TERMO-LR Experiment on the Luna-27 Lander: Study of Thermophysical,Physicomechanical, and Electromagnetic Properties of the Lunar Soil

Solar System Research - The device is being developed for the TERMO-LR experiment on the Luna-27 lunar lander; it is intended for contact geophysical measurements of various properties of the lunar...     

On a possible mechanism responsible for the differential energy spectrum of relativistic electrons and non-linear low-frequency spectra of cosmic radio sources

The paper suggests an explanation of the deviations from the power law which are observed in frequency spectra of discrete radio sources at decametric wavelengths. It has been shown that a possible mechanism of the deviations is a combined effect of the stimulated and spontaneous scattering of relativistic electrons in the turbulent plasma of a source, as well as ionization energy losses thereof. The distribution function of the relativistic electrons, empirically established in an earlier paper (Braudeet al., 1971) has been derived from the kinetic equation. For a number of discrete sources the turbulence energy density and the plasma concentration are deduced with the aid of experimental data on low-frequency radio spectra.

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Some properties of the He-w star HD 35502

This is a preliminary study of the star HD 35502. Its magnetic field has been measured in different phases of its period. Preliminary values of the magnetic field parameters have been obtained based on a central quadrupole model. The effective magnetic field Be varies over 0-5000 G, the average surface magnetic field ranges over 6300-6700 G, the field at the poles is Bp=7000 G, and the angle between the quadrupole axis and the axis of rotation is β = 80o. As a first approximation, the surface helium is concentrated around the (negative) pole and for τ > 1 its abundance is reduced by approximately 2-4 dex, which confirms the hypothesis of helium diffusion under the action of gravitation and wind in a stable atmosphere. The chemical elements Si and Cr are concentrated in four spots on the magnetic equator between the magnetic poles, or in a ring coincident with the magnetic equator; precisely which is not clear at present.     

Vertical amplitude reduction of Rayleigh waves by a row of piles in a poroelastic half‐space

A row of rigid piles is addressed as the countermeasures for isolating Rayleigh waves in a poroelastic half‐space. The complex characteristic equations for Rayleigh waves are derived via Biot's theory and their existence conditions are given. The piles are modeled as Euler–Bernoulli beams with longitudinal displacements and the diffracted field by each pile is constructed only with Rayleigh waves. Six infinite linear systems of algebraic equations are obtained in terms of the equilibrium of forces and continuity of displacements at the pile–soil interfaces. The systems are subsequently solved in the complex least‐squares sense. The influence of certain pile and soil characteristics such as the permeability of poroelastic soil, spacing between the piles and length of the piles on the isolating performance of a pile barrier is investigated. Computed results show that the permeability of poroelastic soil displays a significant effect on the vertical amplitude reduction of Rayleigh waves. Copyright © 2009 John Wiley & Sons, Ltd.     

Accretion and early degassing of the Earth: Constraints from Pu-U-I-Xe Isotopic systematics

Abstract— A review of problems related to Xe isotopic abundances in meteorites and terrestrial materials leads to four postulates which should be taken into account to build a model of the Earth's accretion and early evolution. 1. The pre-planetary accretion time scale was shorter than the ¹²⁹I half-life, 17 Ma, so the initial ratio of ¹²⁹I/¹²⁷I had not been decreased considerably when planetary accretion started; therefore, this must also be the case for the ²⁴⁴Pu abundance. 2. The initial relative abundance of involatile refractory ²⁴⁴Pu in proto-planetary materials should be the same as in chondrites, that is, ²⁴⁴Pu/²³⁸U = 0.0068; this value corresponds to initial ²⁴⁴Pu 0.30 ppb in the bulk silicate earth. In contrast, I is a highly volatile element; its initial abundance, accretion history and even the present-day mean concentrations in principal terrestrial reservoirs are poorly known. 3. There is much less fission Xe in the upper mantle, crust, and atmosphere than is predictable from the fission of ²⁴⁴Pu (Xe(Pu)) based on the above argument. Therefore, Xe(Pu) has been mainly released from these reservoirs. 4. A mechanism for Xe(Pu) escape from the complementary upper mantle-crust-atmosphere reservoirs, for example, atmospheric escape via collisions of a growing Earth with large embryos and/or hydrodynamic hydrogen flux, etc., operated during the Earth's accretion. These postulates have been used as a background for a balance model of homogeneous Earth accretion which envisages: growth of the Earth due to accumulation of planetesimals; fractionation inside the Earth and segregation of the core; degassing via collision and fractionation; and escape of volatiles from the atmosphere. During the post-accretion terrestrial history, the processes described by the model are continuous fractionation, degassing and recycling of the upper mantle and crust. The lower mantle is considered as an isolated reservoir. Depending on the scenario invoked, the accretion time scale varies within the limits of 50–200 Ma. In the light of recent experimental data, the latter value is inferred to the most realistic version which explains a high Xe(U)/Xe(Pu) ratio in the upper mantle. Contrary to previous suggestions, the ¹²⁹I-¹²⁹Xe subsystem is considered to be meaningless with regard to the terrestrial accretion time scale. The terrestrial inventory of ¹²⁹Xe(I) is controlled by the initial abundance of volatile elements (including I and Xe) in proto-terrestrial materials and the subsequent degassing history of the Earth. The residence time of a volatile element (e.g., Xe) in the bulk mantle (bm) during accretion, < t (Xe)_bm>, is approximated by the ratio of < t (Xe)_bm> m _bm(t)/φ_{bm, mf} ≤ 10 Ma, where m _bm(t) is the mantle mass, and φ_{bm, mf} is the rate of metal/silicate fractionation, which provided segregation of the core; φ_{bm, mf} is determined by involatile siderophile element abundances in the upper mantle. This relationship implies a link between the abundance of involatile siderophile and volatile incompatible elements. A short <t(Xe)_bm> reflects a high degassing rate due to extremely high φ_{bm, mf} 10²⁰ g/year. A small ratio of the atmospheric amount of Xe over the total amount of this gas in prototerrestrial materials, ≤0.01, is in accord with the process of Xe escape and fractionation in the primary Earth atmosphere.     

3种贝类糖胺聚糖的粗提及含量比较

以企鹅珍珠贝、菲律宾蛤仔和锯齿巴非蛤全脏器为原料,经酶解、离心去蛋白、醇沉、分离、洗涤、干燥,得糖胺聚糖(GAG)粗制品,分别测定并比较3种贝类的GAG的含量和得率。结果表明,企鹅珍珠贝的GAG质量分数为22.35%,菲律宾蛤仔为18.69%,锯齿巴非蛤为20.36%,由此得出企鹅珍珠贝的GAG的含量比其他两种贝类高,是较好的GAG来源。     

Lithium depletion in the brown dwarf binary GJ 569Bab

GJ 569Bab is the first brown dwarf binary for which the mass of each component has been derived by solving the astrometric and spectroscopic orbit of the pair, i.e., independently of any theoretical assumption. This allows us to test the predictions of the various evolutionary models available in the literature. Particularly interesting are the predictions of lithium depletion for the mass (0.08–0.05M_⊙) and likely age (300–800 Myr) of the substellar components. High‐resolution optical spectra of GJ 569B (the pair is not resolved) obtained with HIRES at the Keck telescope show that there has been significant lithium depletion in both components. We will compare these results to state‐of‐the‐art theoretical calculations. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Cosmic Ray Acceleration Inside Molecular Clouds

Acceleration of charged particles by neutral gas turbulence in giant molecular clouds is considered. The gamma-ray emission from these clouds is estimated. It is shown that molecular clouds can be the counterparts of some of unidentified sources.     

Estimating the dark halo mass from the relative thickness of stellar disks

We analyze the relationship between the mass of a spherical component and the minimum possible thickness of stable stellar disks. This relationship for real galaxies allows the lower limit on the dark halo mass to be estimated (the thinner the stable stellar disk is, the more massive the dark halo must be). In our analysis, we use both theoretical relations and numerical N-body simulations of the dynamical evolution of thin disks in the presence of spherical components with different density profiles and different masses. We conclude that the theoretical relationship between the thickness of disk galaxies and the mass of their spherical components is a lower envelope for the model data points. We recommend using this theoretical relationship to estimate the lower limit for the dark halo mass in galaxies. The estimate obtained turns out to be weak. Even for the thinnest galaxies, the dark halo mass within four exponential disk scale lengths must be more than one stellar disk mass.     

Numerical simulations of the Hyades dynamics and the nature of the moving Hyades cluster

We present our numerical simulations of the dynamical evolution of the Hyades open cluster. The simulations were performed usinga modified NBODY6 algorithm that included tidal forces and a realistic orbit of the cluster in a gravitational field described by the Miyamoto-Nagai potential. Our goal was to study the nature of movingclu sters. We show that the stars that were earlier cluster members could be later identified within a sphere of 50 pc in diameter around the Sun. The number of such stars for the chosen initial mass and virial radius of the cluster does not exceed ten. The maximum space velocity of these stars relative to the core of the current cluster does not exceed 3 km s^?1. Our numerical simulations confirm the assumption that some of the moving clusters near the Sun could consist of stars that have escaped from open clusters in the course of their dynamical evolution.