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211.
212.
Viscosity deviations from ideal mixing for 1,4-dioxane + water mixtures over the entire range of composition at temperatures
of (293.15, 303.15 and 313.15) K and atmospheric pressure were calculated from experimental viscosity data presented in a
previous work. The temperature range was extended to 323.15 K with data from the literature. This system exhibits very large
positive deviations due to strong heteromolecular interactions and also due to size differences of the unlike molecules. The
viscosity data as well as their corresponding relative functions were used to test the applicability of two correlative equations:
the reduced Redlich-Kister equation and the recently proposed Herráez equation. These relative functions are important to
reduce the effect of temperature and, consequently, to reveal the effects of different types of interactions. Their correlation
abilities at different temperatures, and using different numbers of parameters, are discussed for the case of limited experimental
data. Generally, good agreement between experimental and calculated data was obtained with both equations provided more than
three parameters were employed. 相似文献
213.
Noureddine Igbida 《Nonlinear Analysis: Theory, Methods & Applications》2009,71(9):3805-3813
In this paper, we study some equivalent formulations in divergence form for the optimization problem where and k>0 in Ω. This is the so called dual equation of Monge-Kantorovich problem. 相似文献
214.
Zhou XS Liu L Fortgang P Lefevre AS Serra-Muns A Raouafi N Amatore C Mao BW Maisonhaute E Schöllhorn B 《Journal of the American Chemical Society》2011,133(19):7509-7516
We measured single-molecule conductances for three different redox systems self-assembled onto gold by the STMBJ method and compared them with electrochemical heterogeneous rate constants determined by ultrafast voltammetry. It was observed that fast systems indeed give higher conductance. Monotonous dependency of conductance on potential reveals that large molecular fluctuations prevent the molecular redox levels to lie in between the Fermi levels of the electrodes in the nanogap configuration. Electronic coupling factors for both experimental approaches were therefore evaluated based on the superexchange mechanism theory. The results suggest that coupling is surprisingly on the same order of magnitude or even larger in conductance measurements whereas electron transfer occurs on larger distances than in transient electrochemistry. 相似文献
215.
Khiar N Salvador Á Chelouan A Alcudia A Fernández I 《Organic & biomolecular chemistry》2012,10(12):2366-2368
Reported is a single high yielding step approximation to mixed olefin/sulfinamide ligands enclosing a chiral sulfur atom as the sole chiral center. The synthetic design is validated by a rapid optimization of the substituent at the sulfinyl sulfur, and by the synthesis of an efficient, highly enantioselective catalyst for the Rh-catalyzed 1,4-addition of boronic acids to both, cyclic and acyclic olefins. 相似文献
216.
Changes in sugar composition and cellulose content during the secondary cell wall biogenesis in cotton fibers 总被引:1,自引:0,他引:1
Two cotton cultivars TX19 and TX55 (Gossypium hirsutum L. cv.) were planted in the greenhouse and fibers were harvested at different stages of development. The percentage of sugars
present on the fibers was determined by High Performance Liquid Chromatography and the cellulose content was determined using
the anthrone method. The percentage of sugars (sucrose, glucose, fructose, and galacturonic acid) showed statistically significant
changes during fiber development. The decrease in the percentages of these sugars as the secondary cell wall develops was
associated with an increase in the cellulose content. It is important to point out that these analyses were done on intact
fibers, no cell wall extractions and purifications were performed. 相似文献
217.
Noureddine Belmadoui 《Tetrahedron》2006,62(7):1372-1377
Irradiation of dyad 1 in aqueous acetone leads to the introduction of an acetonyl substituent at the naphthalene 5-position, to give photoproduct 2. The proposed reaction mechanism involves electron transfer from the naphthalene excited singlet state to the ketone. Neither thymine dimers, nor acetone photoadducts involving the thymine ring were detected. These photoproducts would arise from the thymine triplet excited state, which in dyad 1 must be efficiently depopulated via a fast intramolecular energy transfer to the naphthalene chromophore, due to the lower energy of its excited triplet state. 相似文献
218.
219.
Evaluation of the acoustic and non-acoustic properties of sound absorbing materials using a three-microphone impedance tube 总被引:1,自引:0,他引:1
Olivier Doutres Yacoubou Salissou Noureddine Atalla Raymond Panneton 《Applied Acoustics》2010,71(6):506-509
This paper presents a straightforward application of an indirect method based on a three-microphone impedance tube setup to determine the non-acoustic properties of a sound absorbing porous material. First, a three-microphone impedance tube technique is used to measure some acoustic properties of the material (i.e., sound absorption coefficient, sound transmission loss, effective density and effective bulk modulus) regarded here as an equivalent fluid. Second, an indirect characterization allows one to extract its non-acoustic properties (i.e., static airflow resistivity, tortuosity, viscous and thermal characteristic lengths) from the measured effective properties and the material open porosity. The procedure is applied to four different sound absorbing materials and results of the characterization are compared with existing direct and inverse methods. Predictions of the acoustic behavior using an equivalent fluid model and the found non-acoustic properties are in good agreement with impedance tube measurements. 相似文献
220.
Sorption study of an anionic dye - benzopurpurine 4B - on calcined and uncalcined Mg-Al layered double hydroxides 总被引:1,自引:0,他引:1
In this paper, the elimination from aqueous solution of the pollutant benzopurpurine 4B by Mg-Al-CO3 hydrotalcite and its modified form Mg-Al-500 has been studied. Mg-Al-CO32− layered double hydroxide with an Mg/Al molar ratio of 2.0 was synthesized by the co-precipitation method, and its modification was carried out by calcination. The affinity of these materials with a mixture of benzopurpurine 4B was studied as a function of dye-adsorbent contact time, initial pH of the solution, initial dye concentration and temperature. The results indicate that HDLs were effective in removing benzopurpurine 4B anionic dye. Their saturated adsorption capacities are very high, particularly for the calcined material Mg-Al-500 compared to the standard one Mg-Al-CO32−.The characterisation of the solid Mg-Al-500, both fresh and after removal of the dye by X-ray diffraction and infrared spectroscopy, shows that the benzopurpurine 4B adsorption on this calcined phase is enhanced by reconstruction of a matrix hydrotalcite intercalated by the dye, with basal spacing of 23.77 Å, which is larger than that of Mg-Al-CO32− LDHs (7.57 Å). 相似文献