A comparison of two algorithms for the assignment problem

State-of-the-art computational results have shown that the shortest augmenting path (SAP) methods are more efficient than other primal-dual and primal-simplex based methods for solving the linear assignment problem on uniprocessor computers. There is, however, some controversy concerning their merits when compared with Bertsekas' auction algorithm on multiprocessor computers. In this study we investigate the performance of these competing methods on the Alliant FX/8. For each method, theoretical motivation, sources of parallelism and computational results are presented.     

Characterization of synthesizedA-zeolite

Confirmations of the successful synthesis of a particular zeolite demand investigation of the crystals by XRD, SEM, MAS-NMR and chemical analysis. In this work, we have used the DTA exothermic lattice breakdown of theA-zeolite, which gives typical peaks at around 900–1200°C for characterization. The effects ofpH, concentration, time of crystallization and temperature were studied and it was quickly and easily possible to distinguishA-zeolite formation from others originating from the synthesis matrix under different conditions by using DTA/TG analyses. The parameters were optimized for the synthesis of the zeolite and DTA measurements yielded enough information to identify theA-zeolite; this was confirmed by XRD and SEM.     

Periodic unfolding and Robin problems in perforated domains

The periodic unfolding method was introduced in 2002 by D. Cioranescu et al. for the study of classical periodic homogenization. In this Note, we extend this method to perforated domains introducing also a boundary unfolding operator. As an application, we study the homogenization of some elliptic problems with Robin condition on the boundary of the holes. To cite this article: D. Cioranescu et al., C. R. Acad. Sci. Paris, Ser. I 342 (2006).     

Two New and a Known Compound from Lawsonia inermis

A new obtusafuran derivative, lawsonicin ( 1 ), and a new naphthaquinone, lawsonadeem ( 2 ), along with a known constituent, vomifoliol ( 3 ), were isolated from the aerial parts of Lawsonia alba and characterized by chemical transformation and spectroscopic experiments, including 2D‐NMR techniques.     

The crystal and molecular structure of DI-trans-β-styrylmercury

The structure of di-trans-β-styrylmercury has been determined by single crystal X-ray methods from counter data. The compound crystallizes in the orthorhombic space group Pbcn with unit cell dimensions a 15.413(6), b 11.161(9), c 7.668(5) Å, V 1319(1) ų, D_calc 2.049 g/cm³, and Z = 4. The crystal was solved by conventional heavy atom techniques. The crystal consists of individual molecular units with the mercury atom located on a two fold axis of symmetry. The CHgC fragment is nearly linear with an angle of 178°. The β-styryl groups are oriented so that a dihedral angle of 66.8° is formed between the planes defined by HgC(1)C(2) and HgC(1)′C(2)′ fragments. The HgC bond distance is 2.07(4) Å.     

Synthesis and antimycobacterial activity of some beta-carboline alkaloids

In view of the attributed medicinal properties of beta-carboline alkaloids, some new O-acyl derivatives of beta-carboline alkaloid--harmol, were prepared and tested for possible antimycobacterial activity against Mycobacterium tuberculosis H37Rv.     

Metal chelates of phosphonate-containing ligands-II: stability constants of some beta-styrylphosphonic acid metal chelates

The synthesis and properties of beta-styrylphosphonic acid (SPA) are reported. The values of the protonation constants of the ligand were determined potentiometrically at different ionic strengths and in the temperature range 0-65 degrees. The enthalpy and entropy of protonation have been calculated by using the van't Hoff isochore. The protonation process is endothermic and is stabilized by a relatively large positive entropy change. The stability constants of the complexes formed between SPA and the bivalent Mg, Ca, Ba, Co, Ni and Pd ions at 25 degrees and ionic strength of 0.12M KNO(3) were also determined. All measurements were carried out in 18% dimethylformamide-water mixture.     

Co-activation of Gi and Gq proteins exerts synergistic effect on human platelet aggregation through activation of phospholipase C and Ca2+ signalling pathways

Our previous studies have shown that subthreshold concentrations of two platelet agonists exert synergistic effects on platelet aggregation. Here we studied the mechanism of synergistic interaction of 5-hydroxytryptamine (5-HT) and epinephrine mediated platelet aggregation. We show that 5-HT had no or little effect on aggregation but it did potentiate the aggregation response of epinephrine. The synergistic interaction of 5-HT (1-5 microM) and epinephrine (0.5-2 microM) was inhibited by alpha2-adrenoceptor blocker (yohimbine; IC50= 0.4 microM), calcium channel blockers (verapamil and diltiazem with IC50 of 10 and 48 mM, respectively), PLC inhibitor (U73122; IC50=6 microM) and nitric oxide (NO) donor, SNAP (IC50=1.6 microM)). The data suggest that synergistic effects of platelet agonists are receptor-mediated and occur through multiple signalling pathways including the activation PLC/Ca2+ signalling cascades.     

Microdetermination of phenols, carboxylic acids and phenolic acids by potentiometric and visual titrations in dimethylformamide

Potentiometric titration of phenols with sodium methoxide in dimethylformamide, with a glass-calomel electrode system, is limited to monohydric phenols substituted with electron-attracting groups and dihydric phenols in which the two -OH groups are substituted in isolated benzene rings. Brilliant Orange has proved to be a suitable indicator in the titration of all types of mono- and dihydric phenols. Titan Yellow is recommended as indicator for the titration of carboxylic acids. Simultaneous visual titration of -OH and -COOH groups is also described. A detailed study with 62 structurally different compounds covering the various groups is reported, and a suitable procedure for the microdetermination of each class of these compounds with an error of +/- 0.2% absolute or less is presented.