Optical waveguide lightmode spectroscopy technique–based immunosensor development for deoxynivalenol determination in wheat samples

Contamination by deoxynivalenol (DON), a trichothecene mycotoxin produced by Fusarium species, occurs in cereals worldwide; therefore, efforts have been made toward the development of rapid and sensitive methods for the detection of this compound. In our investigation, optical waveguide lightmode spectroscopy (OWLS) technique has been applied to label-free detection of DON in both competitive and in direct immunoassay formats using DON-specific polyclonal antibodies. After immobilizing the antibody or the antigen conjugate for the direct or indirect measurement, the sensor chip was used in a flow-injection analyzer system. The direct method was found to result in an unstable sensor response and sensitivity insufficient to determine DON in different grains. In contrast, a competitive immunosensor format provided reproducible quantitative detection in the sub-ppt range. For competitive sensor investigation with the sensitized chip, first the optimal dilution rate of polyclonal antibodies was determined. For the measurements, antibody stock solution was diluted to 8 μg mL⁻¹. During the competitive measurement, standard solutions were mixed with the antibodies at the appropriate concentration, and the mixture was incubated for 1 min and injected into the OWLS system. The sensitive detection range of the competitive detection method was between 0.01 and 50 ng mL⁻¹. After the establishment of the indirect method, spiked wheat flour samples were investigated. Results obtained with spiked samples showed that OWLS detection has a potential for quick determination of DON in wheat samples.     

An electrochemical impedance spectroscopy study of polymer electrolyte membrane fuel cells electrocatalyst single wall carbon nanohorns-supported

Electrochemical impedance spectroscopy (EIS) was used to study the polymer electrolyte membrane fuel cells (PEMFC) performance when using single wall carbon nanohorns (SWNH) to support Pt nanoparticles. Additionally, as-prepared and oxidized SWNH Pt-supports were compared with conventional carbon black. Two different oxidizing treatments were considered: oxygen flow at 500 degrees C and reflux in an acid solution at 85 degrees C. Both oxidizing treatments increased SWNH surface area; oxygen treatment increased surface area 4 times while acid treatment increased 2.6 times. The increase in surface area should be related to the opening access to the inner tube of SWNH. Acid treatment of SWNH increased chemical fragility and decreased electrocatalyst load in comparison with as-prepared SWNH. On the other hand, the oxygen treated SWNH sample allowed to obtain the highest electrocatalyst load. The use of as-prepared and oxygen treated SWNH showed in both cases catalytic activities 60% higher than using conventional carbon black as electrocatalyst support in PEMFC. Moreover, EIS analysis indicated that the major improvement in performance is related to the cathode kinetics in the as-prepared SWNH sample, while concerning the oxidized SWNH sample, the improvements are related to the electrokinetics in both anode and cathode electrodes. These improvements should be related with differences in the hydrophobic character between SWNH and carbon black.     

Psychological safety and social support in groupware adoption: A multi-level assessment in education

In this paper, the authors propose that psychological safety, a sense of interpersonal trust and being valued in a work team, is an important determinant of groupware technology adoption in an educational setting. They develop and test a model of antecedents and consequences of psychological safety. Data were collected from 361 university students, organized in 36 teams. Results of multi-level regression analysis reveal positive individual-level effects of perceived tutor support and perceived peer support on psychological safety. Furthermore, our findings show a positive unique group-level effect of perceived tutor support on psychological safety, where an individual’s level of self-consciousness strengthens this positive impact. In addition, findings of structural equation modeling demonstrate that both perceived usefulness and perceived ease of use partially mediate the positive effect of psychological safety on groupware usage. Psychological safety also shows a positive direct effect on groupware usage. Finally, a student’s offline communication frequency with his tutor and peers appears to strengthen the impact of psychological safety on perceived usefulness, perceived ease of use, and groupware usage.     

The significance of event information for 6- to 16-month-old infants' perception of containment.

Four experiments familiarized 6-, 9-, 12-, and 16-month-old infants to a solid block that was repeatedly lowered into a semitransparent container. In test trials the end state, containment, was either compatible or incompatible with the objects' size and position. In Experiment 1, infants saw the block and box successively before they observed the end state. This forced infants to attend to each object individually and memorize its size and position while observing the end state. In Experiments 2 and 3, the block and container were shown simultaneously, the block suspended above the container at a distance of either 25 cm (Experiment 2) or 2 cm (Experiment 3). The shorter distance made direct comparison easier to perform. In Experiment 4, the full event was shown in which the block was lowered inside the container from a distance of 25 cm. Infants' perception of containment was related to the visual information that was available. When the event made it easier to grasp the relevant information, infants could perceive whether the block could pass in the container at a progressively younger age. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The relation between perception and behavior, or how to win a game of Trivial Pursuit.

The authors tested and confirmed the hypothesis that priming a stereotype or trait leads to complex overt behavior in line with this activated stereotype or trait. Specifically, 4 experiments established that priming the stereotype of professors or the trait intelligent enhanced participants' performance on a scale measuring general knowledge. Also, priming the stereotype of soccer hooligans or the trait stupid reduced participants' performance on a general knowledge scale. Results of the experiments revealed (a) that prolonged priming leads to more pronounced behavioral effects and (b) that there is no sign of decay of the effects for at least 15 min. The authors explain their results by claiming that perception has a direct and pervasive impact on overt behavior (cf. J. A. Bargh, M. Chen, & L. Burrows, 1996). Implications for human social behavior are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Unitary events in multiple single-neuron spiking activity: II. Nonstationary data.

In order to detect members of a functional group (cell assembly) in simultaneously recorded neuronal spiking activity, we adopted the widely used operational definition that membership in a common assembly is expressed in near-simultaneous spike activity. Unitary event analysis, a statistical method to detect the significant occurrence of coincident spiking activity in stationary data, was recently developed (see the companion article in this issue). The technique for the detection of unitary events is based on the assumption that the underlying processes are stationary in time. This requirement, however, is usually not fulfilled in neuronal data. Here we describe a method that properly normalizes for changes of rate: the unitary events by moving window analysis (UEMWA). Analysis for unitary events is performed separately in overlapping time segments by sliding a window of constant width along the data. In each window, stationarity is assumed. Performance and sensitivity are demonstrated by use of simulated spike trains of independently firing neurons, into which coincident events are inserted. If cortical neurons organize dynamically into functional groups, the occurrence of near-simultaneous spike activity should be time varying and related to behavior and stimuli. UEMWA also accounts for these potentially interesting nonstationarities and allows locating them in time. The potential of the new method is illustrated by results from multiple single-unit recordings from frontal and motor cortical areas in awake, behaving monkey.     

Seeing one thing and doing another: Contrast effects in automatic behavior.

Research on automatic behavior demonstrates the ability of stereotypes to elicit stereotype-consistent behavior. Social judgment research proposes that whereas traits and stereotypes elicit assimilation, priming of exemplars can elicit judgmental contrast by evoking social comparisons. This research extends these findings by showing that priming exemplars can elicit behavioral contrast by evoking a social comparison. In Study 1, priming professor or supermodel stereotypes led, respectively, to more and fewer correct answers on a knowledge test (behavioral assimilation), but priming exemplars of these categories led to the reverse pattern (behavioral contrast). In Study 2, participants walked away faster after being primed with an elderly exemplar. In Study 3, the proposition that contrast effects reflect comparisons of the self with the exemplar was supported. (PsycINFO Database Record (c) 2010 APA, all rights reserved)