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617B(4,4) = 2rr2At 2 (Yamamoto et al., 1984) AbstractThe defect crystal structures of r/-, y-and 0-alumina obtained from dehydroxylation of well crystallized bayerite and boehmite have been derived from the analysis of their X-ray powder diffraction patterns and from the Rietveld refinement of their neutron powder diffraction patterns. Profile analysis of the various reflection zones in these defect spinel structures shows different coherent domain sizes which can be associated with the tetrahedral and octahedral aluminium and the oxygen sublattices. These observations have been used to define the nature of the crystal structures, and to give insight into the transformation mechanisms. The very large surface energies of these phases are evident in the observation of * Present address: Materials Data, Inc., PO Box 791, Livermore, CA 94550, USA.t To whom all correspondence should be directed.0108-7681/91/050617-14503.00 a nearly three-coordinated surface AI atom in the 7/ phase, and are the reason for the stability of the defect spinel structures of the transition aluminas. The reduction of surface area and the ordering of the tetrahedral AI sublattice which occurs on heating causes the spinel framework to collapse so that the structure, which exhibits tetragonal character at the early stage of the transition, settles into monoclinic 0-alumina displacively at the later stage, and eventually transforms to hexagonal corundum reconstructively. Thus 0-alumina should be considered the ultimate rather than the intermediate structural form into which the transition aluminas could evolve on the way to corundum. The overall crystal structure of the transition aluminas should therefore be viewed intrinsically as spinel deformed rather than as tetragonally deformed. Crystal data at room temperature: r/-alumina, cubic, Fd3m, a = 7.914 (2) A, RB = 6.24, Rp = 6-50, R, = 8.43%; y-alumina, cubic, Fd3m, a = © 1991 International Union of Crystallography 618 r/, ,/ AND 0 TRANSITION ALUMINAS 7.911 (2),~, Rs = 10.53, Rp = 7-61, R,. = 10.25%; 0-alumina, monoclinic, C2/m, a = 11.854(5), b = 2-904 (1), c = 5-622 ,~, /3 = 103.83 (7) °, Re = 15-02, Rp = 9"37, R,. = 11"93%.

At present, over 30000 powder diffraction patterns are available as references. It is proposed that the patterns on file as well as new patterns submitted for publication be assigned quantitative quality factors. A simple-to-use figure of merit, FN, covering both accuracy in the measurement of the positions of the diffraction lines and completeness of the pattern, has been derived: FN=(1/ld2Ol)(N/Nposs), where Nposs is the number of independent diffraction lines possible up to the Nth observed line and Id201 is the average absolute discrepancy between observed and calculated 20 values. This figure of merit provides a rapid evaluation of powder patterns, in much the same way as the R factor provides a rating for single-crystal structure determinations. This figure of merit also provides a means to assess the reliability of a unit derived solely from powder data. The present FN ranking scheme is shown to be superior to de Wolffs M20 for ranking patterns. It is recommended that use of the latter be discontinued for that purpose. Guidelines are given on the use and implementation of the FN rating of powder diffraction patterns.

Particles with properties similar to those associated with human hepatitis B were found in serum from woodchucks with chronic hepatitis and hepatocellular carcinoma. It is suggested that woodchuck hepatitis virus is a second member of a novel class of viruses represented by the human hepatitis B virus. Recently, considerable information concerning the morphology of the human hepatitis B virus (HBV) and its genome structure has accumulated. Thus, HBV is thought to be a 40-to 50-nm double-layered virus (1) containing a circular, partially double-stranded DNA genome (2, 3) and a DNA polymerase (4). In vitro, the DNA polymerase fills in a large heterogeneous single-stranded region in the genome, generating a fully double-stranded circular DNA (3).Antigenic determinants on the surface of the HBV (HBsAg) are found also on spherical and tubular particles approximately 20 nm in diameter that occur in the blood in vast excess over the 40-to 50-nm DNA-containing particles (1, 5). The smaller particles are free of nucleic acid and apparently represent excess viral coat protein.The properties of HBV distinguish it from any known class of DNA-containing viruses. In fact, evidence presented in this paper indicates that HBV belongs to a novel class of DNA viruses which may be causative agents of hepatitis in species other than human beings. In this report, we describe the probable occurrence of one such virus in a colony of woodchucks (Marmota monax) at the Penrose Research Laboratory at the Philadelphia Zoo.MATERIALS AND METHODS Animals. The animals used in this study were from a colony of woodchucks (M. monax) at the Penrose Research Laboratory, which has been studied for 18 years, from 1960 to 1978, with the objective of identifying diseases that may serve as animal models for human diseases (6). As of 1 May 1977, the records on this colony, which included postmortem studies of 102 animals, contained 23 cases of primary hepatocellular carcinoma (22.5 %). These cancers occurred at a mean age of 59 months, with a range of 23-106 months. All of the animals with hepatomas had degenerative and regenerative changes in the uninvolved liver, suggesting preexisting chronic active hepatitis as reported (7). In addition, 3 of the 102 woodchucks had developed acute hepatitis judged to be the cause of death. Several animals without hepatocellular tumors had inflammatory and regenerativechanges in the liver consistent with chronic active hepatitis. A more complete review of the postmortem studies will be published elsewhere (8).Histology. Tissues fixed in 6.6% neutral formalin were embedded in tissue-Prep (Fisher Scientific), sectioned at 5 ,um, and stained with hematoxylin and eosin, allochrome, Weigert-Van Greson light green, Verhoeff, Prussian blue, and Gomori's silver stain.Materials. HBsAg-positive plasma was kindly supplied by B. S. Blumberg (Institute for Cancer Research, Philadelphia, PA). Avian myeloblastosis (AMV) DNA polymerase was a gift of L. Loeb (Institute for Cancer Research, Philadelphia). S1 nuclease was pur...

We demonstrate the first self-powered system driven by a nanogenerator (NG) that works wirelessly and independently for long-distance data transmission. The NG was made of a free cantilever beam that consisted of a five-layer structure: a flexible polymer substrate, ZnO nanowire textured films on its top and bottom surfaces, and electrodes on the surfaces. When it was strained to 0.12% at a strain rate of 3.56% S(-1), the measured output voltage reached 10 V, and the output current exceeded 0.6 μA (corresponding power density 10 mW/cm(3)). A system was built up by integrating a NG, rectification circuit, capacitor for energy storage, sensor, and RF data transmitter. Wireless signals sent out by the system were detected by a commercial radio at a distance of 5-10 m. This study proves the feasibility of using ZnO nanowire NGs for building self-powered systems, and its potential application in wireless biosensing, environmental/infrastructure monitoring, sensor networks, personal electronics, and even national security.