Predicting ground-state configurations and electronic properties of the thermoelectric clathrates Ba8_{8}Alx_{x}Si46−x_{46-x} and Sr8_{8}Alx_{x}Si46−x_{46-x}

The structural and electronic properties of the clathrate compounds Ba$_{8}$Al$_{x}$Si$_{46-x}$ and Sr$_{8}$Al$_{x}$Si$_{46-x}$ are studied from first principles, considering an Al content $x$ between 6 and 16. Due to the large number of possible substitutional configurations we make use of a special iterative cluster-expansion approach, to predict ground states and quasi-degenerate structures in a highly efficient way. These are found from a simulated annealing technique where millions of configurations are sampled. For both compounds, we find a linear increase of the lattice constant with the number of Al substituents, confirming experimental observations for Ba$_{8}$Al$_{x}$Si$_{46-x}$. Also the calculated bond distances between high-symmetry sites agree well with experiment for the full compositional range. For $x$ being below 16, all configurations are metallic for both materials. At the charge-balanced composition ($x=16$), the substitutional ordering leads to a metal-semiconductor transition, and the ground states of Ba$_{8}$Al$_{16}$Si$_{30}$ and Sr$_{8}$Al$_{16}$Si$_{30}$ exhibit indirect Kohn-Sham band gaps of 0.36 and 0.30 eV, respectively, while configurations higher in energy are metals. The finding of semiconducting behavior is a promising result in view of exploiting these materials in thermoelectric applications.Comment: 9 figure

Social preferences for ecosystem services in a biodiversity hotspot in South America

Identifying which ecosystem services are relevant to different stakeholders and understanding stakeholders’ perceptions of such services is useful for making informed decisions, especially in regions of the world where the achievement of biodiversity conservation goals is threatened by economically productive activities. In this article, we assess social preferences for ecosystem services in a biodiversity hotspot in central Chile. We use a consultative case study to ask local stakeholders (n = 70) from the Campana Peñuelas Biosphere Reserve to identify the most important ecosystem services the area provides for them and inquire about the perceived vulnerability of the services to changes in the future. We also explore the association between the perceived importance of ecosystem services and the sociodemographic and cultural characteristics of the respondents, which allows us to identify contrasting stakeholder perceptions of different ecosystem services. The most important services for local actors were the drinking water, fresh air and climate change control, genetic pool of plant communities in central Chile, and educational value. From the perspective of local actors, the services that could be threatened by negative changes in the future in terms of their provision included the possibilities of developing conservation activities focused on iconic threatened animal and plant species, water regulation, food from agriculture, and drinking water. Contrasting perceptions about the importance of ecosystem services emerged among stakeholders. While small farmers and members of local organizations attributed higher importance values to provisioning services, scientists and rangers and administrators of protected areas as well as teachers, NGO members and local government employees attributed more importance to the regulating and cultural services associated with threatened species. Our results can serve as a source of information for the planning and decision-making processes related to the search for socially and ecologically sustainable solutions for land use managemen

Aço inoxidável: fatos significativos para o ortodontista praticante

Abstract. Stainless steel is one of the most widely used materials in current orthodontics. Archwires, brackets, bands, ligatures, tubes, among other appliances, are manufactured using different types of this alloy. The first evidence of the use of this alloy in the orthodontic field dates back to the mid-1920s, when it was introduced as a material to manufacture wires. The alloy has ever since gained popularity among orthodontists and its further development has led to its widespread use in today’s different orthodontic techniques. Despite being available for more than 80 years, and the fact that most orthodontists use it on a daily basis, there is still a lack of knowledge about the basic principles, composition, and properties of thismaterial by these professionals. Therefore, the purpose of this literature review is to discuss the main characteristics and properties of stainless steel that are useful in the orthodontic practice for orthodontists to take advantage of this remarkable material.El acero inoxidable es uno de los materiales más ampliamente utilizados en la ortodoncia actual. Los arcos de alambre, brackets, bandas, ligaduras, tubos, entre otros aparatos, se fabrican utilizando diferentes tipos de esta aleación. La primera evidencia del uso de esta aleación en el campo de la ortodoncia se remonta a mediados de la década de los veinte cuando se introdujo como un material para fabricar alambres. Desde ese entonces, esta aleación ha ganado popularidad entre los ortodoncistas y su desarrollo posterior ha llevado al uso extendido en las diferentes técnicas de ortodoncia de la actualidad. A pesar de haber estado disponible por más de ochenta años, y del hecho que la mayoría de los ortodoncistas lo usan a diario, todavía existe un desconocimiento acerca de los principios básicos, composición y propiedades de este material por parte de estos profesionales. Por lo tanto, el objeto de esta revisión de la literatura es discutir las principales características y propiedades del acero inoxidable que son útiles en la práctica de la ortodoncia para que los ortodoncistas se beneficien de este notable material.O aço inoxidável é um dos materiais mais largamente empregados na ortodontia atual. Os arcos de arame, aparelhos, bandas, ligaduras, tubos, dentre outros aparelhos, são fabricados com diferentes tipos desta liga. A primeira evidencia do uso desta liga no campo da ortodontia remonta a meados da década dos vinte quando foi introduzido um material para fabricar arames. Desde essa altura, essa liga ganhou popularidade dentre os ortodontistas e seu desenvolvimento subsequente levou a ampliar seu uso nas diferentes técnicas de ortodontia da atualidade. Embora estivesse disponível por mais de 80 anos, e apesar do fato de que a maioria dos ortodontistas utilizam esse material diariamente, ainda existe um desconhecimento sobre os princípios básicos, composição e propriedades deste material por parte destes profissionais. Portanto, o escopo desta revisão da literatura é discutir as principais características e propriedades do aço inoxidável que são benéficas na prática da ortodontia para que os ortodontistas se beneficiem deste notável material

Reliability of coracohumeral distance and subcoracoid tendons in subacromial pain syndrome

This study investigated the intra-rater reliability of a novice ultrasound (US) examiner and the interrater reliability of two examiners (novice, expert) in the measures of coracohumeral distance at rest (CHD) and at 60° of elevation without (CHD60) or with weights (CHD60w), tendon thickness of the long head of the biceps (LHB) and subscapularis (SCP). Twenty-one patients with subacromial pain syndrome (SAPS) and 20 asymptomatic participants were included. Intra and inter-rater reliability were tested with intraclass-correlation-coefficient (ICC), differences between raters were analyzed with Bland–Altman plots. Intra-rater reliability for CHD, CHD60 and CHD60w was excellent (ICC = 0.97– 0.98) in asymptomatic participants, and good-to-excellent (0.88–0.93) in SAPS, while intra-rater reliability for LHB and SCP was good-to-excellent in asymptomatic participants (0.88–0.97) and in SAPS (0.90–0.92). Inter-rater reliability for CHD, CHD60 and CHD60w was moderate-to-good (0.70– 0.90) in asymptomatic participants and good (0.85–0.87) in SAPS, in contrast inter-rater reliability for LHB and SCP was poor in asymptomatic participants (0.10–0.46) and poor-to-moderate (0.49–0.61) in SAPS. Bland–Altman plots revealed systematic and/or proportional bias for tendons’ thickness. A novice showed good-to-excellent intra-rater reliability in all US measures, whereas in comparison to an expert a novice can measure reliably CHD, CHD60 and CHD60w, but not LHB and SCP, where more training is recommended.University of Antwerp (grant number: 37063)Research Foundation Flanders—FWO (grant number: 1158121N

¿Racionalidad económica versus sustentabilidad ecológica?

Sustainable agriculture production systems aim to maintain the stock of natural capital, but cropping in the Pampean Region can lead to natural capital degradation because evaluation of alternatives activities is done by simplified cost-benefits analysis, which neglects ecological cost and overestimates profitability. The objectives of this paper were: a) to quantify the soil natural capital degradation by means of main nutrient budget (Nitrogen, Phosphorus and Potassium) in the Pampean Region during the last 30 years and b) to analyse the variation in crop profitability when the nutrient reposition costs is incorporated in the conventional economical analysis. Nitrogen, Phosphorus and Potassium annual budget, was calculated for maize, soybean and wheat crops for each year of the 1970-1999 period, as the difference between exported nutrients (harvest) and those incorporated by fertilization for each year. Gross margin of these crops were recalculated including nutrients reposition costs. Nitrogen, Phosphorus and Potassium budgets of Pampean Region were negative for these three crops. Close to 23 millions of Ton of nutrients were lost, during 1970-1999 period, in the Pampean Region, being soybean crop responsible for 45,6% of this lost, wheat for 28 % and maize for 26%. Nutrients reposition costs of 1825 $.ha-1 for soybean, 697$.ha-1 for wheat crop and 1461 $.ha-1 for maize for the 30 years studied were obtained. These figures represent the 20,6$. ha-1 para el cultivo de soja, 697 $. ha-1 para el trigo y 1461$. ha-1 para el maíz, lo que representó el 20,6%, 20,0% y 18,7% de los márgenes brutos promedios de la década del '80 y '90, a pesos constantes, respectivamente. Estos resultados muestran claramente que el análisis costo beneficio, al no incluir el costo de degradación del capital natural del suelo, sobrestimó los beneficios de la actividad agrícola. Esto pone de manifiesto el divorcio existente entre la racionalidad económica utilizada para la elección de las alternativas productivas y la posibilidad de sustentar los sistemas agrícolas desde el punto de vista ecológico. Se concluye que, para avanzar hacia el logro de sistemas agrícolas sustentables es necesario que los costos de degradación del capital natural producido por la actividad agrícola se cuantifiquen desde el punto de vista ecológico y se tomen en cuenta en los análisis económicos

Responding to the Popular Demand: Itinerary for the Socio-Political Learning of Situated Agroecologies in Chile

Agroecology has proven to be successful in responding to the demands and needs of a collective due to the relevance of its approach and proposals, which are built collaboratively between all the actors under a specific context that focuses on the actions developed. This is facilitated when spaces of horizontal interaction are generated through dialogues between different perspectives and experiences. In this perspective, agroecological training in higher education, i.e., university level, requires structural changes that go beyond the incorporation of technical content. Based on a critical documentary analysis of the records generated in the implementation of teaching innovation projects, the learning itinerary in agroecology is presented, consisting of four certifications based on transformational learning and supported by active methodologies. The potentialities, including marketing potential, of the proposed learning itinerary relate to curricular design, the articulation of the itinerary, the suitability of the learning methodologies used, the performance of the teachers, and the participation of the students. It is concluded that the implementation of flexible itineraries allows for addressing the transformation processes necessary for an agroecological transition in which we see a convergence of students’ skills, the learning objectives, and the requirements of the various actors with which they interact.Universidad de Santiago de Chile USA 155

Autonomous Demand and Technical Change: Exploring the Kaldor-Verdoorn Law on a Global Level

This paper aims to explain labour productivity through the lens of a Kaldorian perspective. To assess the relationship between output, demand, capital accumulation, and labour productivity, we apply Panel Structural Vector Autoregressive (P-SVAR) modelling to a dataset of 52 countries observed over a long-time span as provided by the Penn World Table. Findings validate the Kaldorian perspective and show that demand shocks – measured by government expenditures and exports – produce positive and persistent effects on labour productivity. Findings are confirmed even when the full sample is broken down to consider developed and developing countries separately