Variation of the chemical composition of tomato cultivars (Lycopersicon esculentum Mill.) according to resistance against the tomato yellow leaf curl virus (TYLCV)

BACKGROUND: Tomato producers are looking for alternatives to protect their crops against the tomato yellow leaf curl virus (TYLCV), including replacement of cultivars with other more resistant ones. Major chemical components, sugars, mineral composition, organic acids, lycopene, total phenols and hydroxycinnamic acids were determined in six tomato cultivars, three of them (Boludo, Dorothy and Tyna) resistant, and the other three (Daniela, Dominique and Thomas), non‐resistant against TYLCV. RESULTS: The Daniela cultivar showed the greatest difference with respect to the others, mostly due to the higher content of soluble solids. The major significant differences between the mean values according to the cultivar and resistance against the TYLCV were observed for total soluble solids, pH, ascorbic acid, total phenols and hydroxycinnamic acids. High coefficients of correlation were found between glucose and fructose, and among ferulic, caffeic and p‐coumaric acids. CONCLUSION: Linear discriminant analysis made it possible to differentiate tomato samples according to the cultivar. A clear varietal influence on the chemical composition was observed; however, resistance or non‐resistance against TYLCV does not seem to influence the chemical composition. Copyright © 2008 Society of Chemical Industry     

Diffuse conditions for efficient solution of multislab radiation transport problems

In this article, we make use of recently developed spectral nodal methods for anisotropically scattering media and we derive mathematical conditions for the diffuse reflection and transmission of radiation in the discrete ordinates formulation of particle transport theory for plane-parallel applications. The conditions arise from a suitable reformulation of spatially discretized equations defined on the boundary layers of a multislab domain. As a result, the boundary layers can be removed from the radiation transport calculations and replaced with exact and numerically stable equivalent conditions. In order to illustrate the applicability and computational merit of our discrete ordinates conditions for diffuse reflection and transmission in radiation transport calculations, we perform numerical experiments with atmospheric radiative transfer and nuclear reactor core models.     

Non-linear optimization technique for partial solution of generalized eigenvalue problems

This paper presents an alternative to the subspace iteration and Lanczos techniques, both of which are now used to solve partial eigenvalues and eigenvectors of large generalized linear first order symmetric matrix systems. It is based on non-linear optimization of a modified Rayleigh quotient. The elements of the eigenvector are the decision variables. Orthogonality constraints with respect to the two matrices are incorporated in the sequential unconstrained optimization scheme. By imposing normality with respect to one of the matrices, the Hessian matrix reduces to a much simpler form for which the Woodburry transformation may be used. This, in combination with the fact that the banded structure of the matrices is maintained, results in a number of operations of the same order as the two standard methods. Shifting is readily integrated. Numerical comparison with existing techniques demonstrate the practicality of this method.     

Simulating the variability of dispersed large PV plants

A model to simulate the fluctuations generated by a fleet of dispersed photovoltaic (PV) plants solely based on irradiance data measured at one single location is proposed. This simple model has been satisfactorily tested to quantify the power variability of a generic PV fleet, simply by defining two parameters: mean PV plant size and the number of plants in the PV fleet. Specifically, the model provides series of simulated power outputs that may be used in the grid operator simulation programmes, reproducing critical parameters, such as daily maximum fluctuation or the reserves required to offset these fluctuations. The model is created and validated against experimental 1‐s data collected throughout 2013 at six PV plants in Spain dispersed over 1100 km², totaling 17 MWp. Likewise, the model has been succesfully tested against another irradiance dataset, four sites across the state of Colorado, USA, and spread over 2400 km². Copyright © 2015 John Wiley & Sons, Ltd.     

Noise emission evolution on construction sites. Measurement for controlling and assessing its impact on the people and on the environment

The noise produced by the construction activities is one of the main acoustic polluting elements in society. However, there is no specific regulation for this activity, which shows its own emission features that make it remarkably different from other activities.     

Determination of Ca,Cd, Cu,Fe, K,Mg, Mn,Mo, Na,Se, and Zn in Foodstuffs by Atomic Spectrometry After Sample Preparation Using a Low-Cost Closed-Vessel Conductively Heated Digestion System

Establishing fast, simple, low-cost, and efficient sample preparation procedures to determine elements in foodstuffs is a relevant aspect for nutritional and health purposes. For this reason, the recently proposed closed-vessel conductively heated digestion system (CHDS) was evaluated for the digestion of milk powder, chocolate powder, and soluble coffee samples aiming for Ca, Cu, Fe, K, Mg, Mn, Na, and Zn determinations by high-resolution continuum source flame atomic absorption spectrometry (HR-CS FAAS) and Cd, Mo, and Se determinations by inductively coupled plasma mass spectrometry with tandem configuration (ICP-MS/MS). The accuracy was evaluated by analyzing two milk certified reference materials digested by the CHDS and a microwave oven for comparison. When using the CHDS, recoveries for the analytes varied from 91 to 104 %. For microwave digestions, recoveries within the 94–109 % intervals were obtained. The method was then applied to the samples. For comparative purposes, the analytes were also determined in the samples after microwave digestion, and the results between the two digestion systems showed no differences based on a paired t test at a 95 % confidence level. Similar analytical blanks were obtained because quartz digestion tubes were used in both digestion systems. The CHDS with quartz tubes is an interesting alternative for laboratories dedicated to large-scale routine analysis because volatile elements usually found in very low concentrations in food samples such as Cd and Se can also be determined.     

Laminar counterflow parallel-plate heat exchangers: Exact and approximate solutions

Multilayered, counterflow, parallel-plate heat exchangers are analyzed numerically and theoretically. The analysis, carried out for constant property fluids, considers a hydrodynamically developed laminar flow and neglects longitudinal conduction both in the fluid and in the plates. The solution for the temperature field involves eigenfunction expansions that can be solved in terms of Whittaker functions using standard symbolic algebra packages, leading to analytical expressions that provide the eigenvalues numerically. It is seen that the approximate solution obtained by retaining the first two modes in the eigenfunction expansion provides an accurate representation for the temperature away from the entrance regions, specially for long heat exchangers, thereby enabling simplified expressions for the wall and bulk temperatures, local heat-transfer rate, overall heat-transfer coefficient, and outlet bulk temperatures. The agreement between the numerical and theoretical results suggests the possibility of using the analytical solutions presented herein as benchmark problems for computational heat-transfer codes.     

Evaluation of the impact of access to electricity: A comparative analysis of South Africa,China, India and Brazil

Most developing countries include rural electrification programs in their efforts to improve social conditions. There are, however, several obstacles to the evaluation of such programs and therefore of their social, economic, environmental and energy impacts on the target population, particularly on impoverished communities located in remote areas. Evaluation of the efficacy of public policies aimed at rural electrification in South Africa, China, India and Brazil enables such actions to be quantified and re-considered so as to bolster the sustainability of their planning and implementation and also so as to enable comprehension of the significance of access to electricity in relation to other aspects of the drive to improve living standards. The provision of electric energy amounts to more than access to a public service and should be considered an essential right, in a context of social equity and justice, which permits social integration and the access to other equally essential services.     

The renewable energy market in Brazil: Current status and potential

Renewable energy offers a range of options with which to meet the growing demand for energy, particularly in the context of the pursuit (especially in developing countries) of economic development which takes into account social and environmental issues. Brazil has abundant natural sources of renewable energy, such as wind and solar power, hydraulic energy, small hydroelectric plants, ethanol and bio-diesel. These sources form part of the Brazilian strategy aimed at satisfying the demand for 6300 MW of fresh capacity per year arising out of projected economic growth of 5.1% per year over the next 10 years. Renewable energy sources currently provide 47.2% of the internal supply of primary energy in Brazil. Brazil has been pursuing a strategy of maintaining its renewable energy matrix and developing and providing incentives for further low carbon initiatives.In this study we set out an overview of the renewable energy options available in Brazil, their current status, the main positive results obtained to date and future potential. We describe the market for renewable energy in Brazil and examine specific public policies aimed at overcoming barriers to this market, thereby promoting its consolidation and expansion.     

Dynamics of glyphosate and aminomethylphosphonic acid in a forest soil in Galicia, north-west Spain

Residues of the herbicide glyphosate (N-phosphonomethylglicine) and its main metabolite, aminomethylphosphonic acid (AMPA), were determined in a forest soil in north-west Spain, previously treated with 5 and 8 l ha(-1) of glyphosate. Both products were monitored in the solid and liquid soil phases for an 8-week period after the treatment. Soil samples were extracted by KH2PO4. Concentrated extracts and liquid phase samples were derivatized with 9-fluorenylmethyl chloroformate (FMOC) before determination by HPLC using an anion exchange column and spectrofluorometric detection. The treated soil peaked at 6.9 microg g(-1) of glyphosate, whereas soil water samples peaked at 0.74 microg ml(-1) of glyphosate. One month after the treatment, both glyphosate and AMPA concentrations in soil and water samples were almost negligible. AMPA peaked at 0.77 microg ml(-1) in soil water samples. Glyphosate and AMPA exhibited high vertical mobility in the treated soil, quickly reaching high concentrations in subsurface horizons where the degradation is slower.