Contributions to the study of organic osmium reagents

The reaction of osmium is examined with two thiourea derivatives and four heterocyclic nitrogen compounds containing the SH-group attached to the ring, and five new colorimetric methods for the determination of osmium in the range 1.04–41.44 μg Os/ml are proposed,     

Insulated wall potential stabilization modes in gas discharges

Arguments for demonstrating the contribution of the ion current in the process of wall potential stabilization at a positive value and the results of some experiments supporting this viewpoint, are presented. It is also shown that the variation in gas pressure leads to a change in the number of possible stabilization modes. It is argued that the values of the stable wall potentials are determined by the secondary emission properties of the wall surface, the tube configuration and the values of the charged particle fluxes to the wall. The wall-cathode and wall-anode capacitances may influence only the direction in which the wall potential will drift during the stabilization process, in the case when two stable values of the wall potential exist.     

Continuous‐wave optical parametric oscillator based infrared spectroscopy for sensitive molecular gas sensing

Over the past 10 years, with the advent of new crystals designs and a new generation of pump lasers, continuous‐wave (cw) optical parametric oscillators (OPOs) have developed into mature monochromatic light sources. Nowadays, cw OPOs can fulfill a wide variety of criteria for sensitive molecular gas sensing. It can access the mid‐infrared wavelength region, where many molecules have their fundamental rotational‐vibrational transitions, with high power. This high power combined with wide wavelength tuning and narrow linewidth creates excellent conditions for sensitive, high‐resolution spectroscopy. OPOs combined with robust methods, such as photoacoustic spectroscopy and cavity‐enhanced spectroscopy, are well suited for field measurements and remote‐sensing applications. The wide tunability of cw OPOs allows detection of larger molecules with broad absorption band structures, and its fast scanning capabilities allow rapid detection of trace gases, the latter is a demand for life‐science applications. After a short introduction about the physical principle of cw OPOs, with its most recent physical developments, this review focuses on sensitive molecular gas sensing with a variety of spectroscopic applications in atmospheric and life sciences.     

ESR study of some asymmetric-triazine copper(II) complexes having high antiviral activity

Electron paramagnetic resonance (EPR) spectroscopy and molecular dynamics calculations have been used to compare the chemical environments of Cu(II) in three substituted asymmetric-triazine (as-triazine) complexes with a closely related complex that was reported previously to have Superoxide dismutase (SOD) and antiviral activities. The structure most strongly associated with the biological activity appears to be planar with two 6-membered chelate rings having 2N2O coordination around the copper atom.     

Simple Zeros of the Riemann Zeta-Function

Assuming the Riemann Hypothesis, Montgomery showed by meansof his pair correlation method that at least two-thirds of thezeros of Riemann's zeta-function are simple. Later he and Taylorimproved this to 67.25 percent and, more recently, Cheer andGoldston increased the percentage to 67.2753. Here we proveby a new method that if the Riemann and Generalized LindelöofHypotheses hold, then at least 70.3704 percent of the zerosare simple and at least 84.5679 percent are distinct. Our methoduses mean value estimates for various functions defined by Dirichletseries sampled at the zeros of the Riemann zeta-function. 1991Mathematics Subject Classification: 11M26.     

Viscoplastic creep of rocks around a lined tunnel

A rock-support analysis is done assuming that the rock behaves elastic/viscoplastically while the support can be any kind of nonlinear support. The case of circular tunnels is considered and the formulation of the mathematical problem is discussed. Furthermore, the creep of rock around a tunnel with nonlinear supports (called “yieldable” or “self-adapting” supports) to limit the closure of the tunnel is studied. It is shown that the ultimate ground reaction is not unique since it depends on the loading history such as excavation layout and support design. For relatively small pressures exerted by the support, it is shown that the onset of failure by dilatancy can be determined. Two kinds of solutions are given: a simplified approximate one, which is easy to apply and with which the qualitative discussion of the solution is simple and revealing, and a more rigorous general elaborate numerical solution obtained by using computer programs.