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91.
One way to increase students’ participation in science, technology, engineering, and mathematics (STEM) fields is to target their motivation. Researchers have conducted a growing number of interventions addressing students’ motivation in STEM; however, this body of work has not been adequately reviewed. We systematically reviewed experimental and quasi-experimental studies (n = 53) targeting adolescent students’ motivation for STEM subjects. While some interventions showed positive effects on a variety of motivational constructs and academic outcomes, others showed mixed or non-significant effects. We recommend that researchers more frequently examine moderating variables that might limit interventions’ results, including individual-level variables such as gender, contextual-level variables such as the subject in which an intervention was conducted, and design-level variables such as intervention length. Additionally, researchers might better align their interventions with motivation theory. Future research should address these limitations so that the results of successful interventions can better inform educational policy and practice.  相似文献   
92.
This article compares the psychopathology of the physically abusing parent and that of the borderline patient in four specific areas: common personality characteristics; personal history; psychopathology; and psychodynamics of the abusive act. The first major personality characteristic is the umbrella characteristic of arrested emotional development, the other four characteristics are: poor self image, emotionally isolated, depressive loneliness and poorly suppressed aggression. These correlate with the four major characteristics of the core borderline personality. The personal history for both abusing parents and borderline patients indicate maternal deprivation in preverbal development. The abusing parent's psychopathology is very similar to that of the borderline patient. They both have poor ego strength, a punitive superego and use primitive ego-defenses of denial, splitting and projection. The act of abuse is related to these ego defects but in particular projective identification plays a major role. Further research is indicated and tentative implications are made as regards psychodynamically oriented treatment.  相似文献   
93.
A common approach to Lyapunov's stability control is to design a controller such that a Lyapunov function can be derived for the control system to ensure stability. This procedure often leads to a discontinuous controller. When the controller is implemented, the discontinuous terms are replaced with continuous functions to avoid chattering of the control signal. Two associated problems have been overlooked during this procedure. One is that discontinuous control systems are non-smooth, which violates the fundamental assumptions of solution theories and the applicability of Lyapunov's stability theory is questionable. Another problem is that the replacement of discontinuous terms may weaken stability, which can be critical. In this paper, we discuss proper stability analysis of discontinuous control systems using the extended Lyapunov's second method based on Filippov's solution concept for non-smooth systems. We further propose to utilize the concept of Lyapunov exponents to quantitatively analyze the stability of continuous control systems obtained by replacing the discontinuous terms in the discontinuous controllers. An example involving the stabilization of a two-link non-fixed-base robotic manipulator is presented for demonstration. This research fills the gap in designing continuous Lyapunov's stability controllers regarding limited available Lyapunov functions.  相似文献   
94.
Until recently the identification of the authorship of written works has—like that of paintings—been largely subjective, but the application of the computer to analysis of literary structure has opened up important new possibilities. It has shown that simple frequency patterns are of much less diagnostic value than groupings of words and their position in sentences. Stylometry, as this new investigative method is called, has the merit of knowing no language barriers—it is equally applicable, for example, to classical Greek, English, and Swedish.  相似文献   
95.
文中对计算电子结构的集团Bethe晶格方法进行了改进。简化了原子集团的选取方式,提出了求解复数Dyson方程组的矩阵解方法和平均集团Bethe晶格方法。研究了Penrose tiling的局部、整体和平均电子状态密度。发现了Penrose tiling的局部电子状态密度对准周期点阵的长程有序性特别敏感的性质。提出了计算Penrose tiling局部及整体电子状态密度应遵循的原则.得出了某些合金的准晶相可能是电子化合物的结论。  相似文献   
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Under the federal government's current policy on funding university research, institutions which can best identify and encourage the higher performers amongst their academic staff will fare better than others. However, in order to secure a strong position in competing for these government funds universities will need to know more about the research activity of their academic staff and how staff in different disciplines are likely to respond to the increased use of performance indicators. This paper reports the views of staff from one Australian university on such issues. One of the main findings is that potential research output is influenced by a range of factors including the differences in research styles, methods and strategies and the degree of dependence on funds. Such findings favour the differential use of performance measures depending on the nature of the research undertaken rather than the use of measures which are intended to standardise research output within or across disciplines.  相似文献   
99.
Plexiform lesions (PLs), which are often accompanied by perivascular infiltrates of mononuclear cells, represent the hallmark lesions of pulmonary arteries in humans suffering from severe pulmonary arterial hypertension (PAH). Endothelial progenitor cells (EPCs) have been recently implicated in the formation of PLs in human patients. PLs rarely develop in rodent animal models of PAH but can develop spontaneously in broiler chickens. The aim of the present study was to confirm the presence of EPCs in the PLs in broilers. The immune mechanisms involved in EPC dysfunction were also evaluated. Lungs were collected from commercial broilers at 1 to 4 weeks of age. The right/total ventricle ratios indicated normal pulmonary arterial pressures for all sampled birds. Immunohistochemistry was performed to determine the expressions of EPC markers (CD133 and VEGFR-2) and proangiogenic molecule hepatocyte growth factor (HGF) in the lung samples. An EPC/lymphocyte co-culture system was used to investigate the functional changes of EPCs under the challenge of immune cells. PLs with different cellular composition were detected in the lungs of broilers regardless of age, and they were commonly surrounded by moderate to dense perivascular mononuclear cell infiltrates. Immunohistochemical analyses revealed the presence of CD133+ and VEGFR-2+ cells in PLs. These structures also exhibited a strong expression of HGF. Lymphocyte co-culture enhanced EPC apoptosis and completely blocked HGF-stimulated EPC survival and in vitro tube formation. Taken together, this work provides evidence for the involvement of EPCs in the development of PLs in broilers. It is suggested that the local immune cell infiltrate might serve as a contributor to EPC dysfunction by inducing EPC death and limiting their response to angiogenic stimuli. Broiler chickens may be valuable for investigating reversibility of plexogenic arteriopathy using genemodified inflammation-resistant EPCs.  相似文献   
100.
It is highly desirable to design hollow structures with multi-scale functions by mimicking cells for the construction of micro/nanoreactors. Herein, we report the construction of hollow-structured submicrometer-photoreactors with bimetallic catalysts loaded within mesoporous silicas. The synthesis parameters are optimized to study the evolution of hollow structure through hydrothermal treatment and an ‘adhesive-contraction’ formation mechanism is proposed. AuPt@HMZS catalysts exhibited a broader absorbance region under visible light and the adsorption edge displayed a red-shift, indicating the strong metal–metal interactions at the alloy interface. The reaction performance of the coupled Au-Pt catalysts can be tuned to achieve excellent catalytic activity in cinnamyl alcohol oxidation to cinnamic acid for 3.1 mmol g−1 with 99% selectivity. The proposed strategy to build hollow structures as multifunctional micro/nanoreactors is promising for the design of high-performance and sustainable catalysts for chemical synthesis.  相似文献   
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