bluuebunny/crossref_metadata_2025 huggingface dataset:
Constructing weighing matrices by the method of weaving
Authors: Craigen R.
Published: June 2007

We describe a way of obtaining new weighing matrices from old, which we call weaving because it involves distributing rows and columns of given matrices along the columns and rows of an array to form a partitioned matrix whose blocks have rank one. The method generalizes both the direct sum and direct product of matrices. We use the method to construct some new weighing matrices of relatively small order. © 1995 John Wiley & Sons, Inc.
Some graphs with characteristic polynomials which are not solvable by radicals
Authors: Godsil C. D.
Published: June 2007

We show that “almost all” trees have characteristic polynomials which are not solvable by radicals.
Graphs with constant link and small degree or order
Authors: Hall J. I.
Published: June 2007

The graph G has constant link L if for each vertex x of G the graph induced by G on the vertices adjacent to x is isomorphic to L. For each graph L on 6 or fewer vertices we decide whether or not there exists a graph G with constant link L. From this we are able to list all graphs on 11 or fewer vertices which have constant link.
Representing groups by graphs with constant link and hypergraphs
Authors: Vogler Walter
Published: June 2007

A graph L is called a link graph if there is a graph G such that for each vertex of G its neighbors induce a subgraph isomorphic to L. Such a G is said to have constant link L. We prove that for any finite group Γ and any disconnected link graph L with at least three vertices there are infinitely many connected graphs G with constant link L and AutG ⋍ Γ. We look at the analogous problem for connected link graphs, namely, link graphs that are paths or have disconnected complements. Furthermore we prove that for n, r ≥ 2, but not n = 2 = r, any finite group can be represented by infinitely many connected r‐uniform, n‐regular hypergraphs of arbitrarily large girth.
A criterion for the planarity of a graph
Authors: Breitenbach Jerome R.
Published: June 2007

In a recent paper, Carsten Thomassen [Carsten Thomassen, Planarity and duality of finite and infinite graphs. J. Combinatorial Theory Ser. B 29 (1980) 244–271] has shown that a number of criteria for the planarity of a graph can be reduced to that of Kuratowski. Here we present another criterion which, as well, is easily proved via Kuratowski's. The criterion is based on the observation that the imbedding of a graph in a plane imposes a cyclic ordering, say clockwise, on the edges incident with each vertex, and that these cyclic orderings are related.
Decomposition of snarks
Authors: Cameron Peter J. , Chetwynd Amanda G. , Watkins John J.
Published: June 2007

There are several methods for constructing snarks (cubic graphs with chromatic index 4). We study the reverse process of splitting a snark into smaller snarks which compose it. We also introduce the notion of a “prime” snark.
On the equality of the grundy and ochromatic numbers of a graph
Authors: Erdös P. , Hare W. R. , Hedetniemi S. T. , Laskar R.
Published: June 2007

It is proved in this note that the Grundy number, Γ(G), and the ochromatic number, χ0(G), are the same for any graph G.
Labelled graphs with vertices of degree at least three
Authors: Goulden I. P. , Jackson D. M.
Published: June 2007

The generating function for labelled graphs in which each vertex has degree at least three is obtained by the Principle of Inclusion and Exclusion. Asymptotic and explicit values for the coefficients are calculated in the connected case. The results are extended to bipartite graphs.
Subcontraction‐equivalence and Hadwiger's conjecture
Authors: Woodall D. R.
Published: June 2007

The concept of subcontraction‐equivalence is defined, and 14 graph‐theoretic properties are exhibited that are all subcontraction‐equivalent if Hadwiger's conjecture is true. Some subsets of these properties are proved to be subcontraction‐equivalent anyway. Hadwiger's conjecture is expressed as the union of three independent and strictly weaker subconjectures. As a first step toward one of these subconjectures, it is proved that a graph that does not have Km+1 as a subcontraction must contain an independent set consisting of at least 1/2(m − 1) of its vertices.
On unavoidable hypergraphs
Authors: Chung F. R. K. , Erdös P.
Published: June 2007

A r‐uniform hypergraph H (or a r‐graph, for short) is a collection E = E(H) of r‐element subsets (called edges) of a set V = V(H) (called vertices). We say a r‐graph H is (n, e)‐unavoidable if every r‐graph with n vertices and e edges must contain H. In this paper we investigate the largest possible number of edges in an (n, e)‐unavoidable 3‐graph for fixed n and e. We also study the structure of such unavoidable 3‐graphs.
Longest paths and cycles in bipartite oriented graphs
Authors: Min Zhang Ke
Published: June 2007

In this paper we obtain two sufficient conditions, Ore type (Theorem 1) and Dirac type (Theorem 2), on the degrees of a bipartite oriented graph for ensuring the existence of long paths and cycles. These conditions are shown to be the best possible in a sense.
Diameter increase caused by edge deletion
Authors: Schoone A. A. , Bodlaender H. L. , Van Leeuwen J.
Published: June 2007

We consider the following problem: Given positive integers k and D, what is the maximum diameter of the graph obtained by deleting k edges from a graph G with diameter D, assuming that the resulting graph is still connected? For undirected graphs G we prove an upper bound of (k + 1)D and a lower bound of (k + 1)D − k for even D and of (k + 1)D − 2k + 2 for odd D ⩾ 3. For the special cases of k = 2 and k = 3, we derive the exact bounds of 3D − 1 and 4D − 2, respectively. For D = 2 we prove exact bounds of k + 2 and k + 3, for k ⩽ 4 and k = 6, and k = 5 and k ⩾ 7, respectively. For the special case of D = 1 we derive an exact bound on the resulting maximum diameter of order θ(√k). For directed graphs G, the bounds depend strongly on D: for D = 1 and D = 2 we derive exact bounds of θ(√k) and of 2k + 2, respectively, while for D ⩾ 3 the resulting diameter is in general unbounded in terms of k and D. Finally, we prove several related problems NP‐complete.
The number of maximal independent sets in connected graphs
Authors: Füredi Zoltán
Published: June 2007

Generalizing a theorem of Moon and Moser, we determine the maximum number of maximal independent sets in a connected graph on n vertices for n sufficiently large, e.g., n > 50.
On the construction and enumeration of minimal blocks
Authors: Read Ronald C. , Hu Guanzhang
Published: June 2007

In this paper a method is given for constructing and enumerating the minimal blocks on a given number of vertices using the graphs on a smaller number of vertices. Minimal blocks having up to 12 vertices have been constructed in this way.
On k‐leaf connectivity of a random graph
Authors: Luczak Thomasz
Published: June 2007

We prove that, in a random graph with n vertices and N = cn log n edges, the subgraph generated by a set of all vertices of degree at least k + 1 is k‐leaf connected for c > 1/4. A threshold function for k‐leaf connectivity is also found.
An historical note: Euler's Königsberg letters
Authors: Sachs Horst , Stiebitz Michael , Wilson Robin J.
Published: June 2007

In this paper we discuss three little known letters on the Königsberg bridges problem. These letters indicate more clearly Euler's attitude to the problem and to his solution of it.
Chromatic factorizations of a graph
Authors: Hakimi S. Louis , Schmeichel Edward F.
Published: June 2007

Let n1 ⩾ n2 ⩾ …︁ ⩾ nk ⩾ 2 be integers. We say that G has an (n1, n2, …︁, nk‐chromatic factorization if G) can be edge‐factored as G1 ⊕ G2 ⊕ …︁ ⊕ Gk with χ(Gi) = nAi, for i = 1,2,…, k. The following results are proved:

If (n1 − 1)n2 …︁ nk < χ(G) ⩽ n1n2 …︁ nk, then G has an (n1, n2, …︁, nk)‐chromatic factorization.

If n1 + n2 + …︁ + nk − (k ‐ 1) ⩽ n ⩽ n1n2 …︁ nk, then Kn has an (n1, n2, …︁, nk)‐chromatic factorization.
The reconstruction conjecture is true if all 2‐connected graphs are reconstructible
Authors: Yongzhi Yang
Published: June 2007

It is shown that the Reconstruction Conjecture is true for all finite graphs if it is true for the 2‐connected ones.
Some unavoidable subdigraphs of tournaments
Authors: Petrović Vojislav
Published: June 2007

Let H(n, i) be a simple (n − 1)‐path v1 → v2 → …︁ → vn with an additional arc v1vi (3 ⩽ i ⩽ n). We prove that for each n and i (3 ⩽ i ⩽ n), with few exceptions, every n‐tournament Tn contains a copy of H(n, i).
Rectilinear drawings of graphs
Authors: Thomassen Carsten
Published: June 2007

We consider graphs drawn in the plane such that every edge crosses at most one other edge. We characterize, in terms of two forbidden sub‐configurations, which of these graphs are equivalent to drawings such that all edges are straight line segments. As a consequence we obtain a complete characterization of the pairs of dual graphs that can be represented as geometric dual graphs such that all edges except one are straight line segments.
Average distance in graphs with removed elements
Authors: Bienstock D. , Györi E.
Published: June 2007

The average distance in a graph is defined as the average length of a shortest path between two vertices, taken over all pairs of vertices. This parameter can be contrasted with the diameter as a description of the metrical properties of the graph. If a vertex or edge is removed from a graph, in the worst case the average distance will increase. In this paper we consider the question, How small can the increase be if we choose the vertex or edge appropriately? If the graph is a cycle, the increase is roughly by a factor of 4/3. P. Winkler conjectured that any graph contains a vertex whose removal will not increase the average distance by more than a factor of 4/3. A similar conjecture can be made about removed edges, provided, for example, that the graph is 2‐edge‐connected. We prove the stronger statement that the edge version of the conjecture is true if the graph has no vertices of degree one. We also give an asymptotic affirmative answer for the vertex version.
Claw‐free graphs are edge reconstructible
Authors: Ellingham M. N. , Pyber L. , Yu Xingxing
Published: June 2007

The Edge Reconstruction Conjecture states that all graphs with at least four edges are determined by their edge‐deleted subgraphs. We prove that this is true for claw‐free graphs, those graphs with no induced subgraph isomorphic to K1,3. This includes line graphs as a special case.
On minimum degree in Hamiltonian path graphs
Authors: Hendry George R. T.
Published: June 2007

For integers p and s satisfying 2 ⩽ s ⩽ p − 1, let m(p,s) denote the maximum number of edges in a graph G of order p such that the minimum degree in the hamiltonian path graph of G equals s. The values of m(p, s) are determined for 2 ⩽ s ⩽ p/2 and for (2p − 2)/3 ⩽ s ⩽ p − 1, and upper and lower bounds on m(p, s) are obtained for p/2 < s < (2p − 2)/3.
A characterization of radius‐critical graphs
Authors: Fajtlowicz Siemion
Published: June 2007

A graph G is radius‐critical if every proper induced connected subgraph of G has radius strictly smaller than the original graph. Our main purpose is to characterize all such graphs.
On the maximum number of pairwise compatible euler cycles
Authors: Fleischner H. , Hilton A. J. W. , Jackson Bill
Published: June 2007

B. Jackson [4] made the following conjecture: If G is an Eulerian graph with δ(G) ≥ 2k, then G has a set of 2k ‐ 2 pairwise compatible Euler cycles (i.e., every pair of adjacent edges appears in at most one of these Euler cycles as a pair of consecutive edges). We verify this conjecture in the case where every circuit of G is a block of G.
Kanonische Transformationen, Lagrangesche und Poissonsche Klammern
Authors: Schräpel H. D.
Published: June 2007

Die Abhängigkeit der Lösungen der Hamiltonschen Gleichungen von ihren Anfangswerten wird untersucht. Mit Hilfe von zwei bekannten Sätzen folgen symmetrische Beziehungen in den Ableitungen. Weitere Bedingungen liefern erste Integrale. Schließlich werden die entwickelten Theoreme auch kanonische Transformationen erweitert.
Stationary Fundamental Solution for an Ideal Fluid in Uniform Motion
Authors: Dragoş L. , Homentcovschi D.
Published: June 2007

The fundamental solution of the system of equations describing an ideal fluid, linearized about an uniform motion, as well as the fundamental matrix of same system are given. As an application the perturbation caused by mass, momentum and energy sources, moving with constant relocity along the direction of an uniform current is determined.
Die inkompressible Strömung am Staupunkt schlanker Körper
Authors: Oswatitsch K.
Published: June 2007

In der üblichen Näherungstheorie für die inkompressible, stationäre Umströmung nicht angestellter schlanker Körper und Flügel wird mit Quellbelegungen von Körperachsen oder Flügelebenen gearbeitet. Dabei treten am Belegungsbeginn logarithmische Singularitäten der Geschwindigkeit auf. Dieser in einem kleinen Bereich auftretende Staupunktsfehler wird behoben.
Dynamic Response of a Circular Beam on a Wieghardt‐Type Elastic Foundation
Authors: Celep Z.
Published: June 2007

Starting from the two dimensional formulation of the Wieghardt‐type elastic foundation, the deflection of the foundation surface subjected to an arbitrarily distributed circular load is determined using the method of harmonic analysis. Based on this result, the dynamic response of a circular beam resting on a Wieghardt‐type elastic foundation and subjected to a harmonic load is obtained. Numerical results are plotted for the free vibration as well as for the two types of forced vibration of the circular beam.
On the Rotation of an Axially Symmetric Body in Couple Stress Fluids
Authors: Ramkissoon H.
Published: June 2007

The Stokes' flow due to the rotation of an axially symmetric body in couple stress fluids is examined. General solutions are obtained and with the aid of a concentrated point couple, a simple formula for the couple experienced by the body is derived in terms of the angular velocity of the flow field. The results are then applied to the particular case of a sphere.
Rounding Error Analysis of Interval Algorithms
Authors: Stummel F.
Published: June 2007

Using the linearization method, a rounding error analysis of interval algorithms is established. It is shown that the interval midpoints and radii are approximate solutions of real evaluation algorithms and of certain linear systems uniquely associated to each interval algorithm. In addition, interval data and interval rounding condition numbers are defined which yield optimal bounds of the possible magnitude of the interval radii. These concepts and tools are applied to the following numerical examples: evaluation of a polynomial, continued fraction expansion, summation procedure, and Cramer's rule for two linear equations in two unknowns.
Zufallsschwingungen unter schmalbandiger Parametererregung
Authors: Schmidt G. , Wenzel V.
Published: June 2007

Untersucht werden die Schwingungen eines Systems mit schmalbandiger Zufallsparametererregung und nichtlinearen Dämpfungs‐ und Rückstellkräften, dabei wird die Integralgleichungsmethode benutzt. für die Verteilungsdichte der Resonanzamplituden und die Wahrscheinlichkeit von Amplituden oberhalb eines bestimmten Niveaus werden Formeln und numerische Beispiele angegeben.
Zur Dimension der Äste von Verzweigungsdiagrammen
Authors: Collatz L.
Published: June 2007

In den Anwendungen sind sehr viele verschiedenartige Verzweigungsaufgaben auf Computern durchgerechnet worden (s. z. B. Ockendon [9] und viele andere), bei denen zuweilen merkwürdige Verzweigungsphänomene auftreten. Hier sollen nur die Erscheinungen mit verschiedenen Dimensionen der einzelnen Äste betrachtet werden, und auch nur Fälle, in denen die Äste durch analytische Ausdrücke gegeben sind. Schließlich sollen sich die Betrachtungen auf einfache Fälle beschränken, bei denen man die Äste explizit ausrechnen und angeben kann, so daß man sicher sein kann, alle Äste erfaßt zu haben. Daher werden nur einfache Modellbeispiele herausgegriffen, während die in den Anwendungen auftretenden Fälle häufig so kompliziert sind, daß man nur noch numerisch rechnen kann.
Eigenvectors of H‐Selfadjoint Matrices
Authors: Lancaster P. , Rózsa P.
Published: June 2007

Properties of the right eigenvectors associated with the conjugate pairs of complex eigenvalues of H‐selfadjoint matrices are investigated. Making use of the solution of certain matrix equations, explicit formulae are obtained expressing the connection between the complete sets of right Jordan chains corresponding to the complex conjugate eigenvalues.
The Time Dependent Deformation of a Capsule in an Arbitrary Stokes Flow
Authors: Brunn P. O.
Published: June 2007

This paper is concerned with the time‐dependent deformation of a spherical capsule suspended in a viscous fluid. The basic assumptions are that (a) the flow in the fluid regions is governed by the Stokes' equations, (b) the deformation is small, and (c) the membrane is purely elastic. Condition (b) requires either the elastic time scale to be small in comparison with a characteristic flow time (i.e., a sufficiently stiff membrane and/or a sufficiently weak flow field) or the inside fluid to be highly viscous. It also allows us to employ a linearly elastic constitutive equation for the membrane, as first approximation. The general results obtained are compared with corresponding results for surface tension droplets. The case of sedimentation in a quiescent fluid, a capsule freely suspended in a linear flow field, and steady‐state results for quadratic flow fields (with emphasis on circular Poiseuille flow) are studied.
Über die Maximumnormkonvergenz der Methode der finiten Elemente bei geringsten Regularitätsvoraussetzungen
Authors: Yserentant H.
Published: June 2007

In dieser Arbeit werden Aussagen über die Maximumnonrm des Fehlers bei Anwendung der Methode der finiten Elemente bewiesen, ohne dabei von Regularitätseigenschaften des kontinuierlichen Problems und seiner Diskretisierung Gebrauch zu machen. Die erzielten Ergebnisse gelten für ebene elliptische Randwertprobleme zweiter Ordnung. Sie lassen sich in zwei Gruppen einteilen. Zum einen wird gezeigt, Daß sich der Maximumnormfehler im wesentlichen durch den Energienormfehler abschätzen läßt, und zum anderen, daß die Maximumnormkonvergenz der Methode der finiten Elemente ein rein lokales Phänomen darstellt, unabhängig von der Regularität des kontinuierlichen Problems und der Quasiuniformität der benutzten Elementeinteilung. Der lokale Fehler in der Maximumnorm läßt sich immer durch den Maximumnormfehler eines lokalisierten Problems und den lokalen Fehler in der L2‐Norm abschätzen.
A Unifying Method for Some Computations in Renewal Theory
Authors: Hinderer K.
Published: June 2007

In renewal theory the residual life time Yt, the spent life time Zt and the total life time Lt play an important role. A unifying method is presented for the computation of the (joint) probability distribution, of the (mixed) moments, of the (joint) densities and of other quantities of interest. As examples we compute, among others, for the Poisson process the probability distribution of Yt/Lt and the correlation coefficient of Zt and Lt.
On the Method of Characteristics in Rate‐Type Viscoelasticity
Authors: Mihâilesću‐Suliciu M. , Suliciu I.
Published: June 2007

This paper deals with the standard method of characteristics for a system of partial differential equations encountered in viscoelasticity (and also in viscoplasticity, electric transmission lines, etc.). The second law of thermodynamics implies the existence of a nonlinear functional called the total energy, which for the exact solutions of the considered problems is a nonincreasing function of time. A sufficient condition on the integration step is given such that the total energy of the numerical solution be also a non‐increasing function of the number of time integration steps. An example is given showing that, if this condition is violated then the numerical solution diverges in time.
The Theory of the General Motion of a Thin Profile at a Small Incidence in an Inviscid Incompressible Fluid
Authors: Homentcovschi D.
Published: June 2007

The paper gives an analytical method to study the motion of the thin aerofoil in an incompressible inviscid fluid. The only restriction imposed to the aerofoil motion is that the incidence angle be small. The solution needs the solving of a first kind Volterra type integral equation which, in the case of the rectilinear motion of the aerofoil, coincides with the Wagner's integral equation. The theory is next applied to study the case of the incidence variation of the flat plate in rectilinear motion and to the case of the flat plate having a circular motion at a small incidence angle.
Effective Realization of Numerical Integration Method for Stiff Problems
Authors: Griepentrog E. , Möbius A.
Published: June 2007

The theoretical part of this paper shows that, by means of a suitable chosen predictor, only one Newton iteration step is needed in order to get the desired consistency and stability properties of an implicit numerical integration method. Furthermore, an algorithm for this Newton step is suggested, whose effort depends only on the number of the stiff solution components. In the practical considerations the introduced principles are applied to a mixed extrapolation method based on the trapezoidal rule. Special cheap methods for the error estimation and stepsize control are developed.
More Generalised Discrete Gronwall Inequalities
Authors: Beesack P. R.
Published: June 2007

The most general linear discrete Gronwall inequality is first considered, and best possible solutions of the inequality are obtained by elementary methods which are discrete analgoues of those used for Volterra integral equations. Upper bounds are also obtained for solutions in case the kernel is of a generalised Abel type, improving and extending recent work of S. Mc Kee.
Dynamik von Mehrkörpersystemen mit elastischen Bauteilen
Authors: Bremer H.
Published: June 2007

In vielen Fällen wird es notwendig, die Bauteilelastizitäten in Mehrkörpersystemen zu berücksichtigen, Beispielsweise bei der Berechnung von leichten und schnellen Industrierobotern. Das Differentialgleichungssystem der Bewegungsgleichungen umfaßt dann die großen Starrkörperbewegungen und die relative überlagerten elastischen Deformationen, die als vergleichsweise klein angenommen werden können. Für die Bestimmung dieser Gleichungen wird, ausgehend von einem Einbalkensystem, für Mehrkörpersysteme ein rekursives Vorgehen vorgeschlagen.
Transient Thermoelastic Problem in an Infinite Body Containing a Penny‐Shaped Crack Due to Time and Position Dependent Temperature Condition
Authors: Noda N. , Matsunaga Y.
Published: June 2007

Es wird das Problem der Übergangswärmespannung für einen unendlichen Körper mit einen pfennigförmigen Riß behandelt. Das elastische Medium wird durch ein zeit‐ und ortsabhängiges Temperaturfeld auf der Rißoberfläche abgekühlt. Mit einem Differenzenverfahren für die Zeitvariable kann man die analytische Lösung bezüglich der Ortsvariablen erhalten. Die Bestimmung der Temperatur wird auf die Lösung einer dualen Integralgleichung für Eulersche Variable reduziert. Das Wärmespannungsproblem führt auf eine singuläre Integralgleichung bekannten Typs. Die numerischen Ergebnisse werden als Funktionen der Fourier‐Zahl dargestellt.
Instationäre und stationäre Strömungen von Flüssigkeiten mit Momentenspannungen
Authors: Förste J.
Published: June 2007

Für die Bewegungsgleichungen einer inkompressiblen Flüssigkeit mit Momentenspannungen wird im instationären Fall ein Anfangs‐Randwertproblem und im stationären Fall ein Randwertproblem formuliert. Für beide Probleme wird das Existenz und Einzigkeitsproblem und das asymptotische Verhalten untersucht.
A Pseudo Spectral Chebyshev Scheme for Forward Acoustic Modeling
Authors: Raggio G.
Published: June 2007

A pseudo spectral scheme using Chebyshev polynomials is presented to model wave propagation in inhomogeneous acoustic media. The computational domain is a square with Neumann and Dirichlet boundary conditions. An explicit modified Euler time marching scheme is used; thus the time steps are severely restricted by the clustering of the Chebyshev abscissa near the end points. Specifically, a numerical experiment is presented to estimate the order of accuracy of reflection and transmission coefficients at an interface. It was found to be proportional to the square of the grid spacing.
On Absolute Convergence of the Successive Approximations for Integral Equations with Analytic Nonlinearity
Authors: Wagner W.
Published: June 2007

The paper deals with the representation of solutions of integral equations with analytic nonlinearity in such a form, which is suitable for Monte Carlo estimation. The results concern solutions, in a neighbourhood of which the successive approximations converge. The method is based on a special shift transformation of the integral equation.
Magnetohydrodynamic Effects on a Fluid Film Squeezed between Two Rotating Naturally Permeable Discs: Similarity Solutions
Authors: Hamza E. A. , Bhatt B. S.
Published: June 2007

The motion of a fluid film squeezed between two rotating parallel naturally permeable discs has been studied in the presence of a magnetic field applied perpendicular to the surface. We have obtained the similarity solutions using regular perturbations and numerical technique. The combined effects of magnetic field, centrifugal inertial forces, and the permeabilities of the porous medium on the velocity profiles, the load capacity and the torques that the fluid exerts on the surfaces have been determined. In general, the results are similar to HAMZA [1] except that the slippage of the fluid particles at the boundaries pushes the fluid away from the rotating axis.
Energy dissipation in fractal-forced flow
Authors: Cheskidov Alexey , Doering Charles R. , Petrov Nikola P.
Published: June 2007

The rate of energy dissipation in solutions of the body-forced three-dimensional incompressible Navier-Stokes equations is rigorously estimated with a focus on its dependence on the nature of the driving force. For square integrable body forces, the high Reynolds number (low viscosity) upper bound on the dissipation is independent of the viscosity, consistent with the existence of a conventional turbulent energy cascade. On the other hand, when the body force is not square integrable, i.e., when the Fourier spectrum of the force decays sufficiently slowly at high wave numbers, there is significant direct driving at a broad range of spatial scales. Then the upper limit for the dissipation rate may diverge at high Reynolds numbers, consistent with recent experimental and computational studies of “fractal-forced” turbulence.
Asymmetrization of spatial distribution of δ-dopants
Authors: Pankratov E. L.
Published: June 2007

It has recently been shown, that growth of a multilayer structure with one or more delta-layers at high temperature leads to the spreading and asymmetrization of the dopant distribution. In this work the analytical and numerical analysis of a dopant dynamics in a delta-doped area of a multilayer structure has been prepared by using a “macroapproach.” Some reasons for asymmetrization of a delta-dopant distribution are illustrated. The spreading of a delta-layer has been estimated for an example of specific materials of a multilayer structure with a delta-layer.
Effects of rapid thermal annealing on the properties of GaNxAs1−x
Authors: Liu Z. L. , Chen P. P. , Wang C. , Li T. X. , Cui H. Y. , Li Y. J. , Chen X. S. , Lu W.
Published: June 2007

We report the effect of rapid thermal annealing on the valence-band splitting behavior of GaNxAs1−x films grown by molecular beam epitaxy. The light- and heavy-hole valence-band splitting induced by the elastic strain is observed in both photomodulated reflectance and photoluminescence spectra for as-grown GaNxAs1−x epilayers. The valence-band splitting energy increases with the nitrogen composition. This splitting is decreased with the increase of annealing temperature by the rapid thermal annealing temperature process. These properties have been well explained by strain relaxation model including both in-plane strain at GaAs/GaNAs interface and internal strain in GaNAs epilayer. These strain effects have been confirmed by x-ray diffraction and Raman measurements.
Influence of chemical stresses in the permeation, one-side and two-side charging processes
Authors: Ko Sun-Chien , Zhang Tong-Yi , Lee Sanboh
Published: June 2007

Chemical stresses induced during a diffusion process have a great influence on the diffusion process by enhancing the diffusion coefficient. The effective diffusion coefficient is a function of the concentration when chemical stresses are taken into account. The diffusion equation with the effective diffusion coefficient is numerically solved for the three cases, namely, permeation through a membrane, one-side charging and two-side charging of membranes, with the flux continuity boundary conditions, which include the surface effect, i.e., the adsorption, absorption and desorption reactions. The results indicate that chemical stresses enhance the diffusion process. If chemical stresses are neglected, both two-side charging and one-side charging have the same concentration profiles. However, when the chemical stresses are fed back to the diffusion, the concentration level for the two-side charging is higher than that for the one-side charging. The surface effect is also investigated by changing the ratio of the drift velocity in surface to the drift velocity in bulk, showing that the diffusion process is promoted by the increase of the drift velocity ratio.
The phase of the de Haas–van Alphen oscillations, the Berry phase, and band-contact lines in metals
Authors: Mikitik G. P. , Sharlai Yu. V.
Published: June 2007

It is pointed out that measurements of the phase of the de Haas–van Alphen oscillations can give information on the degeneracy of electron-energy bands in a metal even though this degeneracy occurs far away from its Fermi level. As an illustration of this statement, the published experimental data on the de Haas–van Alphen effect in LaRhIn5, graphite, and zinc are discussed.
On diamagnetic domains in layered conductors
Authors: Peschansky V. G. , Stepanenko D. I.
Published: June 2007

The magnetic susceptibility and domain structure of a layered conductor are calculated under conditions of a substantial de Haas–van Alphen effect for arbitrary orientation of the external magnetic field with respect to the layers. It is shown that the amplitude of the magnetic susceptibility is an oscillatory function of the angle between the magnetic field and the normal to the layers, with a sharp maximum along preferred directions of magnetic field. The possibility of propagation of low-frequency weakly damped modes of the electromagnetic field is discussed with allowance for the induced magnetism of the conduction electrons.
Boundary bound states in the Bose–Hubbard-like chain
Authors: Zvyagin A. A.
Published: June 2007

The degenerate Hubbard-like chain with open boundary conditions is studied with the help of the Bethe ansatz. The special case of the Bose–Hubbard-like chain is studied in detail. Boundary bound states, which appear as a consequence of local potential(s) applied to the edge(s) of the open chain, are studied in the ground state.
Rebonding of Se to As and Ge in Ge33As12Se55 films upon thermal annealing: Evidence from x-ray photoelectron spectra investigations
Authors: Wang R. P. , Choi D. Y. , Rode A. V. , Madden S. J. , Luther-Davies B.
Published: June 2007

We have measured and analyzed x-ray photoelectron spectra (XPS) of as-grown and annealed Ge33As12Se55 films compared with bulk material. We found that the as-grown film contains a large number of separated Se clusters which can coalesce with As and Ge after annealing at high temperatures. In addition, both the Ge and As 3d spectra show the presence of oxides. While the Ge oxidation increases with an increasing annealing temperature, As oxidation is almost unaffected by annealing. The difference could be due to their different electro-negativities. Our results suggest that, while thermal annealing is effective to move the film toward the bond structure of bulk glass, the simultaneous surface oxidation must be suppressed in order to achieve high quality films.
Electron beam induced coloration and luminescence in layered structure of WO3 thin films grown by pulsed dc magnetron sputtering
Authors: Karuppasamy A. , Subrahmanyam A.
Published: June 2007

Tungsten oxide thin films have been deposited by pulsed dc magnetron sputtering of tungsten in argon and oxygen atmosphere. The as-deposited WO3 film is amorphous, highly transparent, and shows a layered structure along the edges. In addition, the optical properties of the as-deposited film show a steplike behavior of extinction coefficient. However, the electron beam irradiation (3.0 keV) of the as-deposited films results in crystallization, coloration (deep blue), and luminescence (intense red emission). The above changes in physical properties are attributed to the extraction of oxygen atoms from the sample and the structural modifications induced by electron bombardment. The present method of coloration and luminescence has a potential for fabricating high-density optical data storage device.
The influence of a capping layer on optical properties of self-assembled InGaN quantum dots
Authors: Wang Q. , Wang T. , Parbrook P. J. , Bai J. , Cullis A. G.
Published: June 2007

Optical properties of InGaN quantum dots (QDs) with and without a GaN capping layer have been investigated, showing a major difference between each other. Compared with the InGaN QDs with a GaN capping layer, those grown under identical conditions but without the GaN capping layer showed much stronger photoluminescence (PL) emission and a ∼350 meV blueshift in emission energy. The excitation power-dependent PL measurements indicated that the emission energy of the QDs with the capping layer showed a large blueshift with increasing excitation power, while there was a negligible shift in the QDs without the capping layer. The major difference between them is attributed to existence of a strong quantum-confined Stark effect (QCSE) in the QDs with the capping layer, while there is no clear QCSE observed in the uncapped QDs. The transition energy has been calculated for both QDs within the framework of effective-mass approximation and variational approach, showing a good agreement with the experimental data. The results obtained should be highly taken into account in investigating the optical properties of InGaN QDs on a GaN surface.
Structure and magnetism of MnAs nanocrystals embedded in GaAs as a function of post-growth annealing temperature
Authors: Kwiatkowski A. , Wasik D. , Kamińska M. , Bożek R. , Szczytko J. , Twardowski A. , Borysiuk J. , Sadowski J. , Gosk J.
Published: June 2007

Self-organized Ga(Mn)As nanoclusters, embedded in GaAs, were formed during post-growth thermal annealing of Ga1−xMnxAs layers. Structural and magnetic properties of such composites were systematically studied as a function of the annealing temperature. Small (∼3 nm) Mn-rich zinc-blende Mn(Ga)As clusters, coherent with the GaAs matrix, were formed at the annealing temperature of 500 °C. An increase of the annealing temperature of up to 600 °C led to the creation of 10–20 nm large NiAs-type hexagonal MnAs nanocrystals. Magnetization measurements showed that the MnAs nanoprecipitates were superparamagnetic, with a distribution of blocking temperatures that depended on the MnAs cluster size. Some intermediate paramagnetic clusters (structurally disordered clusters) were also observed.
Seven-dimensional quantum dynamics study of the H+NH3→H2+NH2 reaction
Authors: Yang Minghui , Corchado Jose C.
Published: June 2007

Initial state-selected time-dependent wave packet dynamics calculations have been performed for the H+NH3→H2+NH2 reaction using a seven-dimensional model and an analytical potential energy surface based on the one developed by Corchado and Espinosa-Garcia [J. Chem. Phys. 106, 4013 (1997)]. The model assumes that the two spectator NH bonds are fixed at their equilibrium values. The total reaction probabilities are calculated for the initial ground and seven excited states of NH3 with total angular momentum J=0. The converged cross sections for the reaction are also reported for these initial states. Thermal rate constants are calculated for the temperature range 200–2000K and compared with transition state theory results and the available experimental data. The study shows that (a) the total reaction probabilities are overall very small, (b) the symmetric and asymmetric NH stretch excitations enhance the reaction significantly and almost all of the excited energy deposited was used to reduce the reaction threshold, (c) the excitation of the umbrella and bending motion have a smaller contribution to the enhancement of reactivity, (d) the main contribution to the thermal rate constants is thought to come from the ground state at low temperatures and from the stretch excited states at high temperatures, and (e) the calculated thermal rate constants are three to ten times smaller than the experimental data and transition state theory results.
High current density GaN∕CsBr heterojunction photocathode with improved photoyield
Authors: Liu Zhi , Sun Yun , Pianetta Piero , Maldonado Juan R. , Pease R. F. W. , Schuetter Scott
Published: June 2007

A four fold improvement in photoyield has been observed in GaN films coated with CsBr films (CsBr∕GaN) relative to CsBr∕Cr photocathodes reported in previous studies. A model is presented involving photoemission from intraband states in the CsBr film and direct electron injection through the CsBr film from the GaN substrate. The lifetime of the films at high current density >90A∕cm2 is limited by the temperature rise in the GaN films caused by the high photon absorption at 257nm. The lifetime can be improved by utilizing a cooled substrate or a high thermal conductivity substrate under the GaN films.
Emitter degradation in quantum dot intermediate band solar cells
Authors: Martí A. , López N. , Antolín E. , Cánovas E. , Luque A. , Stanley C. R. , Farmer C. D. , Díaz P.
Published: June 2007

The characteristics of intermediate band solar cells containing 10, 20, and 50 InAs quantum dot (QD) layers embedded in otherwise “standard” (Al,Ga)As solar cell structures have been compared. The short-circuit current densities of the cells decreased and the quantum efficiencies of the devices showed a concomitant reduction in the minority carrier lifetime in the p emitters with increasing number of QD layers. Dislocations threading up from the QDs toward the surface of the cells, and revealed by bright field scanning transmission electron microscopy, are the most likely cause of the deterioration in the electrical performance of the cells.
Bmi-1
is a target gene for SALL4 in hematopoietic and leukemic cells
Authors: Yang Jianchang , Chai Li , Liu Fang , Fink Louis M. , Lin Pei , Silberstein Leslie E. , Amin Hesham M. , Ward David C. , Ma Yupo
Published: June 2007

Bmi-1
and
SALL4
are putative oncogenes that modulate stem cell pluripotency and play a role in leukemogenesis. Murine Sall4 also has been shown to play an essential role in maintaining the properties of ES cells and governing the fate of the primitive inner cell mass. Here, we demonstrate that transcription from the Bmi-1 promoter is strikingly activated by SALL4 in a dose-dependent manner by using a luciferase reporter gene assay. Both promoter deletion construct studies and ChIP from a myeloid stem cell line, 32D, demonstrate that SALL4 binds to a specific region of the Bmi-1 promoter. Deletion of one copy of Sall4 by gene targeting in mouse bone marrow significantly reduced Bmi-1 expression. Reducing SALL4 expression by siRNA in the HL-60 leukemia cell line also results in significant down-regulation of Bmi-1. Furthermore, Bmi-1 expression is up-regulated in transgenic mice that constitutively overexpress human SALL4, and the levels of Bmi-1 in these mice increase as they progress from normal to preleukemic (myelodysplastic syndrome) and leukemic (acute myeloid leukemia) stages. High levels of H3–K4 trimethylation and H3–K79 dimethylation were observed in the SALL4 binding region of the Bmi-1 promoter. These findings suggest a novel link between SALL4 and Bmi-1 in regulating self-renewal of normal and leukemic stem cells. An increase in histone H3–K4 and H3–K79 methylation within the Bmi-1 promoter provides an epigenetic mechanism for histone modifications in SALL4-mediated Bmi-1 gene deregulation.
AFLP‐based genetic linkage maps of the blue mussel (Mytilus edulis)
Authors: Lallias D. , Lapègue S. , Hecquet C. , Boudry P. , Beaumont A. R.
Published: June 2007

We report the construction of the first genetic linkage map in the blue mussel, Mytilus edulis. AFLP markers were used in 86 full‐sib progeny from a controlled pair mating, applying a double pseudo‐test cross strategy. Thirty‐six primer pairs generated 2354 peaks, of which 791 (33.6%) were polymorphic in the mapping family. Among those, 341 segregated through the female parent, 296 through the male parent (type 1:1) and 154 through both parents (type 3:1). Chi‐square goodness‐of‐fit tests revealed that 71% and 73% of type 1:1 and 3:1 markers respectively segregated according to Mendelian inheritance. Sex‐specific linkage maps were built with mapmaker 3.0 software. The female framework map consisted of 121 markers ordered into 14 linkage groups, spanning 862.8 cM, with an average marker spacing of 8.0 cM. The male framework map consisted of 116 markers ordered into 14 linkage groups, spanning 825.2 cM, with an average marker spacing of 8.09 cM. Genome coverage was estimated to be 76.7% and 75.9% for the female and male framework maps respectively, rising to 85.8% (female) and 86.2% (male) when associated markers were included. Twelve probable homologous linkage group pairs were identified and a consensus map was built for nine of these homologous pairs based on multiple and parallel linkages of 3:1 markers, spanning 816 cM, with joinmap 4.0 software.
A method for jaw movement registration
Authors: HONÉE G. L. J. M. , MEIJER A. A.
Published: June 2007

The procedure is described of an indirect method of recording jaw movement by measuring intervals between electrical pulses generated by a light beam passing two photovoltaic cells attached to the upper and lower jaw. A general description of the basic electronic system is given. An example of registration of the border movement lines of a subject is shown.
The mechanics of the temporomandibular joint—a theoretical and electromyographical study
Authors: BARBENEL J. C.
Published: June 2007

summary

A theoretical analysis of the force actions at the temporomandibular joint is presented. The equations of equilibrium of the mandible under a static load are derived and the solutions yielding the minimum joint force are explored. Using integrated electromyography, an estimate is presented of the forces at the joint with the mandible supporting a static load on the incisor and canine teeth. The conclusion reached is that the joint is load bearing during function.
The management of children and adolescents suffering from amelogenesis imperfecta and dentinogenesis imperfecta
Authors: GIBBARD P. D.
Published: June 2007

summary

A brief history and the aims of treatment of amelogenesis imperfecta and dentinogenesis imperfecta are described. In a description of a system of management of these conditions the advantages and possibilities of early treatment is stressed. Conserving the primary dentition makes the restoration of the permanent teeth easier because the correct jaw relationships are maintained. Long‐term observation of the developing dentition allows problems to be overcome or intercepted at the most propitious time. Semi‐permanent restorations for the newly erupted permanent teeth and the rationale for their use are described. An approach to providing adolescents with crowns for all their teeth, restoring groups of teeth, is described and the problems of partially erupted teeth are discussed. Some possibilities of simplifying and improving the types of restoration available, such as the use of composite materials as facings, are described. The special needs of young patients and the problems associated with treating them are indicated throughout.
The mandible and osteoporosis (1)
Authors: HENRIKSON PER‐ÅKE , WALLENIUS KJELL
Published: June 2007

summary

Transverse segments 3–4 cm long were excised post mortem from the radius and from the edentulous mandible in twenty‐four females and twenty‐six males, aged 46–92 years. In order to obtain a value for the density of the minerals in the two different bones, the specific gravities of the specimens were determined by application of Archimedes' principle. Intra‐individually, the specific gravity was found to vary inversely with age (P <0.01). A statistical correlation was also found in this respect between the mandible and the radius in the material as a whole (P <0.0l).
The mandible and osteoporosis(2)
Authors: HENRIKSON PER‐ÅKE , WALLENIUS KJELL , ÅSTRAND KURT
Published: June 2007

summary

Transverse sections, 3–4 cm long, were obtained post mortem from the radii and from edentulous mandibles of fifty patients (twenty‐four females and twenty‐six males) aged 46–92 years. The mineral density of the sections was measured by roentgen absorption. A significant negative correlation was found between the mineral density and age (P<0.01). A statistically significant correlation was found between the variation of the mineral density of the mandible and that of the radius (P<0.01).
Coefficient of thermal expansion of some anterior restorative materials by a new dilatometric technique
Authors: HARRINGTON E. , MCCABE J. F.
Published: June 2007

An accurate method of determining the coefficient of thermal expansion of restorative materials has been devised and found to be suitable for routine testing. It is suggested that this method could be adapted for standard specification tests.

The method is independent of sample shape and regularity. Values of coefficient of thermal expansion for several anterior restorative materials are presented. The importance of realistic conditions for sample treatment is discussed.
Late results of treatment of functional disorders of the masticatory system
Authors: AGERBERG GÖRAN , CARLSSON GUNNAR E.
Published: June 2007

A questionnaire was se111 to 104 persons who had 3–5 years earlier been examined and treated because of functional disorders of the lmaslicatory system. The questionnaires were filled in and returned by eighty‐two persons.

The pain and disorders reported by the patients before treatment bad been described by three out of four as severe. After trextnwnt 75% reported liltle or no trouble while 7%, still had severe pain and disorders. After diagnosis of the probable cause of the complaint, treatment had consisted usually of splints, occlusal grinding, fitting or correclion of dentures, and/or mandibular exercises.

Half of the patients reported substantial improvement or complete recovery witbin 2 months and about four‐Rfths within 2 year of the beginning of treatment. while 16% reported no improvement.

About one‐third of the participants, predominantly elderly persons. reported in the questionnaire that they still required treatment. The lindings indicated the need of followin_p up patients with functional disorders of the masticatory syslem in order Lo evalunle residual symptoms, to rc‐institute suitable slomatognathic lrealmenl or to refer the palients for other treatlllcnl.
A clinical evaluation of silicate and composite restorations after 3 years of use
Authors: ERIKSEN HARALD M.
Published: June 2007

Silicate cement and composite resin restorations have been evaluated clinically after 3 years of use. The composite resin restorations had retained their anatomical form and marginal adaptation better than the silicate cements but their colour matching qualities were inferior to that of the silicates.