The reduction of magnesium salts in ethereal solvents with potassium or sodium yields magnesium in the form of a fine black powder. This magnesium metal exhibits unusual reactivity toward alkyl and aryl halides. For example, bromobenzene reacts with the magnesium yielding phenylmagnesium bromide in a few minutes at -78". Rieke, Bales / Reactions of Highly Reactive Magnesium Metal

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Change in yield and deformation associated with physical aging was studied on a series of polycarbonates (bisphenol-A polycarbonate, polyestercarbonates, and phenolphthalein-bisphenol-A copolycarbonates) and a polysulfone. A combination of tensile and biaxial yield measurements, dynamical mechanical analysis, and high-resolution density measurements were performed. These data indicate that both free volume arguments and molecular entanglement arguments are inadequate for explaining the differences in large-scale deformation associated with physical aging for the polymers and the superiority of polyestercarbonates over the other resins. The local intramolecular and intermolecular conformation in the glassy state, as predicated by molecular structure, is apparently an important key to understanding physical aging in polycarbonate-type polymers.

This study identifies developments relevant to new academic librarians' perceptions of librarianship. Through use of the long interview and document analysis, the researchers developed a grounded theory consisting of six categories that weigh upon novice librarians' perceptions of the profession: (1) deciding upon a career, (2) experiencing graduate school, (3) continuing education, (4) defining the work, (5) evaluating the work, and (6) (re)imagining the future. The categories are analyzed to theorize how perceptions shift from the decision to pursue a new career through the first few years of professional work, and these processes' educational implications are considered.

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