1,720,971 research outputs found
Determinazione simultanea delle fasi particolato e gassosa di IPA aerodispersi mediante campionamento con membrane filtranti funzionalizzate
No full textAttualmente il campionamento dei microinquinanti organici semivolatili come le PCDD/F i PCB e i PAH viene effettuato attraverso la captazione del particolato su membrane filtranti e in alcuni casi impiegando cartucce di materiale adsorbente o assorbente.
I sistemi di campionamento a membrana filtrante sono molto più semplici dei metodi che coinvolgono anche l'impiego di cartucce idonee alla captazione della frazione volatile degli analiti.
Infatti i sistemi per la determinazione del particolato vengono spesso
automatizzati e permettono il campionamento su più filtri.
Campionatori che permettono il campionamento del particolato e della
frazione semivolatile spesso vengono impiegati per singole misure mentre sistemi automatizzati che consentono di cambiare simultaneamente i filtri e le cartucce sono assai rari da incontrare per la elevata complessità e l’elevato costo.
Poiché la frazione semivolatile degli analiti che viene persa con l’utilizzo delle sole membrane filtranti non è prevedibile, un corretto campionamento prevede l’utilizzo dei due sistemi in serie o in parallelo; in questo modo comunque si aumentano sia i costi che la complessità delle analisi, con conseguente possibilità di errori.
Si stanno pertanto sperimentando membrane funzionalizzate al
fine di campionare in un unico stadio sia gli inquinanti in fase particellare che in fase vapore; i primi risultati ottenuti sono molto incoraggianti, sia in termini di
semplificazione del campionamento che riguardo alle modalità delle successive fasi di trattamento ed analisi dei campioni raccolti
Anaerobic Digestion Manure Conversion and Recycling
No full textManure production is currently growing with the demand of meat products. Manure is a nutrient-rich biomass containing carbon, nitrogen, sulfur and phosphorous compounds which can at the same time be useful as fertilizing agents and harmful as pollutants in large quantities. Nitrogen and phosphorous can pollute surface and groundwater, leading to algal blooms and damage to aquatic ecosystems, while carbon, nitrogen and sulfur can lead to atmospheric emissions which can be strongly odorous, dangerous for human health and act as greenhouse gases. Composting and anaerobic digestion are two ways to treat manure to reduce these impacts, but only anaerobic digestion can also recover the energy still contained in manure. This chapter shows the basis of anaerobic digestion with a focus on manure as biomass. The effect on the anaerobic digestion of manure composition, which can vary widely depending on livestock species and feedstock, is explored. The most common types of anaerobic digestion reactors are summarized, detailing their advantages and disadvantages. The operative parameters to check for and control in managing an anaerobic digestion reactor are analyzed thoroughly, examining their effect on the process and how they interact in a complex system. Finally, as biogas is a green energy source and methane is an important energy carrier, its production and characteristics are evaluated, with a special focus on manure anaerobic digestion
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Simultaneous sampling of vapor and particle-phase carcinogenic polycyclic aromatic hydrocarbons on functionalized glass fiber filters
Full text linkThe sampling of polycyclic aromatic hydrocarbons (PAHs) in the atmosphere is often performed on filters, which retain only aerosol particles, disregarding the vapor fraction; after the filter, an adsorbent (e.g., polyurethane foam, PUF, or styrene/divinylbenzene, XAD) is sometimes used for sampling vapors not retained from the filter. However, the use of an adsorbent may lead to many disadvantages: contaminations, analysis time and costs, and size problems when developing automated or personal samplers. In this work, a functionalized glass fiber filter for the simultaneous sampling of aerosol particles and vapor fraction is presented for the sampling of PAHs in air. A low sampling efficiency was observed for 3 ring PAHs, but all carcinogenic PAHs (according to IARC) were totally retained on functionalized filters. On the other hand, a comparison with normal filter sampling was performed, and results obtained confirm that > 10% of benzo(a)pyrene can be lost from normal filters. Together with size reduction, another advantage of the functionalized filter is an enhancement in the extraction and purification recovery. © Taiwan Association for Aerosol Research
Bone char material for Volatile Organic Compounds (VOCs) adsorption: Effect of the activation on surface characteristics and performance
Full text linkAir pollution is a problem of great concern, with increasing atmospheric concentrations of toxic Volatile Organic Compounds (VOCs) such as BTEX (benzene, toluene, ethylbenzene and o-xylene).
We report the development of adsorbant materials derived from tuna fish bones. Tuna Bone Char (TBC) was obtained with a pyrolysis process; and activated with K2CO3 treatment (indicated as KTBC, due to the potassium carbonate activation). Characterisation showed that the activation protocol led to a significant increase in the surface area – from 97.45 to 1826.59 m2/g for TBC and KTBC; furthermore, the activated material also showed higher porosity (total pore volume of 2.22 cm3/g, micropore volume of 0.38 cm3/g).
BTEX dynamic adsorption tests showed KTBC excellent adsorption properties, particularly with o-xylene (adsorption capacity q of 147 mg/g). The higher adsorption of o-xylene was explained considering its kinetic diameter matching KTBC pore size dimension. KTBC also showed to be very efficient in humid conditions (q = 61.2 mg/g). Repeated tests with the same powder indicated a 20 % decrease after the first cycle, with no further decrease in additional cycles. Empirical regression models for q0 and kTh (Thomas model), and τ and KYN (Yoon-Nelson model) were developed for BTEX breakthrough curves and showed agreement with experimental breakcurve data (R2 > 0.905).
These results show that bone char can be used for gaseous pollutants with the activation playing a key role in surface modification and performance enhancement. This research offers a sustainable and effective route to convert marine biowaste into advanced adsorbents for VOC and air pollution control
Extractable denuders for selective sampling of vapour phase organics in the atmosphere
No full text: Extractable denuders were designed to collect trace atmospheric semivolatile organic compounds with high volume (38.30 and 200 L/ min) samplers. Denuders were made of multichannel ceramic support coated with sodium silicate and functionalised with phenyl moieties. Polycyclic aromatic hydrocarbons, polychlorinated biphenyls, polychlorinated dibenzodioxins and polychlorinated dibenzofurans and chlorobenzenes in ambient air of a sub-urban area of Monterotondo, Italy, were sampled. Samplings were of 24 h, 48 h and 1 week period. Precision was determined using field triplicates and compared to the conventional high volume sampler methods. The fraction of analytes in the particle phase measured with the filter/ PUF system ranged from 0.2 % for naphthalene to 98.5 % for benzo(ghi)perylene; this fraction measured with the denuder ranged from 0.5 % for naphthalene to 99.0 % for benzo(ghi)perylene. A paired t-test indicated that these values were significantly (t = 3.58, P < 0.01) higher for the denuder. Results showed good repeatability (0.4-4.6 %), sampling efficiency (>99 %) and good capacity as variations in experimental efficiency were not observed also for longer (1 week) period sampling. As significant changes in efficiency were observed (0.7-5.6 %), the developed denuder cannot be reused more than once. However, it is possible to regenerate the denuder with a new silanization step. A good linear correlation was found plotting the vapour/particle distribution ratio versus the vapour pressure (R2 ranged between 0.59 and 0.84) and versus the octanol/air partition coefficient (R2 ranged between 0.85 and 0.88) of each selected SVOCs, in good agreement with the theoretical models for partitioning of SVOCs
Variations on the Author
Full text link“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
Full text linkWe 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
Full text linkWe 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
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