Norma Francenia Santos-Sánchez

This work presents a linear control strategy applied to an agitated tank reactor for pH and volume regulation, based on the linearization of a mathematical model in which both concentration and volume are considered time-varying variables. The linearization is performed around an operating point in order to compute the gains of an LQR controller. Different penalty matrices Q and R are evaluated to obtain different closed-loop plant performances. The pH setpoints were selected according to the Mexican Official Standard NOM-002-SEMARNAT-1996. The simulation results provide evidence of the feasibility of the proposed approach. Spanish-language metadata / Metadatos en españolTítulo en español:Control lineal óptimo aplicado a un proceso de control de pH y volumen: evaluación de viabilidad económica Resumen:Este trabajo presenta una estrategia de control lineal aplicada a un reactor de tanque agitado para la regulación del pH y el volumen, basada en la linealización de un modelo matemático en el que tanto la concentración como el volumen se consideran variables dependientes del tiempo. La linealización se realiza en torno a un punto de operación con el fin de calcular las ganancias de un controlador LQR. Se evalúan diferentes matrices de penalización Q y R para obtener distintos desempeños de la planta en lazo cerrado. Los valores de referencia de pH se seleccionaron de acuerdo con la Norma Oficial Mexicana NOM-002-SEMARNAT-1996. Los resultados de simulación proporcionan evidencia de la viabilidad del enfoque propuesto. Palabras Claves:Modelo lineal, control por realimentación de estados, control de pH, control de volumen, LQR, viabilidad económica. Smart citations: SciteAI. Dimensions.Open Alex.

Summary Coffee production is an economically important crop in 13 of Mexico’s 31 states. The states of Chiapas, Veracruz, Oaxaca, Puebla, and Nayarit account for 90% of all production. Twenty-five percent of the coffee crop production takes place in rural areas identified as socially and economically marginalized and food insecure. These marginalized areas transect four of the five states above (Chiapas, Veracruz, Oaxaca, and Puebla). The state of Oaxaca ranks third in terms of extreme marginalization (Secretaría de Agricultura y Desarrollo Rural [SADER], 2023). Oaxaca has approximately 28,000 small coffee producers. The region has taken significant strides to ele­vate and distinguish its coffee. In 2020, the origin of Oaxacan coffee was officially recognized and granted the “Pluma” namesake. In 2022, Pluma met the Mexican Standard 255, a validation of quality and compliance. The Pluma origin signifies and describes the geographical range, soil, and climate where that coffee is produced within the state of Oaxaca. The Mexican Standard 255 validates the homogenous sensory and physical attributes for the Pluma origin. Together, these brand the Pluma origin as a product worthy of a higher demand for production at a higher price point. Since the quality of Oaxacan coffee has already been recognized and is coveted in the international marketplace, this adds value to the region’s specialty coffee.

Oaxaca, Mexico, coffee (Coffea arabica L.) received its denomination of origin "Pluma" (NOM-255-SE, 2022). Previous studies indicate that the intrinsic characteristics of coffee originate from chemical components that intervene in the organoleptic attributes evaluated during cupping. The objective was to analyze the physical and chemical attributes of medium roasted Coffea arabica L. beans from the farms: “La Virginia” (1058 meters above sea level; masl), “La Palma” (1149 masl) and “Nuestra Señora del Carmen” (1343 masl) located in the area of Pluma, state of Oaxaca, Mexico. The physical analysis was performed according to NOM 255-SE-2022, the chemical analysis was attached to the AOAC, 2012, the evaluation of the organoleptic quality was established with respect to the quality standards of the Specialty Coffee Association and the statistical analysis was carried out by Principal Component Analysis. The physical analysis shows that the beans from the "Nuestra Señora del Carmen" farm have greater integrity than the other two farms, categorizing them as "premium" quality. The chemical analysis allowed establishing the existence of a correlation between altitude and the content of lipids, proteins, and titratable acidity, which influence the sensory characteristics of the coffee beverage, mainly in the body and acidity.

El presente capítulo consiste en una compilación de los resúmenes de 15 conferencias presentadas de forma virtual en la 6ª Reunión de Resonancia Magnética Nuclear organizada por la Universidad Tecnológica de la Mixteca y la Sociedad Mexicana de Resonancia Magnética Nuclear. Con la participación de conferenciantes nacionales e internacionales. Los conferenciantes internacionales son ampliamente reconocidos en el ámbito de la RMN. Los temas abordados en las conferencias fueron la química de proteínas, química de productos naturales, química de materiales, química de alimentos, RMN del estado sólido y desarrollo de nuevos métodos para el estudio de macromoléculas en disolución.

La espectroscopía de RMN es una técnica poderosa para el estudio de propiedades y composición de alimentos y plantas. Las propiedades pueden estudiarse a través de experimentos de RMN en el dominio del tiempo. Mientras que el estudio de la composición y cuantificación de metabolitos se puede llevar a cabo a partir experimentos de RMN en el dominio de la frecuencia. Esto se puede lograr a partir de dos enfoques generales. El primero consiste en adquirir las huellas dactilares de metabolitos a partir de un análisis multivariante de datos de RMN en 1D y 2D ya sea en el dominio del tiempo o frecuencia. La adquisición de huellas dactilares por RMN suele ser una herramienta rápida y eficaz para discriminar entre grupos de muestras relacionadas a partir de la identificación de las regiones espectrales más distintivas. Un segundo enfoque consiste en realizar perfiles de metabolitos con los espectros de RMN, principalmente de 1H, a partir de extractos de muestras. Esto normalmente permite identificar alrededor de 40 metabolitos en un extracto sin fraccionar. Los perfiles también se utilizan para realizar tanto análisis cualitativos como cuantitativos para comparar grupos de muestras. Los perfiles de metabolitos permiten explorar los orígenes de la variabilidad entre los grupos de muestras estudiadas. Los dos enfoques conjuntamente generan el fenotipo metabólico de una planta. En el presente capítulo se describen las técnicas más representativas para la obtención de huellas dactilares en el dominio del tiempo y la frecuencia, y los métodos de procesado de espectros para la generación de perfiles metabólicos. Así como la descripción del análisis de componentes principales, uno de los métodos de análisis multivariante más empleado para el estudio de perfiles metabólicos en RMN incluyendo el procesamiento previo de los datos espectrales.

Nacobbus aberrans ranks among the “top ten” plant-parasitic nematodes of phytosanitary importance. It causes significant losses in commercial interest crops in America and is a potential risk in the European Union. The nematicidal and phytotoxic activities of seven plant extracts against N. aberrans and Solanum lycopersicum were evaluated in vitro, respectively. The chemical nature of three nematicidal extracts (EC_50,48h ≤ 113 µg mL⁻¹) was studied through NMR analysis. Plant extracts showed nematicidal activity on second-stage juveniles (J2): (≥87%) at 1000 µg mL⁻¹ after 72 h, and their EC₅₀ values were 71.4–468.1 and 31.5–299.8 µg mL⁻¹ after 24 and 48 h, respectively. Extracts with the best nematicidal potential (EC_50,48h < 113 µg mL⁻¹) were those from Adenophyllum aurantium, Alloispermum integrifolium, and Tournefortia densiflora, which inhibited L. esculentum seed growth by 100% at 20 µg mL⁻¹. Stigmasterol (1), β-sitosterol (2), and α-terthienyl (3) were identified from A. aurantium, while 1, 2, lutein (4), centaurin (5), patuletin-7-β-O-glucoside (6), pendulin (7), and penduletin (8) were identified from A. integrifolium. From T. densiflora extract, allantoin (9), 9-O-angeloyl-retronecine (10), and its N-oxide (11) were identified. The present research is the first to report the effect of T. densiflora, A. integrifolium, and A. aurantium against N. aberrans and chemically characterized nematicidal extracts that may provide alternative sources of botanical nematicides.

Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) causes COVID-19 (Coronavirus disease 2019). This disease was detected in the city of Wuhan in China in December 2019. People infected with COVID-19 shows varying manifestations, depending on their health and age. The most common symptoms are fever, cough, myalgia, fatigue, odynophagia, and dyspnea. Infected adults older 60 years of age are the group of patients most susceptible to severe COVID-19 states and present comor-bidity in the presence of chronic diseases. On the other hand, it is also essential to have tests to detect SARS-COV-2 in people and follow the evolution of COVID-19 quickly, reliably, and cheap. To achieve this, there are real-time reverse transcription pol-ymerase chain reaction (RT-PCR) tests, isothermal nucleic acid amplification, and enzyme immunostimulation. Currently, there are no drug treatments to prevent infection and to combat the virus's effects. However, different research groups that are conduct-ing in vitro, in vivo, and in silico tests to find drugs able to provide an immune response and to control infection in humans with SARS-CoV-2. Chloroquine, hydroxychloroquine, remdesivir, interferon-alpha 2b, and oseltamivir are some pharmacological options evaluated in clinical trials for prophylaxis of COVID-19. The purpose of this review is to establish a reference framework for taxonomic classification of SARS-CoV-2 and the relationship they have with other CoVs, as well as their structure and propaga-tion pathways in humans. The characteristics and symptoms presented by patients with COVID-19, the detection methods, and possible treatments are also presented.

An antioxidant is a substance that at low concentrations delays or prevents oxidation of a substrate. Antioxidant compounds act through several chemical mechanisms: hydrogen atom transfer (HAT), single electron transfer (SET), and the ability to chelate transition metals. The importance of antioxidant mechanisms is to understand the biological meaning of antioxidants, their possible uses, their production by organic synthesis or biotechnological methods, or for the standardization of the determination of antioxidant activity. In general, antioxidant molecules can react either by multiple mechanisms or by a predominant mechanism. The chemical structure of the antioxidant substance allows understanding of the antioxidant reaction mechanism. This chapter reviews the in vitro antioxidant reaction mechanisms of organic compounds polyphenols, carotenoids, and vitamins C against free radicals (FR) and prooxidant compounds under diverse conditions, as well as the most commonly used methods to evaluate the antioxidant activity of these compounds according to the mechanism involved in the reaction with free radicals and the methods of in vitro antioxidant evaluation that are used frequently depending on the reaction mechanism of the antioxidant.

Agro-industrial residues are a potential source of antioxidant compounds, which in general are phenolic compounds with a large chemical variability. The structure and the complexity of the phenolic compounds (polyphenols) determine their antioxidant capacity, pretreatments, and extraction methods. This chapter gives an overview of the chemical complexity of the phenolic compounds found in extractable and non-extractable fractions of agro-industrial residues, and representative compounds that are present in such residues are shown. Moreover, extraction methods described in this review showed the use of nonconventional technologies and chemical, enzymatic, or thermic treatments, useful to transform non-extractable polyphenols (NEP) to extractable polyphenol (EP) and then apply the EP extraction methods and recover antioxidants.

Phenolic compounds are secondary metabolites found most abundantly in plants. These aromatic molecules have important roles, as pigments, antioxidants, signaling agents, the structural element lignan, and as a defense mechanism. The expression of phenolic compounds is promoted by biotic and abiotic stresses (e.g., herbivores, pathogens, unfavorable temperature and pH, saline stress, heavy metal stress, and UVB and UVA radiation). These compounds are formed via the shikimate pathway in higher plants and microorganisms. The enzymes responsible for the regulation of phenolic metabolism are known, and shikimic acid is a central metabolite. The shikimate pathway consists of seven reaction steps, beginning with an aldol-type condensation of phosphoenolpyruvic acid (PEP) from the glycolytic pathway, and D-erythrose-4-phosphate, from the pentose phosphate cycle, to produce 3-deoxy-D-arabino-heptulosonic acid 7-phosphate (DAHP). A key branch-point compound is chorismic acid, the final product of the shikimate pathway. The shikimate pathway is described in this chapter, as well as factors that induce the synthesis of phenolic compounds in plants. Some representative examples that show the effect of biotic and abiotic stress on the production of phenolic compounds in plants are discussed.