Magellanic Cloud Periphery Carbon Stars IV: The SMC

The kinematics of 150 carbon stars observed at moderate dispersion on the periphery of the Small Magellanic Cloud are compared with the motions of neutral hydrogen and early type stars in the Inter-Cloud region. The distribution of radial velocities implies a configuration of these stars as a sheet inclined at 73+/-4 degrees to the plane of the sky. The near side, to the South, is dominated by a stellar component; to the North, the far side contains fewer carbon stars, and is dominated by the neutral gas. The upper velocity envelope of the stars is closely the same as that of the gas. This configuration is shown to be consistent with the known extension of the SMC along the line of sight, and is attributed to a tidally induced disruption of the SMC that originated in a close encounter with the LMC some 0.3 to 0.4 Gyr ago. The dearth of gas on the near side of the sheet is attributed to ablation processes akin to those inferred by Weiner & Williams (1996) to collisional excitation of the leading edges of Magellanic Stream clouds. Comparison with pre LMC/SMC encounter kinematic data of Hardy, Suntzeff, & Azzopardi (1989) of carbon stars, with data of stars formed after the encounter, of Maurice et al. (1989), and Mathewson et al. (a986, 1988) leaves little doubt that forces other than gravity play a role in the dynamics of the H I.Comment: 30 pages; 7 figures, latex compiled, 1 table; to appear in AJ (June 2000

Thoughts about talk in romantic relationships: Similarity makes for attraction (and happiness, too)

Abstract OnlyThis current study assessed whether heterosexual dating partners are similar in their values about communication and how well such similarities predict partners’ attraction to one another and satisfaction with their relationship. Participants were 135 couples who described themselves as “seriously involved”; and had been dating for an average of 15 months. They completed a version of Burleson and Samter's (1990) Communication Functions Questionnaire, which assesses the value placed on several distinct communication skills and activities, and multiple measures of interpersonal attraction and relationship satisfaction. Correlational analyses indicated that partners’ evaluations of communication skills and activities were not significantly related. However, degree of similarity in couples’ communication values was moderately related to the assessments of attraction and satisfaction, demonstrating that partners with similar communication values were more attracted to one another and more satisfied with their relationship. In particular, similarities in the value placed on affectively oriented forms of communication such as ego support, comforting, and conflict management were significantly associated with indices of partner attraction and relationship satisfaction. Subsidiary analyses indicated that the similarities in couples’ communication values were not due to convergence (the tendency to become more similar over time). The results are discussed in terms of how cognitive similarities, especially those directly implicated in the conduct of a relationship, may contribute to the health and well being of that relationship

Mechanistic distinctions between agrin and laminin-1 induced aggregation of acetylcholine receptors

BACKGROUND: One of the earliest steps in synaptogenesis at the neuromuscular junction is the aggregation of nicotinic acetylcholine receptors at the postsynaptic membrane. This study presents quantitative analyses of receptor and α-Dystroglycan aggregation in response to agrin and laminin-1, alone or in combination. RESULTS: Both laminin and agrin increased overall expression of receptors on the plasma membrane. Following a 24 hour exposure, agrin increased the number of receptor aggregates but did not affect the number of α-Dystroglycan aggregates, while the reverse was true of laminin-1. Laminin also increased receptor concentration within aggregates, while agrin had no such effect. Finally, the spatial distribution of aggregates was indistinguishable from random in the case of laminin, while agrin induced aggregates were closer together than predicted by a random model. CONCLUSIONS: Agrin and laminin-1 both increase acetylcholine receptor aggregate size after 24 hours, but several lines of evidence indicate that this is achieved via different mechanisms. Agrin and laminin had different effects on the number and density of receptor and α-Dystroglycan aggregates. Moreover the random distribution of laminin induced (as opposed to agrin induced) receptor aggregates suggests that the former may influence aggregate size by simple mass action effects due to increased receptor expression