3,828 research outputs found
Ediacaran Obduction of a Fore-Arc Ophiolite in SW Iberia: A Turning Point in the Evolving Geodynamic Setting of Peri- Gondwana
The Calzadilla Ophiolite is an ensemble of mafic and ultramafic rocks that represents the
transition between lower crust and upper mantle of a Cadomian (peri-Gondwanan) fore arc. Mapping and
structural analysis of the ophiolite demonstrates that it was obducted in latest Ediacaran times, because the
Ediacaran-Early Cambrian sedimentary series (Malcocinado Formation) discordantly covers it. The ophiolite
and emplacement-related structures are affected by Variscan deformation (Devonian-Carboniferous),
which includes SW verging overturned folds (D1) and thrusts (D2), upright folds (D3), extensional faults (D4),
and later faults (D5). These phases of deformation are explained in the context of Variscan tectonics as the
result of the progressive collision between Gondwana and Laurussia. Qualitative unstraining of Variscan
deformation reveals the primary geometry of Ediacaran-Cambrian structures and uncovers the generation of
east verging thrusts as responsible for the primary obduction of the Calzadilla Ophiolite. Restoration of
planar and linear structures associated with this event indicates an Ediacaran, east directed obduction of the
ophiolite, that is, emplacement of the Cadomian fore arc onto inner sections of the northern margin of
Gondwana. According to regional data, the obduction separates two extension-dominated stages in the
tectonic evolution of the African margin of northern Gondwana preserved in southern Europe. Preobduction
extension brought about the onset and widening of fore-arc and back-arc basins in the external part
of the continent, while postobduction extension facilitated the formation of extensional migmatitic domes,
an oceanward migration of back-arc spreading centers across peri-Gondwana, and the eventual opening
of a major basin such as the Rheic Ocean
Black hole entropy quantization
Ever since the pioneer works of Bekenstein and Hawking, black hole entropy
has been known to have a quantum origin. Furthermore, it has long been argued
by Bekenstein that entropy should be quantized in discrete (equidistant) steps
given its identification with horizon area in (semi-)classical general
relativity and the properties of area as an adiabatic invariant. This lead to
the suggestion that black hole area should also be quantized in equidistant
steps to account for the discrete black hole entropy. Here we shall show that
loop quantum gravity, in which area is {\it not} quantized in equidistant steps
can nevertheless be consistent with Bekenstein's equidistant entropy proposal
in a subtle way. For that we perform a detailed analysis of the number of
microstates compatible with a given area and show consistency with the
Bekenstein framework when an oscillatory behavior in the entropy-area relation
is properly interpreted.Comment: 4 pages, 4 figures. Version to be published in PR
A microscopic NN to NN*(1440) potential
By means of a NN to NN*(1440) transition potential derived in a
parameter-free way from a quark-model based NN potential, we determine
simultaneously the and coupling constants.
We also present a study of the target Roper excitation diagram contributing to
the reaction.Comment: Talk presented at the Fourth International Conference on Perspectives
in Hadronic Physics (ICTP, Trieste, Italy, May 2003). To appear in EPJA. 6
pages, 9 figures, needs svepj.clo and svjour.cl
2D granular flows with the rheology and side walls friction: a well balanced multilayer discretization
We present here numerical modelling of granular flows with the
rheology in confined channels. The contribution is twofold: (i) a model to
approximate the Navier-Stokes equations with the rheology through an
asymptotic analysis. Under the hypothesis of a one-dimensional flow, this model
takes into account side walls friction; (ii) a multilayer discretization
following Fern\'andez-Nieto et al. (J. Fluid Mech., vol. 798, 2016, pp.
643-681). In this new numerical scheme, we propose an appropriate treatment of
the rheological terms through a hydrostatic reconstruction which allows this
scheme to be well-balanced and therefore to deal with dry areas. Based on
academic tests, we first evaluate the influence of the width of the channel on
the normal profiles of the downslope velocity thanks to the multilayer approach
that is intrinsically able to describe changes from Bagnold to S-shaped (and
vice versa) velocity profiles. We also check the well balance property of the
proposed numerical scheme. We show that approximating side walls friction using
single-layer models may lead to strong errors. Secondly, we compare the
numerical results with experimental data on granular collapses. We show that
the proposed scheme allows us to qualitatively reproduce the deposit in the
case of a rigid bed (i. e. dry area) and that the error made by replacing the
dry area by a small layer of material may be large if this layer is not thin
enough. The proposed model is also able to reproduce the time evolution of the
free surface and of the flow/no-flow interface. In addition, it reproduces the
effect of erosion for granular flows over initially static material lying on
the bed. This is possible when using a variable friction coefficient
but not with a constant friction coefficient
Reakcija p(d, d ′ ) i konstanta vezanja σNN∗ (1440)
We make use of a NN → NN∗ (1440) transition potential derived from a quark model in a parameter-free way, to study the Roper excitation diagram contributing to the reaction p(d, d ′ ). We also determine the πNN∗ (1440) and σNN∗ (1440) coupling constants.Primjenjujemo prijelazni potencijal NN → NN∗ (1440), izveden iz kvarkovskog modela bez parametara, radi proučavanja doprinosa Roperovog dijagrama uzbude reakciji p(d, d ′ ). Također određujemo konstante vezanja πNN∗ (1440) i σNN∗ (1440)
Reakcija p(d, d ′ ) i konstanta vezanja σNN∗ (1440)
We make use of a NN → NN∗ (1440) transition potential derived from a quark model in a parameter-free way, to study the Roper excitation diagram contributing to the reaction p(d, d ′ ). We also determine the πNN∗ (1440) and σNN∗ (1440) coupling constants.Primjenjujemo prijelazni potencijal NN → NN∗ (1440), izveden iz kvarkovskog modela bez parametara, radi proučavanja doprinosa Roperovog dijagrama uzbude reakciji p(d, d ′ ). Također određujemo konstante vezanja πNN∗ (1440) i σNN∗ (1440)
Rational exploitation of a granite outcrop
[Abstract] This piece analizes the possibilities of mining exploitation in a little outcrop of rOSfl granite. The zone has been researched, recognizing the main structural discontinuities, and characterizing the rock mass by the geomechanic classificationofBARTON. Two core drilling have been made to study the evolution ofthe deeper bed. The volume ofthe bed has been calculated by geometric calculation in the researched area. The theories ofCASTAING and RABU have been developed to estimate the useful volume of the bed for a minimum block size of 1 m3. We have implerríented a computer program in base ofEXCEL 4.0. The result is a useful volume of 51.67 %. By the application of the reduction coefficients ofsterility and irregularity, the maximum estimated efficiency of the exploitation is 33 %
Lagrangean Duals and Exact Solution to the Capacitated p-Center Problem
In this work we study the Capacitated p-Center Problem (CpCP) and we propose an
exact algorithm to solve it. We study two auxiliary problems and their relation to CpCP, and we propose two different Lagrangean duals based on each of the auxiliary problems. The lower and upper bounds provided by each of the Lagrangean duals reduce notably the set of candidate radii and allow to solve the problem with an exact algorithm based on binary search. The results obtained with experimental testing on various data sets from literature
show the efficiency of the proposal that outperforms previous proposals
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