Accretion of Planetary Material onto Host Stars

Accretion of planetary material onto host stars may occur throughout a star's life. Especially prone to accretion, extrasolar planets in short-period orbits, while relatively rare, constitute a significant fraction of the known population, and these planets are subject to dynamical and atmospheric influences that can drive significant mass loss. Theoretical models frame expectations regarding the rates and extent of this planetary accretion. For instance, tidal interactions between planets and stars may drive complete orbital decay during the main sequence. Many planets that survive their stars' main sequence lifetime will still be engulfed when the host stars become red giant stars. There is some observational evidence supporting these predictions, such as a dearth of close-in planets around fast stellar rotators, which is consistent with tidal spin-up and planet accretion. There remains no clear chemical evidence for pollution of the atmospheres of main sequence or red giant stars by planetary materials, but a wealth of evidence points to active accretion by white dwarfs. In this article, we review the current understanding of accretion of planetary material, from the pre- to the post-main sequence and beyond. The review begins with the astrophysical framework for that process and then considers accretion during various phases of a host star's life, during which the details of accretion vary, and the observational evidence for accretion during these phases.Comment: 18 pages, 5 figures (with some redacted), invited revie

Laparoscopic nephrectomy: analysis of 34 patients

OBJECTIVE: To analyze the clinical experience of laparoscopic nephrectomy for benign and malignant diseases at a university hospital. METHODS: From February 2000 to March 2003, 34 patients (14 men and 20 women) underwent transperitoneal laparoscopic total nephrectomy at the Hospital das Clinicas - FMRP-USP: 28 (82.3%) patients had benign diseases and 6 (17.7%) malignant neoplasias. Benign diseases were represented by: urinary stones (N-9, 32.1%), chronic pyelonephritis (N-8, 28.6%), vesicoureteral reflux (N-4, 14.3%), ureteropelvic obstruction (N-3, 10.7%), multicystic kidney (N-2, 7.1%) and pyonephrosis (N-2, 7.1%). Patients age range was 2-79 years (mean - 35,1 years). RESULTS: In 32/34 patients the procedures were accomplished successfully. In 2 (5.8%) cases of pyonephrosis, open conversion was necessary due to perinephric abscess and difficulties in dissection of renal hilum. Two patients had intraoperative complications (1 duodenum serous laceration an 1 vascular lesion of renal hilum), but both were managed laparoscopically. Two (5.8%) post operative complications (1 delayed bleeding and 1 pancreatic fistula) required open surgical exploration. The mean time of hospital stay was 58h (18 to 240h). CONCLUSION: Laparoscopic nephrectomy proved to be a method safe and associated with a low rate of morbidity, shorter hospital stay and no casualties