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A note on the wedge reversion antisymmetry operation and 51 types of physical quantities in arbitrary dimensions
No full textThe paper by Gopalan [(2020). Acta Cryst. A76, 318–327] presented an enumeration of the 41 physical quantity types in non‐relativistic physics, in arbitrary dimensions, based on the formalism of Clifford algebra. Gopalan considered three antisymmetries: spatial inversion, 1, time reversal, 1′, and wedge reversion, 1†. A consideration of the set of all seven antisymmetries (1, 1′, 1†, 1′†, 1†, 1′, 1′†) leads to an extension of the results obtained by Gopalan. It is shown that there are 51 types of physical quantities with distinct symmetry properties in total.It is shown that there are 51 types of physical quantities in arbitrary dimensions with distinct transformations by wedge reversion symmetry. In the paper by Gopalan [(2020). Acta Cryst. A76, 318–327] only 41 types were enumerated.
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Verification of the crystal lattice and magnetic symmetry of selected materials
No full textLink archiwalny https://depotuw.ceon.pl/handle/item/403
The relation of anisotropic peak broadening with lattice symmetry in powder diffraction
No full textLattice relaxation, i.e. small lattice symmetry lowering, could lead to unresolved peak splitting in powder diffraction, which results in anisotropic, i.e. -dependent, peak broadening. Recently Gregorkiewitz & Boschetti [1] derived formulas for (with being an interplanar distance) for each split peak component in the following minimal relaxation schemes: (i) cubic to tetragonal, (ii) cubic to rhombohedral, (iii) hexagonal to orthorhombic/monoclinic, (iv) tetragonal to orthorhombic, (v) orthorhombic to monoclinic, (vi) monoclinic to anorthic (triclinic). Anisotropic peak broadening caused by lattice relaxation can be parameterized by the variance of those slightly dispersed peaks’ positions [2]. For all relaxation schemes the variances are expressed as fourth-order polynomials in , , indices [2]:,with , Popa [3] provided symmetry restrictions for each Laue class for coefficients. Stephens’ phenomenological model of anisotropic peak broadening [4] assumes that each crystallite in a powder sample is generally triclinic and that only the average lattice constants over the entire sample satisfy the restrictions of a given lattice symmetry. Consequently, peak broadening can also be expressed as fourth-order polynomials in , , . However, anisotropic peak broadening caused by the lattice relaxation gives more constraints [2] between the coefficients as compared with those listed in [3, 4]. The seminal papers by Popa [3] and Stephens [4] and the recent paper by Gregorkiewitz & Boschetti [1] are connected by expressing the parameters in terms of lattice parameter increments [2].References:[1] Gregorkiewitz, M. & Boschetti, A. (2024). , 439;[2] Fabrykiewicz, P. (2025) , 245;[3] Popa, N. C. (1998). , 176;[4] Stephens, P. W. (1999). , 281.Acknowledgements:Thanks are due to Martin Meven (RWTH Aachen University and Forschungszentrum Jülich GmbH), Radosław Przeniosło and Izabela Sosnowska (University of Warsaw) for inspiring discussions
A note on the relation of anisotropic peak broadening with lattice symmetry in powder diffraction
No full textA bridge is established between the Gregorkiewitz & Boschetti [Acta Cryst. (2024), A80, 439–445] and Stephens [J. Appl. Cryst. (1999), 32, 281–289] formalisms of anisotropic peak broadening in powder diffraction. The paper by Gregorkiewitz & Boschetti presented formulas describing position shifts of low symmetry peaks due to different lattice relaxation schemes. Anisotropic peak broadening caused by lattice relaxation can be parameterized by the variance of slightly dispersed peaks’ positions. The calculated variances are compared with formulas from the widely used phenomenological model of anisotropic peak broadening by Stephens. Specific relations between anisotropic peak broadening parameters can be a hint of a possible unresolved peak splitting due to lattice symmetry lowering
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
The relation of anisotropic peak broadening with lattice symmetry in powder diffraction
No full textLattice relaxation, i.e. small lattice symmetry lowering, could lead to unresolved peak splitting in powder diffraction, which results in anisotropic, i.e. -dependent, peak broadening. Recently Gregorkiewitz & Boschetti [1] derived formulas for (with being an interplanar distance) for each split peak component in the six minimal relaxation schemes. Anisotropic peak broadening caused by lattice relaxation can be parameterized by the variance of those slightly dispersed peaks’ positions [2]. For all relaxation schemes the variances are expressed as fourth-order polynomials in , , indices [2]:,with . Popa [3] provided symmetry restrictions for each Laue class for coefficients. Stephens’ phenomenological model of anisotropic peak broadening [4] assumes that each crystallite in a powder sample is generally triclinic and that only the average lattice constants over the entire sample satisfy the restrictions of a given lattice symmetry. Consequently, peak broadening can also be expressed as fourth-order polynomials in , , . However, anisotropic peak broadening caused by the lattice relaxation gives more constraints [2] between the coefficients as compared with those listed in [3, 4]. The seminal papers by Popa [3] and Stephens [4] and the recent paper by Gregorkiewitz & Boschetti [1] are connected by expressing the parameters in terms of lattice parameter increments [2].References:[1] M. Gregorkiewitz & A. Boschetti, (2024) 439;[2] P. Fabrykiewicz, (2025) 245;[3] N. C. Popa, (1998) 176;[4] P. W. Stephens, (1999) 281.Acknowledgements:Thanks are due to Martin Meven (RWTH Aachen University and Forschungszentrum Jülich GmbH), Radosław Przeniosło and Izabela Sosnowska (University of Warsaw) for inspiring discussions
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
A note on the wedge reversion antisymmetry operation and 51 types of physical quantities in arbitrary dimensions
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