Modelling biological efficacy decrease and rate of degradation of chlorpyrifos-methyl on wheat stored under controlled conditions

Insecticide residue degradation and pest survival were observed in wheat treated with a low dose of chlorpyrifos-methyl. Treated wheat was stored in small batches at three controlled temperatures and two levels of moisture content of grain, in equilibrium with r.h. in order to stabilise the water activity in the grain during a storage period of 126 d after insecticide application. Every 3 weeks, samples were taken from treated and untreated control grain in each storage condition. Chlorpyrifos-methyl residues declined regularly with time of storage and an exponential negative regression was fitted with high correlation coefficients in most situations of storage temperature and grain water activity (Aw). A multivariate model to show the respective influence of controlled variables involved in the model of residues breakdown (time, Aw, and temperature) was built up through a multiple regression. This model showed the respective importance of the water activity of grain kernels, temperature and formulation of chlorpyrifos-methyl and their combinations on the decline of residues. Simultaneously, the effectiveness of the residues was checked through bioassays with two target species: Sitophilus oryzae and Tribolium castaneum. Taking into account the intentionally low initial applied dose of chlorpyrifos-methyl, the period after application achieving complete kill of the two test insects was rather short and did not exceed 105 d for S. oryzae in the best conditions for control, i.e. low moisture content and temperature. For high Aw (0.8) and storage temperature 30°C, T. castaneum was effectively controlled (more than 95% kill) only on the day after the treatment, survival occurring at the next test date 21 d after the application. High moisture content and temperature and their interactions were the main variables influencing the decrease in the biological effectiveness with time. The concentration threshold for insect survival was slightly below 1 ppm chlorpyrifos-methyl and was influenced by storage and grain conditions. Implications of these findings on storage pest management practices and on the ability to predict the period of biological effectiveness of residues of chlorpyrifos-methyl are discussed.     

Digital Control of a Power Conditioner for Fuel Cell/Super-capacitor Hybrid System

This article proposes a digital control scheme to operate a proton exchange membrane fuel cell module of 1.2 kW and a super-capacitor through a DC/DC hybrid converter. A fuel cell has been proposed as a primary source of energy, and a super-capacitor has been proposed as an auxiliary source of energy. Experimental validation of the system implemented in the laboratory is provided. Several tests have been performed to verify that the system achieves excellent output voltage (V₀) regulation and super-capacitor voltage (V_SC) control under disturbances from fuel cell power (P_FC) and output power (P₀) as well as other perturbations described in analysis results.     

Assessment of the suitability of soil amendments to reduce 137Cs and 90Sr root uptake in meadows

In situ remediation strategies are an alternative approach in the management of radioactive contaminated areas, especially when based on modification of soil properties by the addition of amendments. Here, this strategy is applied to reduce 137Cs and 90Sr soil-plant transfer in meadows from areas of Russia, Belarus, and Ukraine affected by the Chernobyl fallout. Meadows were established on podzolic and peaty soils. Amendments covered a wide range of materials, such as loamy and sandy soils, polygorskite clay, phosphorite, turf, and sapropel. Field experiments showed the poor efficiency of most of the materials: only the polygorskite clay provoked a notable reduction (1.5-2-fold) in 137Cs root uptake. Subsequent laboratory characterization showed the lack of significant changes in the radiocesium interception potential and soil solution composition in the amended soils, a fact that helped to explain the lack of effect on the reduction of transfer. Moreover, a laboratory methodology based on the quantification of the adsorption potential of the amendments and the reversibility of the adsorption process was applied. This methodology was first proposed for the correct selection of the suitable materials to be used to decrease radionuclide root uptake in future remediation actions and then validated with data of the previous field experiments.     

A new approach to constrained open pit pushback design using dynamic cut-off grades

An integral part of open pit optimization is deciding which section of the ultimate pit to mine during a specific period. For a given period there are often operational and marketing constraints that restrict what can be removed or processed. The operational constraints arise from a number of different limitations such as safe slope of internal mining walls, mill and mining capacity. Traditional methods for pushback (phase) design that incorporate these constraints are ad-hoc and can lead to suboptimal solutions. Another important optimization decision that must be made is the cut-off grade to be used for a specific period. In this paper, a new method is presented that generates near maximal expected profit and dynamically defines the optimal cut-off grade for each mining period or pushback over the life-of-mine, thus deciding whether a block is ore or waste during the optimization process. More specifically, a method for converting a fractional linear program solution into an integral solution known as pipage rounding is applied to an integer program formulation of a pushback design optimization problem. The proposed method aims to produce a set of pushbacks in a way that the total discounted profit to be generated through production scheduling is maximized. Two case studies demonstrate the applied aspects of the proposed method.     

Book Review

Autonomous Agents and Multi-Agent Systems -     

Guanidinium-based potentiometric SO2 gas sensor

An SO2 gas sensor was developed by using a hydrogen sulfite-selective electrode positioned behind a gas-permeable membrane (GPM). The hydrogen sulfite-selective electrode was prepared by incorporating a multicyclic guanidinium ionophore in a plasticized poly(vinyl chloride) membrane. This gas sensor presents important advantages over the conventional Severinghaus-type SO2 gas sensor that contains a pH electrode immersed in an internal solution behind the GPM. The Severinghaus gas sensor suffers interferences from weak acids that can cross the GPM as gases and change the pH of the internal solution. In contrast, in the proposed sensor, the excellent selectivity of the HSO3- electrode and the ability of the GPM to discriminate gaseous from nongaseous species combine to generate the most selective potentiometric SO2 gas sensor reported to date.     

Inhibitory effect of melanins from Agaricus bisporus polyphenol oxidase and two different substrates on carboxypeptidases A and B activity

In recent years, some beneficial effects on health of melanins that are formed as a result of polyphenol oxidase action have been discovered. However, it is also known that similar polymers have a detrimental effect on proteases activity. Thus, the aim of this work was to assay whether melanins from two different substrates act as carboxypeptidase A and carboxypeptidase B inhibitors. It was found that melanin synthesized from l-tyrosine decreases both the apparent affinity between carboxypeptidases and their substrates and the maximum reaction rate. Consequently, it is possible to conclude that these melanins inhibit CPA and CPB activity in a mixed way. On the contrary, no inhibition was found in the case of melanin synthesized from 4-methylcatechol.     

Intravascular Ultrasound Tissue Characterization with Sub-class Error-Correcting Output Codes

Intravascular ultrasound (IVUS) represents a powerful imaging technique to explore coronary vessels and to study their morphology and histologic properties. In this paper, we characterize different tissues based on radial frequency, texture-based, and combined features. To deal with the classification of multiple tissues, we require the use of robust multi-class learning techniques. In this sense, error-correcting output codes (ECOC) show to robustly combine binary classifiers to solve multi-class problems. In this context, we propose a strategy to model multi-class classification tasks using sub-classes information in the ECOC framework. The new strategy splits the classes into different sub-sets according to the applied base classifier. Complex IVUS data sets containing overlapping data are learnt by splitting the original set of classes into sub-classes, and embedding the binary problems in a problem-dependent ECOC design. The method automatically characterizes different tissues, showing performance improvements over the state-of-the-art ECOC techniques for different base classifiers. Furthermore, the combination of RF and texture-based features also shows improvements over the state-of-the-art approaches.