Lagrangean heuristics combined with reoptimization for the 0-1 bidimensional knapsack problem

First, this paper deals with lagrangean heuristics for the 0-1 bidimensional knapsack problem. A projected subgradient algorithm is performed for solving a lagrangean dual of the problem, to improve the convergence of the classical subgradient algorithm. Secondly, a local search is introduced to improve the lower bound on the value of the biknapsack produced by lagrangean heuristics. Thirdly, a variable fixing phase is embedded in the process. Finally, the sequence of 0-1 one-dimensional knapsack instances obtained from the algorithm are solved by using reoptimization techniques in order to reduce the total computational time effort. Computational results are presented.     

A comparative study of heavy-atom effects on the room-temperature phosphorescence of biologically important purines

Room-temperature phosphorescence (r.t.p.) of nine biologically important purines on filter paper is studied. The heavy-atom effect leads to a significant enhancement of r.t.p. signals, with the trend being Tl⁺ > Pb²⁺ ? I — ? Sm³⁺ for most purines. Absolute limits of detection range from 40 pg (purine) to 19 ng (theophylline).     

Scale-up synthesis of zinc borate from the reaction of zinc oxide and boric acid in aqueous medium

Synthesis of zinc borate was conducted in a laboratory and a pilot scale batch reactor to see the influence of process variables on the reaction parameters and the final product, 2ZnO·3B₂O₃·3.5H₂O. Effects of stirring speed, presence of baffles, amount of seed, particle size and purity of zinc oxide, and mole ratio of H₃BO₃:ZnO on the zinc borate formation reaction were examined at a constant temperature of 85 °C in a laboratory (4 L) and a pilot scale (85 L) reactor. Products obtained from the reaction in both reactors were characterized by chemical analysis, X-ray diffraction, particle size distribution analysis, thermal gravimetric analysis and scanning electron microscopy. The kinetic data for the zinc borate production reaction was fit by using the logistic model. The results revealed that the specific reaction rate, a model parameter, decreases with increase in particle size of zinc oxide and the presence of baffles, but increases with increase in stirring speed and purity of zinc oxide; however, it is unaffected with the changes in the amount of seed and reactants ratio. The reaction completion time is unaffected by scaling-up.     

The effect of pH on the room-temperature phosphorescence properties of several purine and pyrimidine derivatives

Room-temperature phosphorescence (RTP) spectra of eleven purines and pyrimidines adsorbed on Whatman No. 40 filter paper have been determined in acidic, neutral and basic media. RTP excitation and emission wavelengths do not vary significantly with pH. For most compounds, use of basic (pH approximately 13) solutions yields stronger RTP signals than use of neutral or acidic (pH approximately 1.6) solutions. Exceptions are adenine, theobromine and theophylline, which give larger RTP signals when in neutral than in basic conditions. The existence of differences in phosphorescence quantum yields between the various ionic species as well as of specific pH-related interactions with the substrate is discussed. Absolute limits of detection, ranging between 0.4 and 38 ng for selected compounds, depend on the pH of the analyte solution.     

Synthesis and Structure of a Copper Complex of a Macrocyclic Ligand with Dissimilar HN+N(Amino)O2 and N2(Imino)O2 Inners

Abstract The copper complex [Cu(C₂₃H₂₇Br₂N₄O₂)(H₂O)(NO₃)]₂ was synthesized and characterized by X-ray diffraction. The complex crystallizes in the triclinic system with space group P-1, lattice parameters: a = 13.2293(18) (?), b = 14.184(20) (?), c = 16.522(23) (?), α = 91.923(2)°, β = 111.777(2)°, γ = 111.259(2)°, V = 2632.0(6) ?³, Z = 4, D _c = 0.88 Mg m⁻³. In the title compound [Cu(C₂₃H₂₇Br₂N₄O₂)(H₂O)(NO₃)]₂, the coordination polyhedron of the Cu atom is a square-planar environment. The structure consists of mononuclear units in which the copper(II) ions are linked in the plane by N, N′ iminato and O, O′ phenoxo atoms. In addition the crystal lattice contains one water molecule per unit. Graphical Abstract Dissymmetric ligand was efficiently synthesized and used to prepfsare a copper(II) complex which was characterized by X-ray diffraction      

Oligomeric cadmium-phthalocyanine complexes: novel supramolecular free radical structures

Certain cadmium-metallated phthalocyanines give rise to EPR active triple-decker sandwich complexes containing two Cd ions and three phthalocyanine (Pc) ligands. These have been shown to form when the ligands bear either eight non- peripheral alkyl or alkenyl substituents or eight peripheral 2-ethylhexyl groups. They can be derived either from three equivalents of a cadmium phthalocyanine precursor or from a 2:1 mixture of a cadmium phthalocyanine (CdPc) and a metal-free phthalocyanine (H(2)Pc). The mode of their formation has been investigated by a series of "cross" experiments. The results indicate that the triple-decker structures are formed by a self-assembly process. This is deduced from results that show that they can disassemble and reassemble with incorporation of differently substituted ligands derived from either an H(2)Pc or CdPc. The reassembled structures in these cross experiments can contain more than one ligand that originated from either the added CdPc or, and more surprisingly, the H(2)Pc compound. Mass spectrometry has also established that higher order oligomers can be formed when steric requirements between the alkyl substituents on adjacent rings in the stack are reduced. Thus an isotopic cluster for a Cd(5)Pc(6) complex has been observed when the eight peripheral substituents are hexyl chains and tetrameric complexes are formed when two different ligands are incorporated within a stack, with one carrying substituents at the peripheral sites and the other bearing substituents at the non-peripheral sites.     

Usefulness of cyclodextrin media for the determination of α-cypermethrin by photochemically induced fluorescence: analytical applications to natural waters

The photochemically induced fluorescence (PIF) spectral properties of α-cypermethrin in organic solvents (hexane, dichloromethane, acetonitrile, ethanol) and in cyclodextrin aqueous solutions (β-CD and 2-hydroxypropyl-β-CD, 2-HP-β-CD) were investigated. The photolysis kinetics of α-cypermethrin were evaluated in the various media. The PIF signal was found to be significantly enhanced in the CD media relative to the organic solvents. The stoichiometry and the formation constants of the α-cypermethrin inclusion complexes formed with the CDs were determined. The analytical performances of the PIF method were improved in the presence of HP-β-CD relative to the other media, and a CD-enhanced PIF analytical method was developed. The limits of detection and limits of quantification ranged, respectively, between 6 and 98 ng/mL and between 24 and 343 ng/mL, depending on the medium. Application to the analysis of tap water and Senegal natural water samples collected close to agricultural areas and spiked with α-cypermethrin yielded satisfactory recoveries going from about 77% to 98%. An interference study of foreign species, including pesticides and inorganic ions likely to be present in natural waters, was also carried out. Figure Photolysis reaction of α-cypermethrin in presence of HP-β-CD     

Spectrofluorimetric Study of an Inclusion Complex of 2-Hydroxypropyl-β-Cyclodextrin with the Antitumour 11-Methyl Benzophenothiazine. Analytical Application to Urine

The electronic absorption and fluorescence spectral properties of 11-methyl-12H-benzo[a]phenothiazine (11-MeBPHT) were investigated in various media (water, ethanol, β-cyclodextrin (β-CD) and 2-hydroxypropyl-β-cyclodextrin (HP-β-CD) aqueous solutions). Fluorescence quantum yields were respectively about 20 and 2 times larger in HP-β-CD and β-CD than in water. The formation of a 1:1 stoichiometry inclusion complex between 11-MeBPHT and HP-β-CD (association constant K _f=118±3 M⁻¹ at 20 °C) was studied in aqueous medium by fluorescence spectroscopy. Analytical figures of merit were satisfactory for 11-MeBPHT with linear dynamic ranges over at least two orders of magnitude and limits of detection (LODs) between 0.2 and 1 ng/ml according to the medium. An analytical application to the determination of 11-MeBPHT in human urine samples by the standard addition procedure led to satisfactory recovery percentages (91–108%).     

Photochemical analysis studies-V Photochemical enhancement of the fluorescence signal of the antimalarial plasmocid in liquid solution and on silica-gel thin layers

Ultraviolet irradiation converts the antimalarial plasmocid into a highly fluorescent photoproduct. The effect of pH, solvent composition and irradiation time on the photochemical enhancement of the fluorescence signal of plasmocid has been investigated in solution and on silica-gell thin layers. A significant increase in the fluorescence intensity in very acidic medium is explained by the formation of a triprotonated plasmocid species. The photochemical-fluorescence enhancement factors are particularly large, ranging between about 10 and 20 on silica-gel thin layers. Linear calibration plots are obtained over a concentration range of nearly three orders of magnitude. The photochemical-fluorimetric detection limit of plasmocid on thin layers is 10 ng. The results presented demonstrate the potential of thin-layer phototochemical fluorimetry as a sensitive analytical method.     

Toxicological study of pesticides in air and precipitations of Paris by means of a bioluminescence method

A detailed toxicological study on several pesticides, including chlorothalonil, cyprodynil, dichlobénil, pendimethaline, trifluraline, and α-endosulfan, present at trace levels in air and total atmospheric precipitations of Paris is presented. The pesticides contained in the atmospheric samples, collected during sampling campaigns in February–March 2007, are identified and quantified by a high-performance liquid chromatographic (HPLC)-UV detection method. The toxicity measurements are performed by means of the Microtox® bioluminescence method, based on the evaluation of the bioluminescence inhibition of the Vibrio fischeri marine bacteria at two exposure times to the pesticide solutions. The specific toxicity, corresponding to the particular toxicity of the compound under study and represented by the EC₅₀ parameter, is determined for these pesticides. Also, the global toxicity, which is the toxicity of all micro-pollutants present in the sample under study, is estimated for the extracts of air and atmospheric precipitation (rainwater) samples. The specific toxicities strongly vary with the nature of the pesticide, the EC₅₀ parameter values being comprised between 0.17 and 0.83 mg/mL and 0.15 and 0.66 mg/mL, respectively, for exposure times of 5 and 15 min. The importance of the atmospheric samples’ global toxicity and the respective contribution of the toxic potency of the various pesticides contained in these samples are discussed.