Study of the peak effect phenomenon in single crystals of 2H-NbSe2

The weakly pinned single crystals of the hexagonal 2H-NbSe₂ compound have emerged as prototypes for determining and characterizing the phase boundaries of the possible order-disorder transformations in the vortex matter. We present here a status report based on the ac and dc magnetization measurements of the peak effect phenomenon in three crystals of 2H-NbSe₂, in which the critical current densities vary over two orders of magnitude. We sketch the generic vortex phase diagram of a weakly pinned superconductor, which also utilizes theoretical proposals. We also establish the connection between the metastability effects and pinning.     

Multifunctional redox catalysts as selective enhancers of oxidative stress

Certain cancer cells proliferate under conditions of oxidative stress (OS) and might therefore be selectively targeted by redox catalysts. Among these catalysts, compounds containing a chalcogen and a quinone redox centre are particularly well suited to respond to the presence of OS. These catalysts combine the specific electrochemical features of quinones and chalcogens. They exhibit high selectivity and efficiency against oxidatively stressed rat PC12, human Jurkat and human Daudi cells in cell culture, where their mode of action most likely involves the catalytic activation of existent and the generation of new reactive oxygen species. The high efficiency and selectivity shown by these catalysts makes them interesting for the development of anti-cancer drugs.     

Short-time vibrational dynamics of acetylene versus its isotopic variants

The short-time intramolecular dynamics of highly vibrationally excited HCCD and DCCD, as determined by classical trajectories, have qualitative features distinct from HCCH and from one another. The possible differences are also considered from the point of view of the symmetries of the normal modes. The short-time evolution will be reflected in the coarse-grained frequency spectrum and could be detectable via stimulation emission pumping.     

Antioxidant-induced yellowing of textiles

The yellowing of white and pastel coloured textiles and garments has been a problem for many years in the textile industry. In the last 15 years much evidence has been published which suggests that a large proportion of storage yellowing is attributable not to the yellowing of fibre substrate or textile finish but to the yellowing of phenolic antioxidants which migrate onto the textiles from polyethylene and polypropylene packaging. These mobile phenolic compounds interact with atmospheric pollutants, particularly oxides of nitrogen, to give yellow compounds. A brief outline of the problems of yellowing is given, together with the identification of the yellow substances produced by BHT (2,6-di-tert-butyl-4-methyl phenol) and possible mechanisms of their formation. Prophylactic measures that can be taken by the garment manufacturer and finisher to prevent or minimise yellowing are also discussed.     

Complex formation in concentrated sulfuric acid between boric acid and quinalizarin or alizarin

The complex formation in concentrated sulfuric acid between boric acid and quinalizarin (1,2,5,8-tetrahydroxyanthraquinone) or alizarin (1,2-dihydroxyanthraquinone) was studied by spectrophotometry. Both systems contained only one species, viz. a complex between one boric acid and one hydroxyanthraquinone molecules. The reactions of boric acid with hydroxyanthraquinones are discussed and compared with the reaction of boric acid with 1,1'-dianthrimide.     

Novel nonperipheral octa-3-hydroxypropylthio substituted metallo-phthalocyanines: synthesis,characterization, and investigation of their electrochemical,photochemical and computational properties

The current study describes the synthesis, electrochemical, computational, and photochemical properties of octa (3-hydroxypropylthio) substituted cobalt (II) ( 4 ), copper (II) ( 5 ), nickel (II) ( 6 ) and zinc(II) ( 7 ) phthalocyanine derivatives. These novel compounds were characterized by elemental analysis,¹H,¹³C NMR, FT-IR, UV-Vis, and MS. The redox behaviors of these metallo-phthalocyanines were investigated by the cyclic voltammetric method. The optimized molecular structure and gauge-including atomic orbital (GIAO)¹H and¹³C NMR chemical shift values of these phthalocyanines in the ground state had been calculated by using B3LYP/6–31G(d,p) basis set. The outcomes of the optimized molecular structure were given and compared with the experimental NMR values. The photochemical properties including photodegradation and singlet oxygen generation of zinc(II) phthalocyanine were studied in DMSO solution for the determination of its photosensitizer behaviors.     

Pseudorapidity distributions of charged particles from Au + Au collisions at the maximum RHIC energy,square root[s(NN)] = 200 GeV

We present charged-particle multiplicities as a function of pseudorapidity and collision centrality for the 197Au+197Au reaction at square root[s(NN)] = 200 GeV. For the 5% most central events we obtain dN(ch)/deta/(eta = 0) = 625+/-55 and N(ch)/(-4.7< or =eta < or =4.7) = 4630 +/- 370, i.e., 14% and 21% increases, respectively, relative to square root[s(NN)] = 130 GeV collisions. Charged-particle production per pair of participant nucleons is found to increase from peripheral to central collisions around midrapidity. These results constrain current models of particle production at the highest RHIC energy.     

The synthesis of a leukotriene with SRS-like activity

The synthesis and biological characteristics of an SRS-like leukotriene are described.