Transonic Dislocation Propagation in Diamond

The motion of line defects (dislocations) has been studied for over 60 years but the maximum speed at which they can move is unresolved. Recent models and atomistic simulations predict the existence of a limiting velocity of dislocation motions between the transonic and subsonic ranges at which the self-energy of dislocation diverges, though they do not deny the possibility of the transonic dislocations. We use femtosecond x-ray radiography to track ultrafast dislocation motion in shock-compressed single-crystal diamond. By visualizing stacking faults extending faster than the slowest sound wave speed of diamond, we show the evidence of partial dislocations at their leading edge moving transonically. Understanding the upper limit of dislocation mobility in crystals is essential to accurately model, predict, and control the mechanical properties of materials under extreme conditions

Simultaneous Bright- and Dark-Field X-ray Microscopy at X-ray Free Electron Lasers

The structures, strain fields, and defect distributions in solid materials underlie the mechanical and physical properties across numerous applications. Many modern microstructural microscopy tools characterize crystal grains, domains and defects required to map lattice distortions or deformation, but are limited to studies of the (near) surface. Generally speaking, such tools cannot probe the structural dynamics in a way that is representative of bulk behavior. Synchrotron X-ray diffraction based imaging has long mapped the deeply embedded structural elements, and with enhanced resolution, Dark Field X-ray Microscopy (DFXM) can now map those features with the requisite nm-resolution. However, these techniques still suffer from the required integration times due to limitations from the source and optics. This work extends DFXM to X-ray free electron lasers, showing how the $10^{12}$ photons per pulse available at these sources offer structural characterization down to 100 fs resolution (orders of magnitude faster than current synchrotron images). We introduce the XFEL DFXM setup with simultaneous bright field microscopy to probe density changes within the same volume. This work presents a comprehensive guide to the multi-modal ultrafast high-resolution X-ray microscope that we constructed and tested at two XFELs, and shows initial data demonstrating two timing strategies to study associated reversible or irreversible lattice dynamics

胸部外科手術後のPeak cough flow とMaximum phonation time の関係

研究論文Original Articles　手術後の肺活量（VC）が咳嗽力（PCF）に影響を及ぼすことは明らかだが，最大発声持続時間（MPT）で評価される声門閉鎖機能低下がPCF に及ぼす影響は明らかとなっていない．本研究では呼吸器外科手術後の患者28 例においてMPT とPCF の関係を明らかにすることを目的とし，手術後1 日目〜5 日目にPCF，MPT，VC を測定した．手術後5 日目までPCF およびMPT は，手術前と比較し有意に低下した（p <0.05）． またPCF とMPT の回復率には手術後1 日目のみに相関関係を認めた（r= 0.53，p <0.05）．PCF とVC の回復率は手術後1 日目〜5 日目まで相関を認めた（r = 0.41-0.27，p <0.05）．手術後の声門閉鎖機能低下が咳嗽力に及ぼす影響は，人工呼吸器離脱後１日目までで，その後はVC の影響を強く受けると考えられた．　The vital capacity（ VC） after thoracic surgery affects peak cough flow（ PCF）.　However, the influence of glottic closure deterioration evaluated by maximum phonation time （MPT） on PCF is not clear. We clarified the relationship between coughing and vocal cord function in 28 patients after thoracic surgery. We measured the PCF, MPT, and VC on postoperative days 1 to 5. On postoperative day 1, the mean PCF decreased to 58.0% and the mean MPT decreased to 62.5%. The mean PCFs and MPTs on postoperative days 1 to 5 were significantly lower than the preoperative PCF and MPT, respectively （p < 0.05）. There was a positive correlation between the rates of change in the PCF and MPT only on postoperative day 1 （r = 0.53, p < 0.05）. There was also a positive correlation between the rates of change in the PCF and VC on postoperative days 1 to 5 （r = 0.41–0.27, p < 0.05）. Cough intensity was affected by the vocal cord function on postoperative day 1. However, after postoperative day 2, the cough intensity was not influenced by the vocal cord function. Declining glottal closure function（ vocal cord function） immediately after surgery affects the cough intensity and vocal function. The influence of reduction in glottic closure function after surgery on coughing decline was observed up to 1 day after the withdrawal of ventilatory support. After the secondpostoperative day, the PCF was strongly influenced by the VC

Risk factors for decreased walking ability in hospitalized patients with aspiration pneumonia

Objective To evaluate the factors that influence walking ability in patients hospitalized due to aspiration pneumonia. Methods This retrospective observational study evaluated patients hospitalized with aspiration pneumonia. The primary endpoint was preservation of walking ability. Univariate and multivariate logistic regression analyses were performed with the preservation of walking ability as the dependent variable. Results A total of 143 patients were enrolled in this study. The patients were divided into two groups: those whose walking ability decreased after hospitalization ( n  = 61) and those whose walking ability was maintained after hospitalization ( n  = 82). Multivariate logistic regression analyses showed that A-DROP (odds ratio [OR] 3.006; 95% confidence interval [CI] 1.452, 6.541; P  < 0.01), the Geriatric Nutritional Risk Index (OR 0.919; 95% CI 0.875, 0.960; P <  0.001) and days to initial mobilization (OR 1.221; 95% CI 1.036, 1.531; P <  0.05) were the independent early predictors for preservation of walking ability. Conclusion Nutritional status and early mobilization were important risk factors affecting the maintenance of walking ability in patients hospitalized due to aspiration pneumonia. Thus, a combination of nutrition and early rehabilitation is needed for these patients. Registry of Research Studies involving Human Subjects This study was registered with the University Hospital Medical Information Network Clinical Trial Registry (UMIN 000046923)

The severity of nutrition and pneumonia predicts survival in patients with aspiration pneumonia: A retrospective observational study

Abstract Introduction Aspiration pneumonia is a common problem among older adults; it has a high mortality rate and the prevalence is increasing. Reports on the risk factors for mortality in patients with aspiration pneumonia are limited. This study aimed to evaluate the risk factors for 90‐day survival in patients with aspiration pneumonia. Methods This retrospective observational study was conducted at Seirei Mikatahara General Hospital between 1 April 2015 and 31 March 2016. Patients with aspiration pneumonia who had dysphagia or aspiration confirmed by modified water swallow test or VideoEndoscopic examination of swallowing were included. The primary endpoint was 90‐day survival. We performed univariate and multivariate logistic regression analyses with survival and non‐survival at 90 days as the independent variables. Results A total of 276 patients were recruited for this study. The A‐DROP score (odds ratio [OR] = 2.440; 95% confidence interval [CI], 1.400–4.270; p < 0.01), Geriatric Nutritional Risk Index score (OR = 0.383; 95% CI, 0.178–0.824; p < 0.05) and sex (OR = 0.365; 95% CI, 0.153–0.869; p < 0.05) were independent early predictors of mortality. Conclusion The results suggest that nutritional status and the severity of pneumonia are important factors that predict life expectancy in patients with aspiration pneumonia

Hugoniot and released state of calcite above 200 GPa with implications for hypervelocity planetary impacts

International audienceCarbonate minerals, for example calcite and magnesite, exist on the planetary surfaces of the Earth, Mars, and Venus, and are subjected to hypervelocity collisions. The physical properties of planetary materials at extreme conditions are essential for understanding their dynamic behaviors at hypervelocity collisions and the mantle structure of rocky planets including Super-Earths. Here we report laboratory investigations of laser-shocked calcite at pressures of 200-960 GPa (impact velocities of 12-30 km/s and faster than escape velocity from the Earth) using decay shock techniques. Our measured temperatures above 200 GPa indicated a large difference from the previous theoretical models. The present shock Hugoniot data and temperature measurements, compared with the previous reports, indicate melting without decomposition at pressures of ~110 GPa to ~350 GPa and a bonded liquid up to 960 GPa from the calculated specific heat. Our temperature calculations of calcite at 1 atm adiabatically released from the Hugoniot points suggest that the released products vary depending on the shock pressures and affect the planetary atmosphere by the degassed species. The present results on calcite newly provide an important anchor for considering the theoretical EOS at the extreme conditions, where the model calculations show a significant diversity at present

Liquid structure of tantalum under internal negative pressure

In situ femtosecond x-ray diffraction measurements and ab initio molecular dynamics simulations were performed to study the liquid structure of tantalum shock-released from several hundred gigapascals (GPa) to the ambient condition on the nanosecond timescale. The results show that the internal negative pressure applied to the liquid tantalum reached -5.6 (0.8) GPa, suggesting the existence of a liquid-gas mixing state due to cavitation. This is the first direct evidence to prove the classical nucleation theory which predicts that liquids with high surface tension can support GPa regime tensile stress

Ultrafast olivine-ringwoodite transformation during shock compression

International audienceMeteorites from interplanetary space often include high-pressure polymorphs of their constituent minerals, which provide records of past hypervelocity collisions. These collisions were expected to occur between kilometre-sized asteroids, generating transient high-pressure states lasting for several seconds to facilitate mineral transformations across the relevant phase boundaries. However, their mechanisms in such a short timescale were never experimentally evaluated and remained speculative. Here, we show a nanosecond transformation mechanism yielding ringwoodite, which is the most typical high-pressure mineral in meteorites. An olivine crystal was shock-compressed by a focused high-power laser pulse, and the transformation was time-resolved by femtosecond diffractometry using an X-ray free electron laser. Our results show the formation of ringwoodite through a faster, diffusionless process, suggesting that ringwoodite can form from collisions between much smaller bodies, such as metre to submetre-sized asteroids, at common relative velocities. Even nominally unshocked meteorites could therefore contain signatures of high-pressure states from past collisions

Direct imaging of shock wave splitting in diamond at Mbar pressure

International audienceUnderstanding the behavior of matter at extreme pressures of the order of a megabar (Mbar) is essential to gain insight into various physical phenomena at macroscales—the formation of planets, young stars, and the cores of super-Earths, and at microscales—damage to ceramic materials and high-pressure plastic transformation and phase transitions in solids. Under dynamic compression of solids up to Mbar pressures, even a solid with high strength exhibits plastic properties, causing the induced shock wave to split in two: an elastic precursor and a plastic shock wave. This phenomenon is described by theoretical models based on indirect measurements of material response. The advent of x-ray free-electron lasers (XFELs) has made it possible to use their ultrashort pulses for direct observations of the propagation of shock waves in solid materials by the method of phase-contrast radiography. However, there is still a lack of comprehensive data for verification of theoretical models of different solids. Here, we present the results of an experiment in which the evolution of the coupled elastic–plastic wave structure in diamond was directly observed and studied with submicrometer spatial resolution, using the unique capabilities of the x-ray free-electron laser (XFEL). The direct measurements allowed, for the first time, the fitting and validation of the 2D failure model for diamond in the range of several Mbar. Our experimental approach opens new possibilities for the direct verification and construction of equations of state of matter in the ultra-high-stress range, which are relevant to solving a variety of problems in high-energy-density physics

Evidence of shock-compressed stishovite above 300 GPa

International audienceSio 2 is one of the most fundamental constituents in planetary bodies, being an essential building block of major mineral phases in the crust and mantle of terrestrial planets (1-10 M E). Silica at depths greater than 300 km may be present in the form of the rutile-type, high pressure polymorph stishovite (P4 2 /mnm) and its thermodynamic stability is of great interest for understanding the seismic and dynamic structure of planetary interiors. previous studies on stishovite via static and dynamic (shock) compression techniques are contradictory and the observed differences in the lattice-level response is still not clearly understood. Here, laser-induced shock compression experiments at the LcLS-and SAcLA XfeL light-sources elucidate the high-pressure behavior of stishovite on the lattice-level under in situ conditions on the Hugoniot to pressures above 300 GPa. We find stishovite is still (meta-)stable at these conditions, and does not undergo any phase transitions. this contradicts static experiments showing structural transformations to the cacl 2 , α-pbo 2 and pyrite-type structures. However, rate-limited kinetic hindrance may explain our observations. these results are important to our understanding into the validity of eoS data from nanosecond experiments for geophysical applications