Publications by authors named "Kazuyuki Sakamoto"

Article Synopsis
  • π-Conjugated molecules are key for future molecular nanoelectronics, but creating them on surfaces is challenging.
  • Researchers synthesized [18]-polyene-linked Zn-porphyrin cooligomers using a two-step reaction on copper surfaces, where alkyl groups were transformed into alkenyl groups, leading to extended cooligomers.
  • The resulting structures were analyzed with advanced microscopy and spectroscopy, showing that the [18]-polyene linkers exhibit metallic properties, potentially aiding in constructing advanced nanocarbon structures.
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  • The photoelectron momentum microscope (PMM) at BL6U creates a new method for μm-scale momentum-resolved photoelectron spectroscopy, significantly reducing radiation damage by projecting photoelectron data onto a 2D detector.
  • This technique enables detailed 3D measurements of valence band structures and can analyze variations based on factors like photon energy, polarization, detection position, and temperature.
  • The study showcases examples, including band structure visualization of Ir thin films, detailed measurements of Au(111) surface states, and the effects of temperature on valence band dispersion in 1T-TaS2, while comparing the benefits of different PMMs for these applications.
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  • The study examines how the combination of spin-orbit coupling and crystal symmetry in thin materials can create unique spin-polarized bands, which could result in new physical properties.
  • Specifically, it discusses bilayer materials where breaking inversion symmetry can lead to oppositely polarized spins in different layers.
  • The research demonstrates that growing a Tl bilayer on Ag(111) with lattice mismatch reveals hidden spins and creates a new phenomenon of band splitting in both spin and space, achieved by carefully tuning the interface interaction strength.
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Objectives: Muscarinic M (M ) receptors mediate cholinergic smooth muscle contraction of the bladder. Current drugs targeting bladder M receptors for micturition disorders have a risk of cholinergic side effects due to excessive receptor activation and insufficient selectivity. We investigated the effect of ASP8302, a novel positive allosteric modulator (PAM) of M receptors, on bladder function in rats.

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Muscarinic M (M) receptors mediate a wide range of acetylcholine (ACh)-induced functions, including visceral smooth-muscle contraction and glandular secretion. Positive allosteric modulators (PAMs) can avoid various side effects of muscarinic agonists with their spatiotemporal receptor activation control and potentially better subtype selectivity. However, the mechanism of allosteric modulation of M receptors is not fully understood, presumably because of the lack of a potent and selective PAM.

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Spatially controlling the Fermi level of topological insulators and keeping their electronic states stable are indispensable processes to put this material into practical use for semiconductor spintronics devices. So far, however, such a method has not been established yet. Here we show a novel method for doping a hole into n-type topological insulators BiX (X= Se, Te) that overcomes the shortcomings of the previous reported methods.

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  • A new O/H2O2 mixed gas sterilization method was tested for its effectiveness in eliminating microorganisms and inactivating bacterial endotoxin at low temperatures, showing a significant over 6-log reduction in the bacteria Geobacillus stearothermophilus.
  • This method demonstrated a notable reduction in endotoxin activity, with a decrease to 0.29 EU/device on medical tools, compared to much higher levels detected after traditional sterilization methods.
  • The results suggest that O/H2O2 mixed gas sterilization is safer and more effective than conventional methods, potentially enhancing the safety of reusable medical devices in regenerative medicine.
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  • The study focuses on spin-momentum locking in materials without inversion symmetry, highlighting its importance in distinguishing between Rashba-type and Zeeman-type spin-orbit coupling (SOC) effects on superconductivity.
  • Evidence is presented for Rashba-type SOC in crystalline atomic-layer superconductors, which shows an unusually large increase in the upper critical magnetic field, approximately three times the conventional limit.
  • The findings indicate that dynamic spin-momentum locking significantly reduces the influence of conditions that typically break Cooper pairs, offering new insights into how superconductivity can persist under strong magnetic fields.
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The electrons in 2D systems with broken inversion symmetry are spin-polarized due to spin-orbit coupling and provide perfect targets for observing exotic spin-related fundamental phenomena. We observe a Fermi surface with a novel spin texture in the 2D metallic system formed by indium double layers on Si(111) and find that the primary origin of the spin-polarized electronic states of this system is the orbital angular momentum and not the so-called Rashba effect. The present results deepen the understanding of the physics arising from spin-orbit coupling in atomic-layered materials with consequences for spintronic devices and the physics of the superconducting state.

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  • Understanding charge mobility in organic materials is crucial for developing advanced organic semiconductor devices.
  • Previous research on rubrene single crystals has suggested a band-like carrier transport mechanism, but there are inconsistencies in the findings.
  • The study reveals that the actual electronic band dispersion is narrower than reported, indicating that molecular vibrations may play a significant role in hole mobility, thus suggesting a more complex approach to improving organic semiconductors.
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Bladder dysfunctions associated with benign prostatic hyperplasia are not sufficiently alleviated by current pharmacotherapies. Lysophosphatidic acid (LPA) is a phospholipid with diverse biological effects. LPA modulates prostate and urethral contraction via the type 1 LPA (LPA) receptor, suggesting the potential of the LPA receptor as a therapeutic target.

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Article Synopsis
  • Current treatments for voiding dysfunctions are lacking, prompting research into lysophosphatidic acid (LPA) and its role in urethral contraction during urine voiding.
  • The study examined the effects of ASP6432, a new LPA antagonist, and tamsulosin on urethral pressure during both filling and voiding phases in rats.
  • Results indicated that ASP6432 significantly reduced urethral pressure and improved voiding dysfunction caused by a nitric oxide synthase inhibitor, while tamsulosin showed no effect, suggesting ASP6432's potential in treating lower urinary tract diseases.
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Current pharmacotherapies for lower urinary tract symptoms associated with benign prostate hyperplasia (LUTS/BPH) are in need of improvement. Lysophosphatidic acid (LPA) is a phospholipid with various biologic functions. However, its exact role in the lower urinary tract and its target receptor subtype have not been fully elucidated.

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Self-assembled organic molecules can potentially be an excellent source of charge and spin for two-dimensional (2D) atomic-layer superconductors. Here we investigate 2D heterostructures based on In atomic layers epitaxially grown on Si and highly ordered metal-phthalocyanine (MPc, M = Mn, Cu) through a variety of techniques: scanning tunneling microscopy, electron transport measurements, angle-resolved photoemission spectroscopy, X-ray magnetic circular dichroism, and ab initio calculations. We demonstrate that the superconducting transition temperature (T) of the heterostructures can be modified in a controllable manner.

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A totally anisotropic peculiar Rashba-Bychkov (RB) splitting of electronic bands was found on the Tl/Si(110)-(1×1) surface with C_{1h} symmetry by angle- and spin-resolved photoelectron spectroscopy and first-principles theoretical calculation. The constant energy contour of the upper branch of the RB split band has a warped elliptical shape centered at a k point located between Γ[over ¯] and the edge of the surface Brillouin zone, i.e.

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Scanning tunneling microscopy (STM) observation reveals that a cyclic thiazyl diradical, BDTDA (= 4,4'-bis(1,2,3,5-dithiadiazolyl)), forms a well-ordered monolayer honeycomb lattice consisting of paramagnetic corners with unpaired electrons on a clean Cu(111) surface. This BDTDA lattice is commensurate with the triangular lattice of Cu(111), with the former being 3 × 3 larger than the latter. The formation of the BDTDA monolayer structure, which is significantly different from its bulk form, is attributed to an interaction with the metal surface as well as the intermolecular assembling forces.

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Article Synopsis
  • - The study explores the relationship between the surface state of a Z(2) topological insulator and the bulk electronic structure, particularly focusing on Sb(2)Te(3)(0001) using photoemission experiments and calculations.
  • - The topological surface state (TSS) exhibits distinct features, such as a consistent spectral signature and linear dispersion, even as it interacts with the topmost valence band.
  • - Observations reveal a "kink" in the TSS dispersion and hybridization gaps, providing insight into the weak surface-bulk mixing seen in recent transport experiments on Sb(2)Te(3).
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  • The study explores the electronic structure of the Tl/Si(111) surface using both experimental methods and theoretical calculations.
  • It identifies a unique spin-orbit-split surface state, where the spin polarization direction changes as you move through the surface's symmetry points.
  • A significant energy splitting of about 0.6 eV is noted, due to the localization of the unoccupied surface state near heavy Tl atoms, leading to out-of-plane spin-polarized valleys that help reduce backscattering.
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  • The addition of valley degrees of freedom to spin-polarized electronic systems can enhance the functionality of next-gen devices, but challenges in valley polarization have hindered progress.
  • This research demonstrates a method to achieve 100% spin-polarized valleys using the Rashba effect in a system with C3 symmetry, significantly improving polarization compared to typical Rashba systems.
  • The findings suggest that this new system, built on a silicon substrate, could lead to more efficient silicon-based spintronic devices by reducing spin-charge backscattering.
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  • This text discusses the effects of 2-aminoethoxydiphenylborate (2-APB) on smooth muscle contractility, focusing on its role as a modulator of intracellular signaling for Ca(2+) sensitization.
  • The study finds that while 2-APB has minimal impact on contractions induced solely by calcium, it significantly reduces the heightened contractions triggered by carbachol-induced sensitization.
  • It concludes that the inhibitory effects of 2-APB on smooth muscle contractions are primarily linked to the rho kinase pathway, highlighting a new area of research for this compound.
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Article Synopsis
  • The research focuses on creating low-dimensional molecular structures, particularly one-dimensional (1D) structures, which are crucial for enhancing the performance of electronic and magnetic devices.
  • Traditionally, these structures have been created using slow and complex methods that are not suitable for large-scale production.
  • The study reveals a method to self-assemble ordered cobalt-phthalocyanine chains on a metal surface using fractional atomic steps, allowing for effective charge and spin transport via both the molecules and the surface electrons.
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Surface and bulk structural changes of LiNi(0.5)Mn(0.5)O(2) were investigated during electrochemical reaction using synchrotron X-ray scattering and a restricted reaction plane consisting of two-dimensional epitaxial-film electrodes.

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  • A unique form of the Rashba effect occurs at a specific point in the Brillouin zone where time-reversal symmetry is disrupted, challenging the previous understanding that this symmetry is essential for Rashba splitting.
  • Experimental results from photoemission studies on a Bi/Si(111)-(√3 x √3) surface back this claim and align with theoretical predictions based on first-principles calculations.
  • The unusual Rashba effect can be explained by the two-dimensional characteristics of the surface and results in a nontraditional spin structure at a location maintaining time-reversal invariance.
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The polarization vector of the Rashba spin, which must be parallel to the two-dimensional (2D) plane in an ideal system, is found to change abruptly and definitely to the direction perpendicular to the surface at the K point of the Brillouin zone of a real hexagonal system, the Tl/Si(111)-(1x1) surface. This finding obtained experimentally by angle-resolved and spin-resolved photoemission measurements is fully confirmed by a first-principles theoretical calculation. We found that the abrupt rotation of the Rashba spin is simply understood by the 2D symmetry of the hexagonal structure.

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We report the energy dispersions of the highest occupied molecular orbitals (HOMO)-derived bands of a pentacene (Pn) thin film, whose in-plane structure resembles closely that of the ab plane of a low-density bulk Pn phase. Our present photoemission result indicates that the overlap of the pi-orbitals of adjacent Pn molecules is larger than what was expected from theoretical calculations. Further, of the two HOMO-derived bands, the large dispersion width of the band with higher binding energy suggests that this one mainly contributes to the bandlike charge transport in a Pn crystal.

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