Static and dynamic mechanical testing of a polymer with potential use as heart valve material

Synthetic tri-leaflet heart valves generally fail in the long-term use (more than 10 years). Tearing and calcification of the leaflets usually cause failure of these valves as a consequence of high tensile and bending stresses borne on the material. The primary purpose of this study was to explore the possibilities of a new polymer composite to be used as synthetic tri-leaflet heart valve material. This composite was comprised of polystyrene-polyisobutylene-polystyrene (Quatromer), a proprietary polymer, embedded with continuous polypropylene (PP) fibers. Quatromer had been found to be less likely to degrade in vivo than polyurethane. Moreover, it was postulated that a decrease in tears and perforations might result from fiber-reinforced leaflets reducing high stresses on the leaflets. The static and dynamic mechanical properties of the Quatromer/PP composite were compared with those of an implant-approved polyurethane (PU) for cardiovascular applications. Results show that the reinforcement of Quatromer with PP fibers improves both its static and dynamic properties as compared to the PU. Hence, this composite has the potential to be a more suitable material for synthetic tri-leaflet heart valves.

Modelagem matemática e experimental da perda de injetividade em poços canhoneados

Water injection in oil reservoirs is a recovery technique widely used for oil recovery. However, the injected water contains suspended particles that can be trapped, causing formation damage and injectivity decline. In such cases, it is necessary to stimulate the damaged formation looking forward to restore the injectivity of the injection wells. Injectivity decline causes a major negative impact to the economy of oil production, which is why, it is important to foresee the injectivity behavior for a good waterflooding management project. Mathematical models for injectivity losses allow studying the effect of the injected water quality, also the well and formation characteristics. Therefore, a mathematical model of injectivity losses for perforated injection wells was developed. The scientific novelty of this work relates to the modeling and prediction of injectivity decline in perforated injection wells, considering deep filtration and the formation of external cake in spheroidal perforations. The classic modeling for deep filtration was rewritten using spheroidal coordinates. The solution to the concentration of suspended particles was obtained analytically and the concentration of the retained particles, which cause formation damage, was solved numerically. The acquisition of the solution to impedance assumed a constant injection rate and the modified Darcy´s Law, defined as being the inverse of the normalized injectivity by the inverse of the initial injectivity. Finally, classic linear flow injectivity tests were performed within Berea sandstone samples, and within perforated samples. The parameters of the model, filtration and formation damage coefficients, obtained from the data, were used to verify the proposed modeling. The simulations showed a good fit to the experimental data, it was observed that the ratio between the particle size and pore has a large influence on the behavior of injectivity decline.

Estudo de tensoativos na organofilização de argila bentonítica para uso em fluido de perfuração à base de óleo

Due to the great challenges encountered in drilling wells, there is a need to develop fluids with appropriated properties and able to meet all the requirements of drilling operations. The physicochemical and rheological properties must be carefully controlled so that a fluid can exercise all its functions. In perforations sensitive to contact with water and "offshore", it becomes necessary the use of oil based drilling fluids, but the bentonite clay cannot be used without a previous surface modification so that their surfaces become hydrophobic. Lately, the oil companies in Brazil use imported organoclays in the preparation of oil-based drilling fluids. The study aimed to modify a calcium clay to increase the affinity of the same organic phase of oil-based drilling fluids, applying three surfactants (OCS, CTAB and UTM 150) at different concentrations. The results indicated that the surfactants UTM 150 and CTAB showed better results compared to OCS. Considering the type of surfactant and concentration as variables used in the statistical analysis, the results indicated that only the surface tension and concentration of calcium oxide in response to organophilization process showed statistically significant effects. The organophilizated clay has potential for application in oil-based drilling fluids.

A Note on Iterations-based Derivations of High-order Homogenization Correctors for Multiscale Semi-linear Elliptic Equations

This Note aims at presenting a simple and efficient procedure to derive the structure of high-order corrector estimates for the homogenization limit applied to a semi-linear elliptic equation posed in perforated domains. Our working technique relies on monotone iterations combined with formal two-scale homogenization asymptotics. It can be adapted to handle more complex scenarios including for instance nonlinearities posed at the boundary of perforations and the vectorial case, when the model equations are coupled only through the nonlinear production terms.

Canais calcificados

A abordagem Endodôntica tem como grandes objetivos a manutenção funcional e estética do dente no sistema estomatognático. O sucesso desta abordagem terapêutica depende da realização eficiente da desinfeção, conformação e obturação do canal radicular. Estas etapas podem tornar-se difíceis de realizar na presença de dentes calcificados. A localização e manipulação dos canais calcificados são considerados um grande desafio durante a abordagem Endodôntica. Na tentativa de localização dos canais podem ocorrer erros de procedimento, como perfurações, fraturas de instrumentos e desvios do trajeto original do canal. Atualmente, vários recursos clínicos são utilizados para auxiliar estes procedimentos, como radiografias, microscópio operatório e o ultrassom. A calcificação pode ser resultado do processo fisiológico de envelhecimento, ou da deposição de dentina como mecanismo de defesa da polpa contra agentes agressores externos. Os dentes com calcificação não costumam apresentar sintomatologia, sendo o diagnóstico muitas vezes acidental. Clinicamente, a coroa dentária apresenta coloração alterada, e radiograficamente os canais apresentam os seus limites pulpares apagados, revelando obstrução parcial ou completa da câmara pulpar e dos canais, devido à deposição excessiva de dentina. A abordagem apropriada para dentes calcificados pode ser um dilema para o clínico. Esta deve ser feita a partir de decisão prudente entre a intervenção Endodôntica para o dente envolvido e outras intervenções restauradoras estéticas disponíveis. A maioria da literatura não apoia a intervenção Endodôntica a menos que seja detetado patologia apical ou sintomatologia do dente envolvido. A observação e o exame periódico do dente calcificado são as opções geralmente adotadas.

Modified atmosphere packaging effects on the postharvest quality of papaya fruit

Export of Fijian papaya (Carica papaya) fruit to destinations such as New Zealand has increased significantly over the last several years. Shipment by sea rather than air is the preferred method, given the capacity for larger volumes and reductions in cost. Long shipping times, however, can compromise fruit quality, although the use of modified atmosphere packaging (MAP) may provide a viable solution for extending fruit storage life. In a collaborative ACIAR project, Australian and Fijian researchers investigated the potential of using MAP to extend storage life of a Fijian papaya ('Fiji Red') fruit based on simulated sea transport conditions. Fruit were packed in one of three MAP environments within cartons, consisting of either a (1) Low Density Polyethylene (LDPE) bag with 10 g of KMnO4, (2) Polyamide Film (PF) bag with macro-perforations or (3) without a bag (control fruit). Fruit were held for 1, 2 or 3 weeks at 10°C before being unpacked, ripened and assessed for quality. On day 6 after outturn, fruit with the highest overall quality were those held in LDPE bags. LDPE fruit generally coloured up faster at outturn than PF or control fruit, had less overall moisture loss and scored high in flavour. Headspace carbon dioxide and oxygen concentrations within the LDPE bags were also near recommended levels for maintaining optimum storage-life quality. The LDPE bag provided the most suitable conditions for long term storage of fresh papaya fruit and is therefore the recommended MAP type for use with sea freight export out of Fiji.

La colecistectomía laparoscópica en el Hospital Vicente Corral Moscoso de Cuenca, 1994-2008

Antecedentes. La colecistectomía laparoscópica (CL, Cole-Lap) es el tratamiento de elección en la patología biliar benigna, la que presenta una elevada incidencia en nuestra ciudad y país. En el hospital Vicente Corral, cirujanos en formación y docentes, han participado en el desarrollo de esta técnica desde su inicio. Objetivo. Describir y compartir la experiencia de 14 años de colecistectomía laparoscópica en el Hospital Vicente Corral M. Métodos. Se presenta la casuística descriptiva y retrospectiva de 2.200 pacientes intervenidos por colecistectomía laparoscópica desde mayo de 1994 hasta enero 2008. Resultados. De 2.200 CL, el 79% son de sexo femenino, con promedio de edad de 43 años, con diagnóstico intraoperatorio de colecistitis crónica litiásica en el 82%. Se presentaron complicaciones entre mayores y menores en el 38%, las perforaciones de vesícula con salida de la bilis y las hemorragias provenientes de la arteria cística fueron las más frecuentes. La lesión de la vía biliar principal se registró en el 0.12%. En las 100 primeras cirugías se presentaron 25 complicaciones, mientras que en las 100 últimas fueron 34. El tiempo operatorio promedio fue de 35 minutos en el 2008. Discusión. La colecistectomía laparoscópica demuestra, en nuestro estudio, ser un procedimiento seguro y efectivo en pacientes con colecistitis calculosa aguda o crónica.

Unwrapping microcomputed tomographic images for measuring cortical osteolytic lesions in the 5T2 murine model of myeloma treated by bisphosphonate

International audience

Materiales Biocerámicos en endodoncia

En endodoncia durante las últimas décadas se han realizado avances en el campo de los materiales biocerámicos que pueden ser utilizados para: obturación retrógrada, recubrimiento pulpar, reparación de perforaciones, tratamiento de dientes con ápices abiertos, reparación de defectos de reabsorción y también se usan como cementos selladores, atribuyéndoseles grandes ventajas comparadas con los selladores tradicionales. Los materiales biocerámicos han demostrado la capacidad de superar algunas de las limitaciones de las generaciones anteriores de materiales de endodoncia, pues presentan excelentes propiedades fisicoquímicas y biológicas por lo que en la actualidad su uso es recomendado ampliamente en la práctica clínica. Este artículo se centra en la revisión de los nuevos materiales biocerámicos utilizados en endodoncia, sus características fisicoquímicas, biológicas, sus ventajas y desventajas, así como su uso en aplicaciones clínicas.

Idade e crescimento do tubarão-crocodilo, Pseudocarcharias kamoharai, no Oceano Atlântico

Dissertação de Mestrado, Biologia Marinha, Faculdade de Ciências e Tecnologia, Universidade do Algarve, 2014

Análise comparativa entre simuladores de linha de fluxo e diferenças finitas para um reservatório de petróleo submetido a injeção de água

Water injection is the most widely used method for supplementary recovery in many oil fields due to various reasons, like the fact that water is an effective displacing agent of low viscosity oils, the water injection projects are relatively simple to establish and the water availability at a relatively low cost. For design of water injection projects is necessary to do reservoir studies in order to define the various parameters needed to increase the effectiveness of the method. For this kind of study can be used several mathematical models classified into two general categories: analytical or numerical. The present work aims to do a comparative analysis between the results presented by flow lines simulator and conventional finite differences simulator; both types of simulators are based on numerical methods designed to model light oil reservoirs subjected to water injection. Therefore, it was defined two reservoir models: the first one was a heterogeneous model whose petrophysical properties vary along the reservoir and the other one was created using average petrophysical properties obtained from the first model. Comparisons were done considering that the results of these two models were always in the same operational conditions. Then some rock and fluid parameters have been changed in both models and again the results were compared. From the factorial design, that was done to study the sensitivity analysis of reservoir parameters, a few cases were chosen to study the role of water injection rate and the vertical position of wells perforations in production forecast. It was observed that the results from the two simulators are quite similar in most of the cases; differences were found only in those cases where there was an increase in gas solubility ratio of the model. Thus, it was concluded that in flow simulation of reservoirs analogous of those now studied, mainly when the gas solubility ratio is low, the conventional finite differences simulator may be replaced by flow lines simulator the production forecast is compatible but the computational processing time is lower.

Estudo do processo de combustão in-situ em reservatórios maduros de óleos médios e leves (high pressure air injection)

Nearly 3 x 1011 m3 of medium and light oils will remain in reservoirs worldwide after conventional recovery methods have been exhausted and much of this volume would be recovered by Enhanced Oil Recovery (EOR) methods. The in-situ combustion (ISC) is an EOR method in which an oxygen-containing gas is injected into a reservoir where it reacts with the crude oil to create a high-temperature combustion front that is propagated through the reservoir. The High Pressure Air Injection (HPAI) method is a particular denomination of the air injection process applied in light oil reservoirs, for which the combustion reactions are dominant between 150 and 300°C and the generation of flue gas is the main factor to the oil displacement. A simulation model of a homogeneous reservoir was built to study, which was initially undergone to primary production, for 3 years, next by a waterflooding process for 21 more years. At this point, with the mature condition established into the reservoir, three variations of this model were selected, according to the recovery factors (RF) reached, for study the in-situ combustion (HPAI) technique. Next to this, a sensitivity analysis on the RF of characteristic operational parameters of the method was carried out: air injection rate per well, oxygen concentration into the injected gas, patterns of air injection and wells perforations configuration. This analysis, for 10 more years of production time, was performed with assistance of the central composite design. The reservoir behavior and the impacts of chemical reactions parameters and of reservoir particularities on the RF were also evaluated. An economic analysis and a study to maximize the RF of the process were also carried out. The simulation runs were performed in the simulator of thermal processes in reservoirs STARS (Steam, Thermal, and Advanced Processes Reservoir Simulator) from CMG (Computer Modelling Group). The results showed the incremental RF were small and the net present value (NPV) is affected by high initial investments to compress the air. It was noticed that the adoption of high oxygen concentration into the injected gas and of the five spot pattern tends to improve the RF, and the wells perforations configuration has more influence with the increase of the oil thickness. Simulated cases relating to the reservoir particularities showed that smaller residual oil saturations to gas lead to greater RF and the presence of heterogeneities results in important variations on the RF and on the production curves

Técnicas e sistemas de desobturação canalar no retratamento endodôntico não cirúrgico

Na prática clínica, a diversidade de instrumentos manuais, rotatórios ou reciprocantes, dificulta a seleção do sistema a aplicar no retratamento dentário não cirúrgico. O presente trabalho teve como objetivo comparar diferentes instrumentos quanto a diferentes parâmetros: capacidade de remoção de Gutta-Percha (GP), extrusão apical de detritos, fratura de instrumentos, e ocorrência de iatrogenias. Neste trabalho foram utilizadas 111 publicações posteriores a 2011, obtidas via PubMed e Science Direct. A análise da bibliografia indica que, independentemente do sistema, não é possível remover todo o material obturador das paredes radiculares, sendo esta tarefa dificultada em canais curvos e na área apical. Verifica-se que a remoção de GP melhora no sentido: limas H, ProTaper, e Mtwo. O sistema Reciproc foi associado a melhores desempenhos e a menores tempo de trabalho, do que os sistemas de rotação contínua. Nenhum dos instrumentos analisados é capaz de evitar a extrusão apical de detritos na totalidade. Apesar de resultados dispares, a maioria dos estudos assume que o sistema Reciproc provoca menor extrusão apical de detritos. Em Endodontia, as duas principais causas da fratura de instrumentos são a fadiga cíclica e a torsão. A maioria dos estudos concordam que o movimento reciprocante, como o do Reciproc, aumenta a resistência à fractura e a resistência à torsão, mantendo a anatomia original do canal. Relativamente à produção de perfurações e fracturas radiculares, a superioridade dos instrumentos NiTi relativamente às limas manuais não foi clara. De acordo com a literatura, o sistema Reciproc, constituído por liga de NiTi M-Wire, está associado a menos eventos iatrogénicos. Finalmente, conclui-se que futuros estudos seriam benéficos para esclarecer o potencial dos diferentes sistemas estudados.

Eficacia de terapias biológicas de tipo anti-angiogénico en el cáncer colorrectal metastásico revisión sistemática de la literatura

Introducción: El cáncer colorrectal (CCR) se encuentra entre los 5 tipos de cáncer con mayor incidencia a nivel mundial. Alrededor del 20% de los casos son diagnosticados en estadios metastásico, donde el tratamiento inicialmente era quimioterapia con una supervivencia global a 5 años de 12 a 14 meses. Es así que se investiga el papel de la angiogénesis tumoral, orientado al desarrollo de terapias, implementando su uso en estadios avanzados. Metodología: Se realizó una búsqueda sistemática en las bases de datos Embase, PubMed, SciELO y LILIACS con términos estandarizados a través de la herramienta MeSH y DECS bajo los lineamientos establecidos en las guías de revisiones sistemáticas y meta-análisis (Manual Cochrane). Se tomaron estudios clínicos aleatorizados controlados con pacientes con CCR metastásico, que hayan recibido quimioterapia sola o combinada con terapias antiangiogénicas, publicados en inglés y español entre el 2003 y 2013. Resultados: 6 artículos cumplieron con criterios de inclusión. Estos reportaron 15.8 meses en promedio de supervivencia global en el tratamiento de quimioterapia asociada a terapias biológicas frente a 14.4 meses con solo quimioterapia. Los eventos adversos de tipo vascular aumentaron más en el grupo de antiangiogénicos, reportando muertes debidas a perforaciones intestinales. Conclusiones: Los regímenes de quimioterapia asociadas a terapias antiangiogénicas brindan una mayor supervivencia global y libre de progresión, al igual que mayor número de tasas de respuesta. Son terapias con eventos adversos importantes pero que deberá seleccionarse bien al paciente para disminuir su riesgo de eventos. Palabras claves: Cáncer colorrectal metastásico, terapia anti-angiogénica, quimioterapia en segunda línea, receptor del factor de crecimiento de endotelio vascular, supervivencia global.