bluuebunny/crossref_metadata_2025 huggingface dataset:
Some nordhaus‐‐ gaddum‐type results
Authors: Goddard Wayne , Henning Michael A. , Swart Henda C.
Published: June 2007

A Nordhaus‐‐Gaddum‐type result is a (tgiht) lower or upper bound on the sum or product of a parameter of a graph and its complement. In this paper some variations are considered. First, the sums and products of ψ(G1) and ψ(G2) are examined where G1 ⊕ G2 = K(s, s), and ψ is the independence, domination, or independent domination number, inter alia. In particular, it is shown that the maximum value of the product of the domination numbers of G1 and G2 is [(s/2 + 2)2] for s ≥ 3. Thereafter it is shown that for H1 ⊕ H2 ⊕ H3 = Kp, the maximum product of the domination numbers of H2, H2, and H3 is p3/27 + Θ(p2).
RUSSELL'S ALTERNATIVE TO THE AXIOM OF CHOICE
Authors: Brunner Norbert , Howard Paul
Published: June 2007

We prove the independence of some weakenings of the axiom of choice related to the question if the unions of wellorderable families of wellordered sets are wellorderable.
Diagnosis and treatment of stable angina in older people
Authors: Beckett Nigel , Peters Ruth
Published: June 2007

Our series Prescribing in older people gives practical advice for successful management of the special problems experienced by this patient group. Here, the authors describe the difficul ties encountered when diag nosing stable angina in older patients and discuss avail able treatments. Copyright © 2007 Wiley Interface Ltd
Über Mehrschrittverfahren der nichtlinearen Optimierung
Authors: Richter Claus
Published: June 2007

Die Aufgabe der nichtlinearen Optimierung wird in bekannter Weise als Variationsungleichung formuliert. Dadurch lassen sich Iterationsverfahren mit quadratischen Teilproblemen als Newton‐Verfahren zur Lösung der Ungleichung interpretieren. Eine gegenüber Schwetlick leicht modifizierte Konsistenzforderung an die in der linearisierten Variationsungleichung auftretende Matrix ermöglicht es, die Verwendung von zweiten Ableitungen zu vermeiden und die quadratische Struktur der zu lösenden Teilprobleme zu erhalten. Die Variationsungleichung mit konsistenter Approximation der Matrix wird als speziell gestörte Variationsungleichung aufgefaßt. Unter Verwendung von Resultaten, die auf Robinson und Schwetlick zurückgehen, gelingt es, lokal überlineare Konvergenz nachzuweisen. Für spezielle vorgeschlagene Realisierungen werden konkrete Abschätzungen über das Konvergenzverhalten angegeben.
On the Elastodynamic Theory of Thick Circular Plates
Authors: Celep Zekâi
Published: June 2007

Considering elastodynamic deformation of circular plates, this paper presents a generalization of the method of initial functions in cylindrical coordinates. The governing equations of the theory are derived from the three dimensional elastodynamic equations. The method is applied to the free vibration of the clamped circular plate. Numerical results are obtained and displayed in figures. They are compared with the foregoing results. Besides, the variations of the characteristic quantities of the plate are given along the plate thickness.
Laminare, instationäre Strömung im Ringraum zwischen zwei Rohren, von denen das innere harmonisch schwingt
Authors: Farah M. N.
Published: June 2007

In dieser Arbeit wird untersucht, wie die laminare Strömung im Ringraum zwischen zwei Rohren von der harmonischen Schwingung des Innenzylinders beeinflußt wird. Im Rahmen einer Störungsrechnung zweiter Ordnung wird die Durchflußmenge und die Leistung des schwingenden Innenzylinders errechnet. Die Rechnung ergibt: a) Bei sehr langsamen Schwingungen (quasistatischer Fall) erhöht sich der Durchfluß gegenüber der konzentrischen Ruhelage. Durch wachsendes Radienverhältnis × = r1/r2* wird dieser Effekt verstärkt. Der Grenzwert ω → 0 wird mit der exakten Lösung von Cardwell verglichen. b) Für höhere Frequenzen mindert sich der Durchfluß, bis ein Minimalwert erreicht wird, der weit unter dem Durchfluß bei konzentrischer Ruhelage liegt. c) Für sehr hohe Frequenzen steigt der Durchfluß wieder allmählich an, bis er asymptotisch einen Wert erreicht, der noch unter der Ruhelage liegt. d) Die erforderliche Leistung/Länge L zur Aufrechterhaltung der vorgegebenen harmonischen Schwingung des Innenzylinders wächst mit steigender Frequenz.
Potentialdarstellung einer asymptotischen Lösung der Gleichung ΔΔu–x2Δu = f
Authors: Mazilu P.
Published: June 2007

Potentialtheoretische Methoden werden angewendet bei der Untersuchung der singulären Störungen der harmonischen und biharmonischen Differentialgleichung. Mit Hilfe dieser Methoden kann die Johnsche Grenzschichtabschätzung für homogene Gleichungen erhalten werden. Die harmonische Funktion, die man bei dieser Abschätzung findet, wird bestimmt durch eine Funktionalgleichung in Raum der harmonischen Funktionen. Außerdem wird auch die Ausdehnung dieses Ergebnisses auf inhomogene Gleichungen möglich.
Coupled Thermoelastic Problem in Three‐Dimensions
Authors: Tanigawa Y. , Takeuti Y.
Published: June 2007

A new technique is proposed to the coupled thermoelastic problems in three‐dimensions. In the basic relations we introduce an additive harmonic function and then it is possible to separate both thermal and elastic fundamental differential equations Taking advantage of this technique we will be able to obtain the exact solution for the whole time range in the three‐dimensional transient thermal stress problem of a circular cylinder. Several numerical results in temperature and stress distribution are given for the sake of comparison to the classical results.
Response of a Multidegree‐of‐Freedom System of Variable Coefficients to Random Excitation
Authors: Szopa J.
Published: June 2007

This paper presents a method of determining probabilistic characteristics concerning the response of a multidegree‐of‐freedom system with variable coefficients to random excitation. This method is based on the application of a stochastic Volterra integral equation of the second kind and not on the multidegree impulsive response (Green's function) difficult to calculate for this type of the systems. On the Basis of the suggested method there have been carried out numerical calculations concerning the variance of the response of the two‐degree‐of‐freedom system with variable mass.
Conservation Laws for a Dynamical System in Group Variables
Authors: Hussain M.
Published: June 2007

In this paper we consider a conservative dynamical system whose position is specified by group variables and the Lagrangian for which is a function of the time derivatives of the parameters of real displacement. After obtaining the Euler‐Lagrange equations for the system, a generalisation of the fundamental invariance identities has been done which is further used to establish Noether' theorem. At the end necessary and sufficient conditions are derived for parameter invariance. The theory is based upon the concept of a mechanical system but the results obtained can be applied to all problems in mathematical physics admitting a Lagrangian function.
Castigliano' Theorem and its Limits
Authors: Hartmann F.
Published: June 2007

This paper demonstrates that Castigliano' Theorem is not applicable to elastic plates and bodies if their behaviour is governed by the Cauchy‐Navier differential equation (classical mechanics).
Anwendung eines direkten Verfahrens zur numerischen Behandlung von selbstadjungierten, positiv definiten Eigenwertaufgaben bei linearen gewöhnlichen Differentialgleichungen mit stückweise stetigen Koeffizientenfunktionen
Authors: Dähnn J.
Published: June 2007

Für eine Klasse von Eigenwertaufgaben bei linearen gewöhnlichen Differentialgleichungen mit stückweise stetigen Koeffizientenfunktionen wird die Anwendbarkeit einer direkten numerischen Lösungsmethode nachgewiesen, bei der die Eigenwerte als Nullstellen einer transzendenten charakteristischen Gleichung erhalten werden. Zur Berechnung von werten der charakteristischen Funktion wird für Differentialgleichungen zweiter Ordnung ein numerisch stabiler Algorithmus angegeben. Praktische Rechnungen für die Hillsche Differentialgleichung zeigen, daß sich das Ritzsche Verfahren bei der Berechnung der kleinsten Eigenwerte und das direkte Verfahren bei der Berechnung der größeren Eigenwerte hinsichtlich ihrer guten numerischen Eigenschaften ergänzen.
The Boundary Integral Equation Method for Plates Resting on a Two‐Parameter Foundation
Authors: Balaš J. , Sládek V. , Sládek J.
Published: June 2007

In the paper the boundary integral equation method for solving the problem of a plate resting on a two‐parameter foundation is presented. Three boundary value problems are considered, and three cases are to be distinguished as regards a characteristic parameter of the foundation. The boundary integral equation solution for a clamped circular plate under a concentrated load is compared to the analytical one.
Zur analytischen Lösung geometrischer Optimierungsaufgaben mittels Dualität bei Steuerungsproblemen. Teil II
Authors: Andrejewa J. A. , Klötzler R.
Published: June 2007

Im Teil I der gleichlautenden Arbeit wurden Grundlagen zur Dualität bei Steuerungsproblemen bereitgestellt und auf zwei geometrische Optimierungsprobleme angewandt: Die Bestimmung ebener konvexer Bereiche größten bzw. kleinsten Umfangs bei vorgegebener Dicke Δ und vorgeschriebenem Durchmesser D. Im vorliegenden Teil II schließt sich unter gleichen Nebenbedingungen die Behandlung zweier weiterer Beispiele an: Das Problem des ebenen konvexen Bereichs größten Flächeninhalts und des konvexen Körpers größter Oberfläche.
Explicit Error Estimates for Difference Schemes Solving the Stationary Constant Coefficient Diffusion‐Convection‐Reaction Equation
Authors: Stoyan G.
Published: June 2007

Some difference schemes for the cited (stationary) equation are considered and their accuracy is estimated by known quantities only. The results are useful for any Peclét number and imply uniform convergence (with respect to a small diffusion coefficient) up to forth order in h in the linear case and of first order in the mildly nonlinear case.
Materialgleichungen zur Beschreibung des sekundären und tertiären Kriechverhaltens anisotroper Stoffe
Authors: Betten J.
Published: June 2007

In diesem Artikel werden Konstitutivgleichungen für das sekundäre und tertiäre Kriechstadium eines anisotropen Materials formuliert. Zur Untersuchung des sekundären Kriechverhaltens wird die Existenz eines Kriechpotentials angenommen. Unter Berücksichtigung der Darstellungstheorie für Tensorfunktionen liefert die Kriechpotentialhypothese nur eingeschränkte Formen der Konstitutivgleichungen auch bei Annahme eines allgemeinen Kriechpotentials für den anisotropen Fall. In der tertiären Phase wird der Kriechprozeß durch einen Schadenstensor charakterisiert. Es werden einige mögliche Darstellungen der Konstitutivgleichungen diskutiert unter Einbeziehung einer (Anfangs‐) Anisotropie des Materials (i.a. durch Walzen) und eines anisotropen Kriechschadens. Diese Gleichungen werden aufgrund von Theoremen für tensorwertige Tensorfunktionen formuliert.
Dynamic Investigation of Multi‐Mass Drive System by Means of Torsional Waves. Part I: Formulation of the Problem and Numerical Solution
Authors: Nadolski W. , Pielorz A. , Mioduchowski A.
Published: June 2007

In the paper the continuous model of a multi‐mass drive system is considered. The method of dynamical analysis is based on the theory of propagation of one‐dimensional torsional elastic waves. Discussion is presented for the system consisting of N shafts and N + 1 rigid bodies. Numerical results for a system consisting of 2 shafts and 3 rigid bodies are presented in graphical form.
Modified Propagation of Ultrasonic Surface Waves by Thin Elastic or Viscous Films
Authors: Schultrich B.
Published: June 2007

The mechanical properties of thin films often differ from those of bulk material and depend on technological parameters. But they can be determined in the coating‐substrate composite directly by means of ultrasonic surface waves. For thin layers in relation to wavelength, the displacement field within the layer is expanded in powers d/Λ. The corresponding equation system given for the general case is evaluated for elastic and viscous coatings in lowest order of d/Λ. An elastic covering layer causes a relative change in velocity proportional to ω η d where the factor is determined by the elastic and inertial differences between film and substrate. By a viscous coating the surface wave is attenuated proportional to ω3ηd. The elastic case confirms in the first order the results of a plate theory approximation given formerly by Achenbach and Keshava. However, their higher order terms prove to be incomplete from the viewpoint of the present systematic expansion.
Eigenwertschranken für Eigenwertaufgaben mit partiellen Differentialgleichungen
Authors: Goerisch F. , Haunhorst H.
Published: June 2007

Betrachtet werden Eigenwertaufgaben Mφ = ΛNφ, wobei M und N symmetrische lineare Operatoren in einem Prähilbertraum sind. Zur Berechnung von unteren Schranken für die Eigenwerte wird ein neues Verfahren vorgeschlagen. Es wird an Hand der Aufgabe

erläutert, die bei der Bestimmung von Beulwerten eingespannter rechteckiger Platten auftritt; für den kleinsten positiven Eigenwert werden genaue untere und obere Schranken angegeben. Das vorgeschlagene Verfahren ist eng mit einer von N. J. Lehmann entwickelten Methode verwandt, es kann aber sehr viel leichter auf Eigenwertaufgaben Mφ = ΛNφ angewandt werden, bei denen M und N partielle Differentialoperatoren sind.
Stability of Cylindrical Shells, by Various Nonlinear Shell Theories
Authors: Simitses G. J. , Shaw D. , Sheinman I.
Published: June 2007

The buckling of axially‐loaded, imperfect, circular, cylindrical, thin shells is studied. A solution methodology, based on two different shell theory approximations to the kinematic relations, is developed and described. The two approximations are those of Sanders and Donnell. Critical loads (limit point loads) are obtained for two shell geometries, one isotropic and one laminated. Several parametric studies are performed in order to establish the accuracy of the Donnell approximation. This is accomplished by comparison to the results obtained by the Sanders kinematic relations, which are considered to be very accurate for thin shells. The parametric studies include the effect of cylinder to radius ration on the critical loads, as well as the effect of the radius to thickness ratio. Moreover, the imperfection sensitivity of the two geometries is investigated by both shell theory approximations.
Inequalities for the Eigenvalues of a Non‐Negative Definite Matrix and a Generalization
Authors: Goller H. , Krafft O.
Published: June 2007

In the first part it is shown that some known inequalities for eigenvalues, e.g. for eigenvalues of sums or products of non‐negative definite matrices, easily follow from a variant of the Courant‐Fischer minimax theorem. This variant establishes a relation between the k‐th of the ordered eigenvalues and a matrix of rank k. Furthermore, the problem of determining extremal ellipsoids which are centered at a point d ≠ 0 and which are tangential at the unit sphere is discussed as a generalized eigenvalue problem.
Das Stabilitätsverhalten der verallgemeinerten Mathieuschen, Kohnschen und Weigandschen Differentialgleichung
Authors: Eicher N.
Published: June 2007

Für eine Klasse von zeitvarianten Schwingungssystemen wird das Stabilitätsverhalten untersucht. Aufgrund einer geeigneten Berechnungsmethode lassen sich allgemeingültige Bereichsgrenzenformeln für alle Parameterresonanzen herleiten. Eine anschließende Diskussion des Stabilitätsverhaltens der zu dieser Klasse gehörenden Schwingungsgleichungen ergibt wesentliche Unterschiede. Für harmonische Erregungen werden Stabilitätskarten angegeben und beurteilt. Es wird auf die bekannten Transformationen, welche die Differentialgleichungen innerhalb der Klasse ineinander überführen, eingegangen und deren Grenzen aufgezeigt.
Analystische Berechung der Drehschwingungen mehrstufiger Stirnradgetriebe
Authors: Schulz R.
Published: June 2007

Für ein N‐stufiges Stirnradgetriebe mit Übersetzungsverhältnissen der einzelnen Stufen, die wesentliche von 1 verschieden sind, werden explizite Näherungsformeln für die Stabilitätsgrenzen und die dynamischen Zusatzbelastungen, die durch die Zahnsteifeerregung hervorgerufen werden, abgeleitet. Es werden dabei die Störungstheorie endlichdimensionaler Operatoren und das Integralgleichungsverfahren verwendet.
Zur Anisotropie deformierbarer Körper bei großen Verformungen
Authors: Balke H.
Published: June 2007

Der Anisotropiebegriff für mechanische Eigenschaften deformierbarer Körper bei großen Verformungen wird diskutiert. Grundlage der Diskussion ist die genaue Abgrenzung von Objektivitäts‐ und Symmetrieforderungen an die konstitutiven Gleichungen. Als Beispiele werden Potentiale der Fließ‐ oder Kriechtheorie in raumfesten und mitgeführten Koordinaten, Kriechgleichungen und hypoelastisches Material betrachtet. Dabei wird auf existierende Inkonsequenzen in der Literatur eingegangen.
Stopping Check for Systems with Friction‐Affected Constraints
Authors: Klepp H. J.
Published: June 2007

A multi‐body system with several degrees of freedom and friction‐affected constraints (guidances and journal bearings) is considered. It is supposed that the original system and all systems, which must be considered as result of sticking coordinates, are kineto‐statically determinate structures. It is also assumed that the relative velocities in the constraints depend respectively on one of the generalized coordinates and its derivative. A criterion is presented, which establishes the state of the system, when relative movements in some constraints with friction stop simultaneously. As an example a system with four degrees of freedom and seven friction‐affected constraints is considered.
Direct numerical simulation of a plane turbulent wall-jet including scalar mixing
Authors: Ahlman Daniel , Brethouwer Geert , Johansson Arne V.
Published: June 2007

Direct numerical simulation is used to study a turbulent plane wall-jet including the mixing of a passive scalar. The Reynolds and Mach numbers at the inlet are Re=2000 and M=0.5, respectively, and a constant coflow of 10% of the inlet jet velocity is used. The passive scalar is added at the inlet enabling an investigation of the wall-jet mixing. The self-similarity of the inner and outer shear layers is studied by applying inner and outer scaling. The characteristics of the wall-jet are compared to what is reported for other canonical shear flows. In the inner part, the wall-jet is found to closely resemble a zero pressure gradient boundary layer, and the outer layer is found to resemble a free plane jet. The downstream growth rate of the scalar is approximately equal to that of the streamwise velocity in terms of the growth rate of the half-widths. The scalar fluxes in the streamwise and wall-normal direction are found to be of comparable magnitude. The scalar mixing situation is further studied by evaluating the scalar dissipation rate and the mechanical to mixing time scale ratio.
Penetration of plasma into the wafer-focus ring gap in capacitively coupled plasmas
Authors: Babaeva Natalia Y. , Kushner Mark J.
Published: June 2007

In plasma etching equipment for microelectronics fabrication, there is an engineered gap between the edge of the wafer and wafer terminating structures, such as focus rings. The intended purpose of these structures is to make the reactant fluxes uniform to the edge of the wafer and so prevent a larger than desired edge exclusion where useful products cannot be obtained. The wafer-focus ring gap (typically<1 mm) is a mechanical requirement to allow for the motion of the wafer onto and off of the substrate. Plasma generated species can penetrate into this gap and under the beveled edge of the wafer, depositing films and possibly creating particles which produce defects. In this paper, we report on a computational investigation of capacitively coupled plasma reactors with a wafer-focus ring gap. The penetration of plasma generated species (i.e., ions and radicals) into the wafer-focus ring gap is discussed. We found that the penetration of plasma into the gap and under the wafer bevel increases as the size of the gap approaches and exceeds the Debye length in the vicinity of the gap. Deposition of, for example, polymer by neutral species inside the gap and under the wafer is less sensitive to the size of the gap due the inability of ions, which might otherwise sputter the film, to penetrate into the gap.
Creation of high-energy phonons by four-phonon processes in anisotropic phonon systems of HeII
Authors: Adamenko I. N. , Nemchenko K. E. , Slipko V. A. , Kitsenko Yu. A. , Wyatt A. F. G.
Published: June 2007

The problem of the creation of high-energy phonons (h-phonons) by a pulse of low-energy phonons (l-phonons) moving from a heater to a detector in superfluid helium is solved. The rate of h-phonon creation is obtained, and it is shown that the h-phonons created occupy a much smaller solid angle in momentum space than the l-phonons. An analytical expression for the creation rate of h-phonons, along the symmetry axis of a pulse, is derived. It allows us to get useful approximate analytical expressions for the creation rate of h-phonons. The time dependences of the parameters describing the l-phonon pulse are obtained. This shows that half of the initial energy of l-phonon pulse can be transferred into h-phonons. The results of the calculations are compared with experimental data, and we show that this theory explains a number of experimental results. The value of the momentum that separates the l- and h-phonon subsystems is found.
Coherent current states in a two-band superconductor
Authors: Yerin Y. S. , Omelyanchouk A. N.
Published: June 2007

Homogeneous current states in thin films and Josephson current in superconducting microbridges are studied within the framework of a two-band Ginzburg–Landau theory. By solving the coupled system of equations for two order parameters the depairing current curves and Josephson current–phase relation are calculated for different values of phenomenological parameters γ and η. Coefficients γ and η describe the coupling of order parameters (proximity effect) and their gradients (drag effect), respectively. For definite parameter values the dependence of the current j on the superfluid momentum q contains local minima and corresponding bistable states. It is shown that a Josephson microbridge made from two-band superconductors can demonstrate π-junction behavior.
Spin dynamics and magnetic phase transitions in the quasi-two-dimensional antiferromagnet Mn[C10H6(OH)(COO−)]2×2H2O
Authors: Dergachev K. G. , Kobets M. I. , Khatsko E. N. , Khrustalev V. M. , Pashchenko V. A.
Published: June 2007

The angular and frequency dependence of the linewidth of the EPR absorption spectrum of the metalorganic antiferromagnet Mn[C10H6(OH)(COO−)]2×2H2O are investigated at high temperature (T=250K). The behavior of the EPR spectrum at high temperatures is described by a diffusion model for quasi-two-dimensional magnetic structures. Estimates are made for the diffusion coefficient D, the times of the beginning τ1 and end τ2 of the diffusion regime, and the nondiffusive contribution to the EPR linewidth. The temperature dependence and field dependence of the magnetic susceptibility and magnetization in the temperature region 1.8–25K in pulsed magnetic field up to 150kOe along the principal magnetic axes. A weak ferromagnet moment along the easy axis of the antiferromagnet and the spin-reorientation magnetic phase transitions at H1=5kOe (spin-flop transition) and H2≈97±2kOe and H3≈100±2kOe (spin-flip transitions) for the easy and medium axes of magnetization.
Imaging properties of a metallic photonic crystal
Authors: Xiao D. , Kim K. W. , Zavada J. M.
Published: June 2007

Imaging effects in metallic photonic crystals (PCs) are examined theoretically based on the finite difference time-domain method. The analysis shows that, in metallic PC-based systems, far-field images do form at the opposite side of the PC “lens” and more importantly, follow the rule of geometric optics with respect to the changes in the source position as a direct proof of negative refraction. However, the comparison of ideal left-handed media with a metallic PC suggests that the focusing effect in the PC based system is different from that of the ideal left-handed media in many aspects, due to the inhomogeneous nature of the PC. Particularly, strong dependence on the individual geometry as well as the frequency in the PC-based system renders the effective index sensitive to the variations and potentially limits its application as a superlens.
Interdiffused InAs∕InGaAlAs quantum dashes-in-well structures studied by surface photovoltage spectroscopy
Authors: Ivanov Ts. , Donchev V. , Wang Y. , Djie H. S. , Ooi B. S.
Published: June 2007

We report the study of interband optical transitions in the interdiffused InAs quantum dash (QD) in InAlGaAs quantum well (QW) structures using room temperature surface photovoltage (SPV) spectroscopy. SPV signals have been detected from all relevant portions of both the as-grown and interdiffused structures including the QD, QW, and cladding layer. The effect of group-III intermixing on the interband optical transition energies in the interdiffused structures has also been revealed by the SPV spectroscopy, and the results have been confirmed by photoluminescence measurements. The SPV investigation shows that the compositional intermixing occurs not only between the dash and the surrounding well but also between the well and the surrounding barrier. The results demonstrate the potential of the SPV spectroscopy as a nondestructive, contactless method to characterize optical transitions in complex semiconductor nanostructures at room temperature.
On the structure of the first hydration layer on NaCl(100): Role of hydrogen bonding
Authors: Cabrera-Sanfelix Pepa , Arnau Andres , Darling George R. , Sanchez-Portal Daniel
Published: June 2007

The authors have investigated the structure and energetics of the first hydration layer on NaCl(100) by means of density functional calculations. They have analyzed in detail the role of the hydrogen bond between the adsorbed molecules for the determination of the most favorable structures. They have shown that, using the water dimers as basic building blocks, very stable structures can be constructed. They discuss here two important examples: (i) a model with (1×1) periodicity at 2 ML coverage, and (ii) icelike bilayers with a c(4×2)unit cell at 1.5 ML. Both structures present high adsorption energies per water molecule of ∼570meV, in comparison to the 350meV adsorption energy obtained for the previously studied (1×1) structures composed of weakly interacting monomers. Based on these findings, they propose an interpretation for the experimental observations of Toennies et al. [J. Chem. Phys. 120, 11347 (2004)], who found a transition of the periodicity of the first hydration layer on NaCl(100) from (1×1) to c(4×2) upon electron irradiation. According to the model, the transition would be driven by the partial desorption of (1×1) bilayer structures corresponding to a local coverage of 2 ML and the further rearrangement of the remaining water molecules to form a quasihexagonal structure with c(4×2) periodicity at coverage close to 1.5 ML.
Numerical analyses of effective dielectric constant of multiphase microporous media
Authors: Wang Moran , Pan Ning
Published: June 2007

This paper provides a full numerical tool set for modeling and predicting an effective apparent dielectric constant of multiphase microporous media, which includes a multiparameter random generation-growth algorithm for generating microstructures of multiphase porous media and a lattice Boltzmann solver for the electric potential transport equations through porous structures. After being validated by the theoretical solutions for simple geometries, the present methods are used to investigate the phase distribution effects on the effective dielectric constant of multiphase microporous media, including the effects of particle size, structure anisotropy, and phase aggregation caused by wetting characteristics between phases for multiphase cases. The resultant predictions at the end agree well with the existing experimental data for both two-phase and three-phase cases.
Characterization of pattern transfer in the fabrication of magnetic nanostructure arrays by block copolymer lithography
Authors: Kubo T. , Parker J. S. , Hillmyer M. A. , Leighton C.
Published: June 2007

The authors report the fabrication of large-area antidot arrays using cylinder-forming polystyrene-polyisoprene-polylactide triblock terpolymer templates. 30nm antidots were generated after removal of the minority polymer component by aqueous degradation, oxygen reactive ion etching, and subsequent Ar ion beam milling to transfer the pattern to an underlying Ni80Fe20 film. Emphasis was placed on characterization of the pattern transfer, which was tracked using a combination of atomic force microscopy, magnetometry, and magnetotransport. It is demonstrated that variable temperature magnetometry and transport measurements are excellent probes of the progress of the ion milling into underlying magnetic layers.
Direct printing of organic transistors with 2μm channel resolution
Authors: Lee Hee Hyun , Brondjik J. J. , Tassi N. G. , Mohapatra S. , Grigas M. , Jenkins P. , Dimmler K. J. , Blanchet Graciela B.
Published: June 2007

Organic materials offer the possibility of printing flexible electronic devices with large area coverage in a printing press. Usually this vision conflicts with the requirement of high-resolution feature formation. The authors demonstrate here that thin film transistors with 2μm channel length can be printed using a reel-to-reel compatible process. The development of a dry printing method used in combination with a high-resolution, solvent resistant plates, and sintered metallic nanoinks enables high-resolution printing of functional liquid inks. In addition, dry printing allows for the sequential printing of solid films overcoming the severe solvent incompatibility issues faced by standard printing techniques.
Optical response of artificial opals oriented along the ΓX direction
Authors: Galisteo-López J. F. , Galli M. , Balestreri A. , Andreani L. C. , López C.
Published: June 2007

The optical response of artificial opals in the surroundings of the [100] crystallographic direction has been measured by means of microreflectance and transmittance spectroscopies. The results indicate that for such sample orientation, the optical properties are determined entirely by low dispersion bands responsible for out-of-plane diffraction. This is corroborated by phase-sensitive spectroscopy which shows strong anomalies in the measured phase above the onset of diffraction. Such anomalies translate into group velocity values of ±c∕20, evidencing slow and superluminal light propagation. These findings could be relevant in developing future routes for enhanced light-matter interaction.
Sampling of broadband terahertz pulses with thick electro-optic crystals
Authors: Kampfrath Tobias , Nötzold Jan , Wolf Martin
Published: June 2007

The authors show by experiment and theory that thick electro-optic crystals are suitable media for sampling electromagnetic radiation from 0.3to50THz with 10fs visible laser pulses. For example, the detection of frequencies above 10THz with a 250μm thick, ⟨110⟩-oriented ZnTe crystal is as efficient as that with a 10μm thin crystal. This surprising behavior and a much flatter detector response arise because phase-matching oscillations are greatly smeared out by the broad spectrum of the sampling pulse and the crystal dispersion.
Magnetoresistive anisotropy and magnetoresistivity in strained La0.65Ca0.35MnO3 films near the metal-insulator transition
Authors: Egilmez M. , Patterson R. , Chow K. H. , Jung J.
Published: June 2007

Magnetotransport properties of strained La0.65Ca0.35MnO3 thin films with thickness between 10 and 1000nm were investigated at temperatures near the metal-insulator transition and in magnetic fields up to 0.7Tesla. The reduction of the thin film thickness, which in turn produces an increasing epitaxial lattice strain, dramatically increases the “in-plane” magnetic anisotropy and the magnetoresistivity.
Growth of zinc oxide nanopillars on an iridium/yttria-stabilized zirconia/silicon substrate
Authors: Prinz Günther M. , Reiser Anton , Röder Tobias , Schirra Martin , Feneberg Martin , Röder Uwe , Sauer Rolf , Thonke Klaus , Gsell Stefan , Schreck Matthias , Stritzker Bernd
Published: June 2007

Zinc oxide nanopillars were grown by a self-catalyzed growth process on an epitaxial Ir/yttria-stabilized zirconia/Si(111) multilayer structure in an optically heated tube furnace. The pillars obtained stand upright parallel to each other with their c-axis perpendicular to the sample surface. Problems due to alloying of Zn with Si are completely avoided, and no irregularities of the pillars in the initial growth phase are found. Cathodoluminescence measurements show narrow linewidths below 700μeV due to the excellent crystal quality. Termination of ZnO pillars with a flat metallic iridium layer is an attractive issue towards an optical cavity for laser action.
Integration of optical waveguides and microfluidic channels both fabricated by femtosecond laser irradiation
Authors: Osellame Roberto , Maselli Valeria , Vazquez Rebeca Martinez , Ramponi Roberta , Cerullo Giulio
Published: June 2007

A femtosecond laser is used to fabricate both microfluidic channels and high quality optical waveguides, intersecting each other on a single glass substrate. Fluorescence in fluids filling the microfluidic channels has been selectively excited in several points by coupling light in the optical waveguides. Waveguide-microchannel integration opens several prospects for in situ sensing in lab-on-a-chip devices.
A relaxation-assisted 2D IR spectroscopy method
Authors: Kurochkin Dmitry V. , Naraharisetty Sri Ram G. , Rubtsov Igor V.
Published: June 2007

A method of two-dimensional infrared (2D IR) spectroscopy called relaxation-assisted 2D IR (RA 2DIR) is proposed that utilizes vibrational energy relaxation transport in molecules to enhance cross-peak amplitudes. This method substantially increases the range of distances accessible by 2D IR and is capable of identifying long-range connectivity patterns in molecules. RA 2DIR is illustrated in interactions among CN and CO modes in 3-cyanocoumarin and 4-acetylbenzonitrile, where the distances between the CN and CO groups are ≈3.1 and ≈6.5 Å, respectively. A 6-fold increase in cross-peak amplitude was observed in 4-acetylbenzonitrile when the dual-frequency RA 2DIR method was used.
Centromeres were derived from telomeres during the evolution of the eukaryotic chromosome
Authors: Villasante Alfredo , Abad José P. , Méndez-Lago María
Published: June 2007

The centromere is the DNA region of the eukaryotic chromosome that determines kinetochore formation and sister chromatid cohesion. Centromeres interact with spindle microtubules to ensure the segregation of chromatids during mitosis and of homologous chromosomes in meiosis. The origin of centromeres, therefore, is inseparable from the evolution of cytoskeletal components that distribute chromosomes to offspring cells. Although the origin of the nucleus has been debated, no explanation for the evolutionary appearance of centromeres is available. We propose an evolutionary scenario: The centromeres originated from telomeres. The breakage of the ancestral circular genophore activated the transposition of retroelements at DNA ends that allowed the formation of telomeres by a recombination-dependent replication mechanism. Afterward, the modification of the tubulin-based cytoskeleton that allowed specific subtelomeric repeats to be recognized as new cargo gave rise to the first centromere. This switch from actin-based genophore partition to a tubulin-based mechanism generated a transition period during which both types of cytoskeleton contributed to fidelity of chromosome segregation. During the transition, pseudodicentric chromosomes increased the tendency toward chromosomal breakage and instability. This instability generated multiple telocentric chromosomes that eventually evolved into metacentric or holocentric chromosomes.
Small‐Scale Extrusion of Corn Masa By‐Products
Authors: Rosentrater K. A. , Richard T. L. , Bern C. J. , Flores R. A.
Published: June 2007

Corn masa by‐product streams are high in fiber and are amenable for utilization in livestock feed rations. This approach is a potentially viable alternative to landfilling, the traditional disposal method for these processing residues. Suspended solids were separated from a masa processing waste stream, blended with soybean meal at four levels (0, 10, 20, and 30% wb), and extruded in a laboratory‐scale extruder at speeds of 50 rpm (5.24 rad/sec) and 100 rpm (10.47 rad/sec) with temperature profiles of 80‐90‐100°C and 100‐110‐120°C. Processing conditions, including dough and die temperatures, drive torque, specific mechanical energy consumption, product and feed material throughput rates, dough apparent viscosity, and dough density, were monitored during extrusion. The resulting products were subjected to physical and nutritional characterization to determine the effects of processing conditions for these blends. Extrudate analysis included moisture content, water activity, crude protein, in vitro protein digestibility, crude fat, ash, product diameter, expansion ratios, unit and true density, color, water absorption and solubility, and durability. All blends were suitable for extrusion at the processing conditions used. Blend ratio had little effect on either processing parameters or extrudate properties; extrusion temperature and screw speed, on the other hand, significantly affected both processing and product properties.
Application of Response Surface Methodology in the Development of Gluten‐Free Bread
Authors: McCarthy D. F. , Gallagher E. , Gormley T. R. , Schober T. J. , Arendt E. K.
Published: June 2007

The formulation of gluten‐free (GF) bread of high quality presents a formidable challenge as it is the gluten fraction of flour that is responsible for an extensible dough with good gas‐holding properties and baked bread with good crumb structure. As the use of wheat starch in GF formulations remains a controversial issue, naturally GF ingredients were utilized in this study. Response surface methodology was used to optimize a GF bread formulation primarily based on rice flour, potato starch, and skim milk powder. Hydroxypropylmethylcellulose (HPMC) and water were the predictor variables. Analyses of the treatments from the design were made 24 hr after baking. Specific volume and loaf height increased as water addition increased (P < 0.01). Crumb firmness decreased as water levels increased (P < 0.01). Significant interactions (P < 0.01) between HPMC and water were found for the number of cells/cm2. The number of large cells (>4 mm2) decreased with increasing levels of HPMC and water. Optimal ingredient levels were determined from the data obtained. The optimized formulation contained 2.2% HPMC and 79% water flour/starch base (fsb) and measured responses compared favorably to predicted values. Shelf‐life analysis of the optimized formulation over seven days revealed that, as crumb firmness increased, crust firmness and crumb moisture decreased.
Milling Quality and White Salt Noodle Color of Chinese Winter Wheat Cultivars
Authors: Zhang Yan , Quail K. , Mugford D. C. , He Zhonghu
Published: June 2007

Improvement of milling quality is an important aspect in wheat breeding programs. However, the milling quality of Chinese wheats remains largely unexplored. Fifty‐seven Chinese winter wheat cultivars from four regions were used to investigate the variation of milling quality parameters and to determine the associations between milling quality traits and color of noodle sheet. Substantial variation was presented for all measured parameters in this germplasm pool. Complete soft, hard, and medium‐hard types were observed. Soft wheat and hard wheat show significant differences in flour ash content, flour bran area, and flour color grade. No simple trait can be used to select for flour milling quality. High flour ash content and bran speck area contributed negatively to brightness of dry flour. Correlation coefficients (r) between L* value of dry flour and flour ash content and bran speck area were ‐0.47 and ‐0.65 for hard cultivars, and ‐0.51 and ‐0.72 for soft cultivars, respectively. Flour color grade (FCG) was significantly and positively associated with bran speck area; r = 0.56 and 0.73 for hard and soft wheats, respectively. There was a high correlation between FCG and L* value of flour water slurry (r = ‐0.95). Strong associations were also established between milling quality index (MQI) and FCG, L* value of dry flour, flour‐water slurry, and white salted noodle sheet for both hard and soft wheats. In conclusion, substantial progress could be achieved in improvement of milling quality in Chinese winter wheats through genetic selection, and FCG and MQI could be two important parameters for evaluation of milling quality in breeding programs.
Effect of Starch Granule Size Distribution and Elevated Amylose Content on Durum Dough Rheology and Spaghetti Cooking Quality
Authors: Soh H. N. , Sissons M. J. , Turner M. A.
Published: June 2007

To obtain an indication of the effect of increasing the starch amylose content above normal levels (27–74%) and increasing the percentage of B‐type starch granules (11–60%) on durum dough properties and the quality of the spaghetti derived from these doughs, the reconstitution approach was used. Reconstituted flours were prepared from a common Wollaroi gluten, solubles and tailings fraction combined with starches containing varying B‐granule contents, or with starches from maize with varying amylose content. An increased B‐granule content increased farinograph water absorption. Cooked spaghetti firmness was highest with B‐type granules at 32–44% (volume percentage basis), which is ≈10–15% higher than normally found in durum starch. Increasing the amylose content in the starch caused the dough to be more extensible, increased spaghetti firmness, and decreased water absorption with optimum quality of amylose at 32–44%. The information indicates there would be benefit in producing durum wheats with slightly elevated B‐granule and amylose contents.
Granule Bound Starch Synthase I (GBSSI) Gene Effects Related to Soft Wheat Flour/Starch Characteristics and Properties
Authors: Geera B. P. , Nelson J. E. , Souza E. , Huber K. C.
Published: June 2007

Eight soft spring wheat (Triticum aestivum L.) genotypes representing the four granule bound starch synthase I (GBSSI) classes were evaluated with respect to flour/starch characteristics and pasting behaviors. Native starch was isolated from genotype straight‐grade flours (94.8–98.1% of starch recovered) to approximate the starch populations of the parent flours. As anticipated, amylose characteristics varied among the genotypes according to GBSSI class and accounted for the primary compositional difference between genotypes. Total (TAM), apparent (AAM), and lipid‐complexed (LAM) amylose contents ranged from 1.0–25.5 g, 0.7–20.4 g, and 0.3–5.6 g/100 g of native starch, respectively, and gradually decreased with the progressive loss of active Wx alleles. In addition, genotype flour total starch (FTS) and A‐type starch granule contents, which ranged from 81.7–87.6 g/100 g of flour (db) and 61.6–76.8 g/100 g of native starch (db), respectively, generally decreased with an increase in waxy character in parallel with amylose characteristics, as likely secondary effects of Wx gene dosage. Though amylose characteristics predominantly accounted for the majority of genotype flour pasting properties, FTS content and ratios of A‐ to B‐type granules also exhibited significant influence. Thus, loss of one or more Wx genes appeared to induce measurable secondary effects on starch characteristics and properties.
Flour Pasting Properties of Wild‐Type and Partial Waxy Soft Wheats in Relation to Growing Environment‐Induced Fluctuations in Starch Characteristics
Authors: Geera B. P. , Nelson J. E. , Souza E. , Huber K. C.
Published: June 2007

To relate growing environment‐induced differences in wheat (Triticum aestivum L.) flour pasting properties with fluctuations in starch characteristics, starch characteristics of flours milled from wild‐type and partial waxy wheat genotypes grown at two diverse locations (irrigated vs. rainfed) over two successive crop years (2000, 2001) were analyzed. The crop year or growing location that possessed the highest peak and breakdown viscosity values exhibited the highest mean flour total starch (FTS) content, while that exhibiting the highest trough, final, and setback viscosities possessed the highest mean A‐type granule content. Correlation analysis across growing environments provided additional evidence for associations between flour pasting properties and flour/starch characteristics. Fluctuations in mean FTS content were associated with flour peak (r = 0.95) and breakdown (r = 0.93) viscosity differences, while variability in A‐type granule content was strongly correlated with fluctuations in trough (r = 0.82), final (r = 0.96), and setback (r = 0.99) viscosities. Peak viscosity was also negatively correlated with total (r = ‐0.78) and lipid‐complexed (r = ‐0.72) amylose contents. Of the flour/starch characteristics measured, variability in FTS and A/B‐type granule contents best explained growing environment‐induced fluctuations in flour pasting properties.
Properties of Starch Noodles as Affected by Sweetpotato Genotype
Authors: Collado Lilia S. , Corke Harold
Published: June 2007

Starch was extracted from 14 sweetpotato genotypes from the Philippines. The Rapid Visco‐Analyzer (RVA) viscoamylographs of the starches showed Type A pasting curves, characterized by a high pasting peak followed by a high degree of shear‐thinning. The major difference among genotypes was in the sharpness of the peak, with some showing a very sharp peak while others showed a broad peak. This difference was related to time from onset of pasting to peak viscosity, and to stability ratio (holding viscosity/peak viscosity), which were also highly correlated (r = 0.84, P < 0.01) to each other. Stability ratio was also correlated to noodle firmness (r = 0.95, P < 0.01), rehydration (cooked weight) (r = ‐0.89, P < 0.01), and swelling volume of the starch (r = ‐0.62, P < 0.05). The amylose content was correlated significantly only to peak viscosity (r = ‐0.84, P < 0.01). Significant differences in texture and cooking quality of the starch noodles produced from the different genotypes was found. It was shown that the RVA viscoamylographs could be used to detect differences in pasting characteristics of sweetpotato starch which are related to quality of noodle produced.