2,159 research outputs found
Chalcogen-height dependent magnetic interactions and magnetic order switching in FeSeTe
Magnetic properties of iron chalcogenide superconducting materials are
investigated using density functional calculations. We find the stability of
magnetic phases is very sensitive to the height of chalcogen species from the
Fe plane: while FeTe with optimized Te height has the double-stripe-type
magnetic ordering, the single-stripe-type ordering
becomes the ground state phase when Te height is lowered below a critical value
by, e.g., Se doping. This behavior is understood by opposite Te-height
dependences of the superexchange interaction and a longer-range magnetic
interaction mediated by itinerant electrons. We also demonstrate a linear
temperature dependence of the macroscopic magnetic susceptibility in the
single-stripe phase in contrast to a constant behavior in the double-stripe
phase. Our findings provide a comprehensive and unified view to understand the
magnetism in FeSeTe and iron pnictide superconductors.Comment: 4 pages, 4 figure
Enhanced spin density wave in LaOFeSb
We predict atomic, electronic, and magnetic structures of a hypothetical
compound LaOFeSb by first-principles density-functional calculations. It is
shown that LaOFeSb prefers a stripe-type antiferromagnetic phase (i.e., spin
density wave (SDW) phase) to the non-magnetic (NM) phase, with a larger Fe spin
moment and greater SDW-NM energy difference than those of LaOFeAs. The SDW
phase is found to favor the orthorhombic structure while the tetragonal
structure is more stable in the NM phase. In the NM-phase LaOFeSb, the
electronic bandwidth near the Fermi energy is reduced compared with LaOFeAs,
indicating smaller orbital overlap between Fe states and subsequently
enhanced intra-atomic exchange coupling. The calculated Fermi surface in the NM
phase consists of three hole and two electron sheets, and shows increased
nesting between two hole and two electron sheets compared with LaOFeAs.
Monotonous changes found in our calculated material properties of LaOFePn
(Pn=P, As, and Sb), along with reported superconducting properties of doped
LaOFeP and LaOFeAs, suggest that doped LaOFeSb may have a higher
superconducting transition temperature.Comment: 5 pages with 3 figures and 1 table, double colum
Low-velocity anisotropic Dirac fermions on the side surface of topological insulators
We report anisotropic Dirac-cone surface bands on a side-surface geometry of
the topological insulator BiSe revealed by first-principles
density-functional calculations. We find that the electron velocity in the
side-surface Dirac cone is anisotropically reduced from that in the
(111)-surface Dirac cone, and the velocity is not in parallel with the wave
vector {\bf k} except for {\bf k} in high-symmetry directions. The size of the
electron spin depends on the direction of {\bf k} due to anisotropic variation
of the noncollinearity of the electron state. Low-energy effective Hamiltonian
is proposed for side-surface Dirac fermions, and its implications are presented
including refractive transport phenomena occurring at the edges of tological
insulators where different surfaces meet.Comment: 4 pages, 2 columns, 4 figure
Skin care benefits of bioactive compounds isolated from Zanthoxylum piperitum DC. (Rutaceae)
Purpose: To investigate skin care efficacies of Zanthoxylum pipetitum extract and isolated compounds.
Methods: Ethanol extracts of leaves, branches and fruits of what were partitioned into n-hexane, chloroform, ethyl acetate, n-butanol and aqueous layers and some fractions were further analyzed to isolate five compounds. The isolated compounds were identified based on the proton and carbon nuclear magnetic resonance (NMR) spectra. Cosmetic efficacy tests of the extracts and isolated compounds were evaluated by in vitro tests.
Results: Phytochemical studies of the chloroform and ethyl acetate layers led to the isolation of five compounds; quercitrin (1), afzelin (2), hydroxy-α-sanshool (3), α-sanshool (4) and hyperoside (5). In activity tests, the extracts showed inhibitory activity against inflammation response and melanin synthesis, and induction of procollagen type I C-peptide (PIP). Among the isolated compounds, hydroxy-α-sanshool (3) and α-sanshool (4) displayed significant anti-inflammatory activity.
Conclusion: The results demonstrate that Z. piperitum extract and its active compounds possess a significant potential as a cosmeeutical agent for enhancing skin quality
Imbalanced loss-integrated deep-learning-based ultrasound image analysis for diagnosis of rotator-cuff tear
A rotator cuff tear (RCT) is an injury in adults that causes difficulty in moving, weakness, and pain. Only limited diagnostic tools such as magnetic resonance imaging (MRI) and ultrasound Imaging (UI) systems can be utilized for an RCT diagnosis. Although UI offers comparable performance at a lower cost to other diagnostic instruments such as MRI, speckle noise can occur the degradation of the image resolution. Conventional vision-based algorithms exhibit inferior performance for the segmentation of diseased regions in UI. In order to achieve a better segmentation for diseased regions in UI, deep-learning-based diagnostic algorithms have been developed. However, it has not yet reached an acceptable level of performance for application in orthopedic surgeries. In this study, we developed a novel end-to-end fully convolutional neural network, denoted as Segmentation Model Adopting a pRe-trained Classification Architecture (SMART-CA), with a novel integrated on positive loss function (IPLF) to accurately diagnose the locations of RCT during an orthopedic examination using UI. Using the pre-trained network, SMART-CA can extract remarkably distinct features that cannot be extracted with a normal encoder. Therefore, it can improve the accuracy of segmentation. In addition, unlike other conventional loss functions, which are not suited for the optimization of deep learning models with an imbalanced dataset such as the RCT dataset, IPLF can efficiently optimize the SMART-CA. Experimental results have shown that SMART-CA offers an improved precision, recall, and dice coefficient of 0.604% (+38.4%), 0.942% (+14.0%) and 0.736% (+38.6%) respectively. The RCT segmentation from a normal ultrasound image offers the improved precision, recall, and dice coefficient of 0.337% (+22.5%), 0.860% (+15.8%) and 0.484% (+28.5%), respectively, in the RCT segmentation from an ultrasound image with severe speckle noise. The experimental results demonstrated the IPLF outperforms other conventional loss functions, and the proposed SMART-CA optimized with the IPLF showed better performance than other state-of-the-art networks for the RCT segmentation with high robustness to speckle noise. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.1
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