Search results for "DF"

DFT analysis of titanium complexes with oxygen-containing bidentate ligands

2003

Strength of the TiO co-ordinate bond in several titanium complexes with bidentate ligands has been investigated by means of DFT. Mutual interaction of particular donors and their influence on Lewis acidity of the central atom have also been studied. The energy of ligand binding ranges from −19 to −454 kJ/mol, depending on the kind of donors. Calculations confirm that a strong donor, alkoxide anion, co-ordinatively saturates the titanium and makes binding of new ligands less exoenergetic. On the contrary, two oxygen atoms of similar donor number do not have much influence on each other. Strength of the TiO bonds in titanium complexes with certain oxygen-containing bidentate ligands has bee…

Theoretical study of isomerism in phenoxyimine-based precursors of coordinative olefin polymerization catalysts

2010

Precursors of post-metallocene olefin polymerization catalysts, unlike their predecessors, are usually octahedral transition metal complexes with multidentate ligands. Such ligands may wrap around the central atom in many ways, thus yielding several isomeric species. For a wide range of phenoxyimine (FI) ligands with different substituents, all the theoretically predicted diastereomers of group 4 and 5 complexes are available synthetically. However, only one of the isomers is usually preferred, and this is determined by the nature of the substituents in the FI ligand. The origin and mechanism of such preference has not been completely elucidated. We attempted to describe it quantitatively o…

Le attività motorie nel paziente diabetico complicato e non

2011

Hidden Markov random field model and Broyden–Fletcher–Goldfarb–Shanno algorithm for brain image segmentation

2018

International audience; Many routine medical examinations produce images of patients suffering from various pathologies. With the huge number of medical images, the manual analysis and interpretation became a tedious task. Thus, automatic image segmentation became essential for diagnosis assistance. Segmentation consists in dividing the image into homogeneous and significant regions. We focus on hidden Markov random fields referred to as HMRF to model the problem of segmentation. This modelisation leads to a classical function minimisation problem. Broyden-Fletcher-Goldfarb-Shanno algorithm referred to as BFGS is one of the most powerful methods to solve unconstrained optimisation problem. …

Understanding the participation of 3-nitropyridine in polar Diels–Alder reactions. A DFT study

2015

The reactivity of 3-nitropyridine acting as an electrophilic dienophile in polar Diels-Alder (P-DA) reactions toward three different dienes of increased nucleophilicity has been theoretically studied using DFT methods at the MPWB1K/6-31G(d) level. It has been observed that this aromatic heterocyclic system suffers cycloaddition reactions yielding isoquinoline derivatives. The present DFT study establishes that while the P-DA reactions with isoprene and 1-methoxy-1,3-butadiene take place through a two-stage one-step mechanism, the use of the strong nucleophilic Danishefsky's diene changes the mechanism to a two-step one with formation of a zwitterionic intermediate. These P-DA reactions are …

Association between dietary fibre intake and fruit, vegetable or whole-grain consumption and the risk of CVD: results from the PREvención con DIeta M…

2016

Prospective studies assessing the association between fibre intake or fibre-rich food consumption and the risk of CVD have often been limited by baseline assessment of diet. Thus far, no study has used yearly repeated measurements of dietary changes during follow-up. Moreover, previous studies included healthy and selected participants who did not represent subjects at high cardiovascular risk. We used yearly repeated measurements of diet to investigate the association between fibre intake and CVD in a Mediterranean cohort of elderly adults at high cardiovascular risk. We followed-up 7216 men (55-80 years) and women (60-80 years) initially free of CVD for up to 7 years in the PREvención con…

Mediterranean diet and dietary protein supplementation as possible predicting variables of weight management: An update of the protein project

2015

Introduction: The Mediterranean diet is known to support the prevention of several chronic diseases and excessive weight gains. However, relevant investigations were performed in a clinical setting and healthy and physical active individuals were not considered. The aim of this study was therefore to understand the effects of protein supplements intake on body mass index (BMI) in healthy active individuals following the Mediterranean diet. Materials and methods: A face-to-face questionnaire was administered to 667 subjects, 627 living in a Mediterranean area (MD) and 40 in a non-Mediterranean area (NMD); questionnaire enquired dietary behaviors, including a comparison between dietary patter…

A generalized integration formula for indefinite integrals of special functions

2020

An integration formula for generating indefinite integrals which was presented in Conway JT [A Lagrangian method for deriving new indefinite integrals of special functions. Integral Transforms Spec...

Elektrónová a pásová štruktúra CuMnAs študovaná optickou a fotoemissinou spektroskopiou

2017

Tetragonal phase of CuMnAs progressively appears as one of the key materials for antiferromagnetic spintronics due to efficient current-induced spin-orbit torques whose existence can be directly inferred from crystal symmetry. Theoretical understanding of spintronic phenomena in this material, however, relies on the detailed knowledge of electronic structure (band structure and corresponding wave functions) which has so far been tested only to a limited extent. We show that AC permittivity (obtained from ellipsometry) and UV photoelectron spectra agree with density functional calculations. Together with the x-ray diffraction and precession electron diffraction tomography, our analysis confi…

Controlling the Formation of Sodium/Black Phosphorus IntercalationCompounds Towards High Sodium Content

2021

The solid-state synthesis of pure sodium-black phosphorus intercalation compounds (Na-BPICs) has been optimized in bulk for two stoichiometric ratios. Specifically, in-situ X-Ray diffraction (XRD) allowed the precise identification of the optimal temperature range for the formation of Na-BPICs: 94°C–96°C. Moreover, as the undesired formation of Na3P takes place at this very same range, we succeeded in introducing a new synthetic route based on a fast-thermal ball milling implementation that results in the bulk production of BPIC without Na3P in 9 out of 10 cases. Finally, by combining XRD, Raman spectroscopy, and DFT calculations we developed a new structural model for Na-based BPICs showin…