2,368 research outputs found
Surface and lightning sources of nitrogen oxides over the United States: Magnitudes, chemical evolution, and outflow
We use observations from two aircraft during the ICARTT campaign over the eastern United States and North Atlantic during summer 2004, interpreted with a global 3-D model of tropospheric chemistry (GEOS-Chem) to test current understanding of regional sources, chemical evolution, and export of NOx. The boundary layer NOx data provide top-down verification of a 50% decrease in power plant and industry NOx emissions over the eastern United States between 1999 and 2004. Observed NOx concentrations at 8â12 km altitude were 0.55 ± 0.36 ppbv, much larger than in previous U.S. aircraft campaigns (ELCHEM, SUCCESS, SONEX) though consistent with data from the NOXAR program aboard commercial aircraft. We show that regional lightning is the dominant source of this upper tropospheric NOx and increases upper tropospheric ozone by 10 ppbv. Simulating ICARTT upper tropospheric NOx observations with GEOS-Chem requires a factor of 4 increase in modeled NOx yield per flash (to 500 mol/ flash). Observed OH concentrations were a factor of 2 lower than can be explained from current photochemical models, for reasons that are unclear. A NOy-CO correlation analysis of the fraction f of North American NOx emissions vented to the free troposphere as NOy (sum of NOx and its oxidation products) shows observed f = 16 ± 10% and modeled f = 14 ± 9%, consistent with previous studies. Export to the lower free troposphere is mostly HNO3 but at higher altitudes is mostly PAN. The model successfully simulates NOy export efficiency and speciation, supporting previous model estimates of a large U.S. anthropogenic contribution to global tropospheric ozone through PAN export
RELICS: Strong Lens Models for Five Galaxy Clusters From the Reionization Lensing Cluster Survey
Strong gravitational lensing by galaxy clusters magnifies background
galaxies, enhancing our ability to discover statistically significant samples
of galaxies at z>6, in order to constrain the high-redshift galaxy luminosity
functions. Here, we present the first five lens models out of the Reionization
Lensing Cluster Survey (RELICS) Hubble Treasury Program, based on new HST
WFC3/IR and ACS imaging of the clusters RXC J0142.9+4438, Abell 2537, Abell
2163, RXC J2211.7-0349, and ACT-CLJ0102-49151. The derived lensing
magnification is essential for estimating the intrinsic properties of
high-redshift galaxy candidates, and properly accounting for the survey volume.
We report on new spectroscopic redshifts of multiply imaged lensed galaxies
behind these clusters, which are used as constraints, and detail our strategy
to reduce systematic uncertainties due to lack of spectroscopic information. In
addition, we quantify the uncertainty on the lensing magnification due to
statistical and systematic errors related to the lens modeling process, and
find that in all but one cluster, the magnification is constrained to better
than 20% in at least 80% of the field of view, including statistical and
systematic uncertainties. The five clusters presented in this paper span the
range of masses and redshifts of the clusters in the RELICS program. We find
that they exhibit similar strong lensing efficiencies to the clusters targeted
by the Hubble Frontier Fields within the WFC3/IR field of view. Outputs of the
lens models are made available to the community through the Mikulski Archive
for Space TelescopesComment: Accepted to Ap
RELICS: High-Resolution Constraints on the Inner Mass Distribution of the z=0.83 Merging Cluster RXJ0152.7-1357 from strong lensing
Strong gravitational lensing (SL) is a powerful means to map the distribution
of dark matter. In this work, we perform a SL analysis of the prominent X-ray
cluster RXJ0152.7-1357 (z=0.83, also known as CL 0152.7-1357) in \textit{Hubble
Space Telescope} images, taken in the framework of the Reionization Lensing
Cluster Survey (RELICS). On top of a previously known galaxy multiply
imaged by RXJ0152.7-1357, for which we identify an additional multiple image,
guided by a light-traces-mass approach we identify seven new sets of multiply
imaged background sources lensed by this cluster, spanning the redshift range
[1.79-3.93]. A total of 25 multiple images are seen over a small area of ~0.4
, allowing us to put relatively high-resolution constraints on the
inner matter distribution. Although modestly massive, the high degree of
substructure together with its very elongated shape make RXJ0152.7-1357 a very
efficient lens for its size. This cluster also comprises the third-largest
sample of z~6-7 candidates in the RELICS survey. Finally, we present a
comparison of our resulting mass distribution and magnification estimates with
those from a Lenstool model. These models are made publicly available through
the MAST archive.Comment: 15 Pages, 7 Figures, 4 Tables Accepted for publication in Ap
On the relative role of convection, chemistry, and transport over the South Pacific Convergence Zone during PEM-Tropics B: A case study
A mesoscale 3D model (MesoâNH) is used to assess the relative importance of convection (transport and scavenging), chemistry, and advection in the vertical redistribution of HOx and their precursors in the upper tropical troposphere. The study is focused on marine deep convection over the South Pacific Convergence Zone (SPCZ) during the PEMâTropics B Flight 10 aircraft mission. The model reproduces well the HOx mixing ratios. Vertical variations and the contrast between north and south of the SPCZ for O3 are captured. Convection uplifted O3âpoor air at higher altitude, creating a minimum in the 9â12 km region, in both modeled and observed profiles. The model captured 60% of the observed HCHO variance but fails to reproduce a peak of HCHO mixing ratio at 300 hPa sampled during the northern spirals. Simulated HCHO mixing ratios underestimate observations in the marine boundary layer. In the model, convection is not an efficient process to increase upper tropospheric HCHO, and HCHO is unlikely to serve as a primary source of HOx. Convection plays an important role in the vertical distribution of CH3OOH with efficient vertical transport from the boundary layer to the 10â15 km region where it can act as a primary source of HOx. The SPCZ region acts as a barrier to mixing of tropical and subtropical air at the surface and at high altitudes (above 250 hPa). The 400â270 hPa region over the convergence zone was more permeable, allowing subtropical air masses from the Southern Hemisphere to mix with tropical air from NE of the SPCZ and to be entrained in the SPCZârelated convection. In this altitude range, exchange of subtropical and tropical air also occurs via airflow, bypassing the convective region SW and proceeding toward the north of the SPCZ
Sources of upper tropospheric HO\u3csub\u3e\u3cem\u3ex\u3c/em\u3e\u3c/sub\u3e over the South Pacific Convergence Zone: A case study
A zeroâdimensional (0âD) model has been applied to study the sources of hydrogen oxide radicals (HOx = HO2 + OH) in the tropical upper troposphere during the Pacific Exploratory Mission in the tropics (PEMâTropics B) aircraft mission over the South Pacific in MarchâApril 1999. Observations made across the Southern Pacific Convergence Zone (SPCZ) and the southern branch of the Intertropical Convergence Zone (ITCZ) provided the opportunity to contrast the relative contributions of different sources of HOx, in a nitrogen oxide radical (NOx)âlimited regime, in relatively pristine tropical air. The primary sources of HOx vary significantly along the flight track, in correlation with the supply of water vapor. The latitudinal variation of HOx sources is found to be controlled also by the levels of NOx and primary HOx production rates P(HOx). Budget calculations in the 8â to 12âkm altitude range show that the reaction O(1D) + H2O is a major HOx source in the cloud region traversed by the aircraft, including SPCZ and the southern branch of the ITCZ. Production from acetone becomes significant in drier region south of 20°S and can become dominant where water vapor mixing ratios lie under 200 ppmv. Over the SPCZ region, in the cloud outflow, CH3 OOH transported by convection accounts for 22% to 64% of the total primary source. Oxidation of methane amplifies the primary HOx source by 1â1.8 in the dry regions
Single-Nucleotide Polymorphisms in Nucleotide Excision Repair Genes, Cigarette Smoking, and the Risk of Head and Neck Cancer
Cigarette smoking is associated with increased head and neck cancer (HNC) risk. Tobacco-related carcinogens are known to cause bulky DNA adducts. Nucleotide excision repair (NER) genes encode enzymes that remove adducts and may be independently associated with HNC, as well as modifiers of the association between smoking and HNC
Single nucleotide polymorphisms in nucleotide excision repair genes, cancer treatment, and head and neck cancer survival
Head and neck cancers (HNC) are commonly treated with radiation and platinum-based chemotherapy, which produce bulky DNA adducts to eradicate cancerous cells. Because nucleotide excision repair (NER) enzymes remove adducts, variants in NER genes may be associated with survival among HNC cases both independently and jointly with treatment
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