Generic Defect Research Articles

The growth of linear perturbations in generic defect models for structure formation

We study the growth of linear perturbations induced by a generic causal scaling source as a function of the cosmological parameters $h$, $\Omega^m_0$ and $\Omega^\Lambda_0$. We show that for wavenumbers $k \gsim 0.01 h/Mpc$ the spectrum of density and velocity perturbations scale in a similar way to that found in inflationary models with primordial perturbations. We show that this result is independent of the more or less incoherent nature of the source, the small scale power spectrum of the source and of deviations from scaling which naturally occur at late times if $\Omega^m_0 \neq 1$.

Geodesics around line defects in elastic solids

Topological defects in solids, usually described by complicated boundary conditions in elastic theory, may be described more simply as sources of a gravity-like deformation field in the geometric approach of Katanaev and Volovich. This way, the deformation field is described by a non-Euclidean metric that incorporates the boundary conditions imposed by the defects. A possible way of gaining some insight into the motion of particles in a medium with topological defects (e.g., electrons in a dislocated metal) is to look at the geodesics of the medium around the defect. In this work, we find the exact solution for the geodesic equation for an elastic medium with a generic line defect, the dispiration, that can either be a screw dislocation or a wedge disclination for particular choices of its parameters.

Performance budgeting resuscitated: why is it still inviable?

Performance budgeting had been tried once and failed. Is there any reason to believe that the new performance budgeting will work? After reviewing existing studies on performance budgeting, the paper proposes that two obstacles continue to undermine its success. They are the poor quality of performance measures and their rare acceptance by budgetary decisionmakers. Unfortunately, these two impediments result from the generic defect of performance budgeting: i.e., its attempt at both comprehensiveness and rationality. The paper concludes by suggesting ways by which performance measures can be better utilized.

Opportunities in silicon photovoltaics and defect control in photovoltaic materials

Silicon is the dominant semiconductor material in use for terrestrial photovoltaic cells. The critical issues in cell design, materials specification and cell processing are reviewed. Specific attention is given to light trapping, minority carrier lifetime control and novel microstructures for enhancing photon absorption. Relevant topics in generic defect control are discussed with particular emphasis on compound semiconductor materials.

Clinical and biochemical aspects of carnitine deficiency and insufficiency: transport defects and inborn errors of beta-oxidation.

Carnitine is required for entry of long chain fatty acids into mitochondria where beta-oxidation occurs. Primary carnitine deficiency, due to a generic defect in cellular carnitine transport, exists in myopathic and systemic forms. Secondary carnitine deficiency may be due to multiplicity of inherited abnormalities, including deficiencies in carnitine palmitoyl-transferase acyl-CoA dehydrogenases, electron transfer flavoprotein, and 3-ketoacyl-CoA-thiolase. The clinical features, diagnosis, and treatment of these conditions are described.

Operation of the Water-to-Sodium Leak Detection System at the Experimental Breeder Reactor II

A water-to-sodium leak detection system was installed at the Experimental Breeder Reactor II in April 1975. The system is designed for early detection of steam generator leaks, using hydrogen meters at the sodium outlets of the evaporators and superheaters. The leak detectors operate by measuring the rate of diffusion of hydrogen from the liquid sodium through a nickel membrane into a dynamic vacuum system. The advantages of this detection system are rapid response time, high sensitivity, stability, and reliability. The system was operated on an experimental basis for the first two years. During this period, data were obtained on detector stability, reliability, maintenance needs, computer interface requirements, calibration, and background hydrogen-level fluctuations. A generic defect in the original detectors was also discovered, requiring redesign of the units. When the new units were installed and proven to be reliable, the system was made fully operational. The data from the hydrogen meters are now used as the primary basis for detection of water-to-sodium leaks.

Numerical Simulation of an Industrial Cumulus and Comparison with Observations

Abstract A two-dimensional field-of-flow numerical model of cloud development is used to study a cloud that formed over a refinery as a result of heat dissipated to the atmosphere. The observed vertical structure of the atmosphere provided initial conditions. The wind necessarily was simplified to a unidirectional flow. The cloud-initiating perturbation consisted of sensible and latent heat equal to the waste heat rejected to the atmosphere by the refinery. When conditions were matched to those reported, the simulated cloud agreed in most particulars with the observations. Sensitivity tests showed that the simulated cloud depends too strongly on ambient wind speed and shear. This perhaps is a generic defect of two-dimensional formulations. The response of the simulated cloud to expected changes in heat flux density appears more realistic than its response to small changes in ambient wind. The cloud evolution consists of bubbles forming and breaking away from the main cloud mass, then moving downwind and d...

E.S.R. studies of radiation damage and structure in oxide glasses not containing transition group ions: A contemporary overview with illustrations from the alkali borate system

Electron spin resonance (e.s.r.) is a particularly powerful method for identifying and characterizing radiation-induced defects in vitreous materials. This paper reviews the fundamental principles and the present state of the art in applying e.s.r. techniques to achieve these ends in oxide glasses which do not contain transition group ions. A wide variety of generic defect types are discussed in some detail by means of examples from the alkali borate system. These include oxygen-associated trapped hole centers and oxygen-vacancy-associated trapped electron centers, as well as several electron and hole-type centers which are associated with interstitial cations and anions, respectively. Probable analogs in other oxide glasses are pointed out. Special emphasis is placed on the kinds of structural information which can be obtained from these studies.