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991.
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
992.
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
993.
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
994.
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
995.
996.
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
997.
Rasa Pauliukaite Mariana Emilia Ghica Madalina Barsan Christopher M. A. Brett 《Journal of Solid State Electrochemistry》2007,11(7):899-908
The polymer redox mediator, poly(neutral red) (PNR), has been synthesised and characterised electrochemically to investigate
the best electropolymerisation and mediation conditions for application in enzyme biosensors and to clarify the mechanism
of action. Neutral red was electropolymerised by potential cycling on carbon film electrode substrates by allowing the monomer
to be oxidised during the full 20 cycles of polymerisation or reducing the positive limit of the potential window after the
first 2 cycles to impede monomer oxidation with a view to obtaining longer polymer chains and a lesser degree of branching.
Comparison was made with glassy carbon substrates. The PNR films on carbon film electrodes were characterised using cyclic
voltammetry and electrochemical impedance spectroscopy, as well as in glucose biosensors prepared with PNR. Glucose oxidase
enzyme was immobilised by encapsulation in silica sol-gel and compared with that obtained by cross-linking with glutaraldehyde.
The biosensors were evaluated by chronoamperometry in 0.1 M phosphate buffer saline solution, pH 7.0, and showed evidence
of electron transfer between the enzyme cofactor flavin adenine dinucleotide and PNR dissolved in the enzyme layer competing
with PNR-mediated electrochemical degradation of H2O2 formed during the enzymatic process.
This paper is dedicated to Professor Dr. Algirdas Vaskelis on the occasion of his 70th birthday. 相似文献
998.
Woll MG Fisk JD LePlae PR Gellman SH 《Journal of the American Chemical Society》2002,124(42):12447-12452
A stereoselective synthetic route is reported for the introduction of side chains at the 3-position of trans-2-aminocyclopentanecarboxylic acid (ACPC). Ring opening of the aziridine 2-benzyloxymethyl-6-azabicyclo[3.1.0]hexane with selected nucleophiles occurs in a regioselective manner and provides ACPC precursors with functional groups at the 3-position, trans to the 2-amino group. Oligomers composed of the 3-substituted ACPC residues maintain the 12-helical conformation displayed by the nonsubstituted analogues, as shown by their similar circular dichroism signatures. The added diversity of the new residues provides good dispersion of NMR signals, allowing the assignment of nearly all the NOE signals of a selected hexamer in aqueous solution. The NOEs between protons on nonadjacent residues are characteristic of the 12-helix. 3-Substituted ACPC residues allow one to arrange specific functional groups in a geometrically defined fashion, which should facilitate the design of beta-peptides for biological applications. 相似文献
999.
Matthew S. Johnson Keith T. Kuwata Chi-Kin Wong Mitchio Okumura 《Chemical physics letters》1996,260(5-6):551-557
The infrared spectrum of the ionic cluster I−(H2O) was recorded from 3170 to 3800 cm−1 by vibrational predissociation spectroscopy. A strong multiplet observed at 3415 cm−1 and a narrow band at 3710 cm−1 were assigned as a hydrogen-bonded OH stretch and free OH stretch respectively, indicating that H2O forms a single hydrogen bond with the iodide anion. Ab initio vibrational frequencies and intensities were computed at the second-order Møller-Plesset (MP2) level for the minimum energy configuration, a nearly linear hydrogen-bonded isomer, and for a low-lying saddlepoint, a symmetric C2v bridged isomer. The spectrum predicted for the hydrogen-bonded isomer agreed well with experiment. 相似文献
1000.
Ana C. D. Medeiros Lidiane P. Correia Mônica O. da S. Simões R. O. Macêdo 《Journal of Thermal Analysis and Calorimetry》2007,88(2):311-315
A number of disintegrants
are available on the market. They improve tablets’ disintegration. The
objective of this work is the comparison of the technological quality parameters
of disintegrants using different analytical techniques. Three batches of disintegrants
and their binary mixtures (water:disintegrants) were investigated. Cooling
experiments were used from –30 up to 200°C. The data obtained showed
calorimetric differences between the samples. In the binary mixtures water
showed different crystallization behaviour from the one found in the literature.
According to the results DSC technique helped the quality control of different
disintegrants. 相似文献