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81.
Machann J Etzel M Thamer C Haring HU Claussen CD Fritsche A Schick F 《Magma (New York, N.Y.)》2011,24(1):29-33
Object
Intramyocellular lipids (IMCL) were shown to be metabolically highly active. In order to get insight into short-term regulation of IMCL and to reveal related problems with standardization in metabolic studies using the common signal ratio IMCL/Cr3, relative concentration changes from morning to evening in the same day were examined under four different nutritional and exercise conditions. 相似文献82.
Vallerga J Tremsin A Raffanti R Siegmund O 《Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment》2011,633(Z1):S255-S258
Imaging microchannel plate (MCP) detectors with cross strip (XS) readout anodes require centroiding algorithms to determine the location of the amplified charge cloud from the incident radiation, be it photon or particle. We have developed a massively parallel XS readout electronic system that employs an amplifier and ADC for each strip and uses this digital data to calculate the centroid of each event in real time using a field programmable gate array (FPGA). Doing the calculations in real time in the front end electronics using an FPGA enables a much higher input event rate, nearly two orders of magnitude faster, by avoiding the bandwidth limitations of the raw data transfer to a computer. We report on our detailed efforts to optimize the algorithms used on both an 18 mm and 40 mm diameter XS MCP detector with strip pitch of 640 microns and read out with multiple 32 channel "Preshape32" ASIC amplifiers (developed at Rutherford Appleton Laboratory). Each strip electrode is continuously digitized to 12 bits at 50 MHz with all 64 digital channels (128 for the 40 mm detector) transferred to a Xilinx Virtex 5 FPGA. We describe how events are detected in the continuous data stream and then multiplexed into firmware modules that spatially and temporally filter and weight the input after applying offset and gain corrections. We will contrast a windowed "center of gravity" algorithm to a convolution with a special centroiding kernel in terms of resolution and distortion and show results with < 20 microns FWHM resolution at input rates > 1 MHz. 相似文献
83.
Barbara Siegmund Erich Leitner Ingo Mayer W. Pfannhauser Pavel Farkas Jana Sádecká Milan Kovác 《Zeitschrift für Lebensmitteluntersuchung und -Forschung A》1997,205(1):73-75
5,6-Dihydro-2,4,6-trimethyl-4H-1,3,5-dithiazine (thialdine) is an aroma-active compound that has been isolated from different species of meat. In this study
we have investigated the formation of thialdine using the simultaneous distillation–extraction according to Likens–Nickerson for the extraction of aroma compounds. Three isomers of thialdine were identified in the aroma extract of cooked and dried
hen meat. It was shown that these compounds are not genuine substances from the sample examined, but that they are artefacts
formed during sample preparation.
Received: 30 October 1996 相似文献
84.
Seiferlein M Humpf HU Voss KA Sullards MC Allegood JC Wang E Merrill AH 《Molecular nutrition & food research》2007,51(9):1120-1130
Fumonisins B1 and B2 (FB1 and FB2) are the most abundant members of the fumonisins--mycotoxins that are produced by Fusarium verticillioides and are natural inhibitors of ceramide synthase. Their hydrolyzed forms, HFB1 and HFB2 (also called AP1 and AP2) are found in some foods, and they are not only inhibitors of ceramide synthase but also undergo acylation by this enzyme. This study characterized the conversion of HFB1 and HFB2 by ceramide synthase to their respective N-acylated metabolites using rat liver microsomes and palmitoyl-CoA or nervonoyl-CoA as cosubstrates, and examined animals that had been dosed with hydrolyzed fumonisins to ascertain if acylation occurs in vivo. Using an HPLC-MS/MS method that allowed the sensitive and selective detection of the acylation products, both HFB1 and HFB2 were found to be metabolized in vitro to nervonoyl- or palmitoyl-HFB1 and -HFB2 (i.e. C24:1-HFB1/2 and C16-HFB1/2, respectively). The apparent vmax was considerably higher for formation of C24:1HFB1 (157 pmol/min/mg protein) than for formation of C16HFB1 (8.7 pmol/min/mg protein). The acylation products also inhibited ceramide synthase and significantly reduced the number of viable cells in an in vitro [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT)] assay using a human colonic cell line (HT29). Furthermore, HPLC-MS/MS analysis of tissues from rats given intraperitoneal doses of HFB1 confirmed that formation of N-acyl-HFB1 occurs in vivo to produce metabolites with fatty acids of various chain lengths. The contribution of acylated HFB1 and HFB2 metabolites to fumonisin toxicity in vivo warrants further investigation. 相似文献
85.
86.
Barbara Siegmund W. Pfannhauser 《Zeitschrift für Lebensmitteluntersuchung und -Forschung A》1999,219(5):336-341
In the present study the changes of the volatile fraction of heat-treated chicken meat in the course of chill storage were observed by using different techniques. It was the aim of the study to compare the results obtained by the new technique of the electronic nose to those gained by GC-MS and GC olfactometry (using comparative aroma extract dilution analysis). Chill storage at 4 °C of cooked chicken meat showed large increases in concentration as well as in flavour dilution factors of typical lipid oxidation products such as saturated and unsaturated aldehydes as well as alkylated furans, especially within the first 24 h. These results were confirmed by cluster analysis of selected lipid oxidation products. Analysing the chicken meat with an electronic nose showed results which are highly correlated with those obtained by commonly used and well-known gas chromatographic techniques. 相似文献
87.
C Hoffmann M Zschiesche G Franke A Hoffmann B Terhaag KU M?ritz W Siegmund 《Canadian Metallurgical Quarterly》1997,35(11):496-503
Both single and multiple dose bioequivalence studies are required to assess the quality of modified release formulations of drugs. In bioequivalence studies of drugs with enzyme autoinducing properties such as carbamazepine (CBZ), the standard multiple dose study design must be modified to guarantee equivalence of drug elimination. This problem was considered with regard to carbamazepine 400 retard AWD (test) whose bioavailability relative to a listed reference (Tegretal 400 retard) was studied in 2 randomized, open, crossover studies both with 18 healthy volunteers of Caucasian origin (20-36 years, 61.5-92 kg, 172-195 cm). The single dose study was done with 400 mg CBZ. Serum concentration time profiles of CBZ and its active metabolite CBZ-10,11-epoxide were determined until 144 h after administration. The multiple dose study was performed with 400 mg CBZ b.i.d. for 15 days (first 2 days: 200 mg b.i.d.) followed by a 7-day study with the alternative investigational product. 24-hour serum concentration time profiles of CBZ and its metabolite were measured on days 15 and 22 of the study. The quantitative drug analysis was done with an HPLC method the quality of which fulfilled the requirements of bioequivalence studies. Test was considered bioequivalent to reference with regard to the extent of absorption, if the 90% confidence intervals of the AUC0-infinity ratio (single dose) and AUC0-24h ratio (multiple dose) were within the range of 0.80-1.25, and with regard to rate of absorption if the 90% confidence intervals of the Cmax/AUC ratio (single dose) or AUCF0-24h ratio were within 0.70-1.43. The point estimators (90% confidence limits) of the AUC ratio (test/reference) of CBZ were 0.979 (0.94, 1.02) for the single and 1.01 (0.947, 1.076) for the multiple dose comparison. The point estimator (90% confidence limits) of the Cmax/AUC ratio was 0.989 (0.959, 1.020) and of the AUCF0-24h ratio 1.066 (0.937, 1.212). There were no circadian time differences in any pharmacokinetic parameter. In conclusion: Carbamazepine 400 retard AWD tablets were bioequivalent to reference with regard to extent and rate of absorption after both single and multiple dose administration. 相似文献
88.
89.
Wolfram Lokotsch Siegmund Lang Dietmar Möbius Fritz Wagner 《Journal of the American Oil Chemists' Society》1996,73(11):1459-1464
The continuous production of aleuritic acid decyl ester has been investigated with LipozymeTM as biocatalyst in a fixed-bed reactor. To avoid the limiting effects of mean substrate solubility, the direct synthesis without
organic solvents was chosen, whereby a yield of 90% was obtained depending on the residence time. A comparison of different
reaction paths to synthesize a centrally dihydroxylated decyl ester indicated a preference for transesterification of the
methyl ester. Under external compression, the interfacial behavior of several enzymatically produced hydroxy wax esters was
determined with a Langmuir film balance to find a structure/efficiency relationship. Brewster-angle microscopy allowed direct
visualization of a wax ester monolayer at the air/water interface. 相似文献
90.
Raimund Multzsch Wolfram Lokotsch Beate Steffen Siegmund Lang Jürgen O. Metzger Hans J. Schäfer Siegfried Warwel Fritz Wagner 《Journal of the American Oil Chemists' Society》1994,71(7):721-725
Wax esters from fatty alcohols and uncommon fatty acids were synthesized in yields up to 90% when commercially available microbial
lipases fromRhizomucor miehei (Lipozyme™) andCandida antarctica (SP 435) were used with limited water content in nonpolar solvents under mild conditions. The corresponding fatty acids were
prepared by chemical conversion of naturally occurring resources (agricultural surpluses). Also, when phenylboronic acid was
added as solubilizing agent in a nonpolar solvent, the direct enzymatic monoacylation of glycerol with uncommon fatty acids
was successful. The measurement of π/A-isotherms by means of a Langmuir film balance indicated medium film pressures, medium
or large molecular areas, and interesting phase behavior. The monolayer of a wax ester at the air/water interface could be
directly visualized by Brewster angle microscopy. 相似文献