Search results for "value"
showing 10 items of 5321 documents
Numerical investigations of single mode gyrotron equation
2009
A stationary problem with the integral boundary condition arising in the mathematical modelling of a gyrotron is numerically investigated. The Chebyshev's polynomials of the second kind are used as the tool of calculations. The main result with physical meaning is the possibility to determine the maximal value of electrons efficiency. First published online: 14 Oct 2010
Complex Ground-State and Excitation Energies in Coupled-Cluster Theory
2021
Since in coupled-cluster (CC) theory ground-state and excitation energies are eigenvalues of a non-Hermitian matrix, these energies can in principle take on complex values. In this paper we discuss the appearance of complex energy values in CC calculations from a mathematical perspective. We analyze the behaviour of the eigenvalues of Hermitian matrices that are perturbed (in a non-Hermitian manner) by a real parameter. Based on these results we show that for CC calculations with real-valued Hamiltonian matrices the ground-state energy generally takes a real value. Furthermore, we show that in the case of real-valued Hamiltonian matrices complex excitation energies only occur in the context…
A study of coronene?coronene association using atom?atom pair potentials
1996
A study of the coronene—coronene association using different interaction potentials based on an atom-atom pair potential proposed by Fraga has been performed. The interaction potentials employed differ in the way the electrostatic and/or dispersion contributions are computed. The influence of both contributions on the geometries predicted for the coronene dimer is discussed in order to analyze the effectiveness of the different interaction potentials. The stationary points found in each interaction energy hypersurface are characterized by calculating the Hessian eigenvalues. Results are discussed in the light of those previously reported for the benzene dimer. Stacked-displaced structures a…
Transfer coefficients for the liquid–vapor interface of a two-component mixture
2011
Abstract We present the excess entropy production for heat and mass transport across an interface of a non-ideal two-component mixture, using as interface variables the excess densities proposed by Gibbs. With the help of these variables we define the interface as an autonomous system in local equilibrium and study its transport properties. The entropy production determines the conjugate fluxes and forces, and equivalent forms are given. The forms contain finite differences of intensive variables into and across the surface as driving forces. These expressions for the fluxes serve as boundary conditions for integration across heterogeneous systems that are far from global equilibrium. The r…
Conventional, non-conventional extraction techniques and new strategies for the recovery of bioactive compounds from plant material for human nutriti…
2019
Considering a large number of variations in the chemical structures of bioactive compounds (BACs) that are valuable to humans and a large number of their sources, it is necessary to build a standard and integrated extraction and analytical approaches for obtaining these compounds. From this perspective, the main purpose of this Special Issue of Food Research International was to publish research related to the extractions with data about isolation of BACs from plant matrices for human nutrition. This Special Issue includes both, conventional and innovative extraction techniques, highlighting their characteristics and advantages in relation to the target matrix. Many of presented works conta…
Improved embedded molecular cluster model
2002
We demonstrate that boundary effects (i.e., displacements of the cluster boundary atoms from their lattice sites and the difference between effective charges of the perfect crystal atoms and those of the cluster atoms in the case of a cluster with no point defect in it) in an embedded molecular cluster (EMC) model can be radically reduced. A new embedding scheme is proposed. It includes search for the structural elements (SE) of which perfect crystal is composed, use of corresponding to these SE expression for the total energy, and application of the degree of localization of equations consistent with the wave functions of the cluster. To get equations for the cluster wave functions, the pr…
Determination of the stoichiometry of mixed microcrystals K x Cs y ZnCl 4 using instrumental neutron activation analysis
1998
Instrumental neutron activation analysis (INAA) has been employed as an absolute method for the determination of the stoichiometry of mixed microcrystals KxCsyZnCl4 with a weight ranging between 20 and 50 μg. The reliability of the method has been checked with the pure substances KCl, NaCl, CsCl and RbCl, for which the mean value of the ratio Cl/X was found to be 1.04 (3).
Site-Specific Information on Membrane Protein Folding by Electron Spin Echo Envelope Modulation Spectroscopy
2010
Compared to folding of soluble proteins, folding of membrane proteins is complicated by the fact that it requires an amphiphilic environment. Few existing techniques can provide structurally resolved information on folding kinetics. For the major plant light harvesting complex LHCII, it is demonstrated that changes in water accessibility of a particular amino acid residue can be followed during folding by measuring the hyperfine interaction of spin labels with deuterium nuclei of heavy water. The incorporation of residue 196 into the hydrophobic core of a detergent micelle was investigated. The technique provides a time constant that is similar to the one found with fluorescence spectroscop…
Interaction effects of enniatin B, deoxinivalenol and alternariol in Caco-2 cells.
2015
Enniatin B (ENN B), deoxinivalenol (DON) and alternariol (AOH) are secondary metabolites of filamentous fungi. These mycotoxins are contaminants of vegetables and cereals. They are cytotoxic and their effects are enhanced by their mixtures. The objectives of this study were to compare the cytotoxicity of ENN B, DON and AOH alone or in combination in human adenocarcinoma (Caco-2) cells and to evaluate the type of interactions of mycotoxin mixtures by the isobologram analysis. Cells were treated with concentrations ranging from 1.85 to 90μM (AOH) and from 0.312 to 10μM (for ENN B and DON), individually and in combination of two and three mycotoxins (from 1.85 to 30μM for AOH and from 0.312 to…