Phase-field simulation of core-annular pipe flow

Phase-field methods have long been used to model the flow of immiscible fluids. Their ability to naturally capture interface topological changes is widely recognized, but their accuracy in simulating flows of real fluids in practical geometries is not established. We here quantitatively investigate the convergence of the phase-field method to the sharp-interface limit with simulations of two-phase pipe flow. We focus on core-annular flows, in which a highly viscous fluid is lubricated by a less viscous fluid, and validate our simulations with an analytic laminar solution, a formal linear stability analysis and also in the fully nonlinear regime. We demonstrate the ability of the phase-field method to accurately deal with non-rectangular geometry, strong advection, unsteady fluctuations and large viscosity contrast. We argue that phase-field methods are very promising for quantitatively studying moderately turbulent flows, especially at high concentrations of the disperse phase.Comment: Paper accepted for publication in International Journal of Multiphase Flo

Pathogen survival and host resistance in the eyespot disease of maize caused by Kabatiella zeae Narita and Hiratsuka

Twenty-two inbreds and the crosses of 3 tester lines (MS153, W64A B84) with 14 inbreds were artificially inoculated with K. zeae. Data on proportion of disease (X) for each genotype were collected periodically, transformed by the Gompertz equation (-1n - 1n(X)), and regressed on time. The k values (regression coefficients) differed statistically among genotypes. Genotypes with the largest k values had the highest levels of disease. A regression analysis of the k values on days to tasseling yielded negative regression coefficients that were significant for the inbreds and for each group of crosses with the 3 testers. Early maturing genotypes were more susceptible, yet it was clear that factors other than maturity conditioned susceptibility. The reaction of the F(,1) crosses to the disease varied according to the susceptibility of the tester lines regardless of maturity;The inbreds and hybrids were quantitatively inoculated in the greenhouse and the number of lesions/plant recorded. The greenhouse data did not correlate with the k values obtained for the genotypes in the field;The survival of K. zeae in maize residues was studied in a no-till field where eyespot inoculum was present. The residues were removed at different intervals. The disease appeared later and at lower severity in plots where infested residues were removed before planting or early in the season than in plots where residues were present on the soil the full season. Residues collected from the no-till plots and spread in a disease-free field initiated eyespot lesions only when collected early in the season (May-June). In another experiment, the disease appeared later and the initial level was lower in plots that had the lowest amount of disease the previous season. In some experiments, the early season differences in disease severity among treatments persisted until harvest and, in others, these differences disappeared as the season progressed;Infested leaf residues and laboratory cultured stromatic hyphae of K. zeae rapidly lost their potential for conidial production after several consecutive cycles of wetting and drying in the laboratory. The sporulation potential decreased to about 0.01% of the original inoculum with five cycles of wetting and drying

HeteroGenius: A Framework for Hybrid Analysis of Heterogeneous Software Specifications

Nowadays, software artifacts are ubiquitous in our lives being an essential part of home appliances, cars, cell phones, and even in more critical activities like aeronautics and health sciences. In this context software failures may produce enormous losses, either economical or, in the worst case, in human lives. Software analysis is an area in software engineering concerned with the application of diverse techniques in order to prove the absence of errors in software pieces. In many cases different analysis techniques are applied by following specific methodological combinations that ensure better results. These interactions between tools are usually carried out at the user level and it is not supported by the tools. In this work we present HeteroGenius, a framework conceived to develop tools that allow users to perform hybrid analysis of heterogeneous software specifications. HeteroGenius was designed prioritising the possibility of adding new specification languages and analysis tools and enabling a synergic relation of the techniques under a graphical interface satisfying several well-known usability enhancement criteria. As a case-study we implemented the functionality of Dynamite on top of HeteroGenius.Comment: In Proceedings LAFM 2013, arXiv:1401.056

Myers-Pospelov Model as an Ensemble of Pais-Uhlenbeck Oscillators: Unitarity and Lorentz Invariance Violation

We study a generalization of a Pais-Uhlenbeck oscillator for fermionic variables. Next, we consider an ensemble of these oscillators and we identify a particular case of the Myers-Pospelov model which is relevant for effective theories of quantum gravity. Finally, by taking the advantage of this connection, we analyze, for this model, the unitarity at one loop order in the low energy regime where no ghost states can be created on-shell. This energy regime is the relevant one when we consider the Myers-Pospelov model as a true effective theory coming from new space-time structure.Comment: 8 pages, 5 figures, to appear in Eur.Phys.Jour.

Library Preparation for Whole Genome Bisulfite Sequencing of Plant Genomes

Epigenetic mechanisms are a key interface between the environment and the genotype. These mechanisms regulate gene expression in response to plant development and environmental stimuli, which ultimately affects the plant’s phenotype. DNA methylation, in particular cytosine methylation, is probably the best studied epigenetic modification in eukaryotes. It has been associated to the regulation of gene expression in response to cell/tissue differentiation, organism development and adaptation to changing environments. Whole genome bisulfite sequencing (WGBS) is considered the gold standard to study DNA methylation at a genome level. Here we present a protocol for the preparation of whole genome bisulfite sequencing libraries from plant samples (grapevine leaves) which includes detailed instructions for sample collection and DNA extraction, sequencing library preparation and bisulfite treatment

Tree-level unitarity, causality and higher-order Lorentz and CPT violation

Higher-order effects of CPT and Lorentz violation within the SME effective framework including Myers-Pospelov dimension-five operator terms are studied. The model is canonically quantized by giving special attention to the arising of indefinite-metric states or ghosts in an indefinite Fock space. As is well-known, without a perturbative treatment that avoids the propagation of ghost modes or any other approximation, one has to face the question of whether unitarity and microcausality are preserved. In this work, we study both possible issues. We found that microcausality is preserved due to the cancellation of residues occurring in pairs or conjugate pairs when they become complex. Also, by using the Lee-Wick prescription, we prove that the $S$ matrix can be defined as perturbatively unitary for tree-level $2\to 2$ processes with an internal fermion line.Comment: 19 pages, 2 figure

Interplay between attenuation- and virulence-factors of Babesia Bovis and their contribution to the establishment of persistent infections in cattle

Bovine babesiosis is an acute and persistent tick-borne global disease caused mainly by the intraerythrocytic apicomplexan parasites Babesia bovis and B. bigemina. B. bovis infected erythrocytes sequester in blood capillaries of the host (cytoadhesion), causing malaria-like neurological signs. Cytoadhesion and antigenic variation in B. bovis are linked to the expression of members of the Variant Erythrocyte Surface Antigen (VESA) gene family. Animals that survive acute B. bovis infection and those vaccinated with attenuated strains remain persistently infected, suggesting that B. bovis parasites use immune escape mechanisms. However, attenuated B. bovis parasites do not cause neurological signs in vaccinated animals, indicating that virulence or attenuation factors play roles in modulating parasite virulence phenotypes. Artificial overexpression of the SBP2t11 protein, a defined attenuation factor, was associated with reduced cytoadhesion, suggesting a role for this protein as a key modulator of virulence in the parasite. Hereby, we propose a model that might be functional in the modulation of B. bovis virulence and persistence that relies on the interplay among SBP2t, VESA proteins, cytoadhesion, and the immune responses of the host. Elucidation of mechanisms used by the parasite to establish persistent infection will likely contribute to the design of new methods for the control of bovine babesiosis