61 research outputs found
Geochemical Constraints for the Bulk Composition of the Moon
© 2018, Pleiades Publishing, Ltd. Abstract: The bulk composition of the silicate Moon (crust + mantle, BSM) is determined on the basis of inversion of gravitational and seismic data. It is shown that the mantle refractory oxides form two different groups depending on the thermal state. By the bulk Al2O3 content of ~3.0â4.6 wt %, the cold BSM models span the range of Al2O3 content of the silicate Earth (Bulk Silicate Earth, BSE), whereas the hot BSM models are significantly enriched in the Al2O3 content of ~5.1â7.3 wt % (Al2O3 content of ~1.2â1.7 Ă BSE) relative to BSE. In contrast, apart from the distribution of temperature, both BSM models are characterized by almost constant values of bulk FeO contents (~12.2â13.2 wt %) and MG# values (80.0â81.5), which are strongly distinct from those for BSE (~8 wt % FeO and 89 MG#). The results show that, for the geophysically possible distribution of temperatures, the silicate fraction of the Moon is enriched in FeO and depleted in MgO relative to BSE
Towards Computing Inferences from English News Headlines
Newspapers are a popular form of written discourse, read by many people,
thanks to the novelty of the information provided by the news content in it. A
headline is the most widely read part of any newspaper due to its appearance in
a bigger font and sometimes in colour print. In this paper, we suggest and
implement a method for computing inferences from English news headlines,
excluding the information from the context in which the headlines appear. This
method attempts to generate the possible assumptions a reader formulates in
mind upon reading a fresh headline. The generated inferences could be useful
for assessing the impact of the news headline on readers including children.
The understandability of the current state of social affairs depends greatly on
the assimilation of the headlines. As the inferences that are independent of
the context depend mainly on the syntax of the headline, dependency trees of
headlines are used in this approach, to find the syntactical structure of the
headlines and to compute inferences out of them.Comment: PACLING 2019 Long paper, 15 page
Analysing the Transverse Structure of the Relativistic Jets of AGN
This paper describes a method of fitting total intensity and polarization profiles in VLBI images of astrophysical jets to profiles predicted by a theoretical model. As an example, the method is used to fit profiles of the jet in the Active Galactic Nucleus Mrk501 with profiles predicted by a model in which a cylindrical jet of synchrotron plasma is threaded by a magnetic field with helical and disordered components. This fitting yields model Stokes Q profiles that agree with the observed profiles to within the 1-2 \sigma uncertainties; the I model and observed profiles are overall not in such good agreement, with the model I profiles being generally more symmetrical than the observed profiles. Consistent fitting results are obtained for profiles derived from 6cm VLBI images at two distances from the core, and also for profiles obtained for different wavelengths at a single location in the VLBI jet. The most striking success of the model is its ability to reproduce the spine-sheath polarization structure observed across the jet. Using the derived viewing angle in the jet rest frame, \delta' approximately 83 degrees, together with a superluminal speed reported in the literature, \beta apparent = 3.3, yields a solution for the viewing angle and velocity of the jet in the observer's frame \delta degrees and \beta approximately 0.96. Although these results for Mrk501 must be considered tentative, the combined analysis of polarization profiles and apparent component speeds holds promise as a means of further elucidating the magnetic field structures and other parameters of parsec-scale AGN jets
Thermodynamic Tree: The Space of Admissible Paths
Is a spontaneous transition from a state x to a state y allowed by
thermodynamics? Such a question arises often in chemical thermodynamics and
kinetics. We ask the more formal question: is there a continuous path between
these states, along which the conservation laws hold, the concentrations remain
non-negative and the relevant thermodynamic potential G (Gibbs energy, for
example) monotonically decreases? The obvious necessary condition, G(x)\geq
G(y), is not sufficient, and we construct the necessary and sufficient
conditions. For example, it is impossible to overstep the equilibrium in
1-dimensional (1D) systems (with n components and n-1 conservation laws). The
system cannot come from a state x to a state y if they are on the opposite
sides of the equilibrium even if G(x) > G(y). We find the general
multidimensional analogue of this 1D rule and constructively solve the problem
of the thermodynamically admissible transitions.
We study dynamical systems, which are given in a positively invariant convex
polyhedron D and have a convex Lyapunov function G. An admissible path is a
continuous curve along which does not increase. For x,y from D, x\geq y (x
precedes y) if there exists an admissible path from x to y and x \sim y if
x\geq y and y\geq x. The tree of G in D is a quotient space D/~. We provide an
algorithm for the construction of this tree. In this algorithm, the restriction
of G onto the 1-skeleton of (the union of edges) is used. The problem of
existence of admissible paths between states is solved constructively. The
regions attainable by the admissible paths are described.Comment: Extended version, 31 page, 9 figures, 69 cited references, many minor
correction
Near-Field Scanning Optical Microscope Combined with Digital Holography for Three-Dimensional Electromagnetic Field Reconstruction
International audienceNear-field scanning optical microscopy (NSOM) has proven to be a very powerful imaging technique that allows overcoming the diffraction limit and obtaining information on a scale much smaller than what can be achieved by classical optical imaging techniques. This is achieved using nanosized probes that are placed in close proximity to the sample surface, and thus allow the detection of evanescent waves that contain important information about the properties of the sample on a subwavelength scale. In particular, some aperture-based probes use a nanometer-sized hole to locally illuminate the sample. The far-field radiation of such probes is essential to their imaging properties, but cannot be easily estimated since it highly depends on the environment with which it interacts. In this chapter, we tackle this problem by introducing a microscopy method based on full-field off-axis digital holography that allows us to study in details the three-dimensional electromagnetic field scattered by a NSOM probe in different environments. We start by describing the NSOM and holography techniques independently, and continue by highlighting the advantage of combining both methods. We present a comparative study of the reconstructed light from a NSOM tip located in free space or coupled to transparent and plasmonic media. While far-field methods, such as back focal plane imaging, can be used to infer the directionality of angular radiation patterns, the advantage of our technique is that a single hologram contains information on both the amplitude and phase of the scattered light, allowing to reverse numerically the propagation of the electromagnetic field towards the source. We also present Finite Difference Time Domain (FDTD) simulations to model the radiation of the NSOM tip as a superposition of a magnetic and an electric dipole. We finally propose some promising applications that could be performed with this combined NSOM-holography technique
Geochemical Constraints for the Bulk Composition of the Moon
© 2018, Pleiades Publishing, Ltd. Abstract: The bulk composition of the silicate Moon (crust + mantle, BSM) is determined on the basis of inversion of gravitational and seismic data. It is shown that the mantle refractory oxides form two different groups depending on the thermal state. By the bulk Al2O3 content of ~3.0â4.6 wt %, the cold BSM models span the range of Al2O3 content of the silicate Earth (Bulk Silicate Earth, BSE), whereas the hot BSM models are significantly enriched in the Al2O3 content of ~5.1â7.3 wt % (Al2O3 content of ~1.2â1.7 Ă BSE) relative to BSE. In contrast, apart from the distribution of temperature, both BSM models are characterized by almost constant values of bulk FeO contents (~12.2â13.2 wt %) and MG# values (80.0â81.5), which are strongly distinct from those for BSE (~8 wt % FeO and 89 MG#). The results show that, for the geophysically possible distribution of temperatures, the silicate fraction of the Moon is enriched in FeO and depleted in MgO relative to BSE
Pas d'adoption pléniÚre de l'enfant de la concubine
International audience(Civ. 1re, 28 févr. 2018, n° 17-11.069, D. 2018. 509 ; ibid. 1083, point de vue H. Fulchiron ; AJ fam. 2018. 226, obs. M. Saulier ; Gaz. Pal. 2018, n° 12, p. 27, obs. P. Le Maijat ; Dr. fam. 2018, n° 5, comm. 131, obs. A. MoliÚre
PhysEth1107004KronrodLO.fm
Abstract-We model the internal structure of the Moon, initially homogeneous and later differentiated due to partial melting. The chemical composition and the internal structure of the Moon are retrieved by the Monte Carlo inversion of the gravity (the mass and the moment of inertia), seismic (compressional and shear velocities), and petrological (balance equations) data. For the computation of phase equilibrium relations and physical properties, we have used a method of minimization of the Gibbs free energy combined with a Mie Gr@uneisen equation of state within the CaO FeO MgO Al 2 O 3 -SiO 2 system. The lunar models with a different degree of constraints on the solution are considered. For all models, the geophysically and geochemically permissible ranges of seismic velocities and concentrations in three mantle zones and the sizes of Fe 10%S core are estimated. The lunar mantle is chemically stratified; different mantle zones, where orthopyroxene is the dominant phase, have different concentrations of FeO, Al 2 O 3 , and CaO. The silicate portion of the Moon (crust + mantle) may contain 3.5-5.5% Al 2 O 3 and 10.5-12.5% FeO. The chemical boundary between the middle and the lower mantle lies at a depth of 620-750 km. The lunar models with and without a chemical boundary at a depth of 250-300 km are both possible. The main parameters of the crust, the mantle, and the core of the Moon are estimated. At the depths of the lower mantle, the P and S velocities range from 7.88 to 8.10 km/s and from 4.40 to 4.55 km/s, respectively. The radius of a Fe 10%S core is 340 ± 30 km. In the present work, we suggest a new model of the constitution and internal structure of the Moon. This model is based on the hypothesis of the magma ocean; it involves modern mathematical processing of the P and S travel time data Keywords PETROLOGICAL AND GEOPHYSICAL CONSTRAINTS Models of the Magma Ocean The early differentiation of the Moon with the for mation of the continental feldspar crust, which has a thickness of about 50-60 km and ~25% Al 2 O 3 , as well as the age of the lunar rocks, have motivated the hypothesis of the Magma Ocean. The latter is com monly understood as the outer lunar shell, which had undergone partial melting By analyzing the thermoelastic stresses, Solomon [1986] showed that there is no tectonic evidence for a large scale expansion or compression of the Moon over the past four billion years (after a period of its intense bombardment). He estimated the lunar radius to have been changed by about a kilometer, which dis agrees with the concept of extensive melting. The set of petrological, geochemical, and geophysical data offers no reasons to believe that the Moon had ever been totally molten and formed a continuous magma ocean. This is also supported by the lunar asymmetry (the center of figure of the Moon is offset by 2 km from the center of mass). By analyzing the volumetric effects of differentiation of the Moon, The melting depth of 500-600 km well agrees with the experimental data on the crystallization of lunar basalts and green and picrite glass [Ringwood and Ess ene, 1970; Some information on the thickness of MO can be inferred from the geophysical data. The results of the Apollo mission infer that one or a few seismic bound aries exist in the mantle at a depth of 400-750 km In our works Seismic Data The seismic data are a kind of the Rosetta Stone for understanding the internal structure of the Moon. Processing the data obtained in the experiment that lasted for eight years (1969)(1970)(1971)(1972)(1973)(1974)(1975)(1976)(1977) and included seis mic measurements at four landing sites of Apollo 12, 14, 15, and 16 missions revealed the seismic structure of the lunar interiors shown in The mathematical processing of travel times of P and S waves suggests a zonal structure of the lunar mantle
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