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81.
Prostaglandin D2 synthase (PGDS) (beta-trace protein) is a highly abundant cerebrospinal fluid (CSF) glycoprotein. A number of studies have been performed to determine the potential value of this protein for the diagnosis of various neurological disorders. The measurement of total PGDS levels in CSF has proved marginally useful for this purpose, but promising results were obtained while investigating changes in the posttranslational modifications (PTM) pattern. Using 2-DE analysis, we previously showed that PGDS is differentially expressed in ante- and post mortem CSF samples. In the present study, we examined whether the PGDS isoforms may help to distinguish stroke and neurodegenerative disease patients from healthy subjects. The pattern of PGDS PTM was analyzed in CSF from patients with various neurological disorders (n = 44) using IEF/immunoblotting techniques. Strong alterations of this pattern were detected in patients with different forms of degenerative dementia. These findings are consistent with PGDS being altered in some neurological diseases and provide new opportunities for clinical applications. 相似文献
82.
A procedure of analysis for small-angle X-ray scattering (SAXS) data has been established to obtain density fluctuation of supercritical fluids near the critical point. It is indispensable for the certain analysis to utilize both of high-quality SAXS data measured under stable thermodynamic condition and accurate P–ρ–T data in supercritical region. As a standard example, SAXS measurements have been performed for supercritical CO2, which is a suitable sample satisfying the condition for both experiment and analysis. The measurements were carried out along four isothermal conditions at reduced temperature of Tr = T/Tc = 1.020, 1.022, 1.043 and 1.064. Comparing the experimental density fluctuation with calculated one from the most reliable equation of state, the differences are within 8% at most. 相似文献
83.
用硅胶-氧化铝柱色谱预分离和色谱-质谱分析研究了两种褐煤超临界流体抽提物中脂肪烃馏分组成结构特征。结果表明,除主要成份正构烷烃(C_(13)~C_(33))外,尚有少量的类异戊二烯烃(姥鲛烷、植烷等)和萜烷。其中萜烷以五环三萜为主(C_(27)、C_(29)~C_(32)藿烷类化合物),并有一定量的C_(27)、C_(29)和C_(30)藿烯,倍半萜和三环二萜烷含量很少。未检出甾烷。此外,还检出一完整系列的烯烃。试验结果表明,超临界流体抽提条件对褐煤抽出物各组分、含量及其分布有一定的影响。 相似文献
84.
超临界流体萃取仪器的研制 总被引:1,自引:1,他引:1
本文报道了以国产原配件为基础,成功地研制了分析规模的超临界流体萃取仪器、并对仪器性能进行了全面考察,仪器性能稳定,重现性良好(RSD<3.1%),定量线性关系可靠,可满足定量萃取的要求。 相似文献
85.
Theoretical study of the effect of frit quality on chromatography using computational fluid dynamics
Summary Frits at both ends of a chromatographic column, especially for a preparative column, have significant influence on the flow
distribution within the column and thus the column efficiency. However, frits have received little attention from chromatographers
in the past. Here a theoretical study was conducted with the aid of CFD software FLUENT to investigate the effect of frits
on the performance of homogeneous and heterogeneous chromatographic columns. A dimensionless number,FQ, was applied to characterize frit quality. This study visualized how frit quality affects the flow distribution and the concentration
band, the shape of eluted pulse at the colum exit and column efficiency. Simulation results show that the development length
of the flow distribution is related toFQ but has nothing to do with the packing heterogeneity. The curvature of the concentration band in a column depends onFQ and packing quality. This study shows column efficiency can be improved significantly by increasingFQ and/or frit permeability. 相似文献
86.
87.
The adverse effects of injection solvent strength on microbore packed column SFC band broadening are demonstrated and a solventless injection system that eliminates these effects is introduced. The injection system removes solvent in a GC-like manner using a retention gap and an on-column capillary GC syringe. The analyte is delivered to the analytical column in a solvent-free plug of supercritical fluid mobile phase. 相似文献
88.
Raman spectra of intramolecular vibration mode for each guest species in the methane + tetrafluoromethane (CF4) mixed-gas hydrate crystal have been measured at 291.1 K. Both of pure guest species generate the structure-I hydrate in the present pressure ranges. Isothermal phase-equilibrium curve exhibits two discontinuous points around the equilibrium methane compositions (water-free) in the gas phase of 0.3 and 0.8. At the above points, the Raman spectra of both guest molecules have been drastically changed. One of the most important findings is that the crystal of methane + tetrafluoromethane mixed-gas hydrate shows the structural phase-transition (from the structure-I to the structure-II and back to the structure-I) caused by composition changes. 相似文献
89.
90.
Summary The coupling of carbon dioxide supercritical fluid chromatography with Fourier transform infrared spectrometry (SFC-FTIR)
is a powerful tool for the separation and on-line identification of non-volatile compounds. The IR transparency of carbon
dioxide in the Fermi resonance bands region versus its density has been studied. Functional groups with stretching vibrations
outside the transparent window of carbon dioxide are examined. SFC-FTIR separations allow Gram-Schmidt reconstruction chromatograms
or IR window chemigrams with high quality spectra to be obtained. This SFC-FTIR lightpipe (flow cell, beam condensing optics,
narrow band detector) has allowed detection limits of 250ng for benzonitrile and 70ng for methyl benzoate to be reached. The
feasibility of very rapid SFC-FTIR separations is shown along with the subsequent peak spectra. 相似文献