Time zero determination for FEL pump-probe studies based on ultrafast melting of bismuth

A common challenge for pump-probe studies of structural dynamics at X-ray free-electron lasers (XFELs) is the determination of time zero (T₀)-the time an optical pulse (e.g., an optical laser) arrives coincidently with the probe pulse (e.g., a XFEL pulse) at the sample position. In some cases, T₀ might be extracted from the structural dynamics of the sample's observed response itself, but generally, an independent robust method is required or would be superior to the inferred determination of T₀. In this paper, we present how the structural dynamics in ultrafast melting of bismuth can be exploited for a quickly performed, reliable and accurate determination of T₀ with a precision below 20 fs and an overall experimental accuracy of 50 fs to 150 fs (estimated). Our approach is potentially useful and applicable for fixed-target XFEL experiments, such as serial femtosecond crystallography, utilizing an optical pump pulse in the ultraviolet to near infrared spectral range and a pixelated 2D photon detector for recording crystallographic diffraction patterns in transmission geometry. In comparison to many other suitable approaches, our method is fairly independent of the pumping wavelength (UV-IR) as well as of the X-ray energy and offers a favorable signal contrast. The technique is exploitable not only for the determination of temporal characteristics of the experiment at the interaction point but also for investigating important conditions affecting experimental control such as spatial overlap and beam spot sizes.

A Case of Dermatomyositis with Severe Myalgia and Muscle Weakness Testing Positive for Anti-melanoma Differentiation-associated Gene 5 Antibody

We report a case of a woman with typical dermatomyositis (DM) with skin manifestations, severe myalgia and muscle weakness complicated by interstitial lung disease (ILD) and pneumomediastinum. Pneumomediastinum persisted despite treatment with immunosuppressive therapy (steroids and cyclosporine). After the test for anti-melanoma differentiation-associated gene 5 (MDA5) antibody came out positive, we doubled the cyclosporine dose and her condition improved. Despite typical clinical features of DM, in cases complicated by pneumomediastinum or steroid resistance, measurement of anti-MDA5 antibody may be useful for immunosuppressant dose titration.

Towards characterization of photo-excited electron transfer and catalysis in natural and artificial systems using XFELs

The ultra-bright femtosecond X-ray pulses provided by X-ray Free Electron Lasers (XFELs) open capabilities for studying the structure and dynamics of a wide variety of biological and inorganic systems beyond what is possible at synchrotron sources. Although the structure and chemistry at the catalytic sites have been studied intensively in both biological and inorganic systems, a full understanding of the atomic-scale chemistry requires new approaches beyond the steady state X-ray crystallography and X-ray spectroscopy at cryogenic temperatures. Following the dynamic changes in the geometric and electronic structure at ambient conditions, while overcoming X-ray damage to the redox active catalytic center, is key for deriving reaction mechanisms. Such studies become possible by using the intense and ultra-short femtosecond X-ray pulses from an XFEL, where sample is probed before it is damaged. We have developed methodology for simultaneously collecting X-ray diffraction data and X-ray emission spectra, using an energy dispersive spectrometer, at ambient conditions, and used this approach to study the room temperature structure and intermediate states of the photosynthetic water oxidizing metallo-protein, photosystem II. Moreover, we have also used this setup to simultaneously collect the X-ray emission spectra from multiple metals to follow the ultrafast dynamics of light-induced charge transfer between multiple metal sites. A Mn-Ti containing system was studied at an XFEL to demonstrate the efficacy and potential of this method.

A Case of Streptobacillus moniliformis Infection with Cutaneous Leukocytoclastic Vasculitis

A 71-year-old man presented with a high fever, polyarthralgia, petechiae and palpable purpura accompanied by livedoid change on his legs and feet. Histopathological findings of the purpura revealed perivascular infiltration of neutrophils, mononuclear cells, and nuclear debris, and extravasation of red cells mainly in the upper dermis: all signs consistent with leukocytoclastic vasculitis. Small vessel thrombi, which are characteristic features of septic vasculopathy, were also observed. Direct immunofluorescence showed negative results. Blood culture revealed the growth of gram-negative bacilli. Subsequently, 16S rRNA sequencing of DNA confirmed the organism as Streptobacillus moniliformis, which is the causative pathogen of rat-bite fever. He had frequently encountered wild rats in his house although there was no evidence of rat bite on his body. Empiric therapy with intravenous administration of ceftriaxone in combination with azithromycin hydrate led to a prompt resolution of the symptoms. Precise history-taking related to contact with rats and detection of skin eruptions suggestive of leukocytoclastic vasculitis on the extremities, especially on the feet, can be clues to Streptobacillus moniliformis infection. Familiarity with its cutaneous features is important for early diagnosis; the evidence herein may also help in understanding its underlying pathogenesis.

Surface freezing and surface coverage as key factors for spontaneous formation of colloidal fibers in vacuum drying of colloidal suspensions

In this study, we investigated vacuum drying of droplets of colloidal suspension. Because of the loss of the latent heat of vaporization, the drying droplet was cooled and then formed ice. Colloidal fibers consisting of packed particles spontaneously formed when the droplet froze from the gas-liquid interface. Conversely, we observed formation of sponge-like porous structures of particles when the whole droplet almost simultaneously froze. However, the freezing mode was not the only factor for formation of colloidal fibers. We found that the surface coverage of particles on the gas-liquid interface was also important. Owing to drying, some particles accumulated at the interface before freezing. When the surface coverage was higher than a threshold value, formation of fibers was severely restricted even in the surface freezing mode. Our results clearly show the important roles of surface freezing and the surface coverage of particles on the gas-liquid interface in formation of colloidal fibers.

Abstract 105: The Novel Heart-specific Ring-finger Protein 207 Regulates Energy Metabolism in Cardiomyocytes

Background: Ring-finger proteins constitute a large protein family in the human genome and play essential roles in various biological processes. However, little is known about heart-specific Ring-finger proteins and those relations with cardiac functions. We performed the comprehensive analysis of the expression profiles of various kinds of Ring-finger proteins and found that Ring-finger protein 207 (RNF207) was largely expressed in the heart. The purpose of our study was to elucidate a role of RNF207 in the heart.

Methods and Results: First, we confirmed that RNF207 was predominantly expressed in the heart at the mRNA and protein level. Next, we examined whether the expression of RNF207 changed in transverse aortic constriction (TAC) model mice and coronary ischemic heart failure model mice . 4 weeks after TAC, mRNA level of RNF207 was significantly decreased to approximately 40% of that in sham mice. Moreover, we found that the protein level of RNF207 in the mice with heart failure was significantly reduced to around 70% of that in sham mice. Considering the well-known facts that the heart is a high-energy demanding organ and that the levels of ATP in cardiomyocytes are reduced in those model mice, we hypothesized that RNF207 got involved in cardiac energy metabolism. To investigate the hypothesis, we depleted RNF207 in rat neonatal cardiomyocytes (RNC) and performed metabolomic analysis. Metabolomic analysis revealed that ATP concentration and NADH/NAD + ratio were significantly lower and mitochondrial function was significantly reduced in RNF207 depleted RNC, compared to control NRC. Next, to elucidate the molecular mechanism by which RNF207 had effect on cardiac energy metabolism, we explored RNF207-associated proteins by mass spectrometric analysis. We identified voltage-dependent anion channel 1 (VDAC1) as a RNF207-associated protein. It has been shown that mitochondrial protein VDAC1 plays a crucial role in mitochondrial functions, such as energy metabolism. We confirmed that RNF207 directly interacted with VDAC1 by in vitro binding assay. Our results strongly indicate that RNF207 functions as a regulator of cardiac energy metabolism.

Conclusion: RNF207 is a novel heart-specific protein and regulates energy metabolism in cardiomyocytes.

Ultrafast energy- and momentum-resolved dynamics of magnetic correlations in the photo-doped Mott insulator Sr2IrO4

Measuring how the magnetic correlations evolve in doped Mott insulators has greatly improved our understanding of the pseudogap, non-Fermi liquids and high-temperature superconductivity. Recently, photo-excitation has been used to induce similarly exotic states transiently. However, the lack of available probes of magnetic correlations in the time domain hinders our understanding of these photo-induced states and how they could be controlled. Here, we implement magnetic resonant inelastic X-ray scattering at a free-electron laser to directly determine the magnetic dynamics after photo-doping the Mott insulator Sr2IrO4. We find that the non-equilibrium state, 2 ps after the excitation, exhibits strongly suppressed long-range magnetic order, but hosts photo-carriers that induce strong, non-thermal magnetic correlations. These two-dimensional (2D) in-plane Néel correlations recover within a few picoseconds, whereas the three-dimensional (3D) long-range magnetic order restores on a fluence-dependent timescale of a few hundred picoseconds. The marked difference in these two timescales implies that the dimensionality of magnetic correlations is vital for our understanding of ultrafast magnetic dynamics.

Formation of defect-fluorite structured NdNiOxHy epitaxial thin films via a soft chemical route from NdNiO3 precursors

A new phase of oxyhydride NdNiO_xH_y with a defect-fluorite structure was obtained by a soft chemical reaction of NdNiO₃ epitaxial thin films on a substrate of SrTiO₃ (100) with CaH₂.

Ultraviolet photochemical reaction of [Fe(III)(C2O4)3](3-) in aqueous solutions studied by femtosecond time-resolved X-ray absorption spectroscopy using an X-ray free electron laser

Time-resolved X-ray absorption spectroscopy was performed for aqueous ammonium iron(III) oxalate trihydrate solutions using an X-ray free electron laser and a synchronized ultraviolet laser. The spectral and time resolutions of the experiment were 1.3 eV and 200 fs, respectively. A femtosecond 268 nm pulse was employed to excite [Fe(III)(C2O4)3](3-) in solution from the high-spin ground electronic state to ligand-to-metal charge transfer state(s), and the subsequent dynamics were studied by observing the time-evolution of the X-ray absorption spectrum near the Fe K-edge. Upon 268 nm photoexcitation, the Fe K-edge underwent a red-shift by more than 4 eV within 140 fs; however, the magnitude of the redshift subsequently diminished within 3 ps. The Fe K-edge of the photoproduct remained lower in energy than that of [Fe(III)(C2O4)3](3-). The observed red-shift of the Fe K-edge and the spectral feature of the product indicate that Fe(III) is upon excitation immediately photoreduced to Fe(II), followed by ligand dissociation from Fe(II). Based on a comparison of the X-ray absorption spectra with density functional theory calculations, we propose that the dissociation proceeds in two steps, forming first [(CO2 (•))Fe(II)(C2O4)2](3-) and subsequently [Fe(II)(C2O4)2](2-).

Vacuum space charge effects in sub-picosecond soft X-ray photoemission on a molecular adsorbate layer

Vacuum space charge induced kinetic energy shifts of O 1s and Ru 3d core levels in femtosecond soft X-ray photoemission spectra (PES) have been studied at a free electron laser (FEL) for an oxygen layer on Ru(0001). We fully reproduced the measurements by simulating the in-vacuum expansion of the photoelectrons and demonstrate the space charge contribution of the high-order harmonics in the FEL beam. Employing the same analysis for 400 nm pump-X-ray probe PES, we can disentangle the delay dependent Ru 3d energy shifts into effects induced by space charge and by lattice heating from the femtosecond pump pulse.

High-precision x-ray FEL pulse arrival time measurements at SACLA by a THz streak camera with Xe clusters

The accurate measurement of the arrival time of a hard X-ray free electron laser (FEL) pulse with respect to a laser is of utmost importance for pump-probe experiments proposed or carried out at FEL facilities around the world. This manuscript presents the latest device to meet this challenge, a THz streak camera using Xe gas clusters, capable of pulse arrival time measurements with an estimated accuracy of several femtoseconds. An experiment performed at SACLA demonstrates the performance of the device at photon energies between 5 and 10 keV with variable photon beam parameters.

One-minute mental status examination for category fluency is more useful than mini-mental state examination to evaluate the reliability of insulin self-injection in elderly diabetic patients

AIMS/INTRODUCTION

We investigated the factors associated with the reliability of insulin self-injection in elderly diabetic patients receiving insulin therapy.

MATERIALS AND METHODS

We enrolled diabetic patients aged ≥65 years and receiving insulin therapy, and assessed their cognitive function by the mini-mental state examination and 1-min mental status examination for category fluency. We also observed their technique of insulin self-injection, and evaluated whether or not patients were able to inject insulin by themselves according to nine defined details in terms of insulin self-injection. The predictive factors for the reliability of insulin self-injection were determined by univariate and multivariate logistic regression analysis. There were 278 participants (135 males, 143 females) enrolled in the present study.

RESULTS

According to multivariate logistic regression analysis, only the 1-min mental status examination score was found to be a significant independent predictor of the reliability of insulin self-injection (odds ratio 0.75; 95% confidence interval 0.62-0.90; P = 0.002).

CONCLUSIONS

The 1-min mental status examination for category fluency can be considered more useful than mini-mental state examination to evaluate the reliability of insulin self-injection in elderly diabetic patients receiving insulin therapy.