237 research outputs found
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
The influence of peroxy radicals on ozone production
No full textDie vorliegende Arbeit liefert einen Beitrag zum Verständnis der Rolle des RO x bei der troposphärischen Ozonbildung. Troposphärisches Ozon (O 3 ) spielt eine wichtige Rolle bei der Selbstreinigung der Atmosphäre. Andererseits führen erhöhte Ozonkonzentrationen zu gesundheitlichen Beeinträchtigungen beim Menschen und Schäden an Pflanzen und Umwelt. Die Anwesenheit von flüchtigen organischen Verbindungen (VOCs) führt zur Bildung von Peroxyradikalen (RO x ), die das normale photochemische Gleichgewicht zwischen Ozon und Stickoxiden zu Gunsten erhöhter OzonKonzentrationen verschieben. Im Rahmen der Arbeit wurde ein chemischer Verstärker zur Messung der GesamtPeroxyradikalkonzentration gebaut. RO x reagiert im Einlass des Gerätes mit hinzugefügtem NO und CO in einer Kettenreaktion und bildet dabei NO 2 . Dieses wird mit einem Luminoldetektor nachgewiesen. Der Detektor wird alle 2 Stunden kalibriert. Die Kettenlänge wird durch eine Kalibrierung des Gerätes mit HO 2 Radikalen bestimmt, die durch die Photolyse von H 2 O gebildet werden. Der Verstärkungsfaktor wurde in Bezug auf eine Querempfindlichkeit gegen Wasserdampf korrigiert. Die Messgenauigkeit ist etwa 70% bei 60% relativer Feuchte. Messungen am Taunus Observatorium auf dem Kleinen Feldberg in den Sommermonaten der beiden Jahre 1998 und 1999 werden vorgestellt. Die Ozon und RO x Konzentrationen sind gut miteinander korreliert. Allerdings ist die Tagestemperatur die für die Ozon und RO x Konzentrationen bei weitem wichtigste Einflussgröße und ist daher der beste Parameter zur statistischen Beschreibung von photochemischen Vorgängen. Auf der Grundlage der Messungen am Kleinen Feldberg wurde ein einfaches statistisches Modell zur Vorhersage des Ozonmaximums erstellt. Mit den Parametern Temperatur und Ozonkonzentration am Vortag konnte das statistische Modell bereits 80% der Variation der Ozonkonzentration erklären. Durch die Berücksichtigung der RO x Messungen am Vormittag konnte lediglich eine Verbesserung der erklärten Varianz um 0.5% erzielt werden. Um einen Hinweis auf den Einfluss anthropogener Emissionen zu bekommen, wurde der Wochengang von Ozon, RO x und NO x ebenfalls untersucht. Die Zunahme des Ozonmischungsverhältnisses am Wochenende bei gleichzeitigem Rückgang des Mischungsverhältnisses der Stickoxide wird damit erklärt, dass am Kleinen Feldberg eine VOClimitierte Situation vorgefunden wurde. Die Ozonbildungsrate auf Basis der Reaktion zwischen RO x und NO wurde für Tage mit einem Maximum der Globalstrahlung über 600 W m tdatensatz niedrig (r = 0,46). Die beobachtete Änderung des Ozonmischungsverhältnisses wurde mit dem berechneten mittleren Tagesgang der Ozonbildungsrate verglichen. Die Ozonbildungsrate lag um die Mittagszeit bei etwa 5 ppbv h Verlustprozesse zu erklären. Am Abend werden etwa 2 ppbv O 3 pro Stunde abgebaut. Im Rahmen einer Messkampagne im Juni/Juli 2000 am Meteorologischen Observatorium Hohenpeißenberg fanden Messungen der Konzentrationen von RO x , OH, einer Reihe von VOCs, und anderen relevanten Spurengasen statt. Die Messdaten werden mit Hilfe eines auf der Annahme des lokalen photostationären Gleichgewichts der Radikale basierenden Modells interpretiert. Die Modellergebnisse stimmten sehr gut mit den Messungen überein. Die Überschätzung der Konzentration an 2 Tagen wurde durch den Einfluss sauerstoffhaltiger VOCs erklärt. Das '' Recycling" der HO 2 Radikale (die Reaktion zwischen HO 2 und NO) ist die wichtigste Quelle für OH und die wichtigste Senke für RO x . Durch die erhöhte NOKonzentration am Vormittag wird HO 2 sehr schnell in OH umgewandelt, das wiederum für die VOCOxidation und RO x Bildung verantwortlich ist. Die wichtigste OHSenke und RO x Quelle ist die Oxidation von Isopren und den Terpenen. Um die Rolle der photochemischen Ozonbildung auf regionaler Skala zu untersuchen, wurden Ozonmessungen aus ganz Deutschland auf unterschiedlichen zeitlichen und räumlichen Skalen statistisch untersucht. Die Netto Änderungsrate der Ozonkonzentration war tagsüber an 3 nahe zusammenliegenden Stationen sehr ähnlich. Die OzonMessdaten von 277 deutschen Messstationen wurden mit den an einer Waldmessstelle nahe Königstein gemessenen Ozonwerten korreliert. Die Ozonmessungen in Königstein erklären 50% der Varianz der sommerlichen Ozonmessungen zwischen 11:00 und 16:00 MEZ an Stationen, die in einem Umkreis von etwa 250 km von Königstein liegen. Auf das ganze Jahr bezogen, liegt diese ''charakteristische Entfernung" bei etwa 350 km. Diese Ergebnisse deuten darauf hin, dass die Prozesse, die einen wichtigen Einfluss auf die Ozonkonzentration ausüben, auf regionalen Skalen von einigen hundert Kilometern aktiv sind. Zusammenfassend lässt sich sagen, dass die gemessenen RO x Konzentrationen mit den aufgrund der Oxidation der VOCs durch OH berechneten Konzentrationen konsistent sind. Obwohl die RO x Konzentationen für die chemische Modellierung von Bedeutung sind, tragen RO x Messungen nur wenig zu einer Verbesserung der Qualität von kurzfristigen statistischen Ozonprognosen bei. Keywords: Ozone, Troposphere, Peroxy Radicals, Free Radicals, Photochemistry, Chemical Amplifie
Recommended from our members
Suffering in silence: bodily politics in post-1995 French cinema
No full textDeveloping earlier research by the author that had sought to trace the specificity of the current wave of socio-politically engaged film, this article focuses in on the body, suggesting that it has become a core vector of ‘raw’ expressivity in recent French cinema due to the withdrawal of the discourse of the organised left as mediating instance. Brooks’ celebrated analysis of melodrama and the political philosophy of Rancière and Laclau and Mouffe are drawn upon to examine the political work done by Cabrera’s Retiens la nuit and Devers’ La Voleuse de St Lubin. Engaging with the objectified, embodied and isolated social suffering that runs through current cinema, the two films’ significance lies in their exploration of the possibilities of and obstacles to its articulation within an oppositional politics
Ligand regulation of the quaternary organization of cell surface M3 muscarinic acetylcholine receptors analyzed by fluorescence resonance energy transfer (FRET) imaging and homogenous time-resolved FRET
No full textFlp-In T-REx 293 cells expressing a wild type human M muscarinic acetylcholine receptor construct constitutively and able to express a Receptor Activated Solely by Synthetic Ligand (RASSL) form of this receptor on demand maintained response to the muscarinic agonist carbachol but developed response to clozapine-N-oxide only upon induction of the RASSL. The two constructs co-localized at the plasma membrane and generated strong ratiometric fluorescence resonance energy transfer (FRET) signals consistent with direct physical interactions. Increasing levels of induction of the FRET-donor RASSL did not alter wild type receptor FRET-acceptor levels substantially. However, ratiometric FRET was modulated in a bell-shaped fashion with maximal levels of the donor resulting in decreased FRET. Carbachol, but not the antagonist atropine, significantly reduced the FRET signal. Cell surface homogenous time-resolved FRET, based on SNAP-tag technology and employing wild type and RASSL forms of the human M receptor expressed stably in Flp-In TREx 293 cells, also identified cell surface dimeric/oligomeric complexes. Now, however, signals were enhanced by appropriate selective agonists. At the wild type receptor large increases in FRET signal to carbachol and acetylcholine were concentration-dependent with EC values consistent with the relative affinities of the two ligands. These studies confirm the capacity of the human M muscarinic acetylcholine receptor to exist as dimeric/oligomeric complexes at the surface of cells and demonstrate that the organization of such complexes can be modified by ligand binding. However, conclusions as to the effect of ligands on such complexes may depend on the approach used
Neobuthus awashensis Kovarik et Lowe 2012
No full textNeobuthus awashensis Kovařík et Lowe, 2012 (Figs. 1–6, 158, 161–165) Neobuthus awashensis Kovařík & Lowe, 2012: 7–16, figs. 5–6, 18–21, 34–38, 44–47, 67–74, 86, 89, 92, 95–96, 100–101; Kovařík et al., 2015: 30. TYPE LOCALITY AND TYPE REPOSITORY. Ethiopia, Awash, Metahara env., 08°54' N 39°54' E, 960-1050 m a.s.l., FKCP. TYPE MATERIAL. Ethiopia, Awash, Metahara env., 08°54' N 39°54' E, 960-1050 m a.s.l., 1♀ (paratype), 2008, leg. V. Trailin, 2♀1♀ im. (allotype and paratypes), XI.2010, leg. T. Mazuch and P. Novák, 32♂ (holotype and paratypes) 18♀ (paratypes) 11♀ ims, 5♂ ims (paratypes), 19.-22.VII.2011, leg. F. Kovařík. Most types are in the collection of the second author (FKCP), two paratypes (♂ ♀) are in the collection of the first author (GL). OTHER MATERIAL EXAMINED. Ethiopia, 11°43'22" N 40° 56'52" E, 457 m a.s.l. (Locality No. 12 EMA), 20.XI. 2012, 1♀1♀ im., leg. F. Kovařík (UV detection), FKCP; 11°43'30" N 40°58'45" E, 404 m a.s.l. (Locality No. 12EM), 20.XI.2012, 1♂, leg. F. Kovařík (UV detection), FKCP; Gewane, 10°09'38" N 40°39'45" E, 631 m a.s.l. (Locality No. 12 EO), 23.XI.2012, 1♂ 1♀, leg. F. Kovařík, (UV detection), FKCP; 09°08'10.4" N 40°09' 45.5" E, 835 m a.s.l. (Locality No. 12ER), 24.XI.2012, 12♂ 1♀ 1juv., leg. F. Kovařík (UV detection), FKCP, 26.-27.XI.2014, 8♂ 2♀ 2juvs, FKCP, 3♂ 2juvs, GL, leg. F. Kovařík; Awash, Metahara env., 08°54' N 39°54' E, 960-1050 m a.s.l. (Locality No. 12 EX), 25.XI.2012, 7♂ 6♀ 5juvs., 27.-30.XI.2014, 7♂ 1♀, topotypes, leg. F. Kovařík (UV detection), FKCP. EMENDED DIAGNOSIS. Total length 18–22 mm (males), 22.5–30 mm (females); carapace with area between anterior median carinae fuscous; tergites with fuscous pigmentation unbroken across median area; pedipalp relatively slender, males with femur L/ W 2.50 –2.70, patella L/ W 2.45 –2.70, chela L/ W 4.63 –5.08; chela movable finger with 5–6 subrows of primary denticles, 3–5 external accessory denticles flanking proximal end of each subrow; trichobothria d 2 usually absent from femur and patella; posterior margins of carapace and tergites usually bearing 2–4 macrosetae; pedipalps, legs, metasoma and telson with short, stout macrosetae in males, and long, fine setae in females; males with coxae sparsely granulated, sternites III–VI lightly shagreened to smooth, sternite VII finely granulated with 4 weak, granulated carinae; females with sternites III–VI smooth, sternite VII sparsely shagreened with 4 weak carinae, median carinae granulated; metasoma I–III with median lateral carinae present in both sexes; lateral surface of metasoma V in males densely granulated, with granules separated; soles of telotarsi with relatively sparse setation, leg III of adults with 6–9 macrosetae in retroinferior series of basitarsus, 12–19 ventral macrosetae on telotarsus; pectine teeth: 17–21 (males), 15–18 (females).Published as part of Lowe, Graeme & Kovařík, František, 2016, Scorpions of the Horn of Africa (Arachnida, Scorpiones). Part V. Two new species of Neobuthus Hirst, 1911 (Buthidae), from Ethiopia and Eritrea, pp. 1-46 in Euscorpius 224 on page
E-Learning and M-Learning Problems
No full textThe use of online teaching in education is expanding at a rapid rate. Some may be tempted to view technology as an educational panacea (Herrington & Herrington, 1998). However, the existence of any technology does not guarantee that good educational material will be provided or that effective learning will happen (Boddy, 1997). Online teaching has the “potential to be just as inflexible and inappropriate as any other form of poor instruction” (Bennett, Priest & Macpherson, 1999, p. 208). Problems associated with online learning are often overlooked or not fully investigated (Hara & Kling, 1999). It is important not to be blinded by technology. We need to recognize and study these problems to obtain a broader picture of the impact of technology in teaching. This author is an early and enthusiastic adopter of technology in teaching. However, he has learned through experience and research that it is important to identify problems, both real and perceived, in order to develop strategies to overcome them. For example, innovators are prepared to be relatively understanding of technical problems, but the bulk of users are not likely to be as forgiving (Freeman, 1997). </jats:p
E-Learning and M-Learning Problems
No full textThe use of online teaching in education is expanding at a rapid rate. Some may be tempted to view technology as an educational panacea (Herrington & Herrington, 1998). However, the existence of any technology does not guarantee that good educational material will be provided or that effective learning will happen (Boddy, 1997). Online teaching has the “potential to be just as inflexible and inappropriate as any other form of poor instruction” (Bennett, Priest & Macpherson, 1999, p. 208). Problems associated with online learning are often overlooked or not fully investigated (Hara & Kling, 1999). It is important not to be blinded by technology. We need to recognize and study these problems to obtain a broader picture of the impact of technology in teaching. This author is an early and enthusiastic adopter of technology in teaching. However, he has learned through experience and research that it is important to identify problems, both real and perceived, in order to develop strategies to overcome them. For example, innovators are prepared to be relatively understanding of technical problems, but the bulk of users are not likely to be as forgiving (Freeman, 1997).</jats:p
Taxonomy, phylogeny and eco-biogeography of southern African white-eyes (Zosterops spp.) Aves: order Passeriformes, Family: Zosteropidae
No full textIncludes abstract.Includes bibliographical references (p. 193-216).The aim of this study was to incorporate all lines of evidence to establish the true taxonomy and phylogeny of southern African Zosterops. Character data sets used include plumage and morphometric measures, vocal characters and molecular (mitochondrial and nuclear) DNA sequences. A broad scale phylogeographic analysis was also performed to establish the evolutionary process driving the diversity observed among these birds
Skeletal fluorosis in marsupials: A comparison of bone lesions in six species from an Australian industrial site
No full text- …
