Suspension properties of hexagonal BN powders: effect of pH and oxygen content

Suspension characteristics for two types (HCV and HCP) of hexagonal boron nitride (h-BN) powder have been examined and correlated to the amount of boric oxide present (B₂O₃) on the BN surface. The effects of B₂O₃ on the suspension behavior of HCV-BN and HCP-BN were determined by measuring the zeta () potential and viscosity as a function of pH. Results indicate the poor suspension quality of HCV-BN powders is linked to the increased presence of B₂O₃ on the particle surface. Because of its weak ionization characteristics, B₂O₃ acts to prevent stable suspension formation by decreasing the double layer length, thereby lowering the barrier to agglomeration. Hence, as the amount of B₂O₃ increases on the HCV-BN powder surfaces, the stability decreases and the particles agglomerate, rapidly settling out of higher viscosity suspensions. In contrast, HCP-BN having less B₂O₃ on the powder surface, exhibits higher -potentials and increased stability against agglomeration. Therefore, HCP-BN forms suspensions of single, unagglomerated particles which are less viscous, settle at a slower rate and are more suitable for slip casting operations.     

Human type 10 17β-hydroxysteroid dehydrogenase: molecular modelling and substrate docking

17β-hydroxysteroid dehydrogenases catalyze the oxidoreduction of hydroxy/oxo groups at position C17 of steroid hormones, thereby constituting a prereceptor control mechanism of hormone action. At present, 11 different mammalian 17β-hydroxysteroid dehydrogenases have been identified, catalyzing the cell- and steroid-specific activation and inactivation of estrogens and androgens. The human type 10 17β-hydroxysteroid dehydrogenase (17β-HSD-10) is a multifunctional mitochondrial enzyme that efficiently catalyzes the oxidative inactivation at C17 of androgens and estrogens. However, it also mediates oxidation of 3-hydroxy groups of androgens, thereby reactivating androgen metabolites. Finally, it is involved in β-oxidation of fatty acids by catalyzing the L-hydroxyacyl CoA dehydrogenase reaction of the β-oxidation cycle. These features and expression profiles suggest a critical role of 17β-HSD-10 in neurodegenerative and steroid-dependent cancer forms. Since no three-dimensional structure of 17β-HSD-10 is available, homology modelling was carried out to understand the molecular basis of these substrate specificities. The structure obtained displays the properties of a one-domain, /β fold enzyme of the SDR family. The active site is located within a large, hydrophobic cleft, which forms optimal contacts with the different steroid surfaces. The data provide explanations for the substrate specificities toward the various classes of sex steroid hormones. The model is suitable to explore substrate and inhibitor characteristics that may be used in the development of novel strategies in the treatment of degenerative or malignant diseases.     

Optimization of quality costs

The main goals of quality management in all industries are customer satisfaction by delivery of defect-free products and the radical reduction of defect rates and quality costs in the production. Controlled technological processes are the most important way to reach these goals. These principles are standard in mechanical engineering and are in use with great success. The properties in electronics production are different from the properties in mechanical engineering. During the assembly of electronic devices, processes are sensitive to the influences (environmental, parameter variation, etc.), that act on these processes. These influences are very strong, especially in the production of small batches of assemblies and a high mix of products. Processes can become uncontrolled, the defect rates can rise, and it is necessary to have inspection and repair processes after the different technological processes. But what about the quality costs? Is it sensible to do these quality control steps from the economical point of view? What is the right inspection strategy—no inspection or 100% inspection or statistical process control? To answer these questions new simple and powerful quality cost models have been developed at the Electronics Technology Laboratory and are in use in electronic producing industries. The quality costs are the “measurement system” to compare different inspection strategies with each other. The costs are calculated by the use of mathematical models—the quality cost models. To analyze and optimize the quality processes of a complete production line we use the method “Dynamic Programming”, developed by the American scientist, Bellman in the early 1950s of the 20th century.     

Influence of branching on the properties of poly(ethylene terephthalate) fibers

A series of branched poly(ethylene terephthalate) samples was prepared by employing 0.07–0.42 mol % trimethylolpropane (TMP) for melt polycondensation. These polymers were characterized with respect to molar mass, intrinsic viscosity, and melt viscosity. Spinning into fibers took place at spinning speeds ranging from 2500 to 4500 m/min. The molecular orientation of the fibers as measured by birefringence and polarized fluorescence decreases with growing amounts of TMP, as does crystallinity. Thus with slightly branched polymers, higher spinning speeds than with a linear polymer can be used to achieve a certain property profile. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 728–734, 1999     

An improved potential drop method for measuring and monitoring defects in metallic structures

In the developed form described the direct current potential drop method is a reliable and relatively accurate procedure for the measuring and surveillance of surface cracks in metallic materials. There are also significant possibilities in practice of surveying cracks on the inaccessible side of the structure. The basis for the improvement in accuracy, in particular for short cracks, is firstly an improved measuring technique and secondly calibration curves determined using an electrolytic tank. Practical experience gained in conventional plants is to date positive. The opportunity exists of benefitting from the advantages that would be brought about by an increased use of the potential drop method in plant surveillance. In nuclear plants specifically this would achieve a reduction in the testing personnel's exposure to radiation.     

Elevated kidney glucosyltransferase activity in genetic prediabetic mice

Glucosyltransferase activity in the renal cortex of genetic diabetic KK mice was significantly increased at 40 days of age when compared to that of Swiss albino and F1 hybrid mice. This increase in enzyme activity in the absence of glucose intolerance can be regarded as an earlier genetic marker for the diagnosis of diabetic microangiopathy.     

Human type 10 17 beta-hydroxysteroid dehydrogenase: molecular modelling and substrate docking

17 beta-hydroxysteroid dehydrogenases catalyze the oxidoreduction of hydroxy/oxo groups at position C17 of steroid hormones, thereby constituting a prereceptor control mechanism of hormone action. At present, 11 different mammalian 17 beta-hydroxysteroid dehydrogenases have been identified, catalyzing the cell- and steroid-specific activation and inactivation of estrogens and androgens. The human type 10 17 beta-hydroxysteroid dehydrogenase (17 beta-HSD-10) is a multifunctional mitochondrial enzyme that efficiently catalyzes the oxidative inactivation at C17 of androgens and estrogens. However, it also mediates oxidation of 3 alpha-hydroxy groups of androgens, thereby reactivating androgen metabolites. Finally, it is involved in beta-oxidation of fatty acids by catalyzing the L-hydroxyacyl CoA dehydrogenase reaction of the beta-oxidation cycle. These features and expression profiles suggest a critical role of 17 beta-HSD-10 in neurodegenerative and steroid-dependent cancer forms. Since no three-dimensional structure of 17 beta-HSD-10 is available, homology modelling was carried out to understand the molecular basis of these substrate specificities. The structure obtained displays the properties of a one-domain, alpha/beta fold enzyme of the SDR family. The active site is located within a large, hydrophobic cleft, which forms optimal contacts with the different steroid surfaces. The data provide explanations for the substrate specificities toward the various classes of sex steroid hormones. The model is suitable to explore substrate and inhibitor characteristics that may be used in the development of novel strategies in the treatment of degenerative or malignant diseases.     

Subjective and behavioral presence measurement and interactivity in the collaborative augmented reality game TimeWarp

Presence is usually assessed via a variety of subjective and objective measures. However, constraints often result in subjective measurements using questionnaires as a key method of data collection. In this paper we present a study of 44 participants of a collaborative augmented reality game known as TimeWarp which used both subjective and objective behavioral measures. Behavior as coded from video recordings of one scene of the game and self-reports about feelings of presence were compared. Our findings indicate that pointing behavior and verbal responses to the virtual content are correlated negatively to sense of presence. We further investigated the influence of subjectively perceived interactivity on perceived presence. We found that the interaction possibilities perceived by the participants predicted their experience of social presence with the virtual characters in the game. Furthermore, playing together with another person did not result in decreased social presence of the virtual characters. Implications for presence research are discussed.     

Interference-Free Determination of REEs in Electronic Waste Using ICP Optical Emission Spectroscopy

Recently, the demand for REEs （rare earth elements） has been heavily increasing, as they are used in many high-tech products （e.g., because of their specific magnetic behavior）. As a result, the supply situation for REEs is worsening and the world market is depending on Chinese exports, so that it may be worthwhile to recycle e-waste （electronic waste） in European countries. This article describes an analytical method to analyze REEs in different kinds of e-waste with the help of a simultaneous ICP-OES （ICP optical emission spectrometer）. The task is challenging because samples show significant differences in terms of major, minor and trace element concentrations. Depending on the field of application, the level of matrix elements and target elements differs completely, resulting in a wide variety of spectral interferences. The method presented in this article allows an accurate quantification of REEs as well as a high sample throughput. In addition to REEs, other elements of economic interest can be determined in the same way. The development of a sample preparation process is another important issue and considered as well.     

Is there semantic interference in delayed naming?

The semantic interference effect in the picture–word interference task is interpreted as an index of lexical competition in prominent speech production models. Janssen, Schirm, Mahon, and Caramazza (2008) challenged this interpretation on the basis of experiments with a novel version of this task, which introduced a task-switching component. Participants either named the picture or read the word, depending on the word's color. Janssen et al. reported semantic interference in picture naming, regardless of whether the word appeared simultaneously with the picture (immediate naming) or 1,000 ms after the picture (delayed naming). Because picture name retrieval is completed in less than 1,000 ms, the finding in delayed naming was taken as evidence against the lexical competition account. In 3 sets of experiments conducted in German and English, we tested for semantic effects in Janssen et al.'s task-switching version and in the standard picture–word interference task. Using identical materials, we obtained sizeable interference effects in the standard task (Experiments 2, 4, and 6) but no effects in the task-switching version (Experiments 1, 3, and 5). When the word reading trials of the task-switching version were replaced with no-go trials (Experiment 7), semantic interference reemerged in immediate naming but was still absent in delayed naming. The experiments question the reliability of Janssen et al.'s critical finding and suggest that theoretical inferences about the origin of semantic effects in the standard picture–word interference task based on results from the task-switching version used by Janssen et al. are difficult to draw. (PsycINFO Database Record (c) 2011 APA, all rights reserved)