Peculiarity of a magnetic structure in a quasi-one-dimensional columbite Co0.4Ni0.6Nb2O6

Quasi-one-dimensional (Q1D) spin chain systems have great potential applications in high-density information storage devices, quantum information and computers, because of their quantum magnetism properties. The low-dimensional magnetic behavior has been investigated in ANb2O6, (A = Mn, Fe, Co or Ni) compounds, the structural and magnetic properties are very interesting because the system presents weakly interacting Ising chains, which leads to this quasi-one-dimensional magnetic order. Our investigation combines specific heat and magnetic measurements; x-ray and neutron diffraction (ND). In this work, we present a Co/Ni orthorhombic structure, called columbite, which crystallizes with Pbcn space group, whose formula is Co0.4Ni0.6Nb2O6. Co for Ni substitution induces a continuous lattice volume decrease, preserving the orthorhombic crystal structure. Magnetic susceptibility and specific heat measurements reveal that antiferromagnetic order occurs at 3.4 K, as a consequence of weak interchain interactions. Partial substitution of the magnetic ion tends to change the magnetic ordering observed in the CoNb2O6 and NiNb2O6. Lastly, we present this magnetic structure changes with the Ni-Co substitution

Eficiência de campo em diferentes operações mecanizadas na cafeicultura

Coffee is a prominent culture in Brazil, so much that in recent years the coffee crop has passed major changes, such as the intensive use of mechanization that has become a viable alternative for most producers, enabling increased capacity and reduction production costs. Currently in areas totally suitable for mechanization, all operations during the crop cycle are performed mechanically by different machines and implements. This experiment was carried out in Alfenas-MG, in order to determine the work capacity and efficiency of field machines used in different mechanized operations in the coffee crop. The performance data were treated statistically by Pearson correlation (p), wich allowed to determine the influence of operating speed and average length of streets in the performance parameters. Based on the results the parameters of operating performance, effective field capacity and time required were highly correlated as the operating speed of mechanized sets. The holes preparation, raking and gathering showed the worst results of field efficiency, while other operations evaluated showed values above 70%, considered acceptable.O café é uma cultura de destaque no Brasil, tanto que, nos últimos anos, passou por grandes modificações, com a utilização intensa da mecanização, que se tornou uma alternativa viável para grande parte dos produtores, possibilitando aumento da capacidade operacional e redução dos custos de produção. Atualmente, em áreas totalmente aptas à mecanização, todas as operações durante o ciclo da cultura são realizadas, mecanicamente, por diferentes máquinas e implementos. Conduziu-se, o presente estudo, no município de Alfenas-MG, para determinar a capacidade de trabalho e a eficiência de campo de máquinas utilizadas nas diferentes operações da lavoura cafeeira. Os dados de desempenho obtidos foram tratados estatisticamente pela correlação de Pearson (p), o que permitiu determinar a influência da velocidade operacional e comprimento médio das entrelinhas, nos parâmetros de desempenho. Com base nos resultados, os parâmetros de desempenho operacional, capacidade de campo efetiva e tempo demandado apresentaram alta correlação com a velocidade operacional dos conjuntos mecanizados. As operações de preparo de covas, varrição e recolhimento apresentaram os menores resultados de eficiência de campo, enquanto as demais operações avaliadas apresentaram valores acima de 70%, considerados aceitáveis

Estudo técnico e econômico de diferentes operações mecanizadas na cafeicultura

After the adoption of mechanization in coffee growing many formerly manual operations are now performed by machines, allowed increased production capacity and reduce costs. The knowledge and application of technical and economic criteria for obtaining production costs are of paramount importance as they allow the estimated costs show strength and are reliable, providing better market competitiveness. With the objective of conduct a technical and economic analysis of different mechanized operations in coffee the work was carried out in Alfenas- MG, which assessed the time required to perform various operations mechanized sets and also their respective fixed and variable costs were analyzed. The analysis of each set was performed by the product of total hours spent in each operation, in terms of production costs. Based on data obtained times of repairs and maintenance directly affect the mechanical availability of mechanized sets. The depreciation and fuel costs are the main components that make up the fixed and variable costs, respectively. The coffee gathering and sweeping operations are the worst technical feasibility and hence economical, featuring superior unproductive costs to production costs.Com a adoção da mecanização na cafeicultura, diversas operações, antes manuais, passaram a ser realizadas por máquinas, o que permitiu aumento da capacidade produtiva e redução dos custos. O conhecimento e aplicação de critérios técnicos e econômicos para obtenção dos custos de produção são de suma importância, pois permitem que os custos estimados apresentem solidez e sejam confiáveis, proporcionando melhor competitividade ao produtor. Objetivando-se, realizar uma análise técnica e econômica de diferentes operações mecanizadas na cafeicultura, o trabalho foi conduzido no município de Alfenas- MG, onde foram analisados tempos necessários para a realização de diversas operações dos conjuntos mecanizados e também os seus respectivos custos fixos e variáveis. A análise de cada conjunto foi realizada pelo produto de horas totais despendidas em cada operação, em função dos custos de produção. Com base nos dados obtidos, os tempos de reparos e manutenção afetam diretamente a disponibilidade mecânica dos conjuntos mecanizados. A depreciação e os custos com combustível são os principais componentes que compõem os custos fixos e variáveis, respectivamente. As operações de recolhimento e varrição do café de chão são as operações com a menor viabilidade técnica e econômica, apresentando custos improdutivos superiores aos custos produtivos

Viabilidade técnica e econômica de diferentes sistemas de colheita do café

This study was conducted to analyze the technical and economic viability for different coffee crops harvest systems, applied in Southern Minas Gerais, Brazil. In the harvest of 2014, the operational performance of three mechanic harvest systems for coffee trees were evaluated, as well as their productivity and operational costs, compared to manual and semi-mechanic systems. Based on data outcome, it is possible to assure that the mechanic harvest for coffee trees yields greater cost reduction and an increase in productivity in relation to other systems, and it is either economically viable. Soil declivity is an influencing factor on productivity for mechanic systems, and harvesters that work under such conditions suffer a decrease in operational efficiency and productivity, due to a higher demand of time during harvest.Objetivou-se, no presente trabalho, analisar a viabilidade técnica e econômica de diferentes sistemas de colheita em lavouras de café, localizadas na região Sul do estado de Minas Gerais. Na safra 2014, foram avaliados os parâmetros de desempenho operacional de três sistemas de colheita mecanizada do cafeeiro, como também suas produtividades e os custos operacionais, posteriormente comparados aos sistemas manual e semimecanizado. Com base nos resultados obtidos é possível afirmar que a colheita mecanizada do cafeeiro promove grandes reduções de custos e aumento da produtividade, em relação aos demais sistemas, demonstrando ser o mais viável economicamente. A declividade é um fator que influencia na produtividade dos sistemas mecanizados, e as máquinas que trabalham em áreas, nessas condições, têm reduzidas sua eficiência operacional e produtividade devido ao maior tempo desperdiçado na operação de colheita

Magnetômetro de efeito Kerr espectral : primeiros resultados

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description of the methodological approach

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Height and body-mass index trajectories of school-aged children and adolescents from 1985 to 2019 in 200 countries and territories: a pooled analysis of 2181 population-based studies with 65 million participants

Summary Background Comparable global data on health and nutrition of school-aged children and adolescents are scarce. We aimed to estimate age trajectories and time trends in mean height and mean body-mass index (BMI), which measures weight gain beyond what is expected from height gain, for school-aged children and adolescents. Methods For this pooled analysis, we used a database of cardiometabolic risk factors collated by the Non-Communicable Disease Risk Factor Collaboration. We applied a Bayesian hierarchical model to estimate trends from 1985 to 2019 in mean height and mean BMI in 1-year age groups for ages 5–19 years. The model allowed for non-linear changes over time in mean height and mean BMI and for non-linear changes with age of children and adolescents, including periods of rapid growth during adolescence. Findings We pooled data from 2181 population-based studies, with measurements of height and weight in 65 million participants in 200 countries and territories. In 2019, we estimated a difference of 20 cm or higher in mean height of 19-year-old adolescents between countries with the tallest populations (the Netherlands, Montenegro, Estonia, and Bosnia and Herzegovina for boys; and the Netherlands, Montenegro, Denmark, and Iceland for girls) and those with the shortest populations (Timor-Leste, Laos, Solomon Islands, and Papua New Guinea for boys; and Guatemala, Bangladesh, Nepal, and Timor-Leste for girls). In the same year, the difference between the highest mean BMI (in Pacific island countries, Kuwait, Bahrain, The Bahamas, Chile, the USA, and New Zealand for both boys and girls and in South Africa for girls) and lowest mean BMI (in India, Bangladesh, Timor-Leste, Ethiopia, and Chad for boys and girls; and in Japan and Romania for girls) was approximately 9–10 kg/m2. In some countries, children aged 5 years started with healthier height or BMI than the global median and, in some cases, as healthy as the best performing countries, but they became progressively less healthy compared with their comparators as they grew older by not growing as tall (eg, boys in Austria and Barbados, and girls in Belgium and Puerto Rico) or gaining too much weight for their height (eg, girls and boys in Kuwait, Bahrain, Fiji, Jamaica, and Mexico; and girls in South Africa and New Zealand). In other countries, growing children overtook the height of their comparators (eg, Latvia, Czech Republic, Morocco, and Iran) or curbed their weight gain (eg, Italy, France, and Croatia) in late childhood and adolescence. When changes in both height and BMI were considered, girls in South Korea, Vietnam, Saudi Arabia, Turkey, and some central Asian countries (eg, Armenia and Azerbaijan), and boys in central and western Europe (eg, Portugal, Denmark, Poland, and Montenegro) had the healthiest changes in anthropometric status over the past 3·5 decades because, compared with children and adolescents in other countries, they had a much larger gain in height than they did in BMI. The unhealthiest changes—gaining too little height, too much weight for their height compared with children in other countries, or both—occurred in many countries in sub-Saharan Africa, New Zealand, and the USA for boys and girls; in Malaysia and some Pacific island nations for boys; and in Mexico for girls. Interpretation The height and BMI trajectories over age and time of school-aged children and adolescents are highly variable across countries, which indicates heterogeneous nutritional quality and lifelong health advantages and risks