bluuebunny/crossref_metadata_2025_split huggingface dataset:
51V NMR Chemical Shifts Calculated from QM/MM Models of Vanadium Chloroperoxidase
Authors: Waller Mark P. , Bühl Michael , Geethalakshmi K. R. , Wang Dongqi , Thiel Walter 
Published: April 2007

Abstract51V NMR chemical shifts calculated from QM/MM‐optimized (QM=quantum mechanical; MM=molecular mechanical) models of vanadium‐dependent chloroperoxidase (VCPO) are presented. An extensive number of protonation states for the vanadium cofactor (active site of the protein) and a number of probable positional isomers for each of the protonation states are considered. The size of the QM region is increased incrementally to observe the convergence behavior of the 51V NMR chemical shifts. A total of 40 models are assessed by comparison to experimental solid‐state 51V NMR results recently reported in the literature. Isotropic chemical shifts are found to be a poor indicator of the protonation state; however, anisotropic chemical shifts and the nuclear quadrupole tensors appear to be sensitive to changes in the proton environment of the vanadium nuclei. This detailed investigation of the 51V NMR chemical shifts computed from QM/MM models provides further evidence that the ground state is either a triply protonated (one axial water and one equatorial hydroxyl group) or a doubly protonated vanadate moiety in VCPO. Particular attention is given to the electrostatic and geometric effects of the protein environment. This is the first study to compute anisotropic NMR chemical shifts from QM/MM models of an active metalloprotein for direct comparison with solid‐state MAS NMR data. This theoretical approach enhances the potential use of experimental solid‐state NMR spectroscopy for the structural determination of metalloproteins.
Wavelength shifts in solid‐state circular dichroism spectra: A possible explanation
Authors: Castiglioni Ettore , Abbate Sergio , Longhi Giovanna , Gangemi Roberto 
Published: April 2007

AbstractWe have devised an artificial sampling approach generating “absorption flattening” (AF) on the UV–Vis spectrum of a solution of a chiral compound: Tris (ethylendiamine)cobalt(III) chloride (Λ‐Co(en)3Cl3). We have observed a concomitant red shift of the CD maxima. Related CD and absorption spectra have been calculated from spectra recorded on diluted homogeneous solutions, thus monitoring the effect of AF on both types of data. Experimental data are in good agreement with calculated spectra. Simulations with suitable bandshapes show that the red shift of the CD spectrum is due to AF. On the basis of these results, we conclude that AF is an important cause of distortions in CD spectra for inhomogeneous samples. Plans to compensate or at least to take into account this effect are presented. Chirality, 2007. © 2007 Wiley‐Liss, Inc.
HPLC on chiral support with polarimetric detection: Application to conglomerate discovery
Authors: Roussel Christian , Vanthuyne Nicolas , Jobert Jean‐Laurent , Loas Andrei I. , Tanase Anca E. , Gherase Dragos 
Published: April 2007

AbstractIn conglomerates, each single crystal contains only one of the two possible enantiomeric forms—either dextrorotatory or levorotatory. The analysis of a single crystal by liquid chromatography on chiral support associated with chiroptical detection is a very efficient tool to reveal the occurrence of a conglomerate. In terms of rapidity and easiness, this method compares favorably with the classical methods used to show this occurrence. Two examples are provided. Chirality, 2007. © 2007 Wiley‐Liss, Inc.
Central limit theorems for extreme Sojourns of stationary Gaussian processes
Authors: Berman Simeon M. 
Published: April 2007

AbstractLet X(t), t ≧ 0, be a real stationary Gaussian process, and, for u > 0 and t >0, let Lt(u) be the time spent by X(s), 0 ≦ s ≦ t, above the level u. Here u is taken to be a function u(t) of t, and Lt is defined as Lt(u(t)). It is shown that the distribution of (Lt – ELt)/(Var Lt)1/2 converges, for t → ∞ and u(t) → ∞, to a standard normal distribution under various conditions relating the growth of u(t) to the decay of the covariance and other functions associated with it.
Electron transport in bifurcated tokamak equilibria
Authors: Garabedian Paul , Taylor Mark 
Published: April 2007

AbstractTransport of ions and electrons is calculated by the Monte Carlo method in tokamak plasmas without axial symmetry. Turbulence is modeled by time‐averaged equations of electrostatics and magnetostatics that describe quasineutrality and equilibrium. Good agreement with experimental measurements is obtained by allowing for small three‐dimensional asymmetries in the electric and magnetic fields.
Time series transformations in clocked queueing networks
Authors: Percus Ora E. , Percus J. K. 
Published: April 2007

AbstractWe consider a network in which message packets arriving on a clock cycle are directed along paths which may have segments in common. When they do, the messages involved are queued and transmitted, one per cycle. The statistics of queue length are investigated by an expansion of the time series in a channel about the regime of independent arrivals. Results for the second stage of such a network are in good agreement with computer simulations.
Regularity for quasilinear second‐order subelliptic equations
Authors: Xu Chao‐Jiang 
Published: April 2007

AbstractIn this paper, we study the regularity of solutions of the quasilinear equation

where X = (X1,…,Xm) is a system of real smooth vector fields, Aij, B ϵ C∞(Ω × ℝ Rm+1). Assume that X satisfies the Hörmander condition and (Aij(x, z,ζ)) is positive definite. We prove that if u ϵ S2,α(Ω) (see Section 2) is a solution of the above equation, then u ϵ C∞ (Ω).
Removal of boundary singularities of pseudo‐holomorphic curves with Lagrangian boundary conditions
Authors: Oh Yong‐Geun 
Published: April 2007

AbstractWe give a proof of the theorem of removing isolated singularities of pseudo‐holomorphic curves with Lagrangian boundary conditions and bounded symplectic area. The proof is a combination of some Lp‐type estimates, standard techniques of geometric P.D.E., and some ideas from symplectic geometry and calibration theory.
Solution of a nonlinear heat equation with arbitrarily given blow‐up points
Authors: Merle Frank 
Published: April 2007

AbstractWe consider the equation

where I ⊂ ℝ u is scalar‐valued and p > 1.It has been proven that if u(t) blows up at time T, the blow‐up points are finite in number and located in I°.Our aim is to prove that this result is optimal. That is, for any given points x1,…,xk in I° there is a solution u such that its blow‐up points are exactly x1,…,xk.
Stability of viscous shock waves associated with a system of nonstrictly hyperbolic conservations laws
Authors: Liu Tai‐Ping , Xin Zhouping 
Published: April 2007

AbstractWe introduce a simple model of two conservation laws which is strictly hyperbolic except for a degenerate parabolic line in the state space. Besides classical shock waves, it also exhibits overcompressive, marginal overcompressive, and marginal undercompressive shock waves. Our purpose is to study the behavior of the corresponding viscous waves, in particular the manner in which these waves are stable. There are several basic differences between classical shock waves and other types of shock waves. A perturbation of an overcompressive shock wave gives rise to a new wave. Monotone marginal overcompressive waves behave distinctly from the nonmonotone ones. Analytical techniques used in our study include characteristic‐energy and weighted‐energy methods, and nonlinear superposition through time‐invariants. Although we carry out our analysis for a simple model, the general phenomena would hold for overcompressive waves which occur in other physical models.
Axially symmetric harmonic maps minimizing a relaxed energy
Authors: Hardt Robert , Lin Fang‐Hua , Poon Chi‐Cheung 
Published: April 2007

AbstractHere we obtain various results on the class of axially symmetric harmonic maps from B3 to S2. We find some new classes of non‐minimizing harmonic maps exhibiting unusual singular behavior. Optimal partial regularity estimates are obtained for mappings which minimize, among axially symmetric maps, various relaxed energies which have been studied in [4]and [11].
Refined asymptotics for the blowup of ut — δu = up
Authors: Filippas Stathis , Kohn Robert V. 
Published: April 2007

AbstractThis work is concerned with positive, blowing‐up solutions of the semilinear heat equation ut — δu = up in Rn. Our main contribution is a sort of center manifold analysis for the equation in similarity variables, leading to refined asymptotics for u in a backward space‐time parabola near any blowup point. We also explore a connection between the asymptotics of u and the local geometry of the blowup set.
Phase transitions and generalized motion by mean curvature
Authors: Evans L. C. , Soner H. M. , Souganidis P. E. 
Published: April 2007

AbstractWe study the limiting behavior of solutions to appropriately rescaled versions of the Allen‐Cahn equation, a simplified model for dynamic phase transitions. We rigorously establish the existence in the limit of a phase‐antiphase interface evolving according to mean curvature motion. This assertion is valid for all positive time, the motion interpreted in the generalized sense of Evans‐Spruck and Chen‐Giga‐Goto after the onset of geometric singularities.
Solutions of superlinear elliptic equations and their morse indices
Authors: Bahri A. , Lions P. L. 
Published: April 2007

AbstractWe consider here solutions of semilinear second‐order elliptic equations with superlinear nonlinearities. And we present some relationships between their Morse Indices and some qualitative properties. In particular we show that for, “uo;subcritical” nonlinearities, bounds on solutions are equivalent to bounds on their Morse indices.
Morse theory for periodic solutions of hamiltonian systems and the maslov index
Authors: Salamon Dietmar , Zehnder Eduard 
Published: April 2007

AbstractIn this paper we prove Morse type inequalities for the contractible 1‐periodic solutions of time dependent Hamiltonian differential equations on those compact symplectic manifolds M for which the symplectic form and the first Chern class of the tangent bundle vanish over π2 (M). The proof is based on a version of infinite dimensional Morse theory which is due to Floer. The key point is an index theorem for the Fredholm operator which plays a central role in Floer homology. The index formula involves the Maslov index of nondegenerate contractible periodic solutions. This Maslov index plays the same role as the Morse index of a nondegenerate critical point does in finite dimensional Morse theory. We shall use this connection between Floer homology and Maslov index to establish the existence of infinitely many periodic solutions having integer periods provided that every 1‐periodic solution has at least one Floquet multiplier which is not equal to 1.
Undecidability results for restricted universally quantified formulae of set theory
Authors: Parlamento F. , Policriti A. 
Published: April 2007

AbstractThe problem of establishing whether there are sets satisfying a formula in the first order set theoretic language ℒ︁ϵ based on =,ϵ, which involves only restricted quantifiers and has an equivalent ∀∃‐prenex form ((∀∃)0‐formula), is neither decidable nor semidecidable. In fact, given any ω‐model of ZF – FA, where FA denotes the Foundation Axiom, the set of existential closures of (∀∃)0‐formulae true in the model is a productive set. Undecidability arises even when dealing with restricted universal quantifiers only, provided a predicate is_a_pair(x), meaning that x is a pair of distinct sets, is added to ℒ︁ϵ. If satisfiability refers to ω‐models of ZF – FA in which a form of Boffa's antifoundation axiom holds, then semidecidability fails as well; in fact, given any such model, the set of existential closures of formulae involving only restricted quantifiers and the predicate is_a_pair which are true in it, is a productive set. These results are all proved by making use of appropriate codings of Turing machine computations in the set theoretic language.
Solution of the inverse spectral problem for an impedance with integrable derivative part II
Authors: Coleman Carol Flynn , McLaughlin Joyce R. 
Published: April 2007

AbstractThe inverse eigenvalue problem for a Sturm‐Liouville equation in impedance form with Dirichlet boundary conditions on a unit interval is solved. The solution of this nonlinear problem requires the investigation of a combined map from the logarithmic derivative of the impedance, assumed to be square integrable, to two sequences of spectral data. The first is the sequence of Dirichlet eigenvalues, shown to be locally bounded with square roots differing from the sequence of integral multiples of π by a square summable sequence. The second sequence has as first term the mean of the logarithmic derivative of the impedance. Each term in the remainder of the sequence is the logarithm of the product of the impedance and the derivative of an eigenfunction evaluated at an endpoint. It is shown that this second sequence is a locally bounded square summable sequence.The combined map is a real analytic isomorphism. A uniqueness result follows from the asymptotics and analyticity shown in the first paper and properties of Riesz bases. The existence is shown by giving a closed form of the solution.It is also shown that the same map solves the inverse Sturm‐Liouville problem in impedance form with Neumann boundary conditions. © 1993 John Wiley & Sons, Inc.
On –δu = K(x)u5 in ℝ3
Authors: Li Yanyan 
Published: April 2007

AbstractIn this paper, we study the equation –Δu = K(x)u5 in ℝ3 and provide a large class of positive functions K(x) for which we obtain infinitely many positive solutions which decay at infinity at the rate of |x|−1. © 1993 John Wiley & Sons, Inc.
Decay rates for nonconvex systems of conservation laws
Authors: Zumbrun Kevin 
Published: April 2007

AbstractWe study decay of solutions for hyperbolic systems of conservation laws which are not genuinely nonlinear. For a generic class of such systems, we determine sharp (algebraic) rates of decay in the total variation of the wave speed, for solutions with compact initial support. Our analysis involves generalized characteristic arguments and the random choice difference scheme of Glimm. © 1993 John Wiley & Sons, Inc.
Space‐time large deviations for interacting particle systems
Authors: Pra P. Dai 
Published: April 2007

AbstractWe prove a process‐level large deviation principle for the space‐time empirical averages of continuous‐time systems on an infinite lattice. Our methods rely on the Donsker‐Varadhan large deviation theory for Markov processes, and allow us to express the rate function rather explicitly in terms of the Markov generator of the infinite particle system. We can prove our principle for a large class of spin systems with no particle exchange, as well as for infinite diffusion processes whose drift is the gradient of a finite range Hamiltonian. © 1993 John Wiley & Sons, Inc.
Stability of travelling waves for non‐convex scalar viscous conservation laws
Authors: Jones Christopher K. R. T. , Gardner Robert , Kapitula Todd 
Published: April 2007

AbstractTravelling waves of a viscous conservation law (so‐called viscous profiles) are shown to be stable in polynomialy weighted L∞ spaces. There is no assumption of convexity on the nonlinear term and thus earlier results of Il'in and Oleǐnik, Sattinger, and Kawashima and Matsumura are generalized. The method uses the semigroup of the linearized equation with solutions of the full problem expressed by the variation of constants formula. Estimates are derived for the semigroup through a new technique for estimating the resolvent. © 1993 John Wiley & Sons, Inc.
Zero relaxation and dissipation limits for hyperbolic conservation laws
Authors: Chen Gui‐Qiang , Liu Tai‐Ping 
Published: April 2007

AbstractWe are interested in hyperbolic systems of conservation laws with relaxation and dissipation, particularly the zero relaxation limit. Such a limit is of interest in several physical situations, including gas flow near thermo‐equilibrium, kinetic theory with small mean free path, and viscoelasticity with vanishing memory. In this article we study hyperbolic systems of two conservation laws with relaxation. For the stable case where the equilibrium speed is subcharacteristic with respect to the frozen speeds, we illustrate for a model in viscoelasticity that no oscillation develops for the nonlinear system in the zero relaxation limit. For the marginally stable case where the equilibrium speed may equal one of the frozen speeds, we show for a model in phase transitions that no oscillation arises when the dissipation is present and goes to zero more slowly than the relaxation. Our analysis includes the construction of suitable entropy pairs to derive energy estimates. We need such energy estimates not only for the compactness properties but also for the deviation from the equilibrium of the solutions for the relaxation systems. The theory of compensated compactness is then applied to study the oscillation in the zero relaxation limit. © 1993 John Wiley & Sons, Inc.
Periodic limit of inverse scattering
Authors: Zhang Taiyan , Venakides Stephanos 
Published: April 2007

AbstractI t is well known that a p‐periodic potential Q(x) can be reconstructed from spectral data of the corresponding Hill operator −(d2/dx2) + Q(x) in terms of a Riemann θ‐function. We regard the periodic potential Q(x) as the pointwise limit of a scattering potential QN,c(x) (defined to equal Q(x) when −Np ≦ x ≦ Np, to equal zero when x < Np) and to equal c2 when x > (Np) as N → ∞ and c2 → ∞. The scattering potential QN,c(x) can be recovered from the scattering data of the corresponding Schrödinger operator in terms of a Dyson determinant according to a well known‐theory. We derive the Riemann θ‐function corresponding to the periodic potential Q(x) by taking the above limit of the Dyson determinant for the scattering potential.We first calculate the scattering data of the potential QN,c(x) through recursive formulas in terms of the left transmission and reflection coefficients T and R of the potential which is equal to Q(x) when 0 ≦ x ≦ p and equal to zero otherwise. We use these data to express the Dyson determinant of QN,c(x). We then expand the Dyson determinant into a Fredholm series and compute the main contributions to the expansion in the asymptotic limit N → ∞ and c2 → ∞ using a method developed by Lax, Levermore, and Venakides in their study of the small dispersion limit of the initial value problem of Korteweg‐de Vries equation. The computation of the leading order contributions reduces to a quadratic functional maximization problem constrained by a positivity condition and by a mass quantization condition. The solutions to this maximization problem constitute the differentials on a Riemann surface, the main ingredients for the Riemann θ‐function corresponding to the periodic potential. The limit of the Dyson determinant for QN,c(x) as N → ∞ and c2 → ∞ is shown to equal the exact Riemann θ‐function corresponding to the periodic potential Q(x) times an exponential function with exponent being a quadratic polynomial in x. Our calculation includes the correct phase shifts of the θ‐function. © 1993 John Wiley & Sons, Inc.
Sup‐norm stability for Glimm's scheme
Authors: Young Robin 
Published: April 2007

AbstractWe consider the Cauchy problem for a general N × N system of conservation laws. Existence of solutions was proved by Glimm using his celebrated random choice scheme. In this paper, we obtain a third‐order interaction estimate analagous to that obtained by Glimm for 2×2 systems. By using this estimate, and identifying a global cancellation effect, we obtain L∞‐stability for solutions generated by Glimm's scheme. As an immediate consequence we have L1‐stability and L∞‐decay, obtained by Temple for 2×2 systems. © 1993 John Wiley & Sons, Inc.
Analytic dependence of riemann mappings for bounded domains and minimal surfaces
Authors: Wu Sijue 
Published: April 2007

AbstractIn this paper, we prove that the functional which takes a closed Lavrentiev curve to the corresponding Riemann mapping is locally Lipl on the set Ω of all closed Lavrentiev curves. This set is a subset of BMO(T). It is, however, not open in BMO(T). We also prove that the previous functional is analytic for certain classes of closed Lavrentiev curves, including the class of curves which have some symmetry with respect to the unit circle. These classes of curves are submanifolds of BMO(T). Finally, we consider the functional which takes a Lavrentiev curve (closed or not) in n‐dimensional Euclidean space to the corresponding minimal surface, and we study the differentiability and analyticity of this functional on certain function spaces. © 1993 John Wiley & Sons, Inc.
Newton's method and periodic solutions of nonlinear wave equations
Authors: Craig Walter , Wayne C. Eugene 
Published: April 2007

AbstractWe prove the existence of periodic solutions of the nonlinear wave equation

satisfying either Dirichlet or periodic boundary conditions on the interval [O, π]. The coefficients of the eigenfunction expansion of this equation satisfy a nonlinear functional equation. Using a version of Newton's method, we show that this equation has solutions provided the nonlinearity g(x, u) satisfies certain generic conditions of nonresonance and genuine nonlinearity. © 1993 John Wiley & Sons, Inc.
Disorder of particle chains as a dynamical problem of transition to chaos: Analogy to simulation induced chaos
Authors: Beloshapkin V. V. , Tretyakov A. G. , Zaslavsky G. M. 
Published: April 2007

AbstractThe problem of the equilibria of particle chains with nearest and next‐to‐nearest neighbor interaction has been reduced to the dynamical system, given by 4D or 2D web‐maps. It is shown that at the same time these maps can represent difference schemes for differential equations used in computational simulation. An analogy between particle disordering, dynamical chaos, and simulation induced chaos is established. © 1994 John Wiley & Sons, Inc.
On the zeros of some continuous analogues of matrix orthogonal polynomials and a related extension problem with negative squares
Authors: Dym Harry 
Published: April 2007

AbstractA new proof of a recent theorem of Ellis, Gohberg, and Lay, which identifies the number of roots of a “continuous” matrix orthogonal polynomial in the open upper halfplane with the number of negative eigenvalues of a related integral operator is presented. A related extension problem is then formulated and solved in assorted classes of functions which are analytic in the open upper half plane, apart from a finite number of poles. A discrete analogue of this extension problem is also formulated and solved. © 1994 John Wiley & Sons, Inc.
Sets of conductivity and elasticity tensors stable under lamination
Authors: Francfort Gilles A. , Milton Graeme W. 
Published: April 2007

AbstractA complete characterization is obtained of any set of constitutive (conductivity or elasticity) tensors that is stable under lamination between any two of the elements of the set. The conditions are local and are expressed in terms of the curvature and tangent plane at points on the boundary of the set. They are checked to hold for several well‐known examples of sets stable under a more general process of homogenization. A companion paper investigates the link between these conditions and quasiconvexity. © 1994 John Wiley & Sons, Inc.
A Unified theory of tokamaks and stellarators
Authors: Garabedian P. R. 
Published: April 2007

AbstractComputational methods are described to study the equilibrium, stability, and transport of a fusion plasma confined by a magnetic field with toroidal geometry. Misconceptions in conventional theories of transport are analyzed and new results more consistent with experimental observations are presented. Specifications are given for an advanced stellarator designed to compete with tokamaks as a fusion reactor. © 1994 John Wiley & Sons, Inc.