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QzqiTime-resolved photolttminescence spectroscopy has been used to investigate carrier decay dynamics~t ifl> in a InXGa, -XASI.-,,NV (x-O.03, y -0.01) epilayer grown on GaAs by metal organic chemical vapor deposition. Time-resolved photohrmineseence (PL) measurements, performed for various 4%L excitation intensities and sample temperatures, indicate that the broad PL emission at low -gm temperature is dominated by localized exciton recombination. Lifetimes in the range of 0.07-0.34 a ns are measured; these photo luminescence iifetimes are significantly shorter than corresponding values obtained for GaAs. In particular, we observe an emission energy dependence of ,the decay lifetime at 10 K, whereby the Iifetime decreases with increasing emission energy across the PL spectrum. This behavior is characteristic of a distribution of localized states, which arises from alloy fluctuations. @ 2000 American institute of l&ecentIy, the quatemary InGaAsN alloy system has attracted a great deal of attention due to its potential application in devices such as next generation multifunction solar cells and optoelectronic devices for optical I-7 The alloy is of fundamental and technocommunications. logical interest because it exhibits an extremely large band gap bowing coefficient (b --14eV) between the HI-N and HI-As bhanes.x The extremely large bowing coefficient permits the InXGal _XAsl _YNYquaternary alloy to maintain lattice match to GaAs, with a wide range of tunable band gap energies smaller than the GSAS band gap for x-3y. Studies of InGaAsN solar cell structures with 1 eV band gap have shown that the quatemary suffers from a short minority carrier diffusion length.z3 More recent work has found that significantly improved minority hole diffusion-lengths may be obtained by thermally annealing the InGaAsN after growth, although minority electron diffusion lengths remain short.' In this letter, we report the results of time-resolved PL spectroscopy studies of an InGaAsN epilayer. Tfds letter is one of the first investigations of the carrier dynamics witfdn InGaAsN.A 3-pm-thick, htGaAsN epilayer was grown at a growth temperature of 590 "C by metal organic chemicaI vapor deposition on a semi-insulating GSAS substrate and terminated with a 5 nm GaAs calp.Trimethylindium, trimethylgallium, arsine, and dimethy:lhydrazine were used as source gases. The nominal In and N molar fractions were 0.03 and 0.01, respectively. The Irr/N incorporation ratio of three has been shown to provide lattice match to GaAs!'9 As grown, the unintentionally doped lhtGaAsN film was p type. After growth, the sample was annealed at 600 "C for 30 min in a nitrogen ambient in order to improve the electrical and optic al properties of the material. 1 Photohtminescence (PL) measurements for various sample temperatures and excitation intensities were performed with the sample mounted on a cold -a)Et&~~i~rnaikjiimg@physksmed" finger and cooled by a closed-cycle helium refrigerator. The sample was optically pumped with 580 nm laser pulses of 10 ps width and ...

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Leukocyte reduction in red blood cell and platelet transfusions using third-generation filters is indicated for selected patients who are likely to receive long-term transfusion support, to prevent recurrent febrile reactions and to prevent or delay alloimmunization to leukocyte antigens. Leukocyte-depleted transfusions may also be indicated to delay or prevent refractoriness to platelet transfusion.

The effect of anticoagulation on platelet size stability was studied using blood collected in seven different anticoagulants and stored at room temperature for up to eight hours. The mean platelet volume (MPV) value was most stable in blood collected in 15% ACD and ACD/Na2EDTA. In blood collected in Na2EDTA, K3EDTA, or 11.9% ACD, there was an increase in MPV in the first two hours, after which the MPVs remained stable up to eight hours. Sodium citrate and heparin proved unreliable for the measurement of platelet volume. Platelet counts were stable (less than 5% variation) in all anticoagulants except heparin, which had 16% variation for the eight hours of study. Simultaneously, RBC counts and mean corpuscular volume (MCV) measurements were stable in all seven anticoagulants, with sodium citrate producing the most variation. A negative correlation was observed between MCV and pH of the anticoagulated blood. WBC counts showed less than 3% variation in all anticoagulants except sodium citrate and heparin. Separate experiments demonstrated that electrolyte composition, pH, tonicity, and method of calcium chelation all influenced the stability of the MPV. Of the anticoagulants studied, ACD/Na2 EDTA appeared to provide the best conditions of anticoagulation for both routine clinical and research laboratory measurement of the MPV. It inhibited platelet activation but left the platelets in their normal discoid shape. Platelets could be removed from the anticoagulant and studied in functional assays for up to eight hours after blood drawing. Both platelet counts and MPVs remained stable in blood collected in ACD/Na2 EDTA anticoagulant for up to eight hours at room temperature. In 52 volunteers studied, an inverse correlation (r = -0.72, P less than 0.001) was observed between platelet count and MPV, suggesting that the circulating platelet mass may be a more important indicator of platelet homeostasis than either the platelet count or the mean platelet volume alone.