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Study of organic and inorganic size-segregated chemical composition of different types of tropospheric aerosol.
No full textTropospheric aerosol influences several important chemical and physical processes in the troposphere, due to its high variability in terms of origin, chemical composition, size-distribution and spatial distribution. In fact local and regional, biogenic and anthropogenic, primary and secondary sources as well as long-range transport affect aerosol properties over independent regions and layers.
For these reasons organic and inorganic chemical composition at the different size ranges must be well characterized in order to understand and properly described in models the physical and chemical processes occurring in the troposphere.
The present thesis provides a detailed description of factors controlling size-segregated inorganic and organic chemical properties of different types of tropospheric aerosol. Size segregated aerosol samples were collected during the experiments performed in 2006 within the European Project MAP (Marine Aerosol Production Project, http://macehead.nuigalway.ie/map/), and during three intensive campaigns performed in 2007 and 2008 within the Italian project MIUR-AEROCLOUDS (Study of the Direct and Indirect Aerosol Effects on Climate). A chemical characterization of both water soluble and water insoluble organic fractions and water insoluble inorganic ions was accomplished.
In the framework of the Project MAP, main primary and secondary marine aerosol chemical components were investigated under clean marine conditions with relation to seasonal oceanic biological activity. Typical marine aerosol features were observed. Non sea salt sulphate (nss-SO4=) and ammonium (NH4+) dominated the submicrometer inorganic fraction, nitrate (NO3-) and sea salt are mainly distributed in the supermicrometer fraction but sea salt largely controlled the chemical composition of the supermicrometer particles. Water soluble (WSOM) and water insoluble (WIOM) organic matter mostly distributed in submicrometer particles with a large contribution. Primary organic matter (OM) resulted mostly insoluble and mainly produced by bubble bursting processes at the sea surface, as shown by Bubble Bursting experiments performed during MAP and thus indicating the prevalent secondary origin of WSOM.
The overall results clearly evidenced that concentration of the main secondary components (nss-SO4=, NH4+, WSOM, MSA) are driven by seasonality of oceanic biological productivity.
Furthermore, a new secondary component, alkylammonium salts, has been detected in marine aerosol samples. Dimethyl- (DMA+) and diethyl- (DEA+) ammonium, resulted the most abundant organic species, second only to MSA, detected in fine particles. These two species accumulate in submicrometer marine aerosol via acid-base reaction between gaseous biogenic amines and acidic sulphates. DMA+ and DEA+ show in analogy to the other biogenic secondary components, a variation in concentration clearly driven by biological activity. This result point to a potential important new source of marine SOA and atmospheric nitrogen at the global scale with a seasonal variation connected to the oceanic biological productivity.
In the framework of the project AEROCLOUDS, night-time and daytime size segregated aerosol samples were collected concurrently at the urban site of Torre Sarca (Milan), at the urban background site of Ispra (VA), at the rural site of San Pietro Capofiume (Bologna), at the mountain site of Mt. Cimone (2165 m a.s.l.) and at the urban background site of Montelibretti (Rome), during three typical patterns of the aerosol climatology in Italy:
• Aerosol accumulation in summer anticyclonic conditions (14 to18 July 2007);
• Aerosol accumulation in winter anticyclonic conditions (6 to 10 February 2008);
• Saharan dust long-range transport in spring (23 to 27 May 2007).
At the stations located within the Po basin (Milan, Ispra and San Pietro Capofiume), the main chemical aerosol components exhibited typical seasonal features observed in other highly populated and industrialized European areas. Organic compounds and nitrate maximises in winter. Sulphate exhibits higher background levels and a higher relative contribution in summer as its formation is related to photochemical activity. Sulphate and nitrate mainly occur as ammonium salts in the fine fraction as suggested by ionic balance. The winter maximum of organics, nitrate and ammonium mass concentration results in an increase in particulate matter levels due to different mechanisms which during stable atmospheric conditions occur favouring gas to
particles conversion of semi-volatile components such as ammonium nitrate and organics. The enhanced nucleation and condensation together with higher emission of fine particles accounts for a net increase of fine aerosol mass with respect to coarse mass as suggested by higher PM1/PM10 mass ratio in winter. Furthermore different diurnal cycle of boundary layer between wintertime and summertime induces differences in diurnal variation of aerosol concentration and chemical composition because in winter, when daytime mixing is very limited in height and time, the diurnal variability in aerosol mass concentration and chemical composition is less pronounced than in summer.
The night-time-daytime WSOC/TC ratio values during wintertime and summertime highlighted that higher photochemical activity enhances atmospheric oxidation processes converting biogenic and anthropogenic emissions of organic compounds into a more water soluble form and, therefore, secondary organic aerosol (SOA) formation.
At the mountain site of Mt. Cimone, differently from the Po valley stations, the daytime aerosol concentrations showed a clear seasonal pattern with the highest concentration in summer and the lowest in winter. This trend likely reflected the higher efficiency of vertical air masses transport during warmer months suggesting that daytime valley breezes and convective processes might transport polluted air masses from the regional boundary layer to the mountain site. Conversely, wintertime and night-time observations were less affected by influences from the PBL and are representative of the free tropospheric European baseline as suggested by fine aerosol chemical composition rich in sulphate and water-soluble organic compounds and poor in fine particulate nitrate and water insoluble carbonaceous compounds.
The impact of dust transport resulted in the increase in bulk aerosol mass concentration during dust transport, in the increased concentration of water soluble calcium in the coarse fraction and in the decrease in PM1/PM10 mass ratio values at all stations with respect to regional background conditions. These changes are all attributable to enrichment into coarse particles of crustal material of Saharan origin.
Furthermore we observed two chemical features indicating aerosol ageing during transport from North-African regions: the increase of WSOC contribution to TC and the
shift of nitrate size distribution in the coarse range at Mt. Cimone showing that mineral dust occurred at synoptic scale.
The impact of Saharan dust transport strongly affected total mass and chemistry of background aerosol at Mt. Cimone, while in urban and polluted sites at lower elevation, the impact on aerosol chemistry was much less pronounced even if specific markers such as calcium revealed that transport occurred
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
"Determination of electrical power to be supplied to LOBI heaters", University of Pisa Report, DCMN - NT 011(80), Pisa (I), June 1980
No full textThe document deals with the description of an analytical and numerical model to determine the electrical power to be supplied to hollow rods, available in the LOBI experimental simulator, in order to simulate the performance of the nuclear fuel. Hollow rods are easy to construct but have a thermal capacity much lower than the reference nuclear fuel rods. The difference becomes important in transient conditions. In those conditions electrical power must be controlled in order to reproduce the temperature transient expected on the surface of the nuclear fuel rods. A complex software was developed to determine the electrical power transient based on the inverse solution for transient conduction heat transfer, i.e. the Fourier equation. Reference conditions (surface temperature and heat flux) were calculated by the RELAP code for nuclear fuel in the expected experimental conditions and were transformed into electrical power to be supplied to LOBI heaters during the actual experimental conditions (obviously if the Relap prediction were wrong – to be demonstrated a posteriori – the calculated transient for electrical power resulted inconsistent with the occurring thermal-hydraulic conditions). The program was used in a number of experiments performed in LOBI. LOBI was a Pressurized Water Reactor (PWR) simulator installed in the EC center of Ispra Italy supported by EURATOM
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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