Influence of mechanical forces on the self-organisation of biomolecular systems

Mechanical forces play a crucial role in shaping the development of tissues and organisms. Nature has evolved intricate ways of utilising mechanical cues in order to achieve various objectives. In this dissertation, we examine the role played by mechanical forces in regulating the function of biological systems at the level of many molecules. We employ computational simulations, using minimal coarse-grained models. This allows us to capture the essential information about the investigated systems as well as to derive general phenomenological insights. We begin with the study of mechanosensitive protein channels, which are a class of transmembrane proteins responsible for sensing the osmotic pressure on cells and protecting them against lysis. Recent experiments suggest that such channels separate into liquid-like clusters, but the functional role of this aggregation is still unknown. We examine the collective behaviour of such proteins and we reveal that a dynamic self-assembly of channels, driven by changes in membrane tension, can control the osmotic pressure equilibration and the volume of the whole cell. We then focus on the growth of membrane protrusions, or tubes, which are thin elongated structures used by cells to sense mechanical stimuli. We investigate the influence of proteins linking the membrane to cytoskeletal components on pulling membrane tubes. We find that the force required to extrude a tube has an intriguing non-linear dependence on the concentration of cortex attachments. Subsequently, we turn our attention to the study of the mechanically-induced self-assembly of fibronectin, a structural protein constituent of the extracellular matrix. We examine the emergent fibrillar architectures and show how the morphologies of these networks change depending on various mechanical parameters. Finally, we explore how a nanoparticle adsorbed on a deformable elastic membrane senses the substrate’s mechanical properties through gradients in the membrane’s bending rigidity. We hope that the results presented in this dissertation will spur further discussions and experimental studies related to the functional role played by mechanical forces in regulating the collective macromolecular behaviour at the nanoscale

A rational family of singular perturbations. The trichotomy theorem.

Treballs finals del Màster en Matemàtica Avançada, Facultat de matemàtiques, Universitat de Barcelona, Any: 2017, Director: Xavier Jarque i Ribera[en] The main focus of this paper will be studying the so called Escape Trichotomy for the singular perturbation family of functions. However, to be able to understand it, there will first be necessary to know some concepts and results about complex dynamical systems and more particularly, the asymptotic behaviour of rational maps on the complex sphere. First, we will introduce the fundamental dynamical systems concepts, such as orbits, fixed and periodic points, attracting and repelling cycles and so on. Then, we will introduce a simpler way of studying a dynamical systems, conjugacies, by establishing if its behaviour under iterations may be similar to another, better known one. We will continue by introducing the concept of critical points and why they are a major point of interest in dynamics

About the connectivity of Fatou components for some families of rational maps

[eng] Rational iteration is the study of the asymptotic behaviour of the sequences given by the iterates of a rational map on the Riemann sphere. According to Montel's theory on normal families, the phase space (also called the dynamical plane) is divided in two completely in­ variant sets known as the Fatou set (an open set where the dynamics is tame) and the Julia set (a closed set where the dynamics is chaotic). The main topic of this thesis is the study of the connectivity of the Fatou components for certain families of rational maps. On the one hand, we consider a family of singular perturbation and extend previous results on singular perturbations of Blaschke products. The main result is to show that the dynamical planes for the corresponding maps present Fatou components of arbitrarily large connectivity and determine precisely these connectivities. On the other hand, we consider a different problem related to root-finding algorithms. More precisely, we study the Chebyshev-Halley methods applied to a symmetric family of polynomials of arbitrary degree. The main goal is to show the existence of parameters such that the immediate basins of attraction corresponding to the roots of unity are infinitely connected. Moreover, we also prove that the corresponding dynamical plane contains a connected component of the Julia set, which is a quasiconforrnal deformation of the Julia set of the map obtained by applying Newton's method.[cat] La iteració racional és l'estudi del comportament asimptòtic de les seqüencies donades pels iterats d'una funció racional sobre l'esfera de Riemann. Segons la teoria de Montel sobre les famílies normals, l'espai de fases (també anomenat pla dinàmic) es divideix en dos conjunts totalment invariants coneguts com a conjunt de Fatou (unió de components oberts on la dinàmica és essencialment senzilla) i el conjunt de Julia (un conjunt tancat on la dinàmica és caòtica). El tema principal d'aquesta tesi és l'estudi de la connectivitat de les components de Fatou pera determinar les famílies de funcions racionals. D'una banda, l'autor considera una familia de pertorbacions singulars i amplia els resultats anteriors sobre pertorbacions singulars dels productes de Blaschke. El resultat principal és mostrar que els plans dinàmics d'aquestes funcions presenten components de Fatou de connectivitat arbitràriament grans i determinen precisament aquestes connectivitats. D'altra banda, l’autor considera un problema diferent relacionat amb els algorismes de recerca d'arrel. Més precisament, estudia els mètodes Chebyshev-Halley aplicats a una família simètrica de polinomis de grau arbitrari. L'objectiu principal és mostrar l'existència de paràmetres de manera que les conques d'atracció immediates corresponents a les arrels de la unitat tinguin connectivitat infinita. A més, també demostra que el pla dinàmic corresponent conté una component connexa del conjunt de Julia, que és una deformació quasiconforme del conjunt de Julia de la funció obtinguda aplicant el mètode de Newton

Dynamic clustering regulates activity of mechanosensitive membrane channels

Experiments have suggested that bacterial mechanosensitive channels separate into 2D clusters, the role of which is unclear. By developing a coarse-grained computer model we find that clustering promotes the channel closure, which is highly dependent on the channel concentration and membrane stress. This behaviour yields a tightly regulated gating system, whereby at high tensions channels gate individually, and at lower tensions the channels spontaneously aggregate and inactivate. We implement this positive feedback into the model for cell volume regulation, and find that the channel clustering protects the cell against excessive loss of cytoplasmic content

Near-Earth Asteroids Data mining on Astronomical Databases: EuroNEAR experience

Program available at: http://www.imcce.fr/hosted_sites/naroo/program.htmlInternational audienceIn the framework of EuroNEAR network several databases around the world were datamined. The main scientifi c objective was the astrometry of Near-Earth Asteroids (NEAs) for both precovery and secure orbits of these objects. The article presents few aspects of data-mining and the developed procedures for accomplishing these objectives

About the connectivity of Fatou components for some families of rational maps

Programa de Doctorat en Matemàtica i Informàtica[eng] Rational iteration is the study of the asymptotic behaviour of the sequences given by the iterates of a rational map on the Riemann sphere. According to Montel's theory on normal families, the phase space (also called the dynamical plane) is divided in two completely in­ variant sets known as the Fatou set (an open set where the dynamics is tame) and the Julia set (a closed set where the dynamics is chaotic). The main topic of this thesis is the study of the connectivity of the Fatou components for certain families of rational maps. On the one hand, we consider a family of singular perturbation and extend previous results on singular perturbations of Blaschke products. The main result is to show that the dynamical planes for the corresponding maps present Fatou components of arbitrarily large connectivity and determine precisely these connectivities. On the other hand, we consider a different problem related to root-finding algorithms. More precisely, we study the Chebyshev-Halley methods applied to a symmetric family of polynomials of arbitrary degree. The main goal is to show the existence of parameters such that the immediate basins of attraction corresponding to the roots of unity are infinitely connected. Moreover, we also prove that the corresponding dynamical plane contains a connected component of the Julia set, which is a quasiconforrnal deformation of the Julia set of the map obtained by applying Newton's method.[cat] La iteració racional és l'estudi del comportament asimptòtic de les seqüencies donades pels iterats d'una funció racional sobre l'esfera de Riemann. Segons la teoria de Montel sobre les famílies normals, l'espai de fases (també anomenat pla dinàmic) es divideix en dos conjunts totalment invariants coneguts com a conjunt de Fatou (unió de components oberts on la dinàmica és essencialment senzilla) i el conjunt de Julia (un conjunt tancat on la dinàmica és caòtica). El tema principal d'aquesta tesi és l'estudi de la connectivitat de les components de Fatou pera determinar les famílies de funcions racionals. D'una banda, l'autor considera una familia de pertorbacions singulars i amplia els resultats anteriors sobre pertorbacions singulars dels productes de Blaschke. El resultat principal és mostrar que els plans dinàmics d'aquestes funcions presenten components de Fatou de connectivitat arbitràriament grans i determinen precisament aquestes connectivitats. D'altra banda, l’autor considera un problema diferent relacionat amb els algorismes de recerca d'arrel. Més precisament, estudia els mètodes Chebyshev-Halley aplicats a una família simètrica de polinomis de grau arbitrari. L'objectiu principal és mostrar l'existència de paràmetres de manera que les conques d'atracció immediates corresponents a les arrels de la unitat tinguin connectivitat infinita. A més, també demostra que el pla dinàmic corresponent conté una component connexa del conjunt de Julia, que és una deformació quasiconforme del conjunt de Julia de la funció obtinguda aplicant el mètode de Newton

An overview of energy intensity of drinking water production and wastewater treatment

Drinking water has long been a free resource, but its cost is rising due to increased pollution of both surface and aquifer water sources. Drinking water requires special treatment to be potable and usable by the general public, treatments that consume a certain amount of energy. In addition, the treatment process of wastewater before it is discharged into the environment consumes energy. According to the study, the energy required for wastewater treatment is significantly greater than the energy required for preparing drinking water. Water treatment is a significant source of GHG emissions due to the use of energy and chemicals, and reducing energy consumption would significantly reduce our overall carbon footprint. Furthermore, the UN’s Sustainable Development Goals encourage access to safe drinking water and sanitation while also calling for greater resource efficiency. This research aims to provide an overview of the energy used in water treatment. This study attempts to depict the energy used in water treatment. Electricity consumption for water supply and wastewater treatment is substantial and has a significant environmental impact, particularly in countries where electricity is generated using fossil fuels

Economic and Environmental Analysis of Investing in Solar Water Heating Systems

Solar water heating (SWH) systems can provide a significant part of the heat energy that is required in the residential sector. The use of SWH systems is motivated by the desire to reduce energy consumption and especially to reduce a major source of greenhouse gas (GHG) emissions. The purposes of the present paper consist in: assessing the solar potential; analysing the possibility of using solar energy to heat water for residential applications in Romania; investigating the economic potential of SWH systems; and their contribution to saving energy and reducing CO2 emissions. The results showed that if solar systems are used, the annual energy savings amount to approximately 71%, and the reduction of GHG emissions into the atmosphere are of 18.5 tonnes of CO2 over the lifespan of the system, with a discounted payback period of 6.8–8.6 years, in accordance with the savings achieved depending on system characteristics, the solar radiation available, ambient air temperature and on heating load characteristics. Financially, the installation of SWH systems determines net savings of 805–1151 Euro in a 25-year period in the absence of governmental subsidies. According to the sensitivity analysis, installing a SWH system with subsidies of up to 50% determines the reduction of the discounted payback period to 3.1–3.9 years and the increase of net savings to 1570–1916 Euro. These results indicate that investing in these systems is cost-effective for Romanian households as long as the governmental subsidies increase

Applying Deep Learning Methods for Mammography Analysis and Breast Cancer Detection

Breast cancer is a serious medical condition that requires early detection for successful treatment. Mammography is a commonly used imaging technique for breast cancer screening, but its analysis can be time-consuming and subjective. This study explores the use of deep learning-based methods for mammogram analysis, with a focus on improving the performance of the analysis process. The study is focused on applying different computer vision models, with both CNN and ViT architectures, on a publicly available dataset. The innovative approach is represented by the data augmentation technique based on synthetic images, which are generated to improve the performance of the models. The results of the study demonstrate the importance of data pre-processing and augmentation techniques for achieving high classification performance. Additionally, the study utilizes explainable AI techniques, such as class activation maps and centered bounding boxes, to better understand the models’ decision-making process