SR XRF and micro-PIXE studies on ancient metallurgy of thirteen Dacian gold bracelets

A thorough microscopic investigation by SR XRF and micro-PIXE brings insight into the probable techniques used in the manufacture of thirteen Dacian gold bracelets, one of the most spectacular archaeological finds ever on the territory of Romania.     

Barbilian’s metrization procedure in the plane yields either Riemannian or Lagrange generalized metrics

In the present paper we answer two questions raised by Barbilian in 1960. First, we study how far can the hypothesis of Barbilian’s metrization procedure can be relaxed. Then, we prove that Barbilian’s metrization procedure in the plane generates either Riemannian metrics or Lagrance generalized metrics not reducible to Finslerian or Langrangian metrics.     

The kinetics of oxiranes addition to bis/2-hydroxyalkyl/disulfides and bis/2-hydroxyalkyl/sulfides in the presence of N,N-dimethylcyclohexylamine

Rate constants for the reaction of oxiranes with bis/2-hydroxyalkyl/disulfides, bis/2-Hydroxyalkyl/sulfides, and 1,6-Hexanediol in the presence of N,N-dimethylcyclohexylamine were studied at the temperature range of 50–90°C. A mechanism of these reactions has been proposed and its kinetic equation has been presented.     

Enantioselective organocatalytic α-sulfenylation of substituted diketopiperazines

The asymmetric organocatalytic α-sulfenylation of substituted piperazine-2,5-diones is reported, with cinchona alkaloids as chiral Lewis bases and electrophilic sulfur transfer reagents. Catalyst loadings, the type of sulfur transfer reagent, temperature, and solvent were investigated in order to optimize the reaction conditions. The effects of ring substitution and the type of catalyst on the yield and enantioselectivity of the reaction are reported.     

Decomposition of Methylene Blue in Water by Corona Discharges

The decomposition of methylene blue (MB) in aqueous solution was investigated using a pulsed corona discharge. The discharge was ignited in the gas bubbled in the solution through several needle electrodes. The influence of treatment time, volume of the treated solution and initial concentration of the dye in solution on MB degradation was studied. The effect of the nature of the gas introduced was also investigated. For the same energy input, MB conversion increased in the order air < argon < oxygen. When using oxygen, the decomposition of MB exceeded 95% after ~20 min plasma treatment. Higher efficiency was obtained for higher treated volume and higher initial concentration. At 90% conversion the yield obtained with oxygen was ~5 g/kWh for an initial concentration of 150 mg/l and a treated volume of solution of 100 ml.