High resistivity measurement of SiC wafers using different techniques

To establish fast, nondestructive, and inexpensive methods for resistivity measurements of SiC wafers, different resistivity-measurement techniques were tested for characterization of semi-insulating SiC wafers, namely, the four-point probe method with removable graphite contacts, the van der Pauw method with annealed metal and diffused contacts, the current-voltage (I-V) technique, and the contactless resistivity-measurement method. Comparison of different techniques is presented. The resistivity values of the semi-insulating SiC wafer measured using different techniques agree fairly well. As a result, application of removable graphite contacts is proposed for fast and nondestructive resistivity measurement of SiC wafers using the four-point probe method. High-temperature van der Pauw and room-temperature Hall characterization for the tested semi-insulating SiC wafer was also obtained and reported in this work.     

Age differences in memory performance and memory ratings as measured in a sample survey.

Age differences in memory performance were studied in a probability sample of a cross-section of 1,491 adults living in the Detroit metropolitan area, with an oversample of those age 60 and older. Both a recall and a recognition measure were adapted to the survey context by querying respondents about the nature of the questions asked in an immediately preceding interview. Subjective memory assessment was also measured, using global memory ratings performed by the respondent, his or her spouse, and the interviewer. A clear, age-related decline in memory performance was found in this population sample. Subjective memory assessment also declined across age groups, but the relation was weaker. On the basis of multiple regression analyses of the recognition measure and the respondent's self-rated memory, which were judged to have the best measurement qualities, a substantial part of these age differences can be accounted for by differences in sociodemographic composition between age groups, by cognitive functioning and physical health. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Interpenetrated Gel Polymer Binder for High‐Performance Silicon Anodes in Lithium‐ion Batteries

Silicon has attracted ever‐increasing attention as a high‐capacity anode material in Li‐ion batteries owing to its extremely high theoretical capacity. However, practical application of silicon anodes is seriously hindered by its fast capacity fading as a result of huge volume changes during the charge/discharge process. Here, an interpenetrated gel polymer binder for high‐performance silicon anodes is created through in‐situ crosslinking of water‐soluble poly(acrylic acid) (PAA) and polyvinyl alcohol (PVA) precursors. This gel polymer binder with deformable polymer network and strong adhesion on silicon particles can effectively accommodate the large volume change of silicon anodes upon lithiation/delithiation, leading to an excellent cycling stability and high Coulombic efficiency even at high current densities. Moreover, high areal capacity of ～4.3 mAh/cm² is achieved based on the silicon anode using the gel PAA–PVA polymer binder with a high mass loading. In view of simplicity in using the water soluble gel polymer binder, it is believed that this novel binder has a great potential to be used for high capacity silicon anodes in next generation Li‐ion batteries, as well as for other electrode materials with large volume change during cycling.     

Activities and well-being in older age: Effects of self-concept and educational attainment.

The positive effect of activities on well-being is proposed to be mediated by self-conceptualizations and facilitated by socioeconomic status. The hypothesized processes were estimated with LISREL VIII using data from a large cross-sectional survey with a sample of 679 adults aged 65 and older who were representative of older adults living in the Detroit area. Findings indicate that the frequency of performing both leisure and productive activities yields an effect on physical health and depression and that these effects are mediated in part by a sense of self as agentic, but less clearly by a sense of self as social. Furthermore, socioeconomic status, operationalized as formal educational attainment, facilitates the effect of leisure to a greater extent than that of productive activities. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The perfume of carabao mangoes (Mangifera indica L.)

A solvent extract of the pulp of Carabao mangoes (Mangifera indica) as well as the emanation of the intact fruit by SPME were investigated. The profile of the pulp is based on terpinolene, fatty acids, 2,5-dimethyl-4-hydroxy-3[2H]-furanone and its methyl ether. The SPME profile is characterized by monoterpenes, ethyl esters and by pairs of unusual unsaturated fatty acid esters: ethyl and methyl (Z)-5-octenoates, ethyl and methyl (Z)-4-decenoates and ethyl and methyl (Z,Z)-4,7-decadienoates. Synthetic samples of the new esters have been prepared for structure confirmation. The typical smell of tropical fruits is associated with 2-propanethiol.     

The offshore trend: Structural changes in the wind power sector

In recent years, the wind power sector has begun to move offshore, i.e. to use space and good wind speeds on the open sea for large scale electricity generation. Offshore wind power, however, is not just technologically challenging but also a capital intensive and risky business that requires particular financial and organizational resources not all potential investors might have. We therefore address the question, what impact offshore wind power may have on ownership and organizational structures in the wind power sector. We compare on- and offshore wind park ownership in Denmark, the UK and Germany. The analysis shows that offshore wind power in all three countries is dominated by large firms, many of which are from the electricity sector. In Denmark and the UK, also investors from the gas and oil industry play an important role in the offshore wind business. This development represents a major shift for countries such as Germany and Denmark, in which the wind power sector has grown and matured on the basis of investments by individuals, farmers, cooperatives and independent project developers. The structural changes by which offshore wind power is accompanied have consequences for turbine manufacturers, project developers, investors, associations and policy makers in the field.     

Interviewing older adults: Validity of self-reports of satisfaction.

Respondents in a personal interview study were asked to evaluate several domains of their lives using several different response scales that included both verbal and pictorial response alternatives. Structural equation models were specified to permit estimation of the validity of these survey measures. Across all of the items, the concept factors explain an average of about one half of the total variance, method factors explain about one tenth of the variance, and the remaining one third or so of the variance is unique to each item. Comparisons of the validity of the reports by respondents of different ages indicate that method factors explain almost twice as much of the variance in the responses of older respondents as in those of younger respondents. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Optical and nuclear characterization of Xe-induced nanoporosity in SiO2

We performed RBS, infrared (IR) and C-V measurements in order to follow the evolution of Xe, bubbles/cavities and other defects (with a focus on NBOHC: non-bridging oxygen hole center) and dielectric constant (k), in high dose Xe implantation in SiO₂. As-implanted sample provides the lowest value of k which increases with post thermal annealing. In the meantime, the concentration of negatively charged defects decreases with annealing while Xe out-diffuses after annealing at 1100 °C leaving Xe free cavities in the sample. By combining these results one can determine the contribution of nanoporosity in dielectric constant evolution.     

Ver?nderung der Malat- und Citratgehalte bei der Herstellung von Sauerteigbroten

Zusammenfassung Die Veränderung von mehleigenem Malat und Citrat wurde über die einzelnen Phasen verschiedener Varianten der Sauerteigführung und der Teigherstellung bei Roggenmischbrot, Mischbrot und Weizenmischbrot verfolgt. Der stärkste Abbau der beiden Säuren erfolgte bei Vollsauerführung. Bei Grundsauerführung ist der Restgehalt von Malat und Citrat im Teig und Brot bei längerer Stehzeit des Grundsauers höher als bei kurzer Stehzeit.In Richtung auf höhere Malat- und Citratgehalte wirken ferner: Kurze Teigführung mit Schnellknetung und ohne Teigruhe, niedrigere Saueranteile bei höherem Weizenanteil.In der Brotkrume lagen die Malatwerte zwischen 1,6 und 36 mg/ 100 g i. Tr., die Citratwerte zwischen 11 und 22 mg/ 100 g i. Tr.Damit ist es nicht möglich, zwischen reiner Sauerteigführung und kombinierter Führung zu unterscheiden.

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Changes of malate and citrate content in the production of sour dough bread1. Mixed rye and wheat bread with one and two stage sour dough

Summary Changes in malate and citrate content were followed during the phases of sour dough, production dough making and bread production. Different methods of the sour dough process and different proportions of rye and wheat flour were used. Highest reduction of malate and citrate values in bread occured when using the two stage sour dough process. When one stage sour dough was used, malate and citrate in the dough and bread were higher with longer fermentation times.Other factors favouring higher malate und citrate in bread were a short dough process using rapid kneading without a dough rest period and use of a lower proportion of sour dough in the bread while increasing the wheat content.Malate content of bread crumb was in the range of 1.6 and 36 mg/100 g dry matter, citrate content in the range of 11 and 22 mg/ 100 g dry matter.From these findings it can be concluded that it is impossible to distinguish pure sour dough bread and bread produced by combination of sour dough and bread improvers containing lactic and acetic acids.