Systematic errors in weak lensing: application to SDSS galaxy–galaxy weak lensing     

Rachel Mandelbaum  Christopher M. Hirata  Uro&#; Seljak  Jacek Guzik  Nikhil Padmanabhan  Cullen Blake  Michael R. Blanton  Robert Lupton  Jonathan Brinkmann 《Monthly notices of the Royal Astronomical Society》2005,361(4):1287-1322

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Virial masses of galactic haloes from galaxy–galaxy lensing: theoretical modelling and application to Sloan Digital Sky Survey data     

Jacek Guzik  Uro&#; Seljak 《Monthly notices of the Royal Astronomical Society》2002,335(2):311-324

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Evolution of depressions on Comet 67P/Churyumov-Gerasimenko: Role of ice metamorphism     

Konrad J. Kossacki  Jacek Leliwa-Kopystyński  Slawomira Szutowicz 《Icarus》2006,184(1):221-238

This work is intended to investigate the influence of temperature-dependent metamorphism of ice on the shape of small depressions in the surface of cometary nuclei. We are mainly interested in the role of initial cohesivity of a nucleus. For this purpose we simulate sublimation of ice from the facets of initially cylindrical depressions in ice of different initial structure. The simulations account for the diurnal and orbital changes of insolation and its dependence on the current shape of the depressions. Our model includes heat transport in the cometary material and metamorphism of ice. We present the results obtained for the nucleus of the Comet 67P/Churyumov-Gerasimenko, target of the ESA cornerstone mission Rosetta.  相似文献   

Correlations between diffuse interstellar bands and atomic lines     

G. A. Galazutdinov  Giulio Manicò  Valerio Pirronello  Jacek Kre&#;owski 《Monthly notices of the Royal Astronomical Society》2004,355(1):169-177

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Influence of solar activity on the state of the wheat market in medieval England     

Lev A. Pustil’nik  Gregory Yom Din 《Solar physics》2004,223(1):335-356

The database of professor Rogers (1887), which includes wheat prices in England in the Middle Ages, was used to search for a possible influence of solar activity on the wheat market. Our approach was based on the following: (1) Existence of the correlation between cosmic ray flux entering the terrestrial atmosphere and cloudiness of the atmosphere. (2) Cosmic ray intensity in the solar system changes with solar activity, (3) Wheat production depends on weather conditions as a nonlinear function with threshold transitions. (4) A wheat market with a limited supply (as it was in medieval England) has a highly nonlinear sensitivity to variations in wheat production with boundary states, where small changes in wheat supply could lead to bursts of prices or to prices falling. We present a conceptual model of possible modes for sensitivity of wheat prices to weather conditions, caused by solar cycle variations, and compare expected price fluctuations with price variations recorded in medieval England. We compared statistical properties of the intervals between wheat price bursts during the years 1249-1703 with statistical properties of the intervals between the minima of solar cycles during the years 1700-2000. We show that statistical properties of these two samples are similar, both for characteristics of the distributions and for histograms of the distributions. We analyze a direct link between wheat prices and solar activity in the 17^th century, for which wheat prices and solar activity data (derived from ¹⁰Be isotope) are available. We show that for all 10 time moments of the solar activity minima the observed prices were higher than prices for the corresponding time moments of maximal solar activity (100% sign correlation, on a significance level < 0.2%). We consider these results a direct evidence of the causal connection between wheat prices bursts and solar activity.  相似文献   

Impact Break-Up of Cometary Nuclei – Conclusions from Impact Experiments     

Leliwa-Kopystyński  Jacek 《Earth, Moon, and Planets》2002,90(1-4):283-291

Experiments of impact-generated break-up of icy and icy/mineral targets were performed. Formulae for the velocity of ejecta and for energy of disruption were fitted to the experimental data. An assumption that these formulae can be extrapolated for kilometer-size bodies enabled us to discuss the consequences of impacts on cometary nuclei and on planetesimals. It was found that the porosity of the targets as well as their composition (mineral to total mass ratio), are the crucial parameters.  相似文献   

Potential causes of differences between ground and surface air temperature warming across different ecozones in Alberta, Canada     

Jacek A. Majorowicz  Walter R. Skinner 《Global and Planetary Change》1997,15(3-4)

Analysis and modelling of temperature anomalies from 25 selected deep wells in Alberta show that the differences between GST (ground surface temperature) warming for the northern Boreal Forest ecozone and the combined Prairie Grassland ecozone and Aspen Parkland transition region to the south occur during the latter half of this century. This corresponds with recent changes in surface albedo resulting from permanent land development in the northern areas and also to increases in natural forest fires in the past 20 years. Differences between GST and SAT (surface air temperature) warming are much higher in the Boreal Forest ecozone than in the Prairie Grassland ecozone and Aspen Parkland transition region. Various hypotheses which could account for the existing differences between the GST and SAT warming in the different ecozones of Alberta, and western Canada in general, are tested. Analysis of existing data on soil temperature, hydrological piezometric surfaces, snowfall and moisture patterns, and land clearing and forest fires, indicate that large areas of Alberta, characterised by anomalous GST warming, have experienced widespread changes to the surface landscape in this century. It is postulated that this has resulted in a lower surface albedo with a subsequent increase in the absorption of solar energy. Heat flow modelling shows that, after climatic SAT warming, permanent clearing of the land is the most effective and likely cause of the observed changes in the GST warming. The greater GST warming in the Boreal Forest ecozone in the latter half of this century is related to landscape change due to land development and increasing forest fire activity. It appears to account for a portion of the observed SAT warming in this region through a positive feedback loop with the overlying air. The anthropogenic effect on regional climatic warming through 20th century land clearing and landscape alteration requires further study. In future, more accurate quantification of these various forcings will be necessary in order to distinguish between, and to detect, the variety of natural and anthropogenic influences and on climate.  相似文献   

On the practical stability of the triangular points in the restricted three-body problem     

Jacek Olszewski 《Celestial Mechanics and Dynamical Astronomy》1971,4(1):3-14

This paper contains a proposal of a new way of treating astrodynamical stability problems. A definition of a practical stability and a direct method of its examination are presented. The method has been applied to the triangular points problem for variety of ande values in the case of the linearized equation system as well as in the general one. The results are shown in a form which facilitates the comparison with results published by other authors.  相似文献   

Structure and chemistry of (111) twin boundaries in MgAl<Subscript>2</Subscript>O<Subscript>4</Subscript> spinel crystals from Mogok     

Nina Daneu  Aleksander Rečnik  Takashi Yamazaki  Tadej Dolenec 《Physics and Chemistry of Minerals》2007,34(4):233-247

The atomic scale structure and chemistry of (111) twins in MgAl₂O₄ spinel crystals from the Pinpyit locality near Mogok (Myanmar, formerly Burma) were analysed using complementary methods of transmission electron microscopy (TEM). To obtain a three-dimensional information on the atomic structure, the twin boundaries were investigated in crystallographic projections and Using conventional electron diffraction and high-resolution TEM (HRTEM) analysis we have shown that (111) twins in spinel can be crystallographically described by 180° rotation of the oxygen sublattice normal to the twin composition plane. This operation generates a local hcp stacking in otherwise ccp lattice and maintains a regular sequence of kagome and mixed layers. In addition to rotation, no other translations are present in (111) twins in these spinel crystals. Chemical analysis of the twin boundary was performed by energy-dispersive X-ray spectroscopy (EDS) using a variable beam diameter (VBD) technique, which is perfectly suited for analysing chemical composition of twin boundaries on a sub-nm scale. The VBD/EDS measurements indicated that (111) twin boundary in spinel is Mg-deficient. Quantitative analyses of HRTEM (phase contrast) and HAADF-STEM (Z-contrast) images of (111) twin boundary have confirmed that Mg²⁺ ions are replaced with Be²⁺ ions in boundary tetrahedral sites. The Be-rich twin boundary structure is closely related to BeAl₂O₄ (chrysoberyl) and BeMg₃Al₈O₁₆ (taaffeite) group of intermediate polysomatic minerals. Based on these results, we conclude that the formation of (111) twins in spinel is a preparatory stage of polytype/polysome formation (taaffeite) and is a result of thermodynamically favourable formation of hcp stacking due to Be incorporation on the {111} planes of the spinel structure in the nucleation stage of crystal growth. The twin structure grows as long as the surrounding geochemical conditions allow its formation. The incorporation of Be induces a 2D-anisotropy and exaggerated growth of the crystal along the (111) twin boundary.  相似文献   

Analysis of Current Movements and Deformations of the Earth’s Crust in Fennoscandia from GNSS Data     

Steblov  G. M.  Agibalov  A. O.  Mel’nik  G. E.  Perederin  V. P.  Perederin  F. V.  Sentsov  A. A. 《Izvestiya Physics of the Solid Earth》2022,58(4):459-468

Izvestiya, Physics of the Solid Earth - Abstract—An analysis of the displacement rates of GNSS points indicates that the values of current deformations gradually decrease from the center of...  相似文献