Sizes of pure and doped helium droplets from single shot x-ray imaging.

Advancements in x-ray free-electron lasers on producing ultrashort, ultrabright, and coherent x-ray pulses enable single-shot imaging of fragile nanostructures, such as superfluid helium droplets. This imaging technique gives unique access to the sizes and shapes of individual droplets. In the past, such droplet characteristics have only been indirectly inferred by ensemble averaging techniques. Here, we report on the size distributions of both pure and doped droplets collected from single-shot x-ray imaging and produced from the free-jet expansion of helium through a 5 µm diameter nozzle at 20 bars and nozzle temperatures ranging from 4.2 to 9 K. This work extends the measurement of large helium nanodroplets containing 109-1011 atoms, which are shown to follow an exponential size distribution. Additionally, we demonstrate that the size distributions of the doped droplets follow those of the pure droplets at the same stagnation condition but with smaller average sizes.

Simultaneous Dimensional and Analytical Characterization of Ordered Nanostructures.

The spatial and compositional complexity of 3D structures employed in today's nanotechnologies has developed to a level at which the requirements for process development and control can no longer fully be met by existing metrology techniques. For instance, buried parts in stratified nanostructures, which are often crucial for device functionality, can only be probed in a destructive manner in few locations as many existing nondestructive techniques only probe the objects surfaces. Here, it is demonstrated that grazing exit X-ray fluorescence can simultaneously characterize an ensemble of regularly ordered nanostructures simultaneously with respect to their dimensional properties and their elemental composition. This technique is nondestructive and compatible to typically sized test fields, allowing the same array of structures to be studied by other techniques. For crucial parameters, the technique provides sub-nm discrimination capabilities and it does not require access-limited large-scale research facilities as it is compatible to laboratory-scale instrumentation.

Precise measurement of the electron beam current in a TEM.

Modern quantitative TEM methods such as the ζ-factor technique require precise knowledge of the electron beam current. To this end, a macroscopic Faraday cup was designed and constructed. It can replace the viewing screen in the projection chamber of a TEM and guarantees highly accurate measurement of the electron beam with precision only limited by the used amperemeter. The easy to install, affordable device is shown to be highly apt for precision measurement of currents >5pA. The Faraday cup results are used for an assessment and a comparison of various other beam current measurement methods. It is found that the built-in screen amperemeter of the used TEM is quite inaccurate and that measurements using the screen in general tend to underestimate the current. If present, the drift tube of a spectrometer can also be used as a Faraday cup, but certain described peculiarities have to be taken into account. Direct ultrafast electron detection cameras allow precise measurement at very small currents. For the electron counting technique, which exploits single electron detection capabilities of STEM detectors, a systematic current underestimation was observed and investigated. This results in a reformulated routine for the method and with these improvements it is demonstrated to be capable of accurate high-precision measurements for currents <5pA.

How to Recognize Animals' Vulnerability: Questioning the Orthodoxies of Moral Individualism and Relationalism in Animal Ethics.

Keywords: moral individualism; relationalism; vulnerability; recognizability; immanent critique.

Electron ptychographic phase imaging of light elements in crystalline materials using Wigner distribution deconvolution.

Recent development in fast pixelated detector technology has allowed a two dimensional diffraction pattern to be recorded at every probe position of a two dimensional raster scan in a scanning transmission electron microscope (STEM), forming an information-rich four dimensional (4D) dataset. Electron ptychography has been shown to enable efficient coherent phase imaging of weakly scattering objects from a 4D dataset recorded using a focused electron probe, which is optimised for simultaneous incoherent Z-contrast imaging and spectroscopy in STEM. Therefore coherent phase contrast and incoherent Z-contrast imaging modes can be efficiently combined to provide a good sensitivity of both light and heavy elements at atomic resolution. In this work, we explore the application of electron ptychography for atomic resolution imaging of strongly scattering crystalline specimens, and present experiments on imaging crystalline specimens including samples containing defects, under dynamical channelling conditions using an aberration corrected microscope. A ptychographic reconstruction method called Wigner distribution deconvolution (WDD) was implemented. Experimental results and simulation results suggest that ptychography provides a readily interpretable phase image and great sensitivity for imaging light elements at atomic resolution in relatively thin crystalline materials.

An easy-to-build, low-budget point-of-care ultrasound simulator: from Linux to a web-based solution.

BACKGROUND: Hands-on training in point-of-care ultrasound (POC-US) should ideally comprise bedside teaching, as well as simulated clinical scenarios. High-fidelity phantoms and portable ultrasound simulation systems are commercially available, however, at considerable costs. This limits their suitability for medical schools. A Linux-based software for Emergency Department Ultrasound Simulation (edus2TM) was developed by Kulyk and Olszynski in 2011. Its feasibility for POC-US education has been well-documented, and shows good acceptance. An important limitation to an even more widespread use of edus2, however, may be due to the need for a virtual machine for WINDOWS® systems. Our aim was to adapt the original software toward an HTML-based solution, thus making it affordable and applicable in any simulation setting. METHODS: We created an HTML browser-based ultrasound simulation application, which reads the input of different sensors, triggering an ultrasound video to be displayed on a respective device. RFID tags, NFC tags, and QR Codes™ have been integrated into training phantoms or were attached to standardized patients. The RFID antenna was hidden in a mock ultrasound probe. The application is independent from the respective device. RESULTS: Our application was used successfully with different trigger/scanner combinations and mounted readily into simulated training scenarios. The application runs independently from operating systems or electronic devices. CONCLUSION: This low-cost, browser-based ultrasound simulator is easy-to-build, very adaptive, and independent from operating systems. It has the potential to facilitate POC-US training throughout the world, especially in resource-limited areas.

Patient position and hypoxemia during propofol sedation for colonoscopy: a randomized trial.

AIM: To evaluate the benefits of the left lateral position in avoiding hypoxemic events in patients undergoing colonoscopy. METHODS: We conducted a randomized, prospective, controlled trial at two study sites in Germany. Patients undergoing colonoscopy under propofol sedation were randomized to either the supine or left lateral position. The primary outcome was oxygen desaturation (SaO2<90%). Secondary outcome measures were apneic events, hypotension, patient satisfaction, propofol dosage, cecal intubation time, and adenoma detection. RESULTS: A total of 412 patients were randomized 1:1 to undergo colonoscopy in the supine or left lateral position. No severe adverse events were observed in either group. Intention-to-treat analysis revealed no significant difference in the frequency of desaturation in the left lateral arm compared with the supine arm (6.8% vs. 12.1%; P=0.064). Patients in the left lateral arm showed lower apnea rates (9.4% vs. 16.2%; P= .040), but had more episodes of hypotension (12.3% vs. 2.9%; P<0.001). The frequency of repositioning was higher in the left lateral group. No significant differences were observed in patient satisfaction and cooperation, propofol dosage, or adenoma detection rate. Patients who were repositioned to facilitate endoscope passage were excluded from per-protocol analysis. The incidence of hypoxemia was lower for the left lateral than for the supine group in per-protocol analysis (1.8% vs. 11.2%; P=0.003). CONCLUSION: The positioning of patients in the left lateral position during propofol sedation for colonoscopy results in lower desaturation rates provided the position can be maintained throughout endoscopy. ClinicalTrials.gov NCT02001792.

[Life-threatening bleeding in obsessive-compulsive disorder]. / Lebensbedrohliche Blutung infolge Zwangsstörung.

We report on a case of life-threatening hemorrhoidal bleeding due to obsessive-compulsive disorder. The patient had irrational fears and felt compelled to defecate at least 3 times a day. This required massive abdominal pressing and caused inguinal hernias and prolapsed hemorrhoids. Severe obsessive-compulsive rituals may often result in physical complications. Conversely, obsessive-compulsive disorder should be considered when patients present with uncommon physical complaints, particularly skin symptoms or abnormalities in the context of micturition and defecation.

Helium superfluidity. Shapes and vorticities of superfluid helium nanodroplets.

Helium nanodroplets are considered ideal model systems to explore quantum hydrodynamics in self-contained, isolated superfluids. However, exploring the dynamic properties of individual droplets is experimentally challenging. In this work, we used single-shot femtosecond x-ray coherent diffractive imaging to investigate the rotation of single, isolated superfluid helium-4 droplets containing ~10(8) to 10(11) atoms. The formation of quantum vortex lattices inside the droplets is confirmed by observing characteristic Bragg patterns from xenon clusters trapped in the vortex cores. The vortex densities are up to five orders of magnitude larger than those observed in bulk liquid helium. The droplets exhibit large centrifugal deformations but retain axially symmetric shapes at angular velocities well beyond the stability range of viscous classical droplets.

Anomalous signal from S atoms in protein crystallographic data from an X-ray free-electron laser.

X-ray free-electron lasers (FELs) enable crystallographic data collection using extremely bright femtosecond pulses from microscopic crystals beyond the limitations of conventional radiation damage. This diffraction-before-destruction approach requires a new crystal for each FEL shot and, since the crystals cannot be rotated during the X-ray pulse, data collection requires averaging over many different crystals and a Monte Carlo integration of the diffraction intensities, making the accurate determination of structure factors challenging. To investigate whether sufficient accuracy can be attained for the measurement of anomalous signal, a large data set was collected from lysozyme microcrystals at the newly established `multi-purpose spectroscopy/imaging instrument' of the SPring-8 Ångstrom Compact Free-Electron Laser (SACLA) at RIKEN Harima. Anomalous difference density maps calculated from these data demonstrate that serial femtosecond crystallography using a free-electron laser is sufficiently accurate to measure even the very weak anomalous signal of naturally occurring S atoms in a protein at a photon energy of 7.3 keV.

Pentacene thin-film transistors encapsulated by a thin alkane layer operated in an aqueous ionic environment.

The encapsulation of pentacene thin-film transistors (TFTs) by a 50 nm thick layer of a long chain alkane (C44H90) enables the operation in an aqueous solution of 1 mM NaCl. It is the first time that pentacene TFTs operate successfully in a liquid environment. This opens new perspectives for biocompatible sensor devices based on pentacene TFTs.

Neural Stem Cell Spreading on Lipid Based Artificial Cell Surfaces, Characterized by Combined X-ray and Neutron Reflectometry.

We developed a bioadhesive coating based on a synthetic peptide-conjugate (AK-cyclo[RGDfC]) which contains multiples of the arginyl-glycyl-aspartic acid (RGD) amino acid sequence. Biotinylated AK-cyclo[RGDfC] is bound to a supported lipid bilayer via a streptavidin interlayer. Layering, hydration and packing of the coating is quantified by X-ray and neutron reflectometry experiments. AK-cyclo[RGDfC] binds to the streptavidin interlayer in a stretched-out on edge configuration. The highly packed configuration with only 12% water content maximizes the number of accessible adhesion sites. Enhanced cell spreading of neural stem cells was observed for AK-cyclo[RGDfC] functionalized bilayers. Due to the large variety of surfaces which can be coated by physisorption of lipid bilayers, this approach is of general interest for the fabrication of biocompatible surfaces.