22 research outputs found
Anisotropic Behavior of Knight Shift in Superconducting State of Na_xCoO_2yH_2O
The Co Knight shift was measured in an aligned powder sample of
Na_xCoO_2yH_2O, which shows superconductivity at T_c \sim 4.6 K. The
Knight-shift components parallel (K_c) and perpendicular to the c-axis (along
the ab plane K_{ab}) were measured in both the normal and superconducting (SC)
states. The temperature dependences of K_{ab} and K_c are scaled with the bulk
susceptibility, which shows that the microscopic susceptibility deduced from
the Knight shift is related to Co-3d spins. In the SC state, the Knight shift
shows an anisotropic temperature dependence: K_{ab} decreases below 5 K,
whereas K_c does not decrease within experimental accuracy. This result raises
the possibility that spin-triplet superconductivity with the spin component of
the pairs directed along the c-axis is realized in Na_xCoO_2yH_2O.Comment: 5 pages, 5 figures, to be published in Journal of Physical Society of
Japan vol. 75, No.
Approach to the metal-insulator transition in La(1-x)CaxMnO3 (0<x<.2): magnetic inhomogeneity and spin wave anomaly
We describe the evolution of the static and dynamic spin correlations of
LaCaMnO, for x=0.1, 0.125 and 0.2, where the system evolves
from the canted magnetic state towards the insulating ferromagnetic state,
approaching the metallic transition (x=0.22).
In the x=0.1 sample, the observation of two spin wave branches typical of two
distinct types of magnetic coupling, and of a modulation in the elastic diffuse
scattering characteristic of ferromagnetic inhomogeneities, confirms the static
and dynamic inhomogeneous features previously observed at x0.1. The
anisotropic q-dependence of the intensity of the low-energy spin wave suggests
a bidimensionnal character for the static inhomogeneities. At x=0.125, which
corresponds to the occurence of a ferromagnetic and insulating state, the two
spin wave branches reduce to a single one, but anisotropic. At this
concentration, an anomaly appears at {\bf q}=(1.25,1.25,0), that could be
related to an underlying periodicity, as arising from (1.5,1.5,0)
superstructures.
At x=0.2, the spin-wave branch is isotropic. In addition to the anomaly
observed at q, extra magnetic excitations are observed at larger q, forming
an optical branch. The two dispersion curves suggest an anti-crossing behavior
at some {\bf q'} value, which could be explained by a folding due to an
underlying perodicity involving four cubic lattice spacings
Pre-conditioning with synthetic CpG-oligonucleotides attenuates myocardial ischemia/reperfusion injury via IL-10 up-regulation
Hearts from Mice Fed a Non-Obesogenic High-Fat Diet Exhibit Changes in Their Oxidative State, Calcium and Mitochondria in Parallel with Increased Susceptibility to Reperfusion Injury
High-fat diet with obesity-associated co-morbidities triggers cardiac remodeling and renders the heart more vulnerable to ischemia/reperfusion injury. However, the effect of high-fat diet without obesity and associated co-morbidities is presently unknown.To characterize a non-obese mouse model of high-fat diet, assess the vulnerability of hearts to reperfusion injury and to investigate cardiac cellular remodeling in relation to the mechanism(s) underlying reperfusion injury.Feeding C57BL/6J male mice high-fat diet for 20 weeks did not induce obesity, diabetes, cardiac hypertrophy, cardiac dysfunction, atherosclerosis or cardiac apoptosis. However, isolated perfused hearts from mice fed high-fat diet were more vulnerable to reperfusion injury than those from mice fed normal diet. In isolated cardiomyocytes, high-fat diet was associated with higher diastolic intracellular Ca2+ concentration and greater damage to isolated cardiomyocytes following simulated ischemia/reperfusion. High-fat diet was also associated with changes in mitochondrial morphology and expression of some related proteins but not mitochondrial respiration or reactive oxygen species turnover rates. Proteomics, western blot and high-performance liquid chromatography techniques revealed that high-fat diet led to less cardiac oxidative stress, higher catalase expression and significant changes in expression of putative components of the mitochondrial permeability transition pore (mPTP). Inhibition of the mPTP conferred relatively more cardio-protection in the high-fat fed mice compared to normal diet.This study shows for the first time that high-fat diet, independent of obesity-induced co-morbidities, triggers changes in cardiac oxidative state, calcium handling and mitochondria which are likely to be responsible for increased vulnerability to cardiac insults