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Contextualización: las actividades antropogénicas influyen en el ciclo de nitrógeno y fósforo en aguas superficiales, siendo un problema ambiental significativo. Vacío de conocimiento: en la actualidad, no existen investigaciones que aborden el estudio de los iones de NO3- (Nitratos) y PO43- (Fosfatos) mediante métodos espectrofotométricos en la cuenca del río Cesar. Propósito: esta investigación, estudió las concentraciones de NO3- y PO43- en el río Cesar, entre Zambrano (La Guajira) y Las Pitillas (Cesar), durante estaciones lluviosas y secas. Metodología: se utilizaron métodos espectrofotométricos para detección de NO3- y PO43- Resultados y conclusiones: la concentración de NO3- osciló entre 0.460 ± 044 mg.L-1 en San Juan y 1.182 ±  0.032 mg.L-1 en Salguero en la estación lluviosa, mientras que la estación seca fluctuaron entre 0.936± 0.151 mg.L-1 en Zambrano y 1.865 ± 0.150 mg.L-1 en Las Pitillas. En cuanto a PO43-, los valores oscilaron entre 1.514 ± 0.022 mg.L-1 en San Juan y 2.739 ± 0.022 mg.L-1 en Salguero en la estación lluviosa, mientras que la estación seca variaron entre 2.405 ± 0.156 mg.L-1 en San Juan y 5.553 ± 0.143 mg.L-1 en Salguero. Comparando con los límites establecidos por la Organización Mundial de la Salud (OMS, 2004), solo en Salguero (5.553 ± 0.143 mg.L-1) superó el valor permisible para PO43- durante la estación seca. El Índice de Contaminación por Nutrientes (NPI) indicó una contaminación moderada en Salguero en la estación seca. Finalmente, la cuenca del río Cesar estudiada no presenta riesgo de eutrofización atribuible a las actividades antropogénicas en la zona. Contextualization: Anthropogenic activities influence the nitrogen and phosphorus cycle in surface waters, being a significant environmental problem.   Knowledge gap: At present, there is no research that addresses the study of NO3- (Nitrates) and PO43- (Phosphates) ions by spectrophotometric methods in the Cesar River basin (Colombia).   Purpose: This research studied the concentrations of NO3- and PO43- in the Cesar River, between Zambrano and Las Pitillas, during rainy (September 2022) and dry (January 2023) seasons, in areas with grazing, agricultural and domestic activities, to evaluate the Nutrient Pollution Index (NPI).  Methodology: Spectrophotometric methods were used to detect NO3- and PO43-.  Results and conclusions: NO3- concentration ranged between 0.460  ±±  0.044 mg.L-1 at San Juan and 1.182 ±±  0.032 mg.L-1 at Salguero in the rainy season, while in the dry season it fluctuated between 0.936 ±±  0.151 mg.L-1 at Zambrano and 1.865 ±  0.150 mg.L-1 at Las Pitillas.  As for PO43-, values ranged between 1.514 ±  0.022 mg.L-1 at San Juan and 2.739 ±  0.022 mg.L-1 at Salguero in the rainy season, while the dry season ranged between 2.405 ±  0.156 mg L-1 in San Juan and 5.553 ±  0.143 mg.L-1 in Salguero. Compared with the limits established by the World Health Organization (WHO, 2004), only in Salguero (5.553 ±  0.143 mg.L-1) exceeded the permissible value for PO43- during the dry season. Finally, the NPI indicated moderate pollution in Salguero during the dry season. 

The removal of sulfate ions from natural waters, as well as from industrial effluents of different origins, is a problem, considering that most of the proposed processes are inefficient and have a high cost, mainly when reducing the sulfate ion concentration to values below 500 mg.L−1 is required. The flotation technique, combined with precipitation, has proven to be efficient for the removal of heavy metal ions. However, there is not enough research to confirm its efficiency for the removal of sulfate ions. This article presents the results of sulfate ion removal from synthetic solutions prepared in an acidic medium, applying the co-precipitation techniques with polyaluminum chloride (PAC) and solid/liquid separation by dissolved air flotation (DAF). The effect of the pH, the [PAC: sulfate ions] ratio, the effect of saturated water flow with air, and the flocculant and collector doses were studied. The achieved results confirm that it is possible to reduce the concentration of sulfate ions from 1 800 to 350 mg.L−1 (80% removal) from synthetic solutions by applying the flotation technique combined with precipitation. La eliminación de iones sulfatos desde aguas naturales, así como de efluentes industriales de diferentes orígenes, es un problema, considerando que la mayoría de los procesos propuestos son ineficientes y de alto costo, principalmente cuando se requiere reducir la concentración de iones sulfato a valores inferiores a 500 mg.L−1. La técnica de flotación combinada con precipitación ha demostrado ser eficiente para la eliminación de iones d metales pesados. Sin embargo, no hay suficientes investigaciones que confirmen su eficiencia para la eliminación de iones sulfato. Este articulo presenta los resultados de la remoción de iones sulfato desde soluciones sintéticas preparadas en un medio acido, aplicando las técnicas de co-precipitación con policloruro de aluminio (PAC) y separación solido/liquido mediante flotación por aire disuelto (FAD). Se estudiaron el efecto del pH, la razón [PAC: iones sulfato], el efecto del flujo de agua saturada con aire y las dosis de floculante y colector. Los resultados alcanzados confirman que es posible reducir la concentración de iones sulfato de 1 800 a 350 mg.L−1 (80% de remoción) desde soluciones sintéticas aplicando la técnica de flotación combinada con precipitación.

Introduction: Dental caries is a disease caused by the interaction of several factors, including diet, since the development of the biological environment that promotes cariogenic bacterial metabolism often depends on it. Objectives: To determine the prevalence of caries in preschool children from Huaura, Peru, and to confirm if there is an association between their salivary pH and body mass index (BMI) and the level of knowledge about oral health of one of their parents. Materials and methods: A non-experimental, correlational, and cross-sectional study was conducted in 126 preschoolers equally distributed in 3 age groups (3, 4, and 5 years old). The association between the presence of caries and the variables considered was determined by means of the chi-square test of independence, with a confidence level of 95% and a type I error of 5%. In addition, a multiple logistic regression analysis was performed to calculate the probability of caries development in relation to each risk factor. Results: The prevalence of caries was 80.2% (95%CI:73.2-87.2); furthermore, salivary pH (p=0.012) and the level of parental knowledge (p<0.001) were significantly associated with caries occurrence. Regarding the multiple regression analysis, an OR=0.12 (95%CI:0.02-0.63) was obtained for pH and an OR=0.50 (95%CI:0.35-0.74) for the level of parental knowledge in relation to the probability of caries development. Conclusion: The level of parental knowledge about oral health and high salivary pH levels of preschoolers were protective factors against caries development in the study population. On the other hand, no association was found between BMI and the presence of caries in 5-year-old preschoolers. Introducción. La caries dental es una condición causada por la interacción de múltiples factores, entre ellos la dieta, ya que, con frecuencia, de ella depende el desarrollo del medio biológico propicio para el metabolismo bacteriano cariogénico. Objetivo. Determinar la prevalencia de caries en preescolares de Huaura, Perú, y confirmar si hay una asociación con el pH salival y el índice de masa corporal (IMC) de los preescolares, y con el nivel de conocimiento en salud bucal de uno de sus padres. Materiales y métodos. Estudio no experimental, correlacional y transversal realizado en 126 preescolares distribuidos equitativamente en 3 grupos etarios (3, 4 y 5 años). La asociación entre presencia de caries y las variables consideradas se determinó mediante la prueba de independencia de chi cuadrado, con un nivel de confianza del 95% y error tipo I del 5%; además, se realizó un análisis de regresión logística múltiple para calcular la probabilidad de ocurrencia de caries en relación con cada factor de riesgo. Resultados. La prevalencia de caries fue de 80.2% (IC95%:73.2-87.2); además, el pH salival (p=0.012) y el nivel de conocimiento de los padres (p<0.001) se asociaron significativamente con la ocurrencia de caries. En cuanto al análisis de regresión múltiple, se obtuvo un OR=0.12 (IC95%:0.02-0.63) para el pH y un OR=0.50 (IC95%:0.35-0.74) para el nivel de conocimiento de los padres en relación con la probabilidad de presentar caries. Conclusión. El nivel de conocimiento sobre salud bucal de los padres y los niveles altos de pH salival de los preescolares fueron factores protectores frente al desarrollo de caries en la población de estudio. Por otra parte, no se encontró asociación entre IMC y presencia de caries en los preescolares de 5 años.

Fuel cells are electrochemical energy conversion devices that convert hydrogen and oxygen into water, producing electricity and heat in the process and providing fuel efficiency and reductions in pollutants. Demand for this technology is growing rapidly. Fuel cells are being commercialized for stationary and portable electricity generation, and as a replacement for internal combustion engines in automobiles. Proton Exchange Membrane (PEM) fuel cells in particular are experiencing an upsurge. They have high power density and can vary their output quickly to meet shifts in power demand. Until now, there has been little written about this important technology. This book lays the groundwork for fuel cell engineers, technicians and students. It covers the fundamental aspects of fuel cell design, electrochemistry of the technology, heat and mass transport, system design and applications to bring this technology to professionals at all levels. * Comprehensive guide for engineers, researchers and policymakers* Covers theory and practice of PEM fuel cells* Contains hundreds of original illustrations and real-life engineering examples

In this research, the concentration-depth profiles reached by titanium and nitrogen particles, on the surface of AISI/SAE 1020 carbon steel substrates, by using of ion implantation technique, are studied. The ions are surface deposited by means of high voltage pulsed discharges and electric arc discharge under high vacuum conditions. The concentration and position distribution of the metallic and non-metallic species are obtained by simulation of the interaction of ions with the matter, stopping and ranges of ions in the matter, by the computer program transport of ions in matter. The implantation dose is calculated from the discharge data and the previously established study parameters in this work. From the simulation results, the depth profiles demonstrated that titanium and nitrogen ions may reach up to 300 Å and 600 Å and concentrations of 1.478 x 1016 ions⁄cm2 and 2.127 x 1016 ions⁄cm2, respectively. The formation of titanium microdroplets upon the surface of the substrates is identified from the micrographs obtained by the scanning electron microscopy technique; furthermore, the presence of titanium and nitrogen implanted on the surface of the substrate is verified through the elemental composition analysis by the energy dispersive spectroscopy, validating the effect of ion implantation on ferrous alloys.

▪ Abstract  The plant hormone abscisic acid (ABA) plays a major role in seed maturation and germination, as well as in adaptation to abiotic environmental stresses. ABA promotes stomatal closure by rapidly altering ion fluxes in guard cells. Other ABA actions involve modifications of gene expression, and the analysis of ABA-responsive promoters has revealed a diversity of potential cis-acting regulatory elements. The nature of the ABA receptor(s) remains unknown. In contrast, combined biophysical, genetic, and molecular approaches have led to considerable progress in the characterization of more downstream signaling elements. In particular, substantial evidence points to the importance of reversible protein phosphorylation and modifications of cytosolic calcium levels and pH as intermediates in ABA signal transduction. Exciting advances are being made in reassembling individual components into minimal ABA signaling cascades at the single-cell level.

This book is an essential guide for understanding Lithium-ion batteries and the standards that govern them. This comprehensive resource covers everything from the basics of Lithium-ion battery systems to the intricacies of safety, design, and regulatory requirements. The book explains the differences between Lithium-ion batteries and other battery systems, highlighting the critical importance of system integration and design. It offers insights into battery system architectures, terminology, and the safety features that can be specified for Lithium-ion cells. The reader will find a detailed exploration of safety concerns, including failure modes in electronic components and high voltage systems, as well as an in-depth discussion on the differences between standards and regulatory requirements, both in the U.S. and internationally. The book also covers industry-specific standards, providing a comprehensive list of applicable regulations for various battery system architectures. Additionally, it includes practical information on the shipping and labeling of Lithium-ion batteries, with special attention to prototype and damaged batteries. This is the go-to resource for understanding and navigating the complex world of Lithium-ion battery standards and regulations.

En el presente trabajo se estudió la remoción de iones cobre y níquel utilizando cáscaras de maní mediante pruebas en lote en sistemas monocomponente y bicomponente (pruebas de remoción simultánea). En este estudio se evaluó el efecto de las variables pH, tiempo de contacto, concentración de biosorbente, concentración del ión metálico. El resultado mostró que las cáscaras de maní fueron un biosorbente relativamente efectivo para la eliminación de estos iones, alcanzándose remoción que varió entre 4,3% y 68,3% para iones cobre y entre 3,6% y 47,6% para iones níquel. La máxima remoción de los iones cobre y níquel se alcanzó en pH 3. La cinética de adsorción de ambos iones se produce rápidamente durante los primeros 15 minutos lográndose eliminaciones cercanas a 60,0 % para el cobre y 43,0 % para el níquel, no obstante, los valores máximos de adsorción se alcanzan a los 30 minutos (cobre) y 60 minutos (níquel). Se observó que a medida que aumenta la concentración del biosorbente la eliminación de los iones cobre y níquel disminuye levemente. Las pruebas de remoción simultánea mostraron que la eliminación de iones níquel (45,7%) fue inferior que la de iones cobre (69,9%), estos resultados fueron muy similares a los alcanzados en las pruebas individuales de remoción de ambos iones.

One particular challenge in reducing the loss of biodiversity by 2010, as agreed on at the Earth Summit in 2002, is to assign conservation tasks to geographic or administrative entities (e.g., countries or regions) on different geographical scales. To identify conservation tasks, it is imperative to determine the importance of a specific area for the global survival of a species. So far, these national or subnational responsibilities for the conservation of species have been included differently in methods prioritizing conservation. We reviewed how 12 European and 3 non-European methods determined national conservation responsibilities and evaluated the international importance of a biological population. Different countries used different methodologies, which made a direct comparison of assessments of national responsibilities among countries extremely difficult. Differences existed in the importance criteria used. Criteria included population decline, range reduction, rarity status, degree of isolation of a population, endemism, proportional distribution, and geographic location. To increase comparability, it is imperative to develop criteria for which data are generally available and to standardize the methodology among countries. A standardized method would allow conservation decisions to be based on the conservation status of a species and on the responsibility of a geographic or administrative entity for the survival of a species. We suggest that such a method should use a scalable index of proportional distribution, taxonomic status, and the distribution pattern of a taxon or species as key elements. Such a method would allow for the creation of hierarchical lists and would be highly relevant for parts of the world with multiple political jurisdictions or state unions and for nations with regional governmental structures. Conservation priorities could then be reasonably set by combining national responsibility assessments with the international conservation status of a species.

Iron is an essential nutrient for virtually all organisms. The IRT1 (iron-regulated transporter) gene of the plant Arabidopsis thaliana, encoding a probable Fe(II) transporter, was cloned by functional expression in a yeast strain defective for iron uptake. Yeast expressing IRT1 possess a novel Fe(II) uptake activity that is strongly inhibited by Cd. IRT1 is predicted to be an integral membrane protein with a metal-binding domain. Data base comparisons and Southern blot analysis indicated that IRT1 is a member of a gene family in Arabidopsis. Related sequences were also found in the genomes of rice, yeast, nematodes, and humans. In Arabidopsis, IRT1 is expressed in roots, is induced by iron deficiency, and has altered regulation in plant lines bearing mutations that affect the iron uptake system. These results provide the first molecular insight into iron transport by plants.