Combining astrometry and JUICE -- Europa Clipper radio science to improve the ephemerides of the Galilean moons

The upcoming JUICE and Europa Clipper missions to Jupiter's Galilean satellites will provide radio science tracking measurements of both spacecraft. Such data are expected to significantly help estimating the moons' ephemerides and related dynamical parameters. However, the two missions will yield an imbalanced dataset, with no flybys planned at Io, condensed over less than six years. Current ephemerides' solutions for the Galilean moons, on the other hand, rely on ground-based astrometry collected over more than a century which, while being less accurate, bring very valuable constraints on the long-term dynamics of the system. An improved solution for the Galilean satellites' complex dynamics could however be achieved by exploiting the existing synergies between these different observation sets. To quantify this, we merged simulated JUICE and Clipper radio science data with existing ground-based astrometric and radar observations, and performed the inversion. Our study specifically focusses on the resulting formal uncertainties in the moons' states, as well as Io's and Jupiter's tidal dissipation parameters. Adding astrometry stabilises the moons' state solution, especially beyond the missions' timelines. It furthermore reduces the uncertainties in $1/Q$ (inverse of the tidal quality factor) by a factor two to four for Jupiter, and about 30-35\% for Io. Among all data types, classical astrometry data prior to 1960 proved particularly beneficial. We also show that ground observations of Io add the most to the solution, confirming that ground observations can fill the lack of radio science data for this specific moon. We obtained a noticeable solution improvement when exploiting the complementarity between all different observation sets. These promising simulation results thus motivate future efforts to achieve a global solution from actual JUICE and Clipper radio science data

TRIS II: search for CMB spectral distortions at 0.60, 0.82 and 2.5 GHz

With the TRIS experiment we have performed absolute measurements of the sky brightness in a sky circle at $\delta = +42^{\circ}$ at the frequencies $\nu =$ 0.60, 0.82 and 2.5 GHz. In this paper we discuss the techniques used to separate the different contributions to the sky emission and give an evaluation of the absolute temperature of the Cosmic Microwave Background. For the black-body temperature of the CMB we get: $T_{cmb}^{th}=(2.837 \pm 0.129 \pm 0.066)K$ at $\nu=0.60$ GHz; $T_{cmb}^{th}=(2.803 \pm 0.051 ^{+0.430} _{-0.300})K$ at $\nu=0.82$ GHz; $T_{cmb}^{th}=(2.516 \pm 0.139 \pm 0.284)K$ at $\nu=2.5$ GHz. The first error bar is statistic (1$\sigma$) while the second one is systematic. These results represent a significant improvement with respect to the previous measurements. We have also set new limits to the free-free distortions, $-6.3 \times 10^{-6} < Y_{ff} < 12.6 \times 10^{-6}$, and slightly improved the Bose-Einstein upper limit, $|\mu| < 6 \times 10^{-5}$, both at 95% confidence level.Comment: accepted for publication in The Astrophysical Journa

Combining astrometry and JUICE-Europa Clipper radio science to improve the ephemerides of the Galilean moons

Context. The upcoming JUICE and Europa Clipper missions targeting Jupiter s Galilean satellites will provide radio science tracking measurements of both spacecraft. Such data are expected to significantly help estimating the moons ephemerides and related dynamical parameters (e.g. tidal dissipation parameters). However, the two missions will yield an imbalanced dataset, with no flybys planned at Io, condensed over less than six years. Current ephemerides solutions for the Galilean moons, on the other hand, rely on ground-based astrometry collected over more than a century which, while being less accurate, bring very valuable constraints on the long-term dynamics of the system. Aims. An improved solution for the Galilean satellites complex dynamics could however be achieved by exploiting the existing synergies between these different observation sets. Methods. To quantify this, we merged simulated radio science data from both JUICE and Europa Clipper spacecraft with existing ground-based astrometric and radar observations, and performed the inversion in different configurations: either adding all available ground observations or individually assessing the contribution of different data subsets. Our discussion specifically focusses on the resulting formal uncertainties in the moons states, as well as Io s and Jupiter s tidal dissipation parameters. Results. Adding astrometry stabilises the moons state solution, especially beyond the missions timelines. It furthermore reduces the uncertainties in 1/Q (inverse of the tidal quality factor) by a factor two to four for Jupiter, and about 30- 35% for Io. Among all data types, classical astrometry data prior to 1960 proved particularly beneficial. Overall, we also show that ground observations of Io add the most to the solution, confirming that ground observations can fill the lack of radio science data for this specific moon. Conclusions. We obtained a noticeable solution improvement when making use of the complementarity between all different observation sets. The promising results obtained with simulations thus motivate future efforts to achieve a global solution from actual JUICE and Clipper radio science measurements

Orientational order parameters of a de Vries–type ferroelectric liquid crystal obtained by polarized Raman spectroscopy and x-ray diffraction

The orientational order parameters 〈P2〉 and 〈P4〉 of the ferroelectric, de Vries–type liquid crystal 9HL have been determined in the SmA* and SmC* phases by means of polarized Raman spectroscopy, and in the SmA* phase using x-ray diffraction. Quantum density functional theory predicts Raman spectra for 9HL that are in good agreement with the observations and indicates that the strong Raman band probed in the experiment corresponds to the uniaxial, coupled vibration of the three phenyl rings along the molecular long axis. The magnitudes of the orientational order parameters obtained in the Raman and x-ray experiments differ dramatically from each other, a discrepancy that is resolved by considering that the two techniques probe the orientational distributions of different molecular axes. We have developed a systematic procedure in which we calculate the angle between these axes and rescale the orientational order parameters obtained from x-ray scattering with results that are then in good agreement with the Raman data. At least in the case of 9HL, the results obtained by both techniques support a “sugar loaf” orientational distribution in the SmA* phase with no qualitative difference to conventional smectics A. The role of individual molecular fragments in promoting de Vries–type behavior is considered

Characterization of metabolic profiles and lipopolysaccharide effects on porcine vascular wall mesenchymal stem cells

The link between metabolic remodeling and stem cell fate is still unclear. To explore this topic, the metabolic profile of porcine vascular wall mesenchymal stem cells (pVW-MSCs) was investigated. At the first and second cell passages, pVW-MSCs exploit both glycolysis and cellular respiration to synthesize adenosine triphosphate (ATP), but in the subsequent (third to eighth) passages they do not show any mitochondrial ATP turnover. Interestingly, when the first passage pVW-MSCs are exposed to 0.1 or 10 μg/ml lipopolysaccharides (LPSs) for 4 hr, even if ATP synthesis is prevented, the spare respiratory capacity is retained and the glycolytic capacity is unaffected. In contrast, the exposure of pVW-MSCs at the fifth passage to 10 μg/ml LPS stimulates mitochondrial ATP synthesis. Flow cytometry rules out any reactive oxygen species (ROS) involvement in the LPS effects, thus suggesting that the pVW-MSC metabolic pattern is modulated by culture conditions via ROS-independent mechanisms

Resonance locking in giant planets indicated by the rapid orbital expansion of Titan

Saturn is orbited by dozens of moons, and the intricate dynamics of this complex system provide clues about its formation and evolution. Tidal friction within Saturn causes its moons to migrate outwards, driving them into orbital resonances that pump their eccen- tricities or inclinations, which in turn leads to tidal heating of the moons. However, in gi- ant planets, the dissipative processes that determine the tidal migration timescale remain poorly understood. Standard theories suggest an orbital expansion rate inversely pro- portional to the power 11/2 in distance1, implying negligible migration for outer moons such as Saturn’s largest moon, Titan. Here, we use two independent measurements ob- tained with the Cassini spacecraft to measure Titan’s orbital expansion rate. We find Titan rapidly migrates away from Saturn on a timescale of roughly 10 Gyr, corresponding to a tidal quality factor of Saturn of Q ≃ 100, which is more than a hundred times smaller than most expectations. Our results for Titan and five other moons agree with the predic- tions of a resonance locking tidal theory2, sustained by excitation of inertial waves inside the planet. The associated tidal expansion is only weakly sensitive to orbital distance, motivating a revision of the evolutionary history of Saturn’s moon system. In particular, it suggests Titan formed significantly closer to Saturn and has migrated outward to its current position

Cluster Monte Carlo Simulations of the Nematic--Isotropic Transition

We report the results of simulations of the Lebwohl-Lasher model of the nematic-isotropic transition using a new cluster Monte Carlo algorithm. The algorithm is a modification of the Wolff algorithm for spin systems, and greatly reduces critical slowing down. We calculate the free energy in the neighborhood of the transition for systems up to linear size 70. We find a double well structure with a barrier that grows with increasing system size, obeying finite size scaling for systems of size greater than 35. We thus obtain an estimate of the value of the transition temperature in the thermodynamic limit.Comment: 4 figure

Ascorbic Acid, Alcohol, and Environmental Chemicals a

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73093/1/j.1749-6632.1987.tb23775.x.pd