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Abstract  

The photolysis of W(CO)6in CH2Cl2 produces (CO)5WCH2Cl2. The high reactivity of (CO)5WCH2Cl2 (1) was exploited to synthesize a vinylidene complexes via the acetylene-vinylidene rearrangement. The addition of a terminal acetylene (H-C≡C-COOCH3) to a solution of (1) produced the η2-acetylene-pentacarbonyltungsten complex (CO)5W(η2-HC≡C-COOCH3) in good yield. The production of the vinylidene complex (CO)5W=C=CH-COOCH3in equilibrium with the acetylene complex in the reaction medium was verified experimentally by reaction with excess imine. The heterocyclic organometallic compound of tungsten obtained was separated and purified and its structure was studied by IR, 1H NMR, 13C NMR and mass spectrometry in comparison with the thermal analysis and elemental analysis data. The final aim of this investigation is the development of a new alternative route to a β-lactame with antibacterial activity.

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Abstract  

Silicon has been found to be an essential element for the growth and development of many ecomomically important plants such as sugarcane, rice, oats, and wheat. A method is described for the quantitative determination of silicon in plant samples. Measurements were made with two Ge(Li) detectors matched with a multiplexing unit to provide a single amplified signal to a computerized analyzer system. For those materials containing greater than 0.5 weight percent silicon, the reaction29Si(n, p)29Al (1273 keV) provides a direct measurement of the quantity of silicon provided the irradiation is done in a special boron nitride capsule to reduce interferences from thermal neutron reactions and a correction is made for the single escape line from28Al (1268 keV). For lesser quantities of silicon, a technique which utilizes the fast neutron reaction28Si(n, p)28Al is preferred. Corrections for the interference produced by the presence of phosphorus31P(n, α)28Al are made by determining the phosphorus content following the instrumental analysis using a unique application of neutron activation analysis, i. e., measurement of tungsten in tungstomolybdophosphoric acid produced when molybdate and tungstate ions are added to dissolved samples of the plant material containing phosphorus. Aluminum, which may also produce an interference by thermal neutron reaction27Al(n, γ)28Al, is determined directly from the original activation data after subtracting out the effect of the phosphorus. Thus, three irradiations in the pneumatic sample irradiator are necessary; one short irradiation (1 min) without thermal neutron shielding, a longer irradiation (6 min) in the boron capsule, and a final irradiation of the tungstomolybdophosphoric acid provide all data required to accurately determine silicon in plant materials. A computer program has been developed that provides rapid reduction of the data in final report format. Elements such as sodium, chlorine, calcium, manganese, potassium, and magnesium extrinsic to the analysis for silicon are also determined by this method. The method has been tested on a large number of samples and reliable results are obtained with less than 0.2 g of sample.

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Abstract  

The use of the antibiotic agent tetracycline for analytical purposes in solvent extraction procedures is presented. Individual extraction curves for the lanthanides, zinc, scandium, uranium, thorium, neptunium and protactinium were obtained. Separation of those elements one from another, and of uranium from selenium, bromine, antimony, barium, tantalum and tungsten was carried out. In all cases benzyl alcohol was the diluent used to dissolve tetracycline hydrochloride. Sodium chloride was used as supporting electrolyte for the lanthanide separations and sodium perchlorate for the other elements mentioned. Stability or formation constants for the lanthanide complexes as well as for thorium complex with tetracycline were determined by using the methods of average number of ligands, the limiting value (for thorium), the two parameters and the weighted least squares. For the lanthanides, the stability constants of the complexes Ln(TC)3 go from 9.35±0.22 for lanthanum up to 10.84±0.11 for lutetium. For the Th(TC)4 complex the formation constant is equal to 24.6±0.3. Radioisotopes of the respective elements were used for the determinations. When more than one radioelement was present in an experiment, a multichannel analyser coupled to Ge(Li) or NaI(Tl) detectors was used for counting the activities. When only one radioisotope was used, counting of the radioisotopes was made with a single-channel analyser (integral mode counting) coupled to a NaI(Tl) detector. Uranium was determined by activation analysis (epithermal neutrons). Radioisotopes of the elements were obtained by irradiation in the IPEN swimming-pool reactor. The natural radioisotope2 3 4Th was used as label in the thorium experiments. In some separation procedures such as in the case of the pair uranium-neptunium, and of the pair scandium-zinc, the separation was obtained by properly adjusting the pH value of the aqueous phases, before the extraction operation. In other cases, addition of masking agents to the extraction system was required in order to perform the separation between the elements under study. In this way ethylenediaminetetraacetic acid (EDTA) was used as masking agent for scandium and the lanthanides in order to allow separation of uranium from those elements. Diethylenetriaminepentaacetic acid (DTPA) was used as masking agent for thorium in order to extract uranium into the organic phase. Separations of protactinium from thorium, and of uranium from protactinium and thorium, were accomplished by using sodium fluoride as masking agent for protactinium and DPTA as masking agent for thorium and protactinium at the same time. In the case of the separation of the lanthanides one from another it is necessary to resort to a multi-stage extraction procedure since the stability constants for those elements are too close.

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fabrication, thermal processing and characterization of novel electroceramic materials with tetragonal tungsten bronze structure. In general, a special interest was directed on modelling relaxation processes in polar dielectric ceramics and investigating the

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tungsten oxide. Sensors and Actuators B: Chemical, 76, 624–628. Chen Y.C. Study on the temperature effect, hysteresis and drift of pH-ISFET devices based on amorphous tungsten oxide

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Journal of Thermal Analysis and Calorimetry
Authors: Imre Miklós Szilágyi, Eero Santala, Mikko Heikkilä, Marianna Kemell, Timur Nikitin, Leonid Khriachtchev, Markku Räsänen, Mikko Ritala, and Markku Leskelä

paratungstate (APT), (NH 4 ) 10 [H 2 W 12 O 42 ]·4H 2 O at 200–250 °C [ 46 , 47 ], though other studies could not confirm this [ 48 ]. The thermal behavior of APT is very well known as it is an important starting material for making tungsten oxides, tungsten

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samples depends on the type of tungsten precursor (WCl 6 > (NH 4 ) 6 H 2 W 12 O 40 > H 2 WO 4 ) [ 18 ]. Here we present the photocatalytic degradation of Malachite Green (MG) with composite thin films TiO 2 /WO 3 . Since 1933 [ 19 ], the MG dye

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Acta Alimentaria
Authors: M. Anke, M. Seifert, W. Arnhold, S. Anke, and U. Schäfer

Brill, W.J., Ela, S.W. & Breznak, J.A. (1987): Termite killing by molybdenum and tungsten compounds. Naturwiss. , 74 , 494–495. Breznak J.A. Termite killing by molybdenum

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. “Continuous flow synthesis of tungsten oxide (WO3) nanoplates from tungsten(VI) ethoxide” M. Gimeno-Fabra , P. Dunne , D. Grant , P. Gooden , E. Lester * Chemical Engineering Journal 2013 , 226 , 22 – 29 . “A continuous

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Reaction Kinetics, Mechanisms and Catalysis
Authors: Susana Pinto-Castilla, Santiago Marrero, Yraida Díaz, Joaquín L. Brito, Pedro Silva, and Paulino Betancourt

, Boudart , M 1985 Compounds of molybdenum and tungsten with high specific surface area: II. Carbides . J Solid State Chem 59 : 348 – 356 10.1016/0022-4596(85)90302-0 . 13. Zhao , Z , Liu

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