1,720,988 research outputs found
Thermoelectric properties of iron-based superconductors and parent compounds
No full textHerewith, we review the available experimental data of thermoelectric transport properties of iron-based superconductors and parent compounds. We discuss possible physical mechanisms into play in determining the Seebeck effect, from whence one can extract information about Fermi surface reconstruction and Lifshitz transitions, multiband character, coupling of charge carriers with spin excitations and its relevance in the unconventional superconducting pairing mechanism, nematicity, quantum critical fluctuations close to the optimal doping for superconductivity, correlation. Additional information is obtained from the analysis of the Nernst effect, whose enhancement in parent compounds must be related partially to multiband transport and low Fermi level, but mainly to the presence of Dirac cone bands at the Fermi level. In the superconducting compounds, large Nernst effect in the normal state is explained in terms of fluctuating precursors of the spin density wave state, while in the superconducting state it mirrors the usual vortex liquid dissipative regime. A comparison between the phenomenology of thermoelectric behavior of different families of iron-based superconductors and parent compounds allows to evidence the key differences and analogies, thus providing clues on the rich and complex physics of these fascinating unconventional superconductors
Evidence of the isoelectronic character of F doping in SmFeAsO1−x F x : a first-principles investigation
No full textWe study the electronic structure of the SmFeAsO1−x F x alloy by means of first-principle calculations. We find that, contrary to common believe, F-doping does not change the charge balance between electrons and holes free-carriers in SmFeAsO1−x F x . For energies within a narrow energy range accross , the effect of F-doping on the band structure dispersion is tiny in both the paramagnetic and stripe antiferromagnetic phase. The charge balance between the conducting FeAs-layer and the SmO1−x F x charge reservoir layer is not influenced by the compositional change. The additional charge carried by fluorine, with respect to the oxygen, is compensated by a change in the oxidation state of the Sm ion from 3+ to 2+. A comparison with the SmFe1−x Co x AsO system shows that such charge compensation by the Sm ion is not shared by donors substituting at the Fe site
A current and controversial issue: tax treatment of foreign exchange differences and their impact on tax planning strategies
No full textFil: Caglieris, Federico Jesús. Universidad Nacional del Litoral. Facultad de Ciencias Económicas; Argentina.El presente trabajo trata sobre el análisis impositivo de las diferencias de cambio. Esto implica estudiar en profundidad cómo impactan en los impuestos nacionales (IVA, GANANCIAS) y provinciales (INGRESOS BRUTOS) las diferencias de cambio positivas que pueda percibir un contribuyente. Dicha investigación se basa en que las citadas diferencias de cambio pueden ser de montos importantes por las variantes fluctuaciones del contexto en que vivimos.
Se analiza también su relación con las normativas de facturación y retenciones vigentes en nuestro país, así como también la vinculación de las diferencias de cambio con las normas emanadas de la LEY N° 11.683 y de la LEY ANTIEVASIÓN.
Para concluir, se analiza si en cada impuesto las diferencias de cambio se encuentran gravadas de acuerdo a la normativa legal y se aclara, a su vez, su tratamiento (deducibilidad o no) en el caso de ser diferencias de cambio negativas, resumiendo también cómo esta temática puede influir en estrategias de planificación fiscal que el asesor profesional en ciencias económicas debe brindarle al contribuyente.This paper focuses on the tax analysis of foreign exchange differences. It involves an in-depth study of how positive foreign exchange differences perceived by a taxpayer impact national taxes (IVA, GANANCIAS) and provincial taxes (INGRESOS BRUTOS). The research is based on the fact that such foreign exchange differences can represent significant amounts due to the highly volatile economic environment in which we live.
The paper also examines their relationship with current invoicing and withholding regulations in our country, as well as the connection between foreign exchange differences and the rules arising from LEY N° 11.683 and the LEY ANTIEVASIÓN.
Finally, it analyzes whether such differences are taxable under each applicable tax according to the current legal framework, and clarifies their treatment (deductible or not) in cases where the foreign exchange differences are negative. The paper also summarizes how this issue may influence tax planning strategies that a professional advisor in economic sciences should provide to the taxpayer
Role of Dirac cones in magnetotransport properties of REFeAsO (RE = rare earth) oxypnictides
No full textIn this work we study the effect of the rare earth element in iron oxypnictides of composition REFeAsO (RE = rare earth). On one hand we carry out density functional theory calculations of the band structure, which evidence the multiband character of these compounds and the presence of Dirac cones along the Y-Γ and Z-R directions of the reciprocal space. On the other hand, we explore transport behavior by means of resistivity, Hall resistance and magnetoresistance measurements, which confirm the dominant role of Dirac cones. By combining our theoretical and experimental approaches, we extract information on effective masses, scattering rates and Fermi velocities for different rare earth elements
Crystallochemistry, thermodynamic and physical properties of the intermetallic compound Cu3−x(As,Sb)
No full textDuring the investigation of the Cu-As-Sb ternary system, we identified the ternary intermetallic Cu3− x(As,Sb)compound. Its crystal structure was solved and refined by single crystal and powder X-ray diffraction. While the binary Cu3− xAs and Cu3− xSb phases crystallize in the hexagonal Cu3P-type (hP24, P63cm) and cubic anti-BiF3-type (cF16, Fm3m), respectively, Cu3− x(As,Sb) adopts the cubic Cu6AsSb prototype (cP32, Pm3n). Crystallochemical reasons lead to the exclusion that its structure could be of the UH3-type. Cu3− x(As,Sb) is isotypic with Cu12− xTeSb3; their crystal structure is a stuffed ternary derivative of the Cr3Si-type. SEM-EDX analyses reveal very large compositional ranges for this compound, mostly concerning the Sb/As ratio: 71.1− 73.9 at.% Cu, 4.0− 24.5 at.% As and 2.5− 23.5 at.% Sb, corresponding to about Cu2.5-2.8As0.23-0.98Sb0.23-0.92 (x = 0.2− 0.5).The lattice parameter and, consequently, the unit cell volume regularly expand while increasing the Sb/As compositional ratio: a ≈ 7.47 Å for Cu3− xAs0.75Sb0.25, a ≈ 7.65 Å for Cu3− xAs0.25Sb0.75 (averaged values).Cu3− x(As,Sb) forms either by a peritectic reaction for As-rich compositions, or congruently for the equiatomic Sb/As and Sb-rich compositions. The decomposition- or melting-temperature values decrease as a function of the Sb/As compositional ratio [e.g. peritectic at 710 ◦C for Cu3− xAs0.75Sb0.25 (Cu72As21Sb7), congruent melting at 690 ◦C for Cu3− xAs0.50Sb0.50 (Cu72As14Sb14), and at 675 ◦C for Cu3−xAs0.25Sb0.75 (Cu72As7Sb21)].Physical properties (electrical resistivity and magnetic susceptibility) indicate that Cu3− x(As,Sb) behaves as a good metal with electrical resistivity decreasing as the Sb/As compositional ratio increases; a peculiar anomaly in
the electrical resistivity behavior (heavy-fermions like) was observed at low temperature, the origin of which needs further investigation. The compound is a standard diamagnet
Theoretical and experimental investigation of magnetotransport in iron chalcogenides
No full textWe explore the electronic, transport and thermoelectric properties of Fe1+ySexTe1-x compounds to clarify the mechanisms of superconductivity in Fe-based compounds. We carry out first-principles density functional theory (DFT) calculations of structural, electronic, magnetic and transport properties and measure resistivity, Hall resistance and Seebeck effect curves. All the transport properties exhibit signatures of the structural/magnetic transitions, such as discontinuities and sign changes of the Seebeck coefficient and of the Hall resistance. These features are reproduced by calculations provided that antiferromagnetic correlations are taken into account and experimental values of lattice constants are considered in DFT calculations. On the other hand, the temperature dependences of the transport properties can not be fully reproduced, and to improve the agreement between experiment and DFT calculations it is necessary to go beyond the constant relaxation time approximation and take into account correlation effects
Yb-doped Gd2O2CO3: Structure, microstructure, thermal and magnetic behaviour
No full textStructural and microstructural features, as well as thermal and magnetic properties of Yb-doped Gd2O2CO3,
were investigated with the aim to clarify the location and the oxidation state of Yb within the structure, and its
role in driving the extent of the (Gd1-xYbx)2O2CO3 solid solution. Yb is found in the 3+ oxidation state and it
enters the structure only at the rare earth atomic site; the solubility limit results to be located in the close
vicinity of x=0.25, and thermal analyses reveal a linear decrease of the decomposition temperature with
increasing the Yb amount, in agreement with literature data. The structural analysis allows to exclude longrange
clusterization of Yb and Gd, since both rare earths randomly distribute over the 4f atomic position, but
relying on the results of the microstructural analysis, the presence of compositional inhomogenities at the local
scale cannot be excluded
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
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
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