Evaluating cost impacts on reverse logistics using an Economic Order Quantity (EOQ) model with environmental and social considerations

Central European Journal of Operations Research - Societal awareness and legislation changes concerning sustainability have affected how organizations generate value for stakeholders, as well as...     

On the spectral norm of algebraic numbers

In this paper we continue to study the spectral norms and their completions ([4]) in the case of the algebraic closure $ \overline {\mathbb Q} $ of ? in ?. Let $ \widetilde{\overline{\mathbb{Q}}} $ be the completion of $ \overline {\mathbb Q} $ relative to the spectral norm. We prove that $ \widetilde{\overline{\mathbb{Q}}} $ can be identified with the R‐subalgebra of all symmetric functions of C(G), where C(G) denotes the ?‐Banach algebra of all continuous functions defined on the absolute Galois group G = Gal$ {\overline {\mathbb Q}} / {\mathbb Q} $. We prove that any compact, closed to conjugation subset of ? is the pseudo‐orbit of a suitable element of $ \widetilde{\overline{\mathbb{Q}}} $. We also prove that the topological closure of any algebraic number field in $ \widetilde{\overline{\mathbb{Q}}} $ is of the form $\widetilde{\mathbb{Q}[x]}$ with x in $ \widetilde{\overline{\mathbb{Q}}} $.     

A Hybrid Improvement Heuristic for the One-Dimensional Bin Packing Problem

We propose in this work a hybrid improvement procedure for the bin packing problem. This heuristic has several features: the use of lower bounding strategies; the generation of initial solutions by reference to the dual min-max problem; the use of load redistribution based on dominance, differencing, and unbalancing; and the inclusion of an improvement process utilizing tabu search. Encouraging results have been obtained for a very wide range of benchmark instances, illustrating the robustness of the algorithm. The hybrid improvement procedure compares favourably with all other heuristics in the literature. It improved the best known solutions for many of the benchmark instances and found the largest number of optimal solutions with respect to the other available approximate algorithms.     

Imidazol(in)ium carboxylates as N-heterocyclic carbene ligand precursors for Suzuki-Miyaura reactions

Simple catalysts formed in situ from palladium acetate and a variety of imidazolium and imidazolinium carboxylates and dithiocarboxylates have been screened in the coupling of aryl halides with trans-2-phenylvinylboronic acid. Imidazol(in)ium carboxylates show an excellent activity, which compares to that displayed by the parent imidazol(in)ium chlorides, whereas imidazol(in)ium dithiocarboxylates are poorly efficient. Interestingly, the base employed exerts a profound influence on the trans/cis stereochemistry of the coupling product.     

Effects of UV photon irradiation on SiOx (0 < x < 2) structural properties

Thin films of a-SiO_x (0 < x < 2) were prepared by reactive r.f. magnetron sputtering from a polycrystalline-silicon target in an Ar/O₂ gas mixture. The oxygen partial pressure in the deposition chamber was varied so as to obtain films with different values of x. The plasma was monitored, during depositions, by optical emission spectroscopy (OES) system. Energy dispersive X-ray (EDX) measurements and infra-red (IR) spectroscopy were used to study the compositional and structural properties of the deposited layers.Structural modifications of SiO_x thin films have been induced by UV photons’ bombardment (wavelength of 248 nm) using a pulsed laser. IR spectroscopy and X-ray photoemission spectroscopy (XPS) were used to investigate the structural changes as a function of x value and incident energy. SiO_x phase separation by spinodal decomposition was revealed. The IR peak position shifted towards high wavenumber values when the laser energy is increased. Values corresponding to the SiO₂ material (only Si⁴⁺) have been found for laser irradiated samples, independently on the original x value. The phase separation process has a threshold energy that is in agreement with theoretical values calculated for the dissociation energy of the investigated material.For high values of the laser energy, crystalline silicon embedded in oxygen-rich silicon oxide was revealed by Raman spectroscopy.     

Study of interactions of various ionic species with solvents toward the design of receptors

In earlier studies, the interactions of isolated ionic species with various solvents were investigated using ab initio calculations. The ionic species investigated included cations (proton, hydronium, ammonium, and metal cations) and anions (single electron, hydroxide, and halide anions). However in the present study, we investigate the interactions of these ionic species with the solvent in the presence of other competing ionic species. We also elaborate on how the information obtained from these extensive studies have been employed in designing and synthesizing various kinds of novel ionophores and receptors.     

Effect of cyclodextrins on physico-chemical and release properties of Eudragit RS 100 microparticles containing glutathione

The objective of this work was to develop a novel microparticulate system based on the mucoadhesive polymer Eudragit-RS 100 and cyclodextrins (CDs), potentially useful for the oral administration of Glutathione (γ–glutamylcysteinylglycine, GSH). For this purpose, an oil-in-oil (O/O) emulsion-solvent evaporation method was used for the preparation of microparticles (MPs) containing GSH alone or together with one of the following CDs: α-, β-, γ-, methyl-β-(Me-β-), hydroxypropyl-β-(HP-β-) or sulfobutylether-β-cyclodextrin (SBE_7m-β-CD). MPs were obtained by emulsifying a mixture of Eudragit RS 100, GSH, CD and magnesium stearate in acetone or acetonitrile with a mixture of liquid paraffin and Span 80. Size, encapsulation efficiency, and drug release of the prepared MPs were evaluated. The results clearly indicated that all the examined properties were dependent on the water-miscible solvents and CD used. In particular, MPs prepared by using acetone or acetonitrile showed different size distributions with mean diameters in the ranges 82–350 and 15–22 μm, respectively. Moreover, encapsulation efficiency values were found to be high in all cases (71–99%) and was significantly affected by the CD type. The GSH release rates were evaluated employing dissolution media with different pH values (1.2, 6.8 and 7.4) and the following rank order was obtained for MPs prepared using acetone: MPs incorporating Me-β-CD > MPs without CD > MPs incorporating the remaining CDs. On the other hand, MPs prepared using acetonitrile gave the highest GSH release rate. Finally, stability of GSH encapsulated in MPs containing HP-β-CD to enzymatic attack by pepsin A, α-chymotrypsin, and γ-glutamyltranspeptidase was also investigated.     

Synthesis and N.m.r. studies of bis-trisubstituted phosphine platinum(o) and palladium(o) complexes with push-pull olefins

Summary Platinum(0) and palladium(0) complexes of the type: P₂M(R₁R₂C=CR₃R₄) (P=trisubstituted phosphine; R₁, R₂, R₃ and R₄ are different groups having electron acceptor or electron donor properties; M=Pt or Pd) with so called pushpull olefins, have been prepared and characterized. In some cases unusual patterns in the n.m.r. spectra of olefinic protons were observed. The spectra were analyzed by computer simulation and general rules for ABMX patterns for this type of complexes are given.     

Screening and analytical confirmation of sulfonamide residues in milk by capillary electrophoresis-mass spectrometry

A new methodology is proposed to automate the monitoring of sulfonamide residues in milk samples. It combines a screening unit for the total amount of sulfonamide with capillary electrophoresis-mass spectrometry (CE-MS) equipment for processing the samples containing a detectable level of sulfonamide. The screening unit consists of continuous-flow system (CFS) to precipitate the proteins connected on-line to the CE-MS equipment, in which a common characteristic ion of all sulfonamides was monitored with the MS detector by flushing the sample through the capillary. The confirmatory method is based on the purification and preconcentration of sulfonamides in a CFS unit and posterior analysis by CE-MS. The sample treatment unit was also on-line connected to the CE-MS equipment. In order to increase sensitivity, the flow rate of the sheath liquid was diminished from 0.5 to 0.2 microL.min(-1) by increasing the content in water from 0 to 50% and the formic acid from 0.5 to 1.5% in this liquid and by applying an overimposed pressure of 5 mbar during the electrophoretic separation. The method allowed the analysis of 30 samples per hour.     

Selective spectrofluorimetric method for paracetamol determination through coumarinic compound formation

A spectrofluorimetrical selective method was designed for determination of paracetamol in tablets. This important technique can be characterized by its sensitivity, simplicity, celerity and cheaper cost than current official methods. The employed methodology involves coumarinic compound formation obtained by reaction between paracetamol and ethylacetoacetate (EAA) in the presence of sulphuric acid as catalyst. The reaction product is highly fluorescent at 478 nm, being excited at 446 nm.The linear concentration range of the application was 0.1-0.4 μg/ml of paracetamol and the detection limit was 57 ng/ml.The influence of different variables was studied and optimized through chemometric techniques. Applying the above-mentioned method good results were obtained with regard to pharmaceutical formulations containing paracetamol. Therefore, it is relevant to suggest this profitable technique for medicament control analysis.