Small-scale filament eruptions as the driver of X-ray jets in solar coronal holes.

Solar X-ray jets are thought to be made by a burst of reconnection of closed magnetic field at the base of a jet with ambient open field. In the accepted version of the 'emerging-flux' model, such a reconnection occurs at a plasma current sheet between the open field and the emerging closed field, and also forms a localized X-ray brightening that is usually observed at the edge of the jet's base. Here we report high-resolution X-ray and extreme-ultraviolet observations of 20 randomly selected X-ray jets that form in coronal holes at the Sun's poles. In each jet, contrary to the emerging-flux model, a miniature version of the filament eruptions that initiate coronal mass ejections drives the jet-producing reconnection. The X-ray bright point occurs by reconnection of the 'legs' of the minifilament-carrying erupting closed field, analogous to the formation of solar flares in larger-scale eruptions. Previous observations have found that some jets are driven by base-field eruptions, but only one such study, of only one jet, provisionally questioned the emerging-flux model. Our observations support the view that solar filament eruptions are formed by a fundamental explosive magnetic process that occurs on a vast range of scales, from the biggest mass ejections and flare eruptions down to X-ray jets, and perhaps even down to smaller jets that may power coronal heating. A similar scenario has previously been suggested, but was inferred from different observations and based on a different origin of the erupting minifilament.

Early coronary angiography and induced hypothermia are associated with survival and functional recovery after out-of-hospital cardiac arrest.

BACKGROUND: The rate and effect of coronary interventions and induced hypothermia after out-of-hospital cardiac arrest (OHCA) are unknown. We measured the association of early (≤24h after arrival) coronary angiography, reperfusion, and induced hypothermia with favorable outcome after OHCA. METHODS: We performed a secondary analysis of a multicenter clinical trial (NCT00394706) conducted between 2007 and 2009 in 10 North American regions. Subjects were adults (≥18 years) hospitalized after OHCA with pulses sustained ≥60min. We measured the association of early coronary catheterization, percutaneous coronary intervention, fibrinolysis, and induced hypothermia with survival to hospital discharge with favorable functional status (modified Rankin Score≤3). RESULTS: From 16,875 OHCA subjects, 3981 (23.6%) arrived at 151 hospitals with sustained pulses. 1317 (33.1%) survived to hospital discharge, with 1006 (25.3%) favorable outcomes. Rates of early coronary catheterization (19.2%), coronary reperfusion (17.7%) or induced hypothermia (39.3%) varied among hospitals, and were higher in hospitals treating more subjects per year. Odds of survival and favorable outcome increased with hospital volume (per 5 subjects/year OR 1.06; 95%CI: 1.04-1.08 and OR 1.06; 95%CI: 1.04, 1.08, respectively). Survival and favorable outcome were independently associated with early coronary angiography (OR 1.69; 95%CI 1.06-2.70 and OR 1.87; 95%CI 1.15-3.04), coronary reperfusion (OR 1.94; 95%CI 1.34-2.82 and OR 2.14; 95%CI 1.46-3.14), and induced hypothermia (OR 1.36; 95%CI 1.01-1.83 and OR 1.42; 95%CI 1.04-1.94). INTERPRETATION: Early coronary intervention and induced hypothermia are associated with favorable outcome and are more frequent in hospitals that treat higher numbers of OHCA subjects per year.

MAG4 versus alternative techniques for forecasting active region flare productivity.

MAG4 is a technique of forecasting an active region's rate of production of major flares in the coming few days from a free magnetic energy proxy. We present a statistical method of measuring the difference in performance between MAG4 and comparable alternative techniques that forecast an active region's major-flare productivity from alternative observed aspects of the active region. We demonstrate the method by measuring the difference in performance between the "Present MAG4" technique and each of three alternative techniques, called "McIntosh Active-Region Class," "Total Magnetic Flux," and "Next MAG4." We do this by using (1) the MAG4 database of magnetograms and major flare histories of sunspot active regions, (2) the NOAA table of the major-flare productivity of each of 60 McIntosh active-region classes of sunspot active regions, and (3) five technique performance metrics (Heidke Skill Score, True Skill Score, Percent Correct, Probability of Detection, and False Alarm Rate) evaluated from 2000 random two-by-two contingency tables obtained from the databases. We find that (1) Present MAG4 far outperforms both McIntosh Active-Region Class and Total Magnetic Flux, (2) Next MAG4 significantly outperforms Present MAG4, (3) the performance of Next MAG4 is insensitive to the forward and backward temporal windows used, in the range of one to a few days, and (4) forecasting from the free-energy proxy in combination with either any broad category of McIntosh active-region classes or any Mount Wilson active-region class gives no significant performance improvement over forecasting from the free-energy proxy alone (Present MAG4). KEY POINTS: Quantitative comparison of performance of pairs of forecasting techniques Next MAG4 forecasts major flares more accurately than Present MAG4 Present MAG4 forecast outperforms McIntosh AR Class and total magnetic flux.

Tooth bleaching and pit and fissure stain.

PURPOSE: To investigate if tooth whitening had any effect on the shade of occlusal pit and fissure stains and whether reservoirs in bleaching trays affected bleaching of occlusal pit and fissure stains. METHODS: 96 extracted molars were randomly divided into three paired groups for whitening using a 10% carbamide peroxide solution (Opalescence) or a 22% carbamide peroxide solution (Nite White Excel 3), or tap water for a control. One of each pair utilized reservoirs in their custom bleaching trays. Three dentists evaluated the shade of a specified occlusal area of pit and fissure stain twice before bleaching and twice after bleaching. RESULTS: Pit and fissure stain showed significant lightening of shade for either of the bleaching systems (P < 0.0005) but not the control (P = 0.816). There was no significant difference in pit and fissure stain shade lightening following treatment between those groups utilizing reservoirs in the custom trays and those without reservoirs (P = 0.658).