RESUMO
Relativistic electron-positron plasmas are ubiquitous in extreme astrophysical environments such as black-hole and neutron-star magnetospheres, where accretion-powered jets and pulsar winds are expected to be enriched with electron-positron pairs. Their role in the dynamics of such environments is in many cases believed to be fundamental, but their behavior differs significantly from typical electron-ion plasmas due to the matter-antimatter symmetry of the charged components. So far, our experimental inability to produce large yields of positrons in quasi-neutral beams has restricted the understanding of electron-positron pair plasmas to simple numerical and analytical studies, which are rather limited. We present the first experimental results confirming the generation of high-density, quasi-neutral, relativistic electron-positron pair beams using the 440 GeV/c beam at CERN's Super Proton Synchrotron (SPS) accelerator. Monte Carlo simulations agree well with the experimental data and show that the characteristic scales necessary for collective plasma behavior, such as the Debye length and the collisionless skin depth, are exceeded by the measured size of the produced pair beams. Our work opens up the possibility of directly probing the microphysics of pair plasmas beyond quasi-linear evolution into regimes that are challenging to simulate or measure via astronomical observations.
RESUMO
AIM: The aim of this study was to review our 18-year experience in the treatment of viable hydatid liver cysts (HLCs) with double percutaneous aspiration and ethanol injection (D-PAI) and to provide indications for the clinical management of HLCs. MATERIALS AND METHODS: From January 1989 to December 2007, 127 patients (100 males; 13-80 years) with 184 viable HLCs (137 univesicular, 47 multivesicular; 2.8-20 cm) underwent D-PAI. RESULTS: Ultrasonography (US) showed complete disappearance of 125/184 (68%) cysts; in the remaining 59 cases, an inactive solid (37 cases, 20%) or liquid pattern (22 cases, 12%) was observed with volume decreases of 50-80%. The final US pattern was unmodified during the follow-up in 96.8%. Local recurrences were observed in 5 patients (3.9%): 4 patients with 8 multivesicular cysts and 1 patient with a bilocular cyst (with a solid pattern on US) that ruptured into the biliary tree 2 years after the procedure and disappeared after endoscopic sphincterectomy. The mortality rate was 0.8%, and the overall morbidity was 8.6%. The mean hospital stay was 2.9 days. The time of healing for smaller cysts (<5 cm) was shorter than that of large cysts (≥5 cm) (P < 0.001). CONCLUSION: Our long-term results confirm the high effectiveness of D-PAI in the treatment of HLCs. These results suggest that multilocular cysts require closer follow-up than unilocular cysts.
RESUMO
The effect of a root canal filling material on the level of lead in blood of rhesus monkeys was examined by anodic stripping voltometry. Blood-lead levels after root canal treatment with N2 cement were elevated when compared to preoperative controls. Lead 210 was incorporated into the leadfree N2 cement to identify the source of lead. Analyses of blood samples for 210Pb indicated that the lead originated from the filling material.
