The relational antecedents of project-entrepreneurship: Network centrality, team composition and project performance

The relational antecedents of project-based enterprises have not yet received systematic investigation. These ventures are typically created by individual freelancers who are usually embedded in networks of collaborative relationships that convey the information and resources required to carry out new projects. Using a relational perspective of entrepreneurial discovery and team composition, we analyze the performance determinants of project-entrepreneurs, namely the individuals who are responsible for launching and carrying out those projects. We argue that project-entrepreneurs’ performance is related to their degree of centrality within the social network, and their familiarity with the selected project-team as captured by the distribution of ties among team members. We test our hypotheses within the Hollywood Film Industry over the period 1992–2003. The findings point to the existence of diminishing returns to centrality and performance benefits from assembling teams that combine old-timers and newcomers. The theoretical contributions and implications of the study are discussed.     

Examining and elaborating upon the nature of elementary prospective teachers’ conceptions of partitive division with fractions

The purpose of this study was to examine and elaborate upon elementary prospective teachers’ (PSTs) conceptions of partitive division with fractions. We examined the degree to which PSTs’ conceptions were connected (i.e., capable of translating between representations correctly; aware that partitive division generates a unit rate for its quotient) and flexible (i.e., capable of differentiating between opportunities to partition or iterate (or both) when solving a partitive division task; aware that partitioning or iterating (or both) could be associated with the operation of division, as appropriate). Seventeen PSTs participated in task-based interviews prior to instruction in a mathematics content course for teachers. These PSTs demonstrated disconnected conceptions of partitive division with fractions when they incorrectly translated between representations and either inconsistently or did not express awareness that the purpose of the task was to generate a unit rate. These PSTs demonstrated rigid conceptions of partitive division with fractions such that they did not express awareness that the process of iterating could be associated with the operation of division, even when they obtained a correct answer by iterating. Results extend prior research by looking beyond PSTs’ performance on tasks to elaborate upon PSTs’ conceptions of the operation of partitive division. This study contributes new insights into PSTs’ conceptions that can be used by mathematics teacher educators to inform the design of future instructional interventions.     

Children's friendship choices: Effects of school behavior

This study addresses three issues: (a) Which attributes characterize children's friendship choices? (b) Which show sex differences? (c) Which dimensions of teacher ratings of behavior contribute to peer selections? The issue of peer-teacher relatedness is addressed by obtaining peer nominations for certain attributes and independent measures of behavior that have been shown to be related to peer popularity. The results demonstrate that: (a) Peer acceptance is indexed by “Like to Sit By,” and this pattern is generally similar for boys and girls, with the exception of the dimension “Good at Games,” which characterizes boys' choosing peers. (b) The data on peer acceptance and rejection do not result in simple, bipolar dimensions, since these are not highly negatively correlated. (c) When peer nominations are assessed for possible teacher influences, an interesting sex difference emerges: girls prefer not to sit next to children whom their teachers rate as high in behavior problems.     

Modeling imitation and emulation in constrained search spaces

Social transmission of behavior can be realized through distinct mechanisms. Research on primate social learning typically distinguishes two forms of information that a learner can extract from a demonstrator: copying actions (defined as imitation) or copying only the consequential results (defined as emulation). We propose a decomposition of these learning mechanisms (plus pure individual learning) that incorporates the core idea that social learning can be represented as a search for an optimal behavior that is constrained by different kinds of information. We illustrate our approach with an individual-based model in which individuals solve tasks in abstract “spaces” that represent behavioral actions, results, and benefits of those results. Depending on the learning mechanisms at their disposal, individuals have differential access to the information conveyed in these spaces. We show how different classes of tasks may provide distinct advantages to individuals with different learning mechanisms and discuss how our approach contributes to current empirical and theoretical research on social learning and culture.     

Specific impairment in developmental reading disabilities: a working memory approach

Children with developmental reading disabilities (RD) frequently display impaired working memory functioning. However, research has been divergent regarding the characteristics of the deficit. Our investigation addressed this controversy by assessing Baddeley's working memory model as a whole rather than focusing on particular aspects of it, as has been done by much of the research to date. Participants included 20 children with RD and 20 typical readers between the ages of 9 and 13. The phonological loop, visual-spatial sketchpad, and central executive were assessed according to Baddeley's model. The results demonstrated that children with RD have an impaired phonological loop but intact visual-spatial sketchpad and central executive functioning as compared to controls. In terms of the phonological loop, the deficit appears to be specific to the phonological store. Furthermore, our research supports a relationship between phonological processing and phonological loop functioning.     

香港科技大学土工离心机先进模拟技术在岩土工程中的应用(英文)

研究目的:采用香港科技大学的先进土工离心模拟技术来研究和解决复杂的岩土工程问题。创新要点:1.验证竖向钻孔开挖技术(应力释放)对建筑纠偏的有效性;2.研究隧道坍塌对其邻近既有隧道的影响;3.研究基坑开挖对坑中既有桩基承载力的影响;4.揭示不同颗粒级配形成的土坡在水位上升和动力荷载作用下的破坏模式。研究方法:1.用香港科技大学全球首台离心机中的双向震动台(见图5)模拟地震荷载对土坡的影响;2.用香港科技大学全球第二台四轴机械手(见图6)模拟不停机情况下的钻孔开挖。重要结论:1.竖向钻孔开挖技术能有效地对建筑物进行纠偏;2.隧道坍塌会对其邻近既有隧道产生很大的附加弯矩,尤其是拱脚处的弯矩可增加多达228%;3.基坑开挖后坑中桩基的承载力取决于桩土接触面的粗糙程度,粗糙的桩-土接触面在剪切过程中倾向于发生剪胀,这会增大桩周围土的水平土压力,从而使桩基承载力增加;4.当水位上升时,颗粒均匀,级配差的松散砂土坡容易发生静态液化;相反地,颗粒级配好的松散砂土坡(风化土)不太可能发生静态液化,而只是发生整体滑动破坏;5.离心机双向震动台实验显示松散的风化岩土坡在0.3g的地震加速度作用下不会发生液化,可以抵御香港地区的地震荷载(0.08g到0.11g)。     

Enhanced production of thermostable laccases from a native strain of Pycnoporus sanguineus using central composite design

研究目的：优化获得血红密孔菌（P.sanguineus）的最佳培养基组成,提高耐热漆酶的产量。创新要点：获得了目前文献报道的最高水平的漆酶活力。研究方法：通过单因素试验研究了不同培养基（番茄汁、麦麸、麦芽提取物和葡萄糖细菌蛋白胨培养基）和不同组合诱导剂（大豆油、阿魏酸、没食子酸、二甲基苯胺、酸性蓝62和活性蓝19分别与硫酸铜组合诱导剂）对P.sanguineus产耐热漆酶的影响。在此基础上采用中心组合试验设计,进一步研究了番茄汁培养基结合硫酸铜和大豆油组合诱导剂对P.sanguineus产耐热漆酶的影响。利用SAS10.0和响应面分析方法对试验结果进行了统计分析和建立回归模型。重要结论：通过中心组合设计优化得出P.sanguineus产耐热漆酶的最优培养基条件：以36.8%番茄汁为培养基,以3 mmol/L硫酸铜和1%大豆油作为组合诱导剂。该条件下在10 L搅拌槽生物反应器中漆酶活力达到了143 000 IU/L（2,2＇-联氮双（3-乙基苯并噻唑啉-6-磺酸）为底物,pH值为3.0）。     

Validity of the VmaxST portable metabolic measurement system

The aim of this study was to assess and compare the validity of the portable VmaxST telemetry metabolic measurement device with that of a standard measurement system (Vmax29). Thirty asymptomatic, moderately active males provided written, informed consent and completed two maximal graded treadmill exercise tests (Bruce) using the VmaxST and the Vmax29 metabolic measurement systems. Tests were performed in random order on separate days to obtain peak values for time to exhaustion, heart rate, systolic and diastolic blood pressure, oxygen consumption (VO2), carbon dioxide production (VCO2), ventilation (VE), and respiratory exchange ratio (RER). Multivariate analysis of variance revealed no significant main effect (P = 0.88) between the two systems across any variable, suggesting similar measurement capabilities between the two systems. Linear regression analyses revealed moderate to high coefficients of determination for VO2 (r2 = 0.99), VCO2 (r2 = 0.99), VE r2 = 0.99), and RER (r2 = 0.89). Furthermore, Bland-Altman analyses demonstrated that the VmaxST yielded similar values to the Vmax29, suggesting good agreement between the two systems. Agreement was confirmed when the differences between the methods resulted in a small range as identified by the 95% limits of agreement. Findings from the current study confirm that the VmaxST is a valid device for measuring metabolic and physiological variables during exercise within a controlled laboratory setting.