Nickel-containing MCM-41 materials, influence of the preparation procedures on the catalytic activity in toluene hydrogenation

Summary  Vezetéknév     

Effect of the surface/bulk doping of lanthanum manganite on the oxygen mobility, reactivity and catalytic activity in the CO oxidation

Summary  Vezetéknév     

Palladium(II) complexes with the new P,N-type ligand (2-oxazoline-2-ylmethyl)di-isopropylphosphine as intermediates in CO/ethylene or CO/methyl acrylate insertion

The ligand (i-Pr)₂PCH₂(oxazoline) (1a), of the P,N-donor type, was reacted with [PdMeCl(COD)] to yield the square planar methylpalladium(II) complex [PdClMe(P,N)] (P,N = 1a) (2a), from which the complex [PdMe(P,N)OTf] (OTf = OSO₂CF₃) (3a) was obtained by AgOTf-promoted chloride abstraction. The alkyl complexes

(P,N = 1a) (5a, R = H; 7a, R = C(O)OMe) have been isolated from the initial CO/ethylene or CO/methyl acrylate insertion steps into the Pd–Me bond of 3a, respectively, and spectroscopically characterized. Complexes 2a, 3a and 7a have been fully characterized by single crystal X-ray diffraction. Complex 7a is still a rare example of a structurally characterized CO/methyl acrylate stepwise insertion product. These complexes are relevant to the alternating copolymerization of olefins and carbon monoxide catalyzed by palladium complexes. In addition, the centrosymmetric dinuclear complex trans-[Pd(μ-Cl){(i-Pr)₂PCH₂(oxazoline)}]₂(OTf)₂ (6) has been obtained and characterized by X-ray diffraction; it appears to be the first dinuclear complex of the type [Pd(μ-Cl)(P,N)]₂ to be characterized by X-ray crystallography.

Résumé

Le ligand (i-Pr)₂PCH₂(oxazoline) (1a), de type donneur P,N, réagit avec [PdClMe(COD)] pour former le complexe plan carré méthylpalladium(II) [PdClMe(P,N)] (P,N = 1a) (2a), à partir duquel le complexe [PdMe(P,N)OTf] (OTf = OSO₂CF₃) (3a) a été obtenu par abstraction de chlorure à l'aide de AgOTf. Les complexes alkyles

(P,N = 1a) (5a, R = H; 7a, R = C(O)OMe), ont été isolés lors des premières étapes d'insertion de CO/éthylène ou de CO/acrylate de méthyle, respectivement, dans la liaison Pd–Me de 3a, et caractérisés par méthodes spectroscopiques. Les complexes 2a, 3a et 7a ont été complètement caractérisés par diffraction des rayons X sur monocristal. Le complexe 7a est un exemple encore rare de produit d'insertion par étapes de CO/acrylate de méthyle qui ait été caractérisé structuralement. Ces complexes sont pertinents pour la copolymérisation alternée d'oléfines et de monoxyde de carbone catalysée par les complexes du palladium. En outre, le complexe dinucléaire centrosymétrique trans-[Pd(μ-Cl){(i-Pr)₂PCH₂(oxazoline)}]₂(OTf)₂ (6) a été obtenu et caractérisé par diffraction des rayons X; il s'agit du premier complexe dinucléaire de type [Pd(μ-Cl)(P,N)]₂ à être caractérisé par diffraction des rayons X.     

Hydrodechlorination of chloroalkanes on supported platinum catalysts

Summary  Vezetéknév     

The activity of Au supported on various types of carbon in the ring transformation reactions of methyloxirane

Summary  Vezetéknév     

Distribution and location of selenium and other elements in different mitochondrial compartments of human liver by neutron activation analysis

Summary  Vezetéknév     

Diffusion of 99Tc in granite under aerobic and anoxic conditions

Summary  Vezetéknév     

Oscillatory reactions in the lactic acid/acidic bromate system with a tetraazamacrocyclic nickel(ii) complex as catalyst

Summary  Vezetéknév     

Systematic errors in isothermal micro- and nanocalorimetry</o:p>

Summary  Vezetéknév     

Theoretical prediction of the structural,elastic, electronic,optical and thermal properties of the cubic perovskites CsXF3 (X = Ca,Sr and Hg) under pressure effect

Some physical properties of the cubic perovskites CsXF₃ (X = Ca, Sr and Hg) have been investigated using pseudopotential plane-wave method based on the density functional theory. The calculated lattice parameters within GGA and LDA agree reasonably with the available experimental data. The elastic constants and their pressure derivatives are predicted using the static finite strain technique. We derived the bulk and shear moduli, Young's modulus, Poisson's ratio and Lamé’s constants for ideal polycrystalline aggregates. The analysis of B/G ratio indicates that CsXF₃ (X = Ca, Sr and Hg) are ductile materials. The thermal effect on the volume, bulk modulus, heat capacity and Debye temperature was predicted.     

Synthesis of amino-modified magnetite nanoparticles coated with Hepama-1 and radiolabeled with 188Re for bio-magnetically targeted radiotherapy

Summary  Elérh     

Synthesis,characterization and X-ray crystal structure of cyclam derivatives. Part III. Formation and electrochemically induced isomerization of copper complexes of 1,8-bis(N,N-dimethylcarbamoylmethyl)-4,11-dimethyl-1,4,8,11-tetraazacyclotetradecane

The synthesis, spectroscopic study and X-ray structural data of two different isomers of [copper(II)1,8-bis(N,N-dimethylcarbamoylmethyl)-4,11-dimethyl-1,4,8,11-tetraazacyclotetradecane] (BF₄)₂ are reported. This study clearly shows that the two complexes are of I and trans-III configurations, respectively (Bosnich representation). The electrochemical activation of these two derivatives is also reported as well as that of related compounds. Although interconversion between the two copper species cannot be chemically induced, the electrochemical reduction of both complexes promotes the isomerization process. © 2000 Académie des sciences / Éditions scientifiques et médicales Elsevier SAScyclam derivatives / copper / electrochemical activation / tetraazamacrocycles     

99mTc-Exorphin-glucuronide in tumor diagnosis: Preparation and biodistribution studies in rats

Summary  Elérh     

Determination of lead,cadmium and mercury in blood for assessment of environmental exposure: A comparison between inductively coupled plasma–mass spectrometry and atomic absorption spectrometry

A biomonitoring method for the determination of Pb, Cd, and Hg at background levels in whole blood by inductively coupled plasma-mass spectrometry is described. While this method was optimized for assessing Pb, Cd and Hg at environmental levels, it also proved suitable for assessing concentrations associated with occupational exposure. The method requires as little as 200 μl of blood that is diluted 1 + 49 for direct analysis in the inductively coupled plasma-mass spectrometer. Method performance is compared to well-established AAS methods. Initial method validation was accomplished using National Institute of Standards and Technology (NIST) Standard Reference Material 966, Toxic Metals in Bovine Blood. Method detection limits (3s) are 0.05 μg dl^− 1 for Pb, 0.09 μg l^− 1 for Cd; and 0.17 μg l^− 1 for Hg. Repeatability ranged from 1.4% to 2.8% for Pb; 3% to 10% for Cd; and 2.6% to 8.8% for Hg. In contrast, AAS method detection limits were 1 μg dl^− 1, 0.54 μg l^− 1, and 0.6 μg l^− 1, for Pb, Cd, and Hg, respectively. Further performance assessments were conducted over a 2-year period via participation in four international External Quality Assessment Schemes (EQAS) operated specifically for toxic metals in blood. This includes schemes operated by (a) the New York State Department of Health's Wadsworth Center, Albany, NY, USA (b) L′Institut National de Santé Publique du Québec, Centre de Toxicologie du Québec, Canada, (c) Friedrich-Alexander University, Erlangen, Germany, and (d) the University of Surrey, Guildford, UK Trace Elements scheme. The EQAS data reflect analytical performance for blind samples analyzed independently by both inductively coupled plasma-mass spectrometry and AAS methods.     

Analyse des lanthanides,du hafnium,du scandium,du chrome,du manganese,du cobalt,du cuivre et du zinc dans les mineraux et les roches par activation neutronique

Résumé Pour utiliser au mieux les possibilités de l'analyse par activation et de la spectrométrie γ à l'aide des détecteurs à semi-conducteurs, nous proposons des schémas de séparations rapides qui permettent d'effectuer les analyses de routine des lanthanides, du scandium, du chrome, du manganèse, du cobalt, du cuivre et du zinc, dans la plupart des minéraux et des roches avec une précision comprise entre 3 et 10%. La méthode a été appliquée à une grande variété d'échantillons et testée sur des standards. Nous montrons par quelques exemples tout son intérêt dans les études géochimiques systématiques des éléments de transition.     

Dosage de l'arsenic,du selenium,du telure,dans le soufre elementaire

Résumé Ces trois éléments et particulièrement l'arsenic sont des poisons pour les catalyseurs d'oxydation d'anhydride sulfureux en anhydride fulfurique. L'analyse par activation permet de doser simultanément ces trois éléments dans le soufre. Après irradiation le soufre est mis en solution en présence de soude et de sulfure de carbone. L'analyse est effectuée de manière instrumentale lorsque les teneurs en As, Se et Te sont supérieures à 1 ppm. Pour les concentrations inférieures on effectue des séparations chimiques avec ajoute d'entra?neurs.     

3He activation analysis for S,Cl, K and Ca

Résumé On utilise trois radioisotopes facilement détectés³⁸Cl,^34mCl et³⁸K, produits à partir du soufre, du chlore, de la potasse et du calcium pour doser ces éléments par activation au³He. On a analysé un certain nombre d'échantillons de fa?on non-destructive en utilisant différentes réactions nucléaires pour examiner la précision de la méthode et l'étendue des interférences. On donne les fonctions d'excitation absolue pour les réactions nucléaires aux hélions 3.

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Work was performed under the auspices of the U. S. Atomic Energy Commission.     

The influence of crystal packing on second-order non-linear optical properties of new chiral ferrocenyl materials

New chiral enantiomerically pure ferrocenyl chromophores for non-linear optics (NLO) have been synthesized and their crystal structures were determined by X-ray analysis. The correlation between crystal packing and bulk NLO efficiency was studied exemplifying again the difficulty to preview crystal packing from the molecular structure. © 2000 Académie des sciences / Éditions scientifiques et médicales Elsevier SASferrocene / chiral non-racemic / non-linear optics / X-ray structure/ crystal packing     

IRMM-3100a: A new certified isotopic reference material with equal abundances of 233U, 235U, 236U and 238U

The new so-called Quad-IRM (“Quadruple Isotope Reference Material”) was prepared from highly enriched ²³³U, ²³⁵U, ²³⁶U and ²³⁸U isotopic materials using an optimized combination of gravimetrical mixing and mass spectrometry. Within the mixing process the isotope ratios were adjusted to about n(²³³U)/n(²³⁵U)/n(²³⁶U)/n(²³⁸U) = 1/1/1/1 and certified with expanded relative uncertainties of 0.0054% per mass unit (coverage factor k = 2). This new isotope reference material is ideal for verifying the inter-calibration of multi-detector systems in isotope mass spectrometry.The certified n(²³³U)/n(²³⁶U) ratio of IRMM-3100a was derived from the mass metrology data of the gravimetrical mixing of highly enriched ²³³U and ²³⁶U materials. It was verified by thermal ionization mass spectrometry (TIMS) measurements using the classical total evaporation (TE) and modified total evaporation (MTE) methods. The n(²³⁴U)/n(²³⁶U), n(²³⁵U)/n(²³⁶U) and n(²³⁸U)/n(²³⁶U) ratios were then determined by TIMS using the n(²³³U)/n(²³⁶U) ratio for internal normalization and using a multi-dynamic measurement procedure in order to circumvent any possible influence and uncertainties from Faraday cup efficiencies and amplifier gain factors. The certified n(²³⁵U)/n(²³⁶U) and n(²³⁸U)/n(²³⁶U) ratios were additionally verified using the classical and modified total evaporation methods using two TIMS instruments at IRMM and one TIMS instrument at IAEA-SGAS. The verification data can be regarded as results obtained at three independent instruments at two different nuclear safeguards laboratories.     

Analyse par activation neutronique du vanadium,du chrome,du hafnium,du zirconium,du thallium,du rubidium et du cesium dans les argiles,les zircons et les feldspaths

Résumé Nous donnerons ici quelques exemples d'application de l'analyse par activation neutronique à l'étude de problèmes géochimiques: (1) Distribution des alcalins rares et du thallium dans les feldspaths; (2) Mesure du rapport Zr/Hf dans les zircons; (3) Dosage du Vanadium dans les argiles. Les trois types de roches ou minéraux qui ont fait l'objet de ces travaux montrent bien nous semble t-il la souplesse d'utilisation de la méthode.