Synthesis of type A zeolites from natural kaolinite for their application in CO2 capture processes

Climate change is the greatest environmental threat of the 21st century, with major economic, social and environmental consequences. The level of carbon dioxide (CO2) emissions has increased by 31%, therefore, both governments and the scientific community are taking steps to mitigate emissions into the atmosphere. The most economically sustainable method is the use of low cost adsorbents that perform a selective adsorption of CO2 with respect to other inert gases such as N2. Clay minerals are highly available materials on the planet, are a low cost raw material and have great versatility for various processes in the field of adsorption and catalysis. The present work describes the synthesis of type A zeolite from a hydrothermal process in basic medium using metacaolinite as a starting material. Several parameters such as temperature and time were modified to evaluate the relationship between the formation conditions of the zeolite and its CO2 adsorption capacity. Synthesized catalysts were characterized by X-ray diffraction (XRD), N2 adsorption-desorption at -196 ºC, nuclear magnetic resonance of solids (NMR) and infrared spectroscopy (IR). In addition, the absorption capacity of CO2 with type A zeolites has been evaluated, and all the results were compared with the commercial zeolites. With respect to the results obtained, it can be said that the bands obtained by IR for the synthesized Zeolites are similar to those of the commercial Zeolite. On the other hand, the NMR results show that the synthesized and commercial zeolite present the same chemical environment. Finally, the textural parameters corroborate that in all cases the surface area is low from 12 m2g-1 for kaolinite to 7 m2g-1 for commercial zeolite AUniversidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

The Competitive Struggle to Win Tournaments: The Allies’ Race to Capture Adolf Hitler’s Eagle’s Nest

Tournament theory posits that there are situations where winning matters a lot and, as a result, agent rewards are not proportional to performance. According to tournament theorists, the large pay differentials that exist between organizational levels are intended to motivate agents to exert greater effort in an attempt to win the prize. Although a large corpus of literature on tournaments has emerged over time, little is known about the social dynamics involved in tournaments. This article addresses this gap through a historical narrative concerning how Allied forces in World War II competed to capture Adolf Hitler’s famed Bavarian reception house, known to the world as the Eagle’s Nest

Surfactant effect in heteroepitaxial growth. The Pb - Co/Cu(111) case

A MonteCarlo simulations study has been performed in order to study the effect of Pb as surfactant on the initial growth stage of Co/Cu(111). The main characteristics of Co growing over Cu(111) face, i.e. the decorated double layer steps, the multiple layer islands and the pools of vacancies, disappear with the pre-evaporation of a Pb monolayer. Through MC simulations, a full picture of these complex processes is obtained. Co quickly diffuses through the Pb monolayer exchanging place with Cu atoms at the substrate. The exchange process diffusion inhibits the formation of pure Co islands, reducing the surface stress and then the formation of multilayer islands and the pools of vacancies. On the other hand, the random exchange also suppress the nucleation preferential sites generated by Co atoms at Cu steps, responsible of the step decoration.Comment: 4 pages, latex, 2 figures embedded in the tex

Acaparamiento de tierras y acumulación capitalista: aspectos clave en América Latina

__Abstract__ We introduce this special issue by explaining seven characteristics of land grabbing in Latin America. These features are not unique to the region. By highlighting them – arguing, for instance, that a key aspect in Latin America is intra-regional land grabbing driven by (trans)Latina companies – we hope to inspire new cross-regional comparisons to understand the dynamics of “global” land grabbing. Our focus on Latin America challenges some problematic generalisations in the literature, for instance, that land grabs occur mainly in fragile states. We interrogate the relationship between land grabbing and the “foreignisation” narrative, and the need to revisit the broader question of land concentration. Thus we build upon the literature locating land grabs and the land question within the political economy of global capitalism

Solving non-uniqueness in agglomerative hierarchical clustering using multidendrograms

In agglomerative hierarchical clustering, pair-group methods suffer from a problem of non-uniqueness when two or more distances between different clusters coincide during the amalgamation process. The traditional approach for solving this drawback has been to take any arbitrary criterion in order to break ties between distances, which results in different hierarchical classifications depending on the criterion followed. In this article we propose a variable-group algorithm that consists in grouping more than two clusters at the same time when ties occur. We give a tree representation for the results of the algorithm, which we call a multidendrogram, as well as a generalization of the Lance and Williams' formula which enables the implementation of the algorithm in a recursive way.Comment: Free Software for Agglomerative Hierarchical Clustering using Multidendrograms available at http://deim.urv.cat/~sgomez/multidendrograms.ph

Sensitive CO and 13CO survey of water fountain stars Detections towards IRAS 18460-0151 and IRAS 18596+0315

 This is the author accepted manuscript. The final version is available from EDP Sciences via the DOI in this recordContext. Water fountain stars represent a stage between the asymptotic giant branch (AGB) and planetary nebulae phases, when the mass loss changes from spherical to bipolar. These types of evolved objects are characterized by high-velocity jets in the 22 GHz water maser emission. Aims. The objective of this work is to detect and study in detail the circumstellar gas in which the bipolar outflows are emerging. The detection and study of thermal lines may help in understanding the nature and physics of the envelopes in which the jets are developing. Methods. We surveyed the CO and 13CO line emission towards a sample of ten water fountain stars through observing the J = 1 → 0 and 2 → 1 lines of CO and 13CO, using the 30 m IRAM radio-telescope at Pico Veleta. All the water fountains visible from the observatory were surveyed. Results. Most of the line emission arises from foreground or background Galactic clouds, and we had to thoroughly analyse the spectra to unveil the velocity components related to the stars. In two sources, IRAS 18460-0151 and IRAS 18596+0315, we identified wide velocity components with a width of 35 - 40 km s-1 that are centred at the stellar velocities. These wide components can be associated with the former AGB envelope of the progenitor star. A third case, IRAS 18286-0959, is reported as tentative; in this case a pair of narrow velocity components, symmetrically located with respect to the stellar velocity, have been discovered. We also modelled the line emission using an LVG code and derived some global physical parameters, which allowed us to discuss the possible origin of this gas in relation to the known bipolar outflows. For IRAS 18460-0151 and IRAS 18596+0315, we derived molecular masses close to 0.2 M⊙, mean densities of 104 cm-3, and mass-loss rates of 10 -4 M⊙ yr-1. The kinetic temperatures are rather low, between 10 and 50 K in both cases, which suggests that the CO emission is arising from the outer and cooler regions of the envelopes. No fitting was possible for IRAS 18286-0959, because line contamination can not be discarded in this case. Conclusions. The molecular masses, mean densities, and mass-loss rates estimated for the circumstellar material associated with IRAS 18460-0151 and IRAS 18596+0315 confirm that these sources are at the end of the AGB or the beginning of the post-AGB evolutionary stages. The computed mass-loss rates are among the highest ones possible according to current evolutionary models, which leads us to propose that the progenitors of these water fountains had masses in the range from 4 to 8 M ⊙. We speculate that CO emission is detected in water fountains as a result of a CO abundance enhancement caused by current episodes of low-collimation mass-loss. © ESO, 2013.MICINNJunta de Andalucí

Introduction to Special Section: The Quest for Sustainability of Heavily Stressed Aquifers at Regional to Global Scales

This is the peer reviewed version of the following article: Butler, J. J., Gomez-Hernandez, J. J., Perrone, D., & Hyndman, D. (2021). Introduction to special section: The quest for sustainability of heavily stressed aquifers at regional to global scales. Water Resources Research, 57, e2021WR030446, which has been published in final form at https://doi.org/10.1029/2021WR030446. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving.The authors acknowledge financial support from the United States National Science Foundation (NSF), via grant EAR 1542320, to organize the Chapman meeting. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the NSF.Butler Jr., JJ.; Gómez-Hernández, JJ.; Perrone, D.; Hyndman, DW. (2021). Introduction to Special Section: The Quest for Sustainability of Heavily Stressed Aquifers at Regional to Global Scales. Water Resources Research. 57(8):1-4. https://doi.org/10.1029/2021WR030446S1457

Knowledge Management and Analysis of Scientific Biotechnology Trends in Venezuela

This paper presents a study on knowledge management and analysis of scientific Biotechnology trends in Venezuela, providing an overview of the science profile as well as regional development and its relation to issues of topics covered by Biotechnology based on the analysis of scientific publications for the period of 1995 to 2010. The survey was accomplished in database ISI/Web of Science using 60 terms selected by experts in Biotechnology and 803 register has been organized. Scientific indicators were produced using data/ text mining tools. It was possible to find a greater number of scientific publications in areas such as Ecology and Health, showing a greater frequency in these terms: DNA, PCR and Biodiversity. Results pointed out The United States of America as the main foreign partner-country of scientific publications followed by Spain and France. It was possible to verify cooperation network with others Latin American countries: Brazil, Colombia and Chile

Identification of critical variables in conventional transformers in distribution networks

Transformers are essential equipment to the operation of electrical power systems, a failure causes the lack of electricity supply to end-users, affecting the operating indicators of companies in the distribution sector. The investigation presents an identification of the faults in transformers through a fishbone diagram, an evaluation of the variables that cause the identified failure using the cross-impact matrix method and a proposal to improve the performance. The results will enable a plan to be developed for taking action with monitoring plans to avoid faults that could put the electrical asset at risk and achieve a better performance of the distribution network

General relativistic null-cone evolutions with a high-order scheme

We present a high-order scheme for solving the full non-linear Einstein equations on characteristic null hypersurfaces using the framework established by Bondi and Sachs. This formalism allows asymptotically flat spaces to be represented on a finite, compactified grid, and is thus ideal for far-field studies of gravitational radiation. We have designed an algorithm based on 4th-order radial integration and finite differencing, and a spectral representation of angular components. The scheme can offer significantly more accuracy with relatively low computational cost compared to previous methods as a result of the higher-order discretization. Based on a newly implemented code, we show that the new numerical scheme remains stable and is convergent at the expected order of accuracy.Comment: 24 pages, 3 figure