RESUMO
Muonic atom spectroscopy-the measurement of the x rays emitted during the formation process of a muonic atom-has a long standing history in probing the shape and size of nuclei. In fact, almost all stable elements have been subject to muonic atom spectroscopy measurements and the absolute charge radii extracted from these measurements typically offer the highest accuracy available. However, so far only targets of at least a few hundred milligram could be used as it required to stop a muon beam directly in the target to form the muonic atom. We have developed a new method relying on repeated transfer reactions taking place inside a 100 bar hydrogen gas cell with an admixture of 0.25% deuterium that allows us to drastically reduce the amount of target material needed while still offering an adequate efficiency. Detailed simulations of the transfer reactions match the measured data, suggesting good understanding of the processes taking place inside the gas mixture. As a proof of principle we demonstrate the method with a measurement of the 2p-1s muonic x rays from a 5 µ g gold target.
RESUMO
PURPOSE: Primary non-refluxing megaureter (pMU) is a multifaceted and challenging congenital pathology of the urinary tract. We report our 23-year experience with this anomaly in terms of presentation, diagnostic work-up and management. MATERIALS AND METHODS: We retrospectively reviewed the medical records of 212 children diagnosed with pMU between 1986 and 2009 at our institution. Mean follow-up was 45.17 (0-192) months. RESULTS: Of the total, 168 (79 %) children presented with upper urinary tract dilation on perinatal ultrasound screening. In 44 (21 %) patients, the diagnosis was made following diagnostic work-up of a urinary tract infection (UTI, 18 %) or flank pain (3 %). In total, 203 of 254 pMUs (79.9 %) were successfully treated conservatively during the 23-year observation period. Forty-eight children (23 %) underwent ureteric reimplantation. UTIs occurred in 91 of 212 children (43 %). Of these, 41 (45 %) occurred despite antibacterial infection prophylaxis. Within the past three decades, there has been a marked shift from surgical toward conservative therapy at our institution. CONCLUSION: Neonatal renal ultrasound is the method of choice to timely identify children with pMU and, alongside dynamic renography, to monitor the clinical course. Nowadays, only a minor subset of children with asymptomatic course requires surgical correction. Antibacterial prophylaxis has the potential to reduce the risk of febrile UTIs. Prospective randomized studies are warranted to provide evidence of the beneficial effect of antibacterial prophylaxis.