Parallel Matrix-free polynomial preconditioners with application to flow simulations in discrete fracture networks

We develop a robust matrix-free, communication avoiding parallel, high-degree polynomial preconditioner for the Conjugate Gradient method for large and sparse symmetric positive definite linear systems. We discuss the selection of a scaling parameter aimed at avoiding unwanted clustering of eigenvalues of the preconditioned matrices at the extrema of the spectrum. We use this preconditioned framework to solve a $3 \times 3$ block system arising in the simulation of fluid flow in large-size discrete fractured networks. We apply our polynomial preconditioner to a suitable Schur complement related with this system, which can not be explicitly computed because of its size and density. Numerical results confirm the excellent properties of the proposed preconditioner up to very high polynomial degrees. The parallel implementation achieves satisfactory scalability by taking advantage from the reduced number of scalar products and hence of global communications

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

Atividade antibacteriana e antifúngica de extratos etanólicos de Aster lanceolatus Willd., Asteraceae.

Conhecida popularmente como áster-arbustiva, margarida-de-são-miguel e monte-cassino, Aster lanceolatus é uma planta ornamental de corte. Sabendo-se que não existem estudos que atestem a atividade biológica desta espécie, procurou-se neste trabalho atividades antibacteriana e antifúngica. Para tanto se utilizaram extratos brutos etanólicos de duas porções distintas, das flores e dos caules com folhas. Para a atividade antibacteriana, oito bactérias patogênicas foram submetidas a ensaio de difusão em gel e concentração inibitória mínima. Demonstrou-se atividade do extrato bruto etanólico de flores contra Streptococcus pyogenes, em difusão em gel e atividade de extrato bruto etanólico de caules e folhas contra Salmonella typhimurium e Streptococcus pyogenes em concentração inibitória mínima. Para a atividade antifúngica, utilizaram-se três fungos patogênicos em ensaios de crescimento micelial em placas e bioautografia direta. No ensaio de crescimento micelial em placas verificou-se a inibição de Fusarium oxysporum e na bioautografia direta, inibição do Cylindrocladium spathulatum. Os resultados delinearam uma nova fonte de pesquisa, as plantas ornamentais. Estas podem ser fonte de constituintes químicos capazes de servirem como protótipos para novos agentes terapêuticos e para tratamento sanitário de plantas medicinais

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

Barrett’s esophagus: results from an Italian cohort with tight endoscopic surveillance

Background and aim: Barrett’s Esophagus represent a condition that predisposes to the development of esophageal adenocarcinoma. The aim of the present study was to analyze the demographic and clinical characteristics of patients with BE, to establish the presence of risk factors for this condition, and to determine the frequency of dysplastic lesions as well as the evolution towards adenocarcinoma under tight endoscopic control. Methods: In this study, we retrospectively collected and analyzed data from a cohort of patients with Barrett’s Esophagus identified through endoscopic records of ULSS7 in Northern Italy, who underwent upper esophago-gastroduodenoscopy over a 10-year period from July 2008 to December 2020. Results: A total of 264 patients were identified as having BE and included in the study. Mean follow-up was 6.7 years (range: 3 months-13 years). Demographic characteristics of the study population included mean age of 62.7 years (range 33-90 years), with 62.5% of the study population being aged 60 or older, and a male predominance. Females were significantly older than males (65.7 years, range 37-90 vs 61.9 years, range 33-87, p=0.043, respectively). Conclusions: The present study confirms the importance of tight endoscopic control in the management of BE, favoring early detection of BE degeneration towards high grade dysplasia or adenocarcinoma. In a subset of patients with high-risk factors including male sex, cigarette smoking and heavy alcohol intake, it may be worthwhile to consider endoscopic control over time in order to detect the development of BE. (www.actabiomedica.it)

Estabilidade de genótipos elites de azevém na Campanha gaúcha.

O objetivo deste trabalho foi avaliar a estabilidade de 8 genótipos, sendo 6 cultivares durante dois anos consecutivos.Claudia Cristina Gulias Gomes, editora técnica

Avaliação de Panicum maximum em Bagé - RS.

Panicum maximum Jacq. é uma espécie originária da África, de alta qualidade forrageira, exigente em fertilidade do solo e adaptada a vários tipos de clima e solos. No Brasil, desde meados da década de 1980, vem sendo conduzido o programa de melhoramento genético desta forrageira pela Embrapa.Claudia Cristina Gulias Gomes, editora técnica

Osteomalacia: The Missing Link in the Pathogenesis of Bisphosphonate-Related Osteonecrosis of the Jaws?

Background. Bisphosphonate-related osteonecrosis of the jaw (BRONJ) is a well-documented adverse event from treatment with nitrogen-containing bisphosphonates (NBPs). During a preliminary histomorphometric study aimed at assessing the rate of bone remodeling in the jaws of patient with surgically resected BRONJ, we found a defect of bone mineralization (unpublished data). We hypothesized that osteomalacia could be a risk factor for BRONJ in patients taking NBPs. Therefore, we looked for static and dynamic histomorphometric evidence of osteomalacia in biopsies from subjects with and without BRONJ.Methods. This case-control study used histomorphometric analysis of bone specimens of patients using NBPs (22 patients with BRONJ and 21 patients without BRONJ) who required oral surgical interventions for the treatment/prevention of osteonecrosis. Patients were given tetracycline hydrochloride according to a standardized protocol before taking bone biopsies from their jaws. Biopsies with evidence of osteomyelitis or necrosis at histology were excluded from the study. Osteomalacia was defined as a mineralization lag time >100 days, a corrected mean osteoid thickness >12.5 mm, and an osteoid volume >10%.Results. In all, 77% of patients with BRONJ were osteomalacic compared with 5% of patients without BRONJ, according to histomorphometry. Because osteomalacia was found almost exclusively in NBP users with BRONJ, this is likely to be a generalized process in which the use of NBPs further deteriorates mechanisms of bone repair.Conclusions. Osteomalacia represents a new and previously unreported risk factor for disease development. This finding may contribute to a better understanding of the pathogenesis of this disease and help with the development of strategies to increase the safety of NBP administration