1,721,066 research outputs found
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Bio-based composites from bagasse using carbohydrate enriched cross-bonding mechanism: A formaldehyde-free approach
Get PDFIn this study, cross-bonded self-binding and bone glue-bonded particleboards were manufactured from sugarcane (Saccharum officinarum L.) bagasse with different pre-treatments of particles. Six types of panels were manufactured from bagasse particles with and without bone glue. The physical, mechanical, and thermal properties of the panels were examined according to the standards. Fourier Transform Infrared (FTIR) spectroscopy and thermogravimetric analysis (TG) were performed to investigate the changes in the chemical bonds and thermal stability of the fabricated composites, respectively. It was found that cross-bonded bagasse self-binding (TC) and bone glue-bonded (T3) panels fabricated from non-boiled bagasse particles showed higher physical and mechanical properties compared to the other types of panels. Non-boiled bagasse particles with bone glue panels showed the highest mechanical properties, i.e., modulus of rupture (MOR = 26.22 MPa), modulus of elasticity (MOE = 4302 MPa), tensile strength = 8.35 MPa, and hardness = 1.72 MPa. TC and T3 panels also showed higher thermal stability compared to the other types of panels. A new peak at 3331-3334 cm-1 for the N-H stretching vibration in the FTIR analysis represents the presence of bone glue in the cross-bonded particleboards. Thus, this research advances the production of formaldehyde-free bagasse particleboard, introducing the cross-bonding technique and sustainable bone glue
Production and characterisation of pine wood powders from a multi-blade shaft mill
Get PDFWood is an important raw material for the manufacture of consumer products and in achieving societal goals for greater sustainability. Wood powders are feedstock for many biorefining and conversion techniques, including chemical, enzymatic and thermochemical processes and for composite manufacture, 3D printing and wood pellet production. Size reduction, therefore, is a key operation in wood utilisation and powder characteristics, such as shape, particle size distribution and micromorphology play a role in powder quality and end-use application. While in a green state, the native chemical composition and structure of wood are preserved. Powders are commonly produced from wood chips using impact mills, which require pre-sized, pre-screened and pre-dried chips. These steps necessitate repeated handling, intermediate storage and contribute to dry matter losses, operation-based emissions and the degradation of the wood chemistry.This thesis investigated a new size reduction technology, known as the multi-blade shaft mill (MBSM). The MBSM performance was studied through the milling of Scots pine (Pinus sylvestris L.) wood using a designed series of experiments and through modelling with multi-linear regression (MLR) analyses. Light microscopy combined with histochemical techniques were used to investigate particle micromorphology and distribution of native extractives in powders. The aim was to evaluate the technical performance of the MBSM with relation to operational parameters, to characterise the produced powders and to evaluate the technology through comparison with impact milling.The results showed that the MBSM could effectively mill both green and dry wood. Produced powders showed distinct differences compared to those obtained using a hammer mill (HM). The specific milling energy of the MBSM was lowest for green wood and within the range of other established size reduction technologies. However, much narrower particle size distributions were observed in MBSM powders and they had significantly greater amounts of finer particles. Particles with high aspect ratio and sphericity were a characteristic of MBSM powders and this Production and characterisation of pine wood powders from a multi-blade shaft mill was true for wood milled above and below its fibre saturation point. MBSM powders from green wood showed evidence of higher specific surface area, larger pore volume and greater micropore diameter than those from HM powder. Preliminary microscopic examination suggested that cell walls in MBSM powders showed evidence of retaining their original native wood structure. Consequently, their extractive content appeared intact. This was in contrast to HM powder and it may reflect the differences between the two size reduction mechanisms. According to the produced MLR models, the results suggest that MBSM milling is more akin to a sawing process and opposite to that of impact-based mills
Production and characterisation of pine wood powders from a multi-blade shaft mill
No full textWood is an important raw material for the manufacture of consumer products and in achieving societal goals for greater sustainability. Wood powders are feedstock for many biorefining and conversion techniques, including chemical, enzymatic and thermochemical processes and for composite manufacture, 3D printing and wood pellet production. Size reduction, therefore, is a key operation in wood utilisation and powder characteristics, such as shape, particle size distribution and micromorphology play a role in powder quality and end-use application. While in a green state, the native chemical composition and structure of wood are preserved. Powders are commonly produced from wood chips using impact mills, which require pre-sized, pre-screened and pre-dried chips. These steps necessitate repeated handling, intermediate storage and contribute to dry matter losses, operation-based emissions and the degradation of the wood chemistry.This thesis investigated a new size reduction technology, known as the multi-blade shaft mill (MBSM). The MBSM performance was studied through the milling of Scots pine (Pinus sylvestris L.) wood using a designed series of experiments and through modelling with multi-linear regression (MLR) analyses. Light microscopy combined with histochemical techniques were used to investigate particle micromorphology and distribution of native extractives in powders. The aim was to evaluate the technical performance of the MBSM with relation to operational parameters, to characterise the produced powders and to evaluate the technology through comparison with impact milling.The results showed that the MBSM could effectively mill both green and dry wood. Produced powders showed distinct differences compared to those obtained using a hammer mill (HM). The specific milling energy of the MBSM was lowest for green wood and within the range of other established size reduction technologies. However, much narrower particle size distributions were observed in MBSM powders and they had significantly greater amounts of finer particles. Particles with high aspect ratio and sphericity were a characteristic of MBSM powders and this Production and characterisation of pine wood powders from a multi-blade shaft mill was true for wood milled above and below its fibre saturation point. MBSM powders from green wood showed evidence of higher specific surface area, larger pore volume and greater micropore diameter than those from HM powder. Preliminary microscopic examination suggested that cell walls in MBSM powders showed evidence of retaining their original native wood structure. Consequently, their extractive content appeared intact. This was in contrast to HM powder and it may reflect the differences between the two size reduction mechanisms. According to the produced MLR models, the results suggest that MBSM milling is more akin to a sawing process and opposite to that of impact-based mills.</p
Struktureller Elektronentransfer und spektroskopische Studien von Übergangsmetall-Komplexen mit redoxaktiven "Non- Innocent"-Liganden
No full textIn this doctoral thesis structural and electronic properties of transition metal complexes of redox-active non-innocent ligands such as nitrosyl, 4,6-di-tert-butyl-N-phenyl-o-iminobenzoquinone and 3,5-di-tert-butyl-o-quinone are described. Additionally, the thesis covers the synthesis, mode of binding and electron transfer behaviors of metal complexes of an air-stable chiral diphosphine derived chelating ligand, R,R-QuinoxP.
In the first part of my thesis the synthetic aspects, the structural, spectroscopic and electronic properties of new transition metal (Ru and Re) nitrosyl complexes are described. The actual form of coordinated NOm (m = +/0/−) is established based on the experimental results supported by calculations.
In Chapter 2, different oxidation states of [Ru(OEP)(NO)(X)]n+ (n = +2, +1, 0, −1, OEP = octaethylporphyrin dianion) with varying axial sixth ligands X (H2O, pyridine, 4-cyanopyridine, 4-dimethylaminopyridine) are studied spectroscopically and the electronic structures of the complexes have been rationalized through DFT calculations.
Chapter 3 describes the complex (PPh4)4[(CN)4(NO)Re(μ-O)Re(NO)(CN)4] , an oxo-bridged rhenium dinitrosyl complex with cyanide as a co-ligand. The complex has been structurally and spectroscopically characterized. Crystal structure analysis confirms the linear coordination of the nitrosyl groups and of the linear mode of Re-O-Re unit. The complex exhibits two sharp ν(NO) bands at 1710 and 1670 cm−1 and two sharp ν(CN) bands at 2118 and 2129 cm−1 in CH3CN.
In the second part of this thesis several complexes with 1,2-dioxolene type non-innocent ligands (Q or QO) or sometimes combining two non-innocent ligands Q and NO in one system are described.
Chapter 4 describes four ruthenium o-iminoquinone complexes with the objective of establishing the metal-ligand valence state distribution. The complexes are isolated in the monocationic form and have also been characterized crystallographically. The C1-O1, C2-N1 bond lengths and the C-C intra-ring distances suggest that Q binds to the metal center in the iminosemiquinonato (Q·−) oxidation state, resulting in an [RuIII(Q·–)] electronic formulation in all four cases.
Chapter 5 deals with two paramagnetic complexes [Ru(NO)(Q)(terpy)](PF6)2 and [Ru(NO)(Q)(tppz)](PF6)2 combining three redox sensitive components such as RuII/RuIII, NOm and (Q)n. The co-ligands terpy and tppz are redox invariant in the present cases. The most stable positional isomer of [Ru(NO)(Q)(terpy)](PF6)2 with NO trans to the O donor atom of Q was isolated and characterized by single crystal X-ray analysis. In conjunction with the experimental Ru-N-O angle and the metrical parameters in the quinonoid ligand especially the C1-O1 distance and with ν(NO), the EPR studies at 9.5 and 285 GHz reveal a narrow radical-type signal, suggesting [RuII(NO+)(Q·−)(terpy)]2+ as the most valid oxidation state formulation.
Chapter 6 describes the structural, electrochemical and spectroscopic properties of [Cl(Q)Ru(μ-tppz)Ru(Q)Cl]n. The complex [Cl(Q)Ru(μ-tppz)Ru(Q)Cl](PF6)2, containing five component redox system [(Q)n-Rum-(μ-tppzx)-Rum'-(Q)n'], has been structurally characterized as anti isomer, the only configuration obtained. The combined structural and spectroscopic results allow the oxidation state assignment as [(Q·−)-RuIII-(μ-tppzo)-RuIII-(Q·−)]. One-electron oxidation of [Cl(Q·−)RuIII(μ-tppz0)RuIII(Q•−)Cl]2+ results in the appearance of a rhombic EPR signal as is typical for distorted ruthenium (III). The emergence (on first oxidation) and subsequent disappearance (on second oxidation) of an intense near-infrared band at 1853 nm strongly suggests a mixed-valent configuration with a low-energy IVCT transition and a sizeable comproportionation constant 106.1
Chapter 7 describes a detail spectroelectrochemical (UV-Vis-NIR and EPR) and theoretical studies of the redox series [Ru(QO)3]n, [Os(QO)3]n and [Ru(Q)3]n (n = +2 to −2). The [Ru(QO)3]0 and [Os(QO)3]0 complexes were reported earlier by Pierpont et. al. and the redox states of (QO) in the complexes have been formulated as semiquinonato (QO·−) and catecolate (QO2−), respectively. Based on this assignment the newly synthesized complex [Ru(Q)3]0 can also be attributed to antiferromagnetically coupled tris-iminosemiquinonato [RuIII(QO·−)3] system. Consequently the compound [RuIII(Q·−)3]0 is EPR-silent and shows unshifted 1H-NMR lines.In dieser Arbeit werden die strukturellen sowie elektronischen Eigenschaften von Übergangsmetallkomplexen mit redoxaktiven Liganden wie Nitrosyl, 4,6-Di-tert-butyl-N-phenyl-o-iminobenzochinon und 3,5-Di-tert-butyl-o-benzochinon vorgestellt. Zusätzlich werden in dieser Arbeit die Synthese, die Bindungsverhältnisse und das Elektronentransferverhalten von Übergangsmetallkomplexen mit dem luftstabilen chiralen chelatisierenden Diphosphinliganden R,R-QuinoxP beschrieben.
Im ersten Teil dieser Arbeit werden die synthetischen Aspekte, die Strukturen, spektroskopische- und elektronische Eigenschaften neuer Nitrosylkomplexe mit den Übergangsmetallen Ru und Re beschrieben. Die tatsächliche Form des koordinierten NOm (m = +/0/-) wurde durch experimentelle Ergebnisse und von quantenchemischen Rechnungen unterstützt.
Im zweiten Kapitel werden die verschiedenen Oxidationsstufen des [Ru(OEP)(NO)(X)]n+ (n = +2, +1, 0, −1, OEP = Octethylporphyrindianion) mit verschiedenen axialen Liganden X (H2O, Pyridin, 4-Cyanopyridin, 4-Dimethylaminopyridin) spektroskopisch untersucht. Die elektronische Struktur der Komplexe wurde zufriedenstellend durch DFT Rechnungen geklärt.
In Kapitel 3 wird der Komplex (PPh4)4[(CN)4(NO)Re(μ-O)Re(NO)(CN)4], eine sauerstoffverbrückte Rheniumdinitrosylverbindung mit Cyanid als Co-Ligand, beschrieben. Der Komplex ist strukturell und spektroskopisch charakterisiert. Molekülstrukturanalyse bestätigen die lineare Anordnung der Nitrosylgruppen sowie der Re-O-Re Einheit. Die Verbindung weist zwei scharfe ν(NO) Banden bei 1710 cm−1 und 1670 cm−1 und zwei deutliche ν(CN) Banden bei 2118 und 2129 cm-1 in Acetonitril auf.
Im zweiten Teil dieser Arbeit werden verschiedene Komplexe mit 1,2-Dioxolen-artigen "non-innocent" Liganden (Q bzw. Q0) oder die Kombination zweier nicht unschuldiger Liganden Q und NO in einem System, beschrieben.
In Kapitel 4 werden vier Ruthenium o-Iminochinonkomplexe und die tatsächliche Verteilung der Ladung zwischen Metall und Ligand, diskutiert. Die Verbindungen wurden in der monokationischen Form isoliert und ebenfalls kristallographisch analysiert. Die C1−O1, C2−N1 Bindungslängen sowie die C−C Abstände im Ring legen die Vermutung nahe, dass Q an das Metallzentrum in der Iminosemichinonform (Q·−) gebunden ist. Somit ergibt sich für alle Verbindungen die Formulierung [RuIII(Q·−)].
Kapitel 5 beinhaltet die zwei paramagnetischen Komplexe [Ru(NO)(Q)(terpy)](PF6)2 und [Ru(NO)(Q)(tppz)](PF6)2 bei denen drei redoxaktive Komponenten, RuII/RuIII, NOm und (Q)n verknüpft sind. Die Co-Liganden terpy und tppz sind in diesem Falle nicht redoxaktiv. Das stabilste Isomer des [Ru(NO)(Q)(terpy)](PF6)2 mit NO trans zum Sauerstoffdonor von Q wurde isoliert und strukturell charakterisiert. In Verbindung mit dem experimentellen Ru−N−O Winkel, den Bindungsabständen im Chinonliganden vor allem der C1−O1 Abstand, mit ν(NO) und den ESR-Messungen bei 9.5 und 285 GHz die ein schmales radikalisches Signal zeigen, kann [RuII(NO+)(Q·−)(terpy)]2+ als gültige Formulierung angenommen werden.
In Kapitel sechs werden die Struktur, Elektrochemie und die spektroskopischen Eigenschaften des [Cl(Q)Ru(μ-tppz)Ru(Q)Cl]n beschrieben. Die Verbindung [Cl(Q)Ru(μ-tppz)Ru(Q)−Cl](PF6)2 beinhaltet fünf Redoxsysteme [(Q)n-Rum-(μ-tppzx)-Rum'-(Q)n'] und kann über die Einkristallanalyse als anti Isomer identifiziert werden.
Durch die spektroskopischen und strukturellen Ergebnisse kann die Verbindung als [(Q·−)-RuIII-(μ-tppzo)-RuIII-(Q·−)] formuliert werden. Ein-Elektronenoxidation des [Cl(Q·−)RuIII(μ-tppz0)RuIII(Q·−)Cl]2+ führt zu einem rhombischen ESR-Signal, welches typisch für verzerrtes Ruthenium(III) ist. Das Erscheinen (während der ersten Oxidation) und anschließendes Verschwinden (nach der zweiten Oxidation) einer starken NIR-Bande bei 1850 nm deutet auf einen gemischtvalenten Zustand mit einem energetisch tief liegenden IVCT Übergang hin. Die Komproportionierungskonstante von 106.1 ist beträchtlich.
Kapitel 7 beschreibt im Detail die Spektroelektrochemie (UV-Vis-NIR und ESR) und theoretische Rechnungen der Redoxprodukte der Reihe [Ru(QO)3]n, [Os(QO)3]n und [Ru(Q)3]n (n = +2 bis −2). Über die Verbindungen [Ru(QO)3]0 und [Os(QO)3]0 wurde schön früher von Pierpont et al. berichtet. Die Oxidationstufe des Liganden (QO) wurde als Semichinon (QO·−) beziehungsweise als Catechol (QO2-) formuliert. Darauf basierend kann der neu dargestellte Komplex [Ru(Q)3]0 als antiferromagnetisch gekoppelte Trisiminosemichinonato [RuIII(Q·−)3] Verbindung aufgefasst werden. Der Komplex zeigt kein ESR-Signal und weist 1H-NMR-Signale an den erwarteten Positionen
Bioderived Chemical Extraction from Spruce Needles : Adding Value to Forest Logging Residues
No full textDispelling the Myths Behind First-author Citation Counts
Get PDFWe 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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