Stark Broadening Parameters for Neutral Oxygen Spectral Lines     

N. Alonizan  R. Qindeel  N. Ben Nessib  S. Sahal-Bréchot  Milan S. Dimitrijević 《Journal of Astrophysics and Astronomy》2015,36(4)

Stark broadening parameters for nine neutral oxygen (O I) lines have been determined within the impact approximation and the semiclassical perturbation method. The atomic data have been taken from the TOPbase and NIST atomic databases. The electron and proton Stark widths and shifts and ion broadening parameter values for these O I lines have been calculated for electron density of 10 ¹⁶ cm ^?3 and for 4 different electron temperatures in the range of 5000 K to 40000 K. These Stark broadening parameters are compared with our previous results (Ben Nessib, N. et al. 1996, Physica Scripta, 54, 603–613), where we calculated Stark broadening parameters for only four O I spectral lines and where Stark widths and shifts were compared with experimental and theoretical data available in the literature. In the present paper, we have also compared our results with the Griem’s book (Griem, H. R. 1974, Spectral line broadening by plasmas) and VALD (Ryabchikova, T. et al. 2015, Physica Scripta, 90, 054005) values.  相似文献   

Line Shape Variability in a Sample of AGN with Broad Lines     

D. Ilić  L. Č. Popović  A. I. Shapovalova  A. N. Burenkov  V. H. Chavushyan  A. Kovačević 《Journal of Astrophysics and Astronomy》2015,36(4)

The spectral variability of active galactic nuclei (AGN) is one of the key features that enables us to study in more detail, the structure of AGN emitting regions. Especially, the broad line profiles that vary both in flux and shape, give us invaluable information about the kinematics and geometry of the broad line region (BLR) where these lines are originating from. We give here a comparative review of the line shape variability in a sample of five type 1 AGNs, those with broad emission lines in their spectra, of the data obtained from the international long-term optical monitoring campaign coordinated by the Special Astrophysical Observatory of the Russian Academy of Science. The main aim of this campaign is to study the physics and kinematics of the BLR on a uniform data set, focusing on the problems of the photoionization heating of the BLR and its geometry, where, in this paper, we give for a first time, a comparative analysis of the variabilty of five type 1 AGNs, discussing their complex BLR physics and geometry in the framework of the estimates of the supermassive black hole mass in AGN.  相似文献   

Selenium deficiency as a consequence of human activity and its correction     

Vadim Ermakov  Larisa Jovanović 《Journal of Geochemical Exploration》2010

Problems of sustainable development in connection with the change of biogeochemical cycle of selenium and overcoming its deficiency in Russia, Serbia, Belarus and other countries are reported. The history of the biological role of selenium as an essential trace element is discussed. A special program of «Overcoming of selenium deficiency» has been developed by researches of Russia, Serbia and Belarus in view of high morbidity rates for cardiovascular, tumor and endemic diseases affecting the population of both the above and some other countries, including children, prevalence of selenium deficiency among livestock species and aggravation of the environmental situation as a result of man-made processes.  相似文献   

Hydrogeological conditions for the forming and quality of mineral waters in Serbia     

Tanja Petrović  Milena Zlokolica-Mandić  Nebojša Veljković  Dragana Vidojević 《Journal of Geochemical Exploration》2010

In the past researches conducted on the territory of Serbia, 5 regional geotectonic units have been distinguished with registered occurrences of 230 mineral springs. Recent analyses of the bottled mineral waters quality have not included systematic examinations of micro-components present in these waters. Based on the analyses of the bottled mineral waters (EuroGeoSurveys Geochemistry Expert Group), it has been observed that the water quality is greatly influenced by the chemical composition of igneous intrusions, regardless of the fact that the analyzed waters have been taken from different aquifers (Neogene sediments, limestone, flysch, schist).  相似文献   

Synthetic pulsational line profile variations     

R. Oreiro  J. H. Telting  R. H. Østensen  M. Briquet  C. Aerts  U. Heber  M. Vučković 《Astrophysics and Space Science》2010,329(1-2):211-216

We have produced simulated time series of high resolution spectroscopy for sdBs. We present the first results of testing classical mode identification techniques. Here, in particular, we analyse the behaviour of individual spectral lines and discuss the results and applicability of the moment method.  相似文献   

Hydrochemical properties of transition zone between fresh groundwater and seawater in karst environment of the Adriatic islands,Croatia   总被引：3，自引：3，他引：0  

Josip Terzić  Zoran Peh  Tamara Marković 《Environmental Earth Sciences》2010,59(8):1629-1642

Eastern coast of the Adriatic Sea consists of karstified carbonates. It belongs to the well-known Dinaric karst region. The coast is extremely indented and there are 718 islands with numerous rock crags and reefs. Some of the inhabited islands use their own water resources for public water supply, or plan to do it in the future. Since karst rocks are extremely permeable, the seawater intrudes into underground water resources, thereby forming the wedge. A wide transition zone occurs between this seawater wedge and fresh water aquifers. Consequently, island groundwater reserves turn brackish to a certain extent. In this study, 77 water samples were collected from a wide variety of water resources. Comprehensive statistical and mathematical multivariate analysis of these data was performed. Simple statistical approach showed several useful correlations among some parameters, and more complex multivariate techniques extracted three factors in connection with three natural processes: (1) mixing with the seawater, (2) carbonate dissolution and (3) human influence (pollution) and nitrogen transformation processes. The results of this study demonstrate that in situ measurement of electrical conductivity is adequate for the very rough field estimation of numerous parameters.  相似文献   

An assessment of global and regional climate change based on the EH5OM climate model ensemble     

Čedo Branković  Lidija Srnec  Mirta Patarčić 《Climatic change》2010,98(1-2):21-49

An analysis of climate change for global domain and for the European/Mediterranean region between the two periods, 1961–1990 (representing the twentieth century or “present” climate) and 2041–2070 (representing future climate), from the three-member ensemble of the EH5OM climate model under the IPCC A2 scenario was performed. Ensemble averages for winter and summer seasons were considered, but also intra-ensemble variations and the change of interannual variability between the two periods. First, model systematic errors are assessed because they could be closely related to uncertainties in climate change. A strengthening of westerlies (zonalization) over the northern Europe is associated with an erroneous increase in MSLP over the southern Europe. This increase in MSLP is related to a (partial) suppression of summer convective precipitation. Global warming in future climate is relatively uniform in the upper troposphere and it is associated with a 10% wind increase in the subtropical jet cores. However, spatial irregularities in the low-level temperature signal single out some regions as particularly sensitive to climate change. For Europe, the largest near-surface temperature increase in winter is found over its north-eastern part (more than 3°C), and the largest summer warming (over 3.5°C) is over south Europe. For south Europe, the increase in temperature averages is almost an order of magnitude larger than the increase in interannual variability. The magnitude of the warming is larger than the model systematic error, and the spread among the three model realisations is much smaller than the magnitude of climate change. This further supports the significance of estimated future temperature change. However, this is not the case for precipitation, implying therefore larger uncertainties for precipitation than for temperature in future climate projections.  相似文献   

A modeling study of the physical processes affecting the development of seasonal hypoxia over the inner Louisiana-Texas shelf: Circulation and stratification     

Lixia Wang  Dubravko Justić 《Continental Shelf Research》2009,29(11-12):1464-1476

The physical processes affecting the development of seasonal hypoxia over the Louisiana-Texas shelf were examined using a high-resolution, three-dimensional, unstructured-grid, Finite Volume Coastal Ocean Model (FVCOM). The model was forced with the observed freshwater fluxes from the Mississippi and Atchafalaya Rivers, surface winds, heat fluxes, tides and offshore conditions. The simulations were carried out over a six-month period, from April to September 2002, and the model performance was evaluated against several independent series of observations that included tidal gauge data, Acoustic Doppler Current Profiler (ADCP) data, shipboard measurements of temperature and salinity, vertical salinity and sigma-t profiles, and satellite imagery. The model accurately described the offshore circulation mode generated over the Louisiana-Texas shelf by the westerly winds during summer months, as well as the prevalent westward flow along the coast caused by the easterly winds during the rest of the study period. The seasonal cycle of stratification also was well represented by the model. During 2002, the stratification was initiated in early spring and subsequently enhanced by the intensity and phasing of riverine freshwater discharges. Strong stratification persisted throughout the summer and was finally broken down in September by tropical storms. The model simulations also revealed a quasi-permanent anticyclonic gyre in the Louisiana Bight region formed by the rotational transformation of the Mississippi River plume, whose existence during 2002 was supported by the satellite imagery and ADCP current measurements. Model simulations support the conclusion that local wind forcing and buoyancy flux resulting from riverine freshwater discharges were the dominant mechanisms affecting the circulation and stratification over the inner Louisiana-Texas shelf.  相似文献   

Engineering-Geological Problems in the Moravian Karst,Czech Republic     

Milena AMALIKOVA 《《地质学报》英文版》2001,75(3):303-307

The Moravian karst belongs to one of the famous karst regions in Central Europe. It is situated in Moravia in the eastern part of the Czech Republic. According to the geology it is of Devonian age and the main rocks are of different types of limestones. The process of karstification is still active. They are many caves with rich stalagmites and stalactites and the Macocha abyss, the depth of which is 138.5 m. The underground Punkva River flows through the main part of the karst, forming beautiful underground lakes. Typical karst phenomena, such as sinkholes and deep canyons, may be observed on the surface of the terrain. Because of the karstification, water erosion and frost weathering, many steep unstable slopes and walls originated. To solve the stability from a geotechnical point of view is not easy. This requests a special engineering-geological knowledge and experience.  相似文献   

S(IV) Autoxidation in Atmospheric Liquid Water: The Role of Fe(II) and the Effect of Oxalate     

Irena Grgićc  Marjeta Pozničc  Mirko Bizjak 《Journal of Atmospheric Chemistry》1999,33(1):89-102

The reactivity of dissolved iron compounds towards different pollutants and photooxidants in atmospheric liquid water depends upon the oxidation state and speciation of iron. Our measurements of the oxidation state of dissolved iron eluted from aerosol particles (Dae: 0.4–1.6 m) collected in the urban atmosphere of Ljubljana showed that a large fraction of the iron content is present as Fe(II). The concentration ratio [Fe(II)]/[Fe(III)] varied between 0.9 and 3.1. The kinetics of S(IV) autoxidation catalyzed by Fe(II) under the conditions representative for acidified atmospheric liquid water and the influence of oxalate on this reaction under dark conditions was investigated. The reaction rate is the same if Fe(II) or Fe(III) is used as a catalyst under the condition that Fe(II) can be oxidized in Fe(III), which is the catalytically active species. Oxalate has a strong inhibiting effect on the S(IV) autoxidation in the presence of Fe(II). The reaction is autocatalytic with an induction period, that increases with higher concentrations of oxalate. The inhibiting effect of oxalate differs according to whether iron is initially in the Fe(II) or Fe(III) state. However, in both cases the inhibition by oxalate is a result of the formation of complexes with the catalyst.  相似文献