Prevention of benzene-induced myelotoxicity by nonsteroidal anti-inflammatory drugs.

Benzene affects hematopoietic progenitor cells leading to bone marrow depression and genotoxic effects such as micronucleus formation. Progenitor cell proliferation and differentiation are inhibited by prostaglandins produced by macrophages. Administration of benzene to DBA/2 or C57BL/6 mice caused a dose-dependent bone marrow depression and a significant increase in marrow prostaglandin E level and both were prevented by the coadministration of indomethacin and other inhibitors of the cyclooxygenase component of prostaglandin H synthase. Levels of benzene that decreased bone marrow cellularity also caused genotoxic effects measured as increased micronucleated polychromatic erythrocytes in peripheral blood, which was also prevented by the coadministration of indomethacin. These results suggest a possible role for prostaglandin synthase in benzene myelotoxicity; a mechanism by which this might occur is presented

New Experimental Equipment Recreating Geo-Reservoir Conditions in Large, Fractured, Porous Samples to Investigate Coupled Thermal, Hydraulic and Polyaxial Stress Processes

Abstract Use of the subsurface for energy resources (enhanced geothermal systems, conventional and unconventional hydrocarbons), or for storage of waste (CO2, radioactive), requires the prediction of how fluids and the fractured porous rock mass interact. The GREAT cell (Geo-Reservoir Experimental Analogue Technology) is designed to recreate subsurface conditions in the laboratory to a depth of 3.5 km on 200 mm diameter rock samples containing fracture networks, thereby enabling these predictions to be validated. The cell represents an important new development in experimental technology, uniquely creating a truly polyaxial rotatable stress field, facilitating fluid flow through samples, and employing state of the art fibre optic strain sensing, capable of thousands of detailed measurements per hour. The cell’s mechanical and hydraulic operation is demonstrated by applying multiple continuous orientations of principal stress to a homogeneous benchmark sample, and to a fractured sample with a dipole borehole fluid fracture flow experiment, with backpressure. Sample strain for multiple stress orientations is compared to numerical simulations validating the operation of the cell. Fracture permeability as a function of the direction and magnitude of the stress field is presented. Such experiments were not possible to date using current state of the art geotechnical equipment

Activation of Small Alkanes in Ga-Exchanged Zeolites: A Quantum Chemical Study of Ethane Dehydrogenation

Quantum chemical calculations on the mechanism of ethane dehydrogenation catalyzed by Ga-exchanged zeolites have been undertaken. Two forms of gallium, adsorbed dihydridegallium ion GaH2+Z- and adsorbed gallyl ion [GaO]+Z-, were considered. It was found that GaH2+Z- is the likely active catalyst. On the contrary, [GaO]+Z- cannot be a working catalyst in nonoxidative conditions, because regeneration of this form is very difficult. Activation of ethane by GaH2+Z- occurs via an “alkyl” mechanism and the gallium atom acts as an acceptor of the ethyl group. The “carbenium” activation of ethane, with gallium abstracting a hydride ion, is much (ca. 51 kcal/mol) more difficult. The catalytic cycle for the “alkyl” activation consists of three elementary steps:  (i) rupture of the ethane C−H bond; (ii) formation of dihydrogen from the Brønsted proton and hydrogen bound to Ga; (iii) formation of ethene from the ethyl group bound to Ga. The best estimates (MP2/6-311++G(2df,p)//B3LYP/6-31G*) for the activation energies of these three steps are 36.9, ca. 0, and 57.9 kcal/mol, respectively