Synthesis of donor-acceptor poly(perylene diimide-altoligothiophene) copolymers as n-type materials for polymeric solar cells

Donor-acceptor alternated copolymers based on perylene diimide units linked in bay positions with oligothiophene units were prepared and used as acceptor material in polymeric solar cells. The copolymers have exhibited ambipolar electrochemical properties, high electronic affinities and wide electronic absorption in the visible spectrum. The spectroscopical characterization of the copolymer blends with poly-3-hexylthiophene showed evidences indicative of a charge transfer from the perylene-based copolymers to the polythiophene. All-polymeric solar cells were prepared with the blends and the photovoltaic characterization of these devices showed conversion efficiencies of 0.8% and 0.4%. The results demonstrate the potentialities of perylene-based copolymers as processable photoactive acceptor in organic solar cells.     

Chaotic neurodynamics for autonomous agents

Mesoscopic level neurodynamics study the collective dynamical behavior of neural populations. Such models are becoming increasingly important in understanding large-scale brain processes. Brains exhibit aperiodic oscillations with a much more rich dynamical behavior than fixed-point and limit-cycle approximation allow. Here we present a discretized model inspired by Freeman's K-set mesoscopic level population model. We show that this version is capable of replicating the important principles of aperiodic/chaotic neurodynamics while being fast enough for use in real-time autonomous agent applications. This simplification of the K model provides many advantages not only in terms of efficiency but in simplicity and its ability to be analyzed in terms of its dynamical properties. We study the discrete version using a multilayer, highly recurrent model of the neural architecture of perceptual brain areas. We use this architecture to develop example action selection mechanisms in an autonomous agent.     

The effects of a monetary incentive on the accuracy of post-training self-reinforcement behavior.

96 paid undergraduates classified as high or low self-reinforcers during a baseline phase were randomly assigned to 1 of 2 criterion groups and trained to a 40 or an 80% criterion on a 4-choice discrimination task. Ss' self-reinforcement behavior was assessed during a posttraining phase, and a rating scale evaluating confidence in the accuracy of their choice during the posttraining phase was given. The higher training level was associated with a higher self-reinforcement (SR) accuracy, while high baserate was associated with a greater SR frequency and more indiscriminate SR behavior. Incentive did not improve SR accuracy. Confidence ratings of females were related to training level, baseline grouping, and incentive, while in males the ratings were related to training level and baseline grouping. (French summary) (20 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The Canadian origin of functional age research.

Certain concepts and areas of research demand an interdisciplinary focus. Within the confines of these topics the academic origins of the participants and major contributors matter little, since a breadth of knowledge is required that spans more than a single discipline. However, these general areas frequently come to be associated more with one discipline than others, even though the latter are highly relevant. Such is true of the concept of functional age, which evolved from a biological base to draw adherents from many quarters and which finally established its strongest linkages with psychology. Functional age research had its origins in Canada with the work of I. M. Murray (see record 1951-07356-001). This note describes that contribution and its impact. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Various foods of intermediate humidity on the Chilean market

Water activity, moisture content, pH, total sugars and sodium chloride content of commercial foods with reduced water content found in Chilean supermarkets were determined. The sample included meat, dairy, fruits and confectionary products. Principles involved in the reduction of water activity are discussed for each case.     

Influence of cylinder‐on‐plate or block‐on‐ring sliding configurations on friction and wear of pure and filled engineering polymers

Polyamides, polyesters and polyacetals are often used in line contacts under reciprocating or continuous sliding. These contacts are simulated on cylinder‐on‐plate (COP) or block‐on‐ring (BOR) tribotests. Comparative tests for pure, oil‐filled and solid lubricated polymers at 100N and 0.3m/s are presented for relative material classification. Differences are discussed according to the sliding geometries. Thermal effects dominate friction and wear behaviour: the polymer glass transition temperature is exceeded in COP tests while the temperature is lower in BOR tests. Thick and brittle films are observed for pure polymers in BOR tests, promoting higher friction. The test configuration is mainly important for evaluation of internal lubricants. The efficiency of oil‐lubricated polymers is not demonstrated in COP tests, while solid lubricants are not efficient in BOR tests. Deformation restricts the diffusion of oil lubricants in COP tests while solid lubricants are deposited on the polymer surface rather than being incorporated in the transfer film in BOR tests. Copyright © 2007 John Wiley & Sons, Ltd.     

Hexachlorocyclohexanes and endosulfans in urban, rural, and high altitude air samples in the Fraser Valley, British Columbia: evidence for trans-Pacific transport

High-volume air samples collected over the period Aug. 14-30, 2001, in the Lower Fraser Valley, BC, Canada, were used to assess urban/rural differences of organochlorine pesticides (OCPs) for ground level samples and to attempt to directly measure events of trans-Pacific inputs through the mid-troposphere. Hexachlorocyclohexanes (alpha- and gamma-isomers; 2-25 pg m(-3)) and endosulfan1 and -2 (5-150 pg m(-3)) were detected in all ground level samples. Seven air samples were collected during mid-troposphere flights (approximately 4400 m altitude) over the Lower Fraser Valley. These flights occurred concurrently with ground level sampling. Trajectory analysis identified three events of substantial mid-troposphere, trans-Pacific flow where 10-day back trajectories stemmed from potential source regions in Asia. These events were also characterized by higher air concentrations of alpha-HCH at 4400 m as compared to the ground level stations. This represents the first event-based, aircraft measurement of advection inputs of OCPs in the mid-troposphere of the west coast of North America.     

Hydrophilic trans‐Cyclooctenylated Noncanonical Amino Acids for Fast Intracellular Protein Labeling

Introduction of bioorthogonal functionalities (e.g., trans‐cyclooctene‐TCO) into a protein of interest by site‐specific genetic encoding of non‐canonical amino acids (ncAAs) creates uniquely targetable platforms for fluorescent labeling schemes in combination with tetrazine‐functionalized dyes. However, fluorescent labeling of an intracellular protein is usually compromised by high background, arising from the hydrophobicity of ncAAs; this is typically compensated for by hours‐long washout to remove excess ncAAs from the cellular interior. To overcome these problems, we designed, synthesized, and tested new, hydrophilic TCO‐ncAAs. One derivative, DOTCO‐lysine was genetically incorporated into proteins with good yield. The increased hydrophilicity shortened the excess ncAA washout time from hours to minutes, thus permitting rapid labeling and subsequent fluorescence microscopy.     

Universities and the challenge of lifelong learning

Communities and their Universities: the challenge of lifelong learning J. ELLIOT, H. FRANCIS, R. HUMPHREYS & D. ISTANCE (Eds), 1996 London: Lawrence & Wishart. pp. 250, £14.99 ISBN 0-85315-850-9     

Optical properties of pulsed generation in capillary gas laserswith internal-mirror waveguide resonators

The angular distribution and coherence of pulsed capillary lasers with the optical feedback implemented by waveguide Fabry-Perot resonators with internal mirrors have been theoretically studied. We have shown that spatially-coherent, low divergence radiation can be generated even for short pulse duration if the cavity parameters (the refractive index of the capillary wall and the waveguide dimensions) are properly chosen