132 research outputs found
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
Formal deduction of the Saint-Venant-Exner model including arbitrarily sloping sediment beds and associated energy
In this work we present a deduction of the Saint-Venant-Exner model through
an asymptotic analysis of the Navier-Stokes equations. A multi-scale analysis
is performed in order to take into account that the velocity of the sediment
layer is smaller than the one of the fluid layer. This leads us to consider a
shallow water type system for the fluid layer and a lubrication Reynolds
equation for the sediment one. This deduction provides some improvements with
respect to the classical Saint-Venant-Exner model: (i) the deduced model has an
associated energy. Moreover, it allows us to explain why classical models do
not have an associated energy and how to modify them in order to recover a
model with this property. (ii) The model incorporates naturally a necessary
modification that must be taken into account in order to be applied to
arbitrarily sloping beds. Furthermore, we show that this modification is
different of the ones considered classically, and that it coincides with a
classical one only if the solution has a constant free surface. (iii) The
deduced solid transport discharge naturally depends on the thickness of the
moving sediment layer, what allows to ensure sediment mass conservation.
Moreover, we include a simplified version of the model for the case of
quasi-stationary regimes. Some of these simplified models correspond to the
generalization of classical ones such as Meyer-PeterM\"uller and
Ashida-Michiue models. Three numerical tests are presented to study the
evolution of a dune for several definition of the repose angle, to see the
influence of the proposed definition of the effective shear stress in
comparison with the classical one, and by comparing with experimental data.Comment: 44 pages, sumbitted to Advances in Water Resources 17 july 201
A two-layer shallow water model for bedload sediment transport: convergence to Saint-Venant-Exner model
A two-layer shallow water type model is proposed to describe bedload sediment
transport. The upper layer is filled by water and the lower one by sediment.
The key point falls on the definition of the friction laws between the two
layers, which are a generalization of those introduced in Fern\'andez-Nieto et
al. (ESAIM: M2AN, 51:115-145, 2017). This definition allows to apply properly
the two-layer shallow water model for the case of intense and slow bedload
sediment transport. Moreover, we prove that the two-layer model converges to a
Saint-Venant-Exner system (SVE) including gravitational effects when the ratio
between the hydrodynamic and morphodynamic time scales is small. The SVE with
gravitational effects is a degenerated nonlinear parabolic system. This means
that its numerical approximation is very expensive from a computational point
of view, see for example T. Morales de Luna et al. (J. Sci. Comp., 48(1):
258-273, 2011). In this work, gravitational effects are introduced into the
two-layer system without such extra computational cost. Finally, we also
consider a generalization of the model that includes a non-hydrostatic pressure
correction for the fluid layer and the boundary condition at the sediment
surface. Numerical tests show that the model provides promising results and
behave well in low transport rate regimes as well as in many other situations
Trastornos especĂficos del desarrollo del lenguaje: bases neurobiolĂłgicas
Studies of twins, familial aggregates and particular phenotypic conditions have shown an inherited basis for some dysphasias or specific developmental language impairments (SLI). This predisposition is usually multifactorial but the analysis of some families allows to postulate an autosomal dominant transmission of deficits in specific modular aspects of linguistic competences. Moreover, neuroimaging studies have shown modifications of normal volumetric interhemispheric asymmetries, and in group of SLI with receptive prominent disorder coexist epileptiform activity in wakefulness and non-REM sleep EEG; in some of these cases, antiepileptic drugs, specially steroids, can significantly ameliorate the language processing. As many patients with SLI have a difficulty for discrimination of subtle temporal indices, a hypothesis can also be made of a dysfunction in various subcortical structures (thalamus, basal ganglia, cerebellum) modulating the cerebral cortex in phonological processing
ACYNETOBACTER BAUMANII EXTREMELY RESISTANT OUTBREAK CONTROL IN ICU: A MULTIDISCIPLINARY APPROACH
Hallazgos neurorradiolĂłgicos de la Acidosis GlutĂĄrica tipo I
Glutaric aciduria type I is a rare disorder of organic acid metabolism caused by
deficiency of glutaryl-CoA dehydrogenase, a mitochondrial enzyme. Improper
degeneration of amino acids: tryptophan, lysine, and hydroxylysine, results in
increased levels of glutaric acid, which typically becomes clinically manifest as
an acute dystonic crisis in young children. Accumulation of glutaric acid causes
neurotoxicity in the basal ganglia and fronto-temporal cortex which can lead to
progressive dystonia, hypotonia, permanently impaired speech and seizures.
Because dietary and drug therapy may alter the natural history of the disease,
early diagnosis of such patients is critical. We report the magnetic resonance
(MR) imaging findings in a 16 year-old girl with this disorder who presented with
a chronic dystonic syndrome and previously diagnosed of brain paralysis. MR
imaging demonstrated bilateral involvement of the putamina and periventricular
white matter, and bilateral temporal atrophy and widened Silvian fissure
Linking Self-Incompatibility, Dichogamy, and Flowering Synchrony in Two Euphorbia Species: Alternative Mechanisms for Avoiding Self-Fertilization?
Background: Plant species have several mechanisms to avoid selfing such as dichogamy or a self-incompatibility response.
Dichogamy in a single flower may reduce autogamy but, to avoid geitonogamy, plants must show flowering
synchronization among all their flowers (i.e. synchronous dichogamy). It is hypothesized that one species would not
simultaneously show synchronous dichogamy and self-incompatibility because they are redundant mechanisms to reduce
selfing; however, this has not been accurately assessed.
Methodology/Principal Findings: This expectation was tested over two years in two natural populations of the closely
related Mediterranean spurges Euphorbia boetica and E. nicaeensis, which completely avoid autogamy by protogyny at the
cyathia level. Both spurges showed a high population synchrony (Z,79), and their inflorescences flower synchronously. In E.
nicaeensis, there was no overlap among the cyathia in anthesis of successive inflorescence levels and the overlap between
sexual phases of cyathia of the same inflorescence level was uncommon (4â16%). In contrast, E. boetica showed a high
overlap among consecutive inflorescence levels (74â93%) and between sexual phases of cyathia of the same inflorescence
level (48â80%). The flowering pattern of both spurges was consistent in the two populations and over the two successive
years. A hand-pollination experiment demonstrated that E. nicaeensis was strictly self-compatible whereas E. boetica was
partially self-incompatible.
Conclusions/Significance: We propose that the complex pattern of synchronized protogyny in E. nicaeensis prevents
geitonogamous crosses and, consequently, avoids selfing and inbreeding depression. In E. boetica, a high probability of
geitonogamous crosses may occur but, alternatively, this plant escapes selfing through a self-incompatibility response. We
posit that synchronous dichogamy and physiological self-incompatibility do not co-occur in the same species because each
process is sufficiently effective in avoiding self-fertilization.España Ministerio de Ciencia y TecnologĂa PLO CGL2005-03731; CGL2008-02533-EEspaña Ministerio de Ciencia y TecnologĂa MA CGL2009-0825
Idiopathic epilepsies with seizures precipitated by fever and SCN1A abnormalities.
Epilepsia. 2007 Sep;48(9):1678-85. Epub 2007 Jun 11.
Idiopathic epilepsies with seizures precipitated by fever and SCN1A abnormalities.
Marini C, Mei D, Temudo T, Ferrari AR, Buti D, Dravet C, Dias AI, Moreira A, Calado E, Seri S, Neville B, Narbona J, Reid E, Michelucci R, Sicca F, Cross HJ, Guerrini R.
SourceEpilepsy, Neurophysiology and Neurogenetic Unit, Institute of Child Neurology and Psychiatry, IRCCS Stella Maris Foundation, Calambrone, Pisa, Italy.
Abstract
PURPOSE: SCN1A is the most clinically relevant epilepsy gene, most mutations lead to severe myoclonic epilepsy of infancy (SMEI) and generalized epilepsy with febrile seizures plus (GEFS+). We studied 132 patients with epilepsy syndromes with seizures precipitated by fever, and performed phenotype-genotype correlations with SCN1A alterations.
METHODS: We included patients with SMEI including borderline SMEI (SMEB), GEFS+, febrile seizures (FS), or other seizure types precipitated by fever. We performed a clinical and genetic study focusing on SCN1A, using dHPLC, gene sequencing, and MLPA to detect genomic deletions/duplications on SMEI/SMEB patients.
RESULTS: We classified patients as: SMEI/SMEB = 55; GEFS+= 26; and other phenotypes = 51. SCN1A analysis by dHPLC/sequencing revealed 40 mutations in 37 SMEI/SMEB (67%) and 3 GEFS+ (11.5%) probands. MLPA showed genomic deletions in 2 of 18 SMEI/SMEB. Most mutations were de novo (82%). SMEB patients carrying mutations (8) were more likely to have missense mutations (62.5%), conversely SMEI patients (31) had more truncating, splice site or genomic alterations (64.5%). SMEI/SMEB with truncating, splice site or genomic alterations had a significantly earlier age of onset of FS compared to those with missense mutations and without mutations (p = 0.00007, ANOVA test). None of the remaining patients with seizures precipitated by fever carried SCN1A mutations.
CONCLUSION: We obtained a frequency of 71%SCN1A abnormalities in SMEI/SMEB and of 11.5% in GEFS+ probands. MLPA complements DNA sequencing of SCN1A increasing the mutation detection rate. SMEI/SMEB with truncating, splice site or genomic alterations had a significantly earlier age of onset of FS. This study confirms the high sensitivity of SCN1A for SMEI/SMEB phenotypes
the WAF method for non-homogeneous SWE with pollutant
This paper deals with the extension of the WAF method to discretize Shallow Water Equations with pollutants. We consider two different versions of the WAF method, by approximating the intermediate waves using the flux of HLL or the direct approach of HLLC solver. It is seen that both versions can be written under the same form with different definitions for the approximation of the velocity waves. We also propose an extension of the method to non-homogeneous systems. In the case of homogeneous systems it is seen that we can rewrite the third component of the numerical flux in terms of an intermediate wave speed approximation. We conclude that â in order to have the same relation for non-homogeneous systems â the approximation of the intermediate wave speed must be modified. The proposed extension of the WAF method preserves all stationary solutions, up to second order accuracy, and water at rest in an exact way, even with arbitrary pollutant concentration. Finally, we perform several numerical tests, by comparing it with HLLC solver, reference solutions and analytical solutions
Building and surroundings: thermal coupling
Energy building performance can be different according to outdoor conditions or urban environment, at the same time that this last assess, buildings are also affected by the building envelope, as obvious consequence of the thermal and Aeraulic coupling existing between the indoor and outdoor conditions in buildings. Thus, in this coupling is fundamental to typify the transmission phenomenon through the building envelope. Doing this, it is possible to estimate transmission heating losses and gains and also the superficial temperatures of the envelope. In order to assess the transient behaviour of the building envelope it is necessary to develop a predictive model, precise enough, to be integrated in a simulating tool. Detailed and multidimensional models, based in numerical methods, like Finite Element Method (FEM), has a high precision, but its complexity imply resources consumption and computational time, too high to be integrated in these kind of tools. On the contrary, simplified methods are good enough because they are simple and fast, with an acceptable precision in almost all the situations. The present work is focused: (a) Firstly, to develop a simplified RC-network model. The aim of the model is to characterize and to implement with
precision the behaviour of a wall in a simulating software tool based on urban environment, (b) secondly, to express in form of equivalences, the different indoor and outdoor excitations that can exist in the building envelope, and (c) finally, to calibrate the simplified model through its characteristic parameters. For a homogeneous wall and two types of excitations, it has been obtained the characteristic parameters of the model that represent the better adjustment to the real wall. In a first step, it has been obtained the results of the proposal model and a reference model based on FEM, in terms of wall external surface heat flow. Results of both models have been compared, and the resultant characteristic parameters of the model have been obtained through an optimisation method. Results for the wall and for the excitations under analysis show: (1) Characteristic longitude ec, or capacitive node position, it is determined according to a certain value of Fo equal to 2 for both excitations, this value remains constant in time, (2) useful wall thickness, on the contrary, vary as time function, according to a logarithmic law for both excitations, although this function is different depending on the considered excitation, (3) using a constant excitation, coefficients from the previous logarithmic function depends on the range of the excitation, while these are practically independent of the lineal
excitation gradient
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