Publications by authors named "Takahisa Koyama"

A high-flux sub-micrometre focusing system was constructed using multilayer focusing mirrors in Kirkpatrick-Baez geometry for 100 keV X-rays. The focusing mirror system had a wide bandwidth of 5% and a high peak reflectivity of 74%. Performance was evaluated at the undulator beamline BL05XU of SPring-8, which produced an intense 100 keV X-ray beam with a bandwidth of 1%.

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Understanding the pressure-induced structural changes in liquids and amorphous materials is fundamental in a wide range of scientific fields. However, experimental investigation of the structure of liquid and amorphous material under in situ high-pressure conditions is still limited due to the experimental difficulties. In particular, the range of the momentum transfer (Q) in the structure factor [S(Q)] measurement under high-pressure conditions has been limited at relatively low Q, which makes it difficult to conduct detailed structural analysis of liquid and amorphous material.

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While polymorphism is prevalent in crystalline solids, polyamorphism draws increasing interest in various types of amorphous solids. Recent studies suggested that supercooling of liquid phase-change materials (PCMs) induces Peierls-like distortions in their local structures, underlying their liquid-liquid transitions before vitrification. However, the mechanism of how the vitrified phases undergo a possible polyamorphic transition remains elusive.

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  • The BL09XU beamline at SPring-8 has been revamped for specialized hard X-ray photoelectron spectroscopy (HAXPES) with improved optical instruments.
  • It now features two HAXPES analyzers and dual crystal monochromators (Si(220) and (311)) to enable detailed resonant analyses with excellent energy resolution (under 300 meV) across a wide energy spectrum (4.9-12 keV).
  • Additionally, a diamond crystal-based X-ray phase retarder has been added to fine-tune polarization, achieving high polarization (over 0.9) within the 5.9-9.5 keV range, coupled with focusing mirrors in the analyzers for
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  • Advances in X-ray free-electron lasers (XFELs) have enhanced coherent diffractive imaging (CDI), enabling single-particle imaging (SPI) of non-crystalline objects without needing cryogenic conditions.
  • The new CDI technique achieves high resolution using multilayer mirrors to focus X-rays, increasing spatial resolution to 2 nanometers and fluence to over 3 × 10^10 J/cm².
  • This improved capability allows for better exploration of the structure and function of biomolecular complexes, potentially revolutionizing our understanding of dynamic biological processes.
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  • This study focuses on the development of advanced double-multilayer monochromators that produce high-energy pink X-ray beams for improved imaging applications at the SPring-8 facility.
  • The new design utilizes pairs of W/BC multilayer mirrors to achieve significant bandwidth increases and high photon energies, surpassing traditional Si double-crystal monochromators.
  • Results show a substantial increase in photon flux, enabling quicker and more detailed X-ray imaging of large objects like fossils and electronic devices.
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  • Researchers have identified bimodal behavior in the arrangement of silicon's second shell in SiO glass under pressure, which aligns with theoretical studies on SiO liquid at high temperatures.
  • At low pressures, SiO glass maintains a tetrahedral structure with clear separation between the first and second silicon shells, similar to the structure in SiO liquid.
  • However, at high pressures, the second shell collapses into the first shell, leading to a disruption of the local tetrahedral symmetry observed in both SiO glass and liquid.
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  • - The study focuses on enhancing the focusing capabilities of X-ray free-electron lasers (XFEL) to achieve ultrahigh-intensity X-ray pulses, particularly aiming for sub-10 nm focusing, which has been challenging due to stability issues in the light source.
  • - Researchers used a combination of reflective Kirkpatrick-Baez (KB) mirrors and speckle interferometry to analyze and optimize the alignment of the XFEL beam, allowing for precise control of the focused beam profile.
  • - As a result of this optimization, they successfully generated a focused X-ray beam with a diameter of 5.8 nm and demonstrated that this method could potentially achieve a remarkable intensity of 10 W/cm² with XFEL sources.
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Chlamydomonas reinhardtii is a well-established microalgal model species with a shorter doubling time, which is a promising natural source for the efficient production of high-value carotenoids. In the microalgal carotenoid biosynthetic pathway, lycopene is converted either into β-carotene by lycopene β-cyclase or into α-carotene by lycopene ε-cyclase (LCYE) and lycopene β-cyclase. In this study, we overexpressed the LCYE gene in C.

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  • - A new focusing optics system is introduced that can generate a probe with sub-micrometre precision for soft X-ray angle-resolved photoemission spectroscopy (ARPES).
  • - The design includes a monolithic Wolter-type mirror featuring large acceptance, achromatism, and minimized comatic aberration, achieving a focused beam size of 0.4 µm (vertical) by 4 µm (horizontal).
  • - With a photon energy of 1000 eV, the system demonstrated a high throughput of 59% and maintained a tolerance of 1.6 mrad for pitching errors, making it suitable for stable ARPES applications.
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Cross-linking of antigen-specific IgE bound to the high-affinity IgE receptor (FcεRI) on the surface of mast cells with multivalent antigens results in the release of mediators and development of type 2 inflammation. FcεRI expression and IgE synthesis are, therefore, critical for type 2 inflammatory disease development. In an attempt to clarify the relationship between eosinophilic chronic rhinosinusitis (ECRS) and mast cell infiltration, we analyzed mast cell infiltration at lesion sites and determined its clinical significance.

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Background: Type 2 chronic rhinosinusitis (CRS), especially eosinophilic CRS (ECRS), is an intractable upper airway inflammatory disease. Establishment of serum biomarkers reflecting the pathophysiology of CRS is desirable in a clinical setting. As IgG4 production is regulated by type 2 cytokines, we sought to determine whether serum IgG4 levels can be used as a biomarker for CRS.

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Intense sub-micrometre focusing of a soft X-ray free-electron laser (FEL) was achieved by using an ellipsoidal mirror with a high numerical aperture. A hybrid focusing system in combination with a Kirkpatrick-Baez mirror was applied for compensation of a small spatial acceptance of the ellipsoidal mirror. With this system, the soft X-ray FEL pulses were focused down to 480 nm × 680 nm with an extremely high intensity of 8.

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Here a direct comparison is made between various X-ray wavefront sensing methods with application to optics alignment and focus characterization at X-ray free-electron lasers (XFELs). Focus optimization at XFEL beamlines presents unique challenges due to high peak powers as well as beam pointing instability, meaning that techniques capable of single-shot measurement and that probe the wavefront at an out-of-focus location are desirable. The techniques chosen for the comparison include single-phase-grating Talbot interferometry (shearing interferometry), dual-grating Talbot interferometry (moiré deflectometry) and speckle tracking.

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The surface contamination of reflective X-ray optics has long been a serious problem that degrades beam quality. We evaluated the total organic content at the surface by gas chromatography to clarify the source of contamination. We found that various materials that can become contamination sources are used around the optical elements.

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In this report, we analyse X-ray induced damage of BC-coated bilayer materials under various irradiation geometries, following the conditions of our experiment performed at the free-electron-laser facility SACLA. We start with the discussion of structural damage in solids and damage threshold doses for the experimental system components: BC, SiC, Mo and Si. Later, we analyze the irradiation of the experimentally tested coated bilayer systems under two different incidence conditions of a linearly polarized X-ray pulse: (i) grazing incidence, and (ii) normal incidence, in order to compare quantitatively the effect of the pulse incidence on the radiation tolerance of both systems.

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Background: IgG4 production is regulated by type 2 (IL-4 and IL-13) and regulatory (IL-10) cytokines involved in the pathophysiology of chronic rhinosinusitis (CRS). We sought to determine the pathophysiological characteristics of IgG4-positive cells in sinonasal tissues in CRS, especially eosinophilic CRS (ECRS).

Methods: IgG4-positive cells in uncinate tissues (UT) and nasal polyps (NP) were examined by immunohistochemistry.

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  • - The study focused on analyzing systematic errors in an X-ray single-grating interferometer that uses the Talbot effect.
  • - Identified errors from the X-ray camera were addressed, and a solution was presented to eliminate these systematic errors.
  • - Successful measurements of wavefront errors from multilayer focusing mirrors were achieved, showing accuracy better than λ/12 with two different cameras.
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  • The text describes the soft X-ray free-electron laser (FEL) beamline of the SPring-8 Compact free-electron LAser (SACLA), detailing its design and performance.* -
  • A prototype machine, the SPring-8 Compact SASE Source test accelerator, was moved to the SACLA undulator hall to specifically support this soft X-ray beamline.* -
  • The system can generate both soft and hard X-ray FELs simultaneously, achieving a pulse energy of 110 µJ at a 12.4 nm wavelength with an electron beam energy of 780 MeV.*
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Cutting-edge hard X-ray microscopy strongly depends on sophisticated focusing optics and ultrabright X-ray sources at synchrotron-radiation and X-ray free-electron laser (XFEL) facilities. These facilities typically provide two-dimensional nanofocusing X-ray beams by combining one-dimensional focusing mirrors. However, single-reflecting two-dimensional focusing mirrors with an ellipsoidal surface, which are well-known to possess high efficiency, have limited microfocusing applications.

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  • Understanding fracture phenomena at high strain rates is crucial for various scientific fields, including applied science, technology, and fundamental science like geology and laser interactions.
  • Successful research in this area requires detailed analysis at multiple scales, from atomic to macroscopic, which has typically been done through large-scale simulations.
  • Recent advancements using a combination of high-power laser and femtosecond x-ray probes have allowed for real-time monitoring of these dynamic fracture processes in tantalum, revealing critical data related to spallation and stress responses in materials.
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Background: IL-22 is an IL-10-family cytokine that regulates chronic inflammation. We investigated the role of IL-22 and its receptor, IL-22R1, in the pathophysiology of chronic rhinosinusitis with nasal polyps (CRSwNP).

Methods: IL-22 and IL-22R1 protein and mRNA expression in NP and in uncinate tissues (UT) from CRS and non-CRS patients was examined using immunohistochemistry and real-time PCR, respectively.

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  • Ellipsoidal mirrors are more efficient for focusing x-rays than traditional elliptical-cylinder mirrors, but their use is limited due to the challenges in achieving precise surface measurements needed for nano-focusing.
  • A new surface metrology system was developed using stitching interferometric techniques, which involve measuring small sections of the mirror and correcting systematic errors from off-axis aberrations.
  • The new system demonstrated a high measurement repeatability of 0.51 nm for an ellipsoidal mirror, meeting the stringent requirements for surface precision and paving the way for improved nano-focusing x-ray optics.
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