Short- and Medium-term Atmospheric Effects of Very Large Solar Proton Events

Long-term variations in ozone have been caused by both natural and humankind related processes. In particular, the humankind or anthropogenic influence on ozone from chlorofluorocarbons and halons (chlorine and bromine) has led to international regulations greatly limiting the release of these substances. These anthropogenic effects on ozone are most important in polar regions and have been significant since the 1970s. Certain natural ozone influences are also important in polar regions and are caused by the impact of solar charged particles on the atmosphere. Such natural variations have been studied in order to better quantify the human influence on polar ozone. Large-scale explosions on the Sun near solar maximum lead to emissions of charged particles (mainly protons and electrons), some of which enter the Earth's magnetosphere and rain down on the polar regions. "Solar proton events" have been used to describe these phenomena since the protons associated with these solar events sometimes create a significant atmospheric disturbance. We have used the National Center for Atmospheric Research (NCAR) Whole Atmosphere Community Climate Model (WACCM) to study the short- and medium-term (days to a few months) influences of solar proton events between 1963 and 2005 on stratospheric ozone. The four largest events in the past 45 years (August 1972; October 1989; July 2000; and October-November 2003) caused very distinctive polar changes in layers of the Earth's atmosphere known as the stratosphere (12-50 km; -7-30 miles) and mesosphere (50-90 km; 30-55 miles). The solar protons connected with these events created hydrogen- and nitrogen- containing compounds, which led to the polar ozone destruction. The hydrogen-containing compounds have very short lifetimes and lasted for only a few days (typically the duration of the solar proton event). On the other hand, the nitrogen-containing compounds lasted much longer, especially in the Winter. The nitrogen oxides were predicted to increase substantially due to these solar events and led to mid- to upper polar stratospheric ozone decreases of over 20%. These WACCM results generally agreed with satellite measurements. Both WACCM and measurements showed enhancements of nitric acid, dinitrogen pentoxide, and chlorine nitrate, which were indirectly caused by these solar events. Solar proton events were shown to cause a significant change in the polar stratosphere and need to be considered in understanding variations during years of strong solar activity

Fifteen-year, single-center experience with the surgical management of intrahepatic cholangiocarcinoma: Operative results and long-term outcome

Background. Limited data exist regarding the role of extended liver resection for the management of intrahepatic cholangiocarcinoma (ICC) most of which derive from small single-center or larger multicenter series. In the current report, we present our experience with the surgical management of ICC, analyze operative results, and investigate prognostic factors in resected patients. Methods. A total of 7 patients underwent operative exploration for ICC between 1991 and 2005; 54 patients were resected, and 18 patients were deemed unresectable based on intraoperative findings. Demographics, pathology, anatomic characteristics, operative results, and survival were analyzed. Results. The resectability rate was 71%, with negative margins achieved in 78% of the resected patients. Extended liver resections were performed in 24 (44%) of the 72 patients. Perioperative mortality after resection was 7%, with 11% morbidity. The 1-, 3- and 5-year survival rates after resection were 80%, 49% and 25%, respectively, and were significantly greater than for patients with unresectable disease (P <. 001). R1 liver resections conferred increased 5-year survival compared with patients deemed unresectable (P =.03). None of the factors evaluated proved to be independent prognostic factors on multivariate analysis. Conclusions. R0 resection of ICC provides the best chance for prolonged survival, whereas R1 resection appears to be superior to nonoperative treatment. Declining operative mortality as a result of improved intraoperative and perioperative care justifies the performance of extended liver resections in these patients, although benefit has to be evaluated with respect to nodal involvement