Atrial fibrillation (AF) is a leading cause of total and fatal ischemic stroke. Stroke risk after AF ablation appears to be favorably affected; however, it is largely unknown whether the benefit ...extends to all stroke CHADS2 risk profiles of AF patients.
To determine if ablation of atrial fibrillation reduces stroke rates in all risk groups.
A total of 4212 consecutive patients who underwent AF ablation were compared (1:4) with 16,848 age-/sex-matched controls with AF (no ablation) and to 16,848 age-/sex-matched controls without AF. Patients were enrolled from the large ongoing prospective Intermountain Atrial Fibrillation Study and were followed for at least 3 years.
Of the 37,908 patients, the mean age was 65.0 ± 13 years and 4.4% (no AF), 6.3% (AF, no ablation), and 4.5% (AF ablation) patients had a prior stroke (P < .0001). The profile of CHADS2 scores between comparative groups was similar: 0-1 (69.3%, no AF; 62.3%, AF, no ablation; 63.6%, AF ablation), 2-3 (26.5%, no AF; 29.7%, AF, no ablation; 28.7%, AF ablation), and ≥4 (4.3%, no AF; 8.0%, AF, no ablation; 7.7%, AF ablation). A total of 1296 (3.4%) patients had a stroke over the follow-up period. Across all CHADS2 profiles and ages, AF patients with ablation had a lower long-term risk of stroke compared to patients without ablation. Furthermore, AF ablation patients had similar long-term risks of stroke across all CHADS2 profiles and ages compared to patients with no history of AF.
In our study populations, AF ablation patients have a significantly lower risk of stroke compared to AF patients who do not undergo ablation independent of baseline stroke risk score.
Chemical components of organic aerosol (OA) selectively absorb light at short wavelengths. In this study, the prevalence, sources, and optical importance of this so-called brown carbon (BrC) aerosol ...component are investigated throughout the North American continental tropospheric column during a summer of extensive biomass burning. Spectrophotometric absorption measurements on extracts of bulk aerosol samples collected from an aircraft over the central USA were analyzed to directly quantify BrC abundance. BrC was found to be prevalent throughout the 1 to 12 km altitude measurement range, with dramatic enhancements in biomass-burning plumes. BrC to black carbon (BC) ratios, under background tropospheric conditions, increased with altitude, consistent with a corresponding increase in the absorption Aangstrom exponent (AAE) determined from a three-wavelength particle soot absorption photometer (PSAP). The sum of inferred BC absorption and measured BrC absorption at 365 nm was within 3 % of the measured PSAP absorption for background conditions and 22 % for biomass burning. A radiative transfer model showed that BrC absorption reduced top-of-atmosphere (TOA) aerosol forcing by ~ 20 % in the background troposphere. Extensive radiative model simulations applying this study background tropospheric conditions provided a look-up chart for determining radiative forcing efficiencies of BrC as a function of a surface-measured BrC : BC ratio and single scattering albedo (SSA). The chart is a first attempt to provide a tool for better assessment of brown carbon's forcing effect when one is limited to only surface data. These results indicate that BrC is an important contributor to direct aerosol radiative forcing.
Many centers use radiofrequency (RF) energy at 25–35 W for 30–60 seconds. There is a safety concern about using higher power, especially on the posterior wall.
The purpose of this study was to ...examine complication rates for atrial fibrillation (AF) ablations performed with high-power, short-duration RF energy.
We examined the complication rates of 4 experienced centers performing AF ablations at RF powers from 45–50 W for 2–15 seconds per lesion. In total, 13,974 ablations were performed in 10,284 patients. On the posterior wall, 11,436 ablations used 45–50 W for 2–10 seconds, and 2538 ablations used power reduced to 35 W for 20 seconds. Esophageal temperature monitoring was used in 13,858 (99.2%).
Demographics were age 64 ± 11 years, male 68%, left atrial size 4.4 ± 0.7 cm, paroxysmal AF 37%, persistent AF 42%, longstanding AF 20%, antiarrhythmic drugs failed 1.4 ± 0.7, hypertension 54%, diabetes 15%, previous cerebrovascular accident/transient ischemic attack 7%, and CHA2DS2-VASc score 2.1 ± 1.4. Procedural time was 116 ± 41 minutes. Complications were death in 2 (0.014%; 1 due to stroke and 1 due to atrioesophageal fistula), pericardial tamponade in 33 (0.24%; 26 tapped, 7 surgical), strokes <48 hours in 6 (0.043%), strokes 48 hours–30 days in 6 (0.043%), pulmonary vein stenosis requiring intervention in 2 (0.014%), phrenic nerve paralysis in 2 (0.014%; both resolved), steam pops 2 (0.014%) without complications, and catheter char 0 (0.00%). There was 1 atrioesophageal fistula in 11,436 ablations using power 45–50 W on the posterior wall and 3 in 2538 ablated with 35 W on the posterior wall (P = .021), although 2 of the 3 had no esophageal monitoring during a fluoroless procedure.
AF ablations can be performed at 45–50 W for short durations with very low complication rates. High-power, short-duration ablations have the potential to shorten procedural and total RF times and create more localized and durable lesions.
Volatile element delivery and retention played a fundamental part in Earth's formation and subsequent chemical differentiation. The heavy halogens-chlorine (Cl), bromine (Br) and iodine (I)-are key ...tracers of accretionary processes owing to their high volatility and incompatibility, but have low abundances in most geological and planetary materials. However, noble gas proxy isotopes produced during neutron irradiation provide a high-sensitivity tool for the determination of heavy halogen abundances. Using such isotopes, here we show that Cl, Br and I abundances in carbonaceous, enstatite, Rumuruti and primitive ordinary chondrites are about 6 times, 9 times and 15-37 times lower, respectively, than previously reported and usually accepted estimates. This is independent of the oxidation state or petrological type of the chondrites. The ratios Br/Cl and I/Cl in all studied chondrites show a limited range, indistinguishable from bulk silicate Earth estimates. Our results demonstrate that the halogen depletion of bulk silicate Earth relative to primitive meteorites is consistent with the depletion of lithophile elements of similar volatility. These results for carbonaceous chondrites reveal that late accretion, constrained to a maximum of 0.5 ± 0.2 per cent of Earth's silicate mass, cannot solely account for present-day terrestrial halogen inventories. It is estimated that 80-90 per cent of heavy halogens are concentrated in Earth's surface reservoirs and have not undergone the extreme early loss observed in atmosphere-forming elements. Therefore, in addition to late-stage terrestrial accretion of halogens and mantle degassing, which has removed less than half of Earth's dissolved mantle gases, the efficient extraction of halogen-rich fluids from the solid Earth during the earliest stages of terrestrial differentiation is also required to explain the presence of these heavy halogens at the surface. The hydropilic nature of halogens, whereby they track with water, supports this requirement, and is consistent with volatile-rich or water-rich late-stage terrestrial accretion.
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IJS, KISLJ, NUK, SBMB, UL, UM, UPUK
With the advent of cardiac resynchronization therapy, it was unclear what percentage of biventricular pacing would be required to obtain maximal symptomatic and mortality benefit from the therapy. ...The optimal percentage of biventricular pacing and the association between the amount of continuous pacing and survival is unknown.
The purpose of this study was to assess the optimal percentage of biventricular pacing and any association with survival in a large cohort of networked patients.
A large cohort of 36,935 patients followed up in a remote-monitoring network, the LATITUDE Patient Management system (Boston Scientific Corp., Natick, Massachusetts), was assessed to determine the association between the percentage of biventricular pacing and mortality.
The greatest magnitude of reduction in mortality was observed with a biventricular pacing achieved in excess of 98% of all ventricular beats. Atrial fibrillation and native atrial ventricular condition can limit a high degree of biventricular pacing. Incremental increases in mortality benefit are observed with an increasing percentage of biventricular pacing.
Every effort should be made to reduce native atrioventricular conduction with cardiac resynchronization therapy systems in an attempt to achieve biventricular pacing as close to 100% as possible.
Sample return missions have provided the basis for understanding the thermochemical evolution of the Moon. Mare basalt sources are likely to have originated from partial melting of lunar magma ocean ...cumulates after solidification from an initially molten state. Some of the Apollo mare basalts show evidence for the presence in their source of a late-stage radiogenic heat-producing incompatible element-rich layer, known for its enrichment in potassium, rare-earth elements, and phosphorus (KREEP). Here we show the most depleted lunar meteorite, Asuka-881757, and associated mare basalts, represent ancient (~3.9 Ga) partial melts of KREEP-free Fe-rich mantle. Petrological modeling demonstrates that these basalts were generated at lower temperatures and shallower depths than typical Apollo mare basalts. Calculated mantle potential temperatures of these rocks suggest a relatively cooler mantle source and lower surface heat flow than those associated with later-erupted mare basalts, suggesting a fundamental shift in melting regime in the Moon from ~3.9 to ~3.3 Ga.
Assimilating recent observations improves model outcomes for real-time assessments of groundwater processes. This is demonstrated in estimating time-varying recharge to a shallow fractured-rock ...aquifer in response to precipitation. Results from estimating the time-varying water-table altitude (h) and recharge, and their error covariances, are compared for forecasting, filtering, and fixed-lag smoothing (FLS), which are implemented using the Kalman Filter as applied to a data-driven, mechanistic model of recharge. Forecasting uses past observations to predict future states and is the current paradigm in most groundwater modeling investigations; filtering assimilates observations up to the current time to estimate current states; and FLS estimates states following a time lag over which additional observations are collected. Results for forecasting yield a large error covariance relative to the magnitude of the expected recharge. With assimilating recent observations of h, filtering and FLS produce estimates of recharge that better represent time-varying observations of h and reduce uncertainty in comparison to forecasting. Although model outcomes from applying data assimilation through filtering or FLS reduce model uncertainty, they are not necessarily mass conservative, whereas forecasting outcomes are mass conservative. Mass conservative outcomes from forecasting are not necessarily more accurate, because process errors are inherent in any model. Improvements in estimating real-time groundwater conditions that better represent observations need to be weighed for the model application against outcomes with inherent process deficiencies. Results from data assimilation strategies discussed in this investigation are anticipated to be relevant to other groundwater processes models where system states are sensitive to system inputs.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Geophysical methods can provide three‐dimensional (3D), spatially continuous estimates of soil moisture. However, point‐to‐point comparisons of geophysical properties to measure soil moisture data ...are frequently unsatisfactory, resulting in geophysics being used for qualitative purposes only. This is because (1) geophysics requires models that relate geophysical signals to soil moisture, (2) geophysical methods have potential uncertainties resulting from smoothing and artifacts introduced from processing and inversion, and (3) results from multiple geophysical methods are not easily combined within a single soil moisture estimation framework. To investigate these potential limitations, an irrigation experiment was performed wherein soil moisture was monitored through time, and several surface geophysical datasets indirectly sensitive to soil moisture were collected before and after irrigation: ground penetrating radar, electrical resistivity tomography (ERT), and frequency domain electromagnetics (FDEM). Data were exported in both raw and processed form, and then snapped to a common 3D grid to facilitate moisture prediction by standard calibration techniques, multivariate regression, and machine learning. A combination of inverted ERT data, raw FDEM, and inverted FDEM data was most informative for predicting soil moisture using a random regression forest model (one‐thousand 60/40 training/test cross‐validation folds produced root mean squared errors ranging from 0.025–0.046 cm3/cm3). This cross‐validated model was further supported by a separate evaluation using a test set from a physically separate portion of the study area. Machine learning was conducive to a semi‐automated model‐selection process that could be used for other sites and datasets to locally improve accuracy.
Core Ideas
Various geophysical methods (e.g., frequency domain electromagnetics FDEM, ground penetrating radar, electrical resistivity tomography ERT) are sensitive to soil moisture (volumetric water content VWC).
Machine learning provides methods for data fusion and less need for assumptions/advanced data processing.
Raw and processed geophysical data were evaluated in traditional and machine learning models to predict VWC.
Random regression forest models using FDEM and ERT information gave the highest overall VWC accuracy.
Models yielded good results even when trained on only half of a physically separated portion of the dataset.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
This software spotlight presents the Geophysical Remediation Monitoring Method Selection Tool (GRM-MST). The GRM-MST is a spreadsheet-based tool designed to help practitioners identify geophysical ...methods to monitor remediation operations that are well suited to (1) the planned remedy or remedies, and (2) site-specific conditions that might limit the effectiveness of some geophysical methods.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
We describe an ongoing search for pulsars and dispersed pulses of radio emission, such as those from rotating radio transients (RRATs) and fast radio bursts, at 350 MHz using the Green Bank ...Telescope. With the Green Bank Ultimate Pulsar Processing Instrument, we record 100 MHz of bandwidth divided into 4096 channels every 81.92 mu s. This survey will cover the entire sky visible to the Green Bank Telescope ( delta > -40degrees, or 82% of the sky) and outside of the Galactic Plane will be sensitive enough to detect slow pulsars and low dispersion measure (<30 pc cm super(-3)) millisecond pulsars (MSPs) with a 0.08 duty cycle down to 1.1 mJy. For pulsars with a spectral index of -1.6, we will be 2.5 times more sensitive than previous and ongoing surveys over much of our survey region. Here we describe the survey, the data analysis pipeline, initial discovery parameters for 62 pulsars, and timing solutions for 5 new pulsars. PSR J0214 + 5222 is an MSP in a long-period (512 days) orbit and has an optical counterpart identified in archival data. PSR J0636 + 5129 is an MSP in a very short-period (96 minutes) orbit with a very low mass companion (8 M sub(J)). PSR J0645 + 5158 is an isolated MSP with a timing residual RMS of 500 ns and has been added to pulsar timing array experiments. PSR J1434 + 7257 is an isolated, intermediate-period pulsar that has been partially recycled. PSR J1816 + 4510 is an eclipsing MSP in a short-period orbit (8.7 hr) and may have recently completed its spin-up phase.
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