Effects of hydrogen assisted stress corrosion on damage tolerance of a high-strength duplex stainless steel wire for prestressing concrete

The study brings new insights on the hydrogen assisted stress corrosion on damage tolerance of a high-strength duplex stainless steel wire which concerns its potential use as active reinforcement for concrete prestressing. The adopted procedure was to experimentally state the effect of hydrogen on the damage tolerance of cylindrical smooth and precracked wire specimens exposed to stress corrosion cracking using the aggressive medium of the standard test developed by FIP (International Prestressing Federation). Stress corrosion testing, mechanical fracture tests and scanning electron microscopy analysis allowed the damage assessment, and explain the synergy between mechanical loading and environment action on the failure sequence of the wire. In presence of previous damage, hydrogen affects the wire behavior in a qualitative sense, consistently to the fracture anisotropy attributable to cold drawing, but it does not produce quantitative changes since the steel fully preserves its damage tolerance.

Proposal of a new indicator to define ductility applied to corroded steel reinforcement on concrete structures = Propuesta de un nuevo indicador para definir la ductilidad aplicada a la corrosión del acero de refuerzo en estructuras de hormigón

The carbonation of concrete or the chlorides ingress in such quantity to reach the level of bars is triggers of reinforcement corrosion. One of the most significant effects of reinforcing steel corrosion on reinforced concrete structures is the decline in the ductility-related properties of the steel. Reinforcement ductility has a decisive effect on the overall ductility of reinforced concrete structures. Different Codes classify the type of steel depending on their ductility defined by the minimum values of several parameters. Using indicators of ductility associating different properties can be advantageous on many occasions. It is considered necessary to define the ductility by means of a single parameter that considers strength values and deformation simultaneously. There are a number of criteria for defining steel ductility by a single parameter. The present experimental study addresses the variation in the ductility of concrete-embedded steel bars when exposed to accelerated corrosion. This paper analyzes the suitability of a new indicator of ductility used in corroded bars.

Response-reinforcement learning is dependent on N-methyl-d-aspartate receptor activation in the nucleus accumbens core

The nucleus accumbens, a site within the ventral striatum, is best known for its prominent role in mediating the reinforcing effects of drugs of abuse such as cocaine, alcohol, and nicotine. Indeed, it is generally believed that this structure subserves motivated behaviors, such as feeding, drinking, sexual behavior, and exploratory locomotion, which are elicited by natural rewards or incentive stimuli. A basic rule of positive reinforcement is that motor responses will increase in magnitude and vigor if followed by a rewarding event. It is likely, therefore, that the nucleus accumbens may serve as a substrate for reinforcement learning. However, there is surprisingly little information concerning the neural mechanisms by which appetitive responses are learned. In the present study, we report that treatment of the nucleus accumbens core with the selective competitive N-methyl-d-aspartate (NMDA) antagonist 2-amino-5-phosphonopentanoic acid (AP-5; 5 nmol/0.5 μl bilaterally) impairs response-reinforcement learning in the acquisition of a simple lever-press task to obtain food. Once the rats learned the task, AP-5 had no effect, demonstrating the requirement of NMDA receptor-dependent plasticity in the early stages of learning. Infusion of AP-5 into the accumbens shell produced a much smaller impairment of learning. Additional experiments showed that AP-5 core-treated rats had normal feeding and locomotor responses and were capable of acquiring stimulus-reward associations. We hypothesize that stimulation of NMDA receptors within the accumbens core is a key process through which motor responses become established in response to reinforcing stimuli. Further, this mechanism, may also play a critical role in the motivational and addictive properties of drugs of abuse.

Gray's Reinforcement Sensitivity Theory: a psychometric critique

This study identifies valid orthogonal scales of Gray's animal learning paradigms, upon which his Reinforcement Sensitivity Theory (RST) is based, by determining a revised structure to the Gray-Wilson Personality Questionnaire (GWPQ) (Wilson, Gray, & Barrett, 1990). It is also determined how well Gray's RST scales predict the surface scales of personality, which were measured in terms of Eysenck Personality Profiler (EPP) scales, the EPQ-R and the learning styles questionnaire (LSQ) scales. First, results suggest that independent pathways of RST scales may exist in humans. Second, Fight seems related to Anxiety and not the Fight/Flight system as proposed by RST. Third. a remarkably consistent story emerges in that Extraversion scales are predicted by Fight, Psychoticism scales are predicted by Active-avoidance, Fight and/or Flight, and Neuroticism scales tend not to be predicted at all (except for Anxiety). Fourth, Gray's revised scales are Unrelated to gender and age effects and show a predictable overlap with the LSQ and original GWPQ scales. It is concluded that Gray's model of personality might provide a stable biological basis of many surface scales of personality, but that there must also be other influences on personality. These results question the finer structure of Gray's RST whilst also showing that RST has greater range of applicability than a strict interpretation of theory implies. (C) 2002 Elsevier Science Ltd. All rights reserved.

Reinforcement drives rapid allopatric speciation

Allopatric speciation results from geographic isolation between populations. In the absence of gene flow, reproductive isolation arises gradually and incidentally as a result of mutation, genetic drift and the indirect effects of natural selection driving local adaptation(1-3). In contrast, speciation by reinforcement is driven directly by natural selection against maladaptive hybridization(1,4). This gives individuals that choose the traits of their own lineage greater fitness, potentially leading to rapid speciation between the lineages(1,4). Reinforcing natural selection on a population of one of the lineages in a mosaic contact zone could also result in divergence of the population from the allopatric range of its own lineage outside the zone(4-6). Here we test this with molecular data, experimental crosses, field measurements and mate choice experiments in a mosaic contact zone between two lineages of a rainforest frog. We show that reinforcing natural selection has resulted in significant premating isolation of a population in the contact zone not only from the other lineage but also, incidentally, from the closely related main range of its own lineage. Thus we show the potential for reinforcement to drive rapid allopatric speciation.

The new reinforcement sensitivity theory: Implications for personality measurement

In this article, we review recent modifications to Jeffrey Gray's (1973, 1991) reinforcement sensitivity theory (RST), and attempt to draw implications for psychometric measurement of personality traits. First, we consider Gray and McNaughton's (2000) functional revisions to the biobehavioral systems of RST Second, we evaluate recent clarifications relating to interdependent effects that these systems may have on behavior, in addition to or in place of separable effects (e.g., Corr 2001; Pickering, 1997). Finally, we consider ambiguities regarding the exact trait dimension to which Gray's It reward system corresponds. From this review, we suggest that future work is needed to distinguish psychometric measures of (a) fear from anxiety and (b) reward-reactivity-from trait impulsivity. We also suggest, on the basis of interdependent system views of RST and associated exploration using formal models, that traits that are based upon RST are likely to have substantial intercorrelations. Finally, we advise that more substantive work is required to define relevant constructs and behaviors in RST before we can be confident in our psychometric measures of them.

Effects of special educator peer coaching on general educator effectiveness in inclusive classroom settings

This dissertation investigated the effects of a peer coaching relationship between a special education teacher and two general education teachers. More specifically, a two-tier multiple baseline design across subjects was used to evaluate the effects of peer coaching on the general education teachers' use of effective instructional practices (EIPs) and subsequent effects on the engagement rate and academic performance of students with and without disabilities. The peer coaching process included modeling, direct support, and feedback on the use of effective instructional practices including getting student attention, giving specific directions, asking specific questions with wait time, contingent positive reinforcement, positive error correction, precorrection, prompting, and proximity control. A 30-second partial interval recording procedure was used to observe the general education teachers' use of effective instructional practices and student engagement rates. Student participants' academic performance was measured using weekly quizzes. ^ Peer coaching resulted in an overall increase in the teachers' use of EIPs. One general education teacher had a 30% increase in average EIP use from 46% during the baseline phase to 76% during intervention. Student engagement for her two student participants with and without disabilities indicated an increase from 54% to 69% and from 47% to 65% respectively. Results for the second general education teacher indicated a 34% increase in average EIP use from 55% during the baseline to 89% during intervention. Student engagement for the two student participants with and without disabilities in her class increased from 48% to 83% and from 29% to 71% respectively. Student academic performance showed a small increase. In follow-up observations, the effects of peer coaching on teacher use of EIPs and student engagement and academic performance were maintained. ^ The results of this study suggest that using peer coaching to support general education teachers can be an effective method to improve the educational outcomes of students with and without disabilities in general education. Further research is needed to investigate the effects of peer coaching with other special and general educator partnerships and other student participants. ^

Cognitive behavior therapy for anxiety disorders in youth: Treatment specificity and mediation effects

The present study investigated the efficacies of Individual CBT (ICBT), Parent Relationship Skill Training (RLST, which targets increasing parental acceptance of youth and increasing autonomy granting) and Parent Reinforcement Skills Training (RLST, which targets increasing parental positive reinforcement and decreasing negative reinforcement). The specific aims were to examine treatment specificity and mediation effects of parenting variables. ICBT was used as a baseline comparison condition. The sample consisted of 253 youth (ages 5-16 years; M = 9.38; SD = 2.42) and their parents. To examine treatment outcome and specificity, the data were analyzed using analysis of variance within a structural equation modeling framework. Mediation was analyzed via structural equation modeling using MPlus. Results indicated that ICBT, RLST, and RFST produced positive treatment outcomes across all indices of change (i.e., clinically significant improvement, anxiety symptom reduction) and across all informants (i.e., youths and parents). RLST was associated with incremental reduction in youth anxiety symptoms beyond ICBT, as per youth report. Treatment specificity effects were found for participants in RFST in terms of parental reinforcement, as per parent report only. Treatment mediation was not found for any of the hypothesized parenting variables (i.e., parental acceptance, parental autonomy granting, parental reinforcement). The results support the use of CBT involving only the youth and the parent and youth together for treating youth anxiety. The findings’ implications are further discussed in terms of the need to conduct further meditational treatment outcome designs in order to continue to advance theory and research in youth anxiety treatment.

Basalt Fibre Reinforced Polymer Strengthening of Normal Strength Reinforced Concrete Floor Slabs Subject to Arching Effects

With ever increasing demands to strengthen existing reinforced concrete structures to facilitate higher loading due to change of use and to extend service lifetime, the use of fibre reinforced polymers (FRPs) in structural retrofitting offers an opportunity to achieve these aims. To date, most research in this area has focussed on the use of glass fibre reinforced polymer (GFRP) and carbon fibre reinforced polymer (CFRP), with relatively little on the use of basalt fibre reinforced polymer (BFRP) as a suitable strengthening material. In addition, most previous research has been carried out using simply supported elements, which have not considered the beneficial influence of in-plane lateral restraint, as experienced within a framed building structure. Furthermore, by installing FRPs using the near surface mounted (NSM) technique, disturbance to the existing structure can be minimised.
This paper outlines BFRP NSM strengthening of one third scale laterally restrained floor slabs which reflect the inherent insitu compressive membrane action (CMA) in such slabs. The span-to-depth ratios of the test slabs were 20 and 15 and all were constructed with normal strength concrete (~40N/mm2) and 0.15% steel reinforcement. 0.10% BFRP was used in the retrofitted samples, which were compared with unretrofitted control samples. In addition, the bond strength of BFRP bars bonded into concrete was investigated over a range of bond lengths with two different adhesive thicknesses. This involved using an articulated beam arrangement in order to establish optimum bond characteristics for use in strengthening slab samples.

Effects of infiltration pressure on mechanical properties of Al–12Si/graphite composites for piston engines

In this work results for the flexural strength and the thermal properties of interpenetrated graphite preforms infiltrated with Al-12wt%Si are discussed and compared to those for packed graphite particles. To make this comparison relevant, graphite particles of four sizes in the range 15–124 μm, were obtained by grinding the graphite preform. Effects of the pressure applied to infiltrate the liquid alloy on composite properties were investigated. In spite of the largely different reinforcement volume fractions (90% in volume in the preform and around 50% in particle compacts) most properties are similar. Only the Coefficient of Thermal Expansion is 50% smaller in the preform composites. Thermal conductivity of the preform composites (slightly below 100 W/m K), may be increased by reducing the graphite content, alloying, or increasing the infiltration pressure. The strength of particle composites follows Griffith criterion if the defect size is identified with the particle diameter. On the other hand, the composites strength remains increasing up to unusually high values of the infiltration pressure. This is consistent with the drainage curves measured in this work. Mg and Ti additions are those that produce the most significant improvements in performance. Although extensive development work remains to be done, it may be concluded that both mechanical and thermal properties make these materials suitable for the fabrication of piston engines.