Search results for "Homogeneous"

Increasing offensive or defensive efficiency? An analysis of Italian and Spanish football☆

2009

This paper analyses technical efficiency of Italian and Spanish football during three recent seasons, to shed light on the sport performance of professional football clubs. To achieve this we have used mathematical optimisation methods, particularly DEA models, which enable the calculation of the frontiers of efficient production. Some of the most interesting results are the following. Firstly, the Spanish league is clearly more homogeneous and competitive than the Italian league. Secondly, to obtain a better classification in the Italian league, it is much more important to improve defensive, rather than offensive, efficiency. The popular maxim holds in Italy: the best attack begins with a…

On the solution growth of single crystals of solid solutions

1986

Abstract Homogeneous solid solution crystals are needed for studying the behaviour of systems with a glass state or incommensurate phases. A simple solution growth procedure is described. It is based on a temperature difference growth method with thermally enforced convection and the use of equilibrated solid and liquid solutions. First results of its application to the [(CH3)4N]2ZnCl 4−xBrx and the Rb1−x(NH4)xH2PO4 systems are presented.

Tetraallylsilane π-Complexation: Synthesis and Structure of [Cu5Cl5(CH2-CH=CH2)4Si]

2009

By alternating-current electrochemical technique, starting from CuCl2·2H2O and tetraallylsilane (TAS), crystals of the π complex [Cu5Cl5(CH2–CH=CH2)4Si] (I) were obtained, FTIR characterized and structurally investigated. The structure of I is monoclinic, space group P21/n, a = 12.292(3), b = 12.083(3), c = 13.356(3) A, β = 90.19(3)°, V = 1983.7(9) A3 [at 100(2) K], Z = 4; R1 = 0.0379, wR2 = 0.1040 for 3583 reflections. The TAS molecule behaves as a tetradentate cross-bridged ligand linking four (Cu5Cl5)∞ fragments through the C=C bonds. The influence of the inorganic part and ligand symmetries combined with their conformational abilities on the overall crystal symmetry is discussed.

Benzoato and Thiobenzoato Ligands in the Synthesis of Dinuclear Palladium(III) and ‐(II) Compounds: Stability and Catalytic Applications

2015

New palladium(III) compounds of formula Pd2[(C6H4)PPh2]2[OXC(C6H5)]2Cl2 [3a (X = O); 3b (X = S)] were obtained by the oxidation of the analogous palladium(II) ones with PhICl2 and were characterized by 31P, 1H, and 13C NMR spectroscopy at 223 K. Compound 3a was also structurally characterized by single-crystal X-ray diffraction methods, which revealed a Pd–Pd distance of 2.5212(10) A. DFT calculations were conducted to study the stability of all of these new palladium(III) and -(II) compounds with focus on the influence of the OS substitution of the donor atom in the ligand. The palladium(II) compounds Pd2[(C6H4)PPh2]2[OXC(C6H5)]2 [2a (X = O), 2b (X = S)] were also tested as precatalyst in …

Homogeneous and supported copper complexes of cyclic and open-chain polynitrogenated ligands as catalysts of cyclopropanation reactions

1999

CuI and CuII complexes of cyclic and open-chain polyaza compounds have been tested as catalysts in the benchmark cyclopropanation reaction of styrene with ethyl diazoacetate. In general, only small amounts of copper are needed to promote the reaction. The catalytic activity depends on the structure of the ligand, e.g. amine–amides are more efficient than polyamines, and on the oxidation state of copper, CuII being more active than CuI. Given that CuI is the active species, these changes of behavior must be related to the stabilities of the complexes. The nature of the counterion also has a noticeable influence on the catalytic activity, the role of which is discussed. XAS measurements sugge…

Facile Synthesis and Self‐Assembly of Zinc (2‐Diethoxyphosphorylethynyl)porphyrins

2019

Rationally integrable vector fields and rational additive group actions

2016

International audience; We characterize rational actions of the additive group on algebraic varieties defined over a field of characteristic zero in terms of a suitable integrability property of their associated velocity vector fields. This extends the classical correspondence between regular actions of the additive group on affine algebraic varieties and the so-called locally nilpotent derivations of their coordinate rings. Our results lead in particular to a complete characterization of regular additive group actions on semi-affine varieties in terms of their associated vector fields. Among other applications, we review properties of the rational counterpart of the Makar-Limanov invariant…

Timescale-dependent stock market comovement: BRICs vs. developed markets

2014

This paper examines the differences in the asset return comovement of the BRIC countries (Brazil, Russia, India and China), the other developed economies in their regions (Canada, Hong Kong and Australia) and the major industrialized economies (the U.K., Germany and Japan) with respect to the U.S. for different return periods. The novelty of the paper is that the stock return indices are decomposed to several timescales using wavelet analysis and that the results are further used as inputs for the dynamic conditional correlation (DCC) framework, which is used as a measure of comovement. The results propose that the level of stock market comovement depends on regional aspects, the level of d…

Das Onkozytom der Niere

1988

The angiographic findings in ten patients with renal oncocytoma are described. Characteristic features include: absence of encasement, vascular occlusions, arterio-venous shunts and contrast lakes (8/10). Spoke-wheel arrangement of tumor vessels (8/10). Homogeneous tumour contrast during the capillary phase (7/10). Sharp demarcation from the kidney and surroundings (9/10) and a peritumoral halo (4/10). If the suspicion of an oncocytoma is raised by CT examination of a space-occupying lesion (part I), angiography should be performed to confirm the diagnosis and help in planning surgical treatment.

Polyhedral Oligomeric Silsesquioxane Based Catalyst for the Efficient Synthesis of Cyclic Carbonates

2015

In this work, the synthesis of a novel imidazolium-based polyhedral oligomeric silsesquioxane (POSS-mim-Cl) material is presented. The new nanometer-size organosilica based compound was employed for chemical fixation of CO2 into epoxide under homogeneous conditions. The target reaction was represented by the obtention of cyclic carbonates starting from epoxides and CO2. Particularly, styrene oxide was chosen as reference substrate. In addition, different parameters (solvent, temperature, pressure of CO2, and mass of the catalyst) were modified to find the best condition for CO2 conversion. The catalyst POSS-mim-Cl displayed good catalytic performances, the best results being obtained at 40 …