Brookite Formation in TiO2?Ag Nanocomposites and Visible‐Light‐Induced Templated Growth of Ag Nanostructures in TiO2

TiO₂? Ag‐nanocomposites exhibit various desirable properties that make them suitable for a variety of applications, for example in photocatalysis and as bactericidal coatings. In this work, a new method for processing TiO₂? Ag nanocomposites is presented. The nanocomposite films are fabricated from one precursor solution with high silver loading of up to 50%. The resulting films exhibit a microstructure consisting of TiO₂? Ag_xO nanocomposites with a largely XRD‐amorphous TiO₂ matrix containing brookite nanocrystals. This specific microstructure absorbs in the visible range so that photoreduction of Ag ions can be accomplished by using visible light. The thin films can be patterned using simple shadow masks. The illuminated areas show a high density of self‐organized nanoparticles (SNPs) and nanorods (SNRs), which are templated by the TiO₂ porous network. The particle size can be tuned by varying the irradiation time. Most of the SNPs and SNRs form faceted crystals, which are mostly a combination of {111} and {110}. The application of these films as substrates for surface‐enhanced Raman scattering is shown. Enhancement factors as high as 4.6 × 10⁶ could be obtained using rhodamine 6G dye molecules. More applications should involve photocatalytic water purification using visible light.     

Crosslinking behavior of dextran modified with hydroxyethyl methacrylate upon irradiation with visible light—Effect of concentration,coinitiator type,and solvent

This study presents the synthesis of a crosslinkable dextran as starting material for the development of new hydrogels as drug delivery system in dental applications. 2‐Hydroxyethyl methacrylate (HEMA) was coupled to dextran after activation with carbonyldiimidazole as monitored by FTIR and ¹H‐NMR spectroscopy. The Dex‐HEMA was crosslinked by visible light in the presence of camphorquinone (CQ) as photoinitiator and a coinitiator in a proper solvent. Aliphatic or aromatic amines were used as coinitiators and the content of the coinitiator was varied from 0.25 to 3.0 mol %. Diphenyliodonium chloride was added as a third component to the above photoinitiation system. It was observed that, the degree of swelling decreased upon an increase of Dex‐HEMA concentration and the water content in the solvent system due to formation of more crosslinking points, that is, increasing crosslink density (P_x). The type of coinitiator shows a prominent impact on the swelling behavior and crosslinking efficiency of hydrogels. Special cryofixation and cryofracture techniques were used to investigate the surface and interior of swollen Dex‐HEMA hydrogel samples by SEM. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Conjugated‐Polymer‐Based Lateral Heterostructures Defined by High‐Resolution Photolithography

Solution processing of polymer semiconductors provides a new paradigm for large‐area electronics manufacturing on flexible substrates, but it also severely restricts the realization of interesting advanced device architectures, such as lateral heterostructures with defined interfaces, which are easily accessible with inorganic materials using photolithography. This is because polymer semiconductors degrade, swell, or dissolve during conventional photoresist processing. Here a versatile, high‐resolution photolithographic method is demonstrated for patterning of polymer semiconductors and exemplify this with high‐performance p‐type and n‐type field‐effect transistors (FETs) in both bottom‐ and top‐gate architectures, as well as ambipolar light‐emitting field‐effect transistors (LEFETs), in which the recombination zone can be pinned at a photolithographically defined lateral heterojunction between two semiconducting polymers. The technique therefore enables the realization of a broad range of novel device architectures while retaining optimum materials performance.     

Contaminants, diet, plasma fatty acids and smoking in Greenland 1999-2005

OBJECTIVES: The purpose of this study is to monitor and assess human exposure to pollution in the Arctic which presents a potential future health risk for the local populations. Epidemiological studies in Greenland have shown that human blood levels of several organic contaminants are very high, especially in the North where people depend on local food. In East Greenland (Ittoqqortoormiit (Scoresbysund)) the population shows the highest blood levels of several persistent organic pollutants found in Arctic countries, especially PCB, the levels of which exceed Canadian guideline levels. As in other Arctic countries, the predominant source of these contaminants is the local diet. However, other factors such as smoking may influence the metabolism and thereby the accumulation of toxic substances. STUDY DESIGN: This project is part of the human health program of the ongoing circumpolar "Artic Monitoring and Assessment Programme". Lifestyle, anthropometric factors, and dietary survey results covering 500 men and women from 6 Greenlandic districts were analyzed along with other factors blood lipids, fatty acid profiles, heavy metals and concentrations of persistent organic pollutants (POPs). RESULTS: The dietary survey showed that the traditional food on the average provided 20-30% of the total energy intake. However, the relative monthly meal intake of seal, whale, polar bear, fish and game, and the composition of imported food, varied between districts. Seal and polar bear intake, and, in particular all the plasma n-3 fatty acids, were significantly correlated with organic contaminant concentrations, (betaHCH, chlordanes, DDTs, Hexachlorobenzene, Mirex, PCBs, and toxaphenes) p<0.01(). After adjusting for age, district, dietary factors or plasma n-3 fatty acids, smoking was significantly correlated with high levels of all the above mentioned POPs. CONCLUSION: The main predictors of high contaminant levels in Greenland were age, district, male gender, smoking and high plasma n-3/n-6 ratio as a marker of high dietary intake of local marine mammals.     

Effect of Interface Regions on the Thermoelectric Properties of Alternating ZnO/ZnO:Al Stripe Structures

A series of bar-shaped samples consisting of lateral arrangements of alternating ZnO:Al and ZnO stripes was fabricated by radiofrequency (RF)-sputtering and microfabrication techniques on glass substrates. Throughout the series, the number of interfaces between ZnO and ZnO:Al was varied whilst the material fractions of ZnO:Al and ZnO within the bars were not altered. Lateral thermoelectric transport parameters, i.e., Seebeck effect and electrical resistivity, were measured as a function of temperature for all microstructured samples and two reference samples of ZnO:Al and undoped ZnO. The transport direction through the bar was perpendicular to the stripe direction, such that the electrons and phonons have to pass all interfaces. The transport coefficients of the microstructured samples show clear dependence on the number of interfaces between ZnO and ZnO:Al. Thermoelectric measurements, photoluminescence, and Raman measurements indicate that this is due to diffusion of Al donors along the grain boundaries into the undoped ZnO stripes, which takes place during the fabrication process. Modeling of the dependence of the Seebeck coefficient and the resistivity of the series of samples on the basis of a network model accounting for donor diffusion supports these findings.     

Synthesis,characterization and comparative OFET behaviour of indenofluorene–bithiophene and terthiophene alternating copolymers

The synthesis of alternating copolymers of tetraalkylindenofluorene with bithiophene and terthiophene using Suzuki polycondensation route is reported. We report on the optical and electrochemical properties of these copolymers. AFM analysis of the microscopic morphology of thin deposits showed that the copolymer with terthiophene units produced the more ordered films, with well-defined fibrillar structures, resulting from highly-regular dense packing due to strong π–π interchain interactions, in contrast to the amorphous bithiophene copolymer. Upon testing these materials in FETs the terthienyl copolymers displayed the higher charge mobilities among the studied compounds, with values of over 10^?4 cm² V^?1 s^?1 being obtained.     

Pulsed flow for enhanced cleaning in food processing

The use of slow (～1 Hz) flow oscillation imposed on a stationary flow of liquid has been shown to enhance shear stresses imposed on a surface and to mitigate fouling or enhance cleaning. Examples of the application of pulsed flow are presented in this paper. A new measuring technique in combination with tailored CFD simulations was developed for monitoring the cleaning of complex piping equipment with pulsed flow. A time-independent and isotropic approach to model the wall shear stress is introduced. The optical monitoring procedure uses a model food soil consisting of starch as matrix material and phosphorescent zinc sulfide crystals as optical tracer. Investigations of pulsed flow cleaning published prior to this work focused on tests with straight pipes, whereas difficulties in industrial cleaning operations more often arise while operating piping systems and plant components with complex geometries. Therefore cleaning experiments were performed in a CIP test rig simulating industrial cleaning processes. The results with pulsed flow show an enhancement of cleaning efficiency at locations difficult to access using stationary flow.     

优化乙醇和食糖混合生产过程

新型控制系统平台帮助糖类产品生产商,根据变化的市场需要,最优化食用糖和纯乙醇的混合生产过程。     

Measuring strain distributions in amorphous materials.

A number of properties of amorphous materials including fatigue, fracture and component performance are governed by the magnitude of strain fields around inhomogeneities such as inclusions, voids and cracks. At present, localized strain information is only available from surface probes such as optical or electron microscopy. This is unfortunate because surface and bulk characteristics in general differ. Hence, to a large extent, the assessment of strain distributions relies on untested models. Here we present a universal diffraction method for characterizing bulk stress and strain fields in amorphous materials and demonstrate its efficacy by work on a material of current interest in materials engineering: a bulk metallic glass. The macroscopic response is shown to be less stiff than the atomic next-neighbour bonds because of structural rearrangements at the scale of 4-10 A. The method is also applicable to composites comprising an amorphous matrix and crystalline inclusions.