1,639,657 research outputs found
What can 14 CO measurements tell us about OH?
No full textThe possible use of 14CO measurements to constrain hydroxyl radical (OH) concentrations in the atmosphere is investigated. 14CO is mainly produced in the upper atmosphere from cosmic radiation. Measurements of 14CO at the surface show lower concentrations compared to the upper atmospheric source region, which is the result of oxidation by OH. In this paper, the sensitivity of 14CO mixing ratio surface measurements to the 3-D OH distribution is assessed with the TM5 model. Simulated 14CO mixing ratios agree within a few molecules 14CO cm¿3 (STP) with existing measurements at five locations worldwide. The simulated cosmogenic 14CO distribution appears mainly sensitive to the assumed upper atmospheric 14C source function, and to a lesser extend to model resolution. As a next step, the sensitivity of 14CO measurements to OH is calculated with the adjoint TM5 model. The results indicate that 14CO measurements taken in the tropics are sensitive to OH in a spatially confined region that varies strongly over time due to meteorological variability. Given measurements with an accuracy of 0.5 molecules 14CO cm¿3 STP, a good characterization of the cosmogenic 14CO fraction, and assuming perfect transport modeling, a single 14CO measurement may constrain OH to 0.2¿0.3×106 molecules OH cm¿3 on time scales of 6 months and spatial scales of 70×70 degrees (latitude×longitude) between the surface and 500 hPa. The sensitivity of 14CO measurements to high latitude OH is about a factor of five higher. This is in contrast with methyl chloroform (MCF) measurements, which show the highest sensitivity to tropical OH, mainly due to the temperature dependent rate constant of the MCF¿OH reaction. A logical next step will be the analysis of existing 14CO measurements in an inverse modeling framework. This paper presents the required mathematical framework for such an analysis
Seasonal measurements of total OH reactivity emission rates from Norway spruce in 2011
Full text linkNumerous reactive volatile organic compounds (VOCs) are emitted into the atmosphere by vegetation. Most biogenic VOCs are highly reactive towards the atmosphere's most important oxidant, the hydroxyl (OH) radical. One way to investigate the chemical interplay between biosphere and atmosphere is through the measurement of total OH reactivity, the total loss rate of OH radicals. This study presents the first determination of total OH reactivity emission rates (measurements via the comparative reactivity method) based on a branch cuvette enclosure system mounted on a Norway spruce (Picea abies) throughout spring, summer and autumn 2011. In parallel VOC emission rates were monitored by a second proton-transfer-reaction mass spectrometer (PTR-MS), and total ozone (O3) loss rates were obtained inside the cuvette. Total OH reactivity emission rates were in general temperature and light dependent, showing strong diel cycles with highest values during daytime. Monoterpene emissions contributed most, accounting for 56–69% of the measured total OH reactivity flux in spring and early summer. However, during late summer and autumn the monoterpene contribution decreased to 11–16%. At this time, a large missing fraction of the total OH reactivity emission rate (70–84%) was found when compared to the VOC budget measured by PTR-MS. Total OH reactivity and missing total OH reactivity emission rates reached maximum values in late summer corresponding to the period of highest temperature. Total O3 loss rates within the closed cuvette showed similar diel profiles and comparable seasonality to the total OH reactivity fluxes.
Total OH reactivity fluxes were also compared to emissions from needle storage pools predicted by a temperature-only-dependent algorithm. Deviations of total OH reactivity fluxes from the temperature-only-dependent emission algorithm were observed for occasions of mechanical and heat stress. While for mechanical stress, induced by strong wind, measured VOCs could explain total OH reactivity emissions, during heat stress they could not. The temperature-driven algorithm matched the diel variation of total OH reactivity emission rates much better in spring than in summer, indicating a different production and emission scheme for summer and early autumn. During these times, unmeasured and possibly unknown primary biogenic emissions contributed significantly to the observed total OH reactivity flux
Hohenpeissenberg Photochemical Experiment (HOPE 2000) : measurements and photostationary state calculations of OH and peroxy radicals
No full textMeasurements of OH, total peroxy radicals, non-methane hydrocarbons (NMHCs) and various other trace gases were made at the Meteorological Observatory Hohenpeissenberg in June 2000. The data from an intensive measurement period characterised by high solar insolation (18-21 June) are analysed. The maximum midday OH concentration ranged between 4.5x106 molecules cm-3 and 7.4x106 molecules cm-3. The maximum total ROx (ROx =OH+RO+HO2+RO2) mixing ratio increased from about 55 pptv on 18 June to nearly 70 pptv on 20 and 21 June. A total of 64 NMHCs, including isoprene and monoterpenes, were measured every 1 to 6 hours. The oxidation rate of the NMHCs by OH was calculated and reached a total of over 14x106 molecules cm-3 s-1 on two days. A simple photostationary state balance model was used to simulate the ambient OH and peroxy radical concentrations with the measured data as input. This approach was able to reproduce the main features of the diurnal profiles of both OH and peroxy radicals. The balance equations were used to test the effect of the assumptions made in this model. The results proved to be most sensitive to assumptions about the impact of unmeasured volatile organic compounds (VOC), e.g. formaldehyde (HCHO), and about the partitioning between HO2 and RO2. The measured OH concentration and peroxy radical mixing ratios were reproduced well by assuming the presence of 3 ppbv HCHO as a proxy for oxygenated hydrocarbons, and a HO2/ RO2 ratio between 1:1 and 1:2. The most important source of OH, and conversely the greatest sink for peroxy radicals, was the recycling of HO2 radicals to OH. This reaction was responsible for the recycling of more than 45x106 molecules cm-3 s-1 on two days. The most important sink for OH, and the largest source of peroxy radicals, was the oxidation of NMHCs, in particular, of isoprene and the monoterpenes
Precision results of 25-OH-D2, 25-OH-D3, and tD control levels.
No full textPrecision results of 25-OH-D2, 25-OH-D3, and tD control levels.</p
Laser-induced fluorescence study of OH in flat flames of 1–10 bar compared with resonance CARS experiments
Full text linkKohse-Höinghaus K, Meier U, Attal-Trétout B. Laser-induced fluorescence study of OH in flat flames of 1–10 bar compared with resonance CARS experiments. Applied Optics. 1990;29(10):1560-1569.Laser-induced fluorescence (LIF) measurements of OH were performed in flat stoichiometric CH4/air flames burning at 1, 3, 5, 7, and 9.6 bar, which had previously been investigated using OH resonance CARS. In the LIF study, line shape information and temperatures were extracted from excitation spectra; in addition, OH profiles as a function of height above the burner surface and an estimate of the OH concentration for the different flames were obtained. The perspectives and feasibility of quantitative fluorescence measurements in high pressure flames are discussed, particularly in comparison with the application of resonance CARS
Vibrational spectroscopic study of poldervaartite CaCa[SiO3(OH)(OH)]
No full textWe have studied the mineral poldervaartite CaCa[SiO<sub>3</sub>(OH)(OH)] which forms a series with its manganese analogue olmiite <i>CaMn</i><i>[SiO<sub>3</sub>(OH)]</i>(OH) using a range of techniques including scanning electron microscopy, thermogravimetric analysis, Raman and infrared spectroscopy. Chemical analysis shows the mineral is reasonably pure and contains only calcium and manganese with low amounts of Al and F. Thermogravimetric analysis proves the mineral decomposes at 485 <sup>o</sup>C with a mass loss of 7.6% compared with the theoretical mass loss of 7.7%. A strong Raman band at 852 cm<sup>-1</sup> is assigned to the SiO stretching vibration of the SiO<sub>3</sub>(OH) units. Two Raman bands at 914 and 953 cm<sup>-1</sup> are attributed to the antisymmetric vibrations. Intense prominent peaks observed at 3487, 3502, 3509, 3521 and 3547 cm<sup>-1</sup> are assigned to the OH stretching vibration of the SiO<sub>3</sub>(OH) units. The observation of multiple OH bands supports the concept of the non-equivalence of the OH units. Vibrational spectroscopy enables a detailed assessment of the molecular structure of poldervaartite
Alterações na ingestão de alimento após a injeção de 8-OH-DPAT e MM-77 no núcleo arqueado do hipotálamo
Full text linkDissertação (Mestrado) - Universidade Federal de Santa Catarina, Centro de Ciências Biológicas. Programa de Pós-Graduação em NeurociênciasEstudos em nosso laboratório mostraram que 8-hidroxi-2-(di-npropilamino)-tetralina (8-OH-DPAT) injetado no Núcleo Arqueado (NARC) provocou hipofagia somente na fase de estro. Neste contexto, a proposta do presente estudo foi investigar a localização do receptor 5-HT1A no circuito serotonérgico do NARC por meio a injeção de um antagonista considerado de ação pós-sinaptica, 1-(2-methoxyphenyl)-4-(4-succinimidobutyl) piperazine (MM-77), em ratas em diestro e estro. Ratas adaptadas a consumir uma dieta rica em sacarose 10% e com cânulas cronicamente implantadas no NARC foram pré-tratadas com o veículo (ácido ascórbico 5%) ou MM-77 (doses de 0,37 e 0,74nmol) seguida pela injeção de 8-OH-DPAT (6nmol) ou veículo. Os resultados mostraram que ratas em diestro apresentaram um consumo de alimento maior do que o grupo em estro. A injeção isolada de 8-OH-DPAT no NARC provocou hipofagia nas duas fases do ciclo estral. Enquanto o tratamento do NARC com ambas as doses de MM-77 provocou hiperfagia nas ratas em estro, somente a maior dose provocou um discreto aumento no consumo de alimento nas ratas em diestro. Quando injetado após a dose menor de MM-77, o 8-OH-DPAT impediu o aparecimento da hiperfagia. Por outro lado, quando administrado com a dose maior de MM-77, o 8-OH-DPAT reduziu a intensidade da resposta hiperfágica induzida pelo MM-77. Em diestro, essa interação entre efeitos induzidos pelo MM-77 e pelo 8-OH-DPAT aparentemente esteve ausente uma vez que a redução no consumo de alimento induzido pela injeção de 8-OH-DPAT não foi afetada pelo tratamento prévio com MM-77 no NARC. No que se refere à duração do comportamento ingestivo, a injeção de 8-OH-DPAT suprimiu o aumento na duração da resposta ingestiva provocada pela menor dose de MM-77 e atenuou a elevação dessa resposta induzida pela maior dose de MM-77 nos animais em estro. Em diestro, a redução na duração da ingestão de alimento provocada pela injeção de 8-OH-DPAT não foi afetada pelo tratamento prévio com MM-77, efeito semelhante àquele observado na resposta de ingestão de alimento. O aumento na latência para iniciar o consumo de alimento induzida pelo tratamento com 8-OH-DPAT no NARC de ratas em estro foi afetada pelo tratamento prévio com MM-77. Enquanto essa variável não foi afetada pelo MM-77 injetado isoladamente, a sua administração reduziu (dose menor) ou suprimiu (dose maior) a elevação na latência para iniciar o consumo de alimento induzido pelo 8-OH-DPAT. Por outro lado, este efeito não foi observado nas ratas em diestro. Esses resultados indicam que o MM-77 isolado remove uma influência inibitória sobre a ingestão de alimento quando injetado no NARC. Além disso, essa influência inibitória parece ser sensível ao nível de hormônios ovarianos no sangue porque os efeitos hiperfágicos do MM-77 foram mais intensos durante o estro. Os resultados também indicam que a ativação de receptores 5-HT1A, que antecipam o final da alimentação, interfere com os efeitos desencadeados pelo MM-77, que isoladamente retarda a atuação dos sinais que induzem o término da resposta ingestiva. Considerando que o MM-77 seja um antagonista de receptor pós-sináptico, os dados do presente sugerem que o receptor 5-HT1A estaria localizado em neurônios pré-sinápticos, pois, em estro e diestro, o MM-77 foi incapaz de impedir a redução da ingestão de alimento induzida pelo 8-OH-DPAT. Por outro lado, os efeitos do 8-OH-DPAT sobre a latência para iniciar o consumo de alimento (mecanismos de saciedade) parecem ser mediados por receptor 5-HT1A pós-sináptico, uma vez que o tratamento prévio com MM-77 suprimiu o retardo na latência para iniciar a resposta ingestiva induzida pelo 8-OH-DPAT durante o estro.Studies in our laboratory showed that 8-hydroxy-2-(di-npropilamino)-tetralin (8-OH-DPAT) injected into the arcuate nucleus (ARCN) caused hypophagia only at the stage of estrus. In this context, the purpose of this study was to investigate the location of the 5-HT1A receptor in the NARC serotonergic circuit through the injection of an antagonist with considered post-synaptic action, 1 - (2-methoxyphenyl) -4 - (4-succinimidobutyl ) piperazine (MM-77), in rats in diestrus and estrus. Rats adapted to consume a diet enriched with 10% sucrose bearing cannuli chronically implanted in ARCN were pre-treated with vehicle (5% ascorbic acid) or MM-77 (doses of 0.37 and 0.74 nmol) followed by injection of 8-OH-DPAT (6 nmol) or vehicle. The results showed that rats in diestrus had a higher food intake than the group in estrus. A single injection of 8-OH-DPAT in ARCN caused hypophagia in both phases of the estrous cycle. While the NARC treatment with both doses of MM-77 caused hyperphagia in female rats in estrus, only the highest dose caused a slight increase in food intake in rats in diestrus. When injected after the lower dose of MM-77, 8-OH-DPAT prevented the onset of hyperphagia. On the other hand, when administered with the higher dose of MM-77, 8-OH-DPAT reduced the intensity of the hyperphagic response induced by the MM-77.In diestrus, this interaction between the effects evoked by MM-77 and 8-OH-DPAT apparently has been absent since the reduction in food intake induced by injection of 8-OH-DPAT was not affected by pre-treatment with MM-77 in NARC. In adiction, the injection of 8-OH-DPAT suppressed the increase in the duration of ingestive response caused by the lower dose of MM-77 and attenuated the elevation of this response induced by the higher dose of MM-77 in animals in estrus. In diestrus, the reduction in the duration of food intake induced by injection of 8-OH-DPAT was not affected by pre-treatment with MM-77, an effect similar to that was observed in response of food intake. The increase in latency to begin food intake induced by treatment with 8-OH-DPAT in ARCN of rats in estrus cycle was affected by pre-treatment with MM-77. While this variable was not affected by MM-77 injected alone, its administration reduced (lower dose) or suppressed (higher dose) the increase in latency to begin food intake induced by 8-OH-DPAT. On the other hand, this effect was not observed in rats in diestrus. These results indicate that the MM-77 alone removes an inhibitory influence on food intake when injected into the ARCN. Furthermore, this inhibitory influence seems to be sensitive to the level of ovarian hormones in the blood because the hyperphagic effects of MM-77 were more intense during estrus. The results also indicate that activation of 5-HT1A receptors, in anticipation to the end of food intake, interferes with the effects triggered by MM-77, which alone slows the action of signals that induce the termination of ingestive response. Whereas the MM-77 is an antagonist of postsynaptic receptor, the present data suggest that 5-HT1A receptor would be located in presynaptic neurons, because in both different estrous cycle stages evaluated, the MM-77 was unable to prevent the reduction of food intake induced by 8-OH-DPAT. On the other hand, the effects of 8-OH-DPAT on the latency to begin food intake (satiety mechanisms) appear to be mediated by 5-HT1A postsynaptic receptor, since pretreatment with MM-77 suppressed the delay in the response latency to start feeding behavior induced by 8-OH-DPAT during estrus
Oh what a lovely mess!: Reflexiones sobre la traducción de textos teatrales
Full text link[ES] Se analizan en esta aportación dos textos dramáticos traducidos de Oh What a Lovely War! / ¡Oh, qué bonita es la guerra! de Joan Littlewood (The Theatre Workshop). Por un lado, la versión del texto teatral, publicada en 1969 en la colección Cuadernos para el Diálogo y, por otro, la versión cinematográfica de Richard Attemborough subtitulada. Se plantea un análisis comparativo de las traducciones con los respectivos originales, y se plantean reflexiones respecto a la calidad de los productos traducidos
Oh life!
No full textOH!LIFE™ focuses on experiments in packaging of an oeuvre. The deliverables will be 6 artist books titled OH!LIFE™, or Cest la vie—the OH referring to the artist herself. The books—OH DEAR, OH MY GOD,OH SHIT,OHAYO and OH YES; are autobiographies, with visual and written explorations and translations of her life. The content and materials of the deliverables aim to reproduce specific sensations. The books also include highly experimental forms and illustrative techniques. What is most important is that this is not a traditional oeuvre, but an experimental packaging of the ephemeral.Bachelor of Fine Art
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