Search

TEMPUS is a new detector system being developed for photon science. It is based on the Timepix4 chip and, thus, it can be operated in two distinct modes: a photon‐counting mode, which allows for conventional full‐frame readout at rates up to 40 kfps; and an event‐driven time‐stamping mode, which allows excellent time resolution in the nanosecond regime in measurements with moderate X‐ray flux. In this paper, the initial prototype, a single‐chip device, is introduced, and the readout system described. Moreover, and in order to evaluate its capabilities, some tests were performed at PETRA III and ESRF for which results are also presented. [ABSTRACT FROM AUTHOR]

Monitoring the processes inside crystalline materials under their operating conditions is of great interest in optoelectronics and scientific instrumentation. Early defect detection ensures the proper functioning of multiple crystal-based devices. In this study, a combination of acoustic emission (AE) sensing and cross-polarization imaging is proposed for the fast characterization of the crystal's structure. For the experiments, tellurium dioxide (TeO2) crystal was chosen due to its wide use in acousto-optics. Studies were performed under uniaxial compression loading with a simultaneous acquisition of AE signals and four polarized optical images. An analysis of the temporal dependencies of the AE data and two-dimensional maps of the light depolarization features was carried out in order to establish quantitative criteria for irreversible damage initiation and crack-like defect formation. The obtained results reveal the polarization image patterns and the AE pulse duration alteration specific to these processes, and they open up new possibilities for non-destructively monitoring in real-time the structure of optically transparent crystals under their operating conditions. [ABSTRACT FROM AUTHOR]

Organic spintronics has emerged as a promising field for exploring novel spin-based phenomena and devices, offering the potential for low-power, flexible, and biocompatible electronics. The interface between metallic ferromagnetic and semiconducting organic layers plays a pivotal role in spin injection, transport, and extraction processes in these devices. Therefore, achieving a comprehensive understanding of the magnetic properties at these interfaces is essential for advancing device performance and functionality. This work explores the magnetic properties at the interface between thin Fe film and the C60 layer. We employ a multi-technique approach, combining the magneto-optic Kerr effect, which provides a global assessment of magnetic properties, and depth-resolved grazing incidence nuclear resonance scattering (GINRS) under X-ray standing wave conditions, enabling us to probe magnetism with high spatial resolution within the interfacial region. GINRS measurements reveal intriguing behavior at the interface, characterized by reduced hyperfine fields in diffused 57Fe layers. This observation suggests the formation of superparamagnetic clusters, which significantly influence the magnetic properties at the interface. These findings provide valuable insights into the complex interplay between ferromagnetic materials and organic semiconductors at the nanoscale, offering potential avenues for tailoring magnetoresistance effects in organic spintronic devices and contributing to the fundamental understanding of spin-dependent phenomena in organic spintronics. [ABSTRACT FROM AUTHOR]

Resonant oscillators with stable frequencies and large quality factors help us to keep track of time with high precision. Examples range from quartz crystal oscillators in wristwatches to atomic oscillators in atomic clocks, which are, at present, our most precise time measurement devices1. The search for more stable and convenient reference oscillators is continuing2–6. Nuclear oscillators are better than atomic oscillators because of their naturally higher quality factors and higher resilience against external perturbations7–9. One of the most promising cases is an ultra-narrow nuclear resonance transition in 45Sc between the ground state and the 12.4-keV isomeric state with a long lifetime of 0.47 s (ref. 10). The scientific potential of 45Sc was realized long ago, but applications require 45Sc resonant excitation, which in turn requires accelerator-driven, high-brightness X-ray sources11 that have become available only recently. Here we report on resonant X-ray excitation of the 45Sc isomeric state by irradiation of Sc-metal foil with 12.4-keV photon pulses from a state-of-the-art X-ray free-electron laser and subsequent detection of nuclear decay products. Simultaneously, the transition energy was determined as 12,389.59 + 0.12 syst ± 0.15 stat eV with an uncertainty that is two orders of magnitude smaller than the previously known values. These advancements enable the application of this isomer in extreme metrology, nuclear clock technology, ultra-high-precision spectroscopy and similar applications.Resonant X-ray excitation of the 45Sc nuclear isomeric state was achieved by irradiation of a Sc-metal foil with 12.4-keV photon pulses from a state-of-the-art X-ray free-electron laser, allowing a high-precision determination of the transition energy. [ABSTRACT FROM AUTHOR]

Background: Severe acute respiratory syndrome corona virus (SARS‐CoV‐2) infection frequently causes severe and prolonged disease but only few specific treatments are available. We aimed to investigate safety and efficacy of a SARS‐CoV‐2‐specific siRNA‐peptide dendrimer formulation MIR 19® (siR‐7‐EM/KK‐46) targeting a conserved sequence in known SARS‐CoV‐2 variants for treatment of COVID‐19. Methods: We conducted an open‐label, randomized, controlled multicenter phase II trial (NCT05184127) evaluating safety and efficacy of inhaled siR‐7‐EM/KK‐46 (3.7 mg and 11.1 mg/day: low and high dose, respectively) in comparison with standard etiotropic drug treatment (control group) in patients hospitalized with moderate COVID‐19 (N = 52 for each group). The primary endpoint was the time to clinical improvement according to predefined criteria within 14 days of randomization. Results: Patients from the low‐dose group achieved the primary endpoint defined by simultaneous achievement of relief of fever, normalization of respiratory rate, reduction of coughing, and oxygen saturation of >95% for 48 h significantly earlier (median 6 days; 95% confidence interval [CI]: 5–7, HR 1.75, p =.0005) than patients from the control group (8 days; 95% CI: 7–10). No significant clinical efficacy was observed for the high‐dose group. Adverse events were reported in 26 (50.00%), 25 (48.08%), and 28 (53.85%) patients from the low‐, high‐dose and control group, respectively. None of them were associated with siR‐7‐EM/KK‐46. Conclusions: siR‐7‐EM/KK‐46, a SARS‐CoV‐2‐specific siRNA‐peptide dendrimer formulation is safe, well tolerated and significantly reduces time to clinical improvement in patients hospitalized with moderate COVID‐19 compared to standard therapy in a randomized controlled trial. [ABSTRACT FROM AUTHOR]

Within this work, we report the results of nuclear inelastic scattering experiments of the low-spin phase of the iron(II) mononuclear SCO complex Fe[HBpz3]2 and density functional theory based calculations performed on a model molecule of the complex. We show that the calculated partial density of vibrational states based on the structure of a single iron(II) center which is linked by three pyrazole rings to borat is in good accordance with the experimentally obtained 57Fe-pDOS and assign the molecular vibrations to the prominent optical phonons. [ABSTRACT FROM AUTHOR]

Keywords: Allergic rhinitis; cytokines; IL-13; IL-4; siRNA EN Allergic rhinitis cytokines IL-13 IL-4 siRNA 2829 2832 4 09/02/22 20220901 NES 220901 Allergic rhinitis (AR) is a chronic inflammatory disease of upper airways characterized by sneezing, itching, nasal congestion, and rhinorrhea. Anti-inflammatory effect of siRNAs targeted il-4 and il-13 in a mouse model of allergic rhinitis The mouse anti-IL-4 and IL-13 siRNAs3,4 as well as branched (dendrimeric) cationic peptide LTP for nucleic acids delivery into mammalian cells, including lymphocytes (important source of IL-4 and IL-13)5 were designed and tested previously. [Extracted from the article]

Within this work, we report the results of nuclear inelastic scattering experiments of the low-spin phase of the iron(II) mononuclear SCO complex Fe[HBpz3]2 and density functional theory based calculations performed on a model molecule of the complex. We show that the calculated partial density of vibrational states based on the structure of a single iron(II) center which is linked by three pyrazole rings to borat is in good accordance with the experimentally obtained 57Fe-pDOS and assign the molecular vibrations to the prominent optical phonons. [ABSTRACT FROM AUTHOR]

Ultra-thin Fe film is deposited obliquely on the Tris(8-hydroxyquinolinato) aluminum (Alq3) layer to study the interface magnetism and compared with the normally deposited film of the same thickness. The overall magnetic property of the film, as observed using magneto-optic Kerr effect measurements, is understood precisely through interface resolved grazing incident nuclear resonance scattering (GINRS) measurements under x-ray standing wave (XSW) conditions. To excite XSW modes, the bilayer is deposited between high dense Ag and Pt layers to make a waveguide structure, where the position of the antinode is varied by changing incident angles. The Fe layer is enriched with 57Fe isotope during deposition to make it active for GINRS measurements. Compared with obliquely deposited 57Fe film, reduced hyperfine fields at the interface of normally deposited 57Fe/Alq3 film, providing evidence for the deep penetration of 57Fe atoms into Alq3 film. Due to the large shadowing effect at oblique angle deposition, Fe atoms try to organize into isolated superparamagnetic clusters to minimize their surface/interface energy. On the other hand, besides the relatively deep penetration in the normally deposited thin film, ferromagnetism is observed due to the connecting bigger 57Fe clusters. Our results demonstrate that deposition geometry has a direct and crucial bearing on the interfacial microstructure, which can control diffusion at the Alq3 interfaces and tune magnetic anisotropy in the ferromagnetic layer. [ABSTRACT FROM AUTHOR]

FeCoB/MgO bilayer is prepared to study the interface magnetism and its role in azimuthal angle-dependent magnetic properties. As observed in magneto-optic Kerr effect measurements, unusual hysteresis loops are understood precisely through interface resolved grazing incident nuclear resonance scattering (GINRS) measurements under x-ray standing wave (XSW) conditions. To excite XSW modes, the bilayer is deposited between a Pt waveguide structure, where the position of the anti-nodes is varied by changing incident angles. As GINRS is an isotope sensitive technique, the FeCoB layer is enriched with 57Fe isotope during deposition. The formation of a high-density 57FeCoB layer at the 57FeCoB/MgO interface with a hyperfine field ~34.25 T is found and attributed to the increasing volume of FeCo at the interface. Boron diffusion from 57FeCoB to the MgO layer is found to be responsible for FeCo rich FeCoB layer near the interface. The azimuthal angle-dependent unusual shape of hysteresis loops is described in terms of coupled magnetization reversal between the bulk and interface parts of FeCoB layer. In contrast to some studies in literature, no evidence of the formation of an oxide layer is observed at the interface. [ABSTRACT FROM AUTHOR]

The light-driven sodium-pumping rhodopsin KR2 from Krokinobacter eikastus is the only non-proton cation active transporter with demonstrated potential for optogenetics. However, the existing structural data on KR2 correspond exclusively to its ground state, and show no sodium inside the protein, which hampers the understanding of sodium-pumping mechanism. Here we present crystal structure of the O-intermediate of the physiologically relevant pentameric form of KR2 at the resolution of 2.1 Å, revealing a sodium ion near the retinal Schiff base, coordinated by N112 and D116 of the characteristic NDQ triad. We also obtained crystal structures of D116N and H30A variants, conducted metadynamics simulations and measured pumping activities of putative pathway mutants to demonstrate that sodium release likely proceeds alongside Q78 towards the structural sodium ion bound between KR2 protomers. Our findings highlight the importance of pentameric assembly for sodium pump function, and may be used for rational engineering of enhanced optogenetic tools. The Na+-pumping KR2 rhodopsin from Krokinobacter eikastus is a light-driven non-proton cation pump whose mechanism of pumping remains to be understood. Here authors solved crystal structures of the O-intermediate state of the pentameric form of KR2 and its D116N and H30A mutants, which sheds light on the mechanism of non-proton cation light-driven pumping. [ABSTRACT FROM AUTHOR]

The vibronic properties of two dimeric iron (II) high-spin complexes [5CpFeX]2 (5Cp = Pentaisopropyl-cyclopentadienyl, X = OH-(1), Br-(2)) have been studied using nuclear inelastic scattering (NIS). In order to assign the experimentally observed bands to the particular modes, theoretical calculations using density functional theory (DFT) have been performed based on the structural data obtained by X-ray crystallography. The calculated partial density of vibrational states (pDOS) reproduces the experimental data. Thus, we were able to assign almost each of the experimentally observed NIS bands to their corresponding molecular vibrational modes. [ABSTRACT FROM AUTHOR]

Fe–N–C catalysts are very promising materials for fuel cells and metal–air batteries. This work gives fundamental insights into the structural composition of an Fe–N–C catalyst and highlights the importance of an in‐depth characterization. By nuclear‐ and electron‐resonance techniques, we are able to show that even after mild pyrolysis and acid leaching, the catalyst contains considerable fractions of α‐iron and, surprisingly, iron oxide. Our work makes it questionable to what extent FeN4 sites can be present in Fe–N–C catalysts prepared by pyrolysis at 900 °C and above. The simulation of the iron partial density of phonon states enables the identification of three FeN4 species in our catalyst, one of them comprising a sixfold coordination with end‐on bonded oxygen as one of the axial ligands. [ABSTRACT FROM AUTHOR]

Fe–N–C catalysts are very promising materials for fuel cells and metal–air batteries. This work gives fundamental insights into the structural composition of an Fe–N–C catalyst and highlights the importance of an in‐depth characterization. By nuclear‐ and electron‐resonance techniques, we are able to show that even after mild pyrolysis and acid leaching, the catalyst contains considerable fractions of α‐iron and, surprisingly, iron oxide. Our work makes it questionable to what extent FeN4 sites can be present in Fe–N–C catalysts prepared by pyrolysis at 900 °C and above. The simulation of the iron partial density of phonon states enables the identification of three FeN4 species in our catalyst, one of them comprising a sixfold coordination with end‐on bonded oxygen as one of the axial ligands. [ABSTRACT FROM AUTHOR]

In order to correctly analyse high-resolution rocking curves of high-quality crystals, a special effort is needed to estimate the systematic contributions coming from the experimental setup. This article highlights the main areas that require special analytical treatment and presents results obtained using different approaches to the problem, as well as some typical results for high-quality silicon and diamond crystals. [ABSTRACT FROM AUTHOR]

The performance of a cryogenically cooled double-crystal silicon monochromator was studied under high-heat-load conditions with total absorbed powers and power densities ranging from 8 to 780 W and from 8 to 240 W mm-2, respectively. When the temperature of the first crystal is maintained close to the temperature of zero thermal expansion of silicon, the monochromator shows nearly ideal performance with a thermal slope error of 0.6 mrad. By tuning the size of the first slit, the regime of the ideal performance can be maintained over a wide range of heat loads, i.e. from power densities of 110 W mm-2 (at total absorbed power of 510 W) to 240 W mm-2 (at total absorbed power of 240 W). [ABSTRACT FROM AUTHOR]

We report the results of optical pump-nuclear resonance probe experiments on the SCO complex [FeII(L-PtII(t-but-tpy))2](BF4)2 with L being 2,6-di(pyrazol-1-yl)-4-(trimethylsilylethynyl)pyridine) and t-but-tpy being 4,4′,4″-Tri-tert-Butyl-2,2′:6′,2″-terpyridine using a novel experimental set-up at the beamline P01, Petra III, DESY Hamburg. We investigate the changes in the spin state of the complex when it is excited by laser pulses of 766 nm wavelength and pulse width < 100 ps. Our simulations of the nuclear forward scattering data indicate a dominant low spin state along with some high spin fraction in the absence of laser pulses. We observe clear changes in the time-spectrum following the instant at which the laser pulse hits the sample. Furthermore, these alterations are recorded as the relative timing of the laser pulses with respect to the synchrotron pulses is varied. [ABSTRACT FROM AUTHOR]

Iron(II) spin crossover complexes display a reversible transition from low-spin (LS) state to high-spin (HS) state by e.g. variation of temperature, pressure or by irradiation with light. Therefore, these systems are promising candidates for information storage materials. In view of practical device applications thin films of these materials are needed. The SCO-compound [Fe(Htrz)2(trz)] (BF4) (1) switches between the LS and the HS state with a 50 K wide thermal hysteresis loop above room temperature. We have prepared thin films of 1 on a SiO2 substrate by spin coating. The spin states of the films have been characterized by Mössbauer spectroscopy in reflection mode using a MIMOS II spectrometer. A low quadrupole splitting (LS state) at 300 K and a high quadrupole splitting (HS state) at 400 K were found for the film, as well as for bulk powder of 1. This confirms that a spin crossover occurs above room temperature. Furthermore, synchrotron based nuclear resonance scattering measurements from 80 K to 400 K indicate that the hyperfine parameters are similar to those of the bulk powder of 1. DFT calculations reproduce the experimentally determined Fe-vibrational density of states of the bulk and of the thin film sample of 1. These results indicate that a higher fraction of HS Fe atoms is present in the film of 1. Therefore, we conclude different SCO properties of the thin film and the bulk material of 1. [ABSTRACT FROM AUTHOR]