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91.
The in vitro activity of Δ9- and Δ6-desaturases was determined in the microsomal fraction of C3H/S normal mouse liver, SS1K fast growing hepatoma, and SS1H slow growing hepatoma. These tumors are two different sublines of a spontaneous hepatoma transplanted in 1949 by J.W. Wilson, Brown University, Providence, R.I., into C3H/ST W: strain. The activity of the two enzymes showed a parallel decrease in the two studied hepatomas. These alterations could be attributed to a fundamental change in structure or function in the tumors. The fatty acid desaturase activity seems to be independent of cell division in malignant tissues. 相似文献
92.
Single crystals of so-called “FeYb2S4 spinel” were prepared and their crystal structure was solved. The cubic cell, space group Fd3m, has a lattice constant . From X-rays determinations, its content is (Fe0.76 Yb2.16 S4) × 8. Iron is divalent and ytterbium is trivalent. Ytterbium is in two series of octahedral sites, which are partially filled : 0.96 Yb and 0.04 ? on every 16d position, 0.12 Yb and 0.88 ? on every 16c position. Only 0.76 iron atom is in every 8a position of the spinel. 相似文献
93.
Essential fatty acid (EFA) deficient rats were injected intraportally with a solution of 1-14C-linoleic acid during a 1 min period. Livers were quickly frozen, pulverized, and the lipids extracted and fractioned by
thin layer chromatography. The incorporation of 1-14C-linoleic acid into liver lipids was measured. The results were compared with those previously obtained from normal rats.
No significant differences were observed in the total radioactivity recovered from lipid extracts. While the distribution
of radioactivity into the 1–2 diacylglycerol fraction remained unchanged in both groups of rats, in the EFA deficient rats
the 1-14C-linoleic acid incorporation was actually directed to the phospholipid fractions instead of to the triacylglycerol fractions
as was observed in the normal rats. 相似文献
94.
95.
Analysis of Amadori compounds by high-performance cation exchange chromatography coupled to tandem mass spectrometry 总被引:3,自引:0,他引:3
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. 相似文献
96.
Abrahamsson C Löwgren A Strömdahl B Svensson T Andersson-Engels S Johansson J Folestad S 《Applied spectroscopy》2005,59(11):1381-1387
The scope of this work is a new methodology to correct conventional near-infrared (NIR) data for scattering effects. The technique aims at measuring the absorption coefficient of the samples rather than the total attenuation measured in conventional NIR spectroscopy. The main advantage of this is that the absorption coefficient is independent of the path length of the light inside the sample and therefore independent of the scattering effects. The method is based on time-resolved spectroscopy and modeling of light transport by diffusion theory. This provides an independent measure of the scattering properties of the samples and therefore of the path length of light. This yields a clear advantage over other preprocessing techniques, where scattering effects are estimated and corrected for by using the shape of the measured spectrum only. Partial least squares (PLS) calibration models show that, by using the proposed evaluation scheme, the predictive ability is improved by 50% as compared to a model based on conventional NIR data alone. The method also makes it possible to predict the concentration of active substance in samples with other physical properties than the samples included in the calibration model. 相似文献
97.
Chauchard F Roussel S Roger JM Bellon-Maurel V Abrahamsson C Svensson T Andersson-Engels S Svanberg S 《Applied optics》2005,44(33):7091-7097
By use of time-resolved spectroscopy it is possible to separate light scattering effects from chemical absorption effects in samples. In the study of propagation of short light pulses in turbid samples the reduced scattering coefficient and the absorption coefficient are usually obtained by fitting diffusion or Monte Carlo models to the measured data by use of numerical optimization techniques. In this study we propose a prediction model obtained with a semiparametric modeling technique: the least-squares support vector machines. The main advantage of this technique is that it uses theoretical time dispersion curves during the calibration step. Predictions can then be performed by use of data measured on different kinds of sample, such as apples. 相似文献
98.
99.
Tomas Englund 《Pedagogy, Culture & Society》1994,2(1):5-29
During the last decade the comprehensive school system in Sweden has been called into question. Recent trends - marketisation, privatisation, religious-isation, language-isation - appear to Indicate a future school system characterised by regression to a segregationist, family-reproducing type of school, with great scope for private alternatives, and a strictly subject-based school giving priority to traditional areas of knowledge, a traditional view of knowledge, a Christian foundation, a fine-tooth system of grades and a strong evaluation system. This article is written as a commentary on the current course of events, with an attempt to stress the conceivable long-term consequences. 相似文献
100.
The minimization of page faults in a demand paging environment where program behavior is described by the LRU stack model is studied. Previous work on this subject considered a specific type of stack probability distribution. As there exist practical situations which do not satisfy this assumption, we extend the analysis to arbitrary distributions. The minimization is stated as an optimization problem under constraints, a method to obtain a class of optimal solution is presented, and a fixed-space replacement algorithm to implement these solutions is proposed. The parameters of this replacement algorithm can be varied to adapt to specific stack probability distributions and to the number of allocated pages in memory. This paper also determines a necessary and sufficient condition for the optimality of the LRU algorithm. 相似文献