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991.
Francesco Fornasiero Darren Tang Ali Boushehri John Prausnitz C.J. Radke 《Journal of membrane science》2008,320(1-2):423-430
A novel evaporative cell is used to measure steady-state gradient-driven diffusion rates of water through hydrogel membranes in the absence of external mass-transfer resistance. In this cell, the bottom surface of a hydrogel membrane is exposed to pure water vapor at known activity (aw) less than unity, while a sealed liquid-water reservoir bathes the upper membrane surface. Induced by the chemical-potential gradient between the two surfaces, the water evaporation rate is monitored by the rate of weight loss of the water reservoir.Results at ambient temperature are compared with those from measured water flux through soft-contact-lens (SCL) materials and with other published experimental results. Concentration-dependent water diffusivities are obtained by interpreting measured water fluxes for 0.11 ≤ aw ≤ 0.93 with extended Maxwell–Stefan (EMS) diffusion theory. Thermodynamic non-ideality is taken into account through Flory–Rehner polymer–solution theory. Shrinking/swelling is modeled by conservation of the total polymer mass assuming volume additivity. In spite of correction for thermodynamic non-ideality, EMS–water-diffusion coefficients increase with the water volume fraction, especially strongly for those hydrogel materials with low liquid-saturated water contents. The evaporation cell described here provides a simple robust method to establish water transport rates through soft-contact-lenses and other hydrogel membranes without the need to correct for external mass-transfer resistance. 相似文献
992.
T. Arecchi M. Bellini C. Corsi R. Fontana M. Materazzi L. Pezzati A. Tortora 《Optics and Spectroscopy》2006,101(1):23-26
Nondestructive techniques have seen successful growth in the last few years, and, among them, optical ones are widespread
and extremely well received in the field of painting diagnostics because of their effectiveness and safety. At present, many
techniques for nondestructive investigations of paintings are available; nevertheless, none of them is suitable for a quantitative
characterization of varnish. However, varnish removal, either partial or complete, is a fundamental part of the cleaning process,
which is an essential step in painting conservation. This critical process has been carried out, up to now, without the possibility
of any non-destructive measurement for assessing the actual varnish thickness, but with microscopic observation of a detached
microfragment. Optical coherence tomography (OCT) is a noninvasive technique that is well established for biomedical applications.
In this work, we present a novel application of OCT to measure the varnish film thickness for painting diagnostics.
The text was submitted by the authors in English. 相似文献
993.
Abstract A group is called metahamiltonian if all its non-abelian subgroups are normal; it is known that locally soluble metahamiltonian
groups have finite commutator subgroup. Here the structure of locally graded groups with finitely many normalizers of (infinite)
non-abelian subgroups is investigated, and the above result is extended to this more general situation.
Keywords: normalizer subgroup, metahamiltonian group
Mathematics Subject Classification (2000): 20F24 相似文献
994.
Evaluation of the number of components by the Davis-Giddings single chromatogram method is applied to capillary gas chromatograms of a dichloromethane extract of camomile. Various runs with OV-1 or Carbowax 20M as the stationary phase were done under different experimental conditions (column temperature programming rate and column length). The results showed that the number of components obtained by this statistical procedure does not depend greatly on the nature of the stationary phase or on the experimental conditions. The component number of the camomile extract was about 200 and the stand-alone probability at unit resolution was 0.2–0.3. 相似文献
995.
New Pd(II) and Pt(II) 3,6-bis(2′-pyridyl)pyridazine (dppn) mononuclear complexes of the type M(dppn)Cl2 were prepared and characterized. From M(dppn)Cl2, the bimetallic homonuclear complexes M(dppn)MCl4 were prepared by reaction with Pd(PhCN)2Cl2 or K2PtCl4. Bimetallic heteronuclear species of the type M(dppn)M′Cl4, were prepared reacting the mononuclear complexes with the stoichiometric amount of M′Cl2 (M′ = Cu, Co, Ni). All the described reaction give product in high yield. The isolated compounds, almost completely insoluble in most organic solvents, were characterized by elemental analysis, IR, ESR, reflectance spectra, and magnetic moment measurements. On the basis of these data the geometries around the metals are discussed. 相似文献
996.
In 1979 Kazhdan and Lusztig defined, for every Coxeter group W, a family of polynomials, indexed by pairs of elements of W, which have become known as the Kazhdan-Lusztig polynomials of W, and which have proven to be of importance in several areas of mathematics. In this paper, we show that the combinatorial concept of a special matching plays a fundamental role in the computation of these polynomials. Our results also imply, and generalize, the recent one in [Adv. in Math. 180 (2003) 146-175] on the combinatorial invariance of Kazhdan-Lusztig polynomials. 相似文献
997.
Combinatorial Expansions of Kazhdan-Lusztig Polynomials 总被引:2,自引:0,他引:2
We introduce two related families of polynomials, easily computableby simple recursions into which any KazhdanLusztig (andinverse KazhdanLusztig) polynomial of any Coxeter groupcan be expanded linearly, and we give combinatorial interpretationsto the coefficients in these expansions. This yields a combinatorialrule for computing the KazhdanLusztig polynomials interms of paths in a directed graph, and a completely combinatorialreformulation of the nonnegativity conjecture [15, p. 166]. 相似文献
998.
Properties of blends of semicrystalline perfluoropolymers in fluoroelastomers strongly depend on the size of the dispersed phase and are at the best when dispersed phase dimension is well below 0.1 μm, i.e. in the nano-scale region. This fine dispersion is obtained with an innovative mixing technology based on microemulsion polymerization. Further increase of properties can be obtained by generating chemical links between fluoroelastomer and semicrystalline fluoropolymer. Nano-blends combine the performing properties of fluoroelastomers with those of semicrystalline perfluoropolymers. For example, these nano-blends have at the same time the sealing and mechanical properties of fluoroelastomers and the exceptional thermal and chemical resistance, low permeability and low friction coefficient of semicrystalline perfluoropolymers. In addition, as dispersed phase size is below visible light wavelength, finished items made with these nano-blends are optically transparent even when they contain as much as 40 wt.% of semicrystalline perfluoropolymer. 相似文献
999.
1000.
Girolamo Cirrincione Anna Maria Almerico Gaetano Dattolo Enrico Aiello Patrizia Diana Francesco Mingoia 《Journal of heterocyclic chemistry》1992,29(5):1309-1312
Rearrangement under acidic conditions of the pyrrolylbenzotriazinone 7 afforded the pyrrolylbenzamides 10 and 11 . By thermal rearrangement instead, the first fully aromatic derivative of the pyrrolo[3,4-c]isoquinoline ring system 9 was obtained. 相似文献