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 2927
  • 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.
  • Publication
    Evaluation of streamflow forecast during flash flood events in Puerto Rico
    ( 2023-07-24) Trossi Torres, Gerardo ; Muñoz Barreto, Jonathan ; College of Engineering ; Morales Vélez, Alesandra C. ; Tarafa Vélez, Pedro J. ; Department of Civil Engineering ; Tirado Corbalá, Rebecca
    When studying water processes, understanding the hydrological cycle is vital. In addition, hydrological models can aid in predicting meteorological events, which is crucial for emergency management preparation. This study assessed the National Water Model v2.1, managed by the National Oceanic and Atmospheric Administration, to determine its ability to produce dependable streamflow forecasts for Puerto Rico, which was added to the model in 2021. The study analyzed five significant rainfall events in 2022, including four flash floods and one hurricane, and examined rainfall estimations and streamflow forecasts. While the model had the correct tendency to produce streamflow forecasts, it needed more accuracy and precision due to inadequate rainfall estimates used to generate the forecast. Accurate data is essential for reliable streamflow forecasting using hydrological models. Although the model can be utilized to monitor streamflow, it is essential to note that slight over and underestimation can occur.
  • Publication
    Efecto de la L-Carnitina en el desempeño productivo y parámetros fisicoquímicos en pollos parrilleros de crecimiento rápido y crecimiento lento en el trópico
    ( 2023-05-12) Arzola Torres, Carlos J. ; Latorre Acevedo, José R. ; College of Agricultural Sciences ; Domenech Pérez, Katherine ; Arcelay Ruiz, Enid ; Department of Animal Science ; Velázquez Augusto, Wesley
    El objetivo de este estudio fue examinar el impacto de la L-Carnitina (0, 50 y 100 mg/kg) en el desempeño productivo y parámetros fisicoquímicos de pollos parrilleros Cornish Rock Cross de crecimientos rápido y lento. El diseño experimental fue de Bloques Completamente Aleatorizados, con 18 unidades experimentales. Los datos de desempeño productivo se recopilaron desde la semana de entrega hasta la semana de matanza. Los parámetros fisicoquímicos, como luminosidad (L*), intensidad roja (a*), intensidad amarilla (b*), pH, terneza (WBS), capacidad de retención de agua (CRA), presencia de "White Stripping" y "Woody Breast", se determinaron 24 horas postmortem (7, 8, 9 y 10 semanas). No hubo un incremento en peso final, ganancia en peso, consumo de alimento y eficiencia en conversión en aves de crecimiento rápido con mayor inclusión de L-carnitina (p<0.05). La inclusión de L-carnitina no afectó los parámetros fisicoquímicos; sin embargo, estos sí fueron afectados por el crecimiento y por la edad de matanza. Las aves de crecimiento rápido obtuvieron carne más clara, menos roja, menos amarilla, y valores de pH más bajos a la 7ma semana que luego incrementaron con la edad (p<0.05). Para ambos tipos de crecimiento se observó mayor terneza a la 8va semana (p<0.05).
  • Publication
    Synthesis and characterization of robust porous pillar-layered structure coordination polymers for gas storage and delivery
    ( 2023-07-07) Urcia Romero , Silvana R. ; Hernández Maldonado, Arturo J. ; College of Engineering ; Martínez Iñesta, María ; Pagán Torres, Yomaira ; Suleiman Rosado, David ; Department of Chemical Engineering ; Vega Olivencia, Carmen A.
    The CO2 adsorption capacity and structural changes of three isoreticular porous coordination polymers (PCPs), Co2(pzdc)2(bpy)(H2O)n, Zn2(pzdc)2(bpy)(H2O)m, and Ni2(pzdc)2(bpy)(H2O)m (pzdc: pyrazine-2,3-dicarboxylate; bpy: 4,4’-bipyridine), were studied. Co2(pzdc)2(bpy)(H2O)n was characterized by evaluating changes in lattice parameters after CO2 adsorption up to 50 atm using in situ synchrotron X-ray powder diffraction. The effective pore size increased by ~2% with gas adsorption in the 1 to 50 atm pressure range, doubling the adsorption capacity. Hysteretic behavior during CO2 adsorption was observed, indicating structural changes analyzed by in situ synchrotron diffraction using Rietveld refinement. Rotation of carboxylate groups coordinating with the Co(II) metal node caused minor changes in unit cell volume (ΔV ≈ 6 Å3), unlike Cu2(pzdc)2(bpy), where pillar rotations and significant lattice expansion (ΔV ≈ 60 Å3) occurred upon CO2 adsorption. Co, Zn, and Ni-based PCP materials exhibited good thermal stability up to ~250 °C according to high-temperature in situ X-ray diffraction. CO2 adsorption and desorption isotherms at 25 °C for various pressures showed a relationship between hysteretic behavior and pore structural expansion/contraction induced by PCP surface interaction with CO2. Physisorption-level CO2 adsorption was observed, with adsorbent-adsorbate interactions approximately 50% stronger than reported for Cu2(pzdc)2(bpy). The reduction in pore size in the Co-, Zn-, and Ni-PCP samples resulted from changes in coordination of the metallic nodes, forming different crystalline systems. This is attributed to the characteristic ability of these metals, influencing crystal formation and growth kinetics.
  • Publication
    Culturable actinobacteria from two marine sponges from the genus 𝘈𝘱𝘭𝘺𝘴𝘪𝘯𝘢 in southwest Puerto Rico
    ( 2023-07-06) Lebrón López, Nicolle E. ; Schizas, Nikolaos V. ; College of Arts and Sciences - Sciences ; Cruz Motta, Juan J. ; Weil Machado, Ernesto F. ; Department of Marine Sciences ; Tavárez Vargas, Héctor S.
    Actinobacteria are the most biotechnologically valuable prokaryotes and are best known as a source of diverse secondary metabolites. However, there is scarce information on marine actinobacterial diversity in the Caribbean Sea. For this study, the marine sponges Aplysina fistularis and Aplysina fulva were examined for the presence of Actinobacteria through culture-dependent methods. Sponge specimens were collected by SCUBA diving in the La Parguera Natural Reserve in Lajas, Puerto Rico. A total of 62 strains of Actinobacteria were isolated from the collected sponge samples and identified through phylogenetic analysis based on the 16S rRNA gene. The isolated Actinobacteria were phylogenetically allocated to 18 genera. Comparing both sponge species, A. fulva yielded more Actinobacteria isolates (39) than A. fistularis (24) and in terms of genus diversity, a higher variety of Actinobacteria was observed from A. fulva than from A. fistularis. Even though a culture-dependent approach can give us valuable insight into the sponge’s microbiome and is an important basis for the study of the compounds that are produced by Actinobacteria, this strategy is limited because it does not reveal all the Actinobacteria that may be present in a sponge since a small portion of bacteria are culturable. Moreover, a partial sequence of the 16S rRNA gene often does not contain enough phylogenetic information to provide species-level resolutions. Ecological and phylogenetic studies of marine Actinobacteria will improve our understanding of the actinobacterial diversity associated with different marine ecosystems and could lead to the discovery of useful bioactive compounds.