Recent insights into xerogel and aerogel mineral composites for CO 2 mineral sequestration

Supercritically dried composites have already been analysed and proposed as carbon dioxide sequesters. However, the economical and energetic costs of the supercritical drying process had to be re-evaluated, and were eventually found not to enhance the feasibility of the proposed route for CO2 mineral sequestration. Different composites series were synthesised with the only difference being the drying method. The structures of the porous matrix were characterised as well as their ability to capture CO2. The first results showed that the xerogel matrix is as good a host as the aerogel one, and also avoids expensive procedures such as supercritical drying for sample preparation without losing CO2 capture capacity and enhancing the efficiency of the whole carbon sequestration process. In this case, the sample preparation was simplified as much as possible, with the aim of reducing energetic and economic costs. Although good carbonation efficiencies were obtained with these cheap samples, the first results showed that previous high carbonation efficiencies could not be repeated.Junta de Andalucía TEP115Ministerio de Ciencia e Innovación PIA42008-3

Removal of basic yellow cationic dye by an aqueous dispersion of Moroccan stevensite

The aim of this study was to investigate the adsorption of basic yellow, a cationic dye, from aqueous solution by natural stevensite, with 104m2/g of specific surface area. The kinetics and the effects of several experimental parameters such as the pH of the solution, adsorbent dose and initial dye concentration were researched using a batch adsorption technique. The results showed that an alkaline pH favoured basic yellow adsorption and the adsorption reached equilibrium in about 20min. It was concluded that the adsorption process was governed by the electrostatic interaction. The isothermal data were fitted by means of Langmuir and Freundlich equations, and a monolayer adsorption capacity of 454.54mg/g was calculated. Finally, a good agreement was found between the pseudo-second order model and the experimental data. A high maximum adsorption capacity was obtained (526mg/g) and a maximum surface density of ~9 dye molecules/nm2 was estimated, involving a columnar arrangement of the adsorbed molecules.Agencia Española de Cooperación Internacional A/018025/08Junta de Andalucía TEP11

Three Essays on Evaluating the Impact of Natural Resource Management Programs

This dissertation is composed of three papers describing the nexus between natural resource management programs, farmer well-being, and productivity. Our study sheds light on the effectiveness of actions that have been or could be implemented to address the “triangle of poverty.” This triangle connects low farm productivity to high poverty, which forces farmers to increase the pressure on natural resources thus further degrading the environment and resulting in even lower productivity and more poverty. Natural resource management (NRM) imbeds key agricultural policies, which aim at handling resource degradation while enhancing productivity particularly among smallholder farmers. Technologies promoted through the use of NRM programs encompass conservation agriculture, water and integrated pest management, agroforestry, and silvopastoral activities. Although most of these technologies have been promoted since the early 1960s, it was not until 1989 when the CGIAR emphasized the value of NRM technologies as tools to ensure the sustainability of agricultural systems. Since then, the implementation of NRM programs have evolved around the following definition: “Sustainable agriculture should involve the successful management of resources for agriculture to satisfy changing human needs while maintaining or enhancing the quality of the environment and conserving natural resources (Consultative Group on International Agricultural Research [CGIAR] 2006, p.4).” In general, these programs aim at developing and disseminating technologies, which improve the quality of soil and water, diversify the agro-ecosystem and build farm capacity to mitigate the effects of climate change. To examine to what extent NRM programs have achieved their aim, in the first essay, meta-regression analysis is used to explore the effect that natural resource management (NRM) programs have on monetary outcomes and on productivity. In doing so, we use a comprehensive dataset of 75 impact evaluation studies and 215 observations from all over the world (equivalent to a sample of 31,991 treated and 42,936 control farmers) to explain why impact varies among studies and across different interventions, regions, and methods. Econometric results from ordered probit, probit, OLS regression, and Bayesian regression models consistently show that NRM programs have a significant positive effect on the monetary outcomes and productivity of beneficiaries relative to control farmers. Overall, NRM technologies increase monetary outcomes on average by 8%, and yields by 13%. Furthermore, the impacts of NRM programs could be larger if: i) participatory methods to transfer the technology to the final user are incorporated in the design; ii) appropriate training to boost the adoption of the technology is provided; iii) NRM technologies are tailored to the rainfall patterns of the intervention area; iv) government units are more efficient in the delivery of technologies; and v) the evaluation of NRM programs account for the time necessary for these programs to produce results. The first essay compiles evidence from a large number of published analyses. We complement this evidence in the following two essays with original empirical analyses of a specific NRM intervention, the Socio-Environmental and Forestry Development Program-II (POSAF-II), which was implemented by the Nicaraguan Ministry of the Environment and Natural Resources (MARENA). The goal was to promote economic development and environmental sustainability. POSAF-II financed a total of 13,477 farmers occupying 69,767 hectares in several major river basins that were severely damaged by Hurricane Mitch in 1998. Therefore, this program represents a unique opportunity to evaluate the economic impact of NRM programs in an area affected by a massive weather event, characterized by high soil degradation and poverty. The second essay is an analysis of the economic impact of natural resource technologies delivered by POSAF-II. We use cross-sectional data for 1,483 households, from 212 treated and control communities. Results obtained through propensity score matching (PSM), ordinary least squares (OLS), weighted least squares regression (WLS) based on PSM, and instrumental variables (IV) regression indicate that POSAF-II has had a positive impact on the total value of agricultural production of beneficiary farmers relative to appropriate control groups. The estimated internal rate of return supports the hypothesis that increasing household income while encouraging the sustainable use of natural resources through the implementation of suitable management programs can be complementary development objectives. The third essay examines the impact of POSAF-II on two critical components of productivity: technological change (TC) and technical efficiency (TE). We use propensity score matching (PSM) to mitigate potential biases from observable variables along with a recently introduced stochastic production frontier (SPF) model that addresses sample selection bias arising from unobservable variables. Our results show that POSAF-II has had a positive impact on both TC and TE. This essay contributes to the literature on impact evaluation by showing how an intervention designed to improve natural resource management can also enhance the income of poor farm households through increases in productivity

Calcium silicates synthesised from industrial residues with the ability for CO2 sequestration

This work explored several synthesis routes to obtain calcium silicates from different calcium-rich and silica-rich industrial residues. Larnite, wollastonite and calcium silicate chloride were successfully synthesised with moderate heat treatments below standard temperatures. These procedures help to not only conserve natural resources, but also to reduce the energy requirements and CO2 emissions. In addition, these silicates have been successfully tested as carbon dioxide sequesters, to enhance the viability of CO2 mineral sequestration technologies using calcium-rich industrial by-products as sequestration agents. Two different carbon sequestration experiments were performed under ambient conditions. Static experiments revealed carbonation efficiencies close to 100% and real-time resolved experiments characterised the dynamic behaviour and ability of these samples to reduce the CO2 concentration within a mixture of gases. The CO2 concentration was reduced up to 70%, with a carbon fixation dynamic ratio of 3.2 mg CO2 per g of sequestration agent and minute. Our results confirm the suitability of the proposed synthesis routes to synthesise different calcium silicates recycling industrial residues, being therefore energetically more efficient and environmentally friendly procedures for the cement industry.Ministerio de Ciencia e Innovación CIT-440000-09-0

Larnite powders and larnite/silica aerogel composites as effective agents for CO2 sequestration by carbonation

This paper presents the results of the carbonation reaction of two sample types: larnite (Ca2SiO4) powders and larnite/silica aerogel composites, the larnite acting as an active phase in a process of direct mineral carbonation. First, larnite powders were synthesized by the reaction of colloidal silica and calcium nitrate in the presence of ethylene glycol. Then, to synthesize the composites, the surface of the larnite powders was chemically modified with 3-aminopropyltriethoxysilane (APTES), and later this mixture was added to a silica sol previously prepared from tetraethylorthosilicate (TEOS). The resulting humid gel was dried in an autoclave under supercritical conditions for the ethanol. The textures and chemical compositions of the powders and composites were characterized.The carbonation reaction of both types of samples was evaluated by means of X-ray diffraction and thermogravimetric analysis. Both techniques confirm the high efficiency of the reaction at room temperature and atmospheric pressure. A complete transformation of the silicate into carbonate resulted after submitting the samples to a flow of pure CO2 for 15 min. This indicates that for this reaction time, 1 t of larnite could eliminate about 550 kg of CO2. The grain size, porosity, and specific surface area are the factors controlling the reaction.Ministerio de Medio Ambiente A266/2007/3-11.1Ministerio de Educación y Ciencia MAT2005-0158

Preparation of an injectable macroporous α-TCP cement

One of the most important characteristics of calcium phosphate cements is their resorbability when implanted in the body. However, the in vivo resorption rate is slow due to the lack of intrinsic open porosity. In this study, macroporous structures were obtained by mixing alpha-tricalcium phosphate (α-TCP) cement with a foamed liquid phase containing different concentrations of sodium hydrogen phosphate and non-ionic (Lutensol) or anionic (Sodium Lauryl Sulfate) surfactant. The cement paste was prepared by hand mixing in a system of two syringes connected by a polyvinyl chloride (PVC) valve, an environmentally friendly method. Solutions with Lutensol (L110) showed greater foamability than solutions with Sodium Lauryl Sulfate (SLS). Scanning Electron Microscopy characterization helped verify that the prepared samples showed a macroporous interconnected structure, and X-ray diffraction analysis evidenced the transformation of α-TCP into calcium deficient hydroxyapatite (CDHA). This study suggests that the calcium phosphate cement samples foamed with Lutensol may be further evaluated as suitable materials for bone filling

Procedure to use phosphogypsum industrial waste for mineral CO 2 sequestration

Industrial wet phosphoric acid production in Huelva (SW Spain) has led to the controversial stockpiling of waste phosphogypsum by-products, resulting in the release of significant quantities of toxic impurities in salt marshes in the Tinto river estuary. In the framework of the fight against global climate change and the effort to reduce carbon dioxide emissions, a simple and efficient procedure for CO 2 mineral sequestration is presented in this work, using phosphogypsum waste as a calcium source. Our results demonstrate the high efficiency of portlandite precipitation by phosphogypsum dissolution using an alkaline soda solution. Carbonation experiments performed at ambient pressure and temperature resulted in total conversion of the portlandite into carbonate. The fate of trace elements present in the phosphogypsum waste was also investigated, and trace impurities were found to be completely transferred to the final calcite. We believe that the procedure proposed here should be considered not only as a solution for reducing old stockpiles of phosphogypsum wastes, but also for future phosphoric acid and other gypsum-producing industrial processes, resulting in more sustainable production.Junta de Andalucía TEP115Ministerio de Ciencia e Innovación PIA42008-3

Edema pulmonar debido a la inducción anestésica con propofol

Pulmonary edema is infrequently reported after administration of propofol. This article describes pulmonary edema in a woman of 45 year old who presented for elective cholecystectomy for minimum access, under general anesthesia with propofol. According to possible hypotheses in previous reports this pulmonary edema could be due to a direct cardiodepressant  effect of propofol for antagonism with calcium channels or to the syndrome related with propofol infusion. Moreover, it is likely that in this case there is an underlying ischemia coexisted whenever a segmental alteration of ventricular contraction was observed on echocardiography.El edema pulmonar se ha informado infrecuentemente después de la administración de propofol. En este artículo se describe el edema pulmonar en una mujer de 45 años de edad que se presentó para colecistectomía electiva por mínimo acceso, bajo anestesia general, con propofol. De acuerdo con posibles hipótesis planteadas en informes previos este edema pulmonar pudo deberse a un efecto cardiodepresor directo del propofol por antagonismo con los canales de calcio o al síndrome relacionado con infusión de propofol. Por otra parte, es probable que en este caso haya coexistido una isquemia subyacente toda vez que se observó una alteración segmentaria de la contracción ventricular en el ecocardiograma

Lo que sabemos de la covid-19

Resumen: Los coronavirus son una gran familia de virus que ya se habían documentado como causantes de resfríos y enfermedades graves como el Síndrome Respiratorio Agudo Severo (SARS) en 2002 y el Síndrome Respiratorio del Medio Oriente (MERS) en 2012. En diciembre de 2019 en la cuidad de Wuhan en la provincia de Hubei, China se originó una nueva enfermedad causada por un coronavirus perteneciente a la familia de los B-coronavirus, que luego se le nombró SARS-CoV-2. La Organización Mundial de la Salud (OMS) declaró esta enfermedad, COVID-19, como pandemia el 11 de marzo de 2020. Hasta la fecha se han contagiado más de 190 millones de personas en el mundo y más de 4 millones han fallecido. Esta revisión bibliográfica ha sido realizada con el propósito de informar a la comunidad médica de Santa Clara y de Cuba acerca de los temas publicados que tratan sobre los aspectos más relevantes de la enfermedad.Palabras claves: Revisión bibliográfica, coronavirus, 2019-nCoV, COVID-19, SARS-CoV-

Desempeño docente a través de entornos virtuales y aprendizaje cooperativo en los estudiantes de Economía de la Universidad Nacional Mayor de San Marcos

En la presente investigación se estudia Determinar relación existente entre desempeño docente a través de entornos virtuales y el aprendizaje cooperativo en los estudiantes de economía de la Universidad Nacional Mayor de San Marcos. La muestra estuvo constituida por 228 sujetos, los cuales fueron seleccionados de manera probabilística y estratificada. Los resultados fueron analizados en el nivel descriptivo, en donde encontró que el 61,4%, expresa el desempeño docente a través de entornos virtuales en el nivel medio, respecto al aprendizaje cooperativo se observa que el 51,8% percibe esta variable en el nivel medio, en nivel inferencial se ha hecho uso de la estadística paramétrica y como tal se ha utilizado Spearman a un nivel de 0,05, dado que los datos no presentan distribución normal. Los resultados indican que el desempeño docente a través de entornos virtuales se relaciona de manera directa, alta y significativa con el aprendizaje cooperativo.In the present investigation, the study of the relationship between teaching performance through virtual environments and cooperative learning in economics students at the Universidad Nacional Mayor de San Marcos is studied. The sample consisted of 228 subjects, who were selected in a probabilistic and stratified way. The results were analyzed at the descriptive level, where he found that 61.4% expressed teaching performance through virtual environments at the middle level, with respect to cooperative learning, it was observed that 51.8% perceived this variable in the medium level, inferential level parametric statistics have been used and as such Spearman has been used at a level of 0.05, since the data do not present a normal distribution. The results indicate that teaching performance through virtual environments is directly, highly and significantly related to cooperative