Theses & Dissertations

Permanent URI for this collection

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

Browse

Recent Submissions

Now showing 1 - 5 of 3035
  • Publication
    Assessing the ecotoxicological impacts of sunscreen components (Benzophenone-3 and TiO2 NPs) through in vivo models
    ( 2024-05-09) Ortiz Román, Melissa I. ; Román Velázquez, Felix R. ; College of Arts and Sciences - Sciences ; Latorre Esteves, Magda ; López Moreno, Martha L. ; Meléndez Martínez, Enrique ; Department of Chemistry ; Rodríguez Barreras, Ruber
    The increasing use of titanium dioxide nanoparticles (TiO2 NPs) and benzophenone-3 (BP-3) in various industrial and personal care applications has raised concerns regarding their potential environmental impacts, particularly in aquatic ecosystems. Both ingredients are widely utilized in sun-protection creams. The toxicity of TiO2 P25 nanoparticles (TiO2 P25 NPs) in zebrafish (Danio rerio) embryos and BP-3 in both D. rerio embryos and Artemia salina was assessed, focusing on LC50, hatching rate, embryo development, and accumulation in tissue. Zebrafish embryos (~2 hpf) were exposed to concentrations ranging from 75 to 250 mg/L of TiO2 P25 NPs for 48 and 96 h. For BP-3, exposure concentrations ranged from 0.10 to 1.5 mg/L over 96 hours for D. rerio eleutheroembryos and 0.100-5.00 mg/L over 48h for A. salina. The Ti4+ concentrations in the tissues were determined using inductively coupled plasma optical emission spectrometry (ICP-OES), and the TiO2 concentrations were calculated. The results revealed TiO2 concentrations of up to 1.27 mg/L after 96 h of exposure, with developmental effects observed but no significant impact on mortality or hatching. LC20 and LC30 were determined experimentally, and LC50 and LC80 were estimated. Additionally, physical malformations were observed in up to 11% of embryos, highlighting the potential teratogenic effects and ecological risks associated with TiO2 NPs. Analytical techniques, such as ultrasound-assisted emulsified liquid-phase microextraction (UA-ELPME) and high-performance liquid chromatography with diode array detection (HPLC-DAD), have been used for tissue analysis and BP-3 concentration determination. Zebrafish eleutheroembryos demonstrated a high absorption rate of BP-3, reaching 79% within 96 h of exposure. Although no significant mortality or hatching changes were observed, developmental effects were evident, with lethal concentrations determined for both organisms. Lethal concentrations for BP-3 were determined (A. salina LC50 at 24h= 3.19 ± 2.02 mg/L; D. rerio embryos LC50 at 24h= 4.19 ± 3.60 mg/L). Physical malformations, including intestinal tract alterations in A. salina, pericardial edema, and spinal deformities in zebrafish embryos, underscore the environmental risks posed by TiO2 NPs and BP-3, highlighting the potential threats to species and ecosystem health.
  • Publication
    Normalized and weighted multivariate functional principal components analysis for clustering
    ( 2024-05-09) Palomino Lescano, Velcy ; Acuña Fernández, Edgar ; College of Engineering ; Santana Morant, Dámaris ; Aparicio Carrasco, Roxana ; Almodóvar Rivera, Israel ; Department of Computer Science and Engineering ; Serrano Rivera, Guillermo
    Most processes in real life are continuous, and thanks to the technological progress in many fields of application, these processes can be recorded at high frequency. Thus, Functional Data Analysis (FDA) has been an active field of research. In this research we focus on Multivariate Functional Principal Components Analysis (MFPCA) when functional variables differ in scale, variability, or domain. We develop different alternatives of normalized and weighted MFPCA. Particularly, when a weighted MFPCA is employed, we provide a strategy to estimate the weights based on the variability of Functional Principal Components (FPC) scores. The performance of normalized and weighted MFPCA are evaluated in the context of clustering using different simulated and real datasets. The simulations include cases of Multivariate Functional Data (MFD) on the same one-dimensional interval and MFD defined on different domains i.e. MFD including multivariate curves and MFD including curves and images. Similarly, real datasets include cases of MFD containing multivariate curves and a MFD consisting of curves and vectors. Normalized and weighted MFPCA can improve the clustering performance. Furthermore, our strategy proposed to estimate the weights in weighted MFPCA is a good alternative, since this provides comparable results to other methods and it is more efficient in running time.
  • Publication
    Characterization of recreational and commercial swordfish (Xiphias gladius) fishery in Puerto Rico
    ( 2024-05-16) Ramos González, Juliebeth ; Cruz Motta, Juan J. ; College of Arts and Sciences - Sciences ; Estevez Amador, René F. ; Rodríguez Ferrer, Grisel ; Department of Marine Sciences ; Lugo Beauchamp, Wilfredo E.
    The swordfish (Xiphias gladius) is a migratory species with a wide distribution in the Atlantic, Pacific, Indian, and Mediterranean Oceans, the high economic value resulted in intense fishing pressure, which consequently led to a significant decline in the population of the Atlantic, reaching levels of exploitation. Concerns about the rapid decline of this species prompted implementation of regulatory measures, including minimum size requirements and catch quotas, aimed at revitalizing populations in Atlantic Ocean. While the precise population status of this species in Puerto Rico remains uncertain, multiple authors assert that movements take place in proximity to the island and are closely linked to feeding and mating areas. In Puerto Rico the characteristics of these fisheries are unknown, consequently the objective of this study was to understand three aspects of it: i) fishing practices, ii) population structure, iii) DNA barcoding for reliable identification. A total of 17 fisher that capture swordfish were identified around the island, which were interviewed to describe the characteristics of the fishing practices. This study revealed that the species is not subject to as significant targeting as initially assumed. The predominant method among fishers is the use of electric reels to target individuals at depths spanning from 400 to 600 meters, with a majority (52.2%) pursuing this activity for commercial gain. A total of seventeen samples of fish were collected during this study, out of which fifteen were subjected to sequencing for the purpose of population structure analysis. Furthermore, DNA barcoding analysis revealed that out of the 15 sequences generated, 13 species were correctly identified, while two were misidentified. Continuing fisheries censuses is recommended and conducting more detailed genetic studies is necessary to obtain more precise conclusions about the origin and status of the population.
  • Publication
    Assessment of ecotoxicity and accumulation capacity of zinc oxide nanoparticles and benzophenone-2 UV filters using in vivo models
    ( 2024-05-10) Casiano Muñiz, Ileska M. ; Román Velázquez, Félix R. ; College of Arts and Sciences - Sciences ; Rivera Portalatín, Nilka ; Meléndez Martínez, Enrique ; Latorre Esteves, Magda ; Department of Chemistry ; Sierra, Heidy
    The presence of ultraviolet (UV) filters in commercial products, such as personal care products (PCPs), has raised significant concerns regarding their environmental and public health impacts. Studies have shown widespread contamination of aquatic environments by UV filters, leading to adverse effects on aquatic organisms. These pollutants can accumulate in sediments, posing risks to aquatic species and potentially affecting ecosystems and humans through the food chain. This research aims to elucidate the underlying mechanisms driving the toxicity of UV filters and their implications for human health. Despite limited research on the effects of Zinc Oxide nanoparticles (ZnO NPs) and Benzophenone-2 (BP-2) on aquatic organisms, knowledge gaps remain. This study evaluated the ecotoxicity and environmental impacts of ZnO NPs and BP-2 using in vivo models. ZnO NPs (32.2 ± 5.2 nm), synthesized and characterized, were tested on zebrafish (Danio rerio) and Artemia salina revealing significant lethal concentrations (86.95 ± 0.21mg/L) and physical malformations in Artemia salina. Zinc was detected in fish tissues post-exposure, particularly in the gastrointestinal (GI) tract, using ICP-OES. BP-2 toxicity was assessed using cytochrome P450 (CYP450) assays, which indicated CYP3A induction at chronic exposure and 10 mg/L concentration. Molecular docking results confirmed the PXR interaction, which suggests an induction mediated through PXR. Additional assays confirmed accumulation in the zebrafish GI tract, and the activity of catalase (CAT) progressively decreased with both prolonged exposure time and higher concentrations of BP-2. These results highlight the crucial role of UV filters in consumer goods and underscore the need to address concerns in this evolving field.
  • Publication
    Numerical modeling of wave transformation in San Juan, Puerto Rico: Comparison between SWAN and SWASH
    ( 2024-05-10) Marenco Barranco, Roy Enrique ; Canals Silander, Miguel ; College of Arts and Sciences - Sciences ; Rodríguez Abudo, Sylvia ; Amador Ramírez, André ; Weil, Ernesto F ; Department of Marine Sciences ; George, Dibin M.
    This study examines the comparison between SWAN and SWASH in a realistic 2D scenario validated using field data to describe wave transformation over a reef environment in San Juan, Puerto Rico. The performance of both models was evaluated using observations collected during a field program by the U.S. Geological Survey between November 2018 and the end of March 2019. SWAN, a phase-averaged model, resolves wave transformation using JONSWAP spectrum, incorporating various physical processes including the wind field, white-capping, wave breaking, and bottom friction. SWASH, a phase-resolving non-hydrostatic model, predicts wave propagation with high resolution and different vertical layer configurations, accounting for wave breaking through shock-capturing mechanisms. SWAN was run with an 8-meter spatial resolution and forced with buoy wind and wave data, showing very good results across a range of sea states. The SWASH wave model was then run for 20 representative sea states and compared with SWAN. SWASH was also run at 8-meter horizontal resolution and was forced with wave buoy data. It was run using three vertical configurations: one-layer, two-layers, and three-layers. A notable improvement in performance was observed when transitioning from a one-layer to a two-layer configuration; however, additional increases in layers did not deliver significant benefits. In general, SWAN predominantly demonstrated superior performance in predicting wave heights across the examined area for most sea states, except in scenarios characterized by longer wave periods (>11 seconds), where SWASH showed marginally better accuracy. This pattern shows the robustness of SWAN's phase-averaged methodology under a diverse array of wave conditions. The results also shed light on the significant computational trade-offs inherent in choosing between the computationally efficient, phase-averaged SWAN model and the more resource-intensive, phase-resolving SWASH model. Despite the latter's sophisticated physics, the heightened computational demands of SWASH did not uniformly result in superior model performance, especially in cases involving sea states with shorter wave periods. The performance of SWASH was comparable to SWAN for lower frequency events, but it’s poor performance in shorter wave periods may have been affected by the limitation of its 8-meter spatial resolution.