Tilted superlattice composition profile determined by photoluminescence and thermal disordering

The composition profile of an (AlAs)_1/2(GaAs)_1/2 tilted superlattice is characterized for the first time. The tilted superlattice sample is thermally disordered, and the energy of the direct band gap photoluminescence peak is measured as a function of increasing layer interdiffusion. The shift in the photoluminescence peak energy after completely disordering the tilted superlattice is 39 meV. A theoretical model is used to simulate the change in band gap as a function of layer interdiffusion for several composition profiles. The profile that gives the best fit to the experimental data is chosen. The tilted superlattice composition profile is found to be sinusoidal, varying from Al_0.40Ga_0.60As to Al_0.60Ga_0.40As.     

Mechanism and dynamics of shrinking island grains in mazed bicrystal thin films of Au

This work investigates the mechanism and dynamics of grain boundary migration driven by capillary forces via in situ electron microscopy, complemented by molecular-dynamics simulations. Using thin films of Au with the mazed bicrystal geometry, the shrinkage of island grains with 90°〈1 1 0〉 tilt grain boundaries was observed by diffraction contrast and high-resolution imaging. The grains remained cylindrical throughout the shrinkage, and there was no measurable grain rotation even at very small sizes. The rate of shrinkage was found to be erratic and inconsistent with parabolic kinetics, accelerating before complete disappearance. Residual defects were found immediately after complete shrinkage, although the type and magnitude of the defects varied from grain to grain. Measurement of the grain boundary shape anisotropy showed a preference for facets on low-index planes of the crystals, including the mirror-symmetry planes of the bicrystal. These facets were also found directly on individual images extracted from high-resolution video recordings of shrinking grains at ～300 °C. The dynamics of boundary motion were found to be limited by nucleation and propagation of steps on these facets. The cylindrical geometry and size of the experimentally observed island grains allow direct comparison with molecular-dynamics simulations on the same length scale, which reproduced many of the experimentally observed features, including non-parabolic shrinkage, absence of systematic grain rotation, step-controlled migration and dislocation debris after complete grain shrinkage. Differences between model and experiment are discussed in terms of the possible role of impurities, surfaces and interfacial steps.     

Shallow subsurface temperature surveys in the basin and range province—II. Ground temperatures in the upsal hogback geothermal area, West-Central Nevada, U.S.A.

Numerous temperature surveys at a depth of 1 m were made in 1973–1985 in the Upsal Hogback and Soda Lakes geothermal areas in west-central Nevada. Whereas the surveys effectively delineated temperature at depth and heat flow within the relatively intense Soda Lakes thermal anomaly, they were not effective at the diffuse Upsal Hogback anomaly, where several perturbing factors that affect shallow subsurface temperatures are exceedingly variable. Albedo is the most important factor in the Upsal Hogback area, even at a depth of 30 m. All possible perturbing factors should be considered when designing a shallow temperature-based prospecting scheme.     

Brief group psychoeducation for bulimia nervosa: Assessing the clinical significance of change.

41 women with bulimia nervosa completed a brief intervention that was designed to promote symptom management. Cutoff scores for the determination of reliable and clinically significant change were calculated for several psychometric instruments that are commonly used as outcome measures in the field of eating disorders. Using these statistical procedures to assess therapeutic change, this study documents the diversity of outcomes that individuals reported following their participation in the intervention. As expected, there was a differential reporting of clinically significant change in favor of specific eating psychopathology relative to personality features and associated psychopathology. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A validity check on MMPI scales of responsibility and dominance.

This study presents evidence on the validity and limits of applicability of the MMPI portion of the responsibility scale and the dominance scale. "25 Minneapolis fire captains did not differ significantly from 262 Minneapolis firemen in mean scores obtained on the MMPI items of the social responsibility and dominance scales. If the attainment of a captaincy is granted as an appropriate criterion, the data appear to constitute evidence against the validity of at least the MMPI portion of the responsibility scale. The criterion may be less appropriate with respect to Dominance." (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Therapist competence ratings in relation to clinical outcome in cognitive therapy of depression.

This study reports on the relationship of therapist competence to the outcome of cognitive-behavioral treatment in the National Institute of Mental Health Treatment of Depression Collaborative Research Program. Outpatients suffering from major depressive disorder were treated by cognitive-behavioral therapists at each of 3 U.S. sites using a format of 20 sessions in 16 weeks. Findings provide some support for the relationship of therapist competence (as measured by the Cognitive Therapy Scale) to reduction of depressive symptomatology when controlling for therapist adherence and facilitative conditions. The results are, however, not as strong or consistent as expected. The component of competence that was most highly related to outcome is a factor that reflects the therapist's ability to structure the treatment. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Survey of computed grain boundary properties in face-centered cubic metals—II: Grain boundary mobility

The absolute grain boundary mobility of 388 nickel grain boundaries was calculated using a synthetic driving force molecular dynamics method; complete results appear in the Supplementary materials. Over 25% of the boundaries, including most of the non-Σ3 highest mobility boundaries, moved by a coupled shear mechanism. The range of non-shearing boundary mobilities is from 40 to 400 m/s GPa, except for Σ3 incoherent twins which have mobilities of 200–2000 m/s GPa. Some boundaries, including all the 〈1 1 1〉 twist boundaries, are immobile within the resolution of the simulation. Boundary mobility is not correlated with scalar parameters such as disorientation angle, Σ value, excess volume or boundary energy. Boundaries less than 15° from each other in five-dimensional crystallographic space tend to have similar mobilities. Some boundaries move via a non-activated motion mechanism, which greatly increases low-temperature mobility. Thermal roughening of grain boundaries is widely observed, with estimated roughening temperatures substantially among boundaries.