Auxetic materials — A review

Auxetic materials are endowed with a behavior that contradicts common sense, when subjected to an axial tensile load they increase their transverse dimension. In case of a compression load, they reduce their transverse dimension. Consequently, these materials have a negative Poisson’s ratio in such direction. This paper reviews research related to these materials. It presents the theories that explain their deformation behavior and reveals the important role represented by the internal structure. Their mechanical properties are explored and some potential applications for these materials are shown.     

The combined effect of melt stirring and ultrasonic agitation on the degassing efficiency of AlSi9Cu3 alloy

The combined effect of high intensity ultrasound and melt stirring on the degassing of AlSi₉Cu₃ using simultaneously the novel MMM (Multi-frequency Multimode Modulated) ultrasonic technology to promote cavitation, and low frequency mechanical vibration to induce melt stirring, was studied. On a first stage single low frequency mechanical vibration experiments were carried out in water in order to visualize and characterize its individual effect on the liquid dynamics. On a second stage ultrasonic vibration combined with different mechanical vibration frequencies, melt temperatures and processing times were tested in liquid AlSi₉Cu₃ alloy and their influence on the degassing efficiency was evaluated and compared with the results of the single MMM ultrasonic degassing technique. Fixed ultrasonic parameters (frequency and electric power) were used, according to the best results obtained in former experimental works developed by the authors. For the experimental conditions used in this research, it was found that melt stirring significantly improves degassing efficiency, and such improvement depends on the metal temperature and the mechanical vibration frequency. The experimental results suggest that combining melt agitation and ultrasonic vibration it is possible to achieve almost the aluminum alloy theoretical density without increasing the processing time.     

Dark energy: recent observations and future prospects

Dark energy presents us with a challenging puzzle: understanding the new physics seen in the acceleration of the expansion of the Universe. Measurements using type-Ia supernovae (SNe) first detected this acceleration, and this approach remains the most direct route to studying the details of the Universe's expansion history that can teach us more about the nature of the dark energy. Such measurements are, however, extremely demanding in both precision and accuracy, since the different dark-energy models predict very small differences in the expansion history. While several cosmological probes may reach the required statistical uncertainties, the key measurement limit will be the systematic uncertainty. The supernova-measurement approach has the advantage of well-studied systematic uncertainties, allowing a next-generation experiment to be pursued. We briefly review the progress to date and examine the promise of future surveys with large numbers of SNe and well-bounded systematics.     

X-Ray luminescence of polycrystalline TbO<Subscript>2</Subscript>-doped Li<Subscript>2</Subscript>B<Subscript>4</Subscript>O<Subscript>7</Subscript>

This paper examines the effect of doping level on the X-ray luminescence of TbO₂-doped polycrystalline lithium tetraborate. It is shown that, when interpreting such spectra, it is convenient to proceed from the terms of free activator and constituent ions. We demonstrate that the emission lines of Tb³⁺ in doped polycrystalline lithium tetraborate are effectively excited in the band between 350 and 650 nm, which is predominantly due to electron transitions from the ⁵ D ₃ and ⁵ D ₄ excited states to spin-orbital levels of the ⁷ F _J ground multiplet. The emission lines of lithium and boron in single-crystal and polycrystalline undoped lithium tetraborate are effectively excited in the band between 274 and 550 nm.     

More on the psychology of false confessions.

Responds to comments by J. T. McCann (see record 1998-00122-001) and A. Reifman (see record 1998-00122-002) concerning S. M. Kassin's article (see record 1997-07781-003) on the psychology of false confessions. It is stated that these commentaries offer interesting perspectives with which to expand what is currently known about the psychology of confession evidence. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Ecological momentary assessment in a behavioral drinking moderation training program.

We assessed predictors of self-reported excessive drinking (>5 drinks) in a sample of heavy drinkers. Participants were randomly assigned to moderation training or a waiting-list control condition. They were trained in ecological momentary assessment (EMA) involving self-monitoring of drinking and other variables on a small hand-held computer, the electronic diary (ED). During the 8-week study, participants were compliant in their use of the ED for both random prompts and the entry of data related to specific drinking episodes. Generalized estimating equations were used to fit models involving predictors related to past history of drinking, aspects of the training program, drinking restraint, and episode-specific mood. The models indicated robust predictors of decreased and increased drinking. Our results suggest that EMA is a useful methodology for assessing drinking and related behaviors. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of task strain, social conflict, and emotional activation on ambulatory cardiovascular activity: Daily life consequences of recurring stress in a multiethnic adult sample.

Ambulatory blood pressure (ABP) may be an independent predictor of cardiovascular endpoints, but little is known about its psychosocial determinants. The acute effects of psychosocial processes on cardiovascular activity during daily life were examined by random-effects regression. Healthy adults (N?=?120) were monitored over a 6-day period with ABP monitors and computer-assisted self-report assessments. Task strain, social conflict, and emotional activation were rated following each ABP measurement, as were activity, posture, and other covariates. Results show that blood pressure) (BP) and heart rate (HR) were elevated during periods of emotional activation (high negative affect or high arousal). Diastolic BP was lower during periods involving high decisional control, and HR was lower during high-control, low-demand activities. There were substantial individual differences in the effects of psychosocial influences on ambulatory cardiovascular activity. Psychological factors are reliable determinants of ABP, which may account for the unique predictive value of ABP. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Negative Affect and Smoking Lapses: A Prospective Analysis.

Relapse is a central problem in smoking treatment. Data collected at the time of relapse episodes indicate that stress and negative affect (NA) promote relapse, but retrospective data are potentially biased. The authors performed a prospective analysis of stress and NA prior to initial lapses in smokers (N = 215). Day-to-day changes in stress (daily negative and positive events and Perceived Stress Scale scores) and NA (multiple momentary affect ratings) did not predict lapse risk on the following day. However, within the lapse day itself, NA was already significantly increasing hours before lapses, but only for episodes attributed to stress or bad mood. Thus, rapid increases in NA, but not slow-changing shifts in stress and NA, were associated with relapse. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Smoking patterns and dependence: Contrasting chippers and heavy smokers.

The authors used ecological momentary assessment to contrast smoking patterns among chippers (CHs; n = 26)--smokers who smoke despite an apparent absence of tobacco dependence--with those seen in heavy smokers (HSs; n = 28). Smoking and nonsmoking settings (activity, mood, etc.) were assessed by means of electronic diary. CHs were not social smokers; like HSs, they smoked half their cigarettes while alone. When smoking, CHs' urge levels equaled those of HSs; between cigarettes, CHs had few urges, whereas HSs reported moderate urges. CHs' smoking was particularly associated with indulgent activities: relaxation, socializing, eating, and drinking alcohol. Outside of these indulgent settings, CHs' (but not HSs') smoking was associated with negative affect. In idiographic analyses, CHs' smoking was under much stronger stimulus control than was that of HSs. The authors propose that the disappearance of stimulus control over use is a characteristic of dependence. (PsycINFO Database Record (c) 2010 APA, all rights reserved)