Biomedical subjects
Publications and source records attributed to N Metoki.
The phonon dispersion curves of the superconductor PuCoGa(5) were studied by inelastic x-ray scattering at room temperature. The experimental data agree well with ab initio lattice dynamics calculations. An accurate description of the phonon spectrum is obtained only when a local Coulomb repulsion U approximately equal 3 eV among 5f electrons is taken into account.
We report inelastic neutron scattering experiments performed to investigate the low energy magnetic excitations on single crystals of the heavy-fermion superconductor PrOs(4)Sb(12). The observed excitation clearly softens at a wave vector Q=(1,0,0), which is the same as the modulation vector of the field-induced antiferro-quadrupolar ordering, and its intensity at Q=(1,0,0) is smaller than that around the zone center. This result directly evidences that this excitonic behavior is derived mainly from nonmagnetic quadrupolar interactions. Furthermore, the narrowing of the linewidths of the excitations below the superconducting transition temperature indicates the close connection between the superconductivity and the excitons.
Inelastic neutron scattering experiments on the S = 1 quasi-one-dimensional bond-alternating antiferromagnet Ni(C9D24N4)(NO2)ClO4 have been performed under magnetic fields below and above a critical field Hc at which the energy gap closes. Normal field dependence of Zeeman splitting of the excited triplet modes below Hc has been observed, but the highest mode is unusually small and smears out with increasing field. This can be explained by an interaction with a low-lying two magnon continuum at q(parallel) = pi that is present in dimerized chains but absent in uniform ones. Above Hc, we find only one excited mode, in stark contrast with three massive excitations previously observed in the structurally similar Haldane-gap material NDMAP [A. Zheludev, Phys. Rev. B 68, 134438 (2003)].
BACKGROUND: Parathyroid hormone (PTH) is vasoactive, and the endothelium is one of the target tissues of this hormone. Hyperparathyroidism is frequently associated with hypertension. OBJECTIVE: To determine if hyperparathyroidism, which develops particularly in elderly women as a compensatory mechanism to osteoporosis, may be a risk factor for ischemic stroke. METHODS: Serum PTH levels and bone mineral density (BMD) in 107 elderly patients with ischemic stroke (>or=65 years old) were assessed on the day of onset. The control group consisted of 107 healthy volunteers matched for age and sex. RESULTS: BMD was significantly lower and serum PTH higher in female stroke patients than in control subjects; there was a negative correlation between these two measurements. One-third of the female stroke patients had a serum PTH level higher than the mean + 2 SD of the control subjects (high PTH group), and the interval between menopause and the stroke was significantly longer in the high PTH group than in the normal PTH group. Multiple logistic analyses revealed hypertension and ischemic heart disease were more prevalent in the high PTH group. BMD and PTH were normal in male stroke patients. CONCLUSION: High serum PTH level may be associated with high incidence of ischemic stroke in women, possibly through the increased incidence of hypertension.
BACKGROUND: Neuroleptic malignant syndrome (NMS) is a dangerous complication in patients with Parkinson's disease (PD). AIMS: To evaluate the efficacy of methylprednisolone pulse therapy compared to placebo in PD patients with NMS. METHODS: In a double blind, placebo controlled study, 20 PD patients with NMS received steroid pulse therapy for three days, and 20 PD patients received placebo. Both groups received levodopa, bromocriptine, and dantrolene. RESULTS: NMS in the steroid group healed within 10 days in 17 patients; median value of duration of illness of NMS in this group was 7 days (range 4-20). NMS in the placebo group healed within 10 days in five patients; in the remaining 15, it persisted for 12-27 days after the onset of NMS; median value of duration illness of NMS in this group was 18 days. Hyperthermia, rigidity, and consciousness improved within 10 days in many patients in the steroid group; these signs persisted more than 10 days in many patients in the placebo group. CONCLUSIONS: Steroid pulse therapy is useful in NMS for reducing the illness duration and improving symptoms.
The magnetic structure of the localized-5f uranium intermetallic compound U3Pd20Si6 has been determined by means of a neutron diffraction experiment. Our data demonstrate that this compound has a collinear coupling of the sublattice ordering of the uranium spins on the 4a and 8c sites. We conclude that higher-order exchange and/or quadrupole interactions are necessary to stabilize this unique collinear structure. We discovered a new type of spin-flop transition against the uniaxial anisotropy induced by this collinear coupling.
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