981 resultados para when leave will be granted
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A large body of research has focused on the observation that second language (L2) learners are limited in their production of temporal and aspectual forms. For example, in L2 English, it has been shown learners use progressive marking with activity verbs and only rarely extend the form to telic verb phrases such as accomplishments or achievements (Bardovi-Harlig and Reynolds, 1995; Bardovi-Harlig, 2000; Robison, 1995). Shirai and Andersen (1995) proposed that activities represent the prototype for the category of progressive aspect and learners generally acquire the prototype first. However, very little research has focused explicitly on advanced learners to see if they eventually extend beyond the prototype. In addition, properties of the native language have not systematically been taken into account. Achievements such as "die" are especially interesting in that they interact differently with markers of progressive aspect across languages. The present study investigated the acquisition of progressive achievements in English by native speakers of Chinese and Korean in order to examine whether there is evidence of universal difficulty, as would be predicted by the prototype account, or whether similarity between the L1 and L2 (as in the case of English and Korean) can facilitate acquisition, as would be predicted by transfer. Our results suggest that the properties of the native language play an important role, supporting the transfer account. However, neither L1 group performs at the level of native speakers. We argue that the acquisition of aspect is influenced by both the properties of the native language and the semantic and pragmatic complexity of the target computation.
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Mode of access: Internet.
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Mode of access: Internet.
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Individual-based models (IBMs) can simulate the actions of individual animals as they interact with one another and the landscape in which they live. When used in spatially-explicit landscapes IBMs can show how populations change over time in response to management actions. For instance, IBMs are being used to design strategies of conservation and of the exploitation of fisheries, and for assessing the effects on populations of major construction projects and of novel agricultural chemicals. In such real world contexts, it becomes especially important to build IBMs in a principled fashion, and to approach calibration and evaluation systematically. We argue that insights from physiological and behavioural ecology offer a recipe for building realistic models, and that Approximate Bayesian Computation (ABC) is a promising technique for the calibration and evaluation of IBMs. IBMs are constructed primarily from knowledge about individuals. In ecological applications the relevant knowledge is found in physiological and behavioural ecology, and we approach these from an evolutionary perspective by taking into account how physiological and behavioural processes contribute to life histories, and how those life histories evolve. Evolutionary life history theory shows that, other things being equal, organisms should grow to sexual maturity as fast as possible, and then reproduce as fast as possible, while minimising per capita death rate. Physiological and behavioural ecology are largely built on these principles together with the laws of conservation of matter and energy. To complete construction of an IBM information is also needed on the effects of competitors, conspecifics and food scarcity; the maximum rates of ingestion, growth and reproduction, and life-history parameters. Using this knowledge about physiological and behavioural processes provides a principled way to build IBMs, but model parameters vary between species and are often difficult to measure. A common solution is to manually compare model outputs with observations from real landscapes and so to obtain parameters which produce acceptable fits of model to data. However, this procedure can be convoluted and lead to over-calibrated and thus inflexible models. Many formal statistical techniques are unsuitable for use with IBMs, but we argue that ABC offers a potential way forward. It can be used to calibrate and compare complex stochastic models and to assess the uncertainty in their predictions. We describe methods used to implement ABC in an accessible way and illustrate them with examples and discussion of recent studies. Although much progress has been made, theoretical issues remain, and some of these are outlined and discussed.
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Human sexual determination is initiated by a cascade of genes that lead to the development of the fetal gonad. Whereas development of the female external genitalia does not require fetal ovarian hormones, male genital development requires the action of testicular testosterone and its more potent derivative dihydrotestosterone (DHT). The "classic" biosynthetic pathway from cholesterol to testosterone in the testis and the subsequent conversion of testosterone to DHT in genital skin is well established. Recently, an alternative pathway leading to DHT has been described in marsupials, but its potential importance to human development is unclear. AKR1C2 is an enzyme that participates in the alternative but not the classic pathway. Using a candidate gene approach, we identified AKR1C2 mutations with sex-limited recessive inheritance in four 46,XY individuals with disordered sexual development (DSD). Analysis of the inheritance of microsatellite markers excluded other candidate loci. Affected individuals had moderate to severe undervirilization at birth; when recreated by site-directed mutagenesis and expressed in bacteria, the mutant AKR1C2 had diminished but not absent catalytic activities. The 46,XY DSD individuals also carry a mutation causing aberrant splicing in AKR1C4, which encodes an enzyme with similar activity. This suggests a mode of inheritance where the severity of the developmental defect depends on the number of mutations in the two genes. An unrelated 46,XY DSD patient carried AKR1C2 mutations on both alleles, confirming the essential role of AKR1C2 and corroborating the hypothesis that both the classic and alternative pathways of testicular androgen biosynthesis are needed for normal human male sexual differentiation.
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Collaboration among researchers is typically seen as the quintessence of academic excellence, leading to improvements in the research quality, capitalization on the diversity of perspectives and gains in productivity. Despite these benefits, many research teams find themselves torn by competition, antagonism and resentment. Desire to be the first author and resultant underperformance of non-first co-authors is often at the root of these conflicts. At the same time little is known about what motivates researchers in general and IS researchers in particular to engage as first authors. To fill this gap, this study uses survey methodology to explore the attitudes of IS researchers and their resulting behavior when it comes to authors order. Qualitative and quantitative evidence collected from 398 IS researchers is used to support our analysis. We find that researchers’ desire to be the first authors is mainly driven by such determinants as career aspirations, visibility, leadership and sense of ownership, and less so by the desire to satisfy their self-esteem and self-actualization needs. In addition, the value placed on being the first author appears to be the function of researchers’ career level, with Ph.D. students attaching significantly higher value to it than senior scholars.
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Mast cell disorders are defined by the accumulation of mast cells in one or more organ systems. Cutaneous forms are mainly observed in children whereas systemic forms are predominant in adults. Mast cells cause symptoms by the release of proinflammatory mediators or by infiltration of various organs. The measurement of serum tryptase has opened the possibility of screening for mastocytosis, which must be taken into consideration in case of severe anaphylactic reactions. Definite diagnosis is established based on a biopsy of skin or bone marrow. An activating mutation of stem cell factor receptor c-kit is often found. Treatment is based on control of the symptoms triggered by mast cell degranulation. Moreover, novel treatment options targeting mast cell proliferation become available for clinical use.
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Telegram from Great North Western Telegraph Company of Canada to S.D. Woodruff from L. Cabot stating that the draft for $5000.00 will be forwarded on Monday or Tuesday, Jan. 16, 1886.