Implicit policies about relations between personality traits and behavioral effectiveness in situational judgment items.

This paper develops the concept of implicit trait policy (ITP), which is a variant of the accentuation effect described by Tajfel (1957). ITPs are implicit beliefs about causal relations between personality traits and behavioral effectiveness. Studies reported here tested the hypotheses (a) that personality traits affect ITPs so that agreeable people, for instance, believe the relation between agreeableness and effectiveness is more strongly positive than disagreeable people do and (b) that ITPs can predict behavior that expresses associated personality traits. Two studies with undergraduate research participants supported the first hypothesis for traits of agreeableness and extraversion (the average correlation between traits and associated ITPs was .31 for agreeableness and .37 for extraversion) but not for conscientiousness. A 3rd study with student participants found that individual differences in ITPs for agreeableness predicted agreeable behavior (the average correlation was .33) in simulated work settings. These results suggest that ITPs may be useful for predicting work behavior that expresses personality traits even though ITPs may not be strongly correlated with the personality traits themselves. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Organic aerosol formation from photochemical oxidation of diesel exhaust in a smog chamber

Diluted exhaust from a diesel engine was photo-oxidized in a smog chamber to investigate secondary organic aerosol (SOA) production. Photochemical aging rapidly produces significant SOA, almost doubling the organic aerosol contribution of primary emissions after several hours of processing at atmospherically relevant hydroxyl radical concentrations. Less than 10% of the SOA mass can be explained using a SOA model and the measured oxidation of known precursors such as light aromatics. However, the ultimate yield of SOA is uncertain because it is sensitive to treatment of particle and vapor losses to the chamber walls. Mass spectra from an aerosol mass spectrometer (AMS) reveal that the organic aerosol becomes progressively more oxidized throughout the experiments, consistent with sustained, multi-generational production. The data provide strong evidence that the oxidation of a wide array of precursors that are currently not accounted for in existing models contributes to ambient SOA formation.     

Gene expression profiling for understanding chemical causation of biological effects for complex mixtures: a case study on estrogens

Gene expression profiling offers considerable potential for identifying chemical causation of effects induced in exposures to complex mixtures, and for understanding the mechanistic basis for their phenotypic effects. We characterized gene expression responses in livers and gonads of fathead minnow (Pimephales promelas) exposed (for 14-21 days) to estrogenic wastewater treatment works final effluents with varying potencies and assessed the extent to which these expression profiles mapped with those induced by individual steroid estrogens present in the effluents (17beta-estradiol and 17alpha-ethinylestradiol) and, thus, were diagnostic of estrogen exposure. For these studies, we adopted a targeted approach (via real-time PCR) with a suite of 12 genes in liver and 21 genes in gonad known to play key roles in reproduction, growth and development (processes controlled by estrogens) and responses were compared with effects on phenotypic end points indicative of feminization. Gene responses to effluent were induced predominantly in a linear (monotonic) concentration-dependent manner but were complex with many genes responding differently between tissue types and sexes. The gene expression profiles for the estrogenic effluents and the individual steroid estrogens had many common features. There were marked differences in the profiles between the two effluents, however, that were not explained by differences in their estrogenic potencies, suggesting that these may have arisen as a consequence of differences in the contents of other chemicals, which may act directly or indirectly with the estrogen-response pathway to alter estrogen-induced gene expression. These data demonstrate that the patterns of gene expression induced by estrogenic effluents, although complex, can be diagnostic for some of the estrogens they contain and provide insights into the mechanistic basis for the phenotypic effects seen.     

On the quenching of semiconductor quantum dot photoluminescence by proximal gold nanoparticles

Luminescent quantum dots (QDs) were proven to be very effective fluorescence resonance energy transfer donors with an array of organic dye acceptors, and several fluorescence resonance energy transfer based biosensing assemblies utilizing QDs have been demonstrated in the past few years. Conversely, gold nanoparticles (Au-NPs) are known for their capacity to induce strong fluorescence quenching of conventional dye donors. Using a rigid variable-length polypeptide as a bifunctional biological linker, we monitor the photoluminescence quenching of CdSe-ZnS QDs by Au-NP acceptors arrayed around the QD surface, where the center-to-center separation distance was varied over a broad range of values (approximately 50-200 Angstrom). We measure the Au-NP-induced quenching rates for such QD conjugates using steady-state and time-resolved fluorescence measurements and examine the results within the context of theoretical treatments based on the F?rster dipole-dipole resonance energy transfer, dipole-metal particle energy transfer, and nanosurface energy transfer. Our results indicate that nonradiative quenching of the QD emission by proximal Au-NPs is due to long-distance dipole-metal interactions that extend significantly beyond the classical F?rster range, in agreement with previous studies using organic dye-Au-NP donor-acceptor pairs.     

A reactive peptidic linker for self-assembling hybrid quantum dot-DNA bioconjugates

Self-assembly of proteins, peptides, DNA, and other biomolecules to semiconductor quantum dots (QD) is an attractive bioconjugation route that can circumvent many of the problems associated with covalent chemistry and subsequent purification. Polyhistidine sequences have been shown to facilitate self-assembly of proteins and peptides to ZnS-overcoated CdSe QDs via complexation to unoccupied coordination metal sites on the nanocrystal surface. We describe the synthesis and characterization of a thiol-reactive hexahistidine peptidic linker that can be chemically attached to thiolated-DNA oligomers and mediate their self-assembly to CdSe-ZnS core-shell QDs. The self-assembly of hexahistidine-appended DNA to QDs is probed with gel electrophoresis and fluorescence resonance energy transfer techniques, and the results confirm high-affinity conjugate formation with control over the average molar ratio of DNA assembled per QD. To demonstrate the potential of this reactive peptide linker strategy, a prototype QD-DNA-dye molecular beacon is self-assembled and tested against both specific and nonspecific target DNAs. This conjugation route is potentially versatile, as altering the reactivity of the peptide linker may allow targeting of different functional groups such as amines and facilitate self-assembly of other nanoparticle-biomolecule structures.     

Correlating the chemical and physical properties of a set of heavy oils from around the world

Variations in the viscosity and other physical properties of heavy oils are poorly understood. The viscosities measured for different heavy oils can vary by orders of magnitude even at the same API gravity, which is the standard metric for lighter oils. Heavy oils are viscoelastic materials, and the shear modulus and the viscosity are coupled. Understanding what controls heavy oil viscosity will provide insight into what controls heavy oil shear modulus. Therefore, using rheology, ultrasonic measurements and molecular beam mass spectroscopy (MBMS) the physical and chemical properties of seven heavy oils from around the globe are explored. The viscoelastic nature of the oils is quantified as a function of temperature. Overall, the heavy oil samples show little correlation between the viscosity or shear modulus and the API gravity, separate resin content or separate asphaltene content as measured from SARA analysis. However, the total resin plus asphaltene content collapses the viscosity and modulus values to provide empirical relations between these quantities. Also, a partial least squares regression analysis provides tight correlations for the chemical signatures from the MBMS. The rapid and quantitative nature of the MBMS make it an attractive substitute for the inconsistencies endemic to SARA analysis.     

The role of ethnicity in observers’ ratings of mother–child behavior.

This study examined the role of ethnicity in untrained observers’ ratings of videotaped mother–child interactions. Participants were Black, White, and Latino undergraduates (N = 109), who rated videotapes of 4 Black, 4 White, and 4 Latino mother–child dyads. Overall, participants of different ethnicities showed more similarities than differences in their ratings of parent–child behavior. There was, however, evidence that participant ethnicity and parent–child ethnicity interacted for ratings of child defiance/negative emotion. Black and White participants differed in their ratings of Black and White children’s defiance/negative emotion, with members of each ethnic group favoring children of their own ethnic group. Intergroup contact appeared to play a role in ratings of parent behavior among Black observers. Black observers who reported low intergroup contact tended to rate Black mothers high on strictness and low on permissiveness. More research is needed to better understand the role of ethnicity in observers’ ratings of parent and child behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Remote semantic memory in patients with Korsakoff's syndrome and herpes encephalitis.

Performance of patients with Korsakoff's syndrome and herpes encephalitis was compared on a retrograde amnesia (RA) test, asking subjects to recall and recognize the definitions of words that had come into the language at different time periods. Performance was also compared on a related test in which participants were asked to produce the words to definitions they were given in free recall and cued recall versions. It was hypothesized that, if the temporal gradient in remote memory results from a shift of information from episodic to semantic memory, then there should be a temporal gradient on these tasks, possibly steeper (i.e., greater relative sparing of early memories) in the patients in the Korsakoff group than in the herpes encephalitis group, who have widespread temporal lobe damage. Furthermore, in comparing semantic and episodic remote memory tests, consolidation theory would predict uniform temporal gradients across such tasks, whereas multiple trace theory would predict a differential pattern. The results showed that patients with Korsakoff's syndrome and patients with herpes encephalitis were significantly impaired across all time periods on the vocabulary tests, with only minimal evidence of temporal gradients, relative to healthy participants, and there was no evidence of a differential pattern of impairment between the two patient groups. Comparison with performance on measures of episodic retrograde amnesia, in which there was a differential pattern of temporal gradient, suggests that the relative preservation of early episodic remote memories in patients with Korsakoff's syndrome does not result from an episodic-to-semantic shift in the quality with which memories are stored. These findings are discussed in relation to existing theories of RA and to the patients' underlying patterns of neuropathology. (PsycINFO Database Record (c) 2010 APA, all rights reserved)