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101.
This paper explores how the rules that guide search affect organizational adaptation in complex and turbulent environments. Our consideration of such rules extends beyond search scope—i.e., exploitation of current technologies vs. exploration of new technologies—to include focus on competition. We consider two types of competitive focus—i.e., external, where the choice of focal technology to be improved is influenced by information about other organizations and internal, where it is not influenced by others. We refer to this expanded set of rules as managerial selection and vary it to explore how it affects organizational adaptation. Employing an agent based simulation model, built on the framework of NKC fitness landscapes, we consider multiple types of interdependencies within and between technologies and across competitors. We show that in the presence of these multiple interdependencies, the ability of organizations to adapt is conditioned as much or more by the focus of search than by its scope. In particular, we observe that in simple and stable environments, organizational adaptation is enhanced by an external focus but in complex and turbulent environments, such external focus is counterproductive.  相似文献   
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The role of sensory feedback in the early ontogeny of motor coordination remains a topic of speculation and debate. On E20 of gestation (the 20th day after conception, 2 days before birth), rat fetuses can alter interlimb coordination after a period of training with an interlimb yoke, which constrains limb movement and promotes synchronized, conjugate movement of the yoked limbs. The aim of this study was to determine how the ability to express this form of motor learning may change during prenatal development. Fetal rats were prepared for in vivo study at 4 ages (E18–21) and tested in a 65‐min training‐and‐testing session examining hind limb motor learning. A significant increase in conjugate hind limb activity was expressed by El9, but not El 8 fetuses, with further increases in conjugate hind limb activity on E20 and E21. These findings suggest substantial development of the ability of fetal rats to modify patterns of interlimb coordination in response to kinesthetic feedback during motor training before birth.  相似文献   
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Adolescence is a critical developmental period with long‐term implications for the health and well‐being of the individual and for society as a whole. The most significant factors to adolescents' health are found in their environments, and in the choices and opportunities for health‐enhancing or health‐compromising behaviors that these contexts present (e.g., exposure to violence, supportive families). Inadequate contexts represent a failure to invest in and protect adolescents, a choice to alienate rather than integrate them into society. This article describes a number of societal trends, including growing poverty and income disparities, government instability, the changing health‐care system, the spread of HIV/AIDS, increased migration and urbanization, changing family and cultural contexts, and new information technology. The health implications of these trends for the well‐being of adolescents in the 21st century are contemplated.  相似文献   
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Fetal cardiac function was measured at 24, 30, and 36 weeks gestation and quantified in terms of heart rate, variability, and episodic accelerations. Children's representational capacity was evaluated at 27 months in terms of language and play. Thirty‐ and 36‐wcek‐old fetuses that displayed greater heart‐rate variability and more episodic accelerations, and fetuses that exhibited a more precipitous increase in heart‐rate variability and acceleration over gestation achieved higher levels of language competence. Thirty‐six‐week‐old fetuses with higher heart‐rate variability and accelerations, and steeper growth trajectories over gestation, achieved higher levels of symbolic play. Cardiac patterning during gestation may reflect an underlying neural substrate that persists through early childhood: Individual variation in rate of development could be stable, or efficient cardiac function could positively influence the underlying neural substrate to enhance cognitive performance.  相似文献   
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In this study, three factors appear to influence significantly whether a child in foster care would be returned to the parent. The factors proved to be the number of persons in the parent's home, the number of friends in the neighborhood, and the frequency with which the parent saw those friends.  相似文献   
108.
Political models of the business cycle have typically been ignored because they appear inconsistent with rational behavior and because empirical evidence is inconclusive. This paper addresses the second issue, demonstrating for U.S. real GNP, unemployment, and inflation that electoral cycles (persistent patterns across electoral terms) are significant, but apparently only for Republican incumbents, and that partisan cycles (persistent differences between parties) are also significant. These findings are consistent with the conjecture that a minority party is more constrained by electoral concerns, whereas a majority party is freer to pursue partisan objectives.  相似文献   
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