Since landing on Mars, the NASA InSight lander has witnessed eight Phobos and one Deimos transits. All transits could be observed by a drop in the solar array current and the surface temperature, but ...more surprisingly, for several ones, a clear signature was recorded with the seismic sensors and the magnetometer. We present a preliminary interpretation of the seismometer data as temperature‐induced local deformation of the ground, supported by terrestrial analog experiments and finite‐element modeling. The magnetic signature is most likely induced by changing currents from the solar arrays. While the observations are not fully understood yet, the recording of transit‐related phenomena with high sampling rate will allow more precise measurements of the transit times, thus providing additional constraints for the orbital parameters of Phobos. The response of the seismometer can potentially also be used to constrain the thermoelastic properties of the shallow regolith at the landing site.
Plain Language Summary
The geophysical lander, InSight, has been operating on the surface of Mars since November 2018. Since then, the Martian moons Phobos and Deimos have been partially blocking the Sun, as seen from the InSight landing site, multiple times. Multiple InSight instruments have been measuring the effect of those transits; this surprisingly includes the seismometer and the magnetometer. We conclude that temperature‐induced deformation and tilt are responsible for the seismic measurements. The change observed in the magnetometer measurements are most likely the result of a drop in the solar array currents. We do not observe atmospheric modulations with InSight's weather station during the transit. These observations help constrain orbital parameters of the Martian moons, and the seismometer signal might allow investigating thermoelastic properties of the shallow Martian material.
Key Points
Multiple geophysical InSight instruments observe unexpected signals during Phobos transits
Local ground deformation due to surface temperature drops explain the tilt signals seen by the seismometer
The drop in the solar array currents results in a change of the magnetic field
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Part of the InSight mission, the SEIS instrument (Seismic Experiment for Interior Structures), is planned to arrive on Mars in November 2018. In order to prepare its future recordings on the red ...planet, special attention was directed towards calibrating the seismometer in-situ on the Martian surface. Besides relative calibrations, we studied the possibility of actively calibrating the two kinds of seismometers onboard SEIS, the Very Broad Band seismometers (VBB) and the Short Period seismometers (SP) and extended the analysis towards a possible absolute calibration. For that purpose, we developed additional noise models at low frequency and elaborate on how they will be sensed by the seismic sensors from long-period data recorded by the seismometer. Such work will improve SEIS capabilities to unveil the inner structure of Mars by checking SEIS well-being and with applications such as gravimetry with the main Phobos tide. The current calibration procedure is planned to take one hour to calibrate the VBB sensors using the SP sensors, and determine the VBB gain with an accuracy of 0.4%, good enough to resolve the state of the Martian core.
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DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
The tidal response of Mars, due to the Sun and the Martian moons, Phobos and Deimos, provides information about the interior structure of Mars. By using the Very Broad Band (VBB) seismometer of ...Seismic Experiment for Interior Structure (SEIS) as a gravimeter on the surface of Mars, the InSight mission will provide the long‐period data suited to tidal analysis: most notably, the proximity of Phobos implies that degree 2, 3, 4, and further tides will be detectable by the VBB and are expected to provide information about the rheology at different depths within Mars. In order to expedite the recovery of these tidal signals in the SEIS measurements, we model the tides raised by Phobos using a tidal potential deduced from JPL Horizons ephemerides. From this potential, we calculate the expected tidal acceleration at InSight's location and gravimetric factors using a set of plausible interior models of Mars. To simulate the expected long period signal on the VBB seismometer, we use the InSight Auxiliary Payload Sensor Suite data to model the noise seen at low frequency by SEIS mainly due to temperature and pressure variations. Based on this synthetic signal, by applying filtering methods such as stacking and matched filtering to these synthetic data, we show that by recovering the gravimetric factors, it should be possible to constrain the state of the core and its size with an accuracy of 125 km after two Earth years.
Plain Language Summary
On Mars since November 26, 2018, the NASA InSight mission made weather measurements of the atmosphere's temperature, wind, and pressure. It has also put a seismometer at the surface of Mars to see Mars quakes. However, the seismometer can also be used to measure the tides due to the Martian moon Phobos: by deforming the surface of the planet, the Phobos tides will create a change in the gravity at the surface of Mars, which can be recorded. As Phobos is closer to Mars than the Moon is to Earth, the shape of the tides on Mars is more complicated, but can be used to determine the interior structure of Mars. In particular, its deepest part, the core, is not well determined: it is still unsure whether it is liquid or solid, and how big it is. We model the expected tides at InSight's location and noises due to temperature and pressure variations based on the measurements made to guess what the seismometer will record. This study shows that after two Earth years, we should be able to see the Phobos tides accurately enough to know the core state and size with an accuracy of 125 km.
Key Points
The Phobos tides of degree 2, 3, and 4 should be detectable by the Very Broad Band seismometer on InSight's Seismic Experiment for Interior Structure (SEIS)
We model these tides, the Martian interior and SEIS low frequency noise with recent InSight data
Over 2 Earth years, determining the core state and size with 125 km accuracy should be possible
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Tidal Constraints on the Martian Interior Pou, L.; Nimmo, F.; Rivoldini, A. ...
Journal of geophysical research. Planets,
November 2022, 2022-11-00, 20221101, 2022-11, Volume:
127, Issue:
11
Journal Article
Peer reviewed
Open access
We compare several recent Martian interior models and evaluate how these are impacted by the tidal constraints provided by the Love number k2 and the secular acceleration in longitude s of its main ...moon, Phobos. The expression of the latter is developed up to harmonic degree 5 to match the accuracy of the current observations. We match a number of current interior structure models to the recent measurements of the tidal parameters and derive estimations of the possible core radius, temperature profile, and attenuation in the Martian interior. Our estimation of the core radius is 1,820 ± 80 km, consistent with recent seismic measurements. The attenuation profiles in the Martian interior at the main tidal period of Phobos are similar between the considered models, giving a range for the degree‐2 bulk tidal attenuation Q2 = 93.0 ± 8.40 but diverge at seismic frequencies. At seismic frequencies, model shear attenuation Qμ ranges between 100 and 4,000 in the lower mantle, so that a measurement of seismic shear attenuation could be used as an effective means for distinguishing between the models considered. Other constraints such as elastic lithosphere thickness and Chandler Wobble period favor a thicker elastic lithosphere and models with a frequency dependence α of the shear attenuation between 0.15 and 0.4. Improved constraints on the Martian interior should be possible with additional seismic and radio observations from the InSight mission.
Plain Language Summary
The largest moon of Mars, Phobos, raises tides on the red planet causing its surface to be deformed. The size of this tidal bulge depends on the elastic properties of Mars, while viscosity and anelasticity inside the planet cause the tidal bulge to be misaligned with the position of Phobos on its orbit. This misalignment between Phobos and the tidal bulge of Mars creates an acceleration in longitude for the moon, which can be measured and used with the size of the tidal bulge to constraint the interior of Mars. Both the size and orientation of the tidal bulge can be used as tidal constraints to probe the size of the core of Mars, the temperature profile in its interior, and how strong the viscous dissipation is in its mantle. Our current estimates give a wide range of possible attenuation in the Martian mantle, favoring larger core sizes with larger elastic thickness of the lithosphere, the rigid outermost layer of a solid planet. Knowledge of the Martian interior could be further improved with future seismic and radio measurements from the InSight mission.
Key Points
We develop a formulation to calculate the secular acceleration of Phobos due to tidal dissipation in Mars
Using the Love number k2 and the secular acceleration s, we obtain for Mars a core size of 1,820 ± 80 km and a bulk Q of 93.0 ± 8.40
We discuss several means to distinguish between Mars models using seismological, rotational, and lithospheric observations
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Ruthenium nanoparticles were prepared by reduction of RuCl3 in a liquid polyol. The mean particle size was restricted to the 1−6 nm range by appropriate choice of the reduction temperature and the ...acetate ion concentration in the solution. Very narrow particle diameter distributions were obtained. In some samples, among nearly isotropic particles, platelets with aspect ratios as low as 1/4 were detected. Colloidal solutions in toluene were obtained by coating the metal particles with dodecane thiol. Self-assemblies of 4-nm-sized coated particles were studied on a transmission electron microscope grid. The dodecane thiol concentration in the colloidal solution was found to determine, within the particle monolayer, the formation of either columnar units made up of edgewise stacked platelets, or a hexagonal network with a mean distance between the particles of 2 nm. The stacking of hexagonal arrays of particles was also studied, and both closed-packed and noncompact stackings were found. In the noncompact stacking, moiré images resulted from the twisting of the two hexagonal layers with respect to each other. Reconstructions of moiré patterns were observed to favor the 6-fold and 2-fold sites.
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IJS, KILJ, NUK, PNG, UL, UM
Implement a sensitive UHPLC method for the assay of ganciclovir in human plasma.
We developed and validated a chromatographic method coupled to ultraviolet detection for quantification of ...ganciclovir, with a short run time using a small volume of human plasma. Comparison of system performance was made with respect to analysis time, efficiency and sensitivity.
Correlation coefficients (r) of the calibration curves ranged from 0.999744 to 0.999784. Within-day and between-day imprecision and inaccuracy, specificity and recovery were also evaluated for validation. The method was precise and accurate and the retention time was 0.7min. The calibration curves were linear between 0.5 and 30μg/mL. There was a good correlation between HPLC and UHPLC techniques.
We developed a method that is currently applied in a clinical study assessing GCV plasma concentration variability after ganciclovir and valganciclovir administration.
► A method assessing GCV plasma concentration after ganciclovir administration. ► Pharmacokinetic study in renal transplantation patients. ► An approach allowing dose adjustment to achieve a target plasma exposure. ► GCV determination to improve outcome in SOT patients infected by CMV. ► Plasma samples were determined by HPLC and UHPLC and both results were correlated.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Abstract Objective Our aim was to assess our experience with the use and management of everolimus after orthotopic liver transplantation (OLT). Materials and Methods Among the 759 patients who ...underwent transplantation from 1988 to 2008, 25 (3.2%) received immunosuppression with everolimus. Their mean age was 55.6 years. We analyzed indications for use, time between transplantation and introduction of everolimus, as well as its efficacy, side effects, and patient survival. Results The indications for everolimus treatment were: extended hepatocellular carcinoma (HCC) in the explanted liver (n = 6; 24%); HCC recurrence during follow-up (n = 4; 16%); de novo tumor (n = 6; 24%); refractory rejection (n = 3; 12%); side effects of calcineurin inhibitors (CNI; n = 3; 12%); and other causes (n = 3; 12%). Mean time between OLT and everolimus treatment was 40 ± 33 months (range, 10 days–178 months). Mean follow-up after conversion was 10 ± 9 months (range, 1.5–25 months). More than half of the patients resolved the event for which the drug was indicated: 75% of patients with refractory rejection; 60% of those with renal insufficiency; and 100% of those converted for neurotoxicity or hepatotoxicity. Two patients with recurrent HCC and 1 with extended HCC died at a mean time of 10.5 months. The 6 cases of de novo tumors were operated and are healthy. Side effects were dyslipidemia in 8 and infection in 2. Five patients (20%) discontinued the drug. Conclusions In the early posttransplantation period, everolimus is indicated for refractory rejection or as prophylaxis for recurrence of extended tumors. In any time but especially in the late period, everolimus is indicated for patients with serious side effects due to a CNI or to a de novo tumor.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Abstract Preemptive therapy with ganciclovir has been recommended in the pediatric liver transplant strategy to avoid the development of posttransplant lymphoproliferative disorder (PTLD) from an ...high Epstein-Barr virus (EBV) is detected. We sought viral load to analyze the response to preemptive therapy with valganciclovir (VGC) in children with liver transplantations and an high quantitative EBV-PCR. Methods From June 2005 to December 2007, we tested 979 EBV-PCR among 80 pediatric liver transplant recipients, from those 21/80 PCR were tested from the date of transplantation and 59/80 belonged to the historical cohort (7/59 had a prior history of PTLD). Patients were divided into 2 groups depending upon whether they did ( n = 22) or did not ( n = 19) receive VGC treatment. The response to VGC was considered complete, if the PCR was negative at 30 and 60 days of treatment; and partial, when the PCR decreased at least 50%. Ganciclovir blood levels tested in 109 cases instances and correlated with the EBV-PCR. Results A total of 369 (33%) positive PCR were detected in 36/80 patients (mean, 75,000 copies; range = 5000–4,200,000). Among the 22 episodes treated for 30 days, 34% showed complete responses, 41%, partial, and 23%, no response. Among the non-treated group the rates were 6%, 25%, and 68%, respectively ( P = .01). However, no differences were observed among those episodes treated for 60 days. At the administered doses, hardly any patient reached the recommended ganciclovir therapeutic level at 2 hours (6 μ/mL). However, the mean PCR was lower when the ganciclovir levels were greater than 4 mg/L when compared with lower levels ( P = .03). Conclusion After 30 days of treatment there was a response to VGC in the EBV viral load. There was high interpatient variability of ganciclovir serum concentrations, suggesting the need for pharmacokinetic monitoring to optimize treatment. There was a relationship between the concentration of ganciclovir and the EBV viral load.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
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