Simultaneous development of semigrabens orthogonal and oblique to the extension direction: physical modeling of natural analogues in Northeastern Brazil

A modelagem física é uma ferramenta cada vez mais usada na geologia para fornecer informação sobre os diversos estágios evolutivos (nucleação, desenvolvimento e geometria) de estruturas geológicas em várias escalas. No caso particular da simulação da tectônica distensional, a modelagem proporciona uma melhor compreensão da geometria e evolução de falhas e da arquitetura tectonoestratigráfica de bacias rifte. Neste trabalho foi utilizado um aparato tipo caixa de areia para estudar a nucleação e o desenvolvimento de bacias influenciadas por estruturas prévias no embasamento, com trend variável em relação à direção de distensão. Para tal, foram realizados dois tipos de experimentos para: (i) simular o desenvolvimento individual (independente) de semigrabens com abertura ortogonal ou oblíqua à direção de distensão; (ii) simular o desenvolvimento simultâneo desses semigrabens ortogonais ou oblíquos à direção de distensão. Em ambos os casos foram utilizados os mesmos materiais analógicos (areia de quartzo e uma mistura de areia e gesso, simulando o material sin e pré-tectônico, respectivamente) bem como foram mantidas as demais condições de contorno. Os resultados obtidos foram comparados com um análogo natural representado pela Bacia do Rio do Peixe (uma das bacias interiores eocretáceas do Nordeste do Brasil). Os modelos permitiram observar o desenvolvimento segmentado das falhas de borda, com geometria lístrica, frequentemente formando rampas de revezamento, além do desenvolvimento de falhas internas às bacias localizadas nas suas porções mais basais, similares àquelas observadas nas seções sísmicas do análogo natural. Os resultados confirmam a influência da herança tectônica do embasamento na geometria dos depocentros rifte.The physical modeling tool is being increasingly used in geology to provide information about the evolutionary stages (nucleation, growth and geometry) of geological structures at various scales. In the simulations of extensional tectonics, modeling provides a better understanding of fault geometry and evolution of the tectonic-stratigraphic architecture of rift basins. In this study a sandbox type apparatus was used to study the nucleation and development of basins influenced by previous structures in the basement, variably oriented as regards to the main extensional axis. Two types of experiments were conducted in order to: (i) simulate the individual (independent) development of half-grabens oriented orthogonal or oblique to the extension direction; (ii) simulate the simultaneous development of such half-grabens, orthogonal or oblique to the extension direction. In both cases the same materials (sand mixed with gypsum) were used and the same boundary conditions were maintained. The results were compared with a natural analogue represented by the Rio do Peixe Basin (one of the eocretaceous interior basins of Northeast Brazil). The obtained models allowed to observe the development of segmented border faults with listric geometry, often forming relay ramps, and the development of inner basins faults that affect only the basal strata, like the ones observed in the seismic sections of the natural analogue. The results confirm the importance of basement tectonic heritage in the geometry of rift depocenters

Simultaneous development of semigrabens orthogonal and oblique to the extension direction: physical modeling of natural analogues in Northeastern Brazil

The physical modeling tool is being increasingly used in geology to provide information about the evolutionary stages (nucleation, growth and geometry) of geological structures at various scales. In the simulations of extensional tectonics, modeling provides a better understanding of fault geometry and evolution of the tectonic-stratigraphic architecture of rift basins. In this study a sandbox type apparatus was used to study the nucleation and development of basins influenced by previous structures in the basement, variably oriented as regards to the main extensional axis. Two types of experiments were conducted in order to: (i) simulate the individual (independent) development of half-grabens oriented orthogonal or oblique to the extension direction; (ii) simulate the simultaneous development of such half-grabens, orthogonal or oblique to the extension direction. In both cases the same materials (sand mixed with gypsum) were used and the same boundary conditions were maintained. The results were compared with a natural analogue represented by the Rio do Peixe Basin (one of the eocretaceous interior basins of Northeast Brazil). The obtained models allowed to observe the development of segmented border faults with listric geometry, often forming relay ramps, and the development of inner basins faults that affect only the basal strata, like the ones observed in the seismic sections of the natural analogue. The results confirm the importance of basement tectonic heritage in the geometry of rift depocenters

Evaluation of a quality improvement intervention to reduce anastomotic leak following right colectomy (EAGLE): pragmatic, batched stepped-wedge, cluster-randomized trial in 64 countries

Background Anastomotic leak affects 8 per cent of patients after right colectomy with a 10-fold increased risk of postoperative death. The EAGLE study aimed to develop and test whether an international, standardized quality improvement intervention could reduce anastomotic leaks. Methods The internationally intended protocol, iteratively co-developed by a multistage Delphi process, comprised an online educational module introducing risk stratification, an intraoperative checklist, and harmonized surgical techniques. Clusters (hospital teams) were randomized to one of three arms with varied sequences of intervention/data collection by a derived stepped-wedge batch design (at least 18 hospital teams per batch). Patients were blinded to the study allocation. Low- and middle-income country enrolment was encouraged. The primary outcome (assessed by intention to treat) was anastomotic leak rate, and subgroup analyses by module completion (at least 80 per cent of surgeons, high engagement; less than 50 per cent, low engagement) were preplanned. Results A total 355 hospital teams registered, with 332 from 64 countries (39.2 per cent low and middle income) included in the final analysis. The online modules were completed by half of the surgeons (2143 of 4411). The primary analysis included 3039 of the 3268 patients recruited (206 patients had no anastomosis and 23 were lost to follow-up), with anastomotic leaks arising before and after the intervention in 10.1 and 9.6 per cent respectively (adjusted OR 0.87, 95 per cent c.i. 0.59 to 1.30; P = 0.498). The proportion of surgeons completing the educational modules was an influence: the leak rate decreased from 12.2 per cent (61 of 500) before intervention to 5.1 per cent (24 of 473) after intervention in high-engagement centres (adjusted OR 0.36, 0.20 to 0.64; P < 0.001), but this was not observed in low-engagement hospitals (8.3 per cent (59 of 714) and 13.8 per cent (61 of 443) respectively; adjusted OR 2.09, 1.31 to 3.31). Conclusion Completion of globally available digital training by engaged teams can alter anastomotic leak rates. Registration number: NCT04270721 (http://www.clinicaltrials.gov)