Abstract A Brazilian Tensile Strength (BTS) laboratory test for meta-andesite was modeled using a Finite/Discrete Element Method (FDEM or FEM-DEM). These hybrid methodologies allow modeling the transition from continuous to discontinuous that happens on mechanical tests of rock samples. This article presents the calibration and the simulation of BTS tests using some parameters previously calibrated on UCS modeling of the same material. Irazu, a two-dimensional software developed by Geomechanica, was used to simulate the tests based on the tensile strength and the fracture pattern. The model shows that, in BTS test simulation, the mode II (shear) happens mainly on the rock-platen contact. The mode I (traction) rules the fractures on the BTS test as observed in laboratory tests. The model represents, with great fidelity, the results obtained in the physical test.

Abstract Finite/discrete element methods (FDEM) are hybrid numerical models that use algorithms to analyze the transition from continuous to discontinuous. This type of formulation allows modeling physical laboratory tests with greater proximity to reality. This article proposes to simulate the average behavior of a uniaxial compression test campaign. The tests were modeled and calibrated based on the strength and the fracture pattern using Geomechanica Inc. Irazu two-dimensional software. The simulated results were analyzed by the mean standard deviation of approximately 3000 elements in the middle third of the model, the same region where the clip gages are located in the physical test. The obtained results show that FDEM can replicate the laboratory test with great similarity.

Abstract Mining projects are often budgeted in millions of dollars, making it of interest to the investor to measure a project’s uncertainties and risks, which include the changes in the commodity price. The simulation of asset prices is valid because it enables displaying, with a degree of certainty, the future behavior of a financial asset. One of the most commonly used mathematical forecast models is the Geometric Brownian Motion (GBM) model. This article aims at simulating the forecast price of an iron ore commodity with the GBM method based on the historical price series and comparing it to other forecast approaches used in the financial market. The results of this study indicate that the model has limitations, which should be considered. However, it is an overall good tool to support the economic evaluation of a project, if performed along with other approaches.

Abstract Introduction: Advances in modern medicine have led to people living longer and healthier lives. Frailty is an emerging concept in medicine yet to be explored as a risk factor in cardiac surgery. When it comes to CABG surgery, randomized controlled clinical trials have primarily focused on low-risk (ROOBY, CORONARY), elevated-risk (GOPCABE) or high-risk patients (BBS), but not on frail patients. Therefore, we believe that off-pump CABG could be an important technique in patients with limited functional capacity to respond to surgical stress. In this study, the authors introduce the new national, multicenter, randomized, controlled trial "FRAGILE", to be developed in the main cardiac surgery centers of Brazil, to clarify the potential benefit of off-pump CABG in frail patients. Methods: FRAGILE is a two-arm, parallel-group, multicentre, individually randomized (1:1) controlled trial which will enroll 630 patients with blinded outcome assessment (at 30 days, 6 months, 1 year, 2 years and 3 years), which aims to compare adverse cardiac and cerebrovascular events after off-pump versus on-pump CABG in pre-frail and frail patients. Primary outcomes will be all-cause mortality, acute myocardial infarction, cardiac arrest with successful resuscitation, low cardiac output syndrome/cardiogenic shock, stroke, and coronary reintervention. Secondary outcomes will be major adverse cardiac and cerebrovascular events, operative time, mechanical ventilation time, hyperdynamic shock, new onset of atrial fibrillation, renal replacement therapy, reoperation for bleeding, pneumonia, length of stay in intensive care unit, length of stay in hospital, number of units of blood transfused, graft patency, rate of complete revascularization, neurobehavioral outcomes after cardiac surgery, quality of life after cardiac surgery and costs. Discussion: FRAGILE trial will determine whether off-pump CABG is superior to conventional on-pump CABG in the surgical treatment of pre-frail and frail patients. Trial registration: ClinicalTrials.gov, ID: NCT02338947. Registered on August 29th 2014; last updated on March 21st 2016.

ResumoObjetivo:Verificar se os modelos de estratificação da complexidade em cirurgias de cardiopatias congênitas atualmente disponíveis (RACHS-1, escore básico de Aristóteles e escore de mortalidade do STS-EACTS) se adequam ao nosso serviço, determinando o de melhor acurácia em discriminar a mortalidade hospitalar.Métodos:Procedimentos em pacientes menores de 18 anos foram alocados nas categorias propostas pelos modelos de estratificação da complexidade. O desfecho de mortalidade hospitalar foi calculado para cada categoria dos três modelos. Análise estatística foi realizada para verificar se as categorias apresentavam distintas mortalidades dentro de cada modelo. A capacidade discriminatória dos modelos foi determinada pelo cálculo de área sob a curva ROC e uma comparação entre as curvas dos três modelos foi realizada.Resultados:360 pacientes foram alocados pelos três modelos. Houve diferença estatisticamente significante entre as mortalidades das categorias propostas pelos modelos de RACHS-1 (1) - 1,3%, (2) - 11,4%, (3) - 27,3%, (4) - 50%, (P<0,001); escore básico de Aristóteles (1) - 1,1%, (2) - 12,2%, (3) - 34%, (4) - 64,7%, (P<0,001); e escore de mortalidade do STS-EACTS (1) - 5,5%, (2) - 13,6%, (3) - 18,7%, (4) - 35,8%, (P<0,001). Os três modelos tiveram semelhante capacidade discriminatória para o desfecho de mortalidade hospitalar pelo cálculo da área sob a curva ROC: RACHS-1- 0,738; STS-EACTS- 0,739; Aristóteles- 0,766.Conclusão:Os três modelos de estratificação da complexidade atualmente disponíveis na literatura tiveram utilidade com distintas mortalidades entre as categorias propostas, com semelhante capacidade discriminatória para o desfecho de mortalidade hospitalar.

AbstractObjective:To determine whether stratification of complexity models in congenital heart surgery (RACHS-1, Aristotle basic score and STS-EACTS mortality score) fit to our center and determine the best method of discriminating hospital mortality.Methods:Surgical procedures in congenital heart diseases in patients under 18 years of age were allocated to the categories proposed by the stratification of complexity methods currently available. The outcome hospital mortality was calculated for each category from the three models. Statistical analysis was performed to verify whether the categories presented different mortalities. The discriminatory ability of the models was determined by calculating the area under the ROC curve and a comparison between the curves of the three models was performed.Results:360 patients were allocated according to the three methods. There was a statistically significant difference between the mortality categories: RACHS-1 (1) - 1.3%, (2) - 11.4%, (3)-27.3%, (4) - 50 %, (P<0.001); Aristotle basic score (1) - 1.1%, (2) - 12.2%, (3) - 34%, (4) - 64.7%, (P<0.001); and STS-EACTS mortality score (1) - 5.5 %, (2) - 13.6%, (3) - 18.7%, (4) - 35.8%, (P<0.001). The three models had similar accuracy by calculating the area under the ROC curve: RACHS-1- 0.738; STS-EACTS-0.739; Aristotle- 0.766.Conclusion:The three models of stratification of complexity currently available in the literature are useful with different mortalities between the proposed categories with similar discriminatory capacity for hospital mortality.