7,754 research outputs found
Optical study of MgTiO: Evidence for an orbital-Peierls state
Dimension reduction due to the orbital ordering has recently been proposed to
explain the exotic charge, magnetic and structural transitions in some
three-dimensional (3D) transitional metal oxides. We present optical
measurement on a spinel compound MgTiO which undergoes a sharp
metal-insulator transition at 240 K, and show that the spectral change across
the transition can be well understood from the proposed picture of 1D Peierls
transition driven by the ordering of and orbitals. We further
elaborate that the orbital-driven instability picture applies also very well to
the optical data of another spinel CuIrS reported earlier.Comment: 5 pages, 6 figures, to be published in Phys. Rev.
A Primary Study of Heavy Baryons Lambda_Q, Xi_Q, Sigma_Q and Omega_Q
We perform a preliminary study of the 1/2+ and 3/2+ ground-state baryons
containing a heavy quark in the framework of the chiral SU(3) quark model. By
using the calculus of variations, masses of Lambda_Q, Sigma_Q, Xi_Q, Omega_Q,
Sigma_Q^*, Xi_Q^* and Omega_Q^*, where Q means c or b quark, are calculated.
With taking reasonable model parameters, the numerical results of established
heavy baryons are generally in agreement with the available experimental data,
except that those of Xi_Q are somewhat heavier. For Omega_b with undetermined
experimental mass and nobserved Xi_b^*, Omega_b^*, reasonable theoretical
predictions are obtained. Interactions inside baryons are also discussed.Comment: 5 page
A tunable coupling scheme for implementing high-fidelity two-qubit gates
The prospect of computational hardware with quantum advantage relies
critically on the quality of quantum gate operations. Imperfect two-qubit gates
is a major bottleneck for achieving scalable quantum information processors.
Here, we propose a generalizable and extensible scheme for a two-qubit coupler
switch that controls the qubit-qubit coupling by modulating the coupler
frequency. Two-qubit gate operations can be implemented by operating the
coupler in the dispersive regime, which is non-invasive to the qubit states. We
investigate the performance of the scheme by simulating a universal two-qubit
gate on a superconducting quantum circuit, and find that errors from known
parasitic effects are strongly suppressed. The scheme is compatible with
existing high-coherence hardware, thereby promising a higher gate fidelity with
current technologies
Global water cycle
The primary objective is to determine the scope and interactions of the global water cycle with all components of the Earth system and to understand how it stimulates and regulates changes on both global and regional scales. The following subject areas are covered: (1) water vapor variability; (2) multi-phase water analysis; (3) diabatic heating; (4) MSU (Microwave Sounding Unit) temperature analysis; (5) Optimal precipitation and streamflow analysis; (6) CCM (Community Climate Model) hydrological cycle; (7) CCM1 climate sensitivity to lower boundary forcing; and (8) mesoscale modeling of atmosphere/surface interaction
Accelerated Calvarial Healing in Mice Lacking Toll-Like Receptor 4
The bone and immune systems are closely interconnected. The immediate inflammatory response after fracture is known to trigger a healing cascade which plays an important role in bone repair. Toll-like receptor 4 (TLR4) is a member of a highly conserved receptor family and is a critical activator of the innate immune response after tissue injury. TLR4 signaling has been shown to regulate the systemic inflammatory response induced by exposed bone components during long-bone fracture. Here we tested the hypothesis that TLR4 activation affects the healing of calvarial defects. A 1.8 mm diameter calvarial defect was created in wild-type (WT) and TLR4 knockout (TLR4-/-) mice. Bone healing was tested using radiographic, histologic and gene expression analyses. Radiographic and histomorphometric analyses revealed that calvarial healing was accelerated in TLR4-/- mice. More bone was observed in TLR4-/- mice compared to WT mice at postoperative days 7 and 14, although comparable healing was achieved in both groups by day 21. Bone remodeling was detected in both groups on postoperative day 28. In TLR4-/- mice compared to WT mice, gene expression analysis revealed that higher expression levels of IL-1β, IL-6, TNF-α,TGF-β1, TGF-β3, PDGF and RANKL and lower expression level of RANK were detected at earlier time points (≤ postoperative 4 days); while higher expression levels of IL-1β and lower expression levels of VEGF, RANK, RANKL and OPG were detected at late time points (> postoperative 4 days). This study provides evidence of accelerated bone healing in TLR4-/- mice with earlier and higher expression of inflammatory cytokines and with increased osteoclastic activity. Further work is required to determine if this is due to inflammation driven by TLR4 activation. © 2012 Wang et al
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