Utilization Of Such Materials Research Articles

Epitaxial growth of InP and related alloys

InP has emerged as the third most important semiconductor in the world after Si and GaAs. Since devices invariably require multilayer heterostructures, considerable attention has also been focussed on development of InP-based materials. The utilization of such materials for devices (see Table 1) has increased manifold in recent years not only due to significant advances in epitaxial growth technology but also due to the fact many of their properties are superior to those of Si and GaAs based materials. The superiority of InP due to higher maximum electron drift velocity, peak-to-valley ratio, thermal conductivity and breakdown field, lower ionization coefficient and dielectric constant, MIS structures having low interface state densities, no intrinsic surface states within bandgap, more radiation resistant, etc. over GaAs has already been established for certain device applications. It can be seen from Table 1 that potential applications of InP related alloys have been in the field of microwave, millimeter-wave, ultra-high speed and optoelectronic devices. Such applications have, however, placed stringent demands (i.e. ability to grow high purity and device quality layers, to grow thin and ultra-thin layers with high degree of uniformity in layer thickness, doping and composition and of growing in-situ heterolayers) upon epitaxial growth technology. Keeping these demands in view, an attempt is made in this article to review the salient features of, and recent advances in, various epitaxial growth techniques used for growing InP and lattice matched InP-based materials.

Advances on fluorine ion conductors, basic and applied research

Fluorides which are insulators, often possess a high anionic conductivity due to weak chemical bonding of the F- ion. The examination of the known ionic conductors allows us to point out some general criteria characteristic of high mobility of F-. The mechanisms of conduction determined on the basis of neutron diffraction are described. The possibility of utilization of such materials for thermodynamic measurements, specific electrodes, solid state batteries, electrochromic devices and gas sensors are examined.

Interferon hybrids: prospects for therapy.

Recombinant DNA techniques have led to determination of the structure of human interferons and production of individual molecular species of interferon free from other species and other proteins simultaneously induced in human cell cultures. Comparison of the properties of different molecular species of interferon and molecular hybrids between the various species has indicated the extent to which the various biological properties of interferons may be separated. This information provides a basis for considering the design of particular molecular constructions of interferons with particular desired properties. The production of hybrid interferons from different genes with common restriction enzyme sites provides a method for producing desirable analogs. The current data are here reviewed with respect to potential clinical utility of such materials.

The Forty-Fifth Thomas Hawksley Lecture: The Transmission and Radiation of Acoustic Waves by Structures

Of major interest to architects, designers of vehicles, and acousticians is the control of structure-borne sound. Walls and panels are set into vibration by airborne waves or by vibrating mechanisms. The panel so excited will radiate sound and it may carry the vibrations to other panels or bodies.In this lecture, the author will treat the problem of acoustic transmission through walls and panels in the audible frequency range. At low frequencies the panel vibrates as a plate or a stretched membrane. At higher frequencies the panel may behave as a quasiinfinite sheet. Above a particular ‘critical’ frequency, the wavelength of the bending waves in the panel will be longer than the compressional waves in air at the same frequency. The two wavelengths may be brought into coincidence provided the airborne wave impinges on the panel at an angle θ determined bycos θ = ca/ cbwhere caand cbare the speeds of sound in the air and panel, respectively. At the coincidence angle, an airborne wave striking one side of a panel will set it into a level of vibration such that the magnitude of the airborne wave radiated from the other side may be only a few decibels below that of the incident wave. This effect will be discussed both for airborne waves impinging at individual angles of incidence and for waves at many angles of incidence simultaneously.Measurements on plates, concrete sheets, and masonry walls will be presented and analysed. Analysis of the different types of response to airborne wave excitation will be made. Rules for the selection of simple and complex structures for buildings and vehicles will be suggested.Means for reducing the response of structures to airborne wave and mechanical excitation include the use of damping materials in or on the structure, the introduction of discontinuities and the use of sound-absorbing blankets in the structure. Recent data on damping materials and means for utilizing them to produce maximum reduction of flexural waves will be presented. It will be shown that by proper utilization of such materials a structure-borne wave may be attenuated in a given distance by a factor of 10 or more than when utilized in a conventional manner.

Philosophy's Neglect of the Social Sciences

The problem of the “proper” relation of philosophy and science has been the source of many disputes in our intellectual history. Recently some philosophers and scientists have insisted that technical philosophy is neglecting the results of the social sciences to the detriment of philosophy. The purpose of this paper is to consider the attempts made by contemporary philosophers to utilize material from the behavioral sciences (for a few recent examples, see 2, 15, 19, 20, 23, 24, 29, 38, 41, 50), to review certain of the arguments in favor of the utilization of such material, and to consider the criticisms of that approach.