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 https://libguides.uprm.edu/repositorioUPRM/tesis

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Now showing 1 - 5 of 3159
  • Publication
    Desarrollo de dulce de leche a base de leche de cabra y determinación de sus características fisicoquímicas
    ( 2024-11-26) Llinás Rosario, Denise M. ; Ponce de León González, Leyda ; College of Agricultural Sciences ; Curbelo-Rodríguez, Jaime E. ; Plaza-Delestre, María de L. ; Department of Food Science and Technology ; Zapata Medina, Rocío
    Abstract The principal objective of this investigation was to create a soft candy with different percentages of substitution of goat’s milk (0%, 25%, 50%, 100%) produced locally. In addition, physicochemical, sensory and durability were evaluated for 60 days. The proximal analysis determines that the humidity (21-25) content was similar to what it’s reported on literature, on the other hand the ashes (0.99), protein (1.7-5.8) and fat (1.4-18.9) content was lower than products on the market and the other investigators have done. During the 60 days of storage there were no statistical differences. The lactose crystals growth and changes in temperature could have affected the luminosity (15.85-20.4) values. Hue values represented the brown color (35-45). Also, a and b values were in the scale of red and yellow colors. The formulations 100% and 25% of goat’s milk were less hard, with less viscosity index (-1.24 and -1.29) and adhesiveness (-1.24 and -1.29) but for force parameter there was no significant difference between formulations. Water activity (<0.72) resulted in low values, and it's associated to cooking time. Microbiology results were favorable in coliforms, aerobics and molds. For sensory analysis it was measured with acceptance and preference in flavor. For this analysis we did two panels with 119 people. Panelists showed more acceptance in formulations with a higher percentage of goat’s milks (50 % and 100%). However, they didn’t show preference in any formulation. As a result, there’s viability for the elaboration of dulce de leche with high percentages of goat’s milks.
  • Publication
    Modeling Goldberg polyhedral like water nanobubbles structure stability using density functional theory
    ( 2024-11-26) Herrera Molina, Daniela ; Marín Martín, Carlos ; College of Engineering ; López Encarnación, Juan M. ; Cancelos Mancini, Silvina ; Department of Materials Science and Engineering ; Cruzado, Ivette
    Experimentally, it has been confirmed that water nanobubbles persist in their environment for extended periods. However, according to the Epstein and Plesset theory, their lifetimes should be short, suggesting thermodynamic instability. Although continuum theories have attempted to explain their stability, they lack empirical evidence. To address this issue, we propose a molecular model of water nanobubbles based on Goldberg polyhedral structures (GP) and examine their stability under various conditions using density functional theory (DFT). Due to the higher number of hydrogen atoms than edges in the GP, we have unbound H atoms, resulting in multiple configurations for each GP. We hypothesize that the most stable configurations are the "least polar" structures, where the distribution of free hydrogen atoms around the GP is uniform. We implemented an algorithm to produce the least polar atomistic configurations, and then we used geometric optimization (GO) techniques to minimize the energy of these structures under various conditions in order to verify the stability of our structures and their suitability as a model for water nanobubbles. Geometry optimizations were conducted under the following conditions: isolation, consideration of solvent effects using COSMO (COnductor-like-Screening-Model), and immersion in an explicit solvent (water). This was applied to water structures with GP(1,0), GP(1,1), and GP(2,0) geometries. Additionally, we evaluated the influence of hydrogen configuration by constructing more polar structures and comparing parameters such as total energy, HOMO-LUMO gap, and dipole moment. Our analysis revealed that structures in the least polar configuration remained stable without bond breakage after GO, even under different solvent conditions, suggesting that our model is an effective representation of small water nanobubbles. Furthermore, our research highlighted the influence of hydrogen atom configuration on structural stability. We also observed changes in HOMO and LUMO orbitals between the least polar and other configurations, particularly in proximity to neighboring free hydrogen atoms. This phenomenon was reflected in the dipole moment, which increased with a greater number of adjacent free hydrogen atoms. Consequently, structures with higher dipole moments exhibited bond breakage after geometric optimization, highlighting the influence of polarity on the stability of our proposed structures.
  • Publication
    Development of a biosensor for extracellular vesicle detection using endothelial-derived matrix-bound vesicles as analyte model
    ( 2024-11-25) Ayus Martinez, Sahimy Y. ; Mora, Camilo A. ; College of Engineering ; Domenech, Maribella ; Torres, Madeline ; Department of Chemical Engineering ; Acuña Guzmán, Salvador F.
    The present research explores the use of Matrix-Bound Vesicles (MBVs) as a novel analyte model for the development of an electorchemical biosensor, detecting tissue-specific biomarkers from decellularized extracellular matrices (dECM). MBVs were successfully isolated from endothelial cell-basement membrane, liver, and thyroid cartilage tissues through enzymatic digestion, demonstrating the retention of tissue-specific markers such as VE-cadherin (CD144) and SOX9. The characterization of these vesicles through molecular assays and imaging confirmed their size and morphology, consistent with extracellular vesicles (EVs). Our study also introduced a label-free electrochemical biosensor for the detection of MBVs, leveraging the tissue-specific nature of the vesicles. The biosensing device exhibited a measurable electrochemical response when detecting targeted biomarkers, confirming its potential as a rapid and sensitive detection tool. This research lays a foundation for the development of biosensing technologies that can be translated into clinical diagnostics, particularly for monitoring cardiovascular health and other disease states through the detection of extracellular vesicle biomarker.
  • Publication
    Technical feasibility study using a continuous mixing process and characterization of the stream sampler using DEM simulations
    ( 2024-11-21) Nasrala Alvarez, Juan M. ; Méndez Román, Rafael ; College of Engineering ; Romañach, Rodolfo ; Acevedo Rullán, Aldo ; Department of Chemical Engineering ; Ciri, Umberto
    This work investigates the transition from a traditional batch mixing process to a continuous mixing approach for pharmaceutical manufacturing, emphasizing the integration of advanced Process Analytical Technology (PAT). The study covers material characterization of excipients and active pharmaceutical ingredients (API), optimization of continuous mixing conditions, and real-time monitoring through a microNIR spectrometer with a Partial Least Squares (PLS) model. Material properties confirmed suitability for continuous mixing, demonstrating good flowability properties. Continuous system characterization focused on optimizing gravimetric feeders, mixer speed, and stream sampler parameters to ensure blend uniformity and consistent throughput, achieving an optimal mixer speed of 200 RPM and a stream sampler speed of 8.08 RPM, which supported a throughput of 35.5 kg/h. The PLS model yielded accurate API concentration predictions with low RMSEP, RSEP, and bias, indicating robust control of blend uniformity with an RSD below 0.72%. The stream sampler interface was further assessed through discrete element method (DEM) simulations, examining paddle wheel speed and particle cohesion energy effects on flow dynamics, mean residence time, and internal particle rearrangement. Results showed that higher paddle speed enhanced blend uniformity by reducing mass hold-up and particle fill time, while increased cohesion energy led to reduced flow efficiency and particle consolidation. The research group ended up with a tool capable of simulating possible scenarios, that will provide preliminary results and alternatives for sampling optimizations.
  • Publication
    Epiphytic microbiota of arabica coffee variety Fronton and its role against the phytopathogen Colletotrichum tropicale
    ( 2024-11-12) Velázquez Acosta, Ashley A. ; Massol Deyá, Arturo ; College of Arts and Sciences - Sciences ; Maldonado Ramírez , Sandra ; Montalvo Rodríguez, Rafael ; Department of Biology ; Morales Payan, Pablo
    Epiphytic microorganisms on coffee leaves act as natural biocontrol agents, inhibiting plant pathogens through secondary metabolites and enzymes. This study evaluated the antagonistic potential of epiphytic bacteria against Colletotrichum tropicale, the cause of anthracnose in coffee. The objective was to characterize the epiphytic microbiota of Coffea arabica (var. Fronton) and assess the propagation rate of C. tropicale in plants treated with streptomycin sulfate. Treatments examined the effect of antibiotics on fungal propagation with or without spores. CFUs were quantified, Gram staining performed, and anthracnose incidence and severity evaluated over 75 days. Results showed eight bacterial morphotypes: six Gram-negative and two Gram-positive. A decrease in CFUs was observed in upper leaves treated with antibiotics. Infection rates were 52% in plants treated with both antibiotic and spores, and 42% in plants with spores only. No significant differences in lesion severity or new leaf production were found, suggesting further studies are needed to explore these interactions.