178 research outputs found
Unconventional Anomalous Hall Effect in the Metallic Triangular-Lattice Magnet PdCrO2
We experimentally reveal an unconventional anomalous Hall effect (UAHE) in a
quasi-two-dimensional triangular-lattice antiferromagnet PdCrO2. Using high
quality single crystals of PdCrO2, we found that the Hall resistivity deviates
from the conventional behavior below T* = 20 K, noticeably lower than TN = 37.5
K, at which Cr^{3+} (S=3/2) spins order in a 120 degree structure. In view of
the theoretical expectation that the spin chirality cancels out in the simplest
120 degree spin structure, we discuss required conditions for the emergence of
UAHE within Berry-phase mechanisms.Comment: 4 pages, 5 figures, accepted for publication in PR
Extremely Large Magnetoresistance in the Nonmagnetic Metal PdCoO2
Extremely large magnetoresistance is realized in the nonmagnetic layered
metal PdCoO2. In spite of a highly conducting metallic behavior with a simple
quasi-two-dimensional hexagonal Fermi surface, the interlayer resistance
reaches up to 35000% for the field along the [1-10] direction. Furthermore, the
temperature dependence of the resistance becomes nonmetallic for this field
direction, while it remains metallic for fields along the [110] direction. Such
severe and anisotropic destruction of the interlayer coherence by a magnetic
field on a simple Fermi surface is ascribable to orbital motion of carriers on
the Fermi surface driven by the Lorentz force, but seems to have been largely
overlooked until now.Comment: Phys. Rev. Lett. 111, 056601 (2013
Critical behavior of the metallic triangular-lattice Heisenberg antiferromagnet PdCrO2
We report physical properties of the conductive magnet PdCrO2 consisting of a
layered structure with a triangular lattice of Cr3+ ions (S=3/2). We confirmed
an antiferromagnetic transition at TN=37.5K by means of specific heat,
electrical resistivity, magnetic susceptibility, and neutron scattering
measurements. The critical behavior in the specific heat persists in an
unusually wide temperature range above TN. This fact implies that spin
correlations develop even at much higher temperature than TN. The observed
sub-linear temperature dependence of the resistivity above TN is also
attributed to the short-range correlations among the frustrated spins. While
the critical exponent for the magnetization agrees reasonably with the
prediction of the relevant model, that for the specific heat evaluated in the
wide temperature range differs substantially from the prediction.Comment: 7 pages, 6 figure
Loss of maternal annexin A5 increases the likelihood of placental platelet thrombosis and foetal loss
Antiphospholipid syndrome is associated with an increased risk of thrombosis and pregnancy loss. Annexin A5 (Anxa5) is a candidate autoantigen. It is not known, however, whether endogenous Anxa5 prevents foetal loss during normal pregnancy. We found significant reductions in litter size and foetal weight in Anxa5-null mice (Anxa5-KO). These changes occurred even when only the mother was Anxa5-KO. A small amount of placental fibrin deposition was observed in the decidual tissues, but did not noticeably differ between wild-type and Anxa5-KO mice. However, immunoreactivity for integrin beta 3/CD61, a platelet marker, was demonstrated within thrombi in the arterial canals only in Anxa5-KO mothers. Subcutaneous administration of the anticoagulant heparin to pregnant Anxa5-KO mice significantly reduced pregnancy loss, suggesting that maternal Anxa5 is crucial for maintaining intact placental circulation. Hence, the presence of maternal Anxa5 minimises the risk of thrombosis in the placental circulation and reduces the risk of foetal loss
Structural requirement of leucine for activation of p70 S6 kinase
AbstractThe addition of leucine induced activation of p70S6k in amino acid-depleted H4IIE cells. Whereas the activation of p70S6k by leucine was transient, the complete amino acid stimulated p70S6k more persistently. The effect of leucine on p70S6k was sensitive to rapamycin, but less sensitive to wortmannin. Using various amino acids and derivatives of leucine, we found that the chirality, the structure of the four branched hydrocarbons, and the primary amine are required for the ability of leucine to stimulate p70S6k, indicating that the structural requirement of leucine to induce p70S6k activation is very strict and precise. In addition, some leucine derivatives exhibited the ability to stimulate p70S6k and the other derivatives acted as inhibitors against the leucine-induced activation of p70S6k
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