1,721,205 research outputs found
Mikrosekundenaufgelöste In-situ-SAXS-Experimente zum Nukleations- und Wachstumsverhalten von CdS-Nanopartikeln in wässriger Lösung
Get PDFThis work introduces containment-free SAXS and WAXS experiments on the nucleation and growth of nanoparticles in aqueous solution using two novel experimental setups. These allow getting direct insights into so far not accessible early nucleation and growth states of CdS nanoparticles. The free jet setup accesses very short reaction times in the range from 100 µs up to 2,5 ms. Using this setup, the nucleation and early growth of CdS nanoparticles in aqueous solution was followed in-situ. The SAXS experiments support a spherical bimodal particle size distribution. While the size of one population is growing with time, the other population shows a constant particle size of about 1 nm in diameter. According to the growth behavior of the larger population, a cluster diffusion limited formation process is proposed. The simultaneous WAXS experiments support the existence of the cluster population. Temperature dependent experiments show an energy barrier for the cluster diffusion in water of about 0,6 eV.
The setup for experiments at a free drop enables containment-free scattering experiments of rapidly mixed chemicals starting after a dead time of 100 ms. Using this setup, the formation process of EDTA stabilized CdS nanoparticles was followed via in-situ SAXS experiments. The addition of the stabilizer shows an impact both on the growth speed and on the formation mechanism. Both setups extend the tool box of existing experimental environments and are suitable for applications for various experimental techniques (beyond SAXS and WAXS) to investigate various sample systems. Furthermore, detailed insights into the CdS formation process, both at a so far not accessible time scale below 1 ms and at an extended time scale up to several minutes are provided.Im Rahmen dieser Arbeit werden durch die Nutzung zweier neuartiger experimenteller Aufbauten SAXS- und WAXS-Experimente durchgeführt, welche frei von einem Behältnis im Strahlengang des Röntgenstrahls sind. Es werden dadurch direkte Einblicke in bisher unzugängliche Nukleations- und Wachstumsstadien von CdS-Nanopartikeln in wässriger Lösung ermöglicht. Das Setup zur Messung am freien Strahl erreicht sehr kurze Reaktionszeiten zwischen 100 µs und 2,5 ms. Mit Hilfe dieses Setups wurden die Nukleation und das frühe Wachstum von CdS-Nanopartikeln in wässriger Lösung in-situ untersucht. Die SAXS-Experimente deuten auf eine bimodale Partikelgrößenverteilung von sphärischen Partikeln hin. Während die Größe der einen Population als Funktion der Zeit wächst, zeigt die andere Population einen konstanten Durchmesser von etwa 1 nm. Entsprechend der Entwicklung der Partikelgrößen der wachsenden Population ist ein durch die Diffusion von Clustern limitierter Formationsmechanismus vorgeschlagen. Die simultanen WAXS-Experimente bestätigen die Existenz einer Clusterpopulation. Temperaturabhängige SAXS-Experimente weisen auf eine Diffusionsbarriere der Cluster von 0,6 eV hin.
Das Setup zur Messung am freien Tropfen erlaubt Experimente an schnell gemischten Chemikalienlösungen, beginnend nach einer Totzeit von 100 ms. Mit Hilfe dieses Setups wurde der Formationsmechanismus von EDTA-stabilisierten CdS-Nanopartikeln mittels In-situ-SAXS-Experimenten beobachtet. Es zeigt sich, dass die Zugabe des Stabilisators sowohl eine starke Änderung der Wachstumsgeschwindigkeit hervorruft, wie auch den Reaktionsmechanismus fundamental ändert. Beide Setups erweitern die Auswahl an experimentellen Probenumgebungen und sind über die Methoden der Klein- und Weitwinkelröntgenstreuung hinaus für eine Vielzahl von experimentellen Methoden und zur Untersuchung weiterer Probensysteme einsetzbar. Darüber hinaus sind in dieser Arbeit detaillierte Einblicke in den CdS-Formationsmechanismus gegeben, sowohl auf einer bisher unerreichten Zeitskala unterhalb 1 ms, wie auch auf einer ausgedehnten Zeitskala der Reaktionszeit bis hin zu mehreren Minuten
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
Quaternary Silver Bismuth Chalcogenide Halides Ag - Bi - Q - X (Q = S, Se; X = Cl, Br): Syntheses and Crystal Structures
Get PDFSystematic synthetic investigations of the quaternary systems Ag - Bi - Q - X (Q = S, Se; X = Cl, Br) led to a variety of quaternary phases that exhibit considerable structural diversity with increasing complexity. These include Ag1.2Bi17.6S23Cl8, AgBi4Se5Br3 and numerous members of the homologous double series Agx(N+1)Bi2+(1-x)(N+1)Q2+(2-2x)(N+1)X2+(2x-1)(N+1) denoted (N, x)P. N represents the order number of a given homologue and x is the degree of substitution of Bi by Ag with 1/2 <= x <= 1. Their structures are built up from two alternating types of modules denoted A and B that are stacked parallel to (001). In module A, rows of edge-sharing [MZ6] octahedra (Z = X and/or Q); M = Ag and/or Bi) running parallel to [010] alternate along [100] with parallel chains of paired monocapped trigonal prisms around Bi atoms. The module type denoted B represents NaCl-type fragments of varying thickness. It is defined by the number N of octahedra within the chain of edge-sharing octahedra running diagonally across it in the (010) plane of the structure. The thickness of module B for current members of the series extends from N = 0 to N = 7. All structures exhibit Ag/Bi disorder in octahedrally coordinated metal positions and Q/X (Q = S, Se; X = Cl, Br) mixed occupation of some anion positions. Some of these compounds are narrow gap semiconductors
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
Dispelling 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
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
CuClCu₂TeS₃: Synthesis, structure determination and Raman spectroscopic characterization of a novel zincblende derivative
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