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  • 1
    Electronic Resource
    Electronic Resource
    Stable stratification alteration in a thermal diffusion cloud chamber (2000)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 113 (2000), S. 8085-8092 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The formation of clouds resulting from the homogeneous condensation of vapor phase diluted in a background or carrier gas was studied numerically. The effect of the background gas on the nucleation process in a cloud chamber heated from below is discussed. The computations were performed using 1-propanol as the condensable gas and helium, hydrogen, nitrogen, and argon, respectively, as carrier gases. Results of the simulation conducted show that large differences appear in the cloud formation when operating with hydrogen or helium, and with argon or nitrogen for which the onset of convective motions are predicted. Therefore, the isothermal patterns and streamlines are similar to those obtained in the case of Rayleigh–Bénard instabilities. The influence of the thermal Rayleigh number on the nucleation process is also considered, and it is shown that supersaturation isolines exhibit complex distortions for supercritical thermal Rayleigh numbers. As a consequence, only small zones of important nucleation rate are observed. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1315358
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Bovine serum albumin-gold thiomalate complex: gold-197 Moessbauer, EXAFS and XANES, electrophoresis, sulfur-35 radiotracer, and fluorescent probe competition studies (1984)
    s.l. : American Chemical Society
    Journal of the American Chemical Society 106 (1984), S. 3511-3521 
    Details
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ja00324a019
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  • 3
    Electronic Resource
    Electronic Resource
    Cardiac effects of co-artemether (artemether/lumefantrine) and mefloquine given alone or in combination to healthy volunteers (2000)
    Springer
    European journal of clinical pharmacology 56 (2000), S. 375-381 
    Details
    ISSN: 1432-1041
    Keywords: Key words Healthy volunteers ; QTc ; Benflumetol
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Abstract Co-artemether is an oral tablet of artemether (20 mg) and lumefantrine (120 mg) for the treatment of falciparum malaria. Administration in the presence of mefloquine is likely, as co-artemether may be used following failure of antimalarial prophylaxis or treatment with mefloquine. Objective: The effects on the QTc interval were compared among treatment with three doses of mefloquine (500, 250, 250 mg over 12 h) followed by six doses of co-artemether (6 × 4 tablets over 60 h) and either treatment alone. The study was performed in a randomised, double-blind, parallel group design in 14 healthy male subjects per dose group. Methods: Electrocardiograms (ECGs) were recorded before dosing and repeatedly thereafter. The Bazett formula was used to calculate the QTc interval. The maximum and average QTc intervals for the first, third and sixth dosing intervals of co-artemether treatment were compared among treatments. Drug plasma concentrations were determined at identical times with the ECG recordings for exploratory pharmacokinetic/pharmacodynamic evaluation. Results: No clinically relevant differences in the QTc interval were observed after sequential administration of mefloquine and co-artemether relative to either treatment given alone, and there were no clinically relevant study drug-related effects on the QTc interval after either treatment. Plasma drug measurements revealed adequate systemic exposure to artemether, dihydroartemisinin, lumefantrine and mefloquine, well in line with the clinical setting. No correlation between the length of the QTc interval and plasma drug concentrations was found for any of the compounds. Conclusions: Untoward effects on the QTc interval are unlikely to occur when co-artemether is administered following prophylaxis or treatment with mefloquine.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002280000155
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  • 4
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    Subcritical Thermal Convection of Liquid Metals in a Rapidly Rotating Sphere (2017)
    American Physical Society
    Details
    Publication Date: 2017-08-31
    Print ISSN: 0031-9007
    Electronic ISSN: 1079-7114
    Topics: Physics
    Published by American Physical Society
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  • 5
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    Dynamic domains of the Derviche Tourneur sodium experiment: Simulations of a spherical magnetized Couette flow (2018)
    American Physical Society
    Details
    Publication Date: 2018-03-29
    Electronic ISSN: 2469-990X
    Topics: Physics
    Published by American Physical Society
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  • 6
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    Quasi-geostrophic modes in the Earth's fluid core with an outer stably stratified layer (2015)
    Oxford University Press
    Details
    Publication Date: 2015-07-30
    Description: Seismic waves sensitive to the outermost part of the Earth's liquid core seem to be affected by a stably stratified layer at the core–mantle boundary. Such a layer could have an observable signature in both long-term and short-term variations of the magnetic field of the Earth, which are used to probe the flow at the top of the core. Indeed, with the recent SWARM mission, it seems reasonable to be able to identify waves propagating in the core with period of several months, which may play an important role in the large-scale dynamics. In this paper, we characterize the influence of a stratified layer at the top of the core on deep quasi-geostrophic (Rossby) waves. We compute numerically the quasi-geostrophic eigenmodes of a rapidly rotating spherical shell, with a stably stratified layer near the outer boundary. Two simple models of stratification are taken into account, which are scaled with commonly adopted values of the Brunt–Väisälä frequency in the Earth's core. In the absence of magnetic field, we find that both azimuthal wavelength and frequency of the eigenmodes control their penetration into the stratified layer: the higher the phase speed, the higher the permeability of the stratified layer to the wave motion. We also show that the theory developed by Takehiro & Lister for thermal convection extends to the whole family of Rossby waves in the core. Adding a magnetic field, the penetrative behaviour of the quasi-geostrophic modes (the so-called fast branch) is insensitive to the imposed magnetic field and only weakly sensitive to the precise shape of the stratification. Based on these results, the large-scale and high-frequency modes (1–2 month periods) may be detectable in the geomagnetic data measured at the Earth's surface, especially in the equatorial area where the modes can be trapped.
    Keywords: Geomagnetism, Rock Magnetism and Palaeomagnetism
    Print ISSN: 0956-540X
    Electronic ISSN: 1365-246X
    Topics: Geosciences
    Published by Oxford University Press on behalf of The Deutsche Geophysikalische Gesellschaft (DGG) and the Royal Astronomical Society (RAS).
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  • 7
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    Can core flows inferred from geomagnetic field models explain the Earth's dynamo? (2015)
    Oxford University Press
    Details
    Publication Date: 2015-12-13
    Description: We test the ability of large-scale velocity fields inferred from geomagnetic secular variation data to produce the global magnetic field of the Earth. Our kinematic dynamo calculations use quasi-geostrophic (QG) flows inverted from geomagnetic field models which, as such, incorporate flow structures that are Earth-like and may be important for the geodynamo. Furthermore, the QG hypothesis allows straightforward prolongation of the flow from the core surface to the bulk. As expected from previous studies, we check that a simple QG flow is not able to sustain the magnetic field against ohmic decay. Additional complexity is then introduced in the flow, inspired by the action of the Lorentz force. Indeed, on centennial timescales, the Lorentz force can balance the Coriolis force and strict quasi-geostrophy may not be the best ansatz. When our columnar flow is modified to account for the action of the Lorentz force, magnetic field is generated for Elsasser numbers larger than 0.25 and magnetic Reynolds numbers larger than 100. This suggests that our large-scale flow captures the relevant features for the generation of the Earth's magnetic field and that the invisible small-scale flow may not be directly involved in this process. Near the threshold, the resulting magnetic field is dominated by an axial dipole, with some reversed flux patches. Time dependence is also considered, derived from principal component analysis applied to the inverted flows. We find that time periods from 120 to 50 yr do not affect the mean growth rate of the kinematic dynamos. Finally, we note that the footprint of the inner core in the magnetic field generated deep in the bulk of the shell, although we did not include one in our computations.
    Keywords: Geomagnetism, Rock Magnetism and Palaeomagnetism
    Print ISSN: 0956-540X
    Electronic ISSN: 1365-246X
    Topics: Geosciences
    Published by Oxford University Press on behalf of The Deutsche Geophysikalische Gesellschaft (DGG) and the Royal Astronomical Society (RAS).
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  • 8
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    Bovine serum albumin-gold thiomalate complex: gold-197 Moessbauer, EXAFS and XANES, electrophoresis, sulfur-35 radiotracer, and fluorescent probe competition studies (1984)
    American Chemical Society
    Details
    Publication Date: 1984-06-01
    Print ISSN: 0002-7863
    Electronic ISSN: 1520-5126
    Topics: Chemistry and Pharmacology
    Published by American Chemical Society
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  • 9
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    Full sphere hydrodynamic and dynamo benchmarks (2014)
    Oxford University Press
    Details
    Publication Date: 2014-03-21
    Description: Convection in planetary cores can generate fluid flow and magnetic fields, and a number of sophisticated codes exist to simulate the dynamic behaviour of such systems. We report on the first community activity to compare numerical results of computer codes designed to calculate fluid flow within a whole sphere. The flows are incompressible and rapidly rotating and the forcing of the flow is either due to thermal convection or due to moving boundaries. All problems defined have solutions that allow easy comparison, since they are either steady, slowly drifting or perfectly periodic. The first two benchmarks are defined based on uniform internal heating within the sphere under the Boussinesq approximation with boundary conditions that are uniform in temperature and stress-free for the flow. Benchmark 1 is purely hydrodynamic, and has a drifting solution. Benchmark 2 is a magnetohydrodynamic benchmark that can generate oscillatory, purely periodic, flows and magnetic fields. In contrast, Benchmark 3 is a hydrodynamic rotating bubble benchmark using no slip boundary conditions that has a stationary solution. Results from a variety of types of code are reported, including codes that are fully spectral (based on spherical harmonic expansions in angular coordinates and polynomial expansions in radius), mixed spectral and finite difference, finite volume, finite element and also a mixed Fourier–finite element code. There is good agreement between codes. It is found that in Benchmarks 1 and 2, the approximation of a whole sphere problem by a domain that is a spherical shell (a sphere possessing an inner core) does not represent an adequate approximation to the system, since the results differ from whole sphere results.
    Print ISSN: 0956-540X
    Electronic ISSN: 1365-246X
    Topics: Geosciences
    Published by Oxford University Press on behalf of The Deutsche Geophysikalische Gesellschaft (DGG) and the Royal Astronomical Society (RAS).
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  • 10
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    Torsional Alfvén waves in a dipolar magnetic field: experiments and simulations (2019)
    Oxford University Press
    Details
    Publication Date: 2019
    Description: 〈span〉〈div〉SUMMARY〈/div〉The discovery of torsional Alfvén waves (geostrophic Alfvén waves) in the Earth’s core (Gillet et al. 2010) calls for a better understanding of their properties. We present the first experimental observations of torsional Alfvén waves, performed in the DTS-Ω set-up. In this set-up, 50L of liquid sodium are confined between an inner sphere (〈span〉ri〈/span〉 = 74 mm) and an outer shell (〈span〉ro〈/span〉 = 210 mm). The inner sphere houses a permanent magnet, imposing a dipolar magnetic field (〈span〉Bmax〈/span〉 = 345 mT). Both the inner sphere and the outer shell can rotate around the vertical axis. Alfvén waves are triggered by a sudden jerk of the inner sphere. We study the propagation of these waves when the fluid is initially at rest, and when it spins at a rotation rate up to 15 Hz. We measure the azimuthal magnetic field of the wave at different radii inside the fluid with magnetometers installed in a sleeve. We also record the electric potential signature on the outer shell at several latitudes. Besides, we probe the associated azimuthal velocity field using ultrasound Doppler velocimetry. With a 15 Hz rotation rate, the dynamical regimes we achieve are characterized by dimensionless numbers in the following ranges: Lundquist number 0.5 〈 〈span〉Lu〈/span〉 〈 12, Lehnert number 0.01 〈 〈span〉Le〈/span〉 〈 0.26, Rossby number 〈span〉Ro〈/span〉 ∼ 0.1. We observe that the magnetic signal propagates away from the inner sphere, strongly damped by magnetic diffusion. Rotation affects the magnetic signature in a subtle way. Its effect is more pronounced on the surface electric potentials, which are sensitive to the actual fluid velocity of the wave. The ultrasound Doppler probes provide the first experimental measurement of the fluid velocity of an Alfvén wave. To complement these observations, we ran numerical simulations, using the XSHELLS pseudo-spectral code with parameters as close as possible to the experimental ones. The synthetic magnetic and electric signals match our measurements. The meridional snapshots of the synthetic azimuthal velocity field reveal the formation of geostrophic cylinders expected for torsional Alfvén waves. We establish scaling laws for the magnetic and kinetic energies of Alfvén waves with and without rotation. In both cases, we find that the magnetic energy 〈span〉EM〈/span〉 saturates at a level proportional to $Rm_{jerk}^2$, where 〈span〉Rmjerk〈/span〉 = 〈span〉Ujerkro〈/span〉/η is the magnetic Reynolds number built with the maximum azimuthal velocity of the inner sphere during the jerk. The $E_K^{max}/E_M^{max}$ ratio (where $E_K^{max}$ is the maximum kinetic energy), close to 1 for very short rotation, increases linearly with the jerk duration.〈/span〉
    Print ISSN: 2051-1965
    Electronic ISSN: 1365-246X
    Topics: Geosciences
    Published by Oxford University Press on behalf of The Deutsche Geophysikalische Gesellschaft (DGG) and the Royal Astronomical Society (RAS).
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