bluuebunny/crossref_metadata_2025 huggingface dataset:
FLEXIBLE STRUCTURE MULTIPLE MODELING USING IRREGULAR SELF-ORGANIZING MAPS NEURAL NETWORK
Authors: FATEHI ALIREZA , ABE KENICHI
Published: July 2008

The MMSOM identification method, which had been presented by the authors, is improved to the multiple modeling by the irregular self-organizing map (MMISOM) using the irregular SOM (ISOM). Inputs to the neural networks are parameters of the instantaneous model computed adaptively at every instant. The neural network learns these models. The reference vectors of its output nodes are estimation of the parameters of the local models. At every instant, the model with closest output to the plant output is selected as the model of the plant. ISOM used in this paper is a graph of all the nodes and some of the weighted links between them to make a minimum spanning tree graph. It is shown in this paper that it is possible to add new models if the number of models is initially less than the appropriate one. The MMISOM shows more flexibility to cover the linear model space of the plant when the space is concave.
LMI-BASED ASYMPTOTIC STABILITY ANALYSIS OF NEURAL NETWORKS WITH TIME-VARYING DELAYS
Authors: LI TAO , SUN CHANGYIN , ZHAO XIANLIN , LIN CHONG
Published: July 2008

The problem of the global asymptotic stability for a class of neural networks with time-varying delays is investigated in this paper, where the activation functions are assumed to be neither monotonic, nor differentiable, nor bounded. By constructing suitable Lyapunov functionals and combining with linear matrix inequality (LMI) technique, new global asymptotic stability criteria about different types of time-varying delays are obtained. It is shown that the criteria can provide less conservative result than some existing ones. Numerical examples are given to demonstrate the applicability of the proposed approach.
HAWKING RADIATION, GRAVITATIONAL ANOMALY, AND CONFORMAL SYMMETRY — THE ORIGIN OF UNIVERSALITY
Authors: ISO SATOSHI
Published: July 2008

The universal behavior of Hawking radiation is originated in the conformal symmetries of matter fields near the black hole horizon. We explain the origin of this universality based on (1) the gravitational anomaly and its higher-spin generalizations and (2) conformal transformation properties of fluxes.
A STRONG COUPLING EXPANSION FOR N = 4 SYM THEORY AND OTHER SCFT's
Authors: BERENSTEIN DAVID
Published: July 2008

Recent progress towards understanding a strong coupling expansion for various superconformal field theories in four dimensions is described. First, the case of the maximally supersymmetric Yang Mills theory is analyzed, as well as many calculations that can be done directly at strong coupling and matched to the AdS dual geometry. Also, this understanding is extended to other AdS duals where the sphere is replaced by a Sasaki-Einstein manifold. Particular emphasis is made on matching exactly part of the supergravity dual spectrum of various of these field theories by using wave function methods.
ON THE QUARTIC CURVATURE GRAVITY IN THE CONTEXT OF FRW COSMOLOGY
Authors: IIHOSHI MASAO , KETOV SERGEI V.
Published: July 2008

We consider the purely gravitational fourth-order (in the spacetime curvature) quantum corrections to the Einstein-Hilbert gravity action, coming from superstrings in the leading order with respect to the Regge slope parameter, and study their impact on the evolution of the Hubble scale in the context of the FRW cosmology, in four spacetime dimensions. We propose the generalized Friedmann equations, and rule out the most naive (Bel-Robinson tensor squared) gravity. Our new cosmological equations have exact inflationary solutions without a spacetime singularity.
A DIRECT TEST OF THE GAUGE/GRAVITY DUALITY AND THE STRING THEORETICAL DESCRIPTION OF A BLACK HOLE
Authors: NISHIMURA JUN
Published: July 2008

We perform a direct test of the gauge/gravity duality by studying one-dimensional U (N) gauge theory with 16 supercharges at finite temperature using Monte Carlo simulation. In the 't Hooft large-N limit and in the strong coupling limit, the model is expected to have a dual gravity description in terms of the near-extremal black 0-brane solution in ten-dimensional type IIA supergravity. Our results provide the first example, in which the microscopic origin of the black hole thermodynamics is accounted for by solving explicitly the strongly coupled dynamics of the open strings attached to the D-branes.
FIBER BUNDLE AND MATRIX MODELS
Authors: TSUCHIYA ASATO
Published: July 2008

We extend the large N reduction and the compactification in matrix models to those on manifolds represented as fiber bundles. We also discuss application of our results to the AdS/CFT correspondence and topological field theories.
EMERGENT SPACETIME AND THE COSMOLOGICAL CONSTANT
Authors: YANG HYUN SEOK
Published: July 2008

We address issues on the origin of gravity and the dark energy (or the cosmological constant) from the perspectives of emergent gravity. We discuss how the emergent gravity reveals a noble, radically different picture about the origin of spacetime, which is crucial for a tenable solution of the cosmological constant problem. In particular, the emergent gravity naturally explains the dynamical origin of flat spacetime, which is absent in Einstein gravity.
MODULI STABILIZATION IN STRINGY ISS MODELS
Authors: YAMAZAKI MASAHITO
Published: July 2008

We present a stringy realization of the ISS metastable SUSY breaking model with moduli stabilization. The mass moduli of the ISS model is stabilized by gauging of a U(1) symmetry and its D-term potential. The SUSY is broken both by F-terms and D-terms. It is possible to obtain de-Sitter vacua with a vanishingly small cosmological constant by an appropriate fine-tuning of flux parameters. The content of this article is based on our recent paper1, which is in collaboration with Yu Nakayama (Berkeley) and Tsutomu Yanagida (Tokyo).
SPONTANEOUS SUPERSYMMETRY BREAKING BY LARGE-N MATRICES
Authors: KUROKI TSUNEHIDE , SUGINO FUMIHIKO
Published: July 2008

Motivated by supersymmetry breaking in matrix model formulations of superstrings, we present some concrete models, in which the supersymmetry is preserved for any finite N, but gets broken at infinite N, where N is the rank of matrix variables. The models are defined as supersymmetric field theories coupled to some matrix models, and in the induced action obtained after integrating out the matrices, supersymmetry is spontaneously broken only when N is infinity.
M5-BRANES AND WILSON SURFACES
Authors: CHEN BIN
Published: July 2008

We investigate the M5-brane description of the Wilson surface operators in six-dimensional (2,0) superconformal field theory from AdS/CFT correspondence. We consider the Wilson surface operators in high-dimensional representation, whose description could be M5-brane string soliton solutions in AdS7 × S4 background. We construct such string soliton solutions from the covariant M5-brane equations of motion and discuss their properties. The supersymmetry analysis shows that these solutions are half-BPS. Furthermore, we discuss the operator product expansion of the Wilson surface operators in higher dimensional representation using their corresponding M5-brane configurations.
MATRIX REGULARIZATION OF N = 4 SYM ON R × S3
Authors: ISHIKI GORO
Published: July 2008

We revealed a relationship between the plane wave matrix model (PWMM) and N =4 super Yang-Mills (SYM) theory on R × S3: N =4 SYM on R × S3 is equivalent to the theory around a certain vacuum of PWMM. It is suggested from this relation that N =4 SYM on R × S3 is regularized by PWMM in the planar limit. Because PWMM originally possesses the gauge symmetry and SU(2|4) symmetry, this regularization also preserves these symmetries. In order to check the validity of this matrix regularization method, we calculate the Ward identity and the beta function at the 1-loop level. We find that the Ward identity is satisfied and the beta function vanishes in the continuum limit. The former result is consistent with the gauge symmetry of PWMM. The latter suggests the possibility that the conformal symmety is restored in the continuum limit.
BLACK HOLE BOUND STATES AND THEIR QUANTIZATION
Authors: DE BOER JAN
Published: July 2008

We briefly review the construction of multi-centered black hole solutions in type IIA string theory. We then discuss a decoupling limit which embeds these solutions in M-theory on AdS 3 × S 2 × CY , and discuss some aspects of their dual CFT interpretation. Finally, we consider the quantization of these solutions and applications to the wall-crossing formula and the "fuzzball" proposal.
DOMAIN WALLS WITH NON-ABELIAN FLAVOR SYMMETRY
Authors: FUJIMORI TOSHIAKI
Published: July 2008

Domain walls in gauge theory with non-Abelian flavor symmetry possess normalizable Nambu-Goldstone zero modes associated with spontaneously broken non-Abelian flavor symmetry. We construct the moduli space metric as the effective field theory of walls. The Nambu-Goldstone modes spread between two domain walls and their rotation induces long-range repulsive force. We also construct a bound state of domain walls. This article is based on the work with M. Eto, M. Nitta, K. Ohashi and N. Sakai1.
FINITE-SIZE CORRECTIONS TO DYONIC GIANT MAGNONS
Authors: HATSUDA YASUYUKI
Published: July 2008

We compute finite-size corrections to dyonic giant magnons in two ways1. One is by using classical string solutions corresponding to finite-size dyonic giant magnons called "helical strings". The other is by applying the Lüscher formula known in relativistic quantum field theory to the case in which incoming particles are boundstates. We find these two methods lead the same result.
LARGE WINDING SECTOR OF AdS/CFT
Authors: HAYASHI HIROTAKA , OKAMURA KEISUKE , SUZUKI RYO , VICEDO BENOÎT
Published: July 2008

We find a new family of classical oscillating strings with large winding numbers, which are constructed by interchanging τ and σ of helical strings' solutions. We also give a finite-gap interpretation of interchanging τ and σ. Gauge dual operators are discussed at the end.
D3/D7 HOLOGRAPHIC GAUGE THEORY AND CHEMICAL POTENTIAL
Authors: ISHIHARA MASAFUMI , GHOROKU KAZUO , NAKAMURA AKIHIRO
Published: July 2008

N = 2 supersymmetric Yang-Mills theory with flavor hypermultiplets at finite temperature is studied for finite quark number density (nb) by a dual supergravity background with nontrivial dilaton and axion. The quarks and their number density nb are introduced by embeddings a probe D7 brane. We find a critical value of the chemical potential at the limit of nb = 0, and it coincides with the effective quark mass for nb = 0. At this point, a transition of the D7 embedding configurations occurs between their two typical ones. The phase diagrams of this transition are shown in the plane of chemical potential versus temperature for Yang-Mills theory at finite temperature. In this phase transition, the order parameter is considered as nb. This result seems to be reasonable since this theory is in the quark deconfiment phase.
CHARGED BOUNDARY STATES IN A Z3 EXTENDED MINIMAL STRING
Authors: KAWAMOTO SHOICHI , WHEATER JOHN F. , WILSHIN SIMON
Published: July 2008

In this poster, we study the boundary states of the three-state Potts model coupled to two dimensional gravity, which we call Z3 extended minimal string. We find that two different boundary states of this model can be identified with a shift of the boundary cosmological constant. We also point out that the boundary states are classified with respect to the symmetry of the theory. This presentation is based on Ref. 1 to appear soon.
HAGEDORN BEHAVIOR OF STRINGS IN AdS3/BTZ
Authors: MATSUO TOSHIHIRO
Published: July 2008

We study a finite temperature string in curved space, especially in AdS3 and BTZ black hole background. We extract Hagedorn behavior of strings and argue thermodynamic properties in thermal AdS3 as well as in BTZ black hole background. In particular, we find the Hagedorn temperature of string on AdS3, which depends on the AdS3 curvature scale. We also find a tachyonic divergence for a BTZ black hole of string scale.
HOLOGRAPHY OF ROTATING DUAL GIANT WILSON LOOPS
Authors: MIWA AKITSUGU , SUMITOMO YOSKE , YOSHIDA KENTAROH
Published: July 2008

We briefly review a tunneling picture of rotating D3-brane solutions. By applying the "double Wick rotation" to the Lorentzian solutions, we construct Euclidean solutions. The solutions are composed of dual giant gravitons and spike D3-brane solutions, and their classical actions reproduce expectation values of the k-th symmetric Wilson loops as well as correlation functions of dual giant graviton operators as expected.
CASCADE OF GREGORY-LAFLAMME TRANSITIONS AND U(1) BREAKDOWN IN SUPER YANG-MILLS
Authors: HANADA MASANORI , NISHIOKA TATSUMA
Published: July 2008

We consider black p-branes on square torus. We find an indication of a cascade of Gregory-Laflamme transitions between black p-brane and (p - 1)-brane. Through AdS/CFT correspondence, these transitions are related to the breakdown of the U(1) symmetry in super Yang-Mills on square torus. We argue a relationship between the cascade and recent Monte-Carlo data. This talk is based on Ref. 1.
REFORMULATION OF BOUNDARY STRING FIELD THEORY IN TERMS OF BOUNDARY STATE
Authors: TERAGUCHI SHUNSUKE
Published: July 2008

We reformulate bosonic boundary string field theory in terms of boundary state. In our formulation, we can formally perform the integration of target space equations of motion for arbitrary field configurations without assuming decoupling of matter and ghost. This is a short summary of our contribution to the international workshop "Progress of String Theory and Quantum Field Theory" at Osaka City University (December 7-10, 2007).
STABILITY OF GLOBAL VERTEX SOLUTION IN HIGHER-DIMENSIONAL SPACETIME
Authors: TORII TAKASHI , WATABE HIROSHI
Published: July 2008

It is well known that higher-dimensional black objects with translational invariance are unstable, which is called Gregory-Laflamme instability. There is a question if this instability is eliminated by adding a scalar hair to the black objects. For the first step, we investigate a regular topological string solution and its stability in the five-dimensional Einstein-Higgs system. Linear analysis shows that the string solution is stable against non-uniform perturbations.
A-D-E QUIVERS AND BARYONIC OPERATORS
Authors: TACHIKAWA YUJI , YAGI FUTOSHI
Published: July 2008

We study baryonic operators of the gauge theory on multiple D3-branes at the tip of the conifold orbifolded by a discrete subgroup of SU(2). The string theory analysis predicts that the number and the order of the fixed points of this discrete subgroup acting on S2 are directly reflected in the spectrum of baryonic operators on the corresponding quiver gauge theory constructed from two Dynkin diagrams of the corresponding type. We confirm the prediction by utilizing techniques to enumerate baryonic operators of the quiver gauge theory which includes the gauge groups with different ranks.
D-TERM CHAOTIC INFLATION IN SUPERGRAVITY
Authors: YAMAGUCHI MASAHIDE , KADOTA KENJI
Published: July 2008

Even though the chaotic inflation is one of the most popular inflation models for its simple dynamics and compelling resolutions to the initial condition problems, its realization in supergravity has been considered a challenging task. We discuss how the chaotic inflation dominated by the D-term can be induced in supergravity, which would give a new perspective on the inflation model building in supergravity.
SOLITONS AND ADS STRING SOLUTIONS
Authors: JEVICKI ANTAL , JIN KEWANG
Published: July 2008

In this contribution we describe some soliton based techniques for generating classical AdS string solutions. The methods introduced are useful for further understanding of rotating AdS configurations with spikes which correspond to higher twist operators in SYM theory. The main identification (accomplished in arXiv:0712.1193) between solitons and string spikes is reviewed and extended. We desribe how inverse scattering technique can be applied for reconstructing AdS string configurations from soliton solutions of sinh-Gordon theory (in the example of AdS3).
TESTING PPP BY MEANS OF ZNZ PATTERNED VECM
Authors: BRAILSFORD T. J. , PENM JACK , TERRELL R. D.
Published: July 2008

Vector error-correction models (VECM) are increasingly being used to capture dynamic relationships between financial variables. Estimation and interpretation of such models can be enhanced if zero restrictions are allowed in the coefficient matrices. Conventional use of full-order models may weaken the power of statistical inferences due to over-parameterization. The paper demonstrates the usefulness of this approach for the analysis of exchange rate relationships. Specifically, the paper examines the relationship between the money supply and the Euro and provides a test of purchasing power parity (PPP) in Japan. The latter test results shed light on the adjustment mechanisms through which PPP is achieved. In addition, it is clear that the proposed ZNZ patterned VECM modeling provides better insights from this kind of financial time-series analysis. The paper also shows that causality detection in an I(d) system can be revealed identically from the ZNZ patterned VECMs or the equivalent VAR models.
HIGH-PERFORMANCE PARALLEL VISUALIZATION LIBRARY FOR VARIOUS SIMULATION ENVIRONMENTS
Authors: CHEN LI , OKUDA HIROSHI
Published: July 2008

This paper describes a parallel visualization library for large-scale datasets developed in the HPC-MW project. Three parallel frameworks are provided in the library to satisfy different requirements of applications. Meanwhile, it is applicable for a variety of mesh types covering particles, structured grids and unstructured grids. Many techniques have been employed to improve the quality of the visualization. High speedup performance has been achieved by some hardware-oriented optimization strategies on different platforms, from PC clusters to the Earth Simulator. Good results have been obtained on some typical parallel platforms, thus demonstrating the feasibility and effectiveness of our library.
ACCELERATION OF BIOMOLECULAR DYNAMICS SIMULATIONS ON THE EARTH SIMULATOR
Authors: SUZUKI MASAAKI , OKUDA HIROSHI
Published: July 2008

Replica exchange molecular dynamics (REMD) code has been developed for predicting protein tertiary structure and optimized assuming that simulations are performed on the Earth Simulator. A new parallel programming approach using an MPI/OpenMP model with a three-level hierarchy was developed to circumvent the problems of overhead inherent in the MPI model and shown to achieve an 88% parallel efficiency using a 256-node REMD simulation on the Earth Simulator with this model.
A SHOCK-CAPTURING UPWIND DISCRETIZATION METHOD FOR CHARACTERIZATION OF SiC MESFETs
Authors: ARABSHAHI H. , BENAM M. R.
Published: July 2008

A finite difference shock-capturing upwind discretization method in two dimensions is presented in detail for simulation of homogeneous and nonhomogeneous devices. The model is based on the solutions to the highly coupled nonlinear partial differential equations of the full hydrodynamic model. These solutions allow one to calculate the electron drift velocity and other device parameters as a function of the applied electric field. The hydrodynamic model is able to describe inertia effects which play an increasing role in different fields of micro- and optoelectronics where simplified charge transport models like the drift-diffusion model and the energy balance model are no longer applicable. Results of numerical simulations are shown for a two-dimensional SiC MESFET device, and are in fair agreement with other theoretical or experimental methods.
How can we improve estimates of bulk fault zone hydraulic properties?
Authors: Lunn Rebecca J. , Shipton Zoe K. , Bright Aileen M.
Published: July 2008

The fluid flow properties of faults are highly variable and spatially heterogeneous. We use numerical simulation of flow through field maps of detailed fault zone architecture to demonstrate that flow across the fault zone is controlled by connected high-permeability pathways, which are highly tortuous in mapped fault outcrops. Such small-scale, geometrically complex, fault zone architectural features can never be resolved for
subsurface
faults. Consequently, the key to prediction of subsurface bulk fault zone hydraulic properties is a statistical characterisation of the likelihood and frequency of such connected pathways. We demonstrate for a single architectural feature, the fault core, that thickness variation along strike can be well described by a spatially correlated random field with a spherical covariance structure. These data are from a single site in a specific lithology. To enable such statistics to be used to make predictions at other sites, a large number of similar datasets must be pooled. This will enable us to relate such spatial statistics to gross properties such as host rock lithology and fault throw, which are measurable for subsurface faults.
Fault-related dilation, permeability enhancement, fluid flow and mineral precipitation patterns: numerical models
Authors: Zhang Y. , Schaubs P. M. , Zhao C. , Ord A. , Hobbs B. E. , Barnicoat A. C.
Published: July 2008

Fault-related host rock deformation and dilation control fluid flow and mineralization in many world-class mineral deposits. This numerical modelling study explores the interactions between deformation, faulting, dilation, fluid flow and chemical processes, which are suggested to result in this control, with special attention to fault dilatant jog structures. Our two-dimensional numerical models focus on faulting-related deformation, dilation and permeability enhancement, fluid flow patterns and fluid focusing/mixing locations, while three-dimensional models examine several different cases of fault underlap and overlap. The results show that fault-dilation and faulting-induced permeability enhancement, which are closely associated with tensile failure, represent important ways to generate fluid flow conduits for more effective fluid flow and mixing. Dilation during strike–slip faulting is localized near fault tips (wing crack locations) and jog sites, where fluids are strongly focused and mixed. These locations are the tensile domains of the strike–slip regime. In overlapping-fault (dilatant jog) cases, the magnitude of dilation and the extent of the dilatant region are closely related to the extent of fault overlap. These results provide insight into the transport of fluids through low-permeability rocks with isolated, but more permeable, faults. Gold and quartz precipitation patterns as a result of the coupling of chemical reactions to deformation induced fluid flow velocities are also computed. The rates of precipitation depend on structural and fluid flow conditions and on the geometrical relation between local fluid velocity and chemical concentration gradients generated by mixing. Maximum precipitation rates for gold occur in the dilation zones and in faults where high fluid flow rates, sufficient fluid mixing and high concentration gradients of critical chemical species are all present, while the quartz precipitation rate is predominantly controlled, in this isothermal situation, by the rate of fluid flow across concentration gradients in the aqueous silica concentration.
Fault and fluid interaction in a rifted margin: integrated study of calcite-sealed fault-related structures (southern Corinth margin)
Authors: Benedicto A. , Plagnes V. , Vergély P. , Flotté N. , Schultz R. A.
Published: July 2008

This work integrates microstructural, petrologic, microthermometric and geochemical analysis of calcite-sealed fault-related structures of the major faults of the southern margin of the Corinth rift (Greece). It draws attention to the main deformational processes and fault–fluid interaction in fault zones along the whole margin. Data analysed come from the compact breccia located immediately adjacent to major fault planes. Samples were collected at different positions alongside different faults juxtaposing synrift continental deposits (hanging wall) against the prerift Pindus limestones (footwall). This implies hectometric fault displacements and that the fault zones have recorded a relatively long evolution of deformation. Our study identifies four main deformation features common to all studied faults: calcite cemented breccia, extensional veins, shear veins and fault slip surfaces. The integrated data analysis shows that deformation structures and fault rocks that coexist in the same outcrop formed at different depths and times. During inferred upward fault propagation, the style of deformation evolved from distributed (brecciation) to localized (slip surfaces) and from a closed system with fluid–rock equilibrium during brecciation to a more open one with limited influx of meteoric water during extensional and shear fracturing. This implies relative uplift of the footwall during fault propagation and fault interaction with different water aquifers as the fault propagates upwards. The results demonstrate similar fault evolution and fault–fluid interaction through the entire rifted margin and during the whole rifting period.
Permeability structure and co-seismic thermal pressurization on fault branches: insights from the Usukidani fault, Japan
Authors: Boutareaud Sebastien , Wibberley Christopher A. J. , Fabbri Olivier , Shimamoto Toshihiko
Published: July 2008

Detailed mapping of complex fault zones shows that secondary faults often branch off the principal slip zone. However, the effect of secondary branch faults on the hydrodynamic behaviour of fault zones has not yet been examined, largely because of a lack of hydraulic data and because numerical or analogue modelling of splay faulting is a complex issue. This contribution investigates the thermal pressurization process in cases of slip along a principal slip zone and along splay faults branching off the principal displacement zone. The study is based on porosity and permeability data presented in this paper from the principal and secondary slip zones of an active, clay-rich gouge-bearing strike–slip fault, the Usukidani fault of SW Japan. Modelling constrained by these data suggests that thermal pressurization is a viable process only as long as the rupture remains located in the central gouge zones or in mature splay fault gouge zones. Splaying of the rupture into surrounding microbreccias or into immature or newly generated splay faults of higher permeability will release fluid pressure or inhibit the generation of coseismic excess fluid pressures by thermal pressurization. The modelling results suggest that secondary fault branches can play a key role in controlling fluid pressurization during faulting. Hence, complete investigation of active fault zones needs to include secondary faults and their corresponding hydraulic behaviour, in order to establish the influence of such structures on earthquake mechanics.
Internal geometry of fault damage zones in interbedded siliciclastic sediments
Authors: Johansen Tord Erlend Skeie , Fossen Haakon
Published: July 2008

The geometry, orientation and distribution of deformation bands and fractures in eolian sandstones, siltstones and shales of the San Rafael Desert and Moab Fault area have been investigated. The results show that deformation bands, which are cataclastic in eolian sandstones and disaggregation structures in siltstones, are unevenly distributed throughout the damage zone in the form of individual bands, deformation band zones and deformation band clusters. The density of bands increases with increasing grain size. In thin (<3 m) eolian sandstones deformation band frequency is significantly lower than in thicker eolian sandstones, whereas above this thickness the frequency seems not to be related to layer thickness. Furthermore, large faults do not develop higher concentrations of deformation bands. Somewhat simplified, this suggests that damage zone growth occurs by expansion into its hanging wall and footwall. Still, the highest concentrations of deformation bands occur close to the main fault, which is of importance when considering their effect on fluid flow. Their general fault-parallel conjugate arrangements favour intra-damage zone flow parallel to rather than perpendicular to the fault.
Fault damage zones dominated by high-angle fractures within layer-parallel brittle shear zones: examples from the eastern Alps
Authors: Brosch Franz-Josef , Kurz Walter
Published: July 2008

In this study, we focus on the transition from the host rock to the damage zone within brittle shear zones in order to document the structures forming during the initial phases of deformation, i.e., the fractures that formed prior to the formation of fault breccias and cataclasites. Structural analyses of rock samples from sites of the Talhof– and Palten–Liesing faults in the eastern Alps show that in these cases well-known R- and P-fracture patterns do not play a dominant role in the early stages of the generation of brittle fracture zones. In the studied layered marble and foliated impure quartzite samples, the boundary between the host rock and the damage zone is characterized by the formation of closely spaced fractures at high angles (70–90°) to the shear zone boundaries, being parallel to pre-existing layering/foliation planes. These fractures bound and define slender slab-like or columnar rock elements, here being termed lamellae. It is assumed that subsequent rotation of these lamellae in the bookshelf and domino modes associated with impeded dilation across the actual shear zone boundaries leads to kinking, splitting and final granulation of the lamellae to generate breccias of later fault core zones parallel to the shear zone boundary. In some cases, the observed bending and buckling of lamellae indicate additional ductile deformation subsequent to the development of the dominant lamellar structures formed by brittle fracturing.
Hunter to Gatherer and Back: Immunological Synapses and Kinapses as Variations on the Theme of Amoeboid Locomotion
Authors: Dustin Michael L.
Published: July 2008

The immunological synapse was initially defined as a stable cell-cell junction composed of three concentric supramolecular activation clusters (SMACs) enriched in particular components: a central SMAC with clustered antigen receptors and kinases, a peripheral SMAC rich in β2 integrin adhesion molecule LFA-1, and a distal SMAC marked by a critical tyrosine phosphatase. In the past year the SMACs have each been identified with functional modules of amoeboid motility, and the stability of the immunological synapse has been revealed as a reconfiguration of the motile apparatus from an asymmetric hunting mode, a kinapse, to a symmetric gathering mode, the synapse. The genetic control of this process involves actinomyosin regulators PKCθ and WASp. Crtam is involved in postsynaptic polarity in early kinapses prior to cell division. It is unlikely that the immune system is unique in using symmetrization to stop migration without inactivating motile machinery.
Regulation of MHC Class I Assembly and Peptide Binding
Authors: Peaper David R. , Cresswell Peter
Published: July 2008

Peptide binding to MHC class I molecules is a component of a folding and assembly process that occurs in the endoplasmic reticulum (ER) and uses both cellular chaperones and dedicated factors. The involvement of glycoprotein quality-control chaperones and cellular oxidoreductases in peptide binding has led to models that are gradually being refined. Some aspects of the peptide loading process (e.g., the biosynthesis and degradation of MHC class I complexes) conform to models of glycoprotein quality control, but other aspects (e.g., the formation of a stable disulfide-linked dimer between tapasin and ERp57) deviate from models of chaperone and oxidoreductase function. Here we review what is known about the intersection of glycoprotein folding, oxidative reactions, and MHC class I peptide loading, emphasizing events that occur in the ER and within the MHC class I peptide loading complex.
Decentralization of Natural Resource Governance Regimes
Authors: Larson Anne M. , Soto Fernanda
Published: July 2008

This chapter reviews the literature on natural resource decentralization with an emphasis on forests in developing countries. This literature can be located at the intersection between discussions of good governance and democracy, development, and poverty alleviation, on the one hand, and common property resources, community-based resource management, and local resource rights, on the other. Policies implemented in the name of decentralization, however, are often not applied in ways compatible with the democratic potential with which decentralization is conceived, and only rarely have they resulted in pro-poor outcomes or challenged underlying structures of inequity. Greater attention to who receives decentralized powers, the role of property rights, the notion of “the local,” and the meeting of expert and local knowledge provides insights into key issues and contradictions. Fundamental differences in conceptions of democracy, participation, and development lie behind these contradictions and shape strategies for the redistribution of access to political power and resources, which is implied by decentralization.
Acute liver failure-induced death of rats is delayed or prevented by blocking NMDA receptors in brain
Authors: Cauli Omar , Rodrigo Regina , Boix Jordi , Piedrafita Blanca , Agusti Ana , Felipo Vicente
Published: July 2008

Developing procedures to delay the mechanisms of acute liver failure-induced death would increase patients' survival by allowing time for liver regeneration or to receive a liver for transplantation. Hyperammonemia is a main contributor to brain herniation and mortality in acute liver failure (ALF). Acute ammonia intoxication in rats leads to N-methyl-d-aspartate (NMDA) receptor activation in brain. Blocking these receptors prevents ammonia-induced death. Ammonia-induced activation of NMDA receptors could contribute to ALF-induced death. If this were the case, blocking NMDA receptors could prevent or delay ALF-induced death. The aim of this work was to assess 1) whether ALF leads to NMDA receptors activation in brain in vivo and 2) whether blocking NMDA receptors prevents or delays ALF-induced death of rats. It is shown, by in vivo brain microdialysis, that galactosamine-induced ALF leads to NMDA receptors activation in brain. Blocking NMDA receptors by continuous administration of MK-801 or memantine through miniosmotic pumps affords significant protection against ALF-induced death, increasing the survival time approximately twofold. Also, when liver injury is not 100% lethal (1.5 g/kg galactosamine), blocking NMDA receptors increases the survival rate from 23 to 62%. This supports that blocking NMDA receptors could have therapeutic utility to improve survival of patients with ALF.
Neonatal caffeine induces sex-specific developmental plasticity of the hypoxic respiratory chemoreflex in adult rats
Authors: Montandon Gaspard , Bairam Aida , Kinkead Richard
Published: July 2008

Caffeine is widely used to treat apneas of prematurity during the neonatal period; however, the potential consequences of administering a neonatal caffeine treatment (NCT) during a critical period for respiratory control development are unknown. The present study therefore determined whether NCT in rats alters the hypoxic respiratory chemoreflex measured at adulthood. Newborn rats received either caffeine (15 mg/kg) or water (control) each day from postnatal day 3 to 12. The ventilatory response to a hypoxic challenge (inspired O2fraction = 0.12) was first evaluated in awake adult female and male rats using whole body plethysmography. Results showed that NCT increased the initial phase of the breathing frequency response to hypoxia in males only. This result was confirmed in anesthetized and artificially ventilated adult male rats where NCT also increased the phrenic burst frequency response to hypoxia. RT-PCR assessment of mRNA encoding for adenosine A1Aand A2Areceptors, dopamine D2receptors, and tyrosine hydroxylase in the rat carotid bodies showed that NCT enhanced mRNA expression levels of adenosine A2A, dopamine D2receptors, and tyrosine hydroxylase of males but not females. Subsequent experiments on awake male rats showed that injection of the adenosine A2Areceptor antagonist ZM2413855 (1 mg/kg ip) before ventilatory measurements abolished, in NCT rats, the enhanced respiratory frequency response observed during the early phase of hypoxia. We propose that NCT elicits a sex-specific increase in the hypoxic respiratory chemoreflex, which is related, at least partially, to an enhancement in adenosine A2Areceptors in the rat carotid body.
Indolent course of tubulointerstitial disease in a mouse model of subpressor, low-dose nitric oxide synthase inhibition
Authors: Stoessel Adelina , Paliege Alexander , Theilig Franziska , Addabbo Francesco , Ratliff Brian , Waschke Jens , Patschan Daniel , Goligorsky Michael S. , Bachmann Sebastian
Published: July 2008

Deficiency of nitric oxide (NO) represents a consistent manifestation of endothelial dysfunction (ECD), and the accumulation of asymmetric dimethylarginine occurs early in renal disease. Here, we confirmed in vitro and in vivo the previous finding that a fragment of collagen XVIII, endostatin, was upregulated by chronic inhibition of NO production and sought to support a hypothesis that primary ECD contributes to nephrosclerosis in the absence of other profibrotic factors. To emulate more closely the indolent course of ECD, the study was expanded to an in vivo model with NG-monomethyl-l-arginine(l-NMMA; mimics effects of asymmetric dimethylarginine) administered to mice in the drinking water at subpressor doses of 0.3 and 0.8 mg/ml for 3–6 mo. This resulted in subtle but significant morphological alterations detected in kidneys of mice chronically treated with l-NMMA: 1) consistent perivascular expansion of interstitial matrix components at the inner stripe of the outer medulla and 2) collagen XVIII/endostatin abundance. Ultrastructural abnormalities were detected in l-NMMA-treated mice: 1) increased activity of the interstitial fibroblasts; 2) occasional detachment of endothelial cells from the basement membrane; 3) splitting of the vascular basement membrane; 4) focal fibrosis; and 5) accumulation of lipofuscin by interstitial fibroblasts. Preembedding labeling of microvasculature with anti-CD31 antibodies showed infiltrating leukocytes and agglomerating platelets attaching to the visibly intact or denuded capillaries. Collectively, the data indicate that the mouse model of subpressor chronic administration of l-NMMA is not a robust one (endothelial pathology visible only ultrastructurally), and yet it closely resembles the natural progression of endothelial dysfunction, microvascular abnormalities, and associated tubulointerstitial scarring.
HSP27 is involved in the pathogenesis of kidney tubulointerstitial fibrosis
Authors: Vidyasagar Aparna , Reese Shannon , Acun Zeki , Hullett Debra , Djamali Arjang
Published: July 2008

We hypothesized that heat shock protein 27 (HSP27), a small heat shock protein with actin-remodeling properties, is involved in the pathogenesis of kidney tubulointerstitial fibrosis. We first examined its expression in the rat unilateral ureteral obstruction (UUO) model of kidney fibrosis and epithelial-to-mesenchymal transition (EMT). Immunoblot analyses showed that UUO resulted in significant upregulation of TGF-β1, α-smooth muscle actin (α-SMA), total and phosphorylated HSP27, and phosphorylated p38MAPK. Immunofluorescence studies showed that HSP27 costained with TGF-β1, α-SMA, and E-cadherin in areas of tubulointerstitial injury. We next attempted to translate these studies in an in vitro model of EMT using rat proximal tubular epithelial cells (NRK52E). TGF-β1 (20 ng/ml) treatment resulted in EMT (upregulation of α-SMA and downregulation of E-cadherin) and significant upregulation of total and phosphorylated HSP27 and p38MAPK after 3 days. Real-time PCR analyses showed that HSP27, vimentin, and fibronectin increased whereas E-cadherin mRNA levels decreased. Double-staining immunofluorescence studies showed intracytoplasmic colocalization of HSP27 with both F-actin and E-cadherin in cells undergoing EMT. HSP27 overexpression by transient transfection significantly increased E-cadherin while decreasing E-cadherin repressor Snail levels. In aggregate, these studies show that HSP27 is involved in the pathogenesis of TGF-β1-induced EMT and chronic tubulointerstitial fibrosis. HSP27 overexpression may delay injury by upregulating E-cadherin through downregulation of Snail.
Evidence for a Link Between the Extra-Retinal Component of Random-Onset Pursuit and the Anticipatory Pursuit of Predictable Object Motion
Authors: Barnes G. R. , Collins C.J.S.
Published: July 2008

During pursuit of moving targets that temporarily disappear, residual smooth eye movements represent the internal (extra-retinal) component of pursuit. However, this response is dependent on expectation of target reappearance. By comparing responses with and without such expectation during early random-onset pursuit, we examined the temporal development of the extra-retinal component and compared it with anticipatory pursuit, another form of internally driven response. In an initial task (mid-ramp extinction), a moving, random-velocity target was initially visible for 100 or 150 ms but then extinguished for 600 ms before reappearing and continuing to move. Responses comprised an initial visually driven rapid rise in eye velocity, followed by a secondary slower increase during extinction. In a second task (short ramp), with identical initial target presentation but no expectation of target reappearance, the initial rapid rise in eye velocity was followed by decay toward zero. The expectation-dependent difference between responses to these tasks increased in velocity during extinction much more slowly than the initial, visually driven component. In a third task (initial extinction), the moving target was extinguished at motion onset but reappeared 600 ms later. Repetition of identical stimuli evoked anticipatory pursuit triggered by initial target offset. Temporal development and scaling of this anticipatory response, which was based on remembered velocity from prior stimuli, was remarkably similar to and covaried with the difference between mid-ramp extinction and short ramp tasks. Results suggest a common mechanism is responsible for anticipatory pursuit and the extra-retinal component of random-onset pursuit, a finding that is consistent with a previously developed model of pursuit.
The Role of Filler‐Matrix Interaction on Viscoelastic Response of Biomimetic Nanocomposite Hydrogels
Authors: Sarvestani Alireza S. , He Xuezhong , Jabbari Esmaiel
Published: July 2008

The effect of a glutamic acid (negatively charged) peptide (Glu6), which mimics the terminal region of the osteonectin glycoprotein of bone on the shear modulus of a synthetic hydorgel/apatite nanocomposite, was investigated. One end of the synthesized peptide was functionalized with an acrylate group (Ac‐Glu6) to covalently attach the peptide to the hydrogel phase of the composite matrix. The addition of Ac‐Glu6 to hydroxyapatite (HA) nanoparticles (50 nm in size) resulted in significant reinforcement of the shear modulus of the nanocomposite (∼100% increase in elastic shear modulus). The reinforcement effect of the Glu6 peptide, a sequence in the terminal region of osteonectin, was modulated by the size of the apatite crystals. A molecular model is also proposed to demonstrate the role of polymer‐apatite interaction in improving the viscoelastic behavior of the bone mimetic composite. The predictions of the model were compared with the measured dynamic shear modulus of the PLEOF hydrogel reinforced with HA nanoparticles. This predictive model provides a quantitative framework to optimize the properties of reinforced polymer nanocomposites as scaffolds for applications in tissue regeneration.
The Effect of Stirring on the Morphology of Birnessite Nanoparticles
Authors: Cheney Marcos A. , Bhowmik Pradip K. , Moriuchi Shingo , Villalobos Mario , Qian Shizhi , Joo Sang W.
Published: July 2008

The effect of mechanical stirring on the morphology of hexagonal layer‐structure birnessite nanoparticles produced from decomposition of KMnO4 in dilute aqueous H2SO4 is investigated, with characterization by X‐ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high‐resolution transmission electron microscopy (HRTEM), thermogravimetric analysis (TGA), and N2 adsorption (BET). Mechanical stirring during an initial stage of synthesis is shown to produce black birnessite containing nanofibers, whereas granular particulates of brown birnessite are produced without stirring. This is the first reduction synthesis of black birnessite nanoparticles with dendritic morphology without any use of organic reductant, and suggests that a particular morphology can arise from structural preferences of Mn in acidic conditions rather than particular organic reactants. These results enlighten the possibility of synthesizing nanoparticles with controlled size and morphology.
Gallstone-Induced Perforation of the Common Bile Duct in Pregnancy
Authors: Dabbas N. , Abdelaziz M. , Hamdan K. , Stedman B. , Abu Hilal M.
Published: July 2008

Spontaneous perforation of the extrahepatic biliary system is a rare presentation of ductal stones. We report the case of a twenty-year-old woman presenting at term with biliary peritonitis caused by common bile duct (CBD) perforation due to an impacted stone in the distal common bile duct. The patient had suffered a single herald episode of acute gallstone pancreatitis during the third trimester. The patient underwent an emergency laparotomy, bile duct exploration, and removal of the ductal stone. The postoperative course was uneventful.
Synthesis of PET‐PLA/Drug Nanoparticles and Their Effect with Gold Nanoparticles for Controlled Drug Release in Cancer Chemotherapy
Authors: Kumar K. Sathish , Selvaraj V. , Alagar M.
Published: July 2008

Polyethylene terephthalate‐polylactic acid copolymer (PET‐PLA) was synthesized from bis (2‐hydroxyethyl terephthalate) and L‐lactic acid oligomer in the presence of manganese antimony glycoxide as a catalyst. The synthesized PET‐PLA copolymer was used for controlled drug release systems with gold nanoparticles. Fluorouracil containing PET‐PLA nanocapsules was prepared in the presence of gold nanoparticles by solvent evaporation method. The morphologies of the nanocapsules were characterized using scanning electron microscopy and transmission electron microscopy. Controlled release of Fu and Fu@Au was carried out in 0.1 M phosphate buffer (pH 7.4) and 0.1 M HCl solution. The results indicated that the drug release for gold nanoparticles/fluorouracil (Au@Fu) incorporated PET‐PLA nanocapsules was controlled and slow compared to Fu incorporated PET‐PLA nanocapsules. This may be due to the interaction between the gold nanoparticles and fluorouracil in PET‐PLA nanocapsules.
Silicon‐Based Light Sources for Silicon Integrated Circuits
Authors: Pavesi L.
Published: July 2008

Silicon the material per excellence for electronics is not used for sourcing light due to the lack of efficient light emitters and lasers. In this review, after having introduced the basics on lasing, I will discuss the physical reasons why silicon is not a laser material and the approaches to make it lasing. I will start with bulk silicon, then I will discuss silicon nanocrystals and Er3+ coupled silicon nanocrystals where significant advances have been done in the past and can be expected in the near future. I will conclude with an optimistic note on silicon lasing.