Explanation and Cognition

These essays draw on work in the history and philosophy of science, the philosophy of mind and language, the development of concepts in children, conceptual.

Baryon Interactions in Nuclear and Hypernuclear Matter

The production and structure of Λ hypernuclei are investigated in field theoretical models. The production in coherent p+A reactions is investigated by means of a resonance model. Results of exploratory calculations for associated strangeness production are presented for proton reactions on 40Ca. The target single particle wave functions are obtained from DDRH theory with density dependent Dirac-Brueckner meson-baryon vertices. The dependence of the in-medium vertices on density is discussed.Comment: 5 pages, 2 figs, proceedings for 'HADRON SPECTROSCOPY, Tenth International Conference on Hadron Spectroscopy, Aschaffenburg, Germany 2003'. to be published in the AIP series of conference proceeding

Explaining Explanation

It is not a particularly hard thing to want or seek explanations. In fact, explanations seem to be a large and natural part of our cognitive lives. Children ask why and how questions very early in development and seem genuinely to want some sort of answer, despite our often being poorly equipped to provide them at the appropriate level of sophistication and detail. We seek and receive explanations in every sphere of our adult lives, whether it be to understand why a friendship has foundered, why a car will not start, or why ice expands when it freezes. Moreover, correctly or incorrectly, most of the time we think we know when we have or have not received a good explanation. There is a sense both that a given, successful explanation satisfies a cognitive need, and that a questionable or dubious explanation does not. There are also compelling intuitions about what make good explanations in terms of their form, that is, a sense of when they are structured correctly

Many-body Theory at Extreme Isospin

The structure of nuclei far off beta-stability is investigated by nuclear many-body theory. In-medium interactions for asymmetric nuclear matter are obtained by (Dirac-) Brueckner theory thus establishing the link of nuclear forces to free space interactions. HFB and RPA theory is used to describe ground and excited states of nuclei from light to heavy masses. In extreme dripline systems pairing and core polarization are found to be most important for the binding, especially of halo nuclei. The calculations show that far off stability mean-field dynamics is gradually replaced by dynamical correlations, giving rise to the dissolution of shell structures.Comment: 10 pages, 5 figures, to appear in the proceedings of Nuclear Physics at the Borderline, NPBL2001, Lipari, Sicily, Italy, May 2001 (World Scientific

Effects of CSF hormones and ionic composition on salt/water metabolism

This collaborative agreement between Drs. Severs and Keil began in 1981, arising from a continuing interest in the issue of what, exactly, are the consequences of headward fluid shifts during manned spaceflight. Such shifts were recognized early by both U.S. and Soviet Scientists because of signs and symptoms referable to the head. Some of these include disturbed vision, puffiness in the face and periorbital areas, headache, vestibular dysfunction and distended jugular veins. We posited that the fluid shift had an immediate effect on the brain, and a long-term action requiring a neural interpretation of the flight environment. This would re-adjust both efferent neural as well as hormonal mechanisms to sustain cardiovascular and fluid/electrolyte balance consonent with survival in microgravity. Work along these lines is summarized