Doctorado en Ingeniería (tesis)

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https://hdl.handle.net/10784/81

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A Novel Injectable Piezoelectric Hydrogel for Periodontal Disease Treatment.
(Universidad EAFIT, 2023) Roldán Lopera, Lina María; Correa Vélez, Santiago Alberto
Periodontal disease is a multifactorial, bacterially induced inflammatory condition characterized by the progressive destruction of periodontal tissues. The successful nonsurgical treatment of periodontitis requires multifunctional technologies offering antibacterial therapies and promotion of bone regeneration simultaneously. For the first time, in this study, an injectable piezoelectric hydrogel (PiezoGEL) was developed after combining gelatin methacryloyl (GelMA) with biocompatible piezoelectric fillers of barium titanate (BTO) that produce electrical charges when stimulated by biomechanical vibrations (e.g., mastication, movements). We harnessed the benefits of hydrogels (injectable, light curable, conforms to pocket spaces, biocompatible) with the bioactive effects of piezoelectric charges. A thorough biomaterial characterization confirmed piezoelectric fillers' successful integration with the hydrogel, photopolymerizability, injectability for clinical use, and electrical charge generation to enable bioactive effects (antibacterial and bone tissue regeneration). PiezoGEL showed significant reductions in pathogenic biofilm biomass (∼41%), metabolic activity (∼75%), and the number of viable cells (∼2-3 log) compared to hydrogels without BTO fillers in vitro. Molecular analysis related the antibacterial effects to be associated with reduced cell adhesion (downregulation of porP and fimA) and increased oxidative stress (upregulation of oxyR) genes. Moreover, PiezoGEL significantly enhanced bone marrow stem cell (BMSC) viability and osteogenic differentiation by upregulating RUNX2, COL1A1, and ALP. In vivo, PiezoGEL effectively reduced periodontal inflammation and increased bone tissue regeneration compared to control groups in a mice model. Findings from this study suggest PiezoGEL to be a promising and novel therapeutic candidate for the treatment of periodontal disease nonsurgically.
Aide à la décision en conception préliminaire par l'estimation des impacts environnementaux
(Universidad EAFIT, 2016) Agudelo Gutiérrez, Lina María; Mejía Gutiérrez, Ricardo; Nadeau, Jean Pierre; Pailhes, Jérôme
Analyses of the Morphometric Variation within Caiman crocodilus Species Complex in Colombia
(Universidad EAFIT, 2022) Angulo-Bedoya, Mónica; Webster, Mark; Benítez, Hugo A.; Balaguera-Reina, Sergio; Correa, Santiago; Roberto, Igor J.; Moncada-Jimenez, Juan F.; Mazzotti, Frank J.; Espinoza-Donoso, Sebastian; Lemic, Darija; Correa Vélez, Santiago Alberto; Pinel Peláez, Nicolás
Bacillus sp. strains and their inducible in vitro antagonism : a biochemical and molecular study
(Universidad EAFIT, 2018) Sierra Zapata, Laura; Villegas Escobar, Valeska; Romero Tabarez, Magally
Discovering novel antibiotic substances from natural sources and revitalizing the pipeline for screenings of naturally sourced substances that could render new bioactive compounds, is a priority nowadays in the face of a world crisis of antimicrobial resistance. This research was focused on disclosing an observed antagonism system composed of Bacillus sp. strains producing inducible antimicrobial activity against the plant pathogen Ralstonia solanacearum, a widespread bacterium that causes bacterial wilt disease to a great variety of plant species, including many agriculturally important ones as are bananas. The inducible phenomenon was discovered during the screening of 1493 aerobic endospore forming bacteria against plant pathogens. It was observed that in the presence of the chemical compound Triphenyl Tetrazolium Chloride (TTC), which belongs to the group of synthetic compounds known as tetrazolium salts used to monitor cell respiration, Bacillus sp. strains produced inhibition zones against the bacterial plant pathogen and other pathogenic bacterial species, while in the absence of the compound they did not have any bioactivity. During biochemical characterization, it was evidenced that although the phenomenon was observable across several species of the order Bacillales, strains belonging to B. cereus, B. pumilus and B. subtilis were outstanding in their inducible antagonism potential, among other species tested. Besides, relevant traits revealed that other tetrazolium salts did not induce antagonistic activity and that the addition of antioxidant compounds did not reduce the inducible antagonistic activity. Also, R. solanacearum sensitivity to antibiotics was not increased by the addition of TTC and the inducible activity was independent of the presence of the pathogenic strain. In order to determine genes and pathways that were activated under TTC conditions, transcriptomic and metabolomics analysis were performed. Transcriptomic results revealed that specific pathways of the nitrogen metabolism, such as pyrimidines, purines and histidine biosynthetic routes, were 2 to 5 fold up-regulated in B. subtilis NCIB-3610 cells growing under TTC presence. On the other hand, metabolomic analysis showed that 28 specific compounds were either unique or 3 to 5 fold more abundant in active extracts obtained from inducible conditions, compared to non-induced controls. Data mining on public chemical databases, using intrinsic properties of the selected compounds, suggests that they mostly belong to chemical families of carbamates, imidazoles, pyrrolidines, pyrimidines, dipeptides and oligopeptides, all of which are part of the nitrogen metabolism. Results suggest that Bacillus cells reduction of TTC into triphenyl formazan (TPF) and its further accumulation inside the cells, induces the production of nitrogen-derived compounds, either by activation of nitrogen metabolism biosynthetic pathways or by a biotransformation of TPF into derivatives. Once produced, the compounds are secreted into the medium and act as antimicrobials against other bacteria.
Compendium of publications on: differential operators on manifolds for CAD CAM CAE and computer graphics
(Universidad EAFIT, 2020) Mejía Parra, Daniel; Ruiz Salguero, Oscar Eduardo; Posada Velásquez, Jorge León
This Doctoral Thesis develops novel articulations of Differential Operators on Manifolds for applications on Computer Aided Design, Manufacture and Computer Graphics, as follows: (1) Mesh Parameterization and Segmentation. Development and application of Laplace-Beltrami, Hessian, Geodesic and Curvature operators for topology and geometry – driven segmentations and parameterizations of 2-manifold triangular meshes. Applications in Reverse Engineering, Manufacturing and Medicine. (2) Computing of Laser-driven Temperature Maps in thin plates. Spectral domain - based analytic solutions of the transient, non-homogeneous heat equation for simulation of temperature maps in multi-laser heated thin plates, modeled as 2-manifolds plus thickness. (3) Real-time estimation of dimensional compliance of hot out-of-forge workpieces. A Special Orthogonal SO(3) transformation between 2-manifolds is found, which enables a distance operator between 2-manifolds in R^3 (or m-manifolds in R^n). This process instruments the real-time assessment of dimensional compliance of hot workpieces, in the factory floor shop. (4) Slicing or Level-Set computation for 2-manifold triangular meshes in Additive Manufacturing. Development of a classification of non-degenerate (i.e. non-singular Hessian) and degenerate (i.e. singular Hessian) critical points of non-Morse functions on 2-manifold objects, followed by computation of level sets for Additive Manufacturing. Most of the aforementioned contributions have been screened and accepted by the international scientific community (and published). Non-published material corresponds to confidential developments which are commercially exploited by the sponsors and therefore banned from dissemination.
Compendium on "assessment of intended deformations and kinematic identification of parallel mechanisms under quasi-static condictions"
(Universidad EAFIT, 2010) Durango Idárraga, Sebastián; Ruíz Salguero, Óscar Eduardo
Computational Geometry Contributions Applied to Additive Manufacturing
(Universidad EAFIT, 2022) Montoya Zapata, Diego Alejandro; Ruiz Salguero, Oscar Eduardo; Posada Velásquez, Jorge León
Computational Geometry in Medical Applications
(Universidad EAFIT, 2016) Cortés Acosta, Camilo Andrés; Ruíz Salguero, Óscar Eduardo; Flórez Esnal, Julián
Computational Study of Cell Mobility and Transport Phenomena Through Textile Vascular Grafts Using a Multi-Scale Approach
(Universidad EAFIT, 2015) Valencia Cardona, Raúl Adolfo; García Ruíz, Manuel Julio; Bustamante Osorno, John
Textile vascular grafts are biomedical devices that serve as partial replacement of damaged arterial vessels, prevent aneurysms rupture and restore normal blood flow -- It is believed that the success of a textile vascular graft, in the healing process after implantation, is due to the porous micro-structure of the wall -- Among the key properties that take part in the tissue repair process are the type of fabric and degree of porosity and permeability, defining the ability of a well-controlled environment for the neovascularization, nutrient supply, and cellular transport -- Although the transport of fluids through textiles is of great technical interest in biomedical applications, little is known about predicting the micro-flow pattern and the transport and deposition of individual platelets, related with the graft occlusion -- Often, this information is difficult to obtain experimentally both in vivo and in vitro, representing a great deal of research efforts -- The aim of this work is to investigate how the type of fabric, permeability and porosity affect both the local fluid dynamics at several scales and the fluid-particle interaction among platelets in textile grafts with an anastomosis of end-to-end configuration -- Two types of samples were analyzed: woven and electrospun, this last one has been manufactured -- This study involves both experimental and computational tests -- The experimental tests were performed to characterize the permeability and porosity under static conditions -- The computational tests are based on a multiscale approach where the fluid flow was solved with the Finite Element Method and the discrete particles were solved with the Molecular Dynamic Method -- The fluid-particle interaction was accomplished in one-, two-, and four-ways, where the blood was considered as a suspension of platelets in plasma -- The textile wall was considered as a porous media with two scales of length: straight tubular structure with porous walls for the macro-domain and representative unit cells of fabric for the micro-domain. Additionally, it presents the implementation of a numerical case that includes one of the main applications of textile vascular grafts to repair Abdominal Aortic Aneurysms (AAA) -- The results have shown that the type of fabric in textile vascular grafts and the degree of porosity and permeability affect the local fluid dynamics and the level of penetration of platelet particles through the graft wall at several length scales, thus indicating their importance as design parameters -- It was found that the permeability is strongly depends on the micro-structure of the fabric, changing the local fluid dynamics and the time of residence of platelets inside the wall -- Moreover, the porous walls cause deviations from Poiseuille flow due to leakage flow through the wall from a macroscopic viewpoint -- Lastly, it was possible to observe that the textile wall with different porosities, acting like a barrier between the blood and an aneurysmal zone, affects the flow pattern, the number of platelets adhered to the artificial surface and the time of residence of platelets into the aneurysmal zone -- In conclusion, predicting the flow pattern and the mobility of blood cells through the textile wall before the graft is manufactured, the development of new textile grafts can be improved
Desarrollo de un electrodo bioinspirado para generación de Hidrógeno
(Universidad EAFIT, 2024) Carmona Saldarriaga, Laura; Ossa Henao, Edgar Alexander
Desarrollo de un proceso continuo para medicamentos antiinflamatorios con ingredientes activos de baja solubilidad que garanticen mayor eficacia y mejor solubilidad en excipientes poliméricos
(Universidad EAFIT, 2019) Restrepo Uribe, Laura; Noriega Escobar, María del Pilar
Design and analysis of photovoltaic surfaces based on a multiphysics approach
(Universidad EAFIT, 2023) Espitia Mesa, Gabriel Jaime; Mejía Gutiérrez, Ricardo
Effects of topography on 3D seismic ground motion simulation with an application to the Valley of Aburrá in Antioquia, Colombia
(Universidad EAFIT, 2013) Restrepo Sánchez, Doriam Leidin; Jaramillo Fernández, Juan Diego
This dissertation presents a numerical scheme based upon the finite element framework for the numerical modeling of earthquake-induced ground motion in the presence of realistic topographic variations of the Earth’s crust -- We show that by adopting a non-conforming meshing scheme for the numerical representation of the surficial topography we can obtain very accurate representations of earthquake induced ground motion in mountainous regions -- From the computational point of view, our methodology proves to be accurate, efficient, and more importantly, it allows us to preserve the salient features of multi-resolution cubic finite elements -- We implemented the non-conforming scheme for the treatment of realistic topographies into Hercules, the octree-based finite-element earthquake simulator developed by the Quake Group at Carnegie Mellon University -- We tested the benefits of the strategy by benchmarking its results against reference examples, and by means of convergence analyses -- Our qualitative and quantitative comparisons showed an excellent agreement between results -- Moreover, this agreement was obtained using the same mesh refinement as in traditional flat-free simulations -- Our approach was tested under realistic conditions by conducting a comprehensive set of deterministic 3D ground motion numerical simulations in an earthquake-prone region exhibiting moderate-to-strong surficial irregularities known as the Aburr´a Valley in Antioquia-Colombia -- We proposed a 50 50 25 km3 volume to perform our simulations, and four Mw = 5 rupture scenarios along a segment of the Romeral fault; a significant source of seismic activity of Colombia -- We created and used the Initial Velocity Model of the Aburr´a Valley region (IVM-AbV) which takes geology as a proxy for shear-wave velocity -- Each earthquake model was simulated using three different models: (i) realistic 3D structure with realistic topography; (ii) realistic 3D structure without topography; and (iii) homogeneous half space with realistic topography. Our results show how topographic irregularities greatly modify the ground response -- In particular, they highlight the importance of the combined interaction between source-effects, focusing, soft-soil conditions, and 3D topography -- We provide quantitative evidence of this interaction and show that topographic amplification factors at some locations can be as high as 500 percent, while some other areas experience reductions -- These are smaller than the amplifications, on the order of up to 100 percent
Energy management strategy for a solar race car including meteorologic and probabilistic variable
(2018) Betancur Valencia, Esteban; Osorio Gómez, Gilberto
This thesis describes the energy management strategy for racing solar cars, the racing strategy is treated as an optimal control problem with random variables and uncertain predictions. A computational model is developed for estimating the vehicle performance under speciﬁc circumstances. Two evolutionary heuristic optimization methods are implemented and tested for this case, their eﬀectiveness, convergence and eﬃciency is measured and compared to exhaustive search approaches. The dependency on solar radiation is validated using the computational model with diﬀerent test cases. In order to reduce the uncertainties on the solar radiation estimation, satellite images are used as inputs to image processing and machine learning techniques, their eﬃcacy is compared. Finally, a validation case is executed and diﬀerent scenarios are evaluated with the inclusion of the proposed methods, the experimental performance of a vehicle obtained using the strategy in the World Solar Challenge 2015 is exposed and compared to the predicted results from the simulation.
Engineering estimation of topographic effects in site response analysis
(Universidad EAFIT, 2021) Vergara Gallego, Juan Carlos; Gómez Cataño, Juan David
Despite the irrefutable amount of theoretical and field evidence of the impact of topographic effects on the local response at a site the engineering community still lacks practical methods for its consideration in a standard routinely basis. The incorporation of topographic effects into site response analysis has been a major challenge to engineers as it involves coupling between mechanical and geometric modifications to the incident seismic waves, which at the same time demands for field data that is rarely available to the practicing engineer. On the other hand, it has been observed that the main signature of topographic effects, besides the expected change in frequency con tent, is its spatial variation. These complexities combined to the field data required to build fully coupled mechanical-geometrical models have resulted in complete under consideration of these effects. In this work we follow a rational approach to study the effect of surface topography on the response at local sites after formulating the problem following a diffraction perspective. Since this work is framed in an engineering context our main result is a method to incorporate the effect of surface topography in ground response analysis. Although the method requires numerical simulations we show that if the analyst brings into the problem the dynamic properties of the structure for which the analysis is conducted in the first place very moderate models may be required. These idea leads to the concept of size conditioned response spectra which uses a target structural response spectra to fix the size of the computational model. The resulting numerical domain turns out to be of manageable size thus it can be handled with standard computing resources. Although our proposed approach is limited to surface topography the combination of the theory of diffracted waves and the consideration of the structural response creates new venues to advance in understanding the problem of topographic effects.
Environmental improvement of operating supply chains: a multi-objective approach for the cement industry
(Universidad EAFIT, 2017) Cadavid Giraldo, Nora; Vélez Gallego, Mario César
Nowadays companies worldwide face a growing pressure to reduce the environmental impact of their manufacturing activities -- However, the strategies used to achieve this goal are not clearly defined because of their conflicting relations with financial outcomes -- In parallel, globalization trends imply that as companies grow, usually through mergers and acquisitions, their supply chains become more complex -- The environmental improvement of these supply chains imply not only technical retrofit decisions aiming at adopting cleaner production technologies but also decisions regarding the structure of the supply chain itself -- Making these decisions becomes a difficult task because of the large number of variables involved, and the diversity of the interactions among them -- To tackle this problem, this research aims at providing a multi-objective solution approach for making technological retrofit decisions within an operating supply chain, so that both environmental and financial goals are best met -- The proposed solution approach is applied to the case of an operating cement supply chain in Colombia -- Several computational experiments were conducted, obtained results demonstrates that the proposed model is an e effective tool for multi-objective improvement decisions making, towards a more sustainable production process
Estimación ingenieril de la intensidad sísmica en la vecindad de una formación morfológica
(Universidad EAFIT, 2021-11-13) Sierra Álvarez, Cesar Augusto; Jaramillo Fernandez, Juan Diego
Despite the relevance of topographic effects in seismic response by experimental and theoretical studies, these parameters is not widely used in practice engineering. Nowadays, just a few codes consider these effects, but they do not take into account the frequency of the movement and the relation between the dimensions of the topographic accident and wavelength of the incident field. A two-parameter expression for the quantification of topographic effects in ground response analysis at sites located in the vicinity of a topographic feature is presented. The expression is derived from parametric analysis of convex and concave canonical shapes after identifying that the diffracted field in these geometries remains relatively stable in the low dimensionless frequency regime. The proposed expression is used in the estimation of topographic effects at two sites located in realistic topographic scenarios over a given period range. To show the quality of the approximate formula results are compared with numerical simulation values.
Exploring the role of system operation modes in failure analysis in the context of first generation cyber-physical systems
(Universidad EAFIT, 2018) Ruíz Arenas, Santiago; Horváth, Imre; Mejía Gutiérrez, Ricardo; Rusák, Zoltan
Fabricación y caracterización mecánica de nanomateriales
(Universidad EAFIT, 2018) Múnera, Juan Camilo; Ossa Henao, Edgar Alexander
Freeze casted porous ceramics
(Universidad EAFIT, 2020) Gil-Durán, Santiago; eossa@eafit.edu.co
Scientists have explored different manufacturing methods aiming at obtaining synthetic materials with controlled porosity, among them, Freeze Casting allows a control of the pore characteristics formed within the material by setting process variables like type of medium, particle size, solid content, inclusion of additives, freezing rate, etc. Despite of all the knowledge obtained about freeze casting, there still remain some questions to solve regarding processing-structure relationships, specifically the relations between cooling patterns during freezing and physical characteristics of the final material. The aim of this doctoral work is to understand the relations between cooling patterns during freezing and the structure at the macro and micro levels of the final freeze casted part. The current work comprises the development of a heat transfer model to efficiently and reliably predict the temperature evolution during freezing. In this way, it will be possible to recognize which are the process variables affecting the final pore morphology. The results of this work improved the fundamental knowledge of the process, serving as a tool to predict and control the microstructure obtained in the Freeze Casting process. The problem definition and goals of this work are presented in chapter 1. A brief description of the main literature on freeze casting is presented in chapter 2. The development of a numerical model that calculates the temperature distribution within the experiment domain was carried out in chapter 3. In chapter 4, an alumina tile was produced by freeze casting process in order to test the freezing device, coloidal suspension characteristics and sintering temperature of the sample. Additionally, an analytical model was proposed for predicting the thermal conductivity of the material. Chapter 5 evaluates the effect of solid content and freezing temperature on pore morphology and evaluates how these variables affect the temperature distribution within the experiment domain. Chapter 6 compares the steady solution of the numerical model and the pore morphology obtained experimentally under different process parameters. Finally, conclusions and future work for the study are presented in chapter 7.

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