86,659 research outputs found
From Molecular Building Blocks to Condensed Carbon Nitride Networks: Structure and Reactivity
No full textThe scope of this thesis was defined by three major issues, which have been arising from the requirement to further extend and to deepen research on carbon nitride chemistry from a materials chemistry point of view. Access to highly condensed CNx species and, ultimately, binary carbon nitride C3N4, was primarily sought by using suitable carbon nitride precursor species, based on the following leitmotifs:
1. Gaining a deeper understanding of the reactivity of precursors and the mechanisms governing solid-state reactions, the latter being the key to the directed synthesis of novel precursor systems as well as to extended carbon nitride solids with tailored properties.
2. Developing novel CNx precursors based on the evaluation of reactivity principles and solid-phase reaction trajectories thus established.
3. Providing an experimental basis for the predominantly speculative discussion centered on the structure of graphitic carbon nitride-type systems, with the major focus being on the nature of the structural building-blocks of polymeric CNxHy solids.
The interplay between structural requirements of suitable CNx precursors and their thermal reactivity was demonstrated by a combined 2H solid-state NMR and neutron diffraction study of ammonium dicyanamide, as well as by a comprehensive spectroscopic study of the thermal decomposition of ammonium cyanoureate.
Various novel non-metal dicyanamides and tricyanomelaminates were synthesized, structurally characterized and screened for potential thermally induced solid-state reactivity. Their suitability as CNx precursors for the synthesis of graphitic carbon nitride g-C3N4 was evaluated, leading to the observation that the formation of melamine C3N3(NH2)3 is favored in all systems at elevated temperatures.
Therefore, particular emphasis was placed on the study of the thermal behavior of the prototypic precursor melamine, whose pyrolysis, including the identities of the intermediates, has been a highly controversial issue during the past decades. The present work provides the structures of the two “missing links” in melamine condensation, melam [(H2N)2C3N3]2NH and melon [C6N7NH(NH2)]n. In addition, the identities of two further intermediates were resolved, which could be identified as co-crystallisates made up from melamine and melem in the distinct ratios 2:1 and 1:2, respectively.
Ultimately, the identity of a CNxHy polymer obtained by pyrolysis of melamine at T = 893 -913 K was resolved by a concerted approach based on electron diffraction, solid-state NMR spectroscopy, and theoretical investigations. It was demonstrated that the material commonly associated with a hydrogen-contaminated graphitic carbon nitride material is in fact melon, a 1D polymer composed of NH-bridged heptazine rings first described by Liebig in 1834. Melon represents a so far unique example of a structurally characterized, 1D polymeric carbon nitride material, and at the same time sheds new light on the present discussion regarding the identity and structure of graphitic carbon nitride
Variations on the Author
No full text“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
Cross-Linking Bi2S3 Ultrathin Nanowires: A Platform for Nanostructure Formation and Biomolecule Detection
No full textThis paper describes the use of chemical cross-linking of ultrathin inorganic nanowires; as a bottom-up strategy for nanostructure fabrication as well as a chemical detection platform. Nanowire microfibers are produced by spinning a nanowire dispersion into a cross-linker solution at room temperature. Nanomembranes with thicknesses down to 50 nm were obtained by injecting the nanowire dispersion at the crosslinker-solution/air interface. Furthermore, the sensitivity of the nanowire to amine cross-linkers allowed development of a novel sensing platform for small molecules, like the neurotransmitter serotonin, with detection limits in the picomolar regime
[Newspaper Clipping: Author Claims Evidence of Second JFK Assassin #1]
No full textNewspaper article titled "Author Claims Evidence of Second JFK Assassin." The article states that author Richard J. Whalen concluded "that there is circumstantial evidence to support the theory of a second assassin in the shooting of President John F. Kennedy.
Also By The Same Author: AKTiveAuthor, a Citation Graph Approach to Name Disambiguation
No full textThe desire for definitive data and the semantic web drive for inference over heterogeneous data sources requires co-reference resolution to be performed on those data. In particular, name disambiguation is required to allow accurate publication lists, citation counts and impact measures to be determined. This paper describes a graph-based approach to author disambiguation on large-scale citation networks. Using self-citation, co-authorship and document source analyses, AKTiveAuthor clusters papers, achieving precision of 0.997 and recall of 0.818 over a test group of eight surname clusters
John F. Kennedy telegram to Roosevelt
No full textJersey Homesteads (later the Borough of Roosevelt) was established in the 1930s as an agro-industrial cooperative community. It was established specifically for urban Jewish garment workers, many of whom had emigrated from Europe. President John F. Kennedy sent a telegram to the citizens of Roosevelt, New Jersey, apologizing for not being able to attend the memorial dedication in honor of former President Franklin Delano Roosevelt. (Jersey Homesteads became Roosevelt in 1945 in honor of the president.) President Kennedy expressed his gratitude to the people of Roosevelt for constructing the memorial, and commented that it will serve as a constant reminder of Roosevelt's good works
Wörterbuch zu den Werken Zola's und einiger anderer modernen Schriftsteller. [Nachtrag zu Sachs-Villatte's Wöterbuch.] Von Dr. F. Lotsch
No full textLogarithmic variance profiles and the corresponding f-1 spectra of temperature fluctuations in turbulent Rayleigh-Bénard convection
No full textWe report experimental results for the temperature variance 2(z) and the corresponding frequency spectra P(f) in turbulent Rayleigh-Bénard convection (RBC) in a cylindrical sample of aspect ratioT= D/L = 1:00 (D = 1:12 m is the diameter and L = 1:12 m the height). The measurements were conducted in the Rayleigh-number range 1011 < Ra < 1:35 1014 and Pr ' 0:8. For Ra = 1:35x1014, 2(z) could be described well by a logarithmic dependence on the vertical position z in a range of z 1 < z < z 2 with z 1 ' 70 and z 2 = 0:1L. Here L=(2Nu) is the thickness of a thin thermal sublayer adjacent to the horizontal plate where the heat flux (denoted by the Nusselt number Nu) is carried mostly by thermal diffusion. In the log layer, we found that the temperature spectra had a significant frequency range over which P(f) f with close to 1. As Ra decreased, increased so that the log layer became thinner. At Ra = 2:05 1011, z 2 < z 1 and therefore there was no range for a log layer. Correspondingly, the temperature spectrum near the horizontal plate did not have the f1 scaling form either
Maine author Franklin F. Gould recalls his first glimpse of the outside world
No full textMaine author Franklin F. Gould recalls his first glimpse of the outside world as he relates how, as a young farm boy in the late 1800\u27s, he drove his father\u27s horses on an errand to an icebound river
Mapping the Discipline of the Olympic Games An Author-Cocitation Analysis
No full textThe authors conducted an author cocitation analysis on prominent authors writing about the Olympics during the 1990s. Author cocitation is an established bibliometric technique that can be used to measure the relative similarities of topics written about by the cited authors. This enables a visual representation of the “intellectual space” of the discipline, in this case the Olympics, to be created for the period under review. So core and peripheral research areas are identified, along with their major contributors. The representation appears as a two-dimensional cluster-enhanced map. Subject expertise was then applied to the results to place labels on the generated clusters of authors and their topics
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