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41.
Commensurability between inter-vortex distance and crystal lattice constant is investigated by angular dependent magnetization
in very pure twinned and twin-free NdBa2 Cu3 Oy single crystals. With increasing temperature the incommensurate states split up and become finally commensurate with half
the vortex distance. These new commensurate states are related to a substructure of the intrinsic pinning potential within
the unit cell and discussed with respect to temperature, field, anisotropy, and twin structure. 相似文献
42.
MJ Lazaro AA Herod M Domin Y Zhuo CA Islas R Kandiyoti 《Rapid communications in mass spectrometry : RCM》1999,13(14):1401-1412
Three methods for determining a 'safe' estimate for high-mass limits of MALDI spectra of coal derived liquids were explored, using a sample of coal-tar pitch and its pyridine-insoluble fraction. Co-addition of increasing numbers of single-shot spectra (10, 30, 50 and 100 pulses) showed visually observable reductions in noise levels, consistent with robust and statistically meaningful signals. Three separate types of post-acquisition calculation were used to identify high-mass limits of the spectra. (i) A literature method indicated high-mass limits similar to those observed visually-as a shift from baseline at the highest masses, nearly 350 000 u for the coal tar pitch and about 390 000 u for its pyridine insoluble fraction. (ii) Comparing instrument signal with pre-selected multiples of the standard deviation, upper mass estimates of between 40-60 000 u for the coal-tar pitch and about 95 000 u for its pyridine-insoluble fraction were found. (iii) Calculation of the slope was used to identify 'lift-off' of the spectrum from baseline. The angle between the smoothed spectrum and the baseline was matched to a pre-selected value (e.g. 0.5 degrees and 1 degrees ). However, the arbitrary specification of the key parameter did not establish this last method on a firm basis. The choice of a criterion for estimating high-mass limits of MALDI spectra remains a semi-quantitative procedure; a reasonably conservative high-mass limit may be estimated by comparison of signal with five times the standard deviation. However, evaluation of size exclusion chromatograms of the present samples using polystyrene standards suggests that molecular mass distributions of pitch samples arrived at by MALDI mass spectrometry are, at least partly, determined by the limitations of available instruments. Copyright 1999 John Wiley & Sons, Ltd. 相似文献
43.
Mohd Amran Bin Md Ali Kenzo Okamoto Masayuki Yamaguchi Toshihiro Kasai Atsunori Koshirai 《Journal of Polymer Science.Polymer Physics》2009,47(20):2008-2014
Linear and nonlinear viscoelastic properties for binary blends composed of isotactic polypropylene and polytetrafluoroethylene (PTFE) are studied. It is found that blending a small amount of PTFE greatly enhances the storage modulus in the low frequency region. Further, drawdown force and normal stress difference increase with the PTFE content. Electron microscope observation reveals that PTFE deforms into fine fibers whose diameter is smaller than 0.5 μm. The network structure composed of the fibers is responsible for the marked elastic properties. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 2008–2014, 2009 相似文献
44.
Chen Ruey Shan Mohd Amran Nurul Aishah Ahmad Sahrim 《Journal of Thermal Analysis and Calorimetry》2019,136(1):79-87
Journal of Thermal Analysis and Calorimetry - This paper reports the energy and exergy performance of a photovoltaic/thermal solar-assisted heat pump system (PV/T-SAHPS) with different solar... 相似文献
45.
Amran Waheed Shahid Mahmud Muhammad Saleem Tayyaba Ahmad 《Journal of Saudi Chemical Society》2009,13(3):269-272
The constituents of total lipids and neutral lipid classes, i.e., hydrocarbons, wax esters, sterol esters, triacylglycerols, free fatty acids, 1,3-diacylglycerols, 1,2-diacylglycerols, free sterols, alcohols, and monoacylglycerols of three species of Citrus namely Citrus sinensis, Citrus paradisi, Citrus aurantium were investigated by thin layer and gas chromatography. Palmitic, oleic and linoleic acids were the major components in all the lipids and lipid classes studied. 相似文献
46.
47.
Brett Ammundsen Gary R. Burns Ali Amran Stig E. Friberg 《Journal of Sol-Gel Science and Technology》1994,2(1-3):341-346
A preparative technique based on the gelation of a microemulsion has provided a means of homogeneously dispersing high concentrations of metal oxide precursor salts through silica gel. The microstructures and compositions of gels containing combinations of lithium and manganese nitrate, and of the multiphase materials obtained by firing to a range of temperatures up to 1000°C, have been established. Formation of the mixed metal oxide spinel phase LiMn2O4 within a silica support has been obtained for systems comprising from 10 to 30 wt% metal nitrate by heating to temperatures between 500 and 700°C. 相似文献
48.
F. Lagarde M. B. Amran M. J. F. Leroy C. Demesmay M. Ollé A. Lamotte H. Muntau P. Michel P. Thomas S. Caroli E. Larsen P. Bonner G. Rauret M. Foulkes A. Howard B. Griepink E. A. Maier 《Analytical and bioanalytical chemistry》1999,363(1):5-11
Six interlaboratory studies were organised by the Standard, Measurement and Testing Programme of the European Commission on
the determination of arsenic species (arsenobetaine, arsenocholine, monomethylarsonic acid, dimethylarsinic acid, As(III)
and As(V)) in marine matrices and soil. A step-by-step approach was used and a meeting was held at the end of each study to
help the participants to discover errors and to improve their analytical methods. The successive steps investigated the calibration
procedures on various solutions, the separation and derivatisation techniques on solutions and extracts and the extraction
on mussel and fish tissues. All materials used for the study were monitored for their stability. Verified calibration solutions
and compounds were distributed to the participants in each exercise in order to trace calibration problems. The agreement
between the results improved regularly and at the end of the six campaigns allowed the certification of a reference material
of tuna-fish tissue (BCR-CRM 627) for its total arsenic, arsenobetaine and dimethylarsinic acid contents.
Received: 31 March 1998 / Revised: 20 July 1998 / Accepted: 25 July 1998 相似文献
49.
Aisyah Nur Hanis Azhar Nurul Aini Amran Suzana Yusup Mohd Hizami Mohd Yusoff 《Molecules (Basel, Switzerland)》2022,27(15)
2-acetyl-1-pyrroline (2AP) is the compound that gives out the typical aroma and flavour of pandan leaves (Pandanus amaryllifolius Roxb.). This research incorporates ultrasonic extraction to extract the aromatic compound in pandan leaves. The parameters varied in this study are the extraction time, sonicator amplitude, concentration of solvent and the mass of pandan leaves. The experiment was conducted using a central composite design (CCD) model generated by the response surface methodology (RSM). From the extraction process, it can be deduced that the effect of leaves’ mass is comparably higher than other parameters, while sonicator amplitude gives the most negligible impact on the process. The obtained p-value was 0.0014, which was less than 0.05. The high R-squared 0.9603 and adjusted R-squared 0.8809 indicate the model is well agreed with the actual data. The optimal control variables of ultrasonic extraction of 2AP are at an extraction time of 20 min, 60% of solvent concentration, amplitude of 25% and 12.5 g of pandan leaves, which produced 60.51% of yield of the extract and 1.43 ppm of 2AP. It is found that the mass of pandan leaves and the concentration of solvent have a significant impact on the extraction process of 2AP. 相似文献
50.
There are many reports1 of the pyrolysis of fluorinated organic compounds, including the defluorination of cyclic fluorocarbons over iron to give aromatic compounds. Extending this technique we have investigated the flow pyrolysis of some readily accessible unsaturated fluorocarbons, such as I, II, and III, and found these to be synthetically useful routes to fluorinated dienes, cyclobutenes, and furans. Pyrolyses were carried out using a nitrogen flow over platinum, iron or caesium fluoride heated at 430–700°. The various products can all be rationalized in terms of intermediate allylic radicals, and the solid substrate influences which allylic radicals are formed.We are also investigating the chemistry of those now accessible compounds, such as IV, V, and VI, and some of the preliminary results are described. For example the fluoride ion induced dimerisation of IV gave two major products VII and VIII via a particular interesting mechanism. 相似文献