Towards absolute calibration of optical tweezers

Aiming at absolute force calibration of optical tweezers, following a critical review of proposed theoretical models, we present and test the results of MDSA (Mie-Debye-Spherical Aberration) theory, an extension of a previous (MD) model, taking account of spherical aberration at the glass/water interface. This first-principles theory is formulated entirely in terms of experimentally accessible parameters (none adjustable). Careful experimental tests of the MDSA theory, undertaken at two laboratories, with very different setups, are described. A detailed description is given of the procedures employed to measure laser beam waist, local beam power at the transparent microspheres trapped by the tweezers, microsphere radius and the trap transverse stiffness, as a function of radius and height in the (inverted microscope) sample chamber. We find generally very good agreement with MDSA theory predictions, for a wide size range, from the Rayleigh domain to large radii, including the values most often employed in practice, and at different chamber heights, both with objective overfilling and underfilling. The results asymptotically approach geometrical optics in the mean over size intervals, as they should, and this already happens for size parameters not much larger than unity. MDSA predictions for the trapping threshold, position of stiffness peak, stiffness variation with height, multiple equilibrium points and `hopping' effects among them are verified. Remaining discrepancies are ascribed to focus degradation, possibly arising from objective aberrations in the infrared, not yet included in MDSA theory.Comment: 15 pages, 20 figure

Growth Characteristics of Kikuyu Grass with Different Sources and Doses of Phosphorus

Growth is defined as the increase in size, volume and mass as a function of time. Growth analysis allows evaluating the final growth of the plant as a whole and the contribution of the different organs in total growth (Benincasa, 1988). The experiment had as objective to evaluate specific leaf area (SLA), leaf area per unit of leaf DM, leaf area ratio (LAR), leaf area per unit of whole plant DM, leaf weight ratio (LWR), leaf weight per unit of plant weight, leaf area index (LAI), leaf area per unit of soil area, leaf/stem ratio (LSR), leaf weight per unit stem weight, of 35 days old kikuyu grass with different sources and doses of P

Seasonality of Forage Production of Coastcross-1 with Different Sources and Applications of Phosphorus

Brazil presents high potential for meat production from pastures. However, the feeding of ruminants depends on the conditions and the climate. Approximately 80% of the annual production of dry matter (DM) occurs in the period October to March (spring - summer). In the autumn and winter production is low associated with high humidity and low temperatures in the south and low rainfall in the tropical north. The situation is exacerbated by inadequate management practices and low soil fertility, particularly low levels of phosphorus (P). The objective of this experiment was to evaluate the seasonality of production of DM of coastcross-1 (Cynodon dactylon) with different sources and applications of P for two consecutive years

Validação do zoneamento ecológico do Estado do Paraná para produção de sementes de soja.

Em determinadas regiões do Estado do Paraná, o baixo potencial de germinação, atribuído às condições climáticas desfavoráveis, durante o período de maturação da soja, é o principal fator de eliminação de lotes de sementes. Objetivando avaliar a dimensão do problema o estudo visou determinar as regiões mais apta do Paraná para produção de sementes de soja de elevado padrão fisiológico. Para tal, foram coletadas 121 amostras de sementes da cultivar BR16 (1996/97, 1997/98 e 1998/1999) e 119 amostras da cultivar BRS 133 (1999/2000, 2000/2001 e 20012002). Os parâmetros tomados por base para analisar a qualidade das sementes foram: germinação (%), vigor (TZ 1-3), viabilidade (TZ 1-5), deterioração por umidade (TZ 6-8), dano mecânico (6-8) e lesões de percevejos (TZ 6-8). Para interpretação dos dados, o estado do Paraná foi dividido em três regiões ecológicas: T1, temperatura média do mês mais quente (Fevereiro) >24oC; T2, temperatura média entre 22 e 24oC; T3, temperatura média <22oC. A região T3 que abrange os municípios de Ponta Grossa, Guarapuava, Pato Branco, Marilândia do Sul, Francisco Beltrão e parte de Cascavel, destacou-se, invariavelmente, por apresentar reduzidos índices de sementes com deterioração por umidade, com dano mecânico e com lesões de percevejos, resultando num melhor potencial de germinação, de vigor e de viabilidade. A validação do zoneamento ecológico adiciona uma tecnologia capaz de identificar a região Sul do estado do Paraná, com melhores condições climáticas para produção de sementes de soja de qualidade

Plantations d'eucalyptus et sidérurgie en Amazonie: apports du modèle 3-PG.

Résumé: Le secteur sidérurgique de Carajás, en Amazonie Brésilienne, fait l'objet de contestations environnementales du fait de sa forte consommation en charbon de bois. Ce charbon est essentiellement produit à partir de biomasse de forêts naturelles, avec des impacts directs et indirects sur la déforestation et la dégradation de ces écosystèmes. Les plantations d'eucalyptus à vocation énergétique installées sur des pâturages dégradés constituent une alternative intéressante. Peu de ces plantations ont été mises en place jusqu'à présent et faute d'évaluations valables de leur potentiel de production, une étude a été menée pour présenter une estimation consolidée de la croissance et de la productivité des plantations d'eucalyptus du pôle de Carajás. Celles-ci ont été obtenues à partir du modèle 3-PG (Physiological Principles in Predicting Growth). Son paramétrage a été réalisé à partir de données de croissance du massif d'eucalyptus d'une entreprise de la municipalité de Breu Branco dans l'État du Pará au Brésil. La calibration locale du modèle s'est avérée beaucoup plus performante que l'utilisation de paramètres établis pour des plantations d'eucalyptus dans d'autres régions du Brésil, d'Afrique du sud ou d'Australie. Les simulations réalisées indiquent que l'accroissement moyen annuel actuel de l'ordre de 20 m³ à l'hectare, obtenu pour une période de six ans, pourrait augmenter jusqu'à 30 m³ avec des fertilisations adaptées et un contrôle efficace du sous bois. Elles suggèrent aussi que des productions supérieures seraient obtenues sans déficit hydrique. Cela montre la nécessité de sélectionner les zones de plantation où la saison sèche est la moins marquée autour du pôle de Carajás. La calibration du modèle 3-PG a permis d'améliorer cet outil de gestion des plantations industrielles dans les conditions amazoniennes. (Résumé d'auteur) | Abstract: The Carajás steel industry sector in the Brazilian Amazon has aroused protest on environmental grounds because of its heavy reliance on charcoal. The charcoal is mainly produced from natural forest biomass, with direct and indirect impacts on deforestation and forest ecosystem degradation. Establishing eucalyptus plantations for fuel on degraded pastures could be a workable alternative. Few such plantations exist as yet, and because there are no validated assessments of their production potential, a study was conducted to provide consolidated estimations of the growth and productivity of the Carajás eucalyptus plantations. The estimations were obtained with the 3-PG model (Physiological Principles in Predicting Growth). The model parameters are based on growth data for the eucalyptus plantations established by a company in Breu Branco municipality in Brazil’s Pará State. Calibrating the model with local data proved to be far more effective than using the parameters set for eucalyptus plantations in other areas in Brazil, South Africa or Australia. The simulations made show that the current annual average growth rate, over a six-year period, of about 20 m³ per hectare could increase to 30 m³ with appropriate fertilisation and effective underbrush control. They also suggest that production could be higher without water deficit. Plantation zones shall be selected as a priority in areas where the dry season is the least severe around Carajás. These 3-PG model settings have made it a more effective management tool for industrial plantations in Amazonian conditions

Monitoramento das perdas de grãos na colheita de soja.

Introdução. Sistemas de uma colhedora. Sistema de corte e de alimentação. Sistema de trilha. Sistema de separação e de limpeza. Sistema de transporte, armazenamento e descarga. Determinação das perdas de grãos em soja, com a utilização do copo medidor desenvolvido pela Embrapa Soja.bitstream/item/48247/1/manual-completo3.pdf21. ed