GaN and AlGaN high-voltage rectifiers grown by metal-organic chemical-vapor deposition

In this paper, we report the study of the electrical characteristics of GaN and AlGaN vertical p-i-n junctions and Schottky rectifiers grown on both sapphire and SiC substrates by metal-organic chemical-vapor deposition. For GaN p-i-n rectifiers grown on SiC with a relatively thin “i” region of 2 μm, a breakdown voltage over 400 V, and forward voltage as low as 4.5 V at 100 A/cm² are exhibited for a 60-μm-diameter device. A GaN Schottky diode with a 2-μm-thick undoped layer exhibits a blocking voltage in excess of ∼230 V at a reverse-leakage current density below 1 mA/cm², and a forward-voltage drop of 3.5 V at a current density of 100 A/cm². It has been found that with the same device structure and process approach, the leakage current of a device grown on a SiC substrate is much lower than a device grown on a sapphire substrate. The use of Mg ion implantation for p-guard rings as planar-edge terminations in mesageometry GaN Schottky rectifiers has also been studied.     

The dynamics of market-level change

Health care exhibits a competitive dynamic today that increasingly resembles that in other service industries. Organizations are becoming larger to achieve scale economies and to increase market power. Vertical integration, whether through ownership or complex contracts, is also being pursued both to seek efficiencies and to improve the bargaining position of the organization. External forces that are driving these changes include more aggressive activities on the part of purchasers to contain their costs, developments in information technology, management innovation in other service industries, and advances in medical technology. Within the health care industry, there is a pattern of organizations taking the initiative to respond to these external forces--often in anticipation of them--and other organizations then responding to the pressures in turn placed on them. Although information on strategies is communicated rapidly throughout the country, what is attempted and what succeeds differs a great deal across communities. The nature of current health care institutions in the community, including the presence of large entities with extensive capital and strong management in a particular segment of the health system and the community's experience with managed care are important factors in the path that change takes.     

The influence of the fabrication process on the buckling of thin-walled steel box sections

Steel box sections are usually fabricated from flat plates which are welded at the corners. The welding process can introduce residual stresses and geometric imperfections into the sections which can influence their strength. For some thin-walled sections, large periodic geometric imperfections have been observed in manufactured sections. Subsequent investigations have indicated that the imperfections are in fact buckling deformations i.e. the box section has buckled due to welding residual stresses prior to any application of external load. The welding procedure and the behaviour of the box sections under load has been modelled using a finite element analysis that accounts for both geometric and material non-linearities. Tests have been carried out on box sections with a range of width to thickness ratios for the plate elements. Modelling has been shown to give good correlation with the test results. The conditions for buckling to take place as a result of the welding process have been established. A design method has been proposed.     

GELYMAC: a Macintosh application for calculating DNA fragment size from gel electrophoresis migration data

A program called GELYMAC takes data on the distances migrated by DNA fragments in a one-dimensional electrophoretic gel and, using a cubic-spline best-fit of marker fragment distance migrated versus molecular size, calculates the molecular sizes of the fragments. Written in the Rascal (Real-time Pascal) programming language, the program runs on the Macintosh family of microcomputers. Rapid entry of marker and experimental fragment migration data is afforded using a scroll bar system adjacent to a graphic representation of a gel. Output includes tabular listing of the data, graphic cartoons of the gel, and the fragment locations and molecular sizes for individual gel lanes, and the calibration curve used in data computations.     

Clinical significance of psychotherapy for unipolar depression: A meta-analytic approach to social comparison.

[Correction Notice: An erratum for this article was reported in Vol 55(3) of Journal of Consulting and Clinical Psychology (see record 2008-10745-001). The data presented in Table 2 were incorrect because a row and a column were inadvertently omitted. The corrected Table 2 appears in the erratum.] This study used meta-analysis to study the clinical significance of psychotherapy for symptoms of unipolar depression. The following questions were addressed: How similar is the posttherapy adjustment of depressed adults to that of nondepressed adults? Is this adjustment maintained at follow-up? What dimensions of treatment, therapists, or design are associated with clinical significance? Using the Beck Depression Inventory (BDI), we calculated composite BDI norms from 28 published studies. Sixty effect sizes (from 31 outcome studies utilizing the BDI) were calculated. The results indicated that psychotherapy produces outcomes that have moderate clinical significance and that are well-maintained at follow-up, that individual therapy is associated with greater clinical significance than group treatment, and that type of therapy is not related to improvement. Alternative approaches for operationalizing clinical significance as the return of individuals to normal levels of functioning are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)