutY on cellular mismatch repair ? Correlation of MutY enzymatic parameters with ability to mediate cellular repair ? Importance of high affinity binding of MutY to the OG:A mismatch for high levels of repair     

The demethylation chemistry of 3-substituted 2-methoxypyridines

Upon acylation of 3-amino-2-methoxypyridines, two side products were discovered, a pyridone, 5,6 , and 8 , and a pyridyloxazine, 4 and 9. The ratios of these products can be affected by changes in the reaction parameters. When oxalyl chloride was the acylating agent a pyridone 13 was isolated.