bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of β-PVDF Piezoelectric Transducers’ Positioning on the Acoustic Streaming Flows
Authors: Catarino Susana , Miranda João , Minas Graça
Published: September 2014

This paper reports the numerical and experimental analysis of the acoustic streaming effect in a fluidic domain. The actuation of a piezoelectric transducer generates acoustic waves that propagate to the fluids, generating pressure gradients that induce the flow. The number and positioning of the transducers affect the pressure gradients and, consequently, the resultant flow profile. Two actuation conditions were considered: (1) acoustic streaming generated by a 28 μm thick β-poly(vinylidene fluoride) (β-PVDF) piezoelectric transducer placed asymmetrically relative to the fluidic domain and (2) acoustic streaming generated by two 28 μm thick β-PVDF piezoelectric transducers placed perpendicularly to each other. The transducers were fixed to the lower left corner of a poly(methyl methacrylate) (PMMA)cuvette and were actuated with a 24 Vpp and 34.2 MHz sinusoidal voltage. The results show that the number of transducers and their positioning affects the shape and number of recirculation areas in the acoustic streaming flows. The obtained global flows show great potential for mixing and pumping, being an alternative to the previous geometries studied by the authors, namely, a single transducer placed symmetrically under a fluidic domain.
Synthesis of [13C4]-labeled ∆9-Tetrahydrocannabinol and 11-nor-9-Carboxy-∆9-tetrahydrocannabinol as Internal Standards for Reducing Ion Suppressing/Alteration Effects in LC/MS-MS Quantification
Authors: Karlsen Morten , Liu Huiling , Johansen Jon , Hoff Bård
Published: September 2014

(−)-∆9-Tetrahydrocannabinol is the principal psychoactive component of the cannabis plant and also the active ingredient in some prescribed drugs. To detect and control misuse and monitor administration in clinical settings, reference samples of the native drugs and their metabolites are needed. The accuracy of liquid chromatography/mass spectrometric quantification of drugs in biological samples depends among others on ion suppressing/alteration effects. Especially, 13C-labeled drug analogues are useful for minimzing such interferences. Thus, to provide internal standards for more accurate quantification and for identification purpose, synthesis of [13C4]-∆9-tetrahydro-cannabinol and [13C4]-11-nor-9-carboxy-∆9-tetrahydrocannabinol was developed via [13C4]-olivetol. Starting from [13C4]-olivetol the synthesis of [13C4]-11-nor-9-carboxy-∆9-tetrahydrocannabinol was shortened from three to two steps by employing nitromethane as a co-solvent in condensation with (+)-apoverbenone.
Effects of Heat Acclimation on Photosynthesis, Antioxidant Enzyme Activities, and Gene Expression in Orchardgrass under Heat Stress
Authors: Zhao Xin , Huang Lin , Zhang Xin , Li Zhou , Peng Yan
Published: September 2014

The present study was designed to examine the effects of heat acclimation on enzymatic activity, transcription levels, the photosynthesis processes associated with thermostability in orchardgrass (Dactylis glomerata L.).The stomatal conductance (Gs), net photosynthetic rate (Pn), and transpiration rates (Tr) of both heat-acclimated (HA) and non-acclimated (NA) plants were drastically reduced during heat treatment [using a 5-day heat stress treatment (38/30 °C ‒ day/night) followed by a 3-day recovery under control conditions (25/20 °C ‒ day/night), in order to consolidate the second cycle was permitted]. Water use efficiency increased more steeply in the HA (4.9 times) versus the NA (1.8 times) plants, and the intercellular CO2 concentration decreased gently in NA (10.9%) and HA (25.3%) plants after 20 d of treatments compared to 0 days’. Furthermore, heat-acclimated plants were able to maintain significant activity levels of superoxide disumutase (SOD), catalase (CAT), guaiacol peroxidase (POD), and transcription levels of genes encoding these enzymes; in addition, HA plants displayed lower malondialdehyde content and lower electrolyte leakage than NA plants. These results suggest that maintenance of activity and transcription levels of antioxidant enzymes as well as photosynthesis are associated with variable thermostability in HA and NA plants. This likely occurs through cellular membrane stabilization and improvements in water use efficiency in the photosynthetic process during heat stress. The association between antioxidant enzyme activity and gene expression, both of which may vary with genetic variation in heat tolerance, is important to further understand the molecular mechanisms that contribute to heat tolerance.
Synthesis and Antibacterial Activity of Analogs of 5-Arylidene-3-(4-methylcoumarin-7-yloxyacetylamino)-2-thioxo-1,3-thiazoli-din-4-one
Authors: Cong Nguyen , Nhan Huynh , Van Hung Luong , Thang Tran , Kuo Ping-Chung
Published: September 2014

In an effort to develop new antimicrobial agents, 3-(4-methylcoumarin-7-yloxyacetylamino)-2-thioxo-1,3-thiazolidin-4-one (4) was synthesized by reaction of thiocarbonylbisthioglycolic acid with ethyl (4-methyl-2-oxo-2H-chromen-7-yloxy)aceto- hydrazide (3), which was prepared in turn from 7-hydroxy-4-methylcoumarin (1). The condensation of compound 4 with different aromatic aldehydes afforded a series of 5-(arylidene)-3-(4-methylcoumarin-7-yloxyacetyl-amino)-2-thioxo-1,3-thiozolidin-4-one analogs 5a–h. The structures of these synthetic compounds were elucidated on the basis of IR, 1H-NMR and 13C-NMR spectral data and ESI-MS spectrometric analysis. Compounds 5a–h were examined for their antibacterial activity against several strains of Gram-positive and Gram-negative bacteria.
White Blood Cell Segmentation by Color-Space-Based K-Means Clustering
Authors: Zhang Congcong , Xiao Xiaoyan , Li Xiaomei , Chen Ying-Jie , Zhen Wu , Chang Jun , Zheng Chengyun , Liu Zhi
Published: September 2014

White blood cell (WBC) segmentation, which is important for cytometry, is a challenging issue because of the morphological diversity of WBCs and the complex and uncertain background of blood smear images. This paper proposes a novel method for the nucleus and cytoplasm segmentation of WBCs for cytometry. A color adjustment step was also introduced before segmentation. Color space decomposition and k-means clustering were combined for segmentation. A database including 300 microscopic blood smear images were used to evaluate the performance of our method. The proposed segmentation method achieves 95.7% and 91.3% overall accuracy for nucleus segmentation and cytoplasm segmentation, respectively. Experimental results demonstrate that the proposed method can segment WBCs effectively with high accuracy.
Development of Innovative Aerogel Based Plasters: Preliminary Thermal and Acoustic Performance Evaluation
Authors: Buratti Cinzia , Moretti Elisa , Belloni Elisa , Agosti Fabrizio
Published: September 2014

The thermal and acoustic properties of innovative insulating systems used as building coatings were investigated: Granular silica aerogel was mixed with natural plaster in different percentages. This coating solution is transpiring and insulating, thanks to the use of a natural lime coat and aerogel, a highly porous light material with very low thermal conductivity. The thermal conductivity of the proposed solution was evaluated by means of a Heat Flow meter apparatus (EN ISO 12667), considering different percentages of aerogel. The natural plaster without aerogel has a thermal conductivity of about 0.50 W/m K; considering a percentage of granular aerogel of about 90% in volume, the thermal conductivity of the insulating natural coating falls to 0.050 W/m K. Increasing the percentage of granular aerogel, a value of about 0.018–0.020 W/m K can be reached. The acoustic properties were also evaluated in terms of the acoustic absorption coefficient, measured by means of a Kundt’s Tube (ISO 10534-2). Two samples composed by a plasterboard support, an insulation plaster with aerogel (thicknesses 10 mm and 30 mm respectively) and a final coat were assembled. The results showed that the absorption coefficient strongly depends on the final coat, so the aerogel-based plaster layer moderately influences the final value. The application of this innovative solution can be a useful tool for new buildings, but also for the refurbishment of existing ones. This material is in development: until now, the best value of the thermal conductivity obtained from manufacturers is about 0.015 W/m K.
Microstructural and plasmonic modifications in Ag–TiO2 and Au–TiO2 nanocomposites through ion beam irradiation
Authors: Chakravadhanula Venkata Sai Kiran , Mishra Yogendra Kumar , Kotnur Venkata Girish , Avasthi Devesh Kumar , Strunskus Thomas , Zaporotchenko Vladimir , Fink Dietmar , Kienle Lorenz , Faupel Franz
Published: September 2014

The development of new fabrication techniques of plasmonic nanocomposites with specific properties is an ongoing issue in the plasmonic and nanophotonics community. In this paper we report detailed investigations on the modifications of the microstructural and plasmonic properties of metal–titania nanocomposite films induced by swift heavy ions. Au–TiO2 and Ag–TiO2 nanocomposite thin films with varying metal volume fractions were deposited by co-sputtering and were subsequently irradiated by 100 MeV Ag8+ ions at various ion fluences. The morphology of these nanocomposite thin films before and after ion beam irradiation has been investigated in detail by transmission electron microscopy studies, which showed interesting changes in the titania matrix. Additionally, interesting modifications in the plasmonic absorption behavior for both Au–TiO2 and Ag–TiO2 nanocomposites were observed, which have been discussed in terms of ion beam induced growth of nanoparticles and structural modifications in the titania matrix.
Lateral ordering of PTCDA on the clean and the oxygen pre-covered Cu(100) surface investigated by scanning tunneling microscopy and low energy electron diffraction
Authors: Gärtner Stefan , Fiedler Benjamin , Bauer Oliver , Marele Antonela , Sokolowski Moritz M
Published: September 2014

We have investigated the adsorption of perylene-3,4,9,10-tetracarboxylic acid dianhydride (PTCDA) on the clean and on the oxygen pre-covered Cu(100) surface [referred to as (√2 × 2√2)R45° – 2O/Cu(100)] by scanning tunneling microscopy (STM) and low energy electron diffraction (LEED). Our results confirm the (4√2 × 5√2)R45° superstructure of PTCDA/Cu(100) reported by A. Schmidt et al. [J. Phys. Chem. 1995, 99,11770–11779]. However, contrary to Schmidt et al., we have no indication for a dissociation of the PTCDA upon adsorption, and we propose a detailed structure model with two intact PTCDA molecules within the unit cell. Domains of high lateral order are obtained, if the deposition is performed at 400 K. For deposition at room temperature, a significant density of nucleation defects is found pointing to a strong interaction of PTCDA with Cu(100). Quite differently, after preadsorption of oxygen and formation of the (√2 × 2√2)R45° – 2O/Cu(100) superstructure on Cu(100), PTCDA forms an incommensurate monolayer with a structure that corresponds well to that of PTCDA bulk lattice planes.
Extraarticular Manifestations of Rheumatoid Arthritis Develop in Patients Receiving Anti-Tumor Necrosis Factor-α Treatment: A Retrospective Chart Review from a UK Center
Authors: Negoescu Andra Florina , Tennekone Dilrukshi , Soljak Michael Anthony , Abraham Sonya Marie
Published: September 2014

Objective.

To assess the evolution of preexisting extraarticular manifestations of rheumatoid arthritis (EA-RA) in patients treated with anti-tumor necrosis factor-α (TNF-α), as well as the development of new EA-RA.

Methods.

We assessed EA-RA in 152 patients receiving anti-TNF-α treatment.

Results.

In 22 cases, a new EA-RA developed. In 5 cases, there was evidence of progression of preexisting EA-RA. Regression was found in 4 cases. Some patients were in disease remission when they developed EA-RA, whereas some patients had moderate/high disease activity.

Conclusion.

EA-RA are still present in patients treated with anti-TNF-α. Development of new severe EA-RA is rare in patients receiving anti-TNF therapy.
Le ventre dans l’écriture de Sony Labou Tansi et Tchicaya U Tam'si
Authors: Yengo Patrice
Published: September 2014

L’auteur francophone n’est pas un simple traducteur ; son positionnement d’écrivain dans une langue qui n’est pas la sienne brouille les contours de cette fonction. On voudrait ici rendre compte de cette dynamique singulière, à partir du champ sémantique du ventre, central dans l’œuvre de Tchicaya U Tam’si et de Sony Labou Tansi, auquel ces deux auteurs ont consacré deux de leurs ouvrages au titre homonyme, le Ventre (1964) et Sa majesté le ventre (1972).
De Hemingway au chinois classique : le travail de la langue de l’écrivain taïwanais Wang Wen-hsing
Authors: Marchand Sandrine
Published: September 2014

Dans les années 1970, l’« occidentalisation » de Wang Wen-hsing lui attire les foudres de la critique. On lui reproche, entre autres choses, de mal écrire, d’être incompréhensible et d’écrire dans une langue occidentalisée. Lui-même semble prendre pour modèle son professeur de français, dont le niveau de chinois classique était très élevé. Entre chinois classique, moderne, dialecte de sa région natale (très proche du dialecte de Taïwan), anglais, et français idéalisé, Wang Wen-hsing invente sa propre langue. Dans les manuscrits de son premier roman, il recourt au syllabaire que les enfants utilisent en cours d’apprentissage de la langue chinoise pour remplacer les caractères d’écriture, syllabaire qui disparaît ensuite à la publication. Que nous apprend l’utilisation de ce syllabaire sur le travail créatif de l’auteur ?Wang Wen-hsing est un auteur qui, entre extrême précision et violence, consacre sa vie et toute son énergie au travail de la langue. Quelle langue tente-t-il d’approcher : le chinois normatif des temps anciens, la langue américaine de Hemingway, ou un mélange des deux ?Multilingue à l’intérieur de la langue chinoise moderne, elle-même langue encore proche du chinois classique, abandonné seulement au début du xxe siècle, l’écriture romanesque de Wang Wen-hsing, qui a pour critère de valeur le « tong-shun » (clarté et aisance), est le fruit de l’oralité et d’une langue expérimentale. Ce rapport à la langue vient-il de sa situation d’émigration, de son isolement des milieux politiques et intellectuels, comme cela lui a été reproché lorsque justement on l’accusait d’écrire dans une langue incompréhensible pour le lecteur ? Pourquoi ces romans sont-ils jugés incompréhensibles ? En raison du niveau du lecteur moyen ? Pour des raisons géopolitiques, car il est un émigré en position dominante dans l’île ? Parce que la langue chinoise est dans une période de transition forte ? Toutes ces questions seront posées en référence aux critiques émises contre l’auteur, et dans l’étude de ses manuscrits, qui révèlent un processus particulier d’écriture où la langue chinoise oscille entre traits d’écriture et tentation de l’alphabet.
Un « chaos linguistique » : les textes en français d’Amelia Rosselli (1930-1996)
Authors: Sciarrino Emilio
Published: September 2014

Cet article étudie les textes français d’Amelia Rosselli (1930-1996), auteure trilingue et voix majeure de la poésie italienne du xxe siècle. Il analyse la situation de la langue française dans son œuvre, puis précise le lien du français aux autres langues – l’anglais et l’italien –, qui interagissent dans une forte créativité linguistique. En ce sens, l’étude de manuscrits inédits révèle la genèse d’une poésie multilingue située entre compétence intuitive et performance structurée.
Norme unilingue/Norme multilingue : revisiter le bilinguisme littéraire de l’écrivain franco-ontarien Patrice Desbiens
Authors: Simard Mathieu
Published: September 2014

Issue du modèle aristotélicien ou de l’idéologie romantique, la norme unilingue de la bonne écriture marque les critiques de Patrice Desbiens. Ces derniers voient les traces d’anglais qui parsèment les textes de l’écrivain comme des éléments exogènes intégrés dans une poésie de langue française. Nous proposons de faire contrepoids à cette thèse en nous appuyant sur les trois critères qui, dans la pensée de Mikhaïl Bakhtine, mettent en place une norme multilingue : la dépossession, la déhiérarchisation et la dialogisation des langues.
Du double à la figure - genèse d’un personnage christique chez Dambudzo Marechera
Authors: Leroux Pierre
Published: September 2014

La publication en 1992 de The Black Insider inaugure une série de trois volumes consacrés aux œuvres posthumes de Dambudzo Marechera. Ce premier texte est en fait un avant-texte du roman Black Sunlight, publié en 1980. L’histoire éditoriale de ce dossier génétique, ainsi que l’analyse d’éléments encore inédits – dont une séquence poétique destinée à Black Sunlight – nous permet de faire évoluer notre vision de l’œuvre publiée et du processus créatif caractéristique de l’auteur zimbabwéen. Afin de mieux saisir ces enjeux, nous nous sommes concentrés sur l’évolution d’un personnage, Owen, qui change de nom et de statut pour devenir Nick dans Black Sunlight.
Use of a Nutrition Support Protocol to Increase Enteral Nutrition Delivery in Critically Ill Patients
Authors: Compton Friederike , Bojarski Christian , Siegmund Britta , van der Giet Markus
Published: September 2014

Background

Early enteral nutrition is recommended for patients in intensive care units, but nutrition provision is often hindered by a variety of unit-specific problems.

Objectives

To evaluate the impact of a nutrition support protocol on nutrition prescription and delivery in the intensive care unit.

Methods

Nutrition-related data from 73 patients receiving mechanical ventilation who were treated in an adult medical intensive care unit before introduction of an enteral nutrition support protocol were retrospectively compared with data for 87 patients admitted after implementation of the protocol.

Results

After implementation of the protocol, enteral nutrition was started significantly earlier (P = .007) and enteral feeding goals were reached significantly faster (6 vs 10 days, P < .001) than before. Prescription of enteral nutrition on the first day of invasive mechanical ventilation increased from 38% before to 54% after (P = .03) implementation of the protocol. Prescribed and delivered nutrition doses on the first 2 days of mechanical ventilation also increased significantly (P < .001) after the protocol was implemented. Nasojejunal feeding tubes were used in 52% of patients before and 56% of patients after protocol implementation P = .63). Jejunal tubes were placed earlier after the protocol was implemented than before (median 5 vs 6.5 days), and when a jejunal tube was in place, feeding goals were reached faster (median 2 vs 3 days, P = .002).

Conclusion

Implementing an enteral nutrition support protocol shortened the time to reach feeding goals. Jejunal feeding tubes were necessary in more than half of the patients, and with a jejunal feeding tube in place, feeding goals were reached rapidly.
Pathology of fatal lineage 1 and 2 West Nile virus infections in horses in South Africa
Authors: Williams June H. , Van Niekerk Stephanie , Human Stacey , Van Wilpe Erna , Venter Marietjie
Published: September 2014

Since 2007, West Nile virus (WNV) has been reported in South African horses, causing severe neurological signs. All cases were of lineage 2, except for one case that clustered with lineage 1 viruses. In the present study, gross and microscopic lesions of six South African lineage 2-infected horses and the one lineage 1 case are described. Diagnoses were confirmed by real-time reverse-transcriptase polymerase chain reaction (RT-PCR) of central nervous system (CNS) tissue and one by RT-PCR of a brain virus isolate. The CNS of all cases was negative by RT-PCR or immunohistochemistry (IHC) for African horse sickness (AHS), equine encephalosis virus, equine herpes viruses 1 and 4, other zoonotic flaviviruses, alphaviruses, and shunivirus, and either by immunofluorescence or IHC for rabies. Gross visceral lesions were nonspecific but often mimicked those of AHS. The CNS histopathology of WNV lineage 2 cases resembled the nonsuppurative polioencephalomyelitis reported in the Northern Hemisphere lineage 1 and recent Hungarian lineage 2 cases. Occasional meningitis, focal spinal ventral horn poliomalacia, dorsal and lateral horn poliomyelitis, leucomyelitis, asymmetrical ventral motor spinal neuritis and frequent olfactory region involvement were also seen. Lineage 2 cases displayed marked variations in CNS lesion severity, type and distribution, and suggested various viral entry routes into the CNS, based on findings in experimental mice and hamsters. Lineage 1 lesions were comparable to the milder lineage 2 cases. West Nile virus IHC on CNS sections with marked lesions from all cases elicited only two antigen-positive cells in the olfactory cortex of one case. The presence in the CNS of T-lymphocytes, B-lymphocytes, plasma cells and macrophage-monocytes was confirmed by cluster of differentiation (CD) 3, CD20, multiple myeloma oncogene 1 (MUM1) and macrophage (MAC) 387 IHC.
The effects of energy paths and emission controls and standards on future trends in China's emissions of primary air pollutants
Authors: Zhao Y. , Zhang J. , Nielsen C. P.
Published: September 2014

Abstract. To examine the efficacy of China's actions to control atmospheric pollution, three levels of growth of energy consumption and three levels of implementation of emission controls are estimated, generating a total of nine combined activity-emission control scenarios that are then used to estimate trends of national emissions of primary air pollutants through 2030. The emission control strategies are expected to have more effects than the energy paths on the future emission trends for all the concerned pollutants. As recently promulgated national action plans of air pollution prevention and control (NAPAPPC) are implemented, China's anthropogenic pollutant emissions should decline. For example, the emissions of SO2, NOx, total suspended particles (TSP), PM10, and PM2.5 are estimated to decline 7, 20, 41, 34, and 31% from 2010 to 2030, respectively, in the "best guess" scenario that includes national commitment of energy saving policy and implementation of NAPAPPC. Should the issued/proposed emission standards be fully achieved, a less likely scenario, annual emissions would be further reduced, ranging from 17 (for primary PM2.5) to 29% (for NOx) declines in 2015, and the analogue numbers would be 12 and 24% in 2030. The uncertainties of emission projections result mainly from the uncertain operational conditions of swiftly proliferating air pollutant control devices and lack of detailed information about emission control plans by region. The predicted emission trends by sector and chemical species raise concerns about current pollution control strategies: the potential for emissions abatement in key sectors may be declining due to the near saturation of emission control devices use; risks of ecosystem acidification could rise because emissions of alkaline base cations may be declining faster than those of SO2; and radiative forcing could rise because emissions of positive-forcing carbonaceous aerosols may decline more slowly than those of SO2 emissions and thereby concentrations of negative-forcing sulfate particles. Expanded control of emissions of fine particles and carbonaceous aerosols from small industrial and residential sources is recommended, and a more comprehensive emission control strategy targeting a wider range of pollutants (volatile organic compounds, NH3 and CO, etc.) and taking account of more diverse environmental impacts is also urgently needed.
Measurements of dust deposition velocity in a wind-tunnel experiment
Authors: Zhang J. , Shao Y. , Huang N.
Published: September 2014

Abstract. In this study, we present the results of a wind-tunnel experiment on dust deposition. A new method is proposed to derive dust deposition velocity from PDA (particle dynamics analysis) particle-velocity and particle-size measurements. This method has the advantage that the motions of individual dust particles are directly observed and all relevant data for computing dust deposition velocity is collected using a single instrument, and thus the measurement uncertainties are reduced. The method is used in the wind-tunnel experiment to measure dust deposition velocities for different particle sizes, wind speeds and surface conditions. For sticky-smooth wood and water surfaces, the observed dust deposition velocities are compared with the predictions using a dust deposition scheme, and the entire data set is compared with the data found in the literature. From the wind-tunnel experiments, a relatively reliable data set of dust deposition velocities is obtained, which is valuable for the development and validation of dust deposition schemes.
Air–sea exchange and gas–particle partitioning of polycyclic aromatic hydrocarbons in the Mediterranean
Authors: Mulder M. D. , Heil A. , Kukučka P. , Klánová J. , Kuta J. , Prokeš R. , Sprovieri F. , Lammel G.
Published: September 2014

Abstract. Polycyclic aromatic hydrocarbon (PAH) concentration in air of the central and eastern Mediterranean in summer 2010 was 1.45 (0.30–3.25) ng m−3 (sum of 25 PAHs), with 8 (1–17)% in the particulate phase, almost exclusively associated with particles < 0.25 μm. The total deposition flux of particulate PAHs was 0.3–0.5 μ g m−2 yr−1. The diffusive air–sea exchange fluxes of fluoranthene and pyrene were mostly found net-depositional or close to phase equilibrium, while retene was net-volatilisational in a large sea region. Regional fire activity records in combination with box model simulations suggest that seasonal depositional input of retene from biomass burning into the surface waters during summer is followed by an annual reversal of air–sea exchange, while interannual variability is dominated by the variability of the fire season. One-third of primary retene sources to the sea region in the period 2005–2010 returned to the atmosphere as secondary emissions from surface seawaters. It is concluded that future negative emission trends or interannual variability of regional sources may trigger the sea to become a secondary PAH source through reversal of diffusive air–sea exchange. Capsule: In late summer the seawater surface in the Mediterranean has turned into a temporary secondary source of PAH, obviously related to biomass burning in the region.
Influence of corona discharge on the ozone budget in the tropical free troposphere: a case study of deep convection during GABRIEL
Authors: Bozem H. , Fischer H. , Gurk C. , Schiller C. L. , Parchatka U. , Koenigstedt R. , Stickler A. , Martinez M. , Harder H. , Kubistin D. , Williams J. , Eerdekens G. , Lelieveld J.
Published: September 2014

Abstract. Convective redistribution of ozone and its precursors between the boundary layer (BL) and the free troposphere (FT) influences photochemistry, in particular in the middle and upper troposphere (UT). We present a case study of convective transport during the GABRIEL campaign over the tropical rain forest in Suriname in October 2005. During one measurement flight the inflow and outflow regions of a cumulonimbus cloud (Cb) have been characterized. We identified a distinct layer between 9 and 11 km altitude with enhanced mixing ratios of CO, O3, HOx, acetone and acetonitrile. The elevated O3 contradicts the expectation that convective transport brings low-ozone air from the boundary layer to the outflow region. Entrainment of ozone-rich air is estimated to account for 62% (range: 33–91%) of the observed O3. Ozone is enhanced by only 5–6% by photochemical production in the outflow due to enhanced NO from lightning, based on model calculations using observations including the first reported HOx measurements over the tropical rainforest. The "excess" ozone in the outflow is most probably due to direct production by corona discharge associated with lightning. We deduce a production rate of 5.12 × 1028 molecules O3 flash−1 (range: 9.89 × 1026–9.82 × 1028 molecules O3 flash−1), which is at the upper limit of the range reported previously.
Understanding the anthropogenic influence on formation of biogenic secondary organic aerosols in Denmark via analysis of organosulfates and related oxidation products
Authors: Nguyen Q. T. , Christensen M. K. , Cozzi F. , Zare A. , Hansen A. M. K. , Kristensen K. , Tulinius T. E. , Madsen H. H. , Christensen J. H. , Brandt J. , Massling A. , Nøjgaard J. K. , Glasius M.
Published: September 2014

Abstract. Anthropogenic emissions of sulfur dioxide (SO2) and nitrogen oxides (NOx) may affect concentration levels and composition of biogenic secondary organic aerosols (BSOA) through photochemical reactions with biogenic organic precursors to form organosulfates and nitrooxy organosulfates. We investigated this influence in a field study from 19 May to 22 June, 2011 at two sampling sites in Denmark. Within the study, we identified a substantial number of organic acids, organosulfates and nitrooxy organosulfates in the ambient urban curbside and semi-rural background air. A high degree of correlation in concentrations was found among a group of specific organic acids, organosulfates and nitrooxy organosulfates, which may originate from various precursors, suggesting a common mechanism or factor affecting their concentration levels at the sites. It was proposed that the formation of those species most likely occurred on a larger spatial scale, with the compounds being long-range transported to the sites on the days with the highest concentrations. The origin of the long-range transported aerosols was investigated using the Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model in addition to modeled emissions of related precursors, including isoprene and monoterpenes using the global Model of Emissions of Gases and Aerosols from Nature (MEGAN) and SO2 emissions using the European Monitoring and Evaluation Program (EMEP) database. The local impacts were also studied by examining the correlation between selected species, which showed significantly enhanced concentrations at the urban curbside site and the local concentrations of various gases, including SO2, ozone (O3), NOx, aerosol acidity and other meteorological conditions. This investigation showed that an inter-play of the local parameters such as the aerosol acidity, NOx, SO2, relative humidity (RH), temperature and global radiation seemed to affect the concentration level of those species, suggesting the influence of aqueous aerosol chemistry. The local impacts, however, seemed minor compared to the regional impacts. The total concentrations of organosulfates and nitrooxy organosulfates, on average, contributed to approximately 0.5–0.8% of PM1 mass at the two sampling sites.
How important are atmospheric depressions and mobile cyclones for emitting mineral dust aerosol in North Africa?
Authors: Fiedler S. , Schepanski K. , Knippertz P. , Heinold B. , Tegen I.
Published: September 2014

Abstract. This study presents the first quantitative estimate of the mineral dust emission associated with atmospheric depressions and mobile cyclones in North Africa. Atmospheric depressions are automatically tracked at 925 hPa based on ERA-Interim data from the European Centre for Medium-Range Weather Forecasts for 1989–2008. A set of filter criteria is applied to identify mobile cyclones, i.e. migrating and long-lived cyclones. The shorter term cyclone is used as a synonym for mobile cyclones. Dust emission is calculated with a dust emission model driven by 10 m winds and soil moisture from ERA-Interim. Emission peaks during winter and spring with spatial averages of 250–380 g m−2 per month. Comparison of the dust source activation frequency from the model against SEVIRI satellite observation shows a good agreement in the Bodélé Depression but differences in the north and west of North Africa. Depressions are abundant, particularly in summer when the Saharan heat low is situated over West Africa and during spring in the lee of the Atlas Mountains. Up to 90% (55% annually and spatially averaged) of dust emission occurs within 10 degrees of these depressions, with embedded mechanisms such as nocturnal low-level jets playing a role. Cyclones are rarer and occur primarily north of 20° N in spring in agreement with previous studies and over summertime West Africa consistent with near-surface signatures of African Easterly Waves. Dust emission within 10 degrees of cyclones peaks over Libya with up to 25% in spring. Despite the overall small contribution of 4% annually and spatially averaged, cyclones coincide with particularly intense dust emission events exceeding the climatological mean by a factor of four to eight. Soil moisture weakens dust emission during cyclone passage by about 10%.
Characterization of biomass burning smoke from cooking fires, peat, crop residue and other fuels with high resolution proton-transfer-reaction time-of-flight mass spectrometry
Authors: Stockwell C. E. , Veres P. R. , Williams J. , Yokelson R. J.
Published: September 2014

Abstract. We deployed a high-resolution proton-transfer-reaction time-of-flight mass spectrometer (PTR-TOF-MS) to measure biomass burning emissions from peat, crop-residue, cooking fires, and many other fire types during the fourth Fire Lab at Missoula Experiment (FLAME-4) laboratory campaign. A combination of gas standards calibrations and composition sensitive, mass dependent calibration curves were applied to quantify gas-phase non-methane organic compounds (NMOCs) observed in the complex mixture of fire emissions. We used several approaches to assign best identities to most major "exact masses" including many high molecular mass species. Using these methods approximately 80–96% of the total NMOC mass detected by PTR-TOF-MS and FTIR was positively or tentatively identified for major fuel types. We report data for many rarely measured or previously unmeasured emissions in several compound classes including aromatic hydrocarbons, phenolic compounds, and furans; many of which are suspected secondary organic aerosol precursors. A large set of new emission factors (EFs) for a range of globally significant biomass fuels is presented. Measurements show that oxygenated NMOCs accounted for the largest fraction of emissions of all compound classes. In a brief study of various traditional and advanced cooking methods, the EFs for these emissions groups were greatest for open 3-stone cooking in comparison to their more advanced counterparts. Several little-studied nitrogen-containing organic compounds were detected from many fuel types that together accounted for 0.1–8.7% of the fuel nitrogen and some may play a role in new particle formation.
Iodine oxide in the global marine boundary layer
Authors: Prados-Roman C. , Cuevas C. A. , Hay T. , Fernandez R. P. , Mahajan A. S. , Royer S.-J. , Galí M. , Simó R. , Dachs J. , Großmann K. , Kinnison D. E. , Lamarque J.-F. , Saiz-Lopez A.
Published: September 2014

Abstract. Emitted mainly by the oceans, iodine is a halogen compound important for atmospheric chemistry due to its high ozone depletion potential and effect on the oxidizing capacity of the atmosphere. Here we present a comprehensive dataset of iodine oxide (IO) measurements in the open marine boundary layer (MBL) made during the Malaspina 2010 circumnavigation. Results show IO mixing ratios ranging from 0.4 to 1 pmol mol−1 and, complemented with additional field campaigns, this dataset confirms through observations the ubiquitous presence of reactive iodine chemistry in the global marine environment. We use a global model with organic (CH3I, CH2ICl, CH2I2 and CH2IBr) and inorganic (HOI and I2) iodine ocean emissions to investigate the contribution of the different iodine source gases to the budget of IO in the global MBL. In agreement with previous estimates, our results indicate that, globally averaged, the abiotic precursors contribute about 75% to the iodine oxide budget. However, this work reveals a strong geographical pattern in the contribution of organic vs. inorganic precursors to reactive iodine in the global MBL.
First quasi-Lagrangian in-situ measurements of Antarctic Polar springtime ozone: observed ozone loss rates from the Concordiasi long-duration balloon campaign
Authors: Schofield R. , Avallone L. M. , Kalnajs L. E. , Hertzog A. , Wohltmann I. , Rex M.
Published: September 2014

Abstract. We present ozone measurements made using state-of-the-art ultraviolet photometers onboard three long-duration stratospheric balloons launched as part of the Concordiasi campaign in austral spring 2010. Ozone loss rates calculated by matching air-parcels sampled at different times and places during the polar spring are in agreement with rates previously derived from ozonesonde measurements, for the vortex-average, ranging between 2–7 ppbv (sunlit h)−1 or 25–110 ppbv per day. However, the geographical coverage of these long-duration stratospheric balloon platforms provides new insights into the temporal and spatial patterns of ozone loss over Antarctica. Very large ozone loss rates of up to 200 ppbv day−1 (16 ppbv (sunlit h)−1) are observed for airmasses that are down-wind of the Antarctic Peninsula and/or over the East Antarctic region. The ozone loss rate maximum downstream of the Antarctic Peninsula region is consistent with high PSC occurrence from Calipso and large ClO abundances from MLS satellite observations for 12–22 September 2010.
Air–surface exchange of Hg0 measured by collocated micrometeorological and enclosure methods – Part 1: Data comparability and method characteristics
Authors: Zhu W. , Sommar J. , Lin C.-J. , Feng X.
Published: September 2014

Abstract. Reliable quantification of air-biosphere exchange flux of elemental mercury vapor (Hg0) is crucial for understanding global biogeochemical cycle of mercury. However, there has not been a standard analytical protocol for flux quantification, and little attention has been devoted to characterize the temporal variability and comparability of fluxes measured by different methods. In this study, we deployed a collocated set of micro-meteorological (MM) and enclosure measurement systems to quantify Hg0 flux over bare soil and low standing crop in an agricultural field. The techniques include relaxed eddy accumulation (REA), modified Bowen-ratio (MBR), aerodynamic gradient (AGM) as well as dynamic flux chambers of traditional (TDFC) and novel (NDFC) designs. The five systems and their measured fluxes were cross-examined with respect to magnitude, temporal trend and sensitivity to environmental variables. Fluxes measured by the MM and DFC methods showed distinct temporal trends. The former exhibited a highly dynamic temporal variability while the latter had much gradual temporal features. The diurnal characteristics reflected the difference in the fundamental processes driving the measurements. The correlations between NDFC and TDFC fluxes and between MBR and AGM fluxes were significant (R > 0.8, p < 0.05), but the correlation between DFC and MM instantaneous fluxes were from weak to moderate (R = 0.1–0.5). Statistical analysis indicated that the median of turbulent fluxes estimated by the three independent MM-techniques were not significantly different. Cumulative flux measured by TDFC is considerably lower (42% of AGM and 31% of MBR fluxes) while those measured by NDFC, AGM and MBR were similar (< 10% difference). This implicates that the NDFC technique, which accounts for internal friction velocity, effectively bridged the gap in measured Hg0 flux compared to MM techniques. Cumulated flux measured by REA was ~60% higher than the gradient-based fluxes. Environmental factors have different degrees of impacts on the fluxes observed by different techniques, possibly caused by the underlying assumptions specific to each individual method. Recommendations regarding the application of flux quantification methods were made based on the data obtained in this study.
Intercomparing different devices for the investigation of ice nucleating particles using Snomax® as test substance
Authors: Wex H. , Augustin-Bauditz S. , Boose Y. , Budke C. , Curtius J. , Diehl K. , Dreyer A. , Frank F. , Hartmann S. , Hiranuma N. , Jantsch E. , Kanji Z. A. , Kiselev A. , Koop T. , Möhler O. , Niedermeier D. , Nillius B. , Rösch M. , Rose D. , Schmidt C. , Steinke I. , Stratmann F.
Published: September 2014

Abstract. Seven different instruments and measurement methods were used to examine the immersion freezing of bacterial ice nuclei from Snomax® (hereafter Snomax), a product containing ice active protein complexes from non-viable Pseudomonas syringae bacteria. The experimental conditions were kept as similar as possible for the different measurements. Of the participating instruments, some examined droplets which had been made from suspensions directly, and the others examined droplets activated on previously generated Snomax particles, with particle diameters of mostly a few hundred nanometers and up to a few micrometers in some cases. Data were obtained in the temperature range from −2 to −38 °C, and it was found that all ice active protein complexes were already activated above −12 °C. Droplets with different Snomax mass concentrations covering 10 orders of magnitude were examined. Some instruments had very short ice nucleation times down to below 1 s, while others had comparably slow cooling rates around 1 K min−1. Displaying data from the different instruments in terms of numbers of ice active protein complexes per dry mass of Snomax, nm, showed that within their uncertainty the data agree well with each other as well as to previously reported literature results. Two parameterizations were taken from literature for a direct comparison to our results, and these were a time dependent approach based on a contact angle distribution Niedermeier et al. (2014) and a modification of the parameterization presented in Hartmann et~al.~(2013) representing a time independent approach. The agreement between these and the measured data were good, i.e. they agreed within a temperature range of 0.6 K or equivalently a range in nm of a factor of 2. From the results presented herein, we propose that Snomax, at least when carefully shared and prepared, is a suitable material to test and compare different instruments for their accuracy of measuring immersion freezing.
Influence of isoprene chemical mechanism on modelled changes in tropospheric ozone due to climate and land use over the 21st century
Authors: Squire O. J. , Archibald A. T. , Griffiths P. T. , Jenkin M. E. , Pyle J. A.
Published: September 2014

Abstract. Isoprene is a precursor to tropospheric ozone, a key pollutant and greenhouse gas. Anthropogenic activity over the coming century is likely to cause large changes in atmospheric CO2 levels, climate and land use, all of which will alter the global vegetation distribution leading to changes in isoprene emissions. Previous studies have used global chemistry–climate models to assess how possible changes in climate and land use could affect isoprene emissions and hence tropospheric ozone. The chemistry of isoprene oxidation, which can alter the concentration of ozone, is highly complex, therefore it must be parameterised in these models. In this work we compare the effect of four different reduced isoprene chemical mechanisms, all currently used in Earth-system models, on tropospheric ozone. Using a box model we compare ozone in these reduced schemes to that in a more explicit scheme (the MCM) over a range of NOx and isoprene emissions, through the use of O3 isopleths. We find that there is some variability, especially at high isoprene emissions, caused by differences in isoprene-derived NOx reservoir species. A global model is then used to examine how the different reduced schemes respond to potential future changes in climate, isoprene emissions, anthropogenic emissions and land use change. We find that, particularly in isoprene rich regions, the response of the schemes varies considerably. The wide ranging response is due to differences in the types of peroxy radicals produced by isoprene oxidation, and their relative rates of reaction towards NO, leading to ozone formation, or HO2, leading to termination. Also important is the yield of isoprene-nitrates and peroxyacyl nitrate precursors from isoprene oxidation. Those schemes that produce less of these NOx reservoir species, tend to produce more ozone locally and less away from the source region. Additionally, by combining the emissions and O3 data from all of the global model integrations, we are able to construct isopleth plots comparable to those from the box model analysis. We find that the global and box model isopleths show good qualitative agreement, suggesting that comparing chemical mechanisms with a box model in this framework is a useful tool for assessing mechanistic performance in complex global models. We conclude that as the choice of reduced isoprene mechanism may alter both the magnitude and sign of the ozone response, how isoprene chemistry is parameterised in perturbation experiments such as these is a crucially important consideration. More measurements are needed to validate these reduced mechanisms especially in high-VOC, low-NOx environments.
Aging of secondary organic aerosol generated from the ozonolysis of α-pinene: effects of ozone, light and temperature
Authors: Denjean C. , Formenti P. , Picquet-Varrault B. , Camredon M. , Pangui E. , Zapf P. , Katrib Y. , Giorio C. , Tapparo A. , Temime-Roussel B. , Monod A. , Aumont B. , Doussin J. F.
Published: September 2014

Abstract. A series of experiments was conducted in the CESAM simulation chamber to investigate the evolution of the physical and chemical properties of secondary organic aerosol (SOA) during different forcing. The present experiments represent a first attempt to comprehensively investigate the influence of oxidative processing, photochemistry, and diurnal temperature cycling upon SOA properties. SOA generated from the ozonolysis of α-pinene were exposed to (1) elevated ozone concentrations, (2) light (under controlled temperature conditions), or (3) light and heat (6 °C light-induced temperature increase), and the resultant changes in SOA optical properties (i.e. absorption and scattering), hygroscopicity and chemical composition were measured using a suite of instrumentation interfaced to the CESAM chamber. The complex refractive index (CRI) was derived from integrated nephelometer measurements at 525 nm wavelength, using Mie scattering calculations and measured number size distributions. The particle size growth factor (GF) was measured with a hygroscopic tandem differential mobility analyzer (H-TDMA). An aerosol mass spectrometer (AMS) was used for the determination of the f44 / f43 and O : C ratio of the particles bulk. No change in SOA size or chemical composition was observed during O3 and light exposure at constant temperature; in addition, GF and CRI of the SOA remained constant with forcing. By contrast, illumination of the SOA in the absence of temperature control led to an increase in the real part of the CRI from 1.35 (±0.03) to 1.49 (±0.03), an increase of the GF from 1.04 (±0.02) to 1.14 (±0.02) and an increase of the f44 / f43 ratio from 1.73 (±0.03) to 2.23 (±0.03). These surprising results suggest that SOA properties may be governed more by local temperature fluctuations than by oxidative processing and photochemistry.