École Polytechnique Fédérale de Lausanne
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Measurement of the Branching Fraction Ratios (Formula presented) and (Formula presented) Using Muonic (Formula presented) Decays
No full textThe branching fraction ratios of (Formula presented) and (Formula presented) decays are measured with respect to their muonic counterparts, using a data sample corresponding to an integrated luminosity of (Formula presented) collected by the LHCb experiment in proton-proton collisions at (Formula presented). The reconstructed final states are formed by combining (Formula presented) mesons with (Formula presented) candidates, where the (Formula presented) is reconstructed via the (Formula presented) decay. The results are (Formula presented), (Formula presented), where the first uncertainties are statistical and the second systematic. The two measurements have a correlation coefficient of (Formula presented) and are compatible with the standard model.LPHE-OSPH-SBLPHE-RMLPHE-L
Redox levels in aqueous solution: Effect of van der Waals interactions and hybrid functionals
No full textWe investigate redox levels in aqueous solution using a combination of ab initio molecular dynamics (MD) simulations and thermodynamic integration methods. The molecular dynamics are performed with both the semilocal Perdew-Burke-Ernzerhof functional and a nonlocal functional (rVV10) accounting for van der Waals (vdW) interactions. The band edges are determined through three different schemes, namely, from the energy of the highest occupied and of the lowest unoccupied Kohn-Sham states, from total-energy differences, and from a linear extrapolation of the density of states. It is shown that the latter does not depend on the system size while the former two are subject to significant finite-size effects. For the redox levels, we provide a formulation in analogy to the definition of charge transition levels for defects in crystalline materials. We consider the H+/H2 level defining the standard hydrogen electrode, the OH-/OH- level corresponding to the oxidation of the hydroxyl ion, and the H2O/OH- level for the dehydrogenation of water. In spite of the large structural modifications induced in liquid water, vdW interactions do not lead to any significant structural effect on the calculated band gap and band edges. The effect on the redox levels is also small since the solvation properties of ionic species are little affected by vdW interactions. Since the electronic properties are not significantly affected by the underlying structural properties, it is justified to perform hybrid functional calculations on the configurations of our MD simulations. The redox levels calculated as a function of the fraction α of Fock exchange are found to remain constant, reproducing a general behavior previously observed for charge transition levels of defects. Comparison with experimental values shows very good agreement. At variance, the band edges and the band gap evolve linearly with α. For α 0.40, we achieve a band gap, band-edge positions, and redox levels in overall good agreement with experiment.CSE
An acoustic levitation platform for high-content histological analysis of 3D tissue culture
No full textMiniaturized three-dimensional (3D) cell culture systems, in particular organoids and spheroids, hold great potential for studying morphogenesis, disease modeling, and drug discovery. However, sub-cellular resolution 3D imaging of these biological samples remains a challenge. Histology, the gold standard for ex vivo microscopic interrogation of tissue anatomy, may address this challenge once the associated techniques are adapted. Due to their small size and delicate structure, organoids must be embedded in a supporting hydrogel. The histological sections have low information content because the distribution of the organoids within the gel is not controlled. To address this issue, we introduce an acoustic micromanipulation platform that concentrates and aligns organoids within a histology-compatible hydrogel block. Utilizing an array of micromachined lead zirconate titanate (PZT) transducers, the platform generates localised and precisely controlled acoustic standing waves to levitate organoids to a prescribed plane and fix their positions within a polyethylene glycol diacrylate (PEGDA)-gelatine hydrogel. Organoids from different culture conditions can be co-embedded in a traceable fashion with the use of a custom-design hydrogel grid. Our results demonstrate that more than 70% of spheroids can be positioned within a 150 μm-thick hydrogel block, substantially increasing the information content of histology sections. The platform's versatility, scalability, and ease of use will make histological assessment accessible to every life science laboratory.MICROB
An overview of the professional skills encountered through capstone engineering projects
No full textWe present an analysis of the professional competencies encountered by engineering students during their capstone projects. We collected weekly reflective journals from 32 students completing their capstone projects at ETH Zurich. Through a deductive quantitative content analysis, we identified the professional competencies posing the greatest challenges for students and examined the frequency of their resolution. Additionally, we explored the distribution of challenges across different project phases and assessed their difficulty levels. Our findings reveal that while capstone projects aim to cultivate professional skills, they primarily challenge students' technical abilities. Moreover, most encountered challenges are those directly assessed through project deliverables, such as applying technical foundations that are assessed through technical artifacts and communicating effectively which is assessed through the final presentation. The majority of challenges arise during the implementation, testing, and prototyping phases, with fewer reported during problem definition and solution design phases, suggesting potential disparities in attention and time allocation across project stages. Notably, although the problem definition phase encounters fewer challenges, students perceive the challenges within this stage as more difficult. Consequently, we conclude that allocating additional time and importance to solution design and problem definition phases may effectively foster a broader range of professional skills among students, including creative thinking and decision-making abilities.CHILIAVP-E-LEAR
Toward an Ontological Model for Audiovisual Archive Datafication
No full textWith the initiatives like Collections as Data and Computational Archival Science, archives are no longer seen as a static documentation of objects, but evolving sources of cultural and historical data. This work emphasizes the potential updates in preserving and documenting digital audiovisual (AV) content from a data perspective, considering the recent developments in natural language processing and computer vision tasks, as well as the emergence of interactive and embodied experiences and interfaces for innovatively accessing archival content. As part of Swiss national scientific fund Sinergia project, this work was able to work end-to-end with real-world AV archives like Télévision Suisse Romande (RTS). Resorting to an updated narrative model for mapping data that can be obtained from the content as well as the consumer, this work proposed an experimental attempt to build an ontology to formally sum up the potential new paradigm for preservation and accessibility from a data perspective for modern archives, in the hope for nurturing a digital and data driven mind-set for archive practices.EMPLU
Let There Be Light: Robust Lensless Imaging Under External Illumination With Deep Learning
No full textLensless cameras relax the design constraints of traditional cameras by shifting image formation from analog optics to digital post-processing. While new camera designs and applications can be enabled, lensless imaging is very sensitive to unwanted interference (other sources, noise, etc.). In this work, we address a prevalent noise source that has not been studied for lensless imaging: external illumination e.g. from ambient and direct lighting. Being robust to a variety of lighting conditions would increase the practicality and adoption of lensless imaging. To this end, we propose multiple recovery approaches that account for external illumination by incorporating its estimate into the image recovery process. At the core is a physics-based reconstruction that combines learnable image recovery and denoisers, all of whose parameters are trained using experimentally gathered data. Compared to standard reconstruction methods, our approach yields significant qualitative and quantitative improvements. We open-source our implementations and a 25K dataset of measurements under multiple lighting conditions.LCA
Spin-Polarized Electron Transport Promotes the Oxygen Reduction Reaction
No full textOxygen evolution (OER) and oxygen reduction (ORR) reactions are central to the efficiency of electrolysis and fuel cells, involving the paramagnetic triplet ground state of oxygen and the singlet ground state of water. Here, we demonstrate that spin-polarized currents enhance the ORR activity. Using a silver-coated nickel electrode over a neodymium (Nd) magnet, we observed that ORR performance is maximized when the Ag layer is thinner than the spin diffusion length of silver—conditions under which spin alignment at the electrode–electrolyte interface is maintained. In contrast, thicker Ag layers lead to spin relaxation and diminished electrocatalytic activity. A model description of this system shows that a very weakly spin-polarized injected current leads to a substantial spin-polarization at the interface, indicating that the simultaneous transfer of two-electrons can provide the necessary electrons while maintaining the conservation of the angular momentum during ORR. These findings highlight the critical role of spin-selective charge transfer and offer new insights into the control of reaction pathways in oxygen electrocatalysis.LNETPH-SBLSE
Techno-economic analysis of ammonia to hydrogen and power pathways considering the emerging hydrogen purification and fuel cell technologies
No full textAmmonia serves as a promising hydrogen carrier and energy storage medium due to its high hydrogen content, ease of transport, and well-established production infrastructure. This study presents a comprehensive techno-economic analysis of ammonia-to‑hydrogen (A2H) and ammonia-to-power (A2P) pathways, comparing various process configurations for hydrogen production and power generation. High-temperature ammonia crackers (600 °C) achieve a maximum energy efficiency of 87.55 % and a maximum exergy efficiency of 86.09 %, outperforming lower-temperature crackers (450 °C), which have energy efficiencies ranging from 82.16 % to 86.75 %. Among hydrogen separation technologies, temperature swing adsorption (TSA) incurs the lowest efficiency penalty but at the highest cost, while pressure swing adsorption (PSA) is more energy-intensive but has the lowest levelized cost of hydrogen (LCOH) at 2.81 USD/kg. In the A2P pathway, the integrated system of the high-temperature cracker and solid oxide fuel cell (SOFC) achieves the highest efficiency of 69.55 % and the lowest levelized cost of electricity (LCOE) at 0.145 USD/kWh, underscoring the crucial role of system efficiency in determining LCOE. Conversely, directly combusting hydrogen in a steam Rankine cycle (SRC) results in the lowest efficiency of 33.2 % and the highest LCOE of 0.715 USD/kWh, making it the least viable option. Furthermore, integrating ammonia with existing energy infrastructures creates new opportunities for hydrogen production and power generation. The results highlight ammonia's potential as a cost-effective hydrogen carrier, particularly in renewable-rich regions for large-scale ammonia synthesis and export to high energy cost markets. This study offers insights into optimal strategies for deploying ammonia-based energy solutions, informing future technological developments and policy frameworks for a hydrogen-driven future economy.SCI-STI-FMSCI-STI-JV
