Search results for " Bases"

Crear y gestionar conocimiento en red: agentes y procesos implicados.

2013

El proposito de este articulo es delimitar las funciones y roles de los principales agentes y los procesos que intervienen en la creacion y gestion del conocimiento (CGC) en red desde una plataforma virtual. Recoge, al respecto, algunos de los resultados mas destacados que se derivan de la investigacion “Agentes y procesos en la gestion del conocimiento en red” (I+D+i). El proceso de investigacion seguido ha supuesto, fundamentalmente, la puesta en marcha de 5 redes de CGC desde una plataforma virtual (Moodle) sostenida en el debate como estrategia; tambien la realizacion de un trabajo de campo que considero un cuestionario de autodiagnostico para 15 directivos y especialistas en desarrollo…

Photochemical Synthesis and Reactivity of New Chloro-Bridged Complexes with Tungstenocene (η5-C5H5)(η5-C5H4PPh2)WClX (X = H, Cl) and Tetracarbonylmet…

1999

Chloro-bridged bimetallic complexes (η5-C5H5)[η5-C5H4PPh2M′(CO)4]W(μ-Cl)X [X = Cl (3), × = H (4); M′ = Cr, W] were prepared by photochemical irradiation of (η5-C5H5)[η5-C5H4PPh2M′(CO)5]WClX [X = Cl (1), × = H (2); M′ = Cr, W]. The reactivity of the chloro-bridged complexes towards Lewis bases was studied; by exposure to CO or phosphanes, a facile cleavage of the chloro bridge accompanied by regio- and stereospecific coordination at M′ occurs. The X-ray structure of complex 3 (M′ = W) is reported.

Lewis Base Catalyzed Intramolecular Reduction of Salicylaldehydes by Pinacol-Derived Chlorohydrosilane

2018

2018

Tetrel bonding is the noncovalent interaction of group IV elements with electron donors. It is a weak, directional interaction that resembles hydrogen and halogen bonding yet remains barely explored. Herein, we present an experimental investigation of the carbon-centered, three-center, four-electron tetrel bond, [N–C–N]+, formed by capturing a carbenium ion with a bidentate Lewis base. NMR-spectroscopic, titration-calorimetric, and reaction-kinetic evidence for the existence and structure of this species is reported. The studied interaction is by far the strongest tetrel bond reported so far and is discussed in comparison with the analogous halogen bond. The necessity of the involvement of …

Bessel sequences, Riesz-like bases and operators in Triplets of Hilbert spaces

2016

Riesz-like bases for a triplet of Hilbert spaces are investigated, in connection with an analogous study for more general rigged Hilbert spaces performed in a previous paper. It is shown, in particular, that every \(\omega \)-independent, complete (total) Bessel sequence is a (strict) Riesz-like basis in a convenient triplet of Hilbert spaces. An application to non self-adjoint Schrodinger-type operators is considered. Moreover, some of the simplest operators we can define by them and their dual bases are studied.

On the enhancement of stereoselection by cooperation between chiral auxiliaries. Asymmetric diels-alder reactions with fumaric acid bis ((S)-proline …

1989

Abstract Fumaric acid bis ((S)-proline benzyl ester) amide reacts with cyclopentadiene in thermal and Lewis acid catalyzed Diels-Alder reactions to give the cycloadducts with high yields and diastereomeric ratios up to 100:1.

A Criterion for Attaining the Welch Bounds with Applications for Mutually Unbiased Bases

2008

The paper gives a short introduction to mutually unbiased bases and the Welch bounds and demonstrates that the latter is a good technical tool to explore the former. In particular, a criterion for a system of vectors to satisfy the Welch bounds with equality is given and applied for the case of MUBs. This yields a necessary and sufficient condition on a set of orthonormal bases to form a complete system of MUBs. This condition takes an especially elegant form in the case of homogeneous systems of MUBs. We express some known constructions of MUBs in this form. Also it is shown how recently obtained results binding MUBs and some combinatorial structures (such as perfect nonlinear functions an…

DFT Study of Ethylene and Propylene Copolymerization over a Heterogeneous Catalyst with a Coordinating Lewis Base

2005

The copolymerization of ethylene and propylene over a heterogeneous Ti(III) catalyst containing tetrahydrofuran (THF) as a Lewis base and MgCl2 as a support has been studied by means of DFT. Two feasible models of active sites have been examined thoroughly, and one of them turned out to be favorable in terms of both catalytic activity and the microstructure of the resulting polymer. The external barriers of olefin insertion for this model range from 3.1 to 16.0 kcal/mol and are influenced by a variety of factors, such as the structure of the growing polymer chain and the nature of the incoming olefin as well as the orientation of the ligands around the titanium atom. Stochastic simulations …

New light on an old debate: does the RCN–PtCl2 bond include any back-donation? RCN←PtCl2 backbonding vs. the IR νCN blue-shift dichotomy in organoni…

2019

For a series of organonitrile [RCN (R = Me, CF3, Ph, CH3Ph, CF3Ph)] ligands, the nature of the N–Pt bond in the related cis-/trans-(RCN)2PtCl2 complexes has been computationally investigated by Density Functional Theory. A fragment based bond analysis has been performed in the canonical Kohn–Sham molecular orbitals framework, and it has been ultimately assessed that this bond is characterized both by N→Pt σ and by N←Pt π contributions. Voronoi Deformation Density charges further confirms the occurrence of N←Pt π interactions. Moreover, the Energy Decomposition Analysis-Natural Orbital for Chemical Valence (EDA-NOCV) method shows that the strength of the N←Pt π interaction is not negligible …

Reactome diagram viewer: data structures and strategies to boost performance

2017

Abstract Motivation Reactome is a free, open-source, open-data, curated and peer-reviewed knowledgebase of biomolecular pathways. For web-based pathway visualization, Reactome uses a custom pathway diagram viewer that has been evolved over the past years. Here, we present comprehensive enhancements in usability and performance based on extensive usability testing sessions and technology developments, aiming to optimize the viewer towards the needs of the community. Results The pathway diagram viewer version 3 achieves consistently better performance, loading and rendering of 97% of the diagrams in Reactome in less than 1 s. Combining the multi-layer html5 canvas strategy with a space partit…