Mohammed El-Shahat

Experiments are carried out on partially premixed turbulent flames stabilized in a conical burner. The investigated gaseous fuels are methane, methane diluted with nitrogen, and mixtures of CH4, CO, CO2, H2 and N2, simulating typical products from gasification of biomass, and co-firing of gasification gas with methane. The fuel and air are partially premixed in concentric tubes. Flame stabilization behavior is investigated and significantly different stabilization characteristics are observed in flames with and without the cone. Planar laser induced fluorescence (LIF) imaging of a fuel-tracer species, acetone, and OH radicals is carried out to characterize the flame structures. Large eddy simulations of the conical flames are carried out to gain further understanding of the flame/flow interaction in the cone. The data show that the flames with the cone are more stable than those without the cone. Without the cone (i.e. jet burner) the critical jet velocities for blowoff and liftoff of biomass derived gases are higher than that for methane/nitrogen mixture with the same heating values, indicating the enhanced flame stabilization by hydrogen in the mixture. With the cone the stability of flames is not sensitive to the compositions of the fuels, owing to the different flame stabilization mechanism in the conical flames than that in the jet flames. From the PLIF images it is shown that in the conical burner, the flame is stabilized by the cone at nearly the same position for different fuels. From large eddy simulations, the flames are shown to be controlled by the recirculation flows inside cone, which depends on the cone angle, but less sensitive to the fuel compositions and flow speed. The flames tend to be hold in the recirculation zones even at very high flow speed. Flame blowoff occurs when significant local extinction in the main body of the flame appears at high turbulence intensities. © 2009 Elsevier Inc. All rights reserved.

Experiments are carried out on partially premixed turbulent flames stabilized in a conical burner. The investigated gaseous fuels are methane, methane diluted with nitrogen, and mixtures of CH4, CO, CO2, H2 and N2, simulating typical products from gasification of biomass, and co-firing of gasification gas with methane. The fuel and air are partially premixed in concentric tubes. Flame stabilization behavior is investigated and significantly different stabilization characteristics are observed in flames with and without the cone. Planar laser induced fluorescence (LIF) imaging of a fuel-tracer species, acetone, and OH radicals is carried out to characterize the flame structures. Large eddy simulations of the conical flames are carried out to gain further understanding of the flame/flow interaction in the cone. The data show that the flames with the cone are more stable than those without the cone. Without the cone (i.e. jet burner) the critical jet velocities for blowoff and liftoff of biomass derived gases are higher than that for methane/nitrogen mixture with the same heating values, indicating the enhanced flame stabilization by hydrogen in the mixture. With the cone the stability of flames is not sensitive to the compositions of the fuels, owing to the different flame stabilization mechanism in the conical flames than that in the jet flames. From the PLIF images it is shown that in the conical burner, the flame is stabilized by the cone at nearly the same position for different fuels. From large eddy simulations, the flames are shown to be controlled by the recirculation flows inside cone, which depends on the cone angle, but less sensitive to the fuel compositions and flow speed. The flames tend to be hold in the recirculation zones even at very high flow speed. Flame blowoff occurs when significant local extinction in the main body of the flame appears at high turbulence intensities. © 2009 Elsevier Inc. All rights reserved.

The oxidation reaction of triiodide, I3-, by chlorate is investigated in a slightly acidic and neutral media. The reaction was verified and monitored both potentiometrically and spectrophotometrically. Generally, a slow linear decay preceded by an induction period was observed for the triiodide concentration following the addition of chlorate. The induction period is likely to be related to the time required for the generation of suitable concentrations of plausible intermediates (HIO and HIO2), which are assumed to auto-catalyse the reaction. We examined the effect of acidity and concentrations of both chlorate and triiodide on the induction time for this reaction. The acidity of the medium influenced the induction period, while the oxidation of iodide by chlorate competed with that of iodine as the medium acidity increased, making the reaction more complicated. Therefore, a suitable pH is highly recommended for studying the chlorate-triiodide reaction. A plausible mechanism involving the HIO, HIO2, and I2O species is proposed. © 2010 Cairo University.

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PURPOSE: This work aimed to study and evaluate the effect of subconjunctival bevacizumab injection in patients with corneal neovascularization (CNV) resulting from different ocular surface disorders.

METHODS: Ten eyes with CNV caused by different ocular surface disorders were studied. All eyes had both major and minor vessel CNV caused by factors such as healed corneal ulcers, long-standing chronic inflammatory diseases and corneal ischaemia (caused by contact lenses). All eyes received a single subconjunctival injection of 2.5mg (0.1ml) bevacizumab. Morphological changes in the major and minor vessels were evaluated using slit-lamp biomicroscopy and corneal photography.

RESULTS: Conspicuous recession of the minor vessels of CNV was observed in all eyes at 2 weeks post-injection. The extent of CNV of the major vessels was significantly decreased at 2 weeks post-injection. The level of CNV continued to decrease noticeably for 3 months and then stabilized for the remainder of the 6-month follow-up period. Parameters used for evaluation included the total area of CNV, which amounted to 14.0 ± 5.4% of the corneal surface pre-injection, compared with 9.4 ± 3.9% post-injection (p < 0.01), reflecting a mean decrease in CNV of 33 ± 8%, and the extent of neovascularization, which decreased from 4.3 ± 1.5 clock hours pre-injection to 2.4 ± 1.1 clock hours post-injection (p <0.01). During the 6-month follow-up, none of the 10 eyes showed any complication that could be related to subconjunctival bevacizumab injection.

CONCLUSIONS: Bevacizumab can be used safely and effectively for CNV resulting from different ocular surface disorders. It represents an effective treatment for minor vessel neovascularization caused by long-standing chronic inflammation (e.g. trachoma) or long-standing corneal ischaemia (e.g. contact lenses), as well as for major vessel neovascularization resulting from different causes. Bevacizumab was well tolerated over the 6-month follow-up period.