Long-wavelength light emission from InAs quantum dots covered by GaAsSb grown on GaAs substrates

We fabricated InAs quantum dots (QDs) with a GaAsSb strain-reducing layer (SRL) on a GaAs(0 0 1) substrate. The wavelength of emission from InAs QD is shown to be controllable by changing the composition and thickness of the SRL. An increase in photoluminescence intensity with increasing compositions of Sb and thickness of the GaAsSb SRL is also seen. The efficiency of radiative recombination was improved under both conditions because the InAs/GaAsSb/GaAs hetero-interface band structure more effectively suppressed carrier escape from the InAs QDs.     

A globally convergent Newton method for solving strongly monotone variational inequalities

Variational inequality problems have been used to formulate and study equilibrium problems, which arise in many fields including economics, operations research and regional sciences. For solving variational inequality problems, various iterative methods such as projection methods and the nonlinear Jacobi method have been developed. These methods are convergent to a solution under certain conditions, but their rates of convergence are typically linear. In this paper we propose to modify the Newton method for variational inequality problems by using a certain differentiable merit function to determine a suitable step length. The purpose of introducing this merit function is to provide some measure of the discrepancy between the solution and the current iterate. It is then shown that, under the strong monotonicity assumption, the method is globally convergent and, under some additional assumptions, the rate of convergence is quadratic. Limited computational experience indicates the high efficiency of the proposed method.     

Electron g-factor in a gated InAs-inserted-channel In0.53Ga0.47As/In0.52Al0.48As heterostructure

We report on electron g-factor in an InAs-inserted In_0.53Ga_0.47As/In_0.52Al_0.48As heterostructure. The gate voltage dependence of g-factor is obtained from the coincidence method. The obtained g-factor values are surprisingly smaller than the g-factor value of bulk InAs, and it is close to the bare g-factor value of In_0.53Ga_0.47As. The large change in g-factor is observed by applying the gate voltage. The obtained gate voltage dependence is not simply explained by the energy dependence of g-factor.     

Analytical high-performance affinity chromatography of ovalbumin-derived glycopeptides on columns of concanavalin A-and wheat germ agglutinin-immobilized gels

Concanavalin A (Con A) or wheat germ agglutinin (WGA) was immobilized on a silica-based support, and the chromatographic behaviours of a series of dansylated ovalbumin-derived glycopeptides on small columns of the resultant gels were compared. These columns had high contents of lectins, and allowed differentiation of these glycopeptides. This method was rapid and reproducible, and enabled sensitive detection of these fluorescent glycopeptides. The structural requirement of these glycopeptides to manifest affinity to the immobilized lectins is also discussed, based on binding constants obtained from their retention times.     

Application of negative chemical ionization mass spectrometry to the structure elucidation of perfluorochemicals and related compounds

The negative chemical ionization mass spectra of representative perfluorinated alkanes, cycloalkanes, ethers and tertiary amines have been examined, using Ar at about 0.5 torr as the reagent gas. The compounds chosen are typical of those under study as components of fluorochemical emulsion blood substitutes. Many such PFC's, particularly those with cyclic or branched structures, give intense molecular ions; most give simple spectra with a few major fragment ions at high mass, in marked contrast to the EI spectra which are dominated by m/e 69 (CF₃+) and 131 (C₃F₅+) of no value for structure elucidation. NCI-GC/MS is more sensitive than conventional EI-GC/MS and promises to be more generally useful for structure determination. Specific examples from the various classes will be presented, and their NCI and EI mass spectra compared.     

Synthesis of large macrocyclic tetraaza compounds with a methylene backbone: Cyclo[-NH- (CH2)n-]4, (n = 6, 7, 8, 9 and 10). The formation of 28-, 32-, 36-, 40- and 44-membered rings

A series of macrocyclic tetraamines with 28-, 32-, 36-, 40- and 44-membered rings have been efficiently prepared from the corresponding ditosylamide and monobromoalcohol derivatives in 6 steps via a double condensation reaction. Overall yields were: 41, 41, 46, 29, and 33%, respectively, for 1,8,15,22-tetraazacyclooctacontane ( 11a ), 1,9,17,25-tetraazacyclodotriacontane ( 11b ), 1,10,19,28-tetraazacyclohexatriacontane ( 11c ), 1,11,21,31-tetraazacyclotetracontane ( 11d ) and 1,12,23,34-tetraazacyclotetratetracontane ( 11e ).