Search results for "transition [form factor]"
showing 10 items of 754 documents
An Improved Force Field for O2, CO and CN Binding to Metalloporphyrins
2004
Parametrization of a molecular-mechanics program to include terms specific for five- and six-coordinate transition metal complexes is applied to heme complexes. The principal new feature peculiar to five and six coordination is a term that represents the effect of electron-pair repulsion modified by the ligand electronegativity and takes into account the different possible structures of complexes. The model system takes into account the structural differences of the fixing centre in the haemoglobin subunits. The customary proximal histidine is added. The macrocycle heme IX is wholly considered in our model. The calculations show clearly that certain conformations of heme IX–histidine models…
Marchés du travail et disparités régionales en Pologne
2001
This article evaluates empirically the effect o f market introduction on the level o f regional inequalities and on the polarisation o f economic activities in Poland. We note an increase o f the disparities between regions over the relevant period. The re-polarisation process cannot been explained by a spatial re-allocation of labour force but rather results o f the differentiation of sectoral restructuring between regions the regional diversity o f sectoral adaptation. The search for agglomeration economies explains the spatial concentration o f services and o f added value in the regions where the biggest cities are located. A cumulative process o f agglomeration is observed. Therefore, …
Heterogeneous catalytic degradation of phenolic substrates: catalysts activity
2009
This review article explored the catalytic degradation of phenol and some phenols derivates by means of advanced oxidation processes (AOPs). Among them, only the heterogeneous catalyzed processes based on catalytic wet peroxide oxidation. catalytic ozonation and catalytic wet oxidation were reviewed. Also selected recent examples about heterogeneous photocatalytic AOPs; will be presented. In details, the present review contains: (i) data concerning catalytic wet peroxide oxidation of phenolic compounds over metal-exchanged zeolites, hydrotalcites, metal-exchanged clays and resins. (ii) Use of cobalt-based catalysts, hydrotalcite-like compounds, active carbons in the catalytic ozonation proc…
Parameterization of a comprehensive explicit model for single-ring infiltration
2021
International audience; Comprehensive infiltration models can simultaneously describe transient and steady-state infiltration behaviors, and therefore can be applied to a range of experimental conditions. However, satisfactory model accuracy re- quires proper parameterization, including estimating the transition time from transient to steady-state flow conditions (τcrit). This study focused on improving the estimation of two parameters – τcrit and a second constant called a – used in a comprehensive, explicit, two-term model for single ring infiltration (hereafter referred to as the SA model). Different studies have recommended that a should be as low as 0.45 to as high as 0.91. Furthermore…
Molybdenum–vanadium supported on mesoporous alumina catalysts for the oxidative dehydrogenation of ethane
2006
Abstract Vanadium and/or molybdenum oxides supported on mesoporous alumina have been prepared by a “wet” impregnation method, characterized (by using several physico-chemical techniques TPR, DR-UV–vis, Raman spectroscopies) and tested in the oxidative dehydrogenation (ODH) of ethane. For comparison Mo–V-mixed oxides supported on γ-Al2O3 have also been studied. The characterization results indicate that the main vanadium species in both Mo-free and Mo-containing V-based samples present low aggregation and coordination, whereas molybdenum is present as monomeric or polymeric tetrahedral molybdenum species. Interestingly, no apparent interaction between molybdenum and vanadia takes place. The …
DFT study on complete ethylene decomposition on flat and stepped Pd
2010
Abstract We applied density functional theory (DFT) calculations to study ethylidyne (CCH 3 ) adsorption and decomposition to C and H over flat and stepped Pd surfaces. Our calculations show that ethylidyne is the most stable molecule among all the possible dehydrogenation or decomposition residues of ethylene. We discuss various possible reaction pathways for ethylidyne decomposition and point out that the most probable one is via ethynyl (CCH) species suggested also by experimental observations. Our calculations indicate that the presence of steps modify the potential energy surface by increasing the binding of most of the species, and also lowering the activation barrier for several reac…
Probing the physics of the solar atmosphere with the Multi-slit Solar Explorer (MUSE): I. Coronal Heating
2022
The Multi-slit Solar Explorer (MUSE) is a proposed NASA MIDEX mission, currently in Phase A, composed of a multi-slit EUV spectrograph (in three narrow spectral bands centered around 171A, 284A, and 108A) and an EUV context imager (in two narrow passbands around 195A and 304A). MUSE will provide unprecedented spectral and imaging diagnostics of the solar corona at high spatial (<0.5 arcsec), and temporal resolution (down to ~0.5s) thanks to its innovative multi-slit design. By obtaining spectra in 4 bright EUV lines (Fe IX 171A , Fe XV 284A, Fe XIX-Fe XXI 108A) covering a wide range of transition region and coronal temperatures along 37 slits simultaneously, MUSE will for the first time …
Surface characterization of metal ions loaded TiO2 photocatalysts: structure-activity relationship
2004
Transition metal loaded TiO2 powders were characterised and tested for the photodegradation of some organic acids. Both Lewis and Brønsted surface acid sites were present in the samples containing large amounts of Mo, V and W. The Brønsted sites are associated to the presence of the transition metals as they do not exist in the unloaded support, and in particular to the presence of these metals in high oxidation states. The trend of the pzc values of the various powders matches rather well both with the surface acidity of the samples experimentally determined by NH3 adsorption and with a scale of acidity/basicity for bulk binary oxides. XPS investigation indicates that only the presence of …
Novel procedure for the template synthesis of metal nanostructures
2008
In this work we describe a novel method for the fabrication of a regular and uniform array of Cu nanowires into anodic alumina membranes. It is based on galvanic contact between the metal sputtered film covering the bottom of template and a less noble metal. The growth rate was estimated as function of the immersion time. Nanowires with aspect ratio from 12 to 286 were obtained by adjusting the deposition time. Copper nanowires were found to be polycrystalline with an average crystalline size of about 40 nm. This procedure can be applied for the preparation of a wide range of metallic nanostructures and it can be easily scaled up for industrial processing. Keywords: Displacement deposition,…
Risk Taking by Banks in the Transition Countries
2007
The banking sectors of the transition countries have progressed remarkably in the last 15 years. In fact, banking in most transition countries has largely shaken off the traumas of the transition era. At the start of the 21st century banks in these countries look very much like banks elsewhere. That is, they are by no means problem free but they are struggling with the same issues as banks in other emerging market countries. There have been a surprisingly large number of studies that have told us about the performance of these banks but we know very little about their risk taking behaviour and how the banking environment influences it.