Optical study of localization in theab-plane conductivity of single crystals of YBa2Cu3O6.95 induced by ion damage

We studied the changes in the dc resistivity, Raman scattering, and IR conductivity of single crystals of YBa₂Cu₃O_6.95 induced by damage from low-energy He⁺ ion bombardment. It appears thatT _c , transport properties, and optical conductivity are strongly affected by modest irradiation doses whereas the chemical composition of the sample is not modified. Carrier localization is evidenced by the frequency dependence of the optical conductivity in the strongly damaged crystal and is used to explain the suppression of both the superfluid density andT _c upon irradiation. The temperature dependence of the superfluid density is in agreement with the theoretical predictions for ad-wave superconductor. We also show that the intrinsic residual losses in the FIR are dramatically reduced in the disordered crystal.     

Analysis of the immunologic heterogeneity of HIV-1: I. "Arginine-glutamine trigger" in the fourth position of the central tetrapeptide of the V3 loop of gp120

This article reviews the existing knowledge base concerning the biology of spinal fusion, with the understanding that the focus is weighted toward posterolateral lumbar spinal fusion because of a relative paucity of biologic information on healing of other types of fusions. The discussion focuses first on the basic science of spinal fusion healing from the standpoint of animal modeling. Next, the discussion centers on the multitude of local factors that can affect fusion healing. Finally, the numerous systemic factors known to affect fusion healing are discussed.     

Foot asymmetry in healthy adults: elliptic fourier analysis of standardized footprints

Issues regarding the deaths of patients in the ED arise on a regular basis for emergency physicians. These issues include physician discomfort with death notification, the approach to families after ED deaths, autopsies, donation of organs and tissues, and procedures on the newly dead. If physicians were more comfortable with death notification, not only would families be better served but benefits to society could be realized through the increased use of autopsy and organ/tissue donation. The controversial topic of physician education through practice of medical procedures on the newly dead weighs the benefits to society against the rights of the individual. Improved physician education, including the need for a death notification plan and enlistment of the support of nursing personnel, social workers, and clergy, may improve the experience of events surrounding ED deaths for physicians, families, and society. We review the literature and give recommendations on approaches to deal with these issues.     

Sialon based on natural clay raw materials

Conclusions Conditions were worked out for the synthesis of '-sialon on the basis of natural clay raw materials. It was established that the maximum yield of sialon is obtained from nitriding nonbriquetted mixtures of Novoselitsk kaolin and graphite. It was found that the yield of sialon is increased with a rise in the Al₂O₃SiO₂ ratio in the clay material.We studied the structure of the resulting sialon and also the kinetics of milling. It was shown that at 1450°C there forms 'sialon of variable composition: 0.58 (Al₂O₃·AlN)–0.42 Si₃N₄, and moreover a rise in temperature to 1700–1750°C leads to the displacement of the composition into the region adjacent to the AlN corner in the phase diagram for the Si-Al-O-N system and the appearance of the sialon with the structure of the polytype 15RAlN.Translated from Ogneupory, No. 4, pp. 44–48, April, 1982.     

Optical study of localization in theab-plane conductivity of single crystals of YBa2Cu3O6.95 induced by ion damage

We studied the changes in the dc resistivity, Raman scattering, and IR conductivity of single crystals of YBa₂Cu₃O_6.95 induced by damage from low-energy He⁺ ion bombardment. It appears thatT _c , transport properties, and optical conductivity are strongly affected by modest irradiation doses whereas the chemical composition of the sample is not modified. Carrier localization is evidenced by the frequency dependence of the optical conductivity in the strongly damaged crystal and is used to explain the suppression of both the superfluid density andT _c upon irradiation. The temperature dependence of the superfluid density is in agreement with the theoretical predictions for ad-wave superconductor. We also show that the intrinsic residual losses in the FIR are dramatically reduced in the disordered crystal.On leave from P. N. Lebedev Physics Institute, Russian Academy of Sciences, Moscow, Russia.This work was supported by the Natural Sciences and Engineering Research Council of Canada and the Canadian Institute for Advanced Research. One of us (A.P.) is grateful to the Ontario Center for Materials Research for financial support.