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In recent years and with the rapid development of electric vehicles and batteries, the demand for nickel as an important material in clean energy technologies has increased. Extensive research efforts have been devoted to develop a clean alternative technology capable of obtaining this metal from low-grade laterite. This study investigated the laterite leaching using sodium citrate as an alternative reagent to conventional inorganic acids; the effect of pyro- and hydrometallurgical pretreatments on ore morphology and structure was evaluated. The results showed that although citrate tends to be selective for nickel, its dissolution is associated to the iron. The decreasing core model (SCM) was used to determine the best fit for the experimental data. Using the Arrhenius expression, the apparent activation energy for the nickel and iron solutions was estimated, verifying a chemical reaction control in the process.

We propose a political-ecological approach to community desalination based on our experience installing small desalination plants in three coastal communities in southern Chile. Conceptually, we frame community desalination plants as new hydrosocial assemblages different from large-scale or extractivist desalination, discussing how social participation is key to the community’s reappropriation of nature through desalination plants. We use the literature of scalar politics in water governance as a device for analysing the ongoing political struggles around water and the role that community desalination can play in satisfying the human right to water. Through a multi-method and participatory approach, we demonstrate the situated nature of community desalination development in Chile. We identify three stages in the configuration of the new hydrosocial assemblages: negotiating the installation of the plants, valuing the drinking water produced by the plants, and negotiating to finance their definitive installation as a complementary source of drinking water for these communities. We also show that the community appropriation of these plants depends mainly on the water quality and the institutional arrangements to sustain these small plants over space and time. We analyse how the community scale interacts with municipal, regional, and national scales differently. Finally, we conclude by evaluating, from a hydrosocial perspective, the pros and cons of using this community desalination process to satisfy the human right to water.

We describe how the water commons agenda has been mobilized by different social groups of Chilean society, including water social movements and indigenous people, and the way it was included in the constitutional debate (2021–2022). Although the draft for the new Constitution was rejected in September 2022, we argue that the water commons agenda is still being mobilized as a socioenvironmental project for the 21st century. Simply put, the water commons agenda does not disappear with the defeat of the proposed new Constitution. It continues to challenge the neoliberalization of nature and water imposed during the Pinochet dictatorship, proposing to create new ways to sustain the territories of life. HIGHLIGHTS Water and social crisis in Chile.; Social movements and indigenous people mobilize both the water commons agenda and the constituent process.; Constituent Convention declares water as a common good.; Proposed Constitution is rejected by citizenship.; Water commons agenda for the 21st century.;

Automotive catalysts represent a secondary source for precious metals recovery. These elements are usually obtained from minerals. Recently, methods have been sought to recover them from waste materials. The main route consists of pyrometallurgical treatments at high temperatures with the generation of other pollutants and very high energy consumption. With hydrometallurgy, routes can be developed which favor the aqueous extraction of said elements at room temperature. In an automotive catalyst, there are different metals which can interfere in the recovery process. In this study, sodium citrate (Na3C6H5O7•H2O), nitric acid (HNO3), and hydrochloric acid (HCl) were evaluated as a hydrometallurgical pretreatment to dissolve Fe, Zn, and Pb contained in a spent automotive catalyst and to improve the subsequent extraction of the precious metals contained therein (Au, Ag, and Pt). Afterwards, the aqueous extraction of precious elements with thiourea (SC(NH2)2) was carried out, comparing the effect of the pretreatment reagents. Finally, the feasibility and effect of each pretreatment as a route for precious metals recovery were analyzed with the aim to avoid processes at high temperatures.

A hydrometallurgical treatment under ambient conditions was proposed in order to eliminate and recover the lead and zinc contained in a sample of thermal coal fly ash used to produce energy. By using leaching solutions with conventional inorganic acids (HCl, HNO3, and H2SO4), ferric chloride, and sodium citrate, more than 90% zinc and approximately 40% lead were obtained. The most favorable leaching conditions were set at 0,5 M, with a pH value of 8 for citrate. Two leaching stages were necessary to optimize metal recovery: the first with nitric acid for zinc extraction and the second one with citrate for the lead. The sulfur phases of the metals limited a complete metal extraction.

Forestry plantations on Mapuche lands in southern Chile are a critical socio-environmental issue. Through the lens of political ecology and using methods based on historical review, spatial data representation and ethnographic interviews, we propose the concept of water extractivism. We argue that its development via forestry expansion contributes to the lack of drinking water in Mapuche territory, a South American area with significant claims for land, water, native forests, human rights and political autonomy. Our findings reveal the coloniality of nature as it has been manifested in the development of water extractivism in southern Chile. This process began in 1881 with the dispossession of Mapuche communities from their lands by the state, and it continued during the 20th century with colonisation and the introduction of forestry plantations. The last two decades of socioenvironmental problems have stemmed from forestry plantations related to a lack of drinking water. Decolonialisation struggles deployed by members of the Mapuche communities through direct action politics and in institutional arenas are among the main social responses to the negative consequences of water extractivism. We conclude by valuing the concept of water extractivism as an analytical tool within decolonial political ecology and we discuss the meaning of the current Mapuche decolonial struggles for water and cultural sustainability.

Contexto: Los EAFD (Electric Arc Furnace Dust) son materiales con un elevado contenido metálico que no es aprovechado al desconocerse su composición y el enfoque técnico para tratarlos o reciclarlos de manera segura. Aunque es un coproducto rico en zinc, a menudo la recuperación de este metal es una tarea desafiante. Objetivo: Proponer un método para tratar los EAFD mediante la extracción selectiva de zinc por vía hidrometalúrgica, obteniendo un licor rico en zinc para su posterior recuperación y futura aplicación y un sólido rico en hierro para su recirculación en procesos siderúrgicos. Metodología: Los experimentos se realizaron a través de lixiviaciones por agitación empleando soluciones de citrato de sodio a concentración y agitación moderadas, temperatura y presión ambiente. Algunas de las variables de estudio fueron modificadas a fin de establecer las mejores condiciones para el proceso. Resultados: Luego de realizar una correlación de resultados y análisis de variables, se determinó que es posible alcanzar extracciones por encima del 50% de Zn y por debajo del 3% de Fe con el citrato. Además, que una concentración de 0.5 M y proporción S/L de 25g / 1 L son algunas de las condiciones más favorables para el proceso de extracción. Conclusiones: Es posible un aprovechamiento del residuo EAFD mediante ruta hidrometalúrgica empleando un agente orgánico como solución lixiviante. El método permite extraer selectivamente el metal de interés a condiciones de trabajo moderadas.

A variety of techniques based on the indirect measurement of blood pressure (BP) by Pulse Transit Time (PTT) have been explored over the past few years. Such an approach has the potential in providing continuous and non-invasive beat to beat blood pressure without the use of a cuff. Pulse Arrival Time (PAT) which includes the cardiac pre-ejection period has been proposed as a surrogate of PTT, however, the balance between its questioned accuracy and measurement simplicity has yet to be established. The present work assessed the degree of linear relationship between PAT and blood pressure on 96 h of continuous electrocardiography and invasive radial blood pressure waveforms in a group of 11 young ICU patients. Participants were selected according to strict exclusion criteria including no use of vasoactive medications and presence of clinical conditions associated with cardiovascular diseases. The average range of variation for diastolic BP was 60 to 79 mmHg while systolic BP varied between 123 and 158 mmHg in the study database. The overall Pearson correlation coefficient for systolic and diastolic blood pressure was −0.5 and −0.42, respectively, while the mean absolute error was 3.9 and 7.6 mmHg. It was concluded that the utilization of PAT for the continuous non-invasive blood pressure estimation is rather limited according to the experimental setup, nonetheless the correlation coefficient performed better when the range of variation of blood pressure was high over periods of 30 min suggesting that PAT has the potential to be used as indicator of changes relating to hypertensive or hypotensive episodes.

Abstract From a theoretical approach based on political ecology and environmental justice, we assess how forestry development has generated socio-spatial dynamics of environmental degradation and water scarcity in southern Chile. Through historical-geographical and ethnographic methods, we discuss how and why the spread of forestry plantations has significantly influenced social and environmental degradation of the Mapuche's modes of living. In response, during recent decades a political articulation of a Mapuche social movement is observed. Their demands include land, autonomy, rights and opportunities to frame their own development strategies. Within the internal diversity of this movement, a key principle is reversing the spread of environmental degradation by recovering the native forest and its natural water cycles, which have been disrupted significantly by the increasing of forestry plantations. We explore these dynamics of the Mapuche movement from an environmental justice approach.

Se presenta un estudio sobre el comportamiento frente a la corrosión de barras de acero de refuerzo de un concreto de escoria activado alcalinamente. La escoria de alto horno fue activada mediante el uso de silicato sódico al 5% obteniéndose un material con buenas propiedades cementantes. Las probetas de concreto fueron fabricadas a partir de este cemento, después de mezclar con los agregados fueron reforzadas con barras de acero sismoresistente ASTMA706. Las probetas de concreto reforzado estuvieron sometidas en ambientes contaminados con iones cloruro para simular condiciones marinas. La evaluación electroquímica se realizo aplicando las técnicas de resistencia a la polarización lineal (LPR) y espectroscopia de impedancia electroquímica (EIS). Se logra determinar el comportamiento de la capa pasiva del acero y electroquímico del metal cuando está inmerso en estos materiales cerámicos novedosos.

A detailed description of the electronic system designed to improve the measurements in an experimental AC electrogravimetry setup is presented. This system is committed to acquire appropriated data for determining the Electrogravimetric Transfer Function (EGTF) and provide information regarding the mass transfer in an electrochemical cell in the AC Electrogravimetry Technique, but maintaining a good trade-off between the locking frequency bandwidth and the resolution in the frequency tracking, that is, enlarging the bandwidth of the system to follow signals with frequency as higher as 1 kHz, but maintaining an accurate and continuous tracking of this signal. The enlarged bandwidth allows the study of fast kinetic process in electrochemical applications and the continuous tracking let to achieve a precise measurement with good resolution rather than average frequency records obtained by conventional frequency meters. The system is based on an Analogue-Digital Phase Locked Loop (A-D PLL).En este artículo se presenta una descripción detallada del sistema electrónico diseñado para mejorar las medidas en un sistema experimental de electrogravimetría AC. El sistema diseñado se encarga de adquirir los datos adecuados para determinar la función de transferencia electrogravimétrica (EGTF) y proveer información relacionada con la transferencia de masa en una celda electroquímica en la técnica de electrogravimetría AC, pero manteniendo un buen compromiso entre el ancho de banda de enganche y la resolución en el seguimiento de la frecuencia, es decir, el sistema incrementa el ancho de banda para permitir el seguimiento de señales con frecuencias hasta de 1 kHz, pero conservando un exacto y continuo seguimiento de esta señal. El aumento del ancho de banda permite el estudio de procesos con una cinética rápida en aplicaciones electroquímicas y el seguimiento continuo de la señal permite la obtención de medidas precisas con buena resolución en contraste con los datos de frecuencia promediados entregados por los frecuencímetros convencionales. El sistema se basa en un bucle de enganche de fase analógico-digital (A-D PLL).

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Exploring the concept of Integrated Water Resource Management (IWRM) and using participatory social research methodologies, this paper seeks to expose and understand conflicts between water users from two river basins in Chile, that, despite their location in completely different areas (one a desert, the other an extreme south-austral zone), have similarities in socio-environmental conflict, since in both cases the existence of mega-projects (one, a mine, the other, a hydroelectric plant) has generated diverse visions of development between the directly affected local communities and the transnational corporations. The paper reflects on these similarities and the socio-environmental struggles they are experiencing, concluding that IWRM is the way to raise awareness and seek solutions to environmental conflicts in the current era of "neoliberal ecocide". [ABSTRACT FROM AUTHOR]

Phononic crystals are periodic composite structures with specific resonant features that are gaining popularity in the field as liquid sensors. The introduction of a structural defect in an otherwise periodic regular arrangement can generate a resonant mode, also called defect mode, inside the characteristic band gaps of phononic crystals. The morphology, as well as the frequency in which these defect modes appear, can give useful information on the composition and properties of an analyte. Currently, only gain and frequency measurements are performed using phononic crystal sensors. Other measurements like the transient response have been implemented in resonant sensors such as quartz microbalances showing great results and proving to be a great complimentary measure to the gain and frequency measurements. In the present paper, a study of the feasibility of using the transient response as a measure to acquire additional information about the analyte is presented. Theoretical studies using the transmission line model were realized to show the impact of variations in the concentration of an analyte, in this case, lithium carbonate solutions, in the transient time of the system. Experimental realizations were also performed showing that the proposed measurement scheme presents significant changes in the resulting data, indicating the potential use of this measure in phononic crystal sensors. This proposed measure could be implemented as a stand-alone measure or as a compliment to current sensing modalities.

Una interfaz cerebro-computador (ICC) es un sistema de comunicación que permite generar una señal de control a partir de señales cerebrales como los ritmos sensorimotores y los potenciales evocados y, por consiguiente, constituye una alternativa novedosa de comunicación para personas con discapacidad motora seria (como aquellas que padecen esclerosis lateral amiotrófica, ELA). Este proyecto propone el desarrollo de un prototipo de ICC basado en el registro de potenciales evocados cognitivos P-300 mediante electroencefalografía. El prototipo usa un electroencefalógrafo de seis canales para la adquisición de las señales, y por medio de una matriz de estimulación visual que contiene las letras del abecedario e íconos asociados a ellas permite que el usuario escriba palabras o elabore mensajes con los íconos. Para procesar las señales (filtración, diezmado, entre otros) se utilizaron los programas BCI2000 y MATLAB 7.0. Este último se empleó para programar tres algoritmos lineales de traslación (análisis lineal del discriminante, solución por mínimos cuadrados y análisis lineal del discriminante paso a paso) que permitieran traducir los potenciales evocados en señales de comunicación.Uma interface cérebro-computador (ICC) é um sistema de comunicação que permite gerar um sinal de controle a partir de sinais cerebrais como os ritmos sensorimotores e os potenciais evocados e, por conseguinte, constitui uma alternativa nova de comunicação para pessoas com incapacidade motora séria (como aquelas que padecem esclerose lateral amiotrófica, ELA). Este projeto propõe o desenvolvimento de um protótipo de ICC baseado no registro de potenciais evocados cognitivos P-300 mediante electroencefalografia. O protótipo desenvolvido há uso de um electroencefalógrafo de seis canais para a aquisição dos sinais, e por meio de uma matriz de estimulação visual que contém as letras do abecedário e ícones associados a elas permite que o usuário escreva palavras ou elabore mensagens com os ícones. Para processar os sinais (filtragem, dizimado, entre outros) se utilizaram os programas BCI2000 e MATLAB 7.0. Este último se empregou para programar três algoritmos lineais de translação (análise linear do discriminante, solução por mínimos quadrados e análise linear do discriminante passo a passo) que permitissem traduzir os potenciais evocados em sinais de comunicação.A brain-computer interface (BCI) is a communication system that translates a brain signal (e.g. sensorimotor rhythms, evoked potentials) into a control signal and, therefore, constitutes an innovative communication alternative for people with severe motor disability (such as patients with amyotrophic lateral sclerosis). This project proposes the development of a BCI prototype based on the recording of P300 cognitive potentials using electroencephalography. The prototype uses a six-channel electroencephalograph to acquire the signals, and through a visual stimulation matrix containing the letters of the alphabet and icons associated to each one gives the user the possibility of writing words or elaborating messages with the icons. To process the signals (filtering and decimation, among other methods), the software BCI2000 and MATLAB 7.0 were used. The latter was used to program three different linear translation algorithms (linear discriminant analysis, least squares analysis and stepwise linear discriminant analysis), in order to translate the recorded evoked potentials into communication signals.

Phononic crystals are resonant structures with great potential to be implemented in applications as liquid sensors. The use of the symmetry reduction technique allows introducing relevant transmission features inside bandgaps by creating defect modes in a periodic regular structure. These features can be used as measures to quantify changes in the speed of sound of liquid samples that could be related to the concentration of analytes or the presence of pathogens among other interesting applications. In order to be able to implement this new technology in more challenging applications, such as biomedical applications, it is necessary to have a very precise and accurate measurement. Changes in temperature greatly affect the speed of sound of the liquid samples, causing errors in the measurements. This article presents a phononic crystal sensor that, by introducing additional defect modes, can carry out differential measurements as a temperature compensation mechanism. Theoretical studies using the transmission line model and analytes at various temperatures show that the proposed temperature compensation mechanism enhances the performance of the sensor in a significant way. This temperature compensation strategy could also be implemented in crystals with different topologies.

Basic fundamentals of AC electrogravimetry are introduced. Their main requirements and characteristics are detailed to establish the design of an electronic system that allows the appropriate extraction of data needed to determine the electrogravimetric transfer function (EGTF) and electrochemical impedance (EI), in an experimental set-up for the AC electrogravimetry technique.