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281.
In this article, we address four main questions, including: What is self-regulated learning for? What key strategies do students need to guide and direct their own learning process? What cues in the learning environment trigger self-regulation strategies? What can teachers do to help student to self-regulate their learning, motivation, and effort in the classroom? We illustrate that answers to these questions have changed over time and that changing conceptualizations of the self-regulation process have influenced the assessment tools that were used. We also point to changing classroom conditions as a factor that has affected the assessment of self-regulation. Finally, we formulate some questions that need to be tackled in research on self-regulation and introduce the articles and commentaries in the special issue that provide some cutting-edge work on the use of assessment to register self-regulation over time.  相似文献   
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283.
Abstract

We compared 54 matched pairs of high school students and young adults with mental retardation. One member of each pair had remained successfully employed for 10 or more hours per week at minimum wage or better for at least 6 months, and the other had not. Placement counselors, trainers, or supervisors completed case study questionnaires about their students (or clients). The results indicated successful placements in a variety of positions and communities across the nation. The most important elements contributing to this success are placement agency follow‐up support; home support; the individual's job skills, social ability, and match to job demands; the creativity and persistence of the placement specialist; incentive to employers (e.g., tax credits and employment subsidies) and employer's support of the placement.  相似文献   
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285.
Resumen

En este artículo se presenta una investigación cuyo objetivo es analizar las posibles consecuencias que la situación diglósica puede generar en la adquisición del lenguaje de los niños que la padecen. Se demuestra, mediante un riguroso análisis del lenguaje oral, que tal repercusión es claramente negativa en una circunstancia de no normalización lingüística. Dicha repercusión se materializa en una mayor pobreza morfo-sintáctica de la expresión oral cuando el niño debe desenvolverse en una lengua que no es la materna. Se deduce, por tanto, la conveniencia de que la lengua materna y la escolar sean una misma, al menos, en los primeros niveles de escolarización.  相似文献   
286.
This article discusses two studies on the extent and nature of cross-racial interactions (CRIs) among undergraduate students from two neighboring US–Mexico borderland communities. Of the four participating higher education institutions, two were adjacent to the US–Mexico borderline, while the other two were 45 miles away from the borderline. One study relied on survey responses from over 900 students, while the other relied on focus group data from over 30 students. The participating students were from two universities and two community colleges. Although the students shared some common experiences and attitudes, there were some marked and important differences among them. These differences made a compelling argument for localizing what diversity means and customizing efforts to foster CRIs on college campuses.  相似文献   
287.
Abstract

The aim of this study was to test the hypothesis that magnesium supplementation influences the physical performance of volleyball players, as the efficacy of this approach remains questionable. Twenty-five professional male volleyball players were assigned randomly to experimental (350 mg Mg · d–1, 4 weeks) and control groups (500 mg maltodextrin · d–1, 4 weeks) maintaining inter-group homogeneity of urinary magnesium. Erythrocyte, plasma and urinary magnesium levels, plasma creatine kinase activity, lactate production, maximal oxygen uptake (VO2 max) and plyometric (squat jump, countermovement jump, countermovement jump with arm swing) and isokinetic (peak torque, potency and total work) performances were evaluated before (T0) and after (T1) supplementation. Levels of erythrocyte and urinary magnesium and creatine kinase activity and VO2 max remained within normal ranges in both groups. Plasma magnesium decreased significantly only within the experimental group. Significant decreases in lactate production and significant increases (of up to 3 cm) in countermovement jump and countermovement jump with arm swing values were detected in the experimental group following magnesium supplementation, but not in the control group at T1. It is concluded that magnesium supplementation improved alactic anaerobic metabolism, even though the players were not magnesium-deficient.  相似文献   
288.
Strenuous physical exercise of the limb muscles commonly results in damage, especially when that exercise is intense, prolonged and includes eccentric contractions. Many factors contribute to exercise-induced muscle injury and the mechanism is likely to differ with the type of exercise. Competitive sports players are highly susceptible to this type of injury. AM3 is an orally administered immunomodulator that reduces the synthesis of proinflammatory cytokines and normalizes defective cellular immune fractions. The ability of AM3 to prevent chronic muscle injury following strenuous exercise characterized by eccentric muscle contraction was evaluated in a double-blind and randomized pilot study. Fourteen professional male volleyball players from the First Division of the Spanish Volleyball League volunteered to take part. The participants were randomized to receive either placebo (n?=?7) or AM3 (n?=?7). The physical characteristics (mean±s) of the placebo group were as follows: age 25.7±2.1 years, body mass 87.2±4.1?kg, height 1.89±0.07?m, maximal oxygen uptake 65.3±4.2?ml?·?kg?1?·?min?1. Those of the AM3 group were as follows: age 26.1±1.9 years, body mass 85.8±6.1?kg, height 1.91±0.07?m, maximal oxygen uptake 64.6±4.5?ml?·?kg?1?·?min?1. All participants were evaluated for biochemical indices of muscle damage, including concentrations of aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase, creatine kinase (CK) and its MB fraction (CK-MB), myoglobin, lactate dehydrogenase, urea, creatinine and γ-glutamyltranspeptidase, both before and 30 days after treatment (over the peak of the competitive season). In the placebo group, competitive exercise (i.e. volleyball) was accompanied by significant increases in creatine kinase (494±51 to 560±53?IU?·?l?1, P?<?0.05) and myoglobin (76.8±2.9 to 83.9±3.1?μg?·?l?1, P?<?0.05); aspartate aminotransferase (30.8±3.0 to 31.1±2.9?IU?·?l?1) and lactate dehydrogenase (380±31 to 376±29?IU?·?l?1) were relatively unchanged after the 30 days maximum effort. AM3 not only inhibited these changes, it led to a decrease from baseline serum concentrations of creatine kinase (503±49 to 316±37?IU?·?l?1, P?<?0.05) and myoglobin (80.1±3.2 to 44.1±2.6?IU?·?l?1, P?<?0.05), as well as aspartate aminotransferase (31.1±3.3 to 26.1±2.7?IU?·?l?1, P?<?0.05) and lactate dehydrogenase (368±34 to 310±3?IU?·?l?1, P?<?0.05). The concentration of CK-MB was also significantly decreased from baseline with AM3 treatment (11.6±1.2 to 5.0±0.7?IU?·?l?1, P?<?0.05), but not with placebo (11.4±1.1 to 10.8±1.4?IU?·?l?1). In conclusion, the use of immunomodulators, such as AM3, by elite sportspersons during competition significantly reduces serum concentrations of proteins associated with muscle damage.  相似文献   
289.
Abstract

The aim of present study was to examine the relationships between serum and salivary values of free testosterone, dehydroepiandrosterone, and cortisol before and after a session of resistance exercise. Twenty-eight healthy men (mean age 40 years, s = 4) participated in the present study. Serum and salivary samples were collected at rest and after a multiple-sets resistance exercise protocol, of approximately 25 minutes duration. Concentrations of free testosterone, dehydroepiandrosterone, and cortisol were measured using radioimmunoassay kits. No significant correlation was observed between serum free testosterone and salivary testosterone (r = 0.22 to 0.26, P > 0.05). Serum cortisol was significantly correlated with salivary cortisol before (r = 0.52, P = 0.005) and after (r = 0.62, P = 0.001) the exercise protocol. Serum and salivary concentrations of dehydroepiandrosterone were significantly correlated before (r = 0.68, P < 0.001) and after (r = 0.7, P < 0.001) exercise. The results of the present study suggest that even under exercise conditions, the salivary values of cortisol and dehydroepiandrosterone can reflect the behaviour of these hormones in blood. However, further studies are necessary to verify if salivary testosterone reflects the behaviour of serum free testosterone during resistance exercise.  相似文献   
290.
Perceptron models have been used extensively to model perceptual learning and the effects of discrimination training on generalization, as well as to explore natural classification mechanisms. Here, we assess the ability of existing models to account for the time course of generalization shifts that occur when individuals learn to distinguish sounds. A set of simulations demonstrates that commonly used single-layer and multilayer perceptron networks do not predict transitory shifts in generalization over the course of training but that such dynamics can be accounted for when the output functions of these networks are modified to mimic the properties of cortical tuning curves. The simulations further suggest that prudent selection of stimuli and training criteria can allow for more precise predictions of learning-related shifts in generalization gradients in behavioral experiments. In particular, the simulations predict that individuals will show maximal peak shift after different numbers of trials, that easier contrasts will lead to slower development of shifted peaks, and that whether generalization shifts persist or dissipate will depend on which stimulus dimensions individuals use to distinguish stimuli and how those dimensions are neurally encoded.  相似文献   
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