Search results for "radical"
showing 10 items of 1401 documents
2016
Abstract. We found that ambient and laboratory-generated secondary organic aerosols (SOA) form substantial amounts of OH radicals upon interaction with liquid water, which can be explained by the decomposition of organic hydroperoxides. The molar OH yield from SOA formed by ozonolysis of terpenes (α-pinene, β-pinene, limonene) is ∼ 0.1 % upon extraction with pure water and increases to ∼ 1.5 % in the presence of Fe2+ ions due to Fenton-like reactions. Upon extraction of SOA samples from OH photooxidation of isoprene, we also detected OH yields of around ∼ 0.1 %, which increases upon addition of Fe2+. Our findings imply that the chemical reactivity and aging of SOA particles is strongl…
2010
Abstract. Filter samples of fine and coarse air particulate matter (PM) collected over a period of one year in central Europe (Mainz, Germany) were analyzed for water-soluble organic compounds (WSOCs), including the α- and β-pinene oxidation products pinic acid, pinonic acid and 3-methyl-1,2,3-butanetricarboxylic acid (3-MBTCA), as well as a variety of dicarboxylic acids and nitrophenols. Seasonal variations and other characteristic features in fine, coarse, and total PM (TSP) are discussed with regard to aerosol sources and sinks in comparison to data from other studies and regions. The ratios of adipic acid and phthalic acid to azelaic acid indicate that the investigated aerosol samples w…
2012
Abstract. The oxidation of SO2 to sulfate is a key reaction in determining the role of sulfate in the environment through its effect on aerosol size distribution and composition. Sulfur isotope analysis has been used to investigate sources and chemical processes of sulfur dioxide and sulfate in the atmosphere, however interpretation of measured sulfur isotope ratios is challenging due to a lack of reliable information on the isotopic fractionation involved in major transformation pathways. This paper presents laboratory measurements of the fractionation factors for the major atmospheric oxidation reactions for SO2: Gas-phase oxidation by OH radicals, and aqueous oxidation by H2O2, O3 and a …
ELECTROCHEMICALLY ASSISTED ATOM TRANSFER RADICAL GRAFT COPOLYMERIZATION. PRELIMINARY STUDIES
2012
Atom transfer radical polymerization (ATRP) is a versatile technique for exerting precise control over polymer molecular weights, molecular weight distributions, and complex architectures. It has been recently shown that an externally applied electrochemical potential can reversibly activate the copper catalyst for this process by a one-electron reduction of an initially added air-stable cubric species (Cu(II)/Ligand) [1-2]. In particular Gennaro and co-authors have shown that the polymerization kinetic can be changed modulating the external potential [1-2]. In the last years, an increasing interest has been devoted to synthesis of graft copolymers obtained from commercial polymers for inco…
Efficacy of the antioxidant ebselen in experimental uveitis.
1999
Inflammation results in the production of free radicals. In a model of experimental uveitis upon subcutaneous injection of endotoxin to Lewis rats, i.e., endotoxin-induced experimental uveitis (EIU), we have evaluated the status of the antioxidant capacity of ocular tissues. EIU results in a decrease of glutathione (GSH) content and glutathione peroxidase (GPx) activity in whole eye homogenates 24-h after endotoxin administration. Furthermore, an increase in malondialdehyde (MDA) content was observed in these same samples, thus confirming the involvement of oxidative stress in the pathophysiology of the process. In view of the ability of the antioxidant ebselen as GPx enzyme mimic, we teste…
Role of oxygen and nitrogen species in experimental uveitis: anti-inflammatory activity of the synthetic antioxidant ebselen.
2002
This study was aimed at examining the role of oxygen and nitrogen reactive species in a model of experimental uveitis upon intravitreal injection of bacterial endotoxin to albino New Zealand rabbits. The inflammatory response was evaluated in terms of: (i) the integrity of the blood aqueous barrier (protein and cell content in samples of aqueous humor), (ii) histopathological changes of the eyes, (iii) clinical evaluation (with a score index based on clinical symptoms), and (iv) the concentration of malondialdehyde (MDA), in aqueous humor, as a marker of oxidative stress. Betamethasone was used as reference treatment, superoxide dismutase as quencher of superoxide anion, L-N(G)-nitro-L-argi…
Investigations concerning the COX/5-LOX inhibiting and hydroxyl radical scavenging potencies of novel 4,5-diaryl isoselenazoles
2007
The aim of this study was to investigate 4,5-diaryl isoselenazoles as multiple target non-steroidal anti-inflammatory drugs (MTNSAIDs) which can intervene into the inflammatory processes via different mechanisms of action creating a new class of compounds. Here we describe the synthesis of COX/LOX inhibitors which additionally reduce the level of reactive oxygen species, such as hydroxyl radicals which are well known for supporting inflammation processes in Parkinson's disease, Alzheimer's disease and rheumatoid arthritis.
Conservative management of T1G3 transitional cell carcinoma of the bladder. Risk factor analysis in 165 selected patients
2003
INTRODUCTION AND OBJECTIVE: The management of TlG3 transitional cell carcinoma of the bladder (TCCB), is still controversial. Some Authors support an immediate radical cystectomy. BCG is considered the treatment of choice. Limited encouraging experiences are reported with intravesical chemotherapy. Objectives; Evaluating a selected population of 165 patients with TlG3 TCCB, in absence of Tis, treated conservatively with TUR plus adjuvant intravesical therapy. METHODS: Between January 1976 and December 1999, 165 patients with TlG3 bladder tumors were treated by TUR plus adjuvant intravesical therapy. Patients with previuos T1G3, Tis, more than 3 tumors or greater than 3 em were excluded. A s…
Non-Innocent Base Properties of 3- and 4-Pyridyl-dithia- and Diselenadiazolyl Radicals : The Effect of N-Methylation
2018
International audience; Condensation of persilylated nicotinimideamide and isonicotinimideamide with sulfur monochloride affords double salts of the 3-, 4-pyridyl-substituted 1,2,3,5-dithiadiazolylium DTDA cations of the general formula [3-, 4-pyDTDA][Cl][HCl] in which the pyridyl nitrogen serves as a noninnocent base. Reduction of these salts with triphenylantimony followed by deprotonation of the intermediate-protonated radical affords the free base radicals [3-, 4-pyDTDA], the crystal structures of which, along with those of their diselenadiazolyl analogues [3-, 4-pyDSDA], have been characterized by powder or single-crystal X-ray diffraction. The crystal structures consist of “pancake” π…