Quantitative aspects of the interfacial catalytic oxidation of Dithiothreitol by dissolved oxygen in the presence of carbon nanoparticles

The catalytic nature of particulate matter is often advocated to explain its ability to generate reactive oxygen species, but quantitative data are lacking. We have performed molecular characterization of three different carbonaceous nanoparticles (NP) by 1. identifying and quantifying their surface functional groups based on probe gas-particle titration; 2. studying the kinetics of dissolved oxygen consumption in the presence of suspended NP's and dithiothreitol (DTT). We show that these NP's can reversibly change their oxidation state between oxidized and reduced functional groups present on the NP surface. By comparing the amount of O2 consumed and the number of strongly reducing sites on the NP, its average turnover ranged from 35 to 600 depending on the type of NP. The observed quadratic rate law for O2 disappearance points to a Langmuir-Hinshelwood surface-based reaction mechanism possibly involving semiquinone radical. In the proposed model, the strongly reducing surface site is assumed to be a polycyclic aromatic hydroquinone whose oxidation to the corresponding conjugated quinone is rate-limiting in the catalytic chain reaction. The presence and strength of the reducing surface functional groups are important for explaining the catalytic activity of NP in the presence of oxygen and a reducing agent like DTT

Exposure to carcinogenic polycyclic aromatic compounds and health risk assessment for diesel-exhaust exposed workers

Objectives: Workers' exposure to diesel exhaust in a bus depot, a truck repair workshop and an underground tunnel was determined by the measuring of elemental carbon (EC) and 15 carcinogenic polycyclic aromatic compounds (PACs) proposed by the US Department of Health and Human Services/National Toxicology Program (NTP). Based on these concentration data, the genotoxic PAC contribution to the diesel-exhaust particle (DEP) lung-cancer risk was calculated. Method: Respirable particulate matter was collected during the summer and winter of 2001 (except for in the underground situation) and analysed by coulometry for EC and by GC-MS methods for PACs. The use of potency equivalence factors (PEFs) allowed the studied PAC concentrations to be expressed as benzo[a]pyrene equivalents (B[a]Peq). We then calculated the lung-cancer risk due to PACs and DEPs by multiplying the B[a]Peq and EC concentrations by the corresponding unit risk factor. The ratio of these two risks values has been considered as an estimate of the genotoxic contribution to the DEP cancer risk. Results: For the bus depot and truck repair workshop, exposure to EC and PACs has been shown to increase by three to six times and ten times, respectively, during winter compared to summer. This increase has been attributed mainly to a decrease in ventilation during the cold. With the PEF approach, the B[a]Peq concentration is five-times higher than if only benzo[a]pyrene (B[a]P) is considered. Dibenzopyrenes contribute an important part to this increase. A simple calculation based on unit risk factors indicates that the studied PAC contribution to the total lung-cancer risk attributed to DEPs is in the range of 3-13%. Conclusions: The 15 NTP PACs represent a small but non-negligible part of lung-cancer risk with regard to diesel exposure. From this point of view, the dibenzopyrene family are important compounds to be considere

Characterization of surface functional groups present on laboratory-generated and ambient aerosol particles by means of heterogeneous titration reactions

A Knudsen flow reactor has been used to quantify surface functional groups on aerosols collected in the field. This technique is based on a heterogeneous titration reaction between a probe gas and a specific functional group on the particle surface. In the first part of this work, the reactivity of different probe gases on laboratory-generated aerosols (limonene SOA, Pb(NO3)2, Cd(NO3)2) and diesel reference soot (SRM 2975) has been studied. Five probe gases have been selected for the quantitative determination of important functional groups: N(CH3)3 (for the titration of acidic sites), NH2OH (for carbonyl functions), CF3COOH and HCl (for basic sites of different strength), and O3 (for oxidizable groups). The second part describes a field campaign that has been undertaken in several bus depots in Switzerland, where ambient fine and ultrafine particles were collected on suitable filters and quantitatively investigated using the Knudsen flow reactor. Results point to important differences in the surface reactivity of ambient particles, depending on the sampling site and season. The particle surface appears to be multi-functional, with the simultaneous presence of antagonistic functional groups which do not undergo internal chemical reactions, such as acid-base neutralization. Results also indicate that the surface of ambient particles was characterized by a high density of carbonyl functions (reactivity towards NH2OH probe in the range 0.26-6 formal molecular monolayers) and a low density of acidic sites (reactivity towards N(CH3)3 probe in the range 0.01-0.20 formal molecular monolayer). Kinetic parameters point to fast redox reactions (uptake coefficient ?0&gt;10-3 for O3 probe) and slow acid-base reactions (?0&lt;10-4 for N(CH3)3 probe) on the particle surface. [Authors]]]> Vehicle Emissions ; Aerosols ; Particulate Matter ; Oxidative Stress ; Reactive Oxygen Species ; Biological Markers ; Surface Properties ; Occupational Exposure eng https://serval.unil.ch/resource/serval:BIB_B477DBDA9F10.P001/REF.pdf http://nbn-resolving.org/urn/resolver.pl?urn=urn:nbn:ch:serval-BIB_B477DBDA9F105 info:eu-repo/semantics/altIdentifier/urn/urn:nbn:ch:serval-BIB_B477DBDA9F105 info:eu-repo/semantics/acceptedVersion info:eu-repo/semantics/openAccess Copying allowed only for non-profit organizations https://serval.unil.ch/disclaimer application/pdf oai:serval.unil.ch:BIB_B478041350E0 2022-05-07T01:25:26Z <oai_dc:dc xmlns:dc="http://purl.org/dc/elements/1.1/" xmlns:xs="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:oai_dc="http://www.openarchives.org/OAI/2.0/oai_dc/" xsi:schemaLocation="http://www.openarchives.org/OAI/2.0/oai_dc/ http://www.openarchives.org/OAI/2.0/oai_dc.xsd"> https://serval.unil.ch/notice/serval:BIB_B478041350E0 Négocier pour pacifier. Ambassadeurs et médiateurs durant la guerre de Cent Ans Pibiri, Eva info:eu-repo/semantics/conferenceObject inproceedings La paix des Dames, volet 1, Entre politique, diplomatie et cérémoniel Dumont, Jonathan (ed.) Fragnart, Laure (ed.) Girault, Pierre-Gilles (ed.) Le Roux, Nicolas (ed.) fre oai:serval.unil.ch:BIB_B47924D65A2D 2022-05-07T01:25:26Z <oai_dc:dc xmlns:dc="http://purl.org/dc/elements/1.1/" xmlns:xs="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:oai_dc="http://www.openarchives.org/OAI/2.0/oai_dc/" xsi:schemaLocation="http://www.openarchives.org/OAI/2.0/oai_dc/ http://www.openarchives.org/OAI/2.0/oai_dc.xsd"> https://serval.unil.ch/notice/serval:BIB_B47924D65A2D Cancer du sein et obésité, une liaison dangereuse [Breast cancer and obesity, a dangerous relation]. info:eu-repo/semantics/altIdentifier/pmid/22734178 Zaman, K. Bodmer, A. Pralong, F. Castiglione-Gertsch, M. info:eu-repo/semantics/review article 2012 Revue Médicale Suisse, vol. 8, no. 342, pp. 1101-1104 info:eu-repo/semantics/altIdentifier/pissn/1660-9379 urn:issn:1660-9379 <![CDATA[Obesity is associated with different cancers including breast cancer, whose incidence is increased in postmenopausal women. It has an adverse impact on the prognosis of the patients, regardless of their menopausal status. The fact of receiving a systemic adjuvant therapy does not neutralize the prognostic role of obesity. Moderate weight loss after cancer diagnosis could improve the outcome of the patients, while a weight gain during treatment seems without significant effect. Currently available data are still too incomplete to justify systematic programs to lose weight with an oncologic therapeutic aim. However, it is worth to encourage and support our patients to have an optimal diet, physical activity, and to lose weight as promotion of general health

Longterm survey (7 years) in a population at risk for Lyme borreliosis: what happens to the seropositive individuals?

In 1986, a 26% seroprevalence of IgG- anti-Borrelia burgdorferi antibodies was observed among 950 orienteers and the incidence of new clinical infections was 0.8%. In 1993, a total of 305 seropositive orienteers were reexamined. During that time, 15 cases (4.9%) of definite/probable Lyme disease occurred in this seropositive group (12 skin manifestations and 3 monoarticular joint manifestations). Among the 12 definite cases, 9 showed new clinical infections (7 EM, 1 acrodermatitis chronica atrophicans, 1 arthritis), and 3 were recurrent (2 EM, 1 arthritis). The annual incidence (0.8%) in this seropositive group was identical to the incidence observed among the whole population in 1986. The individual antibody titer decreased slightly but the seroreversion rate was low (7%). Serology was not very helpful in identifying clinical cases and evolutions, and it can be stated, that a positive serology is much more frequent in this risk group than clinical disease

Longitudinal study of Lyme borreliosis in a high risk population in Switzerland

Orienteers from all parts of Switzerland (n = 416) were included in a longitudinal study for Lyme borreliosis. In spring 1986, the seroprevalence was 28.1 %. At the beginning of the study, 84.3 % of orienteers reported a history of tick bite, and 3.8 % reported a past history of Lyme borreliosis. During the first (spring 1986-autumn 1986), second (autumn 1986-spring 1987) and third (spring 1987-autumn 1987) period, rates of seroconversion were 0.6 %, 2.7 % and 2.1 % respectively. During the first and second period, clinical incidence were 1.0 % and 0.25 % respectively. No active Lyme borreliosis was detected during the third period. Among orienteers who seroconverted during the study (n = 16), only two developed clinical symptoms. Hence, Borrelia burgdorferi infection is often asymptomatic

Influence of the substrate's surface morphology and chemical nature on the nucleation and growth of microcrystalline silicon

Hydrogenated microcrystalline silicon (μc-Si:H) layers about 500 nm thick were deposited in the same run on flat and rough substrates (rms = 60 nm) of various chemical nature. This study reveals that the spatial distribution of the microcrystalline/amorphous phases within the layer depends on the substrate's topography. The influence of the chemical nature of the substrate is shown to be preponderant on the layers nucleation. In particular, this study shows that nucleation density is the highest on plasma enhanced chemical vapor deposited silicon dioxide, whereas it is independent of the substrate's surface topography. Finally, the interpretation of Micro-Raman experiments for the evaluation of the respective volume fractions of amorphous/microcrystalline phases in the layers is discussed in relation with their spatial distribution. © 2005 Elsevier B.V. All rights reserved

Biomarkers of oxidative stress and its association with the urinary reducing capacity in bus maintenance workers

<p>Abstract</p> <p>Background</p> <p>Exposure to particles (PM) induces adverse health effects (cancer, cardiovascular and pulmonary diseases). A key-role in these adverse effects seems to be played by oxidative stress, which is an excess of reactive oxygen species relative to the amount of reducing species (including antioxidants), the first line of defense against reactive oxygen species. The aim of this study was to document the oxidative stress caused by exposure to respirable particles <it>in vivo</it>, and to test whether exposed workers presented changes in their urinary levels for reducing species.</p> <p>Methods</p> <p>Bus depot workers (n = 32) exposed to particles and pollutants (respirable PM₄, organic and elemental carbon, particulate metal content, polycyclic aromatic hydrocarbons, NO_x, O₃) were surveyed over two consecutive days. We collected urine samples before and after each shift, and quantified an oxidative stress biomarker (8-hydroxy-2'-deoxyguanosine), the reducing capacity and a biomarker of PAH exposure (1-hydroxypyrene). We used a linear mixed model to test for associations between the oxidative stress status of the workers and their particle exposure as well as with their urinary level of reducing species.</p> <p>Results</p> <p>Workers were exposed to low levels of respirable PM₄(range 25-71 μg/m³). However, urinary levels of 8-hydroxy-2'-deoxyguanosine increased significantly within each shift and between both days for non-smokers. The between-day increase was significantly correlated (p < 0.001) with the concentrations of organic carbon, NO_x, and the particulate copper content. The within-shift increase in 8OHdG was highly correlated to an increase of the urinary reducing capacity (Spearman ρ = 0.59, p < 0.0001).</p> <p>Conclusions</p> <p>These findings confirm that exposure to components associated to respirable particulate matter causes a systemic oxidative stress, as measured with the urinary 8OHdG. The strong association observed between urinary 8OHdG with the reducing capacity is suggestive of protective or other mechanisms, including circadian effects. Additional investigations should be performed to understand these observations.</p