Druck- und Termperaturabhängigkeit der Rekombinationreaktionen von Benzylartigen Radikale

In der vorliegenden Arbeit wurden Kombinationsreaktionen p-F-C6H4CH2 + p-F-C6H4CH2 (+M) → C14H12F2 (+M), p-CH3-C6H4CH2 + p-CH3-C6H4CH2 (+M) → C16H18 (+M) und C6H5CH2 + C6H5CH2 (+M) → C14H14 (+M) in den Druck- und Temperaturbereichen von 0,2-800 bar und 255-420 K (p-fluorobenzylradikal), 2-200 bar und 300-515K (p-methylbenzylradikal ), sowie 1-70 bar und 250K-400K (benzylradikal) untersucht. Helium, Argon, CO2, SF6, CF3H und CF4 wurden hierbei als Badgase verwendet. Weiterhin wurden transiente UV-Absorptionsspektren der drei Radikale für eine Wellenlänge bei 300K bestimmt. Die Radikale wurden durch Laserphotolyse von Cl2 bei 308 nm und anschliessender Wasserstoffabstraktion der Vorläufermoleküle durch die Chloratome erzeugt. Die zeitabhängigen Absorptionssignale des p- fluorobenzyl- und des p-methylbenzylradikals wurden bei 253 nm gemessen. Im Fall des Benzylradikals wurden 260 nm vewendet.Es wurden experimentelle Anzeichen für eine schwache Druckabhängigkeit der Absorptionskoeffizienten der p-fluorobenzyl-, p-methylbenzyl- und Benzylradikale in CO2 im Druckbereich von 1-45 bar gefunden. Die Geschwindigkeitskoeffizienten der drei untersuchten Reaktionen erreichten den druckunabhängigen Bereich unterhalb von 1 bar, so daß die Geschwindigkeitskoeffizienten der Hochdruckgrenzwerte des Energietransfermechanismuses (ET) direkt aus den experimentellen Ergebnissen ohne Extrapolation des fall-off -Bereiches bestimmt werden konnten. Weiterhin wurde die Temperaturabhängigkeit der Geschwindigkeitskoeffizienten untersucht.Die Temperatur- sowie Dichteabhängigkeit von k1 im Fall der p-fluorobenzyl- und p-methylbenzylradikale waren vergleichbar mit denen des Benzylradikals. Das Ausmaß der Erhöhung der Geschwindigkeitskonstanten nahm in der Reihenfolge He < Ar < CO2 für alle drei Radikale zu. Die Abnahme der Geschwindigkeitskoeffizienten nach dem Überschreiten des Maximums wurden bei allen drei Radikalrekombinationsreaktionen, die in dieser Arbeit untersucht

Heterogeneous photocatalytic reduction of ferrate(VI) in UV-irradiated titania suspensions: Role in enhancing destruction of nitrogen-containing pollutants

The results of the heterogeneous photocatalytic reduction of Fe(VI) in UV-irradiated TiO2 suspensions are presented and suggest indirect observation of the formation of Fe(V) by the photoreduction of Fe(VI) with ecb− at TiO2 surfaces. Because Fe(V) selectively and rapidly oxidizes low reactivity pollutants with the production of the non-toxic by-product, Fe(III), the photocatalytic reduction of Fe(VI) has a role in pollution remediation processes. The experiments were conducted as a function of TiO2 suspension concentrations, Fe(VI) concentrations, and pH in basic media. The initial rate of Fe(VI) reduction gave a fractional order with respect to initial Fe(VI) concentrations and adheres to simple Langmuir-Hinshelwood kinetics. Results suggest that the surface reaction (Fe(VI)+ecb−→Fe(V)) is the rate-controlling step. The photocatalytic reduction of Fe(VI) in the presence of less reactive nitrogen-containing species (ammonia, cyanate, and fulvic acid) were also investigated. Enhancement in the rate of Fe(VI) reduction was observed. A reaction scheme involving Fe(V) as an intermediate is presented which explains the faster photocatalytic oxidation of pollutants in the presence of Fe(VI)

Ignition studies of n-heptane/iso-octane/toluene blends

Journal articleIgnition delay times of four ternary blends of n-heptane/iso-octane/toluene, referred to as Toluene Primary Reference Fuels (TPRFs), have been measured in a high-pressure shock tube and in a rapid compression machine. The TPRFs were formulated to match the research octane number (RON) and motor octane number (MON) of two high-octane gasolines and two prospective low-octane naphtha fuels. The experiments were carried out over a wide range of temperatures (650-1250 K), at pressures of 10, 20 and 40 bar, and at equivalence ratios of 0.5 and 1.0. It was observed that the ignition delay times of these TPRFs exhibit negligible octane dependence at high temperatures (T > 1000 K), weak octane dependence at low temperatures (TSaudi Aramco (FUELCOM); King Abdullah University of Science and Technology (KAUST)2018-07-0

Stress proteins on the yeast cell surface determine resistance to osmotin, a plant antifungal protein

6 pages, 7 figures, 24 references. Yun, Dae-Jin et al.--Strains of the yeast Saccharomyces cerevisiae differ in their sensitivities to tobacco osmotin, an antifungal protein of the PR-5 family. However, cells sensitive to tobacco osmotin showed resistance to osmotin-like proteins purified from the plant Atriplex nummularia, indicating a strict specificity between the antifungal protein and its target cell. A member of a gene family encoding stress proteins induced by heat and nitrogen limitation, collectively called Pir proteins, was isolated among the genes that conveyed resistance to tobacco osmotin to a susceptible strain. We show that overexpression of Pir proteins increased resistance to osmotin, whereas simultaneous deletion of all PIR genes in a tolerant strain resulted in sensitivity. Pir proteins have been immunolocalized to the cell wall. The enzymatic digestion of the cell wall of sensitive and resistant cells rendered spheroplasts equally susceptible to the cytotoxic action of tobacco osmotin but not to other osmotin-like proteins, indicating that the cell membrane interacts specifically with osmotin and facilitates its action. Our results demonstrate that fungal cell wall proteins are determinants of resistance to antifungal PR-5 proteins.This work was supported by grants from Pioneer Hi-Bred International, The Consortium for Plant Biotechnology Inc., and U.S. Department of Agriculture Grant 94-37100-0754.Peer reviewe