Effects of azadirachtin on post-embryonic development, energy reserves and α-amylase activity of Plodia interpunctella Hübner (Lepidoptera: Pyralidae)

The effects of azadirachtin on the fourth instar larvae of Plodia interpunctella (Lepidoptera) were investigated. When incorporated into the diet at 2 and 4 ppm, azadirachtin provoked larval weight loss, developmental delay and high larval and pupal mortality. Spectrophotometric assays showed that azadirachtin caused a severe reduction in protein, glycogen and lipid contents 7 days after the beginning of the treatment. In addition, α-amylase activity was reduced in larvaefed azadirachtin.     

New chitosan microspheres supported [bis(2-methylallyl)(1,5-cyclooctadienne)ruthenium(II)] as efficient catalysts for colour degradation in the presence of hydrogen peroxide

This paper concerns the immobilisation of either [bis(2-methylallyl)(1,5-cyclooctadienne)ruthenium(II)] (I) or ruthenium chloride (RuCl₃) (II) on chitosan microspheres (catalyst I and catalyst II, respectively). These heterogenised catalysts were used for the oxidative degradation of two acid dyes, i.e. [Calmagite (Calma) and Acid Blue 25 (AB25)] in aqueous solution at pH 7.0 in the presence of hydrogen peroxide (H₂O₂). Prepared solid supports were characterised by Fourier transform infrared (FTIR) spectral study, thermogravimetry (TG), differential thermogravimetry (DTG) and differential scanning calorimetry (DSC) analyses. The efficiency of decolourisation was justified using UV–visible spectroscopic analysis. The factors affecting dye degradation were studied. Some tests for Calma decolourisation achieved up to 100% colour removal using catalyst I. The pseudo first-order equation was shown to fit degradation kinetics in most cases. However, for some cases, it was necessary to use a reversible equation. The energetic parameters were determined and the activation energy (E _a) was found to be low, between 11 and 36?kJ?mol^?1, confirming that these catalysts were very efficient for the degradation of anionic dyes using H₂O₂. The interpretation of the equilibrium sorption data complies well with the Freundlich adsorption model. The combination of adsorption process and catalytic oxidation made the new developed catalyst systems to achieve a simple and efficient water treatment.     

Earliness–tardiness minimization on a single machine to schedule preventive maintenance tasks: metaheuristic and exact methods

In this paper, we consider the problem of scheduling a set of M preventive maintenance tasks to be performed on M machines. The machines are assigned to execute production tasks. We aim to minimize the total preventive maintenance cost such that the maintenance tasks have to continuously be run during the schedule horizon. Such a constraint holds when the maintenance resources are not sufficient. We solve the problem by two exact methods and meta-heuristic algorithms. As exact procedures we used linear programming and branch and bound methods. As meta-heuristics, we propose a local search approach as well as a genetic algorithm. Computational experiments are performed on randomly generated instances to show that the proposed methods produce appropriate solutions for the problem. The computational results show that the deviation of the meta-heuristics solutions to the optimal one is very small, which confirms the effectiveness of meta-heuristics as new approaches for solving hard scheduling problems.     

Satellite image segmentation using hybrid variable genetic algorithm

Image segmentation is an important task in image processing and analysis. Many segmentation methods have been used to segment satellite images. The success of each method depends on the characteristics of the acquired image such as resolution limitations and on the percentage of imperfections in the process of image acquisition due to noise. Many of these methods require a priori knowledge which is difficult to obtain. Some of them are parametric statistical methods that use many parameters which are dependent on image property. In this article, a new unsupervised nonparametric method is developed to segment satellite images into homogeneous regions without any a priori knowledge. The new method is called hybrid variable genetic algorithm (HVGA). The variability is found in the variable number of cluster centers and in the changeable mutation rate. In addition, this new method uses different heuristic processes to increase the efficiency of genetic algorithm in avoiding local optimal solutions. Experiments performed on two different satellite images (Landsat and Spot) proved the high accuracy and efficiency of HVGA compared with another two unsupervised and nonparametric segmentation methods genetic algorithm (GA) and self‐organizing map (SOM). The verification of the results included stability and accuracy measurements using an evaluation method implemented from the functional model (FM) and field surveys. © 2009 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 19, 199–207, 2009     

Large array of sub-10-nm single-grain Au nanodots for use in nanotechnology

A uniform array of single-grain Au nanodots, as small as 5-8 nm, can be formed on silicon using e-beam lithography. The as-fabricated nanodots are amorphous, and thermal annealing converts them to pure Au single crystals covered with a thin SiO(2) layer. These findings are based on physical measurements, such as atomic force microscopy (AFM), atomic-resolution scanning transmission electron microscopy, and chemical techniques using energy dispersive X-ray spectroscopy. A self-assembled organic monolayer is grafted on the nanodots and characterized chemically with nanometric lateral resolution. The extended uniform array of nanodots is used as a new test-bed for molecular electronic devices.     

Fermentation of date palm juice by curdlan gum production from Rhizobium radiobacter ATCC 6466™: Purification, rheological and physico-chemical characterization

The present study was undertaken to investigate the possibility of using date palm juice byproducts for curdlan production by Rhizobium radiobacter ATCC 6466™ in batch experiments. A number of operational parameters, namely pH value, temperature range, inoculum ratio, agitation speed, carbon concentration, nitrogen source, and fermentation time, were investigated in terms of their optimal values for as well as individual and synergistic effects on curdlan production. The findings indicated that the strain exhibited a high ability to use the natural substrate under investigation. A curdlan production yield of 22.83 g/l was obtained in 500-ml agitated flasks (50 ml) when the strain was cultivated in the optimal medium (pH, 7; ammonium sulphate concentration, 2 g/l; date glucose juice concentration, 120 g/l) operating at 30 °C with an inoculum ratio of 5 ml/100 ml, an agitation speed of 180 rpm, and a fermentation period of 51 h. The purified date byproducts-curdlan (DBP-curdlan) had a molecular weight of 180 kDa, a linear structure composed exclusively of β-(1,3)-glucosidic linkages, a melting temperature (T_m) and glass transition temperature (T_g) of 1.24 and −3.55 °C, respectively. The average measured heights of its molecules were noted to fluctuate between 14.1 ± 0.07 and 211.73 ± 0.6 μm.     

A Clustering-based Approach for Balancing and Scheduling Bicycle-sharing Systems

This paper addresses an inventory regulation problem in bicycle sharingsystems. The problem is to balance a network consisting of a set of stations by using a single vehicle, with the aim of minimizing the weighted sum of the waiting times during which some stations remain imbalanced. Motivated by the complexity of this problem, we propose a two-stage procedure based on decomposition. First, the network is divided into multiple zones by using two different clustering strategies. Then, the balancing problem is solved in each zone. Finally, the order in which the zones must be visited is defined. To solve these problems, different algorithms based on approximate, greedy and exact methods are developed. The numerical results show the effectiveness of the proposed regulation methodology.