bluuebunny/crossref_metadata_2025_split huggingface dataset:
Expanding, homogeneous, ellipsoidal density perturbations. III. A simple theory for the acquisition of angular momentum by tidal torques with the effects of the spin growth on the expansion included
Authors: Caimmi R. 
Published: July 2007

AbstractThe effects of the acquisition of angular momentum on the expansion of homogeneous, ellipsoidal density perturbations is investigated by generalizing the theory of previous papers of this series, where spin grows to the first order in overdensity. A small difference is found to be between the two cases, except for the fact that the body under consideration becomes unbound earlier in the current approach. A comparison is also made with the results of a different theory, where spin grows to the second order in overdensity. Quasi‐oblate triaxial configurations turn out to gain less angular momentum in respect to both oblate and more elongated configurations with same minor to major axis ratio. In all cases of physical interest, the spin growth from the beginning to the maximum ellipsoidal volume exceeds the spin growth from the maximum ellipsoidal volume to the turnaround of the major axis, by a factor of at least 3. It is also inferred that the spin growth from the turnaround of the major axis on, probably does not exceed about one third the angular momentum previously gained.
The pole of (51) Nemausa
Authors: Kristensen L. Kahl 
Published: July 2007

AbstractThe complex lightcurves make (51) Nemausa a good case for the study of general methods for pole determination. From six lightcurves the pole is determined to 20h24m; +53° (1950); the rotation is retrograde with period 7h.782936 ± 0h.000005. Presence of nongeometric scattering is proved by a significant 0.008 mag amplitude. Formulae and photometric elements are given for predictions of the shapes of lightcurves in future oppositions. The precision of the Fourier coefficients may be reduced below the present ±0.003 mag level by avoiding the systematic errors in the observations due to phase factor variations and discontinuities when changing comparison stars.
Compact objects with large masses
Authors: Verozub L. V. 
Published: July 2007

AbstractIt is shown that gravitational theory allows stable equilibrium configurations of the degenerated Fermi gas, whose masses M ≫ M⊙ and sizes are less than α = 2GM/c. They have no events horizon at the distance r = α from the center. Orbits of test particles near the above objects are considered.
Kasner‐like, inflationary and steady‐state solutions in multi‐dimensional cosmology
Authors: Bleyer U. , Zhuk A. 
Published: July 2007

AbstractMulti‐dimensional cosmological models with n(n > 1) Ricci‐flat spaces and a scalar field are discussed classically and with respect to canonical quantization. These models are integrable. Two classes of solutions are obtained. One class of solutions generalizes the Kasner solutions. For special additional conditions we find another solution describing extended inflation connected with a constant volume of the whole multidimensional space (steady‐state).
Oceanic and solid Earth angular momentum
Authors: Brosche P. , Seiler U. 
Published: July 2007

AbstractWe reconsider two hypotheses used in calculating the transfer of angular momentum between the oceans and the solid Earth: (1) The locked‐cean‐ypothesis was already given up some time ago; here we provide a simple manner of understanding the relative importance of the motion and matter term. (2) The isolation hypothesis implied the isolation of the whole Earth in short timescales with regard to angular momentum exchange, and consequently, the neglection of the exchange with the tide‐enerating body. It is shown that for present accuracy requirements this exchange has to be taken into account.
Catalogue of Shakhbazian compact groups of galaxies. V.
Authors: Stoll D. , Tiersch H. , Braun M. 
Published: July 2007

AbstractWe present the position and references (if available) of all the galaxies of the Shakhbazian survey being the largest survey of compact galaxy groups. For the estimation of the coordinates the Digitized Sky Survey was used. This paper contains the data of 48 Shakhbazian groups north of δ > + 2deg;30' (Shkh 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 22, 23, 25, 26, 28, 29, 31, 34, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56).
Dark matter, galaxy sizes and exponential potential
Authors: Capaccioli M. , Longo G. , Capozziello S. , De Ritis R. 
Published: July 2007

AbstractStarting from the standard Newtonian theory, we derive in the propagation equation of perturbations an effectively Yukawalike potential invoked by several authors as an alternative to dark matter. This approach provides with a simple explanation of the segregation observed for dynamically ‘hot’ systems in the plane defined by their effective parameters.
Spectral survey of the Comet Halley atmosphere during an occultation of a star
Authors: Nazarchukd̊ H. K. , Shulman L. M. 
Published: July 2007

AbstractOn November 15, 1985 a star was occulted by Comet Halley. Seven consequent spectra of the star has been obtained with 5‐minute exposition with the TV scanner at 6‐meter telescope. Simultaneously seven spectra of the cometary atmosphere were obtained at the projected distance 40” from the star. A method is developed to calculate the optical thickness of the cometary atmosphere as a function of wave length and the nucleocentric distance. This function is given in the spectral range 3925 Å−4850 Å.
Possible relations between the rotational axis of the Earth's inner core and the magnetic dipole axis
Authors: Greiner‐Mai H. 
Published: July 2007

AbstractThe geomagnetic field is maintained by amagnetohydrodynamic dynamo process within the liquid outer core. The distribution of the associated electric currents is modified if the outer core is bounded by electrically conducting material. Then, eddy currents and the related magnetic fields are generated within these regions. In particular, the relative rigid rotation of the inner core produces a secondary magnetic field, which is superimposed on the dynamo field. The angle between the dipole axis of the total field and the rotational axis of the inner core is an important quantity needed for the theory of polar motion of the Earth. This angle is investigated for a broad spectrum of angular velocities of the inner core.To simplify the mathematical procedure, we model the dynamo field using an axisymmetric field generated by a system of electric currents within the outer core. The conductivity of the mantle is neglected. We find that the position of the dipole axis depends on the angular velocity of the inner core as well as on the distribution of the current system within the outer core. Coincidence of both axes can be reached if the angular velocity is high enough and if the current system is concentrated within a thin sheet near the outer core‐inner core boundary.
A survey of main‐belt asteroids I. Positions and improved orbital elements for 75 numbered asteroids.
Authors: Lagerkvist C.‐I. , Hahn G. , Lundström M. , Lagerros J. S. V. , Hernius O. , Tancredi G. 
Published: July 2007

AbstractMore than 7000 positions of moving objects have been detected on 33 films obtained with the Schmidt telescope at the European Southern Observatory in Chile during August and September 1995. The majority of these asteroids are previously unobserved. This paper presents the astrometric methods as well as the magnitude determinations. The derived positions for the numbered asteroids are presented and for these improved orbital elements have been calculated using all available positions.
Predicted star counts and mean parallaxes down to the 23rd magnitude
Authors: Kharchenko N. , Rybka S. , Yatsenko A. , Schilbach E. 
Published: July 2007

AbstractStar counts and mean parallaxes as a function of B, V, R magnitudes down to 23 are presented. The data were computed by the use of two fundamental equations of stellar statistics. The assumed model considers the Galaxy as a symmetrical system with respect to its rotation axis and to its equatorial plane and as composed of the thin disk (main sequence and red giants), the thick disk and spheroid populations.Numbers of stars and mean parallaxes were derived in bins of galactic longitude and latitude of 30° and 10°, respectively. For the computation of the mean parallaxes depending on Galactic coordinates and magnitudes, series of products of Hermite and Legendre polynomials and of Fourier terms were used.The results of this paper may help in the planning of future survey missions and in the design of new telescopes. In addition, mean parallaxes can be used to derive corrections to absolute parallaxes and proper motions for any position in the sky.
The influence of turbulence on the solar p‐mode frequencies I. Free‐mode approximation
Authors: Rüdiger G. , Hasler K.‐H. , Kitchatinov L. L. 
Published: July 2007

AbstractThe influence of turbulence on the frequencies of free acoustic modes in convection zones is considered. The frequencies are modified via the speed of sound by the turbulence‐induced alterations of the effective pressure: (i) by the correlated fluctuations of temperature and density and (ii) the pressure part of the Reynolds stress. The two effects shift the frequency of low l p‐modes in opposite directions. In addition, the correlation of the density fluctuations with the random velocity — the eddy‐mass flow — is also relevant. It is, in a steady state, balanced by a vertical mean velocity. The balance results in a rather small net effect completely disappearing for highly nonradial oscillations. Both effects of the density fluctuations produce a redshift of the low l p‐mode frequencies. The Reynolds stress, however, makes a blueshift of the frequencies relative to that computed for a laminar gas. This effect dominates for subsonic turbulences. The applied second‐order correlation‐approximation, however, only holds for the lowest frequencies, where the KORONAS (solar minimum) data are indicating a blueshift. Of particular importance for the present concept is the expected cycle‐variations of the lineshifts, i.e. the consideration of the magnetic modification of the various contributions. Observations may show whether the suggested modifications of the solar oscillation theory are correct.
Far infrared study of AGNs: a status report
Authors: Assendorp R. 
Published: July 2007

AbstractWe have initiated a new study into the Far Infrared properties of Active Galaxies. We use several samples of AGNs and try to get as clean IRAS fluxes as possible by inspecting the raw IRAS data. Using high resolution images enables us to resolve galaxies that are confused in the IRAS Point Source Catalogue and IRAS Faint Source Survey.
The knotty structure of the HII dwarf galaxy F348
Authors: Rafanelli P. , Roi S. , Tegon A. , Schulz H. , Di Serego‐Alighieri S. , Komossa S. , Richter G. , Vennik J. 
Published: July 2007

Abstract[OIII] images and blue spectra of the emission‐line dwarf galaxy F348 are presented. In [OIII] light, the object contains two knots about 9” NE of the nucleus and one large extended knot 11” to the SW. The nuclear region is hundred times less luminous in emission‐line light than the knots. Despite the presence of line intensity ratios [OIII]λ5007/Hβ > 3 the prior classification as a Seyfert‐2 object cannot be upheld. This clinches an earlier suggestion by Veron‐Cetty & Veron (1986). In particular, we show that the line spectra can be modeled with photoionization models employing stellar input continua. Also, the line luminosities of the extranuclear knots are typical for giant HII regions. There is neither evidence for tidal tails nor for high velocity differences between the knots. In addition, the linear arrangement of the knots does not support interaction. It rather suggests self‐propagating star formation In this picture, the faintness of the nuclear region can be understood by an edge‐on view. In addition, the nuclear starburst appears to be fading in contrast to the young extranuclear star formation regions. Within the scheme of Melnick (1987), F348 has to be classified as a multiple‐system HII galaxy.
The Hipparcos distances of open clusters and their implication on the local variations of the ΔY/ΔZ ratio
Authors: Efremov Yu. N. , Schilbach E. , Zinnecker H. 
Published: July 2007

AbstractArguments are collected to demonstrate that recent Hipparcos results on the distances of open clusters are in agreement with previous estimates in the Russian literature which have pointed to a shorter distance scale. Evidence of the absence of a universal correaltion between Helium and metal abundances is given. It is suggested that violations of this correlation may explain the apparent contradictions between the relative positions of the main sequences of open clusters found from the Hipparcos distances.
The G‐dwarf problem in the solar neighbourhood: a Lagrangian picture
Authors: Caimmi R. 
Published: July 2007

AbstractRecent data on the empirical metallicity distribution of G dwarfs in the disk solar neighbourhood are fitted in two different ways. We use an extended Poisson distribution in the limit where the probability of star formation is small, and a Gauss distribution in the limit where a large number of physical variables is required to determine stellar metal abundance. Both are found to reproduce the data at the same (acceptable) extent, with a slight preference for the former. The emprirical, differential metallicity distribution of G dwarfs in the disk solar neighbourhood is compared with its theoretical counterpart, in the picture of a closed, comoving model of chemical evolution. The limits of the currently used infall models are discussed and a scenario of galactic formation and evolution is presented. The Galactic history is thought as made of two main phases: contraction (which produces the extended component) and equilibrium (which gives the disk). In this view, the stars observed within the solar cylinder did not necessarily arise from the primordial gas which later collapsed into the disk solar neighbourhood. It is found that the G‐dwarf problem is strongly alleviated, with the possible exception of the low‐metallicity and high‐metallicity tail of the distribution. The best choice of parameters implies: (i) a metal yield in the contraction phase which is larger by a factor of about 5 with respect to the equilibrium phase; (ii) a model halo mass fraction of about 0.3; (iii) a model disk mass fraction of about 0.6. It provides additional support to the idea of a generalized Schmidt star formation law, which is different in different phases of evolution. The model, cumulative, G‐dwarf metallicity distribution in the disk solar neighbourhood is found to predict too may low‐metallicity stars with respect to its empirical counterpart, related to a Poissonian or Gaussian fit. The main resons for the occurrence of a G‐dwarf problem are discussed. Finally, a stochastic process of star formation, related to a Poisson distribution, is briefly outlined.
The REX survey: a search for BL Lac objects
Authors: Maccacaro T. , Caccianiga A. , Della Ceca R. , Wolter A. , Gioia I. M. 
Published: July 2007

AbstractWe present the scientific goals and the strategy of the REX survey, a project which has been recently initiated at the Brera Astronomical Observatory in Milan with the aim of selecting a large and statistically representative sample of BL Lac objects and other kinds of Radio Loud Active Galactic Nuclei. More than 1200 PSPC images (for a total of about 2700 square deg. of sky) have been searched for sources detected also in the VLA NVSS survey (as of June 1977). The data and source selection criteria, the cross‐correlation technique and preliminary results are presented and discussed.
The extragalactic X‐ray background at 0.25 keV
Authors: Warwick R. S. , Roberts T. P. 
Published: July 2007

AbstractWe review recent results from shadowing experiments relating to the intensity of the extragalactic X‐ray background at 0.25 keV. The measurements appear to be converging on a value in the range 20 → 35 keV cm−2 s−1 keV−1. The implication is that over 80% of the background signal at 0.25 keV may have been resolved into discrete sources in the deepest pointed observations carried out by ROSAT.
Recent results from the SHARC Survey
Authors: Romer A. K. , Nichol R. C. , Collins C. A. , Burke D. J. , Holden B. P. , Ulmer M. P. , Pildis R. A. , Metevier A. 
Published: July 2007

AbstractWe review recent results from the SHARC Survey for distant X‐ray clusters of galaxies. We first discuss the SHARC South project which finds no evidence for evolution in the faint end of the X‐ray cluster luminosity function out to a redshift of z ≲ 0.7. We then give an overview of the Bright SHARC project; this project will provide an independent measurement of the evolution of bright (Lx[0.5 ‐ 2keV] > 3 × 1044 erg s−1) X‐ray clusters and allow us to put strong constraints on the value of ω0.
ROSAT HRI Survey of the Large Magellanic Cloud
Authors: Chu You‐Hua , Snowden S. L. 
Published: July 2007

AbstractWe have started a ROSAT HRI survey of the Large Magellanic Cloud (LMC). The current scope of the survey is to map the 30 Doradus region and the bar of the LMC with at least 20 ksec exposure at each position. The survey grid has a 15′ separation between adjacent pointings. The survey has been awarded a total of 39 priority B pointings in AO5–7. The HRI survey of the LMC will provide X‐ray luminosity functions of point sources complete down to ∽ 1 × 1034 erg s−1. In addition, the survey images have resolved small diffuse sources, such as the SNR 0534–69.9 and the superbubble 30 Dor C, and detected diffuse emission on large scales. An HRI mosaic of the LMC is presented and compared to an Hα image.
WFXT: a wide field X‐ray optics
Authors: Chincarini G. , Citterio O. , Conconi P. , Ghigo M. , Mazzoleni F. 
Published: July 2007

AbstractWe describe the main characteristics of a small satellite mission aimed to survey part of the sky in the x‐ray band (WAXS — Wide Angle x‐ray Survey) using a Wide Field of view X‐ray Telescope (WFXT). We demonstrate that using the new technologies we have developed, it is possible to construct x‐ray mirrors according to a new optical design which optimize the angular resolution over a large field of view.
Ba II lines as luminosity indicators: s‐Cepheids and non‐variable supergiants
Authors: Andrievsky S. M. 
Published: July 2007

AbstractBa II line equivalent widths appear to be well correlated with the absolute magnitudes for yellow supergiants. Two Ba II lines 5853.6 Å and 6141.7 Å were applied for investigation of the possible relation between their equivalent widths and Mv for small‐amplitude Cepheids and non‐variable supergiants.
Numerical simulations of the magnetic field distribution in a solar complex of activity
Authors: Tikhomolov E. M. 
Published: July 2007

AbstractPowerful solar complexes of activity are supposed to result from the excitation of Rossby vortices within a thin layer beneath the convection zone. Numerical simulations demonstrate that Rossby vortices generate large‐scale arc‐like magnetic structures. It is shown that the most powerful complex of activity observed in June‐July 1982 was likely to be a result of the excitation of a Rossby anticyclone rather than a cyclone.
Observations of distant solar system bodies
Authors: Magnusson P. , Lagerkvist C.‐I. , Lagerros J. S. V. , Dahlgren M. , Lundsrtöm M. 
Published: July 2007

AbstractMulticolour VRI photometry and astrometry of one Centaur and seven Edgeworth‐Kuiper objects were obtained. One object, 1994 JQ1 may be as red as 5145 Pholus, the reddest minor planet previously known. The Centaur 1995 DW2 has more moderate colour indices, similar to main‐belt asteroids. Seven R‐magnitudes were obtained for 1994 JS, 1995 FB21, and 1995 GY7. No light variation above the expected noise is evident, apart from a few outliers. A total of 47 astrometric positions were obtained for the eight objects. The four nights of observations with the ESO New Technology Telescope covered 0.52 square degrees. Two previosuly unknown object, 1995 FB21 and 1995 GY7, were discovered. We estimate the density of Edgeworth‐Kuiper objects brighter than R = 24 to 5.3 per square degree of sky near the ecliptic.
Application of metabolic flux analysis to identify the mechanisms of free fatty acid toxicity to human hepatoma cell line
Authors: Srivastava Shireesh , Chan Christina 
Published: July 2007

AbstractChronic exposure to elevated levels of free fatty acids (FFAs) has been shown to cause cell death (lipotoxicity), but the underlying mechanisms of lipotoxicity in hepatocytes remain unclear. We have previously shown that the saturated FFAs cause much greater toxicity to human hepatoma cells (HepG2) than the unsaturated ones (Srivastava and Chan, 2007). In this study, metabolic flux analysis (MFA) was applied to identify the metabolic changes associated with the cytotoxicity of saturated FFA. Measurements of the fluxes revealed that the saturated FFA, palmitate, was oxidized to a greater extent than the non‐toxic oleate and had comparatively less triglyceride synthesis and reduced cystine uptake. Although fatty acid oxidation had a high positive correlation to the cytotoxicity, inhibitor experiments indicated that the cytotoxicity was not due to the higher fatty acid oxidation. Application of MFA revealed that cells exposed to palmitate also had a consistently reduced flux of glutathione (GSH) synthesis but greater de novo ceramide synthesis. These predictions were experimentally confirmed. In silico sensitivity analyses identified that the GSH synthesis was limited by the uptake of cysteine. Western blot analyses revealed that the levels of the cystine transporter xCT, but not that of the GSH‐synthesis enzyme glutamyl‐cysteine synthase (GCS), were reduced in the palmitate cultures, suggesting the limitation of cysteine import as the cause of the reduced GSH synthesis. Finally, supplementing with N‐acetylL‐cysteine (NAC), a cysteine‐provider whose uptake does not depend on xCT levels, reduced the FFA‐toxicity significantly. Thus, the metabolic alterations that contributed to the toxicity and suggested treatments to reduce the toxicity were identified, which were experimentally validated. Biotechnol. Bioeng. 2008;99: 399–410. © 2007 Wiley Periodicals, Inc.
Quartz: an autonomous navigation system for MOUT simulations
Authors: Ting Shang‐Ping , Zhou Suiping 
Published: July 2007

AbstractAutonomous navigation systems are important to Military Operations on Urbanized Terrain (MOUT) simulations for generating realistic tactical behaviours for the non‐player characters (or bots). In this paper, we describe our work on Quartz, an autonomous navigation system for MOUT simulations. Novel features of Quartz include qualitative spatial representation and hierarchical spatial reasoning which enables fast situation analysis and human‐like path planning in a dynamic environment. To assess the effectiveness of Quartz, we have integrated it into Twilight City, a virtual environment for MOUT simulations. Experimental results show that Quartz is very effective for quick tactical path generation in dynamic MOUT environments. Copyright © 2007 John Wiley & Sons, Ltd.