1,721,056 research outputs found
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
Trattamento di reflui petrolchimici con fanghi aerobici granulari: effetti della concentrazione del substrato di crescita
Full text linkIl processo a fanghi attivi per il trattamento biologico dei reflui mostra scarsa tolleranza alle fluttuazioni di carico ed è sensibile alla presenza di sostanze tossiche, anche in basse concentrazioni. I sistemi a fanghi aerobici granulari sono caratterizzati da notevole flessibilità, ridotti consumi energetici, elevata sedimentabilità dei fanghi, maggiore resistenza alle sostanze tossiche contenute nei reflui, e sono in grado di trattare elevati carichi organici volumetrici. Tra i reflui industriali, quelli petrolchimici presentano un’estrema variabilità, che deriva dalle numerose tipologie di processo applicate nei diversi impianti. Nello studio proposto si è valutata la trattabilità in un reattore a fanghi granulari (GSBR, granular sludge sequencing batch reactor) di un refluo petrolchimico ad alto tenore di azoto ammoniacale (N-NH4+) prodotto dal ciclo combinato di gassificazione integrata (IGCC), con l’obiettivo di sostituire o integrare il sistema di trattamento attualmente impiegato in raffineria. Per favorire la granulazione, è stato aggiunto nell’influente un substrato organico rapidamente biodegradabile (acetato), il cui dosaggio è stato progressivamente ridotto, e infine sospeso, per ridurre i costi operativi nell’ottica di un’eventuale applicazione del sistema a scala reale. Le prestazioni del processo in termini di efficienze di rimozione di N-NH4+ e sostanza organica (espressa come carbonio organico totale, TOC) sono state buone (rispettivamente 70% e 90%) in condizioni di carico organico elevato, e si sono mantenute tali (così come le caratteristiche morfologiche e di sedimentabilità dei granuli) anche dopo la sospensione del dosaggio di acetato. I risultati hanno dimostrato che: (i) il GSBR può rappresentare una valida alternativa per il trattamento del refluo IGCC; (ii) l’apporto di acetato può essere sospeso una volta completato l’avviamento del GSBR; (iii) la conseguente riduzione dei costi operativi rende interessante l’applicazione del processo a scala reale
Evaluation of nitrous oxide gaseous emissions from a partial nitritation reactor operating under different conditions
No full textIn this study, a laboratory-scale partial nitritation (PN) reactor was fed with a synthetic medium simulating the ammonium-rich wastewater produced by the anaerobic digestion of food waste. The reactor was operated at constant hydraulic retention time (1 d) and nitrogen loading rate (1.5 g N/L d), with different influent alkalinity to ammonium-nitrogen molar ratios (Alk/N, 1 and 1.3) and dissolved oxygen (DO) concentrations (5.0, 3.0, 2.0, 1.5, and 1.0 mg O-2/L). For each operating condition tested, nitrous oxide (N2O) gaseous emissions from the PN reactor were measured via infrared gas-filter correlation, in order to achieve a deeper understanding of process potential environmental impact. As DO concentration ranged between 5.0 and 1.5 mg O-2/L, the partial conversion of ammonium to nitrite was successfully achieved, with negligible nitrate production and nitrous oxide emission. When Alk/N was increased from 1 to 1.3 (DO was not limiting), the increase in ammonium-nitrogen oxidation rate (AOR, from 717 +/- 17 to 945 +/- 21 mg NH4-N/L d) and the simultaneous decrease in N2O-N emission factor (from 0.33% +/- 0.01% to 0.23% +/- 0.01% of AOR) were observed. When DO was set to 1.0 mg O-2/L, PN was irreversibly compromised, and a corresponding increase in N2O-N emission factor was observed (from 0.22% +/- 0.01% to 0.61% +/- 0.03% of AOR). Nitrifier denitrification was suggested as the main pathway contributing to N2O emission. Minimization of anoxic conditions may contribute in reducing greenhouse gas emissions even at low DO concentrations, as long as they are not process-limiting
Further considerations on colpo-suspension by Burch's method in the correction of stress urinary incontinence
No full textSerum concentration of pregnancy-associated beta-1-glycoprotein in normal and at-risk pregnancy
No full text
- …
