Simulation of cup-cone fracture using the cohesive model

The cohesive model is used for the prediction of the crack path during stable crack extension in ductile materials. The problem of crack-path deviation is investigated by means of simulation of crack propagation in a round tensile bar. The respective phenomenon is known as cup-cone fracture. It is shown that the model is able to predict the failure mechanism, which consists of normal fracture in the center and combined normal/shear fracture in the so-called “shear lips” at the specimen’s rim. The damage evolution and crack path predicted by the model are presented. The effect of the normal and shear failure parameters on the crack-deflection point and several aspects of the finite element mesh are discussed.     

Athermal arrayed waveguide gratings in silicon-on-insulator by overlaying a polymer cladding on narrowed arrayed waveguides

Athermal arrayed waveguide gratings (AWGs) in silicon-on-insulator (SOI) are experimentally demonstrated for the first time to our knowledge. By using narrowed arrayed waveguides, and then overlaying a polymer layer, the wavelength temperature dependence of the AWGs is successfully reduced to -1.5 pm/°C, which is more than 1 order of magnitude less than that of normal SOI AWGs. The athermal behavior of the AWGs is obtained with little degradation of their performance. For the central channel, the cross talk is less than -15 dB and the insertion loss is around 2.6 dB. Good characteristics can be maintained with temperatures up to 75 °C. The total size of the device is 350 μm × 250 μm.     

Child negative emotionality and parenting from infancy to preschool: A meta-analytic review.

This meta-analytic review (k = 62 studies; N = 7,613 mother-child dyads) shows that effect sizes for the association between child negative emotionality and parenting were generally small and were moderated by sample and measurement characteristics. The association between more child negative emotionality and less supportive parenting was relatively strong in lower socioeconomic status families, reversed in higher socioeconomic status families, and limited to studies with relatively high percentages of participants from ethnic minorities and studies using parent report to assess negative emotionality. Higher levels of child negative emotionality were associated with more restrictive control in samples with less than 75% 1st-born children, as well as in infants and preschoolers, and in studies using parent report or composite measures to assess both negative emotionality and restrictive parenting. Finally, more child negative emotionality was associated with less inductive control. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Signals of threat do not capture, but prioritize, attention: A conditioning approach.

Research suggests that threatening information captures attention more rapidly than neutral information. However, in most studies threat stimuli differ perceptually from neutral stimuli and are instrumental to perform the task, leaving the question unanswered whether threat is sufficient to capture attention. In experiment 1, we designed a visual search task with stimuli of equal salience (colored circles) that have the potential to lead to efficient search (10 ms/item). In experiment 2, one of the colors (conditioned stimulus, CS+) was made threatening by means of fear conditioning. Participants responded to a target presented in one of the circles. Overall, the search was faster on congruent trials (where the target was presented in the CS+) than on baseline trials (where the CS + was absent). Furthermore, the search was slower on incongruent trials (where the target was presented in another color than the CS+) than on baseline trials. The search on congruent trials was affected by set size (90 ms/item), but to a lesser extent than on baseline trials (105 ms/item). We conclude that threat prioritizes, but does not capture attention. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Fracture toughness evaluation by tensile and charpy-type tests based on micromechanical models of materials

With the aim of applying micromechanical approaches to fracture mechanics, we carried out dynamic tensile tests and instrumented impact tests with Charpy-type specimens both with a V-shaped notch and with a crack. We compared two micromechanical strain-rate-dependent models based on a modified Gurson flow function by simulating various dynamically loaded specimens. The results of the tests indicate that the critical void volume fractionf _c and the characteristic lengthl _c are practically independent of the strain rate and the geometry of the specimen. The behavior of the specimens subjected to strains and fracture can be characterized by the parameters determined in tensile tests and impact tests with the Charpy-type specimens. By the three-dimensional analysis based on the strain-rate-dependent Gurson model, we predict the onset of crack growth inside the Charpy specimen.Fraunhofer Institut für Werkstoffmechanic, Freiburg, Deutschland. Published in Fiziko-Khimicheskaya Mekhanika Materialov, Vol. 30, No. 2, pp. 77–84, March–April, 1994.     

Enhanced Liposomal Drug Delivery Via Membrane Fusion Triggered by Dimeric Coiled-Coil Peptides

An ideal nanomedicine system improves the therapeutic efficacy of drugs. However, most nanomedicines enter cells via endosomal/lysosomal pathways and only a small fraction of the cargo enters the cytosol inducing therapeutic effects. To circumvent this inefficiency, alternative approaches are desired. Inspired by fusion machinery found in nature, synthetic lipidated peptide pair E4/K4 is used to induce membrane fusion previously. Peptide K4 interacts specifically with E4, and it has a lipid membrane affinity and resulting in membrane remodeling. To design efficient fusogens with multiple interactions, dimeric K4 variants are synthesized to improve fusion with E4-modified liposomes and cells. The secondary structure and self-assembly of dimers are studied; the parallel PK4 dimer forms temperature-dependent higher-order assemblies, while linear K4 dimers form tetramer-like homodimers. The structures and membrane interactions of PK4 are supported by molecular dynamics simulations. Upon addition of E4, PK4 induced the strongest coiled-coil interaction resulting in a higher liposomal delivery compared to linear dimers and monomer. Using a wide spectrum of endocytosis inhibitors, membrane fusion is found to be the main cellular uptake pathway. Doxorubicin delivery results in efficient cellular uptake and concomitant antitumor efficacy. These findings aid the development of efficient delivery systems of drugs into cells using liposome-cell fusion strategies.     

An evaluation of graduated driver licensing programs in North America using a meta-analytic approach

Most jurisdictions in North America have some version of graduated driver licensing (GDL). A sound body of evidence documenting the effectiveness of GDL programs in reducing collisions, fatalities and injuries among novice drivers is available. However, information about the relative importance of individual components of GDL is lacking. The objectives of this study are to calculate a summary statistic of GDL effectiveness and to identify the most effective components of GDL programs using a meta-analytic approach. Data from 46 American States, the District of Columbia and 11 Canadian jurisdictions are used and were obtained from the Fatality Analysis Reporting System (FARS) for the U.S. and from Transport Canada's Traffic Accident Information Database (TRAID) for Canada. The timeframe of this evaluation is 1992 through 2006, inclusive. Relative fatality risks and their 95% confidence intervals were calculated using fatality counts and population data for target and comparison groups, both in a pre-implementation and post-implementation period in each jurisdiction. The target groups were 16-, 17-, 18- and 19-year-old drivers. The comparison group was 25–54-year-old drivers. The relative fatality risks of all jurisdictions were summarized using the random effects DerSimonian and Laird model. Meta-regression using Restricted Maximum Likelihood (REML) and Markov Chain Monte Carlo (MCMC) Gibbs sampling was also conducted. Strong evidence in support of GDL was found. GDL had a positive and significant impact on the relative fatality risk of 16-year-old drivers (reduction of 19.1%). Significant effects were found for meta-regression models with 16-, 18- and 19-year-old drivers. These effects include length of night restriction in the learner stage, country, driver education in the learner stage and in the intermediate stage, whether night restrictions are lifted in the intermediate stage for work purposes, passenger restriction in the intermediate stage, whether passenger restrictions in the intermediate stage are lifted if passengers are family members, and whether there is an exit test in the intermediate stage. In conclusion, several GDL program components have an important effect on the relative fatality risk of novice drivers. These results help understand how such effects are achieved.     

Adoption and Use of Interorganizational ICT in a Construction Project

The objective of this research is to explain why actors are not using interorganizational information and communication technology (ICT) in construction projects in the intended way, by determining the mechanisms that influence the way actors use this ICT over time during a construction project. This explorative research results in a theoretical model that contains four key categories that explains the way actors use ICT in construction projects: (1) personal motivation; (2) external motivation; (3) knowledge and skills; and (4) acting opportunities. The model is compared with three existing influential models about the adoption and use of ICT: the unified theory of acceptance and use of technology, the theory of planned behavior, and the technology acceptance model. In these models missing elements are found. In addition, it is found that fundamental characteristics of construction projects, such as the fragmented and temporarily nature of construction projects, and the different working practices, resources, and objectives of the organizations involved cause most of the barriers to the intended use of interorganizational ICT.     

Evaluative conditioning in humans: A meta-analysis.

This article presents a meta-analysis of research on evaluative conditioning (EC), defined as a change in the liking of a stimulus (conditioned stimulus; CS) that results from pairing that stimulus with other positive or negative stimuli (unconditioned stimulus; US). Across a total of 214 studies included in the main sample, the mean EC effect was d = .52, with a 95% confidence interval of .466–.582. As estimated from a random-effects model, about 70% of the variance in effect sizes were attributable to true systematic variation rather than sampling error. Moderator analyses were conducted to partially explain this variation, both as a function of concrete aspects of the procedural implementation and as a function of the abstract aspects of the relation between CS and US. Among a range of other findings, EC effects were stronger for high than for low contingency awareness, for supraliminal than for subliminal US presentation, for postacquisition than for postextinction effects, and for self-report than for implicit measures. These findings are discussed with regard to the procedural boundary conditions of EC and theoretical accounts about the mental processes underlying EC. (PsycINFO Database Record (c) 2010 APA, all rights reserved)