In situ grazing resistance of Vibrio cholerae in the marine environment

Previous laboratory experiments revealed that Vibrio cholerae A1552 biofilms secrete an antiprotozoal factor that prevents Rhynchomonas nasuta from growing and thus prevents grazing losses. The antiprotozoal factor is regulated by the quorum-sensing response regulator, HapR. Here, we investigate whether the antiprotozoal activity is ecologically relevant. Experiments were conducted in the field as well as under field-like conditions in the laboratory to assess the grazing resistance of V. cholerae A1552 and N16961 (natural frameshift mutation in hapR) biofilms to R. nasuta and Cafeteria roenbergensis. In laboratory experiments exposing the predators to V. cholerae grown in seawater containing high and low glucose concentrations, we determined that V. cholerae biofilms showed increased resistance towards grazing by both predators as glucose levels decreased. The relative resistance of the V. cholerae strains to the grazers under semi-field conditions was similar to that observed in situ. Therefore, the antipredator defense is environmentally relevant and not lost when biofilms are grown in an open system in the marine environment. The hapR mutant still exhibited some resistance to both predators and this suggests that V. cholerae may coordinate antipredator defenses by a combination of density-dependent regulation and environmental sensing to protect itself from predators in its natural habitat. © 2011 Federation of European Microbiological Societies

Settlement in Sands Due to Cyclic Loading

Stress controlled undrained cyclic triaxial tests have been conducted on undisturbed sandy and silty soil samples obtained by special sampler in order to minimize the effect of disturbance. The influence of fines content on liquefaction - induced volumetric strains have been studied. The results indicate that cyclic mobility of sands is affected by non – plastic fines content. As fines content increase, cyclic shear strength decreases. Volumetric strain is influenced by fines content as well as shear strain and cyclic stress. At large shear strains amplitudes, an increase in percentage of fines causes more volumetric strains. Volumetric strains of silt samples are affected by cyclic shear stress more than sands

Cosmic axion thermalization

Axions differ from the other cold dark matter candidates in that they form a degenerate Bose gas. It is shown that their huge quantum degeneracy and large correlation length cause cold dark matter axions to thermalize through gravitational self-interactions when the photon temperature reaches approximately 500 eV. When they thermalize, the axions form a Bose-Einstein condensate. Their thermalization occurs in a regime, herein called the `condensed regime', where the Boltzmann equation is not valid because the energy dispersion of the particles is smaller than their interaction rate. We derive analytical expressions for the thermalization rate of particles in the condensed regime, and check the validity of these expressions by numerical simulation of a toy model. We revisit axion cosmology in light of axion Bose-Einstein condensation. It is shown that axions are indistinguishable from ordinary cold dark matter on all scales of observational interest, except when they thermalize or rethermalize. The rethermalization of axions that are about to fall in a galactic potential well causes them to acquire net overall rotation as they go to the lowest energy state consistent with the total angular momentum they acquired by tidal torquing. This phenomenon explains the occurrence of caustic rings of dark matter in galactic halos. We find that photons may reach thermal contact with axions and investigate the implications of this possibility for the measurements of cosmological parameters.Comment: 38 pages, 1 figur

Improving business processes of service companies

This article considers the problem of improving business process through analysis “Highlighting areas of concern”. In the process, we formulated a number of requirements that should meet the functionality of the information system and highlighted advantages of the"Selection concerns" method

Axions and saxions from the primordial supersymmetric plasma and extra radiation signatures

We calculate the rate for thermal production of axions and saxions via scattering of quarks, gluons, squarks, and gluinos in the primordial supersymmetric plasma. Systematic field theoretical methods such as hard thermal loop resummation are applied to obtain a finite result in a gauge-invariant way that is consistent to leading order in the strong gauge coupling. We calculate the thermally produced yield and the decoupling temperature for both axions and saxions. For the generic case in which saxion decays into axions are possible, the emitted axions can constitute extra radiation already prior to big bang nucleosynthesis and well thereafter. We update associated limits imposed by recent studies of the primordial helium-4 abundance and by precision cosmology of the cosmic microwave background and large scale structure. We show that the trend towards extra radiation seen in those studies can be explained by late decays of thermal saxions into axions and that upcoming Planck results will probe supersymmetric axion models with unprecedented sensitivity.Comment: 16 pages, 7 figures; v2: references added, minor clarifying additions, matches published versio

Effects of elastoviscoplastic properties of mucus on airway closure in healthy and pathological conditions

Airway mucus is a complex material with both viscoelastic and viscoplastic properties that vary with healthy and pathological conditions of the lung. In this study, the effects of these conditions on airway closure are examined in a model problem, where an elastoviscoplastic (EVP) single liquid layer lines the inner wall of a rigid pipe and surrounds the air core. The EVP liquid layer is modelled using the Saramito-HB model. The parameters for the model are obtained for the mucus in healthy, asthma, chronic obstructive pulmonary disease (COPD), and cystic fibrosis (CF) conditions by fitting the rheological model to the experimental data. Then the liquid plug formation is studied by varying the Laplace number and undisturbed liquid film thickness. Airway closure is a surface-tension-driven phenomenon that occurs when the ratio of the pulmonary liquid layer thickness to the airway radius exceeds a certain threshold. In previous studies, it has been found that airway epithelial cells can be lethally or sublethally damaged due to the high peak of the wall stresses and stress gradients during the liquid plug formation. Here we demonstrate that these stresses are also related to the EVP features of the liquid layer. Yielded zones of the liquid layer are investigated for the different mucus conditions, and it is found that the liquid layer is in a chiefly unyielded state before the closure, which indicates that this phase is dominated by the elastic behavior and solvent viscosity. This is further confirmed by showing that the elastic coefficient is one of the most critical parameters determining whether the closure occurs. This parameter also largely affects the closure time. The wall stresses are also investigated for the pathological and healthy cases. Their peaks for COPD and CF are found to be the highest due to the viscoelastic extra stress contribution. Contrary to the Newtonian case, the wall stresses for COPD and CF do not smoothly relax after closure, as they rather remain effectively almost as high as the Newtonian peak. Moreover, the local normal wall stress gradients are smaller for the COPD and CF liquid layer due to their higher stiffness causing a smaller curvature at the capillary wave. The local tangential wall stress gradients are also shown to be smaller for these cases because of the slower accumulation of the liquid at the bulge

Human MLH1 deficiency predisposes to hematological malignancy and neurofibromatosis type 1

Heterozygous germ-line mutations in the DNA mismatch repair genes lead to hereditary nonpolyposis colorectal cancer. The disease susceptibility of individuals who constitutionally lack both wild-type alleles is unknown. We have identified three offspring in a hereditary nonpolyposis colorectal cancer family who developed hematological malignancy at a very early age, and at least two of them displayed signs of neurofibromatosis type 1 (NF1). DNA sequence analysis and allele-specific amplification in two siblings revealed a homozygous MLH1 mutation (C676T → Arg226Stop). Thus, a homozygous germ- line MLH1 mutation and consequent mismatch repair deficiency results in a mutator phenotype characterized by leukemia and/or lymphoma associated with neurofibromatosis type 1

Coupled Boltzmann calculation of mixed axion/neutralino cold dark matter production in the early universe

We calculate the relic abundance of mixed axion/neutralino cold dark matter which arises in R-parity conserving supersymmetric (SUSY) models wherein the strong CP problem is solved by the Peccei-Quinn (PQ) mechanism with a concommitant axion/saxion/axino supermultiplet. By numerically solving the coupled Boltzmann equations, we include the combined effects of 1. thermal axino production with cascade decays to a neutralino LSP, 2. thermal saxion production and production via coherent oscillations along with cascade decays and entropy injection, 3. thermal neutralino production and re-annihilation after both axino and saxion decays, 4. gravitino production and decay and 5. axion production both thermally and via oscillations. For SUSY models with too high a standard neutralino thermal abundance, we find the combined effect of SUSY PQ particles is not enough to lower the neutralino abundance down to its measured value, while at the same time respecting bounds on late-decaying neutral particles from BBN. However, models with a standard neutralino underabundance can now be allowed with either neutralino or axion domination of dark matter, and furthermore, these models can allow the PQ breaking scale f_a to be pushed up into the 10^{14}-10^{15} GeV range, which is where it is typically expected to be in string theory models.Comment: 26 pages with 12 .eps figure

Control de cambios / Rastrea los cambios / El camino cambia: Reflexiones sobre un mundo en transformación

“Track changes: Reflecting on a transforming world” was the theme chosen to invite panels, papers, posters and alternative presentations to be part of the 2019 international congress of SIEF that was held in Santiago de Compostela, Galicia (Spain). This introduction includes a description of the content of the congress, the rationale of the choice of plenaries and some reflections about the outcomes of the congress.El lema elegido para presentar paneles, ponencias, posters y presentaciones en formatos alternativos para el congreso internacional 2019 de SIEF -que tuvo lugar en Santiago de Compostela, Galicia (España)- fue “Track changes: Reflecting on a transforming world”. Esta introducción incluye una descripción del contenido del congreso, la idea para la elección de las plenarias y algunas reflexiones sobre los resultados del congreso. &nbsp