Summer mean daily air temperature extremes in Central Spitsbergen     

Ewa Bednorz  Leszek Kolendowicz 《Theoretical and Applied Climatology》2013,113(3-4):471-479

Summer mean daily temperature extremes in Svalbard Lufthavn (Central Spitsbergen) in the period 1975–2010 and daily pressure patterns and directions of air circulation conducive to their occurrence were analyzed. Positive (negative) extremes of daily mean temperatures in the summer were determined as higher (lower) than or equal to the value of the 90th (10th) percentile. The annual number of selected days shows a great year-to-year variability, although the annual number of extremely low mean daily temperature (≤1.3 °C) was decreasing in the 1976–2010 period, with a rate of about 4 days per decade. At the same time, the number of days with extremely high mean daily temperatures (≤8.2 °C) was increasing with a rate of about 2 days per decade. The summer pressure patterns and the air circulation conditions have an impact on the occurrence of the air mean daily temperature extremes. Namely, anticyclones spreading east to the Svalbard Archipelago, accompanied by the Icelandic Low, cause the air inflow from the southerly direction and positive mean daily temperature extremes. A cyclonal system spreading east or southeast towards the archipelago, together with a high-pressure ridge over the North Atlantic, indicates the northern air flow and negative mean daily temperature extremes in summer. The results obtained in this study prove that the summer air temperature in the Atlantic region of the Arctic is partly controlled by air circulation, and despite the intensity and stability of the summer cyclones and anticyclones being weaker than in the winter, their position strongly determines the occurrence of mean daily temperature extremes in the summer.  相似文献   

Thermodynamic stability of various alkylated, dealkylated and rearranged 17α- and 17β-hopane isomers using molecular mechanics calculations     

Ewa Kolaczkowska  Nacer-Eddine Slougui  David S. Watt  Robert E. Maruca  J. Michael Moldowan 《Organic Geochemistry》1990,16(4-6)

The thermodynamic stability of selected alkylated, dealkylated and rearranged 17α- and 17β-hopane isomers in the C₂₇, C₂₈, C₂₉, C₃₀ and C₃₁ families were calculated using molecular mechanics (MM2) methods and, where possible, calculated equilibrium ratios of certain isomers were compared with observed ratios of isomers in thermally mature crude oil samples. Those calculated and observed ratios having similar values include: (1) the relative distributions among 17β(H)/17α(H) and 21β(H)/21α(H)-hopanes including the absence of the 17β(H),21β(H)- and 17α(H),21α(H)-hopanes; (2) the 22R/22S ratios in 30-methyl-17α-hopane and 30-methyl-17β-moretane; (3) the relative distributions among 17α(H)/17β(H)- and 21α(H)/21β(H)-28,30-bisnorhopanes and among 25,28,30-trisnorhopanes, including the relatively greater stability of 17β(H) isomers in contrast to the regular hopane series; and (4) the ratios of 28(18−17S)abeo hopanes with respect to their unrearranged counterparts including the C₂₇ compounds, Ts/Tm.  相似文献   

Dark matter distribution in the Coma cluster from galaxy kinematics: breaking the mass–anisotropy degeneracy     

Ewa L. &#;okas  Gary A. Mamon 《Monthly notices of the Royal Astronomical Society》2003,343(2):401-412

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Dark matter distribution in dwarf spheroidal galaxies     

Ewa L. &#;okas 《Monthly notices of the Royal Astronomical Society》2002,333(3):697-708

We study the distribution of dark matter in dwarf spheroidal galaxies by modelling the moments of their line-of-sight velocity distributions. We discuss different dark matter density profiles, both cuspy and possessing flat density cores. The predictions are made in the framework of standard dynamical theory of two-component (stars and dark matter) spherical systems with different velocity distributions. We compare the predicted velocity dispersion profiles to observations in the case of Fornax and Draco dwarfs. For isotropic models the dark haloes with cores are found to fit the data better than those with cusps. Anisotropic models are studied by fitting two parameters, dark mass and velocity anisotropy, to the data. In this case all profiles yield good fits, but the steeper the cusp of the profile, the more tangential is the velocity distribution required to fit the data. To resolve this well-known degeneracy of density profile versus velocity anisotropy, we obtain predictions for the kurtosis of the line-of-sight velocity distribution for models found to provide best fits to the velocity dispersion profiles. It turns out that profiles with cores typically yield higher values of kurtosis which decrease more steeply with distance than the cuspy profiles, which will allow us to discriminate between the profiles once the kurtosis measurements become available. We also show that with present quality of the data the alternative explanation of velocity dispersions in terms of Modified Newtonian Dynamics cannot yet be ruled out.  相似文献   

Spectral variability in transonic discs around black holes     

Luca Zampieri  Roberto Turolla  Ewa Szuszkiewicz 《Monthly notices of the Royal Astronomical Society》2001,325(3):1266-1274

Transonic discs with accretion rates relevant to intrinsically bright Galactic X-ray sources ( L ≈10³⁸–10³⁹ erg s⁻¹) exhibit a time-dependent cyclic behaviour due to the onset of a thermal instability driven by radiation pressure. In this paper we calculate radiation spectra emitted from thermally unstable discs to provide detailed theoretical predictions for observationally relevant quantities. The emergent spectrum has been obtained by solving self-consistently the vertical structure and radiative transfer in the disc atmosphere. We focus on four particular stages of the disc evolution, the maximal evacuation stage and three intermediate stages during the replenishment phase. The disc is found to undergo rather dramatic spectral changes during the evolution, emitting mainly in the 1–10 keV band during outburst and in the 0.1–1 keV band off-outburst. Local spectra, although different in shape from a blackbody at the disc effective temperature, may be characterized in terms of a hardening factor f . We have found that f is more or less constant, both in radius and in time, with a typical value ∼ 1.65.  相似文献   

Velocity dispersions of dwarf spheroidal galaxies: dark matter versus MOND     

Ewa L. &#;okas 《Monthly notices of the Royal Astronomical Society》2001,327(2):L21-L26

We present predictions for the line-of-sight velocity dispersion profiles of dwarf spheroidal galaxies and compare them to observations in the case of the Fornax dwarf. The predictions are made in the framework of standard dynamical theory of spherical systems with different velocity distributions. The stars are assumed to be distributed according to Sérsic laws with parameters fitted to observations. We compare predictions obtained assuming the presence of dark matter haloes (with density profiles adopted from N -body simulations) with those resulting from Modified Newtonian Dynamics (MOND). If the anisotropy of velocity distribution is treated as a free parameter, observational data for Fornax are reproduced equally well by models with dark matter and with MOND. If stellar mass-to-light ratio of 1 M_⊙/L_⊙ is assumed, the required mass of the dark halo is     , two orders of magnitude larger than the mass in stars. The derived MOND acceleration scale is     . In both cases a certain amount of tangential anisotropy in the velocity distribution is needed to reproduce the shape of the velocity dispersion profile in Fornax.  相似文献   

Visualization of trace-element zoning in fluorapatite using BSE and CL imaging,and EPMA and μPIXE/μPIGE mapping     

Katarzyna Gros  Ewa Słaby  Hans-Jürgen Förster  Przemysław P. Michalak  Frans Munnik  Jens Götze  Dieter Rhede 《Mineralogy and Petrology》2016,110(6):809-821

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Distribution of Selected Critical Elements in the Carboniferous Coal-bearing Series of the Upper Silesian and Lublin Coal Basins (Poland)     

Ewa KRZESZOWSKA  Magdalena KOKOWSKA-PAWLOWSKA  SwiatosIaw KRZESZOWSKI 《《地质学报》英文版》2022,96(1):273-292

The distribution of selected critical elements in the sedimentary rocks of the Carboniferous coal-bearing series within the Polish Coal Basins is presented.Critical elements such as Be,Mg,Si,P,Sc,V,Co,Y,Nb,In,Sb,La,Ce,Hf,Ta,W,Bi were analysed using inductively-coupled plasma mass spectrometry(ICP/MS).Concentrations of elements such as Sb,Bi,In and,to a slightly lesser extent,Nb,as well as Sc,show average concentrations higher than those from the upper continental crust.The average concentrations of elements like Hf,Mg,P,Y,La,and Ce are slightly lower than in the upper continental crust.Other elements,such as Be,Co,Si,Ta,W and V have average concentrations that are similar,but slightly enriched or slightly depleted,relative to the upper continental crust.The research showed enrichment of some critical elements in the analysed samples,but not high enough that extraction would be economically viable.Statistical methods,which include correlation coefficients between elements and cluster analysis,reveal a strong positive correlation between elements like Be,Bi,Nb,Sc,Ta,W and V.Very high,almost total,positive correlation is also noted between La and Ce.  相似文献   

Correlating specific conductivity with total hardness in limestone and dolomite karst waters     

Wies&#x;awa Ewa Krawczyk  Derek C. Ford 《地球表面变化过程与地形》2006,31(2):221-234

Under field conditions modern digital conductivity meters give standardized, rapid and reproducible measurements. Here we investigate the accuracy of their estimates of the composition of karst waters, as total hardness (TH, as mg/L CaCO₃) for limestone and dolomite. These are the fundamental measures of process in carbonate karst geomorphology. PHREEQC theoretical curves for the dissolution of pure calcite/aragonite and dolomite in water at 25 °C are compared with water analyses from karst studies worldwide. Other principal ions encountered are sulphates, nitrates and chlorides (the ‘SNC’ group). From carbonate karsts, 2309 spring, well and stream samples were divided into uncontaminated (SNC < 10%), moderately contaminated (10 < SNC < 20%), and contaminated (SNC > 20%) classes. Where specific conductivity (SpC) is less than 600 µS/cm, a clear statistical distinction can be drawn between waters having little contamination and substantially contaminated waters with SNC > 20%. As sometimes claimed in manufacturers' literature, in ‘clean’ limestone waters TH is close to ¹/2SpC, with a standard error of 2–3 mg/L. The slope of the best‐fit line for 1949 samples covering all SNC classes where SpC < 600 µS/cm is 1·86, very close to the 1·88 obtained for clean limestone waters; however, the value of the intercept is ten times higher. The regression line for clean limestone waters where SpC > 600 µS/cm helps to distinguish polluted waters from clean waters with possible endogenic sources of CO₂. In the range 250 < SpC < 600 µS/cm, dolomite waters can be readily distinguished from limestone waters. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

Bellert's general relativity theory     

Ewa Rydzyńska 《Astrophysics and Space Science》1990,173(2):241-249

In this paper, new ideas from our previous paper (Rydzyska, 1989)-i.e., problems connected with the new equivalence principle-have been developed. It is conformed, that certain static particles from Bellert's space-time are equivalent to a free particle from classic Milne's space-time. Mention is made of the algebraic structure of Bellert's space-time from (Rydzyska, 1990b). The space-time interval in this space-time, and its connection with a probability and the physical meaning of this interval and probability, has been defined. In the last section we derive dynamical equations for Bellert's space-time, i.e., we do the foundations of Bellert's general relativity theory.  相似文献