EXPERIMENTS AND INELASTIC ANALYSIS OF THE LOOP TACK TEST FOR PRESSURE-SENSITIVE ADHESIVES

The loop tack test is studied experimentally and numerically using a model system. The ends of a steel strip are clamped together, giving a teardrop shape, and the loop is pushed downward onto an acrylic foam tape and then pulled upward off the tape. In the finite element analysis, the strip is represented by beam elements and a bilinear elastic-plastic constitutive law. The traction-separation relationship for the pressure-sensitive adhesive (PSA) is modeled with a trapezoidal cohesive zone. Viscoelastic behavior of the PSA is included in one case. Curves of the pulling force versus the top displacement (i.e., tack curves) exhibit a sharp peak just before separation of the loop from the strip. The effects of the PSA parameters, contact length, loop length and thickness, and loading rate are investigated. The numerical results compare more favorably with the experimental results than do those from a previous elastic analysis.     

Silver nanoparticles as selective ionization probes for analysis of olefins by mass spectrometry

Laser desorption/ionization (LDI) using silver nanoparticles (AgNPs) is shown to selectively ionize olefinic compounds, e.g., cholesterol, 1-palmitoyl-2-oleoyl- sn-glycero-3-phosphocholine (POPC), and carotenoids. Selective AgNP LDI can be carried out from complex mixtures without the addition of an organic matrix, sample cleanup, or prefractionation. Results presented in this report are the first to demonstrate the selective ionization of specific compounds from a complex mixture using metal nanoparticles.     

Working memory capacity moderates the predictive effects of drug-related associations on substance use.

Some theories suggest that spontaneously activated, drug-related associations in memory may have a "freer reign" in predicting drug use among individuals with lower working memory capacity. This study evaluated this hypothesis among 145 at-risk youth attending continuation high schools (CHS). This is the 1st study to evaluate this type of dual-process interaction in the prediction of drug use among a sample of at-risk adolescents. The CHS students completed assessments of drug-related memory associations, working memory capacity, and drug use. Control variables included age, gender, ethnicity, and acculturation. Robust multiple regression using least trimmed squares estimation indicated that there was a significant linear by linear interaction between working memory capacity (assessed with the self-ordered pointing task) and drug-related associations (assessed with verb generation and cue-behavior association tasks) in the prediction of alcohol and cigarette use. Consistent with dual-process cognitive theories, drug-related associations in memory predicted drug use more strongly in students with lower levels of working memory capacity. These findings add to the literature implicating the influence of dual cognitive processes in adolescent risk behaviors. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Microfluidic deans switch for comprehensive two-dimensional gas chromatography

A microfluidic Deans switch was used as a comprehensive two-dimensional gas chromatography (GCxGC) modulator. The simplicity and wide temperature range of the Deans switch make it a promising alternative to existing modulation techniques. However, the Deans switch is a low duty cycle modulator; that is, it samples only a small portion of the primary column effluent. Like all low duty cycle modulators, the Deans switch produces inconsistent transfer of components from the primary to the secondary column if the primary peaks are undersampled. Theoretical simulations and experimental studies show that the relative standard deviation (RSD) of the fraction of material transferred from the primary column to the secondary column is less than 1% if the modulation ratio is greater than 2.5. But the RSDs increase rapidly as the modulation ratio is decreased below 2.5. Deans switch GCxGC was validated by analyzing the aromatic content of gasoline. A fast analysis (<10 min) produced narrow primary peaks and a modulation ratio of 1.7. The quantitative results were in good agreement with results obtained with differential flow modulation GCxGC and GC/MS, but the RSDs of single-component levels were approximately three times greater. The Deans switch modulator was also used for a slower gasoline analysis (33 min run time) that produced modulation ratios near 5. In this case, the quantitative results and RSDs were in excellent agreement with the differential flow GCxGC and GC/MS results. These studies demonstrate that a Deans switch can be an effective modulator provided that modulation ratios greater than approximately 2.5 are employed.     

Parameter Estimation for a Generalized Gamma Distribution

It is fairly commonplace in reliability analyses to encounter data which is incompatible with the exponential, Weibull, and other familiar probability models. Such data motivates research to enlarge the group of probability distributions which are useful to the reliability analyst.

In this paper, we examine a three-parameter generalization of the gamma distribution and derive parameter estimation techniques for that distribution. Those techniques, in the general case, depend upon method of moments considerations which lead to simultaneous equations for which closed form solutions are not available. Graphic solution is proposed and aids to the computations are provided. Major concepts in the paper are summarized by means of a numerical example.

Details are given for the special case in which only the scale parameter is unknown. Three unbiased estimators for that parameter are derived along with their variance formulas. Minimum variance considerations are discussed by application of the Cramér-Rao Theorem.     

Affect, personality, and social activity.

Examined relations between social activity and state and trait measures of Positive and Negative Affect. In Study 1, Ss completed scales relevant to 3-factor models of personality and a weekly mood and social activity questionnaire for 13 wks. In Study 2, Ss completed measures of the 5-factor model of personality and a daily mood and social activity survey for 6–7 wks. In within- and between-Ss analyses, socializing correlated significantly with state measures of Positive Affect and with trait measures of Extraversion/Positive Emotionality. These relations were relatively general across various types of positive affect and social events; however, specific types of social events also were differentially related to affect. In contrast, social activity had no consistent association with measures of Negative Affect or the other personality dimensions. The results support a temperamental view of Extraversion. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

锡膏检测--统筹协调各要素

现在有不计其数的文章和实例说明采用二维或三维锡膏检测工艺来控制印刷流程,排除或发现粘贴印刷中出现的错误具有很多优点。作为自动光学检测(AOI)和锡膏检测(SPI)领域的领导者,安捷伦科技公司可以证实大多数公司和人都赞同的一个事实,即当今的制造领域面对日益严峻的芯片规模包装(CSP)挑战,而且部件已经降到0201级,所以制订一定的测试方案非常必要。但是在设计锡膏检测使用模式中碰到的最大问题之一是:在设计一个强有力的生产流程并随后控制这个流程时,要考虑到每一个生产流程有自身的一套变量。在锡膏检测业中最常出现的问题是用户希望只使用一个规则或流程控制模式来建立一个成功的锡膏检测方案。锡膏检测使用模式不同于电子检测和其他过去失败的测试策略,它是一个为用户度身设计的检测战略,需要锡膏检测用户预先工作以建立最佳的流程控制方法。概述了一种可用于成功进行锡膏测试的方法论或思维过程。这一方法论将有助于发现锡膏使用模式,并推进锡膏检测方案合理而有效的实施。     

Antarctic research bases: local sources of polybrominated diphenyl ether (PBDE) flame retardants

Contemporary studies of chemical contamination in Antarctica commonly focus on remnants of historical local releases or long-range transport of legacy pollutants. To protect the continent's pristine status, the Antarctic Treaty's Protocol on Environmental Protection prohibits importation of persistent organic pollutants. However, some polybrominated diphenyl ether (PBDE) congeners exhibit similar properties. Many modern polymer-containing products, e.g., home/office furnishings and electronics, contain percent levels of flame retardant PBDEs. PBDE concentrations in indoor dust and wastewater sludge from the U.S. McMurdo and New Zealand-operated Scott Antarctic research bases were high. Levels tracked those in sludge and dust from their respective host countries. BDE-209, the major constituent in the commercial deca-PBDE product, was the dominant congener in sludge and dust, as well as aquatic sediments collected near the McMurdo wastewater outfall. The pattern and level of BDE-209 sediment concentrations, in conjunction with its limited environmental mobility, suggest inputs from local sources. PBDE concentrations in fish and invertebrates near the McMurdo outfall rivaled those in urbanized areas of North America and generally decreased with distance. The data indicate that reliance on wastewater maceration alone, as stipulated by the Protocol, may permit entry of substantial amounts of PBDEs and other chemicals to the Antarctic environment.