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Internal Parameters (internal + parameter)
Selected AbstractsInternal parameters and optical properties of green II-VI heterostructure lasers with active region composed of multi-sheet electronically-coupled CdSe quantum dotsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 6 2010Aliaksei G. Vainilovich Abstract Optically pumped green-emitting ZnSe-based laser heterostructures of optimized design have been grown by molecular-beam epitaxy and studied. The structures containing five electronically-coupled stacked CdSe quantum dot (QD) sheets demonstrate the minimum threshold power density of 2.2 kW/cm2 and the maximum external quantum efficiency of , 50%. Internal laser characteristics were determined by measuring the differential laser efficiency and laser threshold of a series of samples with different cavity lengths. The characteristic gain and internal quantum efficiency of the structures have been shown to reach the values as high as ,G0 = 114 cm -1 and ,i = 65.4%, while the transparency threshold and internal losses are evaluated as low as IT = 1.22 kW/cm2 and ,i = 2.55 cm -1, respectively. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] A stationary-wave model of enzyme catalysisJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 2 2010Carlo Canepa Abstract An expression for the external force driving a system of two coupled oscillators in the condensed phase was derived in the frame of the Debye theory of solids. The time dependence and amplitude of the force is determined by the size of the cell embedding the coupled oscillators and its Debye temperature (,D). The dynamics of the driven system of oscillators were followed in the two regimes of (a) low ,D and cell diameter, as a model of liquid water, and (b) large ,D and cell diameter, as a model of the core of a protein. The response in potential energy of the reference oscillator was computed for all possible values of the internal parameters of the system under investigation. For protein cores, the region in the parameter space of high maximum potential energy of the reference oscillator is considerably extended with respect to the corresponding simulation for water. © 2009 Wiley Periodicals, Inc. J Comput Chem, 2010 [source] Mechanism and dynamics of organic reactions: 1,2-H shift in methylchlorocarbene,JOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 8 2002Elfi Kraka Abstract The unified reaction valley approach (URVA) was used to investigate the mechanism of the rearrangement of methylchlorocarbene to chloroethene [reaction(1)] in the gas phase with special emphasis on the role of H tunneling. The reaction valley of (1) was explored using different methods (HF, MP2 and DFT/B3LYP) and different basis sets [6,31G(d), 6,31G(d,p) and cc-pVTZ]. Results were analyzed characterizing normal modes, reaction path vector and curvature vector in terms of generalized adiabatic modes associated with internal parameters that are used to describe the reaction complex. For reaction (1), H tunneling plays a significant role even at room temperature, but does not explain the strongly curved Arrhenius correlations observed experimentally. The probability of H tunneling can be directly related to the curvature of the reaction path and the associated curvature couplings. The reaction is preceeded in the forward and reverse direction by energy-consuming conformational changes that prepare the reactant for the actual 1,2-H shift, which requires only little energy. The effective energy needed for CH bond breaking is just 6,kcal,mol,1 for (1). The gas-phase and the solution-phase mechanisms of (1) differ considerably, which is reflected by the activation enthalpies: 11.4 (gas, calculated) and 4.3,kcal,mol,1 (solution, measured). Stabilizing interactions with solvent molecules take place in the latter case and reduce the importance of H tunneling. The non-linearity of the measured Arrhenius correlations most likely results from bimolecular reactions of the carbene becoming more important at lower temperatures. Copyright © 2002 John Wiley & Sons, Ltd. [source] Chain Conformations in the Crystalline Field of Syndiotactic Vinyl Polymers Deriving from 1,3-Diene Monomers.MACROMOLECULAR THEORY AND SIMULATIONS, Issue 8 2004Analysis by Molecular Mechanics Abstract Summary: Conformational energy calculations on the chain conformation in the crystalline field have been performed for various syndiotactic vinyl polymers deriving from 1,3-diene monomers. Energy maps as a function of the independent torsion angles have evidenced for all the polymers minima corresponding to highly extended and to helical chains. Energy minimizations as a function of all the internal parameters for the s(2/1)2 and tcm symmetries have allowed the evaluation of the energy differences between chains having the two symmetries and the prediction of the values of the conformational parameters for each polymer. The results have been compared with the experimental data reported in the literature for some of the studied polymers. Conformational energy map of sPBD12. [source] Comparative Analysis of Muscle Architecture in Primate Arm and ForearmANATOMIA, HISTOLOGIA, EMBRYOLOGIA, Issue 2 2010Yasuhiro Kikuchi With 7 figures and 3 tables Summary A comparative study of myological morphology, i.e. muscle mass (MM), muscle fascicle length and muscle physiological cross-sectional area (an indicator of the force capacity of muscles), was conducted in nine primate species: human (Homo sapiens), chimpanzee (Pan troglodytes), gibbon (Hylobates spp.), papio (Papio hamadryas), lutong (Trachypithecus francoisi), green monkey (Chlorocebus aethiops), macaque monkey (Macaca spp.), capuchin monkey (Cebus albifrons) and squirrel monkey (Saimiri sciureus). The MM distributions and the percentages in terms of functional categories were calculated as the ratios of the muscle masses. Moreover, individual normalized data were compared directly amongst species, independent of size differences. The results show that the different ratios of forearm-rotation muscles between chimpanzee and gibbons may be related to the differences in their main positional behaviour, i.e. knuckle-walking in chimpanzees and brachiation in gibbons, and the different frequencies of arm-raising locomotion between these two species. Moreover, monkeys have larger normalized MM values for the elbow extensor muscles than apes, which may be attributed to the fact that almost all monkeys engage in quadrupedal locomotion. The characteristics of the muscle internal parameters of ape and human are discussed in comparison with those of monkey. [source] | ||||||||||