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 2934
  • Publication
    Weak population structure detected in the commercially important deep-sea queen snapper (𝘌𝘵𝘦𝘭𝘪𝘴 𝘰𝘤𝘶𝘭𝘢𝘵𝘶𝘴) in Puerto Rico
    ( 2023-10-08) González García, María del Pilar ; Schizas, Nikolaos V. ; College of Arts and Sciences - Sciences ; García Sais, Jorge R. ; Harms-Tuohy, Chelsea ; Weil Machado, Ernesto ; Department of Marine Sciences ; Rodriguez, Grisell
    The queen snapper, Etelis oculatus (Valenciennes, 1828), is part of the deep-water snapper complex; an important commercial species in the US Caribbean fishery. However, little is known about the biology and ecology of this species. This study sought to detect the presence of a fine-scale population structure and genetic diversity, as assessed through SNPs derived from the Restriction site Associated DNA Sequencing technique. Results estimated a weak population structure and low genetic diversity in our samples. However, principal component analysis and a model-based clustering method did illustrate a fine-scale subpopulation structure among sampling sites from this study. These results are comparable to the genetic and dispersal patterns observed in shallow-water snapper species in Puerto Rico. This study addressed questions of connectivity that are crucial to understanding the ecological role and biological life historyof the queen snapper which is useful for effective management and conservation of this culturally and commercially important fishery.
  • Publication
    Design, synthesis, characterization, and evaluation of 3D synthetic scaffolds for T and CAR-T cells culture and co-cultures
    ( 2023-11-16) Lizana Vasquez, Gaby del Rocio ; Torres Lugo, Madeline ; College of Engineering ; Domenech Garcia, Maribella ; Torres Garcia, Wandaliz ; Latorre Esteves, Magda ; Department of Chemical Engineering ; Huertas Miranda, Javier A.
    During the manufacturing process of CAR-T cell products, there are many challenges that researchers are currently addressing. One of them is the need to enhance the expansion of T and CAR-T cells, and another is to evaluate the potency of CAR-T cells against tumor spheroids. Therefore, this research aims to design, characterize, and evaluate a thermosensitive terpolymer capable of encapsulating and harvesting cells while reducing mechanical manipulation and allowing microscopic monitoring. For this purpose, three different monomers, including N-isopropylacrylamide, boronic acid, and poly(ethylene glycol), were selected to form a synthetic-based hydrogel scaffold. Different techniques such as the Sol-Gel transition, proton nuclear magnetic resonance (1H-NMR), and Fourier-transformed infrared spectroscopy (FT-IR) were used to characterize the terpolymers resulting from various combinations of monomers. The FT-IR and 1H-NMR spectra confirmed the success of the polymerization and its reproducibility in manufacturing, while the Sol-Gel transition allowed confirming the formation of the hydrogel at 37°C. The feasibility of the most promising terpolymers for 3D in vitro cell culture was evaluated with various cell types, including adherent cancer cell lines SKOV-3, U87-GBM, and patient-derived GSC-GBM. In addition, Jurkat, CD4+ T, Pan-T, and CAR-T suspension cell lines were successfully encapsulated, cultured, and expanded within terpolymer scaffolds. In addition, co-culture experiments of activated T cells with encapsulated U87, and anti-GD2 CAR-T cells with encapsulated GSCs, were performed. Co-culture experiment results provided evidence that T cell migration through the terpolymer matrix to reach the encapsulated spheroids was possible and further analyses of T cell potency could be performed after harvesting cells from terpolymer scaffolds. In conclusion, obtained results indicated that the terpolymer material could be successfully used for cell culture applications and it has the potential to be used in cell potency assays development as well as cell manufacture.
  • Publication
    Calibration model development for the process analytical technology analysis of pharmaceutical powder mixtures using near infrared spectroscopy in a variety of sampling interfaces
    ( 2023-10-12) Martínez Cartagena, Pedro A. ; Romañach, Rodolfo J. ; College of Arts and Sciences - Sciences ; Santana Vargas, Alberto ; Román Velázquez, Felix ; Méndez Román, Rafael ; Department of Chemistry ; Ortiz Bermúdez, Patricia
    This dissertation describes the development of calibration models based on near-infrared (NIR) spectroscopy using a variety of sampling interfaces to monitor the concentration of active pharmaceutical ingredients. The main difference between these interfaces is how the sample is presented to the NIR instrument. The presentation of the sample considerably influences the results obtained from calibration models in terms of errors of prediction and sampling errors. The first chapter of this dissertation provides a description of all the necessary information to execute the work behind all the presented studies. The second chapter presents the challenges of combining different sampling interfaces in calibration model development to monitor surrogate materials using NIR spectroscopy. This study demonstrated that an NIR calibration model was successfully developed using a combination of data of two different interfaces. The selected calibration model showed relatively low errors of prediction and bias considering how the sample was presented to the instrument and it proved to be robust against instrument noise changes. The study behind this chapter was possible due to the collaboration between a pharmaceutical company and the academy. The third chapter presents the experiments that were done using an innovative interface based on the theory of sampling. In this study the theory of sampling was implemented in the design of a chute to find out whether it is possible to achieve a fit-for-purpose representativity for the intended sampling-and-analysis system. The presented innovative sampling interface was further challenged by being subjected to the evaluation of low API concentrations, making a powder fowling assessment and by estimating the sampling errors. The fourth chapter presents the work done in two different peer-reviewed published research papers. These other studies contain another interface optimized by the knowledge of the theory of sampling as well as a combination of two interfaces in a sampling system that was used to monitor active pharmaceutical ingredients in flowing powders. Finally, the fifth chapter presents how the work done in this dissertation contributed to the realms of theory of sampling, process analytical technology and NIR calibration model development and possible future work.
  • 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.