Continuous-wave lasing of single-mode metamorphic quantum dot lasers for the 1.5-μm spectral region

Lasers based on InAs/InGaAs quantum dots grown on metamorphic (In,Ga,Al)As layers deposited by MBE on GaAs substrates exhibited emission near 1.5 μm with a differential quantum efficiency of about 50%. The narrow-stripe lasers operate in a single transverse mode and withstand continuous current density above 20 kA cm^?2 without significant degradation. A maximum continuous-wave output power of 220 mW is obtained. Neither current nor beam filamentation was observed up to the highest pumping levels.     

Temperature dependence of the effective coefficient of Auger recombination in 1.3 μm InAs/GaAs QD lasers

Semiconductor laser heterostructures containing five and ten sheets of InAs/GaAs QDs on GaAs substrates, with an emission wavelength of ～1.3 μm, have been studied. Dependences of the nonradiative lifetime and effective Auger coefficient in QDs are obtained from an analysis of temperature and current dependences of the efficiency of spontaneous radiative recombination. The zero-threshold Auger recombination channel in QDs is shown to dominate at low (below 200 K) temperature, whereas at higher temperatures the quasithreshold channel becomes dominant. The effective 3D Auger coefficient is estimated in the approximation of a spherical QD, and a good agreement with the experimental data is obtained.     

The effect of a two-week anti-orthostatic hypokinesia on the cardiac function and on the latter''s regulation in monkeys

Medical practice guidelines are being developed rapidly and advocated as a crucial component in transforming and improving the delivery of health care services. However, little is known about the ability of hospitals to institute guidelines outside of experimental settings. This article approaches guideline implementation from the viewpoint of process innovation assimilation and presents specific recommendations for organizational tactics leading to successful implementation of practice guidelines.     

Viscoelastic characteristics of mixed compositions based on polyethylene and polypropylene

VNIISV, Tver'. Institute of Chemical Physics, Moscow. Translated from Khimicheskie Volokna, No. 3, pp. 42–43, May–June, 1992.     

Sorption of U(VI) onto Layered Double Hydroxides of Mg and Al with β-Cyclodextrin from Aqueous Solutions

Theoretical Foundations of Chemical Engineering - The possibility of removing U(VI) from aqueous solutions using layered double hydroxides of Mg and Al, which contain β-cyclodextrin...     

Structural states of aluminum-lithium alloy 1469 sheets

The texture and microstructure of the central layers in alloy 1469 sheets and the orientations of hardening T₁-phase precipitates are studied by X-ray diffraction, optical microscopy, and transmission electron microscopy. These studies and X-ray diffraction performed in asymmetric geometry demonstrate that the texture of the material is formed by the broadening of the orientations located near a β skeleton line. The contribution to an X-ray diffraction pattern from two of the four possible versions of the orientations of hardening T₁-phase plates that are caused by a brass-type texture component in the matrix and the orientation relationships between the matrix and the T₁-phase lattices is separated. The microstructure of the sheets is shown to have a two-level character. It is formed by extended (up to several millimeters long) regions fragmented into grains several microns in size. The structural states of the sheet material are discussed in their relation to the crystallographic character of fatigue crack propagation.     

Local triboelectrification of an n-GaAs surface using the tip of an atomic-force microscope

The method of scanning Kelvin-probe microscopy is used to show that the effect of triboelectrification is observed when the tip of an atomic-force microscope interacts with the surface of n-GaAs epitaxial layers. The sign of the change in the potential indicates that the sample surface after triboelectrification becomes more negative. The observed specific features of the phenomena can be attributed to the thermally activated generation of point defects in the vicinity of the sample surface due to deformation caused by the tip.     

Steady states of a biotechnological process for producing lactic acid at a given substrate concentration in the inlet stream

Relationships are derived that form the domain in which the multiplicity of steady states exists for the continuous process of lactic acid production in a fermenter with stirring. Algorithms are described for estimating the technological characteristics of the process under the conditions of multiplicity. Methods and results of calculations are presented for different variants of specifying the concentration of a substrate in the inlet stream, and examples of numerical calculations are given.     

Interaction of Acoustic Waves with Moving Boundaries

Russian Engineering Research - The interaction of an ultrasonic probe with a vibrating boundary surface is considered in a quasi-static approximation. A model of boundary-problem type is expressed...