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排序方式: 共有310条查询结果,搜索用时 15 毫秒
111.
A procedure has been developed to separate and quantitate phospholipids, including phosphatidylinositol and phosphatidylserine,
from animal tissues by means of the Iatroscan TLC/FID technique. The method is based on the use of 0.01 M oxalic acid impregnated
Chromarods-SII and stepwise resolution of the phospholipids in the presence of 1,2-dipalmitoyl-sn-glycero-3-phospho (N,N-dimethylethanolamine) as internal standard. To remove the neutral lipids, the rods are initially developed in a nonpolar
solvent mixture followed by partial scanning. Next, the rods are impregnated with oxalic acid, developed twice in CHCl3/CH3OH/CH3COOH/HCOOH/H2O (80∶35∶2∶1∶3, v/v/v/v/v) and partially scanned for measuring lysophosphatidylcholine, sphingomyelin and phosphatidylcholine.
The subsequent step involves double development in CHCl3/CH3OH/30% NH4OH (60∶35∶0.9, v/v/v) to resolve cardiolipin, internal standard, phosphatidylethanolamine, phosphatidylinositol, phosphatidylserine
and phosphatidic acid. For each phospholipid a linear calibration curve with a highly significant correlation coefficient
was obtained. However, the calibration lines extrapolated to negative intercepts on the ordinate, indicating declining sensitivity
at low phospholipid loads. 相似文献
112.
C Zwicker M Hering J Brecht M Bj?rnsg?rd HJ Kuhne-Velte A Kern 《Canadian Metallurgical Quarterly》1998,38(9):774-778
OBJECTIVE: To determine the clinical implications of atypical glandular cells of uncertain significance (AGCUS) in cervical cytologic smears. STUDY DESIGN: Retrospective analysis. RESULTS: Eighty-eight of 32,181 (0.27%) cervical smears obtained during the study period contained AGCUS. Of the 47 women with AGCUS, 16 had intraepithelial or invasive neoplasms (34%; 95% confidence interval, 21-49%), including 9 low or high grade squamous intraepithelial lesions, 1 adenocarcinoma in situ of the cervix, 3 adenocarcinomas of the cervix, 2 adenocarcinomas of the endometrium and 1 adenoid basal cell carcinoma of the cervix. CONCLUSION: The high prevalence of cervical and endometrial neoplasia among women with the isolated finding of AGCUS on cervical cytologic smears warrants a thorough diagnostic evaluation. 相似文献
113.
Vermeulen F.E. Robinson A.M. James C.R. McMullin J.N. 《Microwave Theory and Techniques》1994,42(10):1932-1938
An asymptotic form of the characteristic equation that describes wave propagation at near-infrared wavelengths in small core hollow circular waveguides is developed. Analytic solutions for the transverse and axial propagation constants are obtained. These demonstrate the transition of the TE11 and TM01 modes to surface waves as the guide radius is increased to values much greater than at cutoff. Relative power density distributions illustrating these mode transitions are shown 相似文献
114.
Monitoring milk fat fractionation: Effect of agitation, temperature, and residence time on physical properties 总被引:1,自引:0,他引:1
Bert Vanhoutte Koen Dewettinck Brecht Vanlerberghe André Huyghebaert 《Journal of the American Oil Chemists' Society》2002,79(12):1169-1176
With the use of two central composite designs, the effects of agitation rate, fractionation temperature, and residence time
on the thermal properties of the stearin and olein milk fat fractions were investigated. The main function of agitation during
fat fractionation was suspending the crystal aggregates and enhancing the heat transfer. For the experimental conditions described
here, crystal aggregation did not seem to be affected by agitation. The effect of fractionation temperature on the physical
properties of the olein fraction was very significant. Triangle diagrams were shown to be a useful tool for monitoring and
designing fractionation processes. They illustrate that oleins with similar melting properties can be produced over a range
of yields of stearin, which is important from an industrial point of view. Crystallizer residence time, which influences production
costs, clearly affects both stearin yield and olein melting properties. For any fractionation temperature, stearin fractions
with virtually identical melting properties and yields can be obtained over a range of olein melting properties. Manipulation
of both the fractionation temperature and residence time allows the fractionation process to be adapted to meet changing market
demands for fractions with different melting properties. 相似文献
115.
The history of X-ray equipment starts at about the same time as Marconi's work on wireless telegraphy and is interwoven with the development of the thermionic valve and filament lamps. This article starts with brief biographical notes on its discoverer, W. C. Rontgen, followed by accounts of its early use, particularly during the South African War (1899-1902). It traces the early evolution of X-ray tubes, including Coolidge's introduction of the heated cathode followed by further improvements before the mid 1930s. 相似文献
116.
The influence of the stress state on the plasticity of transformation induced plasticity-aided steel 总被引:1,自引:0,他引:1
I. Yu. Pyshmintsev M. De Meyer B. C. De Cooman R. A. Savray V. P. Shveykin M. Vermeulen 《Metallurgical and Materials Transactions A》2002,33(6):1659-1667
The influence of the stress state on the plastic deformation of CMnSi, CMnSi(Nb), and CMnAlSi transformation induced plasticity
(TRIP)-aided steel has been analyzed. Imposing hydrostatic pressures up to 800 MPa during tensile deformation made it possible
to change the stress state of the tensile testing specimens. It was found that the ratio of normal to shear stresses has a
pronounced effect on the evolution of the microstructure, the austenite volume fraction change during straining, and the fracture
surface morphology. The CMnAlSi TRIP steel, which has the largest uniform elongation and the smallest equivalent strain at
fracture in the absence of the hydrostatic pressure, had a more pronounced improvement of all plastic characteristics at increasing
hydrostatic pressure. An increased austenite stabilization, brought about by the high hydrostatic pressure, was clearly observed.
The austenite stabilization results in a decrease of 20 °C to 25 °C of M
s
for an increase of 100 MPa of the hydrostatic pressure. The implications of the observations could be far-reaching for new
sheet forming technologies, such as hydroforming, as the full transformation potential is available for crashsensitive structural
parts by avoiding the formation of the martensite during forming operations. 相似文献
117.
G. J. Van Tonder B. H. Usher I. Dennis P. D. Vermeulen 《Mine Water and the Environment》2007,26(2):79-87
Abstract: The main challenge facing many of the coal mines in South Africa is the management of mine water following the closure of
mining operations. The Sigma Colliery is situated in the Free State Province, adjacent to the town of Sasolburg and bordering
the Vaal River, one of the country's largest rivers. The mining includes both opencast and underground operations; however,
this paper will only discuss the main underground operations. There are several aquifer systems overlying the deeper mining,
which was done by bord and pillar and high extraction mining. Detailed conceptual models of the interactions between several
aquifer systems and the rebounding mine voids were constructed using mining and monitoring data. From this, numerical flow
models were used to model the complex flow system where rebound of water levels is expected. The results have led to an accurate
understanding of the complex flow system and the important controls on the final water levels in the area. 相似文献
118.
Huygens D Boeckx P Vermeulen J De Paepe X Park A Barker S Van Cleemput O 《Analytical chemistry》2007,79(22):8644-8649
A new on-line analytical setup for 15N measurements of total dissolved nitrogen (TDN) has been developed through the coupling of a high-temperature catalytic (Ce(IV)O2) oxidation furnace, a Cu reduction furnace, and an isotope ratio mass spectrometer. The detection limit for accurate delta15N measurements is 20 mg of N L-1. For N-containing compounds dissolved in water, a standard deviation on N concentration measurements of 0.2 mg of N L-1, independent of N concentration, has been found. Reproducibility on delta15N increased with increasing N concentration, with standard deviations varying from 0.8 to 0.1 per thousand in the range of 20-100 mg of N L-1. Salt matrixes, in which the N species might be dissolved, could influence the analysis capacity and continuity, mainly at concentrations above 0.1 M. To our knowledge, this system is the first successful on-line setup capable of performing routine delta15N and N concentration measurements of the TDN pool. Potential applications are large and are believed to result in an increased insight in N cycling and dissolved organic nitrogen behavior in terrestrial and aquatic ecosystems. 相似文献
119.
Erikjan Vermeulen Rob Wagemans Cindy Wouters Melanie Knuewer Ewout Huibers 《中国建筑装饰装修》2012,(9):234-237
项目地点:西班牙赫罗纳开放时间:2011年6月项目面积:250平方米设计公司:Concrete建筑事务所设计团队:Erikjan Vermeulen,Rob Wagemans,Cindy Wouters,Melanie Knuewer摄影:Ewout Huibers 相似文献
120.
ABSTRACT Improved methods for the preparation of imidotetraalkyl-pyrophosphates are reported. The dissociation constant of the water soluble tetraethyl analogue was determined by potentiometric titration. The values for the partition constant and aggregation constant of the tetradodecyl analogue were determined by two phase EMF potentiometric titration of which the data were processed through a sophisticated general optimization technique.The application of this method also made it possible to obtain a species distribution curve of the organic phase in terms of variation of pH in the aqueous phase. 相似文献