On the influence of the thickness of the sediment moving layer in the definition of the bedload transport formula in Exner systems

In this paper we study Exner system and introduce a modified general definition for bedload transport flux. The new formulation has the advantage of taking into account the thickness of the sediment layer which avoids mass conservation problems in certain situations. Moreover, it reduces to a classical solid transport discharge formula in the case of quasi-uniform regime. We also present several numerical tests where we compare the proposed sediment transport formula with the classical formulation and we show the behavior of the new model in different configurations

Gastroenteritis eosinofílica

La gastroenteritis eosinofílica es reconocida como una entidad rara y de patogénesis incierta, en la que existe infiltración de eosinófilos en una o más paredes del tracto gastrointestinal; los síntomas y signos se relacionan con el patrón de infiltración y con el sitio comprometido. Se presenta el caso de un paciente condolor abdominal, pérdida de peso, ascitis y eosinofilia periférica, y que respondió adecuadamente

A multilayer shallow water system for polydisperse sedimentation

This work considers the flow of a fluid containing one disperse substance consisting of small particles that belong to different species differing in size and density. The flow is modelled by combining a multilayer shallow water approach with a polydisperse sedimentation process. This technique allows one to keep information on the vertical distribution of the solid particles in the mixture, and thereby to model the segregation of the particle species from each other, and from the fluid, taking place in the vertical direction of the gravity body force only. This polydisperse sedimentation process is described by the well-known Masliyah-Lockett-Bassoon (MLB) velocity functions. The resulting multilayer sedimentation-ow model can be written as a hyperbolic system with nonconservative products. The definitions of the nonconservative products are related to the hydrostatic pressure and to the mass and momentum hydrodynamic transfer terms between the layers. For the numerical discretization a strategy of two steps is proposed, where the first one is also divided into two parts. In the _rst step, instead of approximating the complete model, we approximate a reduced model with a smaller number of unknowns. Then, taking advantage of the fact that the concentrations are passive scalars in the system, we approximate the concentrations of the different species by an upwind scheme related to the numerical flux of the total concentration. In the second step, the effect of the transference terms defined in terms of the MLB model is introduced. These transfer terms are approximated by using a numerical ux function used to discretize the 1D vertical polydisperse model (see Bürger, García, Karlsen and Towers, J. Eng. Math. 60 (2008), 387{425). Finally, some numerical examples are presented. Numerical results suggest that the multilayer shallow water model could be adequate in situations where the settling takes place from a suspension that undergoes horizontal movement

An Efficient Two-Layer Non-hydrostatic Approach for Dispersive Water Waves

In this paper, we propose a two-layer depth-integrated non-hydrostatic system with improved dispersion relations. This improvement is obtained through three free parameters: two of them related to the representation of the pressure at the interface and a third one that controls the relative position of the interface concerning the total height. These parameters are then optimized to improve the dispersive properties of the resulting system. The optimized model shows good linear wave characteristics up to kH ≈ 10, that can be improved for long waves. The system is solved using an efficient formally second-order well-balanced and positive preserving hybrid finite volume/difference numerical scheme. The scheme consists of a two-step algorithm based on a projection-correction type scheme. First, the hyperbolic part of the system is discretized using a Polynomial Viscosity Matrix path-conservative finite-volume method. Second, the dispersive terms are solved using finite differences. The method has been applied to idealized and challenging physical situations that involve nearshore breaking. Agreement with laboratory data is excellent. This technique results in an accurate and efficient method

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 lled by water and the lower one by sediment. The key point falls on the de nition 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 de nition 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 e ects when the ratio between the hydrodynamic and morphodynamic time scales is small. The SVE with gravitational e ects 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 e ects 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 uid 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.Ministerio de Economía y Competitividad MTM 2015-70490-C2-1-RMinisterio de Economía y Competitividad MTM 2015-70490-C2-2-

On a shallow water model for the simulation of turbidity currents

We present a model for hyperpycnal plumes or turbidity currents that takes into account the interaction between the turbidity current and the bottom, considering deposition and erosion effects as well as solid transport of particles at the bed load due to the current. Water entrainment from the ambient water in which the turbidity current plunges is also considered. Motion of ambient water is neglected and the rigid lid assumption is considered. The model is obtained as a depth-average system of equations under the shallow water hypothesis describing the balance of fluid mass, sediment mass and mean ow. The character of the system is analyzed and numerical simulations are carried out using finite volume schemes and path-conservative Roe schemes

Numerical simulations of a dispersive model approximating free-surface Euler equations

In some configurations, dispersion effects must be taken into account to improve the simulation of complex fluid flows. A family of free-surface dispersive models has been derived in Fernández-Nieto et al. (Commun Math Sci 16(05):1169–1202, 2018). The hierarchy of models is based on a Galerkin approach and parameterised by the number of discrete layers along the vertical axis. In this paper we propose some numerical schemes designed for these models in a 1D open channel. The cornerstone of this family of models is the Serre – GreenNaghdi model which has been extensively studied in the literature from both theoretical and numerical points of view. More precisely, the goal is to propose a numerical method for the LDNH2 model that is based on a projection method extended from the one-layer case to any number of layers. To do so, the one-layer case is addressed by means of a projectioncorrection method applied to a non-standard differential operator. A special attention is paid to boundary conditions. This case is extended to several layers thanks to an original relabelling of the unknowns. In the numerical tests we show the convergence of the method and its accuracy compared to the LDNH0 model

A HLLC scheme for nonconservative hyperbolic problems. Application to turbidity currents with sediment transport.

This paper focuses on the generalization of the HLLC Riemann solver for nonconservative problems. First, the general ideas of the extension of the HLLC solvers for nonconservative systems are discussed. Then, two particular HLLC solvers are described for a turbidity current model with sediment transport. Some results concerning the positivity of the corresponding schemes are presented. Several numerical tests are performed to compare the two HLLC solvers among them and with a Roe method

Linfomas cutáneos primarios: estudio retrospectivo clinicopatológico durante el periodo 1997 - 2004 en el Hospital Edgardo Rebagliati Martins, Essalud, Lima, Perú

Introducción: las características clínicopatológicas de los linfomas malignos varían de acuerdo a la geografía. La piel es el segundo lugar de compromiso extranodal de linfoma no Hodgkin .El linfoma primario cutáneo tienen un comportamiento clínico y pronóstico diferente de los linfomas sistémicos Objetivo: el objetivo de este estudio fue determinar la frecuencia relativa de los linfomas cutáneos y examinar la relevancia clínica de la nueva clasificación WHO/EORTC y la sobrevida de los casos peruanos de linfoma primario cutáneo. Material y método:  se realizó un estudio retrospectivo clínicopatológico de 78 casos de linfomas cutáneos, diagnosticados desde 1997 al 2004 en el Hospital Edgardo Rebagliati Martins, Essalud, Lima,Perú. Las historias clínicas, biopsias y pruebas de inmunohistoquímica de los 78 pacientes enrolados fueron revisadas. Resultados: 67/78 (85,9%) fueron linfomas primarios cutáneos y 11/78 (14,1%) fueron linfomas cutáneos secundarios. El linfoma secundario cutáneo más frecuente fue el linfoma /leucemia T del adulto (ATLL) con 72% de los casos. El linfoma primario cutáneo más frecuente fue la micosis fungoide (MF) 30/67 (44,7%) , seguido del ATLL 13/67 (19,4%) y el linfoma T periférico no especificado 4/67 (6%). La sobrevida a 5 años para la MF, ATLL cutáneo y ATLL sistémico fue de 77%. 18% y 0% respectivamente. Conclusión: MF y ATLL cutáneo fueron los linfomas primarios cutáneos más frecuentes en nuestro hospital. La MF posee un buen pronóstico mientras el ATLL cutáneo posee pobre sobrevida

Short-term changes in klotho and FGF23 in heart failure with reduced ejection fraction—a substudy of the DAPA-VO2 study

The klotho and fibroblast growth factor 23 (FGF-23) pathway is implicated in cardiovascular pathophysiology. This substudy aimed to assess the changes in klotho and FGF-23 levels 1-month after dapagliflozin in patients with stable heart failure and reduced ejection fraction (HFrEF). The study included 29 patients (32.2% of the total), with 14 assigned to the placebo group and 15 to the dapagliflozin, as part of the double-blind, randomized clinical trial [DAPA-VO2 (NCT04197635)]. Blood samples were collected at baseline and after 30 days, and Klotho and FGF-23 levels were measured using ELISA Kits. Between-treatment changes (raw data) were analyzed by using the Mann-Whitney test and expressed as median (p25%–p75%). Linear regression models were utilized to analyze changes in the logarithm (log) of klotho and FGF-23. The median age was 68.3 years (60.8–72.1), with 79.3% male and 81.5% classified as NYHA II. The baseline medians of left ventricular ejection fraction, glomerular filtration rate, NT-proBNP, klotho, and FGF-23 were 35.8% (30.5–37.8), 67.4 ml/min/1.73 m2 (50.7–82.8), 1,285 pg/ml (898–2,305), 623.4 pg/ml (533.5–736.6), and 72.6 RU/ml (62.6–96.1), respectively. The baseline mean peak oxygen uptake was 13.1 ± 4.0 ml/kg/min. Compared to placebo, patients on dapagliflozin showed a significant median increase of klotho [Δ+29.5, (12.9–37.2); p = 0.009] and a non-significant decrease of FGF-23 [Δ−4.6, (−1.7 to −5.4); p = 0.051]. A significant increase in log-klotho (p = 0.011) and a decrease in log-FGF-23 (p = 0.040) were found in the inferential analysis. In conclusion, in patients with stable HFrEF, dapagliflozin led to a short-term increase in klotho and a decrease in FGF-23