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11.
Ofelia T. Alas Lucia R. Junqueira Jan van Mill Vladimir V. Tkachuk Richard G. Wilson 《Central European Journal of Mathematics》2011,9(3):603-615
For a topological property P, we say that a space X is star Pif for every open cover Uof the space X there exists Y ? X such that St(Y,U) = X and Y has P. We consider star countable and star Lindelöf spaces establishing, among other things, that there exists first countable pseudocompact spaces which are not star Lindelöf. We also describe some classes of spaces in which star countability is equivalent to countable extent and show that a star countable space with a dense σ-compact subspace can have arbitrary extent. It is proved that for any ω 1-monolithic compact space X, if C p (X)is star countable then it is Lindelöf. 相似文献
12.
J. Y. Bello Cruz R. Díaz Millán 《Journal of Optimization Theory and Applications》2014,161(3):728-737
We propose a direct splitting method for solving a nonsmooth variational inequality in Hilbert spaces. The weak convergence is established when the operator is the sum of two point-to-set and monotone operators. The proposed method is a natural extension of the incremental subgradient method for nondifferentiable optimization, which strongly explores the structure of the operator using projected subgradient-like techniques. The advantage of our method is that any nontrivial subproblem must be solved, like the evaluation of the resolvent operator. The necessity to compute proximal iterations is the main difficulty of other schemes for solving this kind of problem. 相似文献
13.
Ultrasound‐assisted emulsification microextraction coupled with high‐performance liquid chromatography for the simultaneous determination of fragrance allergens in cosmetics and water
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Jessica Pérez‐Outeiral Esmeralda Millán Rosa Garcia‐Arrona 《Journal of separation science》2015,38(9):1561-1569
A simple, inexpensive, and environmentally friendly method based on ultrasound‐assisted emulsification microextraction followed by solidification of floating organic drop and high‐performance liquid chromatography coupled to diode array detection was developed for the simultaneous determination of 18 potentially allergenic fragrance substances. Several parameters affecting the microextraction process were investigated in detail by the “one‐variable‐at‐a‐time” approach. Optimal conditions were the following: 50 μL of 2‐dodecanol as extraction solvent, 10 mL of sample containing 150 g/L of salt, and 5 min of sonication at 35°C. Under the optimized conditions, method showed good linearity in the selected ranges, with squared correlation coefficients ranging from 0.948 to 0.999. Limits of detection ranged from 0.001 to 0.154 μg/mL and enrichment factors from 9 to 237. Precision of the method, expressed as relative standard deviation, was checked at two levels obtaining good results (3.3–14.4%). Recovery studies were made in baby bath water and in eau de cologne showing acceptable accuracy. Finally, the developed method was successfully applied to different commercial cosmetic and water samples. The most commonly found analyte was linalool followed by cinnamal and lilial. Most of the analyzed samples contained at least one of the target compounds. 相似文献
14.
Henno Brandsma Jan van Mill 《Proceedings of the American Mathematical Society》1998,126(11):3407-3411
We show that Kunen's example of a compact L-space, constructed under CH, can be modified so that it has a non-monolithic hyperspace. This answers a question of Bell's. This example is also relevant to a question of Arhangel'skii's.
15.
H. Herrero J. Millán Rodríguez C. Pérez-García 《Zeitschrift für Physik B Condensed Matter》1996,99(3):457-463
The amplitude equation for a convective system under a vertical magnetic field is derived. The coefficients in these equations have been numerically calculated for infinite Prandtl number fluids and for boundary conditions both free and rigid top and bottom. The results confirm that, for realistic parameter values only stationary convection can be present and the pattern is made by convective rolls. 相似文献
16.
Within the class of Tychonoff spaces, and within the class of topological groups, most of the natural questions concerning ‘productive closure’ of the subclasses of countably compact and pseudocompact spaces are answered by the following three well-known results: (1) [ZFC] There is a countably compact Tychonoff space X such that X × X is not pseudocompact; (2) [ZFC] The product of any set of pseudocompact topological groups is pseudocompact; and (3) [ZFC+ MA] There are countably compact topological groups G0, G1 such that G0 × G1 is not countably compact.In this paper we consider the question of ‘productive closure” in the intermediate class of homogeneous spaces. Our principal result, whose proof leans heavily on a simple, elegant result of V.V. Uspenski?, is this: In ZFC there are pseudocompact, homogeneous spaces X0, X1 such that X0 × X1 is not pseudocompact; if in addition MA is assumed, the spaces Xi may be chosen countably compact.Our construction yields an unexpected corollary in a different direction: Every compact space embeds as a retract in a countably compact, homogeneous space. Thus for every cardinal number α there is a countably compact, homogeneous space whose Souslin number exceeds α. 相似文献
17.
SbCl3Br2 may be stabilized by electron donors. Crystalline 1:1 adducts with diethyl ether, tetrahydrofurane, triphenylphosphine oxide and -sulphide were isolated. Their bonding properties, regarding the donor strengths, are discussed. The tetrahydrofurane adduct takes up three molecules of CCl4 in the presences of CCl4 · SbCl3Br2 · OP(C6H5)3 is converted in introbenzene into SbCl3Br2 · O2NC6H5 which, at room temperature, transforms in the course of 15 hours to heteropolar compounds of the general formula [SbClnBr4?n · (O2NC6H5)2]+[SbClmBr6?m]?, with m + n = 6 and n = 1, 2, 3, 4. 相似文献
18.
We show that if every Parovi?enko space of weight is co-absolute with , then . 相似文献
19.
Jan J. Dijkstra Jan van Mill 《Proceedings of the American Mathematical Society》2006,134(8):2281-2283
We present a weakly closed, one-dimensional, line-free subgroup of the separable Banach space that is not homeomorphic to complete Erdos space. The existence of this example disproves a conjecture of Dobrowolski, Grabowski, and Kawamura.
20.
Sonia Millán Griselda Sánchez Luz Alicia Fucugauchi Janos H. Fendler 《Molecular Crystals and Liquid Crystals》2013,570(2-4):153-166
A new nematic phase in lyotropic binary liquid crystalline systems consisting of sodium dodecyl sulfate-water was detected, for the first time, in the absence of additives by utilizing positron annihilation techniques. Lyotropic and thermotropic phase transitions were also investigated by the same methods. The positron annihilation parameters have also indicated a better definition of the concentration ranges at which each phase exists in the system studied. Crossed polarized light microscopy was applied to substantiate these results. 相似文献