Transport of dust across the Solar System: Constraints on the spatial origin of individual micrometeorites from cosmic-ray exposure.

The origin of micrometeorites (MMs) from asteroids and comets is well-established, but the relative contribution from these two classes remains poorly resolved. Likewise, determining the precise origin of individual MMs is an open challenge. Here, cosmic-ray exposure ages are used to resolve the spatial origins of 12 MMs collected from urban areas and Antarctica. Their 26Al and 10Be concentration, produced during cosmic-ray irradiation in space, were measured by accelerator mass spectrometry. These data are compared to results from a model simulating the transport and irradiation of the MM precursors in space. This model, for the first time, considers a variety of orbits, precursor particle sizes, compositions and densities and incorporates non-isotropic solar and galactic cosmic-ray flux profiles, depth-dependent production rates, as well as spherical evaporation during atmospheric entry. While the origin for six MMs remains ambiguous, two MMs show a preferential tendency towards an origin in the Inner Solar System (Near Earth Objects to the Asteroid Belt) and four towards an origin in the Outer Solar System (Jupiter Family Comets to the Kuiper Belt). These findings challenge the notion that dust originating from the Outer Solar System is unlikely to survive long-term transport and delivery to the terrestrial planets. This article is part of the theme issue 'Dust in the Solar System and beyond'.

Sub-micrometer focusing setup for high-pressure crystallography at the Extreme Conditions beamline at PETRA†III.

Scientific tasks aimed at decoding and characterizing complex systems and processes at high pressures set new challenges for modern X-ray diffraction instrumentation in terms of X-ray flux, focal spot size and sample positioning. Presented here are new developments at the Extreme Conditions beamline (P02.2, PETRA III, DESY, Germany) that enable considerable improvements in data collection at very high pressures and small scattering volumes. In particular, the focusing of the X-ray beam to the sub-micrometer level is described, and control of the aberrations of the focusing compound refractive lenses is made possible with the implementation of a correcting phase plate. This device provides a significant enhancement of the signal-to-noise ratio by conditioning the beam shape profile at the focal spot. A new sample alignment system with a small sphere of confusion enables single-crystal data collection from grains of micrometer to sub-micrometer dimensions subjected to pressures as high as 200 GPa. The combination of the technical development of the optical path and the sample alignment system contributes to research and gives benefits on various levels, including rapid and accurate diffraction mapping of samples with sub-micrometer resolution at multimegabar pressures.

Novel experimental setup for megahertz X-ray diffraction in a diamond anvil cell at the High Energy Density (HED) instrument of the European X-ray Free-Electron Laser (EuXFEL).

The high-precision X-ray diffraction setup for work with diamond anvil cells (DACs) in interaction chamber 2 (IC2) of the High Energy Density instrument of the European X-ray Free-Electron Laser is described. This includes beamline optics, sample positioning and detector systems located in the multipurpose vacuum chamber. Concepts for pump-probe X-ray diffraction experiments in the DAC are described and their implementation demonstrated during the First User Community Assisted Commissioning experiment. X-ray heating and diffraction of Bi under pressure, obtained using 20 fs X-ray pulses at 17.8 keV and 2.2 MHz repetition, is illustrated through splitting of diffraction peaks, and interpreted employing finite element modeling of the sample chamber in the DAC.

Simultaneous imaging and diffraction in the dynamic diamond anvil cell.

The ability to visualize a sample undergoing a pressure-induced phase transition allows for the determination of kinetic parameters, such as the nucleation and growth rates of the high-pressure phase. For samples that are opaque to visible light (such as metallic systems), it is necessary to rely on x-ray imaging methods for sample visualization. Here, we present an experimental platform developed at beamline P02.2 at the PETRA III synchrotron radiation source, which is capable of performing simultaneous x-ray imaging and diffraction of samples that are dynamically compressed in piezo-driven diamond anvil cells. This setup utilizes a partially coherent monochromatic x-ray beam to perform lensless phase contrast imaging, which can be carried out using either a parallel- or focused-beam configuration. The capabilities of this platform are illustrated by experiments on dynamically compressed Ga and Ar. Melting and solidification were identified based on the observation of solid/liquid phase boundaries in the x-ray images and corresponding changes in the x-ray diffraction patterns collected during the transition, with significant edge enhancement observed in the x-ray images collected using the focused-beam. These results highlight the suitability of this technique for a variety of purposes, including melt curve determination.

Non-destructive and quantitative imaging of a nano-structured microchip by ptychographic hard X-ray scanning microscopy.

We used hard X-ray scanning microscopy with ptychographic coherent diffraction contrast to image a front-end processed passivated microchip fabricated in 80 nm technology. No sample preparation was needed to image buried interconnects and contact layers with a spatial resolution of slightly better than 40 nm. The phase shift in the sample is obtained quantitatively. With the additional knowledge of the elemental composition determined in parallel by X-ray fluorescence mapping, quantitative information about specific nanostructures is obtained. A significant enhancement in signal-to-noise ratio and spatial resolution is achieved compared to conventional hard X-ray scanning microscopy.

Pump-probe X-ray holographic imaging of laser-induced cavitation bubbles with femtosecond FEL pulses.

Cavitation bubbles can be seeded from a plasma following optical breakdown, by focusing an intense laser in water. The fast dynamics are associated with extreme states of gas and liquid, especially in the nascent state. This offers a unique setting to probe water and water vapor far-from equilibrium. However, current optical techniques cannot quantify these early states due to contrast and resolution limitations. X-ray holography with single X-ray free-electron laser pulses has now enabled a quasi-instantaneous high resolution structural probe with contrast proportional to the electron density of the object. In this work, we demonstrate cone-beam holographic flash imaging of laser-induced cavitation bubbles in water with nanofocused X-ray free-electron laser pulses. We quantify the spatial and temporal pressure distribution of the shockwave surrounding the expanding cavitation bubble at time delays shortly after seeding and compare the results to numerical simulations.

Direct imaging of ultrafast lattice dynamics.

Under rapid high-temperature, high-pressure loading, lattices exhibit complex elastic-inelastic responses. The dynamics of these responses are challenging to measure experimentally because of high sample density and extremely small relevant spatial and temporal scales. Here, we use an x-ray free-electron laser providing simultaneous in situ direct imaging and x-ray diffraction to spatially resolve lattice dynamics of silicon under high-strain rate conditions. We present the first imaging of a new intermediate elastic feature modulating compression along the axis of applied stress, and we identify the structure, compression, and density behind each observed wave. The ultrafast probe x-rays enabled time-resolved characterization of the intermediate elastic feature, which is leveraged to constrain kinetic inhibition of the phase transformation between 2 and 4 ns. These results not only address long-standing questions about the response of silicon under extreme environments but also demonstrate the potential for ultrafast direct measurements to illuminate new lattice dynamics.

Imaging at an x-ray absorption edge using free electron laser pulses for interface dynamics in high energy density systems.

Tuning the energy of an x-ray probe to an absorption line or edge can provide material-specific measurements that are particularly useful for interfaces. Simulated hard x-ray images above the Fe K-edge are presented to examine ion diffusion across an interface between Fe2O3 and SiO2 aerogel foam materials. The simulations demonstrate the feasibility of such a technique for measurements of density scale lengths near the interface with submicron spatial resolution. A proof-of-principle experiment is designed and performed at the Linac coherent light source facility. Preliminary data show the change of the interface after shock compression and heating with simultaneous fluorescence spectra for temperature determination. The results provide the first demonstration of using x-ray imaging at an absorption edge as a diagnostic to detect ultrafast phenomena for interface physics in high-energy-density systems.

Effects of oxaceprol on the microcirculation in ischemia/reperfusion injury.

Oxaceprol, an established drug for treatment of degenerative joint disease, has recently been shown in vitro to reduce leukocyte adhesion to cultured endothelial cells and leukocyte extravasation in vivo in an arthritis animal model. The aim of this study was to examine the effects of Oxaceprol on the microcirculation of striated skin muscle. In the dorsal skinfold chamber of the awake Syrian golden hamster I/R injury was induced by applying a 4-hour complete pressure ischemia. Prior to the ischemia, after 30 minutes, 2 hours and 24 hours of reperfusion the following parameters were assessed in a blinded study: macromolecular leakage, leukocyte rolling fraction, adherent leukocytes, and functional capillary density (FCD). Rhodamine 6G to stain leukocytes in-vivo and FITC Dextran (MW 150,000) was used as a plasma marker. 15 minutes prior to reperfusion the animals received either an i.v. bolus infusion of Oxaceprol (50mg/kg) or an equivalent volume of saline, which was followed by a 45-minute continuous infusion at the same dose. At the conclusion of the experiment samples were collected from the chamber tissue for histological quantification of leukocyte extravasation using an esterase stain. Oxaceprol treatment resulted in a significant decrease of postischemic leukocyte adherence after 0.5 h and 2h of reperfusion. The histological sections revealed a significant reduction in the number of extravasated leukocytes. There was a reduction of macromolecular leakage and treatment also resulted in a preservation of tissue perfusion, as was indicated by a significant increase in FCD in the treatment group compared to the ischemia group. In summary, Oxaceprol was able to protect the tissue from ischemia/reperfusion injury.

New experimental platform to study high density laser-compressed matter.

We have developed a new experimental platform at the Linac Coherent Light Source (LCLS) which combines simultaneous angularly and spectrally resolved x-ray scattering measurements. This technique offers a new insights on the structural and thermodynamic properties of warm dense matter. The < 50 fs temporal duration of the x-ray pulse provides near instantaneous snapshots of the dynamics of the compression. We present a proof of principle experiment for this platform to characterize a shock-compressed plastic foil. We observe the disappearance of the plastic semi-crystal structure and the formation of a compressed liquid ion-ion correlation peak. The plasma parameters of shock-compressed plastic can be measured as well, but requires an averaging over a few tens of shots.

Coherent-pulse 2D crystallography using a free-electron laser x-ray source.

Coherent diffractive imaging for the reconstruction of a two-dimensional (2D) finite crystal structure with a single pulse train of free-electron laser radiation at 7.97 nm wavelength is demonstrated. This measurement shows an advance on traditional coherent imaging techniques by applying it to a periodic structure. It is also significant that this approach paves the way for the imaging of the class of specimens which readily form 2D, but not three-dimensional crystals. We show that the structure is reconstructed to the detected resolution, given an adequate signal-to-noise ratio.

Coherent x-ray diffraction imaging with nanofocused illumination.

Coherent x-ray diffraction imaging is an x-ray microscopy technique with the potential of reaching spatial resolutions well beyond the diffraction limits of x-ray microscopes based on optics. However, the available coherent dose at modern x-ray sources is limited, setting practical bounds on the spatial resolution of the technique. By focusing the available coherent flux onto the sample, the spatial resolution can be improved for radiation-hard specimens. A small gold particle (size <100 nm) was illuminated with a hard x-ray nanobeam (E=15.25 keV, beam dimensions approximately 100 x 100 nm2) and is reconstructed from its coherent diffraction pattern. A resolution of about 5 nm is achieved in 600 s exposure time.

The morphology of lipopigment granules in oligodendrocytes of the cerebellum and spinal cord and in Schwann cells of the N. ischiadicus of the cat, Japanese waltzing mouse, and albino mouse.

In the oligodendrocytes of cerebellum and spinal cord and in the Schwann cells of peripheral nerves of cat, albino mouse, and Japanese waltzing mouse lipopigment bodies of different size and shape are deposited, which exhibit a characteristic internal structure. The following three subtypes can be distinguished: (1) Granules completely surrounded by a membrane and consisting regularly spaced lamellae, (2) granules consisting of a granular matrix with elucidations, and (3) granules with bifurcating stacks of lamellae. Thus, their structure is distinct from that found in nerve cells and other glial cells and allows the diagnosis of oligodendrocyte or Schwann cell. The significance of these granules in relation to function and aging is briefly discussed.

[Oxaceprol reduced leukocyte adhesion and extravasation and preserves perfusion of tissue after ischemia/reperfusion]. / Oxaceprol reduziert die Leukozyten-Adhärenz und -Extravasation und erhält die Perfusion des Gewebes nach Ischämie/Reperfusion (I/R) aufrecht.

The present data indicate that treatment with Oxaceprol results in a significant protection of the microvasculature against I/R injury. The infusion of Oxaceprol during reperfusion leads to a significant reduction in the post-ischemic leukocyte adherence and extravasation as well as an improvement of the nutritive perfusion of the skin muscle. Thus, Oxaceprol treatment would appear to be a promising therapy for the reduction of I/R injury.

Implementation of the microdialysis method in the hamster dorsal skinfold chamber.

The aim of this study was to implement the microdialysis method, a well-established technique for measuring the local concentration of neurotransmitters and metabolites in the brain, in the dorsal skinfold chamber of the awake hamster. First, the effects of implanted, nonperfused microdialysis probes on the microcirculation were examined. Skinfold chambers were prepared with and without probes. Two and 3 days later, the following parameters were assessed: diameter, red blood cell (RBC) velocity, macromolecular leakage, leukocyte rolling fraction, and adherent leukocytes in venules, diameter and macromolecular leakage in arterioles, and functional capillary density (FCD). No significant differences between the animals of the two groups were observed in any of the parameters on either day. Second, the interstitial lactate concentration was measured at two perfusion rates in groups with and without a 4-h tourniquet ischemia. The induction of ischemia resulted in a significant increase in lactate concentration over the control values in the tissue within 1 h to 8000 +/- 860 microM, where it remained until the reperfusion, at which point the concentration returned to control values within 1 h. The microdialysis method provides the opportunity to measure the concentration of metabolites in the extravascular space of the hamster dorsal skinfold chamber.

Can we continue research in splenectomized dogs? Mycoplasma haemocanis: old problem--new insight.

We report the appearance of a Mycoplasma haemocanis infection in laboratory dogs, which has been reported previously, yet, never before in Europe. Outbreak of the disease was triggered by a splenectomy intended to prepare the dogs for a hemorrhagic shock study. The clinical course of the dogs was dramatic including anorexia and hemolytic anemia. Treatment included allogeneic transfusion, prednisone, and oxytetracycline. Systematic follow-up (n = 12, blood smears, antibody testing and specific polymerase chain reaction) gives clear evidence that persistent eradication of M. haemocanis is unlikely. We, therefore, had to abandon the intended shock study. In the absence of effective surveillance and screening for M. haemocanis, the question arises whether it is prudent to continue shock research in splenectomized dogs.