Single-molecule resolution and fluorescence imaging of mixed-mode sorption of a dye at the interface of C18 and acetonitrile/water.

Single-molecule imaging is used for the first time to study the cationic dye, 1,1'-dioctadecyl-3,3,3'3'-tetramethylindocarbocyanine perchlorate (DiI), at the chromatographic interface consisting of acetonitrile/water and a hydrocarbon monolayer (C18) covalently bound to silica. Autocorrelations of burst data agree with our previous single-molecule counting results, showing that most dye molecules are diffusing and that there is a rare specific adsorption site associated with a 0.07-s desorption time. These autocorrelations go further in detecting an even rarer specific adsorption event associated with a 2.6-s desorption time. The latter desorption time would contribute much more significantly to peak tailing in chromatography. In water, the populations of DiI at these two specific adsorption sites are shown to be 11% and 4%, respectively, for the weaker and stronger sites, relative to the diffusing population of DiI. In 60% acetonitrile/water, the relative populations of the specific adsorption sites are 11% and 17%, showing that acetonitrile enhances the population of the stronger specific adsorption site. Fluorescence movies of single and multiple molecules link the stronger specific adsorption sites to specific locations on the surface. The imaging makes rare observations frequent by pinpointing where the events occur spatially. This ability to observe rare events by imaging reveals the presence of a third type of specific adsorption site, for which DiI has a desorption time in excess of 20 s.     

Fate of Staphylococcus aureus on vacuum-packaged ready-to-eat meat products stored at 21 degrees C

The U.S. Department of Agriculture has established standards for the composition and shelf stability of various ready-to-eat meat products. These standards may include product pH, moisture:protein ratio, and water activity (aw) values. It is unclear how closely these standards are based on the potential for pathogen growth or toxin production. Because the vacuum packaging used on most ready-to-eat meat products inhibits mold, Staphylococcus aureus is the pathogen most likely to grow on products with reduced aw and increased percentage of water-phase salt. In this study, 34 samples of various ready-to-eat meat products were inoculated with a three-strain mixture of S. aureus, vacuum packaged, and stored at 21 degrees C for 4 weeks. S. aureus numbers decreased by 1.1 to 5.6 log CFU on fermented products (pH < or = 5.1) with a wide range of salt concentrations and moisture content. Similarly, S. aureus numbers decreased by 3.2 to 4.5 log CFU on dried nonacidified jerky (aw < or = 0.82; moisture:protein ratio of < or =0.8). Products that were not fermented or dried clearly supported S. aureus growth and cannot be considered shelf stable. The product pH and moisture:protein ratio were the two compositional factors most highly correlated (R2 = 0.84) with S. aureus survival and growth for the types of products tested, but pH and aw or pH and percentage of water-phase salt also may provide useful predictive guidance (R2 = 0.81 and 0.77, respectively).     

Lesbian erotic role identification: Behavioral, morphological, and hormonal correlates.

Lesbian scholars hotly debate the validity of "butch" and "femme" erotic roles. Although some dismiss them as social constructs, others maintain they are natural expressions of lesbian sexuality. The authors compared self-described butch and femme lesbians on gender-discriminating behavioral, morphological, and hormonal measures. Butch and femme lesbians did not differ from heterosexual women on sex role personality traits, depressive symptomology, eating disorders, or body dissatisfaction. Butch lesbians, however, recalled more childhood gender-atypical behavior and had higher waist-to-hip ratios, higher saliva testosterone levels, and less desire to give birth. These findings support the validity of butch–femme classification and suggest that butch lesbians are more male-typical compared to femme lesbians. The butch-femme classification may reflect a within-group difference caused by differential exposure to prenatal androgens. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Across the thin blue line: Police officers and racial bias in the decision to shoot.

Police officers were compared with community members in terms of the speed and accuracy with which they made simulated decisions to shoot (or not shoot) Black and White targets. Both samples exhibited robust racial bias in response speed. Officers outperformed community members on a number of measures, including overall speed and accuracy. Moreover, although community respondents set the decision criterion lower for Black targets than for White targets (indicating bias), police officers did not. The authors suggest that training may not affect the speed with which stereotype-incongruent targets are processed but that it does affect the ultimate decision (particularly the placement of the decision criterion). Findings from a study in which a college sample received training support this conclusion. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Selecting the right MBA schools – An application of self-organizing map networks

The self-organizing map (SOM) network, an unsupervised neural computing network, is a categorization network developed by Kohonen. The SOM network was designed for solving problems that involve tasks such as clustering, visualization, and abstraction. In this study, we apply the clustering and visualization capabilities of SOM to group and plot the top 79 MBA schools as ranked by US News and World Report (USN&WR) into a two-dimensional map with four segments. The map should assist prospective students in searching for the MBA programs that best meet their personal requirements. Comparative analysis with the outputs from two popular clustering techniques K-means analysis and a two-step Factor analysis/K-means procedure are also included.     

Hyper-reoriented walking in minimal space

Virtual Reality - We present a new reorientation technique, “hyper-reoriented walking,” which greatly reduces the amount of physical space required in virtual reality (VR) applications...     

Extending continuous versus discontinuous conditioned stimuli before versus after unconditioned stimuli.

Conditioned suppression was used with rats to study the effects of extending CSs before vs after the delivery of unconditioned stimulus/stimuli (UCS). These extensions are termed B and A extensions, respectively. Within-group designs were used to compare the effects of extending CSs when 2-min parts of those CSs were separated by temporal gaps of 6 min vs a separation of no gap. The results were as follows: (1) B extensions weakened conditioning more than did A extensions, with or without gaps; (2) under some conditions, this asymmetrical effect persisted with extended training; (3) gaps between 2-min parts of a B extension had no detectable effect; and (4) under some parameter values, gaps between 2-min parts of an A extension weakened conditioning significantly. These results are better predicted by the Sometimes Opponent-Process model (A. R. Wagner, 1981) than by the Rescorla-Wagner-Frey-Sears real-time model (J. J. Ayres et al, 1987). (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Extending conditioned stimuli before versus after unconditioned stimuli: Implications for real-time models of conditioning.

In four experiments using the conditioned suppression procedure with rats, we compared the effects of extending conditioned stimuli (CSs) before versus after reinforcement (called B vs. A extensions). In Experiments 1 and 2, Group 0 (no extension) received 2-min noise CS trials (3 per day in Experiment 1, 1 per day in Experiment 2) that terminated with a 1-s grid shock unconditioned stimulus (US). For Group B, the CS began 12 min before the US; for Group A, the CS began 2 min before the US but persisted for 10 min past US termination. In Experiments 3 and 4, similar trials (3 per day in Experiment 3, 1 per day in Experiment 4) included a 2-min light CS that always terminated with the US; thus the noise CS became a systematically manipulated context cue in which light-shock pairings were embedded. In Experiments 1 and 2 we found asymmetrical effects of CS extensions: B extensions weakened conditioning more than did A extensions. In Experiments 3 and 4 we found symmetrical effects: A and B extensions weakened context conditioning equally. (PsycINFO Database Record (c) 2010 APA, all rights reserved)