Voids in the tolman-bondi universe

In the paper the void is modeled as a spherical underdense region surrounded by shells changing into the Friedmannian exterior. This model is in fact a single Tolman-Bondi metric, where at the edge of the void the density need not be continuous. In principle, there may exist 72 variations. These models contain also the cases, when in the void itself there is a Minkowskian vacuum; the shell crossing is not excluded, too. Some technical results are obtained for the Tolman-Bondi metric. Using them, the questions of stability and other theoretical problems are investigated. Some observational facts concerning the voids are also used. As the key result a truncation of the possible models is obtained; only 14 models are physically reasonable. This means that the universe is either hyperbolically expanding (this possibility strengthens the proposition of Bonnor and Chamorro, (1990); (1991)), or there is a shell crossing. Thus the discovery of voids is an observational support either for the open universe or for the shell crossing scenario of galaxy formation (Mészáros, 1991), where no anisotropy of microwave background radiation is needed in a baryon dominated universe.     

Solar rotation in the subphotospheric layers

The solar rotation rate at latitudes 0°, 15° and 30° has been inferred by averaging the results of 120 regions of 15°×15°, which have been studied over a total area of about 75° in latitude and 360° in longitude. A local helioseismology technique, the ring diagram analysis method, has been used to analyse the horizontal velocity vectors from about 0.95 R up to the surface. Our results are in very good agreement with those of other authors over most of the depth range. However, near the surface we find sharp local features which are not reported in other studies. The independent measurements of the rotation rate in the north and south hemispheres show asymmetries below 0.975 R . The data used are full-disc dopplergrams taken by Solar Oscillation Investigation/Michelson Doppler Imager (SOI/MDI) on board of the SOlar and Heliospheric Observatory (SOHO) during its first Dynamic Program, between 1996 May and June.     

Ground magnetic survey of a municipal solid waste landfill: pilot study in Argentina

This paper shows the results of a ground magnetic survey carried out to study solid waste landfills. The area located southward of Gualeguaychú town was chosen as a pilot case. This zone was selected considering the available knowledge about the cessation of operations, and the interest of the local authorities in verifying the existence of anomalies indicative of possible dangerous pollutants. The total magnetic field was measured along six profiles, and the corresponding anomalies were calculated. The profiles were modelled in 2.5 D, and along them Eulers deconvolution was used to estimate the depth to the sources. The first and the second derivatives of the residual magnetic field were calculated, in order to sharpen the anomalies. Our interpretation suggests that the characteristics of the modelled bodies and the magnitudes of the detected anomalies do not indicate the presence of drums in the sanitary infill.     

Significance of ancient sulfide PGE and Re–Os signatures in the mantle beneath Calatrava,Central Spain

Spinel lherzolite and wehrlite xenoliths from the Cenozoic Calatrava volcanic field carry the geochemical imprint of metasomatic agents that have affected the subcontinental lithospheric mantle beneath Central Iberia. Some xenoliths (mainly wehrlites) were enriched in REE, Sr, P, and CO₂ by silicic-carbonate-rich metasomatic melts/fluids, while others record the effects of subduction-related hydrous silicate fluids that have precipitated amphibole and induced high Ti/Eu in primary clinopyroxene. The petrographic observations and geochemical data suggest that interstitial glass in the xenoliths represent the quenched products of Si-rich melts that infiltrated the mantle peridotite shortly before the entrainment of the xenoliths in the host magmas that erupted ca 2 million years ago. During their infiltration, the metasomatic melts reacted with peridotite, resulting in silica enrichment, while remobilizing grains of iron-rich monosulfide solid solution (Fe-rich Mss) initially enclosed in, or intergranular to, primary olivine and pyroxenes. In situ laser ablation inductively coupled plasma-mass spectrometry analysis of single sulfide grains reveals that the Fe-rich Mss in glass shows platinum-group element (PGE) patterns and ¹⁸⁷Os/¹⁸⁸Os compositions identical to the Fe-rich Mss occurring as inclusions in, or at grain boundaries of primary silicates. Moreover, independent of its microstructural position, Fe-rich Mss exhibits PGE and ¹⁸⁷Os/¹⁸⁸Os signatures typical of Mss either residual after partial melting or crystallized directly from sulfide melts. Our findings reveal that young metasomatic melt(s)/fluid(s) may carry remobilized sulfides with PGE and Os-isotopic signatures identical to those of texturally older sulfides in the peridotite xenolith. These sulfides thus still provide useful information about the timing and nature of older magmatic events in the subcontinental mantle.     

Sandstone alterations triggered by fire-related temperatures

The aim of the study was to identify and describe changes in two different sandstone types when undergoing different environmental and extreme temperature regimes to assess the possibility of finding insolation weathering and how these sandstones would behave during and after a fire. The first step was the simulation in the laboratory of temperature regimes up to 60 °C which would correspond to extreme events that could be found in insolation cycles even in Central Europe and the second one was the temperature above 200 °C simulating in laboratory conditions the thermal regime of a potential fire situation at temperatures up to 200, 400, 600 and 800 °C. Heating the samples above 400 °C led to gradual changes in mineral composition, colour, surface roughness and physical properties reaching, eventually, total rock breakdown through spalling and granular disaggregation. The different behaviour of sandstones exposed to high temperatures is mainly caused by their different mineral composition with various ratios of minerals that are more or less chemically stable at high temperatures as well as by the differences in the porosity.     

Analysis of the correlations between freeze–thaw and salt crystallization tests

Two of the most popular weathering tests used for dimension stone are EN 12371 freeze–thaw (FT) and EN 12370 Salt Crystallization (SC). These tests are used to assign a durability value to the rocks. Both tests are based on the cyclical growth of crystals in the porous system of the rock, which causes structural stress on the rock matrix that may affect its integrity. The weathering mechanism is the same in both tests although the rate of volume increase is higher for the salt crystals. Due to this similarity, the two tests provide complementary information. The EN (European Norms) recommend evaluating the results together, but do not establish correlations between the results of these two tests for different types of rocks. Knowing these relationships would improve the understanding of the results and the response to weathering of the rock once placed in a building. In this work, several ornamental rocks (sandstones, limestones, dolostones, and a travertine) from the Iberian Peninsula were submitted to FT and SC tests. Rocks were mineralogically and petrographically characterized, and their porous systems were defined by a combination of techniques (scanning electronic microscopy, digital images analysis, and mercury porosimetry). The results of the tests were quantified numerically to compare them. The velocity of propagation of ultrasonic waves was measured before and after the tests. After the statistical analysis, significant correlations were found between the FT and SC tests, and between the connected porosity and the durability index of the rocks.     

Tsunami hydrodynamic force on a building using a SPH real-scale numerical simulation

Natural Hazards - One of the most important aspects in tsunami studies is the behaviour of the wave when it approaches the coast. Information on physical parameters that characterize waves is often...