1,720,974 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
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
Microbial activity response to hydrogen injection in thermophilic anaerobic digesters revealed by genome-centric metatranscriptomics
Full text linkBackground: The expansion of renewable energy produced by windmills and photovoltaic panels has generated a considerable electricity surplus, which can be utilized in water electrolysis systems for hydrogen production. The resulting hydrogen can then be funneled to anaerobic digesters for biogas upgrading (biomethanation) purposes (power-to-methane) or to produce high value-added compounds such as short-chain fatty acids (power-to-chemicals). Genome-centric metagenomics and metatranscriptomic analyses were performed to better understand the metabolic dynamics associated with H2 injection in two different configurations of anaerobic digesters treating acidic wastes, specifically cheese manufacturing byproducts. These approaches revealed the key-genes involved in methanation and carbon fixation pathways at species level. Results: The biogas upgrading process in the single-stage configuration increased the CH4 content by 7%. The dominant methanogenic species responsible for the upregulation of the hydrogenotrophic pathway in this reactor was Methanothermobacter wolfeii UC0008. In the two-stage configuration, H2 injection induced an upregulation of CO2 fixation pathways producing short-chain fatty acids, mainly acetate and butyrate. In this configuration, the abundant species Anaerobaculum hydrogeniformans UC0046 and Defluviitoga tunisiensis UC0050 primarily upregulated genes related to electron transport chains, suggesting putative syntrophisms with hydrogen scavenger microbes. Interestingly, Tepidanaerobacter acetatoxydans UC0018 did not act as an acetate-oxidizer in either reactor configurations, and instead regulated pathways involved in acetate production and uptake. A putative syntrophic association between Coprothermobacter proteolyticus UC0011 and M. wolfeii UC0008 was proposed in the two-stage reactor. In order to support the transcriptomic findings regarding the hydrogen utilization routes, an advanced bioconversion model was adapted for the simulation of the single- and two-stage reactor setups. Conclusions: This is the first study investigating biogas reactor metatranscriptome dynamics following hydrogen injection for biomethanation and carbon fixation to short-chain fatty acids purposes. The same microbes showed different patterns of metabolic regulation in the two reactor configurations. It was observed an effect of the specialized acidogenic reactor on the overall microbial consortium composition and activity in the two-stage digester. There were also suggested the main species responsible for methanation, short-chain fatty acids production, and electron transport chain mechanisms, in both reactor configurations
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
Advanced modelling in anaerobic co-digestion: the multiscale aspects of substrate composition, hydrogen transfer and microbial growth
No full textEn voksende menneskelig befolkning og forbedring af levestandarder kræver, at flere fødevarer, dyrefoder og industrielle varer bliver produceret på verdensplan. Denne kontinuerlige udvikling stiller høje krav til energiproduktion, som i et klimabevidst samfund i stigende omfang skal komme fra vedvarende ressourcer.Anaerob nedbrydning er en vigtig bioenergiteknologi og involverer mikrobiel konvertering af komplekst organisk stof til biogas, som er en alsidig energibærer. Anaerob nedbrydning er længe blevet betragtet som en holdbar løsning til bæredygtig energiproduktion. Grundet vanskelighederne forbundet med at betjene og optimere nedbrydningen er interessen for avancerede informationsteknologier til at levere pålidelig procesovervågning, prognoser og kontrolløsninger stabilt stigende.Fokus i denne afhandling var derfor at implementere og evaluere effekterne af forskellige funktionelle udvidelser i en detaljeret kinetisk biokonversionsmodel og ved at gøre dette, vurdere dets potentiale for anvendelse i forskellige industrielle applikationer. Desuden blev en detaljeret litteraturgennemgang af fortiden, nutiden og fremtiden inden for anaerob nedbrydningsmodellering også inkluderet. Modeludviklingen var en central del af projektet og involverede optimering af de mest følsomme kinetiske og hydrolyseudbytterkonstanter; tilpasning til simulering af co-nedbrydningseksperimenter med et øget antal underlag og under forskellige driftsbetingelser; implementering af modelfunktionaliteter til simulering af in situ og hybrid biogasopgraderingsprocesser; udvidelse af mikrobielle vækstsligninger for at tage højde for dynamiske temperatureffekter; og desuden inkludering af mikrobielle model grupper for at muliggøre simulering af bioaugmenteringsprocessen.Optimeringsprocessen blev udført med en systematisk metode, der omfattede den indledende selektion af parametre til analyse, følsomhedsanalyse af udvalgte parametre ved anvendelse af kalibreringsundersøgelsessimuleringer, numeriske estimeringer af de mest indflydelsesrige parametre og evaluering af det estimerede parameter indstillet gennem simulering af valideringsundersøgelser. Grundig analyse af resultaterne viste, at baseret på deres følsomhed kunne de 44 oprindeligt udvalgte parametre reduceres til 13, og ved at estimere deres værdier numerisk kunne simuleringspasninger forbedres markant. Ved at introducere en standardiseret protokol til parameterestimering og et universelt sæt optimerede parametre resulterede dette arbejde derfor i en forenklet løsning til simulering af anaerobe co-nedbrydningsscenarier.Med hensyn til modeludvidelsen til simulering af komplekse co-nedbrydningsprocesser var værktøjet egnet til simulering af eksperimentelle scenarier både i batch og kontinuerlig drift, mens antallet af potentielle modelunderlag samtidig blev øget. Efterfølgende simuleringer af en række eksperimenter udført i batch og kontinuerlig drift viste, at modellen kunne passe til målte datapunkter med høj nøjagtighed. Desuden indikerede en analyse af samlede flygtige fedtsyresimuleringer også, at der kan opstå store regressionsfejl, når den absolutte skala af målte værdier er lille.I et næste trin involverede modelforlængelsen in situ og hybrid biogasopgraderingsfunktioner tilføjelsen af hydrogenotrofe methanogene archaea og syntrofiske acetatoxiderende bakterier som nye mikrobielle model grupper, sammen med ændringen af gas-væske ligevægtsberegninger ved at overveje eksternt leveret og internt produceret brintstrømme. Efter modelkalibrering med ikke-opgraderede eksperimentelle procesdata blev succesfulde in situ biogasopgraderingssimuleringer valideret med opgraderede procesdata, der viser høj korrelation mellem målinger og simuleringer. Biogasopgraderingsfunktionerne blev også valideret med et sæt eksperimentelle reaktordata og indikerede god modelydelse, dog med højere statistiske fejl. I begge tilfælde blev ændringerne i flygtig fedtsyrekoncentration imidlertid opfanget i mindre grad og fremhævede behovet for en mere detaljeret modellering af acidogenese-trinnet i anaerob nedbrydning.En yderligere modelforbedring vedrørte udvidelsen af temperatureffektberegningen på mikrobiel vækst, specifikt ved at adskille langsigtet og kortsigtet dynamik. Den matematiske implementering blev også valideret gennem anvendelse af data fra to eksperimenter, hvor henholdsvis langvarige og kortvarige temperaturforstyrrelse blev undersøgt. Resultaterne beskrev eksperimentelle tendenser usædvanligt godt. Simuleringen af flygtige fedtsyrekoncentrationer viste sig imidlertid at være udfordrende og understøttede tidligere fund, mens simuleringen af forstyrrelsesdynamik med kort varighed viste sig at kræve mere forskning.Til sidst blev modellen tilpasset til simulering af bioaugmenteringsscenarier og blev derfor udvidet med ti bioaugmentative mikrobielle grupper: dem, der var ansvarlige for de samme konverteringsveje som deres oprindelige modstykker, dog med potentielt forskellige kinetiske parametre. Den forbedrede model blev derefter evalueret med data fra to forskellige eksperimentelle opsætninger, begge med fokus på ammoniakhæmmet operation. Simuleringsresultater var i god overensstemmelse med målte datapunkter og viste den samlede robusthed af modellen ved simulering af sådanne scenarier, med yderligere vægt på behovet for bedre kortvarig forstyrrelsesmodellering.Den samlede vurdering af resultaterne opnået i løbet af PhD-arbejdet viste, at de beskrevne individuelle udvidelser bidrog til forbedring af modelydelsen, og ved at tackle de identificerede udfordringer kan den yderligere udvidede model blive et værdifuldt værktøj i overvågning, kontrol og prognoser af anaerobe nedbrydningsprocesser i fuld skala.A growing human population and the improvement of living standards both require that more food, animal feed and industrial goods are being produced worldwide. This continuous development sets high demands on energy generation, which in a climate-conscious society must be provided from renewable resources to an ever greater extent.Anaerobic digestion that is a prominent bioenergy technology and involves the multistep microbial conversion of complex organic matter to the versatile energy carrier called biogas, has long been considered as a viable solution for sustainable energy generation. Due to the difficulties in operating and optimizing the digestion, however, interest in advanced information technologies to provide reliable process monitoring, forecasting and control solutions has been rising steadily.The focus of present thesis was therefore to implement and evaluate the effects of various functional extensions in a detailed kinetic bioconversion model, and by doing so, assess its potential for being applied in diverse industrial applications. Moreover, a detailed literature review of the past, present and future of anaerobic digestion modelling was also included in the document. As a central part of the project, model development involved the optimization of its most sensitive kinetic and hydrolysis yield constants; its adaptation to simulating co-digestion experiments with an increased number of substrates and under various operation conditions; the implementation of model functionalities for simulating in situ and hybrid biogas upgrading processes; the extension of microbial growth equations to account for dynamic temperature effects; and the inclusion of additional model microbial groups to enable bioaugmentation process simulation.Accordingly, the optimization process was carried out following a systematic method, which comprised of the initial selection of parameters to be analysed, the sensitivity analysis of selected parameters using calibration study simulations, the numerical estimation of the most influential parameters and the evaluation of the estimated parameter set through the simulation of validation studies. Thorough analysis of the results showed that based on their sensitivity, the initially selected 44 parameters could be reduced to 13, and by estimating their values numerically, simulation fits could be improved significantly. By introducing a standardized protocol for parameter estimation and a universal set of optimized parameters, this work therefore provided a simplified solution for simulating anaerobic co-digestion scenarios.With regards to the model extension for simulating complex co-digestion processes, the tool was suited for the simulation of experimental scenarios both in batch and continuous operation, while concurrently the number of potential model substrates was increased. Subsequent simulations of a series of experiments done in batch and continuous operation showed that the model could fit measured data points with high accuracy. Furthermore, analysis concerning total volatile fatty acid simulations also indicated that large regression errors might arise, in case the absolute scale of measured values is small.In the next step, the model extension with in situ and hybrid biogas upgrading functionalities involved the addition of hydrogenotrophic methanogenic archaea and syntrophic acetate oxidizing bacteria as new model microbial groups, along with the amendment of gas-liquid equilibrium calculations by considering externally provided and internally produced hydrogen flows. Following model calibration with non-upgraded experimental process data, in situ biogas upgrading simulations were successfully validated with upgraded process data, showing high correlation between measurements and simulations. As far as hybrid biogas upgrading functionalities are concerned, these were also validated with sets of experimental reactor data and indicated good model performance, although with higher statistical errors. In both cases, however, changes in volatile fatty acid concentration were captured to a smaller degree and highlighted the need for a more detailed modelling of the acidogenesis step in anaerobic digestion.A further model improvement concerned the extension of temperature effect calculation on microbial growth, specifically by separating long-term and short-term dynamics. The mathematical implementation was also validated using data from two experiments, where long-duration and short-duration temperature disturbances were investigated, respectively. The results proved to describe experimental trends exceptionally well. Simulating volatile fatty acid concentrations, nonetheless, was found to be challenging and supported earlier findings, while the simulation of short-duration disturbance dynamics were shown to require more research.Lastly, the model was adapted for the simulation of bioaugmentation scenarios and was therefore extended with ten bioaugmentative microbial groups: those being responsible for the same conversion pathways as their native counterparts, although with potentially different kinetics parameters. The enhanced model was then evaluated with data originating from two different experimental setups, both focusing on ammonia inhibited operation. Simulation results were in good agreement with measured data points and showed the overall robustness of the model in simulating such scenarios, with additional emphasis on the need for better short-duration disturbance modelling. The overall assessment of results obtained during the thesis work showed that the above described individual extensions contributed to the improvement of model performance, and by addressing the identified challenges, a further extended model can become a valuable tool in monitoring, controlling and forecasting full-scale anaerobic digestion processes.<br/
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
- …
