Determination of cadmium in river water samples by flame AAS after on-line preconcentration in mini-column packed with 2-aminothiazole-modified silica gel.

A rapid and sensitive method was developed to determine trace levels of Cd2+ ions in an aqueous medium by flame atomic absorption spectrometry, using on-line preconcentration in a mini-column packed with 100 mg of 2-aminothiazol modified silica gel (SiAT). The Cd2+ ions were sorbed at pH 5.0. The preconcentrated Cd2+ ions were directly eluted from the column to the spectrometer's nebulizer-burner system using 100 microL of 2 mol L(-1) hydrochloric acid. A retention efficiency of over 95% was achieved. The enrichment factor (calculated as the ratio of slopes of the calibration graphs) obtained with preconcentrations in a mini-column packed with SiAT (A = -1.3 x 10(-3) + 1.8 x 10(-3)[Cd2+]) and without preconcentrations (A = 4 x 10(-5) + 3.5 x 10(-5)[Cd2+]), was 51 and the detection limit calculated was 0.38 microg L(-1). The preconcentration procedure was applied to determine trace levels of Cd in river water samples. The optimum preconcentration conditions are discussed herein.     

Efficient synthesis of chiral beta-seleno amides via ring-opening reaction of 2-oxazolines and their application in the palladium-catalyzed asymmetric allylic alkylation

[structure: see text] A set of chiral beta-seleno amides have been efficiently synthesized via the ring-opening reaction of chiral 2-oxazolines by selenium nucleophiles. The present method is applicable to the synthesis of beta-seleno amides containing thioether, alcohol, and ether moieties in good yields. As an application, the synthesis of a selenocysteine derivative has been accomplished. Additionally, these new compounds were evaluated in the palladium-catalyzed asymmetric allylic alkylation, giving the alkylated products in up to 98% ee.     

An ILS heuristic for the traveling tournament problem with predefined venues

The Traveling Tournament Problem with Predefined Venues (TTPPV) is a single round robin variant of the Traveling Tournament Problem, in which the venue of each game to be played is known beforehand. We propose an Iterated Local Search (ILS) heuristic for solving real-size instances of the TTPPV, based on two types of moves. Initial solutions are derived from an edge coloring algorithm applied to complete graphs. We showed that canonical edge colorings should not be used as initial solutions in some situations. Instead, the use of Vizing’s edge coloring method lead to considerably better results. We also establish that the solution space defined by some commonly used neighborhoods in the sport scheduling literature is not connected in the case of single round robin tournaments, which explains the hardness of finding high quality solutions to some problem instances. Computational results show that the new ILS heuristic performs much better than heuristics based on integer programming and that it improves the best known solutions for benchmark instances.     

Catalytic enantioselective arylation of aldehydes: boronic acids as a suitable source of transferable aryl groups

The catalytic enantioselective arylation of several aldehydes using boronic acids as the source of transferable aryl groups is described; the reaction is found to proceed in excellent yields and high enantioselectivities (up to 97% ee) in the presence of a chiral amino alcohol.     

Thermal and morphological characterization of highly porous nanocomposites for possible application in potassium controlled release

The use of fertilizer and water availability are essential factors limiting the agricultural production. The controlled release technology is very promising because it allows the maintenance of fertilizer concentrations within an ideal range avoiding inefficiency and toxicity problems, minimizing the environmental impacts and improving their efficiency. In this context, the nanostructured hydrogels appear as a possible carrier vehicle for these controlled release systems due to their inherent properties, such as biodegradability, low toxicity, and cost, rapid absorption and desorption controlled capacity of water and solutes. In this work, we performed the synthesis of nanostructured hydrogels based on poly(methacrylic acid) (PMAA)/Cloisite-Na⁺ via free radical polymerization. SEM images indicated a similarity in the basic structure of all nanocomposites. The porous diameter of the hydrogels increased with increasing of nanoclay content. EDS analysis showed the ions belonging to nanoclay present in the nanocomposites, confirming the formation of true nanocomposites. TG–DTG and DSC techniques confirmed an improvement in the thermal stability of nanocomposites caused by the addition of nanoclay. For instance, the degradation initial temperature of the hydrogel was increased from 198.5 to 203.5 °C, and inversely, the degradation rate of the 2° thermal event was decreased from 0.694 to 0.472% min °C^?1, when the nanoclay was increased from 0 to 20 mass/%. Moreover, the controlled release investigation showed an improvement in the release time and quantity of the fertilizer released with nanoclay content. This result is very required for this specific application.     

Versatility of the Biginelli reaction: Synthesis of new biphenyl dihydropyrimidin-2-thiones using different ketones as building blocks

A multi-component synthesis of biphenyl dihydropyrimidin-2-thiones from 1-phenylthiourea, aldehydes and ketones or di-ketones has been demonstrated. The reaction proceeded well for aldehydes with electron donor or acceptor substituents under mild conditions.     

Characterization and compatibility of dry extract from Annona muricata L. and pharmaceutical excipients

Journal of Thermal Analysis and Calorimetry - The aim of this study was to characterize and evaluate the compatibility of the dry extract (DE) of leaves of Annona muricata L. with pharmaceutical...     

A rich vehicle routing problem dealing with perishable food: a case study

This paper presents a successful application of operations research techniques in guiding the decision making process to achieve a superior operational efficiency in core activities. We focus on a rich vehicle routing problem faced by a Portuguese food distribution company on a daily basis. This problem can be described as a heterogeneous fleet site dependent vehicle routing problem with multiple time windows. We use the adaptative large neighbourhood search framework, which has proven to be effective to solve a variety of different vehicle routing problems. Our plans are compared against those of the company and the impact that the proposed decision support tool may have in terms of cost savings is shown. The algorithm converges quickly giving the planner considerably more time to focus on value-added tasks, rather than manually correct the routing schedule. Moreover, contrarily to the necessary adaptation time of the planner, the tool is quite flexible in following market changes, such as the introduction of new customers or new products.     

Multi-Objective Biclustering: When Non-dominated Solutions are not Enough

The biclustering technique was developed to avoid some of the drawbacks presented by standard clustering techniques, such as their impossibility of finding correlating data under a subset of features, and, consequently, to allow the extraction of more accurate information from datasets. Given that biclustering requires the optimization of at least two conflicting objectives (residue and volume) and that multiple independent solutions are desirable as the outcome, a few multi-objective evolutionary algorithms for biclustering were proposed in the literature. However, these algorithms only focus their search in the generation of a global set of non-dominated biclusters, which may be insufficient for most of the problems as the coverage of the dataset can be compromised. In order to overcome such problem, a multi-objective artificial immune system capable of performing a multipopulation search, named MOM-aiNet, was proposed. In this work, the MOM-aiNet algorithm will be described in detail, and an extensive set of experimental comparisons will be performed, with the obtained results of MOM-aiNet being confronted with those produced by the popular CC algorithm, by another immune-inspired approach for biclustering (BIC-aiNet), and by the multi-objective approach for biclustering proposed by Mitra & Banka.     

Number concentrations and size distributions of nanoparticles during the use of hand tools in refurbishment activities

Hand tools, such as a sledgehammer, are widely used in refurbishment activities; nonetheless, there is very little knowledge on nanoparticle generation. We measured particle number size distributions (PSDs) and concentrations (PNCs) in the 10–420 nm using a NanoScan scanning mobility particle sizer (SMPS) during the use of hand tools (i.e., sanding and removal of wall) in a real indoor refurbishment environment. Results indicated that refurbishment activities from removal of wall increased average PNCs by ~?6 times over the background while it was ~?1.5 times higher than sanding. The highest total PNC was 1.9?×?10⁵ particles cm^?3 that corresponded to removal of wall activities. For sanding activities, PNC was lower as the coat of the plaster was probably slightly wet. Moreover, comparison between the two principal activities showed a similar peak in the accumulation mode (~?65 nm), with a monomodal pattern. Results suggest that removal of wall activities emitted nanoparticles with a 59% of contribution in the Aitken mode. According to these data, it can be inferred that the application of hand tools in refurbishment activities generates lower total PNC than using electromechanical equipment. This study may contribute to our understanding of nanoparticle generation in refurbishment activities.

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