21 research outputs found
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 Ãœberschreiten
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
Analysis of the effects of certain alcohol and furan-based biofuels on controlled auto ignition
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