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Multiferroics have received a great deal of attention because of their fascinating physics of order-parameter cross-couplings and their potential for enabling new device paradigms. Considering the rareness of multiferroic materials, we have been exploring the possibility of artificially imposing ferroelectricity by structurally tailoring antiferromagnets in thin-film forms. YbFeO(3) (YbFO hereafter), a family of centrosymmetric rare-earth orthoferrites, is known to be nonferroelectric (space group Pnma). Here we report that a YbFO thin-film heterostructure fabricated by adopting a hexagonal template surprisingly exhibits nonferroelastic ferroelectricity with the Curie temperature of 470 K. The observed ferroelectricity is further characterized by an extraordinary two-step polarization decay, accompanied by a pronounced magnetocapacitance effect near the lower decay temperature, ~225 K. According to first-principles calculations, the hexagonal P6(3)/mmc-P6(3)mc-P6(3)cm consecutive transitions are primarily responsible for the observed two-step polarization decay, and the ferroelectricity originates from the c-axis-oriented asymmetric Yb 5d(z(2))-O 2p(z) orbital hybridization. Temperature-dependent magnetization curves further reveal an interesting phenomenon of spontaneous magnetization reversal at 83 K, which is attributed to the competition between two distinct magnetocrystalline anisotropy terms, Fe 3d and Yb 4f moments.

(1) To compare the serum levels of Dickkopf-1 (DKK-1) and bone biomarkers in patients with ankylosing spondylitis (AS) and healthy controls. (2) To examine the effects of anti-tumor necrosis factor-α (TNF-α) therapy for 3 months on bone biomarkers in patients with AS. We measured the levels of DKK-1, osteocalcin, osteoprotegerin, and C-terminal telopeptide of type I collagen (CTX-1) in patients with AS and in healthy controls at baseline and 3 months after initiating anti-TNF-α therapy in AS patients. Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) scores were also measured before and after anti-TNF-α therapy in AS patients. Serum levels of DKK-1 were significantly lower in the AS patients than in the controls (P < 0.0001). Osteocalcin and osteoprotegerin levels were significantly higher in the AS patients than in the controls (P < 0.0001). Serum levels of DKK-1 were not changed after the 3-month anti-TNF-α therapy. Osteocalcin level increased (P < 0.0001), osteoprotegerin level and BASDAI scores decreased (P = 0.025 and P < 0.0001, respectively) significantly after the 3-months anti-TNF-α therapy. Serum DKK-1 level was lower in patients with AS than in healthy controls and did not change after 3 months of anti-TNF-α therapy in the AS patients despite the marked improvement in BASDAI scores. These findings suggest the low serum DKK-1 level is related to the pathogenesis of new bone formation in AS, which is resistant to TNF-α blocking therapy.

Abstract:The construction of Pohang Accelerator Laboratory X-ray Free-Electron Laser (PAL-XFEL), a 0

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