bluuebunny/crossref_metadata_2025 huggingface dataset:
On the linear vertex‐arboricity of a planar graph
Authors: Poh K. S.
Published: June 2007

We prove in this note that the linear vertex‐arboricity of any planar graph is at most three, which confirms a conjecture due to Broere and Mynhardt, and others.
Reduced graphs of diameter two
Authors: Lai Hong‐Jian
Published: June 2007

A graph H is collapsible if for every subset X ⊆ V(H), H has a spanning connected subgraph whose set of odd‐degree vertices is X. In any graph G there is a unique collection of maximal collapsible subgraphs, and when all of them are contracted, the resulting contraction of G is a reduced graph. Interest in reduced graphs arises from the fact [4] that a graph G has a spanning closed trail if and only if its corresponding reduced graph has a spanning closed trail. The concept can also be applied to study hamiltonian line graphs [11] or double cycle covers [8]. In this article, we characterize the reduced graphs of diameter two. As applications, we obtain prior results in [12] and [14], and show that every 2‐edge‐connected graph with diameter at most two either admits a double cycle cover with three even subgraphs or is isomorphic to the Petersen graph.
The chromaticity of complete bipartite graphs with at most one edge deleted
Authors: Teo C. P. , Koh K. M.
Published: June 2007

Let K(p, q), p ≤ q, denote the complete bipartite graph in which the two partite sets consist of p and q vertices, respectively. In this paper, we prove that (1) the graph K(p, q) is chromatically unique if p ≥ 2; and (2) the graph K(p, q) ‐ e obtained by deleting an edge e from K(p, q) is chromatically unique if p ≥ 3. The first result was conjectured by Salzberg, López, and Giudici, who also proved the second result under the condition that q ‐ p ≤ 1.
Maximal chromatic polynomials of connected planar graphs
Authors: Tomescu Ioan
Published: June 2007

In this paper we obtain chromatic polynomials of connected 3‐ and 4‐chromatic planar graphs that are maximal for positive integer‐valued arguments. We also characterize the class of connected 3‐chromatic graphs having the maximum number of p‐colorings for p ≥ 3, thus extending a previous result by the author (the case p = 3).
Circuits in cayley digraphs of finite abelian groups
Authors: Wilkinson Anne Marie
Published: June 2007

We find all possible lengths of circuits in Cayley digraphs of two‐generated abelian groups over the two‐element generating sets and over certain three‐element generating sets.
Zur iterativen Lösungseinschließung bei Anfangswertproblemen mittels Intervallmethoden
Authors: Bauch H.
Published: June 2007

In der vorliegenden Arbeit werden Voraussetzungen für iterative Verfahren zur intervallanalytischen Lösungseinschließung bei Anfangswertproblemen von Systemen gewöhnlicher Differentialgleichungen 1. Ordnung untersucht und Möglichkeiten zur Konvergenzbeschleunigung angegeben.
Über fast homogene turbulente Scherströmungen
Authors: Szablewski W.
Published: June 2007

Auf der Grundlage einfacher mathematischer Ansätze für die Komponenten des Energieaustausches sowie für die Komponenten der Dissipation erhält man eine explizite Beschreibung der Entwicklung einer fast homogenen turbulenten Scherströmung, die mit kürzlich publizierten Messungen in Übereinstimmung steht. Aus der Gleichung der turbulenten Schubspannung folgt formelmäßig eine Abhängigkeit der Komponenten des Energieaustausches von der relativen Schubspannung (Schubspannung relativ zur Turbulenzenergie), die anscheinend durch vorliegende Messungen bestätigt wird.
Sensitivity Analysis for Beams and Plates (The Elementary Solution Approach)
Authors: Komkov V.
Published: June 2007

We consider the linear equations modelling the dynamic behavior of vibrating beams and thin plates. We develop the basic equations for the sensitivity function indicating the dynamic structural response to changes in design. Specifically, the properties of the sensitivity function are developed in detail for the vibrating beam equation. We conclude that the knowledge of an elementary solution of the beam equation, and of the sensitivity function for the elementary solution can be used to determine the sensitivity function for a class of admissible loads applied to the beam.
Zur Lösung der Navier‐Stokes‐Gleichung mit Hilfe eines voll impliziten Iterationsverfahrens
Authors: Zwick W.
Published: June 2007

Wir betrachten die Navier‐Stokes‐Gleichung in der up‐, ωΨ und Ψ‐Formulierung und verwenden zu ihrer Lösung ein voll implizites Iterationsverfahren. In jedem Iterationsschritt wird die linearisierte Navier‐Stokes‐Gleichung gelöst, deren Differentialoperatoren durch verschiedene Differenzenansätze approximiert werden. Zur Lösung der algebraischen Gleichungs‐systeme werden die Matrizen als Produkte aus unteren und oberen Dreiecksmatrizen dargestellt.
Einsatz mathematischer Methoden bei der Hydroenergiegewinnung
Authors: Bauer W. , Buchinger S. , Wacker Hj.
Published: June 2007

Der Einsatz mathematischer Methoden im Bereich der Hydroenergieoptimierung wird an Hand von vier konkreten Projekten demonstriert:

Momentanoptimierung

Tagesoptimierung

Höhensteuerung eines Tagesspeicherkraftwerks

Optimierung des Schwellbetriebes.

Im Gegensatz zu (M1), (M2) und (M3) stellt (M4) erst eine Vorstudie dar, die jedoch eine bessere Approximation der Realität liefert als derzeit verwendete Modelle. Der Einsatz bisher bekannter Optimierungstechniken bei der numerischen Lösung speziell von (M1) stieß auf beträchtliche Schwierigkeiten. Aus diesem Grund wurden Optimierungsverfahren auf Einbettungsbasis entwickelt und mit Erfolg eingesetzt.

Instant Optimization

all days optimization

head control for a small storage plant

optimal floating policy for a river section.
Auto‐oscillation Systems with Inertial Self‐excitation
Authors: Babitsky V. I. , Landa P. S.
Published: June 2007

A class of dynamical systems is described for which self‐excitation of oscillations is due to inertial interaction between the variables. A number of typical examples are presented for autooscillation systems of this type which are relevant to various fields of science and technology. It is shown that the self‐excited oscillations can be periodical, as well as stochastical, depending on the form of nonlinearities.
On the Choice of Steplength in Path Following Methods
Authors: Schwetlick H.
Published: June 2007

A path following method of Newton type widely used in numerical practice is investigated by using a model based on the Kantorovich Theorem. It turns out that within this model a steplength near the maximal steplength accepted by the Kantorovich Theorem is most efficient provided that a uniform accuracy of all points is required. This theoretical result is confirmed by a numerical example taken from nonlinear circuit theory.
On the Convergence of the Higher Order Versions of D. J. Evans' Implicit Matrix Inversion Process
Authors: Alefeld G.
Published: June 2007

The higher order versions of the method introduced by D. J. Evans are investigated. We introduce sufficient conditions for convergence, prove some error estimations and show that under appropriate conditions the iterates are possessing monotonous behaviour. Furthermore we show that these methods can also be used to improve an approximation for the pseudoinverse of a matrix with full column rank.
Nonconvex Problems of Semipermeable Media and Related Topics
Authors: Panagiotopoulos P. D.
Published: June 2007

The present paper deals with B V Ps in the theory of semipermeability potentials. Both the cases of interior and boundary semipermeability problems are studied. After the formulation of the problems in terms of hemivariational inequalities and the definition of the regularised problems an existence result is proved. The proof is constructive and may be used for the approximation of the solution of the problem. Finally, the developed method is applied to certain similar problems arising in the theory of elasticity.
Filmsieden bei der Umströmung der halbunendlichen ebenen Platte und des Keils durch inkompressible Flüssigkeiten
Authors: Schütte V.
Published: June 2007

Im Rahmen der Grenzschichttheorie werden mit Hilfe der Methode der Integralsätze Aufgaben der Umströmung der halbunendlichen ebenen Platte durch eine Flüssigkeit, deren Temperatur außerhalb des Siedebereiches liegt, und der Umströmung des Keils durch eine siedende Flüssigkeit gelöst. Für kleine Werte des Parameters R = (ϱvμv/ϱLμL)0,5 werden analytische Näherungslösungen angegeben, insbesondere Formeln zur Bestimmung der Reibungs‐ und Wärmeübertragungskoeffizienten.
Die automatische Gleichungsgenerierung beliebig strukturierter mechanischer Systeme unter besonderer Berücksichtigung der Anforderungen der Anforderungen aus dem Schienenfahrzeugbau
Authors: Krettek O. , Ofierzyński M.
Published: June 2007

Der Bau von spurgebundenen aber auch spurungebundenen Verkehrsmitteln ist an die strenge Einhaltung geometrischer, kinematischer, Statischer und dynamischer Restriktionen gebunden. Wird nur eine dieser Vorgaben verletzt, kann die Einsetzbarkeit des Fahrzeugs in Frage gestellt sein. Obwohl die entsprechenden Nachweise zum Teil äußerst aufwendig sind, fehlt es bis heute an einem EDV‐Programmsystem, das für sich in Anspruch nehmen kann, die Beziehungen für sämtliche erforderlichen Rechnungsgänge vollautomatisch und modellgetreu auch für verwickelte Mechanismen, wie sie etwa bei Schienenfahrzeuglaufwerken vorkommen, zu generieren und zu lösen. Diese Lücke soll das hier dargestellte graphentheoretisch aufgebaute vorerst allerdings lediglich in Teilen fertiggestellte System schließen. Einzugeben bleiben als einziges die rechnungsbedeutsamen Strukturpunkte sowie die Parameter des Fahrzeugs wie Massen, Längen, Federkennungen u. drgl. m.
A Curved Finite Element of Revolution Shells after Timoshenko's Shear Model
Authors: Rikards R. B. , Goldmanis M. V.
Published: June 2007

This paper discusses solutions of the problems associated with bending and stability of shells of revolution by means of the finite‐element method and using the principle of minimum potential energy and the theory of Timoshenko‐type shells. A curved finite element of third order is proposed to calculate shells of revolution under axisymmetric loads. The convergence properties of the proposed element are examined in the bending and stability problems. As examples are given the problems of bending of a cylindrical shell, deformation of a toroidal shell, stability analysis of a toroidal shell under external pressure and stability analysis of a shall of meridianally variable shape under external pressure.
Complex Swirling Radial Jets
Authors: Filip P. , Kolář V. , Curev A. G.
Published: June 2007

Similarity solutions of single, multiple and antisymmetrical swirling radial jets are presented using a proposed 3‐D formulation of Reichardt's Hypothesis. The derivation of mean velocity field description of the multiple and antisymmetrical swirling radial jets is based on the superposition principle of single swirling radial jet solutions obtained from the linear equations of motion (derived in the frame of Reichardt's procedure). Hence, the method used provides — in contrast to other ones — a means flow analytical description of complex turbulent jets.

Es werden die Ähnlichkeitslösungen des einfachen, mehrfachen und antisymmetrischen Radialstrahles mit Rotation vorgelegt, ausgehend von einer in Vorschlag gebrachten dreidimensionalen Formulierung der Reichardtschen Hypothese. Die Beschreibung des Feldes der gemittelten Geschwindigkeit des mehrfachen und des antisymmetrischen Radialstrahles mit Rotation basiert auf dem Superpositionsprinzip von Lösungen für den einfachen Radialstrahl mit Rotation, die sich aus den linearen Bewegungsgleichungen ergeben, die im Rahmen des Reichardtschen Verfahren erhalten wurden. Die in Vorschlag gebrachte Lösung liefert — zum Unterschied von anderen Methoden — eine analytische Bewschreibung des gemittelten Stromes der komplexen turbulenten Freistrahlen.
Ein objektives Stoffgesetz des plastischen Materialverhaltens
Authors: Backhaus G.
Published: June 2007

Die in früheren Arbeiten des Verfassers entwickelte Spannungs‐Deformations‐Beziehung für beliebige plastische Verformungsvorgänge wird in die Form einer objektiven (bezugssystemindifferenten) Stoffgleichung gebracht. Am Beispiel einer großen Verformung wird gezeigt, daß die Unterschiede zwischen den Rechnungsergebnissen bei Benutzung der ersteren Beziehung (vereinfachte Stoffgleichung) und den Ergebnissen bei Verwendung der objektiven Stoffgleichung vernachlässigbar sind. Die vereinfachte Stoffgleichung kann zur Ermittlung von Größe und Richtung des Spannungs‐Vektors längs Verformungswegen großer Krümmung dienen. Rechnungen unter Verwendung experimentell ermittelbar Materialwerte zeigen, daß für Krümmungswerte unterhalb von 100 bis 10 — abhängig vom Material — die einfache Fließtheorie anwendbar ist.
Über simultane Eigenwertalgorithmen beim Schwingungsproblem
Authors: Meyer A , Döhler B.
Published: June 2007

Es werden Verfahren zur simultanen Berechung einiger Eigenwerte und Eigenvektoren dargelegt, die besonders für großdimensionierte, schwach besetzte Matrizen geeignet sind, und es wird auf die Anwendung bei gedämpften und ungedämpften Schwingungsproblemen eingegangen.
Zur Berechnung der stochastisch erregten Schaufelradbaggernickschwingungen bei Berücksichtigung der Rückkopplung in der Schwingungserregung
Authors: Mohr H. , Renger A.
Published: June 2007

Eine Differentialgleichung, die die stochastischen und selbsterregten Nickschwingungen von Schaufelradbaggern beschreibt, wird unter Berücksichtigung der Rückkopplungseffekte am Schaufelrad hergeleitet und gelöst. Zur Bestimmung analytischer Näherungslösungen sowie zur Stabilitätsuntersuchung wird die Mittelungsmethode für stochastische Schwingungen nach Stratonowitch verwendet. Es wird eine ingenieurmäßige Darstellung dieser Methode gegeben, deren Anwendbarkeit auf die Baggerschwingungen durch numerische Integration der Differentialgleichung unter Verwendung eines Simulationsansatzes für die stochastischen Erregungen bestätigt wird.
Analysis of an Amplitude Equation for Autovibrational Flow Regimes at Resonance External Forces
Authors: Levina G. V. , Nepomnyaschiy A. A.
Published: June 2007

Resonance effects in viscous flows produced by unsteady external forces are studied. With the help of a small parameter method the amplitude equation for a resonance case is derived. It is shown that the amplitude of the secondary regime is proportional to the cubic root amplitude of external force. Possible transitions between supercritical motions are investigated. The map of secondary regimes in dependence on the amplitude equation coefficients is given.
Determination of Optimal Upstream Weighting Parameter for the Finite Element Solution of Transient Transport Equation
Authors: Honma S. , Karadi G.
Published: June 2007

In this study the results of a numerical experiment involving the finite element solution of the convection‐dominated transport equation are presented. It is shown that, for large Peclet numbers, the standard Galerkin approach produces unacceptable oscillations. Although the upstream weighting residual method eliminates this problem for steady state problems, its application to transient flow problems has received considerable criticism, because false dispersion and/or the smearing of steep gradients are observed. The numerical experiments performed for transient problems revealed that the upstream weighting residual method can be improved considerably if the upstream weighting parameter is selected as a function of the Courant number. Based on the results of these numerical experiments, a relationship between the optimal weighting parameter and the Courant number is proposed so that oscillations are eliminated and false dispersion is reduced to an acceptable level.
Zur optimalen Steuerung in Neumannschen Randbedingungen bei Evolutionsgleichungen
Authors: Kampowsky W.
Published: June 2007

Die Arbeit beschäftigt sich mit Problemen optimaler Steuerung, die durch nichtlineare Rand‐Anfangswertprobleme für parabolische Differentialgleichungen zweiter Ordnung beschrieben werden. Es werden Randsteuerungen mit Randbedingungen vom Neumannschen Typ betrachtet. Das Rand‐Anfangswertproblem wird funktionalanalytisch verallgemeinert und als Anfangswertaufgabe für eine Evolutionsgleichung im Rahmen der Theorie monotoner Operatoren untersucht. Im wesentlichen werden notwendige Optimalitätsbedingungen hergeleitet, die aus einer allgemeinen Variationsungleichung und einer adjungierten Evolutionsgleichung bestehen. Die Arbeit ergänzt die Untersuchungen von Randsteuerungen in Dirichletschen Randbedingungen in [5].
A Mixed Finite Element Method for Fourth Order Partial Differential Equations
Authors: Balasundaram S. , Bhattacharyya P. K.
Published: June 2007

This paper deals with a new mixed finite element solution of the Dirichlet problem of fourth order elliptic linear partial differential operators with variable coefficients. As examples, bending problems of elastic plates having variable thickness have been considered, for which the algorithm of this method allows a simultaneous determination of the deflection, the curvature components and the „actual”︁ bending and twisting moments of the plate, the „actual”︁ bending and twisting moments being the components of the Lagrange multiplier of this method. Suitable error estimates are obtained under necessary regularity assumptions on the solution.
On Superlinear Convergence of Some Stable Variants of the Secant Method
Authors: Burdakov O. P.
Published: June 2007

In a recent author's paper four classes of methods of the secant type for solving systems of nonlinear equations were proposed. They are stable with respect to linear dependence of the search directions. If the Jacobian matrix is symmetric, then two of them take into account this property. It is proved here that some four special methods from the classes converge superlinearly.
Optimal Design of an Elastic Plate with Unilateral Elastic Foundation and Rigid Supports, Using the Reissner‐Mindlin Plate Model. I: Continuous Problems
Authors: Hlaváček I. , Lovíšek J.
Published: June 2007

Several optimal design problems with a variational inequality with a monotone operator as common state problem are considered. The inequality represents the bending of a Reissner‐Mindlin plate, resting on a unilateral elastic foundation and on some unilateral rigid piers. Both the thickness of the plate and the stiffness of the foundation play the role of design variables. The cost functionals include the intensity of shear stresses, and reactive forces on the piers or the weight of the plate. The solvability of all the problems is proved.
Excitonic properties of type-I and type-II Si∕Si1−xGex quantum wells
Authors: Chaves Andrey , Costa e Silva J. , Freire J. A. K. , Farias G. A.
Published: June 2007

The exciton properties of Si∕Si1−xGex quantum wells (QWs) are investigated within a variational approach, taking into account interface effects for two possibilities of the band alignment, type I and type II. For the latter, two-dimensional (2D) and three-dimensional (3D) variational wave functions are used in order to give a better description of the exciton confinement, where a large enhancement on the exciton binding energy (about 30% for a 70 Å well width) is found for the 3D case. The effects due to the presence of external electromagnetic fields on exciton energies are also analyzed. Our theoretical results explain the exciton energy blueshifts recently found in photoluminescence experiments for type-I Si∕Si0.82Ge0.18 QWs when electric fields are applied in the growth direction. Exciton energy shifts due to magnetic fields are calculated, and a comparison between such shifts in the 2D and 3D approaches is performed for type-II wells. Numerical results show that interfacial layers of 15 Å thickness for a type-I (type-II) Si∕Si0.82Ge0.18 (Si0.70Ge0.30) QW lead to a variation of about 20 meV (25 meV) in relation to the abrupt well for a 50 Å well width, yielding a blueshift on the exciton total energy.
Synthesis and compressibility of Ti3(Al,Sn0.2)C2 and Ti3Al(C0.5,N0.5)2
Authors: Manoun Bouchaib , Saxena S. K. , Hug Gilles , Ganguly A. , Hoffman E. N. , Barsoum M. W.
Published: June 2007

In this paper we report on the synthesis of a composition, Ti3Al(C0.5,N0.5)2, belonging to the Mn+1AXn family of ternary layered carbides and nitrides. X-ray and selected area diffraction confirm that this compound is isostructural with Ti3SiC2; its a and c-lattice parameters are 3.0404(5) and 18.414(6) Å, respectively. Chemical analysis performed by electron dispersive and electron energy loss spectroscopy confirmed the Ti3AlCN chemistry. Using a synchrotron radiation source and a diamond anvil cell, we also measured the pressure dependencies of the lattice parameters. Up to a pressure of ≈50 GPa, no phase transformations were observed. The bulk modulus is 219±4 GPa, with a pressure derivative, Ko′, of 3.7±0.3. We also fabricated the ternary Ti3AlC2, with some Sn [nominal composition Ti3(AlSn0.2)C2]. Its a and c-lattice parameters are 3.0804(7) and 18.5426(7) Å, respectively. Its bulk modulus is 226±3 GPa, with a pressure derivative, Ko′, of ≈4. In both cases, the compressibility was greater along the c than along the a axes. We also show that in the case of Tin+1AlCn MAX-phases, replacing C by N results in a decrease in both lattice parameters and bulk moduli. The apparent contradiction inherent in this observation can be reconciled by assuming that the addition of N results in the formation of vacancies on the Al and/or X-sites.
Adsorption-state-dependent subpicosecond photoinduced desorption dynamics
Authors: Szymanski Paul , Harris Alex L. , Camillone Nicholas
Published: June 2007

Femtosecond laser excitation has been used to initiate desorption of molecular oxygen from the (111) surface of Pd and to study the adsorption-state dependence of the substrate-adsorbate coupling. The relative populations of the two chemical states, peroxo (O22−) and superoxo (O2−), were varied by changing the total coverage. Two-pulse correlation measurements exhibit a dominant 400fs response and a slower 10ps decay that are relatively independent of the initial O2 coverage. In contrast, the photodesorption yield and the nonlinearity of the fluence dependence show a systematic coverage dependence. The coverage-independent subpicosecond response indicates that the photoinduced desorption from the two states is driven primarily by the same electron-mediated mechanism, while the coverage dependence of the yield indicates that the desorption efficiency from the superoxo state is greater than that from the peroxo state. These results are discussed in the context of the electron-phonon two-temperature model with an empirical adsorbate-electron frictional coupling that depends on both the electronic temperature and the activation energy for desorption. With a coupling strength that decreases as the activation energy decreases, the trends with varying coverage, absorbed fluence, and time delay can all be reproduced. The model is consistent with a transition from a resonantly enhanced (diabatic) regime to an adiabatic regime as the system relaxes, accounting for the biexponential correlation behavior.
Formation and dissociation of MgH2 in epitaxial Mg thin films
Authors: Kelekar R. , Giffard H. , Kelly S. T. , Clemens B. M.
Published: June 2007

We have studied hydride formation and dissociation in epitaxial and textured Mg films capped with Pd. We grew epitaxial Mg in the (001) orientation on (001) Al2O3 and in the (110) orientation on (320) LiGaO2; and as a reference, textured (001) Mg on glass. Using x-ray diffraction techniques, we studied the formation of the hydride at 373 K in 0.6 MPa of H2 gas, and the dissociation of the hydride in air at 355 K. We show that the hydride forms epitaxially relative to the Mg; we find the epitaxial relationship to be MgH2(110)[001]∕∕Mg(001)[100] on Al2O3 and MgH2(200)[001]∕∕Mg(110)[1¯11] on LiGaO2. We provide evidence showing that during hydride dissociation a portion of Mg recrystallization begins at the Mg∕MgH2 interface, as well as at the MgH2∕Pd interface. Finally, we find that the kinetics of hydrogen absorption and desorption depends on the surface orientation and degree of crystallinity of the original Mg, and that hydrogen diffusion is an important factor governing desorption kinetics.
Features of the reflection of TE waves from a nongyrotropic multiferroic slab
Authors: Savchenko A. S. , Tarasenko S. V.
Published: June 2007

The anomalies induced by an anisotropic magnetoelectric interaction in the reflection of a bulk s-polarized wave from the surface of a slab of a nongyrotropic collinear ferroelectric antiferromagnet are investigated in the Kretschmann geometry under the condition that the ferroelectric axis is perpendicular to the interface between media. A number of features of the propagation and localization of TE magnetic polaritons in a ferroelectric antiferromagnetic slab are discussed.
On the dispersion relation of kink-type solitons in one-dimensional ferromagnets
Authors: Galkina E. G. , Ivanov B. A.
Published: June 2007

The nonlinear classical and quantum dynamics of topological solitons (kinks) in a spin chain with appreciable biaxial anisotropy is investigated. Analytical calculations and numerical simulations are carried out for a discrete model with classical spins, and the results are used for analysis of the quantum properties of a kink in the semiclassical approximation. The analysis is based primarily on the lattice pinning potential. The pinning potential is largely determined by the microscopic source of the anisotropy: it is absent for purely exchange anisotropy, and it can be appreciable only for purely single-ion anisotropy. It is shown that under the influence of an external driving magnetic field a kink undergoes Bloch oscillations. The quantum spectrum of the kink consists of a finite number of nonoverlapping bands, equal to S for integer atomic spin S and to 2S for half-integer spin. Various quantum tunneling effects are investigated, including the tunneling transition from one position in the lattice to another and the tunneling change of the topological charge of the kink.
Nucleation dynamics around single microabsorbers in water heated by nanosecond laser irradiation
Authors: Neumann Jörg , Brinkmann Ralf
Published: June 2007

Suspensions containing micro- and nanoabsorbers, which are irradiated by short laser pulses, are used for a manifold of procedures in medicine, biotechnology, and other fields. Detailed knowledge of the bubble nucleation and dynamics, which is induced by the heat transfer from the absorber to the surrounding transparent water, is essential for understanding the underlying processes occurring on a microscopic scale. We investigated the rapid phase change phenomena including temperature, heating rates, pressure generation, bubble nucleation, and initial bubble growth around absorbing micron-sized melanin particles (retinal pigment epithelial melanosomes) during irradiation with 12ns (full width at half maximum) laser pulses at a wavelength of 532nm. The melanosomes were heated at rates in the order of 1010K∕s. A mean bubble nucleation temperature of 136°C was found. The initial bubble expansion was observed by time-resolved microscopy. The expansion velocities range from 10m∕s at 1.5-fold to 85m∕s at 8.5-fold threshold radiant exposure for bubble formation, respectively. The expansion velocity increases in the investigated range almost linearly with the applied radiant exposure.
On the ground and some low-lying excited states of ScB: A multiconfigurational study
Authors: Černušák Ivan , Dallos Michal , Lischka Hans , Müller Thomas , Uhlár Milan
Published: June 2007

The electronic structure of a series of low-lying excited triplet and quintet states of scandium boride (ScB) was examined using multireference configuration interaction (including Davidson’s correction for quadruple excitations) and single-reference coupled cluster (CC) methods with averaged natural orbital (ANO) basis sets. The CC approach was used only for the lowest quintet state. The authors have analyzed eight low-lying triplets Σ−3(2), Σ+3, Π3(3), and Δ3(2) dissociating to Sc(D2)∕B(P2) atoms and eight low-lying quintet states Σ−5, Σ+5, Π5(2), Φ5, and Δ5(3) dissociating to Sc(F4)∕B(P2) atoms. They report the potential energy curves and spectroscopic parameters of ScB obtained with the multireference configuration interaction (MRCI) technique including all singly and doubly excited configurations obtained with the ANO-S basis set. For the two lowest states they obtained also improved ANO-L spectroscopic constants, dipole and quadrupole moments as well as scalar relativistic effects based on the Douglas-Kroll-Hess Hamiltonian. They provide the analysis of the bonding based on Mulliken populations and occupation numbers. Since the two lowest states, Σ−3 and Σ−5, lie energetically very close, their principal goal was to resolve the nature of the ground state of ScB. Their nonrelativistic MRCI(Q) (including Davidson correction) results indicate that the quintet is more stable than the triplet by about 800cm−1. Inclusion of scalar relativistic effects reduces this difference to about 240cm−1. The dissociation energies for Σ−5 ScB range from 3.20to3.30eV while those for the Σ−3 range from 1.70to1.80eV.
Solvation and squeeze out of hexadecane on graphite
Authors: Gosvami N. N. , Sinha S. K. , Hofbauer W. , O’Shea S. J.
Published: June 2007

We have performed simultaneous force and conductivity measurement of hexadecane liquid confined between a conducting atomic force microscope tip and a graphite surface. Both the current and the force data reveal discrete solvation layering of the hexadecane near the surface. We typically observe that the current does not vary with load in a simple way as the layer closest to the surface is compressed, but increases markedly prior to the expulsion of material from the tip-sample gap. We infer that even for a nanoscale asperity there is conformation change of the confined hexadecane under the tip apex prior to squeeze out of the molecules.
Isomers of Au8
Authors: Olson Ryan M. , Gordon Mark S.
Published: June 2007

Using newly developed correlation consistent basis sets for gold, the relative energies for the neutral Au8 geometric isomers have been re-evaluated and the vertical ionization potentials calculated. The results using the correlation consistent basis sets show that second-order Moller-Plesset perturbation theory calculations strongly favor nonplanar Au8 structures for all basis sets that were employed. However, the general trend at the coupled cluster singles and doubles with perturbative triples level of theory is to increasingly favor planar structures as the basis set is improved. The effects of basis set and the effects of core-valence correlation are discussed.
Time-dependent approach to electronically excited states of molecules with the multiconfiguration time-dependent Hartree-Fock method
Authors: Nest M. , Padmanaban R. , Saalfrank P.
Published: June 2007

In this paper the authors show how the multiconfiguration time-dependent Hartree-Fock (MCTDHF) method can be used for the calculation of electronic properties of molecules associated with the population of excited states. In contrast to other methods for correlated electron dynamics, such as configuration interaction, MCTDHF does not rely on a solution of the electronic Schrödinger equation prior to the propagation. The authors apply this approach to the calculation of vertical excitation energies, transition dipole moments, and oscillator strengths for two test molecules, lithium hydride and methane.
Cathodoluminescence characterization of organic semiconductor materials for light emitting device applications
Authors: Wellmann Peter J. , Karl Ulrich , Kleber Sebastian , Schmitt Holger
Published: June 2007

We report the development of a cathodoluminescence-based characterization technique for the investigation of organic semiconductor materials for organic light emitting device (OLED) applications. While photoluminescence is known to predominantly address singlet exciton excitation and recombination processes, cathodoluminescence is able to simultaneously probe singlet and triplet exciton dynamics which is of importance for electroluminescence. Especially, in the case of the so-called triplet harvester materials, the generation of triplet excitons during cathodoluminescence opens the way for materials characterization without device fabrication. The paper (i) shows how cathodoluminescence can be applied for the characterization of organic semiconductor materials, (ii) points out the general measurement factors, (iii) discusses the special features of cathodoluminescence, electroluminescence as well as photoluminescence spectra, and (iv) outlines the potential of cathodoluminescence by presenting a brief study of a triplet harvester material systems. Main emphasis is put on the presentation of the characterization tool to partly replace the necessity of OLED fabrication. For that reason widely used conjugated polymers and small molecule semiconductor systems have been selected.
Fe
∕
Fe
oxide nanocomposite particles with large specific absorption rate for hyperthermia
Authors: Zeng Q. , Baker I. , Loudis J. A. , Liao Y. , Hoopes P. J. , Weaver J. B.
Published: June 2007

Using a water-in-oil microemulsion with cetyl trimethyl ammonium bromide as the surfactant, iron was reduced to form a metallic core on which a passivating oxide shell was grown. Transmission electron microscopy, vibrating sample magnetometry, and heating measurements were used to characterize these monodispersed magnetic Fe∕Fe3O4 composite nanoparticles with respect to the possible application for magnetic hyperthermia treatments of cancer. The aim is to utilize the fact that an iron core (high saturation magnetization) will give a greater heating effect than iron oxide, while the iron oxide coating will allow the nanoparticles to be observed using magnetic resonance imaging so that therapy can be effectively monitored and targeted. The largest specific absorption rate obtained was 345W∕g under an alternating magnetic field of 150Oe at 250kHz.
The Triploid Endosperm Genome ofArabidopsisAdopts a Peculiar, Parental-Dosage-Dependent Chromatin Organization
Authors: Baroux Célia , Pecinka Ales , Fuchs Jörg , Schubert Ingo , Grossniklaus Ueli
Published: June 2007

The endosperm is a seed tissue unique to flowering plants. Due to its central role in nourishing and protecting the embryo, endosperm development is subject to parental conflicts and adaptive processes, which led to the evolution of parent-of-origin–dependent gene regulation. The role of higher-order chromatin organization in regulating the endosperm genome was long ignored due to technical hindrance. We developed a combination of approaches to analyze nuclear structure and chromatin organization in Arabidopsis thaliana endosperm. Endosperm nuclei showed a less condensed chromatin than other types of nuclei and a peculiar heterochromatin organization, with smaller chromocenters and additional heterochromatic foci interspersed in euchromatin. This is accompanied by a redistribution of the heterochromatin mark H3K9me1 from chromocenters toward euchromatin and interspersed heterochromatin. Thus, endosperm nuclei have a specific nuclear architecture and organization, which we interpret as a relaxed chromocenter-loop model. The analysis of endosperm with altered parental genome dosage indicated that the additional heterochromatin may be predominantly of maternal origin, suggesting differential regulation of maternal and paternal genomes, possibly linked to genome dosage regulation.
A Heteromeric Plastidic Pyruvate Kinase Complex Involved in Seed Oil Biosynthesis inArabidopsis
Authors: Andre Carl , Froehlich John E. , Moll Matthew R. , Benning Christoph
Published: June 2007

Glycolysis is a ubiquitous pathway thought to be essential for the production of oil in developing seeds of Arabidopsis thaliana and oil crops. Compartmentation of primary metabolism in developing embryos poses a significant challenge for testing this hypothesis and for the engineering of seed biomass production. It also raises the question whether there is a preferred route of carbon from imported photosynthate to seed oil in the embryo. Plastidic pyruvate kinase catalyzes a highly regulated, ATP-producing reaction of glycolysis. The Arabidopsis genome encodes 14 putative isoforms of pyruvate kinases. Three genes encode subunits α, β1, and β2 of plastidic pyruvate kinase. The plastid enzyme prevalent in developing seeds likely has a subunit composition of 4α4β1, is most active at pH 8.0, and is inhibited by Glu. Disruption of the gene encoding the β1 subunit causes a reduction in plastidic pyruvate kinase activity and 60% reduction in seed oil content. The seed oil phenotype is fully restored by expression of the β1 subunit–encoding cDNA and partially by the β2 subunit–encoding cDNA. Therefore, the identified pyruvate kinase catalyzes a crucial step in the conversion of photosynthate into oil, suggesting a preferred plastid route from its substrate phosphoenolpyruvate to fatty acids.
Structural Evidence for the Evolution of Xyloglucanase Activity from Xyloglucan Endo-Transglycosylases: Biological Implications for Cell Wall Metabolism
Authors: Baumann Martin J. , Eklöf Jens M. , Michel Gurvan , Kallas Åsa M. , Teeri Tuula T. , Czjzek Mirjam , Brumer Harry
Published: June 2007

High-resolution, three-dimensional structures of the archetypal glycoside hydrolase family 16 (GH16) endo-xyloglucanases Tm-NXG1 and Tm-NXG2 from nasturtium (Tropaeolum majus) have been solved by x-ray crystallography. Key structural features that modulate the relative rates of substrate hydrolysis to transglycosylation in the GH16 xyloglucan-active enzymes were identified by structure–function studies of the recombinantly expressed enzymes in comparison with data for the strict xyloglucan endo-transglycosylase Ptt-XET16-34 from hybrid aspen (Populus tremula × Populus tremuloides). Production of the loop deletion variant Tm-NXG1-ΔYNIIG yielded an enzyme that was structurally similar to Ptt-XET16-34 and had a greatly increased transglycosylation:hydrolysis ratio. Comprehensive bioinformatic analyses of XTH gene products, together with detailed kinetic data, strongly suggest that xyloglucanase activity has evolved as a gain of function in an ancestral GH16 XET to meet specific biological requirements during seed germination, fruit ripening, and rapid wall expansion.
The g.243A>G mutation in intron 17 of MUC4 is significantly associated with susceptibility/resistance to ETEC F4ab/ac infection in pigs
Authors: Peng Q.‐L. , Ren J. , Yan X.‐M. , Huang X. , Tang H. , Wang Y.‐Z , Zhang B. , Huang L.‐S.
Published: June 2007

Using a porcine radiation hybrid panel, we assigned the mucin 4 (MUC4) gene to SSC13q41, which harbours the enterotoxigenic Escherichia coli (ETEC) F4ab/ac receptor locus. In addition, we identified two SNPs in intron 17 of MUC4 (DQ124298:g.243A>G and DQ124298:g.334A>G) in the parental population of a White Duroc × Erhualian cross. Association analysis showed that the MUC4 g.243A>G mutation was strongly associated with ETEC F4ab/ac, and especially with F4ac adhesion phenotypes in the White Duroc × Erhualian resource population, indicating that this polymorphism was in a significant linkage disequlibrium with the ETEC F4ab/ac receptor locus. Because of different linkage disequlibrium values between the ETEC F4ab and F4ac adhesion phenotypes and the MUC4 g.243A>G mutation, we argue that the inheritance of F4ab and F4ac receptors might be under the control of two closely linked loci.
Periodontal aspects of restorative dentistry
Authors: RAMFJORD SIGURD P.
Published: June 2007

Current trends in periodontal aspects of restorative dentistry are: (1) Supragingival placement of margins of restorations. (2) Avoidance of overcontoured restoration, and minimal concern with lack of contour. (3) Search for occlusal stability or self‐limited movement patterns of teeth through precise occlusal adjustment and accurate reconstruction of occlusal anatomy in single restorations. (4) Restricted indications for splinting of mobile teeth. (5) Hemisection with fixed bridges in cases of extensive bifurcation involvement. (6) Restricted indications for replacement of lost molars.

The purpose of restorative dentistry is to restore and maintain health and functional comfort of the natural dentition combined with satisfactory aesthetic appearance. Thus, all dental restorations should comply with established requirements for periodontal physiology and health, both with regard to surface and functional characteristics.
Relation between facial morphology and activity of the masticatory muscles
Authors: INGERVALL BENGT , THILANDER BIRGIT
Published: June 2007

The relation between muscle activity and facial morphology was studied in twenty‐five boys and twenty‐seven girls, aged 9–11 years. The activity in the anterior and posterior parts of the temporal muscle, the masseter muscle and the upper lip was recorded bilaterally with the mandible in postural position and during chewing, swallowing and maximal bite. The electromyograms were analysed in respect of maximal mean voltage amplitude and the duration of muscle activity. Facial morphology was studied with the aid of profile roentgenograms and model analysis. The activity in postural position was found to be greater in the posterior than in the anterior part of the temporal muscle. The average mean voltage amplitude in the temporal and masseter muscles was greatest during maximal bite, smaller during chewing and smallest during swallowing. In the orbicularis oris muscle the activity was greater during the opening phase of the chewing cycle than during the closing phase.

In postural position the activity in the anterior and posterior parts of the temporal muscle were positively correlated. The amplitudes in the anterior and posterior parts of the temporal muscle and in the masseter muscle were positively correlated during chewing, swallowing and maximal bite. The amplitudes in these muscles during chewing were positively correlated with those in the same muscles during maximal bite. During swallowing the amplitude in the upper lip was negatively correlated with that in the anterior part of the temporal muscle.

The clearest correlations between muscle activity and facial morphology were found during chewing and maximal bite. During these functions the amplitudes in the temporal and masseter muscles were large in cases with a tendency to parallelism between the jaws bases and between the mandibular occlusal line and the mandibular line. These cases with considerable muscle activity are characterized by rectangular shape of the face in profile and small lower face height.
A new method to determine the dimensional behaviour of dental amalgam
Authors: VRIJHOEF M. M. A. , SPANAUF A. J. , DRIESSENS F. C. M.
Published: June 2007

Literature data was analysed to find the factors which might influence the results of the determination of the dimensional change of dental amalgams during setting, by methods analogous to the test described in ADA Specification no. 1. Included in the paper is a discussion of the different aspects of adaptation of an amalgam restoration to the wall of a cavity. The conclusion was that the ADA dimensional change test is unsatisfactory because its outcome is highly dependent on experimental variables. The experimental problems involved in this test appeared to be unsolvable. A new method to obtain the dimensional change during setting in a clinically relevant way was proposed. This method consists in the determination of the dimensions of preferably cylindrical specimens after setting of the amalgam in a mould.

The results are described of the direct determination of the dimensional change by measurement of the diameter of set cylindrical specimens prepared by clinically simulated packing techniques. The dimensional change also was computed from independent measurements of the adaptation. The correlation between the two series of results was determined and compared with the theoretical prediction.

A good correlation between both sets of data was established.
Stresses and deflections in the floor of model cavity preparations
Authors: FARAH JEAN W. , HOOD JAMES A. A. , CRAIG ROBERT G.
Published: June 2007

In this study the finite element method was used in conjunction with an axisymmetric model of an idealized first molar to determine the stresses, as well as deflections in the floor of a cylindrical cavity preparation as caused by condensers of various sizes.

It was found that for the 0·25 mm thickness of dentine, the 2 mm condenser and a 2 kg load, a tensile stress of approximately 70 MN/m2 was obtained near the centre of the preparation. Under the same load and a 4 mm condenser a tensile stress of only 42 MN/m2 was obtained. Bowen & Rodriguez (1962) and Lehman (1967) reported that the tensile strength of dentine was in the order of 51.7 MN/m2 and 41.5 MN/m2 respectively. Thus it was demonstrated that for certain combinations of load, condenser size, and cavity dimensions, the tensile strength of the dentine in the cavity floor could be exceeded and failure of the cavity floor could ensue.
The effect of dentifrices on restorative materials
Authors: HEATH J. R. , WILSON H. J.
Published: June 2007

summary

The possible interactions between dentifrices and frequently‐used dental materials is discussed. A review is included of the usual constituents of commercial tooth cleaning preparations. Consideration is given to the relevance of certain experimental procedures used for dentifrice abrasion studies.
Factors influencing the determination of the occlusal vertical dimension by means of a screw jack
Authors: TRYDE GERD , McMILLAN D. R. , STOLTZE K. , MORIMOTO T. , SPANNER O. , BRILL N.
Published: June 2007

The screw jack method has recently been introduced as a new approach to assessing the occlusal height in edentulous patients. Its use is psycho‐physical in nature, and is supposed to rely on neurophysiological mechanisms. Its accuracy has been tested, and it was found to be sensitive to two factors; (i) interactions between dentist and patient, and (ii) to time. More clinical and neurophysiological research is required to refine the method, before it can be expected to replace generally accepted methods.
Age changes in the two‐point discrimination threshold in human oral mucosa
Authors: BRILL NIELS , TRYDE GERD , EDWARDS CAROLINE , THOMAS HELEN
Published: June 2007

Fifty young and fifty elderly subjects were tested by a two‐point discrimination method applying an aesthesiometer to the mucous membrane of lips, cheeks and tongue. Two changes characteristic of ageing were disclosed: (1) higher threshold values were found in the older age group concomitant with (2) a greater range of variation in these values. The importance of the perception of tactile stimuli from the structures tested is discussed in relation to adaptation to full dentures. It is suggested that signals arising from lips, cheeks and tongue assist the process of adaptation, whereas signals from the denture foundation can, on occasion, prevent adaptation.
Adjustment visits following provision of complete dentures
Authors: MÄKILÄ EINO
Published: June 2007

The adjustment visits of 259 patients, fitted with complete dentures for one or both jaws, at a denture clinic for the poorer social classes were studied. Only 44 % made one or several adjustment visits. The mean number of their visits was 1.28 and that of all the patients 0.56. The older age group contained a larger number of returning patients than the younger (P < 0.05), and so did the group that had not been given written instructions (P < 0.05). Healthy subjects visited the clinic earlier and also more often than the subjects in poor health (P < 0.05). Sex, previous denture experience and the palatal compression used in taking impressions did not affect the return visits. The most frequent causes of the visits were pain produced by the dentures, and retention difficulties.