bluuebunny/crossref_metadata_2025_split huggingface dataset:
A numerical study on turbulent heat transfer in convective envelopes
Authors: Arlt K. , Rüdiger G. 
Published: July 2007

AbstractVia a two‐dimensional temperature equation we numerically attack the well‐known solar heat flux problem. A spherically symmetric heat flux may enter the convection zone at its bottom and leave in accord to the Stefan‐Boltzmann law. Meridional circulation is involved, radiation is still ignored. In order to establish the eddy conductivity tensor for the simplest rotating turbulences a second‐order correlation approximation is used.The resulting pole‐equator differences vary for various profiles of eddy conductivity and turnover time. They prove to be small only for small stratification or strong outward decrease of turnover time. The fact that we do not observe any latitudinally profiled mean temperature might thus have to do with the real outward drop of the rotational influence on convection.
Long periodic variations of magnetic stars caused by precession
Authors: Gerth E. 
Published: July 2007

AbstractLong‐time observations give evidence of secular variations of the effective magnetic fields for some Ap stars. These secular variations may be interpreted by a precessional motion of the star. The precession of the rotationally flattened star is assumed to be caused either by the orbital motion of a satellite where the plane of the orbit is inclined to the axis of rotation of the star or by rotation of the inner and outer layers of the star around differently inclined axes.
Magnetohydrodynamical model of pulsar rotation. Exact periodic solutions
Authors: Bogoyavlensky O. I. 
Published: July 2007

AbstractA rotaing rigid body with elipsoidal cavity filled with magnetic fluid is considered as a pulsar model. Dynamical equations for the pulsar model are derived and investigated, certain integrable cases are indicated. Three–parameter sets of periodic solution integrable in terms of elliptic functions of the time variable are obtained. A formula is derived for the period of rotation and magneto–rotational oscillations of the pulsar.
Photometrically determined mean surface magnetic fields of Ap stars
Authors: Oetken L. 
Published: July 2007

AbstractThe photometrically determined mean surface magnetic fields BS need a revision. None of the stars for which BS can be measured directly by Zeeman line splitting fulfils the relation between the photometric parameter Δ(V1 – G) and the mean surface field BS, which is used by NORTH, CRAMER and MAEDER to determine BS for other B2 – A3 stars. The ratio BeffMax/BS for stars, which define North's relation, shows unreasonable large values.
Photometric reductions and the lightcurve of (51) Nemausa
Authors: Kristensen L. K. , Gammelgaard P. 
Published: July 2007

AbstractThe lightcurve of (51) Nemausa is determined by 1779 photoelectric observations in B and V and reduction by a rigorous least‐squares method is discussed. For the lost (1026) Ingrid is obtained B(1,0) = 14m.7.
A possible cause of the noncircular pattern of the linear polarization in some (bipolar) reflection nebulae
Authors: Notni P. 
Published: July 2007

AbstractThe scattering of linearly polarized light in reflection nebulae is investigated. The distortion of the centrosymmetric pattern of the polarization vectors is calculated; it is found the linear polarization of the illuminating source in an optically thin nebula leads to an “elliptical” pattern. If foreward scattering angles are strongly favoured, for instance if the nebula is optically moderately thick and light from higher scattering angles is suppressed by extinction, arrays of nearly parallel polarizations may arise. In addition, circular polarisation will always occure. – Both pattern types have been observed in bipolar nebulae. We consider it probable that the investigated mechanism is, at least in part, responsible for these patterns. Detailed modelling of concrete cases is required to finally test whether the proposed mechanism is at work.
General Lagrangian approach to the equations of motion for test particles with internal structure
Authors: Fuchs H. 
Published: July 2007

AbstractThe equations of motion for test particles with internal structure are derived from a general Lagrange principle. The internal structure of the particles is described by sets of unspecified geometric objects, which transform homogeneously both under coordinate and under gauge transformations. Most of the Lagrangian approaches known in the literature are special cases of our general formalism.
On the statistical significance of possible variations in the solar neutrino flux
Authors: Subramanian A. , Lal Siddheshwar 
Published: July 2007

AbstractA statistical study has been made on the flux of the solar neutrinos as recorded in the experiment of DAVIS et al. to see if there is any evidence for its variation with time. It is found that there are certain correlations and fluctuations in the data which when grouped indicate a pattern of temporal variation. The probability that this pattern of variation would have been caused purely by chance is estimated to be ˜ 10−4.
Beobachtungen Kleiner Planeten. VI.
Authors: Börngen F. 
Published: July 2007

AbstractEs wird eine Übersicht über die im Jahr 1985 auf Tautenburger Schmidtplatten gefundenen kleinen Planeten gegeben. Es wurden 95 Objekte entdeckt und für sie 168 Positionen gerechnet. Es handelt sich um 20 numerierte Objekte und 75 Planetoiden mit provisorischer Bezeichnung, von denen zwei keine neue Bezeichnung haben. Für zwölf im Berichtszeitraum numerierte Planeten haben Tautenburger Beobachtungen einen Beitrag geleistet. Zwei in Tautenburg entdeckte Planetoiden wurden mit Nummer und Namen versehen: (3245) Jensch = 1973 UL5 und (3338) Richter = 1973 UX5.
Distance law and formation of satellite systems
Authors: Zhong‐Wei Hu , Zhi‐Xiong Chen 
Published: July 2007

AbstractIn the solar system satellite systems of Jupiter, Saturn and Uranus are typical ones. The distribution of the semi‐major axis of satellite orbits in each system may be expressed by an empirical formula corresponding to the Titius‐Bode law. We found that it can be written as an=B′ ·Bn, whereB′ andBare constants. Values ofB′ andBdepend on formation conditions of each system.Satellites should be formed in the gas‐satellitesimal disk around a planet and by aggregation of satellitesimals. The gas is the major component in the disk and its damping effect must play an important role in the process of aggregation of satellitesimals. It may be proved that radial small perturbation in the disk can cause the gravitational instability and the formation of gaseous rings with increased density, where satellitesimals can easy aggregat into satellites.
Search for nonpotential features in the magnetic field of the solar active region SD 135 on 1984 June 4
Authors: Linke J. , Peregud N. L. , Selivanov V. L. 
Published: July 2007

AbstractWe investigated the structure of the magnetic field in the relatively small and simple solar active region SD 135/1984 in the early, relatively quiet phase on June 24. For this work we used data of the vector magnetograph of SibIZMIR and results of model calculations using a current‐free approximation.We have compared the measured magnetic field with the transverse field of the model calculation. We could not find a significant nonpotential effect greater than the level of sensitivity of the transverse magnetic field, BT 200 G. Hence, we conclude that the global magnetic field structure in the investigated solar active region had a nearly potential configuration. The effects of evolution in the active region on the magnetic field structure remained negligible.
Pyroxene glasses — candidates for the interstellar silicate dust component
Authors: Dorschner J. , Gürtler J. , Henning T. H. , Wagner H. 
Published: July 2007

AbstractExperimental work carried out by Jena University Observatory in collaboration with chemical institutions has shown that pyroxene glasses are very promising candidates for identifying silicate grains in the surroundings of very young objects in molecular clouds, e.g. BN objects and T Tauri stars. The experiments are of importance for gaining optical data that are needed for establishing source models and for understanding the mineralogical status of the grain material. In this paper, steps gone toward both goals in recent work of the Jena dust group are reported.
Mini‐inflation prior to the cosmic confinement transition?
Authors: Boyko V. G. , Jenkovszky L. L. , Kämpfer B. , Sysoev V. M. 
Published: July 2007

AbstractThe onset of the confinement transition in the early universe is studied within the Friedmann model. Exploiting a bag model equation of state for the deconfined matter, which is generalized to include also metastable states, the possibility of a mini‐inflationary epoch is demonstrated. A criterion of metastability is derived to estimate parameters of this mini‐inflation.
The outer core rotation about an inclined axis from geomagnetic secular variations (Mitteilungen des Zentralinstituts für Physik der Erde, Nr. 1832)
Authors: Greiner‐Mai H. 
Published: July 2007

AbstractNon‐axisymmetric motions of the outer core of the Earth are important for the dynamo problem and the excitation of the decade variations of the polar motion. The components of the vector of a rigid rotation of the outer core about an inclined axis were estimated by a first‐order approximation of the frozen‐ field theory of the geomagnetic secular variation from 1903.5 to 1975.5. The trends and quasi‐periodic constituents of these quantities were computed. It was shown that the position and time behaviour of the rotational pole of the outer core differ considerably from the well‐know co‐ordinates of the dipole axis. Some periods of the equatorial components of the rotational vector are comparable with those of the axial component previously derived for a pure axial rotation. Additionally, the time behaviour of the pole path shows events like the well‐known Markowitz wobble but naturally with other extent. These and other results suggested that the investigations are worth to be continued in future by some physical interpretations.
Treatment of a static spherically symmetric matter distribution on the basis of the projective unified field theory
Authors: Avakian R. M. , Chubarian E. V. , Sarkissian A. V. , Schmutzer E. 
Published: July 2007

AbstractIn order to confront the Projective Unified Field Theory with physical experience it is appropriate to apply this theory also to astrophysical objects, for mathematical reasons in particular to a static spherically symmetric matter distribution as a rough model for a star (e.g. neutron star or another exotic compact object). The problem mentioned is treated here as far as possible analytically in order to prepare the basis for the numerical approach.
Some results of cooperative investigations on solar radio emission with RATAN–600
Authors: Krüger A. , Bogod V. M. , Korzhavin A. N. , Gelfreikh G. B. 
Published: July 2007

AbstractResults of cooperative work between the GAO/SAO and ZIAP obtained during eight years in the field of solar radio astronomy are reviewed. Main topics of investigation concern the S–component, coronal millimetre–wave sources, and different kinds of microwave bursts.
Astrometry of the comet Wilson (1986 I)
Authors: Scardia M. , Cremonese G. 
Published: July 2007

AbstractSixteen astrometric positions of comet Wilson (1986 1) (in the pre‐perihelion phase) obtained during 1986 are presented here. These positions and all the M.P.C. observations have been used to determine a set of orbital elements.
Mutual sensitivity of halo and disk parameters in a two‐component model
Authors: Brosche P. , Caimmi R. , Secco L. 
Published: July 2007

AbstractThe mutual interaction between galactic dark halos and visible matter are explored by modelling a galaxy as two homogeneous, concentric and coaxial spheroidal subsystems, one completely lying within the other. The tensor virial theorem in its extended appropriate form is used and a general method outlined, then an application to the Galaxy is done. The values of equatorial semiaxis and axis ratio of the bright subsystem, and of the velocity components of both subsystems, deduced from a number of known observational data, are used in the computations as input parameters. Discussing the results, special effort has been devoted to the mutual sensitivity of halo and disk parameters which we understand in a twofold manner: 1) numerical interdependence between the present parameters of the visible Galaxy and the ones of dark matter, and 2) dependence of the bright component evolution on the characteristics of the dark halo, in which the former was embedded since the beginning. At present, due to the smallness of dark matter inside the bright disk, the halo‐disk interaction is so weak that few informations can be obtained; consequently, the solutions for dark masses and their axis ratios vary in a large range. Nevertheless, if one demands a spherical and isotropic halo, then from ad = 90 kpc a dark mass Md = 1.5 · 1012 M⊙ results in agreement with other independent estimations. Probably this was not the situation in the past when the disk was bigger and contained more dark mass. The dependence on Md/Mb and εd/εb was likely affecting the star formation rate and in this way contributing to the present morphology of the Galaxy and other galaxies.
Surface photometry of the dwarf galaxy VIIZw009
Authors: Richter G.M. , Schmidt K.‐H. , Thänert W. , Stavrev K. , Panov K. 
Published: July 2007

AbstractPhotographic photometry reveals the dwarf galaxy VIIZw009 as an outstanding object with respect to the large colour excess of its central star burst region. It seems to be a similarity to the system IC 10, which also contains at least one star burst region with large internal extinction. The results are supported by the identification of the IRAS source 3550+6657 with VIIZw009.
Perspectives of advance of RATAN‐600 solar observations
Authors: Gogod V. M. 
Published: July 2007

AbstractThe potential possibilities of RATAN‐600 for solar studies are considered which are going on to be realized during the present maximum of solar activity. Different methods of an improvement of the characteristics of the antenna‐receiver system are analyzed. These are:– realization of tracking the Sun during about 4 hours for a day and attaining temporal resolution up to some msec, – realization of radio‐heliographic observations,– realization of a full spectral coverage of the radio telescope from 1,5 to 18 GHz with a frequency reslution up to 1–2 MHz, – combination of all possibilities mentioned above in an adaptable solar observing complex.
New and old arguments to the Eddington‐Lemaǐtre model of the universe
Authors: Liebscher D.‐E. , Treder H.‐J. 
Published: July 2007

AbstractThe interpretation of the Lyman‐α forests of quasars as suggested by Hoell and Priester (1991) supports a Friedmann‐Lemaǐtre model for the universe. The components of the Hubble expansion rate are found by a linear regression of the square of the line‐spacing parameter as a polynomial in the redshift 1 + z with a vanishing linear term. In this essay, we try to restrict the model to the special Eddington‐Lemaǐtre model, which develops the deSitter expansion from the Einstein universe. We show the regression results under this restriction and discuss some of its consequences.
Expanding, homogeneous, ellipsoidal density perturbations. I. The effect of the initial shape at some special stages of evolution
Authors: Caimmi R. 
Published: July 2007

AbstractThis paper investigates the effect of the initial shape of expanding, homogeneous, ellipsoidal density perturbations, at some special stages of evolution, namely at the occurrence of: (i) turn‐around along the axes, (ii) maximum volume, (iii) strong decoupling from the Hubble flow, assumed to take place at overdensities equal to unity. To this aim, previous theory is reviewed and extended involving – among others – a deep analysis on the gravitational force induced on the unit mass at the top axes of the ellipsoid, an explicit expression of the overdensity, and a detailed investigation on the limiting cases of flat (two‐dimensional) and oblong (one‐dimensional) configurations. Then some physical parameters related to the above mentioned stages of evolution are computed for a wide range of initial shapes, in connection with an Einstein‐de Sitter universe and an initial overdensity, which is typical for inhomogeneities with galactic masses in a classical CDM scenario. If the gain of spin by tidal torques grows in proportion to time until either the stage of evolution (i) or (ii), or (iii) is attained, it is found a difference in angular momentum related to the initial shape, which never exeeds a factor of about 3.6, 2.0, 1.4, respectively.
Expanding, homogeneous, ellipsoidal density perturbations. II. A simple theory for the acquisition of angular momentum by tidal torques
Authors: Caimmi R. 
Published: July 2007

AbstractA simple theory is built up for the acquisition of angular momentum by tidal torques in expanding, homogeneous, ellipsoidal density perturbations from the epoch when inhomogencities begin to grow to the present epoch. The expansion is described according to an analytical approximation already known in the literature, which well holds before the turnaround of a sphere with same mass and initial overdensity as the ellipsoid, and holds no longer after a singular configuration (i.e., with a null volume) is attained by the above mentioned sphere. Though calculations at latest stages turn out to be physically meaningless, it is inferred that the spin growth during the virialized phase is negligible with respect to the spin growth during the expansion and relaxation phase. The evolution of typical inhomogeneities with initial axis ratios ϵ2i = 0.7, ϵ3i = 0.5 and masses MB = 1012 MȮ is computed, leading to: (i) a spin parameter λ = 0.054 at the beginning of strong decoupling from the Hubble flow, in cloes agreement with both analytical and numerical attempts related to different theories; (ii) an angular momentum J = 1.62 – 3.17 · 1075 g cm2 s−1 at the turnaround of a sphere with same mass and initial overdensity as the ellipsoid, within the correct order of magnitude deduced for the Galaxy; (iii) an angular momentum J ≈ 3 JD and J ≈ 2JD at the singular configuration and at the turnaround of the above mentioned sphere, respectively, with JD angular momentum gained before the strong decoupling from the Hubble flow. The features (i) and (iii) are common to all masses. The evolution of inhomogeneities with rms overdensities, same initial volume and typical galactic mass MB = 1012 MȮ is computed for a wide range of initial shapes, leading to an non‐dimensional angular momentum Λ with the following behaviour: (i) it is null for both spherical and flat or oblong configuration; (ii) it increases passing from prolate to oblate configurations with same minor axis; (iii) it changes passing from flat to prolate configurations with same middle axis, increasing or increasing and then decreasing according if prolate configurations are spindle‐like enough or ball‐like enough, repectively; (iv) the larger non‐dimensional spin growth occurs for oblate configurations with e3i ≈ 0.6. The above features are common to all masses and peak heights. In conclusion it cannot be asserted, but it may safely be expected, that (contrary to what happens in many other theories) no arbitrary cut‐off on tidal torques has to be advocated in the current theory, to yield an amount of angular momentum close to what has been deduced from observation. A complete answer on this point might come only from a more refined description of the expansion.
Nearby galaxies. III. Gas–to–dust ratio in the interstellar medium of spiral and dwarf irregular galaxies
Authors: Schmidt K. H. , Boller T. 
Published: July 2007

AbstractThe gas‐to‐dust ratio in the interstellar medium of nearby spiral systems and dwarf irregular galaxies has been obtained by using mainly the compiled data by Schmidt and Boller (1992a). The gas‐to‐dust ratio of dwarf irregulars is larger by about one order of magnitude than for spiral galaxies, on the average. A relation between the gas‐to‐dust ratio and the metallicity, represented by the abundance of oxygen, has been detected.
Tidal effects of a massive spheroidal halo on an inner spheroidal contracting visible body: Application to an evolutionary disk‐galaxy model
Authors: Caimmi R. , Secco L. 
Published: July 2007

AbstractThe effects of the tidal interactions between two coaxial, homogeneous spheroids, one (the “Brigt Component”: B) completely embedded in the other (the “Dark Halo”: D), along a quasi‐static contraction, are considered. The aim is to look how the dynamical properties and the final morphology of the B subsystem may be affected by the presence of the D component. Three initial configurations are considered: the quasi‐spherical “Dark Halo” D coincides with the “Visible Component” B (case C); D is flatter than B but the two spheroids have the same semiminor axis (case N); no D component is assumed; the “visible” spheroid is single (case S). The application to an evolutionary disk‐galaxy model is considered under some simple assumptions: i) in cases C and N the spheroidal halo is massive (mass ratio “dark”/“bright” about ten) and dissipationless. For a mass ratio like this, the tidal interaction of the B component over D turns to be negligible in the course of the contraction; adding to that the lack of dissipation, it appears plausible to take the D component as frozen along the evolution; ii) the degree of anisotropy and the angular momentum of B, JB, are conserved. The conservation of JB provides us the time‐independent relationship among the key physical quantities and gives the possibility to draw the evolutionary tracks on the plane (axis ratio σB, semimajor axis aB) without any explicit time‐scale; iii) the global “star formation rate” is parametrized according to a simple “Schmidt power law” proportional to the square of gas density. At every step of the quasi‐static contraction, the structure is determined by the tensor virial theorem extended to a double configuration. The model is very idealized, particularly because there are no available tidal gravitational terms other than for the case of two homogeneous. Nevertheless, the method based on the tensor virial appears powerful to gain insight into the correlations among the physical quantities involved and into their trend along the evolution. One of the main result is a clear indication of a leading role played by the axis ratio of the “Dark‐Halo” component which might be, to the extent that this simple picture can be compared with a real galactic system, a possible new physical parameter to be added to mass and angular momentum for separating spirals from S0 galaxies.
The stability of tension stars
Authors: Wolf C. 
Published: July 2007

AbstractBy studying the cylindrically symmetric solution for matter in 2+1 space‐time dimensions we arrive at stability criteria for such a configuration when the local energy density is proportional to the square of the tension (negative pressure). Our analysis demonstrates that to the post‐Newtonian approximation that such a configuration is stable provided it does not shrink below a certain radius. We find our model provides a reason for how stars form from a two‐dimensional configuration with both a maximum mass and a minimum radius.