We have investigated the possibility that large rock salt formations might be suitable as target masses for detection of neutrinos of energies about
10
PeV
and above. In neutrino interactions at ...these energies, the secondary electromagnetic cascade produces a coherent radio pulse well above ambient thermal noise via the Askaryan effect. We describe measurements of radio-frequency attenuation lengths and ambient thermal noise in two salt formations. Measurements in the Waste Isolation Pilot Plant, located in an evaporite salt bed in Carlsbad, NM yielded short attenuation lengths, 3–
7
m
over 150–
300
MHz
. However, measurements at United Salt's Hockley mine, located in a salt dome near Houston, Texas yielded attenuation lengths in excess of
250
m
at similar frequencies. We have also analyzed early ground-penetrating radar data at Hockley mine and have found additional evidence for attenuation lengths in excess of several hundred meters at
440
MHz
. We conclude that salt domes, which may individually contain several hundred cubic kilometer water-equivalent mass, provide attractive sites for next-generation high-energy neutrino detectors.
A high-energy neutrino event detected by IceCube on 22 September 2017 was coincident in direction and time with a gamma-ray flare from the blazar TXS 0506+056. Prompted by this association, we ...investigated 9.5 years of IceCube neutrino observations to search for excess emission at the position of the blazar. We found an excess of high-energy neutrino events, with respect to atmospheric backgrounds, at that position between September 2014 and March 2015. Allowing for time-variable flux, this constitutes 3.5σ evidence for neutrino emission from the direction of TXS 0506+056, independent of and prior to the 2017 flaring episode. This suggests that blazars are identifiable sources of the high-energy astrophysical neutrino flux.
The Roussillon Basin is a non-silled Miocene sedimentary basin filling a late Oligocene–early Miocene graben. The basin was intensively impacted by the Messinian fluvial erosion, as evidenced in ...exposed sections, in seismic profiles and in deep boreholes drilled for hydrocarbon exploration. As the basin was open to the Mediterranean Sea, the huge drop in sea level at the peak of the Messinian Salinity Crisis is clearly recorded, along with the subsequent sudden marine reflooding and the resulting prograding sedimentary filling, particularly in Gilbert-type fan deltas. Here, the Messinian Erosional Surface (MES) is accurately mapped in a high-resolution document, which corrects the confusion resulting from the set of 1:50,000 scale regional maps. Aim of the 3D reconstruction of the MES is to modernize geological mapping, a crucial challenge for Mediterranean and peripheral areas. Thanks to a reliable chronostratigraphy provided by planktonic foraminifers, calcareous nannofossils, micro- and macro-mammal remains, paleomagnetism and a 10Be cosmogenic nuclide-derived study, our reconstruction is one of the most comprehensive models of changes in sea level from 6 to 3 Ma. After the marine reflooding of the Mediterranean Basin at 5.46 Ma, the fluctuations in sea level recorded in the Roussillon Basin were forced by global changes. Following reflooding, the Prades large olistostrome collapsed prepared by the previous exhumation along the Canigou fault. The olistostrome is a good example of a local accident resulting from Messinian events. The exceptional changes in sea level at the peak of the Messinian Salinity Crisis deeply marked the Roussillon Basin, momentarily overprinting the Pyrenean orogenesis.
•The Messinian Salinity Crisis severely impacted the Roussillon area.•Maps of the Messinian Erosional Surface clarify the regional geological context.•The sudden post-crisis marine reflooding induced proximal Gilbert-type fan deltas.•Sea level controlled lateral-vertical variations in sedimentation.•The Prades olistostrome resulted from isostatic rebounds due to the Messinian Crisis.
The scale of payloads that can be moved in space is effectively dictated by the propellant storage, maximum thrust, and thrust efficiency of the upper-stages on modern launch vehicles. These vehicles ...must control the payload at a single attachment point which leads to restrictive mass and symmetry constraints for the payload design. The research presented here examines an alternative strategy for performing velocity control on large payloads, such as future orbital construction projects and captured asteroids. Starting from a robotic manipulator perspective, an approach is developed to grasp, orient, and translate the payload with multiple cooperative spacecraft that are already in orbit. The approach makes use of a new combinatorial optimization algorithm, path planning with a three-dimensional visibility graph road-map method, and constrained model predictive control. All elements of the strategy are tested in multiple MATLAB simulations.
Using the RICE (Radio Ice Cherenkov Experiment) detector at the South Pole, we have estimated the variation in the index of refraction (n) of the firn, as a function of elevation (z) measured from ...the surface down to z =-150 m. Measurements were made by lowering a dipole transmitter into a dry (5 in (127 mm) caliber) borehole, originally drilled for the RICE experiment in 1998, and determining signal arrival times, as a function of transmitter depth, in the englacial RICE receiver array. We clearly confirm the expected correlation of n
(z) with ice density. Our measurements are in fair agreement with previous laboratory characterizations of the dielectric properties of ice cores. These are the first such in situ measurements to be performed at the South Pole.
Dans un cadre stratigraphique revu le remplissage miocène du bassin molassique rhodano-provençal (BMRP) a été découper en 10 séquences de dépôt (IIIrd). Trois grandes phases d'érosion fluviatile ont ...été caractérisées : entre l'Aquitanien et le Burdigalien inférieur et entre le Burdigalien terminal et le Langhien puis à la base du Tortonien. Les transgressions marines miocènes du BMRP sont contrôlées par l'existence de ces réseaux fluviatiles successifs. Un modèle séquentiel haute fréquence du remplissage par des carbonates bioclastiques de faciès « foramol » du premier complexe de vallées incisées est proposé. Ces réseaux miocènes qui alimentent la plate-forme et le talus du golfe du Lion permettent de mieux comprendre comment l'ouverture du Golfe du Lion, son ralentissement puis son arrêt interagissent avec le raccourcissement alpin. Les vallées aquitano-burdigaliennes sont généralement superposées et emboîtées dans les dépôts oligo-aquitaniens. Ils sont en relation direct avec l'héritage morphostructural de ce bassin d'avant-pays et signent une déformation régionale de grande longueur d'onde rapportée à une remise en compression à la base du Miocène. Les réseaux suivant en quasi-conformité avec les structures pyrénéo-provençales sont en relation avec l'activation des plis et des chevauchements et signent une déformation plicative de plus courte longueur d'onde associée pour le réseau du Burdigalien terminal à un soulèvement régional. Leur superposition souligne la pérennité d'un contrôle tectonique. Leur déboîtement est la conséquence de l'activation des plis et des chevauchements provoquant la migration des dépôts-centres et des réseaux successifs de vallées dont cette déformation amplifie le creusement.
Accurate inertia property estimation is critical to the success of the upcoming asteroid redirect mission. The inertia tensor, center of mass, and total mass of the spacecraft-asteroid combined rigid ...body must be accurately estimated so that solar electric propulsion can be used to redirect an asteroid into an orbit around the Earth. This paper develops an efficient algorithm to solve for those properties. The estimation is framed as a least squares minimization problem subject to convex constraints. A standard least squares approach is not sufficient due to a matrix rank deficiency arising from the fact that a pure torque cannot be applied to the asteroid after capture. The constrained least squares minimization framework allows for fast inertia estimation with a convex optimization solver, in the sense that accurate estimates can be made with only a few force inputs and response measurements. Simulations are performed in MATLAB R2013B using the CVX 2.1 convex optimization solver to assess the algorithm's performance in a typical mission scenario.
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