Large relativistic effects in molecular properties of the hydride of superheavy element 111

Relativistic and electron correlation contributions in the hydride of the recently discovered superheavy element 111 were studied using ab-initio methods within different relativistic approaches. Relativistic effects decrease the (111)H bond distance by 0.42 Å. As a result of this large bond contraction, the bond distance of (111)H (1.51 Å) is comparable to that of the hydride of its lighter congener AuH (1.52 Å), but below that of AgH (1.60 Å). The dissociation energy is relativistically increased by approximately 1.2 eV and the stretching force constant is more than quadrupled from 1.1 mdyn/Å at the nonrelativistic level to 5.0 mdyn/Å at the relativistic level.     

Multiobjective management of mining under water hazard by game theory

The management of an aquifer is studied under the assumption that the solution of the multiobjective programming model describing the management problem should satisfy a certain set of axioms. It is shown that a certain class of multiobjective problems may be solved by a game-theoretical concept leading to a single objective quasiconvex programming problem. The method is generalization of Nash's cooperative game theoretical model, and may lean on Zeuther's bargaining process. The methodology is applied to the Transdanubian Karstic region in Hungary where three objectives are present: mining costs, water supply and environmental protection. Results are compared with the solution previously obtained by compromise programming with an l₁-norm. It is found that results obtained by the two methods are comparable.     

The adsorption of CO on clean and potassium promoted FeO surfaces

The adsorption of CO on a FeO (wustite) surface was investigated using UPS, AES and temperature programmed desorption. These results are compared to those obtained from the same sample following addition of potassium from the decomposition of KOH. CO adsorption was identified following exposure at 300 K to the potassium free surface. The adsorbed species readily desorbs below 500 K. CO adsorption was poisoned by pre-exposure to oxygen at 300 K. This suggests CO is adsorbed at surface oxygen vacancies. CO induced UPS emission features are different from those typically found for CO chemisorbed on transition metal surfaces. The presence of potassium alters the adsorption behavior of CO. The thermal desorption maximum shifts to 625 K. UPS results indicate molecular CO adsorption at 300 K and upon heating to 470 K CO dissociates. The presence of potassium thus promotes CO dissociation on FeO.     

Experimental strategy for characterization of essential dynamical variables in oscillatory systems: effect of double-layer capacitance on the stability of electrochemical oscillators

An experimentally accessible algorithm for changing the time scale associated with a dynamical variable is proposed. In general, a differential controller can be applied to (a) identify the essential species in oscillatory systems and (b) explore their role in the feedback loops. Here, we report on classifying electrochemical oscillators by changing the time scale over which the electrode potential varies; the type of different electrochemical oscillators is identified based on whether the controlled modification of pseudo-capacitance induces or suppresses current oscillations.     

Infrared laser enhanced reactions: V→V and V→T energy transfer in the O3SiF4O2 system

Rapid V→V energy transfer between SiF₄ and O₃ has been observed following laser excitation of either O₃ or SiF₄. A CO₂ laser tuned to either the 9.6 μ P(30) or P(32) transitions was used to promote vibrational excitation in O₃ and SiF₄, respectively. In experiments employing the P(32) transition, the V→V transfer to O₃ and subsequent reaction of O₃² with NO were used to obtain the rate constant of V→T deactivation of SiF₄² by O₂.

Fractional modulation measurements of the chemiluminescence generated by the O₃ + NO reaction were used in experiments employing the P(30) transition to obtain a rate constant for the V→V energy transfer between O₃² and SiF₄.

     

Kinetics and mechanism of the oxidation of sulfite by chlorine dioxide in a slightly acidic medium

The sulfite-chlorine dioxide reaction was studied by stopped-flow method at I = 0.5 M and at 25.0 +/- 0.1 degrees C in a slightly acidic medium. The stoichiometry was found to be 2 SO(3)(2-) + 2.ClO(2) + H(2)O --> 2SO(4)(2) (-) + Cl(-) + ClO(3)(-) + 2H(+) in *ClO(2) excess and 6SO(3)(2-) + 2*ClO(2) --> S(2)O(6)(2-) + 4SO(4)(2-) + 2Cl(-) in total sulfite excess ([S(IV)] = [H(2)SO(3)] + [HSO(3)(-)] + [SO(3)(2-)]). A nine-step model with four fitted kinetic parameters is suggested in which the proposed adduct *SO(3)ClO(2)(2-) plays a significant role. The pH-dependence of the kinetic traces indicates that SO(3)(2-) reacts much faster with *ClO(2) than HSO(3)(-) does.     

A concise total synthesis of the lichen macrolide (+)-aspicilin

The total synthesis of the polyhydroxylated macrolide (+)-aspicilin 5 is described using as a key step a highly diastereoselective allylation of aldehyde 6 with the uniquely functionalized allylstannane 1. (+)-Aspicilin is obtained in 18 steps and 10% overall yield. [structure: see text]     

A mass spectrometric line for tritium analysis of water and noble gas measurements from different water amounts in the range of microlitres and millilitres

This paper describes the procedure followed for noble gas measurements for litres, millilitres and microlitres of water samples in our laboratory, including sample preparation, mass spectrometric measurement procedure, and the complete calibrations. The preparation line extracts dissolved gases from water samples of volumes of 0.2 μ l to 3 l and it separates them as noble and other chemically active gases. Our compact system handles the following measurements: (i) determination of tritium concentration of environmental water samples by the ³He ingrowth method; (ii) noble gas measurements from surface water and groundwater; and (iii) noble gas measurements from fluid inclusions of solid geological archives (e.g. speleothems). As a result, the tritium measurements have a detection limit of 0.012 TU, and the expectation value (between 1 and 20 TU) is within 0.2 % of the real concentrations with a standard deviation of 2.4 %. The reproducibility of noble gas measurements for water samples of 20–40 ml allows us to determine solubility temperatures by an uncertainty better than 0.5 °C. Moreover, noble gas measurements for tiny water amounts (in the microlitre range) show that the results of the performed calibration measurements for most noble gas isotopes occur with a deviation of less than 2 %. Theoretically, these precisions for noble gas concentrations obtained from measurements of waters samples of a few microlitres allow us to determine noble gas temperatures by an uncertainty of less than 1 °C. Here, we present the first noble gas measurements of tiny amounts of artificial water samples prepared under laboratory conditions.     

In celebration of 30 years of Structural Chemistry: launching a series of prefatory reviews

Structural Chemistry -