20 research outputs found
Sustained fluvial deposition recorded in Mars’ Noachian stratigraphic record
Orbital observation has revealed a rich record of fluvial landforms on Mars, with much of this record dating 3.6–3.0 Ga. Despite widespread geomorphic evidence, few analyses of Mars’ alluvial sedimentary-stratigraphic record exist, with detailed studies of alluvium largely limited to smaller sand-bodies amenable to study in-situ by rovers. These typically metre-scale outcrop dimensions have prevented interpretation of larger scale channel-morphology and long-term basin evolution, vital for understanding the past Martian climate. Here we give an interpretation of a large sedimentary succession at Izola mensa within the NW Hellas Basin rim. The succession comprises channel and barform packages which together demonstrate that river deposition was already well established >3.7 Ga. The deposits mirror terrestrial analogues subject to low-peak discharge variation, implying that river deposition at Izola was subject to sustained, potentially perennial, fluvial flow. Such conditions would require an environment capable of maintaining large volumes of water for extensive time-periods, necessitating a precipitation-driven hydrological cycle
Implications of pre-procedural TIMI flow in patients with non ST-segment elevation acute coronary syndromes undergoing percutaneous coronary revascularization: Insights from the ACUITY trial.
Comparison of heparin plus IIb/IIIa inhibition versus bivalirudin with or without IIb/IIIa inhibition in patients with acute coronary syndromes undergoing percutaneous coronary intervention: The ACUITY trial
Safety and efficacy of bivalirudin with and without glycoprotein IIb/IIIa inhibitors in patients with acute coronary syndromes undergoing percutancous coronary intervention: One year results from the randomized ACUITY trial
Comparison of catheterization lab initiated abciximab and double-bolus eptifibatide during percutaneous coronary intervention in acute coronary syndromes: an ACUITY substudy
Drug eluting stents in patients with acute coronary syndromes undergoing percutaneous coronary intervention: The ACUITY trial
Surface and Airborne Arsenic Concentrations in a Recreational Site near Las Vegas, Nevada, USA
Elevated concentrations of arsenic, up to 7058 μg g-1 in topsoil and bedrock, and more than 0.03 μg m-3 in air on a 2-week basis, were measured in the Nellis Dunes Recreation Area (NDRA), a very popular off-road area near Las Vegas, Nevada, USA. The elevated arsenic concentrations in the topsoil and bedrock are correlated to outcrops of yellow sandstone belonging to the Muddy Creek Formation (≈ 10 to 4 Ma) and to faults crossing the area. Mineralized fluids moved to the surface through the faults and deposited the arsenic. A technique was developed to calculate airborne arsenic concentrations from the arsenic content in the topsoil. The technique was tested by comparing calculated with measured concentrations at 34 locations in the NDRA, for 3 periods of 2 weeks each. We then applied it to calculate airborne arsenic concentrations for more than 500 locations all over the NDRA. The highest airborne arsenic concentrations occur over sand dunes and other zones with a surficial layer of aeolian sand. Ironically these areas show the lowest levels of arsenic in the topsoil. However, they are highly susceptible to wind erosion and emit very large amounts of sand and dust during episodes of strong winds, thereby also emitting much arsenic. Elsewhere in the NDRA, in areas not or only very slightly affected by wind erosion, airborne arsenic levels equal the background level for airborne arsenic in the USA, approximately 0.0004 μg m-3. The results of this study are important because the NDRA is visited by more than 300,000 people annually