bluuebunny/crossref_metadata_2025 huggingface dataset:
Pursuit—Evasion games on graphs
Authors: Chung F. R. K. , Cohen Joel E. , Graham R. L.
Published: June 2007

Two players, Red and Blue, each independently choose a vertex of a connected graph G. Red must then pay Blue an amount equal to the distance between the vertices chosen. In this note, we investigate the value ν(G)of this pursuit‐evasion game for various classes of graphs G, as well as those optimal mixed strategies for achieving ν(G). It is shown that some rather counterintuitive behavior can occur. For example, there exist graphs G in which, for any optimal mixed strategy, Red never selects a vertex in the center of G.
On the strong perfect graph conjecture
Authors: Olariu Stephan
Published: June 2007

A graph G is perfect if for every induced subgraph H of G the chromatic number χ(H) equals the largest number ω(H) of pairwise adjacent vertices in H. Berge's famous Strong Perfect Graph Conjecture asserts that a graph G is perfect if and only if neither G nor its complement G¯ contains an odd chordless cycle of length at least 5. Its resolution has eluded researchers for more than 20 years. We prove that the conjecture is true for a class of graphs that we describe by forbidden configurations.
On the number of Hamiltonian cycles in triangulations
Authors: Kratochvil Jan , Zeps Dainis
Published: June 2007

It is proved that if a planar triangulation different from K3 and K4 contains a Hamiltonian cycle, then it contains at least four of them. Together with the result of Hakimi, Schmeichel, and Thomassen [2], this yields that, for n ⩾ 12, the minimum number of Hamiltonian cycles in a Hamiltonian planar triangulation on n vertices is four. We also show that this theorem holds for triangulations of arbitrary surfaces and for 3‐connected triangulated graphs.
On‐line and first fit colorings of graphs
Authors: Gyárfás A. , Lehel J.
Published: June 2007

A graph coloring algorithm that immediately colors the vertices taken from a list without looking ahead or changing colors already assigned is called “on‐line coloring.” The properties of on‐line colorings are investigated in several classes of graphs. In many cases we find on‐line colorings that use no more colors than some function of the largest clique size of the graph. We show that the first fit on‐line coloring has an absolute performance ratio of two for the complement of chordal graphs. We prove an upper bound for the performance ratio of the first fit coloring on interval graphs. It is also shown that there are simple families resisting any on‐line algorithm: no on‐line algorithm can color all trees by a bounded number of colors.
The average distance and the independence number
Authors: Chung F. R. K.
Published: June 2007

We prove that in every connected graph the independence number is at least as large as the average distance between vertices.
Cubic graphs with crossing number two
Authors: Richter Bruce
Published: June 2007

It is proved that every cubic graph with crossing number at least two contains a subdivision of one of eight graphs.
On brittle graphs
Authors: Hoàng C. T. , Khouzam N.
Published: June 2007

Chvátal defined a graph G to be brittle if each induced subgraph F of G contains a vertex that is not a midpoint of any P4 or not an endpoint of any P4. Every brittle graph is perfectly orderable. In this paper, we prove that a graph is brittle whenever it is HHD‐free (containing no chordless cycle with at least five vertices, no cycle on six vertices with a long chord, and no complement of the chordless path on five vertices). We also design an O(n4) algorithm to recognize HHD‐free graphs, and also an O(n4) algorithm to construct a perfect order of an HHD‐free graph. It follows from this result that an optimal coloring and a largest clique of an HHD‐free graph can be found in O(n4) time.
Some remarks on Arc‐connectivity, vertex splitting, and orientation in graphs and digraphs
Authors: Jackson Bill
Published: June 2007

We apply proof techniques developed by L. Lovász and A. Frank to obtain several results on the arc‐connectivity of graphs and digraphs. The first results concern the operation of splitting two arcs from a vertex of an Eulerian graph or digraph in such a way as to preserve local connectivity conditions. The final result is concerned with orienting the edges of a mixed graph (consisting of vertices, undirected edges, and directed arcs) in such a way that the resulting digraph is as arc‐connected as possible.
Regular pseudo‐median graphs
Authors: Bandelt Hans‐Jürgen , Mulder Henry Martyn
Published: June 2007

A graph is pseudo‐median if for every triple u, v, w of vertices there exists either a unique vertex between each pair of them (if their mutual distances sum up to an even number) or a unique triangle whose edges lie between the three pairs of u, v, w, respectively (if the distance sum is odd). We show that a finite pseudo‐median graph is regular if and only if it is the Cartesian product of a hypercube with either a complete graph or a hyper‐octahedron. Every self‐map of a pseudo‐median graph that preserves or collapses edges has an invariant regular pseudo‐median subgraph. Furthermore, the set of all vertices minimizing the total distance to the vertices of a pseudo‐median graph induces a regular pseudo‐median subgraph.
A connection between a convex programming problem and the LYM property on perfect graphs
Authors: Wei Victor K.
Published: June 2007

We derive three equivalent conditions on a perfect graph concerning the optimal solution of a convex programming problem, the length‐width inequality, and the simultaneous vertex covering by cliques and anticliques. By combining proof techniques including Lagrangian dual, Dilworth's Theorem, and Kuhn‐Tucker Theorem, we establish a strong connection between the three topics. This provides new insights into the structure of perfect graphs. The famous Lubell‐Yamamoto‐Meschalkin (LYM) Property or Sperner Property for partially ordered sets is a specialization of our results to a subclass of perfect graphs.
Interval digraphs: An analogue of interval graphs
Authors: Das S. , Sen M. , Roy A. B. , West D. B.
Published: June 2007

Intersection digraphs analogous to undirected intersection graphs are introduced. Each vertex is assigned an ordered pair of sets, with a directed edge uv in the intersection digraph when the “source set” of u intersects the “terminal set” of v. Every n‐vertex digraph is an intersection digraph of ordered pairs of subsets of an n‐set, but not every digraph is an intersection digraph of convex sets in the plane. Interval digraphs are those having representations where all sets are intervals on the real line. Interval digraphs are characterized in terms of the consecutive ones property of certain matrices, in terms of the adjacency matrix and in terms of Ferrers digraphs. In particular, they are intersections of pairs of Ferrers digraphs whose union is a complete digraph.
Locally 4‐by‐4 grid graphs
Authors: Blokhuis A. , Brouwer A. E.
Published: June 2007

We investigate locally grid graphs. The main results are (i) a characterization of the Johnson graphs (and certain quotients of these) as locally grid graphs such that two points at distance 2 have precisely four common neighbors, and (ii) a complete determination of all graphs that are locally a 4 × 4 grid (it turns out that there are four such graphs, with 35, 40, 40, and 70 vertices).
Richmond passes the turning point
Authors: Mitchell Broadus
Published: June 2007

The Richmond Survey was one of the most important whole‐city municipal research studies of last year. We asked Mr. Mitchell as one familiar with local affairs to relate the actual results that followed the sweeping recommendations of the survey.
Surface Selective Withdrawal in Sedimentation Basins
Authors: Chen I. Y. , Lai R. Y. , Karadi G. M.
Published: June 2007

By employing the theory of propagation of columnar disturbance, general criteria for selective withdrawal in sedimentation basins are derived. The stratified fluid is assumed to be two‐layered with different density distribution in each layer. The effects of a free surface are also included in the analysis, but the viscosity is neglected as in most other studies of stratified flow behavior. The criteria for different density profiles are established in terms of the densimetric Froude number. If the actual densimetric Froude number is smaller than its critical value, selective withdrawal will occur. Comparison of the theoretical results with the experimental data obtained by Bohan and Grace [1973] indicate an excellent agreement as long as the thickness of the bottom layer, s, is small compared to that of the top layer. Results obtained by assuming rigid upper boundary instead of free surface are also compared with the results derived in this paper. For weak stratification and small values of s they show excellent agreement. As s increases for strong stratification, the effect of free surface will become increasingly pronounced.
A General Treatise of Plane Thermoelastic Problem in Multiply‐Connected Region Exhibiting Temperature‐Dependent Properties
Authors: Sugano Y.
Published: June 2007

The purpose of this paper is to complete the formulation of plane thermoelastic problem in a multiply‐connected region taking into account the temperature dependencies of material properties in terms of Airy's stress function by deriving the conditions for the single valuedness of the rotation and displacements, i.e., modified Michell's conditions, and to present a method for analyzing the system of the resulting fundamental equations numerically by the use of finite difference method.
Analytische Mechanik der beschränkten Konfigurationsräume
Authors: Baumgarte J.
Published: June 2007

Von besonderem Interesse sind in der Mechanik Bindungen, die eine Begrenzung des Konfigurationsraumes erzwingen. Solche Bindungen werden realisiert durch starre, evtl. masselose Stangen, reibungsfreie Gelenke und insbesondere durch masselose dehnstarre Seile. In dieser Arbeit werden parametrisierte holonome Bindungen eingeführt, die eine allgemeine Beschreibung von Konfigurationsraumbeschränkungen ermöglichen. Über ein Variationsproblem werden die Formeln für Geschwindigkeitssprünge an den Grenzen des Konfigurationsraumes explizit angegeben. In diesen Formeln lassen sich sowohl dissipative Anteile (nichtelastische Vorgänge) als sogar auch Verletzungen der klassischen holonomen Bindungen — wie z. B. Zerstörung von Gelenkverbindungen — explizit angeben.
Konservative Differenzenmethoden zur Modellierung eindimensionaler Diffusionsprozesse mit Unstetigkeiten an einer Phasengrenze
Authors: Friedrich V. , Windisch G.
Published: June 2007

In einem Zweiphasensystem mit bekannter Phasengrenze wird ein eindimensionaler Diffusionsprozeß betrachtet, wobei Bedingungen für die Konservativität an der Phasengrenze, an der Unstetigkeiten auftreten, abgeleitet werden. Mit der Integro‐Interpolationsmethode wird eine Klasse konservativer Differenzenschemata erzeugt. für Spezialfälle werden Bedingungen für die eindeutige Lösbarkeit abgeleitet und Untersuchungen zur Stabilität durchgeführt.
Stabilitätsgebiete expliziter linearer Zweischrittverfahren
Authors: Bachmann K. H.
Published: June 2007

Die Stabilitätsgebiete konsistenter expliziter linearer Zweischrittverfahren werden auf ihre Ausdehnung längs der negativ reellen Achse untersucht. Diese Ausdehnung wird in Abhängigkeit von zwei Parametern dargestellt und kann durch geeignete Parameterwahl beliebig groß gemacht werden. Daher sind Verfahren konstruierbar, die fast A (0)‐stabil sind.
Newton‐Type Decomposition Methods for Equations Arising in Network Analysis
Authors: Hoyer W. , Schmidt J. W.
Published: June 2007

This paper presents two‐ and multilevel Newton‐type decomposition methods for the iterative solution of large nonlinear systems of equations which arise with a special block‐wise sparsity pattern e.g. in electric circuit analysis. The structure of the systems is widely utilized by the proposed algorithms, which only require soling linear subsystems of the sizes of the diagonal blocks. The methods developed are shown to be locally superlinearly convergent.
Existence Regions and Error Bounds for Implicit and Inverse Functions
Authors: Neumaier A.
Published: June 2007

Several theorems are proved which guarantee the existence of implicitly defined functions and inverse functions, respectively, in prescribed domains. As applications, error bounds for inaccurate solution maps of implicit systems of equations and for approximate zeros of systems of equations are derived.
Eine Klasse asymptotisch stabiler autonomer Systeme und Normschranken für spezielle Reaktions‐Diffusions‐Prozesse
Authors: Rautmann R.
Published: June 2007

Durch zwei Annahmen über den Vorzeichenverlauf der beiden Komponenten des Richtungsfeldes wird eine Klasse ebener autonomer Systeme definiert. Die Anfangswertaufgabe dieser Systeme ist global eindeutig lösbar, alle Lösungen sind (asymptotisch) stabil, und es gibt eine global attraktive stationäre Lösung. Für klassische Lösungen spezieller nichtlinearer Reaktions‐Diffusions‐Gleichungssysteme in beschränkten n‐dimensionalen Gebieten ergeben sich so globale asymptotisch stabile Normschranken sowie eine Übersicht über das mögliche Wachstumsverhalten der Lösungen in Abhängigkeit von Normschranken der Anfangswerte.
Hemivariational Inequalities and Substationarity in the Static Theory of v. Kármán Plates
Authors: Panagiotopoulos P. D.
Published: June 2007

The present paper deals with nonconvex BVPs in the framework of v. Kármán plate theory which lead to hemivariational inequalities and substationarity problems. By means of the method of regularization and with the aid of compactness arguments the existence of the solution for coercive and semicoercive problems is proved. Certain approximation results are given, too.
Ein gemischtes und in sich duales Variationsprinzip für beliebig gekrümmte Schalen
Authors: Zuercher J.‐P. , Schumann W.
Published: June 2007

Die vorliegende Arbeit befaßt sich mit einem gemischten, in sich vollständig dualen Variationsprinzip der Schalentheorie. Zwei Skalare und zwei Vektoren bilden die unabhängigen Variablen und führen zu paarweise dualen Differentialausdrücken im Innern und am Rand.
Zur Konvergenz und Stabilität von direkten Mehrschritt‐Verfahren für die spezielle Differentialgleichung y(m) = f(x, y)
Authors: Filippi S. , Röhr H.
Published: June 2007

In dieser Arbeit werden die wichtigsten Konvergenz‐ und Stabilitätssätze von Henrici für y″ = f(x, y) sowohl für die direkten klassischen als auch für die direkten verallgemeinerten Mehrschritt‐ Verfahren auf y(m) = f(x, y), m > 2, erweitert. Ferner wird erstmals für die direkten klassischen und verallgemeinerten Mehrschritt‐ Verfahren eine von der Ordnung m abhängige Stabilitäts‐Barriere aufgestellt.
Allgemeine Variationsprinzipien in den Evolutionsaufgaben der Kontinuumsmechanik und der diskreten Mechanischen Systeme
Authors: Rosenberg J.
Published: June 2007

In der Arbeit wird eine allgemeine Methode zur Formulierung von Variationsprinzipien für Evolutionsrandwertprobleme vorgestellt. Diese Methode geht aus der Wahl der Bilinearform als inneres Produkt hervor. Neben der klassischen Bilinearform wird auch die konvolutorische Form verwendet, deren Einsatz es erlaubt, Variationsprinzipien zu formulieren, die auch die Anfangsbedingungen enthalten. Die dargelegte Methode wird auf die isotherme Strömung viskoser Flüssigkeiten und auf die Mechanik diskreter mechanischer Systeme angewendet.
Potential Flow Past a Cylinder Between Parallel Walls
Authors: Hansen E. B.
Published: June 2007

A solution obtained by an integral equation method is presented. The results have been tested in various ways and the findings indicate that the relative errors are 10−8 or less. No attempt has been made to compare the results with those presented in the references.
Bemerkungen zum d'Alembertschen Prinzip
Authors: Baumgarte J. , Ostermeyer G. P.
Published: June 2007

Bei der Berücksichtigung von Bindungen in mechanischen Systemen liefert das d'Alembertsche Prinzip zwei bekannte Vorgehensweisen: Die Reduktion der Ordnung des Differentialgleichungssystems, oder: Einführung von Zwangskräften. Der erste Weg führt auf die Einführung generalisierter Variabler, die den Bindungen exakt genügen. Aber diese Variablen sind nicht immer einfach zu finden. Der zweite Weg liefert einfach aufzustellende Differentialgleichungen, führt aber zu zusätzlichen Instabilitäten in den Gleichungen, so daß die numerische Lösung die Bindungsgleichungen mit der Zeit erheblich verletzt.

Diese Arbeit beschreibt einen dritten Weg, die Einführung quasi‐generalisierter Variabler. Die resultierenden Bewegungsgleichungen sind einfach aufzustellen (keine Reduktion der Ordnung des Systems!) und ihre numerische Lösung genügt den Bindungsgleichungen exakt (keine Zwangkräfte).
Zur Identifikation mehrfach monotoner Funktionen
Authors: Berg L.
Published: June 2007

Behandelt wird das Ausgleichsproblem für gegebene Näherungswerte einer mehrfach monotonen Funktion. Im allgemeinen Fall werden die Lösungen durch Minimalpolynome eingeschlossen. Im sogenannten Idealfall gibt es ein eindeutig bestimmtes Ausgleichspolynom, dessen Grad in optimaler Weise festgelegt ist. Zur Berechnung dieses Polynoms wird eine Verfahren mit verhältnismäßig geringem Speicherplatzbedarf angegeben.
On Approximate Computation of the Values of the Normal Derivative of Solutions to Linear Partial Differential Equations of Second Order with Application to Abel's Integral Equation
Authors: Gerlach W. , Wolfersdorf L. V.
Published: June 2007

For the numerical computation of the normal derivative of solutions to linear partial differential equations of second order from the boundary values of the solutions an operator method of regularization with unbounded accretive operator is proposed. The method is applied to the numerical solution of Abel's integral equation.
Efficient Numerical Integration on the Surface of a Sphere
Authors: Bažant P. , Oh B. H.
Published: June 2007

Several new numerical integration formulas on the surface of a sphere in three dimensions are derived. These formulas are superior to the existing ones in that for the same degree of approximation they require fewer integration points for functions with central or planar symmetry. Furthermore, a general method of deriving the integration formulas, which achieves conceptual simplicity at the expense of extensive numerical work left for a computer, is demonstrated. In this method, the coefficients of the integration formula are determined from a system of linear algebraic equations directly representing the conditions for a certain number of terms of the three‐dimensional Taylor series expansion of the integrated function about the center of the sphere to vanish, while the unknown locations of the integration points are determined from a condition for the next term (or terms) of the expansion to vanish, and if it cannot be made to vanish, then from a condition for minimizing the magnitude of this term (or these terms). Finally, we formulate a new condition of optimality of the integration formulas which is important for the integration error in certain applications.
Weakly Singular Discrete Gronwall Inequalities
Authors: Dixon J. , McKee S.
Published: June 2007

Generalizations of the classical Gronwall inequality when the kernel of the associated integral equation is weakly singular are presented. The continuous and discrete versions are both given; the former is included since it suggests the latter by analogy. This work is motivated by convergence studies of discretization methods for Volterra integral and integro‐differential equations. The results are all given in a form designed to be of most use to numerical analysts.
Domain Optimization Problem Governed by a State Inequality with a „Flux”︁ Cost Functional
Authors: Haslinger J. , Lovíšek J.
Published: June 2007

Shape optimization with a state unilateral boundary value problem and the flux cost functional is analyzed. Using the penalty method the existence of a solution is proved.
Asymptotic analysis for singularly perturbed convection-diffusion equations with a turning point
Authors: Jung Chang-Yeol , Temam Roger
Published: June 2007

Turning points occur in many circumstances in fluid mechanics. When the viscosity is small, very complex phenomena can occur near turning points, which are not yet well understood. A model problem, corresponding to a linear convection-diffusion equation (e.g., suitable linearization of the Navier-Stokes or Bénard convection equations) is considered. Our analysis shows the diversity and complexity of behaviors and boundary or interior layers which already appear for our equations simpler than the Navier-Stokes or Bénard convection equations. Of course the diversity and complexity of these structures will have to be taken into consideration for the study of the nonlinear problems. In our case, at this stage, the full theoretical (asymptotic) analysis is provided. This study is totally new to the best of our knowledge. Numerical treatment and more complex problems will be considered elsewhere.
Light absorption and emission in semiconductors with band gap fluctuations—A study on Cu(In,Ga)Se2 thin films
Authors: Mattheis Julian , Rau Uwe , Werner Jürgen H.
Published: June 2007

This work investigates the influence of lateral fluctuations of the fundamental band gap on the macroscopic light absorptance and emission spectra of spatially inhomogeneous semiconductors. A model assuming a Gaussian distribution for the local band gaps yields closed-form expressions for the spectral absorptance and emission. Band gap fluctuations broaden the absorption edge of the fundamental band gap, as well as the associated emission peak. The spectral position of the photoluminescence emission peak depends on the length scale of the fluctuations in relation to the characteristic charge carrier transport length. We apply the model to experimental results from Cu(In1−x,Gax)Se2 thin films routinely used as photovoltaic absorbers in thin-film ZnO/CdS/Cu(In,Ga)Se2 heterojunction solar cells. The films feature band gap fluctuations with standard deviations between 15 and 65 meV which would lead to losses in the range of 5–80 mV for the open circuit voltage of solar cells made from these films. The pure ternary compounds CuInSe2 and CuGaSe2 exhibit smaller standard deviations than their quaternary alloys. This experimental finding indicates alloy disorder as one possible source of band gap inhomogeneities. The length scale of the observed fluctuations turns out to be much smaller than the minority carrier diffusion length. Hence, the band gap fluctuations occur on a length scale below 100 nm.
Self-assembled heterogeneous argon/neon core-shell clusters studied by photoelectron spectroscopy
Authors: Lundwall M. , Pokapanich W. , Bergersen H. , Lindblad A. , Rander T. , Öhrwall G. , Tchaplyguine M. , Barth S. , Hergenhahn U. , Svensson S. , Björneholm O.
Published: June 2007

Clusters formed by a coexpansion process of argon and neon have been studied using synchrotron radiation. Electrons from interatomic Coulombic decay as well as ultraviolet and x-ray photoelectron spectroscopy were used to determine the heterogeneous nature of the clusters and the cluster structure. Binary clusters of argon and neon produced by coexpansion are shown to exhibit a core-shell structure placing argon in the core and neon in the outer shells. Furthermore, the authors show that 2 ML of neon on the argon core is sufficient for neon valence band formation resembling the neon solid. For 1 ML of neon the authors observe a bandwidth narrowing to about half of the bulk value.
Effect of surface reactions of low-energy carbon ions on the secondary electron emission of TiN:O thin films
Authors: Montero I. , Mohamed S. H. , García M. , Galán L. , Raboso D.
Published: June 2007

Low-energy secondary electron emission coatings are required for antimultipactor applications in several important technologies and their study and development is also a matter of scientific interest. For this purpose, titanium nitride was deposited on Si(100) substrates by reactive sputtering and the influence of low-energy carbon ion bombardment on the secondary electron emission yield of TiN:O coatings was studied. The composition and chemical bonds formed in the films after carbon ion implantation were analyzed by x-ray photoelectron spectroscopy (XPS). XPS revealed the formation of both carbidic and graphitic bonds. N was displaced while Ti-C bonds were formed up to a limiting value of 0.103 for the carbidic carbon atomic fraction, beyond which a graphitic surface layer was deposited. The secondary electron emission yields for TiN:O were measured before and after low-energy CHn+ ion bombardment and air exposure, and after heating. Initially, the carbon ion implantation reduced the secondary electron emission yield. Then an increase in secondary electron emission was obtained when the excess graphitic carbon was deposited on the sample. On the other hand, subsequent thermal treatment at 700 °C of the carburized samples produced a further reduction of the secondary electron emission yield. The maximum yields are about 53% lower for thermal annealed films than for similarly treated previously measured as-deposited layers. A narrowing of XPS peak line shapes is observed as a consequence of the annealing away of structural and chemical defects in the near-surface region. In addition, secondary electron emission (SEE) yield curves were used in a simulation of multipactor discharge. Both experimental multipactor threshold tests and computer multipactor simulations indicate that SEE yield values for low primary-electron energies are the most influencing parameters on multipactor threshold.
Anisotropy of the normal resistivity and suppression of superconductivity at twin boundaries in HoBa2Cu3O7−δ single crystals with different oxygen content
Authors: Vovk R. V. , Obolensky M. A. , Zavgorodniy A. A. , Bondarenko A. V. , Revyakina M. G.
Published: June 2007

The temperature dependence of the longitudinal and transverse conductivity is investigated in HoBa2Cu3O7−δ single crystals with different oxygen concentrations. It is shown that twin boundaries are efficient centers for scattering of normal carriers and suppression of the superconducting state. It is found that the anisotropy of the normal resistivity ρc∕ρab(T) is described well in the framework of a universal “1/2 law” for thermally activated hopping conduction.
Size acoustic resonance in a nonuniformly magnetized slab of the weak ferromagnet FeBO3
Authors: Strugatsky M. B. , Skibinsky K. M.
Published: June 2007

A theory of the Fabry–Perot acoustic resonance in a thin slab of the easy-plane weak ferromagnet FeBO3 is developed. It is shown that the frequency shift of the resonance peaks observed upon a change of magnetic field can be explained in the framework of a previously developed theory of magnetic linear acoustical birefringence in the iron borate crystal when the experimental boundary conditions are taken into account.
Superparamagnetic resonance of single-domain nanoparticles of LaSrMnO3
Authors: Krivoruchko V. N. , Marchenko A. I. , Prokhorov A. A.
Published: June 2007

The microwave absorption of an ensemble of single-domain nanoparticles of La0.7Sr0.3MnO3 is investigated in the temperature range 5–300K. At low temperatures the resonance spectra demonstrate the appreciable increase in linewidth and downward shift of the resonance field which are typical for superparamagnetic resonance. With increasing temperature the line shape changes, and at T>TB (TB∼100K) one observes a narrowing of the resonance curve and saturation of the resonance field. The line shape of an individual nanoparticle is described by the dynamic Landau–Lifshitz equations with damping. Modeling of the magnetic dynamics of the system is based on the assumption of a random distribution of the directions of the magnetic moments and of the thermal fluctuations of the direction of the anisotropy axis of the particles. The theory takes into account the dependence of the value of the resonance field on the linewidth.
Influence of dissolved oxygen on the thermal expansion and polyamorphism of fullerite C60
Authors: Dolbin A. V. , Vinnikov N. A. , Gavrilko V. G. , Esel’son V. B. , Manzhelii V. G. , Sundqvist B.
Published: June 2007

The temperature dependence of the coefficient of linear thermal expansion α of O2–C60 solutions with 20% and 80% filling of the octahedral cavities with oxygen is investigated in the temperature interval 2.2–24K. Hysteresis of α(T) is observed, attesting to the coexistence of two orientational glasses in these solutions. A comparison of the behavior of these glasses is made. The characteristic times for reorientation of the C60 molecules and for the phase transformations in the solutions are determined. When the temperature of the O2–C60 solution with 20mol.% oxygen is increased to 450°C, a chemical interaction of the oxygen with the C60 molecules is manifested. It proves possible to separate the influences of the chemical and physical sorption of oxygen on the thermal expansion of polycrystalline fullerite C60.
Thermal desorption and IR spectrometric investigation of polyamorphic and polymorphic transformations in cryovacuum condensates of water
Authors: Drobyshev A. , Aldiyarov A. , Zhumagaliuly D. , Kurnosov V. , Tokmoldin N.
Published: June 2007

Simultaneous thermal desorption and IR spectrometric studies of thermally stimulated transformations in thin films of cryovacuum condensates of water are carried out. It is shown that the temperature interval 12–36K is the existence region of a high-density form of amorphous solid water. The transition of amorphous high-density ice to a low-density amorphous state starts at T≈39K and is completed in the temperature region 60–70K. This process is accompanied by pore formation and reaches its maximum intensity at T≈42K. The transition temperature from the glassy amorphous ice to a super-viscous liquid state is determined: Tg=137±2K. Further increase in temperature leads to transformations of a stepped character in the layer. This may be due to competing processes of crystallization via the growth of cubic and hexagonal nuclei and also to direct crystallization of the super-viscous liquid water formed at Tg and existing together with the crystalline phase up to temperatures ∼200K. Anomalous behavior of the sample at temperatures preceding sublimation is revealed. This confirms that a multicomponent system consisting of amorphous and crystalline samples has different values of the equilibrium pressures of the gas phase, corresponding to partial activation energies of sublimation, i.e., at high temperatures amorphous water evaporates at an earlier stage, and then recondenses on the crystalline components.
Efficient and accurate calculations on the electronic structure of B-type poly(dG)∙poly(dC) DNA by elongation method: First step toward the understanding of the biological properties of aperiodic DNA
Authors: Orimoto Yuuichi , Gu Feng Long , Imamura Akira , Aoki Yuriko
Published: June 2007

Elongation method was applied to determine the electronic structures of B-type poly(dG)∙poly(dC) DNA at the ab initio molecular orbital level as a first step toward the calculation of aperiodic DNA. The discrepancy in total energy between the elongation method and a conventional calculation was negligibly small in the order of 10−8hartree∕at. for 14 G-C base pair model. The local density of states for 10 G-C base pair model estimated by the elongation method well reproduced the results by the conventional calculation. It was found that the band gap of the whole system is mainly due to the energy difference between the valence band of guanine and the conduction band of cytosine. Moreover, the electron transfer path through stacking G-C base pairs rather than sugar-phosphate backbones has been confirmed by the authors’ calculations.
Energetic electron beam generation by laser-plasma interaction and its application for neutron production
Authors: Gupta D. N. , Suk H.
Published: June 2007

Acceleration of electrons in the laser and magnetic field in a plasma can lead to the generation of an energetic electron beam. Both axial and azimuthal static magnetic fields play an important role to enhance the electron energy and to collimate the accelerated electrons. If the generated energetic electrons are targeted to a high-Z solid, backed with a sample of uranium-238, a significantly large number of neutrons can be produced by photonuclear reaction initiated by the Bremsstrahlung process. The efficiency of this process is found to be considerably higher than that of the spallation neutron source. The neutron source based on this process can be used as a driver for a subcritical fission reactor.
Formation of In-(2×1) and In islands on Si(100)-(2×1) by femtosecond pulsed laser deposition
Authors: Hafez M. A. , Elsayed-Ali H. E.
Published: June 2007

The growth of indium on a vicinal Si(100)-(2×1) surface at room temperature by femtosecond pulsed laser deposition (fsPLD) was investigated by in situ reflection high-energy electron diffraction (RHEED). Recovery of the RHEED intensity was observed between laser pulses and when the growth was terminated. The surface diffusion coefficient of deposited In on initial two-dimensional (2D) In-(2×1) layer was determined. As growth proceeds, three-dimensional In islands grew on the 2D In-(2×1) layer. The RHEED specular profile was analyzed during film growth, while the grown In islands were examined by ex situ atomic force microscopy. The full width at half maximum of the specular peak decreased during the deposition, indicative of well-ordered growth and an increase of the island size. The In islands developed into elongated-polyhedral, circular, and triangular shapes. The elongated and triangular islands were highly oriented, parallel and perpendicular to the surface terrace edges, while the circular islands show a top flat surface. Deposition of In on Si(100)-(2×1) by fsPLD influenced the formation of the initial In-(2×1) layer and the morphology of the grown islands.
Ferromagnetic resonance study of exchange and dipolar interactions in discontinuous multilayers
Authors: Majchrák Peter , Dérer Ján , Lobotka Peter , Vávra Ivo , Frait Zdeněk , Horváth Denis
Published: June 2007

We studied interlayer and intergranular exchange and dipolar coupling in (Fe97Si3∕SiO2)5 discontinuous multilayer (DM) by means of ferromagnetic resonance (FMR). Due to a strong ferromagnetic exchange coupling (J∼−3ergs∕cm2), the precessional motions of magnetic moments of the granules are coupled, which results in acoustic and optical modes. Moreover, there is a notable FMR line splitting in the optical mode under the external field normal to the DM, which is explained by an interlayer dipolar coupling, only possible for the DMs. The detailed structural analysis and electrical measurements confirmed that the metal nanoparticles were separated by an insulating matrix, and the single-electron transport phenomena (Coulomb blockade and tunneling magnetoresistivity) were observed at low temperatures (77–100K).
Atomic-force-microscope-compatible near-field scanning microwave microscope with separated excitation and sensing probes
Authors: Lai K. , Ji M. B. , Leindecker N. , Kelly M. A. , Shen Z. X.
Published: June 2007

We present the design and experimental results of a near-field scanning microwave microscope working at a frequency of 1GHz. Our microscope is unique in that the sensing probe is separated from the excitation electrode to significantly suppress the common-mode signal. Coplanar waveguides were patterned onto a silicon nitride cantilever interchangeable with atomic force microscope tips, which are robust for high speed scanning. In the contact mode that we are currently using, the numerical analysis shows that contrast comes from both the variation in local dielectric properties and the sample topography. Our microscope demonstrates the ability to achieve high resolution microwave images on buried structures, as well as nanoparticles, nanowires, and biological samples.
Differential mode excitation photoacoustic spectroscopy: A new photoacoustic detection scheme
Authors: Rey J. M. , Sigrist M. W.
Published: June 2007

A robust and simple gas sensor based on a novel photoacoustic scheme named “differential mode excitation photoacoustic spectroscopy (DME-PAS)” is presented. This method takes advantage of the selective excitation of two different modes in a resonant photoacoustic cell. A blackbody light source is used for simplicity in combination with optical correlation to provide a good selectivity. The frequency response of the proposed resonant cell is modeled using the extended Helmholtz resonator theory. The DME-PAS device is tested using acetone vapor and a model developed to describe its response when the gas concentration is varied. The obtained limit of detection is 25ppmm−1 for acetone in room air. Using DME-PAS, the derived gas concentration is affected neither by intensity fluctuations of the light source nor by any microphone drifts.
Ferromagnetic resonance force microscopy on a thin permalloy film
Authors: Nazaretski E. , Martin I. , Movshovich R. , Pelekhov D. V. , Hammel P. C. , Zalalutdinov M. , Baldwin J. W. , Houston B. , Mewes T.
Published: June 2007

Ferromagnetic resonance force microscopy (FMRFM) offers a means of performing local ferromagnetic resonance. The authors have studied the evolution of the FMRFM force spectra in a continuous 50nm thick permalloy film as a function of probe-film distance and performed numerical simulations of the intensity of the FMRFM probe-film interaction force, accounting for the presence of the localized strongly nonuniform magnetic field of the FMRFM probe magnet. Excellent agreement between the experimental data and the simulation results provides insight into the mechanism of FMR mode excitation in a FMRFM experiment.
Linear electric molten zone in semiconductors
Authors: Vallêra António M. , Maia Alves Jorge , Serra João M. , Brito Miguel C. , Gamboa Roberto M.
Published: June 2007

This letter describes how the temperature dependence of the electrical conductivity in semiconductors may be used to produce a linear floating molten zone which is intrinsically stable and uniform along its length. An analytical model and an experimental demonstration of such electric molten zone are both presented. This effect may be of particular interest for crystal growth and semiconductor recrystallization.
Study of the thermal stress in a Pb-free half-bump solder joint under current stressing
Authors: Wu B. Y. , Chan Y. C. , Zhong H. W. , Alam M. O. , Lai J. K. L.
Published: June 2007

The thermal stress in a Sn3.5Ag1Cu half-bump solder joint under a 3.82×108A∕m2 current stressing was analyzed using a coupled-field simulation. Substantial thermal stress accumulated around the Al-to-solder interface, especially in the Ni+(Ni,Cu)3Sn4 layer, where a maximal stress of 138MPa was identified. The stress gradient in the Ni layer was about 1.67×1013Pa∕m, resulting in a stress migration force of 1.82×10−16N, which is comparable to the electromigration force, 2.82×10−16N. Dissolution of the Ni+(Ni,Cu)3Sn4 layer, void formation with cracks at the anode side, and extrusions at the cathode side were observed.
Effect of donor-complex-defect-induced dipole field on InAs∕GaAs quantum dot infrared photodetector activation energy
Authors: Zhao Z. Y. , Yi C. , Lantz K. R. , Stiff-Roberts A. D.
Published: June 2007

In order to understand dopant incorporation in quantum dot infrared photodetectors, three quantum dot (QD) Schottky diodes (undoped, delta doped, and modulation doped) have been investigated. Donor-complex-defect (DX) centers have been observed by photocapacitance quenching in the doped diodes only. When the applied bias increases, the doped samples show a rapid increase in dark current and a resulting dramatic decrease in QD activation energy. The activation energy reduction could be related to a dipole field between positively charged DX centers and electrons in QDs. A transport mechanism is proposed to explain the observed activation energy bias dependence in the doped samples.
Absence of population substructuring in Zimbabwe chicken ecotypes inferred using microsatellite analysis
Authors: Muchadeyi F. C. , Eding H. , Wollny C. B. A. , Groeneveld E. , Makuza S. M. , Shamseldin R. , Simianer H. , Weigend S.
Published: June 2007

The objective of this study was to investigate the population structure of village chickens found in the five agro‐ecological zones of Zimbabwe. Twenty‐nine microsatellites were genotyped for chickens randomly selected from 13 populations, including the five eco‐zones of Zimbabwe (n = 238), Malawi (n = 60), Sudan (n = 48) and six purebred lines (n = 180). A total of 280 alleles were observed in the 13 populations. Forty‐eight of these alleles were unique to the Zimbabwe chicken ecotypes. The average number (±SD) of alleles/locus was 9.7 ± 5.10. The overall heterozygote deficiency in the Zimbabwe chickens (FIT ± SE) was 0.08 ± 0.01, over 90% of which was due to within‐ecotype deficit (FIS). Small Nei's standard genetic distances ranging from 0.02 to 0.05 were observed between Zimbabwe ecotypes compared with an average of 0.6 between purebred lines. The structure software program was used to cluster individuals to 2 ≤ K ≤ 7 assumed clusters. The most probable clustering was found at K = 6. Ninety‐seven of 100 structure runs were identical, in which Malawi, Sudan and purebred lines split out as independent clusters and the five Zimbabwe ecotypes clustered into one population. The within‐ecotype marker‐estimated kinships (mean = 0.13) differed only slightly from the between‐ecotype estimates. Results from this study lead to a rejection of the hypothesis that village chickens are substructured across agro‐ecological zones but indicated high genetic diversity within the Zimbabwe chicken population.
A 12 000‐rad whole‐genome radiation hybrid panel in sheep: application to the study of the ovine chromosome 18 region containing a QTL for scrapie susceptibility
Authors: Laurent P. , Schibler L. , Vaiman A. , Laubier J. , Delcros C. , Cosseddu G. , Vaiman D. , Cribiu E. P. , Yerle M.
Published: June 2007

Whole‐genome radiation hybrid (RH) panels have been constructed for several species, including cattle. RH panels have proven to be an extremely powerful tool to construct high‐density maps, which is an essential step in the identification of genes controlling important traits, and they can be used to establish high‐resolution comparative maps. Although bovine RH panels can be used with ovine markers to construct sheep RH maps based on bovine genome organization, only some (c. 50%) of the markers available in sheep can be successfully mapped in the bovine genome. So, with the development of genomics and genome sequencing projects, there is a need for a high‐resolution RH panel in sheep to map ovine markers. Consequently, we have constructed a 12 000‐rad ovine whole‐genome RH panel. Two hundred and eight hybrid clones were produced, of which 90 were selected based on their retention frequency. The final panel had an average marker retention frequency of 31.8%. The resolution of this 12 000‐rad panel (SheepRH) was estimated by constructing an RH framework map for a 23‐Mb region of sheep chromosome 18 (OAR18) that contains a QTL for scrapie susceptibility.
Identification of 10 882 porcine microsatellite sequences and virtual mapping of 4528 of these sequences
Authors: Karlskov‐Mortensen P. , Hu Z. L. , Gorodkin J. , Reecy J. M. , Fredholm M.
Published: June 2007

A total of 10 882 porcine microsatellite repeats were identified in genomic shotgun sequences from the Sino‐Danish Pig Genome Sequencing Consortium (http://www.piggenome.dk). Of these, 4528 microsatellites were placed on a pig–human comparative map by blast analysis of porcine sequences against the human genome (blast cut‐off threshold =1 × 10−5). All microsatellite sequences placed on the comparative map are accessible at http://www.animalgenome.org/QTLdb/pig.html. These sequences increase the number of identified microsatellites in the porcine genome by several orders of magnitude. They are a new resource of microsatellite sequences for generating markers to be used in linkage studies and in fine mapping and positional cloning of quantitative trait loci.
Mapping quantitative trait loci for osteochondrosis in fetlock and hock joints and palmar/plantar osseus fragments in fetlock joints of South German Coldblood horses
Authors: Wittwer C. , Löhring K. , Drögemüller C. , Hamann H. , Rosenberger E. , Distl O.
Published: June 2007

The aim of this study was to identify quantitative trait loci (QTL) for osteochondrosis (OC) and palmar/plantar osseous fragments (POF) in fetlock joints in a whole‐genome scan of 219 South German Coldblood horses. Symptoms of OC and POF were checked by radiography in 117 South German Coldblood horses at a mean age of 17 months. The radiographic examination comprised the fetlock and hock joints of all limbs. The genome scan included 157 polymorphic microsatellite markers. All microsatellite markers were equally spaced over the 31 autosomes and the X chromosome, with an average distance of 17.7 cM and a mean polymorphism information content (PIC) of 63%. Sixteen chromosomes harbouring putative QTL regions were further investigated by genotyping the animals with 93 additional markers. QTL that had chromosome‐wide significance by non‐parametricZ‐means and LOD scores were found on 10 chromosomes. This included seven QTL for fetlock OC and one QTL on ECA18 associated with hock OC and fetlock OC. Significant QTL for POF in fetlock joints were located on equine chromosomes 1, 4, 8, 12 and 18. This genome scan is an important step towards the identification of genes responsible for OC in horses.
A reappraisal of cantilever bridgework
Authors: CRABB H. S. M.
Published: June 2007

summary

The design and application of spring cantilever and direct cantilever bridgework is evaluated in relation to developments in new materials and the significance of the health of the periodontal tissues. Cantilever bridgework is not advanced as a preferred alternative to conventional fixed bridgework but as a means of meeting certain clinical situations which preclude the use of abutment supports at both ends of a bridge. Lack of success in cantilever bridgework can frequently be attributed to the abuse of design rather than failure of the underlying cantilever principle.
Clinical review of patients with fixed bridges (1)
Authors: MARKÉN K.‐E. , LÖFBERG P.‐G. , HEDEGÅRD B.
Published: June 2007

This report comprises the first part of an investigation into the methodology of clinical examinations of patients with bridges. The complete study is concerned with the following problems.

To what extent do deviations occur between observers in the independent recording of factors of interest in the re‐examination of patients with fixed bridges?

Are the deviations observed systematic?

Does a cumulative and simultaneous examination lead to less deviating results?

Are there any characteristic differences between observers with a greater or lesser degree of clinical experience?