不含BPA的塑料更安全吗？

这篇短文是对另一篇文章的评论,关注的是化学材料安全性问题。发难者认为监管机构对新材料的审批过于简单,无法足以让公众感到这些材料更为安全。作者对此表明了自己的观点：鉴于围绕化学安全性的争论经过多年仍未有定论,我不认为业界及评论人士会就怎样的测试程度才算足够、以及如何为＂安全＂一词赋予确切的定义上达成一致。     

Small signal modeling of GaAs PIN diodes aided by electromagnetic analysis

A systematic procedure is described for determination of GaAs PIN diode equivalent circuit models from measured S‐parameter data combined with an electromagnetic analysis of the feed structure. A new parasitic and intrinsic model topology is proposed, and found to be better suited than prior models for the particular GaAs PIN structures considered in this work. Models were developed for forward bias currents ranging from 0.01 to 100 mA, and example measured and modeled results are included to validate the approach. © 2001 John Wiley & Sons, Inc. Int J RF and Microwave CAE 11: 61–68, 2001.     

Risk taking by adolescents with maladaptive behavior histories.

"High-risk" adolescents with maladaptive behavior histories and control adolescents (15–17 years of age) participated in a laboratory experiment that measured aspects of risk-taking behavior. High-risk adolescents had behavioral profiles entailing combinations of past substance use disorder, early onset substance use, conduct disorder, criminal history, and dropping out of school. A risk-taking task presented participants with "risky" and nonrisky response options. The risky response option offered a low probability of a large monetary reward or a high probability of a smaller monetary loss and resulted in a net loss of monetary earnings. The nonrisky option protected current earnings. High-risk adolescents chose the risky option more often, had lower overall earnings, and were more likely to persist in making (losing) risky responses following a single gain on the risky option. The data replicate previous findings with high-risk adults. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Rehabilitation psychology and public health: Commonalities, barriers, and bridges.

Purpose: Those in rehabilitation and those in public health have worked to find a place in their respective disciplines. In this article, the author attempts to outline some of the commonalities inherent in the two areas, the barriers to joint work, and the bridges that may be able to allow a more comfortable interaction between the two. Conclusion: Practical realities in modern society have created the need for a closer bond among rehabilitation psychology, disability, and public health. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A line-space analysis of light-field representations

We study how to build optimal light-field or plenoptic models. We quantify geometric errors in light-field representations and show how geometric error bounds directly affect rendering artifacts. Artifacts depend on how the light-field is parameterized, stored, reconstructed and rendered. We present the rendering artifacts and relate them to the presence of geometric errors in the four most common light-field implementations.We show how to optimize a light-field model. We take an arbitrary bounded object and construct the best possible representation using each of the four parameterizations. The best representation has the least geometric error bounds. We use two geometric errors, a positional and a directional error. We also quantify pixelation artifacts. Our analysis is useful to decide how to build a light-field model. It helps select a parameterization, build an optimal representation, and choose the samplings of the parameter spaces so that geometric errors and rendering artifacts are minimized.     

Effectiveness of cognitive/relaxation therapy and study-skills training in reducing self-reported anxiety and improving the academic performance of test-anxious students.

Determined whether study-skills training contributed to a treatment program that included relaxation training and cognitive therapy. 45 test-anxious undergraduates were randomly assigned to 1 of 4 treatment conditions: (a) relaxation/cognitive therapy, (b) study-skills training, (c) a combination of relaxation/cognitive therapy and study-skills training, or (d) no treatment. Pre- and posttreatment measures were collected on self-reported state anxiety and classroom examination performance. Findings show that relaxation/cognitive therapy was effective in reducing anxiety but failed to improve classroom test scores. Study-skills training had no significant effect on either measure. The combined therapy both reduced anxiety and improved performance relative to the no-treatment control condition and was significantly more effective than was either treatment alone. (37 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Ultrasonic Imaging of Porosity Variations Produced During Sinteriing

A silicon carbide disk was sintered from 2090° to 2190°C in 25°C steps. After each sintering step, the disk was examined using a precision acoustic scanning system to determine acoustic attenuation and velocity. The bulk density was found to vary non-monotonically with sintering temperature. The density varied as much as 10% from its value at 2090°C during the sintering process. Local density fluctuations occurred in an organized and history-dependent way. These local density fluctuations varied up to ±7% of the bulk density and were made visible by acoustic attenuation and velocity mapping.     

ORGANIC METAMORPHISM IN THE LOWER MISSISSIPPIAN-UPPER DEVONIAN BAKKEN SHALES — II: SOXHLET EXTRACTION1

In this paper, we report on Soxhlet extraction (and subsequent related analyses) of 39 Lower Mississippian-Upper Devonian Bakken shales from the North Dakota portion of the Williston Basin, and analyses of 28 oils from the Basin. Because of the influence of primary petroleum migration, no increase in the relative or absolute concentrations of hydrocarbons or bitumen was observed at the threshold of intense hydrocarbon generation (TIHG), or during mainstage hydrocarbon generation in the Bakken shales. Thus, the maturation indices that have been so useful in delineating the TIHG and mainstage hydrocarbon generation in other studies were of no use in this study, where these events could clearly be identified only by Rock-Eva1 pyrolysis data. The type of primary petroleum migration operative in the Bakken shales led to the selective concentration of certain compound types in the oils of the basin, as well as the selective concentration of certain compound types in the shale extracts. The compositional differences between the crude oils and shale extracts provide evidence of the primary migration mechanism operative in this case, which is believed to have been gaseous solution, although the actual expulsion of oil from the rock, if observed, would probably have appeared to be bulk phase migration. Gaseous-solution bulk-phase primary petroleum migration also left organic-geochemical imprints on the Bakken shales, observable by Soxhlet extraction and to a lesser extent by pyrolysis. The data of this study demonstrate that primary petroleum migration is a very efficient process. Four distinctive classes of saturated hydrocarbon gas chromatograms from the Bakken shales arose from facies, maturation, and primary migration controls. As a consequence of maturation, the percentage of saturated hydrocarbons increased in the shale extract at the expense of decreases in the resins and asphaltenes. Measurements involving resins and asphaltenes appear to be excellent maturation indices in the Bakken shales. Two different and distinct organic facies were present in immature Bakken shales. Rock-Eval pyrolysis analysis was a critical research tool in this study; however, combined use of pyrolysis and Soxhlet extraction allowed organic-geochemical features to be distinguished which would not have been possible by using either analysis alone.     

Early withdrawal from mental health treatment: Implications for psychotherapy practice.

[Correction Notice: An erratum for this article was reported in Vol 46(2) of Psychotherapy: Theory, Research, Practice, Training (see record 2009-08897-009). The fourth author’s name was mistakenly left out of the author byline and table of contents. The correct author listing for this article is presented in the erratum.] Despite more than 50 years of research on client attrition from therapy, obstacles to the delivery and success of treatments remain poorly understood, and effective methods to engage and retain clients in therapy are lacking. This article offers a review of the literature on attrition, highlighting the methodological challenges in effectively addressing the complex nature of this problem. Current interventions for reducing attrition are reviewed, and recommendations for implementing these interventions into psychotherapy practice are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)