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Design and Characterization of a Fully Automated Free-Standing Liquid Crystal Film Holder
No full textWe present the design and characterization of a fully automated free-standing liquid crystal (FSLC) film holder, enabling remote and precise control of liquid crystal (LC) volume release, wiping speed, and temperature. Using 4-octyl-4′-cyanobiphenyl (8CB) as a test material, we systematically investigated the influence of formation parameters on the resulting film thickness and temporal evolution. Thickness measurements performed by monitoring the difference in optical path lengths of two arms of a standard optical intensity autocorrelation setup reveal that the wiping speed is the dominant factor determining both the initial film thickness and the subsequent annealing dynamics, while temperature becomes relevant only at the highest wiping speeds. Faster wiping speeds consistently produce thinner and more uniform FSLC films on the order of 3 µm, due to reduced LC mass deposition. Time-resolved optical and X-ray scattering measurements confirm the presence of an annealing phase following film formation, which can last for between 1 s and 10 min time scales, until a stable smectic configuration is reached. The holder provides a reliable and fully remote tool for generating high-quality FSLC films at rates up to 1 Hz, suitable for optical to hard X-ray experiments where direct access to the sample environment is limited
CP-violation in production of heavy neutrinos from bubble collisions
No full textFirst order phase transitions (FOPT) in the early Universe can be powerful emitters of both relativistic and heavy particles, upon the collision of ultra-relativistic bubble shells. If the particles coupling to the bubble wall have CP-violating interactions, the same collision process can also create a local lepton or baryon charge. This CP-violation can originate from different channels, which have only been partially addressed in the literature. We present a systematic analysis of the different channels inducing CP-violation during bubble collisions: 1) the decay of heavy particles 2) the production of heavy particles and 3) the production of light and relativistic Standard Model (SM) particles.As an illustration of the impact that such mechanisms can have on baryon number and dark matter (DM) abundance, we then introduce a simple model of cogenesis, separating a positive and a negative lepton number in the SM and a dark sector. The lepton number asymmetry in the SM can be used to explain the baryon asymmetry of the Universe (BAU), while the opposite asymmetry in the dark sector is responsible for determining the abundance of DM. Moreover, the masses of light neutrinos can be understood via the inverse seesaw mechanism, with the lepton-violating Majorana mass originating from the FOPT.A typical signal produced by a FOPT is the irreducible gravitational wave (GW) background. We find that a substantial portion of the parameter space can be probed at future observatories like the Einstein Telescope (ET)
Sequential growth of Ag nanoparticles on ripple-patterned Si: Insights from GISAXS/GIWAXS and MD simulations
No full textThe spatial arrangement and morphology of metallic NPs critically influence performance in plasmonic and spintronic applications. Substrate topography, especially ion-irradiation induced ripple patterns, strongly affects NP nucleation, growth dynamics, and final geometry. For Ag-NPs on nanoripple silicon, assembly depends on deposition direction because the morphology is intrinsically asymmetric; GISAXS confirms one slope is steeper. Single-direction deposition promotes uniaxial, ellipsoidal Ag-NPs aligned in the ripple direction, whereas sequential deposition yields truncated NPs with more uniform spacing. GIWAXS indicates an FCC structure with preferred (111) and (200) orientations; d-spacings remain consistent at 0° and 90°, indicating structural stability. Molecular dynamics simulations support these findings, showing single-sided flux favors tilted, elongated growth, while sequential flux forms near-spherical NPs near ridge regions and distributes them across slopes. Together, experiment and simulation establish how coupling surface asymmetry with deposition geometry governs NP shape, ordering, and crystallinity, offering a substrate-guided route to engineering isotropic assemblies
Beyond global metrics in capacitive water deionization: Position-resolved ion concentration from operando X-ray transmission
No full textThe performance of novel electrode materials and the influence of cell geometry or flow rate on capacitive water deionization (CDI) are usually described by global metrics from the analysis of the effluent electrolyte together with the electrochemical response of the system. However, these approaches cannot provide information on local variations of ion concentration and related local efficiency within an operating device. Here, a novel approach of position-resolved operando synchrotron-based X-ray transmission is introduced to determine local ion concentration changes along the flow channel from the inlet (feedwater) to the outlet (effluent water) of a working CDI cell. A specific cell design allows the independent quantification of concentration changes within the bulk electrolyte in the flow channel as well as the two oppositely charged nanoporous electrodes. Results from a 15 mM CsCl feed solution using three flow rates and two carbon materials with hierarchical porosity reveal a complex spatial- and temporal ion distribution in the system. A distinct dependence of local concentration on the flow rate is observed, with generally decreasing local desalination capacity towards the outlet of the cell, particularly for slow flow rates. It is also found that a significantly better overall performance for one of the two materials can be related to dominant counter-ion adsorption within ultramicropores, which ions cannot access in their hydrated state at no applied potential (ionophobicity). Overall, the results demonstrate the unique potential of position-resolved operando X-ray techniques to get mechanistic insight into local ion redistribution in CDI systems, allowing ultimately guiding performance optimization
United by chewing: Hunter-Schreger band-like pattern and wavy enamel in a fossil crocodile suggest functional convergence with mammals and dinosaurs
No full textTooth enamel of most mammals shows alternating light and dark bands, called Hunter-Schreger bands (HSB), in longitudinal sections caused by decussating bundles of prisms, the unit building blocks of mammalian enamel. HSB are thought to increase resistance to abrasive food and mitigate crack propagation and hence are considered a mammalian adaptation to high-efficiency mastication. Using traditional microscopy techniques as well as X-ray diffraction computed tomography (XRD-CT), here we report for the first time the presence of HSB-like features in the tooth enamel of a non-mammalian amniote, Iharkutosuchus, an extinct herbivorous crocodile with strong heterodonty and a unique chewing mechanism. XRD-CT showed that the enigmatic HSB-like pattern in Iharkutosuchus enamel, which lacks mammal-like decussating prisms, has a purely crystallographic origin. Iharkutosuchus teeth also exhibit wavy enamel, a well-known structure in herbivorous ornithopod dinosaurs with shearing-type mastication. The unexpected finding of both enamel features in this herbivorous crocodile speaks for their role in high-efficiency chewing. However, the profoundly different structural background of mammalian and crocodilian HSB demonstrated here and the phylogenetic distribution of both HSB and wavy enamel indicate nanostructure-scale convergences, highlighting the importance of mastication-related challenges in driving dental evolution of amniotes
Advances in High-Order Harmonic Sources and Applications to Free-Electron Laser Pulse Characterization
No full textAttosecond and few-femtosecond light pulses provide the time resolution required to track and control the very first instants of electron dynamics in molecules and condensed matter. Since its first demonstration, High-order Harmonic Generation (HHG) sources have been at the core of experimental schemes aiming at unravelling ultrafast electron motion. This thesis reports advancements in high-order harmonic sources and their applications to both solid-state spectroscopy and Free-Electron Laser (FEL) pulse characterization. First, it demonstrates and rationalizes efficient soft X-ray HHG in the so-called overdriven regime enabled by a custom-designed differentially pumped glass chip. This development directly addresses some of the technical challenges of conventional high-photon-energy HHG sources, providing a more accessible approach. Second, this work presents results on solidstate High-order Harmonic Generation (sHHG) spectroscopy in crystalline, amorphous, and semi-periodic TiO2 samples. The experiment showcases the potential of HHG not only as a source, but also as a spectroscopic probe of the valence electrons governing materials functional properties. Finally, this thesis reports the experimental validation of Double-Blind Holography (DBH) of ultrashort FEL pulses. This is a fully optical platform for single-shot temporal haracterization, phase retrieval, and few-femtosecond resolution delay tagging that is based on the interference with an unknown external field, in this case a standard HHG source. Together, these developments extend the capabilities of high-order harmonic sources, opening new scenarios for investigating and controlling ultrafast electron dynamics in atoms, molecules and condensed matter, both with table-top schemes and at FELs
Heat shock protein 10 as a chaperone modulating α‐synuclein amyloid fibril formation
No full textHSP10 is a well-known human co-chaperone that interacts with HSP60 to comprise the HSP60/10 chaperonin complex which upholds mitochondrial proteostasis. HSP10 also demonstrates independent roles in binding to misfolded proteins and interacts with several amyloidogenic client proteins. Using a variety of biophysical and biochemical methods, we studied the interactions of HSP10 with the amyloidogenic protein α-synuclein (α-syn) associated with Parkinson's disease. HSP10 efficiently inhibited fibril formation of wild type (WT) and disease-mutant A30P α-syn at sufficient concentrations of chaperone by both binding to α-syn monomers and by blocking secondary nucleation on fibril surfaces. However, under sub-stoichiometric conditions, below 1:5 (HSP10:α-syn), the chaperone sequestered multiple A30P α-syn monomers and thereby promoted nucleation of fibril formation with a magnitude comparable to the efficacy of seeding with preformed fibrils. The fibril formation acceleration effect of the HSP10 chaperone was client-specific as it was observed for A30P but not WT α-syn. Our results broaden the scope of HSP10 chaperone activity and can have implications for disease onset in synucleinopathies
Insights into the compatibility of a metastable FeMnCoCr high entropy alloy with a Fe-based shape memory alloy
No full textHigh entropy alloys (HEA) are novel advanced materials that have been subjected to extensive research due totheir outstanding properties and potential for key engineering applications. Given this, research on their processabilitymust be conducted to avoid premature failure during operation. Gas tungsten arc welding is a widelyavailable technology capable of generating high performing and permanent joints. Furthermore, within thistechnology, dissimilar welding is a relevant topic given the frequent necessity to join different materials,allowing for greater design freedom while decreasing material costs. In this study, dissimilar welding of aFeMnCoCr HEA with a Fe-based shape memory alloy was conducted, allowing an inquiry into the compatibilitybetween the two advanced engineering alloys. By employing both conventional and advanced characterizationtechniques, including optical and electron microscopy, atom probe tomography and synchrotron x-ray diffraction,a comprehensive understanding of the effect of processing condition on the microstructure and mechanicalresponse of the joints is obtained. With this work we intend to highlight a pathway for the introduction of HEAsin modern day engineering industry
IPPOG: a global network for particle physics outreach and education
No full textWe present the International Particle Physics Outreach Group (IPPOG), a global network dedicated to connecting students, educators, and the general public with the world of particle physics. In this paper, we outline the need to bridge the existing gap between the particle physics community and the wider audience, and we present the solutions that IPPOG has implemented to overcome it through three pillar Activities: the International Masterclasses and the Global Cosmics hands-on activities network, which have engaged together over 200,000 high-school students to date, and the curation of an Outreach Resource Database and web portal
Investigation of the formation and reduction of hydrogen porosity during laser welding of additively manufactured AlSi10Mg parts
No full textWith the increasing industrial implementation of additively manufactured metal parts, the welding of such components gains importance. Due to size limitations of laser powder-bed fusion (PBF-LB) machines and design constraints, subsequent joining processes are required. However, the weld seam quality of PBF-LB manufactured parts, particularly aluminum parts, is still limited by pore formation in the weld seam. These pores are believed to be primarily caused by the agglomeration of hydrogen. Therefore, this study investigates the pore formation during laser beam welding of PBF-LB manufactured AlSi10Mg parts by means of in-situ high-speed synchrotron X-ray imaging. In addition, an in-situ laser powder drying process is investigated to reduce the hydrogen content of PBF-LB manufactured aluminum parts in order to prevent the formation of hydrogen porosity during the subsequent welding process. Results show that pores predominantly form in the interdendritic region at the solidification front due to the locally increased hydrogen concentration. By applying laser powder dryi