Scattering of light from quasi-homogeneous sources by quasi-homogeneous media

The field generated by scattering of light from a quasi-homogeneous source on a quasi-homogeneous, random medium is investigated. It is found that, within the accuracy of the first-order Born approximation, the far field satisfies two reciprocity relations (sometimes called uncertainty relations). One of them implies that the spectral density (or spectral intensity) is proportional to the convolution of the spectral density of the source and the spatial Fourier transform of the correlation coefficient of the scattering potential. The other implies that the spectral degree of coherence of the far field is proportional to the convolution of the correlation coefficient of the source and the spatial Fourier transform of the strength of the scattering potential. While the case we consider might seem restrictive, it is actually quite general. For instance, the quasi-homogeneous source model can be used to describe the generation of beams with different coherence properties and different angular spreads. In addition, the quasi-homogeneous scattering model adequately describes a wide class of turbulent media, including a stratified, turbulent atmosphere and confined plasmas.     

Computational Investigation of the pH Dependence of Stability of Melanosome Proteins: Implication for Melanosome formation and Disease

Intravesicular pH plays a crucial role in melanosome maturation and function. Melanosomal pH changes during maturation from very acidic in the early stages to neutral in late stages. Neutral pH is critical for providing optimal conditions for the rate-limiting, pH-sensitive melanin-synthesizing enzyme tyrosinase (TYR). This dramatic change in pH is thought to result from the activity of several proteins that control melanosomal pH. Here, we computationally investigated the pH-dependent stability of several melanosomal membrane proteins and compared them to the pH dependence of the stability of TYR. We confirmed that the pH optimum of TYR is neutral, and we also found that proteins that are negative regulators of melanosomal pH are predicted to function optimally at neutral pH. In contrast, positive pH regulators were predicted to have an acidic pH optimum. We propose a competitive mechanism among positive and negative regulators that results in pH equilibrium. Our findings are consistent with previous work that demonstrated a correlation between the pH optima of stability and activity, and they are consistent with the expected activity of positive and negative regulators of melanosomal pH. Furthermore, our data suggest that disease-causing variants impact the pH dependence of melanosomal proteins; this is particularly prominent for the OCA2 protein. In conclusion, melanosomal pH appears to affect the activity of multiple melanosomal proteins.     

Hypnosis training in APA- and non-APA-approved clinical/counseling doctoral programs.

Assessed the status of and attitudes toward hypnosis training in 186 American Psychological Association (APA)-approved and nonapproved doctoral programs. 53% of the departments returned questionnaires within the allotted time period. Results indicate that 30% of the APA-approved and 39% of the non-APA-approved programs offer either a full or partial course in hypnosis. Approximately 60% of the programs in both groups either offer some type of academic course or allow students the opportunity to enhance their previously learned hypnosis skills through practicum courses. Respondent attitudes toward hypnosis were generally positive. (4 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Optical observation of growth and melting dynamics of3He-4He mixture crystals

Crystals grown from 2.1% and 9.3% solutions of³ He in⁴He were observed in a cryostat with optical access from two orthogonal directions (above and from the side). Video films of dynamic processes were recorded at temperatures between 0.5K and 1.8K. Facetted melting of crystals (in contrast with rounded melting which is the general case) was observed below 0.75K. This is in accordance with previous experiments which showed a higher³He concentration along the edges of the crystal. We also recorded morphological growth instabilities of the 9.3% b.c.c. crystals. In the temperature region below about 0.9K where the latent heat is negative no dendritic growth was observed, which we interpret as resulting from opposing effects of temperature and concentration gradients.     

A Cube Model for Competency Development: Implications for Psychology Educators and Regulators.

This article provides a conceptual framework for training in professional psychology focused on the construct of competency. The authors present a 3-dimensional competency model delineating the domains of knowledge, skills, attitudes, and values that serve as the foundation required of all psychologists, the domains of functional competencies that broadly define what psychologists do, and the stages of professional development from doctoral education to lifelong learning through continuing education. The goal in presenting this model is to provide a conceptual frame of reference for those responsible for psychology education, credentialing, and regulation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Interactive design and optimization of flight-vehicle lifting surface structures

A computerized procedure for the design and optimization of flight vehicle structures employing interactive graphics is described. The procedure represents a subsystem of the multi-disciplinary Interactive Structural Sizing and Analysis System (ISSAS), currently being employed at IAI. The paper describes three interactive modules that deal with the primary structural layout, design, finite element modeling and reduction of analytic data for flight vehicle lifting surface structures. The procedure described herein represents a sizable saving in elapsed time and man-hours per design iteration, relative to conventional methods, and provides for the design of superior quality structure in a shorter period of time and at lower cost.     

A collocation finite element method for potential problems in irregular domains

A potentially powerful numerical method for solving certain boundary value problems is developed. The method combines the simplicity of orthogonal collocation with the versatility of deformable finite elements. Bicubic Hermite elements with four degrees-of-freedom per node are used. A subparametric transformation permits the precise positioning of the collocation points for maximum accuracy as well as a unique representation of irregular boundaries. It is shown that by taking advantage of the boundary conditions, a minimum number of collocation points can be used. The method is particularly suitable for potential and mass transport problems where a C¹ continuous solution is required. In contrast to the Galerkin approach, it does not require the evaluation of basis function products and numerical integration, also the coefficient matrix contains only about half as many non-zero terms as the corresponding Galerkin coefficient matrix. This results in approximately a 90 per cent reduction in formulation and a 50 per cent reduction in solution operation, as compared with the Galerkin finite element method, for this type of problem. Examples show that the accuracy of the collocation solution is as good as or better than that of the Galerkin solution.     

Learning About 3d Melting With Solid Helium

Theories of bulk melting rely on a sudden proliferation of crystalline defects in order to destabilize the lattice. However, these scenarios were never confirmed experimentally, as it is impossible to approach the transition sufficiently to see critical behaviour. In experiments investigating plastic flow of solid ⁴He, we observed such critical behaviour involving a dramatic decrease of the resistance to shear near the first order bcc-hcp transition at 1.772K on the melting curve. By measuring the plastic flow over a wide range of shear stress, we were able to differentiate between the contribution of vacancies and of dislocations to this process. We argue that the mechanism by which the crystal loses its shear resistance involves coupling of vacancy diffusion with a transverse phonon which softens as the transition is approached. Dislocations seem to play no fundamental role in this process. These results suggest a refinement of the Lindemann picture, as the phonon mode which plays a dominant role in this process is near the edge of the Brillouin zone.     

Copper converter refractory practices

The articles appearing in the following section are condensations of papers presented at a round table discussion on the subject of “Copper Converter Refractory Practices”, sponsored by the Extractive Metallurgy Division of The Metallurgical Society. The discussion was held during the AIME Annual Meeting in New York City, February 1968. All deletions, and the omission of references, have been made solely because of space limitations, and should not be construed as reflections upon the individual authors or their papers.