Room-temperature continuous-wave lasing from InAs GaAs quantum dot laser grown by molecular beam epitaxy

Quantum dot lasers are predicted to have proved lasing characteristics compared to quantum well and quantum wire lasers. We report on quantum dot lasers with active media of vertically stacked InAs quantum dots layers grown by molecular beam epitaxy. The laser diodes were fabricated and the threshold current density of 220 A/cm(2) was achieved at room temperature with lasing wavelength of 951 nm. The characteristic temperature To was measured to be 333K and 157K for the temperature range of 40-180K and 180-300K, respectively.

Generation of optimized wavelength-tunable optical pulse from an uncooled gain-switched Fabry-Perot semiconductor laser using optical amplifier as external light injection

We present a novel system design that can generate the optimized wavelength-tunable optical pulse streams from an uncooled gain-switched Fabry-Perot semiconductor laser using an optical amplifier as external light source. The timing jitter of gain-switched laser has been reduced from about 3 ps to 600 fs and the pulse width has been optimized by using our system. The stability of the system was also experimentally investigated. Our results show that an uncooled gain-switched FP laser system can feasibly produce the stable optical pulse trains with pulse width of 18 ps at the repetition frequency of 5 GHz during 7 h continuous working. We respectively proved the system feasibility under 1 GHz, 2.5 GHz and 5 GHz operation. (c) 2008 Elsevier B.V. All rights reserved.

Application of matrix-assisted laser desorption/ionization-time of flight-mass spectrometry and sodium dodecyl sulfate-polyacrylamide gel electrophoresis in determining arginine esterase from snake venom

Using matrix-assisted laser desorption/ionization-time of flight-mass spectrometry (MALDI-TOF-MS). The homogeneities and molecular weights of three arginine esterases from snake venom, which possessing therapeutic use in myocardial infarction, were determined and compared, MALDI-TOF-MS is possessed of high accuracy, high sensitivity and rapidity. MALDI-TOF-MS and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) can provide complementary and confirmatory results information. MALDI-TOF-MS can be directly used as an important method for the purification of snake venom complexes successfully.

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometric analysis of phospholipase A(2) and fibrinolytic enzyme, two enzymes obtained from Chinese Agkistrodon blomhoffii Ussurensis venom

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) was used to analyze two enzymes, phospholipase AZ and fibrinolytic enzyme isolated from Chinese Agkistrodon blomhoffii Ussurensis venom. Using sinapinic acid as the matrix, positive ion mass spectra of the enzymes were obtained, In addition to the dominant protein [M+H](+) ions, multimeric and multiply charged ions were also observed in the mass spectra, The higher the concentration of the enzymes, the more multiply charged polymer and multimeric ions were detected, Our results indicate that MALDI-TOFMS can provide a rapid and accurate method for molecular weight determination of snake venom enzymes, Mass accuracies of 0.1 and 0.3 % were achieved by analysis of highly dialyzed phospholipase A2 and fibrinolytic enzyme, and these results are much better than those obtained using sodium dodecyl sulfate-palyacrylamide gel electrophoresis. MALDI-TOFMS thus provides a reliable method to determine the purity and molecular weight of these enzymes, which are of potential use as therapeutants, Copyright (C) 1999 John Wiley & Sons, Ltd.

A study of Aconitum alkaloids from aconite roots in Aconitum carmichaeli Debx using matrix-assisted laser desorption ionization mass spectrometry

In the present paper a study of C-19-diterpene type of aconitum alkaloids, extracted from aconite roots in Aconitum carmichaeli Debx has been made using matrix-assisted laser desorption/ionization time of Eight mass spectrometry (MALDI-TOFMS), The results demonstrated that the aconitum alkaloids from aconite roots can be determined simultaneously by this method, which was found to be superior to other analytical methods with regard to speed and sensitivity. Fourteen known aconitum alkaloids, including aconitines, benzoylaconitines and lipoaconitines, were assigned in the methanol extract and three compounds not reported before have been targeted separation. The evaluation of the efficiency of different extractions has been studied. These results suggested that the differences of the polarity and basicity of aconitine, and benzoylaconitines and lipoaconitines result from the C-8 constituent groups that are easily lost under MALDI, (C) 1998 John Wiley & Sons, Ltd.