33 research outputs found
Superconducting fluctuations in FeSeTe thin films probed via microwave spectroscopy
We investigated the microwave conductivity spectrum of FeSeTe
epitaxial films on CaF in the vicinity of the superconducting transition.
We observed the critical behavior of the superconducting fluctuations in these
films with a dimensional crossover from two-dimensional to three-dimensional as
the film thickness increased. From the temperature dependence of the scaling
parameters we conclude that the universality class of the superconducting
transition in FeSeTe is that of the 3D-XY model. The lower
limit of the onset temperature of the superconducting fluctuations, Tonset,
determined by our measurements was 1.1 Tc, suggesting that the superconducting
fluctuations of FeSeTe are at least as large as those of
optimally- and over-doped cuprates
(5-Benzoyl-3,6-dimethoxynaphthalen-2-yl)(phenyl)methanone
The asymmetric unit of the title compound, C26H20O4, contains two independent conformers. The aromatic rings of the aroyl groups are twisted with respect to the naphthalene ring systems to form dihedral angles of 66.58 (6) and 66.45 (6)° in one conformer, and 75.00 (7) and 81.17 (6)° in the other conformer. The crystal packing is stabilized by weak intermolecular C—H⋯O hydrogen bonds and by C—H⋯π interactions
(8-Bromo-2-hydroxy-7-methoxy-1-naphthyl)(4-chlorobenzoyl)methanone
In the title compound, C18H12BrClO3, the naphthalene ring system and the benzene ring make a dihedral angle of 82.18 (9)°. The conformation around the central C=O group is such that the C=O bond vector forms a larger angle to the plane of the naphthalene ring system than to the plane of the benzene ring, viz. 60.91 (16)° versus 13.94 (16)°. In the crystal structure, two π–π interactions formed between the naphthalene ring systems [centroid–centroid distances of 3.8014 (13) and 3.9823 (13) Å] and intermolecular O—H⋯O and C—H⋯O hydrogen bonds are present
Hierarchy of QM SUSYs on a Bounded Domain
We systematically formulate a hierarchy of isospectral Hamiltonians in
one-dimensional supersymmetric quantum mechanics on an interval and on a
circle, in which two successive Hamiltonians form N=2 supersymmetry. We find
that boundary conditions compatible with supersymmetry are severely restricted.
In the case of an interval, a hierarchy of, at most, three isospectral
Hamiltonians is possible with unique boundary conditions, while in the case of
a circle an infinite tower of isospectral Hamiltonians can be constructed with
two-parameter family of boundary conditions.Comment: 15 pages, 3 figure
Architectures of archaeal GINS complexes, essential DNA replication initiation factors
<p>Abstract</p> <p>Background</p> <p>In the early stage of eukaryotic DNA replication, the template DNA is unwound by the MCM helicase, which is activated by forming a complex with the Cdc45 and GINS proteins. The eukaryotic GINS forms a heterotetramer, comprising four types of subunits. On the other hand, the archaeal GINS appears to be either a tetramer formed by two types of subunits in a 2:2 ratio (α<sub>2</sub>β<sub>2</sub>) or a homotetramer of a single subunit (α<sub>4</sub>). Due to the low sequence similarity between the archaeal and eukaryotic GINS subunits, the atomic structures of the archaeal GINS complexes are attracting interest for comparisons of their subunit architectures and organization.</p> <p>Results</p> <p>We determined the crystal structure of the α<sub>2</sub>β<sub>2 </sub>GINS tetramer from <it>Thermococcus kodakaraensis </it>(<it>Tko</it>GINS), comprising Gins51 and Gins23, and compared it with the reported human GINS structures. The backbone structure of each subunit and the tetrameric assembly are similar to those of human GINS. However, the location of the C-terminal small domain of Gins51 is remarkably different between the archaeal and human GINS structures. In addition, <it>Tko</it>GINS exhibits different subunit contacts from those in human GINS, as a consequence of the different relative locations and orientations between the domains. Based on the GINS crystal structures, we built a homology model of the putative homotetrameric GINS from <it>Thermoplasma acidophilum </it>(<it>Tac</it>GINS). Importantly, we propose that a long insertion loop allows the differential positioning of the C-terminal domains and, as a consequence, exclusively leads to the formation of an asymmetric homotetramer rather than a symmetrical one.</p> <p>Conclusions</p> <p>The DNA metabolizing proteins from archaea are similar to those from eukaryotes, and the archaeal multi-subunit complexes are occasionally simplified versions of the eukaryotic ones. The overall similarity in the architectures between the archaeal and eukaryotic GINS complexes suggests that the GINS function, directed through interactions with other protein components, is basically conserved. On the other hand, the different subunit contacts, including the locations and contributions of the C-terminal domains to the tetramer formation, imply the possibility that the archaeal and eukaryotic GINS complexes contribute to DNA unwinding reactions by significantly different mechanisms in terms of the atomic details.</p
Adaptability and selectivity of human peroxisome proliferator-activated receptor (PPAR) pan agonists revealed from crystal structures
The structures of the ligand-binding domains (LBDs) of human peroxisome proliferator-activated receptors (PPARα, PPARγ and PPARδ) in complexes with a pan agonist, an α/δ dual agonist and a PPARδ-specific agonist were determined. The results explain how each ligand is recognized by the PPAR LBDs at an atomic level