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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PublicationValorization of carbohydrates using polar aprotic solvents and acid Beta catalysts( 2024-06-28)Dependence on fossil fuels depletes resources and harms the environment, necessitating the search for ecologically acceptable and viable alternatives. Biorefineries are proposed as a potential replacement for traditional refineries, using biomass residues as feedstock for chemical synthesis. Acid Beta zeolite catalysts are effective in converting carbohydrates from sustainable biomass into various value-added compunds ¹,² this study investigated the effects of synthesis, characterization, solvent, and acid on the catalytic performance of materials in converting carbohydrates to lactic acid (LA), 5-hydroxymethylfurfural, difructose anhydride (DFA), and 1,6-anhydrosugars. We developed a method for Sn-Beta zeolite synthesis using heptane as a solvent during grafting, achieving over 2% tin content without detectable extraframework tin oxide. Water is essential for producing LA, from C6 sugars using Sn-Beta as a catalyst. Additionally, acetone-H₂O versus gamma-valerolactone (GVL)-H₂O improved LA yield at similar conversion. At 76% conversion, acetone-water 9:1 displayed a 36% yield towards LA versus 18% in GVL-water 9:1. Acetone not only improves the yield to LA but is cheaper, reduces the yields of formic and acetic acid and is easier to separate from the product mixture. On the other hand, the use of pure GVL shifts the product distribution towards dehydrated molecules, yielding DFA from fructose and 1,6-anhydrosugars from aldohexoses. Maximum yields were 75% of DFA at 94% of fructose conversion and 73% of 1,6-anhydromannose yield at 91% of mannose conversion. Both Lewis and Brønsted acid Beta catalysts are effective. To our knowledge, this study is the first to report the production of 1,6-anhydrosugars and DFA from fructose and aldohexoses, respectively, in pure GVL using acid Beta zeolites. This work underscores the importance of solvent selection in catalytic biomass conversion processes and provides novel insights into producing value-added chemicals from carbohydrates.
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PublicationRegularidad global para un problema quasi-lineal sobre regiones irregulares( 2024-05-14)En este trabajo investigamos la existencia, unicidad, estimaciones a priori y continuidad global para un problema eliptico generalizado con condiciones de frontera tipo Neumann o Robin. Ademas, los coeficientes de orden inferior en general no estan acotados. En condiciones minimas, mostramos que el problema admite una solucion debil Holder continua globalmente
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PublicationDetection and characterization of gram-positive and gram-negative bacteria in stormwater from Quebrada del Oro at Mayagüez( 2024-05-10)Rainwater is considered an alternative water source to mitigate the increase in water de- mand; however, due to the impact of climate change, plastic pollution and substances such as per and polyfluoroalkyl affect its quality. Likewise, runoffs reach the surface water providing greater biodiversity that can change its composition. However, this water transports a diversity of micro- organisms that can in turn adhere to different substrates like sediment particules, stones, and structures made by humans. Some microorganisms, such as members of the Enterobacteriaceae family, are commonly used as indicators of fecal contamination in surface waters. In this study, we evalu- ated the detection and quantification of Coliforms, Enterococci, Staphylococci and Actinobacteria from stormwater in Quebrada del Oro stream in Mayagüez. Water was collected in sterile bags at four sampling points across the slope near the UPRM Chemistry Building before reaching the stream and directly from the stream. Samples were plated in Tryptic Soy Agar (TSA) media and incubated at 37°C for 24-48 hours. Plate counting was performed to determine CFU/ml of water. We identified isolates from both runoff rainwater and Quebrada de Oro stream. Then, DNA extraction was performed using a microbiome DNA purification kit for q-PCR analysis. Isolates from both water samples presented Gram-negative and Gram-positive bacteria. Rapid Colilert kit anal- ysis detected the presence of E. coli in runoff water. In the Quebrada del Oro stream we also de- tected coliform bacteria. Coliforms in both samples of rainy days(stream and runoff) were higher than the other groups. Enterococci was the predominant group in the samples of drys days. Enter- obacteriaceae and Enterococci members are distinguished for being indicators of fecal contamina- tion in bodies of water such as rivers, streams and beaches.
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PublicationQuality assessment of images from projection devices using deep neural networks( 2024-05-08)Image quality perception in projectors is critical for enhancing user experience in education, business, and entertainment. This research proposes an automated visual assessment tool for accurate image quality assessment (IQA) in DLP projector images. The research utilizes two types of neural networks: No-Reference IQA (NR-IQA) for evaluating blur, blob, and pixel defects, and Full-Reference IQA (FR-IQA) for evaluating color distortion. The methodology involves neural network models, transitioning from a pre-trained VGG16 to a more complex ResNet, and ultimately a refined ResNet + PyramidNet for NR-IQA for the NR-IQA; and a Simasese pre trained VGG16, and Siamese ResNet models for FR-IQA. For the refined NR-IQA ResNet + PyramidNet model AUC of 94%, 96%, 98, 94% in high-quality, blur, blob, and pixel defects, respectively were achieved, with good test outcomes, particularly in projectors with visual defects. Conversely, the FR-IQA Siamese ResNet model achieved AUC rates of 94% and 96% for high quality and color-altered images, respectively. It also demonstrated good performance with real defective scenarios. Limitations were encountered in both situations, where intentionally unfocused images or the presence of shadows caused misclassification of blur or blobs, or when handling new images captured under varying conditions. Despite the limitations, incorporating a diverse dataset, including both simulated and real defective projector images, significantly enhanced model performance and defect identification accuracy.
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PublicationEvaluación de puntos críticos mutacionales de Lactato dehidrogenasa en ganado Senepol y Holstein que difieren en los genotipos del receptor de prolactina asociados con el pelo corto( 2024-04-12)In this study we evaluated levels of lactate in blood and tissue of Senepol (SEN) and Holstein (HO) cows genotyped for the shorthair gene (homozygous, heterozygous and wild-type). We determined single nucleotide polymorphisms (SNPs) in LDHs (lactate dehydrogenase) candidate genes (LDHA, LDHB, LDHC, LDHD) and estimated MBV (Molecular Breeding Values) and GPTA (Genomic Predicted Transmitting Ability) for different traits. In addition, we observed the medulla characteristics of the hair of these animals. Lower lactate values were obtained in blood (P=0.0164) and tissue (P=0.0365) for homozygous versus heterozygous SEN, which could be due to the truncation of the PRLR that causes an inactivation of gene expression causing a reduction in hair size. We were able to show associations between SNP in LDHs with certain productive, reproductive, and type characteristics. There was no effect of genotype for short hair on the diameter of the medulla and index of the medulla of the rump area (P=0.7259 and P= 0.0871, respectively), however, there was an effect on ribs (P<0.0001) and shoulders (P<0.0001). These results suggest that shorthaired cattle provide greater thermoregulatory capacity by combining several traits associated with hair.