Numerical modeling of the dynamic tensile behavior of irregular fibers

Most fibers are irregular and are often subjected to rapid straining during mechanical processing and end‐use applications. In this article, the effect of fiber dimensional irregularities on the dynamic tensile behavior of irregular fibers was examined using the finite‐element method (FEM). Fiber dimensional irregularities are simulated with sine waves of different magnitude (10, 30, and 50% level of diameter variation). The tensile behavior of irregular fibers was examined at different strain rates (333, 3333, and 30,000%/s). The breaking load and breaking extension of irregular fibers at different strain rates were then calculated from the finite‐element model. The results indicate that strain rate has a significant effect on the dynamic tensile behavior of an irregular fiber, and that the position of the thinnest segment along the fiber significantly affects the simulation results. Under dynamic conditions, an irregular fiber does not necessarily break at the thinnest segment, which is different from the quasi‐static results. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 2855–2861, 2004     

An A to Z guide to DSM-IV conundrums.

The work on the 4th edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV) poses many puzzling conundrums that touch on complicated and important theoretical and practical issues. None of these can be resolved in the DSM-IV, but the authors hope that the Task Force's decisions will be informed by thorough reviews of the currently available evidence and extensive input from all sectors of the mental health field. A. J. Frances et al provide an alphabetical guide to DSM-IV conundrums that they hope will stimulate comments, suggestions, and criticisms about the work of the Task Force. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Responding to threat: Hemispheric asymmetries and interhemispheric division of input.

This investigation examined how hemispheric asymmetry and interhemispheric processing contribute to attentional biases toward emotional information. Participants (n?=?88) named the color of lateralized squares presented concurrently with neutral, positive, or threatening words. A left-hemisphere advantage in color naming was reduced when distractors were emotional, suggesting right-hemisphere priming by emotional stimuli. Furthermore, the advantage of dividing the word and color across visual fields was increased for emotion words when they were frequently presented, indicating a strategic use of interhemispheric division of labor to reduce the distracting effect of emotional words. Finally, participants with high levels of anxious apprehension were most likely to make use of this interhemispheric processing strategy, supporting a processing efficiency theory of cognitive function in anxiety. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Causal inferences about communicators and their effect on opinion change.

An attribution analysis of opinion change viewed message persuasiveness as a function of inferred communicator biases. Recipients infer a knowledge bias (KB) by believing that a communicator's knowledge about external reality is nonveridical and a reporting bias (RB) by believing that a communicator's willingness to convey an accurate version of external reality is compromised. In an experiment with 355 undergraduates, KB expectancies were established by portraying a communicator as having a strong commitment to values represented by the probusiness or proenvironment side of a controversial issue and RB expectancies by portraying his audience as having a strong commitment to one or the other side. In all conditions, the communicator advocated the proenvironment position. Therefore, recipients' expectancies were confirmed in the context of a proenvironment communicator and/or audience and disconfirmed in the context of a probusiness communicator and/or audience. Regardless of the type of bias that Ss expected, they were more persuaded and rated the communicator as more unbiased when their expectancies were disconfirmed. Confirmation of expectancies based on RB, but not KB, was associated with inferences of communicator insincerity and manipulativeness. (21 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The roles of self-esteem and self-consciousness in the Wortman-Brehm model of reactance and learned helplessness.

Studied the conditions under which failure would enhance or inhibit subsequent task performance. Based on the theory of C. B. Wortman and J. W. Brehm (1975), it was expected that small amounts of failure would produce reactance (manifested by improved performance at a subsequent task); large amounts would lead to learned helplessness (i.e., impaired later performance). It was further expected that individual differences in self-esteem and private self-consciousness would serve as moderator variables for the effects. In Exp I, 78 college students were exposed to either a small amount or no failure before working on an anagrams task. As predicted, Ss high in self-consciousness, who showed greater reactance arousal in attitude change studies, performed better on the anagrams task than Ss low in self-consciousness in the small-failure condition, but not in the no-failure condition. In Exp II, 119 Ss were pretreated with either a small amount of failure, an extended amount of failure, or no failure before working on the task. A significant Self-Esteem by Helplessness Training interaction emerged. Low self-esteem Ss (low SEs) performed marginally better than did high SEs in the small-failure condition but significantly worse than high SEs in the extended-failure condition. Questionnaire data from Exp II were consistent with the notion that enhanced performance reflected reactance, whereas impaired performance signified helplessness. (20 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A novel paradigm to investigate regulation of drug intake in rats self-administering cocaine or heroin intravenously.

The purpose of this experiment was to investigate the regulation of drug intake in rats (n?=?20) self-administering heroin or cocaine during daily 5-hr sessions. Operant chambers were equipped with 2 levers and associated stimulus lights. A response on the lever with stimuli signaling an increase in dose size increased the infusion duration by 3 s, and a response on the lever with stimuli signaling a decrease in dose size decreased the infusion duration by 3 s. Results showed that daily and hourly drug intake for cocaine and heroin groups were relatively constant. Significant correlation coefficients were obtained for heroin and cocaine groups for the relationship between interdose interval (IDI) and infusion duration (dose size). These findings indicate that subjects regulated their drug intake by adjusting IDI throughout drug self-administration sessions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Rubber-toughening of plastics

The effects of stress-and strain-history upon the mechanical properties of HIPS (highimpact polystyrene) and of blends containing HIPS and PPO^R resin have been studied in a number of different tests, including repeated creep testing of individual specimens and repeated tensile tests at constant strain-rate upon individual specimens. The results show that craze formation increases volume and lowers Young's modulus in specimens subjected to tensile strain, and that strained specimens recover only slowly towards the properties of the unstrained material. Recovery is accelerated by heating, or by immersion in alcohols. A given initial strain produces a greater reduction in modulus in HIPS, which deforms almost entirely by crazing, than in HIPS/PPO blends, which deform by a combination of crazing and shear band formation. The properties of strained specimens are dominated by the distinctive non-linear mechanical behaviour of crazes, and the problems of constructing models to represent this behaviour are discussed.     

Feeding conditions alter the demand for phencyclidine and ethanol: A behavioral analysis.

This experiment examined the effects of feeding conditions on orally self-administered phencyclidine (PCP) or ethanol in rhesus monkeys using a behavioral≡oral economic analysis. Drug intake was measured as a function of drug cost, which was varied by changes in the fixed ratio (FR) schedule. The monkeys were trained to respond for PCP (0.25 mg/ml) or ethanol (8% wt/vol) with concurrent water available under FR 4-128 schedules. As the FR increased. drug intake decreased in a positively decelerating manner. Results suggest that food deprivation increased the reinforcement value of the drugs as well as significantly increasing consumption of both PCP and ethanol. In addition, ethanol and PCP deliveries showed proportionally greater increases due to food deprivation as FR increased. Together, these results suggest that food deprivation increases the reinforcing efficacy of drugs and this eifect is enhanced as the cost (FR) of the drug increases. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Availability of Sunshine

Tables of sunrise, sunset and maximum possible duration of sunrise for London are given. Average measured sunshine data for London based on a period of 10 years areanalysed to give average hourly and daily durations of sunshine, average sunshine durations for certain intervals of the day and percentage frequencies of days with sunshine duration exceeding a specified duration. Similar data are analysed for Edinburgh, to produce tables of average hourly and daily durations of sunshine throughout the year. To facilitate the application of these data, a design aid in the form of a sunlight availability protractor has been developed. This is described and its applicability discussed.