Damage Spreading at the Corner Filling Transition in the two-dimensional Ising Model

The propagation of damage on the square Ising lattice with a corner geometry is studied by means of Monte Carlo simulations. It is found that, just at $T=T_f (h)$ (critical temperature of the filling transition) the damage initially propagates along the interface of the competing domains, according to a power law given by $D(t) \propto t^{\eta}$. The value obtained for the dynamic exponent ($\eta^{*} = 0.89(1)$) is in agreement with that corresponding to the wetting transition in the slit geometry (Abraham Model) given by $\eta^{WT} = 0.91(1)$. However, for later times the propagation crosses to a new regime such as $\eta^{**} = 0.40 \pm 0.02$, which is due to the propagation of the damage into the bulk of the magnetic domains. This result can be understood due to the constraints imposed to the propagation of damage by the corner geometry of the system that cause healing at the corners where the interface is attached.Comment: 22 pages, including figures Submited to J. Phys.: Condens. Matte

Effect of Gravity and Confinement on Phase Equilibria: A Density Matrix Renormalization Approach

The phase diagram of the 2D Ising model confined between two infinite walls and subject to opposing surface fields and to a bulk "gravitational" field is calculated by means of density matrix renormalization methods. In absence of gravity two phase coexistence is restricted to temperatures below the wetting temperature. We find that gravity restores the two phase coexistence up to the bulk critical temperature, in agreement with previous mean-field predictions. We calculate the exponents governing the finite size scaling in the temperature and in the gravitational field directions. The former is the exponent which describes the shift of the critical temperature in capillary condensation. The latter agrees, for large surface fields, with a scaling assumption of Van Leeuwen and Sengers. Magnetization profiles in the two phase and in the single phase region are calculated. The profiles in the single phase region, where an interface is present, agree well with magnetization profiles calculated from a simple solid-on-solid interface hamiltonian.Comment: 4 pages, RevTeX and 4 PostScript figures included. Final version as published. To appear in Phys. Rev. Let

Engineering squeezed states in high-Q cavities

While it has been possible to build fields in high-Q cavities with a high degree of squeezing for some years, the engineering of arbitrary squeezed states in these cavities has only recently been addressed [Phys. Rev. A 68, 061801(R) (2003)]. The present work examines the question of how to squeeze any given cavity-field state and, particularly, how to generate the squeezed displaced number state and the squeezed macroscopic quantum superposition in a high-Q cavity

A general NMR spectral density and its experimental verification

The authors develop a new general spectral density for use in interpreting nuclear spin-lattice relaxation measurements in molecular solids where molecular and/or intramolecular reorientation is responsible for the relaxation. They show that the simplest case of the general theory fits both the temperature and Lamor frequency dependence of some very complicated relaxation measurements which could not be previously fitted using several standard spectral densities. The relationship of the spectral density to a distribution of molecular potentials is briefly outlined

A symmetric polymer blend confined into a film with antisymmetric surfaces: interplay between wetting behavior and phase diagram

We study the phase behavior of a symmetric binary polymer blend which is confined into a thin film. The film surfaces interact with the monomers via short range potentials. We calculate the phase behavior within the self-consistent field theory of Gaussian chains. Over a wide range of parameters we find strong first order wetting transitions for the semi-infinite system, and the interplay between the wetting/prewetting behavior and the phase diagram in confined geometry is investigated. Antisymmetric boundaries, where one surface attracts the A component with the same strength than the opposite surface attracts the B component, are applied. The phase transition does not occur close to the bulk critical temperature but in the vicinity of the wetting transition. For very thin films or weak surface fields one finds a single critical point at $\phi_c=1/2$. For thicker films or stronger surface fields the phase diagram exhibits two critical points and two concomitant coexistence regions. Only below a triple point there is a single two phase coexistence region. When we increase the film thickness the two coexistence regions become the prewetting lines of the semi-infinite system, while the triple temperature converges towards the wetting transition temperature from above. The behavior close to the tricritical point, which separates phase diagrams with one and two critical points, is studied in the framework of a Ginzburg-Landau ansatz. Two-dimensional profiles of the interface between the laterally coexisting phases are calculated, and the interfacial and line tensions analyzed. The effect of fluctuations and corrections to the self-consistent field theory are discussed.Comment: Phys.Rev.E in prin

The incursion, persistence and spread of peste des petits ruminants in Tanzania: Epidemiological patterns and predictions

Peste des petits ruminants virus, which causes a severe disease in sheep and goats, has only recently been officially declared to be present in Tanzania. An epidemiological study was carried out between September 2008 and October 2010 to investigate the incursion, persistence and spread of the virus in Tanzania. The investigation involved serosurveillance, outbreak investigation and computation of epidemiological indices such as the effective reproductive number, persistence and the threshold level for vaccination. Field and molecular epidemiological techniques were applied to isolate, characterise and trace the origin of the virus in Tanzania. A total of 2182 serum samples from goats and 1296 from sheep from 79 villages across 12 districts were investigated. Village-level prevalence of infection was variable (0.00% – 88.00%) and was higher in pastoral than in agro-pastoral villages. The overall antibody response to the virus was 22.10% (CI 95% = 20.72% – 23.48%). About 68.00% and 73.00% of seropositive goats and sheep, respectively, did not show clinical signs. The proportion of seropositive animals differed significantly (p ≤ 0.001) between age groups, sex and farming practices. Real-time polymerase chain reaction results showed that the isolated strains belong to lineage III, whose origin is in East Africa and the Middle East. This indicates that one of the northern neighbouring countries is most likely the source of infection. The computed overall effective reproductive number, the threshold level of vaccination necessary to eradicate the disease and persistence were 4.75% and 98.00%, respectively. These estimates indicate that achieving elimination of the peste des petits ruminants virus from pastoral flocks will require significant effort and development of highly effective intervention tools

Sodium-dependent phosphate transporters in osteoclast differentiation and function.

Osteoclasts are multinucleated bone degrading cells. Phosphate is an important constituent of mineralized bone and released in significant quantities during bone resorption. Molecular contributors to phosphate transport during the resorptive activity of osteoclasts have been controversially discussed. This study aimed at deciphering the role of sodium-dependent phosphate transporters during osteoclast differentiation and bone resorption. Our studies reveal RANKL-induced differential expression of sodium-dependent phosphate transport protein IIa (NaPi-IIa) transcript and protein during osteoclast development, but no expression of the closely related NaPi-IIb and NaPi-IIc SLC34 family isoforms. In vitro studies employing NaPi-IIa-deficient osteoclast precursors and mature osteoclasts reveal that NaPi-IIa is dispensable for bone resorption and osteoclast differentiation. These results are supported by the analysis of structural bone parameters by high-resolution microcomputed tomography that yielded no differences between adult NaPi-IIa WT and KO mice. By contrast, both type III sodium-dependent phosphate transporters Pit-1 and Pit-2 were abundantly expressed throughout osteoclast differentiation, indicating that they are the relevant sodium-dependent phosphate transporters in osteoclasts and osteoclast precursors. We conclude that phosphate transporters of the SLC34 family have no role in osteoclast differentiation and function and propose that Pit-dependent phosphate transport could be pivotal for bone resorption and should be addressed in further studies

Comparative study of an Eden model for the irreversible growth of spins and the equilibrium Ising model

The Magnetic Eden Model (MEM) with ferromagnetic interactions between nearest-neighbor spins is studied in $(d+1)-$dimensional rectangular geometries for $d = 1,2$. In the MEM, magnetic clusters are grown by adding spins at the boundaries of the clusters. The orientation of the added spins depends on both the energetic interaction with already deposited spins and the temperature, through a Boltzmann factor. A numerical Monte Carlo investigation of the MEM has been performed and the results of the simulations have been analyzed using finite-size scaling arguments. As in the case of the Ising model, the MEM in $d = 1$ is non-critical (only exhibits an ordered phase at $T= 0$). In $d = 2$ the MEM exhibits an order-disorder transition of second-order at a finite temperature. Such transition has been characterized in detail and the relevant critical exponents have been determined. These exponents are in agreement (within error bars) with those of the Ising model in 2 dimensions. Further similarities between both models have been found by evaluating the probability distribution of the order parameter, the magnetization and the susceptibility. Results obtained by means of extensive computer simulations allow us to put forward a conjecture which establishes a nontrivial correspondence between the MEM for the irreversible growth of spins and the equilibrium Ising model. This conjecture is certainly a theoretical challenge and its confirmation will contribute to the development of a framework for the study of irreversible growth processes.Comment: 21 pages, 11 figure

Nuclear-Spin-Relaxation Study of Internal Motion in Two Organic Molecular Solids

We investigate proton spin-lattice relaxation in two powdered organic molecular solids with reorienting methyl (CH3) and tert-butyl [C(CH3)3] groups: 3,5-di-tert-butylphenol (DTBP) and 1,3,5-tri-tert-butylbenzene (TTBZ). The temperature and Larmor frequency dependence of the relaxation rate is considerably more complicated than would be expected on the basis of random reorientations of the CH3 and C(CH3)3 groups. The spectral densities describing the relaxation are broader, and show more structure, than those customarily used to interpret relaxation data. Assuming that the spectral densities may be expressed as linear superpositions of Lorentzians, we are able to obtain a single, nonexponential correlation function which leads to satisfactory fits of the data. Assuming also the validity of the Arrhenius relation, τ=τ∞exp(E/kT), with a constant τ∞, we find that the barriers to rotation for the CH3 and C(CH3)3 groups may be characterized by a distribution of activation energies consisting of a wide background and one (DTBP) or two (TTBZ) δ functions

Sanitary practices and occurrence of zoonotic conditions in cattle at slaughter in Morogoro Municipality, Tanzania: implications for public health

As meat consumption is increasing worldwide to cover for protein demands, also raise concerns and challenges regarding meat hygiene and safety. The current one year follow up study aimed at investigating on sanitary practices and occurrence of zoonotic conditions, during post-mortem examination, in cattle at slaughter in Morogoro Municipality abattoir. Sanitary practices were assessed through direct observation where as routine post-mortem inspection procedures were employed to detect zoonotic conditions in cattle at slaughter. During the study period a total of 30,713 cattle were slaughtered and inspected at the abattoir. Results revealed poor hygienic practices at the level of abattoir surrounding, the slaughter operation area, personnel as well as meat vans. Whole carcasses, lungs, livers, hearts and heads were condemned due to zoonotic conditions at rates of 0.026%, 1.96%, 1.61%, 0.02% and 0.21% respectively. Bovine tuberculosis, Cysticercus bovis cysts, fasciolosis and hydatidosis were the responsible zoonotic conditions for the condemnations. Bovine tuberculosis was a leading zoonotic cause of condemnations accounting for 95.7% of lungs and 100% of all head and carcass condemnations. Cysticercus bovis cysts were ranking the second in serving as causes of condemnations closely followed by fasciolosis and lastly hydatidosis. Occurrence of disease conditions with zoonotic implication in cattle at slaughter, meant for human consumption, may pose significant economic and public health risks to especially disaster-prone marginalized communities. Thus, there is a need to introduce appropriate control measures of livestock diseases to minimize the rate of infection; and eventually reduce economic losses and safeguard public health