122 research outputs found
Greenhouse gas profiling by infrared-laser and microwave occultation: retrieval algorithm and demonstration results from end-to-end simulations
Measuring greenhouse gas (GHG) profiles with global coverage and high accuracy and vertical resolution in the upper troposphere and lower stratosphere (UTLS) is key for improved monitoring of GHG concentrations in the free atmosphere. In this respect a new satellite mission concept adding an infrared-laser part to the already well studied microwave occultation technique exploits the joint propagation of infrared-laser and microwave signals between Low Earth Orbit (LEO) satellites. This synergetic combination, referred to as LEO-LEO microwave and infrared-laser occultation (LMIO) method, enables to retrieve thermodynamic profiles (pressure, temperature, humidity) and accurate altitude levels from the microwave signals and GHG profiles from the simultaneously measured infrared-laser signals. However, due to the novelty of the LMIO method, a retrieval algorithm for GHG profiling is not yet available. Here we introduce such an algorithm for retrieving GHGs from LEO-LEO infrared-laser occultation (LIO) data, applied as a second step after retrieving thermodynamic profiles from LEO-LEO microwave occultation (LMO) data. We thoroughly describe the LIO retrieval algorithm and unveil the synergy with the LMO-retrieved pressure, temperature, and altitude information. We furthermore demonstrate the effective independence of the GHG retrieval results from background (a priori) information in discussing demonstration results from LMIO end-to-end simulations for a representative set of GHG profiles, including carbon dioxide (CO<sub>2</sub>), water vapor (H<sub>2</sub>O), methane (CH<sub>4</sub>), and ozone (O<sub>3</sub>). The GHGs except for ozone are well retrieved throughout the UTLS, while ozone is well retrieved from about 10 km to 15 km upwards, since the ozone layer resides in the lower stratosphere. The GHG retrieval errors are generally smaller than 1% to 3% r.m.s., at a vertical resolution of about 1 km. The retrieved profiles also appear unbiased, which points to the climate benchmarking capability of the LMIO method. This performance, found here for clear-air atmospheric conditions, is unprecedented for vertical profiling of GHGs in the free atmosphere and encouraging for future LMIO implementation. Subsequent work will examine GHG retrievals in cloudy air, addressing retrieval performance when scanning through intermittent upper tropospheric cloudiness
Pressure Evolution of Magnetism in URhGa
In this paper, we report the results of an ambient and high pressure study of
a 5f-electron ferromagnet URhGa. The work is focused on measurements of
magnetic and thermodynamic properties of a single crystal sample and on the
construction of the p-T phase diagram. Diamond anvil cells were employed to
measure the magnetization and electrical resistivity pressures up to ~ 9 GPa.
At ambient pressure, URhGa exhibits collinear ferromagnetic ordering of uranium
magnetic moments {\mu}U ~ 1.1 {\mu}B (at 2 K) aligned along the c-axis of the
hexagonal crystal structure below the Curie temperature TC = 41K. With the
application of pressure up to 5GPa the ordering temperature TC initially
increases whereas the saturated moment slightly decreases. The rather
unexpected evolution is put in the context of the UTX family of compounds.Comment: arXiv admin note: text overlap with arXiv:1611.0327
Monostotic fibrous dysplasia of the spine: report of a case involving a cervical vertebra
Monostotic fibrous dysplasia of the spine is a rare entity. Only 26 cases, of which 11 were located in the cervical spine, are to be found in the literature. We report a 56-year-old male patient with cervicobrachialgia of half year's duration. Radiographs showed a diffuse destruction of the vertebral body and the spinous process of C4. A biopsy of the spinous process confirmed histopathologically a fibrous dysplasia. Due to minor symptoms, no surgical treatment was performed or is planned unless in case of increasing pain, an acute instability or neurological symptom
Development of Fast Helium Beam Emission Spectroscopy for Plasma Density and Temperature Diagnostics
Pressure-induced huge increase of Curie temperature of the van der Waals ferromagnet VI3
Evolution of magnetism in single crystals of the van der Waals compound VI3
in external pressure up to 7.3 GPa studied by measuring magnetization and ac
magnetic susceptibility is reported. Four magnetic phase transitions, at T1 =
54.5 K, T2 = 53 K, TC = 49.5 K, and TFM = 26 K, respectively have been observed
at ambient pressure. The first two have been attributed to the onset of
ferromagnetism in specific crystal-surface layers. The bulk ferromagnetism is
characterized by the magnetic ordering transition at Curie temperature TC and
the transition between two different ferromagnetic phases TFM, accompanied by a
structure transition from monoclinic to triclinic symmetry upon cooling. The
pressure effects on magnetic parameters were studied with three independent
techniques. TC was found to be almost unaffected by pressures up to 0.6 GPa
whereas TFM increases rapidly with increasing pressure and reaches TC at a
triple point at ~ 0.85 GPa. At higher pressures, only one magnetic phase
transition is observed moving to higher temperatures with increasing pressure
to reach 99 K at 7.3 GPa. In contrast, the low-temperature bulk magnetization
is dramatically reduced by applying pressure (by more than 50% at 2.5 GPa)
suggesting a possible pressure-induced reduction of vanadium magnetic moment.
We discussed these results in light of recent theoretical studies to analyze
exchange interactions and provide how to increase the Curie temperature of VI3.Comment: 20 pages, 16 figure
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