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## Selected Abstracts## Multicolor Tunable Emission from Organogels Containing Tetraphenylethene, Perylenediimide, and Spiropyran Derivatives ADVANCED FUNCTIONAL MATERIALS, Issue 19 2010Qun ChenAbstract A dendron-substituted tetraphenylethene low molecular weight gelator (LMWG)compound, LMWG1, is designed and investigated. Gelation-induced fluorescence enhancement is observed for the gel based on LMWG1 and its fluorescence can be reversibly tuned by varying the temperature of the ensemble. The photoinduced energy-transfer can occur between LMWG1 and PI2 (perylene diimide) in the gel phase, but it cannot occur in the corresponding solution. The emission color of the gel of LMWG1 and PI2 can be tuned from cyan, yellow, to red by varying the concentration of PI2. By taking advantage of the photochromic transformation of spiropyran, the emission color of the organogels based on LMWG1 and SP3 can be switched by alternating UV and visible-light irradiations. The emission color can also be tuned by varying the irradiation time. In this way, organogels based on LMWG1 with multiemission color can be achieved in the presence of SP3 after light irradiations. [source] ## Influence of anisotropy on a limit load of weld strength overmatched middle cracked tension specimens FATIGUE & FRACTURE OF ENGINEERING MATERIALS AND STRUCTURES, Issue 5 2003S. ALEXANDROVABSTRACT A plane-strain upper bound limit load solution for weld strength overmatched middle cracked tension specimens (M(T) specimens), is found. It is assumed that the weld material is isotropic, but the base material is orthotropic and its axes of orthotropy are straight and parallel to the axes of symmetry of the specimen. A quadratic orthotropic yield criterion is adopted. The solution is based on a simple discontinuous kinematically admissible velocity field and is an extension of the corresponding solution for the specimen made of isotropic materials. These two solutions are compared to demonstrate the influence of anisotropy on the magnitude of the limit load. [source] ## New phases of thermal SYM and LST from Kaluza-Klein black holes FORTSCHRITTE DER PHYSIK/PROGRESS OF PHYSICS, Issue 7-8 2005T. HarmarkAbstract We review the recently found map that takes any static and neutral Kaluza-Klein black hole, i.e. any static and neutral black hole on Minkowski-space times a circle ,d × S1, and maps it to a corresponding solution for a non- and near-extremal brane on a circle. This gives a precise connection between phases of Kaluza-Klein black holes and the thermodynamic behavior of the non-gravitational theories dual to near-extremal branes on a circle. In particular, for the thermodynamics of strongly-coupled supersymmetric Yang-Mills theories on a circle we predict the existence of a new non-uniform phase and find new information about the localized phase. We also find evidence for the existence of a new stable phase of (2,0) Little String Theory in the canonical ensemble for temperatures above its Hagedorn temperature. [source] ## On explicit solutions to the stationary axisymmetric Einstein-Maxwell equations describing dust disks ANNALEN DER PHYSIK, Issue 10 2003C. KleinAbstract We review explicit solutions to the stationary axisymmetric Einstein-Maxwell equations which can be interpreted as disks of charged dust. The disks of finite or infinite extension are infinitesimally thin and constitute a surface layer at the boundary of an electro-vacuum. The Einstein-Maxwell equations in the presence of one Killing vector are obtained by using a projection formalism. This leads to equations for three-dimensional gravity where the matter is given by a SU(2,1)/S[U(1,1)× U(1)] nonlinear sigma model. The SU(2,1) invariance of the stationary Einstein-Maxwell equations can be used to construct solutions for the electro-vacuum from solutions to the pure vacuum case via a so-called Harrison transformation. It is shown that the corresponding solutions will always have a non-vanishing total charge and a gyromagnetic ratio of 2. Since the vacuum and the electro-vacuum equations in the stationary axisymmetric case are completely integrable, large classes of solutions can be constructed with techniques from the theory of solitons. The richest class of physically interesting solutions to the pure vacuum case due to Korotkin is given in terms of hyperelliptic theta functions. Harrison transformed hyperelliptic solutions are discussed. As a concrete example we study the transformation of a family of counter-rotating dust disks. To obtain algebro-geometric solutions with vanishing total charge which are of astrophysical relevance, three-sheeted surfaces have to be considered. The matter in the disk is discussed following Bi,ák et al. We review the ,cut and glue' technique where a strip is removed from an explicitly known spacetime and where the remainder is glued together after displacement. The discontinuities of the normal derivatives of the metric at the glueing hypersurface lead to infinite disks. If the energy conditions are satisfied and if the pressure is positive, the disks can be interpreted in the vacuum case as made up of two components of counter-rotating dust moving on geodesics. In electro-vacuum the condition of geodesic movement is replaced by electro-geodesic movement. As an example we discuss a class of Harrison-transformed hyperelliptic solutions. The range of parameters is identified where an interpretation of the matter in the disk in terms of electro-dust can be given. [source] ## Volatile organoselenium monitoring in production and gastric digestion processes of selenized yeast by solid-phase microextraction-multicapillary gas chromatography coupled microwave-induced plasma atomic emission spectrometry, APPLIED ORGANOMETALLIC CHEMISTRY, Issue 12 2004J. Sanz LandaluzeAbstract Evolution of volatile organoselenium compounds in the production and gastric digestion of selenized yeast has been monitored. The industrial production of these kinds of material, employed as food supplements, has been simulated in a process of yeast enrichment with inorganic selenium selenium (IV) in different growth media, with variation of the pH value. The in vitro gastric digestion process was carried out with pepsin in an acid and salt mixture. Determination of volatile species of selenium was achieved coupling solid-phase microextraction (SPME) for preconcentration and sample,matrix separation and microwave-induced plasma atomic emission spectrometry, in combination with multicapillary (MC) gas chromatography for separation and detection of the selenium species. The MC column was operated at low temperatures (,30 °C). The method was optimized, using a chemometric approach, with respect to the detection of organoselenium species such as dimethylselenide, diethylselenide and dimethyldiselenide. SPME sampling was carried out in the headspace above the corresponding solutions. Separation is fast, with a chromatogram being obtained in less than 5 min, and the detection limits were at the low parts per billion level for all species investigated. The results of the yeast enrichment process demonstrate inorganic selenium transformation into volatile organic species. The presence of inorganic selenium gave rise to at least five different volatile species after metabolization by yeast, with dimethylselenide and dimethyldiselenide being the predominant species. Commercial pasteurized yeast, containing mainly selenomethionine for use as a food supplement, and tablets were found to be still active under conditions of the simulation of the digestion process, even though producing relatively low amounts of organoselenium compounds. Copyright © 2004 John Wiley & Sons, Ltd. [source] ## On the finite-time singularities of the 3D incompressible Euler equations COMMUNICATIONS ON PURE & APPLIED MATHEMATICS, Issue 4 2007Dongho ChaeWe prove the finite-time vorticity blowup, in the pointwise sense, for solutions of the 3D incompressible Euler equations assuming some conditions on the initial data and its corresponding solutions near initial time. These conditions are represented by the relation between the deformation tensor and the Hessian of pressure, both coupled with the vorticity directions associated with the initial data and solutions near initial time. We also study the possibility of the enstrophy blowup for the 3D Euler and the 3D Navier-Stokes equations, and prove the finite-time enstrophy blowup for initial data satisfying suitable conditions. Finally, we obtain a new blowup criterion that controls the blowup by a quantity containing the Hessian of the pressure. © 2006 Wiley Periodicals, Inc. [source] |