Acid-base, electron-donating and magnetic properties of Nd2O3 and its mixed oxides with alumina catalysts

The electron donor properties of Nd2O3 activated at 300, 500 and 800°C were investigated through studies on the adsorption of electron acceptors of various electron affinities - 7, 7, 8,8-tetracyanoquinodimethane (2.84 eV). 2, 3, 5, 6-tetrachloro-l , 4-benzoquinone (2.40 eV). p-dinitrobenzene (1.77 eV), and m-dinitrobenzene (1.26 eV) in solvents acetonitrile and 1, 4-dioxan. The extent of electron transfer during adsorption has been found from magnetic measurements and electronic spectral data. The corresponding data on mixed oxides of neodymium and aluminium are reported for various. compositions. The acid-base properties of catalysts were also determined using a set of Hammett indicators.

Surface Electron Donor Properties of Dy2O3,Y2O3 and Their Mixed Oxides with Alumina Catalyst

The limit of electron transfer in electron affinity from the oxide surface to the electron acceptor (EA) are reported from the adsorption of EA on DY203, mixed oxides of DY203 with alumina and mixed oxides of Y203 with y-alumina. The extent of electron transfer is understood from magnetic measurements.

Thermal lens technique to study the effect of pH on electronic energy transfer in organic dye mixtures.

The effect of pH on the fluorescence efficiency of fluorescein is evaluated using thermal lens technique. Fluorescence efficiency increases as the sample becomes more and more alkaline. But when fluorescein is mixed with rhodamine B fluorescence quenching of fluorescein takes place with the excitation of rhodamine B. The electronic energy transfer in this mixture is investigated using Optical Parametric Oscillator as the excitation source. The effect of pH on the efficiency of energy transfer in fluorescein–rhodamine B mixture is presented.

A mixed H2/H∞-based semiactive control for vibration mitigation in flexible structures

In this paper, we address this problem through the design of a semiactive controller based on the mixed H2/H∞ control theory. The vibrations caused by the seismic motions are mitigated by a semiactive damper installed in the bottom of the structure. It is meant by semiactive damper, a device that absorbs but cannot inject energy into the system. Sufficient conditions for the design of a desired control are given in terms of linear matrix inequalities (LMIs). A controller that guarantees asymptotic stability and a mixed H2/H∞ performance is then developed. An algorithm is proposed to handle the semiactive nature of the actuator. The performance of the controller is experimentally evaluated in a real-time hybrid testing facility that consists of a physical specimen (a small-scale magnetorheological damper) and a numerical model (a large-scale three-story building)

Estimates of electronic coupling for excess electron transfer in DNA

Electronic coupling Vda is one of the key parameters that determine the rate of charge transfer through DNA. While there have been several computational studies of Vda for hole transfer, estimates of electronic couplings for excess electron transfer (ET) in DNA remain unavailable. In the paper, an efficient strategy is established for calculating the ET matrix elements between base pairs in a π stack. Two approaches are considered. First, we employ the diabatic-state (DS) method in which donor and acceptor are represented with radical anions of the canonical base pairs adenine-thymine (AT) and guanine-cytosine (GC). In this approach, similar values of Vda are obtained with the standard 6-31 G* and extended 6-31++ G* basis sets. Second, the electronic couplings are derived from lowest unoccupied molecular orbitals (LUMOs) of neutral systems by using the generalized Mulliken-Hush or fragment charge methods. Because the radical-anion states of AT and GC are well reproduced by LUMOs of the neutral base pairs calculated without diffuse functions, the estimated values of Vda are in good agreement with the couplings obtained for radical-anion states using the DS method. However, when the calculation of a neutral stack is carried out with diffuse functions, LUMOs of the system exhibit the dipole-bound character and cannot be used for estimating electronic couplings. Our calculations suggest that the ET matrix elements Vda for models containing intrastrand thymine and cytosine bases are essentially larger than the couplings in complexes with interstrand pyrimidine bases. The matrix elements for excess electron transfer are found to be considerably smaller than the corresponding values for hole transfer and to be very responsive to structural changes in a DNA stack

New delay-dependent stability criteria for uncertain neutral systems with mixed time-varying delays and nonlinear perturbations

The problem of stability analysis for a class of neutral systems with mixed time-varying neutral, discrete and distributed delays and nonlinear parameter perturbations is addressed. By introducing a novel Lyapunov-Krasovskii functional and combining the descriptor model transformation, the Leibniz-Newton formula, some free-weighting matrices, and a suitable change of variables, new sufficient conditions are established for the stability of the considered system, which are neutral-delay-dependent, discrete-delay-range dependent, and distributeddelay-dependent. The conditions are presented in terms of linear matrix inequalities (LMIs) and can be efficiently solved using convex programming techniques. Two numerical examples are given to illustrate the efficiency of the proposed method

Synthesis, structure, solution chemistry and the electronic effect of para substituents on the vanadium center in a family of mixed-ligand [(VO)-O-V(ONO)(ON)] compexes

Four tridentate dibasic ONO donor hydrazone ligands derived from the condensation of benzoylhydrazine with either 2-hydroxyacetophenone or its para substituted derivatives (H2L1-4, general abbreviation H2L) have been used as primary ligands and 8-hydroxyquinoline (Hhq, a bidentate monobasic ON donor species) has been used as auxiliary ligand. The reaction of [(VO)-O-IV(acac)21 with H2L in methanol followed by the addition of Hhq in equimolar ratio under aerobic condition afforded the mixed-ligand oxovanadium(V) complexes of the type [(VO)-O-V(L)(hq)] (1-4) in excellent yield. The X-ray structure of the compound [(VO)-O-V(L-4)(hq)] (4) indicates that the H2L4 ligand is bonded with vanadium meridionally in a tridentate dinegative fashion through its deprotonated phenolic-O, deprotonated enolic-O and imine-N atoms. The V-O bond length order is: oxo < phenolato < enolato. H-1 NMR spectra of 4 in CDCl3 solution indicates that it's solid-state structure is retained in solution. Complexes are diamagnetic and exhibit only ligand to metal charge transfer (LMCT) transition band near 530 nm in CH2Cl2 solution in addition to intra-ligand pi-pi* transition band near 335 rim and they display quasi-reversible one electron reduction peak near -0.10 V versus SCE in CH2Cl2 solution. lambda(max) (for LMCT transition) and the reduction peak potential (E-p(c)) values of the complexes are found to be linearly related with the Hammett (sigma) constants of the substituents in the aryloxy ring of the hydrazone ligands. lambda(max) and E-p(c) values show large dependence d lambda(max)/d sigma = 32.54 nm and dE(p)(c)/d sigma = 0.19 V, respectively, on the Hammett constant. (c) 2006 Elsevier B.V. All rights reserved.

Mixed ligand binuclear copper(I) complexes containing (Cu2N8)-N-I chromophores. Observation of emissions from MLCT excited states involving two different ligands

Using the 1:2 condensate (L) of diethylenetriamine and benzaldehyde as the main ligand, binuclear copper(l) complexes [Cu2L2(4,4'-bipyridine)](CIO4)(2).0.5H(2)O (1a) and [Cu2L2(1,2-bis(4-pyridyl)ethane)](CIO4)(2) (1b) are synthesised. The two metal ions in la are bridged by 4,4'-bipyridine and those in 1b by 1,2-bis(4-pyridyl)ethane, From the X-ray crystal structure of la, each metal ion is found to be bound to three N atoms of L and one of the two N atoms of the bridging ligand in a distorted tetrahedral fashion. The Cu(I)-N bond lengths in la lie in the range of 1.998(5)-2.229(6) Angstrom. Electrochemical studies in dichloromethane (DCM) show that the (Cu2N8)-N-I moieties in la and 1b are composed of two essentially non-interacting (CuN4)-N-I cores with Cu-II/I potential of 0.44 V vs. SCE. While la displays metal induced quenching of the inherent emission of 4,4'-bipyridine in DCM solution, 1b exhibits two weak emission bands in DCM solution at 425 and 477 nm (total quantum yield = 3.59 x 10(-5)) originating from MLCT excited states. With the help of Extended Huckel calculations it is established that the higher energy emission in 1b is from Cu(I) --> bridging-ligand charge transfer excited state and the lower energy one in 1b from Cu(I) --> L charge transfer excited state.

Electronic energy transfer in a dinuclear Ru/Os complex containing a photoresponsive dithienylethene derivative as bridging ligand

In order to build up a multicomponent system able to perform useful light-induced functions, a dithienylethene-bridged heterodinuclear metal complex (Ru/Os) has been prepared. The compound was characterized and its photophysical properties studied in detail.

Brussels French une fois: Transfer-induced innovation or system-internal development?

In language contact studies, specific features of the contact languages are often seen to be the result of transfer (interference), but it remains difficult to disentangle the role of intra-systemic and inter-systemic factors. We propose to unravel these factors in the analysis of a feature of Brussels French which many researchers attribute to transfer from (Brussels) Dutch: the adverbial use of une fois. We compare the use of this particle in Brussels French with its occurrence in corpora of other varieties of French, including several that have not been influenced by a Germanic substrate or adstrate. A detailed analysis of the frequency of occurrence, the functions and the distribution of the particle over different syntactic positions shows that some uses of une fois can be traced back to sixteenth-century French, but that there is also ample evidence for overt and covert transfer (Mougeon and Beniak, 1991) from Brussels Dutch.

Sparse polynomial approximation in positive order Sobolev spaces with bounded mixed derivatives and applications to elliptic problems with random loading

In the present paper we study the approximation of functions with bounded mixed derivatives by sparse tensor product polynomials in positive order tensor product Sobolev spaces. We introduce a new sparse polynomial approximation operator which exhibits optimal convergence properties in L2 and tensorized View the MathML source simultaneously on a standard k-dimensional cube. In the special case k=2 the suggested approximation operator is also optimal in L2 and tensorized H1 (without essential boundary conditions). This allows to construct an optimal sparse p-version FEM with sparse piecewise continuous polynomial splines, reducing the number of unknowns from O(p2), needed for the full tensor product computation, to View the MathML source, required for the suggested sparse technique, preserving the same optimal convergence rate in terms of p. We apply this result to an elliptic differential equation and an elliptic integral equation with random loading and compute the covariances of the solutions with View the MathML source unknowns. Several numerical examples support the theoretical estimates.

A mixed-phase bulk orographic precipitation model with embedded convection

A novel analytical model for mixed-phase, unblocked and unseeded orographic precipitation with embedded convection is developed and evaluated. The model takes an idealised background flow and terrain geometry, and calculates the area-averaged precipitation rate and other microphysical quantities. The results provide insight into key physical processes, including cloud condensation, vapour deposition, evaporation, sublimation, as well as precipitation formation and sedimentation (fallout). To account for embedded convection in nominally stratiform clouds, diagnostics for purely convective and purely stratiform clouds are calculated independently and combined using weighting functions based on relevant dynamical and microphysical time scales. An in-depth description of the model is presented, as well as a quantitative assessment of its performance against idealised, convection-permitting numerical simulations with a sophisticated microphysics parameterisation. The model is found to accurately reproduce the simulation diagnostics over most of the parameter space considered.

Solar wind-magnetosphere coupling functions on timescales of 1 day to 1 year

There are no direct observational methods for determining the total rate at which energy is extracted from the solar wind by the magnetosphere. In the absence of such a direct measurement, alternative means of estimating the energy available to drive the magnetospheric system have been developed using different ionospheric and magnetospheric indices as proxies for energy consumption and dissipation and thus the input. The so-called coupling functions are constructed from the parameters of the interplanetary medium, as either theoretical or empirical estimates of energy transfer, and the effectiveness of these coupling functions has been evaluated in terms of their correlation with the chosen index. A number of coupling functions have been studied in the past with various criteria governing event selection and timescale. The present paper contains an exhaustive survey of the correlation between geomagnetic activity and the near-Earth solar wind and two of the planetary indices at a wide variety of timescales. Various combinations of interplanetary parameters are evaluated with careful allowance for the effects of data gaps in the interplanetary data. We show that the theoretical coupling, P�, function first proposed by Vasyliunas et al. is superior at all timescales from 1-day to 1-year.

NAD Biosynthesis Evolution in Bacteria: Lateral Gene Transfer of Kynurenine Pathway in Xanthomonadales and Flavobacteriales

The biosynthesis of quinolinate, the de novo precursor of nicotinamide adenine dinucleotide (NAD), may be performed by two distinct pathways, namely, the bacterial aspartate (aspartate-to-quinolinate) and the eukaryotic kynurenine (tryptophan-to-quinolinate). Even though the separation into eukaryotic and bacterial routes is long established, recent genomic surveys have challenged this view, because certain bacterial species also carry the genes for the kynurenine pathway. In this work, both quinolinate biosynthetic pathways were investigated in the Bacteria clade and with special attention to Xanthomonadales and Bacteroidetes, from an evolutionary viewpoint. Genomic screening has revealed that a small number of bacterial species possess some of the genes for the kynurenine pathway, which is complete in the genus Xanthomonas and in the order Flavobacteriales, where the aspartate pathway is absent. The opposite pattern (presence of the aspartate pathway and absence of the kynurenine pathway) in close relatives (Xylella ssp. and the order Bacteroidales, respectively) points to the idea of a recent acquisition of the kynurenine pathway through lateral gene transfer in these bacterial groups. In fact, sequence similarity comparison and phylogenetic reconstruction both suggest that at least part of the genes of the kynurenine pathway in Xanthomonas and Flavobacteriales is shared by eukaryotes. These results reinforce the idea of the role that lateral gene transfer plays in the configuration of bacterial genomes, thereby providing alternative metabolic pathways, even with the replacement of primary and essential cell functions, as exemplified by NAD biosynthesis.

Transfer reactions in the investigation of light-nuclei nucleosynthesis

Cross sections for the (6)Li(p,gamma)(7)Be, (7)Li(n,gamma)(8)Li (8)Li(n,gamma)(9)Li and (8)Li(p,gamma)(9)Be capture reactions have been investigated in the framework of the potential model. The main ingredients of the potential model are the potentials used to generate the continuum and bound-state wave functions and spectroscopic factors of the corresponding bound systems. The spectroscopic factors for the (7)Li circle times n=(8)Li(gs), (8)Li circle times n=(9)Li(gs) bound systems were obtained from a FR-DWBA analysis of neutron transfer reactions induced by (8)Li radioactive beam on a (9)Be target, while spetroscopic factor for the (8)Li circle times n=(9)Be(gs) bound system were obained from a proton transfer reaction. From the obtained capture reaction cross section, reaction rate for the (8)Li(n,gamma)(9)Li and (8)Li(p,gamma)(9)Be direct neutron and proton capture were determined and compared with other experimental and calculated values.