bluuebunny/crossref_metadata_2025 huggingface dataset:
Half‐ and finite‐range completeness for the equation of transfer of polarized light
Authors: Van Mee C. V. M. Der , Neunzert H.
Published: March 2007

On neglecting reflection by the surface the existence and uniqueness are proved for the solution of the equation of transfer of polarized light in a homogeneous semi‐infinite or finite plane‐parallel medium. A general LL‐space formulation, where 1 ≤ p < ∞, is adopted. The analysis concerns a vector‐valued convolution equation, which is an equivalent form of the equation of radiative transfer and is solved with the help of Wiener‐Hopf factorization, Fredholm index and cone preservation methods. The results are also proved for the equations obtained from the full equation of transfer by means of Fourier expansion and symmetry relations.
Transmutation via the momentum plane
Authors: Carroll R. , Jones D. S.
Published: March 2007

Transmutation methods are developed for equations of the form x2 φ“ + x2(k2” ‐ q̃(x)) φ = (v2 ‐ (1/4)) φ, with v as spectral variable, which correspond to problems in quantum scattering theory at fixed energy k2 (here v ˜ l + (1/2) with l complex angular momentum). Spectral formulas for transmutation kernels are constructed and the machinery of transmutation theory developed by the author for spectral variable k is shown to have a version here. General Kontrorovič‐Lebedev theorems are also proved.
Two remarks on continuation procedures for solving some nonlinear equations
Authors: Descloux J. , Nedelec J. C.
Published: March 2007

Let F be a mapping from Rn+1 into Rn, x(t) be a parametrization for ∣t − t0 ∣ < c, of a smooth solution branch of the equation F(x) = 0, A(t) be the jacobian (n + 1) associated to a standard continuation method used for computing the solution branch. We study for a class of singularities at x(t0) the behaviour, near t = t0, of the determinant of A(t).
Die lösung der maxwellschen gleichungen durch vollständige flächenfeldsysteme
Authors: Kersten H. , Leis R.
Published: March 2007

The paper deals with approximation theorems for the solution of Maxwell's equations governing the mathematical description of the propagation of electromagnetic waves.

The well‐known results ([10]) for the Helmholtz equation are generalized to Maxwell's equations: Systems of electric (resp. magnetic) dipoles are proved to span the space of all solutions of rot H + iωE = 0, rotE ‐ iωH = 0, with n × E prescribed on the boundary. The same result holds for the “Mie‐potentials”

magnified image

Which can be proved by a Lemma of Mie [6].

Two numerical examples for the three‐dimensional boundary value problems (field of a dipole, field of reflection) are presented.
Étude asymptotique des phénomènes acoustiques dans un mélange fluide‐solide thermoélastique
Authors: Fleury F. , Nedelec J. C.
Published: March 2007

Asymptotic study of the macroscopie behaviour of a fluid‐thermoelastic solid mixture. The homogenization theory is applied to the study of small perturbations in a mixture of a thermoelastic solid and a viscous compressible fluid. There appear memory phenomena in the bulk behaviour as well as a modification in the initial data regarding the original problem. The convergence of the formal asymptotic expansion to the solution of the homogenized equations is proved.
Qualitative properties of the boundary derivative of the capacity potential for special classes of annular domains
Authors: Acker A. , Payne L. E.
Published: March 2007

Let U(p) denote the capacity potential in an annular domain Ω (bounded by Jordan curves). We describe the qualitative behavior of ∥Δ∥ on the line segments of ∂Ω which are arbitrary, radial, or ν‐directional (for some vector ν ≠ 0) in the respective cases where Ω is a convex, starlike, or ≠‐convex annular domain. We apply these results to some free‐boundary extremal problems in which the capacity plus weighted area functional is minimized in restricted classes of annular domains Ω.
Ein eindeutigkeitssatz für strahlungslösungen eines übergangsproblems zur schwingungsgleichung mit unbeschränkter trennfläche
Authors: Beck P. , Leis R.
Published: March 2007

We shall derive a Rellich‐type‐estimate for solutions in RN of a transmission problem associated with a second order uniformly elliptic differential operator of Helmholtz‐type. The transitional surface is supposed to be unbounded and a characterization of its behaviour at infinity is given. Using this estimate, we can prove a uniqueness theorem for radiation solutions of the transmission problem.
Erhaltungssätze und schwache lösungen in der gasdynamik
Authors: Bruhn G. , Wendland W.
Published: March 2007

The fundamental laws of Gasdynamics can be formulated very naturally as conservation laws in the form of integral relations. This formulation includes not only continuously differentiable processes but also the very important discontinuous shocks. On the other side one has the tool of weak solutions of the differential equations of Gasdynamics due to P. D. Lax and several other authors. While the conservation laws of integral type are determined by Physics in an unique way the differential equations of Gasdynamics, even if written in divergence form, are not. Hence the question arises which form of the differential equations in the weak sense is the “correct” interpretation of the physical conservation laws. This paper tries to give an answer by investigating the connections between the two formulations. At first the integral equations of Gasdynamics are written in space‐time divergence form. Thus, independently from Gasdynamics, one has Haar's lemma stating that for each weak solution of a partial differential equation (in divergence form) a corresponding integral equation of conservation law type is valid for almost every family member, the family consisting of some simple domains like spheres or squares. Moreover the converse of Haar's lemma is also true. In this paper Haar's lemma is extended to a more general class of domains. This yields that both formulations of conservation laws are essentially equivalent. Additionally a divergence definition due to C. Müller is considered. As is shown by a simple example C. Müller's divergence concept leads to a more general class of solutions, not all of them being solutions of the corresponding conservation laws.
Remarks on perfectly absorbing boundary conditions
Authors: Kołakowski H. , Piskorek A.
Published: March 2007

A mixed problem imitating the Cauchy problem is considered. This problem is also a mixed problem with perfectly absorbing boundary conditions. A theorem about the form of the problem imitating the Cauchy problem for a scalar operator was given in [3]. Some theorems concerning perfectly absorbing boundary condition can be found in [1], [2].
On a free boundary value problem of physical geodesy, II (existence)
Authors: Witsch K. J. , Leis R.
Published: March 2007

The determination of the figure of the earth is considered as a local free boundary value problem of potential theory. In the C1,ε‐topology local existence is proved by means of Legendre transforms. This method also provides an elementary argument for the regularity of the solutions.
A reaction‐diffusion system modelling the spread of bacterial infections
Authors: Blat J. , Brown K. J. , Hadeler K. P.
Published: March 2007

We investigate a system of reaction‐diffusion equations which model the spread of a bacterial infection in a human population. A decoupling technique together with global bifurcation theory is used to study the steady‐state solutions of the system. The asymptotic behaviour of solutions is discussed by using sub and subersolutions and the quasimonotonicity of the system.
On a nonlinear volterra equation
Authors: Wroclaw W. Okrasiński , Meister E.
Published: March 2007

Nonnegative solutions u of the nonlinear Volterra equation u = a * g(u) (g(0) = 0) in mathematical physics are considered. Under certain assumptions the nonhomogenuous equation u = a * g(u) + ƒ is studied. Some approximations of nonnegative solutions of the homogenuous equation are considered by the nonnegative solutions of the nonhomogenuous one.
Exterior stokes problems and decay at infinity
Authors: Specovius‐Neugebauer Maria , Wendland W.
Published: March 2007

We study the exterior Dirichlet and Neumann problem for the 3‐dimensional Stokes equations. By the use of the theory of hydrodynamical potentials, the decay at infinity can be completely characterized in the framework of weighted Sobolev spaces. The results are applied to the theory of weak solutions and to the Whitehead paradox.
On the geometric form of free boundaries satisfying a bernoulli condition. II
Authors: Acker A. , Payne L. E.
Published: March 2007

In the x‐y plane, let Ω be an annular domain whose interior boundary Γ* is a known Jordan curve and whose exterior boundary Γ is a free boundary characterized by the condition that|ΔU| = 1 on Γ, where U is the capacity potential in Ω. We obtain a qualitative description of Γ involving such things as its inflection points and local maxima and minima relative to specified directions. We also extend these results to obtain qualitative properties of the free boundary when it is subjected to various geometric contraints. Our results generalize those in [1].
Generalized herglotz domains
Authors: Colton D. , Wimp J. , Hsiao G. C.
Published: March 2007

Let F(θ k, α) be the far field pattern arising from the scattering of a time harmonic plane acoustic wave of wave number k and direction a by a sound‐soft cylinder of cross section D. Suppose F has the Fourier expansionmagnified imagewhere an = an(k, . Then if ϰ2 is a Dirichlet eigenvalue for D, sufficient conditions are given on D for the existence of a nontrivial sequence |bn| where the bn are independent of such that for all directions magnified imageDomains for which this is true are called generalized Herglotz domains. The conditions for a domain to be a generalized Herglotz domain are given either in terms of the Schwarz function for the analytic boundary ϱD or in terms of the Rayleigh hypothesis in acoustic scattering theory and examples are given showing the applicability of these conditions.
A note on the rate of convergence for certain nonlinear evolution equations
Authors: Alberti P. M. , Crell B. , Neunzert H.
Published: March 2007

We estimate the rate of convergence to the stationary state for evolution equations which admit many H‐theorems with respect to this stationary state.
A free boundary problem and stability for the nonlinear beam
Authors: Miersemann E. , Mittelmann H. D. , Törnig W.
Published: March 2007

The stability bound for the classical nonlinear Euler beam is determined in the case that its deflection is limited by an obstacle parallel to the plane of the beam. Let a clamped or simply supported beam be axially compressed by a force P > P0, where P0 denotes the critical load. So far only a linear theory has been applied to analyze the stability of the solutions in contact with the obstacle and the jumping to a different state. Utilizing a free boundary problem formulation we analytically as well as numerically answer these questions for the nonlinear beam.
On the scattering frequencies of time‐dependent potentials
Authors: Cooper J. , Perla‐Menzala G. , Strauss W. , Werner P.
Published: March 2007

This paper discusses the scattering frequencies associated with the scalar wave equation and a time‐periodic, real, potential. It is shown that the scattering frequencies form a discrete set in the complex plane and depend continuously on the potential. Existence of the scattering frequencies is proved for periodic potentials which are perturbations of a time independent, nonnegative, potential.
Some algorithms of the projective‐Newton method for the finite element space
Authors: Hobot G. , Pokora T. , Mitchell A. R.
Published: March 2007

The paper presents the projective‐Newton method in the finite element space with curved finite elements along the boundary. The properties of this method are studied when the integrals are calculated by numerical quadrature. Some algorithms are derived when ω = {x ϵ R2: 0 < x1, x2 < 1}.
Finite time blow‐up and stability properties of materials with fading memory
Authors: Calderer M. C. , Hsiao G.
Published: March 2007

A detailed analysis of the equations of nonlinear elasticity is carried out for a certain class of initial‐boundary value problems.

In particular, I examine whether the presence in the differential equation of a mechanical mechanism of dissipation is able to prevent instabilities and ensure global existence in time of the solutions.
Stability of a layer of dipolar fluid heated from below
Authors: Straughan B. , Payne L. E.
Published: March 2007

The equations of Bleustein and Green [2] are formulated in a way suitable to describe the convective instability which occurs when a layer of dipolar fluid is heated from below. The linear instability boundary is shown to coincide with the nonlinear stability curve and the critical Rayleigh numbers describing this boundary are found; in particular, the non‐dimensional micro‐length is found to always stabilize.
Ästhetische rechtecksmaße, die maßstabsunabhängig sind
Authors: Benz W. , Wendland W.
Published: March 2007

An aesthetical measure of rectangles which is continuous and does not depend on the scale must be classical. There exist non classical measures which are scale‐independent.
On the geometric form of solutions of a free boundary problem involving galvanization
Authors: Acker A. , Payne L. E.
Published: March 2007

In [6], T. I. Vogel studied a free boundary problem originating in the galvanization process. He showed that if the given boundary Γ* is starlike or convex, then so is the free boundary solution Γ. Our purpose is to generalize Vogel's second result by showing (under certain assumptions) that Γ cannot have more (local) maxima or minima (relative to a given direction) than Γ*; also that Γ cannot have more inflection points or greater total curvature than Γ*. The author has already proven analogous results for the Bernoulli free boundary problem in [1], [2] and [3].
A potential well theory for the heat equation with a nonlinear boundary condition
Authors: Levine H. A. , Smith R. A. , Payne L. E.
Published: March 2007

The present paper employs potential well arguments of a previous work by the authors [6] to obtain a sharp existence‐nonexistence alternative for solutions to the linear heat equation subject to a non‐linear boundary condition.
On a class of probability distributions
Authors: Lehnigk S. H. , Roach G. F.
Published: March 2007

The application of a three parameter class of one‐sided probability distributions is being discussed. For specific parameter values, this class contains as special cases a number of well‐known distributions of statistics and statistical physics, namely, Gauss, Weibull, exponential, Rayleigh, Gamma, chi‐square, Maxwell, and Wien (limiting case of Planck's distribution). One of the three parameters represents scale; the other two represent initial and terminal shape of the associated probability density function. A fourth parameter, shift, may be introduced. The distribution class discussed in this paper was introduced by L. Amoroso [2] in 1924. It is closely connected with a family of linear Fokker‐Planck equations (generalized Feller equation). In fact, the class of probability density functions associated with the distribution class considered here is a special case of the set of all delta function initial condition solutions of the generalized Feller equation for a fixed value of the time variable. It will be shown that, as a function of the logarithm of the independent variable, the logarithm of the cumulative distribution function is asymptotically linear as the independent variable approaches zero from above. This fact leads to a general criterion for the applicability of the presented distribution family relative to given empirical data. The applicability criterion can be used to determine approximate values for the two shape parameters. They can subsequently be used as initial values in any of the established parameter estimation techniques.
Study of an elliptic problem with nonlinear boundary conditions
Authors: Caussignac Ph. , Descloux J. , Rappaz J. , Rappaz J. , Nedelec J. C.
Published: March 2007

We consider the problem of finding on a trapezium a harmonic function u the normal derivative of which is equal on one side to λ exp(u). We prove the existence of a solution branch (λ,u(λ)) with a turning point and, for the case of the square, the presence of bifurcations. The “inverse power” algorithm converges on a part of the branch.
Motion of a vibrating string in the presence of a convex obstacle: A free boundary problem
Authors: Cabannes H. , Neunzert H.
Published: March 2007

Here we study the motion of a vibrating string in the presence of an arbitrary obstacle. We show that if the string always rebounds on the concave parts of the obstacle, it can either rebound or roll on the convex parts. The latter is the case if the velocity of the string is null at the contact point just before contact, or if the contact point propagates at a characteristic speed. Four examples are given. The three first correspond to the same obstacle, a sinusoidal arc, but with different initial conditions. In the first case, the string rebounds on the whole of the obstacle and the motion is explicitly determined when it is periodic. In the second case, the string rolls on the convex part of the obstacle up to the inflexion point and then rebounds on the concave part and unwinds on the convex part. In the third case, the string is initially at rest on the obstacle; then it instantaneously leaves the concave part while it unwinds progressively on the convex part. The fourth case is similar to the third but with a different obstacle; the motion, which is periodic, is determined explicitly.
The electrostatic potential of spherical polyelectrolytes in aqueous solution
Authors: Ohlenbusch H.‐D. , Freeden W. , Törnig W.
Published: March 2007

The electrostatic potential in systems of spherical polyelectrolytes is determined by superposition of spherically symmetric solutions of the linearized Poisson‐Boltzmann equation. The case of constant surface potential is investigated in detail. Higher‐order approximations are given by use of a generalization of the addition theorem for modified Bessel functions.
On the initial layer and the existence theorem for the nonlinear Boltzmann equation
Authors: Lachowicz M. , Neunzert H.
Published: March 2007

The truncated Hilbert expansion including the initial layer terms is considered. This enables us to replace the singulary perturbed Boltzmann equation by a weakly nonlinear equation. In this way the existence of a strong solution of the Boltzmann equation is obtained for initial data close enough to a local Maxwellian. The solution exists in the physically significant time interval on which smooth solutions to the Euler equations exist.
On approximation to convective diffusion equation
Authors: Nigam K. D. P. , Srivastava V. K. , Haque M. W. , Lvov V.
Published: March 2007

A closed‐form analytical solution for the problem of homogeneous and heterogeneous reactions in a isothermal non‐Newtonian laminar flow tubular reactor is presented. A technique is evolved where Galerkin method is applied in Laplace‐transformed domain.
Evolution systems in semiconductor device modeling: A cyclic uncoupled line analysis for the gummel map
Authors: Jerome Joseph W. , Brosowski B.
Published: March 2007

The initial/boundary‐value problem for isothermal, lattice, semiconductor device modeling is described and analyzed. This nonlinear elliptic/parabolic system of reaction/diffusion/convection type is determined by a Maxwell equation, relating space/charge and the electric field, and by two continuity equations for the free electron and hole carrier concentrations. The Einstein relations for Brownian motion are not assumed in this analysis, so that the electrostatic potential, u, and the carrier concentrations, n and p, are the fundamental dependent variables of the system. The boundary conditions are Dirichlet conditions for dependent variable values on the contact portions of the device, and homogeneous Neumann conditions, expressing insulation, on the complement. Complicating the analysis are the transition singularity points between the mixed boundary conditions, and the field dependence of the mobility and diffusion coefficients. By means of a physically motivated analysis of the convective current component, we are able to uncouple the system by a cyclic horizontal line analysis, without an unreasonable time step restriction. The corresponding linear equations are solved by a contractive inner iteration. The outer iteration is shown to converge to a unique solution of the system, under singularity classification at the transition points. The definition of this outer iteration follows the steady‐state Gummel iteration at discrete time steps. An existence theory is a by‐product of the analysis, and is separated from uniqueness theory.
The Galerkin‐averaging method for nonlinear, undamped continuous systems
Authors: Stroucken A. C. J. , Verhulst F. , Eckhaus W.
Published: March 2007

The analysis of initial‐boundary value problems for nonlinear evolution equations with a small parameter is carried out by projection and averaging. The complications of the extension to a second order approximation is discussed and subsequently demonstrated for the perturbed Klein‐Gordon equation. The difference between the case of resonance and nonresonance at first order is emphasized.
An integral equation of the first kind for a free boundary value problem of the stationary Stokes' equations
Authors: Hebeker F. K. , Nedelec J. C.
Published: March 2007

We investigate a free boundary value problem of the stationary Stokes' equations. In a previous paper adapted hydrodynamical potentials have been constructed and their jump relations have been discussed. Here we study a direct method to obtain an equivalent boundary integral equations' system of the first kind. Its solution properties are investigated in the framework of strongly elliptic pseudodifferential operators. For numerical purposes a suitable representation formula for the variational equation is given in terms of integro‐differential operators which avoids the evaluation of hypersingular integrals.
Plane potential flow past a cylinder with porous surface
Authors: Wegert E. , Wolfersdorf L. V. , Meister E.
Published: March 2007

In the paper two models for the potential flow past a cylinder with porous or perforated surface are reduced to nonlinear Riemann‐Hilbert problems for the complex velocity function and general existence and uniqueness theorems for the solution of the problems are derived. Further the problems are reduced to nonlinear singular integral equations of Hilbert type whose solvability is investigated by means of the Schauder and Banach fixed point theorem.
Approximation dans un Problème de Viscoélasticité Périodique
Authors: Teniou D. , Nedelec J. C.
Published: March 2007

We are concerned with equations which derive from a quasistatic periodic problem of viscoelasticity. We give a condition which yields to existence and uniqueness of a periodic solution. Then we prove a finite element method based on equilibrium elements for the space approximation and on the explicit Euler scheme for the time approximation.
Energy properties preserving schemes for Burgers' equation
Authors: Anguelov R. , Djoko J.K. , Lubuma J.M.‐S.
Published: March 2007

The Burgers' equation, a simplification of the Navier–Stokes equations, is one of the fundamental model equations in gas dynamics, hydrodynamics, and acoustics that illustrates the coupling between convection/advection and diffusion. The kinetic energy enjoys boundedness and monotone decreasing properties that are useful in the study of the asymptotic behavior of the solution. We construct a family of non‐standard finite difference schemes, which replicate the energy equality and the properties of the kinetic energy. Our approach is based on Mickens' rule [Nonstandard Finite Difference Models of Differential Equations, World Scientific, Singapore, 1994.] of nonlocal approximation of nonlinear terms. More precisely, we propose a systematic nonlocal way of generating approximations that ensure that the trilinear form is identically zero for repeated arguments. We provide numerical experiments that support the theory and demonstrate the power of the non‐standard schemes over the classical ones. © 2007 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2007
Superconvergence analysis of the Galerkin FEM for a singularly perturbed convection–diffusion problem with characteristic layers
Authors: Franz Sebastian , Linß Torsten
Published: March 2007

We analyze the superconvergence property of the Galerkin finite element method (FEM) for elliptic convection–diffusion problems with characteristic layers. This method on Shishkin meshes is known to be almost first‐order accurate (up to a logarithmic factor) in the energy norm induced by the bilinear form of the weak formulation, uniformly in the perturbation parameter. In the present paper the method is shown to be almost second‐order superconvergent in this energy norm for the difference between the FEM solution and the bilinear interpolant of the exact solution. This supercloseness property is used to improve the accuracy to almost second order by means of a postprocessing procedure. Numerical experiments confirm these results. © 2007 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2007
A new development in polyesters derived from terephthalic acid: A polyether ester based on polyethylene terephthalate
Authors: Ijzermans A. B. , Pluijm F. J. , Huntjens F. J. , Repin J. F.
Published: March 2007

An exploratory investigation has been carried out into a segmented polyether ester which consists of amorphous soft segments of polytertramethylene ether glycol and crystalline short chain hard segments of polyethylene terephthalate. The properties of this block copolymer have been compared with those of polyethylene terephthalate and polytetramethylene terephthalate (PTMT) and with those of the block copolymer based on PTMT. After a description of the preparation and the structure of the polyether ester, the thermal properties are discussed by means of DTA thermograms. From the stress‐strain behaviour, compared with that of the homopolymers, the elastomeric properties of the block copolymers stand out clearly. Processing characteristics are discussed on the basis of the crystallisation behaviour and the relationship between melt viscosity and shear rate. Finally, data about u.v., oxidative and hydrolytic stability are given.
The thermal degradation of perfluoroalkylene‐linked organosiloxane polymers
Authors: Cotter John L. , Knight Graham J. , Wright Walter W.
Published: March 2007

Two perfluoroalkylene‐linked organosiloxane polymers have been studied by thermogravimetry, pyrolysis–gas chromatography–mass spectrometry and fluoride ion analysis. Fluorine transfer processes play an important part in the thermal breakdown.
Electroinitiated emulsion polymerisation of vinyl acetate. II. Characteristics of the emulsion polymerisation
Authors: Tidswell Bryan M. , Train Andrew W.
Published: March 2007

The characteristics of the propagation process for the electroinitiated emulsion polymerisation of vinyl acetate are described when current is varied by a factor of 36 and emulsifier concentration by 128. The order with respect to current is 0.8, whilst with emulsifier concentration, two definite ranges are observed with exponents 0.26 and 1.12 at low and high concentrations respectively. A similar two range effect is observed using particle size measurements. Behaviour at low emulsifier concentration is similar to that described previously for vinyl acetate, involving particle formation mainly by precipitation from solution. At high emulsifier concentrations micelle formation appears to be of increased importance.
Polymerisation reactions initiated by high electric fields. Kinetic applications in the field of free cationic polymerisations
Authors: Brendle Marcel C. C. , Ilvoas Anne‐Marie
Published: March 2007

Free cationic polymerisations were initiated in bulk by field ionisation with a positive tip. Dilatometric measurements obtained with ‘dry’ and ‘ultra‐dry’ styrene, a‐methylstyrene and isobutylvinylether were in agreement with kinetic equations derived by assuming that in the absence of deactivating impurities the space charge is built up only by growing macromolecules.

Determination of the space charge by independent physical methods suggests that the kp values of the literature need to be re‐evaluated. It was also shown that charge injection enhances the degree of dryness (measurable by this process) and is therefore useful in ultimate purification of monomers.
Liquid‐liquid phase separation in multicomponent polymer systems. XIII quasi‐binary phase diagrams with three‐liquid‐phase separation
Authors: Kleintjens L. A. , Schoffeleers H. M. , Domingo L.
Published: March 2007

Using the Gibbs free energy of mixing relation of Flory and Huggins with a concentration‐dependent interaction parameter one can calculate quasi‐binary phase diagrams for solvent‐polymer systems. If the polymer has a very asymmetric molecular weight distribution, separation into three‐liquid‐phases occurs which may result in a cloud‐point curve without stable critical point. In the latter case the spinodal does not touch the stable branches of the cloud‐point curve and the coexistence curves show marked bends and kinks. These phenomena could be qualitatively verified by experiments on the system cyclohexane‐polystyrene. The phase‐volume ratio method for the determination of consolute states itself clearly indicates when situations prevail precluding its applicability.
Electric birefringence of cellulose trinitrate in acetone
Authors: Isles M. , Jennings Barry R.
Published: March 2007

Electric birefringence studies have been made on a sample of high molecular weight cellulose trinitrate in acetone. The molecule is shown to have only a permanent dipole moment and no significant anisotropic polarisability in this solvent. Both the rotary relaxation times obtained from transient time dependent effects and the amplitudes of the observed birefringence have been analysed in terms of theories for rigid rods, weakly bending rods, worm‐like chains and both flexible and stiff random coils. The study indicates that (a) electric birefringence data are sensitive to molecular flexibility and (b) that in this solvent, nitrocellulose of 12% nitrogen content appears to be a stiff, non free draining coil with a dipole moment of the order of a few debye (i.e. ⋍ 10−29 C m) per monomer unit.
Thermally initiated oxidation and ignition of flexible polyurethane foams
Authors: Eaves D. E. , Keen C. V.
Published: March 2007

Oxidation and ignition of flexible polyurethane foams have been investigated by observing the effects of internal and external heating. External temperatures of some 190°C are required to induce combustion. Internal temperatures of 250 −350°C initiate a self‐propagating internal reaction which results in foam ignition when the reaction reaches the foam surface. The stability of a polyurethane foam to such heating increases with the age of the foam.
Diffusion of some dyes in aqueous polymer solutions
Authors: Farag Ahmed A. , Sedahmed G. H. , Farag H. A. , Nagawi A. F.
Published: March 2007

The diffusion of both Direct Blue 76 and acid orange dyes in aqueous dilute polymer solutions was studied using the capillary method. The polymer systems studied included dilute solutions of carboxymethyl cellulose, polyethylene oxide and polyacrylamide. It was found that the diffusion coefficients of the two dyestuffs in carboxymethyl cellulose solutions are higher than that in pure water, while in polyacrylamide solutions the values of the coefficients are lower than that in pure water. In case of polyethylene oxide solutions, the diffusion coefficient of Direct Blue 76 was found to be lower than that in pure water, whereas that of acid orange was found to be higher than that in pure water.

The diffusion coefficients of both dyes were found to decrease with increasing polymer concentration in the case of polyethylene oxide and polyacrylamide, whereas in the case of carboxymethyl cellulose the diffusion coefficients increased with polymer concentration.

With change of temperature, the diffusion coefficients of both dyes in the three polymer solutions were found to obey the Arrhenius equation. The activation energy for diffusion of the two dyes was calculated in pure water, as well as in the different polymer solutions.
Effect of natural ageing on the dielectric properties of some synthetic rubber mixtures
Authors: Hakim Itedal K. , Hanna Faika F.
Published: March 2007

The dielectric constant ε′ and dielectric loss ε″ have been investigated for SBR samples loaded with some white fillers and for perbunan rubber loaded with silica and carbon black in the frequency range from 60 to 107 Hz at room temperature. The samples were exposed to normal weathering conditions for about five years. The results are compared with those obtained five years before and the differences are interpreted.
Temperature drop turbidimetry as a means for the rapid determination of the polydispersities of polymers: Polystyrene
Authors: Afifi‐Effat A. M. , Hay J. N.
Published: March 2007

The molecular weight distributions of fractionated and unfractionated polystyrene samples were determined from turbidimetric data obtained by controlled precipitation from dilute solutions in cyclohexanol by cooling from 90 to 20°C. Estimates of the distributions were obtained by calibration of the temperatures of onset of precipitation and the weight average molecular weight of the polymer in solution, as suggested by Shultz,1 and correcting for the concentration change on precipitation.
Flexible relaxation of rigid‐body docking solutions
Authors: Król Marcin , Tournier Alexander L. , Bates Paul A.
Published: March 2007

Molecular Dynamics (MD) simulations have been performed on a set of rigid‐body docking poses, carried out over 25 protein–protein complexes. The results show that fully flexible relaxation increases the fraction of native contacts (NC) by up to 70% for certain docking poses. The largest increase in the fraction of NC is observed for docking poses where anchor residues are able to sample their bound conformation. For each MD simulation, structural snap‐shots were clustered and the centre of each cluster used as the MD‐relaxed docking pose. A comparison between two energy‐based scoring schemes, the first calculated for the MD‐relaxed poses, the second for energy minimized poses, shows that the former are better in ranking complexes with large hydrophobic interfaces. Furthermore, complexes with large interfaces are generally ranked well, regardless of the type of relaxation method chosen, whereas complexes with small hydrophobic interfaces remain difficult to rank. In general, the results indicate that current force‐fields are able to correctly describe direct intermolecular interactions between receptor and ligand molecules. However, these force‐fields still fail in cases where protein–protein complexes are stabilized by subtle energy contributions. Proteins 2007. © 2007 Wiley‐Liss, Inc.
Quantum‐chemical examination of interaction of cytostatic‐fluorouracil with deoxyribonucleic acids
Authors: Yuldasheva Gulnara , Zhidomirov Georgii M.
Published: March 2007

Within the framework of semiempirical method of quantum chemical PM3, the possibility of formation of paired stack structures under interaction of fluorouracil with pyrimidine and purine nitrogenous bases of nucleotides has been examined. Possible mechanism of transformation of 2‐deoxyuridine‐5‐monophosphate into metabolite‐5‐fluorin‐2‐deoxyuridine‐5‐monophosphate has been given. The calculations that were made allow to suppose that biotransformation of 5‐FU in 5‐fluorin‐2‐deoxyuridine‐5‐monophosphate, most likely, is carried out not in free nucleotides, but in the structure of DNA in two nucleotide triplets UUC and UGU, including the case when directly two nucleotides of deoxyuridine monophosphate, are transformed into 5‐fluorin‐2‐deoxyuridine‐5‐monophosphate. Cytostatic ability of 5‐FU is increased by its capacity to be selectively embedded into nucleotide triplets creating new chemical compounds that violate matrix RNA formation and accordingly violate protein synthesis. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2007
Reaction mechanism of platinum dimer cation with ammonia based on the relativistic density functional study
Authors: Xu Dan , Chen Xian‐Yang , Wang Shu‐Guang
Published: March 2007

The gas‐phase reactions between Pt and NH3 have been investigated using the relativistic density functional approach (ZORA‐PW91/TZ2P). The quartet and doublet potential energy surfaces of Pt + NH3 have been explored. The minimum energy reaction path proceeds through the following steps: Pt(4Σu) + NH3 → q‐1 → d‐2 → d‐3 → d‐4 → d‐Pt2NH+ + H2. In the whole reaction pathway, the step of d‐2 → d‐3 is the rate‐determining step with a energy barrier of 36.1 kcal/mol, and exoergicity of the whole reaction is 12.0 kcal/mol. When Pt2NH+ reacts with NH3 again, there are two rival reaction paths in the doublet state. One is degradation of NH and another is loss of H2. In the case of degradation of NH, the activation energy is only 3.4 kcal/mol, and the overall reaction is exothermic by 8.9 kcal/mol. Thus, this reaction is favored both thermodynamically and kinetically. However, in the case of loss of H2, the rate‐determining step's energy barrier is 64.3 kcal/mol and the overall reaction is endothermic by 8.5 kcal/mol, so it is difficult to take place. Predicted relative energies and barriers along the suggested reaction paths are in reasonable agreement with experimental observations. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2007
Net charge and polarizability of zeolitic Brønsted acidic sites
Authors: Torrens F. , Castellano G.
Published: March 2007

The interacting induced‐dipoles polarization model, implemented in our program POLAR, is used for the calculation of the effective polarizability of the zeolitic bridged OH group, which results much higher than that of the free silanol group. A high polarizability is also calculated for the bridged OH group with a Si4+, in the absence of Lewis‐acid promotion of silanol by Al3+. The crystal polarizability is estimated from the Clausius‐Mossotti relationship. Siliceous zeolites are low‐permittivity isolators. The interaction of a weak base with the zeolitic OH can be considered as a local bond. Only when cations are located in the zeolite micropore, next to tetrahedra that contain trivalent cations, are large electrostatic fields generated. They are short ranged, and the positive cation charges are compensated. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2007
Time evolution of the Neel state
Authors: Soluyanov A. A. , Zagoulaev S. N. , Abarenkov I. V.
Published: March 2007

A quasionedimentional spin chain s = ½ is considered as a lattice consisting of two sublattices. The attention is paid to the states, which are pure spin states of the whole lattice and both sublattices, the value of the sublattices' spins being maximum. It is shown that the Neel state can be considered as a superposition of such states. The exact equation for this superposition coefficients is developed. The possibility of the Neel state to be the eigenstate of a Hamiltonian is discussed. Several model Hamiltonians are examined, the well known ones and few novel Hamiltonians being considered. The time evolution of the Neel state in different models is studied with the help of Fock‐Krylov method. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2007
A Calorimetric Study of the Interaction between Waxy Maize Starch and Lipid
Authors: Abu‐Hardan Madian O. , Hill Sandra E. , Farhat Imad A.
Published: March 2007

There is considerable debate on the definition and measurement of the amount of amylose in starch and whether hydrophobic ligands can form a complex with amylopectin. One method for amylose determination is through the measurement of amylose‐lipid complexation using differential scanning calorimetry (DSC), with the assumption that amylopectin cannot form such a complex. As the sensitivity and methodologies used for DSC improves, the validity of this assumption needs to be tested once again. For the experimental work, α‐L‐lysophosphatidylcholine (LPC, 10% of starch dry weight) was used as the complexing agent and waxy maize starch. Optimisation of the DSC included changing the heating rate from 10ºC/min to 40ºC/min, which resulted in a higher sensitivity enabling the recording of an endotherm associated with the dissociation of a starch‐LPC complex. The observation of the endothermic formation of such complex could only be achieved when a microcalorimeter, which analyses a much larger sample than a standard calorimeter (190 mg of dry starch compared to 13 mg) was used. There are two possible interpretations for these observations: Either waxy maize starch contains traces of amylose (~ 0.5‐0.7%) and the DSC is sufficiently sensitive to detect these amounts or the α‐1,6 glucan long branches of waxy maize starch bind linear aliphatic compounds.
Pilot‐plant fractionation of cottonseed. I. Disintegration of cottonseed meats
Authors: Spadaro J. J. , Persell R. M. , Murphey C. H. , Vix H. L. E. , McCourtney E. J. , Hecker J. L. , Pollard E. F. , Gastrock E. A.
Published: March 2007

Disintegration of cottonseed meats is an important unit operation in the cottonseed fractionation process. The results of tests utilizing a high‐speed, “dissolver‐type” impeller for disintegration by liquid shear are presented including curves to show the effect of moisture, hulls, solvents, peripheral speed, etc.

Over 90% of through‐80‐mesh material can be obtained. Moisture content over 5% appreciably reduced the efficiency and increased power consumption and the viscosity of the slurry. Whole flakes resulted in a finer end product than flakes pre‐pulverized in the dry state. It was found that the presence of hulls slightly increased disintegration, power consumption, and viscosity; that higher speeds (up to 6,000 FPM peripheral speed) were more efficient; and that the effect of solvents was small.
The effect of shortening stability on commercially produced army ration biscuits. II. Development of oxidation during storage
Authors: Stevens Harold H. , Thompson John B.
Published: March 2007

The comparative rates of oxidation of the shortening in 22 lots of biscuits held under three different conditions of packaging at two different storage temperatures have been discussed. Relating stability tests to storage tests is practically impossible considering the numerous conditions of storage which might be encountered. Accelerated tests, however, are valuable for comparative purposes.

Considering only the development of “rancidity”, a 100‐hour shortening appears to be adequate protection up to 12 months of storage at a maximum temperature of 100o F. for either Type I or Type IV Army ration biscuits when stored in either sealed cans or adequate breather‐type containers.

The poor storage life of Army ration biscuits, packaged in fiberboard containers, was shown to be due primarily to the nature of the packaging material.

Insofar as Army ration biscuits are concerned, the addition of N.D.G.A. to lard does not result in a significant increase in biscuit stability.
Chinese tallow nut protein. I. Isolation, amino acid, and vitamin analysis
Authors: Holland Bryant R. , Meinke W. W.
Published: March 2007

Conclusion

The protein of the Chinese tallow nut is quite easily isolated by employing rather mild conditions. On the basis of amino acid values presented, both the protein and flour should be suitable as a protein feed. The relatively low lysine and methionine content however would limit the usefulness of the protein as a supplement to cereal grains. The relatively high thiamin content of the protein, in addition to the presence of smaller amounts of the other B vitamins determined, suggests the possible use of this material in the enrichment of flour for the baking industry. The industrial possibilities in addition to the food value of the protein are yet to be determined.
Fatty acids from the scent glands of the Louisiana muskrat
Authors: Erickson J. L. E. , Hix Homer B.
Published: March 2007

The mixture of fatty acids from muskrat scent glands has been analyzed by the ester fractionation method.

The esters of myristic, palmitic, hexadecenoic, oleic, and linoleic acids were found present as major components in these glands. Unsaturated acids of the C24 and C26 series are also present to the extent of 8.5% of the total fatty acids. Acids present to less than 1% each include decanoic, dodecanoic, stearic, tetracosanoic, dodecenoic, and tetradecenoic acids.

Application of determinants for the solution of simultaneous equations has been presented as a method which greatly simplifies and facilitates the calculations necessary to this type of work.

The possible relationship existing between fatty acids and macrocyclic carbinols has been considered and possible mechanisms for such transformations have been presented.
Application of the antimony trichloride‐spectrophotometric method to the determination of gossypol in cottonseed and cottonseed products
Authors: Hall Catherine M. , Castillon Leah E. , Guice Wilma A. , Boatner Charlotte H.
Published: March 2007

A method is described which permits application of the antimony trichloride spectrophotometric method to the determination of gossypol in a variety of cottonseed products.

Gossypol is determined by means of the following series of operations: 1. extraction of gossypol from cottonseed or cottonseed products by use of chloroform or aqueous ethanol; 2. isolation of gossypol from the extracts by use of aqueous alkali; and 3. application of the antimony trichloride‐spectrophotometric test.

Data are presented to show the results obtained by application of this procedure to the determination of gossypol in pigment glands, raw cottonseed meats, cooked cottonseed meats, hydraulic‐ and screw‐pressed meals, solvent‐extracted meals, gland‐free meals, and oils, both expressed and solvent‐extracted.
Effects of positive youth development programs on school, family, and community systems
Authors: Durlak Joseph A. , Taylor Rebecca D. , Kawashima Kei , Pachan Molly K. , DuPre Emily P. , Celio Christine I. , Berger Sasha R. , Dymnicki Allison B. , Weissberg Roger P.
Published: March 2007

A review of efforts at social system change in 526 universal competence‐promotion outcome studies indicated that 64% of the interventions attempted some type of microsystemic or mesosystemic change involving schools, families, or community‐based organizations in an attempt to foster developmental competencies in children and adolescents. Only 24% of the reports provided quantitative data on the change that occurred in targeted systems. However, studies containing the necessary information produced several mean effect sizes that were statistically significant, and ranged from modest to large in magnitude. These data indicate that attempts to change social systems affecting children and adolescents can be successful. Future work should measure more thoroughly the extent to which the systemic changes that are targeted through intervention are achieved, and investigate how such changes contribute to the development and sustainability of the outcomes that might be demonstrated by participants of competence‐promotion programs.