Transfer printed multi-color integrated devices for visible light communication applications

Integrated multi-color devices for visible light communication applications are fabricated by transfer printing blue-emitting GaN light emitting diodes (LEDs) onto a green-emitting LED array and a colloidal quantum dot color-converter structure

MOVPE studies of zincblende GaN on 3C-SiC/Si(0 0 1)

Cubic zincblende GaN films were grown by metalorganic vapour-phase epitaxy on 3C-SiC/Si (0 0 1) templates and characterized using Nomarski optical microscopy, atomic force microscopy, X-ray diffraction, and transmission-electron microscopy. In particular, structural properties were investigated of films where the growth temperature of a GaN epilayer varied in the range of 830 °C to 910 °C and the gas-phase V/III-ratio varied from 15 to 1200 at a constant reactor pressure of 300 Torr. It was observed that with increasing epi temperature at a constant V/III-ratio of 76, the film surface consisted of micrometer-sized elongated features aligned along [1 –1 0] up to a temperature of 880 °C. The zincblende phase purity of such samples was generally high with a wurtzite fraction of less than 1%. When grown above 880 °C the GaN surface morphology degraded and the zincblende phase purity reduced as a result of inclusions with the wurtzite phase. A progressive narrowing of the 002 reflection with increasing epi growth temperature suggested an improvement of the film mosaicity. With increasing V/III-ratio at a constant growth temperature of 880 °C, the film surface formed elongated features aligned along [1 –1 0] at V/III values between 38 and 300 but the morphology became granular at both lower and higher V/III values. The zincblende phase purity is high at V/III values below 300. A slight broadening of the 002 X-ray diffraction reflection with increasing V/III-ratio indicated a small degradation of mosaicity. Scanning electron diffraction analyses of cross-sectional transmission-electron micrographs taken of a selection of samples illustrated the spatial distribution, quantity and structure of wurtzite inclusions within the zincblende GaN matrix. Within the limits of this study, the optimum epilayer growth conditions at a constant pressure of 300 Torr were identified to be at a temperature around 860 °C to 880 °C and a V/III-ratio in the range of 23 to 76, resulting in relatively smooth, zincblende GaN films without significant wurtzite contamination

Characterization of particle rebound phenomena in the erosion of turbomachinery

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/77337/1/AIAA-44864-924.pd

Surveillance for neuraminidase inhibitor resistance among human influenza A and B viruses circulating worldwide from 2004 to 2008

The surveillance of seasonal influenza virus susceptibility to neuraminidase (NA) inhibitors was conducted using an NA inhibition assay. The 50% inhibitory concentration values (IC50S) of 4,570 viruses collected globally from October 2004 to March 2008 were determined. Based on mean IC50S, A(H3N2) viruses (0.44 nM) were more sensitive to oseltamivir than A(H1N1) viruses (0.91 nM). The opposite trend was observed with zanamivir: 1.06 nM for A(H1N1) and 2.54 nM for A(H3N2). Influenza B viruses exhibited the least susceptibility to oseltamivir (3.42 nM) and to zanamivir (3.87 nM). To identify potentially resistant viruses (outliers), a threshold of a mean IC50 value + 3 standard deviations was defined for type/subtype and drug. Sequence analysis of outliers was performed to identify NA changes that might be associated with reduced susceptibility. Molecular markers of oseltamivir resistance were found in six A(H1N1) viruses (H274Y) and one A(H3N2) virus (E119V) collected between 2004 and 2007. Some outliers contained previously reported mutations (e.g., I222T in the B viruses), while other mutations [e.g., R371K and H274Y in B viruses and H274N in A(H3N2) viruses) were novel. The R371K B virus outlier exhibited high levels of resistance to both inhibitors (>100 nM). A substantial variance at residue D151 was observed among A(H3N2) zanamivir-resistant outliers. The clinical relevance of newly identified NA mutations is unknown. A rise in the incidence of oseltamivir resistance in A(H1N1) viruses carrying the H274Y mutation was detected in the United States and in other countries in the ongoing 2007 to 2008 season. As of March 2008, the frequency of resistance among A(H1N1) viruses in the United States was 8.6% (50/579 isolates). The recent increase in oseltamivir resistance among A(H1N1) viruses isolated from untreated patients raises public health concerns and necessitates close monitoring of resistance to NA inhibitors

African American Families’ Expectations and Intentions for Mental Health Services

A cross-sectional qualitative descriptive design was used to examine the links among expectations about, experiences with, and intentions toward mental health services. Individual face-to-face interviews were conducted with a purposive sample of 32 African American youth/mothers dyads. Content analysis revealed that positive expectations were linked to positive experiences and intentions, that negative expectations were not consistently linked to negative experiences or intentions, nor were ambivalent expectations linked to ambivalent experiences or intentions. Youth were concerned about privacy breeches and mothers about the harmfulness of psychotropic medication. Addressing these concerns may promote African Americans’ engagement in mental health services

Efficiency droop in zincblende InGaN/GaN quantum wells

The decrease in emission efficiency with increasing drive current density, known as ‘droop’, of c-plane wurtzite InGaN/GaN quantum wells presently limits the use of light-emitting diodes based on them for high brightness lighting applications. InGaN/GaN quantum wells grown in the alternative zincblende phase are free of the strong polarisation fields that exacerbate droop and so were investigated by excitation-dependent photoluminescence and photoreflectance studies. Polarisation-resolved measurements revealed that for all excitation densities studied the emission from such samples largely originates from similar microstructures or combinations of microstructures that form within the quantum well layers. Emission efficiency varies significantly with excitation at 10 K showing that non-radiative recombination processes are important even at low temperature. The onset of efficiency droop, as determined by photomodulated reflection measurements, occurred at a carrier density of around 1.2 × 1020 cm−3 – an order of magnitude greater than the value reported for a reference wurtzite quantum well sample using the same method. The high carrier density droop onset combined with the much shorter carrier lifetime within zincblende InGaN/GaN quantum wells indicate they have the potential to effectively delay efficiency droop when used in GaN based light-emitting diodes. However, the material quality of the quantum well layers need to be improved by preventing the formation of microstructures within these layers, and the importance of the role played by non-radiative centres in the QW layer needs to be elucidated, to fully realise the material's potential

Psychosocial Treatment of Children in Foster Care: A Review

A substantial number of children in foster care exhibit psychiatric difficulties. Recent epidemiologi-cal and historical trends in foster care, clinical findings about the adjustment of children in foster care, and adult outcomes are reviewed, followed by a description of current approaches to treatment and extant empirical support. Available interventions for these children can be categorized as either symptom-focused or systemic, with empirical support for specific methods ranging from scant to substantial. Even with treatment, behavioral and emotional problems often persist into adulthood, resulting in poor functional outcomes. We suggest that self-regulation may be an important mediat-ing factor in the appearance of emotional and behavioral disturbance in these children