Fluid Mechanics for Biomedical Applications: Weakly Viscoelastic Electrospray, Flow Focusing and Collapsible Channel Models

Three different research topics are discussed in this thesis: i) weakly-viscoelastic electrospray, ii) the emergence of whipping effect on the Flow Focusing technique, and iii) fluid-structure interaction (FSI) phenomena implementing a 2D collapsible channel model. i) A systematic, theoretical comparison of a Newtonian fluid, and a non-Newtonian one modelled using an Oldroyd-B model was performed, resulting in a better understanding of how the properties of this type of material influence aspects such as meniscus shrinking, the agreement with a 1D-slenderness model, or the minimum flow rate value defining the boundary between electrospray and electrospinning. ii) In order to use Flow Focusing for some applications (e.g. XFEL), chaotic oscillations on the jet, known as whipping, must be avoided. A stability map for axisymmetric and lateral perturbation modes was obtained and compared to previous experimental data, examining the effect of different nozzle geometries on the emergence of the whipping effect and jetting-to-dripping configuration physical boundary. iii) In the last paper, the implemented model overcame some limitations presented in other 2D collapsible channel models, leading to analysis using a non-negligible membrane thickness and large deformations on the flexible wall segment. The multiplicity of solutions and their folding points, and the quantification of the effect of physical parameters such as wall thickness and inertia values on the emergence of self-excited oscillations were investigated.En esta tesis se abordan tres temas de investigación diferentes: i) electrospray débilmente viscoelástico, ii) la aparición del efecto whipping en la técnica de Flow Focusing, y iii) la interacción fluido-estructura (FSI) implementando un modelo de canal colapsable 2D. i) Se ha realizado una comparación sistemática y teórica entre un fluido newtoniano y uno no newtoniano modelado mediante un modelo Oldroyd-B, lo que ha permitido comprender mejor cómo las propiedades de este tipo de material influyen en aspectos como la contracción del menisco, la concordancia con un modelo de esbeltez (slenderness) 1D o el valor mínimo de la tasa de flujo que define la frontera entre el electrospray y el electrospinning. ii) Para poder utilizar el Flow Focusing en algunas aplicaciones (por ejemplo, el XFEL), deben evitarse las oscilaciones caóticas en el chorro, conocidas como whipping. Se obtuvo un mapa de estabilidad para los modos axisimétrico y de perturbación lateral y se comparó con datos experimentales anteriores, examinando el efecto de diferentes geometrías de boquillas en la aparición del efecto whipping y en la frontera física de la configuración de jetting-to-dripping. iii) En el último artículo, el modelo implementado superó algunas limitaciones presentadas en otros modelos de canales colapsables 2D, lo que llevó al análisis de estabilidad global del sistema utilizando un espesor de membrana no despreciable y grandes deformaciones en el segmento de pared flexible. Se investigó la multiplicidad de soluciones y sus folding-points, así como la cuantificación del efecto de parámetros físicos como el grosor de la pared y los valores de inercia en la aparición self-excited oscillations

Homological Region Adjacency Tree for a 3D Binary Digital Image via HSF Model

Given a 3D binary digital image I, we define and compute an edge-weighted tree, called Homological Region Tree (or Hom-Tree, for short). It coincides, as unweighted graph, with the classical Region Adjacency Tree of black 6-connected components (CCs) and white 26- connected components of I. In addition, we define the weight of an edge (R, S) as the number of tunnels that the CCs R and S “share”. The Hom-Tree structure is still an isotopic invariant of I. Thus, it provides information about how the different homology groups interact between them, while preserving the duality of black and white CCs. An experimentation with a set of synthetic images showing different shapes and different complexity of connected component nesting is performed for numerically validating the method.Ministerio de Economía y Competitividad MTM2016-81030-

Fractal Topological Analysis for 2D Binary Digital Images

Fractal dimension is a powerful tool employed as a measurement of geometric aspects. In this work we propose a method of topological fractal analysis for 2D binary digital images by using a graph-based topological model of them, called Homological Spanning Forest (HSF, for short). Defined at interpixel level, this set of two trees allows to topologically describe the (black and white) connected component distribution within the image with regards to the relationship “to be surrounded by”. This distribution is condensed into a rooted tree, such that its nodes are connected components determined by some special sub-trees of the previous HSF and the levels of the tree specify the degree of nesting of each connected component. We ask for topological auto-similarity by comparing this topological description of the whole image with a regular rooted tree pattern. Such an analysis can be used to directly quantify some characteristics of biomedical images (e.g. cells samples or clinical images) that are not so noticeable when using geometrical approaches.Ministerio de Economía y Competitividad TEC2016-77785-PMinisterio de Economía y Competitividad MTM2016-81030-

La Educación Ambiental en el marco de la Extensión

  En el marco de la acción de la Secretaría de Extensión de la Facultad de Ciencias Naturales y Museo de la Universidad Nacional de La Plata, concebimos la extensión como un valioso espacio de articulación y construcción bidireccional entre saberes académicos y populares. A lo largo de los años la Secretaría ha desarrollado numerosas propuestas. Muchas de ellas, por su fuerte identidad, se han instalado en la comunidad y cuentan con gran reconocimiento y participación. Estas raíces nos han guiado para re-pensar nuestras prácticas y abrir nuevos caminos. De este replanteo han surgido los lineamientos estratégicos de la Secretaría, que están concebidos como un instrumento de direccionamiento y orientación que facilite la toma de decisiones en la gestión, apuntando al trabajo en dos ámbitos paralelos, pero fuertemente vinculados: 1) El ámbito académico universitario, tanto a nivel de la Facultad de Ciencias Naturales como de otras unidades académicas de la UNLP y/o de otras universidades. 2) La comunidad en general, organizaciones de la sociedad civil, instituciones, etc. Los lineamientos buscan fortalecer la articulación facultad-comunidad, poniendo el énfasis en la necesidad de atender las diversas problemáticas que configuran la situación ambiental actual de la región, y donde la FCNyM constituye un actor indispensable. Por ello, apuntamos a que las actividades de extensión se alimenten de los planteos epistemológicos, éticos y metodológicos del Saber Ambiental (sensu E. Leff), de manera tal que articule y de coherencia, a manera de eje transversal, a todas las actividades desarrolladas por la Secretaría, alimentándolas y orientándolas. Objetivos Generales. 1) Jerarquizar la Extensión en la FCN y M, apuntando a generar conocimientos a partir de la integración con el medio y aportando al desarrollo social. 2) Conformar un ámbito que apunte a la construcción de un saber ambiental, nacido de una fuerte interacción entre las distintas disciplinas de nuestra Facultad, otras unidades académicas, organizaciones, instituciones, etc. Ejes estratégicos. Proponemos que los objetivos anteriormente mencionados, se plasmen y materialicen a través de los siguientes ejes estratégicos: 1) Fortalecimiento de la Extensión. 2) Construcción de un Saber Ambiental. 3) Vinculación con la comunidad. 4) Formación. 5) Comunicación/Difusión. 6) Planificación/ Gestión. La situación actual se presenta como crítica desde diversas dimensiones. Consideramos que este replanteo ordena, fortalece y enriquece nuestras actividades de extensión y permite posicionarnos mejor frente a la compleja realidad que atraviesa nuestra labor diaria.  

An embedding technique to determine ττ backgrounds in proton-proton collision data

An embedding technique is presented to estimate standard model tau tau backgrounds from data with minimal simulation input. In the data, the muons are removed from reconstructed mu mu events and replaced with simulated tau leptons with the same kinematic properties. In this way, a set of hybrid events is obtained that does not rely on simulation except for the decay of the tau leptons. The challenges in describing the underlying event or the production of associated jets in the simulation are avoided. The technique described in this paper was developed for CMS. Its validation and the inherent uncertainties are also discussed. The demonstration of the performance of the technique is based on a sample of proton-proton collisions collected by CMS in 2017 at root s = 13 TeV corresponding to an integrated luminosity of 41.5 fb(-1).Peer reviewe

Measurement of t(t)over-bar normalised multi-differential cross sections in pp collisions at root s=13 TeV, and simultaneous determination of the strong coupling strength, top quark pole mass, and parton distribution functions

Peer reviewe

Measurement of electroweak WZ boson production and search for new physics in WZ + two jets events in pp collisions at √s=13TeV

A measurement of WZ electroweak (EW) vector boson scattering is presented. The measurement is performed in the leptonic decay modes WZ→ℓνℓ′ℓ′, where ℓ,ℓ′=e,μ. The analysis is based on a data sample of proton-proton collisions at √s=13 TeV at the LHC collected with the CMS detector and corresponding to an integrated luminosity of 35.9 fb−1. The WZ plus two jet production cross section is measured in fiducial regions with enhanced contributions from EW production and found to be consistent with standard model predictions. The EW WZ production in association with two jets is measured with an observed (expected) significance of 2.2 (2.5) standard deviations. Constraints on charged Higgs boson production and on anomalous quartic gauge couplings in terms of dimension-eight effective field theory operators are also presented

Measurement of the t(t)over-bar production cross section, the top quark mass, and the strong coupling constant using dilepton events in pp collisions at root s=13TeV

A measurement of the top quark-antiquark pair production cross section sigma(t (t) over bar) in proton-proton collisions at a centre-of-mass energy of 13 TeV is presented. The data correspond to an integrated luminosity of 35.9 fb(-1), recorded by the CMS experiment at the CERN LHC in 2016. Dilepton events (e(+/-) mu(-/+), mu(+) mu(-), e(+) e(-)) are selected and the cross section is measured from a likelihood fit. For a top quark mass parameter in the simulation of m(t)(MC) = 172.5 GeV the fit yields a measured cross section sigma(t (t) over bar) = 803 +/- 2 (stat) +/- 25 (syst) +/- 20 (lumi) pb, in agreement with the expectation from the standard model calculation at next-to-next-to-leading order. A simultaneous fit of the cross section and the top quark mass parameter in the POWHEG simulation is performed. The measured value of m(t)(MC) = 172.33 +/- 0.14 (stat)(-0.72)(+0.66) (syst) GeV is in good agreement with previous measurements. The resulting cross section is used, together with the theoretical prediction, to determine the top quark mass and to extract a value of the strong coupling constant with different sets of parton distribution functions.Peer reviewe

Search for dark matter in events with a leptoquark and missing transverse momentum in proton-proton collisions at 13 TeV

A search is presented for dark matter in proton-proton collisions at a center-of-mass energy of root s= 13 TeV using events with at least one high transverse momentum (p(T)) muon, at least one high-p(T) jet, and large missing transverse momentum. The data were collected with the CMS detector at the CERN LHC in 2016 and 2017, and correspond to an integrated luminosity of 77.4 fb(-1). In the examined scenario, a pair of scalar leptoquarks is assumed to be produced. One leptoquark decays to a muon and a jet while the other decays to dark matter and low-p(T) standard model particles. The signature for signal events would be significant missing transverse momentum from the dark matter in conjunction with a peak at the leptoquark mass in the invariant mass distribution of the highest p(T) muon and jet. The data are observed to be consistent with the background predicted by the standard model. For the first benchmark scenario considered, dark matter masses up to 500 GeV are excluded for leptoquark masses m(LQ) approximate to 1400 GeV, and up to 300 GeV for m(LQ) approximate to 1500 GeV. For the second benchmark scenario, dark matter masses up to 600 GeV are excluded for m(LQ) approximate to 1400 GeV. (C) 2019 The Author(s). Published by Elsevier B.V.Peer reviewe

Bose-Einstein correlations of charged hadrons in proton-proton collisions at s\sqrt s = 13 TeV

Bose-Einstein correlations of charged hadrons are measured over a broad multiplicity range, from a few particles up to about 250 reconstructed charged hadrons in proton-proton collisions at $\sqrt{s}$ = 13 TeV. The results are based on data collected using the CMS detector at the LHC during runs with a special low-pileup configuration. Three analysis techniques with different degrees of dependence on simulations are used to remove the non-Bose-Einstein background from the correlation functions. All three methods give consistent results. The measured lengths of homogeneity are studied as functions of particle multiplicity as well as average pair transverse momentum and mass. The results are compared with data from both CMS and ATLAS at $\sqrt{s}$ = 7 TeV, as well as with theoretical predictions.[graphic not available: see fulltext]Bose-Einstein correlations of charged hadrons are measured over a broad multiplicity range, from a few particles up to about 250 reconstructed charged hadrons in proton-proton collisions at $\sqrt{s} =$ 13 TeV. The results are based on data collected using the CMS detector at the LHC during runs with a special low-pileup configuration. Three analysis techniques with different degrees of dependence on simulations are used to remove the non-Bose-Einstein background from the correlation functions. All three methods give consistent results. The measured lengths of homogeneity are studied as functions of particle multiplicity as well as average pair transverse momentum and mass. The results are compared with data from both CMS and ATLAS at $\sqrt{s} =$ 7 TeV, as well as with theoretical predictions