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991.
The crystal structure of Sr4Mn2NiO9 has been refined on single crystal. This phase belongs to the series A1+x(A′xB1–x)O3 (x=1/3) related to the 2H-hexagonal perovskite. The structure contains transition metals in chains of oxide polyhedra (trigonal prisms and octahedra); neighboring chains are separated from each other by the Sr atoms. The sequence of the face sharing polyhedra along the chains is two octahedra + one trigonal prism. Mn occupies the octahedra and Ni is disordered in the trigonal prism with ≈80% in the pseudo square faces of the prism and ≈20% at the centre. This result has been confirmed by XANES experiments at Mn K and Ni K edges, respectively. Sr4Mn2NiO9 is antiferromagnetic with a Néel temperature at T=3 K. The Curie constant measured at high temperature is in good agreement with ≈80% of the Ni2+ ions in the spin state configuration S=0. 相似文献
992.
Mançour-Billah S. Aït Hmaïdouch L. El Hadek M. Cohen-Adad R. 《Journal of Thermal Analysis and Calorimetry》2000,62(3):781-795
A program has been written to describe solubility surfaces of the polythermal ternary phase diagram Mg(NO3)2–Al(NO3)3–H2O, using the model proposed by Cohen-Adad et al. [2]. In this work we present the calculation of the solubility surface of Mg(NO3)2×6H2O and Al(NO3)3×9H2O in the phase diagram. The calculated isothermal sections are in a good agreement with experimental determinations. Coefficients
of the fitting equation that describes the solubility field allow drawing any isothermal section. The monovariant line was
also calculated. The chosen model is well adapted to calculations of these solubility surfaces and gives very good results.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
993.
A. Atbir L. Aneflous A. Marrouche M. El Hadek R. Cohen-Adad M.-Th. Cohen-Adad 《Journal of Thermal Analysis and Calorimetry》2000,59(3):893-900
Polytherm diagram of the ternary system KCl–FeCl2 –H2 O between 0 and 70°C. Phase equilibria in the KCl–FeCl2 –H2 O system were studied over the temperature range 0–70°C by conductimetric and analytical methods.
A solubility polytherm of the system was constructed. We have observed the crystallization fields of the KCl and FeCl2 6H2 O (at 0°C), KCl and FeCl2 4H2 O (at 15, 30 and 40°C) and KCl, FeCl2 4H2 O and of a double salt KClFeCl2 2H2 O are obtained at 70°C.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
994.
Bouchra Filali Baba Abdelali Kerbal Najib Bitit Brahim El‐Bali Jean Escudie Henry Ranaivonjatovo Michael Bolte 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(5):e205-e206
The title compound, C19H15NO6, contains a planar isoxazole ring. An intramolecular hydrogen bond is formed between the OH group attached to a phenyl ring and a carbonyl O atom. 相似文献
995.
Mustapha Aitali Larbi El Firdoussi Abdellah Karim Alejandro F. Barrero Miguel Quirs 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(9):1088-1089
The title compound, [(S)‐2‐(anilinomethyl)pyrrolidine‐N,N′]‐chloro(η6‐para‐cymene)ruthenium(II) chloride, [RuCl‐(C10H14)(C11H16N2)]Cl, has been synthesized by the reaction of [RuCl2(p‐cymene)]2 (p‐cymene is para‐isopropyltoluene) with (S)‐2‐(anilinomethyl)pyrrolidine in triethylamine/2‐propanol. The Ru atom is in a pseudo‐tetrahedral environment coordinated by a chloride ligand, the aromatic hydrocarbon is linked in a η6 manner and the amine is linked via its two N atoms. The chloride anion is involved in hydrogen bonding with the diamine moieties through N—H?Cl interactions, with N?Cl distances of 3.273 (4) and 3.352 (4) Å. 相似文献
996.
L. El?i M. Soylak A. Uzun E. Büyükpatr M. Doan 《Fresenius' Journal of Analytical Chemistry》2000,368(4):358-361
A simple flame atomic absorption spectrometric (FAAS) procedure for the determination of lead, bismuth, gold, palladium and
cadmium as impurities in Raney nickel and nickel oxide was developed using a preconcentration step on an Amberlite XAD-16
resin packed column. Lead, bismuth, gold, palladium and cadmium were quantitatively recovered and separated from a solution
containing 1 M HCl and 0.3 M NaI by the column system. Effects of the various parameters such as reagent concentrations, sample
volume, matrix effects, etc. have been investigated. Under optimized conditions, the relative standard deviation of the combined
method of sample treatment, preconcentration and determination with FAAS (n = 7) is generally lower than 12%. The limit of detection (3s, n = 20) was between 10–270 ng/g. The results were used for separation and preconcentration of five trace elements from nickel
matrices.
Received: 8 February 2000 / Revised: 31 March 2000 / Accepted: 7 April 2000 相似文献
997.
Saadia M. El-Ashry Fathalla Belal Mohamed M. El-Kerdawy Dalia R. El Wasseef 《Mikrochimica acta》2000,135(3-4):191-196
A simple and sensitive spectrophotometric method is described for the determination of some phenolic antibiotics namely:
cefadroxil, amoxicillin and vancomycin. The method is based on the measurement of the orange yellow species produced when
the drugs are coupled with diazotized benzocaine in triethylamine medium. The method is applicable over the range of 0.8–12 μg/ml
for cefadroxil, 2–16 μg/ml for amoxicillin and 2–18 μg/ml for vancomycin. The formed compounds absorb at 455 nm for both cefadroxil
and amoxicillin and at 442 nm for vancomycin. The proposed method has detection limits of 0.018 μg for cefadroxil, 0.0034 μg
for amoxicillin and 0.0156 μg for vancomycin.
The stoichiometric ratio for the studied compounds was found to be 1:1 and a proposal of the reaction pathway was made. The
proposed method was applied for the analysis of the cited drugs in their pharmaceutical preparations. The results are in good
agreement with those obtained by the official methods.
Received February 7, 2000. Revision June 14, 2000. 相似文献
998.
One‐Pot synthesis of isothiachromene,isochromene, isoquinoline and tetrahydronaphthalene derivatives
A new series of tetrahydronaphthalene, isothiachromene, isochromene and isoquinoline derivatives were synthesized by reacting cyclohexylidenemalononitrile with active nitriles, active halo compounds, carbon disulfide, aldehydes, isothiocyanates and isocyanates, respectively. 相似文献
999.
Adam Khatir Sam M. M. O. Ahamed F. El Khangi P. Roos 《Journal of Radioanalytical and Nuclear Chemistry》2000,245(2):411-414
This paper presents the activity concentrations of Pu isotopes in surface marine sediments collected from the Sudanese coast of the Red Sea. The following concentration ranges were determined: 238Pu, 4.7–28.6 mBq/kg; 239+240Pu, 53–343 mBq/kg dry weight. The average activity ratios of 238Pu/239+240Pu (0.075±0.045 mBqk/kg) and 239+240Pu/137Cs (0.026±0.025 mBq/kg) are appropriately comparable to the literature values that are characteristic of the global fallout from the atmospheric nuclear weapon tests. However, 239+240Pu/137Cs ratio in sediments collected from the biologically rich fringing reef is an order of magnitude higher compared to other sampling locations. 相似文献
1000.
Rene S. Schwartz Norman G. Lederman Fouad Abd‐El‐Khalick 《School science and mathematics》2000,100(4):181-193
This report describes an evaluation project that aimed to assess the potential of two elementary science specialists, as compared to elementary classroom teachers, to realize the reforms vision for science instruction in elementary classrooms. Participant science specialist background, views of elementary science teaching, and planning and assessment practices were compared to those of regular elementary classroom teachers in the specialist district, as well as in a comparable district not employing specialists. Specialists' views and practices were better aligned with those envisioned by current national reform documents in science education. Despite the constraints imposed by the nature of a program evaluation, the present report provides evidence to suggest that students taught by the science specialists (a) were engaged in open‐ended, inquiry‐oriented, science‐based activities of the kind often advocated, but mostly absent, in elementary school, and (b) demonstrated problem solving and higher order and critical thinking skills. This report is the first to provide empirical support for the advocated “effectiveness” of elementary science specialists in achieving the visions espoused by current reform efforts. 相似文献