Real-Time Aerosol Density Determination Utilizing a Modified Scanning Mobility Particle Sizer—Aerosol Particle Mass Analyzer System

Real time secondary organic aerosol (SOA) density evolution for m-xylene photo-oxidation and α-pinene ozonolysis was obtained using an Aerosol Particle Mass Analyzer (APM)/Scanning Mobility Particle Spectrometer (SMPS) setup, which has been modified to achieve higher transmission of particles and improved sampling frequency. The aerosol density of SOA generated from α-pinene ozonolysis was found to be 1.24 ± 0.03 g/cm³ while the aerosol generated from m-xylene photo-oxidation was determined to be 1.35 ± 0.03 g/cm³. These results confirm the measurement approach from a combined SMPS and Aerodyne Aerosol Mass Spectrometer (AMS) system and are found to be within good agreement with the effective density measurements.     

Trimethylamine as precursor to secondary organic aerosol formation via nitrate radical reaction in the atmosphere

Amines in fine particulate matter have been detected and quantified during ambient studies of winter inversions in Logan, UT, using aerosol mass spectrometry. Amine-related compounds account for 0.5-6 microg m(-3) of fine particulate mass during some wintertime periods. The amine contributions sometimes show a clear diurnal pattern, reaching peak concentrations during the middle of the nightwhile decreasing during the morning and afternoon. Smog chamber reactions show that the reaction of tertiary amines with nitrate radical can account for this behavior in the atmosphere. The lower bound reaction rate of trimethylamine and nitrate radical is estimated at 4.4 x 10(-16) cm3/molecules/s with a conversion rate to the aerosol phase of approximately 65%. This suggests that amines could be a contributor to secondary organic aerosol formation in areas where nitrate radical is a significant player in oxidation chemistry.     

Reduction of deep levels in MOCVD-regrown AlxGa1−x as interfaces by (NH4)2S passivation and in-situ HCl etching

The effects of surface preparation usinginsitu HCl etching and (NH₄)₂S passivation of Al_xGa_1-xAs episurfaces prior to regrowth by MOCVD are analyzed by deep level transient spectroscopy (DLTS), electrochemical profiling (C-V) and room-temperature photoluminescence (PL). Four electron traps were found from the DLTS measurements; a DX-center and three traps previously reported for oxygen-contaminated MOCVD systems. Electrical and optical measurements on quantum well lasers containing a regrown interface in the optical confinement region are also presented. It is demonstrated that both (NH₄)₂S passivation and HClin-situ etching improve the electrical and optical quality of the regrown Al_xGa_1-xAs interfaces, with the best results being obtained when the two methods are used in tandem.     

Effects of layer thickness variations on vertical-cavitysurface-emitting DBR semiconductor lasers

A theoretical analysis of the influence of layer thickness variation in vertical-cavity surface-emitting lasers with distributed Bragg reflectors (DBRs) on lasing wavelength is presented. It is shown that changing the active region length of one of the layers in the DBR mirror by only one unit cell (0.56 nm) is sufficient to produce shifts in the lasing wavelength up to 0.12 nm (for an AlGaAs laser). This could limit the precision with which a desired wavelength, its reproducibility, and its uniformity across a large wafer can be obtained. Possible influences on the linewidth of broad area devices are also discussed     

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)     

The effects of an electromagnetic crystal substrate on a microstrippatch antenna

The effects of a two-dimensional (2D) electromagnetic bandgap substrate on the performance of a microstrip patch antenna are investigated. The microstrip patch antenna is placed on a defect in the electromagnetic bandgap substrate that localizes the energy under the antenna. Finite-difference time-domain calculations are employed to determine the effects of the substrate. The excitation frequency of the antenna near the resonance frequency of the defect mode can be used to control the coupling between antennas that are placed in an array     

A comprehensive program representation of object-oriented software

An extensible representation for object-oriented programs, the Object-oriented Program Dependence Graph (OPDG), is presented. The representation is divided into three layers: a first layer that presents the class inheritance structure, a second layer that combines a traditional control dependence subgraph and a data dependence subgraph with objects, and a third layer that presents the dynamic, runtime aspects of an object-oriented program as an Object Dependence Subgraph. The representation is modular allowing specific tools to only use the portion required for the tool's operation. The complete representation provides information sufficient for most program analysis techniques including data flow analysis, reverse engineering, interactive debuggers and other tools.     

Children's interpersonal perceptions: A social relations analysis of perceiver and target effects.

Children's interpersonal perceptions in an academic context were studied from the sociocultural perspective (L. S. Vygotsky, 1978). The authors predicted that with development, judgments of classmates would show increasing impact of the stimulus target (consensus) and decreasing impact of the perceiver's effect. A social relations analysis estimated perceiver and target effects. A 3-year cross-sequential design permitted study of age differences and longitudinal consistency of the effects. Children's interpersonal perceptions were consensual in middle childhood, and target effects increased with development, whereas perceiver effects declined. Target effects were more consistent than perceiver effects across a 3-year period. Target effects for behaviorally based and environmentally cued judgments, however, were more consistent than target effects on judgments of psychological characteristics. (PsycINFO Database Record (c) 2010 APA, all rights reserved)