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191.
Marek Biesiada Aleksandra Piórkowska 《Monthly notices of the Royal Astronomical Society》2009,396(2):946-950
It is generally expected that quantum gravity theory should yield the model of a space–time foam at short distances leading to Lorentz-invariance violation (LIV) manifested e.g. by energy-dependent modification of the standard relativistic dispersion relation. One direction of research, pursued intensively, is to measure the energy-dependent time-of-arrival delays in photons emitted by astrophysical sources located at cosmological distances. This is tempered, however, by our ignorance of intrinsic emission delays in different energy channels.
In this paper we discuss a test based on gravitational lensing. Monitoring time delays between images obtained in different energy channels, for example optical (low-energy) and TeV photons, may reveal extra delays due to the distorted dispersion relation typical in LIV theories, a test that is free from the systematics inherent in other settings. 相似文献
In this paper we discuss a test based on gravitational lensing. Monitoring time delays between images obtained in different energy channels, for example optical (low-energy) and TeV photons, may reveal extra delays due to the distorted dispersion relation typical in LIV theories, a test that is free from the systematics inherent in other settings. 相似文献
192.
Jan Svoren Marek Husarik Jaroslav Ambroz Jiri Drbohlav Jaroslav Medek 《Earth, Moon, and Planets》2009,105(2-4):361-365
A semi-automated photometric telescope built at the Skalnate Pleso Observatory is described. In December 2000, the 0.3-m f/5 Zeiss astrograph was replaced by a 0.61-m f/4.3 mirror telescope equipped with a CCD camera. The observing programme is created to conform to the photometry of asteroids which are suspected to be of binary nature; photometry of NEAs and MBAs; a long-term photometry for theoretical modelling of the shape of asteroids; and photometry and astrometry of active comets and asteroids. Some results concerning the binary character of the asteroids are described in the paper. 相似文献
193.
194.
In the UG2 ore (Bushveld Complex, South Africa) flotation, normally more than 3% of the gangue minerals, principally chromite with talc and pyroxene, report to the concentrate diluting the PGM recovery and contributing to subsequent processing costs. Previous studies have identified residual talc-like layers on orthopyroxene surfaces in Merensky ore flotation contributing to inadvertent flotation of relatively large particles (20–150 µm) of this mineral. Chromite (75–150 µm) from flotation of UG2 ore has been similarly examined. Statistical comparison of ToF-SIMS analysis of particles from concentrate and tails reveals no significant difference in Cu, Pb, Ni and collector (IBX and DTP) signals between these streams but surface exposure of Mg and Si is favoured in the concentrate. The flotation rate of coarse chromite correlates with the exposures of magnesium and silicon in patches on the chromite surface; higher exposures give earlier flotation. Conversely, there is a negative correlation with signals corresponding to the chromite surface, i.e. Cr, Fe, Al. Flotation of chromite without collector has confirmed this statistical discrimination. Hydrophobic talc-like residual layers, similar to those found on orthopyroxene surfaces, probably from partial alteration, explain this flotation mechanism. 相似文献
195.
Anna Maria Szczucińska Marcin Siepak Anetta Zioła-Frankowska Marek Marciniak 《Environmental Earth Sciences》2010,61(5):921-930
Groundwater outflows (springs and seeps) from porous sediments on European lowlands play a significant role in the surface
water balance. It is therefore important to document these outflows’ water quality and spatial and temporal changes. The present
study focused on changes in iron, manganese, and heavy metals in waters of groundwater outflows in an area of low anthropogenic
impact—the Gryżyna-Grabin Tunnel Valley in western Poland. Eleven outflows were studied for a period of 2 years. Most of the
samples analyzed revealed low element contents and little variation in time and space. Only values of iron and lead were above
World Health Organization limits for drinking water. The concentrations of these elements were also variable in time and space.
The seasonal changes in iron content are probably due to natural, temperature- and pH-controlled reactions of shallow groundwater
with aquifer sediments. On the other hand, the elevated lead content points to regional water contamination. 相似文献
196.
Tatiana Ermolieva Yuri Ermoliev Günther Fischer Matthias Jonas Marek Makowski Fabian Wagner 《Climatic change》2010,103(1-2):277-289
The idea of market-based carbon emission trading and carbon taxes is gaining in popularity as a global climate change policy instrument. However, these mechanisms might not necessarily have a positive outcome unless their value reflects socioeconomic and environmental impacts and regulations. Moreover, the fact that they have various inherent exogenous and endogenous uncertainties raises serious concerns about their ability to reduce emissions in a cost-effective way. This paper aims to introduce a simple stochastic model that allows the robustness of economic mechanisms for emission reduction under multiple natural and human-related uncertainties to be analyzed. Unlike standard equilibrium state analysis, the model shows that the explicit introduction of uncertainties regarding emissions, abatement costs, and equilibrium states makes it almost impossible for existing market-based trading and carbon taxes to be environmentally safe and cost-effective. Here we propose a computerized multi-agent trading model. This can be viewed as a prototype to simulate an emission trading market that is regulated in a decentralized way. We argue that a market of this type is better equipped to deal with long-term emission reductions, their direct regulation, irreversibility, and “lock-in” equilibria. 相似文献
197.
Kerstin?DrostEmail author Ulf?Linnemann Neal?McNaughton Old?ich?Fatka Petr?Kraft Michael?Gehmlich Christian?Tonk Jaroslav?Marek 《International Journal of Earth Sciences》2004,93(5):742-757
The Teplá-Barrandian unit (TBU) of the Bohemian Massif was a part of the Avalonian-Cadomian belt at the northern margin of Gondwana during Neoproterozoic and Early Cambrian times. New detrital zircon ages and geochemical compositions of Late Neoproterozoic siliciclastic sediments confirm a deposition of the volcano-sedimentary successions of the TBU in a back-arc basin. A change in the geotectonic regime from convergence to transtension was completed by the time of the Precambrian-Cambrian boundary. The accumulation of around 2,500 m Lower Cambrian continental siliciclastics in a Basin-and-Range-type setting was accompanied by magmatism, which shows within-plate features in a few cases, but is predominantly derived from anatectic melts displaying the inherited island arc signature of their Cadomian source rocks. The geochemistry of clastic sediments suggests a deposition in a rift or strike-slip-related basin, respectively. A marine transgression during Middle Cambrian times indicates markedly thinned crust after the Cadomian orogeny. Upper Cambrian magmatism is represented by 1,500 m of subaerial andesites and rhyolites demonstrating several geochemical characteristics of an intra-plate setting. Zircons from a rhyolite give a U-Pb-SHRIMP age of 499±4 Ma. The Cambrian sedimentary and magmatic succession of the TBU records the beginning of an important rifting event at the northern margin of Gondwana.
相似文献
Kerstin DrostEmail: |
198.
Kosmulski M Maczka E Marczewska-Boczkowska K Rosenholm JB 《Marine pollution bulletin》2003,46(1):120-122
Electroacoustic method was used to measure the zeta potentials of mineral oxides and calcium carbonate in artificial sea water (pH 8), and the following values were obtained: synthetic hematite: 0.87 mV; goethite: 1.01 mV; fumed silica: -3.56 mV; quartz: -1.38 mV; calcium carbonate: 1.91 mV. The absolute values of the zeta potentials obtained in the present study are substantially lower than the zeta potentials in seawater reported by other authors. Our results indicate that the effect of electrostatic repulsion in the interactions between the particles of these materials in seawater is negligible. 相似文献
199.
Vojtěch Ettler Marek Matura Martin Mihaljevič Petr Bezdička 《Environmental Geology》2006,49(4):610-619
The degree of metal contamination (Zn, Pb, Cu, Ni, Cd) has been investigated in the vicinity of an old unmonitored municipal
landfill in Prague, Czech Republic, where the leachate is directly drained into a surface stream. The water chemistry was
coupled with investigation of the stream sediment (aqua regia extract, sequential extraction, voltammetry of microparticles) and newly formed products (SEM/EDS, XRD). The MINTEQA2 speciation-solubility
calculation showed that the metals (Zn, Pb, Cu, Ni) are mainly present as carbonate complexes in leachate-polluted surface
waters. These waters were oversaturated with respect to Fe(III) oxyhydroxides, calcite (CaCO3) and other carbonate phases. Three metal attenuation mechanisms were identified in leachate-polluted surface waters: (i)
spontaneous precipitation of metal-bearing calcite exhibiting significant concentrations of trace elements (Fe, Mn, Mg, Sr,
Ba, Pb, Zn, Ni); (ii) binding to Fe(III) oxyhydroxides (mainly goethite, FeOOH) (Pb, Zn, Cu, Ni); and (iii) preferential bonding
to sediment organic matter (Cu). These processes act as the key scavenging mechanisms and significantly decrease the metal
concentrations in leachate-polluted water within 200 m from the direct leachate outflow into the stream. Under the near-neutral
conditions governing the sediment/water interface in the landfill environment, metals are strongly bound in the stream sediment
and remain relatively immobile. 相似文献
200.
Ongoing tectonic reactivation of the Outer Carpathians and its impact on the foreland: Results of borehole breakout measurements in Poland 总被引:1,自引:0,他引:1
The direction of present-day maximum horizontal compression (= SHmax = tectonic stress) was interpreted for 62 wells in Poland, using the method of borehole breakout analysis of 4-arm and 6-arm dipmeter logs. The study area covers complex tectonic junction of the Carpathian orogen and its foreland, which comprises the East European Craton (EEC) divided by the Teisseyre–Tornquist zone (TTZ) from the Palaeozoic platform of western Poland. For this area, frequent deviation of the SHmax direction from NW–SE characteristic for the Atlantic ridge push has been interpreted in terms of the ALCAPA tectonic push. In the Upper Silesian segment of the Polish Outer Carpathians (POC), NNE–SSW-oriented SHmax in the accretionary wedge differs significantly from NNW–SSE SHmax in the autochthonous basement. The above discrepancy points to uncoupled type of the suture in this segment of the POC. In this scenario the ALCAPA push involves the nappes and is compensated in the top of the basement, which is expressed by systematic SHmax rotations. In the accretionary wedge of the eastern Małopolska segment, SHmax follows the trend perpendicular to the strike of nappes. It is in general agreement with NNE–SSW-oriented SHmax in the autochthonous basement that also parallels the ALCAPA push direction. Similarity in stress orientation between these structural levels implies coupled suture zone in this segment of the POC. Further to the north, ALCAPA push is transmitted into the foreland plate where it causes N–S orientation of SHmax, as determined for sedimentary cover of the EEC. Within the Baltic portion of the EEC, further SHmax rotation towards the intermediate NNW–SSE position suggests balance between the ALCAPA push and the ridge push components. Within the TTZ, common SHmax rotations from N–S to NW–SE indicate structurally controlled accommodation of the ALCAPA push. In the Palaeozoic platform of western Poland, Mesozoic complex of the Fore-Sudetic Monocline reveals NNE–SSW-directed SHmax that differs from NW–SE-oriented SHmax in the Variscan accretionary wedge. Here, mechanical decoupling along Zechstein evaporates is likely.
Presented set of breakout data from Poland shows that recent compressive reactivation of the Carpathians exerts strong impact on the stress field of the foreland plate at a distance of 700 km from the suture. Due to this effect, the Fore-Carpathian stress domain within the North European stress province can be discriminated. 相似文献