Point-block covariance: A general solution for the two-dimensional stationary random functions

The application of the theory of random functions to problems of ore evaluation may involve computations of the covariance between the mean value of a given block and the functional value at a given point. However, an analytical solution for such a covariance does not exist for nonspherical blocks and for commonly applied models of covariance functions. Further, because this covariance is a function of the spatial arrangements of the block and the point, it has to be evaluated numerically each time for given point—block arrangements. This paper presents a readily available general solution to this problem in the form of a series of graduated curves which, together with some geometric manipulations, may be used to compute the covariance between a pointand a two-dimensional block for all possible point—block arrangements. The availability of the graph thus eliminates the necessity of using the time-absorbing programs on computers for such computations. Finally, many of the approximations that are made in order to avoid cumbersome covariance evaluations are no longer necessary due to the ease of such computations with the help of the graph provided.     

Interaction of hot plasma with radiation of magnetic white dwarfs

The influence of radiation on the electron velocity distribution in a hot nonrelativistic plasma localized near the surface of magnetic white dwarfs is investigated. The part played by the plasma in the formation of cyclotron features in the optical spectrum of these stars is studied. The region of parameters where the transverse temperature of plasma is defined by the brightness temperature of extraordinary radiation at the gyrofrequency is found. When escaping from the plasma in a homogeneous magnetic field, this component forms a cyclotron line in absorption. The ordinary radiation at the gyrofrequency and both modes at higher cyclotron harmonics are in emission or absorption depending on the magnetic field strength and hot plasma density. Possible interpretation of the observed spectral features of magnetic white dwarfs in terms of the developed theory is discussed.     

Evolution and observational signature of diffused antiworld

The existence of macroscopic regions with antibaryon excess in the baryon asymmetric Universe with general baryon excess is the possible consequence of practically all models of baryosynthesis. Diffusion of matter and antimatter to the border of antimatter domains defines the minimal scale of the antimatter domains surviving to the present time. A model of diffused antiworld is considered, in which the density within the surviving antimatter domains is too low to form gravitationally bound objects. The possibility to test this model by measurements of cosmic gamma ray fluxes is discussed. The expected gamma ray flux is found to be acceptable for modern cosmic gamma ray detectors and for those planned for the near future.     

Modeling of type III bursts dynamic spectra

The one-dimensional process of spatially limited electron stream propagation in the solar corona is simulated. It is shown that the beam instability development results either in strong relaxation in velocity space and inhibition of spatial diffusion (high-stream density) or in velocity space relaxation decrease and simultaneous growth of spatial stream length (low-stream density). Assuming a profile of background plasma density to be exponential, dynamic spectra of type III bursts are modeled, which shows that the emission source velocity is constant, and a duration of the burst emission at a given frequency reduces for high-stream densities.     

Facies Structure and Quantitative Parameters of Pleistocene Sediments of the Bering Sea

Lithofacies zoning is described for the first time for the Neo- and Eopleistocene of the Bering Sea. Four lithofacies sedimentation zones are distinguished: (I) terrigenous; (II) siliceous–terrigenous; (III) siliceous, and (IV) volcanoterrigenous ones. Corresponding maps were treated using Ronov volumetric method to quantify sedimentation parameters for distinguished lithofacies zones (subzones) and types of Pleistocene sediments. It was revealed that terrigenous sediments predominate over other sediments. Accumulation of the terrigenous sediments was more intense (by 1.4 times) in the Neopleistocene than in the Eopleistocene. The sedimentation rate of siliceous sediments of the Bowers Ridge in the Eopleistocene was two times higher than in the Neopleistocene.     

The Dergaon (H5) chondrite: Fall,classification, petrological and chemical characteristics,cosmogenic effects,and noble gas records

Abstract— A multiple fall of a stony meteorite occurred near the town of Dergaon in Assam, India, on March 2, 2001. Several fragments weighing <2 kg and a single large fragment weighing ～10 kg were recovered from the strewn field, which extended over several tens of square kilometers. Chemical, petrographic, and oxygen isotopic studies indicate it to be, in most aspects, a typical H5 chondrite, except the unusually low K content of ～340 ppm. A cosmic ray exposure of 9.7 Ma is inferred from the cosmogenic noble gas records. Activities of eleven cosmogenic radionuclides were measured. ²⁶Al and ²²Na activities as well as the ²²Na/²⁶Al activity ratio are close to the values expected on the basis of solar modulation of galactic cosmic rays. The low ⁶⁰Co activity (<1 dpm/kg) is indicative of a small preatmospheric size of the meteorite. Cosmic ray heavy nuclei track densities in olivine grains range from ～106 cm^?2 in samples from the largest fragment to approximately (4–9) × 105 cm^?2 in one of the smaller fragments. The combined track, radionuclide, and noble gas data suggest a preatmospheric radius of ～20 cm for the Dergaon meteorite.     

On the instability of weakly radially anisotropic star clusters

We discuss contradictions existing in the literature in the problem on the stability of collisionless spherical stellar systems, which are the simplest anisotropic generalization of the well-known polytropic models. On the one hand, calculations of the growth rates within the framework of a linear stability theory and N-body simulations suggest that these systems should become stable when the parameter s characterizing the degree of anisotropy of the stellar velocity distribution becomes lower than some critical value s _crit > 0. On the other hand, according to Palmer and Papaloizou, the growth rate should be nonzero up to the isotropic limit s = 0. Using our method of determining the eigenmodes of stellar systems, we show that even though the mode growth rates in weakly radially anisotropic systems of this type are nonzero, they are exponentially small, i.e., decrease as γ ∝ exp(−a/s) when s → 0. For slightly radially anisotropic systems with a finite lifetime, this actually implies stability.     

Dynamical and collisional evolution of Halley-type comets

The number of observed Halley-type comets is hundreds of times less than predicted by models (Levison, H.F., Dones, L., Duncan, M.J. [2001]. Astron. J. 121, 2253–2267). In this paper we investigate the impact of collisions with planetesimals on the evolution of Halley-type comets. First we compute the dynamical evolution of a sub-set of 21 comets using the Mercury integrator package over 100 Myr. The dynamical lifetime is determined to be of the order of 10⁵–10⁶ years in agreement with previous work. The collisional probability of Halley-type comets colliding with known asteroids, a simulated population of Kuiper-belt objects, and planets, is calculated using a modified, Öpik-based collision code. Our results show that the catastrophic disruption of the cometary nucleus has a very low probability of occurring, and disruption through cumulative minor impacts is concluded to be negligible. The dust mantle formed from ejected material falling back to the comet’s surface is calculated to be less than a few centimeters thick, which is insignificant compared to the mantle formed by volatile depletion, while planetary encounters were found to be a negligible disruption mechanism.     

中国汽车工业──改革开放后的重整与国际化

大规模的重整和广泛的国际化是改革开放后中国汽车工业发展的两个主要特征。作者首先从企业组织结构、生产能力与品种结构、规模经济和空间分布等四个方面分析了近二十年来中国汽车工业重整的效果及所形成的行业特征;其次根据利用的外资和技术的来源以及涉及的技术形态分析了其国际化的程度及在世界汽车工业中的位置;最后总结了中国汽车工业面临的若干问题,并提出在散乱的格局和跨国公司竞争的双重压力下,中国汽车工业正处于成长的关键时期。     

Novae in M31 in 1999–2005

We present the results of our study of 19 novae in the galaxy M31 on photographs taken with wide-field telescopes in 1999–2005. Two of the six novae discovered in our program (ShA 65 and ShA 67) have been identified with supersoft X-ray sources, the discovery of one nova (ShA 69) was reported in IAU Circulars, and the other three novae (ShA 66, ShA 68, and ShA 70) are reported for the first time.