Time-spectra of chromospheric activity of old solar-type stars: detection of rotational signals from double wavelet analysis     

Peter Frick  Willie Soon  Elena Popova  Sallie Baliunas   《New Astronomy》2004,9(8):599-609

We introduce a novel technique, called the double wavelet analysis (DWA), for the determination of stellar rotation periods from time serial data. This first paper aims narrowly at the discussion, introduction and application of the DWA technique to records of surface magnetism in solar-type (relatively old) lower main sequence stars that are obtained by the Mount Wilson Observatory (MWO) HK Project. The technique takes a series of careful steps that seek to optimize wavelet parameters and normalization schemes, ultimately allowing fine-tuned, arguably more accurate, estimates of rotation-modulated signals (with, e.g., periods of days to months) in records that contain longer periodicities such as stellar magnetic activity cycles (with, e.g., period of years). The apparent rotation periods estimated from the DWA technique are generally consistent with results from both “first-pass” (i.e., ordinary) global wavelet spectrum and earlier classical periodogram analyses. But there are surprises as well. For example, the rotation period of the ancient subdwarf Goombridge 1830 (HD 103095), previously identified as ≈31 days, suggests under the DWA technique a significantly slower period of 60 days. DWA spectra also generally reveal a shift in the cycle period toward high frequencies (hence shorter periods) compared to the first-pass wavelet spectrum. For solar-type stars analyzed here, the character of the DWA spectrum and slope of the first-pass global wavelet spectrum produce a classification scheme that allows a star's record to be placed into one of three categories.  相似文献   

Gamma-ray burst afterglow emission with a decaying magnetic field     

Elena Rossi  M. J. Rees 《Monthly notices of the Royal Astronomical Society》2003,339(3):881-886

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Constraints on the cosmic neutrino background     

Elena Pierpaoli 《Monthly notices of the Royal Astronomical Society》2003,342(4):L63-L66

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Chemical composition and osmium-isotope systematics of primary and secondary PGM assemblages from high-Mg chromitite of the Nurali lherzolite massif,the South Urals,Russia     

K. N. Malitch  E. V. Anikina  I. Yu. Badanina  E. A. Belousova  E. V. Pushkarev  V. V. Khiller 《Geology of Ore Deposits》2016,58(1):1-19

The isotopic and geochemical characteristics of PGE mineralization in high-Mg chromitite from the banded dunite–wehrlite–clinopyroxenite complex of the Nurali lherzolite massif, the South Urals, Russia is characterized for the first time. Electron microprobe analysis and LA MC-ICP-MS mass spectrometry are used for studying Cr-spinel and platinum-group minerals (PGM). Two processes synchronously develop in high-Mg chromitite subject to metamorphism: (1) the replacement of Mg–Al-rich Cr-spinel, orthopyroxene, and diopside by chromite, Cr-amphibole, chlorite, and garnet; (2) the formation of a secondary mineral assemblage consisting of finely dispersed ruthenium or Ru-hexaferrum aggregate and silicate–oxide or silicate matter on the location of primary Ru–Os-sulfides of the laurite–erlichmanite solid solution series. Similar variations of Os-isotopic composition in both primary and secondary PGM assemblages are evidence for the high stability of the Os isotope system in PGM and for the possibility of using model ¹⁸⁷Os/¹⁸⁸Os ages in geodynamic reconstructions.  相似文献   

Geologically controlled bi-directional exchange of groundwater with a hypersaline lake in the Canadian prairies     

Laurence R. Bentley  Masaki Hayashi  Elena P. Zimmerman  Chris Holmden  Lynn I. Kelley 《Hydrogeology Journal》2016,24(4):877-892

Hypersaline lakes occur in hydrologically closed basins due to evaporitic enrichment of dissolved salts transported to the lakes by surface water and groundwater. At the hypersaline Lydden Lake in Saskatchewan, Canada, groundwater/lake-water interaction is strongly influenced by the geological heterogeneity of glacial deposits, whereby a highly permeable glaciofluvial sand/gravel deposit is underlain by glaciolacustrine deposits consisting of dense clay interspersed with silt/sand lenses. Pressure head distribution in a near shore area indicates a bi-directional flow system. It consists of topographically driven flow of fresh groundwater towards the lake in the sand/gravel aquifer and density-driven, landward flow of saline groundwater in the underlying glaciolacustrine deposits. Electrical resistivity tomography, and chemical and isotopic composition of groundwater clearly show the landward intrusion of saline water in the heterogeneous unit. The feasibility of bi-directional flow and transport is supported by numerical simulations of density-coupled groundwater flow and transport. The results suggest that the geologically controlled groundwater exchange processes have substantial influences on both inputs and outputs of dissolved minerals in hypersaline lakes in closed basins.  相似文献   

A combined-water-system approach for tackling water scarcity: application to the Permilovo groundwater basin,Russia   总被引：1，自引：1，他引：0  

Elena A. Filimonova  Mikhail G. Baldenkov 《Hydrogeology Journal》2016,24(2):489-502

The suitability of a combined water system (CWS) is assessed for meeting drinking-water demand for the city of Arkhangelsk (northwestern Russian Federation), instead of using the polluted surface water of the Northern Dvina River. An appropriate aquifer system (Permilovo groundwater basin) was found and explored in the 1980s, and there were plans then to operate an abstraction scheme using traditional pumping methods. However, the 1980s planned water system was abandoned due to projected impermissible stream depletion such that complete interception of the cone of depression with the riverbed would cause the riverbed to become dry. The design of a CWS is now offered as an approach to addressing this environmental problem. Several sets of major pumping wells associated with the CWS are located on the banks of Vaymuga River and induce infiltration from the stream. The deficiency of the stream flow in dry seasons is compensated for by pumping from aquifer storage. A numerical model was constructed using MODFLOW-2000. The results of the simulation showed the efficiency of the compensation pumping. The streamflow depletion caused by the CWS is equal to the minimum permissible stream flow and is lower than the depletion projected by the abandoned plan. Application of the CWS in the Permilovo groundwater basin makes it possible to meet water demands during water-limited periods and to avoid environmental problems.  相似文献   

Trace element composition and Lu-Hf isotope systematics of zircon from plagiogneisses of the Kola superdeep well: Contribution of a Paleoarchean crust in Mesoarchean metavolcanic rocks     

V. R. Vetrin  E. A. Belousova  V. P. Chupin 《Geochemistry International》2016,54(1):92-111

Zircons have been studied in three samples of Archean plagiogneisses from the Kola superdeep well (SG-3). The crystals consist of cores, magmatic shells, and metamorphic rims. The cores and shells are characterized by similar lowered concentrations of most trace elements, which is typical of zircons from plagiogranitoids, rocks of elevated basicity, and basites. At a wide range of Hf isotope characteristics, the cores and shells have similar average ¹⁷⁶Hf/¹⁷⁷Hf_i, which determines the close composition of their sources. The metamorphic rims have close ¹⁷⁶Hf/¹⁷⁷Hf_i ratio. The minimum age of the crustal contaminant of parental melts is estimated at 3.4 and 3.3 Ga for cores and 3.3–3.2 Ga for shells at almost equal proportions of mantle and crustal components in them. The contribution of Paleoarchean crust established in zircons from plagiogneisses of SG-3 using Lu-Hf isotope systematics is confirmed by the presence of 3.3and 3.4-Ga old zircons in surrounding TTG.  相似文献   

Nickelpicromerite,K<Subscript>2</Subscript>Ni(SO<Subscript>4</Subscript>)<Subscript>2</Subscript>•6H<Subscript>2</Subscript>O,a new picromerite-group mineral from Slyudorudnik,South Urals,Russia     

Elena?V.?BelogubEmail author  Sergey?V.?Krivovichev  Igor?V.?Pekov  Aleksey?M.?Kuznetsov  Vasiliy?O.?Yapaskurt  Vasiliy?A.?Kotlyarov  Nikita?V.?Chukanov  Dmitry?I.?Belakovskiy 《Mineralogy and Petrology》2015,109(2):143-152

A new picromerite-group mineral, nickelpicromerite, K₂Ni(SO₄)₂?·?6H₂O (IMA 2012–053), was found at the Vein #169 of the Ufaley quartz deposit, near the town of Slyudorudnik, Kyshtym District, Chelyabinsk area, South Urals, Russia. It is a supergene mineral that occurs, with gypsum and goethite, in the fractures of slightly weathered actinolite-talc schist containing partially vermiculitized biotite and partially altered sulfides: pyrrhotite, pentlandite, millerite, pyrite and marcasite. Nickelpicromerite forms equant to short prismatic or tabular crystals up to 0.07 mm in size and anhedral grains up to 0.5 mm across, their clusters or crusts up to 1 mm. Nickelpicromerite is light greenish blue. Lustre is vitreous. Mohs hardness is 2–2½. Cleavage is distinct, parallel to {10–2}. D _meas is 2.20(2), D _calc is 2.22 g cm^?3. Nickelpicromerite is optically biaxial (+), α?=?1.486(2), β?=?1.489(2), γ?=?1.494(2), 2V_meas =75(10)°, 2V_calc =76°. The chemical composition (wt.%, electron-microprobe data) is: K₂O 20.93, MgO 0.38, FeO 0.07, NiO 16.76, SO₃ 37.20, H₂O (calc.) 24.66, total 100.00. The empirical formula, calculated based on 14 O, is: K_1.93Mg_0.04Ni_0.98S_2.02O_8.05(H₂O)_5.95. Nickelpicromerite is monoclinic, P2₁/c, a?=?6.1310(7), b?=?12.1863(14), c?=?9.0076(10) Å, β?=?105.045(2)°, V?=?649.9(1) ų, Z?=?2. Eight strongest reflections of the powder XRD pattern are [d,Å-I(hkl)]: 5.386–34(110); 4.312–46(002); 4.240–33(120); 4.085–100(012, 10–2); 3.685–85(031), 3.041–45(040, 112), 2.808–31(013, 20–2, 122), 2.368–34(13–3, 21–3, 033). Nickelpicromerite (single-crystal X-ray data, R?=?0.028) is isostructural to other picromerite-group minerals and synthetic Tutton’s salts. Its crystal structure consists of [Ni(H₂O)₆]²⁺ octahedra linked to (SO₄)^2? tetrahedra via hydrogen bonds. K⁺ cations are coordinated by eight anions. Nickelpicromerite is the product of alteration of primary sulfide minerals and the reaction of the acid Ni-sulfate solutions with biotite.  相似文献   

Resetting of the U-Pb Zircon System in Cambro-Ordovician Intrusives of the Deep Freeze Range, Northern Victoria Land, Antarctica   总被引：5，自引：0，他引：5  

Bomparola  R. M.; Ghezzo  C.; Belousova  E.; Griffin  W. L.; O'Reilly  Suzanne Y. 《Journal of Petrology》2007,48(2):327-364

A detailed in situ isotopic (U–Pb, Lu–Hf) and geochemicalstudy of zircon populations in a composite sequence of foliatedto massive Cambro-Ordovician intrusions in the Deep Freeze Range(North Victoria Land, Antarctica), has highlighted great complexityin zircon systematics. Zircons in deformed granitoids and tonalitesdisplay complex internal textures, a wide spread of concordantU–Pb ages (between 522 and 435 Ma) and unusual trace-elementcompositions (anomalous enrichment of light rare earth elements,U, Th and Y) within single zircon grains. In contrast, zirconsfrom undeformed samples display a limited range of U–Pbages and trace-element compositions. Zircons from all age andtextural populations in most of the deformed and undeformedsamples show a relatively narrow range of _Hf values, suggestingthat the Lu–Hf system remained undisturbed. Inferred emplacementages cover a time interval of about 30 Myr: from 508 to 493Ma for the oldest strongly foliated synkinematic Howard Peaksmegacrystic monzogranites and high-K calc-alkaline mafic tointermediate rocks of the ‘Corner Tonalite’ unit;from about 489 to 481 Ma for the younger massive shoshoniticmafic dyke suite and the high-K calc-alkaline Keinath granite.The observed isotopic and chemical variations in zircon areattributed to a sub-solidus recrystallization under hydrousconditions and varying temperature, in a setting characterizedby a transpressional to extensional stress regime. KEY WORDS: Antarctica; Cambro-Ordovician intrusives; Ross Orogen; zircon U–Pb geochronology  相似文献   

Formation and growth of multiple,distinct ice lenses in frost heave     

Hao Gao  Seyed Ali Ghoreishian Amiri  Signe Kjelstrup  Gustav Grimstad  Benoit Loranger  Elena Scibilia 《国际地质力学数值与分析法杂志》2023,47(1):82-105

This paper presents a fully coupled thermo-hydro-mechanical (THM) model which simulates frost heave in fully saturated soils. The model is able to simulate the formation and growth of multiple distinct ice lenses. The basic equations of the system were derived using the continuum theory of mixtures, nonequilibrium thermodynamics, and fracture mechanics, considering skeleton deformation, water flow and heat transport. Central to this model is the coupled transport of mass due to the temperature gradient across the frozen fringe, which acts as the main driving force of the phenomenon. The model is formulated in terms of measurable physical properties and thus no ad hoc parametrization is required. In an ice-lens-free state, the system is solved as a continuum using the finite element method (FEM). It is then locally treated as a discontinuous system upon the formation of ice lens, by enriching the elements carrying the embedded ice lens(es) using the extended finite element method (X-FEM). The accuracy and efficiency of the proposed model has been verified using several laboratory tests on Devon silt samples at different overburden pressures and thermal boundary conditions. Shut-off pressures have been also estimated and compared with the experimental results.  相似文献