851 research outputs found

    Titan's atmosphere as observed by Cassini/VIMS solar occultations: CH4_4, CO and evidence for C2_2H6_6 absorption

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    We present an analysis of the VIMS solar occultations dataset, which allows us to extract vertically resolved information on the characteristics of Titan's atmosphere between 100-700 km with a characteristic vertical resolution of 10 km. After a series of data treatment procedures, 4 occultations out of 10 are retained. This sample covers different seasons and latitudes of Titan. The transmittances show clearly the evolution of the haze and detect the detached layer at 310 km in Sept. 2011 at mid-northern latitudes. Through the inversion of the transmission spectra with a line-by-line radiative transfer code we retrieve the vertical distribution of CH4_4 and CO mixing ratio. The two methane bands at 1.4 and 1.7 {\mu}m are always in good agreement and yield an average stratospheric abundance of 1.28±0.081.28\pm0.08%. This is significantly less than the value of 1.48% obtained by the GCMS/Huygens instrument. The analysis of the residual spectra after the inversion shows that there are additional absorptions which affect a great part of the VIMS wavelength range. We attribute many of these additional bands to gaseous ethane, whose near-infrared spectrum is not well modeled yet. Ethane contributes significantly to the strong absorption between 3.2-3.5 {\mu}m that was previously attributed only to C-H stretching bands from aerosols. Ethane bands may affect the surface windows too, especially at 2.7 {\mu}m. Other residual bands are generated by stretching modes of C-H, C-C and C-N bonds. In addition to the C-H stretch from aliphatic hydrocarbons at 3.4 {\mu}m, we detect a strong and narrow absorption at 3.28 {\mu}m which we tentatively attribute to the presence of PAHs in the stratosphere. C-C and C-N stretching bands are possibly present between 4.3-4.5 {\mu}m. Finally, we obtain the CO mixing ratio between 70-170 km. The average result of 46±1646\pm16 ppm is in good agreement with previous studies.Comment: 51 pages, 28 figure

    Benchmark Parameters for CMB Polarization Experiments

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    The recently detected polarization of the cosmic microwave background (CMB) holds the potential for revealing the physics of inflation and gravitationally mapping the large-scale structure of the universe, if so called B-mode signals below 10^{-7}, or tenths of a uK, can be reliably detected. We provide a language for describing systematic effects which distort the observed CMB temperature and polarization fields and so contaminate the B-modes. We identify 7 types of effects, described by 11 distortion fields, and show their association with known instrumental systematics such as common mode and differential gain fluctuations, line cross-coupling, pointing errors, and differential polarized beam effects. Because of aliasing from the small-scale structure in the CMB, even uncorrelated fluctuations in these effects can affect the large-scale B modes relevant to gravitational waves. Many of these problems are greatly reduced by having an instrumental beam that resolves the primary anisotropies (FWHM << 10'). To reach the ultimate goal of an inflationary energy scale of 3 \times 10^{15} GeV, polarization distortion fluctuations must be controlled at the 10^{-2}-10^{-3} level and temperature leakage to the 10^{-4}-10^{-3} level depending on effect. For example pointing errors must be controlled to 1.5'' rms for arcminute scale beams or a percent of the Gaussian beam width for larger beams; low spatial frequency differential gain fluctuations or line cross-coupling must be eliminated at the level of 10^{-4} rms.Comment: 11 pages, 5 figures, submitted to PR

    Responses of a wetland ecosystem to the controlled introduction of invasive fish

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    Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/136368/1/fwb12900_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/136368/2/fwb12900.pd

    'Recommendations for deprescribing of medication in the last phase of life: an international Delphi study'.

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    CONTEXT Medications may become inappropriate for patients in the last phase of life and may even compromise their quality of life. OBJECTIVE To find consensus on recommendations regarding deprescribing of medications for adult patients with a life expectancy of six months or less. METHODS Experts working in palliative care or other relevant disciplines were asked to participate in this international Delphi study. Existing tools for deprescribing of medication in the last phase of life were integrated in a list of 42 recommendations regarding potential deprescription of various medication types. In two Delphi rounds, experts were asked to rate their agreement with each recommendation on a 5-point Likert-scale (strongly agree - strongly disagree). Recommendations were accepted, if at least 70% of the experts (strongly) agreed, the interquartile range (IQR) was one or less, and less than 10% strongly disagreed. RESULTS 47 experts from 10 countries participated (response rate 53%). In most cases (76%), consensus was reached on deprescribing recommendations for patients with a life expectancy of six months or less. The highest level of consensus was reached for recommendations on the deprescription of diuretics in case of decreasing fluid intake or increasing fluid loss, lipid modifying agents if prescribed for primary prevention, and vitamin K antagonists and direct oral anticoagulants in case of high bleeding risk. CONCLUSION A high level of consensus was reached on recommendations on potential deprescription of several medications for patients with a life expectancy of six months or less
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