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Ozone
Kinds of Ozone Terms modified by Ozone Selected AbstractsEVIDENCE-BASED EFFICACY OF OZONE FOR ROOT CANAL IRRIGATIONJOURNAL OF ESTHETIC AND RESTORATIVE DENTISTRY, Issue 5 2008BDentSc, Edward Lynch MA, FDSRCS Ed, FDSRCS Lond Guest Expert, PhD Lond [source] EVIDENCE-BASED CARIES REVERSAL USING OZONEJOURNAL OF ESTHETIC AND RESTORATIVE DENTISTRY, Issue 4 2008BDentSc, Edward Lynch MA, FDSRCSEd, FDSRCSLond Guest Expert, PhD Lond [source] USING OZONE TO TREAT DENTAL CARIESJOURNAL OF ESTHETIC AND RESTORATIVE DENTISTRY, Issue 6 2007Nic Hodson BSc, PhD Guest Experts [source] Antioxidant and inflammatory responses of healthy horses and horses affected by recurrent airway obstruction to inhaled ozoneEQUINE VETERINARY JOURNAL, Issue 3 2005C. M. DEATON Summary Reasons for performing study: Inhaled ozone can induce oxidative injury and airway inflammation. Horses affected by recurrent airway obstruction (RAO) have a decreased pulmonary antioxidant capacity, which may render them more susceptible to oxidative challenge. It is currently unknown whether RAO-affected horses are more susceptible to oxidative stress than those unaffected by RAO. Objectives: To determine whether ozone exposure induces greater oxidative stress and airway inflammation in RAO-affected horses in remission than in healthy horses. Methods: Seven healthy control horses and 7 RAO-affected horses were exposed to 0.8 ppm ozone for 2 h at rest. Results: At baseline, bronchoalveolar lavage fluid (BALF) ascorbic acid concentrations were lower in RAO-affected horses than healthy controls. Ozone appeared to preferentially oxidise glutathione rather than ascorbic acid 6 h after exposure. Individual healthy and RAO-affected horses demonstrated oxidation of BALF glutathione after ozone exposure. Overall, RAO-affected horses did not demonstrate increased oxidative stress following ozone exposure, compared with healthy horses. Ozone did not induce significant airway inflammation in either group. Conclusions: RAO-affected horses in remission are not more sensitive to ozone despite a decreased pulmonary antioxidant capacity. Sensitivity to ozone appears to be independent of initial pulmonary antioxidant status. Potential relevance: Horses with high susceptibility to oxidative stress may benefit from antioxidant supplementation. [source] Effect of ozone on oral cells compared with established antimicrobialsEUROPEAN JOURNAL OF ORAL SCIENCES, Issue 5 2006Karin C. Huth Ozone has been proposed as an alternative antiseptic agent in dentistry based on reports of its antimicrobial effects in both gaseous and aqueous forms. This study investigated whether gaseous ozone (4 × 106 µg m,3) and aqueous ozone (1.25,20 µg ml,1) exert any cytotoxic effects on human oral epithelial (BHY) cells and gingival fibroblast (HGF-1) cells compared with established antiseptics [chlorhexidine digluconate (CHX) 2%, 0.2%; sodium hypochlorite (NaOCl) 5.25%, 2.25%; hydrogen peroxide (H2O2) 3%], over a time of 1 min, and compared with the antibiotic, metronidazole, over 24 h. Cell counts, metabolic activity, Sp-1 binding, actin levels, and apoptosis were evaluated. Ozone gas was found to have toxic effects on both cell types. Essentially no cytotoxic signs were observed for aqueous ozone. CHX (2%, 0.2%) was highly toxic to BHY cells, and slightly (2%) and non-toxic (0.2%) to HGF-1 cells. NaOCl and H2O2 resulted in markedly reduced cell viability (BHY, HGF-1), whereas metronidazole displayed mild toxicity only to BHY cells. Taken together, aqueous ozone revealed the highest level of biocompatibility of the tested antiseptics. [source] Kinetics of the gas-phase reaction of CF3OC(O)H with OH radicals at 242,328 KINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 6 2004L. Chen The rate constants, k1, of the reaction of CF3OC(O)H with OH radicals were measured by using a Fourier transform infrared spectroscopic technique in an 11.5-dm3 reaction chamber at 242,328 K. OH radicals were produced by UV photolysis of an O3,H2O,He mixture at an initial pressure of 200 Torr. Ozone was continuously introduced into the reaction chamber during UV irradiation. With CF3OCH3 as a reference compound, k1 at 298 K was (1.65 ± 0.13) × 10,14 cm3 molecule,1 s,1. The temperature dependence of k1 was determined as (2.33 ± 0.42) × 10,12 exp[,(1480 ± 60)/T] cm3 molecule,1 s,1; possible systematic uncertainty could add an additional 20% to the k1 values. The atmospheric lifetime of CF3OC(O)H with respect to reaction with OH radicals was calculated to be 3.6 years. © 2004 Wiley Periodicals, Inc. Int J Chem Kinet 36: 337,344 2004 [source] Rate constants for the gas-phase reaction of CF3CF2CF2CF2CF2CHF2 with OH radicals at 250,430 KINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 1 2004L. Chen The rate constants k1 for the reaction of CF3CF2CF2CF2CF2CHF2 with OH radicals were determined by using both absolute and relative rate methods. The absolute rate constants were measured at 250,430 K using the flash photolysis,laser-induced fluorescence (FP-LIF) technique and the laser photolysis,laser-induced fluorescence (LP-LIF) technique to monitor the OH radical concentration. The relative rate constants were measured at 253,328 K in an 11.5-dm3 reaction chamber with either CHF2Cl or CH2FCF3 as a reference compound. OH radicals were produced by UV photolysis of an O3,H2O,He mixture at an initial pressure of 200 Torr. Ozone was continuously introduced into the reaction chamber during the UV irradiation. The k1 (298 K) values determined by the absolute method were (1.69 ± 0.07) × 10,15 cm3 molecule,1 s,1 (FP-LIF method) and (1.72 ± 0.07) × 10,15 cm3 molecule,1 s,1 (LP-LIF method), whereas the K1 (298 K) values determined by the relative method were (1.87 ± 0.11) × 10,15 cm3 molecule,1 s,1 (CHF2Cl reference) and (2.12 ± 0.11) × 10,15 cm3 molecule,1 s,1 (CH2FCF3 reference). These data are in agreement with each other within the estimated experimental uncertainties. The Arrhenius rate constant determined from the kinetic data was K1 = (4.71 ± 0.94) × 10,13 exp[,(1630 ± 80)/T] cm3 molecule,1 s,1. Using kinetic data for the reaction of tropospheric CH3CCl3 with OH radicals [k1 (272 K) = 6.0 × 10,15 cm3 molecule,1 s,1, tropospheric lifetime of CH3CCl3 = 6.0 years], we estimated the tropospheric lifetime of CF3CF2CF2CF2CF2CHF2 through reaction with OH radicals to be 31 years. © 2003 Wiley Periodicals, Inc. Int J Chem Kinet 36: 26,33, 2004 [source] Effect of Combined Ozone and Organic Acid Treatment for Control of Escherichia coli O157:H7 and Listeria monocytogenes on LettuceJOURNAL OF FOOD SCIENCE, Issue 3 2006Hyun-Gyun Yuk ABSTRACT: This study was conducted to determine the effects of ozonated water (1, 3, and 5 ppm) alone with different exposure times (0.5,1,3, or5min), and combinations of 3 ppm ozone with 1% organic acids (acetic, citric, or lactic acids) during 1-min exposure for inactivating Escherichia coli O157:H7 and Listeria monocytogenes on lettuce and to observe the regrowth of these pathogenic bacteria on treated lettuce during storage for 10 d at 15°C. Results showed that 5 ppm ozone treatment for 5 min gave 1.09-log and 0.94-log reductions of E. coli O157:H7 and L. monocytogenes, respectively, indicating insignificant reductions compared with 3 ppm ozone treatment for 5 min. Treatment with 3 ppm ozone combined with 1 % citric acid for 1 min immersing resulted in 2.31 - and 1.84-log reductions (P < 0.05), respectively. During storage at 15°C for 10 d after combined treatment and packaging, populations of E. coli O157:H7 and L. monocytogenes increased to approximately 9.0-log colony forming unit (CFU) /g, indicating that this treatment did not have a residual antimicrobial effect during storage. Although the storage study did not show control of these pathogens, the combined ozone-organic acid treatment was more effective in reducing population levels of these pathogens on lettuce than individual treatments. [source] Inactivation of Escherichia coli O157:H7 and Salmonella in Apple Cider and Orange Juice Treated with Combinations of Ozone, Dimethyl Dicarbonate, and Hydrogen PeroxideJOURNAL OF FOOD SCIENCE, Issue 4 2005Robert C. Williams ABSTRACT: Inactivation of Escherichia coli O157:H7 and Salmonella in apple cider and orange juice treated with ozone in combination with antimicrobials was evaluated. E. coli O157:H7 or Salmonella was suspended in cider and orange juice, and ozone was pumped into juices (4°C) containing dimethyl dicarbonate (DMDC; 250 or 500 ppm) or hydrogen peroxide (300 or 600 ppm) for up to 90 min (study 1) or 60 min followed by 24-h storage at 4°C (study 2). Study 1: No combination of treatments resulted in a 5-log colony-forming units (CFU) /mL reduction of either pathogen. Study 2: All combinations of antimicrobials plus ozone treatments, followed by refrigerated storage, caused greater than a 5-log CFU/mL reduction, except ozone/DMDC (250 ppm) treatment in orange juice. Ozone treatment in combination with DMDC or hydrogen peroxide followed by refrigerated storage may provide an alternative to thermal pasteurization to meet the 5-log reduction standard in cider and orange juice. [source] Inactivation Kinetics of Foodborne Spoilage and Pathogenic Bacteria by OzoneJOURNAL OF FOOD SCIENCE, Issue 3 2000J.-G. Kim ABSTRACT: Ozone was tested against Pseudomonas fluorescens, Escherichia coli O157:H7, Leuconostoc mesenteroides, and Listeria monocytogenes. When kinetic data from a batch reactor were fitted to a dose-response model, a 2-phased linear relationship was observed. A continuous ozone reactor was developed to ensure a uniform exposure of bacterial cells to ozone and a constant concentration of ozone during the treatment. Survivors plots in the continuous system were linear initially, followed by a concave downward pattern. Exposure of bacteria to ozone at 2.5 ppm for 40 s caused 5 to 6 log decrease in count. Resistance of tested bacteria to ozone followed this descending order: E. coli O157:H7, P. fluorescens, L. mesenteroides, and L. monocytogenes. [source] The Ozone Component of Global Change: Potential Effects on Agricultural and Horticultural Plant Yield, Product Quality and Interactions with Invasive SpeciesJOURNAL OF INTEGRATIVE PLANT BIOLOGY, Issue 4 2009Fitzgerald Booker The productivity, product quality and competitive ability of important agricultural and horticultural plants in many regions of the world may be adversely affected by current and anticipated concentrations of ground-level ozone (O3). Exposure to elevated O3 typically results in suppressed photosynthesis, accelerated senescence, decreased growth and lower yields. Various approaches used to evaluate O3 effects generally concur that current yield losses range from 5% to 15% among sensitive plants. There is, however, considerable genetic variability in plant responses to O3. To illustrate this, we show that ambient O3 concentrations in the eastern United States cause substantially different levels of damage to otherwise similar snap bean cultivars. Largely undesirable effects of O3 can also occur in seed and fruit chemistry as well as in forage nutritive value, with consequences for animal production. Ozone may alter herbicide efficacy and foster establishment of some invasive species. We conclude that current and projected levels of O3 in many regions worldwide are toxic to sensitive plants of agricultural and horticultural significance. Plant breeding that incorporates O3 sensitivity into selection strategies will be increasingly necessary to achieve sustainable production with changing atmospheric composition, while reductions in O3 precursor emissions will likely benefit world food production and reduce atmospheric concentrations of an important greenhouse gas. [source] Inactivation of Salmonella enterica serovar enteritidis in shell eggs by sequential application of heat and ozoneLETTERS IN APPLIED MICROBIOLOGY, Issue 6 2008J.J. Perry Abstract Aims:, To assess the contribution of ozone to lethality of Salmonella enterica serovar Enteritidis in experimentally inoculated whole shell eggs that are sequentially treated with heat and gaseous ozone in pilot-scale equipment. Methods and Results:, Whole shell eggs were inoculated with small populations of Salmonella Enteritidis (8·5 × 104,2·4 × 105 CFU per egg) near the egg vitelline membrane. Eggs were subjected to immersion heating (57°C for 21 min), ozone treatment (vacuum at 67·5 kPa, followed by ozonation at a maximum concentration of approx. 140 g ozone m,3 and 184,198 kPa for 40 min) or a combination of both treatments. Survivors were detected after an enrichment process or enumerated using modified most probable number technique. Ozone, heat and combination treatments inactivated 0·11, 3·1 and 4·2 log Salmonella Enteritidis per egg, respectively. Conclusions:, Sequential application of heat and gaseous ozone was significantly more effective than either heat or ozone alone. The demonstrated synergy between these treatment steps should produce safer shell eggs than the heat treatment alone. Significance and Impact of the Study:, Shell eggs are the most common vehicle for human infection by Salmonella Enteritidis. Many cases of egg-related salmonellosis are reported annually despite efforts to reduce contamination, including thermal pasteurization of shell eggs and egg products. Treatment with ozone-based combination should produce shell eggs safer than those treated with heat alone. [source] The ozone paradox: Ozone is a strong oxidant as well as a medical drugMEDICINAL RESEARCH REVIEWS, Issue 4 2009Velio Bocci Abstract After five decades characterized by empiricism and several pitfalls, some of the basic mechanisms of action of ozone in pulmonary toxicology and in medicine have been clarified. The present knowledge allows to understand the prolonged inhalation of ozone can be very deleterious first for the lungs and successively for the whole organism. On the other hand, a small ozone dose well calibrated against the potent antioxidant capacity of blood can trigger several useful biochemical mechanisms and reactivate the antioxidant system. In detail, firstly ex vivo and second during the infusion of ozonated blood into the donor, the ozone therapy approach involves blood cells and the endothelium, which by transferring the ozone messengers to billions of cells will generate a therapeutic effect. Thus, in spite of a common prejudice, single ozone doses can be therapeutically used in selected human diseases without any toxicity or side effects. Moreover, the versatility and amplitude of beneficial effect of ozone applications have become evident in orthopedics, cutaneous, and mucosal infections as well as in dentistry. © 2009 Wiley Periodicals, Inc. Med Res Rev [source] Microbicidal efficacy of ozonated water against Candida albicans adhering to acrylic denture platesMOLECULAR ORAL MICROBIOLOGY, Issue 4 2005M. Arita Background/aims:, Ozone is known to act as a strong antimicrobial agent against bacteria, fungi, and viruses. We examined the effect of ozonated water on Candida albicans on acrylic denture plate. Methods:, The heat-cured acrylic resins were cultured with C. albicans. After treatment of flowing ozonated water, the number of attached C. albicans was counted. In some experiments, the test samples were treated with ozonated water in combination with ultrasonication. Results:, After exposure to flowing ozonated water (2 or 4 mg/l) for 1 min, viable C. albicans cells were nearly nonexistent. The combination of ozonated water and ultrasonication had a strong effect on the viability of C. albicans adhering to the acrylic resin plates. There were no significant differences in antimicrobial activity against C. albicans between plates immersed in ozonated water with ultrasonication and those treated with commercially available denture cleaners. In addition, electron microscopic analysis revealed that small amounts of C. albicans remained on the plate after exposure to flowing ozonated water or immersion in ozonated water with ultrasonication. Conclusion:, Our results suggest that application of ozonated water may be useful in reducing the number of C. albicans on denture plates. [source] CASIROZ: Root Parameters and Types of Ectomycorrhiza of Young Beech Plants Exposed to Different Ozone and Light RegimesPLANT BIOLOGY, Issue 2 2007eleznik Abstract: Tropospheric ozone (O3) triggers physiological changes in leaves that affect carbon source strength leading to decreased carbon allocation below-ground, thus affecting roots and root symbionts. The effects of O3 depend on the maturity-related physiological state of the plant, therefore adult and young forest trees might react differently. To test the applicability of young beech plants for studying the effects of O3 on forest trees and forest stands, beech seedlings were planted in containers and exposed for two years in the Kranzberg forest FACOS experiment (Free-Air Canopy O3 Exposure System, http:www.casiroz.de) to enhanced ozone concentration regime (ambient [control] and double ambient concentration, not exceeding 150 ppb) under different light conditions (sun and shade). After two growing seasons the biomass of the above- and below-ground parts, beech roots (using WinRhizo programme), anatomical and molecular (ITS-RFLP and sequencing) identification of ectomycorrhizal types and nutrient concentrations were assessed. The mycorrhization of beech seedlings was very low (ca. 5 % in shade, 10 % in sun-grown plants), no trends were observed in mycorrhization (%) due to ozone treatment. The number of Cenococcum geophilum type of ectomycorrhiza, as an indicator of stress in the forest stands, was not significantly different under different ozone treatments. It was predominantly occurring in sun-exposed plants, while its majority share was replaced by Genea hispidula in shade-grown plants. Different light regimes significantly influenced all parameters except shoot/root ratio and number of ectomycorrhizal types. In the ozone fumigated plants the number of types, number of root tips per length of 1 to 2 mm root diameter, root length density per volume of soil and concentration of Mg were significantly lower than in control plants. Trends to a decrease were found in root, shoot, leaf, and total dry weights, total number of root tips, number of vital mycorrhizal root tips, fine root (mass) density, root tip density per surface, root area index, concentration of Zn, and Ca/Al ratio. Due to the general reduction in root growth indices and nutrient cycling in ozone-fumigated plants, alterations in soil carbon pools could be predicted. [source] No interaction between methyl jasmonate and ozone in Pima cotton: growth and allocation respond independently to bothPLANT CELL & ENVIRONMENT, Issue 5 2010D. A. GRANTZ ABSTRACT Ozone (O3) is damaging to plants, inducing signalling pathways involving antagonism between jasmonates and ethylene. These pathways mediate O3 responses, particularly to acute exposure, and their manipulation protected several species against acute and chronic O3. We use chronic daily exposure of up to 163 ppb O3, and twice weekly application of up to 320 µg plant,1 methyl jasmonate (MeJA) to test two hypothesizes: 1) a low rate of MeJA does not affect growth but increases O3 sensitivity; 2) a high rate inhibits growth but reduces O3 sensitivity. Both hypotheses were rejected. Growth declined with increases in both MeJA and O3. MeJA at 40 µg plant,1 caused no direct effect, and at 160 µg plant,1 reduced growth similarly at all O3. Neither rate altered O3 sensitivity. These additive responses are not consistent with protection by MeJA in this system. They may reflect inter-specific differences in signalling, since O3 concentrations used here exceeded some reported acute exposures. Alternatively, parallel responses to O3 and MeJA may suggest that O3 -induced jasmonates play a developmental role in chronic response but no protective role in the absence of lesions characteristic of acute exposure. MeJA appears useful as a probe of these mechanisms. [source] Effects of elevated ozone and low light on diurnal and seasonal carbon gain in sugar maplePLANT CELL & ENVIRONMENT, Issue 7 2001M. A. Topa Abstract The long-term interactive effects of ozone and light on whole-tree carbon balance of sugar maple (Acer saccharum Marsh.) seedlings were examined, with an emphasis on carbon acquisition, foliar partitioning into starch and soluble sugars, and allocation to growth. Sugar maple seedlings were fumigated with ambient, 1·7 × ambient and 3·0 × ambient ozone in open-top chambers for 3 years under low and high light (15 and 35% full sunlight, respectively). Three years of ozone fumigation reduced the total biomass of seedlings in the low- and high-light treatments by 64 and 41%, respectively, but had no effect on whole-plant biomass allocation. Ozone had no effect on net photosynthesis until late in the growing season, with low-light seedlings generally exhibiting more pronounced reductions in photosynthesis. The late-season reduction in photosynthesis was not due to impaired stomatal function, but was associated more with accelerated senescence or senescence-like injury. In contrast, the 3·0 × ambient ozone treatment immediately reduced diurnal starch accumulation in leaves by over 50% and increased partitioning of total non-structural carbohydrates into soluble sugars, suggesting that injury repair processes may be maintaining photosynthesis in late spring and early summer at the expense of storage carbon. The results in the present study indicate that changes in leaf-level photosynthesis may not accurately predict the growth response of sugar maple to ozone in different light environments. The larger reduction in seedling growth under low-light conditions suggests that seedlings in gap or closed-canopy environments are more susceptible to ozone than those in a clearing. Similarly, understanding the effects of tropospheric ozone on net carbon gain of a mature tree will require scaling of leaf-level responses to heterogeneous light environments, where some leaves may be more susceptible than others. [source] Decolorization of RR-120 Dye Using Ozone and Ozone/UV in a Semi-Batch ReactorTHE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 6 2004Mohammad Kazemi Abstract Treatability of RR-120 aqueous dye solutions using O3 and O3/UV was studied in a bench scale set-up. Reduction in colour and chemical oxygen demand (COD) under various pH and initial dye concentrations were investigated. Pseudo first order reaction rate was satisfactorily used for kinetic interpretations in destruction of the dye. The results showed that decolorization with O3 was faster at neutral pH values. While use of UV had a small effect on ozonation at low pH values, UV radiation had a considerable effect at pH values of 7 and above. It was found that ozone utilization efficiency of higher than 95% could be attained in the experimental set up. On a étudié la possibilité de traitement de solutions aqueuses de colorant RR-120 à l'aide d'O3 et O3/UV dans un banc d'essai. La réduction de la demande chimique en oxygène (DCO) et en colorant a été étudiée pour différentes concentrations initiales de colorant. La vitesse de réaction du pseudo-premier ordre a été utilisée avec succès pour les interprétations cinétiques de la destruction du colorant. Les résultats montrent que la décoloration avec l'O3 est plus rapide à des valeurs de pH neutres. Alors que le recours aux UV a un faible effet sur l'ozonation à de faibles valeurs de pH, la radiation par UV a un effet considérable à des valeurs de pH de 7 et au-dessus. On a trouvé qu'une efficacité d'utilisation de l'ozone supérieure à 95% pouvait être atteinte dans l'installation expérimentale. [source] Oxidized nitrogen and ozone interaction with forests.THE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 600 2004I: Experimental observations, analysis of exchange with Douglas fir Abstract Measurements of NOx and O3 exchange to and from a forest canopy are described with reference to canopy and ecosystem processes leading to emission of NO2. The soil below the forested measurement location is shown to be a net source of reactive oxidized nitrogen (as NO). It is shown that a large fraction (around 58% on average) of the emitted NO escapes out of the trunk space to react within and above the canopy. Fluxes of NO2 above the canopy are bi-directional, with large fluxes and most emission events taking place during the day. Deposition is shown to take place without significant changes in the vertical flux; however there appears to be rapid chemical reaction leading to significant flux divergence taking place during emission events. Above the top of the canopy (22 m), changes of 200% in the NO2 flux between 25 and 35 m are not uncommon. Ozone deposition to the forest system has been investigated. The flux is often related to stomatal deposition, but there are periods when large non-stomatal fluxes are observed. At night there is a large vertical divergence in the ozone flux above the canopy, probably related to reaction with NO from the forest soil. The reaction of O3 with volatile organic compounds is found, in general, to be negligible with respect to ozone concentrations and fluxes. Ozone is found to deposit mainly to leaf stomata during the day, with a small but not insignificant contribution from NO reaction. However, the nocturnal ozone budget for the forest changes significantly, with most of the measured deposition accounted for by soil uptake and reaction with NO. The resultant problems related to inadequate treatment of air chemistry when interpreting O3 fluxes in high NO emission environments are identified. Copyright © 2004 Royal Meteorological Society. [source] Decay of a cut-off low and contribution to stratosphere-troposphere exchangeTHE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 564 2000H. Gouget Abstract We present a case study of the decay of a cut-off low over north-west Europe in June 1996, to establish how the stratospheric air initially contained within it was transferred to the troposphere. Two mechanisms for stratosphere-troposphere exchange are examined: direct convective erosion of the base of the low, and filamentation of the outer layers of the low along the flank of the polar jet stream. The approach taken relies on a combination of in-situ ozone and humidity measurements by MOZAIC (Measurement of Ozone and water vapour by Airbus In-service aircraft) aircraft and ozonesondes, and the European Centre for Medium-Range Weather Forecasts analyses. MOZAIC ozone is used to choose two analyses eight days apart at the genesis (14 June 1996) and decay (22 June 1996) of the low which have a consistent ozone/potential-vorticity relationship. Trajectories (both isentropic and three dimensional (3D)) between these two analyses reveal a consistent pattern; at the base of the low (310 K, 450 mb) all the trajectories attain tropospheric PV values whereas, at 320 K, those trajectories that leave the low experience a decrease in PV and those that do not leave the low retain their initial PV. We propose that air parcels leaving the low were stretched into thin filaments along the flank of the jet stream, which made them vulnerable to 3D mixing. A MOZAIC flight on 21 June 1996 provides direct evidence for this process. Up to 22 June 1996 (by which time the low had lost its closed circulation) the satellite images showed very little convection beneath the corresponding PV anomaly. Mixing was only effective at the very base of the stratospheric air at 310 K. On 22 June the remaining remnant of high PV was advected into a region of deep convection over central and eastern Europe, mixing the remaining stratospheric air into the troposphere. Of the initial mass of 1015 kg of stratospheric air contained in the low, 6 × 1014 kg was stripped into filaments along the jet and 4 × 1014 kg remained to be mixed by convection during the period 22,23 June 1996. [source] Effects of in vitro exposure to ozone and/or hyperoxia on superoxide dismutase, catalase, glutathione and lipid peroxidation in red blood cells and plasma of rainbow trout, Oncorhynchus mykiss (Walbaum)AQUACULTURE RESEARCH, Issue 3 2002O Ritola Abstract In aquaculture, ozone is used as a disinfectant. In its production, extensive amounts of oxygen are formed resulting in hyperoxic conditions in culture units. Both ozone and hyperoxia have the potential to be toxic via pro-oxidant mechanisms and to activate antioxidant defence systems in cultured species. To eliminate systemic effects, blood of rainbow trout, Oncorhynchus mykiss (Walbaum), was exposed in vitro for 5 min to ozone/hyperoxia or hyperoxia, and changes in antioxidant defences and lipid peroxidation were measured after exposure. Ozone exposure caused severe damage in red blood cells (rbc) detected as increased lipid peroxidation and oxidized glutathione (GSSG) levels in both plasma and rbc. Oxygen exposure alone increased intracellular lipid peroxidation and GSSG levels 10 min after exposure and was not evident in the plasma at any time. Ozone, but not oxygen exposure, decreased reduced glutathione (GSH) levels in plasma, and the changes were negatively correlated with increased lipid peroxidation in rbc, indicating that extracellular GSH has a dynamic role in the protection of rbc from direct oxidation by ozone. Both ozone and hyperoxic conditions increased superoxide dismutase (SOD) activity in rbc 3 and 6 h after exposure. In contrast, catalase activity was only increased 10 min after oxygen exposure, suggesting other catalase activation mechanisms rather than enzyme induction. The recovery of lipid peroxidation and GSSG levels in rbc after hyperoxia, but not ozone exposure, indicated a capacity to defend against hyperoxia-produced oxidative damage, but an overwhelming of antioxidant defences by ozone in rainbow trout rbc in vitro. [source] The Reaction of Ozone with the Hydroxide Ion: Mechanistic Considerations Based on Thermokinetic and Quantum Chemical Calculations and the Role of HO4, in Superoxide DismutationCHEMISTRY - A EUROPEAN JOURNAL, Issue 4 2010Gábor Merényi Prof. Abstract The reaction of OH, with O3 eventually leads to the formation of . OH radicals. In the original mechanistic concept (J. Staehelin, J. Hoigné, Environ. Sci. Technol.1982, 16, 676,681), it was suggested that the first step occurred by O transfer: OH,+O3,HO2,+O2 and that . OH was generated in the subsequent reaction(s) of HO2, with O3 (the peroxone process). This mechanistic concept has now been revised on the basis of thermokinetic and quantum chemical calculations. A one-step O transfer such as that mentioned above would require the release of O2 in its excited singlet state (1O2, O2(1,g)); this state lies 95.5,kJ,mol,1 above the triplet ground state (3O2, O2(3,g,)). The low experimental rate constant of 70,M,1,s,1 is not incompatible with such a reaction. However, according to our calculations, the reaction of OH, with O3 to form an adduct (OH,+O3,HO4,; ,G=3.5,kJ,mol,1) is a much better candidate for the rate-determining step as compared with the significantly more endergonic O transfer (,G=26.7,kJ,mol,1). Hence, we favor this reaction; all the more so as numerous precedents of similar ozone adduct formation are known in the literature. Three potential decay routes of the adduct HO4, have been probed: HO4,,HO2,+1O2 is spin allowed, but markedly endergonic (,G=23.2,kJ,mol,1). HO4,,HO2,+3O2 is spin forbidden (,G=,73.3,kJ,mol,1). The decay into radicals, HO4,,HO2.+O2.,, is spin allowed and less endergonic (,G=14.8,kJ,mol,1) than HO4,,HO2,+1O2. It is thus HO4,,HO2.+O2., by which HO4, decays. It is noted that a large contribution of the reverse of this reaction, HO2.+O2.,,HO4,, followed by HO4,,HO2,+3O2, now explains why the measured rate of the bimolecular decay of HO2. and O2., into HO2,+O2 (k=1×108,M,1,s,1) is below diffusion controlled. Because k for the process HO4,,HO2.+O2., is much larger than k for the reverse of OH,+O3,HO4,, the forward reaction OH,+O3,HO4, is practically irreversible. [source] Orders-of-Magnitude Reduction of the Contact Resistance in Short-Channel Hot Embossed Organic Thin Film Transistors by Oxidative Treatment of Au-Electrodes,ADVANCED FUNCTIONAL MATERIALS, Issue 15 2007B. Stadlober Abstract In this study we report on the optimization of the contact resistance by surface treatment in short-channel bottom-contact OTFTs based on pentacene as semiconductor and SiO2 as gate dielectric. The devices have been fabricated by means of nanoimprint lithography with channel lengths in the range of 0.3,,m,<,L,<,3.0,,m. In order to reduce the contact resistance the Au source- and drain-contacts were subjected to a special UV/ozone treatment, which induced the formation of a thin AuOx layer. It turned out, that the treatment is very effective (i),in decreasing the hole-injection barrier between Au and pentacene and (ii),in improving the morphology of pentacene on top of the Au contacts and thus reducing the access resistance of carriers to the channel. Contact resistance values as low as 80,,,cm were achieved for gate voltages well above the threshold. In devices with untreated contacts, the charge carrier mobility shows a power-law dependence on the channel length, which is closely related to the contact resistance and to the grain-size of the pentacene crystallites. Devices with UV/ozone treated contacts of very low resistance, however, exhibit a charge carrier mobility in the range of 0.3,cm2,V,1,s,1,<,,,<,0.4,cm2,V,1,s,1 independent of the channel length. [source] Continuous surface modification process with ultraviolet/ozone for improving interfacial adhesion of poly(ethylene terephthalate)/epoxy compositesPOLYMER COMPOSITES, Issue 5 2006Paisan Khanchaitit This study proposed a continuous UV/ozone surface modification process for the production of polymeric fiber-reinforced polymer composite. A gas phase photoreactor using the conventional low-pressure mercury UV lamps and the economically made ozone generators were designed and constructed. Poly(ethylene terephthalate) (PET) fibers and epoxy resin were chosen as a reinforcement and a matrix, respectively. The synergistic effects of UV and various gas species (nitrogen, air, oxygen, air/ozone, and oxygen/ozone) exposure as well as the effects of exposure time, i.e., 2, 5, and 10 min, on the morphology and chemistry of PET-fiber surfaces were investigated by using a scanning electron microscope coupled with energy dispersive x-ray analysis (SEM/EDX). The tensile testing and analysis of fractography of the resulted composites were performed to evaluate the effectiveness of the process. The SEM/EDX results showed that the effects of the treatment were dependent on both the concentration of reactive species present in the gases and the exposure time. The PET fibers treated under UV/O2 + O3 exposure for 5 min yielded the resulting composite with the highest tensile strength value. Under this condition, the tensile strength of the composite can be increased up to 63% in comparison with that of the untreated PET fiber/epoxy composite. The results are of interest for application as an in-line surface modification for composite productions. POLYM. COMPOS., 27:484,490, 2006. © 2006 Society of Plastics Engineers [source] Possible Environmental Factors Underlying Amphibian Decline in Eastern Puerto Rico: Analysis of U.S. Government Data ArchivesCONSERVATION BIOLOGY, Issue 4 2001Robert F. Stallard I examined changes in environmental conditions by examining time-series data sets that extend back at least into the 1980s, a period when frog populations were declining. The data include forest cover; annual mean, minimum, and maximum daily temperature; annual rainfall; rain and stream chemistry; and atmospheric-dust transport. I examined satellite imagery and air-chemistry samples from a single National Aeronautics and Space Administration aircraft flight across the Caribbean showing patches of pollutants, described as thin sheets or lenses, in the lower troposphere. The main source of these pollutants appeared to be fires from land clearing and deforestation, primarily in Africa. Some pollutant concentrations were high and, in the case of ozone, approached health limits set for urban air. Urban pollution impinging on Puerto Rico, dust generation from Africa ( potential soil pathogens), and tropical forest burning ( gaseous pollutants) have all increased during the last three decades, overlapping the timing of amphibian declines in eastern Puerto Rico. None of the data sets pointed directly to changes so extreme that they might be considered a direct lethal cause of amphibian declines in Puerto Rico. More experimental research is required to link any of these environmental factors to this problem. Resumen: Las pasadas tres décadas han visto grandes disminuciones poblacionales de especies de anfibios en altas elevaciones de Puerto Rico oriental, una región única en los trópicos húmedos debido al grado de monitoreo ambiental que se ha llevado a cabo mediante los esfuerzos de las agencias de gobierno de los Estados Unidos. Examiné los cambios en condiciones ambientales mediante el análisis de datos de series de tiempo que se extienden hasta los 1980s, un periodo en el que las poblaciones de ranas estaban declinando. Los datos incluyen cobertura forestal; temperatura diaria media, mínima y máxima anual; precipitación anual; química de la lluvia y arroyos; y el transporte atmosférico de polvo. Examiné imágenes de satélite y muestras de química del aire obtenidos de un solo vuelo de una nave de la NASA a lo largo del Caribe que mostraba parches de contaminantes descritas como capas delgadas de lentes en la inferior troposfera. La mayor fuente de contaminantes parece ser los incendios de tierras clareadas y la deforestación, principalmente en África. Algunas concentraciones de contaminantes fueron altas y en el caso del ozono, se aproximó a los límites de salud establecidos para aire urbano. La contaminación urbana afectando a Puerto Rico, la generación de polvo en África ( patógenos del suelo potenciales) y la quema de bosque tropical (contaminantes gaseosos) han incrementado durante las últimas tres décadas, superponiéndose con el periodo en que oturrieron las disminuciones de anfibios en Puerto Rico oriental. Ninguno de estos conjuntos de datos señaló directamente hacia cambios tan extremos que debieran ser considerados como una causa letal directa de las disminuciones en Puerto Rico. Se requiere de más investigación experimental que vincule a estos factores ambientales con este problema. [source] Air pollution impedes plant-to-plant communication by volatilesECOLOGY LETTERS, Issue 9 2010James D. Blande Ecology Letters (2010) 13: 1172,1181 Abstract Volatile organic compounds (VOCs) emitted by damaged plants convey information to undamaged neighbouring plants, and previous research has shown that these signals are effective over short distances in nature. Many herbivore-induced VOCs react with ozone, which is the most important tropospheric air pollutant in rural areas. We used extrafloral nectar (EFN) secretion as a phenotypic indicator of between-plant communication in Phaseolus lunatus L. (Lima bean) and show that an ozone-rich (80 ppb) atmosphere reduces the distance over which signalling occurs. We found that ozone degrades several herbivore-induced VOCs, a likely mechanism reducing communication distances. Direct exposure to 80-ppb ozone did not affect the VOC emissions from P. lunatus. In addition, we demonstrated that high ozone concentrations, 120 and 160 ppb, induced EFN secretion in exposed plants, whereas more moderate concentrations, 80 and 100 ppb, did not. This suggests that ozone can play a complex role in the indirect defence of P. lunatus. [source] Species-specific responses to atmospheric carbon dioxide and tropospheric ozone mediate changes in soil carbonECOLOGY LETTERS, Issue 11 2009Alan F. Talhelm Abstract We repeatedly sampled the surface mineral soil (0,20 cm depth) in three northern temperate forest communities over an 11-year experimental fumigation to understand the effects of elevated carbon dioxide (CO2) and/or elevated phyto-toxic ozone (O3) on soil carbon (C). After 11 years, there was no significant main effect of CO2 or O3 on soil C. However, within the community containing only aspen (Populus tremuloides Michx.), elevated CO2 caused a significant decrease in soil C content. Together with the observations of increased litter inputs, this result strongly suggests accelerated decomposition under elevated CO2. In addition, an initial reduction in the formation of new (fumigation-derived) soil C by O3 under elevated CO2 proved to be only a temporary effect, mirroring trends in fine root biomass. Our results contradict predictions of increased soil C under elevated CO2 and decreased soil C under elevated O3 and should be considered in models simulating the effects of Earth's altered atmosphere. [source] Association between atmospheric ozone levels and damage to human nasal mucosa in Florence, ItalyENVIRONMENTAL AND MOLECULAR MUTAGENESIS, Issue 3 2003Stefania Pacini Abstract We evaluated the effects of urban air pollutants on human nasal mucosa over an 8-month period on 102 subjects living in Florence, Tuscany, Italy. A group of subjects living in a city with a lower level of pollution (Sassari, Sardinia, Italy) was also analyzed. Nasal mucosa cells were harvested by brushing, a noninvasive procedure. Half of the cells were used for genotoxicity studies using the alkaline comet assay, and half for morphological studies. The levels of DNA damage in the nasal mucosa were considerably higher (+73%) in the subjects living in Florence than in Sassari. High levels of atmospheric ozone in Florence air correlated with DNA damage, and to the prevalence of inflammatory pathologies of the upper respiratory tract, although the ozone concentrations were below the Italian recommended attention level. Furthermore, higher levels of DNA damage were correlated with a dysfunction in the ability to maintain a normal epithelial cell structure. These data suggest an association between ozone air levels and damage in the upper respiratory tract. It remains unclear whether ozone itself or other associated pollutants are responsible for the observed alterations. Environ. Mol. Mutagen. 42:127,135, 2003. © 2003 Wiley-Liss, Inc. [source] In-Situ ozonation of contaminated groundwaterENVIRONMENTAL PROGRESS & SUSTAINABLE ENERGY, Issue 3 2000Michael A. Nimmer This paper presents case studies in the application of insitu ozone sparging to remediate petroleum contaminated groundwater. This technology was developed and installed due to shortcomings with other conventional remedial technologies evaluated for groundwater remediation. The main objective of this study was to develop a system to supply ozone to the groundwater aquifer and to evaluate the system performance in the field. Three different applications were evaluated for this study, all containing petroleum-contaminated groundwater. The ozone sparging system consists of an air compressor, ozone generator, a programmable logic controller, and associated gauges and controls. The mixture of air and ozone is injected into the groundwater aquifer through microporous sparge points contained in various sparge well designs. The initial results from the three applications demonstrated that ozone sparging is a viable alternative to remediate petroleum -contaminated groundwater. Significant reductions in petroleum constituents we re observed shortly after system start-up at all sites. During the one to two years operation at the three sites, a number of maintenance items we re identified; these items we re addressed by modifications to the system design and operation. A long-term evaluation of the system operation has not yet been performed. [source] Earthworm toxicity during chemical oxidation of diesel-contaminated sandENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 8 2005Kyung-Hee Shin Abstract An ecotoxicity test with Eisenia fetida was performed to monitor the removal of diesel and toxicity variation during the ozonation process. The three-dimensional (3-D) cell test was introduced for the monitoring of the ozonation process, and the removal rate based on total petroleum hydrocarbons (TPHs) mass was about 95% near the ozone inlet ports. This high removal rate might be caused by the low soil organic matter (SOM) content and low water content of sand. The use of a fiber-optic transflection dip probe (FOTDP) demonstrated that more than half of the injected ozone was consumed by reactions with diesel or natural ozone-consuming materials. The earthworm toxicity test using Eisenia fetida demonstrated that diesel concentrations in soil exceeding 10,000 mg/kg caused a dose-dependent weight loss in earthworms and increased mortality. Toxic effects were reduced greatly or eliminated after ozonation, and the degradation products of the ozonation were not toxic to the earthworms at the concentrations tested. One specific result was that the sublethal test on the earthworm might be more sensitive for the evaluation of the quality of contaminated soil, for some samples, which did not result in mortality and produced an adverse effect on weight. [source] | |||||||||||||||||||||||||||||||||||||||||||||||||