Living bacteria rheology: population growth, aggregation patterns and cooperative behaviour under different shear flows

The activity of growing living bacteria was investigated using real-time and in situ rheology -- in stationary and oscillatory shear. Two different strains of the human pathogen Staphylococcus aureus -- strain COL and its isogenic cell wall autolysis mutant -- were considered in this work. For low bacteria density, strain COL forms small clusters, while the mutant, presenting deficient cell separation, forms irregular larger aggregates. In the early stages of growth, when subjected to a stationary shear, the viscosity of both strains increases with the population of cells. As the bacteria reach the exponential phase of growth, the viscosity of the two strains follow different and rich behaviours, with no counterpart in the optical density or in the population's colony forming units measurements. While the viscosity of strain COL keeps increasing during the exponential phase and returns close to its initial value for the late phase of growth, where the population stabilizes, the viscosity of the mutant strain decreases steeply, still in the exponential phase, remains constant for some time and increases again, reaching a constant plateau at a maximum value for the late phase of growth. These complex viscoelastic behaviours, which were observed to be shear stress dependent, are a consequence of two coupled effects: the cell density continuous increase and its changing interacting properties. The viscous and elastic moduli of strain COL, obtained with oscillatory shear, exhibit power-law behaviours whose exponent are dependent on the bacteria growth stage. The viscous and elastic moduli of the mutant have complex behaviours, emerging from the different relaxation times that are associated with the large molecules of the medium and the self-organized structures of bacteria. These behaviours reflect nevertheless the bacteria growth stage.Comment: 9 pages, 10 figure

Smart capabilities of a laminated piezoelectric plate model

This paper focuses on the modelling and analysis of actuator and sensor effects for thin laminated plates, which are formed by stacking several layers of different piezoelectric materials. We first discuss features and properties of a two-dimensional asymptotic model for a piezoelectric anisotropic plate, whose unknowns are the Kirchhoff-Love displacement and the electric potential. We prove that the latter is a quadratic polynomial of the plate’s thickness. The polynomial’s coefficients depend on the tangential and transverse displacements of the plate’s middle plane and the material coefficients. The asymptotic laminated plate model is discretized using finite elements. To investigate its smart capabilities we use two discrete optimization problems: the first one, focusing on the actuator effect, aims at obtaining a maximum displacement of the plate’s middle plane; the second one that corresponds to the sensor effect intends to maximize the electric potential at a predefined thickness of the plate. The optimization variables are the thicknesses of the layers, their ordering as well as the location of the applied electric potential (for the actuator problem) or the location of the applied mechanical forces (for the sensor problem). Since we also want to minimize the number of these locations (besides maximizing the above objectives), we obtain a multi-objective optimization problem that we solve using genetic algorithms. Several numerical results are reported

Smart capabilities of a laminated piezoelectric plate model

This paper focuses on the modelling and analysis of actuator and sensor effects for thin laminated plates, which are formed by stacking several layers of different piezoelectric materials. We first discuss features and properties of a two-dimensional asymptotic model for a piezoelectric anisotropic plate, whose unknowns are the Kirchhoff-Love displacement and the electric potential. We prove that the latter is a quadratic polynomial of the plate’s thickness. The polynomial’s coefficients depend on the tangential and transverse displacements of the plate’s middle plane and the material coefficients. The asymptotic laminated plate model is discretized using finite elements. To investigate its smart capabilities we use two discrete optimization problems: the first one, focusing on the actuator effect, aims at obtaining a maximum displacement of the plate’s middle plane; the second one that corresponds to the sensor effect intends to maximize the electric potential at a predefined thickness of the plate. The optimization variables are the thicknesses of the layers, their ordering as well as the location of the applied electric potential (for the actuator problem) or the location of the applied mechanical forces (for the sensor problem). Since we also want to minimize the number of these locations (besides maximizing the above objectives), we obtain a multi-objective optimization problem that we solve using genetic algorithms. Several numerical results are reported

Respiratory hospital admission risk near large composting facilities

AbstractBackgroundLarge-scale composting can release bioaerosols in elevated quantities, but there are few studies of health effects on nearby communities.MethodsA cross-sectional ecological small area design was used to examine risk of respiratory hospital admissions within 2500m of all 148 English large-scale composting facilities in 2008–10. Statistical analyses used a random intercept Poisson regression model at Census Output Area (COA) level (mean population 310). Models were adjusted for age, sex, deprivation and tobacco sales.ResultsAnalysing 34,963 respiratory hospital admissions in 4656 COAs within 250–2500m of a site, there were no significant trends using pre-defined distance bands of >250–750m, >750–1500m and >1500–2500m. Using a continuous measure of distance, there was a small non-statistically significant (p=0.054) association with total respiratory admissions corresponding to a 1.5% (95% CI: 0.0–2.9%) decrease in risk if moving from 251m to 501m. There were no significant associations for subgroups of respiratory infections, asthma or chronic obstructive pulmonary disease.ConclusionThis national study does not provide evidence for increased risks of respiratory hospital admissions in those living beyond 250m of an outdoor composting area perimeter. Further work using better measures of exposure and exploring associations with symptoms and disease prevalence, especially in vulnerable groups, is recommended to support regulatory approaches

Cutaneous necrobiotic xanthogranuloma (NXG)--successfully treated with low dose chlorambucil.

Eur J Dermatol. 2001 Sep-Oct;11(5):458-62. Cutaneous necrobiotic xanthogranuloma (NXG)--successfully treated with low dose chlorambucil. Machado S, Alves R, Lima M, Leal I, Massa A. SourceService of Dermatology, Hospital Geral Santo António, Rua D. Manuel II, Edifício ex: Cicap, 4099-001 Porto, Portugal. [email protected] Abstract We report a case of necrobiotic xanthogranuloma in a 51 year-old white male patient presenting with a 6-year history of multiple indurated violaceous nodules and plaques involving the eyelids, trunk and extremities. He had an associated paraproteinemia (Ig G lambda), elevated sedimentation rate, cryoglobulinemia and hypocomplementemia. No extracutaneous involvement was detected. He was successfully treated with chlorambucil (2 mg/d for 7 months), leading to disappearance of all skin lesions

Necrotizing Enterocolitis with Perforation and Peritoneal Drainage in the Very Low Birth Weight Infant: A Case with Favourable Outcome

A enterocolite necrosante (ECN) constitui o problema gastrointestinal mais grave e mais frequente no recém-nascido (RN) de baixo peso. A melhoria na taxa de sobrevivência tem sido atribuída ao diagnóstico mais precoce e à experiência adquirida no tratamento do recém-nascido pré-termo em estado crítico. Desde 1977 que a drenagem peritoneal como actuação prioritária nos quadros de ECN tem sido preconizada nos recém- -nascidos de peso inferior a 1500 g com perfuração intestinal, e nos de peso superior a 1500 g com instabilidade hemodinâmica. Neste artigo relata-se o caso de um recém-nascido, com 1473 g de peso e 30 semanas de idade gestacional, ECN, sinais de perfuração intestinal e de instabilidade hemodinâmica, o qual foi submetido a drenagem peritoneal com evolução favorável e sem sequelas. Na discussão faz-se referência especial, de acordo com dados de literatura, aos mecanismos que explicam os bons resultados do procedimento em cerca de 2/3 dos casos de ECN com perfuração, os quais estão relacionados com as características particulares da cicatrização nos tecidos imaturos. Em conclusão, admite-se que a drenagem peritoneal deverá constituir a forma de actuação prioritária nos casos de ECN com perfuração e instabilidade hemodinâmica em RN pré-termo de muito baixo peso

Nonuniversality in the pair contact process with diffusion

We study the static and dynamic behavior of the one dimensional pair contact process with diffusion. Several critical exponents are found to vary with the diffusion rate, while the order-parameter moment ratio m=\bar{rho^2} /\bar{rho}^2 grows logarithmically with the system size. The anomalous behavior of m is traced to a violation of scaling in the order parameter probability density, which in turn reflects the presence of two distinct sectors, one purely diffusive, the other reactive, within the active phase. Studies restricted to the reactive sector yield precise estimates for exponents beta and nu_perp, and confirm finite size scaling of the order parameter. In the course of our study we determine, for the first time, the universal value m_c = 1.334 associated with the parity-conserving universality class in one dimension.Comment: 9 pages, 5 figure

Efeito da taxa de secreção de néctar sobre o sucesso de polinização de Passiflora coccinea (Passifloraceae) na Amazônia Central

The pollination of Passiflora coccinea by the hummingbird Phaethornis superciliosus was studied in Central Amazon, Brazil. We hypothesized that a greater nectar secretion rate (NSR) increases the pollination success of single flowers through Ph. superciliosus visiting behavior. For control flowers, NSR was an increasing function of flower base diameter (FBD). The total number of Ph. superciliosus probes per flower was an increasing function of FBD. Additionally, deposition of pollen on stigmas increased with the cumulative number of Ph. superciliosus probes. Our results show that larger P. coccinea flowers secrete nectar at higher rates, are probed more times during each hummingbird visit and are more successful at pollination. This seems to be the first non-manipulative study describing such an effect of NSR on the pollination of single flowers in nature.Estudamos a polinização de Passiflora coccinea por beija-flores Phaethornis superciliosus na Amazônia Central, Brasil. Nossa hipótese é que maiores taxas de secreção de néctar (TSN) aumentam o sucesso da polinização de flores individuais através do comportamento de visitas de Ph. superciliosus. Para flores controladas, a TSN foi uma função positiva do diâmetro da base da flor (DBF). O número total de visitas de Ph. superciliosus por flor foi uma função positiva do DBF. Adicionalmente, a deposição de pólen sobre os estigmas aumentou com o aumento do número acumulado de visitas de Ph. superciliosus. Nossos resultados indicam que flores maiores de P. coccinea secretam néctar em taxas mais altas, são visitadas mais vezes pelos beija-flores, e apresentam maior sucesso de polinização. Este parece ser o primeiro estudo não-manipulativo que descreve este efeito da TSN sobre o sucesso de polinização de flores individuais na natureza.747754Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

Jerimu 8, batata doce rica em carotenos: estabilidade no cozimento doméstico e no processamento de farinhas.

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