Theses & Dissertations

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This collection is exclusively made up of theses, dissertations, and project reports submitted as a requirement for completing a graduate degree at UPR-Mayagüez. If you are a UPRM graduate student and you are looking for information related to the deposit process, please refer to


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Now showing 1 - 5 of 2931
  • Publication
    Effects of bubble rupture on the viability of red blood cells subjected to an resonant acoustic standing wave
    ( 2023-09-22) Lopez Ramos, Edwin C. ; Cancelos Mancini, Silvina ; College of Engineering ; Diaz Rivera, Ruben E. ; Latorre Esteves, Magda M. ; Gutierrez, Jorge G. ; Department of Mechanical Engineering ; Zapata Medina, Rocio
    Medical devices employ acoustic waves as a noninvasive imaging procedure for real time observation and diagnosis of the human body and other non-transparent media. The Food and Drug Administration (FDA) regulates the output parameters for these devices based on mechanical and thermal effects under ultrasonic operation. New technologies for the non-invasive detection and rupturing of bubbles employ resonant acoustic standing waves, a physical phenomenon not comprehensively studied by the FDA. This novel prospective treatment is focused on scenarios where bubble presence in the bloodstream poses a clinical risk. The method relies on generating resonant acoustic standing waves within a limb to non-invasively accelerate dissolution of bubbles present in the bloodstream via bubble rupture. The lack of research regarding the effects of resonant acoustic standing waves limits their application in medical scenarios. As such, the objective of this work consists of determining the effects of resonant acoustic waves and bubble rupture on red blood cell (RBC) viability. For this purpose, acoustic chambers outfitted with transducers were driven at resonant frequencies to rupture bubbles in distilled water, saline solution, and mammalian defibrinated blood. Experiments consisted of rupturing single bubbles below 900µm in diameter in an acoustic chamber and simplified swine thigh transducer assembly. This was done to assess at what electrical powers the transducer must be driven to generate pressure amplitudes that may effectively rupture bubbles in both an in vitro device and a physiologically relevant geometry. A final acoustic chamber was developed using the simplified swine thigh as a benchmark. Experiments with bubble populations were done in defibrinated sheep blood. The results show that single bubble rupture accounted for 56% of the total gas content dissolved after acoustic insonation for pressures above 60kPa. In the case of bubble population experiments, up to 85% of total gas content was dissolved for pressures of 153kPa. The assessment of the effects of both the resonant acoustic standing waves and bubble rupture on defibrinated blood resulted in CBC data within reference values of healthy cells.
  • Publication
    Sequential experimentation and multi-criteria analysis for structural concrete mixtures using fly ash, silica nanoparticles, and plastic aggregates
    ( 2023-11-15) Cotto Ramos, Anamarie ; Torres García, Wandaliz ; College of Engineering ; Cáceres Fernández, Arsenio ; Dávila Padilla, Saylisse ; Acosta Costa, Felipe ; Department of Civil Engineering ; Sánchez Quintero, Dilsom
    This study explored the use of plastic aggregate and supplementary cementitious materials (SCMs) as an alternative to natural aggregates and Portland cement (PC) in concrete production with structural properties (compressive strength ≥ 17 MPa). The goal was to reduce the environmental impact of concrete production while maintaining its mechanical properties at a minimum cost. To optimize these alternative concrete mixtures, the study conducted a series of experimental mixture designs incorporating silica nanoparticles (nS), fly ash (FA), and plastic. A screening experiment was conducted to replace coarse aggregate with plastic wholly and partially, considering all concrete mixture components, two process variables, and various constraints. Sequential experiments investigated the use of SCMs and plastic aggregates to replace both fine and coarse aggregates. Then, prediction models were fitted using Ordinary Least Squares with Stepwise (OLS-SW) and Gaussian processes (GP) followed by an iterative model-based validation process to extract feasible solutions. Finally, characterization tests were performed to understand how the incorporation of SCMs and plastic aggregates affects the mechanical properties of concrete. Results indicated that replacing coarse aggregate with plastic was more viable than replacing fine aggregate. The best prediction model was obtained using GP, having a Mean Absolute Error (MAE) of 2.8 MPa, while the MAE of OLS-SW was 3.4 MPa. The last iteration of the methodology reduced the necessary nS percentage in the optimal mixture, reducing the mixture costs compared with the first iteration from $296.00 to $258.00 for a cubic meter of concrete mixture. An optimal concrete mixture containing 1% nS and 17.7% FA by cementitious material weight and 34.7% plastic by coarse aggregate volume achieved structural strength (19 MPa) at 7 days. Permeability test results indicated that concrete samples containing plastic and SCMs were less permeable (i.e., more durable) than those without these materials. The modulus of elasticity is approximately 44% less than that of mixtures made without plastic and SCMs, making them more ductile. Splitting test results determined a tensile strength of 5.8 MPa (25% of 7-day compressive strength). Lastly, 56-day compressive strength tests carried out on concrete samples subjected to high temperatures (300 °C) determined that this temperature minimally decreased the concrete compressive strength, maintaining its structural strength.
  • Publication
    Dinámica poblacional de 𝘉𝘢𝘵𝘰𝘤𝘦𝘳𝘢 𝘳𝘶𝘧𝘰𝘮𝘢𝘤𝘶𝘭𝘢𝘵𝘢 (De Geer, 1775) (Coleoptera: Cerambycidae) en cultivares de mango en Puerto Rico
    ( 2023-10-20) Maldonado Pinto, Naomi M. ; Cabrera Asencio, Irma ; College of Agricultural Sciences ; Harmsen, Eric W. ; Rosario Pérez, Carlos ; Department of Crops and Agro-Environmental Sciences ; Parés Parés , Carmen P.
    𝘉𝘢𝘵𝘰𝘤𝘦𝘳𝘢 𝘳𝘶𝘧𝘰𝘮𝘢𝘤𝘶𝘭𝘢𝘵𝘢 (De Geer, 1775) (Coleoptera: Cerambycidae), is an introduced cerambycid beetle whose behavior has not been previously studied in Puerto Rico. Therefore, the objectives of this research were to evaluate: (1) the incidence, severity, and relative preference of 𝘉. 𝘳𝘶𝘧𝘰𝘮𝘢𝘤𝘶𝘭𝘢𝘵𝘢 in different cultivars of Mangifera indica and the possible effect of some abiotic factors, (2) chemical and cultural management for the detection and reduction of this pest, and (3) the growth of 𝘉. 𝘳𝘶𝘧𝘰𝘮𝘢𝘤𝘶𝘭𝘢𝘵𝘢 larvae through rearing on an artificial diet. The commercial cultivars, Palmer and Keitt, showed the highest incidence of 𝘉. 𝘳𝘶𝘧𝘰𝘮𝘢𝘤𝘶𝘭𝘢𝘵𝘢 damage. At farm level, Palmer was the cultivar with the highest infestation with more than 50% of infested trees, while the Edward cultivar was not infested by this borer. 𝘉. 𝘳𝘶𝘧𝘰𝘮𝘢𝘤𝘶𝘭𝘢𝘵𝘢 had a preference for cultivars with lower wood density, such as Palmer and Kent, over those with denser wood, such as the Edward cultivar. On the other hand, severity did not prove to be a good tool to measure the damage of this pest. It was not possible to collect 𝘉. 𝘳𝘶𝘧𝘰𝘮𝘢𝘤𝘶𝘭𝘢𝘵𝘢 in the Cross-Vane traps with the lures evaluated. However, low doses of the attractants (Z)-3-hexen-1-ol and nonanal were successful in attracting insects of the order Coleoptera, especially families with xylophages such as Curculionidae, Bostrichidae and Cerambycidae. The repellents beta-pinene and verbenone, and the insecticide Thiamethoxam together were effective in preventing the entry of 𝘉. 𝘳𝘶𝘧𝘰𝘮𝘢𝘤𝘶𝘭𝘢𝘵𝘢 Rearing in artificial nutrient medium produced the longest lifespan of 𝘉. 𝘳𝘶𝘧𝘰𝘮𝘢𝘤𝘶𝘭𝘢𝘵𝘢 larvae, suggesting that this borer has only one generation per year in Puerto Rico.
  • Publication
    Gene expression commonalities between autism and schizophrenia via biooptimatics
    ( 2023-09-19) Suárez Gómez, Deiver ; Isaza Brando , Clara E. ; College of Engineering ; Cabrera Ríos, Mauricio ; González Méndez, Ricardo ; Latorre Esteves, Magda ; Pérez Morales, Jaileene ; Other ; Zapata Medina, Rocío
    In the past, schizophrenia and autism spectrum disorders were diagnosed as a single disorder, but they are now recognized as separate and distinct conditions due to their different symptoms and age of onset. Nevertheless, similarities between schizophrenia and autism spectrum disorders have been found, such as the sharing of genetic information and the absence of typical behaviors reflecting the deterioration of social cognition. Despite these findings, the etiology of both disorders remains uncertain and there is still no objective diagnosis or effective cure. This study aims to help explain the common genetics between both conditions through gene expression data analysis using optimization methods. For this, public case-control studies of blood and brain tissue samples from autism and schizophrenia were examined. An R software package called Optimization-Based Analysis of Micro Arrays (OBAMA) was developed, which includes multiple criteria optimization (MCO), minimum spanning tree (MST), and -for the first time- optimal group formation (OGF) methodologies. With OBAMA, the following analyses were performed: 1) individual analysis of individual datasets, taking into account the characterization of sex to minimize sex bias; 2) meta-analysis of datasets, with the same consideration of sex characterization; 3) maximum correlation structures of individual and meta-analyses; and 4) formation of groups of genes and biological processes in optimal global conditions. The OBAMA package has the advantage of being portable and able to be run on modest computer hardware, such as personal computers. With its use, this study identified the following genes for autism spectrum disorder and schizophrenia: two genes (VNN2, PLGLB1) in blood samples, four genes in brain tissue (HSPA6, RGS1, RNU4_2, CCL4) and a common gene in blood and brain tissue (S100A8). In addition, signaling pathways involved in inflammation, ribosome, metabolism, and cancer were proposed, among others. Finally, we propose groups of genes involved in different biological processes, including metabolic processes, signals, cell communication, responses to stimuli, among others. The results set, which includes genes, pathways, and biological processes, could be crucial in helping to understand the underlying etiology of these two conditions.
  • Publication
    Novel polymer donors and small molecule acceptors in organic photovoltaic devices for wearable technologies
    ( 2023-09-06) Salas Rincón, Ricardo Andrés ; Suleiman Rosado, David ; College of Engineering ; Padovani Blanco, Agnes M. ; Saliceti Piazza, Lorenzo ; Ortiz Rivera, Eduardo I. ; Department of Chemical Engineering ; Acuña Guzmán, Salvador F.
    Organic photovoltaics represent a very suitable alternative to develop cheap, flexible, versatile, and lightweight solar cells with reasonable efficiencies and good installation efficacy. Herein, several single-junction organic photovoltaic devices were manufactured with the main purpose of studying the mechanisms involved in the light harvesting and charge generation and transport processes. Alternating copolymer donor PM6 was used in a bulk heterojunction architecture with the non-fullerene acceptor (NFA) Y6. Also, a new random terpolymer was synthesized by adding a cyclopentadithiophene unit (CPDT) to the PM6 structure. The resulting donor material, called PM6-CPDT, was paired with the same acceptor and new devices were fabricated with the blend. The characterization of the new donor material, including FT-IR, UV-Vis, cyclic voltammetry, TGA, and AFM, showed a close similarity with PM6. Four different individual types of active layer blends, based on the statistical combinations of the two polymer donors with Y6 and with donor:acceptor mass blend ratios of 1:1.2 and 1.2:1 was used to fabricate the devices. The characterization of the devices consisted of applying separately, under 6000 lx of illumination and under the dark, a forward bias from -1 to 1.5 V and recording the current densities generated, and it showed no specific relationship between the type of active layer employed and the current generated by the photovoltaic layouts. Among all devices the maximum value of current density of 334 μA/cm2 was achieved with the PM6-CPDT:Y6 1:1.2 blend under illumination and 25.6 μA/cm2 under the dark, demonstrating a photovoltaic behavior on the cells. The nature of the results led us to conclude that stronger illumination and light intensity could achieve J-V curves that should allow calculations of the performance parameters such as short-circuit current density, open circuit voltage, and efficiency of the solar cells, which will be left for future works.