Impact of combination therapies on HIV risk perceptions and sexual risk among HIV-positive and HIV-negative gay and bisexual men.

The availability of improved HIV treatments may prompt reduced concern about HIV and sexual risk. Gay and bisexual men (N?=?554, 17% HIV-positive) completed measures of treatment attitudes, sexual risk, and assumptions regarding the infectiousness of sexual partners. A substantial minority reported reduced HIV concern related to treatment advances. Reduced HIV concern was an independent predictor of sexual risk, particularly among HIV-positive men. In response to hypothetical scenarios describing sex with an HIV-positive partner, participants rated the risk of unprotected sex to be lower if the partner was taking combination treatments and had an undetectable viral load, relative to scenarios with a seropositive partner not taking combination treatments. Prevention efforts must address attitudinal shifts prompted by recent treatment successes, stressing the continued importance of safer sex, and that an undetectable viral load does not eliminate infection risks. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Use it or lose it: Engaged lifestyle as a buffer of cognitive decline in aging?

Data from the Victoria Longitudinal Study were used to examine the hypothesis that maintaining intellectual engagement through participation in everyday activities buffers individuals against cognitive decline in later life. The sample consisted of 250 middle-aged and older adults tested 3 times over 6 years. Structural equation modeling techniques were used to examine the relationships among changes in lifestyle variables and an array of cognitive variables. There was a relationship between changes in intellectually related activities and changes in cognitive functioning. These results are consistent with the hypothesis that intellectually engaging activities serve to buffer individuals against decline. However, an alternative model suggested the findings were also consistent with the hypothesis that high-ability individuals lead intellectually active lives until cognitive decline in old age limits their activities. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Immunohistochemical localization of a water channel, aquaporin 7 (AQP7), in the rat testis

Cell volume reduction is one of the most distinct morphological changes during spermiogenesis and may be largely attributable to water efflux from the cell. A strong candidate for a water efflux route, aquaporin 7 (AQP7), which is a water channel, was studied immunohistochemically in the rat testis. Immunoreactivity was restricted within the elongated spermatids, testicular spermatozoa, and residual bodies remaining in the seminiferous epithelium. Weak but distinct immunoreactivity was first observed in the cytoplasmic mass of the spermatid at step 8 of spermiogenesis. The Golgi-like apparatus became steadily immunoreactive at step 10. The plasma membrane covering the cytoplasmic mass showed strong immunoreactivity after step 16. At this step, the middle piece of the tail also showed immunoreactivity at the portion protruding into the lumen. The whole head and distal tail, where the elongated spermatid had only a limited amount of cytoplasm, showed no immunoreactivity throughout spermiogenesis. After spermiation, the immunoreactivity of AQP7 remained at the middle piece and in the cytoplasmic droplet in the testicular spermatozoon. The present observations suggest that AQP7 contributes to the volume reduction of spermatids, since this water channel protein is localized on the plasma membrane covering the condensing cytoplasmic mass of the elongated spermatid, and since the seminiferous tubule fluid is hypertonic.     

Vibrational thermodynamics of materials

The literature on vibrational thermodynamics of materials is reviewed. The emphasis is on metals and alloys, especially on the progress over the last decade in understanding differences in the vibrational entropy of different alloy phases and phase transformations. Some results on carbides, nitrides, oxides, hydrides and lithium-storage materials are also covered.Principles of harmonic phonons in alloys are organized into thermodynamic models for unmixing and ordering transformations on an Ising lattice, and extended for non-harmonic potentials. Owing to the high accuracy required for the phonon frequencies, quantitative predictions of vibrational entropy with analytical models prove elusive. Accurate tools for such calculations or measurements were challenging for many years, but are more accessible today. Ab initio methods for calculating phonons in solids are summarized. The experimental techniques of calorimetry, inelastic neutron scattering, and inelastic X-ray scattering are explained with enough detail to show the issues of using these methods for investigations of vibrational thermodynamics. The explanations extend to methods of data analysis that affect the accuracy of thermodynamic information.It is sometimes possible to identify the structural and chemical origins of the differences in vibrational entropy of materials, and the number of these assessments is growing. There has been considerable progress in our understanding of the vibrational entropy of mixing in solid solutions, compound formation from pure elements, chemical unmixing of alloys, order-disorder transformations, and martensitic transformations. Systematic trends are available for some of these phase transformations, although more examples are needed, and many results are less reliable at high temperatures. Nanostructures in materials can alter sufficiently the vibrational dynamics to affect thermodynamic stability. Internal stresses in polycrystals of anisotropic materials also contribute to the heat capacity. Lanthanides and actinides show a complex interplay of vibrational, electronic, and magnetic entropy, even at low temperatures.A “quasiharmonic model” is often used to extend the systematics of harmonic phonons to high temperatures by accounting for the effects of thermal expansion against a bulk modulus. Non-harmonic effects beyond the quasiharmonic approximation originate from the interactions of thermally-excited phonons with other phonons, or with the interactions of phonons with electronic excitations. In the classical high temperature limit, the adiabatic electron-phonon coupling can have a surprisingly large effect in metals when temperature causes significant changes in the electron density near the Fermi level. There are useful similarities in how temperature, pressure, and composition alter the conduction electron screening and the interatomic force constants. Phonon-phonon “anharmonic” interactions arise from those non-harmonic parts of the interatomic potential that cannot be accounted for by the quasiharmonic model. Anharmonic shifts in phonon frequency with temperature can be substantial, but trends are not well understood. Anharmonic phonon damping does show systematic trends, however, at least for fcc metals.Trends of vibrational entropy are often justified with atomic properties such as atomic size, electronegativity, electron-to-atom ratio, and mass. Since vibrational entropy originates at the level of electrons in solids, such rules of thumb prove no better than similar rules devised for trends in bonding and structure, and tend to be worse. Fortunately, the required tools for accurate experimental investigations of vibrational entropy have improved dramatically over the past few years, and the required ab initio methods have become more accessible. Steady progress is expected for understanding the phenomena reviewed here, as investigations are performed with the new tools of experiment and theory, sometimes in integrated ways.     

The ultrapurification of tellurium

High-purity tellurium is used in the preparation of II–VI compounds, particularly CdTe and Cd_x Hg_1?x Te. Distillation of tellurium under low-pressure H₂ reduces the concentrations of iron and silicon. The addition of CdTe to tellurium prior to zone refining, in a quantity less than the eutectic concentration, has been observed to change the segregation behavior of Ca, K, Ga and As, which enables more efficient refining. Emission spectroscopy, spark source mass spectroscopy and the evaluation of Cd_0.21Hg_0.79 Te have been used to characterize these effects.     

Development of orientation coherence in plane-strain deformation

Spatial orientation coherence in 20 pct channel-die compressed aluminum ingot is investigated using the two-point orientation coherence function (OCF) constructed from individual crystallite orientation measurements. It is found that orientation coherence clusters formed in the initially coherence-free ingot during deformation. The orientation coherence cluster consists of a central grain with lattice orientation (φ₁, ϕ, φ₂) surrounded by grains with lattice orientation (π + φ₁, ϕ, φ₂); this coincides with one of the processing-symmetry orientations of the central grain. The observed clustering is compared with simulations of structure evolution based upon the classical full-constraint Taylor model. As is expected, no coherence structure develops in these simulations. A mechanism of formation for the orientation coherence cluster is proposed based upon a requirement of stress equilibrium between neighboring grains, while maintaining, on average, strain compatibility with the overall plane-strain compression deformation mode. A simplified Fourier representation of the conditional two-point OCF is described, and a numerical scheme to obtain the expansion coefficients is proposed and tested. Formerly Visiting Scholar, Department of Mechanical Engineering, Brigham Young University, Provo, UT 84602, is retired.     

Crystal slip modeling of small strain yield behavior in textured copper tubing

A self-consistent polycrystalline model developed by Kr?ner, and Budiansky and Wu (KBW) was used to model small strain (2 and 8 × 10_-6) biaxial yield behavior in textured copper tubing. The results were compared to simulations using the Bishop-Hill model and a lower bound (LB) model which neglected strain compatibility. It was found that the Bishop-Hill model poorly represents texture effects whereas the KBW and LB models give accurate predictions of biaxial yield surfaces at these strain levels. A linear latent hardening law was used with both the KBW and LB model. Varying the latent hardening ratio an order of magnitude had little effect on the yield surface. Introducing the odd 1 coefficients of the generalized spherical harmonic expansion was also found to have negligible effect on the predicted yield loci. Formerly Graduate Student of Mechanical Engineering at Brigham Young University Formerly Graduate Student of Materials Science and Engineering at the University of Florida     

On a class of pseudo‐logarithmic amplifiers suitable for use with digitally switched resistors

This paper describes three circuits that implement pseudo‐logarithmic functions, which are simple and easy to implement. The circuits can be realized using operational amplifiers or current feedback amplifiers. Tuning can be achieved using switched resistors, or active resistors, or tunable transconductors, but are best suited for use with digitally switched resistors. Frequency response and stability considerations for two of the circuits are thoroughly discussed and PSPICE results confirming the theoretical results are presented alongside measured results. Copyright © 2007 John Wiley & Sons, Ltd.     

The perils of eclecticism as therapeutic orientation.

This current article discusses the "perils of eclecticism as therapeutic orientation". Although some who label themselves "eclectic" recognize the importance of a well-articulated theory in their work, the vast majority attempt to avoid theorizing. Their main fear appears to be that a theoretical system will bias their interpretations of clinical or empirical data and thus leave them inflexible and closed-minded. The present author appreciates the possibility of theoretical speculations becoming unmonitored biases, but eclectics must also appreciate that biases cannot be avoided, only the lack of monitoring can be avoided. In fact, to delude oneself into thinking that one has avoided biases is to guarantee that one is operating from an unmonitored bias. (PsycINFO Database Record (c) 2010 APA, all rights reserved)