Tolman's formula in scalar-tensor theories of gravitation

Erevan State University; Institute of Applied Problems of Physics, Armenian Academy of Sciences. Translated from Astrofizika, Vol. 34, No. 2, pp. 265–270, March–April, 1991.     

Fast imaging and inversion of on and off shore electromagnetic data

We consider thin layer algorithms for inversion of electromagnetic data acquired on large experimental grids. These algorithms do not involve targeted search of the model parameters. Instead, they determine an integrated characteristic of the model, i.e. heterogeneous conductance or transverse resistance, using a filtration technique developed for thin layer models, which adequately represent the geo-electric situation by a sequence of laterally homogeneous and heterogeneous layers. The corresponding filter reflects impedance/admittance relations between different components of the electromagnetic field in the stratified part of the model. Convolution of such filters with the data obtained from experimental measurements represents the most time consuming part of the computation. The convolution is carried out using a high performance algorithm, which makes the process of inversion extremely fast. The choice of a particular inversion algorithm is dictated by the specific geo-electric situation in the area of interest and the electromagnetic data subject to interpretation. Typically, most computations can be carried out in up to several minutes using a regular desktop or laptop PC.We restrict our consideration to two simplest algorithms for determination of the conductance of heterogeneous conductive layers (S-algorithm) and the transverse resistance of heterogeneous resistive layer (T-algorithm). The algorithms can be useful for interpretation of data acquired in on- and off-shore conditions with natural and controlled sources. Inversion can be jointly carried out for data sets collected for different source locations, at different frequencies, etc. Likewise, the algorithms can be used for interpreting the data collected using a moving source.Performance of the algorithms is demonstrated on a set of test inversions of numerically simulated data sets. The first group of the examples is typical for environmental applications. It is studied using the S-algorithm applied to natural and controlled source measurements for shallow and deep targets. The T-algorithm is applied for delineation of a gas hydrate type of reservoir using the data numerically simulated for such a problem.In geo-electrical situations that can be addressed using thin layer models, results of inversion hardly require any further elaboration. For instance, this happens when parameters of the heterogeneous layer satisfy thin layer conditions and its thickness can be determined from seismic measurements. When this is not the case, the model found by a thin layer inversion usually reveals correct location of the anomalous body and provides reasonable estimate of its integrated electric properties. In such situations the algorithm works as an imaging technique, which together with seismic information on the layer boundaries provides a justified initial model for a full scale 3D inversion and hopefully allows for avoiding pitfalls associated with a straightforward application of more traditional 3D inversion algorithms.     

Dynamics of occurrence frequency of extreme anomalies of monthly mean air temperature in Georgia in the 20th century and its effect on precipitation and on the river water discharge

The dynamics of the occurrence frequency of extreme anomalies of monthly mean air temperature and its effect on precipitation and river water discharge in the 20th century are studied using weather observations at 40 stations and data on the hydrological regime of 34 rivers in Georgia.     

Effect of field-aligned currents in the polar cap at the recovery phase of a magnetic storm

Unusually great fluctuations in the ΔB module of the geomagnetic field have been observed in the polar cap from the satellite Cosmos-321. They are explained by small-scale two-sheet field-aligned current systems which exist during the periods when magnetic fields having a considerable northward B_z(B_z 10 nT) component are observed in interplanetary space.     

Moment of inertia of a neutron star. II. Relativistic corrections

In part I we suggested an approximate equation to determine the contribution of relativistic effects to the moment of inertia of a superdense star. In the present paper it is tested on model neutron stars with nine different variants of the equation of state of superdense matter. It is established that the approximation error does not exceed 5% for stable configurations. A more accurate version of the Ravenhall—Pethick equation [D. G. Ravenhall and C. J. Pethick, Astrophys. J., 424, 846 (1994)] for the moment of inertia as a function of the mass and radius of a neutron star is derived. Translated from Astrofizika, Vol. 40, No. 4, pp. 507–516, October–December, 1997.     

Photometric and spectroscopic study of silicon Ap-star HD193722

The period of light variationP=1 _. ^d 13316 has been found for the silicon B9 IVp star HD 193722. Spectroscopic study of this star was based on 35 spectrograms with dispersion 4 Å mm^–1 well distributed in phase. The measurements of radial velocities of spectral line components for SiII, HeI, EuII, FeII and SrII allowed us to localize several regions on the surface of the star with enhanced abundance of these elements. The phase of maximum light inU, B andV was found to be the same as the phase of maximum Eu abundance. The coincidence of the regions with larger abundance of Si and He in HD 193 722 disagree with the hypothesis of diffusion in the presence of a magnetic field developed by Michaud (1971), to explain the peculiar chemical composition of Ap-stars.HD 193722 is a silicon B9 IVp star for which the magnetic field has not been measured. In the list by Palmeret al. (1962) its rotational velocityV sini is given as 250 kms^–1. As will be seen below, this value is too high. Megessier (1971) determined from hydrogen line profiles and continuous spectrumT _eff=13 000° and lgg=3.5.The results of photometric and spectroscopic study of HD193722 are given below.     

贵州铝土矿含矿岩系中锂的分布特征及富集机理

锂是我国关键矿产和高新产业发展的战略性资源之一。贵州铝土矿资源丰富,含铝岩系分布广,勘查发现铝土矿(岩)中伴生大量的锂资源。研究认为,全省含铝岩系中Li含量高,变化范围大(0.55×10^-6～2725.03×10^-6),平面上Li含量总体呈北东(务正道成矿区)、南西(修文-清镇成矿区)高,中间(播州-瓮安成矿区)低的分布态势;剖面上Li主要富集在矿系上部的致密状铝土岩(矿)中,Li含量一般>500×10^-6,矿系中土状铝土矿(岩)Li含量一般<30×10^-6;气候温湿、风化及淋滤作用强的陆相湖泊沉积环境,有利于高岭石为主的黏土矿物形成及Li⁺与Al³⁺、Mg²⁺、Fe³⁺、Fe²⁺发生类质同象,或被吸附进入黏土矿物层间构造同迁移同富集,Li与Al₂O₃含量呈正相关关系;成岩成矿后的次生改造阶段,古地磁测量及CIA显示为炎热潮湿的氧化环境...