1,721,425 research outputs found
Coherent X-ray diffraction of the M1 to M2 structural phase transition in a single vanadium dioxide nanocrystal
No full textCorrelated electronic materials are of interest due to strong coupling between lattice, spin and orbital degrees of freedom that give rise to emergent behaviour that is often of considerable utility for next generation technologies. Vanadium dioxide is a prototypical material that undergoes a number of structural phase transitions near room temperature. Here are presented the results of coherent x-ray diffraction measurements on a single vanadium dioxide nanocrystal approximately 440 nm in size. Experimental findings are compared with ab-initio simulations to elucidate the origin of distortions that are observed in the diffraction pattern
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
Deformation of a bismuth ferrite nanocrystal imaged by coherent X-ray diffraction
No full textAbstract. Perovskite materials that contain transition metal-oxides often exhibit multifunctional properties with considerable utility in a device setting. BiFeO3 is a multiferroic perovskite material that exhibits room temperature anti-ferromagnetic and ferroelectric ordering. Optical excitation of BiFeO3 crystals results in an elastic structural deformation of the lattice with a fast response on the pico-second time scale. Here we report on dynamic optical excitation coupled with Bragg coherent X-ray diffraction measurements to investigate the structural properties of BiFeO3 nanoscale crystals. A continuous distortion of the diffraction speckle pattern was ob- served with increasing illumination. This was attributed to strain resulting from photo-induced lattice deformation
Coherent diffraction imaging of a progressively deformed nanocrystal
No full textImaging ordered materials with coherent x rays holds great potential to improve our understanding of phenomena in complex materials systems where emergent behavior can arise due to coupling of spin, lattice, and orbital degrees of freedom. Coherent diffractive imaging (CDI) is a lensless imaging technique for probing the structure of materials in three dimensions. Central to the success of the CDI method is the inversion of propagated wave field information to recover a quantitative image of the illuminated crystalline structure. Present challenges faced with existing approaches to image recovery are often due to nonuniqueness of wave propagated forms of the electron density information that can cause prohibitive stagnation of the reconstruction algorithm. Here we report on a major advancement in image recovery that is able to recover the three-dimensional image of a 492 nm gold single crystal undergoing progressive deformation to a highly strained condition without the use of a priori information. Our findings also demonstrate the significance of robust image recovery techniques for revealing high resolution topological structure
Coherent X-ray diffraction imaging of photo-induced structural changes in BiFeO<sub>3</sub> nanocrystals
No full textMultiferroic materials that exhibit coupling between ferroelectric and magnetic properties are of considerable utility for technological applications and are also interesting from a fundamental standpoint. When reduced to the nanoscale, multiferroic materials often display additional functionality that is dominated by interfacial and confinement effects. Bismuth ferrite (BiFeO3) is one such material with room temperature anti-ferromagnetic and ferroelectric ordering. Optical excitation of BiFeO3 crystals results in an elastic structural deformation of the lattice with a fast response on the pico-second time scale. Here we report on dynamic measurements to investigate the structural properties of BiFeO3 nanoscale crystals using laser excitation and three-dimensional Bragg coherent x-ray diffraction imaging. Tensile strain beyond 8 × 10-2 was observed predominantly at the surface of the nanoscale crystal as evidenced in the reconstructed phase information and was correlated to photo-induced lattice deformation
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
The Needs of Victims: An Empirical Categorization Based on Interpersonal Conflicts
No full textAs a consequence of interpersonal conflicts, needs of the victimized are violated. These needs have to be addressed in order to achieve reconciliation. Due to the heterogeneity of need categories in scholarly research, we scrutinized which need categories can be empirically identified. 478 participants reported on an experienced interpersonal conflict. They responded to 109 items evaluating the perceived need violation for the conflict they reported on. By means of exploratory factor analysis with a random sub-sample (n1 = 239), six need categories were extracted. These are the need for respect, the need for meaning, the need for acceptance, the need for pleasure, the need for self-efficacy, and the need for safety. Confirmatory factor analyses showed that these needs replicated in the second random sub-sample (n2 = 239) as well as across sub-samples with people who had experienced an interpersonal conflict of lower severity of transgression (nA = 257) or higher severity of transgression (nB = 221). In addition, each of the need categories mediated the relationship between the severity of transgression and the desire for revenge. Yet, the results for the two need categories “pleasure” and “safety” have to be interpreted with caution due to a lack of scalar invariance. Among the other four need categories, respect was identified as the only independent mediator variable. Implications for the transformation of interpersonal conflict and further scholarly inquiries are discussed
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