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

Summary  Vezetéknév     

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

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     

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     

Use of new composite materials for the determination of Cu, Cd, Mo, As, and Sb in biological samples by radiochemical neutron activation analysis

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     

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

Summary  Vezetéknév     

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

Summary  Elérh     

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

Summary  Elérh     

A bootstrap‐based method for optimal design of experiments

Bootstrapping can be used for the estimation of parameter variances, and it is straightforward to be implemented but computationally demanding compared with other methods for parameter error estimation. It is not bound to any restrictions such as the distribution of measurement errors. And because of the possible asymmetry of the probability densities of the parameters, the parameter estimation errors acquired by bootstrapping are likely to be more accurate. In this work the feasibility of a bootstrap‐based method for optimal experimental design was evaluated for the Peleg model. The optimal design was performed, based on the Cramér‐Rao lower bound as a benchmark. Afterwards, the optimal design was calculated based on the bootstrap method. It is demonstrated that a bootstrap‐based optimal design of experiments will give comparable results with the Cramér‐Rao lower bound optimal designs, however with slightly different measurement points in time. If the parameter errors obtained from both optimal experimental designs are compared, they deviate for the 2 methods on average by 1.5%. Bootstrapping can be used for problems, which cannot be solved using Cramér‐Rao lower bound because of necessary but invalid assumptions. However, the benefits of the bootstrap method come at the cost of a significant increase in computational effort. Under similar conditions, the computation time for a bootstrap‐based optimal design was 25 minutes compared with 5 seconds when using the Cramér‐Rao lower bound method. As computers get faster and faster over time, the increase in computational demand will probably become less relevant in the future.     

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     

Determination of90Sr and 137Cs concentrations in the IAEA reference material Soil-6

Vezetéknév This revised version was published online in August 2006 with corrections to the Cover Date.     

Computing the Kekulé structure count for alternant hydrocarbons

A fast computer algorithm brings computation of the permanents of sparse matrices, specifically, molecular adjacency matrices. Examples and results are presented, along with a discussion of the relationship of the permanent to the Kekulé structure count. A simple method is presented for determining the Kekulé structure count of alternant hydrocarbons. For these hydrocarbons, the square of the Kekulé structure count is equal to the permanent of the adjacency matrix. In addition, for alternant structures the adjacency matrix for N atoms can be written in such a way that only an N/2 × N/2 matrix need be evaluated. The Kekulé structure count correlates with topological indices. The inclusion of the number of cycles improves the fit. When comparing with previous results, the variance decreases 74%. The calculated standard heat of formation correlates with the logarithm of the Kekulé structure count. This heat increments 349 kJ/mol each time the Kekulé structure count increases by one order of magnitude. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002     

Propriétés thermoélectriques du sélénium liquide pur et dopé à i'lode

Abstract

On a étudié le pouvoir thermoélectrique du sélénium en fonction de la température pour des échantillons de puretés diverses et dopés ayantn subi divers cyles thermiques. II varie beaucoup, passant d'un signe à l'autre; le dopage à l'iode tend à donner une conductibilité de type p.

Thermoelectric power of selenium vs temperature has been studies for samples of variable purity or doped having undergone various thermal treatments. Large variations appear, with either sign; doping with iodine favours p-type conduction.     

International comparison of the determination of cadmium and lead in herb: the Comité Consultatif pour la Quantité de Matière (CCQM) pilot study CCQM-P97

A Comité Consultatif pour la Quantité de Matière (CCQM) inter-laboratory comparison program, CCQM-P97, for the analysis of cadmium and lead in Herba Demodii Styracifolii was organized by the Hong Kong Government Laboratory. The objective of the program was to establish comparability of trace metals analysis in herbal matrices amongst the participating national metrology institutes. The arithmetic mean values of the 13 participants were 0.3186 mg kg⁻¹ (RSD = 11.3%) and 1.650 mg kg⁻¹ (RSD = 11.0%) for cadmium and lead, respectively. The participants using double-isotope dilution mass spectrometry technique for their quantification were found to provide similar mean values to those of non-isotope dilution mass spectrometry users. The observation indicated that trace metal analysis in herbal matrices was not method-dependent, but the use of the highest metrological IDMS approach gave a better precision than other routine calibration methods.     

Influence du milieu de synthèse sur la cristallisation de saponite : proposition de mécanisme réactionnel en milieux acide et basique

Influence of the synthesis medium on the saponite crystallisation: formation mechanism in acidic and basic media. The present work is relative to the hydrothermal synthesis of saponite, a clay mineral having the following chemical formula per half unit cell : M_xMg₃ (Si_4–xAl_x)O₁₀(OH,F)₂, 0.2 < x < 1.20, where M is an hydrated exchangeable cation and x is the layer charge. Syntheses were performed in fluorine medium in the pH range 1 to 12. Two mechanisms can be proposed: in acidic medium, tetrahedral polysilicic acid incorporate Al³⁺ cations and, in basic medium, silica polycondensation occurs around a [Mg(OH)₂] brucite-like layer. To cite this article: M. Jaber, J. Miéhé-Brendlé, C. R. Chimie 8 (2005).     

Greffage de modèles de lignines sur polystyrène par lien imino

The synthesis of oligolignols grafted on polymer (LFP) was engaged in order to further study the properties and the biodegradation mechanisms of the different lignin sub-units in conditions more similar to those involved in the natural polymer. Simplified lignin models were grafted by an imine or amino link to a 1 % amino ethyl polystyrene resin without any protection of the hydroxyl functions. Infrared was used to characterize the supported models. © 2000 Académie des sciences / Éditions scientifiques et médicales Elsevier SASsupported lignine / synthesis / lignin models     

Raman spectroscopic study of the antimonate mineral roméite

Raman spectroscopy has been sued to study the antimony containing mineral roméite Ca₂Sb₂O₆(OH,F,O) from three different origins. Roméite is a calcium antimonate mineral of the pyrochlore group. An intense Raman band at ～518 cm^?1 for roméite is assigned to the SbO ν₁ symmetric stretching mode and the band at 466 cm^?1 to the SbO ν₃ antisymmetric stretching mode. The Raman band at 303 cm^?1 is attributed to the OSbO bending mode. Some variation in band positions is observed and is attributed to the variation in composition between the three mineral samples.