Self-assembled polymeric solid films with temperature-induced large and reversible photonic-bandgap switching

In aqueous solutions the response of polymers and biological matter to external conditions, such as temperature and pH, is typically based on the hydrophobic/hydrophilic balance and its effects on the polymer conformation. In the solid state, related concepts using competing interactions could allow novel functions. In this work we demonstrate that polymeric self-assembly, reversibility of hydrogen bonding, and polymer-additive phase behaviour allow temperature response in the solid state with large and reversible switching of an optical bandgap. A complex of polystyrene-block-poly(4-vinylpyridinium methanesulphonate) and 3-n-pentadecylphenol leads to the supramolecular comb-shaped architecture with a particularly long lamellar period. The sample is green at room temperature, as an incomplete photonic bandgap due to a dielectric reflector is formed. On heating, hydrogen bonds are broken and 3-n-pentadecylphenol additionally becomes soluble in polystyrene, leading to a sharp and reversible transition at approximately 125 degrees C to uncoloured material due to collapse of the long period. This encourages further developments, for example, for functional coatings or sensors in the solid state.     

Discharge characteristics and low‐voltage driving of high‐Xe‐content PDPs

Abstract— High‐Xe‐content PDPs attain improved luminous efficiency, but with sacrifices of higher sustain and address voltages and slower discharge build‐up. By examining PDPs with 3.5–100% Xe contents, it was revealed that space‐charge priming as well as wall‐charge accumulation are effective in obtaining low‐voltage and high‐speed operation. In addition, it was found that the effectiveness is emphasized for higher‐Xe‐pressure PDPs. In this respect, erase addressing is more favorable than write addressing, especially for high‐Xe‐pressure PDPs. The formative time lag of the discharge and diffusion/drift of the space charges are shorter for high Xe contents. In this respect, high‐Xe‐content PDPs have a potential for high‐speed addressing, if driven adequately. The use of space‐charge priming, however, is limited by the duration between the priming and scan pulses. Accumulation of wall charges is limited by ignition of a self‐erase discharge with which all the wall charges are dissipated. Although the highest efficiency and luminance are attained with a 100%‐Xe panel, the optimum Xe gas content, considering the sustain pulse voltage and drive voltage margin, would be 70% Xe + Ne.     

De-Mail und Bürgerportale

Trotz der wachsenden Bedeutung des Internet für die Kommunikation zwischen Bürgern, Beh?rden und Unternehmen sind die Sicherheit, Vertraulichkeit und Rechtsverbindlichkeit des elektronischen Rechts- und Gesch?ftsverkehrs bislang nicht gew?hrleistet. Die geplanten Bürgerportale sind ein wichtiges Instrument zur L?sung der bestehenden Probleme.     

Einfluss von verarbeitungsbedingungen und additiven auf die abbaureaktionen von SIS-blockcopolymeren

SIS block copolymers are used particularly as polymer component in hot melt adhesives. During compounding at temperatures of 170–180°C undesired viscosity decrease occurs occasionally. For that reason the influence of additives and the role of compounding conditions, particularly the oxygen concentration, on the degradation of SIS has been investigated. It was found that primary antioxidants are unable to reduce the degradation of SIS under anaerobic or oxygen deficient conditions, but they are very effective when excess of oxygen is present in the system (e.g. an open mixer or mill). C-radical scavengers reduce the chain scission reaction at high oxygen concentrations, too, but accelerate the decrease of the molecular weight under inert gas atmosphere.     

Lycopene extraction from extruded products containing tomato skin

To determine the lycopene content of extruded products containing 10% tomato skin, the conditions for solvent extraction were optimised. After three extraction cycles at 50 °C each for 15 min at a solvent to meal ratio of 40:1, a maximum of 6.6 ppm lycopene was extracted. However, the extraction was considered incomplete, thus the product was digested by pancreatin prior to extraction. The extracted lycopene content was increased to 23.5 ppm using the optimum conditions of 20 min of digestion with 10 mg mL^?1 pancreatin. To validate the extraction efficiency at optimum conditions, a set of extruded products containing different lycopene concentrations was used. Digestion increased the extracted lycopene content by more than 2.5‐fold between the products. Furthermore, this inclusion significantly improved the correlation coefficient between the red colour and the extracted lycopene content. Therefore, including a digestion step prior to extraction by solvents was necessary to efficiently extract lycopene from extruded products.     

Coping self-talk and cognitive interference in anxious children.

The present study addressed the as-yet-unresolved issue of whether coping self-talk facilitates or interferes with effective task performance. Tests of the relationship between coping cognition and task performance are reported when potentially confounding relationships of negative cognition and task performance are controlled. The results indicate that coping self-talk of high-anxious children was positively correlated with negative thoughts but did not contribute significantly to performance. Implications for the functional value of coping self-talk are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Feeding stimulatory and inhibitory chemicals from an acceptable nonhost plant forManduca sexta: Improved detection by larvae deprived of selected chemosensory organs

The chemical basis of feeding responses to the acceptable nonhost plantVigna sinensis (cowpea) by larvae ofManduca sexta was investigated using chemical isolation techniques directed by a novel chemosensory-based bioassay. The presence of feeding stimulatory and inhibitory compounds in leaves or leaf extracts was determined in a two-choice preference test using leaf disks or glass fiber filter paper disks laced with leaf extract as test substrate and filter paper disks laced with water as control. Larvae strongly prefer the control disks over leaf disks, indicating the presence of feeding inhibitory compounds in the leaf. An ethanol extract of both fresh and dried leaves neither stimulated nor inhibited feeding. The cause of this inactivity was examined by using larvae that respond strongly to either feeding stimulatory or inhibitory compounds due to selective chemosensory deprivation. Larvae having chemosensory organs remaining only on the maxillary palps are stimulated to feed by whole leaf disks and by the ethanol extracts. In contrast, larvae having only the medial and lateral maxillary sensilla styloconica and the epipharyngeal sensilla remaining are strongly inhibited by whole leaf disks and the ethanol extract of fresh leaves. Thus, the ethanol extract contains both feeding stimulatory and inhibitory compounds, which elicit opposite behavioral effects in unoperated larvae, therefore nullifying any stimulatory and inhibitory activity. These compounds can only be demonstrated by using discrimination-enhanced larvae in the choice tests. Further isolation of the feeding stimulatory principle inV. sinensis yielded two separate fractions of neutral compounds, suggesting at least two different chemicals belonging to two different classes: nonpolar and polar lipids. Feeding inhibitory chemicals have apparently polar properties because strong activity was found in the ethyl acetate and methanol extracts of dried leaves. The role of feeding stimulatory and inhibitory compounds in food selection ofM. sexta larvae is discussed.