1,721,041 research outputs found
A Coplanar Waveguide Resonator Technique for the Characterization of Iron-Based Superconductors
Full text linkWe present in detail a coplanar waveguide resonator (CPWR) method for the characterization of superconducting single crystals. It exploits the region of a CPWR where the rf magnetic field is quite homogeneous, by coupling a sample to it. Measurements are performed with and without the crystal, allowing a cavity perturbation approach. From the modifications in the resonance frequency and quality factor of the system it is possible to extract the London penetration depth and its anisotropy, quasiparticle conductivity, surface impedance and, when a coexisting magnetic phase is present, even bulk complex susceptibility
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
Aromatic nitration under tropospheric and combustion conditions. A theoretical mechanistic study
No full textScaling laws for ion irradiation effects in iron-based superconductors
Full text linkWe report on ion irradiation experiments performed on compounds belonging to the BaFe 2As 2 family, each one involving the partial substitution of an atom of the parent compound (K for Ba, Co for Fe, and P for As), with an optimal composition to maximize the superconducting critical temperature Tc. Employed ion beams were 3.5-MeV protons, 250-MeV Au ions, and 1.2-GeV Pb ions, but additional data from literature are also considered, thus covering a wide range of ions and energies. Microwave characterization based on the use of a coplanar waveguide resonator allowed us to investigate the irradiation-induced Tc degradation, as well as the increase of normal state resistivity and London penetration depth. The damage was quantified in terms of displacements per atom (dpa). From this broad and comprehensive set of experimental data, clear scaling laws emerge, valid in the range of moderate irradiation-induced disorder (dpa up to 5 × 10 - 3 were investigated). In these conditions, linear trends with dpa were found for all the modification rates, while a power law dependence on the ion energy was found for heavy-ion irradiation. All these scaling laws are reported and discussed throughout the paper
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
The oxidized soot surface: Theoretical study of desorption mechanisms involving oxygenated functionalities and comparison with temperature programed desorption experiments
No full textThe desorption mechanism for oxygenated functionalities on soot is investigated by quantum
mechanical calculations on functionalized polycyclic aromatic hydrocarbon PAH models and
compared with recently published temperature programed desorption-mass spectrometry results.
Substituents on PAHs of increasing size up to 46 carbon atoms in the parent PAH are chosen to
reproduce the local features of an oxidized graphenic soot platelet. Initially, the study is carried out
on unimolecular fragmentation extrusion, in some cases processes producing HO, CO, or CO2, in
model ketones, carboxylic acids, lactones, anhydrides, in one aldehyde, one peroxyacid, one
hydroperoxide, one secondary alcohol, and one phenol. Then, a bimolecular process is considered
for one of the carboxylic acids. Furthermore, some cooperative effect which can take place by
involving two vicinal carboxylic groups derived from anhydride hydrolysis is investigated for
other four bifunctionalized models. The comparison between the computed fragmentation
desorption barriers for the assessed mechanisms and the temperature at which maxima occur in
TPD spectra for HO, CO, or CO2 desorption offers a suggestion for the assignment of these
maxima to specific functional groups, i.e., a key to the description of the oxidized surface. Notably,
the computations suggest that 1 the desorption mode from a portion of a graphenic platelet
functionalized by a carboxylic or lactone groups is significantly dependent from the chemical and
geometric local environment. Consequently, we propose that 2 not all carboxylic groups go lost at
the relatively low temperatures generally stated, and 3 lactone groups can be identified as
producing not only CO2 but also CO. © 2006 American Institute of Physics
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
Near-field Scanning of Intermodulation Distortion in Superconducting Resonators
No full textTwo-dimensional scanning is combined with a method to locally excite intermodulation distortion (IMD) in a cuprate superconducting microwave resonator. The technique provides local maps of second and third order IMD. The two orders originate from distinct processes and require multiple tones in order to both be excited in a narrow passband. This is the first report where multiple orders of IMD are mapped at their points of origin at the operating frequency of the device. Two samples are shown, one pristine sample and one with an engineered defect, revealing a dominance of the defect in the nonlinearity of the device
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