Band structures and optical properties of GaInAs quantum wires grown by strain-induced lateral ordering

Band structures and optical matrix elements of strained multiple quantum-wires (QWR's) are investigated theoretically via the effective bond-orbital model, which takes into account the effects of valence-band anisotropy and the band mixing. In particular, the Ga$_{1-x}$In$_x$As QWR's grown by strain-induced lateral ordering (SILO) are considered. Recently, long wavelength Ga$_{1-x}$In$_x$As QWR lasers have been fabricated via a single step molecular beam epitaxy technique which uses the SILO process.[1] Low threshold current and high optical anisotropy have been achieved. Multi-axial strains [combinations of biaxial strains in the (001) and (110) planes] for QWR's are considered, Our calculated anisotropy in optical matrix elements (for light polarized parallel versus perpendicular to the QWR's axis) is in good agreement with experiment. We also find that the strain tends to increase the quantum confinement and enhance the anisotropy of the optical transitions.Comment: 11 papges, 10 figure

RAG-1 Mutations Associated with B-Cell-Negative SCID Dissociate the Nicking and Transesterification Steps of V(D)J Recombination

Some patients with B-cell-negative severe combined immune deficiency (SCID) carry mutations in RAG-1 or RAG-2 that impair V(D)J recombination. Two recessive RAG-1 mutations responsible for B-cell-negative SCID, R621H and E719K, impair V(D)J recombination without affecting formation of single-site recombination signal sequence complexes, specific DNA contacts, or perturbation of DNA structure at the heptamer-coding junction. The E719K mutation impairs DNA cleavage by the RAG complex, with a greater effect on nicking than on transesterification; a conservative glutamine substitution exhibits a similar effect. When cysteine is substituted for E719, RAG-1 activity is enhanced in Mn2+ but remains impaired in Mg2+, suggesting an interaction between this residue and an essential metal ion. The R621H mutation partially impairs nicking, with little effect on transesterification. The residual nicking activity of the R621H mutant is reduced at least 10-fold upon a change from pH 7.0 to pH 8.4. Site-specific nicking is severely impaired by an alanine substitution at R621 but is spared by substitution with lysine. These observations are consistent with involvement of a positively charged residue at position 621 in the nicking step of the RAG-mediated cleavage reaction. Our data provide a mechanistic explanation for one form of hereditary SCID. Moreover, while RAG-1 is directly involved in catalysis of both nicking and transesterification, our observations indicate that these two steps have distinct catalytic requirements

STUDYING THE CARRY-OVER EFFECT IN END USER COMPUTER TRAINING: PROPOSITION OF A RESEARCH AGENDA

The carry-over effect in end user computer training refers to the transfer of a person\u27s computer skills from one application to another. The importance of the carry-over effect is unquestionable, but its nature has not been well understood. In this article, a research agenda is developed to analyze the nature, the roles, and the antecedents of the carry-over effect. Three fundamental questions are asked: 1) what is the carry-over effect and how to measure it? 2) What roles does it play in end user computer training? And 3) what factors determine the carry-over effect? Propositions are developed to give directions in further empirical research, and some preliminary evidences are discussed. Potential implications for Information Systems research and practice are discussed

Systematic study of Ga1−x_{1-x}Inx_xAs self-assembled quantum wires with different interfacial strain relaxation

A systematic theoretical study of the electronic and optical properties of Ga$_{1-x}$In$_x$As self-assembled quantum-wires (QWR's) made of short-period superlattices (SPS) with strain-induced lateral ordering is presented. The theory is based on the effective bond-orbital model (EBOM) combined with a valence-force field (VFF) model. Valence-band anisotropy, band mixing, and effects due to local strain distribution at the atomistic level are all taken into account. Several structure models with varying degrees of alloy mixing for lateral modulation are considered. A valence force field model is used to find the equilibrium atomic positions in the QWR structure by minimizing the lattice energy. The strain tensor at each atomic (In or Ga) site is then obtained and included in the calculation of electronic states and optical properties. It is found that different local arrangement of atoms leads to very different strain distribution, which in turn alters the optical properties. In particular, we found that in model structures with thick capping layer the electron and hole are confined in the Ga-rich region and the optical anisotropy can be reversed due to the variation of lateral alloying mixing, while for model structures with thin capping layer the electron and hole are confined in the In-rich region, and the optical anisotropy is much less sensitive to the lateral alloy mixing.Comment: 23 pages, and 8 figure

The financial clouds review

This paper demonstrates financial enterprise portability, which involves moving entire application services from desktops to clouds and between different clouds, and is transparent to users who can work as if on their familiar systems. To demonstrate portability, reviews for several financial models are studied, where Monte Carlo Methods (MCM) and Black Scholes Model (BSM) are chosen. A special technique in MCM, Least Square Methods, is used to reduce errors while performing accurate calculations. The coding algorithm for MCM written in MATLAB is explained. Simulations for MCM are performed on different types of Clouds. Benchmark and experimental results are presented for discussion. 3D Black Scholes are used to explain the impacts and added values for risk analysis, and three different scenarios with 3D risk analysis are explained. We also discuss implications for banking and ways to track risks in order to improve accuracy. We have used a conceptual Cloud platform to explain our contributions in Financial Software as a Service (FSaaS) and the IBM Fined Grained Security Framework. Our objective is to demonstrate portability, speed, accuracy and reliability of applications in the clouds, while demonstrating portability for FSaaS and the Cloud Computing Business Framework (CCBF), which is proposed to deal with cloud portability