Wright-Patterson Air Force Base

About: Wright-Patterson Air Force Base is a other organization based out in Wright-Patterson AFB, Ohio, United States. It is known for research contribution in the topics: Laser & Microstructure. The organization has 5817 authors who have published 9157 publications receiving 292559 citations. The organization is also known as: Wright-Patterson AFB & FFO.

Electronic Core Levels of Zinc Chalcogenides

Abstract: X-ray-induced photoemission studies were used to determine the energy levels of core electrons in ZnO, ZnS, ZnSe, and ZnTe. The investigated energy range extends from the Fermi level to about 1200 eV below the valence band. The observed Auger transitions in these compounds are in good agreement with the measured energy levels. Some of the uncertainties in using this technique for the study of electron energy levels in semiconducting or insulating crystals were investigated and are discussed. The measured energy levels are compared with published experimental data for the respective pure elements. Comparison is also made with energy values predicted by several different types of theoretical calculations. Significant conclusions are: (i) The location of the Zn $3d$ level in the zinc chalcogenides has been unambiguously determined and (ii) the discrepancy between our measured values and the theoretically determined energy values is angular momentum dependent.

Efficacy of probiotics in the treatment of pediatric atopic dermatitis: a meta-analysis of randomized controlled trials

Abstract: Background Several articles describing the efficacy of probiotics in atopic dermatitis (AD) have been published. However, not all studies support a similar outcome. Objective To determine whether probiotics are efficacious in treating AD and to explore whether type of probiotic used, duration of therapy, patient age, severity of disease, and IgE sensitization are factors in determining efficacy. Methods For this meta-analysis of randomized controlled trials describing the efficacy of probiotics in AD, a comprehensive search was performed of databases through January 2008. Three reviewers independently evaluated the studies for methodological qualities. All the data were analyzed, and forest plots were evaluated for the overall efficacy of probiotics in AD and the therapeutic benefit to subgroups of selected patient populations. Results Eleven studies were identified, and data from 10 studies (n = 678) were available to analyze. There was an overall statistically significant difference favoring probiotics compared with placebo in reducing the Scoring of Atopic Dermatitis Severity Index score (mean change from baseline, −3.01; 95% confidence interval, −5.36 to −0.66; P = .01). Children with moderately severe disease were more likely to benefit. Duration of probiotic administration, age, and type of probiotic used did not affect outcome. Conclusion Data from this meta-analysis suggest a modest role for probiotics in pediatric AD. The effect is seen in moderately severe rather than mild disease.

Comparison of Predicted and Measured Formation Flight Interference Effects

Abstract: Results from a wind-tunnel test of two delta-wing aircraft in close proximity are presented and compared with predictions from a vortex lattice method. Large changes in lift, pitching moment, and rolling moment are found on the trail aircraft as it moves laterally relative to the lead aircraft. The magnitude of these changes is reduced as the trail aircraft moves vertically with respect to the lead aircraft. Lift-to-drag ratio of the trail aircraft is increased when the wing tips are slightly overlapped. Wake-induced lift is overpredicted slightly when the aircraft overlap in the spanwise direction. Wake-induced pitching and rolling moments are well predicted. A maximum induced drag reduction of 25% is measured on the trail aircraft, compared with a 40% predicted reduction. Three positional stability derivatives, change in lift and pitching moment with vertical position and change in rolling moment with lateral position, are studied. Predicted boundaries between stable and unstable regions were generally in good agreement with experimentally derived boundaries.

Crystallography of Fatigue Crack Initiation and Growth in Fully Lamellar Ti-6Al-4V

Abstract: Fatigue crack initiation in titanium alloys is typically accompanied by the formation of planar, faceted features on the fracture surface. In the present study, quantitative tilt fractography, electron backscatter diffraction (EBSD), and the focused ion beam (FIB) have been used to provide a direct link between facet topography and the underlying microstructure, including the crystallographic orientation. In contrast to previous studies, which have focused mainly on the α-phase crystal orientation and the spatial orientation of the facets, the present analysis concentrates on the features that lie in the plane of the facet and how they relate to the underlying constituent phases and their crystallographic orientations. In addition, due to the anisotropic deformation behavior of the three basal slip systems, the orientation of the β phase as it relates to facet crystallography was investigated for the first time. The implication of the β-phase orientation on fatigue crack initiation was discussed in terms of its effect on slip behavior in lamellar microstructures. The effect of the local crystallographic orientation on fatigue crack initiation was also investigated by studying cracks that initiated naturally in the earliest stages of growth, which were revealed by FIB milling. The results indicate that boundaries that are crystallographically suited for slip transfer tend to initiate fatigue cracks. Several observations on the effect of the crystallographic orientation on the propagation of long fatigue cracks were also reported.

Role of Blade Passage Flow Structures in Axial Compressor Rotating Stall Inception

Abstract: The influence of three-dimensional flow structures within a compressor blade passage has been examined computationally to determine their role in rotating stall inception. The computations displayed a short length-scale (or spike) type of stall inception similar to that seen in experiments; to the authors’ knowledge this is the first time such a feature has been simulated. A central feature observed during the rotating stall inception was the tip clearance vortex moving forward of the blade row leading edge. Vortex kinematic arguments are used to provide a physical explanation of this motion as well as to motivate the conditions for its occurrence. The resulting criterion for this type of stall inception (which appears generic for axial compressors with tip-critical flow fields) depends upon local flow phenomena related to the tip clearance and it is thus concluded that the flow structure within the blade passages must be addressed to explain the stability of an axial compression system which exhibits such short length-scale disturbances.© 1998 ASME