Tensilely Strained Germanium Nanomembranes as Infrared Optical Gain Media

The use of tensilely strained Ge nanomembranes as mid‐infrared optical gain media is investigated. Biaxial tensile strain in Ge has the effect of lowering the direct energy bandgap relative to the fundamental indirect one, thereby increasing the internal quantum efficiency for light emission and allowing for the formation of population inversion, until at a strain of about 1.9% Ge is even converted into a direct‐bandgap material. Gain calculations are presented showing that, already at strain levels of about 1.4% and above, Ge films can provide optical gain in the technologically important 2.1–2.5 μm spectral region, with transparency carrier densities that can be readily achieved under realistic pumping conditions. Mechanically stressed Ge nanomembranes capable of accommodating the required strain levels are developed and used to demonstrate strong strain‐enhanced photoluminescence. A detailed analysis of the high‐strain emission spectra also demonstrates that the nanomembranes can be pumped above transparency, and confirms the prediction that biaxial‐strain levels in excess of only 1.4% are required to obtain significant population inversion.     

Sources accounting for alliance and cohesion at three stages in group psychotherapy: Variance component analyses.

This study examined patient, therapist, and group variability accounting for alliance and cohesion over three stages in a sample of 145 patients attending short- and long-term psychodynamic group therapy. G-study variance components were estimated for the 14 sources of variation identifiable by the research design. Results indicated that patient variability represented the strongest clinically relevant contribution to both alliance and cohesion. Therapists were important for alliance at all stages, but for cohesion only in the middle stage. The therapist × group interaction was important to the alliance in early therapy and for cohesion within the two first stages, but this contribution then decreased. Group length did not account for any variability in the process measures. Theoretical implications were discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

季铵型阳离子聚丙烯酰胺的无盐染色行为

以季铵型阳离子聚丙烯酰胺作为一种新的阳离子助剂对棉纤维进行处理,应用于活性染料无盐染色,对染色过程中染料与处理后棉纤维之间的吸附类型、吸附热力学及吸附动力学进行了研究。结果表明,无盐染色过程符合Langmuir吸附模型;吸附过程是放热自发进行的,低温有利于染料的吸附;吸附动力学符合二级动力学模型,属于化学吸附过程。与传统有盐染色结果相比,染色后的阳离子化棉纤维色深增加,染料利用率提高。     

Older people and mobile phones: A multi-method investigation

This paper investigates issues related to the use of mobile phones by people aged 60 years and over and characteristics of an ageing-friendly mobile phone. This study combines qualitative and quantitative analysis methods of Delphi interviews, focus group discussions, and online survey. The expert interviews and the focus group discussions covered usage patterns, problems, benefits, and desired and unwanted features. The issues raised in the discussions were translated into an online survey of 100 people. This study revealed that older people are passive users of mobile phones, that they experience fear of consequences of using unfamiliar technology, and that most preferred design features are aids for declining functional abilities. Gender differences in preferred design features were observed, with women focusing on haptic aids and men on perceptual aids.     

Descent via isogeny on elliptic curves with large rational torsion subgroups

We outline PARI programs which assist with various algorithms related to descent via isogeny on elliptic curves. We describe, in this context, variations of standard inequalities which aid the computation of members of the Tate–Shafarevich group. We apply these techniques to several examples: in one case we use descent via 9-isogeny to determine the rank of an elliptic curve; in another case we find nontrivial members of the 9-part of the Tate–Shafarevich group, and in a further case, nontrivial members of the 13-part of the Tate–Shafarevich group.     

Average causal effects from nonrandomized studies: A practical guide and simulated example.

In a well-designed experiment, random assignment of participants to treatments makes causal inference straightforward. However, if participants are not randomized (as in observational study, quasi-experiment, or nonequivalent control-group designs), group comparisons may be biased by confounders that influence both the outcome and the alleged cause. Traditional analysis of covariance, which includes confounders as predictors in a regression model, often fails to eliminate this bias. In this article, the authors review Rubin's definition of an average causal effect (ACE) as the average difference between potential outcomes under different treatments. The authors distinguish an ACE and a regression coefficient. The authors review 9 strategies for estimating ACEs on the basis of regression, propensity scores, and doubly robust methods, providing formulas for standard errors not given elsewhere. To illustrate the methods, the authors simulate an observational study to assess the effects of dieting on emotional distress. Drawing repeated samples from a simulated population of adolescent girls, the authors assess each method in terms of bias, efficiency, and interval coverage. Throughout the article, the authors offer insights and practical guidance for researchers who attempt causal inference with observational data. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Preparation of monodisperse hydrophilic polymer microspheres with N,N′‐methylenediacrylamide as crosslinker by distillation precipitation polymerization

Highly crosslinked cauliflower‐like poly(N,N′‐methylenebisacrylamide) particles were prepared by distillation precipitation polymerization in neat acetonitrile with 2,2′‐azobisisobutyronitrile as initiator. Monodisperse hydrophilic polymer microspheres with various functional groups, such as amide, pyrrolidone and carboxylic acid, with a spherical shape and smooth surface in the size range 120–600 nm were prepared by distillation precipitation copolymerizations of functional comonomers including N‐isopropylacrylamide, N‐vinylpyrrolidone, methacrylic acid with N,N′‐methylenebisacrylamide as crosslinker. The polymer particles were formed and precipitated out from the reaction medium during the distillation of the solvent from the reaction system through an entropic precipitation manner. The effects of the solvent and the degree of crosslinking on the morphology and the loading capacity of the functional groups of the resultant polymer particles were investigated. The resulting polymer particles were characterized with scanning electron microscopy, transmission electron microscopy, dynamic light scattering and Fourier transform infrared spectroscopy. Copyright © 2007 Society of Chemical Industry     

电网企业集团财务管理模式的探讨

通过对电网企业集团财务管理体制现状的分析，探索电网企业集团财务管理模式的方向，指出集中式的财务管理模式将成为电网企业集团财务管理的重要模式。     

Analysis of an automatic phase adjustment system for the output signal of a quantum group frequency and time keeper

An phase locked loop (PLL) system for the output signal of a quantum group frequency and time keeper is studied. A mathematical model of an PLL system is constructed and recommendations are provided for optimizing its parameters. __________ Translated from Izmeritel’naya Tekhnika, No. 3. pp. 21–26, March, 2008.     

基于开关组的禁忌算法在配电网动态重构中的应用

首先定义了一种基于重构次数的配电网优化模型，提出一种基于开关组的禁忌搜索算法求解优化模型。该方法用开关组状态作为编码的网络结构部分，减小了决策变量维数和不可行解的数量;用三进制时间码作为编码的时间部分，统一了码位取值范围，方便了禁忌表长度和终止条件的确定。另外，利用禁构规则来指导禁忌算法中邻域的生成，既减少了候选解个数，又避免了禁忌搜索中死循环的产生，大大提高了搜索的效率和质量。最后，通过与其他方法的比较，验证了所述算法的快速、有效性。