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971.
For lattices with two kinds of points (black and white), distributed according to a translation-invariant joint probability distribution, we study statistical properties of the sequence of consecutive colors encountered by a random walker moving through the lattice. The probability distribution for the single steps of the walk is considered to be independent of the colors of the points. Several exact results are presented which are valid in any number of dimensions and for arbitrary probability distributions for the coloring of the points and the steps of the walk. They are used to derive a few general properties of random walks on lattices containing traps.Presented at the Symposium on Random Walks, Gaithersburg, MD, June 1982. 相似文献
972.
Gasanov R. G. Tumanskii B. L. Tsikalova M. V. Nuretdinov I. A. Gubskaya V. P. Zverev V. V. Fazleeva G. M. 《Russian Chemical Bulletin》2003,52(12):2675-2678
The addition of the ·But (R1) and ·P(O)(OPri)2 (R2) radicals to pyrrolidino[60]fullerenes C60CH2NMeCHX (X = C6H4N(CH2CH2Cl)2, 2,6-(But)2C6H2OH, PhC6H4, and indol-3-yl) was studied by ESR spectroscopy. The rate constants of R1 radical addition to these compounds and dimerization of spin-adducts of the R1 radicals with pyrrolidino[60]fullerenes were determined. Pyrrolidino[60]fullerenes manifest considerably higher reactivity toward the R1 radicals than fullerene C60 and methanofullerenes C60CX1X2 (X1 = X2 = CO2Et; X1 = CO2Me, X2 = OP(OMe)2, X1 = X2 = OP(OEt)2). 相似文献
973.
Vasil"ev A. A. Vielhauer O. Engman L. Pietzsch M. Serebryakov E. P. 《Russian Chemical Bulletin》2002,51(3):481-487
Acylation of meso-2,3-dimethylbutane-1,4-diol with vinyl acetate in the presence of porcine pancreatic lipase (PPL) leads to the dextrorotatory monoacetate of the above diol with enatiomeric excess (ee) 58—64%. Absolute configuration of this scalemic specimen was determined by its sequential transformation to levorotatory lasiol, a metabolite of the Lasius ants. Partial hydrolysis of the corresponding meso-diacetate, mediated by PPL or by the Pseudomonas sp. lipase affords the monoacetate of opposite configuration with ee 72—86%, a formal intermediate in the synthesis of (3S,4R)-faranal. Other microbial lipases used are distinctive in low chemoselectivity. 相似文献
974.
A.?González-PérezEmail author J.?Czapkiewicz J.?M.?Ruso J.?R.?Rodríguez 《Colloid and polymer science》2004,282(10):1169-1173
The specific conductivity of dodecyldimethylbenzylammonium bromide (C12BBr) in aqueous solutions, in the temperature range of 15 to 40 °C, has been measured as a function of molality. The two breaks which were found on the conductivity against molality plots were attributed to the critical micelle concentration, cmc, and second critical micelle concentration, 2nd cmc, respectively. The ratio of the slopes, S, of the three linear fragments on the plots, S2/S1 and S3/S1, was attributed to the degree of ionization of the micelles at cmc and 2nd cmc respectively. It was shown that the values of the 2nd cmc estimated above 27 °C are only apparent due to thermal disintegration of the micelles. In the temperature range of 15 to 27 °C, the values of the 2nd cmc increase gradually and the plot of the 2nd cmc against temperature is concave. The ratio of 2nd cmc/cmc for C12BBr at 25 °C amounts to 15 and appears to be high compared to the literature values for other surfactants. For comparative purposes the cmc and 2nd cmc values were also estimated conductometrically for decyldimethylbenzylammonium bromide (C10BBr) at 25 °C. The 2nd cmc value for this surfactant is higher compared to the value for the C12 homologue by a factor of 2.6.The standard Gibbs free energies of micellization at cmc and at the 2nd cmc were estimated from the experimental data for both surfactants at 25 °C. 相似文献
975.
Luisa Fernanda Rojas Paola Zapata Laura Ruiz-Tirado 《Current Opinion in Green and Sustainable Chemistry》2022
According to the Food and Agriculture Organization of the United Nations, approximately 1.3 billion tons of food is wasted each year, equivalent to approximately one-third of world production. Agri-food wastes are the source of proteins, carbohydrates, lipids, and other essential minerals that have been exploited for value-added products by the development of biorefineries and sustainable business as important elements of circular economies. The innovation and materialization of these types of processes, including the use of disruptive technologies on microbial bioconversion and enzyme technology, such as nanotechnology, metabolic engineering, and multi-omics platforms, increase the perspectives on the waste valorization process. Lignocellulolytic enzymes, pectinases, and proteases are mainly used as catalyzers on agri-food waste treatment, and their production in house might be the trend in near future for agro-industrial countries. Another way to transform the agri-food wastes is via aerobic or anaerobic microbial process from fungal or bacterial cultures; these processes are the key to produce waste enzymes. 相似文献
976.
Summary Packings and stationary phases applied to high resolution separations of proteins, enzymes, and nucleic acids must satisfy
a series of distinct criteria that are different from those usually required by HPLC of low molecular weight non-biologically
active analytes. These requirements have been met through substantial improvements in classical gel media together with novel
developments in silica supports, and have led to a family of products with tailor-made and reproducible properties. Supports
consisting of cross-linked organic gels, and inorganic materials (mostly silicas) are now available with graduated particle
sizes, pore sizes, porosities and surface areas as well as non-porous beads. A whole range of stationary phases, such as reversed
phase, hydrophobic interaction, ion exchanger and affinity packings, were designed for application as chemical sensors for
biopolymer recognition in adsorptive chromatography. The phase systems are operated in the gradient mode, giving high resolution
and high peak capacities. In addition, aqueous liquid-liquid partitioning systems have been developed for the fractionation
of proteins and nucleic acids. Size exclusion media complete the set of HPLC variants enabling a discrimination of proteins
according to their size and shape in an isocratic elution mode. Basically, protein purification and isolation is a multistage
process where-by the HPLC variants are combined in a logistic sequence, utilizing the different selectivities of the phase
systems and thus maximising resolution, speed and throughput. 相似文献
977.
Sourav Pal 《Theoretical chemistry accounts》1985,68(5):379-388
In this paper, we analyse the algebraic structure of the equations for calculating the first order static properties using several approximate versions of Coupled Cluster (CC) methods. In particular, the non-variational and the variational method using a CC wavefunction corresponding to an appropriately defined perturbed Hamiltonian as well as the simple expectation value expression using a CC stationary state are studied under different approximations. Two different models are proposed: (a) use of maximum overlap orbitals where the pertinent approximations are TT
2, T
(1) T
2
(1), (b) use of Hartree-Fock orbitals and T(T
1+T
2), T
(1)(T
1
(1)
+T
2
(1)
) approximations. It is analytically shown that in both these models certain approximate versions of the methods under purview yield identical results for first order static properties.NCL Communication No. 3725 相似文献
978.
N. T. Ul'chenko N. P. Bekker T. V. Chernenko N. K. Yuldasheva A. I. Glushenkova 《Chemistry of Natural Compounds》2003,39(3):249-252
Seed characteristics and the lipid and fatty-acid compositions were determined for the new cotton varieties ASh-25, Omad, 9771-I, Termez-43, and Bukhara-6. 相似文献
979.
The reaction of 1-alkynylcyclobutanols with aryl iodides in the presence of Pd(OAc)2 and Et3N in acetonitrile at 80°C for 24 h gives 2-disubstituted methylenecyclopentan-1-ones in modest to good yields. The tandem insertion-ring expansion process proceeds via the formation of an alkynyl π-complex, followed by migration of a carbon-carbon bond of the tert-alkanol to form the cyclopentanones stereoselectively. 相似文献
980.
A sensitive and selective method using liquid chromatography with electrospray ionization mass spectrometric detection was
developed for the quantification of bilobalide and ginkgolides in canine plasma. The analytes were extracted with diethyl
ether-dichloromethane-isopropanol (6:3:1, v/v) after spiking the samples with daidzein (internal standard). The lower limit
of quantification (LLOQ) of the method was 2.5 μg L−1 for ginkgolide B and 10.0 μg L−1 for bilabolide, ginkgolide A and ginkgolide C. The accuracy of the method was within 15% of the actual values over a wide
range of plasma concentrations. The intra-day and inter-day precision was better than 15% (R.S.D.). Finally, the LC-ESI-MS
method was successfully applied to study the pharmacokinetics of ginkgolides and bilabolide after administration of Ginkgo biloba extracts to dogs. 相似文献