Search results for "NAD"
showing 10 items of 2033 documents
Ziegler–Natta catalysts based on vanadium halides: a DFT study
2003
Abstract Ziegler–Natta ethylene insertion into the carbon–metal bond for a number of fragments containing vanadium on different oxidation states as well as the halogen ligands has been studied by means of DFT. It is shown that the complexation and insertion energies are strongly influenced by the charge on the transition metal atom and, to some extent, by the electronegativity of the halogen atom. Complexation energy varies in the range −129 to −159 kJ/mol for charged species and −64 to −77 kJ/mol for neutral ones. Insertion energy follows a similar pattern and ranges from −28 to −62 and −82 to −100 kJ/mol, respectively. The calculated values are compared with the experimental results and d…
Oxidative dehydrogenation of n-butane on MgO-supported vanadium oxide catalysts
1998
Abstract Vanadium–magnesium oxide (VMgO) catalysts have been prepared, characterized and tested in the ODH of n-butane. The catalysts were prepared by two variations of the wet-impregnation method using aqueous ammonium metavanadate or organically-based methanolic vanadyl acetylacetonate solutions. The catalyst surface area depends on the vanadium content and the preparation method. Catalyst characterization (i.e. XRD, 51V NMR, FTIR, LRS) results indicate the presence of poor crystalline Mg-orthovanadate (Mg3V2O8), while the presence of other Mg-vanadates is not clear. Oxygen isotopic-exchange experiments on VMgO catalysts indicate an R2 process: [ 18 O 2 +2 16 O 2− (s) → ( 18 O 18 O 16 O 1…
2-Tetrahydrofurfuroxo-vanadium-(III) and -(IV) complexes. Synthesis, structures and reactivities of [V2Mg2(μ3,δ2-thffo)2(μ,δ2-thffo)4Cl4]· 2CH2Cl2 an…
1997
Vanadium complexes of 2-tetrahydrofurfuroxide (2-tetrahydrofurylmethoxide) (thffo) with the metal in oxidation state III and IV have been prepared and characterized. The reaction of [VCl3(thf)3] with 1.5 equivalents of [Mg(thffo)2] in tetrahydrofuran (thf) or CH2Cl2 led to the formation of [V2Mg2(µ3,η2-thffo)2(µ,η2-thffo)4Cl4]· 2CH2Cl21. Its structure consists of centrosymmetric tetranuclear molecules and CH2Cl2 of crystallization. Two Mg and two V atoms have distorted octahedral geometry and form a nearly regular Mg2V2 rhombus. The V · · · V distance is 3.266(2) A. The reaction of [VOCl2(thf)2] with Na(thffo) in thf yielded [V2(µ,η2-thffo)2Cl2O2] 2. Two VOCl units are linked by alkoxide ox…
Selective Oxidation of n-Butane and Butenes over Vanadium-Containing Catalysts
2000
Abstract The oxidative dehydrogenation (OXDH) of n-butane, 1-butene, and trans-2-butene on different vanadia catalysts has been compared. MgO, alumina, and Mg–Al mixed oxides with Mg/(Al+Mg) ratios of 0.25 and 0.75 were used as supports. The catalytic data indicate that the higher the acid character of catalysts the lower is both the selectivity to C4-olefins from n-butane and the selectivity to butadiene from both 1-butene or trans-2-butene. Thus, OXDH reactions are mainly observed from n-butane and butenes on basic catalysts. The different catalytic performance of both types of catalysts is a consequence of the isomerization of olefins on acid sites, which appears to be a competitive reac…
Selective oxidative activation of isobutane on a novel vanadium-substituted bimodal mesoporous oxide V-UVM-7
2006
Abstract New vanado-silicates with a bimodal mesoporous system (V-UVM-7) and high vanadium contents (Si/V ≥ 7) have been prepared by a modification of the so-called atrane method. Its morphology consists of aggregation of nano-particles with V-MCM-41 structure, creating a second broader porous system in their interparticle space. Its structure allows to incorporate a high V contents into tetrahedral sites of the framework while keeping vanadium dispersion. V-UVM-7 catalysts are very active and selective for the direct transformation of isobutane to isobutene and methacrolein. Total conversion and methacrolein-to-isobutene ratio in the products increased with increasing vanadium contents. Th…
Ks. prof. Piotr Jaskóła - teolog ekumeniczny
2017
Artykuł stanowi prezentację sylwetki naukowej ks. prof. Piotra Jaskóły – wieloletniego dyrektora Instytutu Ekumenizmu i Badań nad Integracją Wydziału Teologicznego Uniwersytetu Opolskiego oraz współzałożyciela i pierwszego redaktora naczelnego czasopisma „Studia Oecumenica”. W pierwszej części artykułu syntetycznie zaprezentowano najważniejsze osiągnięcia naukowo-badawcze, zamieszczając przy tym krótkie omówienie kluczowych publikacji ks. prof. Jaskóły. W drugiej części przedstawiono obszary jego działalności dydaktyczno-organizacyjnej oraz działania na rzecz promocji młodej kadry naukowej. Artykuł cytuje także fragmenty recenzji, sporządzonych przez uznane autorytety w polskiej teologii, w…
Transcriptional regulation of the proton translocating NADH dehydrogenase genes (nuoA-N) of Escherichia coli by electron acceptors, electron donors a…
1995
The promoter region and transcriptional regulation of the nuoA-N gene locus encoding the proton-translocating NADH:quinone oxidoreductase was analysed. A 560 bp intergenic region upstream of the nuo locus was followed by a gene (designated lrhA for LysR homologue A) coding for a gene regulator similar to those of the LysR family. Disruption of lrhA did not affect growth (respiratory or non-respiratory) or expression of nuo significantly. Transcriptional regulation of nuo by electron acceptors, electron donors and the transcriptional regulators ArcA, FNR, NarL and NarP, and by IHF (integration host factor) was studied with protein and operon fusions containing the promoter region up to base …
Los algoritmos que valoran el riesgo de reincidencia. En especial, VioGen
2021
Las herramientas de evaluación del riesgo más novedosas se asisten de algoritmos para predecir la probabilidad de reincidencia de un delincuente y pueden servir de apoyo en la toma de determinadas decisiones en el ámbito del proceso penal. A ellas dedicamos este estudio, con especial hincapié en una herramienta concreta en el ámbito de la violencia de género, el sistema VioGén. The latest risk assessment tools use algorithms to predict the likelihood of reoffending and can be used to support certain decisions in criminal proceedings. This article focuses on these tools, with special emphasis on a specific one in the field of gender violence, the VioGén system.
Wearables, IoT, and Big Data: The new revolution in cognitive science
2022
A new revolution in cognitive science is now possible thanks to portable devices enabled to measure physiological variables non-intrusively, the Internet of Things that allows information to be collected and stored in real time from different locations, and big data techniques for identifying patterns that can be used to make decisions, predict behavior or create machine learning and artificial intelligence models. Research supported by these technologies will provide valuable insights into the impact that environmental circumstances have on the cognitive processes involved in different tasks, and how this can be detected through biological markers.
Boukharine dirige l’Internationale communiste, 1926-1928 (où l’on voit notamment comment est apparue l’expression « crise générale du capitalisme »)
2020
International audience