Página 1 dos resultados de 2029 itens digitais encontrados em 0.013 segundos

Estudo da degradação de corante têxtil em matrizes aquosas por meio dos processos oxidativos avançados O3-H2O2/UV e foto-Fenton.; Study on the degradation of a textile dye in aqueous matrices by the oxidative processes O3-H2O2/UV and photo-Fenton.

Santana, Caroline Martins
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 04/12/2009 PT
Relevância na Pesquisa
37.43%
A indústria têxtil gera grandes volumes de efluentes com elevada carga orgânica, forte coloração e toxicidade. Neste trabalho, estuda-se o tratamento de solução aquosa contendo o corante Solophenyl Yellow Arle 154% por meio dos processos O3-H2O2/UV e foto-Fenton, avaliando-se as repostas: remoção de cor em 5 minutos, remoção de cor em 60 minutos, taxa máxima de remoção de cor e remoção de COT em 60 minutos. Os experimentos foram realizados em semibatelada com circulação usando um reator fotoquímico com campo de radiação anular coaxial, constituído de corpo cilíndrico em aço com refletor interno de alumínio para 12 lâmpadas fixadas simetricamente na superfície refletora e um tubo reator em quartzo de 0,7 L, posicionados verticalmente no eixo do refletor. Para o processo O3-H2O2/UV foram utilizadas lâmpadas Phillips TUV (36 W, 254 nm). A corrente gasosa contendo O3 foi introduzida no reator por meio de um difusor. Para o processo foto-Fenton foram utilizadas lâmpadas Sylvania (12 W cada, 300 400 nm) e concentração de Fe(II) de 0,25 mmol/L. Em ambos os processos, solução de peróxido de hidrogênio foi adicionada durante os 30 minutos iniciais de tratamento. As amostras foram analisadas por medidas de carbono orgânico total (COT) e remoção de cor (absorbância medida em 405 nm em espectrofotômetro UV-visível). Em ambos os processos utilizou-se o planejamento experimental Doehlert...

Sensibilidade na estimativa da concentração de poluentes fotoquímicos com a aplicação de diferentes parametrizações de camada limite planetária utilizando o modelo de qualidade do ar WRF/Chem; The sensibility of the estimative concentration of photochemical pollutants using different parameterizations of Planetary Boundary Layer with the air quality WRF/Chem model

Silva Júnior, Rosiberto Salustiano da
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 11/09/2009 PT
Relevância na Pesquisa
27.37%
Neste trabalho foi avaliado o impacto na simulação dos poluentes fotoquímicos do uso de diferentes parametrizações da Camada Limite Planetária (CLP) para a Região Metropolitana de São Paulo, utilizando o modelo de mesoescala não-hidrostático Weather Research and Forecasting (WRF) com o acoplamento dos módulos químicos (WRF/Chem). Para análise da acurácia dos resultados obtidos com o modelo, foram utilizadas as medições realizadas pelas estações automáticas da CETESB em superfície, e a validação do perfil vertical da concentração de O3 com base nos dados do experimento de lançamento de ozoniosondas realizado dentro do contexto de um projeto de políticas públicas (recursos FAPESP) realizado durante o período de estudo. A motivação para a realização do presente trabalho foi a grande dificuldade de representação da estrutura da CLP em especial durante o período noturno sobre áreas urbanas. O estudo contou com a utilização inédita do modelo on-line para simulação da composição química da atmosfera da RMSP, e por fim analisou o impacto do acoplamento com o modelo urbano Urban Canopy Model (UCM), com o modelo WRF-Chem. A área de estudo é a Região Metropolitana de São Paulo e adjacências, e o período estudado foi de 28/10 a 01/11/2006. As variações anuais da temperatura do ar...

Posttranslational modification of Gαo1 generates Gαo3, an abundant G protein in brain

Exner, Torsten; Jensen, Ole N.; Mann, Matthias; Kleuss, Christiane; Nürnberg, Bernd
Fonte: The National Academy of Sciences Publicador: The National Academy of Sciences
Tipo: Artigo de Revista Científica
Publicado em 16/02/1999 EN
Relevância na Pesquisa
27.32%
Gαo, the most abundant G protein in mammalian brain, occurs at least in two subforms, i.e., Gαo1 and Gαo2, derived by alternative splicing of the mRNA. A third Gαo1-related isoform, Gαo3, has been purified, representing about 30% of total Go in brain. Initial studies revealed distinct biochemical properties of Gαo3 as compared with other Gαo isoforms. In matrix-assisted laser desorption/ionization peptide mass mapping of gel-isolated Gαo1 and Gαo3, C-terminal peptides showed a difference of +1 Da for Gαo3. Nanoelectrospray tandem mass spectrometry sequencing revealed an Asp instead of an Asn at position 346 of Gαo3. Gel electrophoretic analysis of recombinant Gαo3 showed the same mobility as native Gαo3 but distinct to Gαo1. The conversion of 346Asn→Asp changed the signaling properties, including the velocity of the basal guanine nucleotide-exchange reaction, which points to the involvement of the C terminus in basal guanosine 5′-[γ-thio]triphosphate binding. No cDNA coding for Gαo3 was detected, suggesting an enzymatic deamidation of Gαo1 by a yet-unidentified activity. Therefore, Gα heterogeneity is generated not only at the DNA or RNA levels, but also at the protein level. The relative amount of Gαo1 and Gαo3 differed from cell type to cell type...

Pandemic Spread of an O3:K6 Clone of Vibrio parahaemolyticus and Emergence of Related Strains Evidenced by Arbitrarily Primed PCR and toxRS Sequence Analyses

Matsumoto, Chiho; Okuda, Jun; Ishibashi, Masanori; Iwanaga, Masaaki; Garg, Pallavi; Rammamurthy, Thandavarayan; Wong, Hin-Chung; Depaola, Angelo; Kim, Yung Bu; Albert, M. John; Nishibuchi, Mitsuaki
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Publicado em /02/2000 EN
Relevância na Pesquisa
27.41%
Vibrio parahaemolyticus O3:K6 strains responsible for the increase in the number of cases of diarrhea in Calcutta, India, beginning in February 1996 and those isolated from Southeast Asian travelers beginning in 1995 were shown to belong to a unique clone characterized by possession of the tdh gene but not the trh gene and by unique arbitrarily primed PCR (AP-PCR) profiles (J. Okuda, M. Ishibashi, E. Hayakawa, T. Nishino, Y. Takeda, A. K. Mukhopadhyay, S. Garg, S. K. Bhattacharya, G. B. Nair, and M. Nishibuchi, J. Clin. Microbiol. 35:3150–3155, 1997). Evidence supporting a hypothesis that this clone emerged only recently and is spreading to many countries was obtained in this study. Of 227 strains isolated in a hospital in Bangladesh between 1977 and 1998, only 22 strains isolated between 1996 and 1998 belonged to the new O3:K6 clone (defined by the serovar, the tdh and trh typing, and AP-PCR profiles). The O3:K6 strains isolated from clinical sources in Taiwan, Laos, Japan, Thailand, Korea, and the United States between 1997 and 1998 were also shown to belong to the new O3:K6 clone. The clonality of the new O3:K6 strains was also confirmed by analysis of the toxRS sequence, which has been shown to be useful for phylogenetic analysis of the members of the genus Vibrio. The toxRS sequences of the representative strains of the new O3:K6 clone differed from those of the O3:K6 strains isolated before 1995 at least at 7 base positions within a 1...

Characteristics of Vibrio parahaemolyticus O3:K6 from Asia

Wong, Hin-Chung; Liu, Shu-Hui; Wang, Tien-Kuei; Lee, Chih-Lung; Chiou, Chien-Shun; Liu, Ding-Ping; Nishibuchi, Mitsuaki; Lee, Bok-Kwon
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Publicado em /09/2000 EN
Relevância na Pesquisa
27.35%
A variety of serovars of the food-borne pathogen Vibrio parahaemolyticus normally cause infection. Since 1996, the O3:K6 strains of this pathogen have caused pandemics in many Asian countries, including Taiwan. For a better understanding of these pandemic strains, the recently isolated clinical O3:K6 strains from India, Japan, Korea, and Taiwan were examined in terms of pulsed-field gel electrophoresis (PFGE) typing and other biological characteristics. After PFGE and cluster analysis, all the O3:K6 strains were grouped into two unrelated groups. The recently isolated O3:K6 strains were all in one group, consisting of eight closely related patterns, with I1(81%) and I5(13%) being the most frequent patterns. Pattern I1 was the major one for strains from Japan, Korea, and Taiwan. All recently isolated O3:K6 strains carried the thermostable direct hemolysin (tdh) gene. No significant difference was observed between recently isolated O3:K6 strains and either non-O3:K6 reference strains or old O3:K6 strains isolated before 1996 with respect to antibiotic susceptibility, the level of thermostable direct hemolysin, and the susceptibility to environmental stresses. Results in this study confirmed that the recently isolated O3:K6 strains of V. parahaemolyticus are genetically close to each other...

Comparative Phenotypic, Molecular, and Virulence Characterization of Vibrio parahaemolyticus O3:K6 Isolates

Yeung, P. S. Marie; Hayes, Micaela C.; DePaola, Angelo; Kaysner, Charles A.; Kornstein, Laura; Boor, Kathryn J.
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Publicado em /06/2002 EN
Relevância na Pesquisa
27.35%
Historically, Vibrio parahaemolyticus infections have been characterized by sporadic cases caused by multiple, diverse serotypes. However, since 1996, V. parahaemolyticus serotype O3:K6 strains have been associated with several large-scale outbreaks of illness, suggesting the emergence of a “new” group of organisms with enhanced virulence. We have applied three different molecular subtyping techniques to identify an appropriate method for differentiating O3:K6 isolates from other serotypes. Pulsed-field gel electrophoresis (PFGE) following NotI digestion differentiated seven closely related subtypes among O3:K6 and related strains, which were distinct from PFGE patterns for non-O3:K6 isolates. Ribotyping and tdh sequencing were less discriminatory than PFGE, but further confirmed close genetic relationships among recent O3:K6 isolates. In vitro adherence and cytotoxicity studies with human epithelial cells showed that O3:K6 isolates exhibited statistically higher levels of adherence and cytotoxicity to host cells than non-O3:K6 isolates. Epithelial cell cytotoxicity patterns were determined with a lactate dehydrogenase release assay. At 3 h postinfection, high relative cytotoxicities (>50% maximum lactate dehydrogenase activity) were found among a greater proportion of recently isolated O3:K6 and closely related strains (75%) than among the non-O3:K6 isolates (23%). A statistically significant relationship between adherence and cytotoxicity suggests that the pathogenic potential of some isolates may be associated with increased adherence to epithelial cells. Our findings suggest that enhanced adherence and cytotoxicity may contribute to the apparent unique pathogenic potential of V. parahaemolyticus O3:K6 strains.

Emergence of a unique O3:K6 clone of Vibrio parahaemolyticus in Calcutta, India, and isolation of strains from the same clonal group from Southeast Asian travelers arriving in Japan.

Okuda, J; Ishibashi, M; Hayakawa, E; Nishino, T; Takeda, Y; Mukhopadhyay, A K; Garg, S; Bhattacharya, S K; Nair, G B; Nishibuchi, M
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /12/1997 EN
Relevância na Pesquisa
27.37%
Active surveillance of Vibrio parahaemolyticus infection among hospitalized patients in Calcutta, India, was initiated in January 1994. The incidence of cases of V. parahaemolyticus infection suddenly increased in February 1996 and has remained high since then. One hundred thirty-four strains of V. parahaemolyticus isolated from January 1994 to August 1996 were examined for serovar, the presence of the thermostable direct hemolysin gene (tdh) and tdh-related hemolysin genes (trh1 and trh2), production of urease, and antibiogram. Strains of the O3:K6 serovar appeared for the first time in February 1996. The O3:K6 serovar strains accounted for 50 to 80% of the strains isolated during the high-incidence period (February to August 1996). All of the serovar O3:K6 strains carried the tdh gene but not the trh genes and did not produce urease. All of the isolates except two were sensitive to all of the antibiotics tested. These and the results of analysis by an arbitrarily primed PCR method indicated that the O3:K6 serovar strains belong to a unique clone. When the O3:K6 serovar strains, isolated from travelers arriving in Japan from Southeast Asian countries, were compared by the arbitrarily primed PCR method, the strains isolated between 1982 and 1993 were distinct from Calcutta O3:K6 while the strains isolated in 1995 and 1996 were indistinguishable from the Calcutta O3:K6 strains. The results suggest that this unique O3:K6 clone may have become prevalent not only in Calcutta but also in Southeast Asian countries very recently. Not only the O3:K6 strains but also the non-O3:K6...

Joint Action of O3 and SO2 in Modifying Plant Gas Exchange 1

Olszyk, David M.; Tingey, David T.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /10/1986 EN
Relevância na Pesquisa
27.41%
The joint action of O3 and SO2 stress on plants was investigated by determining the quantitative relationship between air pollutant fluxes and effects on stomatal conductance. Gas exchange measurements of O3, SO2, and H2O vapor were made for Pisum sativum L. (garden pea). Plants were grown under controlled environments, and O3, SO2, and H2O vapor fluxes were evaluated with a whole-plant gas exchange chamber using the mass-balance approach. Maximum O3 and SO2 fluxes per unit area (2 sided) into leaves averaged 8 nanomoles per square meter per second with exposure to either O3 or SO2 at 0.1 microliters per liter. Internal fluxes of either O3 or SO2 were reduced by up to 50% during exposure to combined versus individual pollutants; the greatest reduction occurred with simultaneous versus sequential combinations of the pollutants. Stomatal conductance to H2O was substantially altered by the pollutant exposures, with O3 molecules twice as effective as SO2 molecules in inducing stomatal closure. Stomatal conductance was related to the integrated dose of pollutants. The regression equations relating integrated dose to stomatal conductance were similar with O3 alone, O3 plus added SO2, and O3 plus SO2 simultaneously; i.e. a dose of 100 micromoles per square meter produced a 39 to 45% reduction in conductance over nonexposed plants. With SO2 alone...

Metabolic Basis for Injury to Plants from Combinations of O3 and SO21: Studies with Modifiers of Pollutant Toxicity

Olszyk, David M.; Tingey, David T.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /04/1985 EN
Relevância na Pesquisa
27.38%
Pisum sativum L. cv Alsweet (garden pea) and Lycopersicon esculentum Mill. flacca (mutant tomato) were chosen to evaluate the metabolic basis for plant injury from combinations of O3 + SO2. The plants were exposed under conditions reported to specifically alter O3 or SO2 toxicity; light versus dark exposures, and treatment with the fungal metabolite fusicoccin (FC), the O3 injury inhibitor N-[2-(2-oxo-1-imidazolidiny) ethyl]-N′-phenylurea (EDU), and the SO2 injury stimulator diethyldithiocarbamate (DDTC). Plants were grown in controlled environment chambers and exposed to combinations of O3 (0.05-0.2 microliters per liter) and SO2 (0.1-0.3 microliters per liter) for 2 hours. Peas treated with FC had the same or greater injury (quantified by visual rating) with O3 + SO2 exposures compared to plants not treated with FC. For plants with open stomata in the dark as well as light, i.e. FC-treated peas and tomatoes, there was no change or an increase in foliar necrosis with O3 + SO2 exposures in the dark versus light. Peas treated with EDU had an almost complete absence of O3 injury, no change in SO2 injury, and moderate decreases in injury from combinations of O3 + SO2 compared to plants not treated with EDU. Tomatoes treated with DDTC showed the same or less injury compared to plants not treated with DDTC and exposed to O3 or SO2. The plant responses to the experimental treatments and O3 + SO2 resembled O3 responses more than SO2 responses. The evidence for O3-like responses are: no change or increase in injury in the light versus dark...

Spectral reflectance from a soybean canopy exposed to elevated CO2 and O3

Gray, Sharon B.; Dermody, Orla; DeLucia, Evan H.
Fonte: Oxford University Press Publicador: Oxford University Press
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
27.37%
By affecting the physiology and structure of plant canopies, increasing atmospheric CO2 and O3 influence the capacity of agroecosystems to capture light and convert that light energy into biomass, ultimately affecting productivity and yield. The objective of this study was to determine if established remote sensing indices could detect the direct and interactive effects of elevated CO2 and elevated O3 on the leaf area, chlorophyll content, and photosynthetic capacity of a soybean canopy growing under field conditions. Large plots of soybean (Glycine max) were exposed to ambient air (∼380 μmol CO2 mol−1), elevated CO2 (∼550 μmol mol−1), elevated O3 (1.2× ambient), and combined elevated CO2 plus elevated O3 at the soybean free air gas concentration enrichment (SoyFACE) experiment. Canopy reflectance was measured weekly and the following indices were calculated from reflectance data: near infrared/red (NIR/red), normalized difference vegetation index (NDVI), canopy chlorophyll content index (chl. index), and photochemical reflectance index (PRI). Leaf area index (LAI) also was measured weekly. NIR/red and LAI were linearly correlated throughout the growing season; however, NDVI and LAI were correlated only up to LAI values of ∼3. Season-wide analysis demonstrated that elevated CO2 significantly increased NIR/red...

Sequence-Divergent Chordopoxvirus Homologs of the O3 Protein Maintain Functional Interactions with Components of the Vaccinia Virus Entry-Fusion Complex

Satheshkumar, P. S.; Moss, Bernard
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Publicado em /02/2012 EN
Relevância na Pesquisa
27.4%
Composed of 35 amino acids, O3 is the smallest characterized protein encoded by vaccinia virus (VACV) and is an integral component of the entry-fusion complex (EFC). O3 is conserved with 100% identity in all orthopoxviruses except for monkeypox viruses, whose O3 homologs have 2 to 3 amino acid substitutions. Since O3 is part of the EFC, high conservation could suggest an immutable requirement for interaction with multiple proteins. Chordopoxviruses of other genera also encode small proteins with a characteristic predicted N-terminal α-helical hydrophobic domain followed by basic amino acids and proline in the same relative genome location as that of VACV O3. However, the statistical significance of their similarity to VACV O3 is low due to the large contribution of the transmembrane domain, their small size, and their sequence diversity. Nevertheless, trans-complementation experiments demonstrated the ability of a representative O3-like protein from each chordopoxvirus genus to rescue the infectivity of a VACV mutant that was unable to express endogenous O3. Moreover, recombinant viruses expressing O3 homologs in place of O3 replicated and formed plaques as well or nearly as well as wild-type VACV. The O3 homologs expressed by the recombinant VACVs were incorporated into the membranes of mature virions and...

Root and shoot gas exchange respond additively to moderate ozone and methyl jasmonate without induction of ethylene: ethylene is induced at higher O3 concentrations

Grantz, D.A.; Vu, H.-B.
Fonte: Oxford University Press Publicador: Oxford University Press
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
27.32%
The available literature is conflicting on the potential protection of plants against ozone (O3) injury by exogenous jasmonates, including methyl jasmonate (MeJA). Protective antagonistic interactions of O3 and MeJA have been observed in some systems and purely additive effects in others. Here it is shown that chronic exposure to low to moderate O3 concentrations (4–114 ppb; 12 h mean) and to MeJA induced additive reductions in carbon assimilation (A n) and root respiration (R r), and in calculated whole plant carbon balance. Neither this chronic O3 regime nor MeJA induced emission of ethylene (ET) from the youngest fully expanded leaves. ET emission was induced by acute 3 h pulse exposure to much higher O3 concentrations (685 ppb). ET emission was further enhanced in plants treated with MeJA. Responses of growth, allocation, photosynthesis, and respiration to moderate O3 concentrations and to MeJA appear to be independent and additive, and not associated with emission of ET. These results suggest that responses of Pima cotton to environmentally relevant O3 are not mediated by signalling pathways associated with ET and MeJA, though these pathways are inducible in this species and exhibit a synergistic O3×MeJA interaction at very high O3 concentrations.

Demonstration of a diel trend in sensitivity of Gossypium to ozone: a step toward relating O3 injury to exposure or flux

Grantz, D.A.; Vu, H.-B.; Heath, R.L.; Burkey, K.O.
Fonte: Oxford University Press Publicador: Oxford University Press
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
27.37%
Plant injury by ozone (O3) occurs in three stages, O3 entrance through stomata, overcoming defences, and attack on bioreceptors. Concentration, deposition, and uptake of O3 are accessible by observation and modelling, while injury can be assessed visually or through remote sensing. However, the relationship between O3 metrics and injury is confounded by variation in sensitivity to O3. Sensitivity weighting parameters have previously been assigned to different plant functional types and growth stages, or by differentially weighting O3 concentrations, but diel and seasonal variability have not been addressed. Here a plant sensitivity parameter (S) is introduced, relating injury to O3 dose (uptake) using three independent injury endpoints in the crop species, Pima cotton (Gossypium barbadense). The diel variability of S was determined by assessment at 2h intervals. Pulses of O3 (15min) were used to assess passive (constitutive) defence mechanisms and dose was used rather than concentration to avoid genetic or environmental effects on stomatal regulation. A clear diel trend in S was apparent, with maximal sensitivity in mid-afternoon, not closely related to gas exchange, whole leaf ascorbate, or total antioxidant capacity. This physiologically based sensitivity parameter provides a novel weighting factor to improve modelled relationships between either flux or exposure to O3...

CD36 Mediates Endothelial Dysfunction Downstream of Circulating Factors Induced by O3 Exposure

Robertson, Sarah; Colombo, Elizabeth S.; Lucas, Selita N.; Hall, Pamela R.; Febbraio, Maria; Paffett, Michael L.; Campen, Matthew J.
Fonte: Oxford University Press Publicador: Oxford University Press
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
27.3%
Inhaled pollutants induce the release of vasoactive factors into the systemic circulation, but little information is available regarding the nature of these factors or their receptors. The pattern recognition receptor CD36 interacts with many damage-related circulating molecules, leading to activation of endothelial cells and promoting vascular inflammation; therefore, we hypothesized that CD36 plays a pivotal role in mediating cross talk between inhaled ozone (O3)-induced circulating factors and systemic vascular dysfunction. O3 exposure (1 ppm × 4h) induced lung inflammation in wild-type (WT) mice, which was absent in the CD36 deficient (CD36−/−) mice. Acetylcholine (ACh)-evoked vasorelaxation was impaired in isolated aortas from O3-exposed WT mice but not in vessels from CD36−/− mice. To delineate whether vascular impairments were caused by lung inflammation or CD36-mediated generation of circulating factors, naïve aortas were treated with diluted serum from control or O3-exposed WT mice, which recapitulated the impairments of vasorelaxation observed after inhalation exposures. Aortas from CD36−/− mice were insensitive to the effects of O3-induced circulating factors, with robust vasorelaxation responses in the presence of serum from O3-exposed WT mice. Lung inflammation was not a requirement for production of circulating vasoactive factors...

Non-Stomatal Limitation to Photosynthesis in Cinnamomum camphora Seedings Exposed to Elevated O3

Niu, Junfeng; Feng, Zhaozhong; Zhang, Weiwei; Zhao, Ping; Wang, Xiaoke
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
Publicado em 03/06/2014 EN
Relevância na Pesquisa
27.37%
Ozone (O3) is the most phytotoxic air pollutant for global forests, with decreased photosynthesis widely regarded as one of its most common effects. However, controversy exists concerning the mechanism that underlies the depressing effects of O3 on CO2 assimilation. In the present study, seedlings of Cinnamomum camphora, a subtropical evergreen tree species that has rarely been studied, were exposed to ambient air (AA), ambient air plus 60 [ppb] O3 (AA+60), or ambient air plus 120 [ppb] O3 (AA+120) in open-top chambers (OTCs) for 2 years. Photosynthetic CO2 exchange and chlorophyll a fluorescence were investigated in the second growing season (2010). We aim to determine whether stomatal or non-stomatal limitation is responsible for the photosynthesis reduction and to explore the potential implications for forest ecosystem functions. Results indicate that elevated O3 (E-O3) reduced the net photosynthetic rates (PN) by 6.0-32.2%, with significant differences between AA+60 and AA+120 and across the four measurement campaigns (MCs). The actual photochemical efficiency of photosystem II (PSII) in saturated light (Fv′/Fm′) was also significantly decreased by E-O3, as was the effective quantum yield of PSII photochemistry (ΦPSII). Moreover...

Constraints on the sources of tropospheric ozone from 210Pb-7Be-O3 correlations

Liu, Hongyu; Jacob, Daniel James; Dibb, Jack; Fiore, Arlene; Yantosca, Robert M.
Fonte: Wiley-Blackwell Publicador: Wiley-Blackwell
Tipo: Artigo de Revista Científica
EN_US
Relevância na Pesquisa
27.37%
The 210Pb-7Be-O3 relationships observed in three aircraft missions over the western Pacific (PEM-West A and B, TRACE-P) are simulated with a global three-dimensional chemical tracer model (GEOS-CHEM) driven by assimilated meteorological observations. Results are interpreted in terms of the constraints that they offer on sources of tropospheric ozone (O3). Aircraft observations of fresh Asian outflow show strong 210Pb-O3 correlations in September–October, but such correlations are only seen at low latitudes in February–March. Observations further downwind over the Pacific show stronger 210Pb-O3 correlations in February–March than in September–October. The model reproduces these results and attributes the seasonal contrast to strong O3 production and vertical mixing over east Asia in September–October, seasonal shift of convection from China in September–October to Southeast Asia in February–March, and slow but sustained net O3 production in Asian outflow over the western Pacific in February–March. Seasonal biomass burning over Southeast Asia in February–March is responsible for the positive 210Pb-O3 correlations observed at low latitudes. The model reproduces the observed absence of 7Be-O3 correlations over the western Pacific during September–October...

Dipolar-glass-like relaxor ferroelectric behaviour in the 0.5BaTiO3-0.5Bi(Mg1/2Ti1/2)O3 electroceramic

Wang, Jian; Liu, Yun; Li, Qian; Lau, Kenny; Withers, Ray L.; Li, Zhenrong; Xu, Zhuo
Fonte: American Institute of Physics (AIP) Publicador: American Institute of Physics (AIP)
Tipo: Artigo de Revista Científica Formato: 5 pages
Relevância na Pesquisa
36.86%
In this study, the dielectric and ferroelectric switching behaviour of 0.5BaTiO3-0.5Bi(Mg1/2Ti1/2)O3 (BT-BMT) ceramics are investigated. The BT-BMT ceramic exhibits a typical dipolar-glass-like, dielectric polarisation relaxation. This is attributed to the 15 distinct possible local A4B2 configurations around the O ions and the effect this unavoidable local compositional variability has on the dipole relaxation behaviour of inherent {1-D h111} dipole chains, arising from correlated off-centre displacements of Bi3+ and Ti4+ ions along local {111} directions. On the other hand, switchable polarisation under strong applied electric fields is observed on different length scales accompanied by the appearance of strong polarisation relaxation, as observed via time-delayed piezoresponse hysteresis loop measurements. These experimental results demonstrate that this BT-BMT ceramic is relaxor ferroelectric in nature, although it exhibits dipolar-glass-like dielectric relaxation behaviour.; The authors J.W., Y.L., and R.L.W. acknowledge the support of the Australian Research Council (ARC) in the form of Discovery projects. Y.L. also appreciates support from the ARC Future Fellowships program.

A Filamentous Phage Associated with Recent Pandemic Vibrio parahaemolyticus O3:K6 Strains

Nasu, Hatsumi; Iida, Tetsuya; Sugahara, Tomomi; Yamaichi, Yoshiharu; Park, Kwon-Sam; Yokoyama, Katsushi; Makino, Kozo; Shinagawa, Hideo; Honda, Takeshi
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Publicado em /06/2000 EN
Relevância na Pesquisa
27.37%
A specific serotype, O3:K6, of Vibrio parahaemolyticus has recently been causing epidemics of gastroenteritis in Southeast Asia, Japan, and North America. To examine whether the new O3:K6 strains possess characteristics that may exacerbate outbreaks, we compared V. parahaemolyticus O3:K6 strains with non-O3:K6 strains using strains isolated from individuals with traveler's diarrhea at Kansai Airport Quarantine Station, Osaka, Japan. All 24 O3:K6 strains possessed a common plasmid, pO3K6 (DNA size, 8,782 bp, with 10 open reading frames [ORFs]). The gene organization of pO3K6 was similar to that of Vf33, a filamentous phage previously described in V. parahaemolyticus. We isolated a phage (phage f237) from the culture supernatant of V. parahaemolyticus O3:K6 strain KXV237, which formed a turbid plaque on an indicator strain. The genome of f237 was single-stranded DNA, and the double-stranded DNA obtained by treatment of the genome with DNA polymerase was identical to that of pO3K6 when analyzed by agarose gel electrophoresis after HindIII digestion. Furthermore, the N-terminal amino acid sequence of the f237 major coat protein was found in ORF4 of pO3K6. Our results showed that pO3K6 is a replicative form of f237. Among the ORFs found in the f237 genome...

Photolysis of pure solid O3 and O2 films at 193 nm

Raut, U.; Loeffler, M. J.; Famá, M.; Baragiola, R. A.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 27/05/2010
Relevância na Pesquisa
27.35%
We studied quantitatively the photochemistry of solid O3 and O2 films at 193 nm and 22 K with infrared spectroscopy and microgravimetry. Photolysis of pure ozone destroyed O3, but a small amount of ozone remained in the film at high fluence. Photolysis of pure O2 produced O3 in an amount that increased with photon fluence to a stationary level. For both O2 and O3 films, the O3:O2 ratio at saturation is 0.03, nearly 10-30 times larger than those obtained in gas phase photolysis. This enhancement is attributed to the increased photodissociation of O2 due to photoabsorption by O2 dimers, a process significant at solid state densities. We obtain initial quantum yield for ozone synthesis from solid oxygen, {\Phi} (O3) = 0.18 and for destruction of ozone and oxygen in their parent solids, {\Phi} (- O3) = 1.7 and {\Phi} (-O2) = 0.28. Combined with known photoabsorption cross sections, we estimate probabilities for germinate recombination of 0.15 for O3 fragments and 0.90 for oxygen atoms from O2 dissociation. Using a two-parameter kinetic model, we deduce the average probabilities for the reaction of an O atom with O2 and O3 to be 0.10 and 1, respectively. These probabilities are the same for both O2 and O3 films, even though the distribution of kinetic and internal energy of the photofragments is very different in both cases. This finding suggests efficient energy relaxation of photofragments in the solid occur prior to their reactions with other species.

Minerais e equivalentes sintéticos do sistema Fe2-O3-SO3-H2O

Atendo, D; Hypolito, R
Fonte: Universidade de São Paulo. Instituto de Geociências Publicador: Universidade de São Paulo. Instituto de Geociências
Tipo: info:eu-repo/semantics/article; info:eu-repo/semantics/publishedVersion; ; ; ; ; ; Formato: application/pdf
Publicado em 01/01/1993 POR
Relevância na Pesquisa
37%
O estudo do sistema Fe2-O3-SO3-H2O necessita revisão, pois os trabalhos que abordam o assunto tratam exclusivamente de aspectos ou quimicos ou mineralógicos. Os sulfatos de Fe(III) que ocorrem como minerais podem ser agrupados em: a) Hidrogenossulfatos. Fe:S = 1:2 : romboclásio*, "leucoglaucita". b) Sulfatos ("normais"): Fe:S = 2:3 quenstedtita, coquimbita*, paracoquimbita, kornelita*, lausenita*. c) Hidroxi- e oxi-sulfatos: Fe:S = 7:9 : ferricopiapita*. Fe.S = 1:1 : fibroferrita, hohmannita, amarantita, butlerita*, parabutlerita, metahohmannita. Fe:S = 3:2 : hidrônio jarosita*. Fe:S = 4:1 : "glockerita". Fe:S = 8:1 a 16:3 : sem nome*. Os equivalentes sintéticos dos minerais marcados por um asterisco foram obtidos em experimentos de síntese, e os produtos (H(3)0)Fe4(SO4)2, Fe2(SO4)3, Fe(OH)(SO4) e Fe4(OH)10(SO4) são conhecidos apenas como compostos sintéticos. Os minerais identificados por aspas foram inadequadamente descritos. Conclui-se que sete minerais bem caracterizados e dois incompletamente descritos ainda não foram sintetizados. Por outro lado, quatro compostos são conhecidos apenas como produtos sintéticos.; The study of the Fe2-O3-SO3-H2O system needs revision because the papers concerning the subject stress either chemical or mineralogical aspects. The Fe(III)-sulfates occurring as minerais may be grouped in the following manner: a) Hydrogen-sulfates: Fe:S = 1:2 : rhomboclase*...