bluuebunny/crossref_metadata_2025 huggingface dataset:
Die Onsagerschen Reziprozitätsbeziehungen in der Thermodynamik der Boltzmann‐Volterra‐Materialien
Authors: Mazilu P.
Published: June 2007

Die bekannte Vermutung von Onsager, daß die thermomechanischen Symmetriebeziehungen eine Folge der Zeit‐Mikroreversibilität sind, wird für viskoelastische Boltzmann‐Volterra‐Materialien, die konstitutive Inertialsysteme bilden, bewiesen.
Tensor Functions Representations as Applied to Deriving Constitutive Relations for Skewed Anisotropy
Authors: Basista M.
Published: June 2007

An irreducible, non‐polynomial representation is established for an anisotropic constitutive equation being an explicit relation between two symmetric, second‐order tensors. The considered material anisotropy is characteristic of two non‐orthogonal and mechanically non‐equivalent privileged directions in plane. Particular cases of orthotropy and of cubic symmetry are analyzed in detail. An illustrative example referring to infinitesimal elasticity is presented in order to compare the developed representation with the classical Hooke law.
Bemerkungen zur numerischen Behandlung einer Klasse von schwach singulären Integralgleichungen 1. Art unter Verwendung von Kollokations‐ und Galerkin‐Methoden
Authors: El‐Seoud M. S. Abou
Published: June 2007

Es werden die beiden folgenden Algorithmen zur numerischen Lösung einer Klasse von schwach singulären Integralgleichungen erster Art mit logarithmischem Kern sowohl bezüglich Konvergenzordnung also auch Rechenaufwand verglichen:

das Galerkinverfahren unter Verwendung finiter Elemente mit stückweise konstanten, linearen und quadratischen Ansatzfunktionen,

die Kollokationsmethode mit stückweise konstanten Ansatzfunktionen.

Beide Verfahren werden wir bei mehreren Stützstellenzahlen vergleichen. Solche Klassen von Integralgleichungen resultieren aus dem Dirichletproblem für stark elliptische Differentialgleichungen unter Verwendung der Fundamentallösung. Diese Klassen von Integralgleichungen sind mittels des Galerkinverfahrens in der letzten Zeit untersucht worden — siehe z. B. [7] und [8]. Die Kollokationsmethode zeichnet sich durch ihren einfachen Formalismus sowie durch ihren niedrigen Rechenaufwand aus und wird in der Praxis insbesondere von Ingenieuren viel verwendet. Eine Fehlerabschätzung für die Kollokationsmethode in der Maximum‐Norm wurde u. W. erstmals in [1] hergeleitet. Für Galerkin‐ Verfahren, angewandt auf Randintegralgleichungen für gemischte Randwertprobleme, wurden kürzlich sowohl theoretische als auch experimentielle asymptotische Fehlerabschätzungen in [9] und [10] hergeleitet. Für die Kollokationsmethode unter Benutzung von ungeraden Splinepolynomen erhält man im Falle einer ziemlich allgemeinen Klasse streng elliptischer Pseudodifferentialoperatoren in einer Unabhängigen ein erstes Konvergenzergebnis in verschiedenen Sobolevnormen für die entsprechenden Randintegralgleichungen [3].
Combined Residual Natural and Marangoni Convection in a Liquid Sphere Subjected to a Constant and Variable Micro‐Gravity Field
Authors: Bauer H. F.
Published: June 2007

The combined effect of thermal Marangoni convection induced by a gradient of temperature imposed upon the free surface of a liquid sphere and the residual natural convection steming from the still existing micro‐gravity field in an orbiting space laboratory has been investigated. The case of a constant and linearly dependent axial residual gravity field has been considered, for which the Stokes equation in the approximation of Boussinesq have been solved. By the introduction of a dynamic Bond‐number derived as the ratio of the Grashof number to the Reynoldsnumber based upon the Marangoni flow the predominance of Marangoni‐ (for B̃o → 0) or natural convection (for B̃o → ∞) could be determined. Streamlines, radial‐ and angular velocity distributions have been obtained analytically. The combined effect of Marangoni‐ and natural convection is of importance for space processings. In addition the isothermal lines are presented for various imposed temperature distributions at the free surface of the liquid sphere.
Quasigeneralisierte Variable
Authors: Baumgarte J. , Ostermeyer G. P.
Published: June 2007

The numerical solution of a system of differential and algebraic equations is difficult, because there can appear numerical instabilities with respect to the algebraic equations. This paper deals with a method, which allows to get numerical solutions of the system, satisfying the algebraic constraint equations exactly without reduction of the order of the differential equations. The method is demonstrated by examples from mechanics.
Über Variablentransformationen an klassischen Bewegungsgleichungen
Authors: Gerlich G.
Published: June 2007

Für die Transformation der abhängigen und unabhängigen Veränderlichen bei klassischen Bewegungsgleichungen werden allgemeine, explizite Formeln für die Geschwindigkeits‐ und Beschleunigungsfelder abgeleitet. Diese Formeln liefern ein Kriterium für kanonische Transformationen und werden u. a. mit dem Beispiel der Lorentztransformationen erläutert. Dies führt zu einer rein mathematischen Ableitung des sogenannten Additionstheorems relativistischer Geschwindigkeiten. Die transformierten elektromagnetischen Felder ergeben sich aus der Bewegungsgleichung des Punktelektrons, ohne die Form der Maxwellschen Gleichungen zu verwenden.
A Spline Finite Element Method for the Solution of the Clamped Shallow Cylindrical Shell Problem
Authors: Bhattacharyya P. K. , Suresh K.
Published: June 2007

The paper deals with a spline finite element method for the solution of the problem of the clamped shallow noncircular cylindrical thin elastic shell. An error estimate for the approximate solution is given.
Two Waveguide Bifurcation Problems
Authors: Lüneburg E. , Hurd R. A.
Published: June 2007

We condsider the diffraction of the dominant wave mode in a parallel plate waveguide with hard and soft boundaries incident on a centred half plane on whose two faces hard and soft boundary conditions obtain. A closed form solution of the resulting coupled Wiener‐Hopf system is derived. The modal amplitudes in all three regions are calculated and the relative powers of the low order modes versus the plate spacing are displayed graphically.
Über einen numerischen Zugang zur Lösungs‐ und Eigenwerttheorie von elliptischen Systemen partieller Differentialgleichungen
Authors: Beckert H.
Published: June 2007

Die Approximation von Greenschen Tensoren zu selbstadjungierten Randwertproblemen stark elliptischer Systeme 2m‐ter Ordnung über G ⊂ Rn wird durch die Minimalwerte von Variationsproblemen von oben und mit Hilfe der Dualitätstheorie durch Maximalwerte von unten abgeschätzt. Im wichtigen Fall 2m ≦ n erhalten wir starke Konvergenzaussagen durch Regularisierung und Anwendung der Schauderschen Abschätzungen. Für die zugehörigen Eigenwertprobleme ergeben sich weiter neue Abschätzungen in der Approximationstheorie von Eigenwerten.
Weiteres über Pseudo‐Divisionsverfahren zur Berechung der Standardfunktionen und gewisser Nicht‐Standardfunktionen
Authors: Bittner L.
Published: June 2007

Es werden einige Gesichtspunkte, welche nach Meinung des Verfassers die theoretische Grundlage der sogenannten Pseudo‐Divisionsverfahren (CORDIC) bilden, dargelegt. Es wird eine aditive und multiplikative Darstellung von reellen Argumenten durch Basisargumente angegeben und gezeigt, wie die unausgesprochenen Ideen der Pseudodivisionsverfahren dazu aus genutzt werden können, um neue Algorithmen für gewisse Funktionen, welche eine Art Additions‐ oder Multiplikationstheorem erfüllen, und für ihre Inversen herzuleiten.
Fluidelastische Schwingungen
Authors: Mahrenholtz O.
Published: June 2007

Fluidelastische Schwingungen entstehen aus dem Zusammenwirken von Strömung und Strukturbewegung. Während man das Verhalten schwingender Strukturen gut berechnen kann, trifft dies für das interaktive (Um‐) Strömungsfeld nur bedingt zu. Daher arbeitet man mit Modellen, die an dominanten Phänomenen orientiert sind. Es wird über die wesentlichen Modelle, nämlich Flattern, Formanregung und Wirbelanregung, berichtet. Zur Wirbelanregung werden neuere Erkenntnisse mitgeteilt.
Filmsieden bei der Umströmung der endlichen ebenen Platte durch inkompressible Flüssigkeiten
Authors: Schütte V.
Published: June 2007

Im Rahmen der Grenzschichttheorie wird mit Hilfe der Methode der Integralsätze für den Impuls‐ und Wärmeaustausch die Umströmung der endlichen ebenen Platte, insbesondere die Strömung im Nachlauf der Platte berechnet. Zur Bestimmung der Dampffilmlänge wird eine Extrapolationsformel angegeben.
Hamilton‐Jacobi Theorem in Poincaré‐Chetaev Variables
Authors: Ghori Q. K.
Published: June 2007

A group‐theoretic treatment of the Hamilton‐Jacobi theorem is carried out in the spirit of extending the result to linear non‐holonomic dynamical systems. The theory is illustrated by an example.
Eindimensionale elektrothermische Prozesse und Randwertaufgaben für eine Differentialgleichung 2. Ordnung
Authors: Schleiff M.
Published: June 2007

Ein elektrothermischer Prozeß wird durch die gekoppelten Bilanzgleichungen für das elektrische und das thermische Feld beschrieben. Im stationären, eindimensionalen Fall lassen sich diese Gleichungen zu einer Randwertaufgabe für eine nichtlineare Differentialgleichung 2. Ordnung zusammenfassen. Als Parameter sind in dieser Gleichung die Stromstärke oder die Spannung enthalten, die in ihrer Abhängigkeit voneinander die Strom‐Spannungs‐Kennlinie bilden. Für diese Kennlinie wird eine Integralformel angegeben, durch deren Diskussion sich Aussagen über die Lösbarkeit der Randwertaufgabe herleiten lassen. Dann wird die inverse Aufgabe betrachtet, die Bestimmung der elektrischen Leitfähigkeit als Funktion der Temperatur aus der Strom‐Spannungs‐Kennlinie. Für diese Aufgabe wird durch eine Abelsche Integralgleichung eine geschlossene Lösung konstruiert.
Using Interval Methods for the Numerical Solution of ODE's
Authors: Nickel K. L. E.
Published: June 2007

This is a survey article. It deals with the advantages of using interval methods for the numerical solution of initial value problems for ordinary differential equations.
The Multi‐Grid Method in the Solution of Time‐Dependent Nonlinear Partial Differential Equations
Authors: De Vries H. B.
Published: June 2007

The numerical solution of nonlinear, time‐dependent partial differential equations is discussed. By applying the method of lines such a partial differential equation is converted into a system of ordinary differential equations to which an implicit linear multistep method is applied. Using Newton iteration the nonlinear implicit relations are replaced by a sequence of linear equations. These linear equations are solved by the iterative use of a multi‐level algorithm. Numerical examples are given and a comparison is made with other integration techniques.
Beitrag zur tensoriellen Verallgemeinerung einachsiger Stoffgesetze
Authors: Betten J.
Published: June 2007

Im Aufsatz wird ein Verfahren vorgeschlagen, das eine unmittelbare Übertragung beliebiger einachsiger Stoffgesetze auf eine tensorwertige Funktion gestattet. Benutzt wird eine Interpolationsmethode für Tensorfunktionen, die vom Verfasser bereits in einem früheren Aufsatz vorgestellt wurde. Als Beispiele werden das Norton‐Baileysche Kriechgesetz und die nichtlineare Dehnungs‐Spannungsbeziehung von Ramberg und Osgood tensoriell verallgemeinert.
Über Druckschwankungen in homogener isotroper Turbulenz
Authors: Szablewski W.
Published: June 2007

Auf der Basis des Ähnlichkeitsgesetzes des Spektrums der Turbulenzenergie im Trägheitsbereich k « k0 (k0 Wellenzahl der großen Wirbel) werden Ähnlichkeitsgesetze für die Spektren des mittleren Quadrats der Druckschwankungen und der Schwankungen des Druckgradienten im genannten Bereich hergeleitet. Für die Maxima und ihre Wellenzahlen erhalten wir Potenzgesetze in der Reynoldsschen Zahl Reλ. Der Ermittlung der Zweipunktkorrelation der Druckschwankungen im Trägheitsbereich r » r0 (r0 Breite der Korrelation) wird dann das Ähnlichkeitsgesetz des Spektrums der Druckschwankungen zugrundegelegt. Es resultiert eine Ähnlichkeitsstruktur. Empirisches Element der Theorie ist die universelle Konstante des ‐ 7/3‐Potenzgesetzes des Spektrums der Druckschwankungen.
Generalized Predictor‐Corrector Methods of High Order for the Time Integration of Parabolic Differential Equations
Authors: van Der Houwen P. J. , Sommeijer B. P. , De Vries H. B.
Published: June 2007

A general class of predictor‐corrector methods is presented and explicit expressions for the local truncation error and the stability polynomial are derived. Examples of methods of orders up to 6 are given which are suitable for the integration of semi‐discrete parabolic differential equations. By a large number of numerical experiments we show that the higher order methods are generally more efficient than the lower order methods. As a further illustration we compare the generalized predictor‐corrector methods with the familiar ADI Method confirming our general belief that for smooth parabolic problems high order time integrators are superior to lower order integrators.
On the Disturbance Attenuation andH∞‐Optimization in Structural Analysis
Authors: Zacharenakis E. C.
Published: June 2007

In this paper the disturbance attenuation andH∞‐optimization problems of civil engineering structures via state feedback are investigated. Here the civil engineering structures are considered to be assembled from finite elements obeying linear material laws, their displacements being small and the number of inputs (control forces) being equal to the number of outputs (displacements). The theory of disturbance attenuation andH∞‐optimization problems is introduced, for the first time, to control the civil engineering structures.
Derivation of the viscous Moore-Greitzer equation for aeroengine flow
Authors: Birnir Björn , Hou Songming , Wellander Niklas
Published: June 2007

The viscous Moore-Greitzer equation modeling the airflow through the compression system in turbomachines, such as a jet engine, is derived using a scaled Navier-Stokes equation. The method utilizes a separation of scale argument based on the different spatial scales in the engine and the different time scales in the flow. The pitch and size of the rotor-stator pair of blades provides a small parameter, which is the size of the local cell. The motion of the stator and rotor blades in the compressor produces a very turbulent flow on a fast time scale. The leading order equation, for the fast time and local scales, describes this turbulent flow. The next order equations produce an axisymmetric swirl and a flow pattern analogous to Rayleigh-Bénard convection rolls in Rayleigh-Bénard convection. On a much larger spatial scale and a slower time scale, there exist modulations of the flow including instabilities called surge and stall. A higher order equation, in the small parameter, describes these global flow modulations, when averaged over the small (local) spatial scales, the fast time scale, and the time scale of the vortex rotations. Thus a more general system of spatially global, slow time equations is obtained. This system can be solved numerically without any approximations. The viscous Moore-Greitzer equation is obtained when small inertial terms are dropped from these slow time, spatially global equations averaged once more in the axial direction. The new equations are simulated with two different simplifying assumptions and the results are compared with simulations of the viscous Moore-Greitzer equations.
Shifts of frequency and bandwidth of quartz crystal resonators coated with samples of finite lateral size
Authors: Herrscher M. , Ziegler C. , Johannsmann D.
Published: June 2007

Recently, the viscoelastic properties of polymeric materials were probed by pushing a hemispherical cap of the respective material against the front surface of a quartz crystal resonator and measuring the induced shift of frequency and bandwidth, Δf and ΔΓ, as a function of the contact area, Ac.1 The shift of the resonance parameters was found to be proportional to the contact area, with the constant of proportionality containing the sample’s shear modulus. Confining the contact area to a small spot in the center of the plate is central to this approach, because the resonator would otherwise be overdamped. However, more detailed experiments have shown that there are small deviations from the proportionality of the frequency shift to the contact area. In particular, the ratio of ΔΓ and Δf (the “D-f ratio”), which should reflect intrinsic material properties, was found to slightly depend on contact area. Employing a finite element method simulation, two hypotheses were tested for the nontrivial area dependence of Δf and ΔΓ, which are, first, scattering of the acoustic wave from the acoustically heterogeneous surface and, second, a change of the lateral amplitude distribution, (“energy trapping”) induced by loading the crystal in the center only. It can be concluded that scattering affects the D-f ratio only at very small contact radii (<10μm), whereas in the range of millimeter-sized contacts, the change of energy trapping dominates. Employing a perturbation analysis, a relation of the form Δf≈αAc(1+βAc) is found, where α contains the viscoelastic parameters and the term in brackets is the nontrivial correction. Such a linear dependence agrees well with the results from simulation and experiment. An improved estimate of the material’s shear modulus is obtained by analyzing the ratios Δf∕Ac and ΔΓ∕Ac as a function of contact area Ac, and extrapolating these values to the limit Ac→0.
Microphase separation in polyelectrolytic diblock copolymer melt: Weak segregation limit
Authors: Kumar Rajeev , Muthukumar M.
Published: June 2007

The authors present a generalized theory of microphase separation for charged-neutral diblock copolymer melt. The stability limit of the disordered phase for salt-free melt has been calculated using random phase approximation (RPA) and self-consistent-field theory (SCFT). Explicit analytical free energy expressions for different classical ordered microstructures (lamellar, cylinder, and sphere) are presented. The authors demonstrate that the chemical mismatch required for the onset of microphase separation (χ*N) in charged-neutral diblock melt is higher and the period of ordered microstructures is lower than those for the corresponding neutral-neutral diblock system. Theoretical predictions on the period of ordered structures in terms of Coulomb electrostatic interaction strength, chain length, block length, and chemical mismatch between blocks are presented. SCFT has been used to go beyond the stability limit, where electrostatic potential and charge distribution are calculated self-consistently. Stability limits calculated using RPA are in perfect agreement with the corresponding SCFT calculations. Limiting laws for the stability limit and the period of ordered structures are presented and comparisons are made with an earlier theory. Also, transition boundaries between different morphologies have been investigated.
Er
3
+
diffusion in congruent LiNbO3 crystal doped with 4.5 mol % MgO
Authors: Zhang De-Long , Hua Ping-Rang , Pun E. Y. B.
Published: June 2007

Standard thermal diffusion of Er3+ into X-cut congruent LiNbO3 crystal with the MgO doping level close to the antiphotorefractive threshold concentration, 4.5 mol%, was attempted at the temperature close to Curie point of the crystal. Single-crystal x-ray diffraction, photoluminescence spectroscopy and secondary ion mass spectrometry (SIMS) were used to study the crystalline phase with respect to Er3+ ions and the depth profile of the diffused Er3+ ions. The results show that the thickness of the Er metal film coating should not be thicker than 4.6 nm. In this case, the diffusion is complete, the diffused surface is clean, and the Er3+ ions in the diffused layer still retain the LiNbO3 phase. On the other hand, the diffusion will be incomplete if the initial thickness of the Er metal film is thicker than 4.6 nm. The residual Er3+ ions form ErNbO4 grains on the surface of the crystal. SIMS analysis shows that the diffused Er3+ ions follow a monoexponential decay profile. The experimental results also show that the diffusivity of Er3+ in the X-cut congruent Mg(4.5 mol %):LiNbO3 is similar to 4.69×10−3 μm2/h at 1130 °C. Further vapor transport equilibration treatment following the standard diffusion procedure results in transformation of the diffused Er3+ ions from LiNbO3 into the ErNbO4 phase and, hence, substantial spectral change of the 1.5 μm emission.
Bifurcation picture and stability of gap and out-gap discrete solitons
Authors: Kroon L. , Bogdan M. M. , Kovalev A. S. , Malyuta E. Yu.
Published: June 2007

The dynamics of a quaternary fragment of a discrete system of coupled nonlinear oscillators with modulated frequency parameters is investigated, and the stability of its gap and out-gap soliton-like excitations is studied.
Electrical response of an electrolytic cell submitted to a small direct current electric field when the electrodes are ohmic
Authors: Barbero Giovanni , da Silva Jonatan João , Figueiredo Neto Antonio Martins
Published: June 2007

We theoretically investigate the influence of the ohmic character of the electrodes on the direct current (dc) response and on the ionic relaxation time of an electrolytic cell, in the shape of a slab. The analysis is performed by assuming that the fundamental equations of the problem can be linearized. This implies that, for monovalent ions, the applied difference of potential is smaller than 25 mV. We show that the finite ohmic conductivity of the electrodes is responsible for a reduction of the relaxation time. An explicit expression for the relaxation time, valid when the Debye length is very small with respect to the thickness of the sample is deduced. The analysis of the dc current allows us to determine the contribution of the electrodes to the effective electrical resistance. We show also that the equivalent circuit relevant to the present problem cannot be used to evaluate the relaxation time of the cell.
Properties of GaP(001) surfaces treated in aqueous HF solutions
Authors: Morota Hiroaki , Adachi Sadao
Published: June 2007

Chemically cleaned GaP(001) surfaces in aqueous HF solutions have been studied using spectroscopic ellipsometry (SE), ex situ atomic force microscopy (AFM), x-ray photoelectron spectroscopy (XPS), wettability, and photoluminescence (PL) measurements. The SE data clearly indicate that the solutions cause removal of the native oxide film immediately upon immersing the sample (≤1 min). The SE data, however, suggest that the native oxide film cannot be completely etch-removed. This is due to the fact that as soon as the etched sample is exposed to air, the oxide starts to regrow. The SE estimated roughness is ∼1 nm, while the AFM roughness value is ∼0.3 nm. The XPS spectra confirm the removal of the native oxide and also the presence of regrown oxide on the HF-etched GaP surface. The wettability measurements indicate that the HF-cleaned surface is hydrophobic, which is in direct contrast to those obtained from alkaline-cleaned surfaces (hydrophilic). A slight increase in the PL intensity is also observed after etching in aqueous HF solutions.
Impact dynamics of vibratory microprobe for microcoordinate measurement
Authors: Shih Po-Jen , Shih Wen-Pin
Published: June 2007

This article presents an impact dynamics analysis of the vibratory probe in a microcoordinate measuring machine. The chaotic behavior of the vibratory probe was identified when the driving frequency was changed. A multimode analysis was carried out to investigate the microprobe in both noncontact and contact states. An orthogonal mode transformation was used to maintain continuities when impact occurred. The analytical results indicated that mode coupling and mode coexistence suppressed subbifurcation and pulled down the impact period under particular driving frequencies. To achieve accurate identification of the microprobe in contact with microstructures, the frequency spectra of vibration signals at different contact states were compared. It was shown that the optimum driving frequency should be in the pull-down region. In this region, the dominant frequencies before and after the contact can be clearly separated, resulting in negligible background vibrations.
Large-scale aligned silicon carbonitride nanotube arrays: Synthesis, characterization, and field emission property
Authors: Liao L. , Xu Z. , Liu K. H. , Wang W. L. , Liu S. , Bai X. D. , Wang E. G. , Li J. C. , Liu C.
Published: June 2007

Large-scale aligned silicon carbonitride (SiCN) nanotube arrays have been synthesized by microwave-plasma-assisted chemical vapor deposition using SiH4, CH4, and N2 as precursors. The three elements of Si, C, and N are chemically bonded with each other and the nanotube composition can be adjusted by varying the SiH4 concentration, as revealed by electron energy loss spectroscopy and x-ray photoelectron spectroscopy. The evolution of microstructure of the SiCN nanotubes with different Si concentrations was characterized by high-resolution transmission electron microscopy and Raman spectroscopy. The dependence of field emission characteristics of the SiCN nanotubes on the composition has been investigated. With the increasing Si concentration, the SiCN nanotube exhibits more favorable oxidation resistance, which suggests that SiCN nanotube is a promising candidate as stable field emitter.
Synthesis of germanium nanocrystals in hafnium aluminum oxide matrix
Authors: Zheng F. , Chew H. G. , Choi W. K. , Zhang J. X. , Seng H. L.
Published: June 2007

An examination on the effect of annealing temperature and duration, and the germanium (Ge) concentration on the growth of Ge nanocrystals in hafnium aluminum oxide (HfAlO) matrix, was carried out using a combination of Raman spectroscopy, transmission electron microscopy, and secondary ions mass spectrometry techniques. We found Ge nanocrystals in the HfAlO matrix with a Ge content of 10.5 at. % when annealed at 800 °C. At a relatively higher content of Ge at 23.3 at. % in HfAlO film, a significant outdiffusion of Ge at the film surface or diffusion into the Si substrate occurred, and this imposes a narrow annealing condition for the formation of nanocrystals. We attribute the different nanocrystal formation characteristics in the HfAlO and silicon oxide matrices to the difference crystallization temperatures of HfAlO and silicon oxide films.
Current-induced breakdown of carbon nanofibers
Authors: Suzuki Makoto , Ominami Yusuke , Ngo Quoc , Yang Cary Y. , Cassell Alan M. , Li Jun
Published: June 2007

We present a study of high-field transport in carbon nanofibers (CNFs) and breakdown phenomena due to current stress. In situ measurements with scanning transmission electron microscopy reveal that the failure mode of CNFs is strongly related to the morphology of graphite layers comprising CNFs. Comparison with carbon nanotube (CNT) breakdown is made, demonstrating that the current capacity of CNFs is described by a similar model as that of CNTs with a modification of the current capacity of each graphitic layer. The maximum current density is correlated with resistivity, leading to the conclusion that lower resistivity results in higher current capacity in CNFs.
Stabilization of facial isomer of tris(8-hydroxyquinolinate)aluminum through confinement in silica-surfactant mesostructures
Authors: Li Le-Le , Fang Chen-Jie , Yuan Quan , Yan Chun-Hua
Published: June 2007

The self-assembled nanocomposites of tris(8-hydroxyquinolinate)aluminum (Alq3) confined in the silica-surfactant mesostructures are investigated. In the photoluminescence (PL) spectra, the Alq3 molecules confined in the mesostructures exhibit a significant blueshift by 50nm compared with that of the pristine Alq3. The PL efficiency is enhanced for the nanocomposites prepared at a higher temperature. The spectral analyses reveal that fac-Alq3 molecule, which is hard to prepare due to its relatively thermodynamically unstability, is obtained with this efficient and simple method. PL decay analysis implies experimentally the lifetimes corresponding to facial and meridional isomers.
Photonic crystal Mach-Zehnder interferometer based on self-collimation
Authors: Zhao Deyin , Zhang Jie , Yao Peijun , Jiang Xunya , Chen Xiyao
Published: June 2007

The authors design a photonic crystal Mach-Zehnder interferometer by utilizing the self-collimated beams and the bending and splitting mechanisms of line defects. Using this interferometer, they investigate the phase shift of the reflected and transmitted self-collimated beams over the line defects. In addition, on the basis of the intensity-asymmetric unidirectional-output design, they demonstrate that such interferometers can function as an intensity detector or an ultrafast optical switch when the material of photonic crystal is nonlinear.
Creating shifted resonances at favored optical frequencies
Authors: Liao Chungpin , Chang Hsien-Ming
Published: June 2007

In general, resonance absorption spectra are fixed properties of natural or man-made bulk materials. However, in optical and photonic applications, it will be celebrated if such spectral behaviors can be tailored at will. In particular, e.g., resonance peaks can be created at frequency locations desired. The authors demonstrated that, via the guidance of Clausius-Mossotti equation [K. D. Bonin and V. V. Kresin, Electric-Dipole Polarizabilities of Atoms, Molecules and Clusters (World Scientific, New Jersey, 1997), p. 129] and the assistance of first-principles quantum mechanical simulations, the collective beating of multiple types of artificially implemented dipoles could render favorable resonance(s) originally in absence.
Compressive uniaxially strained silicon on insulator by prestrained wafer bonding and layer transfer
Authors: Himcinschi C. , Reiche M. , Scholz R. , Christiansen S. H. , Gösele U.
Published: June 2007

Wafer level compressive uniaxially strained silicon on insulator is obtained by direct wafer bonding of silicon wafers in cylindrically curved state, followed by thinning one of the wafers using the smart-cut process. The mapping of the wafer bow demonstrates the uniaxial character of the strain induced by the cylindrical bending. The interfacial properties are investigated by infrared transmission imaging, scanning acoustic microscopy, and transmission electron microscopy. UV-Raman spectroscopy is employed to determine the strain in the thin transferred layer as a function of radius of curvature of the initial bending.
Theoretical consideration on the formation of nanotube following the Kirkendall effect
Authors: Prasad S. , Paul A.
Published: June 2007

Theoretical understanding on the formation of nanotube following the Kirkendall effect is developed. The relations for growth rate of the product phase and consumption rate of core and shell are derived considering diffusion-controlled process. The controlling factors to produce good nanotube following the Kirkendall effect are identified.
Polarization-dependent beam switch based on an M-plane GaN∕AlN distributed Bragg reflector
Authors: Schaadt D. M. , Brandt O. , Ghosh Sandip , Flissikowski T. , Jahn U. , Grahn H. T.
Published: June 2007

The authors demonstrate a two-color distributed Bragg reflector (DBR) consisting of 20 periods of alternating [11¯00]-oriented (M-plane) AlN and GaN layers grown on LiAlO2 by molecular-beam epitaxy. Due to the birefringent nature of GaN and AlN, the wavelength region of the stop band depends on the polarization state of the incoming light beam (parallel or perpendicular) with respect to the c axis of the wurtzite crystal structure. In the wavelength range, where the transmittance for one polarization direction and the reflectance for the orthogonal polarization direction are both high, the DBR can be used as a beam switch or polarization filter.
Changes in facial skin temperature associated with unilateral chewing
Authors: BERRY D. C. , YEMM R.
Published: June 2007

The changes in facial skin temperature during prolonged unilateral chewing were investigated by thermography (AGA Thermovision System, Model 665). An increase in skin temperature over the masseter area was demonstrated, but this was not invariable, and not always over the ‘working’ side. The suggestion is made that prolonged bruxism could result in a continuously raised blood flow within the masseter muscle.
An apparatus for the synchronous registration of EMG activity in jaw muscles and of vibrations in the masticatory system
Authors: WIDMALM SVEN‐ERIK , HEDEGÅRD BJÖRN
Published: June 2007

The apparatus described is a combined instrument for simultaneous recording of vibrations and EMG activity. It appears to be a useful means of studying reflex mechanisms in the jaw muscles. It is of especial interest as a method of examining the possible effect of vibrations on different receptors, such as the muscle spindles (Matthews, Hannam & Yemm, 1969).

The test results presented have indicated a satisfactory method for recording of vibration frequencies, the paper speed required for distinct registration suitable for measuring purposes, and the necessity of pre‐test calibration. They have given proof of the simultaneous onset of vibration and contact pressure al tooth contact as well as the occurrence of increased pressure after tooth contact indicating continual muscle fibre contraction.
Masticatory function and oral rehabilitation
Authors: BERRY D. C. , POOLE D. F. G.
Published: June 2007

Examination of many different animal dentitions suggests that in those whose function is mastication rather than merely prehension, tooth wear is not only normal but essential to achieve full efficiency. A similar character is found in man among Eskimos and Aborigines where these people live on completely natural diets, and also in Anglo‐Saxon skulls. It is suggested that attrition should be a normal process in the human dentition, and compensatory mechanisms for the loss of tooth substance are discussed. The significance of the unworn cusp in relation to dental and other diseases of Western civilisation is considered, together with the suggestion that sufficient evidence now exists to justify simple cusp height reduction as a prophylactic measure.
Some physical properties of dental modelling waxes and of their main constituents
Authors: McCRORIE J. W.
Published: June 2007

summary

Details of an X‐ray diffraction study on six dental modelling waxes and on known constituents of modelling waxes are described. The results of thermal expansion, thermal analysis and flow characteristics tests on the materials are given. Application of the knowledge obtained from the investigation is suggested in the formulation of a modelling wax consisting of a binary mixture of paraffin wax and microcrystalline wax.
Induction of apical formation in immature teeth by different endodontic methods of treatment
Authors: VOJINOVIć OLIVERA
Published: June 2007

summary

An experimental study is described of the apex formation and structure in immature permanent teeth after vital amputation, vital extirpation and after the treatment of teeth with necrotic pulp. Experiments in young dogs suggest that after vital amputation of the coronal part of the pulp, root formation was continued through the process of changed odontogenesis. In cases where the pulp had been completely extirpated or after the treatment of pulpless teeth, the process of normal odontogenesis was interrupted and the apex was completely closed by non‐homogeneous vital calcified tissue. On the basis of studies of the structure of this calcified tissue, it was concluded that it was a product of the formative activity of cells originating from the successive differentiation of fibroblasts in the young granulation tissue. The experiments suggest that following vital amputation of the pulp in children, further root odontogenesis is possible. In the treatment of pulpless teeth, the basic target should be stimulation and preservation of the formative activity of the granulation tissue cells in the apical part of the root canal to allow the possibility of calcified callus forming in the wide apical opening.
Some biological considerations in crown and bridge prosthetics
Authors: DAHL BJØRN L.
Published: June 2007

A review is presented of the literature dealing with the biological compatibility of some materials commonly used in crown and bridge prosthetics. The survey covers materials used for temporary and permanent crowns and for temporary and permanent cementation. When available the results of in vitro toxicity tests and implantation studies have been discussed. The tolerance of the oral mucous membranes to some of the materials has also been considered. However, emphasis has been placed on reports dealing with a possible pulp reaction caused by the materials.
Biological tests of a temporary crown and bridge material
Authors: DAHL BJØRN L. , TRONSTAD LEIF , SPÅGBERG LARZ
Published: June 2007

The biological compatibility of an ethylene imine derivative (Scutan) and a self‐curing methyl methacrylate resin (Sevriton) was assessed in in vitro (cell culture) and in vivo (monkey teeth) tests. In vitro, both materials were toxic when freshly prepared, but Scutan less than Sevriton. Set specimens of both materials were non‐toxic in the experiments with 4 h cell‐material contact. In the 24 h experiments, however, Sevriton had a toxic effect. In vivo experiments confirmed that Sevriton may cause reactions in the pulp which makes it unsuitable for use in direct contact with vital dentine. The pulp reaction caused by Scutan, however, was of a mild nature. It was concluded, therefore, that Scutan may safely be used to make temporary crowns and bridges according to a direct technique.
The use of spectrograms for speech analysis in full denture wearers
Authors: PETROVIĆ ANA
Published: June 2007

Some aspects of the physiology of speech are discussed, particularly the correlation between the quality of speech and denture morphology.

It is suggested that an objective method for the evaluation of speech is the use of spectrographic analysis with computer evaluation. The application of this approach to artificial denture wearers is demonstrated.
Collapse of the occlusion—aetiology, symptomatology and treatment
Authors: STERN NOAH , BRAYER LAURENTIU
Published: June 2007

Aetiological factors which lead to occlusal collapse have been surveyed and the clinical symptomatology of this syndrome emphasized. The sequence of periodontal treatment as well as suggestions for re‐establishing and recording new jaw relations are discussed in detail.
Marginal adaptation of composite resins
Authors: AL‐HAMADANI K. K. , CRABB H. S. M.
Published: June 2007

The historical development and important properties of composite resins are briefly reviewed. Experimental work has been undertaken to examine the marginal adaptation of three commercially available composite resins in 100 Class II and Class V restorations; dye penetration tests were used and the measurement of the gap at the tooth/ restoration interface as recorded in photographs obtained by scanning electron microscopy of replicas. In Class V restorations showing marginal leakage by dye penetration the gap at the tooth/restoration interface was in all cases greater cervically than occlusally. The results underline the uncertainty of obtaining a good marginal seal with composite resins both peripherally and along internal line angles.
An alternative treatment in cases with advanced localized attrition
Authors: DAHL BJøRN L. , KROGSTAD OLAF , KARLSEN KJELL
Published: June 2007

A combined orthodontic/prosthetic treatment of patients with advanced localized attrition has been described. In one patient the effect of the orthodontic treatment upon the morphological face height has been studied using an X‐ray cephalographic technique and the results have been discussed.
Biological tests of a silicophosphate cement
Authors: DAHL BJøRN L. , TRONSTAD LEIF , SPÅARNBERG LARZ
Published: June 2007

The biological compatibility of a silicophosphale cement (Fluoro‐Thin®) and a zinc phosphate cement (de Trey's Improved®) has been assessed in in vitro (cell culture) and in vivo (monkey teeth) tests. In the in vitro tests both materials were toxic when freshly prepared, In experiments with prolonged cell‐material contact time, with set specimens of the materials, the zinc phosphate cement appeared to be non‐toxic, whereas the silicophosphate cement was clearly toxic. The in vivo experiments confirmed that a possible pulp reaction caused by zinc phosphate cement is of a mild nature. The silicophosphate cement, however, caused a moderate or severe reaction in the pulp after 8 days of observation, and there was chronic inflammation in most teeth after 36 or 72 days. It was concluded, therefore, that Fluoro‐Thin should not be used as a luting agent or for restorative purposes in direct contact with vital dentine.
Reflex control of the jaw muscles by stimuli from receptors in the periodontal membrane
Authors: KLOPROGGE M. J. G. M.
Published: June 2007

In the opinion of a number of investigators, the only function of the mechano‐receptors in the periodontal membrane is to inhibit closure of the jaws via a reflex pathway when a predetermined pressure on the teeth has been exceeded. In our opinion, the receptor system in the periodontal membrane may also play a role in a complex regulatory system which controls the movements of the lower jaw during chewing. In order to test this hypothesis a study was made of the changes occurring in the contraction pattern of three masticatory muscles of the cat, when the cuspids in the upper jaw were displaced in various directions.

In all the experimental animals used, electromyographic changes in the three muscles investigated, could be recorded as a result of displacement of the cuspids. The results obtained suggest, at least in the case of the temporal and pterygoid muscles, that there are specific reflexogenic zones in the periodontal membrane. These results support the previously suggested hypothesis that a number of the pressure‐sensitive receptors in the periodontal membrane play a role in a regulatory system which controls the movements of the lower jaw—as during chewing—by exerting a reflex influence on the degree of contraction of the masticatory muscles.

In the discussion this hypothesis is worked out in more detail and the extent to which the results fit the chewing pattern of the cat is examined. In the conclusion, the author asks whether the finding of a regulatory system in the cat may also be applied to man.
Masticatory function—a review of the literature
Authors: BATES J. F. , STAFFORD G. D. , HARRISON A.
Published: June 2007

Recently, the authors realized that an evaluation of the literature on mastication had never been undertaken, and it is hoped that this review presented in three parts, will be of value, not only to the dental clinician, but to other scientists working in associated fields.

The first paper discusses the form of the masticatory cycle in the natural and artificial dentitions, including the controversial question of whether tooth contact occurs during function.

The second paper reviews the literature concerning the speed of movement of the mandible, rate of chewing, and the forces developed in chewing.

The final paper describes masticatory efficiency and performance, the effect of food on masticatory function, and incorporates a summary of all these three papers.
Oral ability to recognize forms and oral muscular coordination ability in dentulous young and elderly adults*
Authors: LANDT HORST , FRANSSON BO
Published: June 2007

A study has been carried out to investigate possible differences between a group of dentulous young adults (average 22.5 years of age) and a group of dentulous elderly individuals (65.9 years), when attempting to recognize forms orally and to carry out tasks which demand a fine‐coordination of the oral muscular apparatus.

The results showed, that the older group had reduced ability for both forms of tests used in this study (RF‐test for estimating the oral ability to recognize forms, and MA‐test to estimate oral muscular ability).

The reduced capacity of the older individuals to learn the requirements of the tests as compared with the younger ones, was especially obvious. Furthermore, individual differences in this respect were more obvious for the older than for the younger examinees.

The suggestion is made that in further studies the number of trial‐rounds may be reduced from three to two. certainly for older individuals and for both the RF‐ and the MA‐test.

Because of the obvious correlation between the results of the RF‐ and the MA‐test among older individuals, it is concluded that both forms of tests may measure common or closely related factors, which are reflected by these tests.
Screening in a dental clinic for adult rheumatoid arthritis involving the temporomandibular joint using a statistical discriminant function
Authors: ANDERSON J. A. , BLAIR G. S.
Published: June 2007

The radiological features seen on the temporomandibular joint radiographs of ninety‐nine cases of adult rheumatoid arthritis were used to distinguish this group from a group of eighty‐three control subjects using the method of logistic discrimination. A readily calculable diagnostic score, whose value was verified by a second study involving thirty‐two patients, sixteen of whom suffered from adult rheumatoid arthritis, was estimated. This second study was further used to illustrate how this scoring system would be modified to take account of extra information. Although a long term evaluation of the method is envisaged its clinical application is indicated and its practical value demonstrated.
A method of determining the tensile bond strength of fissure sealant materials
Authors: LOW T. , DAVIES E. H. , VON FRAUNHOFER J. A.
Published: June 2007

A simple and reliable method for the determination of the tensile bond strength of sealant materials to enamel is described. Using this method, the tensile bond strength of Nuva Seal to enamel after 7 days in water at 37°C was found to be 36·6±9·0 kg/cm2 with a coefficient of variation of 24·5%. This method would be useful for screening of new and modified sealant materials and the evaluation of new application procedures to ensure an adequate tensile bond strength for clinical use. A tensile bond strength in the range 26–36 kg/cm2 could be used as the base line value for comparison of new materials and procedures involving fissure sealants.
Biological tests of an experimental glass ionomer (silicopolyacrylate) cement
Authors: DAHL BJøRN L. , TRONSTAD LEIF
Published: June 2007

The biological compatibility of an experimental glass ionomer (silicopolyacrylate) cement has been assessed inin vitro (cell culture) and in vivo (monkey teeth) tests. For comparison a conventional silicate cement (Super Syntrex®) was included in the in vivo experiments. In vitro, the glass ionomer cement was toxic when freshly prepared. The toxicity decreased, however, with increasing setting time. In experiments with prolonged cell‐material contact time with specimens which had set for 24 h, the material appeared to be non‐toxic. The in vivo experiments confirmed previous reports concerning unfavourable pulp reactions caused by silicate cement, while the glass ionomer cement caused mainly a mild pulp reaction after 8 days of observation. Unfortunately no longer‐term observations were obtained since the material had been washed out of the cavities within 36 days.