Organic molecules on metalic surfaces : a thoretical investigation

Orientador: Douglas Soares GalvãoDissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Fisica "Gleb Wataghin"Resumo: Recentemente, a primeira nanoroda molecular foi caracterizada a partir de experimentos com o microscópio de tunelamento eletrônico (STM). Foi demonstrado que a molécula de hidrocarboneto (C44H24) especificamente desenhada poderia rolar sobre a superfície de cobre ao longo da direção [110] da superfície. A molécula consiste em duas rodas baseadas no grupo triptycene as quais são conectadas por um eixo. Nós reportamos um estudo teórico da simulação desse processo. Usamos métodos ab initio (DMol 3) e de dinâmica molecular clássica (UFF). Consideramos diferentes orientações cristalográficas ([111], [110], e [100]) para a superfície de cobre, a fim de determinar como estas diferentes orientações afetam o processo de rolamento molecular. Nossos resultados estão em boa acordância com os dados experimentais disponíveis. As simulações mostraram que o mecanismo de rolamento só é possível para a direção [110]. Para as outras direções ([111] e [100]) a superfície é muito suave e não pode prover o torque necessário para o processo de rolamento. Para estes casos a molécula somente desliza (movimento de translação), sem rolar quando interage com a ponta do microscópio. Para a direção [110] a separação espacial entre as colunas de cobre é suficiente para travar a molécula e criar um torque. Além da superfície correta, a posição relativa da molécula sobre a superfície é muito importante. A molécula deve estar com seu eixo principal paralelo à direção [110]. Este efeito de comensurabilidade, entre a molécula e a superfície, é similar a difusão seletiva na superfície recentemente observada para outras classes de moléculas orgânicas. Os perfis experimentais observados para o empuramento, puxamento e rolamento também podem ser explicados em termos destas características geométricas entre a molécula e as diferentes direções cristalográficas do cobreAbstract: Recently, the first molecular nanowheel was characterized with scanning tunneling micro-scope experiments. It was demonstrated that a specifically designed hydrocarbon molecule (C44H24) could roll over a copper substrate along the [110] direction of a surface. The molecule consists in two wheels based on two triptycene groups which are connected by an axle. We report a theoretical study of the simulations of this process. We used ab initio (DMol 3) and classical molecular dynamics methods (UFF). We have considered different crystallographic orientations ([111], [110], and [100]) for the copper surface, in order to determine how these different orientations affect the molecular rolling processes. Our results are in good agreement with the available experimentally data. The simulations showed that the rolling mechanism is only possible for the [110] direction. For the others directions ([111] and [100]) the surfaces are too smooth and cannot provide the necessary torque to the rolling process. For these cases the molecule just slides (translational movement), without rolling when interact with the STM tip. For the [110] direction the spatial separation among rows of copper atoms is enough to trap the molecule and to create a torque. Besides the correct surface the relative position of the molecule on the surface is very important. The molecule should be with its main axis in the parallel direction to [110]. This commensurability effect, between the molecule and the surface, is similar to the surface selective diffusion recently observed for other classes of organic molecules. The experimental observed pushing, pulling, and rolling profiles can also be explained in terms of these geometrical features between the molecule and the different Cu crystallographic directionsMestradoMestre em Físic

Nutrient transfer by runoff under no tillage in a soil treated with successive applications of pig slurry

AbstractHigh rates and successive applications of pig slurry can cause nutrient transfer by surface runoff. The aim of this study was to evaluate the importance of surface runoff in transferring nitrogen (N), phosphorus (P) and potassium (K) under a no tillage system and for successive applications of pig slurry. The research was carried out in the Agricultural Engineering Department of the Federal University of Santa Maria, Brazil, from 2002 to 2007 in a Typic Hapludalf soil. Pig slurry rates of 0, 20, 40 and 80m3ha−1 were applied, scattered on the surface, before the sowing of each species in a cultivation sequence. On average 119, 238 and 475kgha−1yr−1 of N; 102, 203 and 406kgha−1yr−1 of P and 43, 87 and 173kgha−1yr−1 of K were added, for rates of 20, 40 and 80m3ha−1 of pig slurry, respectively. Samples of water runoff from the soil surface were collected during the entire period and the minerals, N, P and K were determined. Successive applications of pig slurry decreased surface runoff. In relative terms, the K losses were higher than N and P. As regards total nutrients applied through pig slurry, losses through surface runoff were of 2.74, 1.61 and 1.37% of mineral N; 6.29, 5.01 and 3.51% of available P and 17.16, 9.01 and 11.14% of available K, for the three rates of applied pig slurry, respectively. Repeated applications of pig slurry on a no tillage managed soil caused losses of N, P and K from the soil through surface runoff, in the sequence: K>P>N. The losses of N and K are positively related to the volume of surface runoff, whereas the losses of P are positively related to the quantities of P added through pig slurry. Applications of pig slurry along the years decrease the surface runoff

Machine Learning, Compositional and Fractal Models to Diagnose Soil Quality and Plant Nutrition

Soils, nutrients and other factors support human food production. The loss of high-quality soils and readily minable nutrient sources pose a great challenge to present-day agriculture. A comprehensive scheme is required to make wise decisions on system’s sustainability and minimize the risk of crop failure. Soil quality provides useful indicators of its chemical, physical and biological status. Tools of precision agriculture and high-throughput technologies allow acquiring numerous soil and plant data at affordable costs in the perspective of customizing recommendations. Large and diversified datasets must be acquired uniformly among stakeholders to diagnose soil quality and plant nutrition at local scale, compare side-by-side defective and successful cases, implement trustful practices and reach high resource-use efficiency. Machine learning methods can combine numerous edaphic, managerial and climatic yield-impacting factors to conduct nutrient diagnosis and manage nutrients at local scale where factors interact. Compositional data analysis are tools to run numerical analyses on interacting components. Fractal models can describe aggregate stability tied to soil conservation practices and return site-specific indicators for decomposition rates of organic matter in relation to soil tillage and management. This chapter reports on machine learning, compositional and fractal models to support wise decisions on crop fertilization and soil conservation practices

Produtividade e composição do mosto de videiras submetidas à adubação fosfatada no Sul do Brasil

The objective of this work was to evaluate the yield and must composition of 'Cabernet Sauvignon' and 'Chardonnay' grapevines subjected to phosphorus applications to a soil from a high-altitude region of Southern Brazil, during three crop seasons. Experiments 1 and 2 were carried out in 'Cabernet Sauvignon' and 'Chardonnay' commercial vineyards, respectively, in the municipality of Água Doce, located in the Midwestern region of the state of Santa Catarina. The soil from the two vineyards was classified as a Typic Humicryept. The used source of P was triple superphosphate (45% P2O5). From 2011 to 2013, at flowering, a total of 0, 10, 20, 40, and 80 kg ha-1 P2O5 were applied in the crown projection area, to the soil surface, without incorporation, in both vineyards. Soil and leaf P concentration, yield parameters, and must quality were evaluated. The increase in P availability decreased total titratable acidity and tartaric acid in the must of the 'Cabernet Sauvignon' grapevine in the 2013/2014 crop season and increased pH and total soluble solids in the must of the 'Chardonnay' grapevine in the 2011/2012 crop season. Phosphorus application to the soil increases the levels of available phosphorus, but does not result in higher yields for 'Cabernet Sauvignon' and 'Chardonnay' grapevines.O objetivo deste trabalho foi avaliar a produtividade e a composição do mosto de videiras 'Cabernet Sauvignon' e 'Chardonnay' submetidas a aplicações de fósforo em solo de região de altitude no Sul do Brasil, durante três safras. Os experimentos 1 e 2 foram realizados em vinhedos comerciais de 'Cabernet Sauvignon' e de 'Chardonnay', respectivamente, no município de Água Doce, na região Meio-Oeste do estado de Santa Catarina. O solo dos dois vinhedos foi classificado como Cambissolo Húmico. A fonte de P utilizada foi o superfosfato triplo (45% de P2O5). De 2011 a 2013, no florescimento, foram aplicados 0, 10, 20, 40 e 80 kg ha-1 de P2O5 na projeção da copa, na superfície do solo, sem incorporação, em ambos os vinhedos. Avaliaram-se concentração de P no solo e na folha, variáveis de produção e qualidade do mosto. O incremento na disponibilidade de P diminuiu os valores de acidez total titulável e de ácido tartárico no mosto da videira 'Cabernet Sauvignon' na safra de 2013/2014 e aumentou os valores de pH e sólidos solúveis totais no mosto da videira 'Chardonnay' na safra de 2011/2012. A aplicação de fósforo no solo aumenta os níveis de fósforo disponível, mas não resulta em maiores produtividades das videiras 'Cabernet Sauvignon' e 'Chardonnay'

Aspectos da fertilidade do solo e nutrição de Pinus taeda L: Uma revisão

The cultivation of the genus Pinus spp. in Brazil occupies an area of 1.7 million hectares in 2020. Pinus is considered a socioeconomic component, which helps maintain the development of the southern region of the country and the national supply chain. However, the areas destined for pine cultivation usually have acidic soils and low natural fertility, which reduces the nutrients availability, negatively influencing the crop development. However, it is not known if Pinus responds positively to mineral fertilization, nor what is the nutrient of greatest demand regarding plantation development. Thus, the objective of this review is to explore which nutrients are of greatest nutrient need and therefore most responsive to pine growth and productivity. Thus, this review aims to establish a discussion on the importance and current plantation of Pinus taeda, along with answers on fertilization and nutrition of the crop, obtaining data from articles found in scientific databases of international literature, to better inform fertilization practices for this little studied crop. We have seen that mineral fertilization aims to optimize the pine growth, seeking to meet the physiological needs of the plants and thus achieve maximum crop productivity. However, the literature shows that many times the pine does not respond expressively in growth when subjected to mineral fertilization. Thus, studies that consider the effects of nutrient application to the pine crop, over time, are required to better conclude whether the pine crop responds to the nutrient supply.O cultivo do género Pinus spp. no Brasil ocupa uma área de 1,7 milhões de hectares em 2020. O Pinus é considerado uma componente socio-económica, que ajuda a manter o desenvolvimento da região sul do país e da cadeia nacional de abastecimento. Contudo, as áreas destinadas ao cultivo do pinheiro têm geralmente solos ácidos e baixa fertilidade natural, o que reduz a disponibilidade de nutrientes, influenciando negativamente o desenvolvimento da cultura. A fertilização mineral visa optimizar o crescimento do Pinus, procurando satisfazer as necessidades fisiológicas das plantas e assim atingir a máxima produtividade da cultura. Contudo, a literatura mostra que muitas vezes o pinheiro não responde de forma expressiva ao crescimento quando submetido a fertilização mineral. Assim, estudos que consideram os efeitos da aplicação de nutrientes à cultura do pinheiro, ao longo do tempo, são necessários para concluir se a cultura do pinheiro responde ao fornecimento de nutrientes

Estrategia de Negociación Comercial de Uruguay. Visiones de Agentes Involucrados

Uruguay has undergone a gradual trade liberalization process that has opened the economy to the world. The country is currently conducting trade negotiations that can considerably improve its access to developed countries markets. Based on interviews with enterprises, trade unions and government authorities, this paper aims at identifying the main interests of different sectors and agents involved in trade negotiations. MERCOSUR was indicated by the agents as the main subject of trade negotiations, considering the relevant concessions already achieved by the country within this regional agreement. Developed countries are regarded as suppliers of intermediate inputs and capital goods in order to improve competition in regional markets and as potential markets for agricultural and agroindustrial products. Other regional markets are considered to be less important. Uruguay is a small country with a highly specialized productive pattern, so the availability of intermediate inputs of appropriate price and quality was mentioned as an important priority by most of the agentes interviewed. On the other hand, there is no consensus regarding the future direction of trade negotiations; in particular, different opinions concerning the future of MERCOSUR coexist and a short - term view prevails.MERCOSUR, negociación externa, instrumentos de política comercial.

BORON IN PREVENTING OF SHOOT DIEBACK ON EUCALYPTUS BENTHAMII GROWN IN SOIL WITH DIFFERENT WATER REGIMES

The water deficit interferes in the boron (B) uptake by eucalyptus, causing shoot dieback in young plants. The objective of this study was to evaluate the occurrence of shoot dieback in Eucalyptus benthamii submitted to doses of boron and water regimes in a Humic Cambisol of the Southern Plateau of the state of Santa Catarina. The experiment was conducted in greenhouse (Lages-SC) in a completely randomized experimental design, in a 4 x 3 factorial scheme, with three replications, adding 0, 0.55, 1.1 and 2.75 g boron plant-1 in the soil, and three water regimes (60, 80 and 100% of the field capacity). The stem diameter and the plants height were measured, using a visual analysis of dieback. The dry mass and boron contents in the tissues and in the soil, were also determined. Water deficiency affected negatively dry matter but it was not affected by boron application. The highest occurrence of shoot dieback was observed in the treatments without addition of boron and in the more restrictive water regime. Fertilization with 0.55 g boron plant-1 in soil was sufficient to avoid shoot dieback

Adubação nitrogenada em ciclos consecutivos e seu impacto na produção e na qualidade do pêssego

The objective of this work was to evaluate the effect of N fertilization on N content of the leaf, shoot growth, yield and on physico-chemical quality of peach fruits. The experiment was carried out from 2000 to 2002, in an orchard of peach trees, cv. Chimarrita, grafted on Aldrighi rootstock, at Pinto Bandeira city, in Rio Grande do Sul State, Southern Brazil, in a Haplumbrept soil. The treatments were 0, 22, 44, 66, and 88 kg ha-1 N per year. In the growing seasons leaves were collected, oven-dried and analyzed for total N, and the length of selected shoots was determined after leaf abscission. Fruits were collected when ripen, for the determination of diameter, mass, yield, total N, total soluble solids, total titratable acidity and pulp firmness. Remaining fruits were cooled through forced-air system and kept in cold storage for seven days, then pulp firmness was determined. N fertilization in peach trees increases N content in the leaves and in the fruits. N fertilization do not affect the length of shoots, and the diameter, mass, total titratable acidity and pulp firmness of peach fruits.O objetivo deste trabalho foi avaliar o efeito da aplicação de N sobre o teor foliar do nutriente, o crescimento de ramos, a produção e a qualidade química e física dos frutos de pêssego. O experimento foi conduzido no período de 2000 a 2002, em um pomar de pessegueiro da cultivar Chimarrita, enxertada no porta-enxerto Aldrighi, em Pinto Bandeira, RS, em um solo Cambissolo Húmico. Os tratamentos foram 0, 22, 44, 66 e 88 kg ha-1 de N por ano. Em todas as safras, folhas foram coletadas para análise de N total. Após a queda das folhas, foi determinado o comprimento de ramos do ano. Na maturação, os frutos foram colhidos e foram determinados o diâmetro, a massa, a produção, o N total, os sólidos solúveis totais, a acidez total titulável e a firmeza da polpa, esta última repetida após pré-resfriamento com circulação forçada de ar e armazenamento em câmara fria. A aplicação de N em pessegueiros aumenta o teor do nutriente nas folhas e nos frutos. A adubação nitrogenada não afeta o comprimento dos ramos do ano, o diâmetro, a massa, a produção, a acidez total titulável e a firmeza da polpa dos frutos de pêssego