Zur quantitativen Vitamin-B1-Bestimmung in Nahrungsmitteln und biologischem Material

Zusammenfassung Eine fluorometrische Vitamin-B₁-Bestimmungsmethode für Lebensmittel und biologisches Material wird beschrieben. Nach einer sauren und enzymatischen Freisetzung des Vitamins B₁ im Analysengut wird das Vitamin an dem schwach sauren Kationenaustauscher Amberlite CG 50 von Störsubstanzen weitgehend gereinigt und zum fluorescierenden Derivat Thiochrom oxidiert. Das Verfahren ist einfach, reproduzierbar und wenig störanfällig. Die Recovery-Werte sind gut.

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Assay of vitamin B₁ in food and biological material

Summary A fluorometric method for the estimation of the vitamin B₁ content in food and biological materials is described. Acid hydrolysis is followed by enzymatic treatment to liberate the vitamin B₁ of the sample. Interfering substances in the extract are removed to a great extent by chromatography on Amberlite CG 50, a weakly acidic cation exchanger. After oxidation and extraction into an organic medium, the fluorescence of thiochrome is measured. The procedure is simple, reproducible and not susceptible to interference. The recoveries are good.

     

Interphase modification of alkali-resistant glass fibres and carbon fibres for textile reinforced concrete I: Fibre properties and durability

Sizings and coatings are considered to heal severe surface flaws of brittle alkali-resistant glass (ARG) fibres. The interaction between sizings and coatings is varied systematically resulting in different surface modifications and interphase properties in cement matrix composites. Investigations of the durability after accelerated aging are made and the mechanical properties of sized and coated ARG are elucidated as a function of fibre diameter, sizing and coating content, respectively, as well as their chemical formulations under special consideration of nanotubes and nanoclay concentrated within the interphase. Furthermore, the results achieved with nano-dispersed polymer coatings on glass fibres are transferred to carbon fibres.     

Effects of dietary cholesterol upon bile acid metabolism in guinea pig

Cholesterol fed guinea pigs develop a hemolytic anemia accompanied by high cholesterol concentrations in the liver, plasma, and red cells. We have studied the bile acid metabolism of guinea pigs fed a diet with or without cholesterol in a search for the factor(s) which prevent adequate control of their body cholesterol pool and, therefore, its pathological consequences. The results show that in the cholesterol fed guinea pig the synthesis (and excretion) of bile acids was at least three times greater than in controls. This is the result of a doubling of the fractional turnover rate and a smaller increase in the pool size. The major increase of the bile acid pool was in the liver. The main bile acid in gall bladder bile and small intestines was chenodeoxycholic acid, with smaller amounts of 7-ketolithocholic and ursodeoxycholic acids. In the caecum, large intestines, and feces, the major bile acid was lithocholic acid.     

Strategies to cope with negative social identity: Predictions by social identity theory and relative deprivation theory.

Predictions by social identity theory (SIT) and relative deprivation theory (RDT) concerning preferences for strategies to cope with a negative in-group status position were tested. The focus of the present research was a comparison of the theories regarding their differential patterns of prediction. For this purpose, a natural sample within a specific historical situation was investigated: East Germans after the German unification. First, the predictive power of SIT and RDT variables was tested separately. In a second step, a possible integration of the theories was addressed. Combining the SIT variables and RDT variables led to an integrated model indicating a differential pattern of prediction for intergroup strategies. The RDT components explained the collective responses, whereas SIT constructs were related to individual strategies. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of thermal stressing on saturated vegetable oils and isolated triacylglycerols ‐ product analysis by MALDI‐TOF mass spectrometry,NMR and IR spectroscopy

It is well‐known that triacylglycerols in vegetable oils undergo slow oxidative modifications upon storage particularly at elevated temperatures. This has been shown primarily for oils with unsaturated fatty acid residues that are most sensitive towards oxidation. Saturated oils, however, were by far less investigated. In the present study saturated oils (coconut oil) as well as isolated triacylglycerols were exposed to defined thermal stressing and the resulting products were investigated in dependence on temperature and the heating period. Matrix‐assisted laser desorption and ionization spectrometry, ¹³C and ³¹P nuclear magnetic resonance spectroscopy and infrared spectroscopy were used for the characterization of the native as well as the thermally stressed oil samples. These methods were used since they provide both, fast and reliable information on oil composition and can be performed faster than other more established methods. We found that the degradation mechanism of saturated fatty acids is completely different from unsaturated fatty acids. Whereas unsaturated oils are primarily depleted under the cleavage of the double bonds, saturated oils undergo a conversion of one methylene group into a carbonyl group. This was independently demonstrated by all applied methods for the triacylglycerols as well as for the free fatty acids derived after saponification.     

Effectiveness of an Internet‐Based Graduate Engineering Management Course

This research provides engineering educators analytical evidence as to the effectiveness of Internet‐based course instruction. The research examined the University of Missouri‐Rolla's Internet‐based Advanced Production and Operations Management course, with a focus on determining the effectiveness of the Internet‐based education tools used. Over 100 students in five Internet‐based classes and one traditional, in‐class control group were given three sets of surveys, learning style assessments, a course pre‐test, and a course final examination. Multiple conclusions were drawn from this study based on analyses of the data collected. First, the Internet‐based students performed equally as well as the control group as measured by the difference between pre‐test and post‐test scores. Second, the Internet‐based students were found to have had exaggerated time requirement expectations for taking a course in the Internet environment. Third, the students rated the effectiveness and satisfaction positively for the Internet classroom format. Initially, the Internet‐based students were skeptical of electronic lectures but their experiences were positive.