Charles University in Prague

About: Charles University in Prague is a education organization based out in Prague, Czechia. It is known for research contribution in the topics: Population & Large Hadron Collider. The organization has 32392 authors who have published 74435 publications receiving 1804208 citations.

Present Trends and the Future of Zircon in Geochronology: Laser Ablation ICPMS

Abstract: In situ U-Th-Pb geochronology was born some two decades ago with the introduction and development of high-resolution secondary ion mass spectrometry (SIMS or SHRIMP [Sensitive High Mass Resolution Ion MicroProbe]; Compston et al. 1984, Williams 1998, Compston 1999, Davis et al.; this volume, Ireland and Williams, this volume). This technique clearly demonstrated the existence of age heterogeneities within the single crystals of zircon and other accessory phases and therefore the need for high-spatial resolution (tens to hundreds of cubic micrometers) geochronological data. In situ dating by ion probe is capable of achieving an analytical precision that is only an order of magnitude worse than the conventional isotope dilution-thermal ionization mass spectrometry (ID-TIMS) dating technique. It has the advantage, however, of more readily identifying concordant portions of grains, does not require chemical treatment of samples prior to the analysis, is essentially nondestructive, and can achieve greater sample throughputs. A major obstacle to the wider use of ion probe dating has always been the high cost of instrumentation and hence relative scarcity of suitably equipped geologic laboratories. Laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS) emerged in 1985 and rapidly became an important analytical tool for trace element determinations in geological samples (Jackson et al. 1992). It was soon realized that the large variations in radiogenic Pb and Pb/ U isotopic ratios found in nature could be resolved by ICPMS techniques and, when coupled to a laser, ICPMS could be used as a dating tool similar to the ion probe. The pioneering work of Feng et al. (1993), Fryer et al. (1993), Hirata and Nesbitt (1995) and Jackson et al. (1996) illustrated the potential usefulness of laser sampling for in situ dating by ICPMS particularly well. However, these studies and others that followed also revealed the major …

Midterm Clinical and First Reproductive Results of a Randomized Controlled Trial Comparing Uterine Fibroid Embolization and Myomectomy

Abstract: The purpose of this study was to compare the midterm results of a radiological and surgical approach to uterine fibroids. One hundred twenty-one women with reproductive plans who presented with an intramural fibroid(s) larger than 4 cm were randomly selected for either uterine artery embolization (UAE) or myomectomy. We compared the efficacy and safety of the two procedures and their impact on patient fertility. Fifty-eight embolizations and 63 myomectomies (42 laparoscopic, 21 open) were performed. One hundred eighteen patients have finished at least a 12-month follow-up; the mean follow-up in the entire study population was 24.9 months. Embolized patients underwent a significantly shorter procedure and required a shorter hospital stay and recovery period. They also presented with a lower CRP concentration on the second day after the procedure (p < 0.0001 for all parameters). There were no significant differences between the two groups in the rate of technical success, symptomatic effectiveness, postprocedural follicle stimulating hormone levels, number of reinterventions for fibroid recurrence or regrowth, or complication rates. Forty women after myomectomy and 26 after UAE have tried to conceive, and of these we registered 50 gestations in 45 women. There were more pregnancies (33) and labors (19) and fewer abortions (6) after surgery than after embolization (17 pregnancies, 5 labors, 9 abortions) (p < 0.05). Obstetrical and perinatal results were similar in both groups, possibly due to the low number of labors after UAE to date. We conclude that UAE is less invasive and as symptomatically effective and safe as myomectomy, but myomectomy appears to have superior reproductive outcomes in the first 2 years after treatment.