A novel block non-symmetric preconditioner for mixed-hybrid finite-element-based flow simulations

In this work we propose a novel block preconditioner, labelled Explicit Decoupling Factor Approximation (EDFA), to accelerate the convergence of Krylov subspace solvers used to address the sequence of non-symmetric systems of linear equations originating from flow simulations in porous media. The flow model is discretized blending the Mixed Hybrid Finite Element (MHFE) method for Darcy's equation with the Finite Volume (FV) scheme for the mass conservation. The EDFA preconditioner is characterized by two features: the exploitation of the system matrix decoupling factors to recast the Schur complement and their inexact fully-parallel computation by means of restriction operators. We introduce two adaptive techniques aimed at building the restriction operators according to the properties of the system at hand. The proposed block preconditioner has been tested through an extensive experimentation on both synthetic and real-case applications, pointing out its robustness and computational efficiency

On the importance of the heterogeneity assumption in the characterization of reservoir geomechanical properties

The geomechanical analysis of a highly compartmentalized reservoir is performed to simulate the seafloor subsidence due to gas production. The available observations over the hydrocarbon reservoir consist of bathymetric surveys carried out before and at the end of a 10-yr production life. The main goal is the calibration of the reservoir compressibility cM, that is, the main geomechanical parameter controlling the surface response. Two conceptual models are considered: in one (i) cM varies only with the depth and the vertical effective stress (heterogeneity due to lithostratigraphic variability); in another (ii) cM varies also in the horizontal plane, that is, it is spatially distributed within the reservoir stratigraphic units. The latter hypothesis accounts for a possible partitioning of the reservoir due to the presence of sealing faults and thrusts that suggests the idea of a block heterogeneous system with the number of reservoir blocks equal to the number of uncertain parameters. The method applied here relies on an ensemble-based data assimilation (DA) algorithm (i.e. the ensemble smoother, ES), which incorporates the information from the bathymetric measurements into the geomechanical model response to infer and reduce the uncertainty of the parameter cM. The outcome from conceptual model (i) indicates that DA is effective in reducing the cM uncertainty. However, the maximum settlement still remains underestimated, while the areal extent of the subsidence bowl is overestimated. We demonstrate that the selection of the heterogeneous conceptual model (ii) allows to reproduce much better the observations thus removing a clear bias of the model structure. DA allows significantly reducing the cM uncertainty in the five blocks (out of the seven) characterized by large volume and large pressure decline. Conversely, the assimilation of land displacements only partially constrains the prior cM uncertainty in the reservoir blocks marginally contributing to the cumulative seafloor subsidence, that is, blocks with low pressure

Avaliação de genótipos de feijoeiro comum dos grupos carioca e preto na região Sudoeste de Mato Grosso.

O objetivo desse trabalho é obter cultivares mais apropriadas para a agricultura familiar com uso da irrigação no feijoeiro, atendendo também outras regiões do Estado com características climáticas similares

Avaliação de genótipos de feijoeiro comum dos grupos carioca e preto na região Oeste de Mato Grosso.

O objetivo desse trabalho é obter cultivares mais tolerantes a altas temperaturas, menores altitudes e apropriadas para a agricultura familiar que atendam essas condições no estado de Mato Grosso

Estimate of a spatially variable reservoir compressibility by assimilation of ground surface displacement data

Abstract. Fluid extraction from producing hydrocarbon reservoirs can cause anthropogenic land subsidence. In this work, a 3-D finite-element (FE) geomechanical model is used to predict the land surface displacements above a gas field where displacement observations are available. An ensemble-based data assimilation (DA) algorithm is implemented that incorporates these observations into the response of the FE geomechanical model, thus re- ducing the uncertainty on the geomechanical parameters of the sedimentary basin embedding the reservoir. The calibration focuses on the uniaxial vertical compressibility c M , which is often the geomechanical parameter to which the model response is most sensitive. The partition of the reservoir into blocks delimited by faults moti- vates the assumption of a heterogeneous spatial distribution of c M within the reservoir. A preliminary synthetic test case is here used to evaluate the effectiveness of the DA algorithm in reducing the parameter uncertainty associated with a heterogeneous c M distribution. A significant improvement in matching the observed data is obtained with respect to the case in which a homogeneous c M is hypothesized. These preliminary results are quite encouraging and call for the application of the procedure to real gas fields

Oral bacterial microbiota and traumatic injuries of free-ranging Phrynops geoffroanus (Testudines, Chelidae) in southeastern Brazil

During 2006 and 2007, we collected free-ranging Phrynops geoffroanus, from two anthropogenically altered rivers in southeastern Brazil. Oral microbiological samples were taken for isolation of aerobic and facultative anaerobic bacteria; a physical examination was performed;and we evaluated possible effects on the turtles’ health. Twenty-nine species of bacteria were isolated in Piracicaba River turtles (n=10), and twenty-four species in Piracicamirim stream turtles (n=8), most of them gram-negative. In both sites, potential pathogens for reptiles were: Escherichia coli, Klebsiella pneumoniae, Enterobacter agglomerans, Citrobacter freundii, and Bacillus sp. Although boatpropeller lesions were common on the carapace of the turtles, we have not found turtles with signs of clinical diseases. The oral bacterial microbiota of P. geoffroanus inhabiting the Piracicaba River basin are composed of a diverse microbe spectrum, and long-term studies of the effects of pollution and traumatic injuries on this population and its microbial flora are warranted

Upregulated Expression of Toll-like Receptor 4 in Peripheral Blood of Ischaemic Stroke Patients Correlates with Cyclooxygenase 2 Expression

AbstractObjectivesAn inflammatory process following stroke in human brains and systemic inflammatory responses after stroke in humans have been reported by numerous investigators. The aim of the study was to investigate if genes involved in the cyclooxygenase 2 (COX-2) pathway are upregulated at peripheral level in patients after transient ischaemic attack (TIA) and stroke.Design of StudyBlood samples were obtained from two groups of patients undergoing carotid endarterectomy. The first group included 25 patients who presented TIA or ischaemic stroke. The second group included 35 patients who had an asymptomatic internal carotid artery stenosis. Total RNA was isolated and the expression of Toll-like Receptor 4 (TLR4), COX-2, membrane-associated Prostaglandin E synthase (mPGES-1), Prostaglandin E2 receptors (EP3 and EP4) was analysed by real time RT-PCR.ResultsExpression of COX-2 and TLR4 were significantly increased in symptomatic patients (p<0.001). Correlation analysis showed that TLR4 expression significantly correlated with COX-2 expression (R=0.65; p<0.01) in ischaemic stroke patients. This correlation was not observed in TIA and asymptomatic patients.ConclusionsOur results suggest that the peripheral mechanism of inflammatory injury after stroke may be mediated by TLR4 through a COX-2-dependent pathway

Modelling ground rupture due to groundwater withdrawal: applications to test cases in China and Mexico

Abstract. The stress variation induced by aquifer overdraft in sedimentary basins with shallow bedrock may cause rupture in the form of pre-existing fault activation or earth fissure generation. The process is causing major detrimental effects on a many areas in China and Mexico. Ruptures yield discontinuity in both displacement and stress field that classic continuous finite element (FE) models cannot address. Interface finite elements (IE), typically used in contact mechanics, may be of great help and are implemented herein to simulate the fault geomechanical behaviour. Two main approaches, i.e. Penalty and Lagrangian, are developed to enforce the contact condition on the element interface. The incorporation of IE incorporation into a three-dimensional (3-D) FE geomechanical simulator shows that the Lagrangian approach is numerically more robust and stable than the Penalty, thus providing more reliable solutions. Furthermore, the use of a Newton-Raphson scheme to deal with the non-linear elasto-plastic fault behaviour allows for quadratic convergence. The FE – IE model is applied to investigate the likely ground rupture in realistic 3-D geologic settings. The case studies are representative of the City of Wuxi in the Jiangsu Province (China), and of the City of Queretaro, Mexico, where significant land subsidence has been accompanied by the generation of several earth fissures jeopardizing the stability and integrity of the overland structures and infrastructure.</p

Microbiota bacteriana oral e lesões traumáticas no cágado Phrynops geoffroanus (Testudines, Chelidae) no sudeste do Brasil

Entre 2006 e 2007, coletamos amostras microbiológicas da cavidade oral de cágados Phrynops geoffroanus de vida livre, em dois rios antropizados da região sudeste do Brasil, para o isolamento de bactérias aeróbicas e anaeróbicas facultativas, e realizamos um exame físico e avaliamos possíveis efeitos sobre o estado de saúde dos animais. Vinte e nove espécies de bactérias foram isoladas em cágados do rio Piracicaba (n=10), e vinte e quatro espécies em animais do ribeirão Piracicamirim (n=8), a maioria delas gram-negativas. Em ambos os sítios estudados foram isolados patógenos potenciais para répteis, como Escherichia coli, Klebsiella pneumoniae, Enterobacter agglomerans, Citrobacter freundii e Bacillus sp. Embora lesões na carapaça dos cágados, causadas por hélices de barcos, foram um achado comum no exame físico, não encontramos animais com sinais clínicos de doenças. A microbiota bacteriana oral dos cágados que habitam a bacia do rio Piracicaba é composta por um amplo espectro de bactérias, e estudos de longa duração sobre os efeitos da poluição e de lesões traumáticas nesta população e de sua microbiota oral são recomendados.During 2006 and 2007, we collected free-ranging Phrynops geoffroanus, from two anthropogenically altered rivers in southeastern Brazil. Oral microbiological samples were taken for isolation of aerobic and facultative anaerobic bacteria; a physical examination was performed; and we evaluated possible effects on the turtles' health. Twenty-nine species of bacteria were isolated in Piracicaba River turtles (n=10), and twenty-four species in Piracicamirim stream turtles (n=8), most of them gram-negative. In both sites, potential pathogens for reptiles were: Escherichia coli, Klebsiella pneumoniae, Enterobacter agglomerans, Citrobacter freundii, and Bacillus sp. Although boat propeller lesions were common on the carapace of the turtles, we have not found turtles with signs of clinical diseases. The oral bacterial microbiota of P. geoffroanus inhabiting the Piracicaba River basin are composed of a diverse microbe spectrum, and long-term studies of the effects of pollution and traumatic injuries on this population and its microbial flora are warranted

Decompensated cirrhosis as presentation of LKM1/LC1 positive type 2 autoimmune hepatitis in adulthood. A rare clinical entity of difficult management

Background: Autoimmune hepatitis (AIH) is a chronic and aggressive liver disease that rapidly evolves into cirrhosis and end-stage liver disease if not timely diagnosed and treated with immunosuppressive therapy. AIH is classified into type 1 and type 2 according to the autoantibody pattern, with smooth muscle antibodies and/or antinuclear antibodies as serological markers of AIH-1, while antiliver cytosol antibody type 1 and/or antiliver/kidney microsomal antibody type 1 characterize type 2 AIH, which mainly affects children, including infants, and adolescents. Case Summary: We describe a case of type 2 AIH, clinically onset in a 34-year-old woman with decompensated cirrhosis. Only a thorough analysis of the autoantibody profile allowed for a diagnosis of an AIH-2 evolved into cirrhosis. The patient received a moderate corticosteroid therapy without achieving optimal disease control. We discuss the controversial decision of whether or not to treat the patient with immunosuppressive therapy, which should be balanced with the potential risk of infectious and other complications. A review of the literature on the management of patients with autoimmune cirrhosis is also presented. Conclusions: AIH-2 can be clinically onset in adult patients with cirrhosis and its complications, without being preceded by major clinical signs. Due to the difficult management of cirrhosis with immunosuppressive treatments, a patient-tailored strategy with a case-by-case approach is needed to prevent major complications such as infections, potentially precluding liver transplantation the only curative therapy