64 research outputs found
Dinuclear Re(I) Complexes as New Electrocatalytic Systems for CO2 Reduction
A family of dinuclear tricarbonyl rhenium (I) complexes containing bridging 1,2-diazine ligand and halide anions as ancillary ligands and able to catalyze CO2 reduction is presented. Electrochemical studies show that the highest catalytic efficiency is obtained for the complex containing the 4,5-bipenthyl-pyridazine and iodide as ancillary halogen ligands. This complex gives rise to TOF=15 s−1 that clearly outperforms the values reported for the benchmark mononuclear Re(CO)3Cl(bpy) (11.1 s−1). The role of the substituents on the pyridazine ligand and the nature of the bridging halide ligands on the catalytic activity have been deeply investigated through a systematic study on the structure-properties relationship to understand the improved catalytic efficiencies of this class of complexes
Tilt-over mode in a precessing triaxial ellipsoid
The tilt-over mode in a precessing triaxial ellipsoid is studied
theoretically and numerically. Inviscid and viscous analytical models
previously developed for the spheroidal geometry by Poincar\'e [Bull. Astr. 27,
321 (1910)] and Busse [J. Fluid Mech., 33, 739 (1968)] are extended to this
more complex geometry, which corresponds to a tidally deformed spinning
astrophysical body. As confirmed by three-dimensional numerical simulations,
the proposed analytical model provides an accurate description of the
stationary flow in an arbitrary triaxial ellipsoid, until the appearance at
more vigorous forcing of time dependent flows driven by tidal and/or
precessional instabilities.Comment: http://link.aip.org/link/doi/10.1063/1.350435
Dirhenium Coordination Complex Endowed with an Intrinsically Chiral Helical-Shaped Diphosphine Oxide
A one-pot, multicomponent strategy was used to synthesize the first example of the dirhenium carbonyl coordination complex 2, in which the two metal atoms are connected through a chiral helical-shaped diphosphine oxide. Thanks to the flexibility of the helix of helicene 1, complex 2 was isolated in quite a good yield as a stable compound. It was characterized by analytical and spectroscopic techniques as well as by single-crystal X-ray analysis, which confirmed the chemical structure and the peculiar architecture of 2. In addition, computational studies were in agreement with the transitions observed in the experimental UV\u2013vis spectrum, revealing the presence of two bands with maxima at about 520 (metal-to-ligand charge transfer) and 400 nm (IL
Toxic gas removal – metal–organic frameworks for the capture and degradation of toxic gases and vapours
The release of anthropogenic toxic pollutants into the atmosphere is a worldwide threat of growing
concern. In this regard, it is possible to take advantage of the high versatility of MOFs materials in order
to develop new technologies for environmental remediation purposes. Consequently, one of the main
scientific challenges to be achieved in the field of MOF research should be to maximize the
performance of these solids towards the sensing, capture and catalytic degradation of harmful gases
and vapors by means of a rational control of size and reactivity of the pore walls that are directly
accessible to guest molecules.The authors are grateful for the generous support by the
Spanish Ministries of Economy (project: CTQ2011-22787) and
Defense (COINCIDENTE Program) as well as Junta de Andalucia
(P09-FQM-4981)
A simple thermodynamic model of diluted hydrogen gas/plasma for CFD applications
This work describes a simple thermodynamic model of the hydrogen gas at low densities and for temperatures going from those involving quantum rotations of ortho- and para-hydrogen up to the fully ionized state. The closed-form energy levels of Morse rotating oscillator given [D.C. Harris, M.D. Bertolucci, Symmetry and Spectroscopy (Dover, New York, 1989)] (but not those in Morse’s original paper) are shown to provide an internal partition function of H2 that is a sufficiently accurate representation of that exploiting the state-of-the-art spectrum of roto-vibrational levels calculated by Pachucki and Komasa [K. Pachucki, J. Komasa, J. Chem. Phys. 130, 164113 (2009)]. A system of two coupled quadratic equations for molecular dissociation and atomic ionization at thermodynamical and chemical equilibrium is derived according to the statistical mechanics by assuming that the system is an ideal mixture containing molecules, neutral atoms and noninteracting protons and electrons. The system of two equations reduces to a single quartic equation for the ionization unknown, with the coefficients dependent on the temperature and the specific volume. Explicit relations for specific energy and entropy of the hydrogen ideal gas/plasma model are derived. These fully compatible equations of state provide a complete thermodynamic description of the system, uniformly valid from low temperatures up to a fully ionized state, with electrons and ions relaxed to one and the same temperature. The comparison with results of other models developed in the framework of the physical and chemical pictures shows that the proposed elementary model is adequate for computational fluid dynamics purposes, in applications with the hydrogen gas under diluted conditions and when the dissociation and ionization can be assumed at thermodynamical and chemical equilibrium
Subgrid Stabilized Projection Method for 2D Unsteady Flows at High Reynolds Numbers
A subgrid stabilization technique is developed for solving the two-dimensional incompressible Navier–Stokes equations at high Reynolds numbers. The time marching algorithm is based on a well-established fractional-step pressure-correction projection method. The advection–diffusion step is enriched by an implicit subgrid stabilizing term and by an explicit dissipative shock capturing term. The former is calculated by means of a hierarchical finite element setting, the latter is included to avoid Gibbs’ phenomenon in the boundary layer. Convergence tests on prototypical two-dimensional examples are reported and the method is used to simulate the viscous incompressible flows around the airfoil NACA0012 at zero incidence and Reynolds numbers ranging from 105 to 106
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