82,237 research outputs found
Seasonal measurements of total OH reactivity emission rates from Norway spruce in 2011
No full textNumerous 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
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
Regularity for multi-phase variational problems
No full textDe Filippis C, Oh J. Regularity for multi-phase variational problems. JOURNAL OF DIFFERENTIAL EQUATIONS. 2019;267(3):1631-1670.We prove C-1,C-nu -regularity for local minimizers of the multi-phase energy: w bar right arrow integral(Omega)vertical bar Dw vertical bar(p)+a(x)vertical bar Dw vertical bar(q)+b(x)vertical bar Dw vertical bar(s)dx, under sharp assumptions relating the couples (p, q) and (p, s) to the Holder exponents of the modulating coefficients a(.) and b(.), respectively. (C) 2019 Elsevier Inc. All rights reserved
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
Laser-induced fluorescence study of OH in flat flames of 1–10 bar compared with resonance CARS experiments
No full textKohse-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
Chronic High Fructose Intake Reduces Serum 1,25(OH)<sub>2</sub>D<sub>3</sub>Levels in Calcium-Sufficient Rodents
No full textExcessive fructose consumption inhibits adaptive increases in intestinal Ca2+transport in lactating and weanling rats with increased Ca2+requirements by preventing the increase in serum levels of 1,25(OH)2D3. Here we tested the hypothesis that chronic fructose intake decreases 1,25(OH)2D3 levels independent of increases in Ca2+ requirements. Adult mice fed for five wk a high glucose-low Ca2+ diet displayed expected compensatory increases in intestinal and renal Ca2+ transporter expression and activity, in renal CYP27B1 (coding for 1α-hydroxylase) expression as well as in serum 1,25(OH)2D3 levels, compared with mice fed isocaloric glucose- or fructose-normal Ca2+ diets. Replacing glucose with fructose prevented these increases in Ca2+ transporter, CYP27B1, and 1,25(OH)2D3 levels induced by a low Ca2+ diet. In adult mice fed for three mo a normal Ca2+ diet, renal expression of CYP27B1 and of CYP24A1 (24-hydroxylase) decreased and increased, respectively, when the carbohydrate source was fructose instead of glucose or starch. Intestinal and renal Ca2+ transporter activity and expression did not vary with dietary carbohydrate. To determine the time course of fructose effects, a high fructose or glucose diet with normal Ca2+ levels was fed to adult rats for three mo. Serum levels of 1,25(OH)2 D3 decreased and of FGF23 increased significantly over time. Renal expression of CYP27B1 and serum levels of 1,25(OH)2D3 still decreased in fructose- compared to those in glucose-fed rats after three mo. Serum parathyroid hormone, Ca2+ and phosphate levels were normal and independent of dietary sugar as well as time of feeding. Thus, chronically high fructose intakes can decrease serum levels of 1,25(OH)2D3 in adult rodents experiencing no Ca2+ stress and fed sufficient levels of dietary Ca2+. This finding is highly significant because fructose constitutes a substantial portion of the average diet of Americans already deficient in vitamin D.Peer reviewe
Cyber-criminality: Finding a balance between freedom and security. Introduction
No full textThere is no internationally recognized legal definition of the terms “computer crime” or “computer related crime” or “cybercrime”. At the terminological level, the terms “Internet-crime” and “Cybercrime” have increasingly been used. The work introduces the definition of cybercrime, taking into account the Cybercrime Convention and the competence in penal matter of the European Union after the Treaty of Lisbon
Higher jet evaluation transversality of J-holomorphic curves
No full textIn this paper, we establish general stratawise higher jet evaluation transversality of J-holomorphic curves for a generic choice of almost complex structures J (tame to a given symplectic manifold (M, omega)). Using this transversality result, we prove that there exists a subset J(omega)(ram) subset of J(omega) of second category such that for every J is an element of J(omega)(ram), the dimension of the moduli space of (somewhere injective) J-holomorphic curves with a given ramification profile goes down by 2n or 2(n - 1) depending on whether the ramification degree goes up by one or a new ramification point is created. We also derive that for each J is an element of J(omega)(ram) there are only a finite number of ramification profiles of J-holomorphic curves in a given homology class beta is an element of H(2)(M; Z) and provide an explicit upper bound on the number of ramification profiles in terms of c(1)(beta) and the genus g of the domain surface.X1124sciescopuskc
ANALYSIS OF CONTACT CAUCHY-RIEMANN MAPS II: CANONICAL NEIGHBORHOODS AND EXPONENTIAL CONVERGENCE FOR THE MORSE-BOTT CASE
No full textThis is a sequel to the papers Oh and Wang (Real and Complex Submanifolds, Springer Proceedings in Mathematics and Statistics 106 (2014), 43-63, eds. by Y.-J. Suh and et al. for ICM-2014 satellite conference, Daejeon, Korea, August 2014; arXiv:1212.4817; Analysis of contact Cauchy-Riemann maps I: a priori C-k estimates and asymptotic convergence, submitted, preprint, 2012, arXiv:1212.5186v3). In Oh and Wang (Real and Complex Submanifolds, Springer Proceedings in Mathematics and Statistics 106 (2014), 43-63, eds. by Y.-J. Suh and et al. for ICM-2014 satellite conference, Daejeon, Korea, August 2014; arXiv:1212.4817), the authors introduced a canonical affine connection on M associated to the contact triad (M, lambda, J). In Oh and Wang (Analysis of contact Cauchy-Riemann maps I: a priori C-k estimates and asymptotic convergence, submitted, preprint, 2012, arXiv:1212.5186v3), they used the connection to establish a priori W-k'P-coercive estimates for maps w : Sigma -> M satisfying(pi) w = 0, d(w*lambda o j) = 0 without involving symplectization. We call such a pair (w, j) a contact instanton. In this paper, we first prove a canonical neighborhood theorem of the locus Q foliated by closed Reeb orbits of a Morse-Bott contact form. Then using a general framework of the three-interval method, we establish exponential decay estimates for contact instantons (w, j) of the triad (M, lambda, J), with lambda a Morse-Bott contact form and J a CR-almost complex structure adapted to Q, under the condition that the asymptotic charge of (w, j) at the associated puncture vanishes. We also apply the three-interval method to the symplectization case and provide an alternative approach via tensorial calculations to exponential decay estimates in the Morse-Bott case for the pseudoholomorphic curves on the symplectization of contact manifolds. This was previously established by Bourgeois (A Morse-Bott approach to contact homology, Ph.D. dissertation, Stanford University, 2002) (resp. by Bao (On J-holomorphic curves in almost complex manifolds with asymptotically cylindrical ends, Pacific J. Math. 278(2) (2015), 291-324)), by using special coordinates, for the cylindrical (resp. for the asymptotically cylindrical) ends. The exponential decay result for the Morse-Bott case is an essential ingredient in the setup of the moduli space of pseudoholomorphic curves which plays a central role in contact homology and symplectic field theory (SFT).11Nsciescopu
EMBEDDING PROPERTY OF J-HOLOMORPHIC CURVES IN CALABI-YAU MANIFOLDS FOR GENERIC J
No full textIn this paper, we prove that for a generic choice of tame ( or compatible) almost complex structures J on a symplectic manifold (M(2n), omega) with n >= 3 and with its first Chern class c(1) (M, omega) = 0, all somewhere injective J-holomorphic maps from any closed smooth Riemann surface into M are embedded. We derive this result as a consequence of the general optimal 1-jet evaluation transversality result of J-holomorphic maps in general symplectic manifolds that we also prove in this paper.X114sciescopu
- …
