337 research outputs found

    1995 atmospheric trace molecule spectroscopy (ATMOS) linelist

    Get PDF
    The Atmospheric Trace Molecule Spectroscopy (ATMOS) experiment uses a Fourier-transform spectrometer on board the Space Shuttle to record infrared solar occultation spectra of the atmosphere at 0.01-cm^(-1) resolution. The current version of the molecular spectroscopic database used for the analysis of the data obtained during three Space Shuttle missions between 1992 and 1994 is described. It is an extension of the effort first described by Brown et al. [Appl. Opt. 26, 5154 (1987)] to maintain an up-to-date database for the ATMOS experiment. The three-part ATMOS compilation contains Line parameters of 49 molecular species between 0 and 10000 cm^(-1), The main list, with nearly 700,000 entries, is an updated version of the HITRAN 1992 database. The second compilation contains supplemental line parameters, and the third set consists of absorption cross sections to represent the unresolvable features of heavy molecules. The differences between the ATMOS database and other public compilations are discussed

    Heavy ozone enrichments from ATMOS infrared solar spectra

    Get PDF
    Vertical enrichment profiles of stratospheric ^(16)O^(16)O^(18)O and ^(16)O^(18)O^(16)O (hereafter referred to as ^(668)O_3 and ^(686)O_3 respectively) have been derived from space-based solar occultation spectra recorded at 0.01 cm^(−1) resolution by the ATMOS (Atmospheric Trace MOlecule Spectroscopy) Fourier-transform infrared (FTIR) spectrometer. The observations, made during the Spacelab 3 and ATLAS-1, -2, and -3 shuttle missions, cover polar, mid-latitude and tropical regions between 26 to 2.6 mb inclusive (≈ 25 to 41 km). Average enrichments, weighted by molecular ^(48)O_3 density, of (15±6)% were found for ^(668)O_3 and (10±7)% for ^(686)O_3. Defining the mixing ratio of ^(50)O_3 as the sum of those for ^(668)O_3 and ^(686)O_3, an enrichment of (13±5)% was found for ^(50)O_3 (1σ standard deviation). No latitudinal or vertical gradients were found outside this standard deviation. From a series of ground-based measurements by the ATMOS instrument at Table Mountain, California (34.4°N), an average total column ^(668)O_3 enrichment of (17±4)% (1σ standard deviation) was determined, with no significant seasonal variation discernable. Possible biases in the spectral intensities that affect the determination of absolute enrichments are discussed

    Isotopic composition of stratospheric ozone

    Get PDF
    We present a kinetic calculation for the isotopic composition of stratospheric ozone. The calculated enrichments of ^(49)O_3 and ^(50)O_3 are in agreement with atmospheric measurements made at midlatitudes. Integrating the kinetic fractionation processes in the formation and photolysis of ozone, we obtain enrichments of ∼7.5–10.5 and ∼7.5–12.5% (referenced to atmospheric O_2) for δ^(49)O_3 and δ^(50)O_3, respectively, at altitudes between 20 and 35 km; the photolysis in the Hartley band of ozone is responsible for the observed altitude variation. The overall magnitude of the ozone enrichments (∼10%) is large compared with that commonly known in atmospheric chemistry and geochemistry. The heavy oxygen atom in ozone is therefore useful as a tracer of chemical species and pathways that involve ozone or its derived products. For example, the mass anomalies of oxygen in two greenhouse gases, CO_2 and N_2O, are likely the consequences of the transfer of heavy oxygen atoms from ozone

    Testing main Amazonian rivers as barriers across time and space within widespread taxa

    Full text link
    AimPresent Amazonian diversity patterns can result from many different mechanisms and, consequently, the factors contributing to divergence across regions and/or taxa may differ. Nevertheless, the riverâ barrier hypothesis is still widely invoked as a causal process in divergence of Amazonian species. Here we use modelâ based phylogeographic analyses to test the extent to which major Amazonian rivers act similarly as barriers across time and space in two broadly distributed Amazonian taxa.LocalAmazon rain forest.TaxonThe lizard Gonatodes humeralis (Sphaerodactylidae) and the tree frog Dendropsophus leucophyllatus (Hylidae).MethodsWe obtained RADseq data for samples distributed across main river barriers, representing main Areas of Endemism previously proposed for the region. We conduct modelâ based phylogeographic and genetic differentiation analyses across each population pair.ResultsMeasures of genetic differentiation (based on FST calculated from genomic data) show that all rivers are associated with significant genetic differentiation. Parameters estimated under investigated divergence models showed that divergence times for populations separated by each of the 11 bordering rivers were all fairly recent. The degree of differentiation consistently varied between taxa and among rivers, which is not an artifact of any corresponding difference in the genetic diversities of the respective taxa, or to amounts of migration based on analyses of the siteâ frequency spectrum.Main conclusionsTaken together, our results support a dispersal (rather than vicariance) history, without strong evidence of congruence between these species and rivers. However, once a species crossed a river, populations separated by each and every river have remained isolatedâ in this sense, rivers act similarly as barriers to any further gene flow. This result suggests differing degrees of persistence and gives rise to the seeming contradiction that the divergence process indeed varies across time, space and species, even though major Amazonian rivers have acted as secondary barriers to gene flow in the focal taxa.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/152608/1/jbi13676_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/152608/2/jbi13676.pd

    Stratospheric observations of CH_3D and HDO from ATMOS infrared solar spectra: Enrichments of deuterium in methane and implications for HD

    Get PDF
    Stratospheric mixing ratios of CH_3D from 100 mb to 17 mb (≈ 15 to 28 km) and HDO from 100 mb to 10 mb (≈ 15 to 32 km) have been inferred from high resolution solar occultation infrared spectra from the Atmospheric Trace MOlecule Spectroscopy (ATMOS) Fourier-transform interferometer. The spectra, taken on board the Space Shuttle during the Spacelab 3 and ATLAS-1, -2, and -3 missions, extend in latitude from 70°S to 65°N. We find CH_3D entering the stratosphere at an average mixing ratio of (9.9±0.8) × 10^(−10) with a D/H ratio in methane (7.1±7.4)% less than that in Standard Mean Ocean Water (SMOW) (1σ combined precision and systematic error). In the mid to lower stratosphere, the average lifetime of CH_3D is found to be (1.19±0.02) times that of CH_4, resulting in an increasing D/H ratio in methane as air “ages” and the methane mixing ratio decreases. We find an average of (1.0±0.1) molecules of stratospheric HDO are produced for each CH_3D destroyed (1σ combined precision and systematic error), indicating that the rate of HDO production is approximately equal to the rate of CH_3D destruction. Assuming negligible amounts of deuterium in species other than HDO, CH_3D and HD, this limits the possible change in the stratospheric HD mixing ratio below about 10 mb to be ±0.1 molecules HD created per molecule CH_3D destroyed

    The politics of playing along: radio and regulation in democratic Europe

    Get PDF
    The loss of localism has been a common trend in most radio markets in Europe and the United States. Deregulation of ownership led to a concentration phenomenon that has affected local radios in several western democracies. New forms of regulation have been considered as possible ways to stop the erosion of localism by applying rules to markets in the defense of diversity, pluralism, and the local dimension. This article analyses the local radio market in Portugal, by assessing the changes in the legislation and by examining the regulatory action that can, according to its remit, act preventively to avoid market forces to harm these principles.info:eu-repo/semantics/publishedVersio

    Seasonal Variations of Water Vapor in the Lower Stratosphere Inferred from ATMOS/ATLAS-3 Measurements of H2O and CH4

    Get PDF
    Stratospheric measurements of H2O and CH4 by the Atmospheric Trace Molecule Spectroscopy (ATMOS) Fourier transform spectrometer on the ATLAS-3 shuttle flight in November 1994 have been examined to investigate the altitude and geographic variability of H2O and the quantity H = (H2O + 2CH4) in the tropics and at mid-latitudes (8 to 49 deg N) in the northern hemisphere. The measurements indicate an average value of 7.24 +/- 0.44 ppmv for H between altitudes of about 18 to 35 km, corresponding to an annual average water vapor mixing ratio of 3.85 +/- 0.29 ppmv entering the stratosphere. The H2O vertical distribution in the tropics exhibits a wave-like structure in the 16- to 25-km altitude range, suggestive of seasonal variations in the water vapor transported from the troposphere to the stratosphere. The hygropause appears to be nearly coincident with the tropopause at the time of observations. This is consistent with the phase of the seasonal cycle of H2O in the lower stratosphere, since the ATMOS observations were made in November when the H2O content of air injected into the stratosphere from the troposphere is decreasing from its seasonal peak in July-August

    Prevalence of Disorders Recorded in Dogs Attending Primary-Care Veterinary Practices in England

    Get PDF
    Purebred dog health is thought to be compromised by an increasing occurence of inherited diseases but inadequate prevalence data on common disorders have hampered efforts to prioritise health reforms. Analysis of primary veterinary practice clinical data has been proposed for reliable estimation of disorder prevalence in dogs. Electronic patient record (EPR) data were collected on 148,741 dogs attending 93 clinics across central and south-eastern England. Analysis in detail of a random sample of EPRs relating to 3,884 dogs from 89 clinics identified the most frequently recorded disorders as otitis externa (prevalence 10.2%, 95% CI: 9.1-11.3), periodontal disease (9.3%, 95% CI: 8.3-10.3) and anal sac impaction (7.1%, 95% CI: 6.1-8.1). Using syndromic classification, the most prevalent body location affected was the head-and-neck (32.8%, 95% CI: 30.7-34.9), the most prevalent organ system affected was the integument (36.3%, 95% CI: 33.9-38.6) and the most prevalent pathophysiologic process diagnosed was inflammation (32.1%, 95% CI: 29.8-34.3). Among the twenty most-frequently recorded disorders, purebred dogs had a significantly higher prevalence compared with crossbreds for three: otitis externa (P = 0.001), obesity (P = 0.006) and skin mass lesion (P = 0.033), and popular breeds differed significantly from each other in their prevalence for five: periodontal disease (P = 0.002), overgrown nails (P = 0.004), degenerative joint disease (P = 0.005), obesity (P = 0.001) and lipoma (P = 0.003). These results fill a crucial data gap in disorder prevalence information and assist with disorder prioritisation. The results suggest that, for maximal impact, breeding reforms should target commonly-diagnosed complex disorders that are amenable to genetic improvement and should place special focus on at-risk breeds. Future studies evaluating disorder severity and duration will augment the usefulness of the disorder prevalence information reported herein

    Galaxy Collisions - Dawn of a New Era

    Full text link
    The study of colliding galaxies has progressed rapidly in the last few years, driven by observations with powerful new ground and space-based instruments. These instruments have used for detailed studies of specific nearby systems, statistical studies of large samples of relatively nearby systems, and increasingly large samples of high redshift systems. Following a brief summary of the historical context, this review attempts to integrate these studies to address the following key issues. What role do collisions play in galaxy evolution, and how can recently discovered processes like downsizing resolve some apparently contradictory results of high redshift studies? What is the role of environment in galaxy collisions? How is star formation and nuclear activity orchestrated by the large scale dynamics, before and during merger? Are novel modes of star formation involved? What are we to make of the association of ultraluminous X-ray sources with colliding galaxies? To what do degree do mergers and feedback trigger long-term secular effects? How far can we push the archaeology of individual systems to determine the nature of precursor systems and the precise effect of the interaction? Tentative answers to many of these questions have been suggested, and the prospects for answering most of them in the next few decades are good.Comment: 44 pages, 9 figures, review article in press for Astrophysics Update Vol.
    corecore