Northern boundary current variability and mesoscale dynamics: a long-term HF RADAR monitoring in the North-Western Mediterranean Sea     

Bourg  Natacha  Molcard  Anne 《Ocean Dynamics》2021,71(8):851-870

Ocean Dynamics - Coastal waters are globally challenging areas to monitor not only because of the high resolution needed to resolve the scales at stake but also because most satellites are not yet...  相似文献   

Dynamics and transport from the boundary Northern Current toward the Toulon Bay: multi-platform observations and downscaling modelling approaches     

Molcard  Anne  Gramoullé  Anthony  Mazoyer  Camille  Bourg  Natacha  Ourmières  Yann 《Ocean Dynamics》2021,71(10):993-1009

Ocean Dynamics - Coastal regions are vulnerable areas with often high population density, as well as tourism and maritime activities that may have negative impact on the environment. From a...  相似文献   

Titan's atmospheric chemistry: Photolysis of gas mixtures containing hydrogen cyanide and carbon monoxide at 185 and 254 nm     

Buu N. Tran  Robert G. Briggs  Peter Persans 《Icarus》2008,193(1):224-232

The formation of organic compounds in the atmosphere of Titan is an ongoing process of the generation of complex organics from the simplest hydrocarbon, methane. Solar radiation and magnetosphere electrons are the main energy sources that drive the reactions in Titan's atmosphere. Since energy from solar radiation is 200 times greater than that from magnetosphere electrons, we have investigated the products formed by the action of UV radiation (185 and 254 nm) on a mixture of gases containing nitrogen, methane, hydrogen, acetylene, ethylene, and cyanoacetylene, the basic gas mixture (BGM) that simulates aspects of Titan's atmosphere using a flow reactor [Tran, B.N., Ferris, J.P., Chera, J.J., 2003a. Icarus 162, 114-124; Tran, B.N., Joseph, J.C., Force, M., Briggs, R.G., Vuitton, V., Ferris, J.P., 2005. Icarus 177, 106-115]. The present research extends these studies by the addition of carbon monoxide and hydrogen cyanide to the BGM. Quantum yields for the loss of reactants and the formation of volatile products were determined and compared with those measured in the absence of the hydrogen cyanide and carbon monoxide. The GCMS analyses of the volatile photolysis products from the BGM, with added hydrogen cyanide, had a composition similar to that of the BGM while the photolysis products of the BGM with added carbon monoxide contained many oxygenated compounds. The infrared spectrum of the corresponding solid product revealed the absorption band of a ketone group, which was probably formed from the reaction of carbon monoxide with the free radicals generated by photolysis of acetylene and ethylene. Of particular interest was the observation that the addition of HCN to the gas mixture only resulted in a very small change in the C/N ratio and in the intensity of the CN frequency at 2210 cm⁻¹ in the infrared spectrum suggesting that little HCN is incorporated into the haze analog. The C/N ratio of the haze analogs was found to be in the 10-12 range. The UV spectra of the solid products formed when HCN or CO added to the BGM is similar to the UV absorption formed from the BGM alone. This result is consistent with absence of additional UV chromophores to the solid product when these mixtures are photolyzed. The following photoproducts, which were not starting materials in our photochemical studies, have been observed on Titan: acetonitrile, benzene, diacetylene, ethane, propene, propane, and propyne.  相似文献   

Carbon dioxide segregation in 1:4 and 1:9 CO₂:H₂O ices     

Robert Hodyss  Paul V. Johnson  Grazyna E. Orzechowska  Jay D. Goguen  Isik Kanik 《Icarus》2008,194(2):836-842

The mid-infrared spectra of mixed vapor deposited ices of CO₂ and H₂O were studied as a function of both deposition temperature and warming from 15 to 100 K. The spectra of ices deposited at 15 K show marked changes on warming beginning at 60 K. These changes are consistent with CO₂ segregating within the ice matrix into pure CO₂ domains. Ices deposited at 60 and 70 K show a greater degree of segregation, as high as 90% for 1:4 CO₂:H₂O ice mixtures deposited at 70 K. As the ice is warmed above 80 K, preferential sublimation of the segregated CO₂ is observed. The kinetics of the segregation process is also examined. The segregation of the CO₂ as the ice is warmed corresponds to temperatures at which the structure of the water ice matrix changes from the high density amorphous phase to the low density amorphous phase. We show how these microstructural changes in the ice have a profound effect on the photochemistry induced by ultraviolet irradiation. These experimental results provide a framework in which observations of CO₂ on the icy bodies of the outer Solar System can be considered.  相似文献   

Gemini/GMOS spectroscopy of the spheroid and globular cluster system of NGC 3923     

Mark A. Norris  Ray M. Sharples  Terry Bridges  Karl Gebhardt  Duncan A. Forbes  Robert Proctor  Favio Raul Faifer  Juan Carlos Forte  Michael A. Beasley  Stephen E. Zepf  David A. Hanes 《Monthly notices of the Royal Astronomical Society》2008,385(1):40-52

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The early-type galaxies NGC 1407 and NGC 1400 – I. Spatially resolved radial kinematics and surface photometry     

Max Spolaor  Duncan A. Forbes  George K. T. Hau  Robert N. Proctor  Sarah Brough 《Monthly notices of the Royal Astronomical Society》2008,385(2):667-674

This is the first paper of a series focused on investigating the star formation and evolutionary history of the two early-type galaxies NGC 1407 and NGC 1400. They are the two brightest galaxies of the NGC 1407 (or Eridanus-A) group, one of the 60 groups studied as part of the Group Evolution Multi-wavelength Study.
Here, we present new high signal-to-noise ratio long-slit spectroscopic data obtained at the ESO 3.6-m telescope and high-resolution multiband imaging data from the Hubble Space Telescope /Advanced Camera for Surveys and wide-field imaging from Subaru Suprime-Cam. We spatially resolved integrated spectra out to ∼0.6 (NGC 1407) and ∼1.3 (NGC 1400) effective radii. The radial profiles of the kinematic parameters v _rot, σ, h ₃ and h ₄ are measured. The surface brightness profiles are fitted to different galaxy light models and the colour distributions analysed. The multiband images are modelled to derive isophotal shape parameters and residual galaxy images. The parameters from the surface brightness profile fitting are used to estimate the mass of the possible central supermassive black hole in NGC 1407. The galaxies are found to be rotationally supported and to have a flat core in the surface brightness profiles. Elliptical isophotes are observed at all radii and no fine structures are detected in the residual galaxy images. From our results, we can also discard a possible interaction between NGC 1400, NGC 1407 and the group intergalactic medium. We estimate a mass of  ∼1.03 × 10⁹ M_⊙  for the supermassive black hole in NGC 1407 galaxy.  相似文献   

Spitzer observations of M33 and the hot star, H ii region connection     

Robert H. Rubin  Janet P. Simpson  Sean W. J. Colgan  Reginald J. Dufour  Gregory Brunner  Ian A. McNabb  Adalbert W. A. Pauldrach  Edwin F. Erickson  Michael R. Haas  Robert I. Citron 《Monthly notices of the Royal Astronomical Society》2008,387(1):45-62

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The effect of massive binaries on stellar populations and supernova progenitors     

John J. Eldridge  Robert G. Izzard  Christopher A. Tout 《Monthly notices of the Royal Astronomical Society》2008,384(3):1109-1118

We compare our latest single and binary stellar model results from the Cambridge stars code to several sets of observations. We examine four stellar population ratios: the number of blue to red supergiants, the number of Wolf–Rayet stars to O supergiants, the number of red supergiants to Wolf–Rayet stars and the relative number of Wolf–Rayet subtypes, WC to WN stars. These four ratios provide a quantitative measure of nuclear burning lifetimes and the importance of mass loss during various stages of the stars' lifetimes. In addition, we compare our models to the relative rate of Type Ib/c to Type II supernovae to measure the amount of mass lost over the entire lives of all stars. We find reasonable agreement between the observationally inferred values and our predicted values by mixing single and binary star populations. However, there is evidence that extra mass loss is required to improve the agreement further, to reduce the number of red supergiants and increase the number of Wolf–Rayet stars.  相似文献   

The High-Resolution Solar Reference Spectrum between 250 and 550 nm and its Application to Measurements with the Ozone Monitoring Instrument     

Marcel Dobber  Robert Voors  Ruud Dirksen  Quintus Kleipool  Pieternel Levelt 《Solar physics》2008,249(2):281-291

We have constructed a new high resolution solar reference spectrum in the spectral range between 250 and 550 nm. The primary use of this spectrum is for the calibration of the Dutch – Finnish Ozone Monitoring Instrument (OMI), but other applications are mentioned. The incentive for deriving a new high resolution solar reference spectrum is that available spectra do not meet our requirements on radiometric accuracy or spectral resolution. In this paper we explain the steps involved in constructing the new spectrum, based on available low and high resolution spectra and discuss the main sources of uncertainty. We compare the result with solar measurements obtained with the OMI as well as with other UV-VIS space-borne spectrometers with a similar spectral resolution. We obtain excellent agreement with the OMI measurements, which indicates that both the newly derived solar reference spectrum and our characterization of the OMI instrument are well understood. We also find good agreement with previously published low resolution spectra. The absolute intensity scale, wavelength calibration and representation of the strength of the Fraunhofer lines have been investigated and optimized to obtain the resulting high resolution solar reference spectrum.  相似文献   

The NASA Lunar Impact Monitoring Program     

Robert M. Suggs  William J. Cooke  Ronnie J. Suggs  Wesley R. Swift  Nicholas Hollon 《Earth, Moon, and Planets》2008,102(1-4):293-298

NASA’s Meteoroid Environment Office has implemented a program to monitor the Moon for meteoroid impacts from the Marshall Space Flight Center. Using off-the-shelf telescopes and video equipment, the Moon is monitored for as many as 10 nights per month, depending on weather. Custom software automatically detects flashes which are confirmed by a second telescope, photometrically calibrated using background stars, and published on a website for correlation with other observations. Hypervelocity impact tests at the Ames Vertical Gun Range facility have begun to determine the luminous efficiency and ejecta characteristics. The purpose of this research is to define the impact ejecta environment for use by lunar spacecraft designers of the Constellation manned lunar program. The observational techniques and preliminary results will be discussed. The U.S. Government's right to retain a non-exclusive, royalty-free license in and to any copyright is acknowledged.  相似文献