http://www.sciencedirect.com/science/article/pii/S1674987111000247

Recent advances in modeling of tornadoes and twisters consist of significant achievements in mathematical calculation of occurrence and evolution of a violent F5-class tornado on the Fujita scale, and four-dimensional mathematical modeling of a tornado with the fourth coordinate time multiplied by its characteristic velocity.Such a tornado can arise in a thunderstorm supercell filled with turbulent whirlwinds.A theory of the squall storms is proposed.The squall storm is modeled by running perturbation of...     

Mineralogy, conditions of crystallization and melt generation of epidote-bearing porphyries from the Middle Urals, Russian federation

Epidote-bearing porphyritic dikes (whole rock analysis: SiO₂?=?55–65 wt. %, MgO <2.1 wt. %, K₂O <2.5 wt. %, Al₂O₃ >17 wt. %, Na₂O + K₂O?=?5.7–9.4 wt. %) situated in the continental margin zone, the Middle Urals, Russian Federation have been dated using SHRIMP U-Pb zircon techniques and give a Middle Devonian age of 388?±?2 Ma and 389?±?6 Ma. The porphyries contain phenocrysts of magmatic epidote (Ps?=?17–25 %), Ca- and Mn-rich (CaO >9 wt. %; MnO >6 wt. %) almandine garnet, Al-rich (Al₂O₃?=?12–16 wt. %) amphibole, titanite, plagioclase, biotite, muscovite, apatite, and quartz. 60 to 70 % groundmass of the porphyritic dikes consists of fine-grained albite, quartz, and K-feldspar. A variety of thermobarometric estimations, plus comparison with published experimental data indicate that the phenocryst assemblage was stable between 5 and 11 kbar and 690 to 800 °C. Oxygen fugacity was close to or greater than logfo₂ = Ni-NiO + 1. Later stage formation of the quartz-feldspar groundmass took place at hypabyssal conditions, corresponding to 1 to 2 kbar and 660 to 690 °C. The porphyritic dikes are metaluminous to slightly peraluminous (ACNK?=?0.7–1.17). They are enriched in REE and depleted Nb and Ti. They show features typical of subduction-related magmas. Chemical composition and isotopic ratios of ⁸⁶Sr/⁸⁷Sr_i?=?0.709–0.720 suggest that both mantle- and deep crustal-derived materials were involved in their petrogenesis.     

GIS-based cost distribution analysis of new consumer connections to an urban power grid

In this paper, we propose a method of cost distribution analysis of new consumer connections to a city power grid by accounting for spatial restrictions and characteristics of existing networks. In practice, the calculation of connection costs for each new consumer includes the network design and financial expenditure. We suggest that connection costs should be calculated for the whole city based on the normative parameters at the stage when the object location is selected by investors and when power grid development is planned by power companies. The proposed method enables the modeling of new power line connection routes from every parcel of city land to possible points of connection to the operating networks based on the raster design of the area. The optimal path is chosen by one criterion consisting of two components: the costs of both laying new power lines and providing sufficient power reserve in the chosen network connection point. Realized as a computer program, the method has been used to calculate the costs of connections to low-voltage power lines.     

Evolution of the X-ray luminosity and metallicity of starburst blown superbubbles

We have modelled the evolution of hot superbubbles in starbursts, taking into account the rapid changes in the chemical composition of the interior of the superbubbles resulting from the large stellar mass loss, i.e. stellar winds from massive young stars and type II supernovae. We have followed in detail the time-dependent production and mixing of oxygen and iron in the interior of the hot superbubbles and showed that while the oxygen abundance rapidly climbs to over solar values in less than 10 Myr, iron abundance remains always under solar. This highly enhanced oxygen metallicity boosts the early X-ray luminosity of superbubbles while keeping the iron abundance subsolar. This brings theory and X-ray observations of the luminosity and metal content of young starbursts closer together.     

Sources of δ18O Concentration Variability in Greenland Ice Cores: Temperature, North Atlantic Oscillation and Solar Activity

This work concerns possible connection between variations of δ¹⁸O in Greenland ice, temperature, precipitation amount, NAO indices and relative sunspot numbers. The relationships between 10-year averaged values of this data were derived making use of regression analysis methods. It was discovered that February temperature yields the main contribution in variability of δ¹⁸O. The multiple correlation coefficient between weighted night temperature of the most important months and δ¹⁸O equals 0.95±0.01. Besides the local source of δ¹⁸O changes, defined by the amount of precipitation and temperature, an additional source correlated with the level of solar activity has been revealed. The relative contribution of this source in the δ¹⁸O variance is about 0.1. It has been shown that the multiple correlation coefficient between δ¹⁸O and NAO indices is equal to 0.85. Therefore the NAO yields more than 2/3 of the variances of climatic change in Greenland. An independent contribution of solar activity in climatic changes is about 1/3.     

Magnetorotational supernovae. Magnetorotational instability. Jet formation

2D numerical simulations of magnetorotational (MR) supernova mechanism are described. It is shown that magnetic field is amplified due to the differential rotation after core collapse. When magnetic pressure reaches some level, a compression wave starts to move outwards. Moving along steeply decreasing density profile the compression wave transforms quickly into fast MHD shock. The magnetorotational instability (MRI) was found in our simulations. MRI leads to the exponential growth of the components of the magnetic field. The MRI significantly reduces MR supernova explosion time. Configuration of the initial magnetic field qualitatively defines the shape of MR supernova explosion. For the quadrupole-like initial poloidal field the MR supernova explosion develops mainly along equatorial plane, the dipole-like initial field results in MR supernova developing as mildly collimated jet along axis of rotation. The explosion energy of MR supernova found in our simulations is ∼0.5–0.6×10⁵¹ erg.     

An Investigation of the Reliability of HF Acid Mixtures in the Bomb Digestion of Silicate Rocks for the Determination of Trace Elements by ICP‐MS

The influence of the mixtures HF‐HNO₃ and HF‐NH₄F‐HNO₃ in bomb digestion for trace element determination from different rock types was studied using ICP‐MS. It is shown that the HF concentration, not the ratio of reagents in the decomposing mixture, controls the digestion process of a rock. Data for Zr in the granite G‐2 as a function of HF concentration gave the same results as reaction mixtures of various compositions. A complete digestion in 50‐mg sample bombs was achieved by 1.0 ml of HF alone, or with a mixture of other acids at a HF concentration of at least 35% m/m at 196 °C over 18 h. The results of the analysis of basalts BCR‐1, BIR‐1, mica schist SDC‐1, shale SBC‐1, granites G‐2, SG‐1A, garnet‐biotite plagiogneiss GBPg‐1, rhyolite RGM‐1, granodiorite GSP‐1, trachyandesite MTA‐1 and rhyolite MRh‐1 are given and compared against available data. The reproducibility of the element determinations by ICP‐MS and XRF as an independent non‐destructive analysis for a quality check in the range of concentrations typical for routine rock samples is given.     

Recent Russian remote sensing investigations in Antarctica within the framework of scientiifc traverses

This paper includes a short historical review of Russian and Soviet scientiifc traverses to study the Antarctic inland. The ifrst traverse left on April 2, 1956. It resulted in the opening of the ifrst...     

Archaean Kuru-Vaara eclogites in the northern Belomorian Province,Fennoscandian Shield: crustal architecture,timing, and tectonic implications

This paper addresses the relationships between relic amphibole-eclogite facies (AE) eclogites and their host units, Archaean amphibolites, enveloped by Archaean tonalite–trondhjemite–granodiorite (TTG) gneisses, in the Kuru-Vaara study area in the northern Belomorian Province. According to observational constraints, the crystallization of the relic peak omphacite + Mg-garnet ± kyanite assemblage and the subsequent replacement of omphacite by clinopyroxene–plagioclase symplectite occurred before the earliest deformational, metamorphic, and migmatization events that are recorded in the amphibolites. The amphibolites and their TTG hosts have a shared deformational and metamorphic history that is composed of the Archaean and Palaeoproterozoic periods. This history favours the conclusion that the AE metamorphism recorded in the relic eclogites within the amphibolites occurred during the Mesoarchaean to Neoarchaean periods. The deformation and metamorphism of the amphibolite facies of the second period resulted from the Lapland–Kola collisional orogeny at 1.91–1.93 Ga, which led to eclogite–high-pressure granulite (E–HPG) facies conditions in the lowermost portions of the over-thickened crust in Belomorian Province (the southwestern foreland of the Lapland–Kola collisional orogen). The Palaeoproterozoic E–HPG overprint was reported from the Palaeoproterozoic Gridino mafic dikes. Although the ages of the oldest low Th/U zircons are close to the time of the Lapland–Kola collision, the low Th/U 1.9–1.8 Ga zircons reflect a zircon response to regional fluid infiltration in the eclogites during slow exhumation following the Lapland–Kola orogeny and do not record any metamorphic event. Contrary to the Palaeoproterozoic E–HPG overprint, the areal occurrence of the 2.7–2.8 Ga AE eclogites with mid-ocean ridge basalt-like chemistry and their paragenetic link with the TTG gneisses suggest a tectonic regime that involves subduction. This research favours concepts suggesting that the modern-style plate tectonics has operated in some places, at least since the late Mesoarchaean.