174 research outputs found
Coulomb correlations intertwined with spin and orbital excitations in LaCoO
We carried out temperature-dependent (20 - 550 K) measurements of resonant
inelastic X-ray scattering on LaCoO to investigate the evolution of its
electronic structure across the spin-state crossover. In combination with
charge-transfer multiplet calculations, we accurately quantized the
renormalized crystal-field excitation energies and spin-state populations. We
show that the screening of the on-site Coulomb interaction of 3d electrons is
orbital selective and coupled to the spin-state crossover in LaCoO. The
results establish that the gradual spin-state crossover is associated with a
relative change of Coulomb energy versus bandwidth, leading to a Mott-type
insulator-to-metal transition.Comment: 6 pages, 4 figures. Submitted to Phys. Rev. Let
Neutron scattering study of role of partial disorder-type spin fluctuations in conductivity of frustrated conductor MnPt
The spin-frustrated conductor MnPt exhibits a characteristic magnetic
structure called partial disorder in which some spin sites can form magnetic
order through the generation of non-ordered sites that locally relieve the
frustration. Here we report the results of a single-crystal inelastic neutron
scattering study of this compound. The measured momentum correlations
of diffusive magnetic scattering reveal that the paramagnetic phase exhibits
short-range spin fluctuations with the same type of partial disorder. Its
relation to conductivity is also discussed.Comment: 5 pages, 4 figure
Emergence of magnetic long-range order in frustrated pyrochlore NdIrO with metal-insulator transition
In this study, we performed powder neutron diffraction and inelastic
scattering measurements of frustrated pyrochlore NdIrO, which
exhibits a metal-insulator transition at a temperature of 33 K.
The diffraction measurements revealed that the pyrochlore has an
antiferromagnetic long-range structure with propagation vector of
(0,0,0) and that it grows with decreasing temperature below 15 K. This
structure was analyzed to be of the all-in all-out type, consisting of highly
anisotropic Nd magnetic moments of magnitude ,
where is the Bohr magneton. The inelastic scattering measurements
revealed that the Kramers ground doublet of Nd splits below . This suggests the appearance of a static internal magnetic field at the
Nd sites, which probably originates from a magnetic order consisting of
Ir magnetic moments. Here, we discuss a magnetic structure model for the
Ir order and the relation of the order to the metal-insulator transition in
terms of frustration.Comment: 6 pages, 1 table, 3 figure
Distribution Behavior of Technetium to Liquid, Solid Phases and onto Metal Surfaces after Supercritical Water Treatment
Selenoprotein S (SEPS1) gene -105G>A promoter polymorphism influences the susceptibility to gastric cancer in the Japanese population
Null mutation for Macrophage Migration Inhibitory Factor (MIF) is associated with less aggressive bladder cancer in mice
<p>Abstract</p> <p>Background</p> <p>Inflammatory cytokines may promote tumorigenesis. Macrophage migration inhibitory factor (MIF) is a proinflammatory cytokine with regulatory properties over tumor suppressor proteins involved in bladder cancer. We studied the development of bladder cancer in wild type (WT) and MIF knockout (KO) mice given N-butyl-N-(4-hydroxybutyl)-nitrosamine (BBN), a known carcinogen, to determine the role of MIF in bladder cancer initiation and progression.</p> <p>Methods</p> <p>5-month old male C57Bl/6 MIF WT and KO mice were treated with and without BBN. Animals were sacrificed at intervals up to 23 weeks of treatment. Bladder tumor stage and grade were evaluated by H&E. Immunohistochemical (IHC) analysis was performed for MIF and platelet/endothelial cell adhesion molecule 1 (PECAM-1), a measure of vascularization. MIF mRNA was analyzed by quantitative real-time polymerase chain reaction.</p> <p>Results</p> <p>Poorly differentiated carcinoma developed in all BBN treated mice by week 20. MIF WT animals developed T2 disease, while KO animals developed only T1 disease. MIF IHC revealed predominantly urothelial cytoplasmic staining in the WT control animals and a shift toward nuclear staining in WT BBN treated animals. MIF mRNA levels were 3-fold higher in BBN treated animals relative to controls when invasive cancer was present. PECAM-1 staining revealed significantly more stromal vessels in the tumors in WT animals when compared to KOs.</p> <p>Conclusion</p> <p>Muscle invasive bladder cancer with increased stromal vascularity was associated with increased MIF mRNA levels and nuclear redistribution. Consistently lower stage tumors were seen in MIF KO compared to WT mice. These data suggest that MIF may play a role in the progression to invasive bladder cancer.</p
Magnetic Frustration Driven by Itinerancy in Spinel CoV2O4
Localized spins and itinerant electrons rarely coexist in geometrically-frustrated spinel lattices. They exhibit a complex interplay between localized spins and itinerant electrons. In this paper, we study the origin of the unusual spin structure of the spinel CoV2O4, which stands at the crossover from insulating to itinerant behavior using the first principle calculation and neutron diffraction measurement. In contrast to the expected paramagnetism, localized spins supported by enhanced exchange couplings are frustrated by the effects of delocalized electrons. This frustration produces a non-collinear spin state even without orbital orderings and may be responsible for macroscopic spin-glass behavior. Competing phases can be uncovered by external perturbations such as pressure or magnetic field, which enhances the frustration
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