Ciencias Exactas y Ciencias de la Salud
Permanent URI for this collectionhttps://hdl.handle.net/11285/551039
Pertenecen a esta colección Tesis y Trabajos de grado de las Maestrías correspondientes a las Escuelas de Ingeniería y Ciencias así como a Medicina y Ciencias de la Salud.
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- Properties of pectin-based films with SiO2 and corn starch during storage at different temperature(Instituto Tecnológico y de Estudios Superiores de Monterrey, 2021-09-23) Manzanares Meza, Orlando Arturo; Valdez Fragoso, Aurora; puelquio/tolmquevedo; Gómez López, Elda Graciela; Martínez Calderón, Luz María; González Nuñez, Rubén; Escuela de Ingeniería y Ciencias; Campus MonterreyBiopolymer films can prevent food spoilage and maintain the safety of packaged foods, while representing an alternative to reduce the consumption of synthetic plastics. However, their natural origin results in unstable properties over time. Therefore, it is necessary to extend the study of biopolymer films and determine their viability as packaging materials during storage in defined conditions. In this context, the present work investigated the effects of storage for eight weeks at 5, 25, 35 ° C and 75 % of relative humidity (RH) on the mechanical properties, water vapor permeability (WVP), color, morphology, and chemical structure of pectin-based films with SiO2 and corn starch. In general, the evaluated temperature and time of storage had a significant effect (p-value < 5%) on the studied properties of pectin-based films after storage (at t8). At t8, the tensile strength (TS) decreased 38.71, 33.8, and 23.3 % at 5, 25, and 35 ° C, respectively. The elongation at break (EAB) increased 21.9 and 15.8 %, while the elastic modulus (EM) decreased 54.31 and 24.61 % at 5 and 25 ° C, respectively. Furthermore, the WVP of the studied films increased 38.3 and 18.0 % at 5 and 25 ° C, respectively. The effect of temperature on the WVP at t0 and at t8 followed an Arrhenius relationship. The activation energy of water vapor permeation of pectin-based films at t0 was -4.07 kJ mol-1, which decreased to -9.2 kJ mol-1 at t8. The color of the studied films turned brown at all evaluated temperatures at t8. The browning of the films was more pronounced with increasing temperature of storage. The coordinate L* decreased 1.4, 7.1, and 14.6 % at 5, 25, and 35 ° C, respectively. Whereas an inverse behavior was observed in the coordinate a* as it increased 43.7, 95.2, and 152.7 % at 5, 25, and 35 ° C, respectively. The coordinate b* decreased 31.4 % at 5 ° C, however, an increase of 26.1 and 52.7 % was observed at 25 and 35 ° C, respectively. The total color difference (ΔE) increased 540, 403, and 358 % at 5, 25, and 35 ° C, however higher magnitudes were detected with increasing temperature of storage. In contrast, the hue angle (h°) was observed to decrease 2.7, 10.2, and 15.2 % at 5, 25, and 35 ° C, respectively. The yellowness index (YI) displayed a reduction of 30.5 % at 5 ° C, and an inverse behavior at 25 and 35 °C as it increased 35.8 and 79.2 %, respectively. The color change kinetics of pectin-based films were studied as a function of storage time. The effect of different temperature of storage was evaluated on the color kinetics. The changes in color parameters were fitted to zero and first-order models. The zero-order model was selected as it showed the best fit (R2 > 0.88) to the experimental data. Also, the effect of temperature on the color kinetics followed an Arrhenius relationship. The color change activation energy of all color parameters during storage ranged from 10.27 to 54.42 kJ mol-1. Data suggests that the resultant modifications in the properties of the studied films were related to chemical and physical alterations within the pectin-matrix. These alterations occurred by the accumulation of water molecules in pectin-based films during storage. Furthermore, the resultant color changes were related to non-enzymatic browning (NEB) reactions and to the degradation of carotenoids during storage at all conditions. For the first time, the modifications in the properties of pectin-based films during storage were quantified. Although the properties of the studied films were altered, they maintained their macroscopic integrity during storage. Which suggests that the performance of pectin-based films as packaging materials would remain functional during extended storage. Therefore, the quantification of the observed alterations in the properties of pectin-based films could provide relevant data towards the shelf-life estimation of target food products.
- Defect detection with predictive models in the galvanizing process(Instituto Tecnológico y de Estudios Superiores de Monterrey, 2020-12-04) Villareal Garza, Diego; ; Preciado Arreola, José Luis; tolmquevedo; Tercero Gómez, Víctor Gustavo; Chee González, Carlos Arnoldo; School of Engineering and Sciences; Campus MonterreyIn the steel industry, having better control over the final mechanical properties of the steel coils is something highly desired by companies, as this would allow them to reduce the number of defective products they manufacture and reduce the costs associated with them. In a galvanizing line, modeling the yield strength and elongation properties of steel coils can be done before subjecting the coils to the galvanizing process, therefore preventing the waste of zinc, and improving the overall quality control of the line. In this thesis, an ensemble of two quantile random forest regressors was employed to predict the mechanical properties of galvanized steel coils using real-life data from a steel manufacturing company in order to identify defective and non-defective products. The ensemble was designed with goal-specific components in order to optimize the false negative rate and false positive rate of the model. Out of the six clusters of data built from the dataset, four were properly modeled with this approach, while one was best modeled with an individual quantile random forest regressor. Results revealed that a combination of chemistry, segmentation, previous processes, and galvanizing process parameters are required to effectively predict the yield strength and elongation properties. Additional testing of this ensemble model in different industrial contexts and with different performance metrics is recommended to further validate its efficacy.
- Applying a degradation model to describe corrosive behavior in biodegradable stents to explain its influence in mechanical properties(Instituto Tecnológico y de Estudios Superiores de Monterrey) Figueroa Ramos, Aura Celina; CARDENAS FUENTES, DIEGO ERNESTO; 40783; Cárdenas Fuentes, Diego Ernesto; hermlugo, emipsanchez; Galaz Méndez, Ramsés; Fuentes Aguilar, Rita Quetziquel; Escuela de Ingeniería y Ciencias; Campus Ciudad de MéxicoCardiovascular diseases are considered the most common cause of death in the entire world. One of the main pathological processes that lead to coronary heart disease is known as atherosclerosis. It consists of an inflammatory process affecting medium to large blood vessels in the human body. Nowadays, treatment is typically site-specific, and the preferred method depends on the level and extent of the occlusion, also called stenosis. The development of intravascular metal stents in the last decade has increased the quality of life of patients suffering from congenital heart disease and coronary interventions. Stent technology can be classified as permanent or temporary stents. Despite their benefits, permanent metallic stents can cause long-term endothelial dysfunction, delayed reendothelialization, thrombogenicity, mismatch of the stent to the vessel size, artifacts with modern imaging techniques, and permanent physical irritation, which in turn, can cause arterial rupture or the formation of an aneurysm. Thus, research focused on designing temporary scaffolding devices to prevent these adverse effects. The development of biodegradable stents must ensure the stabilization of the vessel wall during the healing process, and, after its dissolution, the vessel must stay intact without a foreign body and with its full capacity of vasodilation. The biggest asset of this type of stents is that they disappear after a defined period of time once the vessel is healed. Depending on the patient, the scaffolding effect is required to last for approximately six to twelve months for the vessel to heal and remodel itself. After this period of time, the stent can be harmful, and it must be removed. Research is focusing on the development of biodegradable stents that must meet three main characteristics: biocompatibility, maintained mechanical properties and scaffolding feature during a period of time and controlled degradation rate. Material characteristics, bulk, and surface properties are all major characteristics to consider in the design of a new stent. These materials must be strong enough, with certain mechanical and chemical properties to guarantee their optimal function. Based on this argument, new stent technology is focused on keeping developing BDS to improve their performance by modifying their degradation rates to ensure their scaffolding feature is maintained for as long as the tissue heals itself. Thus, it is essential to understand how biomaterials behave during a degradation process to describe their corrosion behavior after implantation and maintain their structural properties until the tissue is completely healed.