Uso de "stents" no tratamento de lesões arteriais intimas de origem traumática: relato de caso

O tratamento de lesões arteriais íntimais de origem traumática é controversa pela sua evolução natural ser desconhecida. As opções terapêuticas atuais incluem reconstrução arterial e observação clínica. A idéia da utilização de "stents" para a correção de descolamentos intimais é baseada no seu uso em dissecções, "flaps" e irregularidades da artéria após angioplastia com balão. Descrevemos o tratamento bem sucedido de um descolamento de íntima da artéria femoral superficial causado por ferimento de arma de fogo com a utilização de um "stent" de Palmaz na fase aguda. Um ano após a implantação do "stent", o duplex scan mostrou fluxo normal pela artéria com a exclusão completa do descolamento de íntima, com pulsos distais palpáveis e com o paciente completamente assintomático.Treatment of arterial traumatic intimal lesions is controversial due to its unknown natural history. Current therapeutical options include arterial reconstruction and clinical observation. The idea of using stents to correct intimal flaps is based on their use to correct dissections, flaps, and arterial irregularities after angioplasty. We report the successful treatment of a traumatic intimal flap of the superficial femoral artery, caused by gunshot trauma, with a Palmaz stent in the acute period. One year after the operation, a duplex scan revealed normal flow in the artery and complete exclusion of the intimal flap; distal pulses were palpable, and the patient was completely asymptomatic

Tratamento endovascular para pacientes portadores de Claudicação Intermitente que não melhoram com tratamento clínico

PURPOSE: To study the results including long-term follow-up obtained with endovascular treatment of patients with intermittent claudication who did not experience clinical improvement with conservative treatment. METHODS: From January 1992 to January 2002, 62 of 1380 patients (4.5%) with intermittent claudication underwent endovascular treatment and were followed up for up to 120 months (mean 76 months). The variables analyzed were the functioning of the arterial segment undergoing the endovascular procedure, the evolution of the maximum walking distance, and incidence of related morbidity and mortality. RESULTS: Fifty-two patients (84%) experienced no walking limitation after the procedure, and 6 patients (10%) improved but still exhibited some degree of limitation, for a total improved outcome of 94%. The patency rate was 82%. There was no intraoperative mortality. One primary failure and one immediate thrombosis occurred, and both were surgically corrected. Thrombosis of the treated artery occurred in 6 patients 12, 16, 25, 29, 62, and 66 months after the procedure. These patients started to experience intermittent claudication with a walking distance to onset that was similar to their presurgical distance to onset. During follow-up, a mortality rate of 12.9% (8 patients) was observed, 6 due to myocardial infarctions and 2 due cerebral infarction. Three patients underwent coronary bypasses 22, 36, and 55 months after the endovascular surgery, and 2 patients underwent coronary angioplasty after 6 and 26 months. The mean follow up period was 76 months (range 0-120 months). CONCLUSION: This study shows that endovascular treatment of intermittent claudication brought about a lasting regression of the ischemic conditions in a significant number of patients, with excellent patency rates. It was concluded that this is a good alternative for selected patients, with low rates of complications and positive long-term results.OBJETIVO: Estudar a longo prazo (média de 76 meses de seguimento) os resultados obtidos com o tratamento endovascular em pacientes que não melhoram com o tratamento clínico, MÉTODOS: De Janeiro de 1992 a Janeiro de 2002, 62 pacientes de um grupo de 1380 claudicantes foram submetidos a tratamento endovascular, representando 4,5% do total. As variáveis analisadas foram o funcionamento do segmento arterial submetido ao procedimento endovascular, a evolução da distância máxima de marcha e a ocorrência de morbi-mortalidade. RESULTADOS: Cinqüenta e dois (84%) pacientes não apresentaram restrições à deambulação após o procedimento. Seis pacientes melhoraram, representando um benefício de 94%. Não houve mortalidade intra-operatória. Uma falência primária e uma trombose imediata foram corrigidas cirurgicamente. Seis pacientes apresentaram trombose da artéria tratada 12, 16, 25, 29, 62 e 66 meses após o procedimento e voltaram a apresentar Claudicação Intermitente para as mesmas distâncias referidas antes da cirurgia. Durante o seguimento foi observada taxa de mortalidade de 12,9% (8 pacientes), dos quais 6 por infarto do miocárdio e dois por acidente vascular cerebral. Três pacientes foram submetidos à revascularização miocárdica 22, 36 e 55 meses após o procedimento endovascular e duas angioplastias foram realizadas com 6 e 26 meses de seguimento. O tempo médio de segmento foi de 76 meses (0 a 120 meses). CONCLUSÃO: O tratamento endovascular da Claudicação Intermitente levou a melhora das condições da marcha em um número significativo de pacientes, com excelentes taxas de patência (82,0%). Concluímos que esta é uma boa alternativa para determinados pacientes, com poucas complicações e resultados positivos a longo prazo

The Morphology of the Expanding Ejecta of V2491 Cygni (2008 N.2)

Determining the evolution of the ejecta morphology of novae provides valuable information on the shaping mechanisms in operation at early stages of the nova outburst. Understanding such mechanisms has implications for studies of shaping for example in proto-Planetary Nebulae. Here we perform morpho-kinematical studies of V2491 Cyg using spectral data to determine the likely structure of the ejecta and its relationship to the central system and shaping mechanisms. We use Shape to model different morphologies and retrieve their spectra. These synthetic spectra are compared with observed spectra to determine the most likely morphology giving rise to them, including system inclination and expansion velocity of the nova ejecta. We find the best fit remnant morphology to be that of polar blobs and an equatorial ring with an implied inclination of 80$^{+3}_{-12}$ degrees and an maximum expansion velocity of the polar blobs of 3100$^{+200}_{-100}$ km/s and for the equatorial ring 2700$^{+200}_{-100}$ km/s. This inclination would suggest that we should observe eclipses which will enable us to determine more precisely important parameters of the central binary. We also note that the amplitude of the outburst is more akin to the found in recurrent nova systems.Comment: 9 pages, 7 figures, accepted for publication in MNRA

The Expanding Fireball of Nova Delphini 2013

A classical nova occurs when material accreting onto the surface of a white dwarf in a close binary system ignites in a thermonuclear runaway. Complex structures observed in the ejecta at late stages could result from interactions with the companion during the common envelope phase. Alternatively, the explosion could be intrinsically bipolar, resulting from a localized ignition on the surface of the white dwarf or as a consequence of rotational distortion. Studying the structure of novae during the earliest phases is challenging because of the high spatial resolution needed to measure their small sizes. Here we report near-infrared interferometric measurements of the angular size of Nova Delphini 2013, starting from one day after the explosion and continuing with extensive time coverage during the first 43 days. Changes in the apparent expansion rate can be explained by an explosion model consisting of an optically thick core surrounded by a diffuse envelope. The optical depth of the ejected material changes as it expands. We detect an ellipticity in the light distribution, suggesting a prolate or bipolar structure that develops as early as the second day. Combining the angular expansion rate with radial velocity measurements, we derive a geometric distance to the nova of 4.54 +/- 0.59 kpc from the Sun.Comment: Published in Nature. 32 pages. Final version available at http://www.nature.com/nature/journal/v515/n7526/full/nature13834.htm

Magnetic Flux Transport by turbulent reconnection in astrophysical flows

The role of MHD turbulence in astrophysical environments is still highly debated. An important question that permeates this debate is the transport of magnetic flux. This is particularly important, for instance, in the context of star formation. When clouds collapse gravitationally to form stars, there must be some magnetic flux transport. otherwise the new born stars would have magnetic fields several orders of magnitude larger than the observed ones. Also, the magnetic flux that is dragged in the late stages of the formation of a star can remove all the rotational support from the accretion disk that grows around the protostar. The efficiency of the mechanism which is often invoked to allow the transport of magnetic fields in the different stages of star formation, namely, the ambipolar diffusion, has been lately put in check. We here discuss an alternative mechanism for magnetic flux transport which is based on turbulent fast magnetic reconnection. We review recent results obtained from 3D MHD numerical simulations that indicate that this mechanism is very efficient for decoupling and transport magnetic flux from the inner denser regions to the outskirts of collapsing clouds in the different stages of star formation. We also discuss this mechanism in the context of dynamo processes and speculate that it can play a role both in the solar dynamo and in accretion disk dynamo processes.Comment: 10 pages, 2 figures, review submitted to Physica Script

Production of dust by massive stars at high redshift

The large amounts of dust detected in sub-millimeter galaxies and quasars at high redshift pose a challenge to galaxy formation models and theories of cosmic dust formation. At z > 6 only stars of relatively high mass (> 3 Msun) are sufficiently short-lived to be potential stellar sources of dust. This review is devoted to identifying and quantifying the most important stellar channels of rapid dust formation. We ascertain the dust production efficiency of stars in the mass range 3-40 Msun using both observed and theoretical dust yields of evolved massive stars and supernovae (SNe) and provide analytical expressions for the dust production efficiencies in various scenarios. We also address the strong sensitivity of the total dust productivity to the initial mass function. From simple considerations, we find that, in the early Universe, high-mass (> 3 Msun) asymptotic giant branch stars can only be dominant dust producers if SNe generate <~ 3 x 10^-3 Msun of dust whereas SNe prevail if they are more efficient. We address the challenges in inferring dust masses and star-formation rates from observations of high-redshift galaxies. We conclude that significant SN dust production at high redshift is likely required to reproduce current dust mass estimates, possibly coupled with rapid dust grain growth in the interstellar medium.Comment: 72 pages, 9 figures, 5 tables; to be published in The Astronomy and Astrophysics Revie

Search for dark matter produced in association with bottom or top quarks in √s = 13 TeV pp collisions with the ATLAS detector

A search for weakly interacting massive particle dark matter produced in association with bottom or top quarks is presented. Final states containing third-generation quarks and miss- ing transverse momentum are considered. The analysis uses 36.1 fb−1 of proton–proton collision data recorded by the ATLAS experiment at √s = 13 TeV in 2015 and 2016. No significant excess of events above the estimated backgrounds is observed. The results are in- terpreted in the framework of simplified models of spin-0 dark-matter mediators. For colour- neutral spin-0 mediators produced in association with top quarks and decaying into a pair of dark-matter particles, mediator masses below 50 GeV are excluded assuming a dark-matter candidate mass of 1 GeV and unitary couplings. For scalar and pseudoscalar mediators produced in association with bottom quarks, the search sets limits on the production cross- section of 300 times the predicted rate for mediators with masses between 10 and 50 GeV and assuming a dark-matter mass of 1 GeV and unitary coupling. Constraints on colour- charged scalar simplified models are also presented. Assuming a dark-matter particle mass of 35 GeV, mediator particles with mass below 1.1 TeV are excluded for couplings yielding a dark-matter relic density consistent with measurements