Author's Preface

This paper is focused on the structure, chemical composition, optical and mechanical properties of coatings consisting in an Alsingle bondN matrix incorporating different Au contents (up to 2.5 at.%). The Au was incorporated in the matrix atomically or in the form of very small nanoparticles (< 1 nm). With the increase in the Au content both the refractive index and the coefficient of extinction were increased. The AlN matrix presented a crystalline wurtzite phase, stable up to 1000 °C. With annealing at 400 °C the precipitation of XRD detectable Au nanoparticles was possible, originating SPR light absorption. The Alsingle bondN + Au coatings exhibited hardness values between 15 and 24 GPa, with no significant changes after the annealing treatments at low temperatures. These coatings are of interest to the decorative applications

Uso de diseños jerárquicos en la detección de escalas de heterogeneidad en la especie invasora Sargassum muticum

Invasion of alien species poses serious threats to many ecosystems. Despite the potential of Sargassum muticum to spread and invade new areas, no attention has been given to the study of variability of structural or morphological features across different spatial scales. We employed a hierarchical sampling design to examine patterns of spatial variability of fertility and morphological variables of S. muticum over different spatial scales (quadrats, sites, locations, rias) ranging from metres to tens of kilometres We repeated the sampling in March, April and July to test for the consistency of patterns through time. There was no variability between rias (tens of kilometres apart), but substantial differences occurred at the other scales examined. Fertility and percent cover varied between locations (1.5-3 km apart), whereas morphological variables varied between sites (tens of metres apart) and quadrats (metres apart). Furthermore, patterns of variation were not consistent over time. The study demonstrated the importance of a multi-scale sampling programme for monitoring seaweed invasion.Las especies invasoras representan una seria amenaza para muchos ecosistemas. A pesar del potencial de Sargassum muticum para extenderse e invadir nuevas áreas, no se ha dedicado ninguna atención al estudio de la variabilidad de las características estructurales o morfológicas a diferentes escalas espaciales. Hemos usado un diseño de muestreo jerárquico para examinar patrones de variabilidad espacial de las variables fenológicas y morfológicas de S. muticum a diferentes escalas espaciales (cuadrantes, sitios, localidades, rías) que van desde unos pocos metros a decenas de kilómetros. Repetimos el muestreo en marzo, abril y julio para comprobar la consistencia de los patrones a lo largo del tiempo. No hubo variabilidad entre rías (decenas de kilómetros de separación), pero se encontraron diferencias sustanciales a otras escalas. La fertilidad y el porcentaje de cobertura variaron entre localidades (1.5-3 km) y tiempo, mientras que las variables morfológicas variaron entre sitios (decenas de metros) y cuadrantes (metros). Asimismo, los patrones de variabilidad no fueron consistentes en el tiempo. El estudio demostró la importancia de los programas de muestreo utilizando múltiples escalas espaciales para el seguimiento de algas invasoras

El desafío de la calidad : un mensaje pedagógico básico para el trabajo experimental en química analítica

El trabajo se orienta hacia el logro del mejoramiento de la enseñanza experimental en el laboratorio de química analítica y se realiza desde el modelo de la investigación-acción. La química analítica es una actitud intelectual y se la considera una disciplina científica; la enseñanza de su teoría y de la programación del análisis mediante la aplicación del proceso analítico tiene, como objetivo pedagógico básico, generar una actitud intelectual. Se presenta un enfoque conceptual del proceso analítico total para la enseñanza experimental, orientada para que el estudiante aprenda a obtener información analítica de calidad. Se reúnen y evalúan diferentes prácticos en el laboratorio, de complejidad creciente, analizándose los resultados de las experiencias. El desafío pedagógico invita a revisar con profundidad la concepción sobre la educación permanente en química analítica y, en particular, del trabajo experimental, dado que las nuevas tecnologías sufren rápidos cambios y generalmente no son utilizadas en su máximo rendimiento.The aim of this work is to improve the experimental teaching in Analytical Chemistry Labs. It is being developed from the investigation-action model. Analytical Chemistry is an intelectual attitude. We think about it as a scientific subject. The basic pedagogic aim of teaching theory and programming the analysis applying the analytical process is to incorporate it into mental structures. A conceptual approach to complete analytical process in experimental teaching is shown. The student is guided to obtain qualified analytical information. Different practical works of increasing complexity are gathered and evaluated. The results of these experiencies are analysed. The pedagogic challenge is to revise thoroughly the understanding of everyday teaching in Analytical Chemistry. Specially experimental work, since new technologies undergo quick changes and they are not always efficiently applied

Wear Behavior of a Ni/Co Bilayer Coating by Physical Vapor Deposition on AISI 1045 Steel

Coatings by physical vapor deposition (PVD) have become highly relevant due to their wide range of applications and the rapid rate of coating formation. In this work, AISI steel 1045 was coated with two layers, Ni and Co using the PVD technique. Each coating was deposited with a thickness of 1 μm. After applying the coatings, a post-treatment was applied in an AC plasma reactor using a boron nitride blank in an Ar atmosphere at a pressure of 3 Torr, 0.3 A, and 460 V at 4, 8, and 12h. The post-treatment was characterized by optical emission spectroscopy (OES) in a range of 200-1100 nm. The main species observed by OES were Ar+, N2, N2+, and B+. The coatings on 1045 steel and posttreatment were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). Also, were subjected to tribological tests to analyze wear resistance, using the Pin-on-Disk technique. The coatings on steel 1045 present remarkably better wear properties than the uncoated 1045 steel, being the sample post-treated at 4h that showed a lower wear rate

Absence of quantum-confined Stark effect in GaN quantum disks embedded in (Al,Ga)N nanowires grown by molecular beam epitaxy

Several of the key issues of planar (Al,Ga)N-based deep-ultraviolet light emitting diodes could potentially be overcome by utilizing nanowire heterostructures, exhibiting high structural perfection and improved light extraction. Here, we study the spontaneous emission of GaN/(Al,Ga)N nanowire ensembles grown on Si(111) by plasma-assisted molecular beam epitaxy. The nanowires contain single GaN quantum disks embedded in long (Al,Ga)N nanowire segments essential for efficient light extraction. These quantum disks are found to exhibit intense emission at unexpectedly high energies, namely, significantly above the GaN bandgap, and almost independent of the disk thickness. An in-depth investigation of the actual structure and composition of the nanowires reveals a spontaneously formed Al gradient both along and across the nanowire, resulting in a complex core/shell structure with an Al deficient core and an Al rich shell with continuously varying Al content along the entire length of the (Al,Ga)N segment. This compositional change along the nanowire growth axis induces a polarization doping of the shell that results in a degenerate electron gas in the disk, thus screening the built-in electric fields. The high carrier density not only results in the unexpectedly high transition energies, but also in radiative lifetimes depending only weakly on temperature, leading to a comparatively high internal quantum efficiency of the GaN quantum disks up to room temperature.Comment: This document is the unedited Author's version of a Submitted Work that was subsequently accepted for publication in Nano Letters (2019), copyright (C) American Chemical Society after peer review. To access the final edited and published work see https://doi.org/10.1021/acs.nanolett.9b01521, the supporting information is available (free of charge) under the same lin

Experimenting with ecosystem interaction networks in search of threshold potentials in real-world marine ecosystems

Thresholds profoundly affect our understanding and management of ecosystem dynamics, but we have yet to develop practical techniques to assess the risk that thresholds will be crossed. Combining ecological knowledge of critical system interdependencies with a large-scale experiment, we tested for breaks in the ecosystem interaction network to identify threshold potential in real-world ecosystem dynamics. Our experiment with the bivalves Macomona liliana and Austrovenus stutchburyi on marine sandflats in New Zealand demonstrated that reductions in incident sunlight changed the interaction network between sediment biogeochemical fluxes, productivity, and macrofauna. By demonstrating loss of positive feedbacks and changes in the architecture of the network, we provide mechanistic evidence that stressors lead to break points in dynamics, which theory predicts predispose a system to a critical transition

MoS2 flakes stabilized with DNA/RNA nucleotides: in vitro cell response

Two-dimensional transition metal dichalcogenides (TMDCs), such as MoS2 and WS2, have recently emerged as nanomaterials with potential use in biomedicine. An attractive means to favor their interaction with biological media is the use of proper biomolecules as exfoliating/dispersing agents. Here, MoS2 flakes were stabilized with different small functional biomolecules such as adenosine monophosphate (AMP), guanosine monophosphate (GMP) and flavin mononucleotide (FMN) through the strong nucleotide-MoS2 interaction of Lewis acid-base type, rather than just on the weak dispersive and hydrophobic forces commonly associated with the use of many surfactants. The impact of the nucleotide-stabilized MoS2 flakes on the viability and cell proliferation, on the production of intracellular reactive oxygen species (ROS), and on the preosteoblast differentiation process (early stage) has been also evaluated, as well as the incorporation and intracellular localization of the nanomaterials by MC3T3-E1 and Saos-2 cells. The nucleotide-stabilized MoS2 flakes were found to exhibit excellent biocompatibility. Furthermore, their incorporation did not affect the integrity of the cell plasma membrane, which makes them ideal candidates for delivering drug/gene directly into cells. The in vitro cell response of tumor cells to these nanomaterials differs from that of undifferentiated cells, which provides the basis for their potential use in cancer therapy.publishe

Study on the correlation between plasma electron temperature and penetration depth in laser welding processes

The plasma electron temperature has been estimated starting from the spectroscopic analysis of the optical emission of the laser-generated plasma plume during quite diverse stainless steel welding procedures (c.w. CO2 and pulsed Nd:YAG). Although the optical emissions present different spectral features, a discrete contribution of several iron lines can be highlighted in both types of welding. We have found that the electron temperature decreases as the laser power is enhanced, in static as well as dynamic conditions. Such a result could be useful to develop a closed loop control system of the weld penetration depth

Sex Disaggregated Gender-Based Labor Differentiation among the Elected Barangay Officials in the First District of Cavite

This study was conducted from July 2018 to December 2019 to determine gender role differentiation among elected Barangay (smallest administrative division in the Philippines) officials in the 1st district of Cavite in the Philippines. We used a purposive incidental technique, focusing on 137 samples of male and female Barangay officials. The first district of Cavite Province, consisting of the city of Cavite and municipalities of Noveleta, Kawit, and Rosario, has 134 Barangays with 1,072 elected Barangay seats; of these seats, women occupied 298 (27.8%). In reproductive, productive, community managing, and leisure-related activities, both the female and male elected officials were dominant when it came to choices and decisions within their respective households. Most legislated gender policies addressed the protection and welfare of children, curbing delinquent gangs, and substance dependence and abuse. (The male elected officials dominate access, control of, and benefits from the reproductive, productive, community managing, and leisure activities in their respective household.) Men have access to and control of vehicles and house repairs while women manage finances, and care for sick children. Other household problems, needs, and constraints included waste management, noise nuisances, and teenagers\u27 behaviors - also, (lack of proper knowledge on gender and development) also the difficulty in recalling new terminologies used during gender-related seminars. We suggest that the Barangay council attend orientation and training on the Harmonized Gender and Development Guide (HGDG) and be given materials (to) that would educate them on gender terminologies. Responsible parenting seminars would help families guide their youths; mothers would be given an important role in this program, and fathers, through all-male advocacy groups in the country like KATROPA, which would in turn strengthen family bonding