ABSTRACT
Most large (over a kilometre in diameter) near-Earth asteroids are now known, but recognition that airbursts (or fireballs resulting from nuclear-weapon-sized detonations of meteoroids in the atmosphere) have the potential to do greater damage than previously thought has shifted an increasing portion of the residual impact risk (the risk of impact from an unknown object) to smaller objects. Above the threshold size of impactor at which the atmosphere absorbs sufficient energy to prevent a ground impact, most of the damage is thought to be caused by the airburst shock wave, but owing to lack of observations this is uncertain. Here we report an analysis of the damage from the airburst of an asteroid about 19 metres (17 to 20 metres) in diameter southeast of Chelyabinsk, Russia, on 15 February 2013, estimated to have an energy equivalent of approximately 500 (±100) kilotons of trinitrotoluene (TNT, where 1 kiloton of TNT = 4.185×10(12) joules). We show that a widely referenced technique of estimating airburst damage does not reproduce the observations, and that the mathematical relations based on the effects of nuclear weapons--almost always used with this technique--overestimate blast damage. This suggests that earlier damage estimates near the threshold impactor size are too high. We performed a global survey of airbursts of a kiloton or more (including Chelyabinsk), and find that the number of impactors with diameters of tens of metres may be an order of magnitude higher than estimates based on other techniques. This suggests a non-equilibrium (if the population were in a long-term collisional steady state the size-frequency distribution would either follow a single power law or there must be a size-dependent bias in other surveys) in the near-Earth asteroid population for objects 10 to 50 metres in diameter, and shifts more of the residual impact risk to these sizes.
ABSTRACT
El leiomiosarcoma abdominal es una enfermedad poco frecuente con alto índice de recidivas que lleva a realizar variadas interenciones de resección y en algunos casos sólo paliativas. La sobrevida depende principalmente de la agresividad del tipo histológico. Se describen dos csos de leiomiosarcomas originados en el abdomen, uno de ellos falleció a los cuatro años, el otro a pesar de sus múltiples recidivas presenta una sobrevida hasta la actualidad de 22 años. Se realiza comparación de su evolución y revisión de la literatura
Subject(s)
Male , Female , Adult , Humans , Leiomyosarcoma , Neoplasm Recurrence, Local/prevention & control , Neoplasm Recurrence, Local/drug therapy , Neoplasm Recurrence, Local/radiotherapy , Vena Cava, InferiorABSTRACT
El leiomiosarcoma abdominal es una enfermedad poco frecuente con alto índice de recidivas que lleva a realizar variadas interenciones de resección y en algunos casos sólo paliativas. La sobrevida depende principalmente de la agresividad del tipo histológico. Se describen dos csos de leiomiosarcomas originados en el abdomen, uno de ellos falleció a los cuatro años, el otro a pesar de sus múltiples recidivas presenta una sobrevida hasta la actualidad de 22 años. Se realiza comparación de su evolución y revisión de la literatura(AU)
Subject(s)
Male , Female , Adult , Humans , Leiomyosarcoma/diagnosis , Leiomyosarcoma/radiotherapy , Leiomyosarcoma/surgery , Vena Cava, Inferior/pathology , Vena Cava, Inferior/surgery , Neoplasm Recurrence, Local/drug therapy , Neoplasm Recurrence, Local/prevention & control , Neoplasm Recurrence, Local/radiotherapyABSTRACT
A perfuraçäo coloretal por enema baritado é muito séria e mais freqüente que a mencionada na literatura. Nesse estudo, oito perfuraçöes foram revistas; ocorreram no cólon ascendente (uma), descendente (uma), sigmóide (quatro, e no reto (duas). A afecçäo de base dos pacientes era: enterocolite necrosante do recém-nascido (uma), estenose de colostomia (uma), fecaloma (duas), câncer (duas), trauma (uma) e dor abdominal pós-radioterapia (uma). Na maioria dos enfermos o tratamento consistiu em ressecçäo do segmento perfurado e colostomia; colostomia; a taxa de mortalidade foi de 62,5%. A causa dessa alta mortalidade é a lesäo produzida pela presença de bário e de fezes na cavidade peritoneal e no espaço retro-peritoneal. Säo considerados os mecanismos causadores desse acidente e medidas profiláticas. O número significativo de casos nos quais a responsabilidade médica é envolvida, deveria forçar cirurgöes e radiologistas a sempre tomarem precauçöes para prevenir este sério acidente
