1,720,960 research outputs found
Nitrous Oxide Adsorption and Separation Using CPO-27 Metal-Organic Frameworks
No full textNitrous oxide N2O is a potent greenhouse gas with a high global warming potential approximately 300 times that of carbon dioxide on a 100-year timescale. In addition, it is the leading ozone-depleting substance emitted in the 21st century. The capture of N2O from industrial point sources or from air might therefore become important for environmental protection. Non-point sources such as synthetic fertilizer and manure are the dominant N2O emission sources, while the largest industrial contributors to N2O emission are production of adipic acid and nitric acid. Metal-organic frameworks (MOFs) might be promising materials for the capture of N2O. MOFs are relatively new members of the porous materials family. Due to their interesting properties such as large pore volume, large surface area, and structural regularity these materials gained remarkable interest in the eld of porous materials. Interaction of these materials with greenhouse and energy carrier gases are being extensively investigated for gas storage and separation processes. However, adsorption of N2O on MOFs has only rarely been investigated. This thesis presents a comparative study of the N2O adsorption on a series of isostructural MOFs known as CPO-27 to evaluate their potential for use in separation processes involving N2O. The N2O adsorption properties of the CPO-27-M (M = Mg, Mn, Co, Ni, Cu, and Zn) materials at room temperature were investigated and selectivities for N2O/N2 separation were derived using the ideal adsorbed solution theory. In addition, a detailed structural study was performed by variable-temperature (298 to 185 K) powder synchrotron X-ray diffraction to identify the N2O adsorption sites of the framework and monitor the structural changes that occur during the N2O adsorption.Master's Thesis in Nano ScienceNANO399MAMN-NAN
Synthèse et Caractérisation de Nouveaux Polymères de Coordination Poreux à Base de Cations Métalliques non Toxiques
No full textLes Metal-Organic Frameworks (MOFs) sont des matériaux cristallins généralement poreux constitués de cations métalliques et de ligands organiques. Les propriétés de ces matériaux peuvent être modifiées en faisant varier leur composition. Des propriétés ajustables, des structures variées et des topologies de pores rendent ces matériaux prometteurs pour un large éventail d'applications. Ceux-ci incluent, sans toutefois s'y limiter, le stockage et la séparation du gaz, le relarguage controlé de médicaments, le stockage d'énergie et la capture d'espèces toxiques pour l'environnement. Quelle que soit l'application, la non-toxicité du MOF est toujours souhaitable. Pour cet objectif, j'ai travaillé sur la synthèse et la caractérisation de nouveaux MOFs contenant des cations non toxiques et des ligands fonctionnalisés. Dans deux systèmes différents, Fe(III)-H4DSBDC (acide 1,4-Benzene dicarboxylique, 2,5-dimercapto-) et Mg-H4bpgal (acide 4-(3,4,5- trihydroxyphényl)benzoïque), j'ai synthétisé cinq nouveaux MOFs, résolu leurs structures et caractérisé minutieusement leurs propriétés physicochimiques. Une synthèse exploratoire approfondie a été réalisée dans les deux systèmes pour isoler de nouveaux matériaux. Les structures des matériaux cristallins isolés ont été résolues à l'aide de la diffraction des rayons X combinée à d'autres méthodes de caractérisation structurale. Ces nouveaux matériaux présentent des propriétés variables. Certains présentent une stabilité hydrolyique élevée, certains sont très poreux et certains ont des structures en couches flexibles pouvant accueillir des molécules cationiques.Metal-Organic Framework (MOFs) are crystalline usually porous materials made up from metal cations and organic ligands. Properties of these materials can be altered by varying their composition. Tunable properties, varied structures and pore topologies make these materials promising for wide range of applications. These include, but not limited to, gas storage and separation, drug delivery, energy storage, and environmental remediation. Regardless of the application, non-toxicity of the MOF is always desirable. On this objective, I worked on the synthesis and characterization of new MOFs containing non-toxic cations and functionalized ligands. In two different system, Fe(III)-H4DSBDC (1,4-Benzenedicarboxylic acid 2,5-dimercapto-) and Mg-H4bpgal (4-(3,4,5- trihydroxyphenyl)benzoic acid), I synthesized five new MOFs, solved their structures and thoroughly characterized their physicochemical properties. An extensive exploratory synthesis was performed in both systems to isolate new materials. The structures of the isolated crystalline materials were solved using X-Ray diffraction techniques combined with other structural characterization methods. These new materials exhibited varying properties. Some exhibit high hydrolytic stability, some are highly porous, and some have flexible layered structures that can accommodate cationic molecules
Synthèse et Caractérisation de Nouveaux Polymères de Coordination Poreux à Base de Cations Métalliques non Toxiques
No full textMetal-Organic Framework (MOFs) are crystalline usually porous materials made up from metal cations and organic ligands. Properties of these materials can be altered by varying their composition. Tunable properties, varied structures and pore topologies make these materials promising for wide range of applications. These include, but not limited to, gas storage and separation, drug delivery, energy storage, and environmental remediation. Regardless of the application, non-toxicity of the MOF is always desirable. On this objective, I worked on the synthesis and characterization of new MOFs containing non-toxic cations and functionalized ligands. In two different system, Fe(III)-H4DSBDC (1,4-Benzenedicarboxylic acid 2,5-dimercapto-) and Mg-H4bpgal (4-(3,4,5- trihydroxyphenyl)benzoic acid), I synthesized five new MOFs, solved their structures and thoroughly characterized their physicochemical properties. An extensive exploratory synthesis was performed in both systems to isolate new materials. The structures of the isolated crystalline materials were solved using X-Ray diffraction techniques combined with other structural characterization methods. These new materials exhibited varying properties. Some exhibit high hydrolytic stability, some are highly porous, and some have flexible layered structures that can accommodate cationic molecules.Les Metal-Organic Frameworks (MOFs) sont des matériaux cristallins généralement poreux constitués de cations métalliques et de ligands organiques. Les propriétés de ces matériaux peuvent être modifiées en faisant varier leur composition. Des propriétés ajustables, des structures variées et des topologies de pores rendent ces matériaux prometteurs pour un large éventail d'applications. Ceux-ci incluent, sans toutefois s'y limiter, le stockage et la séparation du gaz, le relarguage controlé de médicaments, le stockage d'énergie et la capture d'espèces toxiques pour l'environnement. Quelle que soit l'application, la non-toxicité du MOF est toujours souhaitable. Pour cet objectif, j'ai travaillé sur la synthèse et la caractérisation de nouveaux MOFs contenant des cations non toxiques et des ligands fonctionnalisés. Dans deux systèmes différents, Fe(III)-H4DSBDC (acide 1,4-Benzene dicarboxylique, 2,5-dimercapto-) et Mg-H4bpgal (acide 4-(3,4,5- trihydroxyphényl)benzoïque), j'ai synthétisé cinq nouveaux MOFs, résolu leurs structures et caractérisé minutieusement leurs propriétés physicochimiques. Une synthèse exploratoire approfondie a été réalisée dans les deux systèmes pour isoler de nouveaux matériaux. Les structures des matériaux cristallins isolés ont été résolues à l'aide de la diffraction des rayons X combinée à d'autres méthodes de caractérisation structurale. Ces nouveaux matériaux présentent des propriétés variables. Certains présentent une stabilité hydrolyique élevée, certains sont très poreux et certains ont des structures en couches flexibles pouvant accueillir des molécules cationiques
Synthèse et Caractérisation de Nouveaux Polymères de Coordination Poreux à Base de Cations Métalliques non Toxiques
No full textMetal-Organic Framework (MOFs) are crystalline usually porous materials made up from metal cations and organic ligands. Properties of these materials can be altered by varying their composition. Tunable properties, varied structures and pore topologies make these materials promising for wide range of applications. These include, but not limited to, gas storage and separation, drug delivery, energy storage, and environmental remediation. Regardless of the application, non-toxicity of the MOF is always desirable. On this objective, I worked on the synthesis and characterization of new MOFs containing non-toxic cations and functionalized ligands. In two different system, Fe(III)-H4DSBDC (1,4-Benzenedicarboxylic acid 2,5-dimercapto-) and Mg-H4bpgal (4-(3,4,5- trihydroxyphenyl)benzoic acid), I synthesized five new MOFs, solved their structures and thoroughly characterized their physicochemical properties. An extensive exploratory synthesis was performed in both systems to isolate new materials. The structures of the isolated crystalline materials were solved using X-Ray diffraction techniques combined with other structural characterization methods. These new materials exhibited varying properties. Some exhibit high hydrolytic stability, some are highly porous, and some have flexible layered structures that can accommodate cationic molecules.Les Metal-Organic Frameworks (MOFs) sont des matériaux cristallins généralement poreux constitués de cations métalliques et de ligands organiques. Les propriétés de ces matériaux peuvent être modifiées en faisant varier leur composition. Des propriétés ajustables, des structures variées et des topologies de pores rendent ces matériaux prometteurs pour un large éventail d'applications. Ceux-ci incluent, sans toutefois s'y limiter, le stockage et la séparation du gaz, le relarguage controlé de médicaments, le stockage d'énergie et la capture d'espèces toxiques pour l'environnement. Quelle que soit l'application, la non-toxicité du MOF est toujours souhaitable. Pour cet objectif, j'ai travaillé sur la synthèse et la caractérisation de nouveaux MOFs contenant des cations non toxiques et des ligands fonctionnalisés. Dans deux systèmes différents, Fe(III)-H4DSBDC (acide 1,4-Benzene dicarboxylique, 2,5-dimercapto-) et Mg-H4bpgal (acide 4-(3,4,5- trihydroxyphényl)benzoïque), j'ai synthétisé cinq nouveaux MOFs, résolu leurs structures et caractérisé minutieusement leurs propriétés physicochimiques. Une synthèse exploratoire approfondie a été réalisée dans les deux systèmes pour isoler de nouveaux matériaux. Les structures des matériaux cristallins isolés ont été résolues à l'aide de la diffraction des rayons X combinée à d'autres méthodes de caractérisation structurale. Ces nouveaux matériaux présentent des propriétés variables. Certains présentent une stabilité hydrolyique élevée, certains sont très poreux et certains ont des structures en couches flexibles pouvant accueillir des molécules cationiques
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
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