The 0-1 bidimensional knapsack problem: Toward an efficient high-level primitive tool

Efficient codes exist for exactly solving the 0-1 knapsack problem, which is a common primitive structure in relaxation and decomposition techniques for the solution of general models. We suggest moving to a higher primitive level by using the bidimensional knapsack, which can be used to enhance linear programming or Lagrangean type classical relaxations.With the ultimate aim of providing an exact and efficient solution to the bidimensional knapsack problem, we describe here a heuristic approach based on surrogate duality. In particular, we consider the usefulness of a specific preprocessing phase before a possible enumerative phase.Extensive numerical experiments, based on test problems from the literature as well as randomly generated instances, show that our code compares favorably with the GP procedure developed by Gavish and Pirkul for the multidimensional case.     

Complexing properties of an N,N′-methylated diaza-crown-ether

The nature and stability of some transition and heavy metal cation complexes of an N,N′-methylated diaza-crown-ether have been determined in 0.1 M Et₄NClO₄ aqueous solution by means of pH metric measurements. The results are compared to previous ones concerning the homologous unmethylated ligand.     

PHOTODYNAMIC KILLING OF Dictyostelium discoideum AMOEBAE MEDIATED BY 4',5'-DIIODOFLUORESCEIN ISOTHIOCYANATE DEXTRAN. A STRATEGY FOR THE ISOLATION OF THERMOCONDITIONAL ENDOCYTOSIS MUTANTS

4′, 5′-Diiodofluorescein dextran has been synthesized by iodination of fluorescein dextran and it was used as a sensitizer in photodynamic killing of amoebae of the cellular slime mold Dictyostelium discoideum. Amoebae from axenic strain AX2 incubated in the presence of 4′,5′-diiodofluorescein dextran efficiently internalized the molecule by fluid-phase pinocytosis. Subsequently, illumination of cells showed dose- and time-dependent loss of viability. The tertiary amine, 2,4- diaza[2,2,2]bicyclooctane, significantly decreased phototoxicity, whereas the presence of D₂O increased phototoxicity. These effects were fully consistent with a role for excited-state singlet oxygen generated inside the endosomal compartments in the mechanism of photoinjury. A strategy was developed to enrich for temperature-sensitive Dictyostelium endocytosis mutants in a nitrosoguanidine mutagenized population. Incubation with 4′,5′-diiodofluorescein dextran at 27°C to load endosomal compartments was followed by light treatment to kill parent-type cells selectively. In contrast, mutants unable to internalize the fluid-phase marker would survive the treatment. Six temperature-sensitive clones were selected that grew normally at 21°C but did not grow at 27°C. They all showed markedly decreased fluid-phase pinocytosis capacity at nonpermissive temperature as compared to their activity at 21 °C. These mutant strains should be useful in studies designed to characterize endocytosis mechanisms in Dictyostelium.     

Relationship between vitamin D status and skin phototype in general adult population

A link between bone mineral density and skin color has been reported recently, and pigmentation has been shown to affect cutaneous vitamin D production. In the present study, we investigated the relationship between phototype, global self-assessed sun exposure, geographical location and vitamin D serum levels in 1191 French adults. When the factors were analyzed separately, individuals with lower phototypes as well as those with lower sun exposure showed significantly lower levels of vitamin D than those with darker phototypes or those with higher sun exposure. However, when factors were analyzed as a whole, the vitamin D status was no longer linked with the phototype, but with sun exposure and geographical location. Since phototypes and global self-assessments of sun exposure were positively linked, our data suggest that lower vitamin D levels in fair-skinned individuals are due to their sun exposure behavior.     

ELECTRON SPIN RESONANCE OF MELANIN FROM HAIR. EFFECTS OF TEMPERATURE, pH AND LIGHT IRRADIATION

Abstract— The variation with temperature, pH and light of the ESR signal of hydrated melanin powders from Japanese black hair has been studied. An explanation of the results is proposed on the basis of quinhydrone type complexes and of acid-base equilibria of melanin and its semiquinone radicals. During exposure to light of wavelengths 254–600 nm, both stable and unstable radicals have been observed. The action spectrum for the formation of stable melanin radicals has been determined.     

Etude comparative des composés TiX2 (X = S,Se, Te). Structures de TiTe2 et TiSeTe

The evolution of crystal-structure and chemical-bond characteristics is studied for the series of isotypical compounds TiX₂, with X = S, Se, Te. The structure determination of TiTe₂ and TiSeTe confirms the existence of an increasing trigonal C_3v distortion of metal sites when the chalcogen electronegativity decreases. The ESCA study shows that this distortion is associated with augmentation of the covalent or metallic character of the bonds. The structural and spectroscopic differences appearing from TiS₂ to TiSe₂ can be interpreted by an orbital delocalization in TiSe₂ and TiTe₂, which would explain the semimetallic behavior of these compounds.     

Purification and characterization of an intracellular β-glucosidase from a Candida sake strain isolated from fruit juices

A yeast strain isolated in the laboratory from fruit juices was studied and classified as Candida sake. The strain produces an intracellular beta-glucosidase when grown with cellobiose as the carbon source. The enzyme was purified by ion-exchange chromatography and gel filtration. The molecular mass of the purified intracellular beta-glucosidase, estimated by gel filtration, was 240 kDa. The tetrameric structure of the beta-glucosidase was determined following treatment of the purified enzyme with sodium dodecyl sulfate. The enzyme exhibited optimum activity at 52 degrees C and pH 4.25 with citrate-phosphate buffer. The enzyme was active against soluble glycosides with the (1-->4)-beta configuration, and from Lineweaver Burk plots, a Km value of 6.9 mmol/L was found for p-nitrophenyl-beta-D-glucopyranoside. The beta-glucosidase was found to be tolerant to glucose inhibition with a Ki value of 0.2 mol/L.     

Microfluidic systems in proteomics

We present the state-of-the-art in miniaturized sample preparation, immunoassays, one-dimensional and multidimensional analyte separations, and coupling of microdevices with electrospray ionization-mass spectrometry. Hyphenation of these different techniques and their relevance to proteomics will be discussed. In particular, we will show that analytical performances of microfluidic analytical systems are already close to fulfill the requirements for proteomics, and that miniaturization results at the same time in a dramatic increase in analysis throughput. Throughout this review, some examples of analytical operations that cannot be achieved without microfluidics will be emphasized. Finally, conditions for the spreading of microanalytical systems in routine proteomic labs will be discussed.     

Ab initio study of some CH3OCXYCH2 radicals: The influence of anomeric effects on their structure and their stability

Optimized equilibrium geometries and rotational transition structures for CH₃OCH XCH₂ (X = H, F, CH₃, NH₂) and CH₃OCF₂CH₂ radicals are obtained by using unrestructed Hartree-Fock (UHF) and second-order Møller-Plesset perturbation (UMP2) theory; a standard 6-31G* basis set is used for geometry optmizations; single-point energies for all stable rotamers are obtained at the UMP4/6-31 + G*//UMP2/6-31G* level. By analysis of rotamers, it is apparent that an anomeric effect exists for X = F and to a lesser extent for X = NH₂. Several isodesmic reactions have been studied for the purpose of obtaining theoretical heats of formation and stabilization energies (SE) of these β substituted radicals and their α isomers; the examination of computed SE shows that in the case of CH₃OCHFCH₂ and CH₃OCF₂CH₂ radicals, a significant extra stabilization induced by the anomeric effect occurs. The question of n_O → σ negative hyperconjugation in β-substituted radicals was explored with the aid of natural bond orbital (NBO) energetic analysis; it appears that n_O → σ delocalization plays a predominant role in the conformational preference and stabilization of β fluoro derivatives; on the other hand, the stabilization arising from the oxygen lone pair into the σ orbital does not appear to be the key factor in the conformational preference of the CH₃OCHNH₂CH₂ radical. © 1994 by John Wiley & Sons, Inc.     

Polymorphism in micro-, submicro-, and nanocrystalline NaNbO3

NaNbO(3) powders with various particle sizes (ranging from 30 nm to several microns) and well-controlled stoichiometry were obtained through microemulsion-mediated synthesis. The effect of particle size on the phase transformation of the prepared NaNbO(3) powders was studied using X-ray powder diffraction, Raman spectroscopy, and nuclear site group analysis based on these spectroscopic data. Coarsened particles exhibit an orthorhombic Pbcm (D(2h)(11), no. 57) structure corresponding to the bulk structure, as observed for single crystals or powders prepared by conventional solid-state reaction. The crystal symmetry of submicron powders was refined with the space group Pmc2(1) (C(2v)(2), no. 26). The reduced perovskite cell volumes of these submicron powders were most expanded compared to all the other structures. Fine particles with a diameter of less than 70 nm as measured from SEM observations showed an orthorhombic Pmma (D(2h)(5), no. 51) crystal symmetry. The perovskite formula cell of this structure was pseudocubic and was the most compact one. A possible mechanism of the phase transformation is suggested.