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String
Kinds of String Terms modified by String Selected AbstractsSTRINGS ATTACHED: NEW PUBLIC MANAGEMENT, COMPETITIVE GRANT FUNDING AND SOCIAL CAPITALFINANCIAL ACCOUNTABILITY & MANAGEMENT, Issue 2 2009Helen Irvine This paper first investigates the impact of New Public Management (NPM) practices, particularly competitive grant funding, on Bushcare New South Wales (NSW), an Australian environmental volunteering organisation. Secondly, identifying such local volunteering organisations as repositories of valuable social capital, it explores the link between volunteering and social capital. Using mixed methods and institutional theory, the study reveals that an increased level of professionalism and accountability is required of Bushcare groups, and that local coordinators face a challenge in balancing local, regional and national priorities without sacrificing Bushcare's mission. These dynamics, it is proposed, have potentially serious social capital implications. [source] String and supergravity motivated cosmologyFORTSCHRITTE DER PHYSIK/PROGRESS OF PHYSICS, Issue 7-8 2005Article first published online: 30 JUN 200, R. Kallosh In this pedagogical lecture we explain some basic part of the standard cosmological model which is most relevant for the fundamental theoretical physics. We stress the common features and differences between early universe inflation and late-time acceleration. We than proceed with some recent attempts to address the issues of cosmology in string theory and higher dimensional supergravity with the emphasis on successes and still unsolved problems. [source] Open problems in string cosmologyFORTSCHRITTE DER PHYSIK/PROGRESS OF PHYSICS, Issue 7-9 2010Article first published online: 16 MAR 2010, N. Toumbas Abstract Some of the open problems in string cosmology are highlighted within the context of the recently constructed thermal and quantum superstring cosmological solutions. Emphasis is given on the high temperature cosmological regime, where it is argued that thermal string vacua in the presence of gravito-magnetic fluxes can be used to bypass the Hagedorn instabilities of string gas cosmology. This article is based on a talk given at the workshop on "Cosmology and Strings", Corfu, September 6,13, 2009. [source] Strings and D-branes in holographic backgroundsFORTSCHRITTE DER PHYSIK/PROGRESS OF PHYSICS, Issue 7-8 2005D. Israël Abstract We review recent progress in the study of non-rational (boundary) conformal field theories and their applications to describe exact holographic backgrounds in superstring theory. We focus mainly on the example of the supersymmetric coset SL(2, ,)/U(1), corresponding to the two-dimensional black hole, and its dual N = 2 Liouville. In particular we discuss the modular properties of their characters, their partition function as well as the exact boundary states for their various D-branes. Then these results are used to construct the corresponding quantities in the CFT of the NS5-brane background, with applications to Little String Theories. [source] Strings in plane wave backgrounds,FORTSCHRITTE DER PHYSIK/PROGRESS OF PHYSICS, Issue 12 2003A. Pankiewicz Abstract I review aspects of string theory on plane wave backgrounds emphasising the connection to gauge theory given by the BMN correspondence. Topics covered include the Penrose limit and its role in deriving the BMN duality from AdS/CFT, light-cone string field theory in the maximally supersymmetric plane wave and extensions of the correspondence to less supersymmetric backgrounds. [source] Ordered Gold Nanoarrays: 3D Ordered Gold Strings by Coating Nanoparticles with Mesogens (Adv. Mater.ADVANCED MATERIALS, Issue 17 200917/2009) Liquid-crystal-coated gold nanoparticles exhibit 3D long-range ordering in strings jacketed by rod-like mesogens (shown in green) with controllable interparticle spacing. The work reported on p. 1746 by Goran Ungar and co-workers demonstrates a new method of assembling ordered metal nanoparticle superlattices, in a step towards developing self-assembled metamaterials. The cover shows red, yellow, and blue nanoparticles lying at different heights and forming a rhombohedral lattice. [source] 3D Ordered Gold Strings by Coating Nanoparticles with MesogensADVANCED MATERIALS, Issue 17 2009Xiangbing Zeng Gold nanoparticles covered with a nematic liquid-crystal ligand laterally attached via a thioalkyl spacer and a thioalkane "diluent" exhibit 3D ordering in strings jacketed by the mesogens with controllable interparticle spacing. The particles form rhombohedral, hexagonal, and rectangular columnar superlattices, not the usual packing modes of spheres. [source] ChemInform Abstract: Dirac Strings and Magnetic Monopoles in the Spin Ice Dy2Ti2O7.CHEMINFORM, Issue 51 2009D. J. P. Morris Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Dynamic Multivalent Lactosides Displayed on Cyclodextrin Beads Dangling from Polymer Strings.CHEMINFORM, Issue 4 2004Alshakim Nelson No abstract is available for this article. [source] Temperature-Dependent and Friction-Controlled Electrochemically Induced Shuttling Along Molecular Strings Associated with ElectrodesCHEMPHYSCHEM, Issue 10 2005Eugenii Katz Dr. Abstract The temperature and solvent composition dependence of the electrochemically stimulated rate of shuttling of the redox-active cyclophane, cyclobis(paraquat- p -phenylene), on a molecular string has been studied. The molecular string includes a ,-donor diiminebenzene-site that is associated on one side with an electrode, and stoppered on the other side with an adamantane unit. The cyclophane rests on the ,-donor site, owing to stabilizing ,-donor,acceptor interactions. Electrochemical reduction of the cyclophane units, to the bis-radical cation cyclophane, results in the shuttling of the reduced cyclophane towards the electrode, a process that is driven by the removal of the stabilizing donor,acceptor interactions, and the electrostatic attraction of the reduced product by the electrode. The latter process is energetically downhill, and is temperature-independent. Upon oxidation of the reduced cyclophane that is associated with the electrode, the energetically uphill shuttling of the oxidized cyclophane to the ,-donor site proceeds. The rate of this translocation process has been found to be temperature-dependent, and controlled by the solvent composition. The experimental results have been theoretically analyzed in terms of Kramers' molecular friction model. The theoretical fitting of the experimental results, using solutions of variable composition, reveals that the rate-constants for the uphill reaction in a pure aqueous solution follow the temperature-dependence of the viscosity of water. The results demonstrate the significance of friction phenomena in shuttling processes within molecular machines. [source] Texts, topoi and the self: a reading of Alfredian spirituality*EARLY MEDIEVAL EUROPE, Issue 1 2005Scott DeGregorio Challenging the allegation that Alfred's spirituality as Asser presents it is no more than a string of textual fictions, this article outlines a context for understanding Alfred's spirituality as a functional process of living texts, or of ,textualizing' the self. The discussion first draws support for this view from the history of early medieval spirituality and then demonstrates the theme's relevance both to Asser's representation of Alfred and to the king's own writings. Attention is given especially to the congruence between Alfred's depiction in the Life and Gregory the Great's teachings on the ideal rector as propounded in the Pastoral Care, a text carefully read and famously translated by Alfred himself. The comparison suggests that the main spiritual models for Alfred's kingly piety may be understood to reside in, and to involve assimilation of, this work of Gregory, making it possible to conceptualize the king's self-presentation in terms of a conscious project to ,live' Gregory's text by bringing the ideals of the Gregorian rector to life in his own person. Such an argument helps to explain Alfred's interest in Gregory, to account for his concern to translate the Pastoral Care, and to legitimize the predominant images associated with the king's spirituality as indicative of a kind of functional piety grounded in the reading of texts, rather than simply reflected, perhaps falsely, in Asser's Life. [source] Survivable wavelength-routed optical network design using genetic algorithmsEUROPEAN TRANSACTIONS ON TELECOMMUNICATIONS, Issue 3 2008Y. S. Kavian The provision of acceptable service in the presence of failures and attacks is a major issue in the design of next generation dense wavelength division multiplexing (DWDM) networks. Survivability is provided by the establishment of spare lightpaths for each connection request to protect the working lightpaths. This paper presents a genetic algorithm (GA) solver for the routing and wavelength assignment problem with working and spare lightpaths to design survivable optical networks in the presence of a single link failure. Lightpaths are encoded into chromosomes made up of a fixed number of genes equal to the number of entries in the traffic demand matrix. Each gene represents one valid path and is thus coded as a variable length binary string. After crossover and mutation, each member of the population represents a set of valid but possibly incompatible paths and those that do not satisfy the problem constraints are discarded. The best paths are then found by use of a fitness function and these are assigned the minimum number of wavelengths according to the problem constraints. The proposed approach has been evaluated on dedicated path protection and shared path protection. Simulation results show that the GA method is efficient and able to design DWDM survivable real-world optical mesh networks. Copyright © 2007 John Wiley & Sons, Ltd. [source] Modeling the three-dimensional structure of H+ -ATPase of Neurospora crassaFEBS JOURNAL, Issue 21 2002Proposal for a proton pathway from the analysis of internal cavities Homology modeling in combination with transmembrane topology predictions are used to build the atomic model of Neurospora crassa plasma membrane H+ -ATPase, using as template the 2.6 Å crystal structure of rabbit sarcoplasmic reticulum Ca2+ -ATPase [Toyoshima, C., Nakasako, M., Nomura, H. & Ogawa, H. (2000) Nature 405, 647,655]. Comparison of the two calcium-binding sites in the crystal structure of Ca2+ -ATPase with the equivalent region in the H+ -ATPase model shows that the latter is devoid of most of the negatively charged groups required to bind the cations, suggesting a different role for this region. Using the built model, a pathway for proton transport is then proposed from computed locations of internal polar cavities, large enough to contain at least one water molecule. As a control, the same approach is applied to the high-resolution crystal structure of halorhodopsin and the proton pump bacteriorhodopsin. This revealed a striking correspondence between the positions of internal polar cavities, those of crystallographic water molecules and, in the case of bacteriorhodopsin, the residues mediating proton translocation. In our H+ -ATPase model, most of these cavities are in contact with residues previously shown to affect coupling of proton translocation to ATP hydrolysis. A string of six polar cavities identified in the cytoplasmic domain, the most accurate part of the model, suggests a proton entry path starting close to the phosphorylation site. Strikingly, members of the haloacid dehalogenase superfamily, which are close structural homologs of this domain but do not share the same function, display only one polar cavity in the vicinity of the conserved catalytic Asp residue. [source] Cover Picture: Fortschritte der Physik 10 / 2010FORTSCHRITTE DER PHYSIK/PROGRESS OF PHYSICS, Issue 10 2010Article first published online: 7 SEP 2010 The cover page of 2010 shows an abstract picture of the so-called string landscape. It is known for some time that, although string theory seems to be unique in ten or eleven space-time dimensions, a vast number of solutions pops out upon compactification to lower dimensions, in particular to fours space-time dimensions. [source] Cover Picture: Fortschritte der Physik 7,9 / 2010FORTSCHRITTE DER PHYSIK/PROGRESS OF PHYSICS, Issue 7-9 2010Article first published online: 21 JUN 2010 The cover page of 2010 shows an abstract picture of the so-called string landscape. It is known for some time that, although string theory seems to be unique in ten or eleven space-time dimensions, a vast number of solutions pops out upon compactification to lower dimensions, in particular to fours space-time dimensions. [source] Cover Picture: Fortschritte der Physik 6 / 2010FORTSCHRITTE DER PHYSIK/PROGRESS OF PHYSICS, Issue 6 2010Article first published online: 6 MAY 2010 The cover page of 2010 shows an abstract picture of the so-called string landscape. It is known for some time that, although string theory seems to be unique in ten or eleven space-time dimensions, a vast number of solutions pops out upon compactification to lower dimensions, in particular to fours space-time dimensions. [source] Cover Picture: Fortschritte der Physik 4,5 / 2010FORTSCHRITTE DER PHYSIK/PROGRESS OF PHYSICS, Issue 4-5 2010Article first published online: 22 MAR 2010 The cover page of 2010 shows an abstract picture of the so-called string landscape. It is known for some time that, although string theory seems to be unique in ten or eleven space-time dimensions, a vast number of solutions pops out upon compactification to lower dimensions, in particular to fours space-time dimensions. [source] Cover Picture: Fortschritte der Physik 2,3 / 2010FORTSCHRITTE DER PHYSIK/PROGRESS OF PHYSICS, Issue 2-3 2010Article first published online: 18 JAN 2010 The cover page of 2010 shows an abstract picture of the so-called string landscape. It is known for some time that, although string theory seems to be unique in ten or eleven space-time dimensions, a vast number of solutions pops out upon compactification to lower dimensions, in particular to fours space-time dimensions. [source] Cover Picture: Fortschritte der Physik 1 / 2010FORTSCHRITTE DER PHYSIK/PROGRESS OF PHYSICS, Issue 1 2010Article first published online: 16 DEC 200 The cover page of 2010 shows an abstract picture of the so-called string landscape. It is known for some time that, although string theory seems to be unique in ten or eleven space-time dimensions, a vast number of solutions pops out upon compactification to lower dimensions, in particular to four space-time dimensions. [source] Towards effective Lagrangians for adelic stringsFORTSCHRITTE DER PHYSIK/PROGRESS OF PHYSICS, Issue 5-7 2009Article first published online: 20 MAR 200, B. Dragovich Abstract p-Adic strings are important objects of string theory, as well as of p-adic mathematical physics and nonlocal cosmology. By a concept of adelic string one can unify and simultaneously study various aspects of ordinary and p-adic strings. By this way, one can consider adelic strings as a very useful instrument in the further investigation of modern string theory. It is remarkable that for some scalar p-adic strings exist effective Lagrangians, which are based on real instead of p-adic numbers and describe not only four-point scattering amplitudes but also all higher ones at the tree level. In this work, starting from p-adic Lagrangians, we consider some approaches to construction of effective field Lagrangians for p-adic sector of adelic strings. It yields Lagrangians for nonlinear and nonlocal scalar field theory, where spacetime nonlocality is determined by an infinite number of derivatives contained in the operator-valued Riemann zeta function. Owing to the Riemann zeta function in the dynamics of these scalar field theories, obtained Lagrangians are also interesting in themselves. [source] Kähler metrics: String vs field theoretical approachFORTSCHRITTE DER PHYSIK/PROGRESS OF PHYSICS, Issue 5-7 2009P. Di Vecchia Abstract We use both a string and a field theoretical approach in order to determine respectively the Kähler metrics of untwisted and twisted open strings attached to magnetized D9 branes in toroidal compactifications. [source] The landscape of string theory (orientifolds and their statistics, D-brane instantons, AdS4 domain walls and black holes)FORTSCHRITTE DER PHYSIK/PROGRESS OF PHYSICS, Issue 7-9 2008D. Lüst Abstract In this talk we discuss various aspects of the string landscape: D-brane model building and their statistics, the generation of non-perturbative superpotentials from D-brane instantons, moduli stabilization by fluxes and non-perturbative effects, the relation between flux vacua and BPS black holes, the construction of AdS4 vacua and related domain wall solutions, transitions between flux vacua and also some constraints on the string landscape from black hole considerations. [source] Compactifications of the heterotic string with unitary bundlesFORTSCHRITTE DER PHYSIK/PROGRESS OF PHYSICS, Issue 11 2006T. Weigand Abstract We describe a large new class of four-dimensional supersymmetric string vacua defined as compactifications of the E8 × E8 and the SO(32) heterotic string on smooth Calabi-Yau threefolds with unitary gauge bundles and heterotic five-branes. The conventional gauge symmetry breaking via Wilson lines is replaced by the embedding of non-flat line bundles into the ten-dimensional gauge group, thus opening up the way for phenomenologically interesting string compactifications on simply connected manifolds. After a detailed analysis of the four-dimensional effective theory we exemplify the general framework by means of a couple of explicit examples involving the spectral cover construction of stable holomorphic bundles. As for the SO(32) heterotic string, the resulting vacua can be viewed, in the S-dual Type I picture, as a generalisation of magnetized D9/D5-brane models. In the case of the E8 × E8 string, we find a natural way to construct realistic MSSM-like models, either directly or via a flipped SU(5) GUT scenario. [source] Moduli stabilization in the heterotic/IIB discretuumFORTSCHRITTE DER PHYSIK/PROGRESS OF PHYSICS, Issue 4 2006G. Curio We consider supersymmetric compactifications of type IIB and the weakly coupled heterotic string with G resp. H -flux and gaugino condensation in a hidden sector included. We point out that proper inclusion of the non-perturbative effects changes the Hodge structure of the allowed fluxes in type IIB significantly. In the heterotic theory it is known that, in contrast to the potential read off from dimensional reduction, the effective four-dimensional description demands for consistency a non-vanishing H2,1 component if a H3,0 component is already present balancing the condensate. The H2,1 component causes a non-Kählerness of the underlying geometry whose moduli space is, however, not well-understood. We show that the occurrence of H2,1 might actually be avoided by using a KKLT-like two-step procedure for moduli stabilization. Independently of the H2,1 issue one-loop corrections to the gauge couplings were argued to cause a not well-controlled strong coupling transition. This problem can be avoided as well when the effects of world-sheet instantons are included. They will also stabilize the Kähler modulus what was accomplished by H2,1 before. [source] Effective supergravity from the weakly coupled heterotic stringFORTSCHRITTE DER PHYSIK/PROGRESS OF PHYSICS, Issue 2-3 2006M.K. Gaillard The motivation for Calabi-Yau-like compactifications of the weakly coupled E8 , E8 heterotic string theory, its particle spectrum and the issue of dilaton stabilization are briefly reviewed. Modular invariant models for hidden sector condensation and supersymmetry breaking are described at the quantum level of the effective field theory. Their phenomenological and cosmological implications, including a possible origin for R-parity, are discussed. [source] Flux compactification of M-theory on compact manifolds with Spin(7) holonomy,FORTSCHRITTE DER PHYSIK/PROGRESS OF PHYSICS, Issue 11-12 2005D. Constantin At the leading order, M-theory admits minimal supersymmetric compactifications if the internal manifold has exceptional holonomy. The inclusion of non-vanishing fluxes in M-theory and string theory compactifications induce a superpotential in the lower dimensional theory, which depends on the fluxes. In this work, we check the conjectured form of this superpotential in the case of warped M-theory compactifications on Spin(7) holonomy manifolds. We perform a Kaluza-Klein reduction of the eleven-dimensional supersymmetry transformation for the gravitino and we find by direct comparison the superpotential expression. We check the conjecture for the heterotic string compactified on a Calabi-Yau three-fold as well. The conjecture can be checked indirectly by inspecting the scalar potential obtained after the compactification of M-theory on Spin(7) holonomy manifolds with non-vanishing fluxes. The scalar potential can be written in terms of the superpotential and we show that this potential stabilizes all the moduli fields describing deformations of the metric except for the radial modulus. All the above analyses require the knowledge of the minimal supergravity action in three dimensions. Therefore we calculate the most general causal ,, =1 three-dimensional, gauge invariant action coupled to matter in superspace and derive its component form using Ectoplasmic integration theory. We also show that the three-dimensional theory which results from the compactification is in agreement with the more general supergravity construction. The compactification procedure takes into account higher order quantum correction terms in the low energy effective action. We analyze the properties of these terms on a Spin(7) background. We derive a perturbative set of solutions which emerges from a warped compactification on a Spin(7) holonomy manifold with non-vanishing flux for the M-theory field strength and we show that in general the Ricci flatness of the internal manifold is lost, which means that the supergravity vacua are deformed away from the exceptional holonomy. Using the superpotential form we identify the supersymmetric vacua out of this general set of solutions. [source] Holonomies of intersecting branesFORTSCHRITTE DER PHYSIK/PROGRESS OF PHYSICS, Issue 7-8 2005Article first published online: 30 JUN 200, J. Kalkkinen Abstract We discuss the geometry of string and M-theory gauge fields in Deligne cohomology. In particular, we show how requiring string structure (or loop space SpinC structure) on the five-brane leads to topological conditions on the flux in the relative Deligne cohomology of the bulk-brain pair. [source] M-theory and gauged supergravities,FORTSCHRITTE DER PHYSIK/PROGRESS OF PHYSICS, Issue 2 2005D. Roest Abstract We present a pedagogical discussion of the emergence of gauged supergravities from M-theory. First, a review of maximal supergravity and its global symmetries and supersymmetric solutions is given. Next, different procedures of dimensional reduction are explained: reductions over a torus, a group manifold and a coset manifold and reductions with a twist. Emphasis is placed on the consistency of the truncations, the resulting gaugings and the possibility to generate field equations without an action. Using these techniques, we construct a number of gauged maximal supergravities in diverse dimensions with a string or M-theory origin. One class consists of the CSO gaugings, which comprise the analytic continuations and group contractions of SO(n) gaugings. We construct the corresponding half-supersymmetric domain walls and discuss their uplift to D- and M-brane distributions. Furthermore, a number of gauged maximal supergravities are constructed that do not have an action. [source] The AdS/CFT correspondence in the PP-wave limitFORTSCHRITTE DER PHYSIK/PROGRESS OF PHYSICS, Issue 6-7 2004M. Petrini We consider the correspondence between IIB string theory on the maximally supersymmetric PP-wave and the BMN sector of ,, = 4 SYM theory. At the level of the interacting (string) theory, the matching between these two descriptions is not yet fully understood. Here we review the tests supporting the simple proposal that relates the 3-string interaction to the correlation functions among the BMN operators. [source] Beam to String Transition of Vibrating Carbon Nanotubes Under Axial TensionADVANCED FUNCTIONAL MATERIALS, Issue 11 2009Xianlong Wei Abstract State-of-the-art nanoelectromechanical systems have been demonstrated in recent years using carbon nanotube (CNT) based devices, where the vibration of CNTs is tuned by tension induced through external electrical fields. However, the vibration properties of CNTs under axial tension have not been quantitatively determined in experiments. Here, a novel in situ method for precise and simultaneous measurement of the resonance frequency, the axial tension applied to individual CNTs and the tube geometry is demonstrated. A gradual beam-to-string transition from multi-walled CNTs to single-walled CNTs is observed with the crossover from bending rigidity dominant regime to extensional rigidity dominant regime occur much larger than that expected by previous theoretical work. Both the tube resonance frequency under tension and transition of vibration behavior from beam to string are surprisingly well fitted by the continuum beam theory. In the limit of a string, the vibration of a CNT is independent of its own stiffness, and a force sensitivity as large as 0.25,MHz (pN),1 is demonstrated using a 2.2,nm diameter single-walled CNT. These results will allow for the designs of CNT resonators with tailored properties. [source] | |||||||||||||||||||||||||||||||||||||||||||||||||||||||