Coherent Structures in Flat-Bed Abutment Flow: Computational Fluid Dynamics Simulations and Experiments

Numerical computations and laboratory experiments are carried out to investigate the three-dimensional structure of large-scale (coherent) vortices induced by bridge abutments on a flat bed. A finite-volume numerical method is developed for solving the unsteady, three-dimensional Reynolds-averaged Navier–Stokes equations, closed with the k–ω turbulence model, in generalized curvilinear coordinates and applied to study the flow in the vicinity of a typical abutment geometry with a fixed, flat bed. The computed flowfields reveal the presence of multiple, large-scale, unsteady vortices both in the upstream, “quiescent,” region of recirculating fluid and the shear-layer emanating from the edge of the foundation. These computational findings motivated the development of a novel experimental technique for visualizing the footprints of large-scale coherent structures at the free surface. The technique relies on digital photography and employs averaging of instantaneous images over finite-size windows to extract coherent eddies from the chaotic turbulent flow. Application of this technique to several abutment configurations yielded results that support the numerical findings.     

Group norms and attitude–behavior consistency: The role of group salience and mood.

This study tested the social identity–self-categorization theory reconceptualization of the role of norms in attitude–behavior relations. Specifically, the study investigated how the effects of in-group norms on the relationship between people's attitudes and their behavior vary as a function of the salience of group membership and mood. Participants' (N?=?131) attitudes toward students being responsible for picking up litter on campus grounds were examined. As expected, the effects of the attitudinal congruency of norms varied as a function of group salience under neutral mood (i.e., deliberative processing) conditions. In-group norms were more influential for high-salience individuals than for low salience individuals in a neutral mood. These findings indicate that in-group norms influence behavioral decision making for individuals high in group salience only when there is an opportunity to carefully process the normative information. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Self-Organizing Maps of Position Weight Matrices for Motif Discovery in Biological Sequences

The identification of overrepresented motifs in a collection of biological sequences continues to be a relevant and challenging problem in computational biology. Currently popular methods of motif discovery are based on statistical learning theory. In this paper, a machine-learning approach to the motif discovery problem is explored. The approach is based on a Self-Organizing Map (SOM) where the output layer neuron weight vectors are replaced by position weight matrices. This approach can be used to characterise features present in a set of sequences, and thus can be used as an aid in overrepresented motif discovery. The SOM approach to motif discovery is demonstrated using biological sequence datasets, both real and simulated     

MBE-grown HgCdTe multi-layer heterojunction structures for high speed low-noise 1.3–1.6 µm avalanche photodetectors

HgCdTe is an attractive material for room-temperature avalanche photodetectors (APDs) operated at 1.3–1.6 μm wavelengths for fiber optical communication applications because of its bandgap tunability and the resonant enhancement of hole impact ionization for CdTe fractions near 0.73. The HgCdTe based separate absorption and multiplication avalanche photodetector is designed and fabricated for backside illumination through a CdZnTe substrate. The multi-layer device structure is comprised of seven layers including 1). n ⁺ contact 2). n ⁻ diffusion buffer 3). n ⁻ absorber 4). n charge sheet 5). n ⁻ avalanche gain 6). p to form junction, and 7).p ⁺ contact. Several wafers were processed into 45 μm × 45 μm and 100 (μm × 100 μm devices. The mean value of avalanche voltage is 63.7 V measured at room temperature. At 1 GHz, the device shows a gain of about 7 for a gain-bandwidth product of 7 GHz. This first demonstration of an all molecular beam epitaxially grown HgCdTe multi-layer heterojunction structure on CdZnTe substrates represents a significant advance toward the goal of producing reliable room temperature HgCdTe high speed, low noise avalanche photodetectors.     

I'm a hypocrite, but so is everyone else: Group support and the reduction of cognitive dissonance.

The impact of social support on dissonance arousal was investigated from a social identity view of dissonance theory. This perspective is seen as augmenting current conceptualizations of dissonance theory by predicting when normative information will impact on dissonance arousal and by indicating the availability of identity-related strategies of dissonance reduction. An experiment was conducted to induce feelings of hypocrisy under conditions of behavioral support or nonsupport. Group salience was either high or low, or individual identity was emphasized. As predicted, participants with no support from the salient in-group exhibited the greatest need to reduce dissonance through attitude change and reduced levels of group identification. Results were interpreted in terms of self being central to the arousal and reduction of dissonance. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Synthesis, structure, dopamine transporter affinity, and dopamine uptake inhibition of 6-alkyl-3-benzyl-2-[(methoxycarbonyl)methyl]tropane derivatives

A series of 6-alkyl-3 beta-benzyl-2-[(methoxycarbonyl)methyl]tropane analogues were synthesized and evaluated as cocaine binding site ligands at the dopamine transporter (DAT). The in vitro affinity (Ki) for the DAT of the 6-alkyl-3 beta-benzyl-2-[(methoxycarbonyl) methyl]tropane analogues was determined by inhibition of [3H]WIN 35,428 in rat caudate putamen tissue. The inhibition of dopamine uptake (IC50) was also measured for selected compounds which demonstrated moderate affinity for the dopamine transporter. The unsubstituted enantiopure analogues (-)-19a (Ki = 33 nM) and surprisingly (+)-20a (Ki = 60 nM) were found to be almost equipotent with the high-affinity binding components of cocaine and WIN 35,065-2 and exhibited slightly more potent dopamine uptake inhibition than both cocaine and WIN 35,065-2. In general, substitution at the 6-position of racemic 19a and 20a with alkyl groups was found to result in decreased activity relative to increased chain length of the substituent. The 3 beta-benzyl-2 beta-[(methoxycarbonyl)methyl]-6 beta-methyltropane (21b; Ki = 57 nM) was the only 6-alkyl derivative to exhibit moderately potent activity. The 6 beta-isomer 21b was 4-fold more potent than the 6 alpha-isomer 19b (Ki = 211 nM) and was nearly equipotent with (-)-19a and (+)-20a as well as with cocaine and WIN 35,065-2. The results of this study further demonstrate the steric constraints associated with the C(6)-C(7) methylene bridge of the tropane ring system for molecular recognition of cocaine analogues at the cocaine binding site(s) on the DAT.     

Differences in reactivity of pulverised coal in air (O2/N2) and oxy-fuel (O2/CO2) conditions

The reactivity of four pulverised Australian coals were measured under simulated air (O₂/N₂) and oxy-fuel (O₂/CO₂) environments using a drop tube furnace (DTF) maintained at 1673 K and a thermogravimetric analyser (TGA) run under non-isothermal (heating) conditions at temperatures up to 1473 K. The oxygen concentration, covering a wide and practical range, was varied in mixtures of O₂/N₂ and O₂/CO₂ in the range of 3 to 21 vol.% and 5 to 30 vol.%, respectively. The apparent volatile yield measured in CO₂ in the DTF was greater than in N₂ for all the coals studied. Pyrolysis experiments in the TGA also revealed an additional mass loss in a CO₂ atmosphere, not observed in a N₂ atmosphere, at relatively high temperatures. The coal burnout measured in the DTF at several O₂ concentrations revealed significantly higher burnouts for two coals and similar burnouts for the other two coals in oxy-fuel conditions. TGA experiments with char also revealed higher reactivity at high temperatures and low O₂ concentration. The results are consistent with a char–CO₂ reaction during the volatile yield experiments, but additional experiments are necessary to resolve the mechanisms determining the differences in coal burnout.     

Image masking for crop yield forecasting using AVHRR NDVI time series imagery

One obstacle to successful modeling and prediction of crop yields using remotely sensed imagery is the identification of image masks. Image masking involves restricting an analysis to a subset of a region's pixels rather than using all of the pixels in the scene. Cropland masking, where all sufficiently cropped pixels are included in the mask regardless of crop type, has been shown to generally improve crop yield forecasting ability, but it requires the availability of a land cover map depicting the location of cropland. The authors present an alternative image masking technique, called yield-correlation masking, which can be used for the development and implementation of regional crop yield forecasting models and eliminates the need for a land cover map. The procedure requires an adequate time series of imagery and a corresponding record of the region's crop yields, and involves correlating historical, pixel-level imagery values with historical regional yield values. Imagery used for this study consisted of 1-km, biweekly AVHRR NDVI composites from 1989 to 2000. Using a rigorous evaluation framework involving five performance measures and three typical forecasting opportunities, yield-correlation masking is shown to have comparable performance to cropland masking across eight major U.S. region-crop forecasting scenarios in a 12-year cross-validation study. Our results also suggest that 11 years of time series AVHRR NDVI data may not be enough to estimate reliable linear crop yield models using more than one NDVI-based variable. A robust, but sub-optimal, all-subsets regression modeling procedure is described and used for testing, and historical United States Department of Agriculture crop yield estimates and linear trend estimates are used to gauge model performance.     

The accuracy of substituted judgments in patients with terminal diagnoses

The effect of the molecular weight of polymer powders and the polymer powder/liquid ratio on the viscoelastic properties after gelation of tissue conditioners was studied by means of a stress relaxation test. The results are summarized as follows. The lower-molecular-weight polymer powders produced the larger flow after gelation especially at long times. The use of a lower powder/liquid ratio produced a greater flow after gelation at both short times and long times. The difference in the molecular weight of polymer powders and the powder/liquid ratio was found to have no influence on changes in viscoelastic properties with the passage of time. It would be possible to control the viscoelastic properties of tissue conditioners suitable for each clinical purpose by making variations in composition and structure.