Abstract To induce temperature changes on the sample surface by the incidence of a monochromatic modulated light beam and detect the changes produced in the thermal radiation emission, is the basic principle of the infrared photothermal radiometry technique. Until now, in order to analyze the thermal response mathematical models based in an one-dimensional model were used considering a sample with a finite thickness and an infinite incidence surface, as well as the linear approximation of the Stefan-Boltzmann Law in the calculus of the heat losses due to thermal radiation. In this work, analytical and numerical models for the 2D heat diffusion in homogenous finite solid samples, are presented. These models were obtained by solving the heat diffusion equation, under cylindrical symmetry, considering mixed boundary conditions to include radiation and convection heat losses through the surfaces of the sample, and a monochromatic Gaussian excitation beam impinging on the front of the sample. The analytical models were obtained by solving the governing equations, considering the well-known linear approximation of the Stefan-Boltzmann law in the calculus of the heat losses due to thermal radiation. To analyse the effects of the nonlinearity of the heat losses by thermal radiation on the thermal transient response, in the numerical model it was taken into account the full expression of the Stefan-Boltzmann law, and the transport equation was solved numerically by means of the Finite Element Method (FEM). The analytical solution for the oscillatory thermal response reveals the close dependence of the thermal response on the ratio of thickness to the radius of the sample, represented by the form factor sf. Both, the analytical and the numerical solutions were employed to simulate the thermal response of homogenous materials, and compared with experimental results reported elsewhere by part of our same research group. Finally, the difference between the thermal response predictions, from the analytical and numerical models, were analyzed.

Abstract: Increasing plant density in canola forage (Brassica napus L. var. oleifera) may improve dry matter (DM) and nutrient yields. Two experiments were conducted to evaluate the effect of plant density on forage chemical composition and yields of DM, crude protein (CP) and net energy for lactation (NEL) in canola. The trials were carried out during the 2011-2012 and 2012-2013 cycles in Matamoros, Coahuila, Mexico. Plant densities at harvest varied from 19.1 to 248 plants m-2. The association between plant density and the response variables were analyzed using simple linear regression (P ≤ 0.05). The increase in plant density enhanced the concentration of CP and NEL in the first cycle, whereas in the second cycle chemical composition was not affected. At low plant densities, the plasticity of canola did not compensate DM, CP and NEL yields, as these variables showed a positive linear relationship (P ≤ 0.05) with plant density. Dry matter yield ranged from 6067 to 9356 kg ha1. Yields of CP and NEL were fitted to a linear function (P ≤ 0.05). Yields of CP (1398 to 2260 kg ha-1) and NEL (29,248 to 54,487 MJ ha-1) in the second year were higher than those observed in the first year, with 842 to 2159 kg ha-1 of CP and 17,533 to 44,617 MJ ha-1 of NEL. Results indicate that DM and nutrient yields in canola forage increased as plant density increased, without affecting forage chemical composition.

Resumen: El aumento en la densidad de población en canola (Brassica napus L. var. oleifera) para forraje puede incrementar los rendimientos de materia seca (MS) y nutrientes. Se realizaron dos experimentos para evaluar el efecto de la densidad de población sobre la composición química del forraje y los rendimientos de MS, proteína cruda (PC) y energía neta para lactancia (ENL) en canola. Los experimentos se hicieron en Matamoros, Coahuila, México durante los ciclos 2011-2012 y 2012-2013. Las densidades de población a la cosecha fluctuaron entre 19.1 y 248 plantas m-2. La asociación entre la densidad de población y las variables de respuesta se analizó mediante regresión lineal simple (P ≤ 0.05). El aumento en la densidad de plantas incrementó la concentración de PC y ENL en el primer ciclo, mientras que en el segundo la composición química no fue afectada. En las bajas densidades, la plasticidad de la canola no compensó el rendimiento de MS, PC y ENL por hectárea, ya que estas variables mostraron una relación lineal positiva (P ≤ 0.05) con la densidad de población. El rendimiento de MS fluctuó de 6,067 a 9,356 kg ha-1. Los rendimientos de PC y ENL se ajustaron a una función lineal (P ≤ 0.05). En el segundo año, los rendimientos de PC (1,398 a 2,260 kg ha-1) y ENL (29,248 a 54,487 MJ ha-1) fueron mayores que los del primero, con 842 a 2,159 kg ha-1 en PC y 17,533 a 44,617 MJ ha-1 en ENL. Los resultados indican que los rendimientos de MS y nutrientes en canola para forraje se incrementaron al aumentar la densidad de población, sin afectar la composición química del forraje.

O uso de cápsulas porosas para extração de solução do solo é interessante por ser um ensaio não-destrutivo. Entretanto, persistem dúvidas sobre a liberação de íons da própria cápsula, que podem contaminar a solução extraída. Foram realizados testes na Faculdade de Ciências Agronômicas/UNESP, Botucatu (SP), com o objetivo de verificar a liberação de Ca e de Mg por cápsulas porosas de porcelana. No primeiro, foram empregados quatro tratamentos: T1 - lavagem das cápsulas com água destilada, forçando sua passagem pelas cápsulas, utilizando uma bomba a vácuo; T2 - lavagem das cápsulas com HCl 0,1 mol L-1, forçando sua passagem pelas cápsulas, utilizando uma bomba a vácuo; T3 - lavagem das cápsulas com água destilada, sem vácuo, e T4 - lavagem das cápsulas com HCl 0,1 mol L-1, sem vácuo, em um tempo de imersão de 24 h (para T3 e T4). No segundo teste, as cápsulas tratadas com HCl 0,1 mol L-1 no primeiro teste foram lavadas com água destilada novamente e deixadas de molho em água destilada e deionizada durante 45 min. Após estes procedimentos, as cápsulas foram imersas em água destilada, tomando-se alícotas desta solução para determinação de pH e dos teores de Ca e Mg após contato com as cápsulas por 0; 0,5; 1,0; 2,0; 4,0 e 24 h. Cada tratamento teve quatro repetições. Não se observou liberação significativa de Ca e Mg das cápsulas porosas para a solução, quando foram preparadas utilizando-se da passagem de HCl 0,1 mol L-1 a vácuo e água destilada, e deixadas, a seguir, em água destilada e deionizada durante 4 h.

The use of porous cups to extract soil solution is interesting because it is a non destructive method. However, there are some uncertainties regarding the possible release of ions from the cups that would contaminate the extracted solution. An experiment was carried out at the College of Agricultural Sciences/UNESP, Botucatu, State of São Paulo (Brazil) to evaluate the Ca and Mg release by ceramic porous cups. Two tests were performed, consisting of four treatments: T1 - washing the cups with distilled water, forcing its passage through the cups with a vacuum pump; T2 - washing the cups with 0.01 mol L-1 HCl, forcing its passage through the cups with a vacuum pump; T3 - washing cups with water, without vacuum; e T4 - washing the cups with 0.01 N HCl, without vacuum. In the second test, the cups treated with 0.01 mol L-1 HCl in the first test were washed again with distilled water and left in purified (distilled and deionized) water taken for 45 minutes. After this, the cups were immersed in distilled water. Sub-samples were after 0, 0.5, 1.0, 2.0, 4.0, and 24.0 h to determine pH, Ca and Mg contents in solution. Each treatment of both tests was carried out in four replicates. The pH values and Ca and Mg release from the cups to solution was not significant when they were washed with 0.01 mol L-1 HCl employing vacuum and distilled water followed by immersion in purified water for 4 h.