Search results for " Formation"
showing 10 items of 1920 documents
Non-thermal pressure support in X-COP galaxy clusters
2018
Galaxy clusters are the endpoints of structure formation and are continuously growing through the merging and accretion of smaller structures. Numerical simulations predict that a fraction of their energy content is not yet thermalized, mainly in the form of kinetic motions (turbulence, bulk motions). Measuring the level of non-thermal pressure support is necessary to understand the processes leading to the virialization of the gas within the potential well of the main halo and to calibrate the biases in hydrostatic mass estimates. We present high-quality measurements of hydrostatic masses and intracluster gas fraction out to the virial radius for a sample of 12 nearby clusters with availab…
The non-Gaussian distribution of galaxies gravitational fields
2016
We perform a theoretical analysis of the observational dependence between angular momentum of the galaxy clusters and their mass (richness), based on the method introduced in our previous paper. For that we obtain the distribution function of astronomical objects (like galaxies and/or smooth halos of different kinds) gravitational fields due to their tidal interaction. Within the statistical method of Chandrasekhar we are able to show that the distribution function is determined by the form of interaction between objects and for multipole (tidal) interaction it is never Gaussian. Our calculation permits to demonstrate how the alignment of galaxies angular momenta depend on the cluster richn…
Impaired crypsis of fish infected with a trophically transmitted parasite
2005
Trophically transmitted parasites may enhance their transmission by altering the phenotype of infected hosts to increase their vulnerability to predation by the next hosts in the life cycle. In an experimental study, we investigated whether the parasite Diplostomum spathaceum (Trematoda) alters cryptic coloration and cryptic behaviour of infected rainbow trout, Oncorhynchus mykiss, so that they would be more conspicuous to avian predators. The parasite reduces the vision of fish by lodging in the eyes and inducing cataract formation, which gives it an opportunity to affect fish crypsis. We examined the effect of the parasite on the ability of fish to adjust their coloration to the environme…
The Internuclear Ophthalmoplegias
1993
Internuclear ophthalmoplegia (INO), which is caused by an ipsilateral medial longitudinal fasciculus (MLF) lesion, is characterized by adduction paresis of lateral gaze, usually with spared convergence [1–4]. In the opposite eye, abduction nystagmus and hypermetric abduction saccades are the main clinical and electro-oculographic abnormalities [1, 5, 6]. The origin of both is still debated. Abduction nystagmus has been explained by (a) an additional horizontal gaze paresis [7]; (b) vergence mechanisms aimed at alignment of the visual axes [8]; (c) interruption of descending excitatory projections from oculomotor nucleus internuclear neurons to contralateral abducens nucleus motoneurons [9];…
Correlation of welded ignimbrites on Pantelleria (Strait of Sicily) using paleomagnetism
2011
Although the oldest volcanic rocks exposed at Pantelleria (Strait of Sicily) are older than 300 ka, most of the island is covered by the 45–50 ka Green Tuff ignimbrite, thought to be related to the Cinque Denti caldera, and younger lavas and scoria cones. Pre-50 ka rocks (predominantly rheomorphic ignimbrites) are exposed at isolated sea cliffs, and their stratigraphy and chronology are not completely resolved. Based on volcanic stratigraphy and K/Ar dating, it has been proposed that the older La Vecchia caldera is related to ignimbrite Q (114 ka), and that ignimbrites F, D, and Z (106, 94, and 79 ka, respectively) were erupted after caldera formation. We report here the paleomagnetic direc…
Partitioning between “wedge-top” river- and wave-dominated successions: an example from the late Tortonian — early Messinian Terravecchia Formation (…
2011
AbstractDetailed field sedimentological and facies analyses have been performed in the Terravecchia Formation cropping out in NW Sicily, in order to differentiate and describe, for the first time, wave- and river-dominated shallow-marine (deltaic) siliciclastic successions. The latter were deposited filling syntectonic basins, developed between the late Tortonian and early Messinian time, within the wedge-top depozone of the Sicilian Foreland Basin System. It has been observed that river-dominated successions, recording the deposition of small fan-deltas are characterized by fining- to coarsening upward, transgressive-regressive sequences which were mostly deposited filling relatively narro…
Equilibrium Studies in Natural Fluids. A Chemical Speciation Model for the Major Constituents of Seawater.
1994
AbstractThe speciation of CI−, OH− and SO42- in synthetic sea water has been studied by Potentiometric measurements (pH-metric and ISE-Na methods) and by literature data analysis, using a well tested complex formation model. Stability constants, together with distribution of hypothesised species in synthetic sea water, as a function of temperature and salinity, are reported. The speciation model proposed in this work is discussed on the basis of chemical and statistical considerations. Comparison with some literature sea water models is given.
Formation Ages and Environments of Early Precambrian Banded Iron Formation in the North China Craton
2016
The North China Craton (NCC) has had a long geological history back to ca. 3.8 Ga ago, but the most important tectonothermal event occurred at the end of the Neoarchean, the most important period of BIF formation. There are three ancient terranes (>2.6 Ga) in the NCC. Most BIFs are distributed along the western margin of the Eastern Ancient Terrane, accounting for about 89 % of the total identified BIF iron ore resources in the NCC. They are considered to have formed on a continental basement in terms of rock association of the BIF-bearing supracrustal sequences which were intruded by slightly younger crustally derived granites. Most BIFs in the NCC show positive Y anomalies, implying that …
Modeling of wind gap formation and development of sedimentary basins during fold growth: application to the Zagros Fold Belt, Iran
2016
Mountain building and landscape evolution are controlled by interactions between river dynamics and tectonic forces. Such interactions have been extensively studied, however a quantitative evaluation of tectonic/geomorphic feedbacks, which is imperative for understanding sediments routing within orogens and fold-and-thrust belts, remains to be undertaken. Here, we employ numerical simulations to assess the conditions of uplift and river incision necessary to deflect an antecedent drainage network during the growth of one, or several, folds. We propose that a partitioning of the river network into internal (endorheic) and longitudinal drainage arises as a result of lithological differences w…
Geometric and morphologic evolution of normal fault planes and traces from 2D to 4D data
2003
Abstract The detailed 3D geometry of normal fault planes is described and analysed using datasets from outcrop studies (2D), seismic surveys (3D) and analogue models (4D). Different geometric configurations of simple isolated normal faults are studied by reference to processes of normal fault propagation. When a normal fault propagates without interacting with other fault zones, the entire border of the principal plane displays characteristic connected secondary structures. These secondary structures cause bifurcations of the principal fault terminations. The along-strike terminations of the principal plane display typical bifurcation configurations (‘ear geometry‘). The orientation of the …