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991.
A model of diffusive transport of benzoic acid through a liquid membrane (LM) separating two aqueous solutions, based on diffusion
layers and the assumption of a steady state, has been developed and tested using experimental results. It has been found that
a model with the apparent partition coefficient dependent on the concentration is able to describe the time dependence of
acid concentration in LM with and without a maximum on that dependence. The quality of the model fit with the single apparent
diffusion coefficient of benzoic acid is the same as the one which takes into account the diffusion of benzoic acid in different
forms (undissociated and dissociated form in aqueous phase, monomer and dimer in organic phase); however, in the second case,
the model becomes overparameterized. Assuming that the partition and diffusion coefficients are constant, the diffusion layer
model corresponds to the model of reversible consecutive reactions. Analytical solution for such case is given. Apart from
the partition equilibrium, also kinetics of partitioning was considered. It was shown that in some basic situations both cases
yield identical results. 相似文献
992.
Piotr Przybylski Marcin Kwit Krystian Pyta Radosław Pankiewicz Grzegorz Schroeder Jacek Gawroński Bogumil Brzezinski 《Tetrahedron: Asymmetry》2010,21(8):973-981
Gossypol Schiff base with (R)-(+)-2-amino-3-benzyloxy-1-propanol 1 was synthesised and resolved by HPLC method into diastereomers to study their atropisomerisation process. The spectroscopic analysis performed by one- and two-dimensional NMR, UV–vis and FT-IR methods indicated that the compound exists in solution as an enamine-oxo tautomer. The ECD measurements and TD-DFT calculations allowed us to unambiguously determine the configuration about the axially chiral biaryl moiety of 1. The conditions of the atropisomerisation processes of diastereopure gossypol Schiff bases (SAX,R)-1 and (RAX,R)-1 were determined on the basis of ECD and NMR measurements. Exposure of the diastereomers of 1 to sunlight and to the light at λ = 254 nm significantly accelerated the atropisomerisation when compared to its rate in the dark. 相似文献
993.
The reaction of [RuHCl(CO)(PPh3)3] with 4-phenylpyrimidine gave a new ruthenium(II) complex, namely [RuHCl(CO)(PPh3)2(pyrim-4-Ph)]. The complex has been studied by IR and UV?Cvis spectroscopy and by X-ray crystallography. The molecular orbitals of the complex have been calculated by density functional theory. The spin-allowed singlet?Csinglet electronic transitions of the complex have been calculated by time-dependent DFT, and the UV?Cvis spectrum of the compound has been discussed on this basis. The emission properties of the complex were also studied. 相似文献
994.
Anna Kamińska Anca M. Parrish 《Journal of Mathematical Analysis and Applications》2010,366(1):389-390
In this note we state the accurate formulas of convexity and concavity constants in Lorentz spaces, correcting the formulas from Kamińska and Parrish (2008) [2]. 相似文献
995.
Andrzej Schinzel 《Journal of Number Theory》2010,130(7):1572-1580
The concept of k-admissible tracks in Shamir's secret sharing scheme over a finite field was introduced by Schinzel et al. (2009) [10]. Using some estimates for the elementary symmetric polynomials, we show that the track (1,…,n) over Fp is practically always k-admissible; i.e., the scheme allows to place the secret as an arbitrary coefficient of its generic polynomial even for relatively small p. Here k is the threshold and n the number of shareholders. 相似文献
996.
A. Dittmar-Wituski A. Grudziński ?. Lademann A. Miko?ajczyk ?. Andraszyk M. Roszak 《Applied Surface Science》2010,256(15):4789-766
In this paper, we present experimental results of target current (TCS) and LEED investigation of well-oriented InSb(1 1 0) and InSb(1 1 1)-A and InSb(1 1 1)-B crystals. TCS results are interpreted in terms of very low electron diffraction (VLEED) and empty band signatures. To examine to which extent the TCS spectra reflect the bulk or surface electronic properties of InSb(1 1 0), thin layers of indium have been evaporated and the corresponding spectrum changes have been investigated. 相似文献
997.
998.
999.
B. Jańczuk I. Choma A. L. Dawidowicz A. Kliszcz T. Białopiotrowicz 《Chromatographia》1990,30(7-8):382-387
Summary Contact angles for water and diiodomethane drops were measured on the surface of thermally and chemically (by Carbowax 20M
bonding) modified porous glasses and on the surface of naphthalene, diphenyl and anthracene. Using the obtained results to
a modified Young equation, dispersion and nondispersion components of the surface free energy of these glasses and organic
substances were calculated.
The work of adhesion (WA) for benzene, naphthalene, diphenyl, anthracene, nitrobenzene was estimated and correlated with the capacity factors, (k′)
of these substances. On the basis of experimental and calculated data it can be stated that the thermal treatment of porous
glasses increases, their hydrophobicity but the Carbowax layer causes hydrophilicity. There is a linear relationship between
k′ and WA which can be helpful for predicting retention data of chromatographed substances on the base of surface free energy which
can be calculated from contact angle measurements. 相似文献
1000.
For each monothetic unitary group without proper co-compact subgroups, we show the existence of a compact semitopological
semigroup (affine) compactification in which the set of idempotents is not closed answering a question of Berglund. 相似文献