On the Interpolation Problem for the Poisson Equation on Collocated Meshes

The appearence of unphysical velocities in highly distorted meshes is a common problem in many simulations. In collocated meshes, this problem arises from the interpolation of the pressure gradient from faces to cells. Using an algebraic form for the classical incompressible Navier-Stokes equations, this problem is adressed. Starting from the work of F. X. Trias et. al. [FX.Trias et al. JCP 258: 246-267, 2014], a new approach for studying the Poisson equation obtained using the Fractional Step Method is found, such as a new interpolator is proposed in order to found a stable solution, which avoid the appearence of these unpleasant velocities. The stability provided by the interpolator is formally proved for cartesian meshes and its rotations, using fully-explicit time discretizations. The construction of the Poisson equation is supported on mimicking the symmetry properties of the differential operators and the Fractional Step Method. Then it is reinterpreted using a recursive application of the Fractional Step Method in order to study the system as an stationary iterative solver. Furthermore, a numerical analysis for unstructured mesh is also provided.This work has been financially supported by the Ministerio de Economía y Competitividad, Spain (project ref. ENE2017-88697-R). D. Santos acknowledges a FI AGAUR-Generalitat de Catalunya fellowship (2020FI B 00839), and N. Valle also acknowledges a FI AGAUR-Generalitat de Catalunya fellowship (2017FI B 00616). The authors thankfully acknowledge these institutions.Peer ReviewedPostprint (published version

Sea seismometer coupling on the sediment

We can obtain the performance of the marine seismometer upon the sediment to know its coupling in the bottom sea. This paper deals with the coupling parameters in order to obtain the geophone response through the frequency. The use of the shake table and vibration calibrator allows to deduce the coupling transfer function between the geophone and the sediment sea without using a detailed model of interaction sensor/seabed.Peer ReviewedPostprint (published version

On the implementation of flux limiters in algebraic frameworks

The use of flux limiters is widespread within the scientific computing community to capture shock dis- continuities and are of paramount importance for the temporal integration of high-speed aerodynamics, multiphase flows and hyperbolic equations in general. Meanwhile, the breakthrough of new computing architectures and the hybridization of supercomputer systems pose a huge portability challenge, particularly for legacy codes, since the computing subroutines that form the algorithms, the so-called kernels, must be adapted to various complex parallel program- ming paradigms. From this perspective, the development of innovative implementations relying on a minimalist set of kernels simplifies the deployment of scientific computing software on state-of-the-art supercomputers, while it requires the reformulation of algorithms, such as the aforementioned flux lim- iters. Equipped with basic algebraic topology and graph theory underlying the classical mesh concept, a new flux limiter formulation is presented based on the adoption of algebraic data structures and kernels. As a result, traditional flux limiters are cast into a stream of only two types of computing kernels: sparse matrix-vector multiplication and generalized pointwise binary operators. The newly proposed formulation eases the deployment of such a numerical technique in massively parallel, potentially hybrid, computing systems and is demonstrated for a canonical advection problem.The work of N. V. and X. Á. F. has been supported by the Government of Catalonia, FI AGAUR predoctoral grants 2019FI_B2_ 000104 and 2019FI_B2_00076. N. V., X. Á. F., J. C., A. O. and F. X. T. have been funded by the Spanish Research Agency, ANUMESOL project ENE2017-88697-R. J. C. has also been funded by Spanish Research Agency, GALIFLOW project ENE2015-70662-P. The studies of this work have been carried out using the MareNostrum 4 supercomputer of the Barcelona Supercomput- ing Center, projects IM-2019-3-0026 and IM-2020-1-0006; the TSUBAME3.0 supercomputer of the Global Scientific Information and Computing Center at Tokyo Institute of Technology; the Lomonosov-2 supercomputer of the shared research facilities of HPC computing resources at Lomonosov Moscow State University; the K-60 hybrid cluster of the collective use center of the Keldysh Institute of Applied Mathematics; the JFF cluster of the Heat and Mass Transfer Technological Center at Technical University of Cat- alonia. The authors thankfully acknowledge these institutions for the compute time and technical support.Peer ReviewedPostprint (published version

An efficient strategy of parcel modeling for polydispersed multiphase turbulent flows

A three-dimensional particle-laden two-phase turbulent flow by employing the Eulerian-Lagrangian method using multiphase Particle-In-Cell model is implemented to analyze the effects of parcel modeling. In order to achieve an optimal trade-off between accuracy and computational cost, a hybrid approach is proposed. This approach is a combination of two typical models: the volume fixed model, in which each parcel has the same volume, and the number fixed model, in which each parcel has the same number of particles. This approach is studied for the particle-laden turbulent flow benchmark case of Boreé et al. [1], with a mass loading of 22%, by using large eddy simulation through a two-way coupling between continuous and polydispersed phases.Linda Bahramian acknowledges the financial support from the Secretariat of Universities and Research of the Generalitat de Catalunya and the European Social Fund, FI AGAUR Grant (2019 FI B 01205). Carles Oliet, as a Serra Húnter lecturer, acknowledges the Catalan Government for the support through this Programme.Peer ReviewedPostprint (published version

A new method for unveiling Open Clusters in Gaia: new nearby Open Clusters confirmed by DR2

Context. The publication of the Gaia Data Release 2 (Gaia DR2) opens a new era in astronomy. It includes precise astrometric data (positions, proper motions, and parallaxes) for more than 1.3 billion sources, mostly stars. To analyse such a vast amount of new data, the use of data-mining techniques and machine-learning algorithms is mandatory. Aims. A great example of the application of such techniques and algorithms is the search for open clusters (OCs), groups of stars that were born and move together, located in the disc. Our aim is to develop a method to automatically explore the data space, requiring minimal manual intervention. Methods. We explore the performance of a density-based clustering algorithm, DBSCAN, to find clusters in the data together with a supervised learning method such as an artificial neural network (ANN) to automatically distinguish between real OCs and statistical clusters. Results. The development and implementation of this method in a five-dimensional space (l, b, ϖ, μα*, μδ) with the Tycho-Gaia Astrometric Solution (TGAS) data, and a posterior validation using Gaia DR2 data, lead to the proposal of a set of new nearby OCs. Conclusions. We have developed a method to find OCs in astrometric data, designed to be applied to the full Gaia DR2 archive

Relating the outcome of HCV infection and different host SNP polymorphisms in a Majorcan population coinfected with HCV–HIV and treated with pegIFN-RBV

Hepatitis C virus (HCV) is one of the major causes of chronic hepatitis, cirrhosis, and hepatocellular carcinoma, and the development of HCV-related disease is accelerated in individuals coinfected with human immunodeficiency-1 virus (HIV). In the present study, we correlated different host single-nucleotide polymorphisms (SNPs) in the IL28B, CTLA4, LDLr, and HFE genes and mitochondrial DNA (mtDNA) haplogroups with the outcome of HCV infection and the response to pegylated-interferon plus ribavirin (pegIFN-RBV) treatment. Our study population consisted of 63 Majorcan patients coinfected with HCV and HIV and 59 anonymous unrelated controls. Whereas the population frequency of IL28B alleles was similar to that found in a North-American cohort of European descent, the frequency of the rs12979860 C allele was lower than that determined in other cohorts from Spain. The frequencies of CTLA4 and LDLr polymorphisms were comparable to those reported in other populations. Significant differences between cases and control cohorts occurred only for the H63D mutation of the HFE gene. There were no other differences in the frequencies of other polymorphisms or mtDNA haplogroups. The IL28B rs12979860 CC genotype was shown to be associated with a rapid virological response, and the spontaneous viral clearance rate for HCV was higher in patients with the CTLA4+49 G allele. There was no relationship between SNPs in the LDLr and HFE genes and mtDNA haplogroups and the response to treatment. Our results suggest that the host genetic background plays a significant role in the pegIFN-RBV response of patients coinfected with HCV and HIV. [Int Microbiol 2014; 17(1):11-20]Keywords: HCV–HIV co-infection · mtDNA haplogroups · SNP polymorphism

Estudio comparativo de los valores de difusión por RM de las radiaciones ópticas en pacientes diagnosticados de síndrome clínico aislado con pacientes controles

Diversos estudis han demostrat que, en pacients amb esclerosi múltiple, existeixen alteracions als paràmetres de difusió mesurats amb Resonància Magnètica als tractes de substància blanca que es mostren aparentment normals en les seqüències convencionals. Amb l'objectiu de demostrar si aquestes alteracions apareixen precoçment en la fase de síndrome clínic aïllada, es van analitzar una sèrie d'estudis de Resonància Magnètica cerebral amb seqüències potenciades en difusió i tractografia de les radiacions òptiques, de pacients amb el diagnòstic de síndrome clínic aïllada i pacients controls, mesurant en tots ells els valors dels paràmetres principals de difusió: coeficient de difusió aparent y fracció d'anisotropia. Amb aquestes exploracions no es van demostrar alteracions als paràmetres de difusió en fases tan precoces de la malaltia als pacients casos davant els controls.Diversos estudios han demostrado que, en pacientes con esclerosis múltiple, existen alteraciones en los parámetros de difusión medidos por Resonancia Magnética en los tractos de sustancia blanca que se muestran aparentemente normales en las secuencias convencionales. Con el objetivo de comprobar si estas alteraciones aparecen precozmente en la fase de síndrome clínico aislado, se analizaron una serie de estudios de Resonancia Magnética cerebral con secuencias potenciadas en difusión y tractografía de las radiaciones ópticas, de pacientes con el diagnóstico de síndrome clínico aislado y pacientes controles, midiendo en las mismas los valores de los parámetros principales de difusión: coeficiente de difusión aparente y fracción de anisotropía. Con estas exploraciones no se demostraron alteraciones en los parámetros de difusión en fases tan precoces de la enfermedad en los pacientes casos frente a los controles

Prevention and control of HPV infection and HPV-related cancers in Colombia- a meeting report.

The Human Papillomavirus (HPV) Prevention and Control Board is an independent multidisciplinary board of international experts that disseminates relevant information on HPV to a broad array of stakeholders and provides guidance on strategic, technical and policy issues in the implementation of HPV control programs. In response to drastic drop of vaccine coverage following the adverse event crisis in Carmen del Bolivar, Colombia, the HPV Prevention and Control Board in collaboration with the Colombian National Cancer Institute and Colombian League Against Cancer convened a meeting in Bogota, Columbia (November 2018). The goal of the meeting was to bring together national and international group of experts to report the disease burden, epidemiology and surveillance of HPV and HPV-related cancers, to discuss the successes and especially the challenges of HPV vaccination and screening in Colombia, as well as the lessons learnt from neighbouring countries. The meeting provided a platform to confer various stakeholder's perspectives, including the role of the Colombian healthcare system and to catalyse various parts of the public health community in Colombia into effective action. The conclusion of the meeting included following suggestions to strengthen HPV prevention and control: 1) Re-introducing school-based vaccine programs, 2) Integrating primary and secondary prevention programs, 3) Developing an innovative crisis communication plan targeting healthcare workers, teachers and general population, 4) Building trust through efficient and timely communication, 5) Building strong relationship with media to ensure a stable vaccination campaign support, and 6) Promoting empathy among healthcare professionals towards patients to build trust and communicate effectively

A General and Predictive Understanding of Thermal Transport from 1D- and 2D-Confined Nanostructures : Theory and Experiment

Altres ajuts: Acord transformatiu CRUE-CSICHeat management is crucial in the design of nanoscale devices as the operating temperature determines their efficiency and lifetime. Past experimental and theoretical works exploring nanoscale heat transport in semiconductors addressed known deviations from Fourier's law modeling by including effective parameters, such as a size-dependent thermal conductivity. However, recent experiments have qualitatively shown behavior that cannot be modeled in this way. Here, we combine advanced experiment and theory to show that the cooling of 1D- and 2D-confined nanoscale hot spots on silicon can be described using a general hydrodynamic heat transport model, contrary to previous understanding of heat flow in bulk silicon. We use a comprehensive set of extreme ultraviolet scatterometry measurements of nondiffusive transport from transiently heated nanolines and nanodots to validate and generalize our ab initio model, that does not need any geometry-dependent fitting parameters. This allows us to uncover the existence of two distinct time scales and heat transport mechanisms: an interface resistance regime that dominates on short time scales and a hydrodynamic-like phonon transport regime that dominates on longer time scales. Moreover, our model can predict the full thermomechanical response on nanometer length scales and picosecond time scales for arbitrary geometries, providing an advanced practical tool for thermal management of nanoscale technologies. Furthermore, we derive analytical expressions for the transport time scales, valid for a subset of geometries, supplying a route for optimizing heat dissipation

Traffic-related air pollution, oxidative stress genes, and asthma (ECHRS)

BACKGROUND: Traffic-related air pollution is related with asthma, and this association may be modified by genetic factors. OBJECTIVES: We investigated the role of genetic polymorphisms potentially modifying the association between home outdoor levels of modeled nitrogen dioxide and asthma. METHODS: Adults from 13 cities of the second European Community Respiratory Health Survey (ECRHS II) were included (n = 2,920), for whom both DNA and outdoor NO(2) estimates were available. Home addresses were geocoded and linked to modeled outdoor NO(2) estimates, as a marker of local traffic-related pollution. We examined asthma prevalence and evaluated polymorphisms in genes involved in oxidative stress pathways [gluthatione S-transferases M1 (GSTM1), T1 (GSTT1), and P1 (GSTP1) and NAD(P)H:quinine oxidoreductase (NQO1)], inflammatory response [tumor necrosis factor alpha (TNFA)], immunologic response [Toll-like receptor 4 (TLR4)], and airway reactivity [adrenergic receptor beta2 (ADRB2)]. RESULTS: The association between modeled NO(2) and asthma prevalence was significant for carriers of the most common genotypes of NQO1 rs2917666 [odds ratio (OR) = 1.54; 95% confidence interval (CI), 1.10-2.24], TNFA rs2844484 (OR = 2.02; 95% CI, 1.30-3.27). For new-onset asthma, the effect of NO(2) was significant for the most common genotype of NQO1 rs2917666 (OR = 1.52; 95% CI, 1.09-2.16). A significant interaction was found between NQO1 rs2917666 and NO(2) for asthma prevalence (p = 0.02) and new-onset asthma (p = 0.04). CONCLUSIONS: Genetic polymorphisms in the NQO1 gene are related to asthma susceptibility among persons exposed to local traffic-related air pollution. This points to the importance of antioxidant pathways in the protection against the effects of air pollution on asthm