247 research outputs found
Epic Significance: Placing Alphonse Mucha\u27s Czech Art in the Context of Pan-Slavism and Czech Nationalism
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Alphonse Mucha is primarily known for his early career producing Parisian Art Nouveau posters. However in 1910, Mucha left Paris to return to his home in the Czech lands where he concentrated on creating works for his country. Unfortunately, the later part of his career receives little to no attention in most art history books. His collection, The Slav Epic, represents ideas of Pan-Slavism, patriotism, and national identity. A leading scholar of national identity was Johann Gottfried Herder, a Czech sympathizer who influenced writers such as Jan Kollár and the historian František Palacký. Mucha’s works provided a visual representation of national identity and collective history specifically called for by these scholars. This thesis seeks to shed light on the late works of this artist, tracing the ever-present Slavonic influences, and also to place them in context within Czech Nationalism and Pan-Slavism in order to establish their historical significance
Anisotropic in-plane optical conductivity in detwinned Ba(Fe1-xCox)2As2
We study the anisotropic in-plane optical conductivity of detwinned
Ba(Fe1-xCox)2As2 single crystals for x=0, 2.5% and 4.5% in a broad energy range
(3 meV-5 eV) across their structural and magnetic transitions. For temperatures
below the Neel transition, the topology of the reconstructed Fermi surface,
combined with the distinct behavior of the scattering rates, determines the
anisotropy of the low frequency optical response. For the itinerant charge
carriers, we are able to disentangle the evolution of the Drude weights and
scattering rates and to observe their enhancement along the orthorhombic
antiferromagnetic a-axis with respect to the ferromagnetic b-axis. For
temperatures above Ts, uniaxial stress leads to a finite in-plane anisotropy.
The anisotropy of the optical conductivity, leading to a significant dichroism,
extends to high frequencies in the mid- and near-infrared regions. The
temperature dependence of the dichroism at all dopings scales with the
anisotropy ratio of the dc conductivity, suggesting the electronic nature of
the structural transition. Our findings bear testimony to a large nematic
susceptibility that couples very effectively to the uniaxial lattice strain. In
order to clarify the subtle interplay of magnetism and Fermi surface topology
we compare our results with theoretical calculations obtained from density
functional theory within the full-potential linear augmented plane-wave method.Comment: 17 pages, 9 figure
Processing and Properties of High-Entropy Ultra-High Temperature Carbides
The research was supported by the EPSRC Programme Grant XMAT [EP/K008749/2]. The authors gratefully acknowledge the financial support from projects: APVV-15-0469 & VEGA 2/0163/16
Direct synthesis of nanocrystalline oxide powders by wet-chemical techniques
In a recent period there is a great need for increasing the knowledge of tailoring the innovative procedures for the synthesis of electroceramic nanopowders and materials with improved quality for specific application. In order to produce electroceramics with desirable microstructure and properties, synthesis of stoichiometric, ultra-fine and agglomerate free powders with narrow size distributions is one of the most important steps. Within this scope, in the present paper we summarize our recent results on direct synthesis of some important perovskites and ferrites nanopowders by wet-chemical techniques
Anisotropic Impurity-States, Quasiparticle Scattering and Nematic Transport in Underdoped Ca(Fe1-xCox)2As2
Iron-based high temperature superconductivity develops when the `parent'
antiferromagnetic/orthorhombic phase is suppressed, typically by introduction
of dopant atoms. But their impact on atomic-scale electronic structure, while
in theory quite complex, is unknown experimentally. What is known is that a
strong transport anisotropy with its resistivity maximum along the crystal
b-axis, develops with increasing concentration of dopant atoms; this
`nematicity' vanishes when the `parent' phase disappears near the maximum
superconducting Tc. The interplay between the electronic structure surrounding
each dopant atom, quasiparticle scattering therefrom, and the transport
nematicity has therefore become a pivotal focus of research into these
materials. Here, by directly visualizing the atomic-scale electronic structure,
we show that substituting Co for Fe atoms in underdoped Ca(Fe1-xCox)2As2
generates a dense population of identical anisotropic impurity states. Each is
~8 Fe-Fe unit cells in length, and all are distributed randomly but aligned
with the antiferromagnetic a-axis. By imaging their surrounding interference
patterns, we further demonstrate that these impurity states scatter
quasiparticles in a highly anisotropic manner, with the maximum scattering rate
concentrated along the b-axis. These data provide direct support for the recent
proposals that it is primarily anisotropic scattering by dopant-induced
impurity states that generates the transport nematicity; they also yield simple
explanations for the enhancement of the nematicity proportional to the dopant
density and for the occurrence of the highest resistivity along the b-axis
Uptake, Transport, and Toxicity of Pristine and Weathered Micro- and Nanoplastics in Human Placenta Cells
BACKGROUND: The first evidence of micro- and nanoplastic (MNP) exposure in the human placenta is emerging. However, the toxicokinetics and toxicity of MNPs in the placenta, specifically environmentally relevant particles, remain unclear. OBJECTIVES: We examined the transport, uptake, and toxicity of pristine and experimentally weathered MNPs in nonsyncytialized and syncytialized BeWo b30 choriocarcinoma cells. METHODS: We performed untargeted chemical characterization of pristine and weathered MNPs using liquid chromatography high-resolution mass spectrometry to evaluate compositional differences following particle weathering. We investigated cellular internalization of pristine and weathered polystyrene (PS; 0.05 - 10 μ m ) and high-density polyethylene (HDPE; 0 - 80 μ m ) particles using high-resolution confocal imaging and three-dimensional rendering. We investigated the influence of particle coating with human plasma on the cellular transport of PS particles using a transwell setup and examined the influence of acute MNP exposure on cell viability, damage to the plasma membrane, and expression of genes involved in steroidogenesis. RESULTS: Chemical characterization of MNPs showed a significantly higher number of unique features in pristine particles in comparison with weathered particles. Size-dependent placental uptake of pristine and weathered MNPs was observed in both placental cell types after 24 h exposure. Cellular transport was limited and size-dependent and was not influenced by particle coating with human plasma. None of the MNPs affected cell viability. Damage to the plasma membrane was observed only for 0.05 μ m PS particles in the nonsyncytialized cells at the highest concentration tested ( 100 μ g / mL ). Modest down-regulation of hsd17b1 was observed in syncytialized cells exposed to pristine MNPs. DISCUSSION: Our results suggest that pristine and weathered MNPs are internalized and translocated in placental cells in vitro. Effects on gene expression observed upon pristine PS and HDPE particle exposure warrant further examination. More in-depth investigations are needed to better understand the potential health risks of MNP and chemicals associated with them under environmentally relevant exposure scenarios. https://doi.org/10.1289/EHP10873
Breaking of four-fold lattice symmetry in a model for pnictide superconductors
We investigate the interplay of onsite Coulomb repulsion and various
mechanisms breaking the fourfold lattice symmetry in a three-band model for the
iron planes of iron-based superconductors. Using cluster-perturbation theory
allows us to locally break the symmetry between the x- and y-directions without
imposing long-range magnetic order. Previously investigated anisotropic
magnetic couplings are compared to an orbital-ordering field and anisotropic
hoppings. We find that all three mechanisms for a broken rotational symmetry
lead to similar signatures once onsite interactions are strong enough to bring
the system close to a spin-density wave. The band distortions near the Fermi
level are independent of differences between the total densities found in xz
and yz orbitals
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