Comprehensive Application of XFEL Microcrystallography for Challenging Targets in Various Organic Compounds

There is a growing demand for structure determination from small crystals, and the three-dimensional electron diffraction (3D ED) technique can be employed for this purpose. However, 3D ED has certain limitations related to the crystal thickness and data quality. We here present the application of serial X-ray crystallography (SX) with X-ray free electron lasers (XFELs) to small (a few μm or less) and thin (a few hundred nm or less) crystals of novel compounds dispersed on a substrate. For XFEL exposures, two-dimensional (2D) scanning of the substrate coupled with rotation enables highly efficient data collection. The recorded patterns can be successfully indexed using lattice parameters obtained through 3D ED. This approach is especially effective for challenging targets, including pharmaceuticals and organic materials that form preferentially oriented flat crystals in low-symmetry space groups. Some of these crystals have been difficult to solve or have yielded incomplete solutions using 3D ED. Our extensive analyses confirmed the superior quality of the SX data regardless of crystal orientations. Additionally, 2D scanning with XFEL pulses gives an overall distribution of the samples on the substrate, which can be useful for evaluating the properties of crystal grains and the quality of layered crystals. Therefore, this study demonstrates that XFEL crystallography has become a powerful tool for conducting structure studies of small crystals of organic compounds.

A versatile pressure-cell design for studying ultrafast molecular-dynamics in supercritical fluids using coherent multi-pulse x-ray scattering

Supercritical fluids (SCFs) can be found in a variety of environmental and industrial processes. They exhibit an anomalous thermodynamic behavior, which originates from their fluctuating heterogeneous micro-structure. Characterizing the dynamics of these fluids at high temperature and high pressure with nanometer spatial and picosecond temporal resolution has been very challenging. The advent of hard x-ray free electron lasers has enabled the development of novel multi-pulse ultrafast x-ray scattering techniques, such as x-ray photon correlation spectroscopy (XPCS) and x-ray pump x-ray probe (XPXP). These techniques offer new opportunities for resolving the ultrafast microscopic behavior in SCFs at unprecedented spatiotemporal resolution, unraveling the dynamics of their micro-structure. However, harnessing these capabilities requires a bespoke high-pressure and high-temperature sample system that is optimized to maximize signal intensity and address instrument-specific challenges, such as drift in beamline components, x-ray scattering background, and multi-x-ray-beam overlap. We present a pressure cell compatible with a wide range of SCFs with built-in optical access for XPCS and XPXP and discuss critical aspects of the pressure cell design, with a particular focus on the design optimization for XPCS.

Spectral-brightness optimization of an X-ray free-electron laser by machine-learning-based tuning

A machine-learning-based beam optimizer has been implemented to maximize the spectral brightness of the X-ray free-electron laser (XFEL) pulses of SACLA. A new high-resolution single-shot inline spectrometer capable of resolving features of the order of a few electronvolts was employed to measure and evaluate XFEL pulse spectra. Compared with a simple pulse-energy-based optimization, the spectral width was narrowed by half and the spectral brightness was improved by a factor of 1.7. The optimizer significantly contributes to efficient machine tuning and improvement of XFEL performance at SACLA.

Femtosecond Reduction of Atomic Scattering Factors Triggered by Intense X-Ray Pulse

X-ray diffraction of silicon irradiated with tightly focused femtosecond x-ray pulses (photon energy, 11.5 keV; pulse duration, 6 fs) was measured at various x-ray intensities up to 4.6×10^{19}  W/cm^{2}. The measurement reveals that the diffraction intensity is highly suppressed when the x-ray intensity reaches of the order of 10^{19}  W/cm^{2}. With a dedicated simulation, we confirm that the observed reduction of the diffraction intensity can be attributed to the femtosecond change in individual atomic scattering factors due to the ultrafast creation of highly ionized atoms through photoionization, Auger decay, and subsequent collisional ionization. We anticipate that this ultrafast reduction of atomic scattering factor will be a basis for new x-ray nonlinear techniques, such as pulse shortening and contrast variation x-ray scattering.

Pair Distribution Function from Liquid Jet Nanoparticle Suspension using Femtosecond X-ray Pulses

X-ray scattering data measured on femtosecond timescales at the SACLA X-ray Free Electron Laser (XFEL) facility on a suspension of HfO2 nanoparticles in a liquid jet were used for pair distribution function (PDF) analysis. Despite a non-optimal experimental setup resulting in a modest Qmax of ~8 Å-1 , a promising PDF was obtained. The main features were reproduced when comparing the XFEL PDF to a PDF obtained from data measured at the PETRA III synchrotron light source. Refining structural parameters such as unit cell dimension and particle size from the XFEL PDF provided reliable values. Although the reachable Qmax limited the obtainable information, the present results indicate that good quality PDFs can be obtained on femtosecond timescales if the experimental conditions are further optimized. The study therefore encourages a new direction in ultrafast structural science where structural features of amorphous and disordered systems can be studied.

Non-thermal structural transformation of diamond driven by x-rays

Intense x-ray pulses can cause the non-thermal structural transformation of diamond. At the SACLA XFEL facility, pump x-ray pulses triggered this phase transition, and probe x-ray pulses produced diffraction patterns. Time delays were observed from 0 to 250 fs, and the x-ray dose varied from 0.9 to 8.0 eV/atom. The intensity of the (111), (220), and (311) diffraction peaks decreased with time, indicating a disordering of the crystal lattice. From a Debye-Waller analysis, the rms atomic displacements perpendicular to the (111) planes were observed to be significantly larger than those perpendicular to the (220) or (311) planes. At a long time delay of 33 ms, graphite (002) diffraction indicates that graphitization did occur above a threshold dose of 1.2 eV/atom. These experimental results are in qualitative agreement with XTANT+ simulations using a hybrid model based on density-functional tight-binding molecular dynamics.

Two-dimensional Kβ-Kα fluorescence spectrum by nonlinear resonant inelastic X-ray scattering

High sensitivity of the Kβ fluorescence spectrum to electronic state is widely used to investigate spin and oxidation state of first-row transition-metal compounds. However, the complex electronic structure results in overlapping spectral features, and the interpretation may be hampered by ambiguity in resolving the spectrum into components representing different electronic states. Here, we tackle this difficulty with a nonlinear resonant inelastic X-ray scattering (RIXS) scheme, where we leverage sequential two-photon absorption to realize an inverse process of the Kβ emission, and measure the successive Kα emission. The nonlinear RIXS reveals two-dimensional (2D) Kβ-Kα fluorescence spectrum of copper metal, leading to better understanding of the spectral feature. We isolate 3d-related satellite peaks in the 2D spectrum, and find good agreement with our multiplet ligand field calculation. Our work not only advances the fluorescence spectroscopy, but opens the door to extend RIXS into the nonlinear regime.

Structural resolution of a small organic molecule by serial X-ray free-electron laser and electron crystallography

Structure analysis of small crystals is important in areas ranging from synthetic organic chemistry to pharmaceutical and material sciences, as many compounds do not yield large crystals. Here we present the detailed characterization of the structure of an organic molecule, rhodamine-6G, determined at a resolution of 0.82 Å by an X-ray free-electron laser (XFEL). Direct comparison of this structure with that obtained by electron crystallography from the same sample batch of microcrystals shows that both methods can accurately distinguish the position of some of the hydrogen atoms, depending on the type of chemical bond in which they are involved. Variations in the distances measured by XFEL and electron diffraction reflect the expected differences in X-ray and electron scatterings. The reliability for atomic coordinates was found to be better with XFEL, but the electron beam showed a higher sensitivity to charges.

Towards pump-probe single-crystal XFEL refinements for small-unit-cell systems

Serial femtosecond crystallography for small-unit-cell systems has so far seen very limited application despite obvious scientific possibilities. This is because reliable data reduction has not been available for these challenging systems. In particular, important intensity corrections such as the partiality correction critically rely on accurate determination of the crystal orientation, which is complicated by the low number of diffraction spots for small-unit-cell crystals. A data reduction pipeline capable of fully automated handling of all steps of data reduction from spot harvesting to merged structure factors has been developed. The pipeline utilizes sparse indexing based on known unit-cell parameters, seed-skewness integration, intensity corrections including an overlap-based combined Ewald sphere width and partiality correction, and a dynamically adjusted post-refinement routine. Using the pipeline, data measured on the compound K₄[Pt₂(P₂O₅H₂)₄]·2H₂O have been successfully reduced and used to solve the structure to an R₁ factor of ∼9.1%. It is expected that the pipeline will open up the field of small-unit-cell serial femtosecond crystallography experiments and allow investigations into, for example, excited states and reaction intermediate chemistry.

Delayed Onset and Directionality of X-Ray-Induced Atomic Displacements Observed on Subatomic Length Scales

Transient structural changes of Al_{2}O_{3} on subatomic length scales following irradiation with an intense x-ray laser pulse (photon energy: 8.70 keV; pulse duration: 6 fs; fluence: 8×10^{2}  J/cm^{2}) have been investigated by using an x-ray pump x-ray probe technique. The measurement reveals that aluminum and oxygen atoms remain in their original positions by ∼20  fs after the intensity maximum of the pump pulse, followed by directional atomic displacements at the fixed unit cell parameters. By comparing the experimental results and theoretical simulations, we interpret that electron excitation and relaxation triggered by the pump pulse modify the potential energy surface and drives the directional atomic displacements. Our results indicate that high-resolution x-ray structural analysis with the accuracy of 0.01 Å is feasible even with intense x-ray pulses by making the pulse duration shorter than the timescale needed to complete electron excitation and relaxation processes, which usually take up to a few tens of femtoseconds.

Single-shot spectrometer using diamond microcrystals for X-ray free-electron laser pulses

A simple spectrometer using diffraction from diamond microcrystals has been developed to diagnose single-shot spectra of X-ray free-electron laser (XFEL) pulses. The large grain size and uniform lattice constant of the adopted crystals enable characterizing the XFEL spectrum at a resolution of a few eV from the peak shape of the powder diffraction profile. This single-shot spectrometer has been installed at beamline 3 of SACLA and is used for daily machine tuning.

Experimental evidence of tetrahedral symmetry breaking in SiO2 glass under pressure

Bimodal behavior in the translational order of silicon's second shell in SiO₂ liquid at high temperatures and high pressures has been recognized in theoretical studies, and the fraction of the S state with high tetrahedrality is considered as structural origin of the anomalous properties. However, it has not been well identified in experiment. Here we show experimental evidence of a bimodal behavior in the translational order of silicon's second shell in SiO₂ glass under pressure. SiO₂ glass shows tetrahedral symmetry structure with separation between the first and second shells of silicon at low pressures, which corresponds to the S state structure reported in SiO₂ liquid. On the other hand, at high pressures, the silicon's second shell collapses onto the first shell, and more silicon atoms locate in the first shell. These observations indicate breaking of local tetrahedral symmetry in SiO₂ glass under pressure, as well as SiO₂ liquid.

Generation of intense phase-stable femtosecond hard X-ray pulse pairs

Coherent nonlinear spectroscopies and imaging in the X-ray domain provide direct insight into the coupled motions of electrons and nuclei with resolution on the electronic length scale and timescale. The experimental realization of such techniques will strongly benefit from access to intense, coherent pairs of femtosecond X-ray pulses. We have observed phase-stable X-ray pulse pairs containing more than 3 × 107 photons at 5.9 keV (2.1 Å) with ∼1 fs duration and 2 to 5 fs separation. The highly directional pulse pairs are manifested by interference fringes in the superfluorescent and seeded stimulated manganese Kα emission induced by an X-ray free-electron laser. The fringes constitute the time-frequency X-ray analog of Young’s double-slit interference, allowing for frequency domain X-ray measurements with attosecond time resolution.

Characterization of photoinduced normal state through charge density wave in superconducting YBa2Cu3O6.67

The normal state of high-T_c cuprates has been considered one of the essential topics in high-temperature superconductivity research. However, compared to the high magnetic field study of it, understanding a photoinduced normal state remains elusive. Here, we explore a photoinduced normal state of YBa₂Cu₃O_6.67 through a charge density wave (CDW) with time-resolved resonant soft x-ray scattering, as well as a high magnetic field x-ray scattering. In the nonequilibrium state where people predict a quenched superconducting state based on the previous optical spectroscopies, we experimentally observed a similar analogy to the competition between superconductivity and CDW shown in the equilibrium state. We further observe that the broken pairing states in the superconducting CuO₂ plane via the optical pump lead to nucleation of three-dimensional CDW precursor correlation. Ultimately, these findings provide a critical clue that the characteristics of the photoinduced normal state show a solid resemblance to those under magnetic fields in equilibrium conditions.

Fine microstructure formation in steel under ultrafast heating and cooling

This study evaluates phase transformation kinetics under ultrafast cooling using femtosecond X-ray diffraction for the operand measurements of the dislocation densities in Fe–0.1 mass% C–2.0 mass% Mn martensitic steel. To identify the phase transformation mechanism from austenite (γ) to martensite (α′), we used an X-ray free-electron laser and ultrafast heating and cooling techniques. A maximum cooling rate of 4.0 × 10³ °C s^–1 was achieved using a gas spraying technique, which is applied immediately after ultrafast heating of the sample to 1200 °C at a rate of 1.2 × 10⁴ °C s^–1. The cooling rate was sufficient to avoid bainitic transformation, and the transformation during ultrafast cooling was successfully observed. Our results showed that the cooling rate affected the dislocation density of the γ phase at high temperatures, resulting in the formation of a retained γ owing to ultrafast cooling. It was discovered that Fe–0.1 mass% C–2.0 mass% Mn martensitic steels may be in an intermediate phase during the phase transformation from face-centered-cubic γ to body-centered-cubic α′ during ultrafast cooling and that lattice softening occurred in carbon steel immediately above the martensitic-transformation starting temperature. These findings will be beneficial in the study, development, and industrial utilization of functional steels.

Shortening X-Ray Pulse Duration via Saturable Absorption

To shorten the duration of x-ray pulses, we present a nonlinear optical technique using atoms with core-hole vacancies (core-hole atoms) generated by inner-shell photoionization. The weak Coulomb screening in the core-hole atoms results in decreased absorption at photon energies immediately above the absorption edge. By employing this phenomenon, referred to as saturable absorption, we successfully reduce the duration of x-ray free-electron laser pulses (photon energy: 9.000 keV, duration: 6-7 fs, fluence: 2.0-3.5×10^{5}  J/cm^{2}) by ∼35%. This finding that core-hole atoms are applicable to nonlinear x-ray optics is an essential stepping stone for extending nonlinear technologies commonplace at optical wavelengths to the hard x-ray region.

Hard X-ray nanoprobe scanner

X-ray scientists are continually striving to improve the quality of X-ray microscopy, due to the fact that the information obtained from X-ray microscopy of materials can be complementary to that obtained from optical and electron microscopes. In contrast to the ease with which one can deflect electron beams, the relative difficulty to deflect X-ray has constrained the development of scanning X-ray microscopes (SXMs) based on a scan of an X-ray small probe. This restriction has caused severe complications that hinder progress toward achieving ultimate resolution. Here, a simple and innovative method for constructing an SXM equipped with a nanoprobe scanner is proposed. The nanoprobe scanner combines X-ray prisms and advanced Kirkpatrick-Baez focusing mirrors. By rotating the prisms on the order of degrees, X-ray probe scanning with single-nanometre accuracy can be easily achieved. The validity of the concept was verified by acquiring an SXM image of a test pattern at a photon energy of 10 keV, where 50 nm line-and-space structures were resolved. This method is readily applicable to an SXM with a single-nanometre resolution and will assist effective utilization of increasing brightness of fourth-generation synchrotron radiation sources.

Suppression of Vps13 adaptor protein mutants reveals a central role for PI4P in regulating prospore membrane extension

Vps13 family proteins are proposed to function in bulk lipid transfer between membranes, but little is known about their regulation. During sporulation of Saccharomyces cerevisiae, Vps13 localizes to the prospore membrane (PSM) via the Spo71–Spo73 adaptor complex. We previously reported that loss of any of these proteins causes PSM extension and subsequent sporulation defects, yet their precise function remains unclear. Here, we performed a genetic screen and identified genes coding for a fragment of phosphatidylinositol (PI) 4-kinase catalytic subunit and PI 4-kinase noncatalytic subunit as multicopy suppressors of spo73Δ. Further genetic and cytological analyses revealed that lowering PI4P levels in the PSM rescues the spo73Δ defects. Furthermore, overexpression of VPS13 and lowering PI4P levels synergistically rescued the defect of a spo71Δ spo73Δ double mutant, suggesting that PI4P might regulate Vps13 function. In addition, we show that an N-terminal fragment of Vps13 has affinity for the endoplasmic reticulum (ER), and ER-plasma membrane (PM) tethers localize along the PSM in a manner dependent on Vps13 and the adaptor complex. These observations suggest that Vps13 and the adaptor complex recruit ER-PM tethers to ER-PSM contact sites. Our analysis revealed that involvement of a phosphoinositide, PI4P, in regulation of Vps13, and also suggest that distinct contact site proteins function cooperatively to promote de novo membrane formation.

Vps13 family proteins are conserved lipid transfer proteins that function at organelle contact sites and have been implicated in a number of different neurological diseases. In the yeast Saccharomyces cerevisiae, Vps13 is encoded by a single gene and is localized to various contact sites by interaction with different adaptor proteins and/or lipids, however its regulation is yet to be clarified. We have previously shown that during the developmental process of sporulation, Vps13 is recruited to de novo membrane structures called prospore membranes (PSMs) by a specific adaptor complex, and Vps13 and its adaptors are required for PSM extension. Here we reveal that loss of an adaptor can be overcome by lowering phosphatidylinositol-4-phosphate (PI4P) levels, either by inhibiting PI 4-kinase on the PSM or recruiting PI 4-phospatase to the PSM and that PI4P levels in the PSM affect Vps13 function. Further, we show that Vps13 forms endoplasmic reticulum (ER)-PSM contact sites, that ER-plasma membrane tethering proteins are recruited to ER-PSM contacts, and these proteins may function in conjunction with Vps13. Thus, our work shines light on both the mechanisms of intracellular remodeling and the function of this important class of lipid transfer proteins.

Atomic-Scale Visualization of Ultrafast Bond Breaking in X-Ray-Excited Diamond

Ultrafast changes of charge density distribution in diamond after irradiation with an intense x-ray pulse (photon energy, 7.8 keV; pulse duration, 6 fs; intensity, 3×10^{19}  W/cm^{2}) have been visualized with the x-ray pump-x-ray probe technique. The measurement reveals that covalent bonds in diamond are broken and the electron distribution around each atom becomes almost isotropic within ∼5  fs after the intensity maximum of the x-ray pump pulse. The 15 fs time delay observed between the bond breaking and atomic disordering indicates nonisothermality of electron and lattice subsystems on this timescale. From these observations and simulation results, we interpret that the x-ray-induced change of the interatomic potential drives the ultrafast atomic disordering underway to the following nonthermal melting.

Determination of X-ray pulse duration via intensity correlation measurement of X-ray fluorescence. Erratum

Corrections to equations and experimental results in the paper by Inoue et al. [(2019). J. Synchrotron Rad. 26, 2050-2054] are made.

Split-pulse X-ray photon correlation spectroscopy with seeded X-rays from X-ray laser to study atomic-level dynamics

With their brilliance and temporal structure, X-ray free-electron laser can unveil atomic-scale details of ultrafast phenomena. Recent progress in split-and-delay optics (SDO), which produces two X-ray pulses with time-delays, offers bright prospects for observing dynamics at the atomic-scale. However, their insufficient pulse energy has limited its application either to phenomena with longer correlation length or to measurement with a fixed delay-time. Here we show that the combination of the SDO and self-seeding of X-rays increases the pulse energy and makes it possible to observe the atomic-scale dynamics in a timescale of picoseconds. We show that the speckle contrast in scattering from water depends on the delay-time as expected. Our results demonstrate the capability of measurement using the SDO with seeded X-rays for resolving the dynamics in temporal and spatial scales that are not accessible by other techniques, opening opportunities for studying the atomic-level dynamics.

Two-color X-ray free-electron laser consisting of broadband and narrowband beams

A simple scheme is proposed and experimentally confirmed to generate X-ray free-electron lasers (XFELs) consisting of broadband and narrowband beams with a controllable intensity ratio and a large photon-energy separation. This unique two-color XFEL beam will open new opportunities for investigation of nonlinear interactions between intense X-rays and matter.

Feasibility study of interferometric phase-contrast X-ray imaging using the hard-X-ray free-electron laser of the SPring-8 Angstrom Compact Free-Electron Laser

Aiming for the fine observation of fast physical phenomena such as phonon propagation and laser ablation, phase-contrast X-ray imaging combined with a crystal X-ray interferometer and the X-ray free-electron laser (XFEL) of the SPring-8 Angstrom Compact Free-Electron Laser has been developed. An interference pattern with 70% visibility was obtained by single-shot exposure with a 15 keV monochromated XFEL. In addition, a phase map of an acrylic wedge was successfully obtained using the fringe scanning method.

Focus characterization of an X-ray free-electron laser by intensity correlation measurement of X-ray fluorescence

This paper proposes and demonstrates a simple method using the intensity correlation of X-ray fluorescence to evaluate the focused beam size of an X-ray free-electron laser (XFEL). This method was applied to the sub-micrometre focused XFEL beam at the SPring-8 Angstrom Compact Free Electron Laser, and the beam size evaluated using the proposed method was consistent with that measured using the knife-edge scan method. The proposed method is readily applicable to extremely small X-ray spots and can be applied for the precise diagnostics of sub-10 nm focused X-ray beams which have recently emerged.

High-resolution micro channel-cut crystal monochromator processed by plasma chemical vaporization machining for a reflection self-seeded X-ray free-electron laser

A high-resolution micro channel-cut crystal monochromator (µCCM) composed of an Si(220) crystal is developed for the purpose of narrowing the bandwidth of a reflection self-seeded X-ray free-electron laser. Subsurface damage on the monochromator, which distorts the wavefront and broadens the bandwidth of the monochromatic seed beam, was removed by using a plasma etching technique. High diffraction performance of the monochromator was confirmed through evaluation with coherent X-rays. Reflection self-seeding operation was tested with the Si(220) µCCM at SPring-8 Angstrom Compact free-electron laser. A narrow average bandwidth of 0.6 eV, which is five times narrower than the value previously reported [I. Inoue et al., Nat. Photonics13, 319 (2019)10.1038/s41566-019-0365-y], was successfully obtained at 9 keV. The narrow-band X-ray beams with high intensity realized in this study will further expand the capabilities of X-ray free-electron lasers.

Generation of an X-ray nanobeam of a free-electron laser using reflective optics with speckle interferometry

Ultimate focusing of an X-ray free-electron laser (XFEL) enables the generation of ultrahigh-intensity X-ray pulses. Although sub-10 nm focusing has already been achieved using synchrotron light sources, the sub-10 nm focusing of XFEL beams remains difficult mainly because the insufficient stability of the light source hinders the evaluation of a focused beam profile. This problem is specifically disadvantageous for the Kirkpatrick-Baez (KB) mirror focusing system, in which a slight misalignment of ∼300 nrad can degrade the focused beam. In this work, an X-ray nanobeam of a free-electron laser was generated using reflective KB focusing optics combined with speckle interferometry. The speckle profiles generated by 2 nm platinum particles were systematically investigated on a single-shot basis by changing the alignment of the multilayer KB mirror system installed at the SPring-8 Angstrom Compact Free-Electron Laser, in combination with computer simulations. It was verified that the KB mirror alignments were optimized with the required accuracy, and a focused vertical beam of 5.8 nm (±1.2 nm) was achieved after optimization. The speckle interferometry reported in this study is expected to be an effective tool for optimizing the alignment of nano-focusing systems and for generating an unprecedented intensity of up to 1022 W cm-2 using XFEL sources.

Determination of X-ray pulse duration via intensity correlation measurements of X-ray fluorescence

A simple method using X-ray fluorescence is proposed to diagnose the duration of an X-ray free-electron laser (XFEL) pulse. This work shows that the degree of intensity correlation of the X-ray fluorescence generated by irradiating an XFEL pulse on metal foil reflects the magnitude relation between the XFEL duration and the coherence time of the fluorescence. Through intensity correlation measurements of copper Kα fluorescence, the duration of 12 keV XFEL pulses from SACLA was evaluated to be ∼10 fs.

P2434Digital zoom decreases radiation exposure dose up to 30% in percutaneous coronary intervention

Background

Interventional cardiology is gaining greater popularity worldwide with each passing year. Reduction of exposure dose is a very imminent and an important issue in cardiology procedure. Although a newer radiation reduction technique, device and procedure are very valuable and expected, we should consider about therapy technique, radiation technique, devices, and the way to protection. Digital zoom digitally enlarges images in real time by up to 2.5-fold at lower doses than those used with traditional field of view changes. In our phantom examination the average dose reduction of digital zoom was 27%.

Methods and results

This study is designated as single-center, retrospective, not-randomized, observation study. 2101 eligible cases were collected. We assigned the cases of PCI without the use of Digital zoom to the Conventional group and those involving the use of Digital zoom to the Digital zoom group. There were 806 patients in the Conventional group and 1195 in the Digital zoom group. Because we had begun using Digital zoom from January 2015 onwards, all patients in the Conventional group had undergone PCI from January 2013 to December 2014 and all patients in the Digital zoom group had undergone PCI from January 2015 to December 2016. In addition, we calculated the RAK/minute and DAP/minute for an accurate assessment. To minimize the difference of characteristics between two groups, propensity score including all baseline variables was performed. Furthermore, Predictors of radiation exposure were investigated using multivariable least square methods. Inter group differences were observed in DAP, RAK, DAP/min, and RAK/min (Digital zoom group vs conventional group: DAP, 16000 cGy cm2 [from 1st quartile to 3rd quartile; 10300–24400] vs 20700 [13400–29500], p<0.001; DAP/min, 557 cGy cm2/min [392–737] vs 782 [571–1010], p<0.01; RAK, 1590 Gy [990–2410] vs 1850 [1220–2720], p<0.01; RAK/min, 54.7 Gy/min [38.5–73.2] vs 71.2 [51.5–93.0], p<0.01). Even after propensity score matching, intergroup differences in DAP (810 cases), DAP/min (811 cases), RAK (746 cases), and RAK/min (744 cases) persisted. Furthermore, the least squares method showed that Digital zoom is an important predictor of DAP (β=0.17, p<0.01) and RAK (β=0.12, p<0.01).

Conclusion

Digital zoom is an old and cost-free technique, but one of most powerful reduction of exposure method. Propensity score adjustment and least square methods show that digital zoom is one of independent effective method.

A micro channel-cut crystal X-ray monochromator for a self-seeded hard X-ray free-electron laser

A channel-cut Si(111) crystal with a channel width of 90 µm was developed for achieving reflection self-seeding in hard X-ray free-electron lasers (XFELs). With the crystal a monochromatic seed pulse is produced from a broadband XFEL pulse generated in the first undulator section with an optical delay of 119 fs at 10 keV. The small optical delay allows a temporal overlap between the seed optical pulse and the electron bunch by using a small magnetic chicane for the electron beam placed between two undulator sections. Peak reflectivity reached 67%, which is reasonable compared with the theoretical value of 81%. By using this monochromator, a monochromatic seed pulse without broadband background in the spectrum was obtained at SACLA with a conversion efficiency from a broadband XFEL pulse of 2 × 10^-2, which is ∼10 times higher than the theoretical efficiency of transmission self-seeding using a thin diamond (400) monochromator.

Fine microstructure formation in steel under ultrafast heating

In this study, phase transformation kinetics was directly evaluated using a femtosecond X-ray diffraction technique for operand measurements of the dislocation densities and carbon concentrations in Fe-0.1mass%C martensitic steel. To identify the reverse transformation mechanism from α′ to γ, we used an X-ray free-electron laser and ultrafast heating. A maximum heating rate of 10⁴ °C/s, which is sufficient to avoid diffusive reversion, was achieved, and the reverse transformation during ultrafast heating was successfully observed. Our results demonstrated that a fine microstructure formed because of a phase transformation in which the dislocation density and carbon concentrations remained high owing to ultrafast heating. Fe–C martensitic steels were also found to undergo a massive reverse transformation during ultrafast heating. The formation of a fine microstructure by a simple manufacturing process, without rare elements such as Ti, Nb, or Mo, can be expected. This study will help further the development of functional steels.

Superfluorescence, Free-Induction Decay, and Four-Wave Mixing: Propagation of Free-Electron Laser Pulses through a Dense Sample of Helium Ions

We report an experimental and numerical study of the propagation of free-electron laser pulses (wavelength 24.3 nm) through helium gas. Ionization and excitation populates the He^{+} 4p state. Strong, directional emission was observed at wavelengths of 469, 164, 30.4, and 25.6 nm. We interpret the emissions at 469 and 164 nm as 4p-3s-2p cascade superfluorescence, that at 30.4 nm as yoked superfluorescence on the 2p-1s transition, and that at 25.6 nm as free-induction decay of the 3p state.

Nonlinear Spectroscopy with X-Ray Two-Photon Absorption in Metallic Copper

X-ray two-photon absorption (TPA) spectrum of metallic copper is measured using a free-electron laser (XFEL). The spectrum differs from that measured by the conventional one-photon absorption (OPA), and characterized by a peak below the Fermi level, which is assigned to the transition to the 3d state. The impact of the XFEL pulse on the OPA spectrum is discussed by analyzing the pulse-energy dependence, which indicates that the intrinsic TPA spectrum is measured.

Systematic-error-free wavefront measurement using an X-ray single-grating interferometer

In this study, the systematic errors of an X-ray single-grating interferometer based on the Talbot effect were investigated in detail. Non-negligible systematic errors induced by an X-ray camera were identified and a method to eliminate the systematic error was proposed. Systematic-error-free measurements of the wavefront error produced by multilayer focusing mirrors with large numerical apertures were demonstrated at the SPring-8 Angstrom Compact free electron LAser. Consequently, wavefront aberration obtained with two different cameras was found to be consistent with an accuracy better than λ/12.

An X-ray harmonic separator for next-generation synchrotron X-ray sources and X-ray free-electron lasers

An X-ray prism for the extraction of a specific harmonic of undulator radiation is proposed. By using the prism in a grazing incidence geometry, the beam axes of fundamental and harmonics of undulator radiation are separated with large angles over 10 µrad, which enables the selection of a specific harmonic with the help of apertures, while keeping a high photon flux. The concept of the harmonic separation was experimentally confirmed using X-ray beams from the X-ray free-electron laser SACLA.

Real-life experience of a stent-less revascularization strategy using a combination of excimer laser and drug-coated balloon for patients with acute coronary syndrome

OBJECTIVES

We aimed to test a novel stent-less revascularization strategy using a combination of excimer laser coronary angioplasty (ELCA) and drug-coated balloon (DCB) for patients with acute coronary syndrome (ACS).

BACKGROUND

Percutaneous coronary intervention with drug eluting stents is a standard invasive treatment for ACS. Some unsolved issues however remain, such as stent thrombosis and bleeding risks associated with dual antiplatelet therapy.

METHODS

Consecutive ACS patients were planned to receive either a DCB application following ELCA without a stent implantation or conventional revascularization with a coronary stent. The endpoints were (i) major cardiac adverse events (MACEs), defined as the composite of cardiac death, myocardial infarctions, and target lesion revascularization; (ii) target vessel revascularization (TVR); and (iii) angiographic outcome.

RESULTS

Since a greater than expected number of patients allocated to the stent-less treatment arm eventually received a bailout stenting, the following 3 as-treated groups were compared; DCB with ELCA group (N = 60), Stent with ELCA group (N = 23), and Stent without ELCA group (N = 85). During a mean follow-up period of 420 ± 137 days, and with angiographic 6- and 12-month-follow-up rates of 96.7%, 87%, and 81.2%, and 50%, 65.2%, and 45.9%, respectively, the MACE rate did not differ across the groups (10%, 4.3%, and 3.5%; P = 0.22) while an incidence of TVR was more common (15%, 0, and 4.7%; P = 0.02) and the diameter stenosis at 6-months of follow-up was greater (25.7 ± 18.2, 14.9 ± 13.1 and 16.2 ± 15.4%; P = 0.002) in the DCB with ELCA group.

CONCLUSIONS

The stent-less revascularization strategy with DCB and ELCA was associated with a higher occurrence of restenosis in ACS patients.

Performance of a hard X-ray split-and-delay optical system with a wavefront division

The performance of a hard X-ray split-and-delay optical (SDO) system with a wavefront division scheme was investigated at the hard X-ray free-electron laser facility SACLA. For the wavefront division, beam splitters made of edge-polished perfect Si(220) crystals were employed. We characterized the beam properties of the SDO system, and investigated its capabilities for beam manipulation and diagnostics. First, it was confirmed that shot-to-shot non-invasive diagnostics of pulse energies for both branches in the SDO system was feasible. Second, nearly ideal and identical focal profiles for both branches were obtained with a spot size of ∼1.5 µm in full width at half-maximum. Third, a spatial overlap of the two focused beams with a sub-µm accuracy was achieved by fine tuning of the SDO system. Finally, a reliable tunability of the delay time between two pulses was confirmed. The time interval was measured with an X-ray streak camera by changing the path length of the variable-delay branch. Errors from the fitted line were evaluated to be as small as ±0.4 ps over a time range of 60 ps.

Characterization of temporal coherence of hard X-ray free-electron laser pulses with single-shot interferograms

Temporal coherence is one of the most fundamental characteristics of light, connecting to spectral information through the Fourier transform relationship between time and frequency. Interferometers with a variable path-length difference (PLD) between the two branches have widely been employed to characterize temporal coherence properties for broad spectral regimes. Hard X-ray interferometers reported previously, however, have strict limitations in their operational photon energies, due to the specific optical layouts utilized to satisfy the stringent requirement for extreme stability of the PLD at sub-ångström scales. The work presented here characterizes the temporal coherence of hard X-ray free-electron laser (XFEL) pulses by capturing single-shot interferograms. Since the stability requirement is drastically relieved with this approach, it was possible to build a versatile hard X-ray interferometer composed of six separate optical elements to cover a wide photon energy range from 6.5 to 11.5 keV while providing a large variable delay time of up to 47 ps at 10 keV. A high visibility of up to 0.55 was observed at a photon energy of 10 keV. The visibility measurement as a function of time delay reveals a mean coherence time of 5.9 ± 0.7 fs, which agrees with that expected from the single-shot spectral information. This is the first result of characterizing the temporal coherence of XFEL pulses in the hard X-ray regime and is an important milestone towards ultra-high energy resolutions at micro-electronvolt levels in time-domain X-ray spectroscopy, which will open up new opportunities for revealing dynamic properties in diverse systems on timescales from femto-seconds to nanoseconds, associated with fluctuations from ångström to nanometre spatial scales.

Multi-wavelength anomalous diffraction de novo phasing using a two-colour X-ray free-electron laser with wide tunability

Serial femtosecond crystallography at X-ray free-electron lasers (XFELs) offers unprecedented possibilities for macromolecular structure determination of systems prone to radiation damage. However, de novo structure determination, i.e., without prior structural knowledge, is complicated by the inherent inaccuracy of serial femtosecond crystallography data. By its very nature, serial femtosecond crystallography data collection entails shot-to-shot fluctuations in X-ray wavelength and intensity as well as variations in crystal size and quality that must be averaged out. Hence, to obtain accurate diffraction intensities for de novo phasing, large numbers of diffraction patterns are required, and, concomitantly large volumes of sample and long X-ray free-electron laser beamtimes. Here we show that serial femtosecond crystallography data collected using simultaneous two-colour X-ray free-electron laser pulses can be used for multiple wavelength anomalous dispersion phasing. The phase angle determination is significantly more accurate than for single-colour phasing. We anticipate that two-colour multiple wavelength anomalous dispersion phasing will enhance structure determination of difficult-to-phase proteins at X-ray free-electron lasers.

X-ray free-electron lasers produce bright femtosecond X-ray pulses. Here, the authors use a two-colour X-ray free-electron laser beam for simultaneous two-wavelength data collection and show that protein structures can be determined with multiple wavelength anomalous dispersion phasing, which is important for difficult-to-phase projects.

Dynamic localization of a yeast development-specific PP1 complex during prospore membrane formation is dependent on multiple localization signals and complex formation

Prospore membrane formation of Saccharomyces cerevisiae provides a powerful model for understanding the mechanisms of de novo membrane formation. Protein phosphatase type1, Glc7, and a sporulation-specific targeting subunit, Gip1, show dynamic localization using multiple localization signals and regulate membrane growth during sporulation.

During the developmental process of sporulation in Saccharomyces cerevisiae, membrane structures called prospore membranes are formed de novo, expand, extend, acquire a round shape, and finally become plasma membranes of the spores. GIP1 encodes a regulatory/targeting subunit of protein phosphatase type 1 that is required for sporulation. Gip1 recruits the catalytic subunit Glc7 to septin structures that form along the prospore membrane; however, the molecular basis of its localization and function is not fully understood. Here we show that Gip1 changes its localization dynamically and is required for prospore membrane extension. Gip1 first associates with the spindle pole body as the prospore membrane forms, moves onto the prospore membrane and then to the septins as the membrane extends, distributes around the prospore membrane after closure, and finally translocates into the nucleus in the maturing spore. Deletion and mutation analyses reveal distinct sequences in Gip1 that are required for different localizations and for association with Glc7. Binding to Glc7 is also required for proper localization. Strikingly, localization to the prospore membrane, but not association with septins, is important for Gip1 function. Further, our genetic analysis suggests that a Gip1–Glc7 phosphatase complex regulates prospore membrane extension in parallel to the previously reported Vps13, Spo71, Spo73 pathway.

Comparison of radial, brachial, and femoral accesses using hemostatic devices for percutaneous coronary intervention

Some studies have suggested that radial access (RA) for percutaneous coronary intervention (PCI) reduces vascular complications and bleeding compared to femoral access (FA). The purpose of this study was to investigate the routine use of hemostatic devices and bleeding complications among RA, brachial access (BA), and FA. Between January 2015 and December 2015, 298 patients treated for PCI with RA were compared with 158 patients using BA and 206 patients using FA. The radial sheath was routinely removed with ADAPTY, the brachial sheath with BLEED SAFE, and the femoral sheath with Perclose ProGlide. In-hospital bleeding complications were investigated. Cardiogenic shock was most frequent in patients in the femoral group (RA 1.3%, BA 2.5%, FA 9.2%, p < 0.0001). The rate of major bleeding was highest in the femoral group (RA 1.0%, BA 2.5%, FA 5.3%, p = 0.01). Blood transfusion rates were highest in the femoral group (RA 0.7%, BA 1.3%, FA 4.4%, p = 0.01). Retroperitoneal bleeding was observed in 1.9% of patients in the femoral group. Patients in the brachial group had large hematomas (RA 0.7%, BA 4.4%, FA 1.5%, p = 0.01). Pseudoaneurysm formation needing intervention occurred most frequently in the brachial group (RA 0%, BA 1.3%, FA 0%, p = 0.04). In conclusion, compared to the brachial and femoral approaches, the radial approach appears to be the safest technique to avoid local vascular bleeding complications. The brachial approach has the highest risk of large hematoma and pseudoaneurysm formation among the three groups.

Inline spectrometer for shot-by-shot determination of pulse energies of a two-color X-ray free-electron laser

An inline spectrometer has been developed to monitor shot-by-shot pulse energies of a two-color X-ray beam. A thin film of diamond allows inline operation with minimum absorption. The absolute pulse energy for each color is determined by the inline spectrometer combined with a total pulse-energy monitor. A negative correlation is found between the two-color pulse energies.

Characterizing transverse coherence of an ultra-intense focused X-ray free-electron laser by an extended Young's experiment

Characterization of transverse coherence is one of the most critical themes for advanced X-ray sources and their applications in many fields of science. However, for hard X-ray free-electron laser (XFEL) sources there is very little knowledge available on their transverse coherence characteristics, despite their extreme importance. This is because the unique characteristics of the sources, such as the ultra-intense nature of XFEL radiation and the shot-by-shot fluctuations in the intensity distribution, make it difficult to apply conventional techniques. Here, an extended Young's interference experiment using a stream of bimodal gold particles is shown to achieve a direct measurement of the modulus of the complex degree of coherence of XFEL pulses. The use of interference patterns from two differently sized particles enables analysis of the transverse coherence on a single-shot basis without a priori knowledge of the instantaneous intensity ratio at the particles. For a focused X-ray spot as small as 1.8 µm (horizontal) × 1.3 µm (vertical) with an ultrahigh intensity that exceeds 10(18) W cm(-2) from the SPring-8 Ångstrom Compact free-electron LAser (SACLA), the coherence lengths were estimated to be 1.7 ± 0.2 µm (horizontal) and 1.3 ± 0.1 µm (vertical). The ratios between the coherence lengths and the focused beam sizes are almost the same in the horizontal and vertical directions, indicating that the transverse coherence properties of unfocused XFEL pulses are isotropic. The experiment presented here enables measurements free from radiation damage and will be readily applicable to the analysis of the transverse coherence of ultra-intense nanometre-sized focused XFEL beams.

Do Lower Target Temperatures or Prolonged Cooling Provide Improved Outcomes for Comatose Survivors of Cardiac Arrest Treated With Hypothermia?

Background

Optimal protocols for targeted temperature management are still unclear. This study investigated whether lower target temperatures and/or prolonged cooling could provide improved outcomes in comatose survivors of cardiac arrest.

Methods and Results

This observational study was conducted using the prospectively collected targeted temperature management database in Hiroshima, Japan. Between September 2003 and September 2014, 237 patients treated with TTM after cardiac arrest were enrolled in this study. The target temperatures and durations were assigned by the treating physicians regardless of the patients’ conditions. Favorable outcomes were defined as a cerebral performance category scale of 1 or 2 at the 90-day follow-up time point. The rate of favorable outcomes were similar between the patients whose protocols of target temperature were <34°C and ≥34°C (40% versus 35%, P=0.41), cooling durations were <28 and ≥28 hours (33% versus 44%, P=0.11), and rewarming durations were <28 and ≥28 hours (35% versus 41%, P=0.39). However, in patients treated with extracorporeal cardiopulmonary resuscitation, target temperatures <34°C were associated with more favorable outcomes (29% versus 8%, P=0.01). The cooling and rewarming durations >28 hours and target temperatures <34°C were associated with more frequent lethal arrhythmia, pneumonia, and/or bleedings.

Conclusions

Prolonged durations of cooling and rewarming ≥28 hours may not improve outcomes and may increase complications. Further studies are necessary to assess the hypothesis that target temperatures <34°C provide improved outcomes in patients treated with extracorporeal cardiopulmonary resuscitation.

Significance of intracellular cations and calcium-regulating hormones on salt sensitivity in patients with essential hypertension

Although the existence of salt sensitivity in essential hypertensives has been well known, the precise mechanism(s) has not yet been elucidated. The aim of this study was to clarify the relation between the responses in blood pressure, extra- and intracellular cations and calcium-regulating hormones to oral NaCl loading in essential hypertensives. After oral NaCl loading, mean blood pressure, urinary excretions of calcium and magnesium, and PLT[Ca2+]i were significantly increased. [Ca2+]o and E[Mg]i were decreased. The changes (delta) in mean blood pressure by NaCl loading positively correlated with delta PLT[Ca2+]i and delta PTH, and negatively with delta[Ca2+]o and delta E[Mg]i. Delta PLT[Ca2+]i positively correlated with delta PTH and negatively with delta[Ca2+]o and delta E[Mg]i. From these results, the blood pressure response to oral NaCl loading is associated with the alternation of [Ca2+]i metabolism in which the changes in magnesium metabolism and calcium-regulating hormones may be involved.

Feasibility study of visibility-based X-ray photon correlation spectroscopy

When coherent X-rays impinge upon a disordered system, a grainy scattering pattern called speckle pattern is observed. If the system evolves with time, the corresponding speckle pattern also changes. Temporal changes in the speckle patterns therefore provide information on the dynamics of the system. This technique, which is called X-ray photon correlation spectroscopy (XPCS) [1], has shown the potential to access dynamic properties of various materials, such as colloidal suspensions, block copolymer, supercooled liquids, alloys, and antiferromagnetic materials. Although XPCS is a powerful technique for material science as recent studies show, it has a limitation of time resolution: dynamics faster than the frame rate of detector cannot be measured. When a two-dimensional (2D) detector is used in XPCS, the time resolution is limited to the order of milliseconds. For improving the time resolution of XPCS, we have extended speckle visibility spectroscopy (SVS) in the region of visible light [2] to the region of X-rays (X-ray SVS; XSVS) [3]. Since the minimum exposure time of the scattering patterns determines the time resolutions of XSVS and SVS, micro- or nano- second dynamics can be measured even with a 2D detector. Thus, XSVS has potential to bridge the time gap between XPCS and inelastic neutron/X-ray scattering techniques, and will be one of the promising tools for various science with the next generation synchrotron X-ray sources, such as diffraction limited storage rings and energy recovery linac based X-ray sources. In this presentation, we will describe the principle of XSVS and show the result of the application of XSVS to Brownian colloidal suspensions. This study was performed under the approval of JASRI (2011A1112, 2011B1131). We acknowledge Drs. N. Yagi and N. Ohta for their kind support in performing experiments.