Search results for " cluster"
showing 10 items of 2162 documents
Selective recognition of fluoride anion in water by a copper(II) center embedded in a hydrophobic cavity
2014
The ability of a water-soluble pentacationic calix[6]arene-based CuII complex to bind anions in water has been explored. Quite remarkably, the complex exhibits strong and selective fluoride binding in the pH range of 6–7. The binding constant at pH 5.9 was evaluated to be 85 000 M−1, which is one of the highest values ever reported for a fluoride probe in water and at this pH. The complex also binds chloride ions, but 1000 times less efficiently. The combination of the calix[6]arene hydrophobic cavity with the CuII complex, presenting its labile site in the endo position, is the reason for the selective recognition process. The single crystal X-ray structure of the organo-soluble parent com…
Thermodynamics of titanium and vanadium reduction in non-aqueous environment calculated at various levels of theory.
2012
Reduction of titanium and vanadium compounds is a process accompanying the activation of coordinative olefin polymerization catalysts. Four density functional theory (DFT) functionals, coupled cluster with single, double, and perturbative triple excitations method CCSD(T) as well as complete active-space second-order perturbation theory method CASPT2 with a complete active-space self-consistent field CASSCF reference wave function were applied to investigate the thermodynamics of titanium and vanadium reduction. The performance of these theoretical methods was assessed and compared with experimental values. The calculations indicate that vanadium(IV) chloride is more easily reduced by trime…
Semiclassical Methods for the Description of Large Metal Clusters
1996
One of the most fascinating aspects of clusters is that they can be made arbitrarily large and therefore provide links between the microscopic and the macroscopic world. It is challenging to study how their physical properties change when going from atoms and small molecules to the bulk limit of condensed matter. But also the models and mathematical tools themselves, which are used in order to tackle the many-body problem, are an object of study for the theoretician. In particular, the question of how far quantum-mechanics must be carried with increasing size and where classical pictures become appropriate is of great interest. In this spirit, we discuss here some semiclassical methods for …
Related haloarchaeal pleomorphic viruses contain different genome types
2012
Archaeal viruses have been the subject of recent interest due to the diversity discovered in their virion architectures. Recently, a new group of haloarchaeal pleomorphic viruses has been discovered. It is distinctive in terms of the virion morphology and different genome types (ssDNA/dsDNA) harboured by rather closely related representatives. To date there are seven isolated viruses belonging to this group. Most of these share a cluster of five conserved genes, two of which encode major structural proteins. Putative proviruses and proviral remnants containing homologues of the conserved gene cluster were also identified suggesting a long-standing relationship of these viruses with their ho…
Regional inequality and economic development in Spain, 1860–2010
2016
Abstract Fifty years ago Jeffrey G. Williamson suggested that during the process of economic development regional income differences trace out an inverted U-shaped pattern. Since then several studies have tested this hypothesis. Yet, most of these only explore particular stages of development. This study, however, investigates the long-term evolution of regional income inequality. Using a novel dataset spanning 150 years, we describe per-capita GDP disparities across Spanish provinces (NUTS3) from 1860 to 2010. Moreover, to gain a deeper understanding of regional inequality, we examine other relevant dimensions: modality, mobility and spatial clustering. Overall, the findings confirm the ex…
Cap Rate as the Interpretative Variable of the Urban Real Estate Capital Asset: A Comparison of Different Sub‐Market Definitions in Palermo, Italy
2017
Real estate capital is in constant competition with other capital assets due to its different and complementary economic functions such as direct use, productive investment, and speculative investment. These features and the resulting opportunities cannot be easily deduced from direct observation of the real estate markets, so some further insights need to be carried out in order to highlight the relationship between prices, rents and performances. This study aims at providing a multifaceted perspective of a specific urban real estate market to overcome the difficulties arising from opacities and informative asymmetries that hinder the decision of investors, by facilitating the comparison o…
Influence of annealing atmosphere on photoelectrochemical response of TiO2 nanotubes anodized under controlled hydrodynamic conditions
2021
[EN] The influence of three annealing atmospheres (air, nitrogen and argon) and the use of controlled hydrodynamic conditions (from 0 to 5000 rpm) on morphological, structural, chemical and photoelectrochemical properties of TiO2 nanotubes have been evaluated. For this purpose, different characterization techniques have been used: Field Emission Scanning Electron Microscopy, Raman Confocal Laser Spectroscopy, X-Ray Diffraction, X-Ray Photoelectron Spectroscopy, Incident Photon-to-electron Conversion Efficiency measurements, ultraviolet-visible absorption spectra, Mott-Schottky analysis and photoelectrochemical water splitting tests. According to the results, it can be concluded that both hy…
Raman spectroscopy and high-overtone driven isomerization of glyoxylic acid in solid argon
2013
High-overtone induced chemistry of glyoxylic acid isolated in a low-temperature argon matrix was investigated using Raman spectroscopy. The Raman spectra of two most stable conformers of glyoxylic acid are presented. Upon excitation in high overtone vibrational bands by 532 nm irradiation of the lowest energy conformer most abundant in neat deposited sample, the isomerization of glyoxylic acid was observed. The process most plausible proceeds via absorption into the fifth vibrational overtone state of the OH group or its combination with the torsional vibrational transition. The assignment of the fundamental vibrational spectra was assisted by quantum chemical harmonic and anharmonic vibrat…
Modeling of Point Defects in Corundum Crystals
1994
Several different approaches including Hartree-Fock ab initio cluster calculations, semiempirical INDO calculations, and atom-atom potentials were used for modeling of the spatial and electronic structure as well as migration mechanisms of both intrinsic defects (self-trapped and defect-trapped holes, O and Al vacancies) and impurities (transition-metal ions like Co, Fe, Mg, Mn, Ti). The atomic structure of all hole centers is found to be similar to V[sub K] centers in alkali halides (two-site model); their formation is energetically favorable. The energy required for 60[degree] hole reorientations inside the basic oxygen triangles is found to be similar to both the energy for hops between …
Neural Network-Based Process Analysis in Sport
2011
Processes in sport like motions or games are influenced by communication, interaction, adaptation, and spontaneous decisions. Therefore, on the one hand, those processes are often fuzzy and unpredictable and so have not extensively been dealt with, yet. On the other hand, most of those processes structurally are roughly determined by intention, rules, and context conditions and so can be classified by means of information patterns deduced from data models of the processes. Self organizing neural networks of type Kohonen Feature Map (KFM) help for classifying information patterns – either by mapping whole processes to corresponding neurons (see Perl & Lames, 2000; McGarry & Perl, 200…