Cell-derived or extracellular vesicles, including microparticles and exosomes, are abundantly present in body fluids such as blood. Although such vesicles have gained strong clinical and scientific ...interest, their detection is difficult because many vesicles are extremely small with a diameter of less than 100 nm, and, moreover, these vesicles have a low refractive index and are heterogeneous in both size and composition. In this review, we focus on the relatively high throughput detection of vesicles in suspension by flow cytometry, resistive pulse sensing, and nanoparticle tracking analysis, and we will discuss their applicability and limitations. Finally, we discuss four methods that are not commercially available: Raman microspectroscopy, micro nuclear magnetic resonance, small-angle X-ray scattering (SAXS), and anomalous SAXS. These methods are currently being explored to study vesicles and are likely to offer novel information for future developments.
The New Advanced Telescope for High ENergy Astrophysics (NewAthena) will be the largest space‐based X‐ray observatory ever built. It will have an effective area above 1.1 m2 at 1 keV, which ...corresponds to a polished mirror surface of about 300 m2 due to the grazing incidence. As such a mirror area is not achievable with an acceptable mass even with nested shells, silicon pore optics (SPO) technology will be utilized. In the PTB laboratory at BESSY II, two dedicated beamlines are in use for their characterization with monochromatic radiation at 1 keV and a low divergence well below 2 arcsec: the X‐ray Pencil Beam Facility (XPBF 1) and the X‐ray Parallel Beam Facility (XPBF 2.0), where beam sizes up to 8 mm × 8 mm are available while maintaining low beam divergence. This beamline is used for characterizing mirror stacks and controlling the focusing properties of mirror modules (MMs) – consisting of four mirror stacks – during their assembly at the beamline. A movable CCD based camera system 12 m from the MM registers the direct and the reflected beams. The positioning of the detector is verified by a laser tracker. The energy‐dependent reflectance in double reflection through the pores of an MM with an Ir coating was measured at the PTB four‐crystal monochromator beamline in the photon energy range 1.75 keV to 10 keV, revealing the effects of the Ir M edges. The measured reflectance properties are in agreement with the design values to achieve the envisaged effective area.
Mirror modules for the optics of the X‐ray observatory NewAthena are assembled and characterized at dedicated synchrotron radiation beamlines. The reflectance of a fully assembled and coated module was determined in a wide energy range.
In this work, the K-shell fluorescence yield for oxygen ωO,K−shell is determined experimentally, employing the radiometrically calibrated X-ray fluorescence instrumentation of the ...Physikalisch-Technische Bundesanstalt (PTB), Germany's National Metrology Institute. Four free-standing thin foils with two different thicknesses of both SiO2 and Al2O3 were used in order to derive an experimental value for this atomic fundamental parameter. Multiple excitation photon energies were applied to record fluorescence spectra of all four samples. The resulting value (ωO,K−shell=0.00688±0.00036) is almost 20 % higher than the commonly used value from the Krause tables M. Krause, Atomic Radiative and Radiationless Yields for K and L shells, J. Phys. Chem. Ref. Data 8(2), 307–327 (1979). In addition, the achieved total uncertainty budget for the new experimental value is reduced significantly in comparison to available literature data. For validation purposes, thin SiO2 layers on Si samples were used. Here, the layer thicknesses derived from X-ray reflectometry are well in line with our X-ray fluorescence quantification results based on the new experimental value for the O K-shell fluorescence yield.
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•The K-shell fluorescence yield for oxygen is determined experimentally.•A 20% deviation to the commonly used value of Krause was found.•The uncertainty budget of the new value is reduced significantly compared to other literature data.•The new experimental value was validated using X-ray reflectometry.
A four-crystal monochromator beamline has been installed by the Physikalisch-Technische Bundesanstalt at a bending magnet of the electron storage ring BESSY II. The monochromatic radiation with very ...high spectral purity and high spectral resolution in the photon energy range from 1.75 to 10
keV is used to calibrate detectors by comparison to a cryogenic electrical substitution radiometer as primary detector standard with relative uncertainties well below 1%. This is one order of magnitude better than all calibrations of non-energy-dispersive detectors in this spectral range previously performed. The beamline is also used for the characterization of optical components.
For the first time the absolute photon mass energy-absorption coefficient of air in the energy range of 10 to 60 keV has been measured with relative standard uncertainties below 1%, considerably ...smaller than those of up to 2% assumed for calculated data. For monochromatized synchrotron radiation from the electron storage ring BESSY II both the radiant power and the fraction of power deposited in dry air were measured using a cryogenic electrical substitution radiometer and a free air ionization chamber, respectively. The measured absorption coefficients were compared with state-of-the art calculations and showed an average deviation of 2% from calculations by Seltzer. However, they agree within 1% with data calculated earlier by Hubbell. In the course of this work, an improvement of the data analysis of a previous experimental determination of the mass energy-absorption coefficient of air in the range of 3 to 10 keV was found to be possible and corrected values of this preceding study are given.
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