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41.
Jim Coykendall 《Proceedings of the American Mathematical Society》1996,124(6):1727-1732
The image of the norm map from to (two rings of algebraic integers) is a multiplicative monoid . We present conditions under which is a UFD if and only if has unique factorization into irreducible elements. From this we derive a bound for checking if is a UFD.
42.
Shao Hua SHI Li Jian LIU 《中国化学快报》2006,17(3):361-364
Poly(N-isopropylacrylamide) (PNIPAM) hydrogel, which is insoluble but shrinkable or swellable in aqueous media when temperature rises or drops across 33oC1,2, has been extensively studied due to its potential applications in the fields of controlled drug … 相似文献
43.
G. Rytwo R. Huterer-Harari S. Dultz Y. Gonen 《Journal of Thermal Analysis and Calorimetry》2006,84(1):225-231
Adsorption
of erythrosin-B (EB) and fast green (FG) to a non-charged organosmectite based
on crystal violet adsorbed up to 100% of the cation exchange capacity (CEC)
was tested. Adsorption isotherms of EB and FG were prepared at 3, 24 and 50°C.
All isotherms are of H-type reaching loads of approximately up to 20% of the
original CEC of the crude montmorillonite (up to 0.15 and 0.10 mol dye kg–1
clay for EB and FG, respectively). Adsorption decreases with temperature,
indicating an exothermic process. Enthalpy was evaluated using van’t
Hoff equation, yielding approximately –20 kJ mol–1
for both dyes. 相似文献
44.
45.
Pérez Pavón JL Guerrero Peña A García Pinto C Moreno Cordero B 《Journal of chromatography. A》2004,1047(1):101-109
The direct coupling of a headspace sampler with a mass spectrometer is proposed as a screening tool for the rapid detection of soil pollution by hydrocarbons from petroleum and derivatives. The samples are subjected to the headspace generation process, with no prior treatment, and the volatiles generated are introduced directly into the mass spectrometer, thereby obtaining a fingerprint of the sample analysed. Suitable treatment of the signal by chemometric techniques allows unequivocal characterisation of the different types of sample. The use of fast gas chromatography with a mass spectrometer detector coupled to the headspace sampler allows identification of the major hydrocarbons present in the mineral and organic polluted samples, interpretation of the results obtained, and demonstrates the analytical potential of headspace-mass spectrometry coupling. 相似文献
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Non-negative matrix factorization (NMF), with the constraints of non-negativity, has been recently proposed for multi-variate data analysis. Because it allows only additive, not subtractive, combinations of the original data, NMF is capable of producing region or parts-based representation of objects. It has been used for image analysis and text processing. Unlike PCA, the resolutions of NMF are non-negative and can be easily interpreted and understood directly. Due to multiple solutions, the original algorithm of NMF [D.D. Lee, H.S. Seung, Nature 401 (1999) 788] is not suitable for resolving chemical mixed signals. In reality, NMF has never been applied to resolving chemical mixed signals. It must be modified according to the characteristics of the chemical signals, such as smoothness of spectra, unimodality of chromatograms, sparseness of mass spectra, etc. We have used the modified NMF algorithm to narrow the feasible solution region for resolving chemical signals, and found that it could produce reasonable and acceptable results for certain experimental errors, especially for overlapping chromatograms and sparse mass spectra. Simulated two-dimensional (2-D) data and real GUJINGGONG alcohol liquor GC-MS data have been resolved soundly by NMF technique. Butyl caproate and its isomeric compound (butyric acid, hexyl ester) have been identified from the overlapping spectra. The result of NMF is preferable to that of Heuristic evolving latent projections (HELP). It shows that NMF is a promising chemometric resolution method for complex samples. 相似文献
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50.
Min-zhi Chen Xiao-liang Wang Fang-fang Tao Qi Xue Ping-chuan 《高分子科学》2007,(1):107-111
The concept of entanglement provides the basis of our current understanding of the flow behavior of polymer melts, Current techniques developed to investigate the degree of interpenetration of polymer chains only provide indirectly the information of the degree of entanglement in a relatively large scale (several to tens of nanometer). In this article, we report ^1H-NMR spectroscopy with dipolar filters under fast magic angle spinning for probing chain interpenetration of polymer glasses at the molecular level. 相似文献