Growth of high-quality GaSb by metalorganic vapor phase epitaxy

The growth of nominally undoped GaSb layers by atmospheric pressure metalorganic vapor phase epitaxy on GaSb and GaAs substrates is studied. Trimethylgallium and trimethylantimony are used as precursors for the growth at 600°C in a horizontal reactor. The effect of carrier gas flow, V/III-ratio, and trimethylgallium partial pressure on surface morphology, electrical properties and photoluminescence is investigated. The optimum values for the growth parameters are established. The carrier gas flow is shown to have a significant effect on the surface morphology. The optimum growth rate is found to be 3–8 μm/ h, which is higher than previously reported. The 2.5 μm thick GaSb layers on GaAs are p-type, having at optimized growth conditions room-temperature hole mobility and hole concentration of 800 cm² V⁻¹ s⁻¹ and 3·10¹⁶ cm^-3, respectively. The homoepitaxial GaSb layer grown with the same parameters has mirror-like surface and the photoluminescence spectrum is dominated by strong excitonic lines.     

Protein C Osaka 10 with aberrant propeptide processing: loss of anticoagulant activity due to an amino acid substitution in the protein C precursor

We studied the molecular basis of protein C deficiency in a family with a history of thromboembolic disease. An approximately 50% reduction in anticoagulant activity despite normal levels of protein C amidolytic activity and antigen was detected in plasma from the proband. All the exons and intron/exon junctions of the protein C gene were studied using a strategy that combined polymerase chain reaction amplification with DNA sequencing of the amplified fragments. We identified a C-to-A change at nucleotide number 1387 of the protein C gene in the proband and his mother, and this mutant was designated protein C Osaka 10. The C-to-A change resulted in the substitution of Ser for Arg at position -1, which is the processing protease cleavage site. The mutant protein C was partially purified from plasma of the patient's mother using barium adsorption followed by ion-exchange column chromatography. It eluted at the same sodium chloride concentration as normal protein C, and thus gamma-carboxylation of the mutant protein appeared to be normal. The apparent molecular weight of this mutant protein C was the same as that of the normal protein on immunoblotting. Amino-terminal sequence analysis showed that the light chain of the mutant protein C had an additional Ser at position-1. Thus, the loss of anticoagulant activity of protein C Osaka 10 can be explained by alteration of the conformation of the Gla domain by the additional Ser in the mutant molecule.     

InSb,GaSb, and GaInSb grown using trisdimethylaminoantimony

GalnSb alloys as well as the constituent binaries InSb and GaSb have been grown by organometallic vapor phase epitaxy using the new antimony precursor trisdimethylaminoantimony (TDMASb) combined with conventional group III precursors trimethylindium (TMIn) and trimethylgallium (TMGa). InSb layers were grown at temperatures between 275 and 425°C. The low values of V/III ratio required to obtain good morphologies at the lowest temperatures indicate that the pyrolysis temperature is low for TDMASb. In fact, at the lowest temperatures, the InSb growth efficiency is higher than for other antimony precursors, indicating the TDMASb pyrolysis products assist with TMIn pyrolysis. A similar, but less pronounced trend is observed for GaSb growth at temperatures of less than 500°C. No excess carbon contamination is observed for either the InSb or GaSb layers. Ga_1-xIn_xSb layers with excellent morphologies with values of x between 0 and 0.5 were grown on GaSb substrates without the use of graded layers. The growth temperature was 525°C and the values of V/III ratio, optimized for each value of x, ranged between 1.25 and 1.38. Strong photoluminescence (PL) was observed for values of x of less than 0.3, with values of halfwidth ranging from 13 to 16 meV, somewhat smaller than previous reports for layers grown using conventional precursors without the use of graded layers at the interface. The PL intensity was observed to decrease significantly for higher values of x. The PL peak energies were found to track the band gap energy; thus, the luminescence is due to band edge processes. The layers were all p-type with carrier concentrations of approximately 10¹⁷ cm³. Transmission electron diffraction studies indicate that the Ga_0.5In_0.5 Sb layers are ordered. Two variants of the Cu-Pt structure are observed with nearly the same diffracted intensities. This is the first report of ordering in GalnSb alloys.     

Analysis and design of combined distributed-feedback/Fabry-Perotstructures for surface-emitting semiconductor lasers

We propose combined distributed-feedback/Fabry-Perot (DFB/FP) structures for surface-emitting semiconductor lasers. The analysis is based on coupled-wave equations modified for surface-emitting lasers. The proposed structures, which exhibit enhanced resonance due to a matching between the gain and field distributions resulting in a reduced threshold compared with simple FP structures, are formed by placing the DFB structure between two DBR mirrors of an FP resonant cavity and introducing phase layers between the DFB region and the mirrors. It was found that the periodic-gain structures are a special case of the combined DFB/FP structures in which the index coupling effect is assumed to be negligible due to a small fill factor or a small refractive-index difference. The effect of complex (gain and index) coupling on the design and the threshold characteristics of the structures is clearly illustrated. Some important design considerations that were neglected in the previous papers are addressed     

Expressed emotion, social skill, and response to negative affect in schizophrenia.

Examined social skills and social perception of 48 schizophrenia/schizoaffective disorder patients (aged 18–55 yrs) in response to negative affect as a function of family expressed emotion (EE). Ss participated in a role-play test, a social perception test, and a problem-solving discussion with a family member and were assessed on several measures of symptomatology. EE of family members was evaluated with the Camberwell Family Interview. On the role-play test, Ss with less critical relatives became more assertive in response to increased negative affect from a confederate portraying either a family member or friend, but Ss with highly critical relatives did not. Ss with highly critical relatives were also less assertive when confronted with negative affect from a confederate portraying a family member rather than a friend. The behaviors of both relatives and Ss during a family problem-solving interaction were related to the EE dimensions of criticism, emotional overinvolvement, and warmth. Patient gender was also related to family problem solving but was independent of EE. S's ratings of affect on a videotaped social perception task were not related to family EE, and there were few differences in psychopathology between Ss with high and low EE relatives.… (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Percutaneous lumbar nucleotomy

The nature of the events whereby the reactive intermediates resulting from the bioactivation of bromobenzene and furosemide induce hepatotoxicity is unknown. To examine a role for disturbances in intracellular calcium homeostasis, secondary to a depletion in cellular reduced glutathione (GSH) and reduced protein thiols (PSHs), isolated mouse hepatocytes were exposed to cytotoxic concentrations of bromobenzene or furosemide. Cytosolic calcium concentration, as well as thiol status, was determined. The incubation of hepatocytes with 3.0 mM bromobenzene, and subsequent additions (1.2 mM) of the agent every hour, resulted in significant GSH depletion. The loss of plasma membrane integrity at 1.5 h preceded both a rise in the cytosolic Ca2+ concentration and depletion of total PSH content. Furosemide (1.0 mM) produced a 70% depletion in cellular GSH content in isolated hepatocytes. The initiation of cell damage occurred concurrently with both a rise in the cytosolic Ca2+ concentration and a depletion of total PSH content 4 h following furosemide addition. Since the increase in cytosolic Ca2+ did not precede cytotoxicity, these results do not support an initiating role for Ca2+ deregulation in bromobenzene and furosemide hepatotoxicities. In addition, depletion of PSH content did not correlate with bromobenzene- or furosemide-induced cytotoxicity.     

Cigarette smoking, serum lipids, folate, and vitamin B12 in lung cancer

The purpose of our study was to evaluate the effects of cigarette smoking and serum lipids, folate, and vitamin B12 on the development of lung cancer in the Turkish population. The study group consisted of patients with histologically proven lung cancer and the control group comprised healthy smokers being followed in our smoking cessation outpatient department. Smoking history was obtained from all subjects and serum total cholesterol, HDL cholesterol, triglycerides, vitamin B12, and folate levels were measured. Pack/years of cigarettes smoked were significantly higher in the subjects with lung cancer than in the control group (p < 0.01). Serum total cholesterol, HDL cholesterol, triglyceride, serum folate, and vitamin B12 levels were within normal limits in both groups (p < 0.05), but serum vitamin B12 levels were statistically significantly higher (p < 0.01) in the cancer group than in the controls. In our study, we did not observe low levels of serum cholesterol, vitamin B12, or folate in the lung cancer patients.     

Cytomegalovirus disease accompanied by severe hypoproteinemia in a patient with adult T-cell leukemia-lymphoma

A 62-year-old Japanese man complained of fever, general fatigue, anorexia and watery diarrhea during remission of adult T-cell leukemia-lymphoma. Laboratory examinations showed severe hypoproteinemia (2.9 g/dl). However, neither intestinal lesions associated with ATL nor findings suggesting protein losing gastroenteropathy were observed. Cytomegalovirus (CMV) antigen detection assay using peripheral blood leukocytes revealed that he had an active CMV infection with hemophagocytic syndrome. Treatment with ganciclovir and methylprednisolone led to an improvement of hypoproteinemia. CMV disease and associated hemophagocytic syndrome should be considered as a cause of hypoproteinemia in an immunocompromised host.