Contamination of Silurian volcanic rocks in the Tagil synform by Precambrian zircon     

V. N. Puchkov  O. M. Rosen  D. Z. Zhuravlev  E. V. Bibikova 《Doklady Earth Sciences》2006,411(2):1381-1384

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A way to synchronize models with seismic faults for earthquake forecasting: Insights from a simple stochastic model     

lvaro Gonzlez  Miguel Vzquez-Prada  Javier B. Gmez  Amalio F. Pacheco 《Tectonophysics》2006,424(3-4):319

Numerical models are starting to be used for determining the future behaviour of seismic faults and fault networks. Their final goal would be to forecast future large earthquakes. In order to use them for this task, it is necessary to synchronize each model with the current status of the actual fault or fault network it simulates (just as, for example, meteorologists synchronize their models with the atmosphere by incorporating current atmospheric data in them). However, lithospheric dynamics is largely unobservable: important parameters cannot (or can rarely) be measured in Nature. Earthquakes, though, provide indirect but measurable clues of the stress and strain status in the lithosphere, which should be helpful for the synchronization of the models.The rupture area is one of the measurable parameters of earthquakes. Here we explore how it can be used to at least synchronize fault models between themselves and forecast synthetic earthquakes. Our purpose here is to forecast synthetic earthquakes in a simple but stochastic (random) fault model. By imposing the rupture area of the synthetic earthquakes of this model on other models, the latter become partially synchronized with the first one. We use these partially synchronized models to successfully forecast most of the largest earthquakes generated by the first model. This forecasting strategy outperforms others that only take into account the earthquake series. Our results suggest that probably a good way to synchronize more detailed models with real faults is to force them to reproduce the sequence of previous earthquake ruptures on the faults. This hypothesis could be tested in the future with more detailed models and actual seismic data.  相似文献   

Modified column flotation of adsorbing iron hydroxide colloidal precipitates     

F. Capponi  M. SartoriM.L. Souza  J. Rubio 《International Journal of Mineral Processing》2006

A promising technique for the removal of heavy metal ions from wastewater streams involved firstly the ions adsorption on a colloidal precipitate (carrier) and then the separation of the loaded flocs (coagula) by a modified column flotation. Here, the effluent feed and the carrier (ferric hydroxide) enter smoothly by the top of the column through a special diffuser, in counter current with rising bubbles (100–600 μm diameter) generated by using recycled water, surfactant and air suction through a venturi. High separation values of the column flotation of the carrier precipitates were achieved, despite the high superficial flow rate and the high Fe^+ 3 concentration utilized (> 60 mg L^− 1 Fe). No rupture of colloidal carrier aggregates was observed and a low split was ensured by monitoring the concentrate (floated product) flow rate. Results indicated that best separation was attained by controlling the medium pH (for best heavy metal ion adsorption onto the carrier), followed by sodium oleate, used as “collector” and optimizing operating parameters (conditioning, flow rates, etc.). The column throughput reached 43 m h^− 1 (m³ m^− 2 h^− 1), which is about 4 times the normal capacity of DAF-dissolved air flotation unit, the most used floater in wastewater treatment. Various metals (Cu, Ni, Pb, etc.) and molybdate ions present in synthetic and real effluent were successfully removed based on this colloidal adsorbing flotation principle. The process was also applied in a pilot scale to treat an industrial electroplating wastewater. Most of toxic metals (Cu, Ni and Zn) were reduced from initial concentrations of about of 2 to 10 mg L^− 1, to below 0.5 to 1.0 mg L^− 1, meeting local municipal discharge limits (but Cd ions). It is believed that flotation separation using medium-sized bubbles has great potential as a clean water and wastewater treatment technology.  相似文献   

Radiolaria – Siliceous plankton through time     

Peter O. Baumgartner 《Swiss Journal of Geoscience》2006,99(1):III-V

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Tracking recorded fires using charcoal morphology from the sedimentary sequence of Prosser Lake, British Columbia (Canada)     

Mihaela D. Enache  Brian F. Cumming 《Quaternary Research》2006,65(2):282-292

Quantitative analyses of variations in morphological features of charcoal were undertaken in a ²¹⁰Pb-dated sediment core from Prosser Lake (British Columbia, Canada). Seven morphological types of charcoal were defined by particle shape, major-minor axis ratio, apparent porosity and progradation to unburned material. The distribution of morphotypes and total charcoal abundances were assessed as a proxy for fire events recorded between 1919 and 2000 and to subsequent mechanisms of transportation-sedimentation to lake sediments. Charcoal morphotypes showed distinct relationships to recorded area burned by fires. Fragile charcoal fragments with highly irregular porosity (termed Type M) displayed the strongest correlation to burned area (r² = 0.51; P = 0.0001) and did not produce any false-positive signal for fires recorded within a radius of 20 km around the lake. We infer that high porosity and low density Type M fragments are aerially transported and directly deposited on the lake, and that the fragility of Type M charcoal prevents significant quantities from being secondarily transported and incorporated into the sedimentary record. We propose that charcoal morphology is an important but underutilized technique that can yield important insights into fire type, proximity and transportation-sedimentation processes.  相似文献   

Middle Weichselian environments on western Yamal Peninsula, Kara Sea based on pollen records     

Andrei A. Andreev  Steven L. Forman  William F. Manley 《Quaternary Research》2006,65(2):275-281

Pollen data from two sections from a coastal cliff on the western Yamal Peninsula (69°43.27′N, 66°48.80′E) document the environmental history during the Karginsky (Middle Weichselian) interstadial. Low pollen concentrations, high amounts of redeposited pollen, and relatively high presence of Artemisia pollen characterize sediments deposited at about 33,000 ¹⁴C yr B.P. Grass-sedge plant associations with few other herbs occupied the area during the late Karginsky interstadial. Artemisia pollen may indicate rather xerophytic vegetation and disturbed soils in the area. The dominance of redeposited pollen reflects scarce (disturbed) vegetation cover and low pollen productivity. The climate was relatively cold and dry. Sediments dated to 32,400 ¹⁴C yr B.P. contain fewer redeposited pollen and concentration of non-redeposited pollen is significantly higher. Pollen contents indicate the dominance of tundra-like grass-sedge vegetation and more humid conditions. Pollen records dated between 30,100 and 25,100 ¹⁴C yr B.P. also reflect scarce tundra-like vegetation during this interval. The presence of Betula nana and Salix pollen may reflect limited presence of shrub communities. This suggests that the climate was somewhat warmer during the latter part of the interstadial. However, generally the pollen records show that harsh environmental conditions prevailed on the Yamal Peninsula during the Karginsky interstadial.  相似文献   

The simultaneous use of piles and prestressed anchors in foundation design     

F.A.B. Danziger  B.R. Danziger  M.P. Pacheco   《Engineering Geology》2006,87(3-4):163-177

The paper presents a simplified design procedure to evaluate the loads in piles and prestressed anchors when simultaneously used in foundations under tension loads and high overturning moments. Although involving some necessary simplifications for the sake of design, the procedure keeps the main features of load transfer from piles and anchors to the surrounding soil. The approximate method has been adopted by the authors in relevant projects in Brazil, whose long term satisfactory performance indicates its appropriate performance. Two practical examples have been selected to illustrate the application of the proposed method. It is shown that anchor prestressing plays an important role in limiting tension loads on the piles and controlling foundation eccentricity. The importance of monitoring for replacement of occasional prestress losses to prevent long-term pile overstressing is illustrated.  相似文献   

Formation of a protoplanetary system through the merging of binary components that are contracting towards the main sequence     

F. V. Sirotkin  V. G. Karetnikov 《Astronomy Reports》2006,50(8):655-663

We have carried out three-dimensional hydrodynamical modeling of the formation of planets through the merging of a binary system comprised of low-mass (～0.5–1 M_⊙) stars in the stage of contracting towards the main sequence. Under certain conditions, the disruption of the more massive component results in the formation of an expanding disk and extended arm. The fragmentation of this arm leads to the formation of planetary-mass clouds (<5 M _J where M _J is the mass of Jupiter), whose orbits can have semimajor axes of 0.4 to 5 AU and substantial (～0.5) eccentricities.  相似文献   

Giant swarms of Precambrian mafic dikes and potential diamond resources of ancient platforms     

M. Z. Glukhovsky 《Geotectonics》2006,40(1):11-24

By the examples of the Siberian Platform and Canadian Shield, it is shown that spatial juxtaposition of Phanerozoic diamond-bearing kimberlite fields with giant swarms of Precambrian mafic dikes is caused by both systematic and incidental events. The first of these include (1) origination of mantle plumes and associated lenses of high-temperature mantle melting in the subequatorial “hot belt” of the early Earth, (2) formation of magma chambers that generated mafic dikes in these asthenospheric lenses, (3) shear stress, and (4) ultrahigh-pressure metamorphism of igneous and country rocks. As a result, the association of diamond-bearing high-density mafic and ultramafic rocks was formed under favorable thermal and fluidal conditions. These processes occurred first in the embryonic (multiplate) Neoarchean tectonic setting at a depth of 40–60 km (present-day elevation marks) and then at a deeper (100–150 km) level during the transition to the Proterozoic true plate tectonics. These processes left behind giant swarms of Precambrian mafic dikes, as well as structurally and genetically related deep-seated morphological and density anomalies. The relatively high position of two lithospheric units of diamond-bearing rocks, each underlain by a thick layer of the cold mantle, prevented these units from thermal and mechanical erosion during subsequent plate-tectonic stages characterized by deeper location of asthenospheric layers. The occurrence of clusters of Phanerozoic diatremes in ancient giant swarms of mafic dikes, as well as the enrichment of pipes in xenogenic diamond-bearing material derived from different levels of the tectonically delaminated lithosphere, may be attributed to incidental events that controlled the fertility of a relatively small number of kimberlite pipes.  相似文献   

Microvariability of line profiles in the spectrum of the star ι Her     

A. F. Kholtygin  G. A. Galazutdinov  T. E. Burlakova  G. G. Valyavin  S. N. Fabrika  B. -C. Lee 《Astronomy Reports》2006,50(3):220-231

We present the results of a search for and analysis of line-profile variations in the spectrum of the star ι Her. The observations were acquired with the 1.8 m telescope of the Bohyunsan Optical Astronomy Observatory (Republic of Korea) in May–June 2004. We obtained 69 spectra of the star with signal-to-noise ratios ≈300 and a time resolution of 5–7 min. Profile variability was revealed for six lines of HI, HeI, and SiIII, in the central parts of the lines. The variability amplitude is ≈(1–2)% in units of the intensity of the adjacent continuum. Evidence was found for cyclic variations of the lines, with periods from ≈7^h to ≈2.9^d. We conclude that ι Her belongs to the group of slowly pulsating stars.  相似文献