We report on the detection in southern Egypt of an impact crater 45 meters in diameter with a pristine rayed structure. Such pristine structures are typically observed on atmosphereless rocky or icy planetary bodies in the solar system. This feature and the association with an iron meteorite impactor and shock metamorphism provides a unique picture of small-scale hypervelocity impacts on Earth's crust. Contrary to current geophysical models, ground data indicate that iron meteorites with masses of the order of tens of tons can penetrate the atmosphere without substantial fragmentation.
Abstract-We detail the Kamil crater (Egypt) structure and refine the impact scenario, based on the geological and geophysical data collected during our first expedition in February 2010. Kamil Crater is a model for terrestrial small-scale hypervelocity impact craters. It is an exceptionally well-preserved, simple crater with a diameter of 45 m, depth of 10 m, and rayed pattern of bright ejecta. It occurs in a simple geological context: flat, rocky desert surface, and target rocks comprising subhorizontally layered sandstones. The high depth-to-diameter ratio of the transient crater, its concave, yet asymmetric, bottom, and the fact that Kamil Crater is not part of a crater field confirm that it formed by the impact of a single iron mass (or a tight cluster of fragments) that fragmented upon hypervelocity impact with the ground. The circular crater shape and asymmetries in ejecta and shrapnel distributions coherently indicate a direction of incidence from the NW and an impact angle of approximately 30 to 45°. Newly identified asymmetries, including the off-center bottom of the transient crater floor downrange, maximum overturning of target rocks along the impact direction, and lower crater rim elevation downrange, may be diagnostic of oblique impacts in well-preserved craters. Geomagnetic data reveal no buried individual impactor masses >100 kg and suggest that the total mass of the buried shrapnel >100 g is approximately 1050-1700 kg. Based on this mass value plus that of shrapnel >10 g identified earlier on the surface during systematic search, the new estimate of the minimum projectile mass is approximately 5 t.
Conventional aortic valve replacement (CAVR) via a full sternotomy is the standard surgical approach for aortic valve replacement. Minimal access aortic valve replacement (MAAVR) is commonly performed via a partial sternotomy and a right minithoracotomy. Such procedures aim not only to reduce the invasiveness but to offer the same quality, safety and results of the conventional approach. Our goal was to compare both procedures by performing a meta-analysis of reports with risk adjustment that performed a propensity-matched analysis. Relevant articles were searched for in Medline, the Cochrane Database of Systematic Reviews and the Scopus database based on predefined criteria and end-points. The early and late outcomes and complications were compared in the selected studies. A total of 4558 patients from 9 studies were enrolled; 2279 (50%) underwent CAVR and 2279 (50%) underwent MAAVR. There was a significantly lower rate of postoperative low output syndrome (1.4% vs 2.3%, P = 0.05) and atrial fibrillation (11.7% vs 15.9%, P = 0.01) in the MAAVR than in the CAVR group, respectively. In contrast, aortic cross-clamp and cardiopulmonary bypass times were significantly longer in the MAAVR group (P < 0.05). Finally, the incidence of early deaths (1.5% vs 2.2%, P = 0.14), stroke (1.4% vs 2%, P = 0.20), myocardial infarction (0.4% vs 0.5%, P = 0.65), renal injury (4.5% vs 6%, P = 0.71), respiratory complications (9% vs 10.1%, P = 0.45), re-exploration for bleeding (4.9% vs 4.1%, P = 0.27) and pacemaker implantation (3.3% vs 4.1%, P = 0.31) was similar in both groups, respectively. In summary, even though MAAVR procedure, either through partial sternotomy or right minithoracotomy, provides patient satisfaction due to the smaller incision and better cosmetics, MAAVR is as safe as the CAVR procedure. Although MAAVR takes slightly longer, it was not associated with greater cardiopulmonary bypass-related adverse effects. Interestingly, MAAVR shows a lower incidence of low cardiac output syndrome and atrial fibrillation.
Using frozen elephant trunk technique to treat Type I acute aortic dissection facilitates positive or stable remodelling in nearly all patients at the stent graft level and distally in two-thirds of the patients. FL thrombosis and aortic remodelling are negatively influenced by the number of exits. New endovascular concepts aiming at reducing the number of exits may prevent negative remodelling.
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