The scanning transmission x-ray microscope at the National Synchrotron Light Source has been used to record x-ray absorption near-edge structure (XANES) spectra from 0.01-square-micrometer regions of organic specimens. The spectral features observed reflect the molecular structure of the dominant absorbing atoms and provide the contrast mechanism for high-resolution imaging with chemical sensitivity. This technique was used with x-ray energies near the carbon K absorption edge to identify and map separate phases in various polymer blends and to map the DNA distribution in chromosomes with a spatial resolution of 55 nanometers.

The copolymerization of 1,2-epoxycyclohexane (cyclohexene oxide, CHO) and carbon dioxide was performed using no other solvent than carbon dioxide itself. A CO2-soluble, ZnO-based catalyst was synthesized and used to catalyze the polymerization. Polymerizations were conducted at different temperatures, pressures, and mole fractions of CHO giving rise to polymer yields as high as 69% with catalyst activities as high as 400 g of polymer/g of Zn. The best results were obtained at temperatures of 100−110 °C and at mole fractions of CHO above X CHO = 0.15. This polymer was >90% polycarbonate with weight average molecular weights (M w) ranging from 50 000 to 180 000.

Clearcutting creates habitat for many species of early successional songbirds; however, little information is available on bird use of small forest openings created by group selection harvests. Group selection harvests are increasing on the White Mountain National Forest due to negative public response to clearcutting. The objective of this study was to determine if avian species richness and composition differ between clearcut and group selection openings, and between mature stands and the uncut portions of group selection stands. Point count surveys were conducted during the 1992 and 1993 breeding seasons within six study blocks in the White Mountain National Forest, NH. Each block consisted of a clearcut stand, a group selection stand and a mature stand. Species richness per stand was signi®cantly higher in clearcut openings (p 0.010) than in group selection openings. Forested areas surrounding group selection openings were similar to mature stands in species richness (p 0.848) and composition. Our data suggest that, relative to avian use, the group selection system does not provide habitat similar to that created by clearcutting in extensive northern hardwood stands. The group selection system appears to retain much of the mature forest bird community while providing for a limited number of early successional bird species. Gradual replacement of clearcutting with group selection harvests could result in reduced avian diversity across large forested tracts. #

Exposure of poly(tetrafluoroethylene) film samples to Me2SO solutions of the potassium salt of benzoin dianion renders metallic gold-colored, air-sensitive film samples. The color and property changes of the film are due to a carbonaceous reduction product, the thickness of which can be controlled by the duration of the exposure to benzoin dianion. Reduced layers of ca. 150-20000 A have been prepared. The chemical structure of the carbonaceous product is complex: it is a cross-linked polymeric carbon containing carbon-carbon single, double, and triple bonds, fluorine and hydrogen bound to sp2 and perhaps sp3 carbon, and a small amount of oxygen. Reduced film samples react with a range of reagents which are reactive toward unsaturation. Strong oxidants completely remove the reduced layer. Chlorine and bromine react readily, turning gold-colored films white and pale yellow, respectively. The reduced layer can be used as a reactive "handle" to incorporate hydroxyl, amino, and carboxylic acid functionalities on the surface of poly (tetrafluoroethylene): Hydroboration followed by oxidation introduces hydroxyl groups. Maleic anhydride adds radically and can be hydrolyzed to carboxylic acids. Substitution reactions of brominated films introduce amino groups.