bluuebunny/crossref_metadata_2025_split huggingface dataset:
Qualitative analysis of radiating breathers
Authors: Birnir Björn 
Published: April 2007

AbstractPerturbed sine‐Gordon equations are investigated numerically to see if they have breather solutions. It is shown that breathers radiate, blow up, and split into kink‐antikink pairs under most perturbations. The two perturbations proven by Birnir, McKean, and Weinstein not to produce radiation, of the first order in the perturbation parameter, a sin(u) + b ucos(u) and 1+3cos(u) ‐ 4cos(u/2) + 4cos(u)log(cos(u/4)), stop radiating first‐order radiation after adjusting the initial breather by the emission of such radiation. The first perturbation is a scaling of the breather, the second is shown to give a quasi‐periodic orbit, which is a two‐breather, on a torus. © 1994 John Wiley & Sons, Inc.
Speed of parallel processing for random task graphs
Authors: Isopi Marco , Newman Charles M. 
Published: April 2007

AbstractThe random graph model of parallel computation introduced by Gelenbe et al. depends on three parameters: n, the number of tasks (vertices); F, the common distribution of T1,…︁, Tn, the task processing times, and p = pn, the probability for a given i < j that task i must be completed before task j is started. The total processing time is Rn, the maximum sum of Ti's along directed paths of the graph. We study the large n behavior of Rn when npn grows sublinearly but superlogarithmically, the regime where the longest directed path contains about enpn tasks. For an exponential (mean one) F, we prove that Rn is about 4npn. The “discrepancy” between 4 and e is a large deviation effect. Related results are obtained when npn grows exactly logarithmically and when F is not exponential, but has a tail which decays (at least) exponentially fast. © 1994 John Wiley L Sons, Inc.
Asymptotics of heavy atoms in high magnetic fields: I. Lowest landau band regions
Authors: Lieb Elliott H. , Solovej Jan Philip , Yngvason Jakob 
Published: April 2007

AbstractThe ground state energy of an atom of nuclear charge Ze in a magnetic field B is evaluated exactly to leading order as Z → ∞. In this and a companion work (see [28]) we show that there are five regions as Z → ∞: B < Z4/3, B ∼ Z4/3, Z4/3 < B < Z3, B ∼ Z3, B > Z3. Regions 1, 2, 3, and 4 (and conceivably 5) are relevant for neutron stars. Different regions have different physics and different asymptotic theories. Regions 1, 2, and 3 are described by a simple density functional theory of the semiclassical Thomas‐Fermi form. Here we concentrate mainly on regions 4 and 5 which cannot be so described, although 3, 4, and 5 have the common feature (as shown here) that essentially all electrons are in the lowest Landau band. Region 5 does have, however, a simple non‐classical density functional theory (which can be solved exactly). Region 4 does not, but, surprisingly, it can be described by a novel density matrix functional theory. © 1994 John Wiley & Sons, Inc.
Smooth approximation of mather sets of monotone twist mappings
Authors: Moser JÜRgen 
Published: April 2007

AbstractIn the theory of monotone twist mappings of a cylinder one constructs for every rotation number α invariant minimal sets Mα. In this paper an approximation of these Mather sets by smooth invariant curves Mvα is devised, which for v → 0 converge to Mα almost everywhere. The main point of the construction is that the approximating curves Mvα form for v > 0 a smooth foliation. The approximation is achieved with the help of a regularized version of the Percival variational problem. © 1994 John Wiley & Sons, Inc.
Pointwise fourier inversion and related eigenfunction expansions
Authors: Pinsky Mark A. 
Published: April 2007

AbstractNecessary and sufficient conditions are found for the convergence at a pre‐assigned point of the spherical partial sums (resp. integrals) of the Fourier series (resp. integral) in the class of piecewise smooth functions on Euclidean space. These results carry over unchanged to spherical harmonic expansions, Fourier transforms on hyperbolic space, and Dirichlet eigenfunction expansions with respect to the Laplace operator on a class of Riemannian manifolds. © 1994 John Wiley & Sons, Inc.
Finite dimensional lie‐poisson approximations to vlasov‐poisson equations
Authors: Scovel Clint , Weinstein Alan 
Published: April 2007

AbstractMany of the basic equations of conservative continuum mechanics (Euler, Vlasov‐Poisson, Vlasov‐Maxwell, MHD, etc.) are Hamiltonian systems with respect to Lie‐Poisson brackets on dual spaces of infinite dimensional Lie algebras. The development of Lie‐Poisson integrators for finite dimensional Lie‐Poisson systems has shown that they are superior in the numerical simulations of these systems, especially with regard to long term phenomena.This paper shows how to truncate one of these systems, the Vlasov‐Poisson equation of plasma physics, to a finite dimensional Lie‐Poisson system. This requires replacing the functions on single‐particle phase space, with their Poisson bracket Lie algebra structure, by a finite dimensional Lie algebra. Replacing the densities by their moments of order up to k about a fixed reference point corresponds to replacing the functions by their Taylor expansions up to order k. Unfortunately, these truncated Taylor expansions do not form a Lie algebra, since the functions which vanish through order k do not form an ideal under Poisson bracket. Geometrically, this corresponds to the fact that canonical transformations which fix the reference point do not form a normal subgroup.Introducing the location of a reference point in phase space as an extra variable and truncating with respect to this moving point turns out to decouple the “location” from “shape” coordinates of a lump of density in phase space, as far as the Poisson bracket is concerned. One can then replace the shape coordinates by a finite number of moments.The central result of the paper is a construction of the decoupling map described above in the general context of the decomposition of a Lie group as a product of subgroups. The main theorem is first proved by the general theory of Poisson reduction, then by explicit calculation, and lastly by showing that the Poisson isomorphism follows from the lift of a natural groupoid isomorphism. The groupoid aspect of the theory also provides natural Poisson maps, useful in the application of Ruth‐type integration techniques, which do not seem easily derivable from the general theory of Poisson reduction. © 1994 John Wiley & Sons, Inc.
Stochastic levi sums
Authors: Watanabe Shinzo 
Published: April 2007

AbstractAn analogy of Levi sums is considered for a class of stochastic partial differential equations to construct their stochastic fundamental solutions. These notions are shown to coincide with Donsker's delta functions, typical generalized Wiener functionals, which have been studied in the frame of the Malliavin calculus. © 1994 John Wiley & Sons, Inc.
On the nonlinear stability of plane waves for the ginzburg‐landau equation
Authors: Kapitula Todd 
Published: April 2007

AbstractI consider the nonlinear stability of plane wave solutions to a Ginzburg‐Landau equation with additional fifth‐order terms and cubic terms containing spatial derivatives. I show that, under the constraint that the diffusion coefficient be real, these waves are stable. Furthermore, it is shown that the radial component of the perturbation decays at a faster rate than the phase component of the perturbation as t → ∞. The result is also applicable to the classical Ginzburg‐Landau equation. © 1994 John Wiley & Sons, Inc.
The rate function of hypoelliptic diffusions
Authors: Arous Gérard Ben , Deuschel Jean‐Dominique 
Published: April 2007

AbstractLet be a hypoelliptic diffusion operator on a compact manifold M. Given an a priori smooth reference measure λ on M, we can then rewrite L as the sum of a λ‐symmetric part L0 and a first‐order drift part Y. The paper investigates the effect of the drift Y on the Donsker‐Varadhan rate function corresponding to the large deviations of the empirical measure of the diffusion. When Y is in the linear span of the first and second‐order Lie brackets of the Xi's, we derive an affine bound relating the rate functions associated with L and L0. As soon as one point exists where Y is not in the linear span of the first and second‐order Lie brackets of the Xi's, we show that such an affine bound is impossible. © 1994 John Wiley & Sons, Inc.
The spectral theory for a pencil of skewsymmetrical differential operators of the third order
Authors: Gelfand Israel M. , Zakharevich Ilya 
Published: April 2007

AbstractWe consider the linear algebra of a pair of skewsymmetrical forms in the space of periodic functions defined by differential operators. By linear transform in the space of functions we reduce this pair to the simplest possible form. In this process, we prove the theorem of reduction in rather general context. © 1994 John Wiley & Sons, Inc.
L1 asymptotic behavior of compressible, isentropic, viscous 1‐D flow
Authors: Zeng Yanni 
Published: April 2007

AbstractWe study the large time behavior in L1 of the compressible, isentropic, viscous 1‐D flow. Under the assumption that the initial data are smooth and small, we show that the solutions are approximated by the solutions of a parabolic system, and in turn by diffusion waves, which are solutions of Burgers equations. Decay rates in L1 are obtained. Our method is based on the study of pointwise properties in the physical space of the fundamental solution to the linearized system. © 1994 John Wiley & Sons, Inc.
Convergence of euler‐stokes splitting of the navier‐stokes equations
Authors: Beale J. Thomas , Greengard Claude 
Published: April 2007

AbstractWe consider approximation by partial time steps of a smooth solution of the Navier‐Stokes equations in a smooth domain in two or three space dimensions with no‐slip boundary condition. For small k > 0, we alternate the solution for time k of the inviscid Euler equations, with tangential boundary condition, and the solution of the linear Stokes equations for time k, with the no‐slip condition imposed. We show that this approximation remains bounded in H2,p and is accurate to order k in Lp for p > ∞. The principal difficulty is that the initial state for each Stokes step has tangential velocity at the boundary generated during the Euler step, and thus does not satisfy the boundary condition for the Stokes step. The validity of such a fractional step method or splitting is an underlying principle for some computational methods. © 1994 John Wiley & Sons, Inc.
On the numerical solution of two‐point boundary value problems II
Authors: Starr Page , Rokhlin Vladimir 
Published: April 2007

AbstractIn a recent paper (L. Greengard and V. Rokhlin, On the Numerical Solution of Two‐Point Boundary Value Problems. in Communications on Pure and Applied Mathematics, Volume XLIV, 1991, pages 419‐452). L. Greengard and V. Rokhlin introduce a numerical technique for the rapid solution of integral equations resulting from linear two‐point boundary value problems for second‐order ordinary differential equations. In this paper, we extend the method to systems of ordinary differential equations. After reducing the system of differential equations to a system of second kind integral equations, we discretize the latter via a high‐order Nyström scheme. A somewhat involved analytical apparatus is then constructed which allows for the solution of the discrete system using O(N.p2.n3) operations with N the number of nodes on the interval, p the desired order of convergence, and n the number of equations in the system. Thus, the advantages of the integral equation formulation (small condition number, insensitivity to boundary layers, insensitivity to endpoint singularities, etc.) are retained, while achieving a computational efficiency previously available only to finite difference or finite element methods.We in addition present a Newton method for solving boundary value problems for nonlinear first‐order systems in which each Newton iterate is the solution of a second kind integral equation; the analytical and numerical advantages of integral equations are thus obtained for nonlinear boundary value problems. © 1994 John Wiley & Sons. Inc.
Hydrodynamical limit for a nongradient system: The generalized symmetric exclusion process
Authors: Kipnis C. , Landim C. , Olla S. 
Published: April 2007

AbstractWe consider a symmetric simple exclusion process where at most two particles per site are permitted. This model turns out to be nongradient. We prove that the particles' densities, under a diffusive rescaling of space and time, converge to the solution of a diffusion equation. We give a variational characterization of the diffusion coefficent. We also prove, for the generator of the process in finite volume, a lower bound on the spectral gap uniform in the volume. © 1994 John Wiley & Sons, Inc.
Morse‐type information on palais‐smale sequences obtained by min‐max principles
Authors: Fang G. , Ghoussoub N. 
Published: April 2007

AbstractIn the context of the min‐max approach to critical point theory, but without the usual compactness assumptions à la Palais‐Smale and the nondegeneracy conditions à la Fredholm, we construct almost critical points with two‐sided estimates on their approximate Morse indices which are arbitrarily close to certain—a priori given—dual sets. This additional topological and analytical information about almost critical sequences can sometimes be crucial in the proof of their convergence and therefore in solving the corresponding variational problem. © 1994 John Wiley & Sons, Inc.
Adaptive finite element methods for conservation laws based on a posteriori error estimates
Authors: Johnson Claes , Szepessy Anders 
Published: April 2007

AbstractWe prove a posteriori error estimates for a finite element method for systems of strictly hyperbolic conservation laws in one space dimension, and design corresponding adaptive methods. The proof of the a posteriori error estimates is based on a strong stability estimate for an associated dual problem, together with the Galerkin orthogonality of the finite‐element method. The strong stability estimate uses the entropy condition for the system in an essential way. ©1995 John Wiley & Sons, Inc.
Nonparabolic dissipative systems modeling the flow of liquid crystals
Authors: Lin Fang‐Hua , Liu Chun 
Published: April 2007

AbstractWe study a simplified system which retains most of the interesting mathematical properties of the original Ericksen‐Leslie equations for the flow of liquid crystals. This is a coupled nonparabolic dissipative dynamic system. We derive several energy laws which enable us to prove the global existence of the weak solutions and the classical solutions. We also discuss uniqueness and some stability properties of the system. ©1995 John Wiley & Sons, Inc.
Stability theory for dissipatively perturbed hamiltonian systems
Authors: Maddocks John H. , Overton Michael L. , Maddocks John H. , Overton Michael L. 
Published: April 2007

AbstractIt is shown that for an appropriate class of dissipatively perturbed Hamiltonian systems, the number of unstable modes of the dynamics linearized at a nondegenerate equilibrium is determined solely by the index of the equilibrium regarded as a critical point of the Hamiltonian. In addition, the movement of the associated eigenvalues in the limit of vanishing dissipation is analyzed. ©1995 John Wiley & Sons,
Inc.
Forced lattice vibrations: Part II
Authors: Deift Percy , Kriecherbauer Thomas , Venakides Stephanos 
Published: April 2007

AbstractThis is the second part of a two‐part series on forced lattice vibrations in which a semi‐infinite lattice of one‐dimensional particles {xn}n≧1,magnified image is driven from one end by a particle x0. This particle undergoes a given, periodically perturbed, uniform motion x0(t) = 2at + h(yt) where a and γ are constants and h(·) has period 2π. Results and notation from Part I are used freely and without further comment. Here the authors prove that sufficiently ample families of traveling‐wave solutions of the doubly infinite system magnified image exist in the cases γ > γ1 and γ1 > γ > γ2 for general restoring forces F. In the case with Toda forces, F(x) = ex, the authors prove that sufficiently ample families of traveling‐wave solutions exist for all k, γk > γ > γk+1. By a general result proved in Part I, this implies that there exist time‐periodic solutions of the driven system (i) with k‐phase wave asymptotics in n of the type magnified image with k = 0 or 1 for general F and k arbitrary for F(x) = ex (when k = 0, take γ0 = ∞ and X0 ≡ 0).
Addendum to “Floer Cohomology of Lagrangian Intersections and Pseudo‐Holomorphic Discs, I”
Authors: Oh Yong‐Geun 
Published: April 2007

AbstractThis is an addendum to the author's earlier paper “Floer Cohomology of Lagrangian Intersection and Pseudo‐Holomorphic Discs, I,” Comm. Pure Appl. Math. 46, 1993, pp. 949–993. The main result of this addendum extends the definition of the Floer cohomology of Lagrangian intersection to the case where the minimal Maslov number is equal to 2. ©1996 John Wiley & Sons, Inc.
Simultaneous Tuning of Chemical Composition and Topography of Copolymer Surfaces: Micelles as Building Blocks
Authors: Zhao Ning , Zhang Xiaoyan , Zhang Xiaoli , Xu Jian 
Published: April 2007

AbstractA simple method is described for controlling the surface chemical composition and topography of the diblock copolymer poly(styrene)‐b‐poly(dimethylsiloxane)(PS‐b‐PDMS) by casting the copolymer solutions from solvents with different selectivities. The surface morphology and chemical composition were characterized by scanning electron microscopy (SEM) and X‐ray photoelectron spectroscopy (XPS), respectively, and the wetting behavior was studied by water contact angle (CA) and sliding angle (SA) and by CA hysteresis. Chemical composition and morphology of the surface depend on solvent properties, humidity of the air, solution concentration, and block lengths. If the copolymer is cast from a common solvent, the resultant surface is hydrophobic, with a flat morphology, and dominated by PDMS on the air side. From a PDMS‐selective solvent, the surface topography depends on the morphology of the micelles. Starlike micelles give rise to a featureless surface nearly completely covered by PDMS, while crew‐cut‐like micelles lead to a rough surface with a hierarchical structure that consists partly of PDMS. From a PS‐selective solvent, however, surface segregation of PDMS was restricted, and the surface morphology can be controlled by vapor‐induced phase separation. On the basis of the tunable surface roughness and PDMS concentration on the air side, water repellency of the copolymer surface could be tailored from hydrophobic to superhydrophobic. In addition, reversible switching behavior between hydrophobic and superhydrophobic can be achieved by exposing the surface to solvents with different selectivities.
Molecular Dynamics Simulations of CN− Dynamics and Spectroscopy in Myoglobin
Authors: Danielsson Jonas , Meuwly Markus 
Published: April 2007

AbstractThe vibrational dynamics of the cyanide anion and the heme group in MbCN (CN complexed to Myoglobin) are investigated using molecular dynamics simulations. A previously calculated quantum‐chemical heme–ligand potential‐energy surface together with a three‐center charge model for the iron–ligand center that captures both polarization and ligand‐to‐metal charge transfer allows for a detailed description of the interactions around the active site. It is found that the CN binding orientation (FeCN or FeNC) to the heme affects the stretching frequency of the ligand, with a 25 cm−1 difference in the fundamental wavenumber between the two orientations as well as a change in bond length. The charge model also captures such crucial interactions as the possible hydrogen bond between the ligand and the His64 residue. This interaction is weakened when the ligand binds in the FeNC conformation but is also sensitive to the protonation state of His64. The structural changes around the active site, the observation of water penetration for the FeNC conformation, the computed IR spectrum, and the energetics suggest that the FeCN conformation with Hisε64 is the most likely one. The water accessibility of the active site is also found to be related to the protonation state of His64. The presence of water in the active site could also affect the IR band of the CN stretch mode. Thus, IR spectroscopy of the CN stretch is a potentially useful reporter of ligand isomers and active‐site structure.
Repetitive Reversible Labeling of Proteins at Polyhistidine Sequences for Single‐Molecule Imaging in Live Cells
Authors: Guignet Emmanuel G. , Segura Jean‐Manuel , Hovius Ruud , Vogel Horst 
Published: April 2007

AbstractSensitive live‐cell fluorescence microscopy and single‐molecule imaging are severely limited by rapid photobleaching of fluorescent probes. Herein, we show how to circumvent this problem using a novel, generic labeling strategy. Small nickel–nitrilotriacetate fluorescent probes are reversibly bound to oligohistidine sequences of exposed proteins on cell surfaces, permitting selective observation of the proteins by fluorescence microscopy. Photobleached probes are removed by washing and replaced by new fluorophores, thus enabling repetitive acquisition of single‐molecule trajectories on the same cell and allowing variation of experimental conditions between acquisitions. This method offers free choice of fluorophores while being minimally perturbing. The strength of the method is demonstrated by labeling engineered polyhistidine sequences of the serotonin‐gated 5‐HT3 receptor on the surface of live mammalian cells. Single‐molecule microscopy reveals pronounced heterogeneous mobility patterns of the 5‐HT3 receptor. After activating the receptor with serotonin, the number of immobile receptors increases substantially, which might be important for receptor regulation at synapses.
LMAN lesions prevent song degradation after deafening without reducing HVC neuron addition
Authors: Scott Luisa L. , Nordeen Ernest J. , Nordeen Kathy W. 
Published: April 2007

AbstractIn some songbirds perturbing auditory feedback can promote changes in song structure well beyond the end of song learning. One factor that may drive vocal change in such deafened birds is the ongoing addition of new vocal‐motor neurons into the song system. Without auditory feedback to guide their incorporation, the addition of these new neurons could disrupt the established song pattern. To assess this hypothesis, the authors determined if neuronal recruitment into the vocal motor nucleus HVC is affected by neural signals that influence vocal change in adult deafened birds. Such signals appear to be conveyed via LMAN, a nucleus in the anterior forebrain that is necessary for vocal change after deafening. Here the authors tested whether LMAN lesions might restrict song degradation after deafening by reducing the addition or survival of new HVC neurons that would otherwise corrupt the ongoing song pattern. Using [3H]thymidine autoradiography to identify neurons generated in adult zebra finches, it was shown here that LMAN lesions do not reduce the number or percent of new HVC neurons surviving for either several weeks or months after [3H]thymidine labeling. However, the authors confirmed previous reports that LMAN lesions restrict vocal change after deafening. These data suggest that neurons incorporated into the adult HVC may form behaviorally adaptive connections without requiring auditory feedback, and that any role such neurons may play in promoting vocal change after adult deafening requires anterior forebrain pathway output. © 2007 Wiley Periodicals, Inc. Develop Neurobiol, 2007.