Methyl tert-butyl ether (MTBE) is widely used as gasoline oxygenate and octane number enhancer for more complete combustion in order to reduce the air pollution caused by motor vehicle exhaust. The possible adverse effects of MTBE on human health are of major public concern. However, information on the metabolism of MTBE in human tissues is scarce. The present study demonstrates that human cytochrome P450 2A6 is able to metabolize MTBE to tert-butyl alcohol (TBA), a major circulating metabolite and marker for exposure to MTBE. As CYP2A6 is known to be constitutively expressed in human livers, we infer that it may play a significant role in metabolism of gasoline ethers in liver tissue.

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In this paper, we investigate the generation and controlling of the optical vortex beam using a dye-doped liquid crystal (DDLC) cell. The spatial distribution of the quasi-sinusoidal orientation of the liquid crystal molecules creates a quasi-sinusoidal phase grating (PG) in the DDLC cell. Depending on the incident light pattern, Trans to Cis photoisomerization of the dye molecules affects the orientation of the liquid crystal molecules. To do so, an amplitude fork grating (FG) is used as a mask, and its pattern is stored in the cell by a pattern printing method as the PG. One of the particular features of the stored grating in the cell is its capability in the diffraction efficiency controlled by the applied electric field. The results show, based on the central defect in the FG pattern, the diffracted probe beam in different orders is optical vortices. As a new technique, this type of stored pattern acts like an amplitude grating but according to the results, its structure is in fact a PG. This technique leads to the vortex beam switching capability by applying an electric field to the cell. The results show that by applying 22 V, all the diffraction orders vanish. Meanwhile, the vortex beams reappear by removing the applied voltage. The diffraction efficiency of the vortex beams as well as its generation dependency on the polarization of the incident beam studied. The maximum efficiency of the first diffraction order for linear polarized incident beam was obtained at 0 V, about 8%. Based on the presented theory, a simulation has been done which shows the Cis form of the dye molecules has been able to change the angle of LC molecules on average about 12.7°. The study of diffracted beam profiles proves that they are electrically controllable vortex beams.

Several isolates of the novel genus Neodidymelliopsis have been recently found in Iranian citrus orchards with severe dieback symptoms. Neodidymelliopsis belongs to Didymellaceae, an important family of Pleosporales, Dothideomycetes. None of the few studies on molecular dating of Ascomycetes have resolved the divergence time of genera in Didymellaceae. Motivated by this fact, we consider the reliable age of a fossil related to extant species of Aigilalus, the estimated mean crown age of Dothideomycetes from other studies as a secondary calibration, also the second fossil which represent common ancestor of Capnodiales to calibrate the reconstructed tree. Our dating analysis is based on four genetic regions of 91 taxa from Capnodiales and Pleosporales, using BEAST analysis. The selected taxa of Pleosporales belong to Aigialaceae and Didymellaceae; including three newly discovered Neodidymelliopsis sp. isolates and one isolate of Didymella sp. from Iran. Our dating analyses suggest that Didymellaceae diverged from Aigialaceae in the Cretaceous, and initial divergence of Didymellaceae happened in the late Eocene followed by two divergences in the late Oligocene and several splits in the Miocene. Furthermore, the results suggest that the Iranian isolates of Neodidymelliopsis sp. and Didymella sp. diverged from other Neodidymelliopsis and Didymella isolates in the Pliocene and the late Miocene, respectively.

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