Neutral-Donor-Bound-Exciton Complexes in ZnO Crystals

Neutral-donor–bound-exciton transitions have been observed in ZnO. The isolated neutral donors are made up of defect pair complexes. The neutral-donor nature of these pair complexes was determined from magneticfield measurements and from two-electron transitions. Excited states of the neutral-donor bound excitons were observed in the form of rotator states analogous to rotational states of the H2 molecule

Excitonic photoluminescence linewidths in AlGaAs grown by molecular beam epitaxy

The linewidths of excitonic transitions were measured in AlxGa1−xAs, grown by molecular beam epitaxy as a function of alloy composition x for values of x≲0.43 using high resolution photoluminescence spectroscopy at liquid helium temperature. The values of the linewidths thus measured are compared with the results of several theoretical calculations in which the dominant broadening mechanism is assumed to be the statistical potential fluctuations caused by the components of the alloy. An increase in the linewidth as a function of x is observed which is in essential agreement with the prediction of the various theoretical calculations. The linewidths of the excitonic transitions in AlxGa1−xAs observed in the present work are the narrowest ever reported in the literature, for example σ=2.1 meV for x=0.36, thus indicating very high quality material.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70175/2/APPLAB-48-11-727-1.pd

GaAs/AlGaAs heterojunction Pnp bipolar transistors grown on (100) Si by molecular beam epitaxy

GaAs/AlGaAs Pnp heterojunction bipolar transistors (HBTs) were fabricated and tested on (100) Si substrates for the first time. A common-emitter current gain of β=8 was measured for the typical devices with an emitter area of 50×50 μm^2 at a collector current density of 1×10^(4) A/cm^2 with no output negative differential resistance up to 280 mA, highest current used. A very high base-collector breakdown voltage of 10 V was obtained. Comparing the similar structures grown on GaAs substrates, the measured characteristics clearly demonstrate that device grade hole injection can be obtained in GaAs on Si epitaxial layers despite the presence of dislocations

A randomised controlled trial of succinylated gelatin (4%) fluid on urinary acute kidney injury biomarkers in cardiac surgical patients

Background Fluid resuscitation is frequently required for cardiac surgical patients admitted to the intensive care unit. The ideal fluid of choice in regard to efficacy and safety remains uncertain. Compared with crystalloid fluid, colloid fluid may result in less positive fluid balance. However, some synthetic colloids are associated with increased risk of acute kidney injury (AKI). This study compared the effects of succinylated gelatin (4%) (GEL) with compound sodium lactate (CSL) on urinary AKI biomarkers in patients after cardiac surgery. Methods Cardiac surgical patients who required an intravenous fluid bolus of at least 500 mL postoperatively were randomly allocated to receive GEL or CSL as the resuscitation fluid of choice for the subsequent 24 h. Primary outcomes were serial urinary neutrophil gelatinase-associated lipocalin (NGAL) and cystatin C concentrations measured at baseline, 1 h, 5 h and 24 h after enrolment, with higher concentrations indicating greater kidney injury. Secondary biomarker outcomes included urinary clusterin, α1-microglobulin and F2-isoprostanes concentrations. Differences in change of biomarker concentration between the two groups over time were compared with mixed-effects regression models. Statistical significance was set at P < 0.05. Results Forty cardiac surgical patients (n = 20 per group) with similar baseline characteristics were included. There was no significant difference in the median volume of fluid boluses administered over 24 h between the GEL (1250 mL, Q1–Q3 500–1750) and CSL group (1000 mL, Q1–Q3 500–1375) (P = 0.42). There was a significantly greater increase in urinary cystatin C (P < 0.001), clusterin (P < 0.001), α1-microglobulin (P < 0.001) and F2-isoprostanes (P = 0.020) concentrations over time in the GEL group, compared to the CSL group. Change in urinary NGAL concentration (P = 0.68) over time was not significantly different between the groups. The results were not modified by adjustment for either urinary osmolality or EuroSCORE II predicted risk of mortality. Conclusions This preliminary randomised controlled trial showed that use of succinylated gelatin (4%) for fluid resuscitation after cardiac surgery was associated with increased biomarker concentrations of renal tubular injury and dysfunction, compared to crystalloid fluid. These results generate concern that use of intravenous gelatin fluid may contribute to clinically relevant postoperative AKI

Effect of C∕Si ratio on deep levels in epitaxial 4H–SiC

Changing the ratio of carbon to silicon during the epitaxial 4H–SiC growth is expected to alter the dominant deep level trap, which has been attributed to a native defect. The C∕Si ratio was changed from one to six during epitaxialgrowth of SiC. Diodes fabricated on the epitaxial layer were then characterized using current-voltage and deep level transient spectroscopy. The single peak at 340K (Z1/Z2 peak), was deconvolved into two traps, closely spaced in energy. The concentration of one of the Z1/Z2 traps decreased with increasing C∕Si ratio. This result opposes theoretical predictions of carboninterstitial components, and supports assignment to a silicon antisite or carbonvacancy relationship. The concentration of the second component of the peak at 340K did not depend on the C∕Si ratio, which would indicate an impurity in an interstitial site

Photofission-Based, Nuclear Material Detection: Technology Demonstration

The Idaho National Engineering and Environmental Laboratory (INEEL), the Los Alamos National Laboratory (LANL), and the Advanced Research and Applications Corporation (ARACOR) [Sunnyvale, California] performed a photonuclear technology demonstration for shielded nuclear material detection during August 21–22, 2002, at the LANL TA-18 facility. The demonstration used the Pulsed Photonuclear Assessment Technique (PPAT) that focused on the application of a photofission-based, nuclear material detection method as a viable complement to the ARACOR Eagle inspection platform. The Eagle is a mobile and fully operational truck and cargo inspection system that uses a 6-MeV electron accelerator to perform real-time radiography. This imaging is performed using an approved “radiation-safe” or “cabinet safe” operation relative to the operators, inspectors, and any stowaways within the inspected vehicles. While the PPAT has been primarily developed for active interrogation, its neutron detection system also maintains a complete and effective passive detection capability