1,720,986 research outputs found
A kinetic study of aerobic propane uptake and cometabolic degradation of chloroform, cis-dichloroethylene and trichloroetylene in microcosms with groundwater/aquifer solids
No full textThe focus of this study was to compare the behavior of different consortiums of aerobic propane-utilizing microorganisms, with respect to both the lag time for growth after exposure to propane, and their ability to transform three chlorinated aliphatic hydrocarbons (CAHs): chloroform (CF), cis-dichloroethylene (c-DCE) and trichloroethylene (TCE). Thirty-three slurry microcosms, representing seven combinations of aquifer solids and groundwater were constructed for this study. The lag time required for establishing propane-utilizing consortiums ranged between 24 and 29 days in 6 of the 7 combinations. Kinetic tests were performed with respect to propane utilization and CAH transformation. After CAH exposure, the ability of the microorganisms to metabolize propane was significantly reduced. CF and TCE were transformed more slowly than c-DCE, the average values of the initial transformation rates being equal to 0.10 ± 0.04, 0.09 ± 0.05 and 0.98 ± 0.18 μmol/(L h), respectively. CF caused the greatest reduction in propane uptake rates, whereas c-DCE exhibited an apparently reversible negative effect on propane uptake rates. The estimates of the Monod half-saturation constants relative to CF, TCE and c-DCE resulted in the 2-3 μmol/L range, but were characterized by a high degree of uncertainty. © 2003 Kluwer Academic Publishers
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
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
Regeneration and modelling of a phosphorous removal and recovery hybrid ion exchange resin after long term operation with municipal wastewater
Full text linkAdsorption represents one of the most promising process for phosphorous (P) removal and recovery from municipal wastewater, but questions about its long-term stability remain. The goals of this work were (i) to assess changes in morphology and adsorption performances of hybrid anion exchanger (HAIX) LayneRT after 2.5 years of operation in a 10 m3 d−1 demonstration plant fed with secondary-treated municipal wastewater, (ii) to optimize the LayneRT regeneration procedure, and (iii) to evaluate the suitability of the ion exchange model to describe P adsorption on LayneRT. LayneRT is composed of hydrated ferric nanoparticles dispersed in a strong base anion exchange resin. Batch and continuous flow adsorption/desorption tests were conducted with the resin used for 2.5 years, regenerated with two alternative solutions: NaOH, reactivating mainly the iron nanoparticles active sites, and NaOH + NaCl, also regenerating the active sites of the ion exchange media. The physicochemical characterization by Scanning Electron Microscope indicated that regeneration by NaOH significantly reduced the deterioration of the resin surface, even after 59 adsorption/desorption cycles. Lab-scale continuous flow tests showed that the resin regenerated with either solution featured P adsorption performances very close to that of the virgin resin. The isotherm tests showed that P adsorption by LayneRT was effectively simulated with the ion exchange model. This study confirms that LayneRT is a durable, resistant and promising media for P recovery from wastewater
Ammonium removal and recovery from municipal wastewater by ion exchange using a metakaolin K-based geopolymer
Full text linkAmong the available technologies for ammonium removal from wastewater, ion exchange represents one of the most promising ones in the perspective to recover ammonium and produce a fertilizing product. However, the vast majority of previous studies on ammonium ion exchange did not evaluate the process robustness under real operational conditions nor optimized the desorption step. In this paper, tests of ammonium removal and recovery were conducted on a metakaolin K-based geopolymer, compared with a high-performing Italian natural zeolite in K-form. Real municipal and saline wastewater was treated in a continuous flow pilot plant equipped with a 60-cm adsorption bed (bed volume 203 mL, sorbent mass 145-173 g, empty bed contact time 10 min). Geopolymer granules showed higher performances in terms of selectivity towards ammonium, operating capacity (8.5 mgN g-1 dry adsorbent at an inlet concentration of 40 mgN L-1), bed volumes of wastewater treated at the selected breakpoint (149). Geopolymer resulted to be a cost-effective adsorbent for wastewater treatment capable to adsorb cations by ion exchange, allowing a fractionated desorption procedure that led to recover ammonium in a solution composed mainly by NH4NO3 (37%wt) and KNO3 (56%wt), potentially usable as fertilizer. The geopolymer robustness was assessed after repeated adsorption/regeneration cycles showing that the geopolymer mechanical and morphological properties did not deteriorate. The results make the tested geopolymer a very promising material for the optimization and scale-up of the ammonium recovery process in a circular economy perspective
Aerobic cometabolism of chloroform by butane-grown microorganisms: long-term monitoring of depletion rates and isolation of a high-performing strain.
No full textThe focus of this microcosm study was to monitor the performances of 17 butane-utilizing microcosms during a long-term (100-250 days) aerobic cometabolic depletion of chloroform (CF). The depletion of the contaminant began after a lag-time variable between 0 and 23 days. All microcosms quickly reached a pseudo steady-state condition, in terms of biomass concentration (with an average of 9.3 x 106 CFU ml(-1)), chloroform depletion rate (5 micromol l(-1) d(-1)) and butane utilization rate (730 micromol l(-1) d(-1)). After about 100 days of CF depletion, a sudden 5- to 7-fold increase of the chloroform rate was observed in two microcosms, where the highest amount of contaminant had been depleted. In one of these high-performing microcosms, an experiment of chloroform depletion in the absence of butane resulted in the depletion of a surprisingly high amount of contaminant (765 micromolCF kg(-1) dry soil in 2 months) and in a marked selection of a single bacterial strain. Bioaugmentation assays conducted with the biomass selected in this microcosm and with a pure culture of the selected strain immediately resulted in very high chloroform depletion rates. Preliminary results of a study conducted with resting cells of the selected strain indicated that it can degrade chloroform concentrations up to 119 microM (14.2 mg l(-1)) without any sign of substrate toxicity, and that it is able to transform vinyl chloride and 1,1,2-trichloroethane
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
Development of an ion exchange process for ammonium removal and recovery from municipal wastewater using a metakaolin K-based geopolymer
Full text linkIon exchange represents a promising process for ammonium removal from municipal wastewater (MWW), in order to recover it for fertilizer production. Previous studies on ammonium ion exchange neglected the assessment of process robustness and the optimization the desorption/recovery step. This study aimed at developing a continuous-flow process of ammonium removal/recovery based on a metakaolin K-based geopolymer, named G13. Process robustness was assessed by operating 7 adsorption/desorption cycles with two types of MWW. These tests resulted in satisfactory and constant performances: operating capacity at 40 mgN L-1 in the inlet = 12 mgN gdry sorbent-1, bed volumes of treated MWW at the selected breakpoint = 199-226, ammonium adsorption yield = 88-91%. Empty bed contact time (EBCT) was decreased from 10 to 5 min without any reduction in performances. The NH4+ adsorption process was effectively simulated by the Thomas model, allowing a model-based assessment of the effect of EBCT reductions on process performances. An innovative desorption procedure led to high ammonium recovery yields (86-100%) and to a desorbed product composed primarily of KNO3 (54%w) and NH4NO3 (39%w), two salts largely used in commercial fertilizers. The energy consumption of ammonium removal/recovery with G13 resulted 0.027 kWh m-3treated WW, with a relevant reduction in comparison to traditional nitrification/denitrification, whereas the operational cost resulted equal to 60-110% of the cost of the benchmark process. These results show that G13 is a promising material to recover ammonium in a circular economy approach.Ion exchange represents a promising process for ammonium removal from municipal wastewater (MWW), in order to recover it for fertilizer production. Previous studies on ammonium ion exchange neglected the assessment of process robustness and the optimization the desorption/recovery step. This study aimed at developing a continuous-flow process of ammonium removal/recovery based on a metakaolin K-based geopolymer, named G13. Process robustness was assessed by operating 7 adsorption/desorption cycles with two types of MWW. These tests resulted in satisfactory and constant performances: operating capacity at 40 mgN L−1 in the inlet = 12 mgN gdry sorbent−1, bed volumes of treated MWW at the selected breakpoint = 199–226, ammonium adsorption yield = 88–91%. Empty bed contact time (EBCT) was decreased from 10 to 5 min without any reduction in performances. The NH4+ adsorption process was effectively simulated by the Thomas model, allowing a model-based assessment of the effect of EBCT reductions on process performances. An innovative desorption procedure led to high ammonium recovery yields (86–100%) and to a desorbed product composed primarily of KNO3 (54%w) and NH4NO3 (39%w), two salts largely used in commercial fertilizers. The energy consumption of ammonium removal/recovery with G13 resulted 0.027 kWh m−3treated WW, with a relevant reduction in comparison to traditional nitrification/denitrification, whereas the operational cost resulted equal to 60–110% of the cost of the benchmark process. These results show that G13 is a promising material to recover ammonium in a circular economy approach
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