Search

Cu2ZnSnSe4 (CZTSe) nanoparticles (NPs) were successfully synthesized via a solvothermal method. Their structural, compositional, morphological, optoelectronic, and electrochemical properties have been characterized by X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), Field-emission scanning electron microscopy (FE-SEM), transmission electron microscope (TEM), UV–vis absorption spectroscopy, and electrochemical impedance spectroscopy (EIS) techniques. Porosimetry and specific surface area in terms of the Brunauer–Emmett–Teller (BET) technique have also been studied. XRD indicates the formation of a polycrystalline kesterite CZTSe phase. Raman peaks at 173 and 190 cm−1 confirm the formation of a pure phase. TEM micrographs revealed the presence of nanoparticles with average sizes of ~90 nm. A BET surface area of 7 m2/g was determined. The CZTSe NPs showed a bandgap of 1.0 eV and a p-type semiconducting behavior. As a proof of concept, for the first time, the CZTSe NPs have been used as a visible-light-driven photocatalyst to Congo red (CR) azo dye degradation. The nanophotocatalyst material under simulated sunlight results in almost complete degradation (96%) of CR dye after 70 min, following a pseudo-second-order kinetic model (rate constant of 0.334 min−1). The prepared CZTSe was reusable and can be repeatedly used to remove CR dye from aqueous solutions. [ABSTRACT FROM AUTHOR]

The purpose of this article is to examine history classroom interactions in Chilean secondary schools in relation to the transmission of historical memories of human rights violations committed by Augusto Pinochet's dictatorship from 1973 to 1990. Corpora of this research are comprised of history lessons filmed in the two types of public schools that coexist in the Chilean educational system, namely government subsidized and partially subsidized schools. This research draws on linguistics resources framed by the sociosemiotic perspective of systemic functional linguistics. We incorporate into this theoretical framework the notions of semantic gravity and semantic density from legitimation code theory in order to understand the variations of levels of specialization and abstraction that build cumulative knowledge and ideological cosmologies when one is dealing with a sensitive and complex aspect of Chilean society.

This study evaluated the behavior of three paint systems exposed to the Antarctic marine environment for 45 months compared to a control of uncoated carbon steel with a determined corrosion rate. At the study site, all environmental conditions, solar radiation, and the concentration of environmental pollutants ( Cl − and SO2) were evaluated. The paint systems differed in terms of the primer and top coat. Coated samples were studied before and after exposure. They were evaluated visually and using SEM to determine adhesion, abrasion, and contact angle; using the Evans X-Cut Tape Test; using ATR-FTIR spectroscopy to analyze the state of aging of the top layer; and using electrochemical impedance spectroscopy (EIS) for coat protection characterization. The corrosion rate obtained for steel was 85.64 µm year−1, which aligned with a C5 environmental corrosivity category. In general, the evaluation in the period studied showed the paint systems had good adhesion and resistance to delamination, without the presence of surface rust, and exhibited some loss of brightness, an increase in the abrasion index, and a decrease in the percentage of reflectance due to aging. EIS showed good protection capability of the three coating schemes. In general, this type of paint system has not previously been evaluated in an extreme environment after 45 months of exposure to the environment. The results showed that the best behavior was found for the system whose top layer was acrylic–aliphatic polyurethane. [ABSTRACT FROM AUTHOR]

A hydrothermal method was successfully employed to synthesize kesterite Cu2ZnSnS4 (CZTS) nanoparticles. X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), field-emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM), and optical ultraviolet-visible (UV-vis) spectroscopy were used for characterization of structural, chemical, morphological, and optical properties. XRD results confirmed that a nanocrystalline CZTS phase corresponding to the kesterite structure was formed. Raman analysis confirmed the existence of single pure phase CZTS. XPS results revealed the oxidation states as Cu+, Zn2+, Sn4+, and S2−. FESEM and TEM micrograph images revealed the presence of nanoparticles with average sizes between 7 nm to 60 nm. The synthesized CZTS nanoparticles bandgap was found to be 1.5 eV which is optimal for solar photocatalytic degradation applications. The properties as a semiconductor material were evaluated through the Mott–Schottky analysis. The photocatalytic activity of CZTS has been investigated through photodegradation of Congo red azo dye solution under solar simulation light irradiation, proving to be an excellent photo-catalyst for CR where 90.2% degradation could be achieved in just 60 min. Furthermore, the prepared CZTS was reusable and can be repeatedly used to remove Congo red dye from aqueous solutions. [ABSTRACT FROM AUTHOR]

Silver nanoparticles (NPs) on glass substrates were obtained by a solid-state thermal dewetting (SSD) process using vacuum-evaporated-silver precursor layers. An exhaustive investigation of the morphological, structural, and surface chemistry properties by systematically controlling the precursor film thickness, annealing temperature, and time was conducted. Thin silver films with thicknesses of 40 and 80 nm were deposited and annealed in air by applying a combined heat-up+constant temperature–time program. Temperatures from 300 to 500 °C and times from 0 to 50 min were assayed. SSD promoted the morphological modification of the films, leading to the Ag NPs having a discrete structure. The size, shape, surface density, and inter-nanoparticle distance of the nanoparticles depended on the initial film thickness, annealing temperature, and time, exhibiting a cubic silver structure with a (111) preferred crystallographic orientation. The prepared NPs were found to be highly enriched in the Ag{111}/Ag{110}/Ag{100} equilibrium facets. SSD not only promotes NP formation but also promotes the partial oxidation from Ag to AgO at the surface level. AgO was detected on the surface around the nanoparticles synthesized at 500 °C. Overall, a broad framework has been established that connects process factors to distinguish resultant Ag NP features in order to develop unique silver nanoparticles for specific applications. [ABSTRACT FROM AUTHOR]

In this work, the performance of copper(II) hexacyanoferrate(III) (CuHCF) as a cathode material for lithium-ion batteries was studied. The compound was synthesized by a precipitation reaction in aqueous solution in a closed system. The morphology and structure show nanoparticles with sizes between 40 and 70 nm with a high agglomeration and a crystalline phase with a cubic structure, respectively. The material exhibited a stable performance with a working potential of around 3.6 V vs Li+/Li and a decrease in the charge transfer resistance due to increased ionic conductivity. The gravimetric capacity obtained is near 60 mAh g-1 during 300 cycles at a rate of C/20, close to the practical capacity. Considering its electrochemical performance, CuHCF could be a promising cathode material for lithium-ion batteries. [ABSTRACT FROM AUTHOR]

The synthesis of Ag2S quantum dots (QDs) deposited on the surface of electrodeposited ZnO nanorods (NRs) by a successive ionic-layer adsorption and reaction (SILAR) method is reported. A Box-Behnken response surface factorial design was used to organize the experiments conducted and identify the effects of three electrochemical parameters and their potential interactions. These parameters include zinc precursor concentration in the electrolytic bath, the electrolytic bath temperature and the electrodeposition time on the morphological and structural properties of the electrochemically grown ZnO nanorods. Morphological, structural and optical characterizations of these NRs heterojunctions were done. A direct band gap for Ag2S QDs, tuned between 2.54 and 2.73 eV by varying the SILAR cycle numbers, was determined. The presence of ZnO nanostructures increases the light scattering capability of the samples, allowing an important quantity of diffuse light near the absorption edge of Ag2S. The photoelectrochemical performance of these ZnO NRs decorated with Ag2S QDs based photoanodes has been evaluated. The SILAR parameters related to the growth of the Ag2S QDs that optimize the performance of this photoelectrode are presented. The effect of a ZnS passivation layer has been studied leading to an increase of about 400% in the short-circuit current density after passivation. [ABSTRACT FROM AUTHOR]

The objective of this article is to review the main contributions of linguistics to the teaching of history and to evaluate its contributions to the ield. More speciically, the themes of historical writing and interactions in the history class will be dealt with. At present, knowledge systems and disciplines are more open to inter- and trans-disciplinary dialog. In this context, linguistics, a science that specializes in language, has permitted the study of how scientiic communities read and write in order to build their knowledge. In the case of history teaching in schools, the contributions of linguistics are varied; among them, the explicit ways in which history is taught and learned through the mediation of language. For this, different references are presented, such as the school of Sydney, Australia; Caroline Cofin, in the United Kingdom; Mary Schleppegrell, in the United Stated, and Teresa Oteíza, Mariana Achugar and the Urdimbre group in Latin America. In reviewing some works by these authors, we provide a panoramic view of some of the focuses that linguistic research in the teaching of history has had in the west to date. It is expected that this article will motivate interdisciplinarity and creativity to employ the language in our history classes. [ABSTRACT FROM AUTHOR]

Copyright of Revista Signos is the property of Pontificia Universidad Catolica de Valparaiso and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Mind-wandering is the occasional distraction we experience while performing a cognitive task. It arises without any external precedent, varies over time, and interferes with the processing of sensory information. Here, we asked whether the transition from the on-task state to mind-wandering is a gradual process or an abrupt event. We developed a new experimental approach, based on the continuous, online assessment of individual psychophysical performance. Probe questions were asked whenever response times (RTs) exceeded 2 standard deviations from the participant’s average RT. Results showed that mind-wandering reports were generally preceded by slower RTs, as compared to trials preceding on-task reports. Mind-wandering episodes could be reliably predicted from the response time difference between the last and the second-to-last trials. Thus, mind-wandering reports follow an abrupt increase in behavioral variability, lasting between 2.5 and 10 seconds. [ABSTRACT FROM AUTHOR]

Abstract: The oxygen concentration in the oxidizer stream (O2 +N2) of laminar coflow ethylene diffusion flames is varied from 17% to 35% in order to study its influence on the flame height, the soot formation/oxidation processes, the smoke point characteristics, and the vertical distributions of radiative flux at a distance of 6.85cm from the flame axis. Measured values for all the investigated parameters are compared with the predictions provided by a numerical model based on a two-equation semiempirical acetylene-based soot model and on the statistical narrow-band correlated-k model to compute thermal radiation. Predictions are in overall reasonable agreement with the experiments for oxygen indices in the range 19–35%, whereas all the investigated parameters are significantly underestimated for an oxygen index of 17%. Measured flame heights based on CH∗ emission below, at, or slightly above the smoke point, as well as predicted stoichiometric flame heights, are found to be proportional to , where , D ∞, S, and Tad are the volumetric flow rate of ethylene, the diffusion coefficient at ambient temperature, the stoichiometric molecular air-to-fuel ratio, and the adiabatic flame temperature. Soot formation processes are found to increase with the oxygen index, leading to higher values of the maximum soot volume fraction and the peak integrated soot volume fraction. In addition, the latter is reached at a nondimensional height (normalized by ζ of approximately 0.05, regardless of the oxygen index within the investigated range. Two regimes are evidenced: The first regime, occurring for oxygen indices lower than 25%, is dominated by soot oxidation and is characterized by an enhancement in both the maximum soot volume fraction and the fuel flow rate at the smoke point with the oxygen index. The second regime, occurring for oxygen indices higher than 25%, is dominated by soot formation; the rate of increase in the maximum soot volume fraction with the oxygen concentration is lower than in the first regime, whereas the fuel flow rate at the smoke point decreases. Finally, the peak of radiative flux increases with the oxygen index, but its rate of increase is also found to be considerably reduced for oxygen indices greater than 25%. [Copyright &y& Elsevier]

The aim of this article is to present a characterization of the stages of the academic genre “History reading test” written by students of History major. The purpose of the research that originates this article was to describe the ways by which historical significance is constructed in the written discourse of future historians. 16 written answers made by first to third year of History majors of the Pontifical Catholic University of Chile from different courses of Chilean History from XV century to XIX century compose the corpus of this investigation. Starting from the systematization proposed by Martin & Rose (2008), it was considered for the analysis of the “History reading test” the analytical framework of the Systemic- Functional Linguistics and the dimensions that build historical significance in the discourse: temporality, evidentiality and causality. The analysis allowed the identification of four stages for building the academic genre of “History reading test”. These stages were grouped into: a) SYNTHESIS, b) CONTEXTUALIZATION, c) ARGUMENTATION, and c) CLOSING. We conclude that one of the main elements that affects the development of the stages and phases are the purpose of the reading test (content of the question or instruction) and the reformulation of the evidence. [ABSTRACT FROM AUTHOR]

Thin films of copper(I) oxide (Cu2O) were electrodeposited on fluorine-doped tin oxide predeposited glass substrates, by reduction of Cu2+ from Cu(II) acetate acid aqueous solutions. The Cu2O was potentiostatically grown at a potential value of −0.450 V (vs. SMSE) at 70 °C. The Cu2O thin films were characterized by means of scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy (XPS), optical transmission, electrochemical impedance spectroscopy, and photoelectrochemical experiments. Through these techniques, it was possible to establish the cubic Cu2O phase with a high crystallinity and a strong preferential growth along the [200] and [220] directions. Cu2O thin films show oxygen vacancies with formation of a nonstoichiometric compound with the presence of Cu(0) in the crystal lattice as determined by XPS analysis. In addition, Cu2O was used as the photoanode for the I− oxidation reaction when the system was illuminated ( Φ0 = 50.0 mW cm−2). The films exhibited a clear n-type semiconductor behavior, which was in agreement with the Mott-Schottky results. This behavior was explained by considering the nonstoichiometry of the oxide. [ABSTRACT FROM AUTHOR]

Copyright of Salud Pública de México is the property of Instituto Nacional de Salud Publica and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The electrochemical synthesis of auto-organized TiO arrays generated by Ti anodization in different non-aqueous electrolytes was analyzed. Propylene carbonate-based electrolytes seem to be good electrolytic media for the controlled growth of titania nanotube structures. Scanning electron microscopy (SEM) analysis indicated that, depending on the media employed in the synthesis of the TiO nanotubes, different aspect ratios (length/diameter) could be obtained. Impedance analysis using the passive pit model gave the electrical properties of the layers during the different stages of nanotubes formation. Mott-Schottky analysis and the impedance results showed that the TiO nanotubes layers were n-type semiconductors with highly defective walls on top of a resistive barrier layer. Photoelectrochemical measurements showed that tetra(4-carboxyphenyl)porphyrin (TCPP) adsorbed onto the TiO nanotube arrays, which could be employed as an efficient photosensitizer for solar-energy conversion by TCPP-sensitized nanotubular TiO electrodes. [ABSTRACT FROM AUTHOR]

Brain processes and social processes are not as separated as many of our Social Psychology and Neuroscience departments. This paper discusses the potential contribution of social neuroscience to the development of a multi-level, dynamic, and context-sensitive approach to prejudice. Specifically, the authors review research on event related potentials during social bias, stereotypes, and social attitudes measurements, showing that electrophysiological methods are powerful tools for analyzing the temporal fine-dynamics of psychological processes involved in implicit and explicit prejudice. Meta-theoretical implications are drawn regarding the social psychological modeling of social attitudes, and for the integration of social neuroscience into a multi-level account of cultural behavior. [ABSTRACT FROM AUTHOR]

Changes in the surface activity of n-Si after being exposed to a solution containing hydroxyl (radical dotOH) radicals were approached. These changes caused by the interaction between silicon and the radical dotOH radicals were characterized by analyzing the nucleation and growth mechanisms of copper electrodeposited on silicon. Thus, both copper depositions on n-Si without prior exposure to hydroxyl radicals and with it at different exposure periods were analyzed. By means of j/t transients analysis a change in the nucleation and growth mechanisms of copper on n-Si was observed, from 3D progressive nucleation diffusion-controlled growth for the system unexposed to the radical to 3D instantaneous nucleation diffusion-controlled growth, when the semiconductor substrate was exposed to the radicals radical dotOH. These changes were corroborated through ex situ Atomic Force Microscopy. [ABSTRACT FROM AUTHOR]

A binder-free CdCO 3 /CdO/Co 3 O 4 compound with a micro-cube-like morphology on a nickel foam (NF) made via a facile two-step hydrothermal + annealing procedure has been developed. The morphological, structural and electrochemical behavior of both the single compounds constituting this final product and the final product itself has been studied. The synergistic contribution effect of the single compounds in the final compounded resulting specific capacitance values are presented and discussed. The CdCO 3 /CdO/Co 3 O 4 @NF electrode exhibits excellent supercapacitive performance with a high specific capacitance ( C S ) of 1.759 × 10 3 F g -1 at a current density of 1 mA cm -2 and a C S value of 792.3 F g -1 at a current density of 50 mA cm -2 with a very good rate capability. The CdCO 3 /CdO/Co 3 O 4 @NF electrode also demonstrates a high coulombic efficiency of 96% at a current density as high as 50 mA cm -2 and also exhibits a good cycle stability with capacitance retention of ca. 100% after 1000 cycles at a current density of 10 mA cm -2 along with a potential window of 0.4 V. The obtained results suggest that the facilely synthesized CdCO 3 /CdO/Co 3 O 4 compound has great potential in high-performance electrochemical supercapacitor devices., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

A CdCO 3 /CdO/Co 3 O 4 composite has been prepared on nickel foam through a combined hydrothermal-annealing method. An asymmetric hybrid supercapacitor (SC) device was assembled with this composite as the positive electrode and activated carbon was the negative electrode. The SC exhibited a high specific capacitance of 84 F g -1 @ 1 mA cm -2 , a maximum energy density of 26.3 W h kg -1 , and a power density of 2290 W kg -1 , along with a wide potential window of 1.5 V and long cycle life (92% after 6000 cycles). SCs assembled in series powered various light-emitting diodes and moved an electrical mini-motor., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

This paper describes the health conditions in Ecuador and, in more detail, the characteristics of the Ecuadorian health system, including its structure and coverage, its financial sources, the physical, material and human resources available, and the stewardship activities developed by the Ministry of Public Health. It also describes the structure and content of its health information system, and the participation of citizens in the operation and evaluation of the health system. The paper ends with a discussion of the most recent policy innovations implemented in the Ecuadorian system, including the incorporation of a chapter on health into the new Constitution which recognizes the protection of health as a human right, and the construction of the Comprehensive Public Health Network.