Solving a multi-objective multi-skilled manpower scheduling model by a fuzzy goal programming approach

Manpower scheduling is an intricate problem in production and service environments with the purpose of generating fair schedules that consider employers’ objectives and employees’ preferences as much as possible. However, sometimes, vagueness of information related to employers’ objectives and employees’ preferences leads to the fuzzy nature of the problem. This paper presents a multi-objective manpower scheduling model regarding the lack of clarity on the target values of employers’ objectives and employees’ preferences. Hence, a fuzzy goal programming model is developed for the presented model. Afterwards, two fuzzy solution approaches are used to convert the fuzzy goal programming model to two single-objective models. Finally, the results obtained by both single-objective models are compared with each other to select the solution that has the greatest degree of the satisfaction level of employers’ objectives and employees’ preferences.     

Determination of acetone in seawater using derivatization solid-phase microextraction

Acetone plays an important role in the chemistry of both the atmosphere and the ocean, due to its potential effect on the tropospheric HO_x (= HO + HO₂) budget, as well as its environmental and health effects. We discuss the development of a mobile, sensitive, selective, economical and facile method for the determination of acetone in seawater. The method consists of derivatizing acetone to its pentafluorobenzyl oxime using 1,2,3,4,5-pentafluorobenzylhydroxylamine (PFBHA), followed by solid-phase microextraction (SPME) and analysis by gas chromatography/mass spectrometry (GC/MS). A detection limit of 3.0 nM was achieved. The buffering capacity of seawater imposes challenges in using the method’s optimum pH (3.7) on seawater samples, requiring calibration standards to be made in buffered salt water and the acidification of seawater samples and standards prior to extraction. We employed the technique for analysis of selected surface seawater samples taken on the Nordic seas during the ARK-XX/1 cruise (R.V. Polarstern). An upper limit of 5.5–9.6 nM was observed for acetone in these waters, the first acetone measurements reported for far North Atlantic and Arctic waters. Simplified schematic of transformations of organic compounds at the atmosphere–ocean interface     

Photocatalytic activities of multilayered ZnO-based thin films prepared by sol–gel route: effect of SnO2 heterojunction layer

In present study, ZnO/SnO₂/ZnO/SnO₂/ZnO multi–layer, ZnO/SnO₂/ZnO triple layer and ZnO single layer films have been deposited on glass substrate by sol–gel dip–coating technique. The structural and optical properties of thin films have been investigated by X-ray diffractometer, UV–visible, photoluminescence spectroscopies and scanning electron microscopy. The structural analysis reveals structural inhomogeneities and different crystallite growth processes as function of number of deposited layers. A comparison between photocatalytic activity of zinc oxide samples toward photodegradation of phenol, 4-aminophenol and 4-nitrophenol has been performed under UV light irradiation. Experiments were conducted to study the effects of operational parameters on the degradation rate. Pseudo-first-order photodegradation kinetics was observed on all films and the reaction constants were determined. The results showed that the photocatalytic activity of ZnO multi–layer film was superior to that of the ZnO single- and triple-layer films. Differences in film efficiencies can be attributed to differences in crystallinity, surface morphology, defect concentration of oxygen vacancy and to presence of SnO₂ sublayer that may act as trap for electrons generated in the ZnO layer thus preventing electron–hole recombination. The results reveal that SnO₂ hetrojunction layers improve crystalline quality, optical and photocatalytic properties of ZnO multilayered films.     

A one-pot three-component reactions for the synthesis of fully substituted spiro indeno[1,2-b]quinoxaline derivatives

An efficient and simple approach of the synthesis of some spiro indeno[1,2-b]quinoxalines via a one-pot three-component reaction of 11H-indeno[1,2-b]quinoxalin-11-one, pyrazolone, and malononitrile in the presence of Na₂CO₃ at 70 °C is reported. This reaction has shown to have high atom economy.     

Alteration of protein profile in rat liver of animals exposed to subacute diazinon: A proteomic approach

Diazinon, an organophosphorus insecticide, is employed to control pests in agriculture. Diazinon may contaminate the environment during the manufacturing process or agricultural application. Previous studies have revealed that diazinon may induce alteration in the protein profile of the liver. Here, a proteomics approach was used to investigate the effects on the protein profile in the liver of rats of subacute oral exposures at 15 mg/kg of diazinon. Liver proteins were separated using 2D‐PAGE, and stained by MS‐compatible silver staining and/or the fluorescent SYPRO® Ruby protein gel stain. Gels were scanned and analyzed using the Image Master software. Differentially displayed protein species were identified using MALDI‐TOF/TOF and MASCOT software. Significantly altered protein species were identified to be involved in apoptosis, cell metabolism, transport, and antioxidant systems. Exposure to diazinon decreased levels of some species of catalase, peroxiredoxin‐6, 3‐ketoacyl‐CoA thiolase, and glucose regulated protein78, whereas the level of protein disulfide‐isomerase A3 increased. Our results suggested that diazinon may induce hepatotoxicity through oxidative stress, apoptosis, and metabolic disorders in rat liver.     

The First Neutral Dinuclear Vanadium Complex Comprising VO and VO2 Cores: Synthesis,Structure, Electrochemical Properties,and Catalytic Activity

A neutral dinuclear vanadium complex containing both oxido and dioxidovanadium cores with hydrazone based ligand, [VO(OCH₃)(CH₃OH)(HL)VO₂] ( 1 ) {H₄L = bis[(E)‐N′‐(5‐bromo‐2‐hydroxybenzylidene)]‐carbohydrazide}, was synthesized and fully characterized by X‐ray crystallography and spectroscopic methods (IR, UV/Vis, NMR). The ligand acts as a trinegative hexadentate N₃O₃ donor ligand to form a dinuclear complex and during the reaction V⁴⁺ is oxidized to V⁵⁺. The coordination polyhedra are a VO₅N distorted octahedron for the mono‐oxidovanadium core and a VO₃N₂ trigonal bipyramid for the dioxidovanadium core. The results of catalytic reactions indicate that 1 is a highly active catalyst in the clean epoxidation reaction of cis‐cyclooctene using aqueous hydrogen peroxide in acetonitrile. Cyclic voltammetric experiments of 1 in DMSO reveal two quasi‐reversible peaks due to the VO³⁺–VO²⁺ and VO₂⁺–VO₂ couples.     

On the mechanism of the conversion of methanol to 2,2,3-trimethylbutane (triptane) over zinc iodide

Methanol is converted to a mixture of hydrocarbons by reaction with zinc iodide at 200 degrees C with one highly branched alkane, 2,2,3-trimethylbutane (triptane), being obtained in surprisingly high selectivity. Mechanistic studies implicate a two-stage process, the first involving heterogeneously catalyzed formation of a carbon-carbon-bonded species, probably ethylene, that undergoes homogeneously catalyzed sequential cationic methylation to higher hydrocarbons. The first stage can be bypassed by addition of olefins, higher alcohols, or arenes, which act as initiators. Rationales for the particular activity of zinc iodide and for the selectivity to triptane are proposed.