1,720,972 research outputs found
Sequencing biological acidification of waste-activated sludge aiming to optimize phosphorus dissolution and recovery
No full textPhosphorus (P) recovery in wastewater treatment plants (WWTP) as pure crystals such as struvite (MgNH4PO4.6H2O), potassium struvite (KMgPO4.6H2O) and calcium phosphates (e.g. Ca3(PO4)2) is an already feasible technique that permits the production of green and marketable fertilizers and the reduction of operational costs. Commercial crystallizers can recovery more than 90% of soluble P. However, most of the P in WWTP sludge is unavailable for the processes (not dissolved). P solubilization and separation are thus the limiting steps in P-crystallization. With an innovative two-step sequencing acidification strategy, the current study has aimed to improve biological P solubilization on waste-activated sludge (WAS) from a full-scale plant. In the first step (P-release), low charges of organic waste were used as co-substrates of WAS pre-fermentation, seeking to produce volatile fatty acids to feed the P-release by Polyphosphate-accumulating organisms, while keeping its optimal metabolic pH (6-7). In this phase, milk serum, WWTP grease, urban organic waste and collective restaurant waste were individually applied as co-substrates. In the second step (P-dissolution), pH 4 was aimed at as it allows the dissolution of the most common precipitated species of P. Biological acidification was performed by white sugar addition, as a carbohydrate-rich organic waste model, which was compared to chemical acidification by HCl (12M) addition. With short retention times (48-96 h) and without inoculum application, all experiences succeeded on P solubilization (37-55% of soluble P), principally when carbohydrate-rich co-substrates were applied. Concentrations from 270 to 450 mg were achieved
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
Fermentação de lodos ativados e resíduos orgânicos como co-substratos visando a solubilização de fósforo para otimizar a recuperação de estruvita
Full text linkTCC(graduação) - Universidade Federal de Santa Catarina. Centro Tecnológico. Engenharia Sanitária e Ambiental.O fósforo (P) é um elemento chave para a manutenção da vida. O P, porém, está sendo transferido rapidamente de reservas minerais para corpos hídricos, causando uma epidemia global de eutrofização de corpos d’água doce e zonas mortas oceânicas. Neste panorama, controlar a cristalização da estruvita, ou, magnésio amônio fosfato hexahidratado (MgNH4PO4.6H2O) é uma forma de obter um fertilizante agrícola com grandes vantagens sobre os fertilizantes minerais e, simultaneamente, de reduzir custos operacionais oriundos da formação espontânea deste cristal em estações de tratamento de esgoto (ETE). As taxas de eficiência na cristalização podem superar 90% de remoção do P dissolvido, porém as taxas de recuperação são muito inferiores quando relacionadas ao P total, visto que apenas uma fração encontra-se disponível (solubilizada). Logo, maximizar a solubilização do P contido no lodo é a etapa mais importante de sua recuperação. Esta pesquisa, realizada no Irstea - Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture, deu continuidade às pesquisas existente na área. O estudo visou otimizar o processo pela aplicação de uma abordagem inovadora: a aplicação de uma etapa de acidificação biológica através do uso de diferentes resíduos alimentares como co-substratos de digestão de lodo ativado em excesso. Os resíduos utilizados foram resíduos sólidos orgânicos urbanos, resíduos de restaurante coletivo, gordura de ETE, soro de leite, maçãs e cenouras. Foi possível simultaneamente favorecer a liberação de P pelas bactérias desfosfatantes e favorecer as formas solúveis de P em função dos baixos pH atingidos. Concentrações superiores a 250 mg.L-1 de P-PO4 3- foram atingidas, sendo que o limite de viabilidade para cristalização da estruvita está em torno de 50 mg.L-1. Foram avaliados métodos de separação do efluente rico em P solúvel e seus impactos na cristalização. Foram atingidas taxas de recuperação em torno de 50% do fósforo total
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
Analyse des transformations du phosphore lors du stockage et du traitement biologique et physico-chimique des lisiers de porc en vue d'un recyclage
No full textPour favoriser le recyclage du phosphore des lisiers de porcs sous la forme d'engrais chimique, facilement exportable et valorisable en dehors des zones de production animale intensive, il est nécessaire de séparer le phosphore de la matière organique. Le phosphore des lisiers étant initialement à plus de 60% sous une forme minérale solide mélangée à la matière organique, nous avons conçu un procédé en 3 étapes : (1) solubilisation du phosphore, (2) séparation solide/liquide puis (3) précipitation. La solubilisation constitue le principal verrou technologique à la mise en place de ce procédé. Nous avons donc étudié trois stratégies/possibilités de solubiliser le phosphore et d'augmenter ainsi la proportion de la fraction dissoute du phosphore. La première stratégie évaluée est l'ajout d acide benzoïque à la ration des porcs et la réduction du taux de protéines. Cette modification de la ration alimentaire réduit le pH des lisiers d une unité environ, augmentant ainsi la proportion de phosphore dissous dans le lisier stocké jusqu'à 20% du phosphore total. Cette augmentation reste toutefois insuffisante pour envisager un procédé de recyclage performant. La seconde stratégie est l'optimisation du relargage de phosphore lors du traitement biologique de l'azote des lisiers par aération intermittente. Les résultats obtenus au cours de ce travail ont montré que les métabolismes de relargage/accumulation du phosphore sont masqués par l'effet du pH lors de ce traitement biologique. En effet, le pH élevé provoque la précipitation du phosphore relargué pendant l'anaérobiose alors que, au contraire, l'acidification du milieu induite par la nitratation, provoque la dissolution des formes minérales pendant l aérobiose. Cette dissolution masque l'accumulation du phosphore par la biomasse pendant l aération. Une augmentation significative de la concentration en phosphore dissous est obtenue en augmentant la concentration d azote nitrifié par cycle (augmentation de la durée des cycles et réduction du temps de séjour). Cependant, la fraction de phosphore dissous par ce biais ne dépasse pas 20-25% du phosphore total. La troisième possibilité est l utilisation de réactifs acides. Dans ce cas, la réduction du pouvoir tampon des lisiers, obtenus avec les régimes alimentaires acidifiants ou après traitement biologique permet d'envisager une forte réduction de réactif lors d'un procédé de dissolution par ajout d'acide puis de précipitation. Suite à la dissolution du P par ajout d'acide, des essais de précipitation ont été effectués avec ajout de soude, de bicarbonate de soude ou de magnésie. La précipitation de la totalité du P a été obtenue a partir de pH 7 et les principales formes obtenues et identifiées sont la struvite et une forme non cristalline de calcium phosphate. Enfin, le logiciel de modélisation géochimique PHREEQCI a été évalué au cours de ce travail et permet de simuler l'effet de l ajout d'acides ou de bases dans le milieu et de donner une description qualitative des phases solides obtenuesTo recycle phosphorus from pig slurry, as a chemical fertilizer which could be easily transported and used far from intensive livestock areas, it is necessary to remove phosphorus from organic matter. Since pig slurry has more than 60% of its phosphorus in solid mineral form we have designed a three step process of solubilisation, solid/liquid separation and precipitation to realise such a reduction. The solubilisation was the main obstacle in the development of this process. We have studied three means to increase the ratio of dissolved phosphorus. The first one was to add benzoic acid and to reduce the amount of protein in the pig feed. The pH was reduced by 1and the dissolved phosphorus ratio increased up to 20% after storage, but it was not sufficient for the recycling process. The second one was to optimise phosphorus release during the biological treatment of nitrogen by sequential aeration. Both biological phosphorus release and uptake were concealed by the effect of pH. The high level of pH led to the precipitation of released phosphorus during the anaerobic stage. Contrary to this, acidification induced by nitrification led to solubilisation of mineral forms of phosphorus which concealed the uptake of phosphorus during the aerobic stage. A significant increase of dissolved phosphorus was obtained by increasing the amount of nitrogen nitrified in one cycle, which was accomplished by increasing the cycle duration and decreasing the hydraulic retention time. However, the ratio of dissolved phosphorus was always less than 20-25%. The third way was to use an acidic reactant. This could be viewed only if the buffer effect was previously reduced by feeding the pigs with the acidifying diet or by biological treatment. After acidic solubilisation, phosphorus was precipitated as struvite and amorphous calcium phosphate by adding either sodium hydroxide, sodium carbonate or magnesium oxide. The geochemical modelling tool PHREEQCI was successfully used to simulate acid or base addition in slurry and was helpful to give a description of the solid phase compositionTOULOUSE-INSA (315552106) / SudocSudocFranceF
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
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