bluuebunny/crossref_metadata_2025_split huggingface dataset:
Surface energy and microstructure in coherent phase transitions
Authors: Kohn Robert V. , Müller Stefan 
Published: April 2007

AbstractWe study a variational problem involving a nonconvex function of Δu, regularized by a higher order term. The motivation comes from the theory of martensitic phase transformation—specifically, a model for the fine scale structure of twinning near an austenite‐twinned‐martensite interface. It is widely believed that the fine scale structure can be understood variationally, through the minimization of elastic and surface energy. Our problem represents the essence of this minimization.Similar variational problems have been considered by many authors in the materials science literature. They have always assumed, however, that the twinning should be essentially one‐dimensional. This is in general false. Energy minimization can require a complex pattern of twin branching near the austenite interface. There are indications that the states of minimum energy may be asymptotically self‐similar. © 1994 John Wiley & Sons., Inc.
The τ‐function of the universal whitham hierarchy, matrix models and topological field theories
Authors: Krichever I. M. 
Published: April 2007

AbstractThe universal Whitham hierarchy is considered from the viewpoint of topological field theories. The τ‐function is defined for this hierarchy. It is proved that the algebraic orbits of Whitham hierarchy can be identified with various topological matter models coupled with topological gravity. © 1994 John Wiley & Sons, Inc.
Hyperbolic conservation laws with stiff relaxation terms and entropy
Authors: Chen Gui‐Qiang , Levermore C. David , Liu Tai‐Ping 
Published: April 2007

AbstractWe study the limiting behavior of systems of hyperbolic conservation laws with stiff relaxation terms. Reduced systems, inviscid and viscous local conservation laws, and weakly nonlinear limits are derived through asymptotic expansions. An entropy condition is introduced for N × N systems that ensures the hyperbolicity of the reduced inviscid system. The resulting characteristic speeds are shown to be interlaced with those of the original system. Moreover, the first correction to the reduced system is shown to be dissipative. A partial converse is proved for 2 × 2 systems. This structure is then applied to study the convergence to the reduced dynamics for the 2 × 2 case. © 1994 John Wiley & Sons, Inc.
Existence and positivity of solutions of a fourth‐order nonlinear PDE describing interface fluctuations
Authors: Bleher Pavel M. , Lebowitz Joel L. , Speer Eugene R. 
Published: April 2007

AbstractWe study the partial differential equation magnified image which arose originally as a scaling limit in the study of interface fluctuations in a certain spin system. In that application x lies in R, but here we study primarily the periodic case × R S1. We establish existence, uniqueness, and regularity of solutions, locally in time, for positive initial data in H1(S1), and prove the existence of several families of Lyapunov functions for the evolution. From the latter we establish a sharp connection between existence globally in time and positivity preservation: if [0], T*) is a maximal half open interval of existence for a positive solution of the equation, with T* < ∞, then limtT* w(t,·) exists in C1(S1) but vanishes at some point. We show further that if T* > (1 + √3)/16π2 √3 then T* = ∞ and limt∞ w(t,.) exists and is constant. We discuss also some explicit solutions and propose a generalization to higher dimensions. © 1994 John Wiley & Sons, Inc.
Decision algorithms for elementary topology I. Topological syllogistics with set and map constructs, connectedness, and cardinality comparison
Authors: Cantone Domenico , Cutello Vincenzo 
Published: April 2007

AbstractIn this paper we give a decision procedure for a topological syllogistic, denoted ℒ2,∞, involving, besides the standard Boolean set operators (∩, ∩, ′ (set complementation)) and predicates ( ϵ (membership), = (equality)), also the Kuratowski closure operator, continuous and closed maps with the notion of direct and inverse images, surjectivity and injectivity, as well as point evaluation, the singleton operator {·}, a predicate for comparing the cardinalities of two given sets, and a predicate expressing that a given set is topologically connected. Several examples are also discussed. © 1994 John Wiley & Sons, Inc.
The relaxation schemes for systems of conservation laws in arbitrary space dimensions
Authors: Jin Shi , Xin Zhouping 
Published: April 2007

AbstractWe present a class of numerical schemes (called the relaxation schemes) for systems of conservation laws in several space dimensions. The idea is to use a local relaxation approximation. We construct a linear hyperbolic system with a stiff lower order term that approximates the original system with a small dissipative correction. The new system can be solved by underresolved stable numerical discretizations without using either Riemann solvers spatially or a nonlinear system of algebraic equations solvers temporally. Numerical results for 1‐D and 2‐D problems are presented. The second‐order schemes are shown to be total variation diminishing (TVD) in the zero relaxation limit for scalar equations. ©1995 John Wiley & Sons, Inc.
Symmetry of the blow‐up set of a porous medium type equation
Authors: Gui Changfeng 
Published: April 2007

AbstractWe study the blow‐up set of a porous medium type equation with source. Under some technical conditions, we prove that if the blow‐up set is a bounded smooth region, then it must be a ball with a certain radius. This problem can be reduced to a sublinear elliptic equation coupled with an overdetermined boundary condition. Roughly speaking, the overdetermined boundary condition forces the domain to be a ball. Because the nonlinear term is sublinear and then non‐Lipschitz, many difficulties arise if one wants to use the moving plane method to reach the goal. In particular, the Hopf boundary lemma is not applicable to this problem. Instead, we investigate various related problems in a half space and a problem in the first quadrant of the entire space, and then use the symmetry results obtained for these problems to overcome the obstacles encountered. ©1995 John Wiley & Sons, Inc.
On the alexandroff‐bakelman‐pucci estimate and the reversed hölder inequality for solutions of elliptic and parabolic equations
Authors: Cabré Xavier 
Published: April 2007

AbstractThe constant appearing in the classical Alexandroff‐Bakelman‐Pucci estimate for subsolutions of second‐order uniformly elliptic equations in nondivergence form was known to depend on the diameter of the domain. Using the Krylov‐Safonov boundary weak Harnack inequality due to Trudinger, we show that the dependence on the diameter may be replaced by dependence on a more precise geometric quantity of the domain. As a consequence, we get dependence on the measure instead of the diameter. We also give new bounds for subsolutions in some unbounded domains, such as domains contained in cones.We apply the Fabes and Stroock reversed Hölder inequality for the Green's function to improve our estimates. We also give a new proof of the reversed Hölder inequality for the Green's function based on the Krylov‐Safonov Harnack inequality.Finally, we find new bounds for subsolutions of uniformly parabolic equations in cylindrical and noncylindrical domains. The constant in the (Alexandroff‐Bakelman‐Pucci‐) Krylov‐Tso estimate was known to depend on the diameter of the base of the cylinder. We get dependence either on the measure of the base or on the height of the cylinder. We also give bounds for subsolutions in noncylindrical domains. ©1995 John Wiley & Sons, Inc.
Compressible helical flows
Authors: Morgulis A. , Yudovich V. I. , Zaslavsky G. M. 
Published: April 2007

AbstractHelical (Beltrami) flow with nonuniform coefficient is considered for the case of compressible fluid and a class of exact solutions is proposed. A paradox of helical flow is discussed and the compressibility is considered as a possible resolution of the paradox. Examples with different symmetries are given for the compressible helical flow and, in particular, the generalization of the ABC (Arnold‐Beltrami‐Childress) flow for the compressible case is proposed. ©1995 John Wiley & Sons, Inc.
Forced lattice vibrations: Part I
Authors: Deift Percy , Kriecherbauer Thomas , Venakides Stephanos 
Published: April 2007

AbstractThis is the First 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) = at + h(yt), where a and γ are constants and h(·) has period 2π. For a wide variety of restoring forces F (i.e., F′ > 0), numerical calculations indicate the existence of a sequence of thresholds γ1 = γ1(a, h, F) > γ2 = γ2(a,h,F) > … > γk = γk(a,h,F) > …, γk → 0, as k → ∞. If γk > γ > γk+1, a k‐phase wave that is well described by the wave form, magnified image emerges and travels through the lattice.The goal of this series is to describe the emergence and calculate some properties of these wave forms. In Part I the authors first consider the case where F(x) = ex (i.e., Toda forces) but h is arbitrary, and show how to compute a basic diagnostic (see J(λ), formula (1.26)) for the system in terms of the solution of an associated scalar Riemann‐Hilbert problem, once a certain finite set of numbers is known. In another direction, the authors consider the case where F(x) is restoring but arbitrary, and h is small. Here the authors prove a general result, asserting that if there exists a sufficiently ample family of traveling‐wave solutions of the doubly infinite lattice, magnified image then it is possible to construct time‐periodic k‐phase wave solutions with asymptotics in n of type (iii) for the driven system (i).In Part II, the authors prove that sufficiently ample families of traveling‐wave solutions of the system (iv) 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.
Equivalent resistance and noise of cascaded mesoscopic cavities
Authors: Macucci M. , Marconcini P. , Iannaccone G. 
Published: April 2007

AbstractSince the time of the early studies on mesoscopic devices, it was recognized that, due mainly to the ballistic nature of transport, their resistances and the other electrical quantities could not be combined following the traditional rules of circuit theory. Here, we focus specifically on the conductance and noise resulting from a chain of cascaded mesoscopic cavities and discuss an existing semiclassical model for conductance and shot noise, recasting it into an equivalent circuit description. Numerical simulations show that such a model fails if the cavities are identical and is only partially valid if cavities are unequal. We discuss possible explanations for such a somewhat surprising behaviour. Copyright © 2007 John Wiley & Sons, Ltd.
Cover Picture: Ring Reversal of a Spirocyclic Patchouli Odorant: Molecular Modeling, Synthesis, and Odor of 6‐Hydroxy‐1,1,6‐trimethylspiro[4.5]decan‐7‐one (Eur. J. Org. Chem. 14/2007)
Authors: Kraft Philip , Bruneau Audrey 
Published: April 2007

AbstractThe cover picture shows shows the superposition of two spirocyclic target molecules, modeled on a recently discovered high‐impact patchouli odorant by ring‐reversal and structural simplification. Yet, despite omission of two methyl substituents, these sterically congested structures proved to be synthetically challenging targets. The synthesis of the first and principal target features a TiCl4‐mediated spiroannulation of the TMS‐enolate of cyclohexanone with 1‐bromo‐4‐chloro‐4‐methylpentane, subsequent dehydration by Appel–Lee bromination with concomitant dehydrohalogenation, and the elegant ketohydroxylation reaction of Plietker. Key odor descriptors for “patchouli” are “camphor”, “woody” and “earthy”, and depending on the molecular shape of the odorants, these are more or less balanced; the first target structure, for instance, is more shifted towards the camphoraceous, in principle an anti‐erogenous, attribute. Yet patchouli oil always had a sensual connotation, and since Indian girls ritually used to perfume their backs with patchouli oil to bewitch a lover, these molecules shine in front of a female back bearing their structural formulae in a lower backpiece fashion tattoo. The molecular design, synthesis and olfactory properties of these new odorants are discussed in the article by P. Kraft and A. Bruneau on p. 2257 ff.
Proteome analysis of the culture environment supporting undifferentiated mouse embryonic stem and germ cell growth
Authors: Buhr Nicolas , Carapito Christine , Schaeffer Christine , Hovasse Agnès , Van Dorsselaer Alain , Viville Stéphane 
Published: April 2007

AbstractThe therapeutical interest of pluripotent cells and ethical issues related to the establishment of human embryonic stem cell (ESC) or embryonic germ cell (EGC) lines raise the understanding of the mechanism underlying pluripotency to a fundamental issue. Establishing a protein pluripotency signature for these cells can be complicated by the presence of unrelated proteins produced by the culture environment. Here, we have analyzed the environment supporting ESC and EGC growth, and established 2‐D reference maps for each constituent present in this culture environment: mouse embryonic fibroblast feeder cells, culture medium (CM) and gelatin. The establishment of these reference maps is essential prior to the study of ESC and EGC specific proteomes. Indeed, these maps can be subtracted from ESC or EGC maps to allow focusing on spots specific for ESCs or EGCs. Our study led to the identification of 110 unique proteins from fibroblast feeder cells and 23 unique proteins from the CM, which represent major contaminants of ESC and EGC proteomes. For gelatin, no collagen‐specific proteins were identified, most likely due to difficulties in resolution and low quantities. Furthermore, no differences were observed between naive and conditioned CM. Finally, we compared these reference maps to ESC 2‐D gels and isolated 17 ESC specific spots. Among these spots, proteins that had already been identified in previous human and mouse ESC proteomes were identified but no apparent ESC‐specific pluripotency marker could be identified. This work represents an essential step in furthering the knowledge of environmental factors supporting ESC and EGC growth.
Entropy‐based equation to assess hillslope sediment production
Authors: Araújo José Carlos de 
Published: April 2007

AbstractA new equation to assess hillslope sediment production, based on physical and probabilistic approaches, is presented. The equation, which allows the computation of the delivery ratio for every event, considers the physical variables of travel distance, stream power, settling velocity and gross erosion. The probability density function that arises from the new formulation is solved using the principle of maximum entropy. Based on data from five watersheds in both tropical and temperate zones, the new delivery parameter Kv is calibrated and associated with vegetation cover and conservation practice. The proposed equation is rationally based in relation to parameter Kv. The entropy‐based equation was applied to assess sediment yield in two other experimental watersheds, showing good predictability for the set (mean absolute error of 20·8%). No systematic error was found in the analysed data. The entropy‐based equation showed good predictability for long‐term sets of data and for high‐erosivity events, but did not perform well for the low‐erosivity ones. Copyright © 2007 John Wiley & Sons, Ltd.
Lattice Boltzmann methods for shallow water flow applications
Authors: Thömmes Guido , Seaïd Mohammed , Banda Mapundi K. 
Published: April 2007

AbstractWe apply the lattice Boltzmann (LB) method for solving the shallow water equations with source terms such as the bed slope and bed friction. Our aim is to use a simple and accurate representation of the source terms in order to simulate practical shallow water flows without relying on upwind discretization or Riemann problem solvers. We validate the algorithm on problems where analytical solutions are available. The numerical results are in good agreement with analytical solutions. Furthermore, we test the method on a practical problem by simulating mean flow in the Strait of Gibraltar. The main focus is to examine the performance of the LB method for complex geometries with irregular bathymetry. The results demonstrate its ability to capture the main flow features. Copyright © 2007 John Wiley & Sons, Ltd.
Thrombin potently enhances swelling‐sensitive glutamate efflux from cultured astrocytes
Authors: Ramos‐Mandujano Gerardo , Vázquez‐Juárez Erika , Hernández‐Benítez Reyna , Pasantes‐Morales Herminia 
Published: April 2007

AbstractHigh concentrations of thrombin (Thr) have been linked to neuronal damage in cerebral ischemia and traumatic brain injury. In the present study we found that Thr markedly enhanced swelling‐activated efflux of 3H‐glutamate from cultured astrocytes exposed to hyposmotic medium. Thr (0.5–5 U/mL) elicited small 3H‐glutamate efflux under isosmotic conditions and increased the hyposmotic glutamate efflux by 5‐ to 10‐fold, the maximum effect being observed at 15% osmolarity reduction. These Thr effects involve its protease activity and are fully mimicked by SFFLRN, the synthetic peptide activating protease‐activated receptor‐1. Thr potentiation of 3H‐glutamate efflux was largely dependent on a Thr‐elicited increases in cytosolic Ca2+ (Ca2+i) concentration ([Ca2+]i). Preventing Ca2+i rise by treatment with EGTA‐AM or with the phospholipase C blocker U73122 reduced the Thr‐increased glutamate efflux by 68%. The protein kinase C blockers Go6976 or chelerythrine reduced the Thr effect by 19%–22%, while Ca/calmodulin blocker W7 caused a 63% inhibition. In addition to this Ca2+‐sensitive pathway, Thr effect on glutamate efflux also involved activation of phosphoinositide‐3 kinase (PI3K), since it was reduced by the PI3K inhibitor wortmannin (51% inhibition). Treating cells with EGTA‐AM plus wortmannin essentially abolished Thr‐dependent glutamate efflux. Thr‐activated glutamate release was potently inhibited by the blockers of the volume‐sensitive anion permeability pathway, NPPB (IC50 15.8 μM), DCPIB (IC50 4.2 μM). These results suggest that Thr may contribute to the excitotoxic neuronal injury by elevating extracellular glutamate release from glial cells. Therefore, this work may aid in search of neuroprotective strategies for treating cerebral ischemia and brain trauma. © 2007 Wiley‐Liss, Inc.
Contrasting potential of nitric oxide and peroxynitrite to mediate oligodendrocyte injury in multiple sclerosis
Authors: Jack Carolyn , Antel Jack , Brück Wolfgang , Kuhlmann Tanja 
Published: April 2007

AbstractNitric oxide (NO) and peroxynitrite (ONOO−) are potential mediators of the injury and cytotoxicity occurring over time to oligodendrocytes in multiple sclerosis (MS) lesions. Our in vitro results indicate that human adult CNS‐derived oligodendrocytes are relatively resistant to NO‐mediated damage. In contrast, human oligodendrocytes are highly susceptible to peroxynitrite‐mediated injury. In situ, we found that inducible nitric oxide synthase (iNOS) was expressed in astrocytes and macrophages in all active demyelinating and remyelinating MS lesions examined, yet no correlation was found between numbers of glial cells expressing iNOS and the extent of oligodendrocyte cell death. Nitrotyrosine groups, indicative of the presence of peroxynitrite in vivo, could be detected on astrocytes, macrophages, and oligodendrocytes in MS lesions. High numbers of nitrotyrosine‐positive oligodendrocytes were found in one MS case that featured extensive oligodendrocyte cell death. Our results indicate that NO alone is unlikely to induce oligodendrocyte injury, whereas its more potent byproduct peroxynitrite is a potential mediator of injury to oligodendrocytes in MS. © 2007 Wiley‐Liss, Inc.
The roles of aquaporin‐4 in brain edema following neonatal hypoxia ischemia and reoxygenation in a cultured rat astrocyte model
Authors: Fu Xuemei , Li Qiuping , Feng Zhichun , Mu Dezhi 
Published: April 2007

AbstractAquaporin‐4 (AQP4), a water channel protein, is abundantly expressed in astrocytes and plays a key role in the development of brain edema. However, it is not clear whether AQP4 contributes to astrocytic swelling in hypoxia–ischemia (HI). To investigate the roles of AQP4 in astrocytic swelling during HI and reoxygenation, we measured AQP4 expression and astrocytic cellular volume in cultured rat astrocytes following HI and reoxygenation. RNA interference was used to knockdown AQP4 expression (AQP4−/−). Real‐time polymerase chain reaction and Western blot analysis were used to detect the inhibitory efficiency of AQP4. We found that the maximal inhibition of AQP4 mRNA and protein in astrocytes after AQP4 siRNA transfection (AQP4−/−) was ∼77 and 85%, respectively, compared to wild‐type AQP4 (AQP4+/+) expression. Cellular volume in both AQP4−/− and AQP4+/+ astrocytes was significantly increased during HI compared to cells cultured in normoxia (P < 0.05). However, cellular volume during HI in AQP4−/− astrocytes was significantly less than that in AQP4+/+ astrocytes (P < 0.05). After reoxygenation, the cellular volume gradually decreased to control levels at 7 days in AQP4−/− but at 5 days in AQP4+/+ astrocytes. The different roles of AQP4 during HI and reoxygenation suggest that AQP4 knockdown may protect against water influx in the formation of astrocyte swelling during HI, and may also delay water clearance in the resolution of astrocyte swelling during reoxygenation. In conclusion, AQP4 mediates bidirectional transport of water across astrocytes during HI and reoxygenation. AQP4 manipulation may serve as a novel therapeutic strategy during different periods of hypoxic–ischemic brain edema in neonates. © 2007 Wiley‐Liss, Inc.
Functional organization of human visual cortex in occipital polymicrogyria
Authors: Dumoulin Serge O. , Jirsch Jeffrey D. , Bernasconi Andrea 
Published: April 2007

AbstractPolymicrogyrias (PMG) are cortical malformations resulting from developmental abnormalities. In animal models PMG has been associated with abnormal anatomy, function, and organization. The purpose of this study was to describe the function and organization of human polymicrogyric cortex using functional magnetic resonance imaging. Three patients with epilepsy and bilateral parasagittal occipital polymicrogyri were studied. They all had normal vision as tested by Humphrey visual field perimetry. The functional organization of the visual cortex was reconstructed using phase‐encoded retinotopic mapping analysis. This method sequentially stimulates each point in the visual field along the axes of a polar‐coordinate system, thereby reconstructing the representation of the visual field on the cortex. We found normal cortical responses and organization of early visual areas (V1, V2, and V3/VP). The locations of these visual areas overlapped substantially with the PMG. In five out of six hemispheres the reconstructed primary visual cortex completely fell within polymicrogyric areas. Our results suggest that human polymicrogyric cortex is not only organized in a normal fashion, but is also actively involved in processing of visual information and contributes to normal visual perception. Hum Brain Mapp 2007. © 2007 Wiley‐Liss, Inc.