نتایج جستجو برای: low nox
تعداد نتایج: 1208697 فیلتر نتایج به سال:
We use 2005–2009 satellite observations of formaldehyde (HCHO) columns from the OMI instrument to infer biogenic isoprene emissions at monthly 1× 1 resolution over the African continent. Our work includes new approaches to remove biomass burning influences using OMI absorbing aerosol optical depth data (to account for transport of fire plumes) and anthropogenic influences using AATSR satellite ...
The U.S. faces the difficult dual challenge of reducing the consumption of transportation fuels and improving air quality. Lean burn gasoline, diesel, and natural gas engines are of interest because they are more fuel efficient than conventional stoichiometric gasoline engines. Unfortunately, the unconverted oxygen in the exhaust prevents the use of the conventional three-way catalytic converte...
We determined 24-hr average ambient concentrations of PM2.5 and its ionic and carbonaceous components in Steubenville, OH, between May 2000 and May 2002. We also determined daily average gaseous co-pollutant concentrations, meteorological conditions, and pollen and mold spore counts. Data were analyzed graphically and by linear regression and time series models. Multiple-day episodes of elevate...
OBJECTIVE Systemic sclerosis (SSc) is characterized by severe and often progressive fibrosis of the skin and multiple internal organs. The mechanisms responsible for these alterations remain obscure, although excessive reactive oxygen species (ROS)-mediated oxidative stress has been implicated. NOX-4 is 1 of 7 isoforms of NADPH oxidase responsible for the generation of ROS. The purpose of this ...
After birth the proliferation of cardiac cells declines, and further growth of the heart occurs by hypertrophic cell growth. In the present study the cell proliferation capacity of mouse embryonic stem (ES) cells versus neonatal cardiomyocytes and the effects of reactive oxygen species (ROS) on cardiomyogenesis and cardiac cell proliferation of ES cells was investigated. Low levels of hydrogen ...
Atmospheric brown carbon (BrC) is a significant contributor to light absorption and climate forcing. However, little is known about a fundamental relationship between the chemical composition of BrC and its optical properties. In this work, light-absorbing secondary organic aerosol (SOA) was generated in the PNNL chamber from toluene photo-oxidation in the presence of NOx (Tol-SOA). Molecular s...
The method of photochemical indicators is a way to evaluate the sensitivity of O3 to its two main precursors, nitrogen oxides (NOx) and reactive organic gases (ROG), directly from ambient measurements. The method is based on identifying measureable species or species ratios that are closely associated with O3-NOx-ROG predictions in photochemical models. Several species of this type have been id...
NOx (NOx ≡ NO + NO2) regulates O3 and HOx (HOx ≡ OH + HO2) concentrations in the upper troposphere. In the laboratory, it is difficult to measure rates and branching ratios of the chemical reactions affecting NOx at the low temperatures and pressures characteristic of the upper troposphere, making direct measurements in the atmosphere especially useful. We report quasi-Lagrangian observations o...
[1] A global three-dimensional model of tropospheric chemistry driven by reanalyzed European Centre for Medium-Range Weather Forecasts meteorological data is used to examine the sources of O3, CO, and nitrogen oxides (NOx = NO + NO2) in the South Pacific troposphere during the NASA Pacific Exploratory Mission to the Tropics (PEMTropics A) in September–October 1996. Aircraft observations up to 1...
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