Prenatal Development of Interlimb Motor Learning in the Rat Fetus

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.     

Modes of Network Governance: Structure, Management, and Effectiveness

This article examines the governance of organizational networksand the impact of governance on network effectiveness. Threebasic models, or forms, of network governance are developedfocusing on their distinct structural properties. Propositionsare formulated examining conditions for the effectiveness ofeach form. The tensions inherent in each form are then discussed,followed by the role that management may play in addressingthese tensions. Finally, the evolution of governance is explored.     

A multiple indicator approach to blockmodeling signed networks

Regardless of whether the focus is on algebraic structures, elaborating role structures or the simple delineation of concrete social structures, generalized blockmodeling faces a pair of vulnerabilities. One is sensitivity to poor quality of the relational data and the other is a risk of over fitting blockmodels to the details of specific networks. Over fitting blockmodels can lead to multiple equally well fitting partitions where choices cannot be made between them on a principled basis. This paper presents a method of tackling these problems by viewing (when possible) observed social relations as multiple indicators of an underlying affect dimension. Quadratic assignment methods using matching coefficients, product moment correlations and Goodman and Kruskal's gamma are used to assess the appropriateness of using the sum of observed relations as input for applying generalized blockmodeling. Data for four groups are used to show the value of this approach within which multiple equally well fitting blockmodels for single relations are replaced by unique (or near-unique) partitions of the summed data. This strategy is located also within a broader problem of blockmodeling three-dimensional networks data and suggestions are made for future work.     

Emerging organizational forms: Work and organization in the 21st century

This article begins with the premise that there is continuous and accelerating change in the Western World in the nature of work and how it is organized. An important contributory force is information technology — itself changing rapidly.When the dynamics of the external environment of organizations are added to changes in IT, we will see new forms of organizations evolving in the business world, such as the ‘starburst’ and ‘internal market’ structures.Michael Scott Morton supplies a diagram to illustrate the framework of research which the ‘1990s’ program at MIT is following — how to balance the dynamic tension between external forces and the internal dimensions of organizations to reward shareholders adequately. He refers to one of Peter Senge's ideas in The Fifth Dimension which is central in creating an organization which learns how to innovate constantly: System Thinking — the search for systemic patterns. It reinforces Scott Morton's argument, and seems a particularly appropriate discipline in a continuously turbulent business environment.     

Gender differences in the initiation and attribution of tactile intimacy

Cultural norms may restrict the demonstration of intimacy between men, such that male adults are relatively unlikely (in comparison to females) to display affection in public by hugging or putting hands around one another's waists. Study 1 examined via a role playing technique how the gender composition of a dyad and types of friendship influence tactile greetings. Males displayed less physical intimacy with male friends than with female (platonic or dating) friends and less than females displayed with their same-sex friends. Study 2 examined subjects' perceptions of and attributions about reciprocal touch. Male-male behavior was rated as less normal as a function of the level of physical touch (going from no touch, hugging, to arms around the waist). The normalcy rating of opposite-sex pairs did not vary as a function of the touch manipulation, but female, same-sex pairs' behavior was rated as less normal in the arms around the waist than in either the no touch or hug conditions. In the male same-sex pairs, hugging was seen as more likely to reflect a sexual relationship than no touch, while arms around one another's waist was rated as even more likely to represent a sexual relationship. It was suggested that homophobia, the fear of appearing or being homosexual, may operate to inhibit physical intimacy between men.     

Confidence regions for the common mean vector of several multivariate normal populations

Suppose that there are independent samples available from several multivariate normal populations with the same mean vector m? but possibly different covariance matrices. The problem of developing a confidence region for the common mean vector based on all the samples is considered. An exact confidence region centered at a generalized version of the well-known Graybill-Deal estimator of m? is developed, and a multiple comparison procedure based on this confidence region is outlined. Necessary percentile points for constructing the confidence region are given for the two-sample case. For more than two samples, a convenient method of approximating the percentile points is suggested. Also, a numerical example is presented to illustrate the methods. Further, for the bivariate case, the proposed confidence region and the ones based on individual samples are compared numerically with respect to their expected areas. The numerical results indicate that the new confidence region is preferable to the single-sample versions for practical use.