Publications by authors named "Kazuki Iida"

The triangular lattice antiferromagnet (TLAF) has been the standard paradigm of frustrated magnetism for several decades. The most common magnetic ordering in insulating TLAFs is the 120° structure. However, a new triple-Q chiral ordering can emerge in metallic TLAFs, representing the short wavelength limit of magnetic skyrmion crystals.

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A large body of knowledge about magnetism is attained from models of interacting spins, which usually reside on magnetic ions. Proposals beyond the ionic picture are uncommon and seldom verified by direct observations in conjunction with microscopic theory. Here, using inelastic neutron scattering to study the itinerant near-ferromagnet MnSi, we find that the system's fundamental magnetic units are interconnected, extended molecular orbitals consisting of three Mn atoms each rather than individual Mn atoms.

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Spin excitation of an ilmenite FeTiO powder sample is measured by time-of-flight inelastic neutron scattering. The dynamic magnetic pair-density function D(r, E) is obtained from the dynamic magnetic structure factor S(Q, E) by the Fourier transformation. The real space spin dynamics exhibit magnon mode transitions in the spin-spin correlation with increasing energy from no-phase-shift to π-phase-shift.

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Na_{2}Co_{2}TeO_{6} is a proposed approximate Kitaev magnet, yet its actual magnetic interactions are elusive due to a lack of knowledge on the full excitation spectrum. Here, using inelastic neutron scattering and single crystals, we determine the system's temperature-dependent magnetic excitations over the entire Brillouin zone. Without committing to specific models, we unveil a distinct signature of the third-nearest-neighbor coupling in the spin waves, which signifies the associated distance as an emerging effective link in the ordered state.

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Introducing magnetic order into a topological insulator (TI) system has attracted much attention with an expectation of realizing exotic phenomena such as the quantum anomalous Hall effect (QAHE) and axion insulator states. The magnetic proximity effect (MPE) is one of the promising schemes to induce the magnetic order on the surface of a TI without introducing disorder accompanied by doping magnetic impurities in the TI. In this study, we investigate the MPE at the interface of a heterostructure consisting of the topological crystalline insulator (TCI) SnTe and Fe by employing polarized neutron reflectometry.

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Although the treatment of municipal wastewater using microbial fuel cells (MFCs) has been extensively studied, scaling the systems up for practical use remains challenging. In this study, a 226 L sewage treatment reactor was equipped with 27 MFC units, and its chemical oxygen demand (COD) removal and electricity production were evaluated. The MFC units were tubular air cores with a diameter of 5 cm and length of 100 cm, which were wrapped with a carbon-based cathode, anion exchange membrane (AEM), and nonwoven graphite fabric.

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Magnetic superconductors are specific materials exhibiting two antagonistic phenomena, superconductivity and magnetism, whose mutual interaction induces various emergent phenomena, such as the reentrant superconducting transition associated with the suppression of superconductivity around the magnetic transition temperature ( ), highlighting the impact of magnetism on superconductivity. In this study, we report the experimental observation of the ferromagnetic order induced by superconducting vortices in the high-critical-temperature (high- ) magnetic superconductor EuRbFeAs Although the ground state of the Eu moments in EuRbFeAs is helimagnetism below , neutron diffraction and magnetization experiments show a ferromagnetic hysteresis of the Eu spin alignment. We demonstrate that the direction of the Eu moments is dominated by the distribution of pinned vortices based on the critical state model.

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The development of shape-controlled noble metal nanocrystals such as nanowires (NWs) is progressing steadily owing to their potentially novel catalytic properties and the ease with which they can be prepared by reducing the metal ions in a particular solution as capping agents. Recently, many reports have been presented on the preparation of shape-controlled Au nanocrystals, such as nanostars and nanoflowers, by a one-pot method using 2-[4-(2-hydroxyethyl)-1-piperazinyl] ethanesulfonic acid (HEPES) as capping and reducing agents. The catalytic activity is depressed due to the adsorption of the capping agent onto a Au surface.

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Novel effects induced by nonmagnetic impurities in frustrated magnets and quantum spin liquid represent a highly nontrivial and interesting problem. A theoretical proposal of extended modulated spin structures induced by doping of such magnets, distinct from the well-known skyrmions has attracted significant interest. Here, we demonstrate that nonmagnetic impurities can produce such extended spin structures in h-YMnO, a triangular antiferromagnet with noncollinear magnetic order.

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The oxidation of a carbon anode has been reported to enhance electricity recovery in a microbial fuel cell (MFC). This study investigates the applicability of electrochemically oxidized graphite felt (EOGF) as the anode for the recovery of electricity from sewage wastewater when polarized at 0.2 V during MFC operation.

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With spin-orbit coupling, both local-moment magnetism and itinerant electrons are expected to behave anisotropically in spin space, but such effects' influence on the formation of unconventional superconductivity has been hitherto unexplored. Here, in an iron-based superconductor, Sr_{1-x}Na_{x}Fe_{2}As_{2}, we report spectroscopic evidence that itinerant electrons "prefer" to be assisted by c-axis polarized magnetic excitations in their formation of superconducting Cooper pairs, against the polarization of the local-moment excitations. Our result naturally explains why the superconductivity competes strongly with the tetragonal magnetic phase in this material, and provides a fresh view on how to make a good superconductor out of a magnetic "Hund's metal.

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Molecular based spin-1/2 triangular lattice systems such as LiZnMoO have attracted research interest. Distortions, defects, and intersite disorder are suppressed in such molecular-based magnets, and intrinsic geometrical frustration gives rise to unconventional and unexpected ground states. LiAMoO (A = In or Sc) is such a compound where spin-1/2 MoO clusters in place of Mo ions form the uniform triangular lattice.

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The central nervous system in adult mammals does not heal spontaneously after spinal cord injury (SCI). However, SCI treatment has been improved recently following the development of cell transplantation therapy. We recently reported that fibroblast growth factor (FGF) 2-pretreated human dental pulp cells (hDPCs) can improve recovery in a rat model of SCI.

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Despite the development of new drugs for multiple myeloma (MM), the prognosis of MM patients with high-risk cytogenetic abnormalities such as t (4; 14) and del17p remains poor. We reported that a novel phenylphthalimide derivative, TC11, induced apoptosis of MM cells in vitro and in vivo, and TC11 directly bound to α-tubulin and nucleophosmin-1 (NPM1). However, TC11 showed low water solubility and poor pharmacokinetic properties.

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Graphene oxide (GO) has recently been shown to be an excellent anode substrate for exoelectrogens. This study demonstrates the applicability of GO in recovering electricity from sewage wastewater. Anaerobic incubation of sludge with GO formed a hydrogel complex that embeds microbial cells via π-π stacking of microbially reduced GO.

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Since the discovery of spin glasses in dilute magnetic systems, their study has been largely focused on understanding randomness and defects as the driving mechanism. The same paradigm has also been applied to explain glassy states found in dense frustrated systems. Recently, however, it has been theoretically suggested that different mechanisms, such as quantum fluctuations and topological features, may induce glassy states in defect-free spin systems, far from the conventional dilute limit.

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Dental pulp cells (DPCs) of various species have been studied for their potentials of differentiation into functional neurons and secretion of neurotrophic factors. In canine, DPCs have only been studied for cell surface markers and differentiation, but there is little direct evidence for therapeutic potentials for neurological disorders. The present study aimed to further characterize canine DPCs (cDPCs), particularly focusing on their neuroregenerative potentials.

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The purpose of this study was to clarify the effect of Chinese propolis on the expression level of neurotrophic factors in dental pulp cells (DPCs). We also investigated that the effects of the conditioned medium (CM) of DPCs stimulated by the propolis against oxidative and endoplasmic reticulum (ER) stresses in human neuroblastoma SH-SY5Y cells, and on neurite extensions in rat adrenal pheochromocytoma PC12 cells. To investigate the effect of the propolis on the levels of neurotrophic factors in DPCs, we performed a qRT-PCR experiment.

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Human dental pulp cells (hDPCs) are a promising resource for regenerative medicine and tissue engineering and can be used for derivation of induced pluripotent stem cells (iPSCs). However, current protocols use reagents of animal origin (mainly fetal bovine serum, FBS) that carry the potential risk of infectious diseases and unwanted immunogenicity. Here, we report a chemically defined protocol to isolate and maintain the growth and differentiation potential of hDPCs.

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The reprogramming of somatic cells into induced pluripotent stem cells (iPSCs) by defined transcription factors has been a well-established technique and will provide an invaluable resource for regenerative medicine. However, the low reprogramming efficiency of human iPSC is still a limitation for clinical application. Here we showed that the reprogramming potential of human dental pulp cells (DPCs) obtained from immature teeth is much higher than those of mature teeth DPCs.

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Nylon hydrolase degrades various aliphatic nylons, including nylon-6 and nylon-66. We synthesized a nylon-66 copolymer (M w = 22,900, M n = 7,400), in which a part of an adipoyl unit (32 % molar ratio) of nylon-66 was replaced with a succinyl unit by interfacial polymerization. To quantify the reaction rate of the enzymatic hydrolysis of nylons at the surface of solid polymers, we prepared a thin layer of nylons on the bottom surface of each well in a polystyrene-based micro-assay plate.

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Lifestyle, particularly smoking and alcohol consumption, may induce and/or inhibit drug metabolism. In order to reveal the effects of smoking and alcohol consumption on the 5-fluorouracil (5-FU)-related metabolic enzymes, namely thymidylate synthase, dihydropyrimidine dehydrogenase (DPD; a sole catabolic enzyme of 5-FU), orotate phosphoribosyl transferase (OPRT) and thymidine phosphorylase, in oral squamous cell carcinomas, the mRNA expression of these enzymes was investigated in 29 surgical specimens and compared by the Brinkman index and drinking years. The surgical specimens were divided into normal and tumor regions and were independently analyzed using quantitative reverse transcription-polymerase chain reaction.

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A virtually salt-free and straightforward bimolecular assembly giving N-unsubstituted pyrroles through fully unmasked α-amino aldehydes, which was enabled by the dual effects of a catalytic ruthenium complex and an alkali metal base, is reported. Either solvent-free or acceptorless dehydrogenation facilitates high atom, step, and pot economy, which are otherwise difficult to achieve in multistep operations involving protection/deprotection.

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