Search results for "Number"
showing 10 items of 3939 documents
Onset of Convection in an Inclined Anisotropic Porous Layer with Internal Heat Generation
2019
The onset of convection in an inclined porous layer which is heated internally by a uniform distribution of heat sources is considered. We investigate the combined effects of inclination, anisotropy and internal heat generation on the linear instability of the basic parallel flow. When the Rayleigh number is sufficiently large, instability occurs and a convective motion is set up. It turns out that the preferred motion at convection onset depends quite strongly on the anisotropy ratio, &xi
Intramolecular proton transfer boosts water oxidation catalyzed by a Ru complex
2015
We introduce a new family of complexes with the general formula [Run(tda)(py)2]m+ (n = 2, m = 0, 1; n = 3, m = 1, 2+; n = 4, m = 2, 32+), with tda2– being [2,2′:6′,2″-terpyridine]-6,6″-dicarboxylate, including complex [RuIV(OH)(tda-κ-N3O)(py)2]+, 4H+, which we find to be an impressive water oxidation catalyst, formed by hydroxo coordination to 32+ under basic conditions. The complexes are synthesized, isolated, and thoroughly characterized by analytical, spectroscopic (UV–vis, nuclear magnetic resonance, electron paramagnetic resonance), computational, and electrochemical techniques (cyclic voltammetry, differential pulse voltammetry, coulometry), …
A new ferromagnetically coupled μ-alkoxo–μ-acetato copper(II) trinuclear complex: [Cu3(H2tea)(Htea)(CH3COO)2](ClO4) (H3tea=triethanolamine)
2005
Abstract A μ-alkoxo–μ-acetato trinuclear copper(II) complex, [Cu3(H2tea)(Htea)(CH3COO)2](ClO4) 1, has been synthesized by reacting copper(II) perchlorate, triethanolamine and sodium acetate. The unit cell contains two centrosymmetric, crystallographically independent trinuclear Cu(II) complexes and two ClO 4 - ions. The crystallographically independent trinuclear Cu(II) complexes differ mainly in some of their geometry parameters. The coordination environment of the central copper atom is square-planar, in one trinuclear entity, and elongated octahedral in the other one (in this last case, the coordination number of the central copper atom increases through the semicoordination of an oxygen…
Complexes of organometallic compounds. L. The correlation between 119Sn mössbauer isomer shifts and calculated partial charges on tin in adducts of t…
1981
Abstract The relationship between Mossbauer isomer shifts, δ, and atomic charges on tin, QSn has been studied for homologous series RnSnhal4−n· L2 [ n = 0−3; L2 = donor atoms of 1, 2-bis(dipheylphosphino)ethane, N, N′-ethylenebes(salicylideneimine) and N, N′-ethylenbes(acetylacetoneimine)] and Snhal4· 2PR3. Semiempirical values of QSn have been calculated by two methods based on the concept of orbital electronegativity equalization upon bond formation. Linear correlations δ/QSn are obtained, which can be function of the coordination number of the metal atom, for terms of the series characterized by different orbital electronegativities of atoms directly bound to tin. Deviations occur for ad…
Global Frequency and Geographical Distribution of Nighttime Streamer Corona Discharges (BLUEs) in Thunderclouds
2021
This is an open access article under the terms of the Creative Commons Attribution-NonCommercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes.
Flume experiments for assessing the dye-tracing technique in rill flows
2021
Abstract Flow velocity controls hillslope soil erosion and is a key hydrodynamic variable involved in sediment transport and deposition processes. The dye-tracer technique is one of the most applied methods for measuring velocity of shallow interrill and rill flow. The technique is based on the injection of a tracer in a specific point and the measurement of its speed to travel the known distance from the injection point to a given channel section. The dye-tracer technique requires that the measured surface flow velocity has to be corrected to obtain the mean flow velocity using a correction factor which is generally empirically deduced. The technique has two sources of uncertainties: i) th…
ELDAR, a new method to identify AGN in multi-filter surveys: the ALHAMBRA test case
2017
We present ELDAR, a new method that exploits the potential of medium- and narrow-band filter surveys to securely identify active galactic nuclei (AGN) and determine their redshifts. Our methodology improves on traditional approaches by looking for AGN emission lines expected to be identified against the continuum, thanks to the width of the filters. To assess its performance, we apply ELDAR to the data of the ALHAMBRA (Advance Large Homogeneous Area Medium Band Redshift Astronomical) survey, which covered an effective area of 2.38 deg2 with 20 contiguous medium-band optical filters down to F814W ≃ 24.5. Using two different configurations of ELDAR in which we require the detection of at lea…
THE MISSING LINK: MERGING NEUTRON STARS NATURALLY PRODUCE JET-LIKE STRUCTURES AND CAN POWER SHORT GAMMA-RAY BURSTS
2011
Short Gamma-Ray Bursts (SGRBs) are among the most luminous explosions in the universe, releasing in less than one second the energy emitted by our Galaxy over one year. Despite decades of observations, the nature of their "central-engine" remains unknown. Considering a binary of magnetized neutron stars and solving Einstein equations, we show that their merger results in a rapidly spinning black hole surrounded by a hot and highly magnetized torus. Lasting over 35 ms and much longer than previous simulations, our study reveals that magnetohydrodynamical instabilities amplify an initially turbulent magnetic field of ~ 10^{12} G to produce an ordered poloidal field of ~ 10^{15} G along the bl…
Basis-set extrapolation techniques for the accurate calculation of molecular equilibrium geometries using coupled-cluster theory
2006
To reduce remaining basis-set errors in the determination of molecular equilibrium geometries, a basis-set extrapolation (BSE) scheme is suggested for the forces used in geometry optimizations. The proposed BSE scheme is based on separating the Hartree-Fock and electron-correlation contributions and uses expressions obtained by straightforward differentiation of well established extrapolation formulas for energies when using basis sets from Dunning's hierarchy of correlation-consistent basis sets. Comparison with reference data obtained at the R12 coupled-cluster level [CCSD(T)-R12] demonstrates that BSE significantly accelerates the convergence to the basis-set limit, thus leading to impro…
Entanglement generation between two spin-s magnetic impurities in a solid via electron scattering
2009
Abstract We present a scheme for generating entanglement between two magnetic impurities in a solid-state system via electron scattering. The scheme applies to impurities of arbitrary quantum spin number. We show that resonance conditions yield generation of a maximally entangled state of the impurities' spins, regardless of the value of the electron–impurity coupling constant and the impurity spin quantum number. The mechanism behind the scheme is explained in terms of resonance-induced selection rules.