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Charge calibration of MALTA2, a radiation hard depleted monolithic active pixel sensor
No full textMALTA2 is a depleted monolithic active pixel sensor (DMAPS) designed for tracking at high rates and typically low detection threshold of 200e−. Threshold calibration is crucial to understanding the charge collection in the pixel. A simple procedure is developed to calibrate the threshold to unit electrons making use of a dedicated charge injection circuit and an Fe-55 source with dominant charge deposition of 1611e−. The injection voltage corresponding to the signal under exposure of Fe-55 is determined and serves as the basis for charge calibration. The charge injection circuit incorporates a capacitance with design value of Cinj=230aF. Experimentally, the average capacitance value for non-irradiated samples is found to be Cinj,exp=255±35aF and varies between sensors by 14% in terms of standard deviation. The deviation from the design value as well as among sensors motivates the need for the presented calibration procedure, which is proposed to be performed for each MALTA2 sensor and reduces the uncertainty down to 3% depending on the sensor
Gas tungsten arc welding of NiTi shape memory alloy and AlCoCrFeNi eutectic high entropy alloy using a niobium interlayer
No full textDissimilar fusion welding of a NiTi shape memory alloy and an AlCoCrFeNii eutectic high entropy alloy wasperformed using a niobium interlayer. The unique properties of these materials complement each other,potentially enabling hybrid structures for advanced applications and smart systems. Gas tungsten arc weldingwith an arc offset technique was employed to create a weld-braze joint at the NiTi-Nb interface while controllingthe heat input. Comprehensive microstructural and phase analysis was carried out using optical and electronmicroscopy, synchrotron X-ray diffraction, and was further supplemented by thermodynamic simulations.Dissolution of the Nb interlayer altered the solidification pathways in the fusion zone, leading to the formation oftopologically close-packed phases (including C14 Laves and σ) and TiNi. Multiple interfacial reactions at theNiTi interface introduced significant strain, which increased hardness but also acted as stress concentratorsduring tensile loading. The addition of the niobium interlayer enabled the formation of a stable, crack-free joint,whereas welding without an interlayer resulted in catastrophic cracking
Pulsar Polarization Array Limits on Ultralight Axionlike Dark Matter
No full textWe conduct the first-ever Pulsar Polarization Array (PPA) analysis to detect the ultralight Axion-Like Dark Matter (ALDM) using the polarization data of 22 millisecond pulsars from the third data release of Parkes Pulsar Timing Array. As one of the major dark matter candidates, the ultralight ALDM exhibits a pronounced wave nature on astronomical scales and offers a promising solution to small-scale structure issues within local galaxies. While the linearly polarized pulsar light travels through the ALDM galactic halo, its position angle (PA) can be subject to an oscillation induced by the ALDM Chern-Simons coupling with electromagnetic field. The PPA is thus especially suited for detecting the ultralight ALDM by correlating polarization data across the arrayed pulsars. To accomplish this task, we develop an advanced Bayesian analysis framework that allows us to construct pulsar PA residual time series, model noise contributions properly and search for pulsar cross-correlations. We find that for an ALDM density of , the Parkes PPA offers the best global limits on the ALDM Chern-Simons coupling, namely , for the mass range of . The crucial role of pulsar cross-correlation in recognizing the nature of the derived limits is also highlighted
Double to Tenfold M -shell Photoionization of Singly Charged Lanthanum Ions
No full textUsing the photon-ion merged-beams technique at the PETRA\,III synchrotron light source, we have measured cross sections for double and up to tenfold photoionization of La ions by a single photon in the energy range 820--1400~eV, where resonances and thresholds occur that are associated with the excitation or ionization of one -shell electron. These cross sections represent experimental benchmark data for the further development of quantum theoretical methods, which will have to provide the bulk of the atomic data required for the modeling of nonequilibrium plasmas such as kilonovae. In the present work, we have upgraded the Jena Atomic Calculator (JAC) and pushed the state-of-the-art of quantum calculations for heavy many-electron systems to new limits. In particular, we have performed large-scale calculations of the La photoabsorption cross section and of the deexcitation cascades, which set in after the initial creation of a hole. Our theoretical results largely agree with our experimental findings. However, our theoretical product-ion charge state distributions are somewhat narrower than the experimental ones, which is most probably due to the simplifications necessary to keep the cascade calculations tractable
A Multi-messenger View of the Transient Sky
No full textIn dieser Arbeit werden Multiwellenlängen-(MWL)-Daten zur Untersuchung der Emissionsprozesse von Gamma-Ray Bursts (GRBs) verwendet. Dabei kommen Beobachtungen des High Energy Stereoscopic System (H.E.S.S.) zum Einsatz, das für sehr hochenergetische (VHE) Gamma-Strahlung sensitiv ist. Im Jahr 2022 beobachtete H.E.S.S. den hellsten GRB aller Zeiten, GRB 221009A (BOAT), ohne eine VHE-Detektion. Daher wurden obere Grenzwerte bestimmt und mit MWL-Daten kombiniert, um die VHE-Emission einzuschränken. Zur Modellierung der Nachglühemission wird ein analytisches Ein-Zonen-Synchrotron-Self-Compton-(SSC)-Modell verwendet, das zum besseren Verständnis der Emissionsmechanismen des BOAT beiträgt. Zusätzlich wird eine Stichprobe langer GRBs, die zwischen 2019 und 2022 von H.E.S.S. beobachtet und anhand definierter Kriterien ausgewählt wurde, analysiert. Für keinen dieser GRBs wird eine VHE-Detektion gefunden, sodass ebenfalls obere Grenzwerte berechnet werden. Wenn möglich, wird die Nachglühemission mit demselben SSC-Modell beschrieben. Während die niederenergetischen Beobachtungen gut durch die Synchrotronkomponente der spektralen Energieverteilung (SED) erklärt werden, schränken die H.E.S.S.-Grenzwerte das SSC-Modell kaum ein. Dies ist hauptsächlich auf die starke Abschwächung der VHE-Gamma-Strahlung durch das extragalaktische Hintergrundlicht (EBL) zurückzuführen. Daraus folgt, dass VHE-Beobachtungen von GRBs mit Rotverschiebungen
Discovery of Goethe’s amber ant: its phylogenetic and evolutionary implications
No full textMuseum collections remain essential scientific resources, especially when revisited using modern analytical techniques. In an interdisciplinary study, we examined the overlooked amber collection of Johann Wolfgang von Goethe (1749–1832), polymath and pioneer of art and natural science. Using synchrotron-based micro-computed tomography (SR-µ-CT), we identified a fossil ant from Baltic amber (Eocene ~ 47–34 Ma) in Goethe’s collections. The specimen is assigned to †Ctenobethylus goepperti (Mayr in Die Ameisen des Baltischen Bernsteins. Beiträge zur Naturkunde Preussens, 1868), which we redescribe and re-diagnose, proposing †Eldermyrmex exsectus Dubovikoff et Dlussky, 2019 as its junior synonym (syn. nov., comb. nov.). We further infer a potential sister-group relationship with the extant genus Liometopum Mayr, 1861, suggesting that †C. goepperti may have been a dominant arboreal species in warm-temperate coniferous forests, a scenario which is supported by its abundance in Baltic amber. Critically, our results document endoskeletal structures in a Cenozoic fossil ant, underscoring both the morphological value of historical collections and the lasting scientific legacy of Goethe’s naturalist vision
Negative-Valent Palladium-Stabilized CoPdN Thin Films as a Catalyst for the Oxygen Evolution Reaction
No full textThe urgent global demand for sustainable energy drives the search for durable and efficient electrocatalysts for water splitting. Cobalt mononitride (CoN) stands out due to its earth abundance, high conductivity, and corrosion resistance, but its thermodynamic instability often results in cobalt-rich secondary phases. Here, we report a scalable reactive cosputtering approach for the controlled synthesis of CoN thin films, along with palladium (Pd) incorporation to enhance activity and stability. Pd doping induces a negative valence state and promotes electron transfer from nitrogen to Pd sites, thereby refining the microstructure, redistributing charge, and shifting the d-band center away from the Fermi level. These synergistic effects reduce the overpotential from 470 to 360 mV at 10 mA·cm–2 in a sample coated on the ITO substrate and deliver markedly improved long-term OER stability with increased catalytically active sites. The turnover frequency showed nearly twice the intrinsic activity with Pd doping. This work establishes Pd-doped CoN as a high-performance, durable electrocatalyst, offering a scalable pathway toward efficient water splitting technologies
Radiation damage and the case for unpatterned fixed targets
No full textAdvances in serial crystallography have reshaped approaches to radiation damage at room temperature. This commentary highlights recent work comparing XFEL and synchrotron experiments, emphasising its implications for serial crystallography at modern X-ray sources
Supraparticles from Titania Nanoplates: Assembly, Photocatalytic Polymer Encapsulation, Functionalization, and Multifunctional Hybrid Supraparticles
No full textDiese Studie beschreibt die Assemblierung von Titandioxid-Nanoplättchen (TNPs) zu dreidimensionalen Suprapartikeln (SPs) mittels einer emulsionsbasierten Assemblierungstechnik unter Verwendung von Dodecyltrimethylammoniumbromid (DTAB) als Tensid. Die SPs weisen Durchmesser von ca. 100 bis ca. 400 nm auf und sind in einer Polystyrolhülle eingeschlossen. Die Verkapselung erfolgt durch oberflächeninitiierte photokatalysierte radikalische Polymerisation (UVP) unter Ausnutzung der intrinsischen photokatalytischen Aktivität der TNPs. Durch Variation der Dauer der UV-Bestrahlung ( λ = 365 nm) lässt sich der Gesamtanteil an organischem Material im Polymer einstellen. Kleinwinkel-Röntgenstreuungsmessungen (SAXS) zeigen einen höheren Ordnungsgrad innerhalb der SPs nach der Polymerisation sowie vergrößerte Abstände zwischen den eingeschlossenen TNPs. Vermutlich beginnt die Polymerisation an der Doppelbindung der nativen Oleylamin-Liganden auf der TNP-Oberfläche, was zu einer Oberflächenpfropfung des Polymers und einer Neuanordnung der TNPs innerhalb der verkapselten SPs führt. Des Weiteren wird die Funktionalisierung der Polymerhülle mit Carbonsäure- oder Azidgruppen demonstriert. Als Machbarkeitsnachweis wurden TNPs mit superparamagnetischen Eisenoxid-Nanowürfeln (SPIONs) zu hybriden SPs assembliert. Die UVP konnte problemlos an diese hybriden SPs angepasst werden, wodurch verkapselte TNP/SPION-basierte SPs entstanden, die die optischen und magnetischen Eigenschaften beider Materialien vereinen
Strengthening and deformation mechanisms in CoCrFeMnNi-based medium- and high-entropy alloys at room and cryogenic temperatures
No full textIn this study, novel non-equiatomic CoCrFeMnNi-based medium- and high-entropy alloys (M/HEAs) weredesigned to activate distinct deformation mechanisms, including twinning-induced plasticity (TWIP) and/ortransformation-induced plasticity (TRIP). Tensile tests were performed at 298 and 173 K. A variety of ex-situmultiscale characterization techniques, strengthening modeling, thermodynamic modeling (CALPHAD method),and ab initio density functional theory (DFT) calculations were employed to investigate the structural andmicrostructural evolution, enabling accurate identification of the strengthening and active deformation mechanismsoperating in the M/HEAs. Strengthening modeling revealed that grain boundary strengthening was theprimary contributor to yield strength at both temperatures. A key finding of this study is that a controlledFCC→HCP martensitic transformation, associated with TRIP, enhances the strength-ductility balance even whenthe resulting HCP phase reaches ~50% volume fraction. This demonstrates that TRIP-enabled metastabilityengineering is a promising strategy for designing high-performance M/HEAs for next-generation structural applicationsin energy, aerospace, and defense