Ground-state emission and gain in ultralow-threshold InAs-InGaAsquantum-dot lasers

Emission spectra and modal optical gain are investigated in ultralow-threshold MBE-grown InAs-InGaAs quantum dot (QD) structures. The record lowest room-temperature inversion current is found to be ~13 A cm^-2. The rate-equation model is proposed describing the optical gain related to the ground-state (GS) transitions in QDs. The ground-state gain goes to the maximum value that corresponds to the total inversion of available levels. The gain cross section for the GS emission is estimated as ~7×10^-15 cm²     

Impact of propene on secondary organic aerosol formation from m-xylene

Propene is widely used in smog chamber experiments to increase the hydroxyl radical (OH) level based on the assumption that the formation of secondary organic aerosol (SOA) from parent hydrocarbon is unaffected. A series of m-xylene/NO(x) photooxidation experiments were conducted in the presence of propene in the University of California CE-CERT atmospheric chamber facility. The experimental data are compared with previous m-xylene/N0(x) photooxidation work performed in the same chamber facility in the absence of propene (Song et al. Environ. Sci. Technol. 2005, 39, 3143-3149). The result shows that, for similar initial conditions, experiments with propene have lower reaction rates of m-xylene than those without propene, which indicates that propene reduces OH in the system. Furthermore, experiments with propene showed more than 15% reduction in SOA yield compared to experiments in the absence of propene. Additional experiments of m-xylene/ NO(x) with CO showed similar trends of suppressing OH and SOA formation. These results indicate that SOA from m-xylene/NO(x) photooxidation is strongly dependent on the OH level present, which provides evidence for the critical role of OH in SOA formation from aromatic hydrocarbons.     

Validation of a multimethod assessment of posttraumatic stress disorders in Vietnam veterans.

There appears to be a high incidence of posttraumatic stress disorders (PTSD) in Vietnam veterans, yet there is little available information on the reliability and validity of any approach to the assessment of these combat-related stress disorders. The present study was designed to determine if responses to the presentation of mild combat stimuli would distinguish the following 3 carefully matched groups of veterans (N?=?30): (a) veterans (mean age 35 yrs) with an exclusive diagnosis of PTSD, (b) inpatients (mean age 36 yrs) on a psychiatry ward who clearly did not have PTSD, and (c) Vietnam veterans (mean age 35 yrs) with combat experience who were well-adjusted at the time of the study. Behavioral, physiological, and self-report measures of anxiety obtained through this laboratory-based assessment clearly distinguished the PTSD Ss from the remaining 2 groups. The utility of this tripartite assessment approach for the reliable identification of PTSD secondary to combat is discussed. (13 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The vitamin D receptor gene start codon polymorphism: a functional analysis of FokI variants

The vitamin D receptor (VDR) gene contains a start codon polymorphism (SCP) which is three codons upstream of a second start site (ATG). The SCP genotype can be determined with the restriction enzyme FokI, where "f" indicates the presence of the restriction site and the first ATG, while "F" indicates its absence. Recent evidence suggests that the ff genotype is correlated with lower bone mineral density (BMD) in some populations. The SCP results in alternate VDRs that differ structurally, with the F variant (F-VDR) being three amino acids shorter than the f variant (f-VDR). To determine whether there are functional differences between the f-VDR and the F-VDR, we studied the two VDR forms expressed in COS-7 cells. The proteins were distinguishable from one another on Western blots by their different mobilities, confirming the larger size of f-VDR. Ligand binding studies showed no significant differences between the affinities of the two VDR forms for [3H]-1,25-dihydroxyvitamin D3 ([3H]-1,25(OH)2D3) (Kd = 131+/-78 pM, f-VDR; Kd = 237+/-190 pM, F-VDR; p = 0.24); however, a 2-fold difference in affinity can not be discriminated by this method. There were no differences in the abilities of the two receptor forms to bind DNA as determined by electrophoretic mobility shift assays. The ability of the two VDR forms to transactivate target genes was investigated using three different vitamin D responsive luciferase reporter constructs: 24-hydroxylase, osteocalcin, and osteopontin. In these transactivation experiments, 1,25(OH)2D3 dose-response (0.1-10 nM) curves revealed that the ED50 values for transactivation were indistinguishable between the two VDR forms. Additionally, cultured human fibroblasts with FF, Ff, and ff genotypes had similar sensitivity to 1,25(OH)2D3 with respect to the induction of 24-hydroxylase mRNA. In summary, we were unable to detect significant differences in ligand affinity, DNA binding, or transactivation activity between f-VDR and F-VDR forms. We must emphasize, however, that the sensitivity of the methods used limits our ability to detect minor differences in VDR affinity and function. In conclusion, we cannot define a mechanism whereby the SCP in the VDR might contribute to population differences in BMD.     

Consensus in personality judgments at zero acquaintance.

This research focused on the target effect on a perceiver's judgments of personality when the perceiver and the target are unacquainted. The perceiver was given no opportunity to interact with the target, a condition we refer to as zero acquaintance. We reasoned that in order to make personality judgments, perceivers would use the information available to them (physical appearance). Consensus in personality judgments would result, then, from shared stereotypes about particular physical appearance characteristics. Results from three separate studies with 259 subjects supported this hypothesis. On two of the five dimensions (extraversion and conscientiousness) on which subjects rated each other, a significant proportion of variance was due to the stimulus target. Consensus on judgments of extraversion appears to have been largely mediated by judgments of physical attractiveness. Across the three studies there was also evidence that the consensus in judgments on these two dimensions had some validity, in that they correlated with self-judgments on those two dimensions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Neuropsychiatric correlates and treatment of lenticulostriatal diseases: a review of the literature and overview of research opportunities in Huntington's, Wilson's, and Fahr's diseases. A report of the ANPA Committee on Research. American Neuropsychiatric Association

This report reviews clinical neuropsychiatric findings and opportunities for research in Huntington's, Wilson's, and Fahr's diseases. Consistent, systematic methodology is lacking among neuropsychiatric studies in these lenticulostriatal diseases. Systematic cross-sectional and longitudinal assessments are needed to ascertain the prevalence of psychiatric disorders as a function of disease course. Preliminary synthesis of existing data suggests the following heuristic relationships in these diseases: depression with parkinsonian states; personality changes with caudate or putamen disease; psychosis, impulsivity, and sexual disorders with caudate disease; dementia and mania with caudate and pallidal diseases; and compulsions with pallidal disease. Correlation of neuropsychiatric findings with disease stage, clinical signs, and radiologic, metabolic, physiologic, and pathologic markers of disease will add to our understanding of these conditions.     

The naming deficit in early Alzheimer's and vascular dementia.

Patients with early Alzheimer's disease (AD) were compared to normal controls and patients with early vascular dementia (VaD) on their naming errors using the Boston Naming Test (H. Goodglass & E. Kaplan, 1983). All naming errors were classified into 3 general error categories: visuoperceptual, semantic, and phonemic. Semantic errors were further classified into coordinate errors (responses that belong to the same semantic category as the target words), superordinate errors (responses that belong to a broader semantic category than the target word), and functional-circumlocutory errors (circumlocutions and responses that functionally describe the target word). The findings indicated that AD participants display more overall naming errors than VaD participants, although the pattern of general errors was similar between the patient groups. However, the qualitative difference between the patient groups was observed within the semantic errors because the AD group made more superordinate errors. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Interpersonal perception and metaperception in nonoverlapping social groups

Consensus, self-other agreement, and meta-accuracy were studied within and across nonoverlapping social groups. Thirty-one target persons were judged on the Big Five factors by 9 informants: 3 family members, 3 friends, and 3 coworkers. Although well acquainted within groups, informants were unacquainted between groups. A social relations analysis conducted within each social group showed reliable consensus on the Big Five personality factors. A model specified to estimate the consistency of a target person's effect on perceptions by others across social groups showed weaker agreement across groups. That is, targets were perceived consensually within groups, but these consensual perceptions differed between groups. The data suggest that personality and identity are context specific; however, there was some evidence of agreement in perceptions across groups.     

Right-shifting the oxyhemoglobin dissociation curve with RSR13: effects on high-energy phosphates and myocardial recovery after low-flow ischemia

The influence of temperature and pH on growth of Leuconostoc mesenteroides subsp. mesenteroides FR52 and production of its two bacteriocins, mesenterocin 52A and mesenterocin 52B, was studied during batch fermentation. Temperature and pH had a strong influence on the production of the two bacteriocins which was stimulated by slow growth rates. The optimal temperature was 20 degrees C for production of mesenterocin 52A and 25 degrees C for mesenterocin 52B. Optimal pH values were 5.5 and 5.0 for production of mesenterocin 52A and mesenterocin 52B respectively. Thus, by changing the culture conditions, production of one bacteriocin can be favoured in relation to the other. The relationship between growth and specific production rates of the two bacteriocins, as a function of the culture conditions, showed different kinetics of production and the presence of several peaks in the specific production rates during growth.     

Multiple-wavelength emission from In/sub x/Ga/sub 1-x/As-GaAs quantum wells grown on a nanoscale faceted GaAs substrate by molecular beam epitaxy

Multiple-wavelength photoluminescence (PL) spanning a 160-nm range from 980 to 1140 nm (77 K) has been obtained from In/sub x/Ga/sub 1-x/As-GaAs quantum wells (QWs) with varying In composition x on a nanoscale faceted (nanofaceted) GaAs substrate grown by molecular beam epitaxy. Five nanofaceted regions which consist of periodic [100]-(n11) (n = 3 or 1) facets along [011~] with different periods were prepared on a single substrate by interferometric lithography and selective growth of GaAs. The pattern period p was varied from infinity (large-area unpatterned) to 210 nm while the lateral width of the (n11) facet region was kept constant at /spl sim/180 to 200 nm within each period. A 5-nm-thick In/sub 0.23/Ga/sub 0.77/As layer was deposited on this multiple-period nanofaceted single GaAs surface in a single-run growth. Orientation-dependent migration and incorporation (ODMI) of In atoms [mass transport of incident In atoms from the (n11) to adjacent [100] facets] results in a variation of x of the In/sub x/Ga/sub 1-x/As layer section on the [100] facet as the width of the [100] facet was changed from /spl sim/20 to /spl sim/200 nm. ODMI induces a higher x on the [100] facet for smaller p. The PL exhibits a polarization dependence which is more pronounced for decreasing p [i.e., the width of [100] facet]. Consistent variations of the PL peak energy and linear polarization along the pattern direction confirm that ODMI results in a variation of the In composition and imply that the In/sub x/Ga/sub 1-x/As layer on a [100] facet has characteristics of a quantum wire as its width is decreased to /spl sim/20 nm for p = 210 nm. A possible application of nanopatterned growth to wavelength-division-multiplexing transmitters is discussed.