High-resolution inelastic x-ray scattering at the high energy density scientific instrument at the European X-Ray Free-Electron Laser.

We introduce a setup to measure high-resolution inelastic x-ray scattering at the High Energy Density scientific instrument at the European X-Ray Free-Electron Laser (XFEL). The setup uses the Si (533) reflection in a channel-cut monochromator and three spherical diced analyzer crystals in near-backscattering geometry to reach a high spectral resolution. An energy resolution of 44 meV is demonstrated for the experimental setup, close to the theoretically achievable minimum resolution. The analyzer crystals and detector are mounted on a curved-rail system, allowing quick and reliable changes in scattering angle without breaking vacuum. The entire setup is designed for operation at 10 Hz, the same repetition rate as the high-power lasers available at the instrument and the fundamental repetition rate of the European XFEL. Among other measurements, it is envisioned that this setup will allow studies of the dynamics of highly transient laser generated states of matter.

Mirror to measure small angle x-ray scattering signal in high energy density experiments.

Small angle x-ray scattering (SAXS) is a well established technique to detect nanometer scale structures in matter. In a typical setup, this diagnostic uses a detector with a direct line of sight to the scattering target. However, in the harsh environment of high intensity laser interaction, intense secondary radiation and high-energy particles are generated. Such a setup would therefore suffer a significant increase of noise due to this background, which could eventually prevent such measurements. In this paper, we present a novel tool consisting of a mosaic graphite crystal that works as a mirror for the SAXS signal and allows us to position the detector behind appropriate shielding. This paper studies the performance of this mirror both by experiment at the European XFEL (X-Ray Free-Electron Laser Facility) laboratory and by simulations.

An approach for the measurement of the bulk temperature of single crystal diamond using an X-ray free electron laser.

We present a method to determine the bulk temperature of a single crystal diamond sample at an X-Ray free electron laser using inelastic X-ray scattering. The experiment was performed at the high energy density instrument at the European XFEL GmbH, Germany. The technique, based on inelastic X-ray scattering and the principle of detailed balance, was demonstrated to give accurate temperature measurements, within [Formula: see text] for both room temperature diamond and heated diamond to 500 K. Here, the temperature was increased in a controlled way using a resistive heater to test theoretical predictions of the scaling of the signal with temperature. The method was tested by validating the energy of the phonon modes with previous measurements made at room temperature using inelastic X-ray scattering and neutron scattering techniques. This technique could be used to determine the bulk temperature in transient systems with a temporal resolution of 50 fs and for which accurate measurements of thermodynamic properties are vital to build accurate equation of state and transport models.

A sensitive EUV Schwarzschild microscope for plasma studies with sub-micrometer resolution.

We present an extreme ultraviolet (EUV) microscope using a Schwarzschild objective which is optimized for single-shot sub-micrometer imaging of laser-plasma targets. The microscope has been designed and constructed for imaging the scattering from an EUV-heated solid-density hydrogen jet. Imaging of a cryogenic hydrogen target was demonstrated using single pulses of the free-electron laser in Hamburg (FLASH) free-electron laser at a wavelength of 13.5 nm. In a single exposure, we observe a hydrogen jet with ice fragments with a spatial resolution in the sub-micrometer range. In situ EUV imaging is expected to enable novel experimental capabilities for warm dense matter studies of micrometer-sized samples in laser-plasma experiments.

Relativistic Electron Streaming Instabilities Modulate Proton Beams Accelerated in Laser-Plasma Interactions.

We report experimental evidence that multi-MeV protons accelerated in relativistic laser-plasma interactions are modulated by strong filamentary electromagnetic fields. Modulations are observed when a preplasma is developed on the rear side of a µm-scale solid-density hydrogen target. Under such conditions, electromagnetic fields are amplified by the relativistic electron Weibel instability and are maximized at the critical density region of the target. The analysis of the spatial profile of the protons indicates the generation of B>10 MG and E>0.1 MV/µm fields with a µm-scale wavelength. These results are in good agreement with three-dimensional particle-in-cell simulations and analytical estimates, which further confirm that this process is dominant for different target materials provided that a preplasma is formed on the rear side with scale length ≳0.13λ_{0}sqrt[a_{0}]. These findings impose important constraints on the preplasma levels required for high-quality proton acceleration for multipurpose applications.

Development of a cryogenic hydrogen microjet for high-intensity, high-repetition rate experiments.

The advent of high-intensity, high-repetition-rate lasers has led to the need for replenishing targets of interest for high energy density sciences. We describe the design and characterization of a cryogenic microjet source, which can deliver a continuous stream of liquid hydrogen with a diameter of a few microns. The jet has been imaged at 1 µm resolution by shadowgraphy with a short pulse laser. The pointing stability has been measured at well below a mrad, for a stable free-standing filament of solid-density hydrogen.

High-intensity laser-accelerated ion beam produced from cryogenic micro-jet target.

We report on the successful operation of a newly developed cryogenic jet target at high intensity laser-irradiation. Using the frequency-doubled Titan short pulse laser system at Jupiter Laser Facility, Lawrence Livermore National Laboratory, we demonstrate the generation of a pure proton beam a with maximum energy of 2 MeV. Furthermore, we record a quasi-monoenergetic peak at 1.1 MeV in the proton spectrum emitted in the laser forward direction suggesting an alternative acceleration mechanism. Using a solid-density mixed hydrogen-deuterium target, we are also able to produce pure proton-deuteron ion beams. With its high purity, limited size, near-critical density, and high-repetition rate capability, this target is promising for future applications.

Measurement of high-dynamic range x-ray Thomson scattering spectra for the characterization of nano-plasmas at LCLS.

Atomic clusters can serve as ideal model systems for exploring ultrafast (∼100 fs) laser-driven ionization dynamics of dense matter on the nanometer scale. Resonant absorption of optical laser pulses enables heating to temperatures on the order of 1 keV at near solid density conditions. To date, direct probing of transient states of such nano-plasmas was limited to coherent x-ray imaging. Here we present the first measurement of spectrally resolved incoherent x-ray scattering from clusters, enabling measurements of transient temperature, densities, and ionization. Single shot x-ray Thomson scattering signals were recorded at 120 Hz using a crystal spectrometer in combination with a single-photon counting and energy-dispersive pnCCD. A precise pump laser collimation scheme enabled recording near background-free scattering spectra from Ar clusters with an unprecedented dynamic range of more than 3 orders of magnitude. Such measurements are important for understanding collective effects in laser-matter interactions on femtosecond time scales, opening new routes for the development of schemes for their ultrafast control.

Nanosecond formation of diamond and lonsdaleite by shock compression of graphite.

The shock-induced transition from graphite to diamond has been of great scientific and technological interest since the discovery of microscopic diamonds in remnants of explosively driven graphite. Furthermore, shock synthesis of diamond and lonsdaleite, a speculative hexagonal carbon polymorph with unique hardness, is expected to happen during violent meteor impacts. Here, we show unprecedented in situ X-ray diffraction measurements of diamond formation on nanosecond timescales by shock compression of pyrolytic as well as polycrystalline graphite to pressures from 19 GPa up to 228 GPa. While we observe the transition to diamond starting at 50 GPa for both pyrolytic and polycrystalline graphite, we also record the direct formation of lonsdaleite above 170 GPa for pyrolytic samples only. Our experiment provides new insights into the processes of the shock-induced transition from graphite to diamond and uniquely resolves the dynamics that explain the main natural occurrence of the lonsdaleite crystal structure being close to meteor impact sites.

Equilibration dynamics and conductivity of warm dense hydrogen.

We investigate subpicosecond dynamics of warm dense hydrogen at the XUV free-electron laser facility (FLASH) at DESY (Hamburg). Ultrafast impulsive electron heating is initiated by a ≤ 300-fs short x-ray burst of 92-eV photon energy. A second pulse probes the sample via x-ray scattering at jitter-free variable time delay. We show that the initial molecular structure dissociates within (0.9 ± 0.2) ps, allowing us to infer the energy transfer rate between electrons and ions. We evaluate Saha and Thomas-Fermi ionization models in radiation hydrodynamics simulations, predicting plasma parameters that are subsequently used to calculate the static structure factor. A conductivity model for partially ionized plasma is validated by two-temperature density-functional theory coupled to molecular dynamic simulations and agrees with the experimental data. Our results provide important insights and the needed experimental data on transport properties of dense plasmas.

Is vestibular rehabilitation as effective in bilateral vestibular dysfunction as in unilateral vestibular dysfunction?

BACKGROUND: Bilateral vestibular dysfunction causes serious disabilities and handicaps. Patients with bilateral dysfunction often restrict their activities and tend to be unsocial. AIM: To compare the effects of vestibular rehabilitation on disability, balance, and postural stability in patients with unilateral and bilateral vestibular dysfunction. DESIGN: Retrospective study. SETTING: Outpatient rehabilitation center. POPULATION: Patients with unilateral (group 1, N.=42) and bilateral vestibular dysfunction (group 2, N.=19). METHODS: All patients were evaluated before and after eight weeks of customized vestibular rehabilitation for disability (Dizziness Handicap Inventory [DHI], Activities-specific Balance Confidence Scale [ABC]), dynamic balance (Timed Up and Go Test [TUG], Dynamic Gait Index [DGI]), and postural stability (static posturography). RESULTS: The differences between DHI, TUG, DGI, and falling index (as assessed by static posturography) scores before and after the exercise program were statistically significant in both groups (P<0.05). There were no significant intergroup differences in any of the parameters evaluated (P>0.05). CONCLUSION: In this study, vestibular rehabilitation was found to be equally effective in unilateral and bilateral vestibular dysfunction patients for improving disability, dynamic balance, and postural stability. CLINICAL REHABILITATION IMPACT: Patients with bilateral dysfunction, causing more disability and greater handicap may indeed regain their functions as in patients with unilateral vestibular dysfunction by receiving appropriate and adequate vestibular rehabilitation.

Resolving ultrafast heating of dense cryogenic hydrogen.

We report on the dynamics of ultrafast heating in cryogenic hydrogen initiated by a ≲300 fs, 92 eV free electron laser x-ray burst. The rise of the x-ray scattering amplitude from a second x-ray pulse probes the transition from dense cryogenic molecular hydrogen to a nearly uncorrelated plasmalike structure, indicating an electron-ion equilibration time of ∼0.9 ps. The rise time agrees with radiation hydrodynamics simulations based on a conductivity model for partially ionized plasma that is validated by two-temperature density-functional theory.

Nasal and paranasal involvement in primary Sjogren`s syndrome.

BACKGROUND: The aim of this study is to investigate nasal and paranasal signs and symptoms of the primary Sjogren`s syndrome patients and compare them with healthy controls. METHODOLOGY: Seventy-seven (7 M, 70 F) primary Sjogren`s syndrome patients and 77 healthy controls were included in the study. Anterior rhinoscopy, nasal endoscopy, 5 component smell discrimination test, nasal clearance analysis with saccharin test and electrorhinomanometer were performed. RESULTS: Nasal crusting was present in 31 and 24 individuals in patient and control groups, respectively. Sinusitis was present in 2 and 1 individuals in patient and control groups, respectively. Nasal polyposis was present in 7 and 1 individuals in patient and control groups, respectively. These differences were not statistically different. CONCLUSION: Although there were some findings in a few patients, nasal findings were insignificant and mild even in patients with severe oral or ocular findings. Rhinomanometry, nasal clearance determination or smell discrimination tests have very little value in the diagnosis or management of primary Sjogren`s syndrome. Nasal polyposis was higher in the patient group, though it did not reach a significant level. Nasal glandular involvement is mild and insignificant in primary Sjogren`s syndrome.

Significance of vitronectin and PAI-1 activity levels in carotid artery disease: comparison of symptomatic and asymptomatic patients.

AIM: Carotid atherosclerosis one of the main risk factors for ischemic stroke. Acute thrombosis after atherosclerotic plaque disruption is a major complication of primary atherosclerosis, leading to acute ischemic syndromes and atherosclerotic progression. PAI-1 is the most important and most rapidly acting physiological inhibitor of tissue-type (t-PA) and urokinase type (u-PA) plasminogen activators. Active PAI-1 form spontaneously converts to the latent with a half-life of ~1 h. Complex formation with vitronectin increases half life of PAI-1 by two- to four-folds. Thus, this inhibitor function of PAI-1 facilitated by Vn that binds the inhibitor and may regulate its activity by the stabilizing the active PAI-1 conformation. In addition, PAI-1/VN complexes may effect vascular structure and function. However, the exact role of these complexes in vascular remodelling are not completely clear. The aim of the present study was determining, correlating and comparing the plasma vitronectin, t-PA and PAI-1 activity levels in asymptomatic and symptomatic patients with carotid artery plaque. METHODS: A total of 37 carotid artery disease patients were included in this study. Blood samples were obtained from Cerrahpasa Medical School, Department of Heart and Vessel Surgery, University of Istanbul. Plasma vitronectin, tPA and PAI-1 activity levels were determined by ELISA. RESULTS: We found plasma PAI-1 activity levels were elevated in the asymptomatic group as compared with symptomatic group (P=0.038). We have also found a positive correlation between PAI-1 activity and vitronectin levels in symptomatic group (r=0.399, P=0.039). CONCLUSION: Decreased PAI-1 activity levels correlate with vitronectin in the symptomatic group; a) may be the consequence a compensatory mechanisms (due to possibilty in increased fibrinolytic activity and decreased vascular remodelling) against disease progression. b) or may be also cause progression of disease by increase of vascular remodelling.

Asymmetric adenoid hypertrophy in a patient with ipsilateral rhinolithiasis: an overlooked entity?

The aim of this article is to present a rhinolithiasis patient with a significant asymmetric adenoid hypertrophy on the same side and to describe possible mechanisms for this clinical entity. Careful nasopharyngoscopy after removal of rhinolith is mandatory not to overlook significant adenoid hypertrophy which may interfere with patients' symptoms. The role of paranasal CT scan in the diagnosis of an asymmetric adenoid hypertrophy in rhinolithiasis patients is also discussed.

Electronic structure of an XUV photogenerated solid-density aluminum plasma.

By use of high intensity XUV radiation from the FLASH free-electron laser at DESY, we have created highly excited exotic states of matter in solid-density aluminum samples. The XUV intensity is sufficiently high to excite an inner-shell electron from a large fraction of the atoms in the focal region. We show that soft-x-ray emission spectroscopy measurements reveal the electronic temperature and density of this highly excited system immediately after the excitation pulse, with detailed calculations of the electronic structure, based on finite-temperature density functional theory, in good agreement with the experimental results.

Steplike intensity threshold behavior of extreme ionization in laser-driven xenon clusters.

The generation of highly charged Xe(q+) ions up to q=24 is observed in Xe clusters embedded in helium nanodroplets and exposed to intense femtosecond laser pulses (λ=800 nm). Laser intensity resolved measurements show that the high-q ion generation starts at an unexpectedly low threshold intensity of about 10(14) W/cm2. Above threshold, the Xe ion charge spectrum saturates quickly and changes only weakly for higher laser intensities. Good agreement between these observations and a molecular dynamics analysis allows us to identify the mechanisms responsible for the highly charged ion production and the surprising intensity threshold behavior of the ionization process.