1,870 research outputs found

    Distribution of Avalanche Sizes in the Hysteretic Response of Random Field Ising Model on a Bethe Lattice at Zero Temperature

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    We consider the zero-temperature single-spin-flip dynamics of the random-field Ising model on a Bethe lattice in the presence of an external field h. We derive the exact self-consistent equations to determine the distribution Prob(s) of avalanche sizes s, as the external field increases from large negative to positive values. We solve these equations explicitly for a rectangular distribution of the random fields for a linear chain and the Bethe lattice of coordination number z=3, and show that in these cases, Prob(s) decreases exponentially with s for large s for all h on the hysteresis loop. We found that for z >3 and for small disorder, the magnetization shows a first order discontinuity for several continuous and unimodel distributions of random fields. The avalanche distribution Prob(s) varies as s^{-3/2} for large s near the discontinuity.Comment: 30 pages, 10 eps figure

    Collusion Resistive Framework for Multimedia Security

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    The recent advances in multimedia and Internet technology rises the need for multimedia security.The frequent distribution of multimedia content can cause security breach and violate copyright protection law.The legitimate user can come together to generate illegitimate copy to use it for unintended purpose.The most effective such kind of attack is collusion,involve group of user to contribute with their copies of content to generate a new copy. Fingerprinting,a unique mark is embedded have one to one corresponds with user,is the solution to tackle collusion attack problem.A colluder involve in collusion leaves its trace in alter copy,so the effectiveness of mounting a successful attack lies in how effectively a colluder alter the image by leaving minimum trace.A framework,step by step procedure to tackle collusion attack, involves fingerprint generation and embedding.Various fingerprint generation and embedding techniques are used to make collusion resistive framework effective.Spread spectrum embedding with coded modulation is most effective framework to tackle collusion attack problem.The spread spectrum framework shows high collusion resistant and traceability but it can be attacked with some special collusion attack like interleaving attack and combination of average attack.Various attacks have different post effect on multimedia in different domains. The thesis provide a detail analysis of various collusion attack in different domains which serve as basis for designing the framework to resist collusion.Various statistical and experimental resuslts are drwan to show the behavior of collusion attack.The thesis also proposed a framework here uses modified ECC coded fingerprint for generation and robust watermarking embedding using wave atom.The system shows high collusion resistance against various attack.Various experiments are are drawn and system shows high collusion resistance and much better performance than literature System

    Tunable Optoelectronic Properties of Triply-Bonded Carbon Molecules with Linear and Graphyne Substructures

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    In this paper we present a detailed computational study of the electronic structure and optical properties of triply-bonded hydrocarbons with linear, and graphyne substructures, with the aim of identifying their potential in opto-electronic device applications. For the purpose, we employed a correlated electron methodology based upon the Pariser-Parr-Pople model Hamiltonian, coupled with the configuration interaction (CI) approach, and studied structures containing up to 42 carbon atoms. Our calculations, based upon large-scale CI expansions, reveal that the linear structures have intense optical absorption at the HOMO-LUMO gap, while the graphyne ones have those at higher energies. Thus, the opto-electronic properties depend on the topology of the {graphyne substructures, suggesting that they can be tuned by means of structural modifications. Our results are in very good agreement with the available experimental data.Comment: main text 29 pages + 4 figures + 1 TOC graphic (included), supporting information 21 page

    Zero-temperature Hysteresis in Random-field Ising Model on a Bethe Lattice

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    We consider the single-spin-flip dynamics of the random-field Ising model on a Bethe lattice at zero temperature in the presence of a uniform external field. We determine the average magnetization as the external field is varied from minus infinity to plus infinity by setting up the self-consistent field equations, which we show are exact in this case. We find that for a 3-coordinated Bethe lattice, there is no jump discontinuity in magnetization for arbitrarily small gaussian disorder, but the discontinuity is present for larger coordination numbers. We have checked our results by Monte Carlo simulations employing a technique for simulating classical interacting systems on the Bethe lattice which avoids surface effects altogether.Comment: latex file with 5 eps figures. This version is substantially revised with new material. Submitted to J. Phys.

    Nonprofessional Phagocytosis Can Facilitate Herpesvirus Entry into Ocular Cells

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    Phagocytosis is a major mechanism by which the mediators of innate immunity thwart microbial infections. Here we demonstrate that human herpesviruses may have evolved a common mechanism to exploit a phagocytosis-like entrapment to gain entry into ocular cells. While herpes simplex virus-1 (HSV-1) causes corneal keratitis, cytomegalovirus (CMV) is associated with retinitis in immunocompromised individuals. A third herpesvirus, human herpesvirus-8 (HHV-8), is crucial for the pathogenesis of Kaposi's sarcoma, a common AIDS-related tumor of eyelid and conjunctiva. Using laser scanning confocal microscopy, we show that successful infection of ocular cell types by all the three viruses, belonging to three divergent subfamilies of herpesviruses, is facilitated by induction of F-actin rich membrane protrusions. Inhibitors of F-actin polymerization and membrane protrusion formation, cytochalasin D and latrunculin B, were able to block infection by all three viruses. Similar inhibition was seen by blocking phosphoinositide 3 kinase signaling, which is required for microbial phagocytosis. Transmission electron microscopy data using human corneal fibroblasts for HSV-1, human retinal pigment epithelial cells for CMV, and human conjunctival epithelial cells for HHV-8 are consistent with the possibility that pseudopod-like membrane protrusions facilitate virus uptake by the ocular cells. Our findings suggest a novel mechanism by which the nonprofessional mediators of phagocytosis can be infected by human herpesviruses

    1-Phenyl­isatin

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    In the title compound, C14H9NO2, the phenyl ring makes a dihedral angle of 50.59 (5)° with the mean plane of the isatin fragment. In the crystal, mol­ecules are linked through weak inter­molecular C—H⋯O hydrogen bonds. The crystal structure also exhibits two slipped π–π inter­actions between the benzene rings of neighbouring mol­ecules [centroid–centroid distance = 3.968 (3) Å, inter­planar distance = 3.484 (3) Å and slippage = 1.899 (3) Å], and between the phenyl rings of neighbouring mol­ecules [centroid–centroid distance = 3.968 (3) Å, inter­planar distance = 3.638 (3) Å and slippage = 1.584 (3) Å]

    Herpes simplex virus infects most cell types in vitro: clues to its success

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    Herpes simplex virus (HSV) type-1 and type-2 have evolved numerous strategies to infect a wide range of hosts and cell types. The result is a very successful prevalence of the virus in the human population infecting 40-80% of people worldwide. HSV entry into host cell is a multistep process that involves the interaction of the viral glycoproteins with various cell surface receptors. Based on the cell type, HSV enter into host cell using different modes of entry. The combination of various receptors and entry modes has resulted in a virus that is capable of infecting virtually all cell types. Identifying the common rate limiting steps of the infection may help the development of antiviral agents that are capable of preventing the virus entry into host cell. In this review we describe the major features of HSV entry that have contributed to the wide susceptibility of cells to HSV infection

    Metal-insulator transitions in tetrahedral semiconductors under lattice change

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    Although most insulators are expected to undergo insulator to metal transition on lattice compression, tetrahedral semiconductors Si, GaAs and InSb can become metallic on compression as well as by expansion. We focus on the transition by expansion which is rather peculiar; in all cases the direct gap at Γ\Gamma point closes on expansion and thereafter a zero-gap state persists over a wide range of lattice constant. The solids become metallic at an expansion of 13 % to 15 % when an electron fermi surface around L-point and a hole fermi surface at Γ\Gamma-point develop. We provide an understanding of this behavior in terms of arguments based on symmetry and simple tight-binding considerations. We also report results on the critical behavior of conductivity in the metal phase and the static dielectric constant in the insulating phase and find common behaviour. We consider the possibility of excitonic phases and distortions which might intervene between insulating and metallic phases.Comment: 12 pages, 8 figure

    CFD modelling of meandering channel during floods

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    The three-dimensional Reynolds-averaged Navier–Stokes (RANS) and continuity equations are solved using a standard computational fluid dynamics (CFD) solver to predict flow in a compound meandering channel. High-quality experimental data from the UK Flood Channel Facility (FCF) are used to validate the computational results. The flow velocities, free-surface elevation, bed shear stress and turbulent kinetic energy are predicted reasonably well. The measured and predicted flows are analysed qualitatively and quantitatively to improve further understanding of mean flow, turbulence and secondary flow structures in a compound meandering channel. The streamwise component of the mean vorticity equation is used to quantify the behaviour of secondary flow circulations in terms of their generation, development and decay along the meandering channel. The turbulent kinetic energy equation is used to understand energy expenditure mechanisms of secondary flow circulations. The numerical results show that one of the shear stresses significantly contributes towards the generation of the streamwise vortex and the production rate of turbulent kinetic energy
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