Acoustic backscattering by Atlantic mackerel as being representative of fish that lack a swimbladder. Backscattering by individual fish   总被引：1，自引：0，他引：1  

Gorska  Natalia; Ona  Egil; Korneliussen  Rolf 《ICES Journal of Marine Science》2005,62(5):984-995

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Scaling features of ambient noise at different levels of local seismic activity: A case study for the Oni seismic station     

Teimuraz Matcharashvili  Tamaz Chelidze  Zurab Javakhishvili  Nato Jorjiashvili  Natalia Zhukova 《Acta Geophysica》2012,60(3):809-832

Investigation of dynamical features of ambient seismic noise is one of the important scientific and practical research challenges. We investigated scaling features of the ambient noises at the Oni seismic station, Georgia, using detrended fluctuation analysis method. Data from this seismic station, located in the epicentral zone of Oni M6.0, 2009, earthquake, were selected to include time periods with different levels of local seismic activity.  相似文献   

Biogenic silica in wetlands and their relationship with soil and groundwater biogeochemistry in the Southeastern of Buenos Aires Province,Argentina     

Natalia Borrelli  M. Osterrieth  A. Romanelli  M. F. Alvarez  J. L. Cionchi  H. Massone 《Environmental Earth Sciences》2012,65(2):469-480

Although phytoliths constitute part of the wetland suspended load, there are few studies focused on the quantification of them in the biogenic silica (BSi) pool. So, the aim of this paper is both to determine BSi content (diatoms and phytoliths) and its relationship with dissolved silica in surface waters, and the influence of soil and groundwater Si biogeochemistry in Los Padres wetland (Buenos Aires Province, Argentina). In the basin of the Los Padres wetland, dissolved silica (DSi) concentration is near 840 ± 232 μmol/L and 211.83 ± 275.92 μmol/L in groundwaters and surface waters, respectively. BSi represents an 5.6–22.1% of the total suspension material, and 8–34% of the total mineralogical components of the wetland bottom sediments. DSi and BSi vary seasonally, with highest BSi content (diatoms specifically) during the spring–summer in correlation to the lowest DSi concentration. DSi (660–917.5 μmol/L) and phytolith (3.35–5.84%) concentrations in the inflow stream are higher than in the wetland and its outflow stream (19.1–113 μmol/L; 0.45–3.2%, respectively), probably due to the high phytolith content in soils, the high silica concentration in the soil solution, and the groundwater inflow. Diatom content (5–16.8%) in the wetland and its outflow stream is higher than in the inflow stream (0.45–1.97%), controlling DSi in this system. The understanding of the groundwater–surface water interaction in an area is a significant element for determining the different components and the role that they play on the local biogeochemical cycle of Si.  相似文献   

Shock experiments in support of the Lithopanspermia theory: The influence of host rock composition,temperature, and shock pressure on the survival rate of endolithic and epilithic microorganisms     

Cornelia MEYER  Jörg FRITZ  Martin MISGAISKI  Dieter STÖFFLER  Natalia A. ARTEMIEVA  Ulrich HORNEMANN  Ralf MOELLER  Jean‐Pierre De VERA  Charles COCKELL  Gerda HORNECK  Sieglinde OTT  Elke RABBOW 《Meteoritics & planetary science》2011,46(5):701-718

Abstract– Shock recovery experiments were performed with an explosive set‐up in which three types of microorganisms embedded in various types of host rocks were exposed to strong shock waves with pressure pulse lengths of lower than 0.5 μs: spores of the bacterium Bacillus subtilis, Xanthoria elegans lichens, and cells of the cyanobacterium Chroococcidiopsis sp. 029. In these experiments, three fundamental parameters were systematically varied (1) shock pressures ranging from 5 to 50 GPa, (2) preshock ambient temperature of 293, 233 and 193 K, and (3) the type of host rock, including nonporous igneous rocks (gabbro and dunite as analogs for the Martian shergottites and chassignites, respectively), porous sandstone, rock salt (halite), and a clay‐rich mineral mixture as porous analogs for dry and water‐saturated Martian regolith. The results show that the three parameters have a strong influence on the survival rates of the microorganisms. The most favorable conditions for the impact ejection from Mars for microorganisms would be (1) low porosity host rocks, (2) pressures <10–20 GPa, and (3) low ambient temperature of target rocks during impact. All tested microorganisms were capable of surviving to a certain extent impact ejection in different geological materials under distinct conditions.  相似文献   

Raman study of MgCO3–FeCO3 carbonate solid solution at high pressures up to 55 GPa     

Anna Spivak  Natalia Solopova  Valerio Cerantola  Elena Bykova  Egor Zakharchenko  Leonid Dubrovinsky  Yuriy Litvin 《Physics and Chemistry of Minerals》2014,41(8):633-638

Magnesite, siderite and ferromagnesites Mg_1?x Fe _x CO₃ (x = 0.05, 0.09, 0.2, 0.4) were characterized using in situ Raman spectroscopy at high pressures up to 55 GPa. For the Mg–Fe-carbonates, the Raman peak positions of six modes (T, L, ν₄, ν₁, ν₃ and 2ν₂) in the dependence of iron content in the carbonates at ambient conditions are presented. High-pressure Raman spectroscopy shows that siderite undergoes a spin transition at ~40 GPa. The examination of the solid solutions with compositions Mg_0.6Fe_0.4CO₃, Mg_0.8Fe_0.2CO₃, Mg_0.91Fe_0.09CO₃ and Mg_0.95Fe_0.05CO₃ indicates that with increase in the amount of the Fe spin transition pressure increases up to ~45 GPa.  相似文献   

Effect of Ecological Factors on the Distribution of Microorganisms in Regosols (Steppe of Priol’khonie, Siberia)     

Olga LOPATOVSKAYA  Anna SEREDKINA  Natalia BELKOVA 《《地质学报》英文版》2014,88(Z1):188-190

正1 Introduction Regosol in Eastern Siberia is intrazonal soil.In Priolkhonie region it occurs among chestnut soils,salt marshes and solonetzes.There are small information about Tagotskij hydrolaccolith in the research articles of geologists,archaeologists,and paleolimnologists when  相似文献   

Formation and age of sphalerite mineralization in carbonate rocks of Bajocian age in the Swiss Jura Mountains: evidence of Mesozoic hydrothermal activity     

Natalia Efimenko  Jens Schneider  Jorge E. Spangenberg  Massimo Chiaradia  Thierry Adatte  Karl B. Föllmi 《International Journal of Earth Sciences》2014,103(4):1059-1082

A combination of petrographic and geochemical techniques was applied to better constrain the origin and evolution of the fluid systems responsible for the formation of disseminated, Cd-rich (up to 0.6 wt%), sphalerite (ZnS) mineralization in the northeastern part of the Jura Mountains, Switzerland. The Rb–Sr ages of sphalerite samples indicate that a main phase of sphalerite formation occurred near the boundary between the late Middle and early Late Jurassic, at around 162 Ma. The negative δ³⁴S values (?22.3 to ?5.3 ‰) suggest that biogenic sulfide sulfur was involved in ZnS precipitation. The strontium isotope composition is more radiogenic than that of contemporaneous seawater, reflecting the interaction of mineralizing fluids with silicate rocks. Lead isotope signatures are very uniform (²⁰⁶Pb^/204Pb = 18.63–18.67, ²⁰⁷Pb^/204Pb = 15.63–15.64, ²⁰⁸Pb^/204Pb = 38.51–38.63), indicating an isotopically well-homogenized fluid system. The basement rocks underlying the Jurassic strata are considered to be the main source of metals for the sphalerite mineralization. The migration of deep-sourced hydrothermal saline metal-bearing fluids into the Bajocian host carbonates containing sedimentary reduced sulfur resulted in the precipitation of sulfides. The period of sphalerite formation near the Middle–Late Jurassic boundary is characterized by enhanced tectonic and hydrothermal activity in Europe, related to the opening of the Central Atlantic and tectonic/thermal subsidence during spreading of the Alpine Tethys. Our study provides evidence that the Bajocian carbonate rocks in the Jura Mountains area were affected by the circulation of deep-sourced metal-bearing hydrothermal fluids in response to these continent-wide tectonothermal events. The presence of sphalerite mineralization and associated geochemical anomalies in Zn and Cd contents in carbonate rocks may also be used to trace basement features.  相似文献   

Paleomagnetic study of NeoArchean–Paleoproterozoic dykes in the Kaapvaal Craton     

Natalia Lubnina  Richard Ernst  Martin Klausen  Ulf Söderlund 《Precambrian Research》2010

431 oriented samples were collected from 27 dolerite dykes at 17 sites, belonging to 2.95, 2.65, and 1.90 Ga swarms, that trend SE, E and NE, respectively from the Bushveld Igneous Complex into the eastern Kaapvaal Craton (ages determined by Olsson et al., 2010; Olsson in Söderlund et al., 2010). Samples were analyzed for paleomagnetism and also anisotropy of magnetic susceptibility (AMS). For the 2.95 Ga SE-trending dykes high temperature/coercivity ‘P’ component has unblocking temperatures up to 590 °C and coercivity 40–90 mT and demonstrate SSW declination and intermediate positive inclination. Based on positive contact and conglomerate tests we argue for a primary origin of this component. The paleopole (BAD), calculated from ‘P’ component, does not correspond to any of the previously obtained Archean–Paleoproterozoic paleopoles for the Kaapvaal Craton, and represents a new key pole for 2.95 Ga. The high-coercivity ‘H’ component for the 2.65 Ga-old E-trending dykes has a SSW declination and steep positive inclination. Paleomagnetic pole (RYK), recalculated from this component, is close to the paleopoles, obtained by Wingate (1998) and Strik et al. (2007) for 2.78 Ga Ventersdorp volcanics. The third group, NE-trending dykes of the 1.90 Ga Black Hill swarm demonstrate an ‘M’ component with dual polarity high-coercivity component with SSE-declination and negative intermediate inclination. The paleopole (BHD), calculated from this component is close to the 1.87 Ga pole of the Kaapvaal Craton obtained by Hanson et al. (2004). Overprint directions include a very well developed thermo-chemical overprint (Dec = 329° Inc = −36°), which is believed to be associated with a ∼0.18 Ga regional ‘Karoo’ thermal event.  相似文献   

The evolution of the Onaping Formation at the Sudbury impact structure     

Richard A. F. GRIEVE  Doreen E. AMES  Joanna V. MORGAN  Natalia ARTEMIEVA 《Meteoritics & planetary science》2010,45(5):759-782

Abstract– The 1.4–1.6 km thick Onaping Formation consists of a complex series of breccias and “melt bodies” lying above the Sudbury Igneous Complex (SIC) at the Sudbury impact structure. Based on the presence of shocked lithic clasts and various “glassy” phases, the Onaping has been described as a “suevitic” breccia, with an origin, at least in part, as fallback material. Recent mapping and a redefined stratigraphy have emphasized similarities and differences in its various vitric phases, both as clast types and discrete intrusive bodies. The nature of the Onaping and that of other “suevitic” breccias overlying impact melt sheets is reviewed. The relative thickness, internal stratigraphic and lithological character, and the relative chronology of depositional units indicate multiple processes were involved over some time in the formation of the Onaping. The Sudbury structure formed in a foreland basin and water played an essential role in the evolution of the Onaping, as indicated by a major hydrothermal system generated during its formation. Taken together, observations and interpretations of the Onaping suggest a working hypothesis for the origin of the Onaping that includes not only impact but also the interaction of sea water with the impact melt, resulting in repeated explosive interactions involving proto‐SIC materials and mixing with pre‐existing lithologies. This is complicated by additional brecciation events due to the intrusion of proto‐SIC materials into the evolving and thickening Onaping. Fragmentation mechanisms changed as the system evolved and involved vesiculation in the formation of the upper two‐thirds of the Onaping.  相似文献   

On the Rees–Sciama effect: maps and statistics     

N. Puchades  M. J. Fullana  J. V. Arnau  D. Sáez 《Monthly notices of the Royal Astronomical Society》2006,370(4):1849-1858

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