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

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.

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

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

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

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

Metal-insulator transitions in tetrahedral semiconductors under lattice change

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 $\Gamma$ 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 $\Gamma$-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

Effect of cadmium chloride on general body colouration and chromatophores of stinging cat fish, Heteropneustes fossilis (Bloch)

Chromatophores, specialized pigment cells in poikilothermic animals, have shown great potential in their use as a cell-based biosensor in the detection of a broad range of environmental toxicants, as structure and number of chromatophores alters significantly under toxicant exposure. Skin coloration of Heteropneustes fossilis is due to melanin containing melanophores. Cadmium, the black listed and non essential heavy metal, is widely used that adversely affects vital activities of aquatic biota. H. fossilis, freshwater Indian stinging catfish, were subjected to exposure of 96 hour LC50 dose (392.92 mg/l) and 25% of 96 hour LC50 dose (98.23mg/l) of cadmium chloride (CdCl2) to evaluate toxic impact of cadmium on colouration and chromatophores. A significant decrease was observed in number of chromatophores after acute (highly significant (F = 70.50; P<0.001) and sub acute (significant (F = 0.29; P<0.05) exposure along with heavy nacrotic, lytic and degenerative changes. Chromatophore gradually changed from reticulate to punctate-stellate and punctuate type as they lost their dendritic processes and aggregation of melanin towards centre. Most of the chromatophores lost their cellular entity due to degenerative changes and melanin was found dispersed in surrounding matrix. Peeling and fading of skin was the common feature in all exposure durations. Fish chromatophores may serve as better biomarkers in reference to metallic pollution and will also be helpful in accessing the health status of economically important fishes as well as worsening status of aquatic bodies

Hysteresis in the Random Field Ising Model and Bootstrap Percolation

We study hysteresis in the random-field Ising model with an asymmetric distribution of quenched fields, in the limit of low disorder in two and three dimensions. We relate the spin flip process to bootstrap percolation, and show that the characteristic length for self-averaging $L^*$ increases as $exp(exp (J/\Delta))$ in 2d, and as $exp(exp(exp(J/\Delta)))$ in 3d, for disorder strength $\Delta$ much less than the exchange coupling J. For system size $1 << L < L^*$, the coercive field $h_{coer}$ varies as $2J - \Delta \ln \ln L$ for the square lattice, and as $2J - \Delta \ln \ln \ln L$ on the cubic lattice. Its limiting value is 0 for L tending to infinity, both for square and cubic lattices. For lattices with coordination number 3, the limiting magnetization shows no jump, and $h_{coer}$ tends to J.Comment: 4 pages, 4 figure

Collusion Resistive Framework for Multimedia Security

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

Nonprofessional Phagocytosis Can Facilitate Herpesvirus Entry into Ocular Cells

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

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]