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71.
Uniform sodium jarosite particles were obtained by forced hydrolysis of ferric salt solutions to which copper sulfate, sodium
sulfate, and sodium nitrate were added. It was found that at the same concentrations of ferric and sulfate ions the particle
size and yield decreased with the lowering of the concentration of sodium ions, but the morphology remained the same. At a
sufficiently small content of sodium in the reacting solution, no precipitation of sodium jarosite particles was observed.
Finally, chemical and XRD analyses showed that small amounts of copper ions are incorporated in the crystal lattice which,
with the change in the Na+/H3O+ ratio, slightly affected the structure of this mineral, but not its other properties.
Received: 12 July 2000 Accepted: 18 August 2000 相似文献
72.
We have recently developed a global optimization methodology for solving combinatorial problems with either deterministic or stochastic performance functions. This method, the Nested Partitions (NP) method has been shown to generate a Markov chain and with probability one to converge to a global optimum. In this paper, we study the rate of convergence of the method through the use of Markov Chain Monte Carlo (MCMC) methods, and use this to derive stopping rules that can be applied during simulation-based optimization. A numerical example serves to illustrate the feasibility of our approach. 相似文献
73.
Borwein, Bojanov, Erdélyi, and others, have studieddensity and approximation properties of those Markov systems of differentiablefunctions on a closed interval [a,b], having the property thatthe system of derivatives is a Markov system on the open interval (a,b).In this paper we show that several of these results are valid for anyMarkov system of continuous functions on a closed interval. 相似文献
74.
Pashirova T. N. Zhil´tsova E. P. Lukashenko S. S. Zakharova L. Ya. Konovalov A. I. 《Russian Chemical Bulletin》2015,64(12):2879-2884
Russian Chemical Bulletin - It is established by spectrophotometry that polyethyleneimines, mono- (MQD) and diquaternized (DQD) hexadecyl derivatives of 1,4-diazabicyclo[2.2.2]octane, and mixed... 相似文献
75.
Shiryaev A. K. Belen´kaya R. S. Shiryaev V. A. Rybakov V. B. Klimochkin Yu. N. 《Russian Chemical Bulletin》2015,64(12):2966-2969
Russian Chemical Bulletin - Methyl adamantane-1-carboxylate and methyl (1-adamantyl)acetate react with acetonitrile in the presence of sodium hydride to give 3-(1-adamantyl)-3-oxopropanenitrile and... 相似文献
76.
77.
M. Violante de Paz Ba´ñez Jose´ A. Aznar Moreno 《Journal of carbohydrate chemistry》2013,32(2):120-140
Biodegradable polymers obtained from renewable natural sources are currently receiving increasing attention because they are an alternative to the traditional petroleum‐based plastics. In the present communication we describe the synthesis of the diol monomers 2,3,4‐tri‐O‐benzyl‐L‐arabinitol (ABnOH) and 2,3,4‐tri‐O‐benzylxylitol (XBnOH), and the diamino monomers 1,5‐diamino‐1,5‐dideoxy‐2,3,4‐tri‐O‐benzyl‐L‐arabinitol (ABnNH 2 ) and 1,5‐diamino‐1,5‐dideoxy‐2,3,4‐tri‐O‐benzylxylitol (XBnNH 2 ), which can be used in the preparation of new potentially biodegradable sugar‐based polymers. As an example, we describe the synthesis and characterization of a polyurethane [PU‐(ABnOH‐HMDI)] and a polyurea [PUR‐(ABnNH2‐HMDI)] by poly addition reaction of ABnOH and ABnNH 2 with 1,6‐hexamethylene diisocyanate. 相似文献
78.
He´ctor J. Sussmann 《Journal of Differential Equations》1979,31(1):31-52
The theory of subanalytic sets is used to prove: If a real analytic control system is completely controllable, then for every point p in the state space there exists a piecewise analytic feedback control that steers every state into p. 相似文献
79.
The aim of this study was to examine the impact of osmotic pressure, regulated by an addition of different NaCl concentrations, on the production parameters and activity of the enzymes involved in the biosynthesis of erythritol from glycerol by Yarrowia lipolytica yeast. In the bioreactor batchcultures, strain A-3 was able to produce from 25.3 g dm?3 to 84.7 g dm?3 of erythritol from 150 g dm?3 of glycerol depending on the initial osmotic pressure. At the osmolality of 4.2 mol kg?3 or higher, a long lag-phase was observed. An enhancement of the production parameters was observed in a culture with the osmotic pressure maintained at an equal level by a step-wise addition of NaCl. The two-hour exposure of strain A-3 cells to 75 g dm?3 of NaCl resulted in decreased activity of glycerol kinase and glycerol-3-phosphate dehydrogenase by about 78 % and 25 %, respectively. The activity of transketolase and erythrose reductase remained unchanged after the salt addition. It was demonstrated that assimilation of glycerol was effective at lower osmotic pressures and that transketolase and erythrose reductase played a significant role in the erythritol formation in Y. lipolytica. 相似文献
80.
Agnieszka Pazik Beata Kami´nska Anna Skwierawska Sandra Nakonieczna Tadeusz Ossowski 《Chemical Papers》2016,70(3):253-264
The synthesis of a new chromogenic N,N′-phenyltetrazole receptor is reported here. The cationbinding properties of this receptor in solution were investigated by naked-eye colour change, electrochemical methods and UV-Vis spectroscopy in various solvents (CH3CN, dimethylsulphoxide (DMSO), DMSO/H2O, CH3CN/H2O and CH3CN/MeOH). In addition, the receptor was used as a sensing material in ion-selective membrane electrodes. The selectivity and sensitivity of these electrodes towards alkali, alkali-earth, transition and heavy metal cations in aqueous solution were tested. The relation between the carrier structure and membrane plasticisers was investigated. 相似文献