Asphalt Oxidation Mechanisms and the Role of Oxidation Products on Age Hardening Revisited

2011 ◽  
Vol 12 (4) ◽  
pp. 795-819 ◽  
Author(s):  
J. Claine Petersen ◽  
Ronald Glaser
Keyword(s):  
Oxidation Products ◽  
Age Hardening ◽  
Asphalt Oxidation ◽  
Oxidation Mechanisms

Asphalt Aging: Dual Oxidation Mechanism and Its Interrelationships with Asphalt Composition and Oxidative Age Hardening

1998 ◽  
Vol 1638 (1) ◽  
pp. 47-55 ◽  
Author(s):  
J. Claine Petersen ◽  
P. Michael Harnsberger
Keyword(s):  
Kinetic Data ◽  
Oxidation Mechanism ◽  
Oxidation Products ◽  
Age Hardening ◽  
Initial Reaction ◽  
Initial Oxidation ◽  
Oxidative Aging ◽  
Microstructural Model ◽  
Dual Mechanism ◽  
Asphalt Oxidation

The kinetic data and chemistry of asphalt oxidative age hardening suggested a sequential, dual mechanism for asphalt oxidation. The dual mechanism rationalizes conflicts between earlier mechanistic investigations and explains the hyperbolic-like, time-versus-property plots characteristic of asphalt oxidative aging. The oxidation kinetics provide further confirmation of the asphalt microstructural model. It is proposed that the rapid initial oxidation rate of asphalt results from reaction of oxygen with limited amounts of highly reactive hydrocarbons. Final oxidation products of this initial reaction are sulfoxides and, most likely, ring aromatization. During this initial reaction, a slower oxidation reaction of asphalt benzylic carbons is initiated; final products are ketones and sulfoxides. The ratio of ketones to sulfoxides formed and the rate of age hardening were found to be dependent on temperature and oxygen pressure. Low-temperature oxidative aging, as occurs in pavements, was found significantly more sensitive to variations in temperature and asphalt composition than 100°C pressure vessel aging.

scholarly journals The Effectiveness of Glutathione Redox Status as a Possible Tumor Marker in Colorectal Cancer

2021 ◽  
Vol 22 (12) ◽  
pp. 6183
Author(s):  
Delia Acevedo-León ◽  
Lidia Monzó-Beltrán ◽  
Segundo Ángel Gómez-Abril ◽  
Nuria Estañ-Capell ◽  
Natalia Camarasa-Lillo ◽  
...  
Keyword(s):  
Colorectal Cancer ◽  
Redox State ◽  
Reduced Glutathione ◽  
Redox Status ◽  
Oxidation Products ◽  
Interventional Study ◽  
Thiol Redox State ◽  
Thiol Redox ◽  
Glutathione Redox

The role of oxidative stress (OS) in cancer is a matter of great interest due to the implication of reactive oxygen species (ROS) and their oxidation products in the initiation of tumorigenesis, its progression, and metastatic dissemination. Great efforts have been made to identify the mechanisms of ROS-induced carcinogenesis; however, the validation of OS byproducts as potential tumor markers (TMs) remains to be established. This interventional study included a total of 80 colorectal cancer (CRC) patients and 60 controls. By measuring reduced glutathione (GSH), its oxidized form (GSSG), and the glutathione redox state in terms of the GSSG/GSH ratio in the serum of CRC patients, we identified significant changes as compared to healthy subjects. These findings are compatible with the effectiveness of glutathione as a TM. The thiol redox state showed a significant increase towards oxidation in the CRC group and correlated significantly with both the tumor state and the clinical evolution. The sensitivity and specificity of serum glutathione levels are far above those of the classical TMs CEA and CA19.9. We conclude that the GSSG/GSH ratio is a simple assay which could be validated as a novel clinical TM for the diagnosis and monitoring of CRC.

scholarly journals Oxidation of the Tryptophan 32 Residue of Human Superoxide Dismutase 1 Caused by Its Bicarbonate-dependent Peroxidase Activity Triggers the Non-amyloid Aggregation of the Enzyme

2014 ◽  
Vol 289 (44) ◽  
pp. 30690-30701 ◽  
Author(s):  
Fernando R. Coelho ◽  
Asif Iqbal ◽  
Edlaine Linares ◽  
Daniel F. Silva ◽  
Filipe S. Lima ◽  
...  
Keyword(s):  
Superoxide Dismutase ◽  
Peroxidase Activity ◽  
Oxidation Products ◽  
Superoxide Dismutase 1 ◽  
Amyloid Aggregation ◽  
Post Translational Modifications ◽  
Covalent Dimer ◽  
Als Patients ◽  
Lateral Sclerosis

The role of oxidative post-translational modifications of human superoxide dismutase 1 (hSOD1) in the amyotrophic lateral sclerosis (ALS) pathology is an attractive hypothesis to explore based on several lines of evidence. Among them, the remarkable stability of hSOD1WT and several of its ALS-associated mutants suggests that hSOD1 oxidation may precede its conversion to the unfolded and aggregated forms found in ALS patients. The bicarbonate-dependent peroxidase activity of hSOD1 causes oxidation of its own solvent-exposed Trp32 residue. The resulting products are apparently different from those produced in the absence of bicarbonate and are most likely specific for simian SOD1s, which contain the Trp32 residue. The aims of this work were to examine whether the bicarbonate-dependent peroxidase activity of hSOD1 (hSOD1WT and hSOD1G93A mutant) triggers aggregation of the enzyme and to comprehend the role of the Trp32 residue in the process. The results showed that Trp32 residues of both enzymes are oxidized to a similar extent to hSOD1-derived tryptophanyl radicals. These radicals decayed to hSOD1-N-formylkynurenine and hSOD1-kynurenine or to a hSOD1 covalent dimer cross-linked by a ditryptophan bond, causing hSOD1 unfolding, oligomerization, and non-amyloid aggregation. The latter process was inhibited by tempol, which recombines with the hSOD1-derived tryptophanyl radical, and did not occur in the absence of bicarbonate or with enzymes that lack the Trp32 residue (bovine SOD1 and hSOD1W32F mutant). The results support a role for the oxidation products of the hSOD1-Trp32 residue, particularly the covalent dimer, in triggering the non-amyloid aggregation of hSOD1.

Study of interaction and adsorption of aromatic amines by manganese oxides and their role in chemical evolution

2016 ◽  
Vol 16 (2) ◽  
pp. 143-155 ◽  
Author(s):  
Brij Bhushan ◽  
Arunima Nayak ◽  
Kamaluddin
Keyword(s):  
Aromatic Amines ◽  
Manganese Oxides ◽  
Oxidation Products ◽  
Gas Chromatography Mass Spectrometry ◽  
Spectroscopy Analysis ◽  
Electron Microscopic ◽  
Microscopic Studies ◽  
The Fourier Transform ◽  
Langmuir Constants

AbstractThe role of manganese oxides in concentrating organic moieties and offering catalytic activity for prebiotic reactions is investigated by studying their interaction with different aromatic amines such as aniline, p-chloroaniline, p-toluidine and p-anisidine. For all amines, metal oxides showed highest adsorption at neutral pH. The order of their adsorption capacity and affinity as revealed by the Langmuir constants was found to be manganosite (MnO) > bixbyite (Mn2O3) > hausmannite (Mn3O4) > and pyrolusite (MnO2). At alkaline pH, these manganese oxides offered their surfaces for oxidation of amines to form coloured oligomers. Analysis of the oxidation products by gas chromatography–mass spectrometry showed the formation of a dimer from p-anisidine and p-chloroaniline, while a trimer and tetramer is formed from p-toluidine and aniline, respectively. A reaction mechanism is proposed for the formation of the oligomers. While field-emission scanning electron microscopic studies confirm the binding phenomenon, the Fourier transform infrared spectroscopy analysis suggests that the mechanism of binding of amines on the manganese oxides was primarily electrostatic. The adsorption behaviour of the studied aromatic amines followed the order: p-anisidine > p-toluidine > aniline > p-chloroaniline, which is related to the basicities and structure of the amines. Our studies confirmed the significance of the role of manganese oxides in prebiotic chemistry.

The First Observation of HOx radicals in the Chengyu Urban Agglomeration

2020 ◽  
Author(s):  
Xinping Yang ◽  
Keding Lu ◽  
Xuefei Ma ◽  
Yuanhang Zhang
Keyword(s):  
New York ◽  
Urban Agglomeration ◽  
Oxidation Products ◽  
Oh Radicals ◽  
Secondary Pollution ◽  
Sensitivity Tests ◽  
Reaction Channels ◽  
Daily Concentration ◽  
Field Campaigns

<p>A comprehensive field campaign was carried out in summer 2019 in Chengdu, which obtained the first complete radical dataset of Chengyu Urban Agglomeration. Observed daily concentration maxima of radicals by the laser-induced-fluorescence (LIF) technique were in the range of (2-10)×10<sup>6</sup> cm<sup>-3</sup> for OH and (4-15)×10<sup>8</sup> cm<sup>-3</sup> for HO<sub>2</sub>. During daytime, OH reactivities were generally high (5-32 s<sup>-1</sup>). The missing reactivity was not be observed within uncertainty, and inorganics, observed VOCs and the calculated oxidation products contributed about one-third in total reactivity, respectively.</p><p>The chemical box model RACM 2 was used to interpret the observed radical concentrations. The model over-predicted OH and HO<sub>2</sub> at noon during the O<sub>3</sub> polluted episode. Constraining the model by the observed HO<sub>2</sub> concentration, the overestimation of OH can be explained almost by the overestimation of HO<sub>2</sub>. Besides, as in the previous field campaigns (e.g. Pennsylvania, Mexico City, New York and so on), the underestimation of the net conversion of OH into HO<sub>2</sub> enlarged with the increasing NO concentration, indicating the conversion of HO<sub>2</sub> into OH still need to be studied based on the discussion above. Different schemes to improve the agreement between observed and modelled HO<sub>2</sub> were explored in this work. The sensitivity tests indicated observed and modelled HO<sub>2</sub> can be agreed well by reducing the HO<sub>2</sub> yield in the reaction of OH and HCHO a half.</p><p>The oxidation rate of primary pollutants dominated by OH radicals was significantly higher than that in winter Beijing, which contributes significantly to secondary pollution, especially O<sub>3</sub>. Besides, the atmospheric self-cleaning ability and recycling efficiency both peaked for about 600 pptv of NO, indicating small amounts of NO can help to maintain the atmospheric oxidation. The campaign emphasizes the important role of HO<sub>2</sub> yield in the reaction channels of OH and VOCs especially, and the need for further laboratory experiments of the HO<sub>2</sub> yield measurement in order to understand radical chemistry in VOC-rich air.</p>

On the Mechanism and Substituent Effects of the Tl(III) Oxidation of Phenylethylenes in Methanol

1973 ◽  
Vol 51 (14) ◽  
pp. 2366-2374 ◽  
Author(s):  
L. Nadon ◽  
M. Tardat ◽  
M. Zador ◽  
S. Fliszar
Keyword(s):  
Substituent Effects ◽  
Oxidation Products ◽  
Rate Determining Step ◽  
Mechanism Of Reaction

The oxidation of phenylethylenes by Tl(NO3)3 in methanol proceeds rapidly and selectively to give the products resulting from the migration of aryl groups, i.e., (i) the 1,1-dimethoxy-2-phenylethanes from the corresponding styrenes, (ii) the phenylacetones from the α-methylstyrenes, and (iii) the two possible deoxybenzoines from the 1,1,-diphenylethylenes. The kinetic results, which indicate the formation of the thallic–organic intermediate to be the rate determining step, are discussed in terms of the mechanism of reaction and show the role of the coordination of Tl(III). Hammett's relationship, with ρ = −4.2, describes the substituent effects for the competitive oxidation of ring-substituted styrenes and α-methylstyrenes. The relative migratory aptitudes of aryl groups, as determined from the oxidation products of ring-substituted 1,1-diphenylethylenes, is correlated to Brown's σ+ constants, with ρ+ = −2.27.

scholarly journals The role of VOC oxidation products in continental new particle formation

2008 ◽  
Vol 8 (10) ◽  
pp. 2657-2665 ◽  
Author(s):  
A. Laaksonen ◽  
M. Kulmala ◽  
C. D. O'Dowd ◽  
J. Joutsensaari ◽  
P. Vaattovaara ◽  
...  
Keyword(s):  
Gas Phase ◽  
Chemical Properties ◽  
High Volume ◽  
Particle Growth ◽  
Particle Formation ◽  
Oxidation Products ◽  
Chemical Compositions ◽  
New Particle Formation ◽  
Voc Oxidation

Abstract. Aerosol physical and chemical properties and trace gas concentrations were measured during the QUEST field campaign in March–April 2003, in Hyytiälä, Finland. Our aim was to understand the role of oxidation products of VOC's such as mono- and sesquiterpenes in atmospheric nucleation events. Particle chemical compositions were measured using the Aerodyne Aerosol Mass Spectrometer, and chemical compositions of aerosol samples collected with low-pressure impactors and a high volume sampler were analysed using a number of techniques. The results indicate that during and after new particle formation, all particles larger than 50 nm in diameter contained similar organic substances that are likely to be mono- and sesquiterpene oxidation products. The oxidation products identified in the high volume samples were shown to be mostly aldehydes. In order to study the composition of particles in the 10–50 nm range, we made use of Tandem Differential Mobility Analyzer results. We found that during nucleation events, both 10 and 50 nm particle growth factors due to uptake of ethanol vapour correlate strongly with gas-phase monoterpene oxidation product (MTOP) concentrations, indicating that the organic constituents of particles smaller than 50 nm in diameter are at least partly similar to those of larger particles. We furthermore showed that particle growth rates during the nucleation events are correlated with the gas-phase MTOP concentrations. This indicates that VOC oxidation products may have a key role in determining the spatial and temporal features of the nucleation events. This conclusion was supported by our aircraft measurements of new 3–10 nm particle concentrations, which showed that the nucleation event on 28 March 2003, started at the ground layer, i.e. near the VOC source, and evolved together with the mixed layer. Furthermore, no new particle formation was detected upwind away from the forest, above the frozen Gulf of Bothnia.

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