Cluster strong lensing in the Millennium simulation: the effect of galaxies and structures along the line-of-sight     

Ewald Puchwein  Stefan Hilbert 《Monthly notices of the Royal Astronomical Society》2009,398(3):1298-1308

We use ray-tracing through the Millennium simulation to study how secondary matter structures along the line-of-sight and the stellar mass in galaxies affect strong cluster lensing, in particular the cross-section for giant arcs. Furthermore, we investigate the distribution of the cluster Einstein radii and the radial distribution of giant arcs. We find that additional structures along the line-of-sight increase the strong-lensing optical depth by  ∼10–25 per cent  , while strong-lensing cross-sections of individual clusters are frequently boosted by as much as  ∼50 per cent  . The enhancement is mainly due to structures that are not correlated with the lens. Cluster galaxies increase the strong-lensing optical depth by up to a factor of 2, while interloping galaxies are not significant. We conclude that these effects need to be taken into account for predictions of the giant arc abundance, but they are not large enough to fully account for the reported discrepancy between predicted and observed abundances.
Furthermore, we find that Einstein radii defined via the area enclosed by the critical curve are 10–30 per cent larger than those defined via radial surface mass density profiles. The contributions of radial and tangential arcs to the radial distribution of arcs can be clearly distinguished. The radial distribution of tangential arcs is very broad and extends out to several Einstein radii. Thus, individual arcs are not well suited for constraining Einstein radii.  相似文献   

Barium partitioning in coccoliths of Emiliania huxleyi     

Gerald Langer  Gernot Nehrke  Heather Stoll 《Geochimica et cosmochimica acta》2009,73(10):2899-443

The coccolithophore Emiliania huxleyi was grown in seawater under different Ba concentrations. The relationship of coccolith Ba/Ca ratio and seawater Ba/Ca ratio was found to be linear. The linear regression yields the apparent Ba exchange coefficient of 0.10. Our data support a recently proposed generic model (Langer G., Gussone N., Nehrke G., Riebesell U., Eisenhauer A., Kuhnert H., Rost B., Trimborn S., and Thoms S. (2006) Coccolith strontium to calcium ratios in Emiliania huxleyi: the dependence on seawater strontium and calcium concentrations. Limnol. Oceanogr.51, 310-320.) developed for explaining apparent exchange coefficients of metabolically inert divalent trace metals, such as Sr, in E. huxleyi. This model represents the first approach combining cell physiological processes and data from inorganic precipitation experiments, which quantitatively explains coccolith apparent Sr and Ba exchange coefficients.  相似文献   

Potentials of monitoring rock fall hazards by GPR: considering as example the results of Salzburg   总被引：1，自引：0，他引：1  

Karl-Heinz Roch  Werner Chwatal  Ewald Brückl 《Landslides》2006,3(2):87-94

A part of the IUGS-UNESCO research project "Landslide Hazard Assessment and Cultural Heritage" (IGCP-Project No. 425) includes testing the application of geophysical methods for assessing hazard risks to people and cultural assets. In this work, Austria contributed with a study on the assessment of rock-fall hazards. As the Old Town of Salzburg is a prime example of such hazards, systematic GPR-measurements were made on major rock surfaces. The aim of the exploration with GPR was to assess the potential of the method for monitoring rock walls. That is, whether structures in the rock mass which could become important when considering the risk of a rock fall, can be imaged. To manage this problem successfully, moving the antenna over the rough rock surface was made as regular as possible. The effects of vegetation lifting the antenna from the rock surface and of overhanging regions could not be avoided. Due to the loss of coupling of the antenna and the change of radiation pattern, some interference of the records occurred. Thus, only after processing could it become clear which reflections came from within the rock. A three-dimensional survey of discontinuities in the rock requires accurate mapping of the rock surface by photogrammetric methods, to get a digital terrain model for the analysis of the GPR records. The results of repeated measurements have proved to be of essential relevance. They have shown that it is possible to reveal changes with time. For the interpretation of such observations, modeling is a very useful tool.  相似文献   

Modelling environmentally friendly fairways using Lagrangian trajectories: a case study for the Gulf of Finland,the Baltic Sea     

Tarmo Soomere  Mihhail Berezovski  Ewald Quak  Bert Viikmäe 《Ocean Dynamics》2011,61(10):1669-1680

We address possibilities of minimising environmental risks using statistical features of current-driven propagation of adverse impacts to the coast. The recently introduced method for finding the optimum locations of potentially dangerous activities (Soomere et al. in Proc Estonian Acad Sci 59:156–165, 2010) is expanded towards accounting for the spatial distributions of probabilities and times for reaching the coast for passively advecting particles released in different sea areas. These distributions are calculated using large sets of Lagrangian trajectories found from Eulerian velocity fields provided by the Rossby Centre Ocean Model with a horizontal resolution of 2 nautical miles for 1987–1991. The test area is the Gulf of Finland in the northeastern Baltic Sea. The potential gain using the optimum fairways from the Baltic Proper to the eastern part of the gulf is an up to 44% decrease in the probability of coastal pollution and a similar increase in the average time for reaching the coast. The optimum fairways are mostly located to the north of the gulf axis (by 2–8 km on average) and meander substantially in some sections. The robustness of this approach is quantified as the typical root mean square deviation (6–16 km) between the optimum fairways specified from different criteria. Drastic variations in the width of the ‘corridors’ for almost optimal fairways (2–30 km for the average width of 15 km) signifies that the sensitivity of the results with respect to small changes in the environmental criteria largely varies in different parts of the gulf.  相似文献   

The dispersion of fibrous amphiboles by glacial processes in the area surrounding Libby,Montana, USA     

William H. Langer  Bradley S. Van Gosen  Gregory P. Meeker  David T. Adams  Todd M. Hoefen 《Environmental Earth Sciences》2011,64(1):157-168

Mining operations began at a world-class vermiculite deposit at Vermiculite Mountain near Libby, Montana, circa 1920 and ended in 1990. Fibrous and asbestiform amphiboles intergrown with vermiculite ore are suspected to be a causative factor in an abnormally high number of cases of respiratory diseases in former mine and mill workers, and in residents of Libby. The question addressed in this report is whether some of the amphibole from Vermiculite Mountain could have been dispersed by Pleistocene glacial processes rather than by human activity after vermiculite mining began. The history of Pinedale glaciation in the Libby area provides a framework for estimating the presence and distribution of asbestiform amphiboles derived from Vermiculite Mountain and found in naturally occurring sediments of Glacial Lake Kootenai that underlie the Libby Valley area. There were two situations where sediments derived from Vermiculite Mountain were deposited into Glacial Lake Kootenai: (1) as lake-bottom sediments derived from meltwater flowing down Rainy Creek when the valley south of Vermiculite Mountain was free of ice but active ice still covered Vermiculite Mountain; and (2) as lake-bottom sediments eroded from the Rainy Creek outwash and re-deposited during a re-advance of the Purcell Trench Glacier lobe near Moyie Springs, Idaho.  相似文献   

Model parameter optimization for site-dependent simulation of ground motion by simulated annealing: Re-evaluation of the Ashigara Valley prediction experiment     

F. Scherbaum  C. Palme  H. Langer 《Natural Hazards》1994,10(3):275-296

More than 40 groups from 10 different countries participated in a weak- and strong-motion prediction experiment at Ashigara Valley which required the blind prediction of time series, spectra and spectral ratios for selected and instrumented sedimentary sites with well-known geotechnical properties. The wide scatter of the results of this experiment have raised a number of questions as to how to model high-frequency ground motion in the presence of available geotechnical and geophysical data. Using a simulated annealing waveform inversion method, we have tried to optimize and automate the model construction for ID site-dependent ground-motion simulation. We found a whole set of successfull models which provide good waveform fit (r > 0.8) for the observed displacement records at site KS2 but also yield sufficiently accurate response spectra and peak value predictions for both surface and downhole site. This shows that ID models are fully adequate to model the site conditions at least for the weak motion data. The resulting successful layer models consistently show a slower, less dense, and slightly thicker low velocity coverage with stronger damping than the official geotechnical model. Furthermore, their statistical properties directly measure the sensitivity of the individual parameters for the simulations. The critical re-evaluation of our own prediction which was based on stochastic simulation shows that although this approach has its greatest merits in situations where little information is available, it can also be successfully applied to model individual records if sufficient care is taken to determine the source parameters. Simulated annealing waveform inversion has shown to be a powerful tool to optimize that process.  相似文献   

Pressure- and temperature-effects on exchange-coupled-pair bands in electronic spectra of some oxygen-based iron-bearing minerals     

M. N. Taran  K. Langer  A. N. Platonov 《Physics and Chemistry of Minerals》1996,23(4-5):230-236

The special properties of spin-allowed transitions of Fe²⁺, exchanged-coupled in pairs with Fe³⁺, (ECP-effect) are studied in single crystals of vivianite, phlogopite, biotite, elbaite and schörl under changing temperature and pressure in the ranges 79≤T[K]≤597 and 10^-4≤P[GPa]≤8. The two Fe²⁺ dd-transitions, known to be subject to ECP-effects, occur at 11000 to 14000 (II) and 8400 to 9150 cm^-1 (III), depending on the structural matrix. With pressure, band energies shift to higher values, while temperature has the opposite effect. Δv is nearly the same in all cases, decrease on temperature, and increase with pressure. Δα/ΔT or Δα/ΔP have similar values for bands II and III in all minerals studied. These observations are interpreted in terms of geometrical and vibrational changes of the octahedra, involved in the pair effects, on changing P and T. They clearly separate the ECP-bands from ordinary dd-transitions and also from IVCT-bands. A unique pressure effect in the spectral range of 17000 to 26000 cm^-1 was found in schörl: a band system that immensly gains intensity on pressure. Two explanations are suggested: (a) traces of Ti³⁺, exchange-coupled to Fe²⁺ show the above pressure effect typical of ECP, (b) there occurs pressureinduced reduction of Ti⁴⁺ in Y-positions, induced by Fe²⁺ in connected Y-octahedra, whereby OH in trans-configuration of Y-octahedra promote this process.  相似文献   

Temperature dependent polarized single crystal absorption spectra of kaemmererite     

M. Andrut  M. Wildner  M. Taran  K. Langer  R. Schulz 《Physics and Chemistry of Minerals》1996,23(4-5):242-243

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Dynamic response of single-span beam bridges to a series of moving loads     

Marian Klasztorny  Jan Langer 《地震工程与结构动力学》1990,19(8):1107-1124

The paper makes a contribution to the problem of a stream of loads crossing a single-span beam bridge. There are considered the basic load models, in the form of a stream of fixed amplitude forces, unsprung masses and viscoelastic oscillators. The matrix equations of motion of the system are formulated and discussed. The problem of dynamic stability and steady-state response of a bridge carrying a periodic stream of inertial loads is formulated and solved. The paper also includes a vibration study of a beam bridge subjected to a uniform stream of moving loads, of a limited or unlimited number of load cycles.  相似文献   

Polarized electronic absorption spectra of synthetic (Mg,Fe)-orthopyroxenes,ferrosilite and Fe3+-bearing ferrosilite     

G. Steffen  K. Langer  F. Seifert 《Physics and Chemistry of Minerals》1988,16(2):120-129

The assignment of spin-allowed Fe²⁺-bands in orthopyroxene electronic absorption spectra is revised by studying synthetic bronzite (Mg_0.8 Fe_0.2)₂Si₂O₆, hypersthene (Mg_0.5 Fe_0.5)₂Si₂O₆ and ferrosilite (Fe₂Si₂O₆). Reheating of bronzite and hypersthene single crystals causes a redistribution of the Fe²⁺-ions over the M1 and M2 octahedra, which was determined by Mössbauer spectroscopy and correlated to the intensity change of the spin-allowed Fe²⁺ d-d bands in the polarized absorption spectra. The 11000 cm^-1 band is caused by Fe²⁺ in M1 (⁵B_2g→⁵A_1g) and Fe²⁺ in M2 (⁵A₁→⁵A₁), the 8500 cm^-1 band by Fe²⁺ in M1 (⁵B_2g→⁵B_1g) and the 5000 cm^-1 band by Fe²⁺ in M2 octahedra (⁵A₁→⁵B₁). The Fe²⁺-Fe³⁺ charge transfer band is identified at 12500cm^-1 in the spectra of synthetic Fe³⁺ -Al bearing ferrosilite. This band shows a strong γ-polarization and therefore is caused by Fe²⁺ -Fe³⁺-ions in edge-sharing octahedra.  相似文献