1,721,224 research outputs found
Polysaccharide-acting enzymes and their applications
No full textBiobased economy is expected to grow substantially in Europe within the coming 20 years. An important part of the bioeconomy is biorefineries in which biomass is processed in a sustainable manner to various exploitable products and energy. Bioeconomy can be seen as an expansion of the biorefinery concept as it also includes the exploitation of biotechnology in processing of non-biological raw materials or production of non-bio products exploiting certain biological principles.Enzymes offer a selective and efficient means to convert biomass and its components including polysaccharides into chemicals, materials, energy, food and feed in a sustainable manner. Due to their specificity enzymes are powerful tools especially in the targeted modification of biomass components. Furthermore, enzymes can be used to overcome some of the challenges related to the utilisation of biomass. Compared to traditional manufacturing systems, biomass can be processed by enzymes in mild conditions with significantly less energy, water and without the need of aggressive chemicals. A wide variety of potential enzymes suitable for processing and upgrading of lignocellulosic polysaccharides and polysaccharide -based materials is currently commercially available and novel enzymes are actively searched for. The role of these enzymes in future lignocellulosic polysaccharide processing and up-grading is dependent on the value addition and economical feasibility reached as well as the wide industrial acceptance of the bioprocessing technologies
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
Influence of chemical and enzymatic treatments on a variety of wood pulps on their dissolution in NaOH-water
No full textDifferent pulps were chemically (nitren) and biologically (enzyme) treated in order to improve the chemical accessibility and dissolution capacity in cold NaOH. The treatments effect on the pulp properties was accessed by studying the changes on their chemical and macromolecular structure and by analyzing the dissolution performance in cold NaOH.The nitren treatment has the effect of removing a large part of the xylan present in a dissolving pulp and is also removing mannans. Increasing the nitren concentrations will extract also cellulose and decrease its mean molar mass. These extractions are favorable for the dissolution in cold NaOH–water, being more effective with higher nitren concentrations. A maximum of 44.7% increase on the dissolution yield was achieved.The new enzymatic treatment shows a higher efficiency on promoting fibers accessibility to NaOH ions, (directly correlated with the enzymatic load), allowing a maximum increase of 150% on the dissolution yield. A slight decrease of the average molar mass was also seen. The different pulps reacted differently to the treatments, showing that the pulping pretreatments have an influence on the enzymatic efficiency. Using a mixture of enzymes and endoglucanase showed that the synergistic effect of these two enzymes is more effective on cellulose activation.Both nitren and enzymatic treatments are improving the pulp chemical accessibility mostly by modifying the structure of the primary wall and S1 wall. This promotes the swelling of these wood cell structures, allowing the access of the NaOH solvating ions into fiber regions not accessible on the original pulp. The nitren is disassembling the fiber surface with extraction of hemicelluloses and degrading the cellulosic structure.The use of this enzyme on the cellulose pulps activation towards dissolution in cold NaOH is of great importance. It presents a high potential in both technical, with further development and industrial implementation, and fundamental research fields, with further studies on mechanisms of cellulose activation.The work was performed in Cemef - Mines ParisTech, Sophia Antipolis, France, and TI / Hamburg University, Germany and financed by Sappi, Tembec, Lenzing, Viskase and Spontex and had support from EPNOE (European Polysaccharide Network of Excellence).Different pulps were chemically (nitren) and biologically (enzyme) treated in order to improve the chemical accessibility and dissolution capacity in cold NaOH. The treatments effect on the pulp properties was accessed by studying the changes on their chemical and macromolecular structure and by analyzing the dissolution performance in cold NaOH.The nitren treatment has the effect of removing a large part of the xylan present in a dissolving pulp and is also removing mannans. Increasing the nitren concentrations will extract also cellulose and decrease its mean molar mass. These extractions are favorable for the dissolution in cold NaOH–water, being more effective with higher nitren concentrations. A maximum of 44.7% increase on the dissolution yield was achieved.The new enzymatic treatment shows a higher efficiency on promoting fibers accessibility to NaOH ions, (directly correlated with the enzymatic load), allowing a maximum increase of 150% on the dissolution yield. A slight decrease of the average molar mass was also seen. The different pulps reacted differently to the treatments, showing that the pulping pretreatments have an influence on the enzymatic efficiency. Using a mixture of enzymes and endoglucanase showed that the synergistic effect of these two enzymes is more effective on cellulose activation.Both nitren and enzymatic treatments are improving the pulp chemical accessibility mostly by modifying the structure of the primary wall and S1 wall. This promotes the swelling of these wood cell structures, allowing the access of the NaOH solvating ions into fiber regions not accessible on the original pulp. The nitren is disassembling the fiber surface with extraction of hemicelluloses and degrading the cellulosic structure.The use of this enzyme on the cellulose pulps activation towards dissolution in cold NaOH is of great importance. It presents a high potential in both technical, with further development and industrial implementation, and fundamental research fields, with further studies on mechanisms of cellulose activation.The work was performed in Cemef - Mines ParisTech, Sophia Antipolis, France, and TI / Hamburg University, Germany and financed by Sappi, Tembec, Lenzing, Viskase and Spontex and had support from EPNOE (European Polysaccharide Network of Excellence)
Ligno-cellulose based materials : "Process forming and Characterization"
No full textL'objectif de ce travail est de développer l'utilisation de la biomasse ligno-cellulosique dans le domaine des matériaux. Ce travail explore trois voies différentes d'utilisation de la ligno-cellulose afin de balayer un large spectre de constituants et de matériaux finaux. La première voie concerne l'incorporation de fibres naturelles dans la fabrication de panneaux utilisant la lignine comme adhésif. Des améliorations dans la fabrication de ces panneaux de fibres ont été apportées, par traitement chimique ou ajout de nouveaux compatibilisants, permettant un renforcement des propriétés mécaniques. La seconde voie a consisté à développer un procédé original de mise en forme sous haute pression testé et mis en place sur du coton dans le but d'obtenir des objets tridimensionnels sans étape de dissolution/régénération de la cellulose. Une fois le protocole défini, les effets des paramètres de mise en forme et de la variété de coton sur la microstructure et les propriétés mécaniques des objets en coton compressé ont été étudiés. Enfin, une troisième voie à consisté à élaborer des matériaux nanocomposites à partir d'hydroxydes double lamellaire modifiés par la lignine (HDL/LS). L'utilisation de cette nanocharge dans l'amidon a montré une capacité de renforcement pour un faible taux de charge. Ce composite amidon-(HDL/LS) a ainsi été utilisé avec une matrice polyéthylène afin d'augmenter la part renouvelable de la matrice sans diminuer significativement ses propriétés mécanique. Ce travail permet d'envisager des développements futurs pour ces différents matériaux développés et offre ainsi de nouvelles possibilités d'utilisation de la biomasse ligno-cellulosique dans l'élaboration de matériaux techniques.This work aims at developing new ligno-cellulosic biomass based materials as a way for giving added value to this raw material. This study aimed at developing three different new ways of using ligno-cellulosic components to get a large overview of the possible technical materials. The first way deals with the preparation of natural fibres filled lignin fibreboard panels. Improvements in panels forming have been achieved by using either chemical treatment or novel compatibilisation to improve the strength of the prepared fibreboards. In a second way, an original forming process by high pressure has been tested and carried out on cotton fibres in order to produce 3D objects without dissolution/coagulation processes of cellulose. After setting up the forming procedure, effects of process parameters and cotton variety on microstructures and mechanical properties of highly compressed cotton have been studied. Finally, a third way was the study of new nanocomposites made of layered double hydroxide modified by lignin (LDH/LS). Using such nanofillers into thermoplastic starch turned out to be an efficient solution to reinforce mechanical properties with low nanofillers loading. This starch-(LDH/LS) nanocomposite was also blended with polyethylene to increase the bio-content without a degradation of the mechanical properties. This study is an advanced basis for a further development of these three different materials and offers a broad range of applications suitable for the preparation of new technical materials
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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