1,695 research outputs found
Multiple Superconducting Phases in New Heavy Fermion Superconductor PrOs4Sb12
The superconducting gap structure of recently discovered heavy fermion
superconductor PrOs4Sb12 was investigated by using thermal transport
measurements in magnetic field rotated relative to the crystal axes. We
demonstrate that a novel change in the symmetry of the superconducting gap
function occurs deep inside the superconducting state, giving a clear
indication of the presence of two distinct superconducting phases with twofold
and fourfold symmetries. We infer that the gap functions in both phases have a
point node singularity, in contrast to the familiar line node singularity
observed in almost all unconventional superconductors.Comment: 4 Pages, 4 Figure
A positive correlation between serum amyloid β levels and depressive symptoms among community-dwelling elderly individuals in Japan
Koji Tsuruga,1 Norio Sugawara,1 Norio Yasui-Furukori,1 Ippei Takahashi,2 Shoko Tsuchimine,1 Ayako Kaneda,1 Shigeyuki Nakaji,2 Kazuhiko Nakamura1 1Department of Neuropsychiatry, 2Department of Social Medicine, Hirosaki University School of Medicine, Hirosaki, Japan Background: Amyloid beta (Aβ) levels have been associated with an increased risk of Alzheimer’s disease (AD). As depression is common before the onset of AD, serum Aß levels could be associated with depressive symptoms. The aim of this study was to investigate whether serum Aβ levels are associated with depressive symptoms and/or cognitive function in community-dwelling elderly individuals. Methods: We examined the association between serum Aβ levels and depression among 419 Japanese community-dwelling elderly individuals aged 60 years and over. Subjects were divided into two subgroups: younger elderly between 60 and 69 years old and older elderly over 69 years old. The Mini-Mental State Examination (MMSE) was used to assess cognitive function, and symptoms of depression were assessed using the Center for Epidemiologic Studies Depression Scale (CES-D). The ability to perform activities of daily living was evaluated using the Tokyo Metropolitan Institute of Gerontology Index of Competence. Serum Aβ levels were measured with a human amyloid beta enzyme-linked immunosorbent assay kit. Results: After controlling for potential confounding variables, a multiple linear regression analysis showed that increased levels of serum Aβ40 and Aβ42 were associated with higher CES-D scores in the older elderly subgroup. Under the same condition, multiple regression showed that serum Aβ levels were not associated with MMSE scores among the total subjects, younger elderly, or older elderly. Conclusion: Serum Aβ levels were associated with depressive symptoms in community-dwelling elderly individuals. The present study indicates the possibility that serum Aβ may be involved in the development of late-onset depression. Keywords: Alzheimer’s disease, depression, dementia, Japanes
Theory of superconductivity of carbon nanotubes and graphene
We present a new mechanism of carbon nanotube superconductivity that
originates from edge states which are specific to graphene. Using on-site and
boundary deformation potentials which do not cause bulk superconductivity, we
obtain an appreciable transition temperature for the edge state. As a
consequence, a metallic zigzag carbon nanotube having open boundaries can be
regarded as a natural superconductor/normal metal/superconductor junction
system, in which superconducting states are developed locally at both ends of
the nanotube and a normal metal exists in the middle. In this case, a signal of
the edge state superconductivity appears as the Josephson current which is
sensitive to the length of a nanotube and the position of the Fermi energy.
Such a dependence distinguishs edge state superconductivity from bulk
superconductivity.Comment: 5 pages, 2 figure
Thermodynamics of Superstring on Near-extremal NS5 and Effective Hagedorn Behavior
We study the thermodynamical torus partition function of superstring on the
near-extremal black NS5-brane background. The exact partition function has been
computed with the helps of our previous works:[arXiv:1012.5721 [hep-th]],
[arXiv:1109.3365 [hep-th]], and naturally decomposed into two parts. The first
part is contributed from strings freely propagating in the asymptotic region,
which are identified as the superstring gas at the Hawking temperature on the
linear-dilaton background. The second part includes the contribution localized
around the `tip of cigar', which characterizes the non-extremality. Remarkably,
the latter part includes massless excitations with non-vanishing thermal
winding, which signifies that the Hagedorn-like behavior effectively appears,
even though the Hawking temperature is much lower than the Hagedorn
temperature. We also explore the high-temperature backgrounds defined by the
orbifolding along the Euclidean time direction. In those cases, the thermal
winding modes localized around the tip are found to be tachyonic, reflecting
the singularities of Euclidean backgrounds caused by orbifolding.Comment: 1+29 pages, no figure; v2 the footnote 1 is enhanced, to appear in
JHE
Anomalous Metal-Insulator Transition in Filled Skutterudite CeOsSb
Anomalous metal-insulator transition observed in filled skutterudite
CeOsSb is investigated by constructing the effective tight-binding
model with the Coulomb repulsion between f electrons. By using the mean field
approximation, magnetic susceptibilities are calculated and the phase diagram
is obtained. When the band structure has a semimetallic character with small
electron and hole pockets at and H points, a spin density wave
transition with the ordering vector occurs due to the
nesting property of the Fermi surfaces. Magnetic field enhances this phase in
accord with the experiments.Comment: 4 pages, 4 figure
Effect of Fermi Surface Topology on Inter-Layer Magnetoresistance in Layered Multiband Systems: Application to LaFeAsO1-xFx
In layered single band systems, the interlayer conductivity depends on the
orientation of the in-plane magnetic field and takes maximum values when the
magnetic field is perpendicular to flat regions of the Fermi surface. Extending
this known results to multi-band systems, we propose an experiment to extract
information about their Fermi surface topology. We discuss application of the
formula to a FeAs-based superconductor, LaFeAsOF. We show that the
magnetically ordered state in the parent compound is clearly distinguished from
the paramagnetic state by the oscillation period in the interlayer
conductivity. We demonstrate that evolution of the Fermi surface topology by
changing the doping concentration is reflected to the interlayer conductivity
oscillation patterns.Comment: 12 pages, 6 figures, corrected Fig.6, added clarifications and refs,
to appear in J. Phys. Soc. Jp
Unusual behaviors in the transport properties of REFeP (RE: La, Ce, Pr, and Nd)
We have investigated the resistivity (), thermoelectric power (TEP) and
Hall coefficient () on high quality single crystals of
REFeP. TEP in CeFeP is extremely large (
0.5mV/K at 290K) with a peak of 0.75mV/K at around 65K. The Hall
mobility also shows a peak at 65K, suggesting carriers with heavy masses
developed at lower temperatures related with the f-hybridized band. Both Pr-
and Nd- systems exhibit an apparent increase of with decreasing
temperature far above their magnetic transition temperatures. In the same
temperature ranges, TEP exhibits unusually large absolute values of -50V/K
for PrFeP and -15V/K for NdFeP, respectively.
For PrFeP, such anomalous transport properties suggest an unusual
ground state, possibly related with the Quadrupolar Kondo effect.Comment: 5 pages, 8 figure
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