bluuebunny/crossref_metadata_2025 huggingface dataset:
Inhibitory effects of thioredoxin reductase antisense RNA on the growth of human hepatocellular carcinoma cells
Authors: Gan Lu , Yang Xiang‐Liang , Liu Qiong , Xu Hui‐Bi
Published: August 2005

Thioredoxin reductase (TrxR) in conjunction with thioredoxin (Trx) is a ubiquitous intracellular oxidoreductase system with antioxidant and redox regulatory roles. In some human tumors, the thioredoxin system is found overexpressed. We have used an antisense approach to investigate whether inhibition of TrxR overexpression can suppress the growth of human hepatocellular carcinoma SMMC‐7721 cells. TrxR cDNA fragment was inserted in the antisense direction into pcDNA3.1/myc‐His and SMMC‐7721 cells were stably transfected with the plasmid construct. The results showed that TrxR antisense RNA could significantly reduce TrxR mRNA level and activity, and suppress the growth of SMMC‐7721 cells. Cell‐cycle analysis showed G2/M phase arrest in SMMC‐7721 cells transfected with TrxR antisense plasmid. TrxR antisense RNA could significantly increase p53 mRNA level and decrease Bcl‐2 mRNA level by reverse transcriptase‐polymerase chain reaction (RT‐PCR). Furthermore a significant decrease in human telomerase reverse transcriptase (hTERT) mRNA level was found in SMMC‐7721 cells transfected with TrxR antisense plasmid. Flow cytometry and telomere fluorescence in situ hybridization (Flow FISH) showed that TrxR antisense RNA could significantly reduce the telomere fluorescence in SMMC‐7721 cells. The results suggested that TrxR antisene RNA inhibited the growth of SMMC‐7721 cells through an accumulation of cell cycle at G2/M phase, an increase in p53 mRNA level and a reduction in telomere fluorescence and Bcl‐2, hTERT mRNA levels. © 2005 Wiley‐Liss, Inc.
Protein structure prediction with the UNRES force‐field using Replica‐Exchange Monte Carlo‐with‐Minimization; Comparison with MCM, CSA, and CFMC
Authors: Nanias Marian , Chinchio Maurizio , Ołdziej Stanisław , Czaplewski Cezary , Scheraga Harold A.
Published: August 2005

Two current methods of global optimization are coupled to produce the Replica‐Exchange method together with Monte Carlo‐with‐Minimization (REMCM). Its performance is compared with each separate component and with other global optimization techniques. REMCM was applied to search the conformational space of coarse grain protein systems described by the UNRES force field. The method consists of several noninteracting copies of Monte Carlo simulation, and minimization was used after every perturbation to enhance the sampling of low‐energy conformations. REMCM was applied to five proteins of different topology, and the results were compared to those from other optimization methods, namely Monte Carlo‐with‐Minimization (MCM), Conformational Space Annealing (CSA), and Conformational Family Monte Carlo (CFMC). REMCM located global minima for four proteins faster and more consistently than either MCM or CFMC, and it converged faster than CSA for three of the five proteins tested. A performance comparison was also carried out between REMCM and the traditional Replica Exchange method (REM) for one protein, with REMCM showing a significant improvement. Moreover, because of its simplicity, REMCM was easy to implement, thereby offering an alternative to other global optimization methods used in protein structure prediction. © 2005 Wiley Periodicals, Inc. J Comput Chem 26: 1472–1486, 2005
Minimum vertex‐diameter‐2‐critical graphs
Authors: Chen Ya‐Chen , Füredi Zoltán
Published: August 2005

We prove that the minimum number of edges in a vertex‐diameter‐2‐critical graph on n ≥ 23 vertices is (5n − 17)/2 if n is odd, and is (5n/2) − 7 if n is even. © 2005 Wiley Periodicals, Inc. J Graph Theory
Two‐dimensional numerical simulation of short‐gate‐length gaAs MESFETs and application to the travelling gunn domain phenomenon
Authors: El‐Ghazaly Samir , Itoh Tatsuo
Published: August 2005

The Boltzmann transport equation is used to derive a set of conservation equations which is capable of describing the electron transport phenomena in a single‐valley semiconductor. These conservation equations are averaged over the different valleys of the conduction band to develop another set of equations that can be used to describe accurately the electron transport phenomena in a multi‐valley semiconductor, such as GaAs, using the equivalent single‐electron gas model whose characteristics are the average weighted characteristics of the constituent gases. The nonstationary effects are included by using energy dependent mobility and electron temperature functions. This program is used to simulate a GaAs MESFET with a 0·5 μm gate length and a 0.2 μm thick active layer. The active layer is doped at 1017 cm−3. A travelling Gunn domain is observed between the gate and the drain. The domain oscillation frequency is much higher than the normal operating frequency of the MESFET. The domain formation's dependence on the gate bias and the active layer thickness are also presented.
Coupling between electromagnetic fields and multiconductor transmission systems using TLM
Authors: Christopoulos C. , Naylor P.
Published: August 2005

The coupling between incident electromagnetic fields and lossless multiconductor transmission systems is studied using transmission‐line modelling‐(TLM) and the impedance parameters of the transmission system. This calculation is a two‐stage procedure:firstly, the field problem is solved, with no conductors present, to give the incident fields; secondly, the multiconductor transmission‐line problem is solved using equivalent voltage and current sources representing coupling from the incident fields. Comparison of these results with previously published work shows excellent agreement. The numerical model presented is particularly suitable for studying electromagnetic compatibility problems.
Characterization of coupled finlines by generalized transverse resonance method
Authors: Schiavon Giovanni , Sorrentino Roberto , Tognolatti Piero
Published: August 2005

The conventional transverse resonance method, which has been widely used for the approximate characterization of a number of guiding structures and leaky wave antennas, is formulated in a generalized form. The transverse resonance viewpoint combined with the generalized matrix representation of discontinuities yields a rigorous transverse equivalent circuit of the guiding structure.

This technique is used to compute the characteristics of both symmetrical and asymmetrical double slot unilateral finlines in terms of phase constant and characteristic impedance of the dominant as well as higher‐order modes. Numerical aspects of this method are discussed.

In a double‐slot finline structure, a coupled‐mode regime is established with the onset of the first higher‐order mode in addition to the dominant quasi‐TEM mode. Symmetrical structures are simply modelled in terms of even and odd mode characteristics, but a more general coupled‐line model, in terms of the C‐mode and the II‐mode must be applied to asymmetrical coupled finlines.
Application of the symmetrized transmission‐line matrix method to the cold modelling of magnetrons
Authors: Allen R. , Clark M. J.
Published: August 2005

Two‐ and three‐dimensional electromagnetic resonance calculations have been performed on rising‐sun magnetron structures. These calculations have been made using the transmission‐line matrix method. Cylindrical coordinates have been used in order to facilitate modelling of the essentially cylindrical device. Recent improvements to the TLM technique, such as the development of the symmetric condensed node for electromagnetics, have been fully exploited. The numerical procedure is described, the modelling process is discussed, and the results obtained are evaluated in comparisons with corresponding empirical data.
Weighted Gaussian quadratures for singular and near ‐singular integrands
Authors: Silvester Peter P.
Published: August 2005

Numerical quadratures encountered in solving integral equations and in finite element analysis often involve singular integrands, or integrands with very rapid local variation whose numerical stability resembles that of singularities. It is shown that specialized quadrature formulae of Gauss–Christoffel type can be generated for such integrands, using a recursive procedure based on the properties of the underlying orthogonal polynomials. Quadrature formulae of moderately high degree can be computed rapidly enough to allow them to be constructed as needed. An algorithm for generating quadrature formulae is given in detail. Singular or near ‐singular functions encountered in finite element analysis typically require three ‐point or four ‐point quadratures; such formulae are readily obtained, to seven ‐figure accuracy, in computing times short enough to regard the formulae as disposable and not worth preserving in tables.
Efficient direct and iterative electrodynamic analysis of geometrically complex MIC and MMIC structures
Authors: Wertgen W. , Jansen R. H.
Published: August 2005

Rigorous full ‐wave analysis techniques are presently receiving much attention in the design of MICs and, in particular, of MMICs due to increasing circuit packing densities and structural complexity. In this paper, the problems associated with such techniques and previous related work are briefly outlined in the introduction. To obtain self ‐consistency, the electrodynamic Green's functions and related terms are then formulated for the shielded (M)MIC problem. The final operator equation for the numerical solutions derived and the associated functions space are presented and discussed. The central portion of the paper describes a new numerical solution using a discretized Green's function database technique. The resulting linear system of equations is solved by direct inversion for geometrical complexities involving up to about 1000 unknowns; for a higher number of unknowns, an iterative solution is generated. As an alternative to the database technique developed, a variety of spectral domain iterative solutions has been written and tested as well. This includes application of the conjugate gradient method to the normal operator equation (CGN algorithm), an implicit iterative Galerkin approximation called the modified planar conjugate gradient technique (MPCG) and monotonically convergent iteration procedure being a version of the conjugate residual algorithm (CR). Supplementary to this, the extraction of (M)MIC design data from the numerical 3D solutions obtained and error considerations are presented. The paper concludes with a variety of analysis examples of medium to high geometrical complexity and with verification of some results by comparison with measurements and with numerical data from other sources.

CPU times required on typical workstations (Micro VAX, HP 9000, etc.) are moderate, thus rendering the techniques presented as useful in the solution of MIC and MMIC design problems.
Computation of the electromagnetic field distribution inside enclosures with apertures using 3‐D FEM
Authors: Ladd Darcy N. , Costache George I.
Published: August 2005

Knowledge of the electromagnetic field distribution inside electronic enclosures due to incident fields is of interest to EMC design engineers. In this paper, a three‐dimensional formulation of the finite element method was developed to solve the electromagnetic field distribution inside metal enclosures with apertures. The formulation was developed using a three‐component vector magnetic potential and a scalar electric potential. The displacement current as well as the conduction current term was included. The region of interest was discretized using eight‐node isoparametric hexahedrons and the potential functions were defined using linear first‐order basis functions. The penetration of a steady‐state electromagnetic field through an aperture into a simple cavity was analysed with the 3‐D FEM program.
Time‐domain calculation of electromagnetic plane‐wave induced surges on overhead transmission lines
Authors: Seltner Ph. , Pardo‐Gibson O. , Auriol Ph.
Published: August 2005

This paper presents a time‐domain method to calculate electromagnetic plane wave induced surges on overhead multiconductor transmission lines. By means of some particular line impulse responses, the method takes into account the distributed nature of the coupling with plane wave radiated fields. A comparison of measured plane‐wave induced voltages reported in the literature and calculated voltages shows a very close agreement.
Propagation of picosecond pulses in superconducting microstrip interconnections on integrated circuits
Authors: Sali S.
Published: August 2005

Studies on the propagation of picosecond pulses in coupled microstrip line interconnections on silicon integrated circuit substrates are presented. The effects of conductor and dielectric losses in the transmission line on the distortion, delay and attenuation of picosecond pulses are studied in detail. A direct comparison is made with the propagation characteristics of interconnects using ordinary metals and high‐temperature superconductors such as YBa2Cu3O7. The results generally show the advantages of using high‐temperature superconductor tracks on low‐loss integrated circuit substrates such as GaAs. However, even in this case, geometrical dispersion can cause distortion on the pulses and it is therefore an important factor to be considered.
Calculation of radiated electromagnetic fields from electronic systems
Authors: Öing S. , John W. , Mrozynski G.
Published: August 2005

The electromagnetic radiation from electronic systems is formulated in terms of an integral equation for the electric and the equivalent magnetic current density, which is numerically solved by the method of moments. The electromagnetic coupling to conducting thin wires, thin plates, and aperture fitted cabinets is taken into account by appropriate operator equations.

In order to solve the integral equation of electrically large conducting structures, suitable basis functions are needed to minimize the computation time. B‐spline functions of the second and third degree are used as a basis in the moment method, which lead to a decrease of the computation time.

A second way to decrease the computation time is given by the possibility of determining which parts of the structure of a printed circuit board (PCB) have to be considered and which parts can be neglected. Examples show that the influence of near source conducting areas to the radiated emissions is strong. It will be shown that this influence depends on the geometrical symmetry, the shape, and the distance of the scattering body.
Efficient analytical‐numerical modelling of ultra‐wideband pulsed plane wave scattering
Authors: Carin Lawrence , Felsen Leopold B.
Published: August 2005

Ultra‐wideband (UWB) pulsed plane wave scattering from a large but finite strip grating in free space is analysed in the frequency domain via decomposition into plane wave spectra, implemented numerically by the method of moments, and then inverted into the time domain (TD). To make this procedure practical under UWB conditions, closed form expressions are derived for interaction integrals involving widely separated expansion and testing functions. These closed forms are based on a judicious choice of the basis functions, and on asymptotic methods for reducing the integrals. Although large separation distances are assumed, the expressions have been found to be accurate for separations as small as 0·1 wavelengths. The TD self terms can also be evaluated efficiently. To test the frequency domain algorithm, comparisons are made with available data in the literature for surface currents and far‐field scattering from multiple strips. New short pulse TD results are shown as well.
Spatially weighted numerical models for the two‐dimensional wave equation: FD algorithm and synthesis of the equivalent TLM model
Authors: Simons N. R. S. , Sebak A. A.
Published: August 2005

In this paper a new TLM model for the two‐dimensional wave equation is introduced. It is synthesized directly from a FD algorithm. The FD algorithm is second‐order‐accurate in both space and time, and is explicitly time‐stepped. The spatial derivatives in the FD algorithm are approximated by the weighted combination of two standard central difference stencils, one oriented as usual, the other rotated by 45° with its arms extended by a factor of (2)1/2. The TLM model is realized as the weighted connection of two original models (with the same geometrical configuration as the FD algorithm). The weighting in the TLM model is accomplished by using a variable intrinsic impedance for specific elemental transmission lines. The FD and TLM methods possess identical dispersion relations if the former is operated at its upper limit of stability. Therefore, under these conditions both represent identical models for the simulation of wave propagation. The propagation characteristics of the new model are investigated and the conditions for approximate numerical isotropy are provided. The numerical implementation (scattering matrix and transfer event) is described. To validate the new model, the calculation of cutoff frequencies of various modes in rectangular waveguide is performed. Comparison with analytical results (for an unfilled waveguide) and other numerical results (for a waveguide partially filled with a dielectric) validate the implementation of the model.
Multiport approach for the analysis of microwave non‐linear networks
Authors: Sobhy M. I. , Hosny E. A. , Nassef M. A.
Published: August 2005

The state and output equations of the overall networks are derived from the state and output equations of individual multiports and knowledge of the interconnections between them. A generalized lumped‐distributed L/D multiport is described by its associated state, output and non‐linear equations in the time domain. Any network can be considered as composed of a set of multiports and independent sources. These equations have been incorporated into a computer‐aided procedure for the analysis of L/D networks. The procedure can be used for the simulation of any non‐linear microwave circuit and offers the facility of developing a multiport equivalent circuit for any linear or non‐linear device or subcircuit. Several examples are successfully analysed using the developed general program.
Circuit model for a symmetrical condensed TLM node
Authors: Mlakar J.
Published: August 2005

An equivalent circuit for a symmetrical condensed TLM node is presented. The basic circuit has twelve ports and consists of 24 1:1 ideal transformers. Three additional conductances model the conductivity of the medium. The circuit is extended with additional ideal transformers giving six ports for short‐circuit and open‐circuit stubs which model the permittivity and permeability of the inhomogeneous medium. The scattering matrix of the 18‐port network is determined symbolically by solving a set of linear circuit equations. The matrix agrees with previously published results for a symmetrical condensed TLM node, obtained from Maxwell's equations.
Efficient implementation issues of finite difference time‐domain codes for Maxwell's equations
Authors: Lovetri Joe , Costache George I.
Published: August 2005

The computer implementation of time‐domain finite difference methods for the solution of Maxwell's equations is considered. As the basis of this analysis, Maxwell's equations are expressed as a system of hyperbolic conservation laws. It is shown that, in this form, all the well‐known differencing schemes can be easily expressed, thus increasing the applicability of the implementation issues to be discussed. Practical issues, such as computational efficiency and memory requirements, are discussed for the implementation of the finite difference schemes. Advanced programming techniques in the C language are used to implement the finite difference schemes discussed. The example of the penetration of electromagnetic energy through a shield with a thick gap is used to check the performance of the methods. It is shown that, for cases where the disturbance remains localized in the computational mesh, these techniques result in memory and CPU time savings.
Transmission‐line matrix method for solving the multidimensional continuity equation
Authors: Gui Xiang , Gao Guang‐Bo , Morkoç Hadis
Published: August 2005

We have extended the one‐dimensional transmission‐line modelling (TLM) of diffusion, drift and recombination of charge carriers in semiconductors to multiple dimensions. Detailed TLM formulation of the continuity transport equation in a more general form is presented.
3‐D edge element analysis of dielectric loaded resonant cavities
Authors: Zhu Zhou Le , Davies J. B. , Fernandez F. A.
Published: August 2005

The eigenmodes in electromagnetic cavities, loaded with arbitrarily shaped dielectric materials, are computed by the edge element method. The computation shows that the well known ‘spurious modes’ no longer appear. Formulae are given and verified so that the number of zero eigenvalues, which come from ∇ × H = 0, may be accurately predicted. Formulae for the order and density of the global matrices are given for a rectangular cavity regularly divided into bricks and tetrahedra, allowing an associated comparison between the contrasting edge and nodal element formulations. Comparison of the computed results with available theoretical and previously published data show the edge element approach to be a robust, accurate and effective method.
Function expansion algorithms for the time‐domain alalysis of shielded structures supporting electromagnetic waves
Authors: Mrozowski Michal
Published: August 2005

Series function expansion algorithms of the time‐domain analysis of boundary value problems are discussed. Electromagnetic fields inside a structure under investigation are expanded into series of basis functions and the expansion coefficients are found by means of the Galerkin method. The numerical cost of algorithms is discussed and a cost efficient approach is proposed for formulations using sine and cosine expansion functions. Compared with conventional time‐domain methods the algorithms described show the time evolution of the expansion coefficients rather than the samples of a physical continuum at discrete nodes.
Characteristics of the general rectangular 2D‐TLM network
Authors: Hoefer Wolfgang J. R. , Sautier Pascal
Published: August 2005

In this paper the traditional square mesh 2D‐TLM algorithm is generalized for rectangular meshes of arbitrary aspect ratio. It is shown that the anisotropic rectangular TLM network can be conceived in such a way that the propagation vector remains independent of the direction of propagation in the infinitesimal approximation. A full dispersion analysis of the rectangular mesh in then performed for the general case, and results are compared to that of the traditional square mesh.
Harmonic balance method applied to the numerical electrical physical modelling of two‐terminal, non‐linear microwave circuits in the frequency domain
Authors: Dalle C.
Published: August 2005

A numerical frequence‐domain modelling of two‐terminal, non‐linear microwave circuits is presented. It basically relies on a process allowing the solution of the frequency‐domain curcuit harmonic balance equations while accounting for the semiconductor device by means of an accurate numerical macroscopic physical model. In its present state of development, the model allows the study of a single two‐terminal device circuit operating in harmonic mode. Its capabilites are illustrated by means of the results of a study devoted to the optimization of the load curcuit configuration of a millimetre‐wave avalanche diode frequency multiplier. The influence of the output load impedance level on the circuit output RF performance has been investigated for different input power levels in direct frequency multiplication mode and in the presence of additional circuit tunings at low harmonic rank idler frequencies.
A non‐linear and distributed modelling procedure of fets
Authors: Ongareau Eric , Aubourg Michel , Obregon Juan J. , Gayral Michel , Bosisio Renato G.
Published: August 2005

This paper describes a rigorous and systematic procedure to derive a non‐linear distributed FET model that an easily be implemented in CAD routines of simulators based on harmonic balance techniques. The new model is derived from a knowldge of the conventional linear lumped equivalent circuit, from non‐linear current sources extracted with pulsed measurements, and from the physical dimensions of the FET.

For fundamental and haromonic requencies, the FET is modelled byNidentical cells. Each cell is made up of a non‐linear two‐port section inserted between two linear four‐port sections that simulate the coupling and the distributed effects along the electrodes of the FET in the width direction only. This non‐linear distributed scaling approach to FET modelling has been applied to the analysis of a submicrometre‐gate GaAs FET at Millimetre‐wave frequencies, and the results were compared to the non‐linear lumped element approach. This approach can be applied to other transistors used in non‐linear regions at microwave and millimetre‐wave frequencies.
T‐versus ABCD‐matrix in circuit analysis
Authors: Tan E. C.
Published: August 2005

The paper describes and compares the wave‐chain and transmission matrix approaches to the calculation of transfer‐function coefficients for ladder circuits (semi‐symbolic analysis). It is found that the wave‐chain matrix approach can be computationally more efficient.
Development of an induction motor drive phase model based on the TLM method
Authors: Selhi H. , Christopoulos C. , Howe A. F. , Hui S. Y. R.
Published: August 2005

This paper describes a phase model of an induction motor based on Transmission‐Line Modelling technique. Its main advantage compared to the existing TLM d‐q model is the possibility of using a small part of the stator self‐inductance of each pahase as a link model to connect the motor to external sources and drives. Unlike the d‐q model, the phase model does not therefore require any additional components for connection purposes. The application of the phase model is demonstrated by and example representing a traction drive ciruit. Identical simulation results to those obtained from a different study based on a d‐q model are derived.
Modelling an insulated gate bipolar transistor using bond graph techniques
Authors: Besbes Kamel
Published: August 2005

Simulators in power electronics are less developed than in other electronic fields. The main modelling methods are between the numerical simulation of semiconductor device equations that hardly simulate circuits, and equivalent circuit models that show poor accuracy. We propose the application of the bond graph techniques to model modular power semiconductor devices. Furthermore, the IGBT is a new power device which combines a bipolar transistor with a MOSFET transistor. We develop a new IGBT bond graph model. The bond graph techniques give us good primary simulation results. We present in this paper the principle and the results of this modelling method.
A method for algebraic analysis of the TLM algorithm
Authors: Witwit A. R. M. , Wilkinson A. J. , Pulko S. H.
Published: August 2005

An analogy is described between the TLM algorithm and discrete state‐space control theory. The analogy is used to derive the characteristic equations corresponding to parametrized model structures. Characteristic equations corresponding to several widely used node structures are derived by this means and found to be consistent with the observed behaviour of corresponding TLM models. An example is given of the use of the analogy in teh predictive mode.
A parallel implementation of the finite difference time‐domain algorithm
Authors: Chew K. C. , Fusco V. F.
Published: August 2005

In this paper a parallel algorithm is created for solving electromagnetic wave scattering problems. The algorithm based on the finite difference time‐domain (FDTD) representation of the Maxwell's equations written in 3L Parallel Fortran for use on a transputer array.

The problem simulated consists of a space (air) where a spherical dielectric scatterer is located. This space is subdivided into fine equisize meshes extending throughout the 3‐D domain; the excitation wave is of sinusoidal form. Geometric decomposition is used as the principal algorithm strategy.

Results are presented for the performance of the classical sequential algorithm and compared with the parallel algorithm in terms of computational speed‐up.
On the potential use of cellular automata machines for electromagnetic field solution
Authors: Simons Neil R. S. , Cuhaci Michel , Adnani Nikhil , Bridges Greg E.
Published: August 2005

In this paper, the potential use of cellular automata machines for electromagnetic field solution is investigated. Cellular automata are computational models that operate on a discrete spatial lattice, evolve in discrete time, and employ simple discrete variables. We specifically examine the lattice gas automata which use simple variables to describe particles that interact with nearest neighbours on the lattice through simple rules. They are suitable for modelling the linear wave equation in two dimensions. A benefit of the cellular automata approach is that low‐cost, special‐purpose digital hardware exists for their efficient evaluation. The current state‐of‐the‐art cellular automata machine is CAM‐8. Computational experiments carried out on CAM‐8 are provided for problems involving plane wave interaction with perfectly conducting and dielectric media in two dimensions. The examples indicate the potential use of lattice gas automata for modelling electromagnetics and their efficient evaluation using cellular automata machines.
Neural network approach to the solution of linear complementarity problems
Authors: Osowski S.
Published: August 2005

The paper presents the application of nonlinear neural optimization networks to solve the linear complementarity problem. Two different approaches are presented and investigated: one leading to linear and the second to quadratic optimization programming. The numerical results of illustrative examples are given and discussed.
Improving the analytical figures of merit of SERS for the analysis of model environmental pollutants
Authors: De Jesús M. A. , Giesfeldt K. S. , Sepaniak M. J.
Published: August 2005

The presence of naphthalene, phenol and benzoic acid derivatives in natural waters constitutes a public health issue. The toxicity and chemical activity of these chemicals and their persistence in the environment depend on the types of functional groups attached to their basic aromatic structure. Surface‐enhanced Raman scattering (SERS) spectroscopy has shown promise for the analysis of aromatic compounds owing to a tremendous enhancement of the analytical response and also a large amount of available structural information. Despite these advantages, SERS has not been established as a routine analytical tool owing to limitations in the analytical figures of merit such as reproducibility and linear dynamic range. This paper reports the use of silver–polydimethylsiloxane nanocomposites in combination with a sample translation technique for the improved qualitative and quantitative analysis of model environmental pollutants in water. This novel approach considerably improves the reproducibility and the sensitivity of the technique by minimizing the thermal and photolytic effects inherent in SERS. The results show a linear dynamic range of at least two orders of magnitude with detection limits as low as 2.9 × 10−8 M and a precision of <10% relative standard deviation. The influences of different experimental variables such as irradiation time, translation rate and pH and the potential use of the technique for the analysis of environmental pollutants are presented. Copyright © 2004 John Wiley & Sons, Ltd.
In vitro polarization‐resolved resonance Raman studies of the interaction of hematin with the antimalarial drug chloroquine
Authors: Frosch T. , Küstner B. , Schlücker S. , Szeghalmi A. , Schmitt M. , Kiefer W. , Popp J.
Published: August 2005

Despite the public health impact of human malaria, the mechanism of hemozoin inhibition by antimalarial drugs such as chloroquine (CQ) is not yet fully understood. Polarization‐resolved resonance Raman spectra of hematin and its complex with CQ were recorded under Q‐band resonance conditions in order to monitor the binding of the 4‐aminoquinoline drug to the heme macrocycle. Upon drug addition, only wavenumber shifts smaller than 2 cm−1 are detected, indicating a non‐covalent interaction in the electronic ground state of the drug–target complex. The decreased resonance Raman intensity of the anomalously polarized mode ν19(a2g) in the perpendicular polarized spectrum of the complex suggests changes of the excited‐state geometry along the corresponding normal coordinate. Copyright © 2004 John Wiley & Sons, Ltd.
A parametrix construction for the fundamental solution of the evolution equation associated with a pseudo‐differential operator generating a Markov process
Authors: Böttcher Björn
Published: August 2005

We use the method proposed by H. Kumano‐go in the classical case to construct a parametrix of the equation $ \textstyle {{\partial u} \over {\partial t}}$ + q (x, D )u = 0 where q (x, D ) is a pseudo‐differential operator with symbol in the class introduced by W. Hoh. In case where –q (x, D ) extends to a generator of a Feller semigroup our construction yields an approximation for the transition densities of the corresponding Markov process. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
New versions of the Colombeau algebras
Authors: Shelkovich V. M.
Published: August 2005

We construct some versions of the Colombeau theory. In particular, we construct the Colombeau algebra generated by harmonic (or polyharmonic) regularizations of distributions connected with a half‐space and by analytic regularizations of distributions connected with an octant. Unlike the standard Colombeau's scheme, our theory has new generalized functions that can be easily represented as weak asymptotics whose coefficients are distributions, i.e., in form of asymptotic distributions . The algebra of asymptotic distributions generated by the linear span of associated homogeneous distributions (in the one‐dimensional case) which we constructed earlier [9] can be embedded as a subalgebra into our version of Colombeau algebra. The representation of distributional products in the form of weak asymptotic series proved very useful in solving problems which arise in the theory of discontinuous solutions of hyperbolic systems of conservation laws [10]–[16], [49] and [50]. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Global existence and nonexistence for a nonlinear wave equation with damping and source terms
Authors: Zhou Yong
Published: August 2005

In this paper we consider a nonlinear wave equation with damping and source term on the whole space. For linear damping case, we show that the solution blows up in finite time even for vanishing initial energy. The criteria to guarantee blowup of solutions with positive initial energy are established both for linear and nonlinear damping cases. Global existence and large time behavior also are discussed in this work. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Representation of the eigenvalues of the p ‐Laplacian by means of a surface integral
Authors: Lamberti Pier Domenico
Published: August 2005

We prove a natural generalization to the p ‐Laplacian of the celebrated Rellich identity. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Boundary value problems on manifolds with fibered boundary
Authors: Savin Anton , Sternin Boris
Published: August 2005

We define a class of boundary value problems on manifolds with fibered boundary. This class is in a certain sense a deformation between the classical boundary value problems and the Atiyah–Patodi–Singer problems in subspaces (it contains both as special cases). The boundary conditions in this theory are taken as elements of theC*‐algebra generated by pseudodifferential operators and families of pseudodifferential operators in the fibers. We prove the Fredholm property for elliptic boundary value problems and compute a topological obstruction (similar to Atiyah–Bott obstruction) to the existence of elliptic boundary conditions for a given elliptic operator. Geometric operators with trivial and nontrivial obstruction are given. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Diagnostic significance of reduced serum caeruloplasmin concentration in neurological disease
Authors: Walshe John M.
Published: August 2005

This study covers patients seen at a Wilson disease clinic between 1960 and 2002. The diagnosis of Wilson disease was confirmed in 316. Of 40 patients with a neurological presentation who were found not to have the disease, caeruloplasmin concentration was found to be reduced in 19. These 19 patients comprised 17 men and 2 women. The various diagnoses included Huntington's disease, multiple sclerosis, subacute sclerosing panencephalitis (SSPE), Hallervorden Spatz syndrome, and acaeruloplasminemia; in 9 no definite diagnosis was made. In view of the marked male preponderance, the lower limit of caeruloplasmin is calculated as for males. In an earlier study this was found to be 33.3 mg/dl (standard deviation, 6.1 mg/dl); therefore, 21.1 mg/dl is taken as the lower limit of normal. Particular attention is paid to 3 patients, 2 of whom had zero concentrations of caeruloplasmin and 1 had a very low level of the protein. Only 1 of these patients conformed to the classical picture of acaeruloplasminemia. The significance of a low caeruloplasmin concentration in patients with a variety of neurological syndromes is not clear but can lead to diagnostic confusion. When the concentration of this protein is very low or absent the diagnosis of acaeruloplasminemia must be considered. © 2005 Movement Disorder Society
On the stationary flows of viscous, incompressible and heat‐conducting fluids
Authors: Łukaszewicz Grzegorz
Published: August 2005

We consider a boundary‐value problem describing the motion of viscous, incompressible and heat‐conducting fluids in a bounded domain in ℝ3. We admit non‐homogeneous boundary conditions, the appearance of exterior forces and heat sources.

Our aim is to prove the existence of a solution of the problem in Sobolev spaces.
Singularities of the Laplacian at corners and edges of three‐dimensional domains and their treatment with finite element methods
Authors: Stephan E. , Whiteman J. R.
Published: August 2005

Three‐dimensional Poisson problems containing boundary singularities are treated. The forms of the solutions for certain problems of this type are derived, where the domains of the problems can be represented in terms either of spherical‐ or of cylindrical‐polar co‐ordinates. These singular forms are used to augment the basis of a standard piecewise polynomial Galerkin space, thus producing an augmented Galerkin technique which is suited to the context of a problem involving a singularity. Error estimates are derived.
Global existence for the Vlasov‐Poisson/Fokker‐Planck equation in many dimensions, for small data
Authors: Triolo L.
Published: August 2005

A global existence result for the Cauchy problem of the Vlasov equation with a diffusive term is given. Smallness of the initial data is needed to show, via a ‘dispersive’ argument, the existence and nearness of the solution to the free one.
Interpolation of coefficients and transformation of the dependent variable in finite element methods for the non‐linear heat equation
Authors: Larsson Stig , Thomée Vidar , Zhang Nai‐Ying , Wendland W.
Published: August 2005

Error estimates are shown for some spatially discrete Galerkin finite element methods for a non‐linear heat equation. The approximation schemes studied are based on the introduction of the enthalpy as a new dependent variable, and also on the application of the Kirchhoff transformation and on interpolation of the non‐linear coefficients into standard Lagrangian finite element spaces.
Non‐characteristic mixed problems for non‐linear symmetric hyperbolic systems
Authors: Zajaczkowski W. M. , Piskorek A.
Published: August 2005

In this paper the existence and uniqueness of solutions of the following initial boundary value problem for non‐linear symmetric hyperbolic equations of the first order

are shown, where M = I+ −S, has the same from as the Kreiss' condition, but S must be sufficiently small (I+ is the unit matrix in the space generated by eigenvectors of the matrix − A·n̄, corresponding to positive eigenvalues) and n̄ is a unit outward vector normal to the boundary. The main result of the paper is obtaining an a priori estimate for non‐linear equations. This estimate is obtained for sufficiently small time and norms of given data functions. The existence of solutions is proved by the method of successive approximations, which can be used because at each step such properties as symmetry of matrices and the numbers of positive and negative eigenvalues of the matrix − A·n̄ are assured. This can be done because we restrict our attention to such systems of equations for which these properties are satisfied for solutions from some neighbourhood of initial data u0. Therefore, using the fact that solutions in the class of continuous functions are sought, these properties can be satisfied for sufficiently small time. Moreover, some examples of initial boundary value problems for equations of hydrodynamics and magnetohydrodynamics are considered.
On properties of the iterative maximum likelihood reconstruction method
Authors: Mülthei H. N. , Schorr B. , Törnig W.
Published: August 2005

In this paper, we continue our investigations6on the iterative maximum likelihood reconstruction method applied to a special class of integral equations of the first kind, where one of the essential assumptions is the positivity of the kernel and the given right‐hand side. Equations of this type often occur in connection with the determination of density functions from measured data. There are certain relations between the directed Kullback–Leibler divergence and the iterative maximum likelihood reconstruction method some of which were already observed by other authors. Using these relations, further properties of the iterative scheme are shown and, in particular, a new short and elementary proof of convergence of the iterative method is given for the discrete case. Numerical examples have already been given in References 6. Here, an example is considered which can be worked out analytically and which demonstrates fundamental properties of the algorithm.
On stationary flows of asymmetric fluids with heat convection
Authors: Łukaszewicz Grzegorz , Waluś Włodzimierz , Piskorek A.
Published: August 2005

Existence, uniqueness and regularity of solutions of equations describing stationary flows of viscous incompressible isotropic fluids with an asymmetric stress tensor have been considered recently.5 In this paper we extend the results of Reference 5 to include heat convection in the hydrodynamic model. We show that the boundary value problem (1.1)–(1.6) below has solutions in appropriate Sobolev spaces, provided the viscosities v and ca + cd are sufficiently large. The proof is based on a fixed point argument. Moreover, we show that the solutions are unique if the heat conductivity κ is large enough.
A source density function
Authors: Lehnigk Siegfried H. , Roach G. F.
Published: August 2005

The delta function initial condition solution of the generalized Feller equation gives rise to a four‐parameter class of one‐sided probability source density functions. Because of this origin, each of these functions represents the instantaneous density of an autonomous Markov diffusion process. As the source location parameter approaches zero the density class to be investigated here reduces to the hyper‐Gamma class. Because of the immense flexibility in shape (as compared with the hyper‐Gamma class) the source density class offers itself to a wide variety of applications in physics and statistics, especially if the observations are far removed from zero. Relative to applications, the natural and paramount concern must be directed toward the parameter estimation problem. This paper provides the analytical foundation for a numerical approach to its solution. The log‐likelihood function for the source density class will be established. Based on it the maximum‐likelihood equations will be derived. For practical numerical reasons, direct maximization of the log‐likelihood function may be more successful than an attempt to solve the (three) maximum‐likelihood equations. Therefore, the analytical properties of the log‐likelihood function will be discussed, as they are essential in the implementation of any numerical optimization routine.
The electric field in the conductive half space as a model in mining and petroleum prospecting
Authors: Goldman Y. , Joly P. , Kern M. , Nedelec J. C.
Published: August 2005

We present a formulation of Maxwell's equations in a conductive medium, in the time domain. In order to restrict the equations to the conductive half space, the solution in the air is represented by an integral boundary operator on the interface. The problem admits a variational formulation, allowing a finite element solution. A mathematical analysis is described for 2D and 3D models, and numerical results are presented.
A penalty approximation for a unilateral contact problem in non‐linear elasticity
Authors: Gwinner J. , Brosowski B.
Published: August 2005

Using Ball's approach to non‐linear elasticity, and in particular his concept of polyconvexity, we treat a unilateral three‐dimensional contact problem for a hyperelastic body under volume and surface forces. Here the unilateral constraint is described by a sublinear function which can model the contact with a rigid convex cone. We obtain a solution to this generally non‐convex, semicoercive Signorinin problem as a limit of solutions of related energy minimization problems involving friction normal to the contact surface where the friction coefficient goes to infinity. Thus we extend an approximation result of Duvaut and Lions for linear‐elastic unilateral contact problems to finite deformations and to a class of non‐linear elastic materials including the material models of Ogden and of Mooney‐Rivlin for rubberlike materials.

Moreover, the underlying penalty method is shown to be exact, that is a sufficiently large friction coefficient in the auxiliary energy minimization problems suffices to produce a solution of the original unilateral problem, provided a Lagrange multiplier to the unilateral constraint exists.
Boundary control of a vibrating plate with internal damping
Authors: Leugering Günter , Schmidt E. J. P. Georg , Meister E.
Published: August 2005

It is shown that finite energy states of a vibrating viscoelastic plate of the Kelvin–Voigt type are, in general, not exactly controllable by L2‐boundary controls. Accordingly, we present a result on approximative controllability. The method is general.
Surface gradients and continuity properties for some integral operators in classical scattering theory
Authors: Kirsch A. , Hsiao G. C.
Published: August 2005

The surface gradients of some of the most important boundary integral operators for the time‐harmonic Helmholtz and Maxwell equations are computed. These results are used to give new and elementary proofs of the continuity properties of these boundary operators in Sobolev and Hölder spaces of arbitrary order.
Some decomposition theorems and their application to non‐linear potential theory and Hodge theory
Authors: Picard Rainer
Published: August 2005

The paper considers Dirichlet (or Neumann type) boundary value problems of generalized potential theory

on Lipschitz manifolds with boundary. Here ϵ denotes a permissible non‐linearity. The existence theory is developed in the framework of monotone operators. The approach covers a variety of applications including fluid dynamics and electro‐ and magneto‐statics. Only fairly weak regularity assumptions are required (e.g. Lipschitz boundary, L∞‐coefficients). As a by‐product we obtain a non‐linear Hodge theorem generalizing a result by L. M. Sibner and R. J. Sibner (‘A non‐linear Hodge‐DeRham theorem’, Acta Math., 125, 57–73 (1970)).