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31.
32.
Bert Schlatterer und Ekkehard Weiset 《Zeitschrift für Lebensmitteluntersuchung und -Forschung A》1982,175(6):392-398
Zusammenfassung Es wird über Sulfonamidbefunde in Nieren und Muskulatur geschlachteter Tiere (36 Rinder, 3 Schweine) berichtet. Gewebeproben wurden vor und nach der Gewebefraktionierung mit einem durch Trimethoprim modifizierten Hemmstofftest (Teststamm:Bac. subtilis BGA) auf Hemmaktivität sowie mit einer dünnschichtchromatographischen Methode (DC) auf Sulfonamide untersucht. Als Indikatorreakti on für die Darstellung der Sulfonamide diente deren Derivatisierung mit Fluorescamin (Fluram) nach zweidimensionaler Trennung. Insgesamt wurden 11 verschiedene Sulfonamide identifiziert. An Hand von Dosis-Wirkungsbeziehungen wurde gezeigt, daß das mit Trimethoprim modifizierte Testsystem mit Ausnahme der enteral angewandten und kaum absorbierbaren Substanzen allen sonst untersuchten Sulfonamiden gegenüber mittel- bis hochgradig sensitiv ist. Hierbei liegt die minimale Hemmkonzentration im Agarlochtest (50 l) zwischen 10 und 25 Nanogramm je Sulfonamid. Der Vergleich der Ergebnisse von mikrobiologischem Test und chemischer Analyse zeigte bei dem vorliegenden Untersuchungsmaterial, daß knapp 30% der mit dem modifizierten Hemmstofftest positiv reagierenden Nierenproben aufgrund des DC-Befundes nicht als sulfonamidhaltig anzusehen waren, während umgekehrt bei den Muskelproben nahezu 30% der mit Hilfe der DC als sulfonamidhaltig erkannten Proben durch den mikrobiologischen Test nicht erfaßt wurden.
Analysis of sulfonamides in tissues of slaughtered animals. Comparison of results from a microbiological test and from thin layer chromatographic analysis after derivatization with fluorescamin
Summary Sulfonamide residues in kidneys and muscles of slaughtered animals (36 cattle, 3 pigs) are reported. Tissue samples were examined prior to and after separation first for inhibitory activity by an inhibition test modified by addition of trimethoprim and subsequently for sulfonamides by thin layer chromatography (TLC). Sulfonamides were demonstrated by derivatisation with fluorescamine (Fluram) after two dimensional separation. A total of 11 different sulfonamides was identified. It could be demonstrated by dosage-activity relationships that the test system modified with trimethoprim was moderately to highly sensitive to all examined sulfonamides with the exception of the enterally applied and hardly absorbable substances. In this test (agar diffusion test, 50 l per well) the minimal inhibotory concentration is between 10 and 25 ng for each of the sulfonamides. Comparing the microbiological test with the chemical analysis it could be demonstrated that nearly 30% of the kidney samples which were positive in the modified inhibition test did not contain sulfonamides according to interpretation of the TLC. On the other hand nearly 30% of the muscle samples containing sulfonamides (found by TLC) did not react to the microbiological test.相似文献
33.
Bert Baumgaertner 《Minds and Machines》2012,22(3):213-234
One feature of vague predicates is that, as far as appearances go, they lack sharp application boundaries. I argue that we would not be able to locate boundaries even if vague predicates had sharp boundaries. I do so by developing an idealized cognitive model of a categorization faculty which has mobile and dynamic sortals (??classes??, ??concepts?? or ??categories??) and formally prove that the degree of precision with which boundaries of such sortals can be located is inversely constrained by their flexibility. Given the literature, it is plausible that we are appropriately like the model. Hence, an inability to locate sharp boundaries is not necessarily because there are none; boundaries could be sharp and it is plausible that we would nevertheless be unable to locate them. 相似文献
34.
35.
Case Study – The Making of an Institutional Crisis: The Mass Release of Inmates by a Correctional Agency
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A US state correctional agency inadvertently released a large numbers of inmates before expiration of their sentences. This created an institutional crisis, for three reasons. First, the correctly timed release of inmates is unequivocally central the agency's core mission. Second, the early releases were consequential, in that serious crimes were committed by those only out of prison because of early release. Third, a citizen alerted the agency of an early‐release calculation for a particular offender, but the agency failed to act on this information. The correctional agency responded to this crisis by changing both its operating procedure and its culture. 相似文献
36.
Chongxin Yuan N.Bert Roozen Otto Bergsma Adriaan Beukers 《Engineering Analysis with Boundary Elements》2013,37(2):250-259
The aircraft fuselage is idealized as a composite cylinder, its vibroacoustic properties are studied both experimentally and numerically, and a minimization of the inner pressure of a composite cylinder is conducted with the genetic algorithm (GA). In the optimization, the Acoustic Transfer Vector (ATV), which comes from the boundary element method, builds the relationship between the structural surface velocity and the sound pressure at the specific filed points. Results show that the noise reduction obtained by the experimental and numerical methods have a good agreement; the optimization method which combines GA and ATV show high efficiency and robustness; increase of the bending stiffness of the cylinder can improve the noise reduction at low frequencies; both the reduction of weight and the increase of noise insulation can be achieved by the optimization of the layup at different regions of the cylinder individually. 相似文献
37.
Bert J. Campo David Bevk Jurgen Kesters Jan Gilot Henk J. Bolink Jun Zhao Jean-Christophe Bolsée Wibren D. Oosterbaan Sabine Bertho Jan D’Haen Jean Manca Laurence Lutsen Guy Van Assche Wouter Maes René A.J. Janssen Dirk Vanderzande 《Organic Electronics》2013,14(2):523-534
The introduction of functional moieties in the donor polymer (side chains) offers a potential pathway toward selective modification of the nanomorphology of conjugated polymer:fullerene active layer blends applied in bulk heterojunction organic photovoltaics, pursuing morphology control and solar cell stability. For this purpose, two types of poly(3-alkylthiophene) random copolymers, incorporating different amounts (10/30/50%) of ester-functionalized side chains, were efficiently synthesized using the Rieke method. The solar cell performance of the functionalized copolymers was evaluated and compared to the pristine P3HT:PCBM system. It was observed that the physicochemical and opto-electronic characteristics of the polythiophene donor material can be modified to a certain extent via copolymerization without (too much) jeopardizing the OPV efficiency, as far as the functionalized side chains are introduced in a moderate ratio (<30%) and that preference is given to side chains with a small molar volume. A range of complementary techniques – UV–Vis spectroscopy, (modulated temperature) differential scanning calorimetry, transmission electron microscopy and X-ray diffraction analysis – indicated that variations in polymer crystallinity, while maintaining a high level of regioregularity, are probably the main factor responsible for the observed differences. 相似文献
38.
This paper describes an algorithm that predicts the shape of material removed by a flat-end milling tool, and this may be used to compute machining strip width and scallop height at different positions of the tool path track. The algorithm computes swept sections, profiles which are swept by a moving tool bottom by passing through given planes. The technique is applicable for finish and semi-finish multi-axis milling strategies that use flat-end tools. For these strategies, the algorithm complexity can be reduced from computation of the 3D envelope of swept volumes to computation of plane-circle intersections. A new adaptive derivative-free method to sample tool motion provides robust means to generate intermediate tool positions. The step length is constrained by and dependent on different geometrical measures. At each point of a tool path, in the plane perpendicular to the cutting direction, the bottom profile of the swept section is an estimate of the profile of material left. By calculating the distance between part geometry and the computed profile of removed material, machining strip width and a scallop profile can be derived. These results can be used by tool path generation and validation routines to accurately determine the step-over between tool path tracks and surface quality. 相似文献
39.
Inside Cover: Site‐Specific Immobilization of the Peptidoglycan Synthase PBP1B on a Surface Plasmon Resonance Chip Surface (ChemBioChem 23/2016)
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40.
Mutations Closer to the Active Site Improve the Promiscuous Aldolase Activity of 4‐Oxalocrotonate Tautomerase More Effectively than Distant Mutations
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Mehran Rahimi Jan‐Ytzen van der Meer Dr. Edzard M. Geertsema Harshwardhan Poddar Dr. Bert‐Jan Baas Prof. Dr. Gerrit J. Poelarends 《Chembiochem : a European journal of chemical biology》2016,17(13):1225-1228
The enzyme 4‐oxalocrotonate tautomerase (4‐OT), which catalyzes enol–keto tautomerization as part of a degradative pathway for aromatic hydrocarbons, promiscuously catalyzes various carbon–carbon bond‐forming reactions. These include the aldol condensation of acetaldehyde with benzaldehyde to yield cinnamaldehyde. Here, we demonstrate that 4‐OT can be engineered into a more efficient aldolase for this condensation reaction, with a >5000‐fold improvement in catalytic efficiency (kcat/Km) and a >107‐fold change in reaction specificity, by exploring small libraries in which only “hotspots” are varied. The hotspots were identified by systematic mutagenesis (covering each residue), followed by a screen for single mutations that give a strong improvement in the desired aldolase activity. All beneficial mutations were near the active site of 4‐OT, thus underpinning the notion that new catalytic activities of a promiscuous enzyme are more effectively enhanced by mutations close to the active site. 相似文献