Announcements

Mathematical Geosciences -     

Domain wall formation in minerals: I. theory of twin boundary shapes in Na-feldspar

Domains of triclinic Na-feldspar which are a direct consequence of structural strain are investigated theoretically. The following conclusions are arrived at. Only two types of twin walls are created by spontaneous strain, namely the Albite- and Pericline twin walls. If intersections occur, rounded corners are predicted. Any third domain wall close to such an intersection must bend into an S-shape. Narrow domains between two twin walls tend to become needle-shaped close to the intersection with a further, perpendicular, twin wall. The combination of the elastic stiffness coefficients c ₄₄ c ₆₆-c ₄₆ ² is expected to become small at temperatures near to the transition temperature. In the same temperature interval elastic fluctuations occur; their amplitudes and propagation directions are given.     

2,4,6-trinitrotoluene transformation by a tropical marine yeast, Yarrowia lipolytica NCIM 3589

Yarrowia lipolytica NCIM 3589, a tropical marine degrader of hydrocarbons and triglycerides transformed 2,4,6-trinitrotoluene (TNT) very efficiently. Though this yeast could not utilize TNT as the sole carbon or nitrogen source, it was capable of reducing the nitro groups in TNT to aminodinitrotoluene (ADNT). In a complete medium containing glucose and ammonium sulphate as the available carbon and nitrogen sources respectively, the culture was able to completely transform 1 mM (227 ppm) of TNT under such conditions. A dual pathway was found to be functional, one of which resulted in the formation of the hydride-Meisenheimer complex (H(-)TNT) as a transiently accumulating metabolite that was subsequently denitrated to 2,4-dinitrotoluene (2,4-DNT), whereas the other pathway resulted in the formation of amino derivatives. The presence of increasing amounts of reducing equivalents in the form of glucose promoted better growth and the nitroreductases of this yeast to reduce the aromatic ring to 2,4-DNT although, the reduction of the nitro groups to amino groups was the major functional pathway. The ability of this tropical marine yeast to transform TNT into products such as 2,4-DNT which in turn could be metabolized by other microbes has implications in the use of this yeast for bioremediation of TNT polluted marine environments.     

Non-linear dynamo waves in an incompressible medium when the turbulence dissipative coefficients depend on temperature

Non-linear - dynamo waves existing in an incompressible medium with the turbulence dissipative coefficients depending on temperature are studied in this paper. We investigate of - solar non-linear dynamo waves when only the first harmonics of magnetic induction components are included. If we ignore the second harmonics in the non-linear equation, the turbulent magnetic diffusion coefficient increases together with the temperature, the coefficient of turbulent viscosity decreases, and for an interval of time the value of dynamo number is greater than 1. In these conditions a stationary solution of the non-linear equation for the dynamo waves amplitude exists; meaning that the magnetic field is sufficiently excited. The amplitude of the dynamo waves oscillates and becomes stationary. Using these results we can explain the existence of Maunders minimum.     

Proxies for land plant biomass: closed system pyrolysis of some methoxyphenols

Methoxyphenols can be used as proxies for terrestrial biomass when investigating the chemical changes in lignin during hydrothermal alteration. The closed system microscale pyrolysis of 2-methoxyphenol (2-MOP) and 2,6-dimethoxyphenol (2,6-DMP), in the presence of water vapour, has been studied in borosilicate glass vessels. 2-MOP was heated isothermally at temperatures of 330°C for 96 h and 2,6-DMP was heated isothermally at 300°C for 118 h. Pyrolysis of the model compound 2-MOP gave a simple product distribution which was composed mainly of 1,2-dihydroxybenzene with lower amounts of 2-methylphenol and phenol. The prominent reaction products from heating 2,6-DMP were 1,2-dihydroxy-6-methoxybenzene and 2-methoxy-6-methylphenol, with minor amounts of 2-MOP, 1,2-dihydroxybenzene and 2-methylphenol. The decreasing amounts of 2,6-DMP with heating time and the concomitant increase in the amounts of 1,2-dihydroxy-6-methoxybenzene suggested that demethylation had occurred.