Nichtporöse Membranen und ihre Anwendung

Non-porous Membranes and their Applications . In recent years membrane systems have gained increasing industrial importance in the separation of multicomponent mixtures. This also applies to porous membranes in which the mass transfer is effected by the difference in electrochemical potential of the permeating components on the feed and permeate sides. After presenting the construction and the mode of operation of non-porous membranes, the article considers industrial membrane processes. Special attention is focussed on development work starting from the research results obtained in the laboratory and culminating in the industrial application. The development of membranes with support-bound ?passive”? or ?active”? transport, such as encountered in some biological membranes, offers interesting insights.     

Sample overloading effects in polymer characterization by field-flow fractionation

There are two subtechniques of field-flow fractionation (FFF), thermal FFF and flow FFF, that have been successfully employed for polymer fractionation and characterization. These techniques are primarily analytical in nature, yielding accurate polymer characteristics from small sample loads (～ 10 μg or less, depending on detection sensitivity). In this study the effects of increasing sample size are examined. Modest increases in load are found to result in shifts toward higher retention volumes. These modest loads also result in some broadening of the sample peaks without a major loss of peak symmetry. Excessive loading, by contrast, appears to give rise both to skewed peaks and to new artifact peaks at higher levels of retention. These observations are discussed in terms of the concentration dependence of various properties (viscosity, diffusivity, thermal diffusivity) which influence polymer transport through the FFF channel. The results are used to indicate upper limits to suitable sample concentrations.     

What children say when the teacher is not around: Conflicting goals in social comparison and performance assessment in the classroom.

Used naturalistic observations and interviews with 42 girls and 41 boys in kindergarten, 1st, 2nd, and 4th grades to examine developmental shifts in the focus of social comparison and the expression of comparative and evaluative interests in relation to possibly conflicting goals. Observers coded the content of peer exchanges and direction of visual gaze during class work times. Ss were then interviewed about help seeking and reading performance in the classroom. Classroom observations revealed that comparisons related to personal aspects of peers declined with age, whereas evaluative comments and comparisons related to performance assessment increased sharply in 1st grade. In the higher grades, blatantly evaluative and comparative statements decreased, whereas more subtle and functional performance-related exchanges continued to increase. Interviews showed that differences in classroom behaviors were associated with knowledge of classroom performance hierarchies, the salience of general ability, and self-evaluation. Data are interpreted in terms of 2 converging processes: self-socialization and goal conflict. Implications for social comparison theory are also discussed. (38 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Broadening dual modality cue utilization in chronic nonparanoid schizophrenics.

Recent evidence suggests that chronic nonparanoid schizophrenics show a narrowed range of cue utilization, especially when cues from more than 1 sensory modality are task relevant. In the present study with 20 male nonparanoid schizophrenic inpatients, it was hypothesized that this deficit can be ameliorated. All Ss were given premeasures of narrowed cue utilization on 2 dual modality tasks. Experimental Ss were then given contingent reinforcement and feedback on 2 tasks, while controls received nonreinforced practice on 1 task and no practice on the other. The major hypothesis was supported; experimental Ss improved (i.e., broadened) significantly more than controls on both tasks. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Polyamine deactivation of integrated poly(dimethylsiloxane) structures investigated by radionuclide imaging and capillary electrophoresis experiments

The poly(dimethylsiloxane) (PDMS) material provides a number of advantageous features, such as flexibility, elasticity, and transparency, making it useful in integrated analytical systems. Hard fused-silica capillary structures and soft PDMS channels can easily be combined by a tight fit, which offers many alternatives for structure combinations. PDMS and fused silica are in different ways prone to adsorption of low levels of organic compounds. The need for modification of the inner wall surface of PDMS channels may often be necessary, and in this paper, we describe an easy and effective method using the amine-containing polymer PolyE-323 to deactivate both fused-silica and PDMS surfaces. The adsorption of selected peptides to untreated surfaces was compared to PolyE-323-modified surfaces, using both radionuclide imaging and capillary electrophoresis experiments. The polyamine modification displayed a substantially reduced adsorption of three hydrophobic test peptides compared to the native PDMS surface. Filling and storage of aqueous solution were also possible in PolyE-323-modified PDMS channels. In addition, hybrid microstructures of fused silica and PDMS could simultaneously be deactivated in one simple coating procedure.     

Analysis of Amadori compounds by high-performance cation exchange chromatography coupled to tandem mass spectrometry

High-performance cation exchange chromatography coupled to tandem mass spectrometry or electrochemical detection was found to be an efficient tool for analyzing Amadori compounds derived from hexose and pentose sugars. The method allows rapid separation and identification of Amadori compounds, while benefiting from the well-known advantages of mass spectrometry, such as specificity and sensitivity. Glucose- and xylose-derived Amadori compounds of several amino acids, such as glycine, alanine, valine, leucine/isoleucine, methionine, proline, phenylalanine, and glutamic acid, were separated or discriminated using this new method. The method is suitable for the analysis of both model reaction mixtures and food products. Fructosylglutamate was found to be the major Amadori compound in dried tomatoes (approximately 1.5 g/100 g) and fructosylproline in dried apricots (approximately 0.2 g/100 g). Reaction of xylose and glycine at 90 degrees C (pH 6) for 2 h showed rapid formation of xylulosylglycine (approximately 12 mol %, 15 min) followed by slow decrease over time. Analysis of pentose-derived Amadori compounds is shown for the first time, which represents a major breakthrough in studying occurrence, formation, and decomposition of these labile Maillard intermediates.     

The determination of olaquindox in pig feeds by high-performance liquid chromatography

A simple, rapid method, based on high performance liquid chromatography, h.p.l.c., is described for the determination of olaquindox in pig feeds. The drug is extracted from the feed by use of a methanol-water mixture, an aliquot is injected on to the h.p.l.c.-column and quantified by u.v.-detection. The method has been tested on feeds and premixes containing olaquindox between 1–400 mg kg^?1.     

Investigation of bulk and solar cell properties of ingots cast from compensated solar grade silicon

In this work, the effect of the concurrent presence of B and P on bulk and solar cell properties of directionally solidified multicrystalline ingots from commercially compensated solar grade silicon (SoG‐Si) feedstock produced by Elkem Solar was investigated. The initial B and P content prior to the directional solidification experiment was 1260 and 762 ppba, respectively. Two reference ingots have been solidified in a silica crucible from 100% electronic grade silicon (EG‐Si) feedstock, with 332 ppba of boron added. All ingots have been cast under similar process parameters. The resistivity measurements by Four Point Probe (FPP) are in good agreement with the net dopant content, i.e., N_A − N_D for p‐type material, measured by Glow Discharge Mass Spectrometer (GDMS). Bulk lifetime measurements show a decrease in the values compared to the EG reference. Lifetime distributions show the highest values of 13 and 19 µs at approximately half ingot height, compared to 30 and 44 µs in the reference ingots. This decrease can be due to the concurrent effect of compensation and of other impurities present in the ingot. However, the content of several transition metals measured by GDMS at half ingot height was not significantly higher than that of the reference ingots. Oxygen content as measured by Fourier Transform Infra‐Red (FTIR) spectroscopy shows no significant difference compared to the references. Solar cells made from the compensated ingots and processed under standard process conditions show efficiency values up to 15.5% and fill factor values up to 78%, comparable to conventional multicrystalline silicon cells. Copyright © 2010 John Wiley & Sons, Ltd.