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901.
Summary. An efficient direct conversion of THP ethers into the corresponding acetates was achieved with acetic anhydride in the presence of CuSO4 · 5H2O as an available and green catalyst in high yields. 相似文献
902.
The use of fenugreek mucilage, a natural polysaccharide and a direct food additive, as a flocculating agent for removal of suspended and dissolved solids from sewage effluent has been reported. A flocculation study has been done by the standard jar test method. The percent removal of suspended solid (SS) and dissolved solid (TDS) was determined by varying the polymer dose, pH and contact time. X-ray diffraction patterns of the solid waste material of mucilage and flocs (so obtained after treatment) were used to suggest the incorporation of the crystalline waste material in the mucilage. The optimal mucilage concentration was found to be 0.16 mg/l. The suitable pH range for maximum solid removal (SS and TDS) was alkaline and the time required for treatment was 1-3 h. 相似文献
903.
In the EURACHEM/CITAC draft ”Quantifying uncertainty in analytical measurement” estimations of measurement uncertainty in
analytical results for linear calibration are given. In this work these estimations are compared, i.e. the uncertainty deduced
from repeated observations of the sample vs. the uncertainty deduced from the standard residual deviation of the regression.
As a result of this study it is shown that an uncertainty estimation based on repeated observations can give more realistic
values if the condition of variance homogeneity is not correctly fulfilled in the calibration range. The complete calculation
of measurement uncertainty including assessment of trueness is represented by an example concerning the determination of zinc
in sediment samples using ICP-atomic emission spectrometry.
Received: 9 February 2002 Accepted: 17 April 2002 相似文献
904.
Aamer Saeed 《Chemistry of Heterocyclic Compounds》2007,43(8):1072-1075
An efficient, rapid, microwave-accelerated one-step synthesis of some 5-aryl-2-(2-hydroxy-phenyl)-1,3,4-oxadiazoles by reaction
of salicylic hydrazide with carboxylic acids in the presence of thionyl chloride under neat conditions is described.
__________
Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1264–1267, August, 2007. 相似文献
905.
The relativistic ground and low-lying excited state potential energy curves of AgH and AuH in the presence of a cylindrical
harmonic confining potential were calculated using the multi-state multi-reference perturbation theory with the spin-free
no-pair Hamiltonian obtained via the third-order Douglas–Kroll transformation, incorporated with the full two-electron Breit–Pauli
spin–orbit operator. The spectroscopic parameters were obtained for both the scalar- and quasi-relativistic potentials. The
spin–orbit coupling constants were calculated for several strengths of the confining potential, and the effects of the applied
potential on the coupling constants were analyzed using configuration interaction.
This paper is dedicated to Serafín Fraga—colleague, mentor, and friend. 相似文献
906.
The boundary effect on the drag on two identical, nonuniformly structured flocs moving along the axis of a cylindrical tube
filled with a Newtonian fluid is investigated at a small to medium larger Reynolds number. A two-layer model is adopted to
simulate various possible structures of a floc, and the flow field inside is described by Darcy–Brinkman model. The results
of numerical simulation reveal that a convective flow is present in the rear region of a floc when Reynolds number is on the
order of 40. The presence of the tube wall and/or the porous structure of a floc has the effect of reducing that convective
flow. For a fixed level of the volume-average permeability of a floc, the influence of the tube wall on the drag depends upon
floc structure; the influence on a nonuniformly structured floc is more significant than that on a uniformly structured floc.
The more nonuniform the floc structure, the more appreciable the deviation of the drag coefficient–Reynolds number curve from
a Stokes’-law-like relation becomes. The smaller the volume-average permeability of a floc and/or the smaller the separation
distance between the two flocs, the greater is the deviation, but the presence of the tube wall has the effect of reducing
that deviation. 相似文献
907.
Antonio Doménech María Teresa Doménech-Carbó María Luisa Vázquez de Agredos Pascual 《Journal of Solid State Electrochemistry》2007,11(9):1335-1346
The preparation of indigo from Indigofera suffruticosa following the procedures attributed to ancient Mayas was electrochemically monitored using the voltammetry-of-microparticles
approach. The mechanism formation of indigotin and indirubin from its precursors, indican and isatan, is discussed. Comparison
of voltammetric profiles for differently prepared and commercial indigos and genuine Maya Blue samples suggests that the preparation
procedure of indigo changed during the Late Classical Maya period.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
908.
Di Bussolo V Caselli M Romano MR Pineschi M Crotti P 《The Journal of organic chemistry》2004,69(21):7383-7386
The reaction of alpha vinyl oxirane 5, prepared through a new route to the d-gulal system, with O-nucleophiles (alcohols and di-O-isopropylidene-alpha-d-monosaccharides) and C-nucleophiles (lithium alkyls) affords, in a completely stereoselective way, the corresponding 2-unsaturated alpha O- and C-glycosides having the same configuration as the starting epoxide. 相似文献
909.
The oxidation of 2-phenyl-3-arylaminoindoles (1a–e) has been studied in acetonitrile, dimethylformamide and propylene carbonate at a new type of platinum electrode with periodical renewal of the diffusion layer and at a rotating platinum electrode by cyclic voltammetry, d.c. and a.c. voltammetry, controlled potential coulometry and spectrometry (e.s.r. and u.v.). In the examined aprotic solvents and in the presence of a base (like water or diphenylguanidine) amines 1a–e undergo a two-electron oxidation to the corresponding imines. In a protophobic medium (acetonitrile or propylene carbonate) 1a–e are oxidized in two one-electron steps, the first of which leads to the formation of a cation radical (identified by e.s.r. spectrum), oxidizable at more positive potentials (second step). The second electron transfer, however, must be simultaneous with, or be immediately followed by, a very fast deprotonation reaction. The same e.e.c. sequence explains the observed bielectronic step of 1a–e in a protophilic aprotic solvent, like dimethylformamide. 相似文献
910.
JongHwa Moon SangHoon Kang YongSam Chung OkHee Lee 《Journal of Radioanalytical and Nuclear Chemistry》2007,271(1):155-158
Instrumental neutron activation analysis was used to assess the concentration of the inorganic trace elements in Korean women’s
blood serums. It was found that a high concentration of Na and Cl incurs an analytical interference, but the 12 elements such
as Br, Ca, Cl, Co, Cr, Cs, Fe, K, Na, Rb, Se and Zn could be determined under the condition of an interference minimization.
Serum samples collected from 63 women were analyzed and the concentration level and range of the elements were evaluated.
NIST SRMs were analyzed simultaneously for quality control. The average values of the Na and Cl determined in the serum samples
were 3,365 and 3,533 mg/l, Ca was 96.4 mg/l and K was 191 mg/l. Besides, Br, Se and Zn have a concentration level of 6.46,
0.13 and 0.98 mg/l, respectively. It was found that there is no significant difference between the present values and the
reported values. 相似文献