Is dark matter created in the gravitation field of galaxies?

Using the heuristic arguments of quantum physics we describe a new mechanism of the creation of short-living particles from the virtual ones in a stationary gravitation field. The mass of these particles is a function of the intensity of gravitation field. We suppose that the particles created in the gravitation field form a part of the non-baryonic dark matter. Having the intensity of gravitation field in a galaxy we can calculate the density of dark matter created in it by the vacuum quantum fluctuation. We calculate the distribution of this dark matter in a model galaxy and show that its total mass is comparable with the visible mass of the galaxy.     

Prediction of Stellar Atmospheric Parameters using Instance-Based Machine Learning and Genetic Algorithms

In this article we present a method for the automated prediction of stellar atmospheric parameters from spectral indices. This method uses a genetic algorithm (GA) for the selection of relevant spectral indices and prototypical stars and predicts their properties, using the k-nearest neighbors method (KNN). We have applied the method to predict the effective temperature, surface gravity, metallicity, luminosity class and spectral class of stars from spectral indices. Our experimental results show that the feature selection performed by the genetic algorithm reduces the running time of KNN up to 92%, and the predictive accuracy error up to 35%. This revised version was published online in July 2006 with corrections to the Cover Date.     

The expansive nondecelerative universe

(a) Hubble's discovery of the expansion of the Universe makes it possible to choose unambiguously from the models described by Friedmann's equations of universe dynamics. (b) From the present temperature of the cosmic microwave background radiation, the specific entropy in the matter era and the model properties of the expansive nondecelerative universe, we can determine the present parameters of our Universe with deviations smaller than 2.2%.     

Results from several persistent train spectra intercompared

Some results following from two contemporary photographical programs (Slovakia and Japan) for persistent meteor train spectra are compared. It shows that even though both programs are not too different according to their lenses and films used, the spectral interval detected is very different. In this respect prism as a dispersion element is more favourable than the grating with blaze wavelength near 610 nm. However, some results previously assumed as typicai for presented persistent trains-e.g. the forbidden Herzberg O₂ emission, the NO₂ continuum and OH red emissions-seem to be substanciated especially due to higher and linear dispersion of those grating spectra.     

Beam Mode Expansion of Corrugated Conical Horns with Phase Correcting Lens: Application to Radioastronomy Receivers

A classical radioastronomy receiver is fed with a corrugated horn and an independent lens, both placed in a cryostat to lower the noise temperature. The beam is focused and directed using a combination of elliptical and plane mirrors. This paper proposes modifying the initial feeding system by placing the lens onto the horn aperture, thereby allowing a size reduction of the horn and lens, and a simplification of their mechanical design. The profiled lens is shaped to correct the phase error on the horn aperture. A quasi-optical model of the horn-plus-lens system has been developed using a Beam Mode Expansion (BME). Results using both a hyperbolic-planar lens and a spherical-elliptical lens, as well as results obtained by using Geometrical Optics (GO) with a Kirchoff–Huygens integration to get the far-field pattern, have been compared with measurements. As a direct application, a full focusing system for the new 40-m radiotelescope at the “Centro Astronómico de Yebes” is presented for the 22, 30 and 45 GHz bands. This paper has developed a QO model for a corrugated conical horn with a phase-correcting lens. This revised version was published online in July 2006 with corrections to the Cover Date.     

Ongonite from Ongon Khairkhan,Mongolia

Summary Albite-topaz kerotophyres, termed ongonites, were discovered byV. I. Kovalenko and coworkers at Ongon Khairkhan in Mongolia in 1970. The type area was revisited, described, resampled, the new data is compared with the earlier data and that from similar rocks elsewhere (Beauvoir and Cinovec granites; Macusani glass).Ongonites are fluorine-rich peraluminous sodic two feldspar granitoids with orthoclase and albite phenocrysts, high modal and normative albite content and the presence of topaz as common accessory mineral. They contain variable amounts of lithium micas or muscovite. Chemically, ongonite is similar to highly fractionated S-type or ilmenite series granitoids. In the type area, F-rich water-poor ongonite melts have intruded to a high crustal level.Ongonite displays a long history of subsolidus reactions and hydrothermal alteration. The hydrothermal alteration may be linked to a spatially associated quartz-wolframite stockwork not genetically related to ongonite. Ongonite has a low W content and an elevated Sn content despite a lack of association with Sn deposits.

---

Ongonite von Ongon Khairkhan, Mongolei

Zusammenfassung Albit-Topas-Keratophyre, auch als Ongonite bezeichnet, wurden 1970 von V. E. Kowalenko und Mitarbeitern bei Ongon Khairkhan in der Mongolei entdeckt. Die TypLokalität wurde beschrieben und beprobt und die neuen Daten werden mit den früher erhaltenen, und denen von ähnlichen Gesteinen in anderen Bereichen (die Granite von Beauvoir und Cinovec, das Glas von Macusani) verglichen.Ongonite sind Fluor- und Aluminiumreiche (Peraluminous), zwei-Feldspat-Natriumgranitoide mit idiomorphen Orthoklasen und Albit, hohem modalem und normativem Albitgehalt, und Topas als verbreitetem Nebenmineral. Sie führen wechselnde Gehalte von Lithiumglimmern oder Muskovit. Chemisch sind Ongonite stark fraktionierten S-Typ Granitoiden vergleichbar oder auch Granitoiden der Ilmenit-Serie. Im Gebiet der Typlokalität sind fluorreiche wasserarme Ongonit-Schmelzen in ein hohes Krustenniveau intrudiert worden.Ongonite zeigen eine lange Geschichte von Subsolidusreaktionen und hydrothermaler Umwandlung. Die hydrothermale Umwandlung kann mit einem räumlich assoziiertem Quarz-Wolframit Stockwerk in Beziehung gesetzt werden, das genetisch nicht mit den Ongoniten zusammenhängt. Ongonit hat einen niedrigen Wolframgehalt und einen erhöhten Zinngehalt, obwohl keine Assoziation mit Zinnlagerstätten zu beobachten ist.

     

A note on the problem of choosing a model of the Universe,IV

The Friedmannian model of the Universe with ultra-relativistic equation of statep=–1/3 withk=0 is nondecelerative, i.e., it expands with the constant velocityv=c during the whole expanding phase of evolution of the Universe. The ultrastable nondecelerative model is the only model of the Universe which fulfills all conditions resulting from the quantum-mechanical and relativistic analysis of the Universe.     

Can Brans-Dicke universes in five dimensions be interpreted as 4-dimensional general relativity cosmologies?

The 5-dimensional Jordan-Brans-Dicke cosmologies in vacuum are found for the Bianchi type I metric, their relation with general relativity cosmologies is studied. Two solutions are possible, both produce effective pressure and energy density in the 4-dimensional G.R.-universes. One is a power-law relation, with two cases, the first one is forp _eff=_eff and the other forp _eff=_eff(– 1 < < 1) has a behaviour as the open flat universe. The second solution is an exponential only valid forp _eff=–_eff. In all cases the three-space expansion reaches infinity ast and the fifth dimension can be made to decrease approaching zero. The scalar field can increase or decrease with time.     

Coronal mass ejection associated with the stationary post-flare arch of 21–22 May 1980

By using a combination of X-ray (HXIS), H (Haleakala), white-light corona (Solwind), and zodiacal light (Helios) images on 21–22 May, 1980 we demonstrate, and try to explain, the co-existence of a coronal mass ejection with a stationary post-flare coronal arch. The mass ejection was seen, both by Solwind and Helios, in prolongation of the path of a powerful spray, whereas the active region filament did not erupt. A tentative comparison is made with other occurrences of stationary, or quasi-stationary post-flare coronal arches.     

Space–time distribution of ancient and active alluvial karst subsidence: examples from the central Ebro Basin,Spain

Space and time variations of alluvial karst subsidence in the central Ebro Basin are analysed in trenches (paleodolines), aerial photographs (historical dolines) and field surveys (present-day active dolines). The measured subsidence rates, as well as a comparison between densities of paleodolines computed in randomly selected scan-lines and density of active dolines computed in maps, suggest that present-day subsidence in favourable areas is more intense than that of Pleistocene times. According to diachronic maps drawn from (a) different aerial photographs taken after 1946 and (b) field surveys on deformations in urbanized areas, subsidence behaved as a nearly steady process while the whole area was used for agriculture. In contrast, rapid changes (through periods of several tens of years) have occurred in urbanized areas, in which dolines expand their boundaries through small marginal collapses, shifting sharply their sinking centres to neighbouring sites. These rapid changes do not have an equivalent in observed paleodolines.