Thermodynamics of arsenates,selenites, and sulfates in the oxidation zone of sulfide ores. X. thermal stability and dehydration features of synthetic analogs of the cobaltomenite–ahlfeldite solid solution series     

M. V. Charykova  E. L. Fokina  V. G. Krivovichev  O. S. Yakovenko  E. V. Klimova  V. V. Semenova 《Geology of Ore Deposits》2015,57(7):570-578

The aim of this study is the experimental investigation of the synthetic analogs of cobaltomenite, CoSeO₃ ? 2H₂O, ahlfeldite, NiSeO₃ ? 2H₂O, members of the cobaltomenite–ahlfeldite solid solution series (Ni _x Co_1–x )SeO₃ ? 2H₂O, and singularities of their dehydration and dissociation. The intermediate members of the cobaltomenite (CoSeO₃ ? 2H₂O)–ahlfeldite (NiSeO₃ ? 2H₂O) series have been synthesized and studied with a combination of X-ray diffraction, scanning electron microscopy, and the simultaneous application of thermogravimetry (TG) and differential scanning calorimetry (DSC) within the temperature range from 25 to 640°C. The complete solid solution series corresponds to the monoclinic space group P2₁/n. Unit-cell dimensions decrease in all crystallographic directions as the amount of Ni increases. The angle β increases from 98.82(1) (cobaltomenite) to 99.05(1)° (ahlfeldite). It has been established that CoSeO₃ ? 2H₂O and NiSeO₃ ? 2H₂O dehydrate at 120–340°C through two stages apparently corresponding, to the formation of intermediate hydrated species CoSeO₃ ? H₂O and NiSeO₃ ? 1/3H₂O. The reaction enthalpies for each dehydration stage of CoSeO₃ ? 2H₂O and NiSeO₃ ? 2H₂O have been determined. Changes of the unit-cell dimensions and dehydration temperatures are rationalized in terms of the Co and Ni site occupancy in the structure of the cobaltomenite–ahlfeldite solid-solution series members.  相似文献   

The thermodynamics of arsenates,selenites, and sulfates in the oxidation zone of sulfide ores. XI. Solubility of synthetic chalcomenite analog and zinc selenite at 25°C     

M. V. Charykova  V. G. Krivovichev  N. M. Ivanova  V. V. Semenova 《Geology of Ore Deposits》2015,57(8):691-698

The aim of this study is the synthesis of CuSeO₃·2H₂O (chalcomenite analog), ZnSeO₃·2H₂O, and ZnSeO₃·H₂O and the investigation of their solubility in water. CuSeO₃·2H₂O has been synthesized from solutions of Cu nitrate and Na selenite, while Zn selenites were synthesized from solutions of Zn nitrate and Na selenite. The samples obtained have been examined with X-ray diffraction and infrared and Raman spectroscopy. The solubility has been determined using the isothermal saturation method in ampoules at 25°C. The solubility has been calculated using the Geochemist’s Workbench (GMB 9.0) software package. Solubility products have been calculated for CuSeO₃·2H₂O (10^–10.63), ZnSeO₃·2H₂O (10^–8.35), and ZnSeO₃·H₂O (10^–7.96). The database used comprises thermodynamic characteristics of 46 elements, 47 base particles, 48 redox pairs, 551 particles in solution, and 624 solid phases. The Eh–pH diagrams of the Zn–Se–H₂O and Cu–Se–H₂O systems were plotted for the average contents of these elements in underground water in oxidation zones of sulfide deposits.  相似文献   

The droughts of 1997 and 2005 in Amazonia: floodplain hydrology and its potential ecological and human impacts     

Javier Tomasella  Patrícia F. Pinho  Laura S. Borma  José A. Marengo  Carlos A. Nobre  Olga R. F. O. Bittencourt  Maria C. R. Prado  Daniel A. Rodriguez  Luz A. Cuartas 《Climatic change》2013,116(3-4):723-746

It is well known that most of the severe droughts in Amazonia, such as that of 1997, are El Niño-related. However, in 2005, the Amazon was affected by a severe drought that was not El Niño-related, as most of the rainfall anomalies that have happened in southwestern Amazonia are driven by sea surface temperature anomalies in the tropical North Atlantic. Earlier studies have analyzed both droughts in terms of their meteorological causes and impacts in terra firme (non-flooded) forests. This study compares the hydrological effects of both droughts on the Amazonian floodplain and discusses their potential ecological and human impacts based on an extensive literature review. The results revealed that the effects of the 2005 drought were exacerbated because rainfall was lower and evaporation rates were higher at the peak of the dry season compared to the 1997 drought. This induced a more acute depletion of water levels in floodplain lakes and was most likely associated with higher fish mortality rates. Based on the fact that the stem growth of many floodplain species is related to the length of the non-flooded period, it is hypothesized that the 1997 drought had more positive effects on floodplain forest growth than the 2005 drought. The fishing community of Silves in central Amazonia considered both droughts to have been equally severe. However, the 2005 drought was widely broadcasted by the press; therefore, the governmental mitigation efforts were more comprehensive. It is suggested that the availability of new communication technology and greater public awareness regarding environmental issues, combined with the new legal framework for assessing the severity of calamities in Brazil, are among the primary factors that explain the difference in societal response between the two droughts.  相似文献   

Apparent Solar Tornado-Like Prominences     

Olga Panasenco  Sara F. Martin  Marco Velli 《Solar physics》2014,289(2):603-622

Recent high-resolution observations from the Solar Dynamics Observatory (SDO) have reawakened interest in the old and fascinating phenomenon of solar tornado-like prominences. This class of prominences was first introduced by Pettit (Astrophys. J. 76, 9, 1932), who studied them over many years. Observations of tornado prominences similar to the ones seen by SDO had already been documented by Secchi (Le Soleil, 1877). High-resolution and high-cadence multiwavelength data obtained by SDO reveal that the tornado-like appearance of these prominences is mainly an illusion due to projection effects. We discuss two different cases where prominences on the limb might appear to have a tornado-like behavior. One case of apparent vortical motions in prominence spines and barbs arises from the (mostly) 2D counterstreaming plasma motion along the prominence spine and barbs together with oscillations along individual threads. The other case of apparent rotational motion is observed in a prominence cavity and results from the 3D plasma motion along the writhed magnetic fields inside and along the prominence cavity as seen projected on the limb. Thus, the “tornado” impression results either from counterstreaming and oscillations or from the projection on the plane of the sky of plasma motion along magnetic-field lines, rather than from a true vortical motion around an (apparent) vertical or horizontal axis. We discuss the link between tornado-like prominences, filament barbs, and photospheric vortices at their base.  相似文献   

A multi-proxy approach for revealing recent climatic changes in the Russian Altai   总被引：2，自引：0，他引：2  

Olga V. Sidorova  Matthias Saurer  Vladimir S. Myglan  Anja Eichler  Margit Schwikowski  Aleksander V. Kirdyanov  Marina V. Bryukhanova  Oksana V. Gerasimova  Ivan A. Kalugin  Andrey V. Daryin  Rolf T. W. Siegwolf 《Climate Dynamics》2012,38(1-2):175-188

For the first time we present a multi-proxy data set for the Russian Altai, consisting of Siberian larch tree-ring width (TRW), latewood density (MXD), δ¹³C and δ¹⁸O in cellulose chronologies obtained for the period 1779–2007 and cell wall thickness (CWT) for 1900–2008. All of these parameters agree well between each other in the high-frequency variability, while the low-frequency climate information shows systematic differences. The correlation analysis with temperature and precipitation data from the closest weather station and gridded data revealed that annual TRW, MXD, CWT, and δ¹³C data contain a strong summer temperature signal, while δ¹⁸O in cellulose represents a mixed summer and winter temperature and precipitation signal. The temperature and precipitation reconstructions from the Belukha ice core and Teletskoe lake sediments were used to investigate the correspondence of different independent proxies. Low frequency patterns in TRW and δ¹³C chronologies are consistent with temperature reconstructions from nearby Belukha ice core and Teletskoe lake sediments showing a pronounced warming trend in the last century. Their combination could be used for the regional temperature reconstruction. The long-term δ¹⁸O trend agrees with the precipitation reconstruction from the Teletskoe lake sediment indicating more humid conditions during the twentieth century. Therefore, these two proxies could be combined for the precipitation reconstruction.  相似文献   

Spatial and temporal variability of the frequency of extreme daily rainfall regime in the La Plata Basin during the 20th century   总被引：1，自引：1，他引：0  

Olga C. Penalba  Federico A. Robledo 《Climatic change》2010,98(3-4):531-550

We analyzed trends, interdecadal variability, and the quantification of the changes in the frequency of daily rainfall for two thresholds: 0.1 mm and percentile 75th, using high quality daily series from 52 stations in the La Plata Basin (LPB). We observed increases in the annual frequencies in spatially coherent areas. This coherence was more marked in austral summer, autumn, and spring, during which the greatest increases occurred in southern Brazil, especially during extreme events. In winter, the low and middle basins of the Río Uruguay and Río Paraná showed negative trends, some of which were significant. Interdecadal variability is well defined in the region with more pronounced positive jumps west of the basin between 1950 and 2000. This variability was particularly more marked during periods of extreme rainfall in summer, autumn, and spring, unlike in winter when extreme daily rainfall in the lower Rio Paraná basin decreased by up to 60%. The changes in the past century during extreme rainfall produced modifications in the annual rainfall cycle. The annual cycle of both indices was broader during the last period which is mainly explained by the strong decreases in winter.  相似文献   

Fractionation analysis of transport engine-generated soot particles with respect to hygroscopicity     

Elena D. Kireeva  Olga B. Popovicheva  Natalia M. Persiantseva  Mikhail A. Timofeyev  Natalia K. Shonija 《Journal of Atmospheric Chemistry》2009,64(2-3):129-147

Combustion-derived particles emitted by various transport engines are analyzed with respect to their morphology and composition. Soot particles collected behind an aircraft gas turbine engine combustor, in the diesel engine exhaust pipe, and at the end of ship pipe demonstrate heterogeneous morphological structures and different chemical identities. Individual particle analysis allows the characterization of emitted soot particles into three fractions, namely C-O, C-O-S, and Fe-C-O, with the dominant presence of chain soot agglomerates, irregular internally mixed soot, and particles of distinct morphology, respectively. The influence of oxygen and sulfur concentrations on the ability of soot to uptake water is proposed as a method for categorizing transport engine-generated particles. Categories of hydrophobic and hydrophilic particles within non-hygroscopic soots can be defined based on the amount of water uptake relative to several reference laboratory-made soots comparable to transport engine emissions. This method of characterizing hydrophobic/hydrophilic and hygroscopic soots in combustion emissions will help to determine the potential impacts of the combustion emissions on CCN/IN formation in the atmosphere.  相似文献   

Galactic synchrotron emission according to the data of the RZF survey conducted at the RATAN-600 radio telescope     

T. A. Semenova  N. N. Bursov  Yu. N. Parijskij 《Astrophysical Bulletin》2009,64(3):270-275

Deep 1–49 cm surveys of the circumzenithal sky area performed using the RATAN-600 radio telescope allowed the spectral index of Galactic synchrotron emission in the 7.6–49 cm wavelength interval to be refined. The data obtained are inconsistent with the model of synchrotron emission adopted to interpret the results of the first year of the WMAP mission, which led to the hypothesis of the early secondary ionization of the Universe at redshifts Z > 10–30. New observations made with the RATAN-600 demonstrated the possibility of deep studies of the intensity and polarization of the microwave background (the E component) in ground-based experiments at short centimeter wavelengths. Galactic synchrotron emission may as well limit the possibilities of space- and ground-based studies of the polarization of cosmic microwave background radiation arising as a result of scattering induced by relic gravitational waves (the B component). The sky area studied with the RATAN-600 is intended to be used to interpret the PLANCK mission data in order to ensure a more detailed account of the role of the Galactic synchrotron emission.  相似文献   

Present rate of uplift in Fennoscandia from GRACE and absolute gravimetry   总被引：2，自引：0，他引：2  

Holger Steffen  Olga Gitlein  Heiner Denker  Jürgen Müller  Ludger Timmen 《Tectonophysics》2009,474(1-2):69

Fennoscandia is a key region for studying effects of glacial isostatic adjustment. The associated mass variations can be detected by the Gravity Recovery and Climate Experiment (GRACE) satellite mission, which observes the Earth's gravity field since April 2002, as well as by absolute gravimetry field campaigns. Since 2003, annual absolute gravity (AG) measurements have been performed in Fennoscandia by the Institut für Erdmessung (IfE, Institute of Geodesy) of the Leibniz Universität Hannover, Germany, within a multi-national cooperation. This offers a unique opportunity for validation and evaluation of the GRACE results. In this preliminary study, the GRACE results are compared to secular gravity changes based on the surveys from 2004 to 2007 with the FG5-220 gravimeter of the IfE.The results from GRACE monthly solutions provided by different analysis centres show temporal gravity variations in Fennoscandia. The included secular variations are in good agreement with former studies. The uplift centre is located west of the Bothnian Bay, the whole uplift area comprises Northern Europe. Nevertheless, the differences between the GRACE solutions are larger than expected and the different centre-specific processing techniques have a very strong effect on possible interpretations of GRACE results. The comparison of GRACE to the AG measurements reveals that the determined trends fit well with results from GRACE at selected stations, especially for the solution provided by the GFZ. Variations of land hydrology clearly influence results from GRACE and the AG measurements.  相似文献   

Estimating masses of selected stars in the Pulkovo program by means of astrometry methods     

Natalia A.Shakht  Denis L.Gorshanov  Olga O.Vasilkova 《天文和天体物理学研究(英文版)》2018,(8)

Stars in the Pulkovo Observatory program are observed with a 65-cm refractor during many years to study their positions and movements. We present examples of two visual binary stars, for which orbits and masses of components were determined, and two astrometric stars, for which masses of their unseen companions were estimated. The first two stars are ADS 14636(61 Cygni) and ADS 7251,and the others are Gliese 623 and ADS 8035(Alpha UMa). Direct astrometric methods are used for estimation of mass-ratio and masses.  相似文献