Titel Deelnemers "Korte inhoud"
"Ricomporre Napoli nell'immaginario: la visione di Raffaele La Capria" "Sabine Verhulst" "NellU+2019indagare la civiltà napoletana, La Capria lumeggia i problemi di una città antichissima e complessa che ha dentro il proprio Sud e dove il connubio tra arcaicità e consumismo ostacola lU+2019uscita dalla decadenza e dal degrado. Scopo precipuo della meditazione lacapriana è ricomporre Napoli nellU+2019immaginario collettivo, tramite una riflessione sul ruolo possibile di questa città soglia fra la civiltà nord-europea e quella mediterranea. È possibile ripensarla come città cosmopolita capace di affrontare le sfide del mondo globalizzato? È la stessa Napoli ad avergli impresso nella mente il geroglifico primordiale dal quale è germogliato la bella immaginazione che ha nutrito insieme la vena della finzione narrativa e quella dei saggi letterari e civili."
"Sensitivity improvement in 5QMAS NMR experiments using FAM-N pulses" "Henri Colaux" "The multiple-quantum magic-angle spinning (MQMAS) experiment is a popular choice for obtaining high-resolution solid-state NMR spectra of quadrupolar nuclei with half-integer spin quantum number. However, its inherently poor sensitivity limits its application in more challenging systems. In particular, the use of higher-order multiple-quantum coherences, which have the potential to provide higher resolution in the isotropic spectrum, results in a further decrease in sensitivity. Here we extend our recent work, which introduced an automated, high-throughput approach to generate amplitude-modulated composite pulses (termed FAM-N) to improve the efficiency of the conversion of three-quantum coherences, and explore the use of similar pulses in five-quantum MAS experiments. We consider three different approaches, and are able to demonstrate that all three provide good enhancements over single pulse conversion in all but the most extreme cases, and work well at a range of spinning rates. We show that FAM-N pulses are robust to variation in the quadrupolar coupling and rf nutation rate, demonstrating their applicability in multisite systems and systems where direct experimental optimisation of complex composite pulses is not feasible. This work will ease the implementation of higher-order MQMAS experiments and enable their application to materials and systems that were previously deemed too difficult to study."
"Hydrostatic Interfaces in Bodies With Nonhydrostatic Lithospheres" "Mark A Wieczorek, Mikael Beuthe, Attilio Rivoldini, Tim Van Hoolst" "©2019. American Geophysical Union. All Rights Reserved. Below the lithospheres of the terrestrial planets, dwarf planets, and moons, density interfaces adjust over geologic time to align with surfaces of constant gravitational potential. It is well known that the shape of such hydrostatic surfaces is controlled by the pseudo-rotational potential, tidal potential, and the induced potential of nonspherical density interfaces in the body. When a lithosphere is present, however, additional gravitational terms must be considered that arise from, for example, surface relief and crustal thickness variations. A first-order formalism is presented for calculating the shape of hydrostatic density interfaces beneath the lithosphere when the gravity field and surface shape of the body are known. Using an arbitrary discretized density profile, the shapes are obtained by solving a simple matrix equation. As examples, lithospheric gravity anomalies account for about 10% of the relief along hydrostatic interfaces in Mars, whereas for the Moon, the lithospheric gravity is the dominant contributor to the core shape. Spherical harmonic degree-1 mass anomalies in the lithosphere generate degree-1 relief along the core-mantle boundary, and for Mars and the Moon, the core is offset from the center of mass of the body by about 90 m. The moments of inertia of the core of these bodies are also misaligned with respect to the principal moments of the entire body. An improved crustal thickness map of Mars is constructed that accounts for gravity anomalies beneath the lithosphere, and the consequences of core relief on the Martian free core nutation are quantified."
"Coupling between the spin precession and polar motion of a synchronously rotating satellite: application to Titan" "Rose-Marie Baland, Alexis Coyette, Tim Van Hoolst" "© 2019, Springer Nature B.V. We here develop, in an angular momentum approach, a consistent model that integrates all rotation variables and considers forcing both by the central planet and a potential atmosphere. Existing angular momentum approaches for studying the polar motion, precession, and libration of synchronously rotating satellites, with or without an internal global fluid layer (e.g., a subsurface ocean) usually focus on one aspect of rotation and neglect coupling with the other rotation phenomena. The model variables chosen correspond most naturally with the free modes, although they differ from those of Earth rotation studies, and facilitate a comparison with existing decoupled rotation models that break the link between the rotation motions. The decoupled models perform well in reproducing the free modes, except for the Free Ocean Nutation in the decoupled polar motion model. We also demonstrate the high accuracy of the analytical forced solutions of decoupled models, which are easier to use to interpret observations from past and future space missions. We show that the effective decoupling between the polar motion and precession implies that the spin precession and its associated mean obliquity are mainly governed by the external gravitational torque by the parent planet, whereas the polar motion of the solid layers is mainly governed by the angular momentum exchanges between the atmosphere (e.g., for Titan) and the surface. To put into perspective the difference between rotation models for a synchronously rotating icy moon with a thin ice shell and classical Earth rotation models, we also consider the case of the Moon, which has a thick outer layer above a liquid core. We also show that for non-synchronous rotators, the free precession of the outer layer in space degenerates into the tilt-over mode."
"The Rotation and Interior Structure Experiment on the InSight Mission to Mars" "William M Folkner, Veronique Dehant, Sebastien Le Maistre, Marie Yseboodt, Attilio Rivoldini, Tim Van Hoolst, Sami W Asmar, Matthew P Golombek" "© 2018, Springer Nature B.V. The Rotation and Interior Structure Experiment (RISE) on-board the InSight mission will use the lander’s X-band (8 GHz) radio system in combination with tracking stations of the NASA Deep Space Network (DSN) to determine the rotation of Mars. RISE will measure the nutation of the Martian spin axis, detecting for the first time the effect of the liquid core of Mars and providing in turn new constraints on the core radius and density. RISE will also measure changes in the rotation rate of Mars on seasonal time-scales thereby constraining the atmospheric angular momentum budget. Finally, RISE will provide a superb tie between the cartographic and inertial reference frames. This paper describes the RISE scientific objectives and measurements, and provides the expected results of the experiment."
"Does replacing grass silage by maize silage in Flemish dairy cattle diets lead to methane reduction?" "Dorien Van Wesemael, Leen Vandaele, Nico Peiren, Veerle Fievez, Sam De Campeneere"
"Obliquity of Mercury: Influence of the precession of the pericenter and of tides" "Rose-Marie Baland, Marie Yseboodt, Attilio Rivoldini, Tim Van Hoolst" "© 2017 Elsevier Inc. Mercury is expected to deviate from the classical Cassini state since this state is defined for a uniformly precessing rigid planet. We develop an extended Cassini state model that includes the variations (or nutations) in obliquity and deviation induced by the slow precession of the pericenter. The model also describes the constant shift over time in mean obliquity and deviation associated with the short-periodic tidal deformations of Mercury, characterized by the tidal love number k2 and by the ratio k2/Q of the tidal Love number over the tidal quality factor, respectively. This model is then used to interpret Mercury's orientation, including the deviation from the classical Cassini state, in terms of parameters of Mercury's interior. We determine and solve analytically the angular momentum equation, highlighting the respective roles of the pericenter precession and tidal deformations on the spin precession behavior. We also show explicitly that Peale's equation is sometimes wrongly cited in the literature, resulting in wrong estimates of the polar moment of inertia, and review the importance of many effects that change the determination of the polar moment of inertia from obliquity measurements. From the observed orientation of Stark, Oberst, Preusker, Gwinner, Peale, Margot, Phillips, Zuber and Solomon (2015b), we estimate that which is ∼ 0.9% smaller than the estimate by Stark et al. (2015b) themselves. That difference is due to our refinements of the Cassini state model (0.1%) and to their wrong use of Peale's equation (0.8%). The difference is smaller than the actual precision (3−4%) on the polar moment of inertia but may be of the order of precision that can be reached with BepiColombo mission (≤ 0.3%). The parameter k2 cannot be estimated from the spin axis orientation, because of its correlation with the polar moment of inertia, which is much more important in determining the obliquity in our improved model. However, it is necessary to include its effect in the model to avoid a systematic error of 0.3% on the determination of the polar moment of inertia. The parameter k2/Q can be estimated from the spin orientation, since its effect can be easily separated from the effect of the polar moment of inertia on the deviation, as this latter parameter is already well determined by its contribution to the obliquity. Given the actual precision on the spin axis orientation, we place an upper limit of about 0.02 on the ratio k2/Q and of about 350 on Q (assuming k2=0.5) at the 1σ level. In the future, the relative precision on the determination of k2/Q from the spin axis orientation could be as good as 30% with BepiColombo, so that the non-elastic parameter of Mercury could be estimated for the first time."
"Methaanreductie via voeding: realiteit of illusie?" "Dorien Van Wesemael"
"Stikstof en Methaan Aanpakken voor een Rundvee Toekomst (SMART)" "Dorien Van Wesemael, Karen Goossens, Leen Vandaele, Nico Peiren, Sam De Campeneere"
"Onderzoek ammoniakemissies in stroomversnelling?" "Karen Goossens, Dorien Van Wesemael, Nico Peiren, Leen Vandaele, Sam De Campeneere"