The enhancement of diffusion by strain of InAs quantum dots in a GaAs matrix

We investigate the annealing behavior of Photoluminescence (PL) from self-assembled InAs quantum dots (QDs) with different thicknesses GaAs cap layers. The diffusion introduced by annealing treatment results in a blue-shift of the QD PL peak, and a decrease in the integrated intensity. The strain present in QDs enhances the diffusion, and the QDs with the cap layers of different thicknesses will experience a strain of different strength. This can lend to a, better understanding of the larger blue-shift of the PL peak of the deeper buried QDs, and the different variance of the full width at half maximum of the luminescence from QDs with the cap layers of different thicknesses.

Optical anisotropy of InAs submonolayer quantum wells in a (311) GaAs matrix

The steplike density of states obtained from reflectance-difference spectroscopy demonstrates that ultrathin InAs layers should be regarded as two-dimensional quantum wells rather than isolated clusters, even for the sample with only 1/3 monolayer InAs in (311)-oriented GaAs. The degree of anisotropy is within the intrinsic anisotropy of (311)-oriented ultrathin quantum wells, indicating that there is little structural or strain anisotropy in the InAs islands. (C) 1998 Elsevier Science B.V.

Influence of two different representations of the G-matrix to the in-medium nucleon-nucleon cross sections

We calculate the in-medium nucleon-nucleon scattering cross sections from the G-matrix using the Dirac-Brueckner-Hartree-Fock (DBHF) approach. And we investigate the influence of the different representations of the G-matrix to the cross sections, the difference of which is mainly from the different effective masses.

Determination and identification of isoflavonoids in Radix astragali by matrix solid-phase dispersion extraction and high-performance liquid chromatography with photodiode array and mass spectrometric detection

The isoflavonoids in Radix astragali were determined and identified by HPLC-photodiode array detection-MS after extraction employing matrix solid-phase dispersion (MSPD). As a new sample preparation method for R. astragali, the MSPD procedure was optimized, validated and compared with conventional methods including ultrasonic and Soxhlet extraction. The amounts of two major components in this herb, formononetin (6) and ononin (2), were determined based on their authentic standards. Four major isoflavonoids, formononetin (6), ononin (2), calycosin (5) and its glycoside (1), and three minor isoflavonoids, (6aR,11aR)-3-hydroxy-9, 10-dimethoxypterocarpan (7), its glycoside (3), and (3R)-7,2'-dihydroxy-3',4'-dimethoxyisoflavone-7-O-beta-D-glycoside (4), were identified based on their characteristic two-band UV spectra and [M + H](+), [aglycone + H](+) and [A1 + H](+) ions, etc. The combined MSPD and HPLC-DAD-MS method was suitable for quantitative and qualitative determination of the isoflavonoids in R. astragali. (C) 2003 Elsevier B.V. All rights reserved.

Enzymatic reaction of the immobilized enzyme on porous silicon studied by matrix-assisted laser desorption/ionization-time of flight-mass spectrometry

Desorption/ionization on silicon mass spectrometry (DIOS-MS) is a matrix-free technique that allows for the direct desorption/ionization of low-molecular-weight compounds with little or no fragmentation of analytes. This technique has a relatively high tolerance for contaminants commonly found in biological samples. DIOS-MS has been applied to determine the activity of immobilized enzymes on the porous silicon surface. Enzyme activities were also monitored with the addition of a competitive inhibitor in the substrate solution. It is demonstrated that this method can be applied to the screening of enzyme inhibitors. Furthermore, a method for peptide mapping analysis by in situ digestion of proteins on the porous silicon surface modified by trypsin, combined with matrix-assisted laser desorption/ionization-time of flight-MS has been developed.

Highly efficient separation of dsDNA fragments on glass chips by using an ultralow viscosity sieving matrix

A novel protocol has been established to separate dsDNA fragments with high efficiency on glass chips by using an ultralow viscosity sieving matrix with added glucose. Low-molecular-weight hydroxypropylmethylcellulose (HPMC), with a viscosity nearly equivalent to that of water, was used to electrophoretically separate fluorescent inter-calator-labeled double-stranded DNA (dsDNA) fragments on microfluidic glass chips. In comparison with conventional sieving protocols, low-molecular-weight HPMC as sieving matrix could result in reduced running cost and analysis time, in addition to a comparable separation efficiency of dsDNA fragments. In this paper, the addition of glucose was investigated to enhance the separation of DNA in the lowest viscosity polymer evaluated. The effect of staining dye and field strength were also evaluated. At an applied electric field strength of 200 V/cm, satisfactory resolution of the PBR322/HaeIII DNA marker could be achieved within 4 min by using 2% HPMC-5 with 6% glucose added. Coelectrophoresing PCR product along with phiX174/HaeIII DNA sizing marker was also demonstrated by using the ultralow viscosity HPMC-5 solution on a glass chip.