405905 research outputs found
Sort by
Atomic‐Scale Insights into Nanoparticle Exsolution at Dislocations in Dislocation‐Engineered Catalysts
No full text
Influence of Severe Accident Management on the In-Containment Combustion Risk in European Pressurized Water Reactors
No full textA System for the Cryogenic Power Management of Quantum Computing Electronics: Development, Integration, and Test
No full textIn view of the post-Moore’s law era, new computational paradigms that could serve as powerful alternatives to the classical computing are under development. One of those paradigms is Quantum Computing (QC). By using the quantum mechanical properties of superposition and entanglement via the manipulation of a large number of qubits, QC systems promise to speed up the finding of solutions to the computational challenges faced in cryptography, optimization of different processes, and quantum systems simulation. These applications position the QC systems as powerful tools for humanity. However, the design, assembly, deployment and operation of a QC system are not simple tasks. This is because QC devices, such as superconductive qubits or semiconductor quantum dots, require an ambient temperature lower than 100mK in order to reduce the influence of heat sources that could disrupt the qubits state information and coherence. Also, the only practical way in which a QC device can be subjected to such low temperatures is by means of a dilution refrigerator, a complex machine with limited room for Devices Under Test (DUTs), electrical connections for DC and RF signals, and cooling power. In order to increase the QC system performance, such a system must be composed by a high number of fault-tolerant qubits. As well as by hardware and software capable of enabling its scalability. Moreover, it is expected that by incorporating cryogenic CMOS ICs as part of QC systems, the number of connections between the qubits and the Room Temperature (RT) electronics will be reduced, relaxing the dilution refrigerator requirementsand allowing the system scalability. In addition, the signal integrity of the signals controlling the qubits could be improved by the shorter interface with the local cryogenic electronics based on ICs. But the most important advantage offered by CMOS IC technology is its potential integration with qubit devices. In particular, the semiconductor gate defined quantum dot, a device that stores and controls an electron operating as qubit. Thus, the development of analog, digital, and mixed-signal cryogenic CMOS ICs has attracted significant attention in the last years. As it has been demonstrated that IC technology can be an important part and key enabler of the QC systems scalability. This work contributes to cryogenic analog MOS circuit design discipline through the development, integration and test of a cryogenic Power Management Unit (PMU) composed by a CMOS IC and additional passive components. The cryogenic PMU is developed with a 22 nm FDSOI technology, as it supplies MOSFETs that can operate at Cryogenic Temperatures (CTs) without significant performance degradation. Ultimately, the goal is to provide a regulated and lownoise voltage supply to other circuit blocks located at CT environments close to 4 K, reducing the amount of DC connections between the RT equipment and the cryogenic electronics. Hence, the QC systems scalability effortsare thereby supported
Spin–orbit effects in the surface state of Fe(001) revealed by full surface Brillouin zone mapping
No full textThe electronic structure of Fe has been experimentally studied using angle-resolved photoemission spectroscopy (ARPES) since the early days of photoemission. Yet, the existence and nature of the Fe(001) surface state remain a subject of ongoing debate. Fe(001) is considered a prototypical transition metal system and moreover, one of the key players in the spintronics research. Here, we present the electronic structure of Fe(001) epitaxially grown on Au(001), mapped by high-resolution ARPES within the entire surface Brillouin zone, to demonstrate for the first time the exact location and extent of the Fe(001) surface state. The experimental results are supported by the relativistic slab calculations performed using density functional theory (DFT). The surface state observed for the pristine Fe(001) surface vanishes after overnight rest of the sample in ultrahigh vacuum as well as after intentional exposure to 5 Langmuir of oxygen which proves that it is not topologically protected. Furthermore, the dispersion of the surface state is found to depend on the relative orientation of the magnetization, which is explained based on the DFT results as related to the Rashba effect. These new experimental and theoretical results contribute to the existing knowledge on the electronic properties of Fe(001) with relevance for the basic research as well as for spintronic effects, such as tunneling anisotropic magnetoresistance
A PEM Electrolysis Cell for In Operando NMR and MRI Investigations of MEA Degradation
No full textProton exchange membrane (PEM) electrolysis is a promising process for sustainable hydrogen production, but its commercialization is delayed by high costs and elusive degradation of membrane electrode assemblies (MEAs) [1]. In operando Nuclear Magnetic Resonance (NMR) and Magnetic Resonance Imaging (MRI) offer the potential to investigate degradation mechanisms during electrolysis, and thus, provide highly relevant insights for enhanced performance [2,3].In a first part of this contribution, a custom-designed miniature PEM electrolysis cell is presented, fitting the spatial constraints of a 1H coil of a commercially available imaging probe. In contrast to tailor-made probes [2,3], this approach allows for a broader range of NMR experiments – including not only 1H spectroscopy and T1 and T2 relaxometry, but also the first MRI and diffusion measurements on operating PEM electrolysis cells. The key design feature was a sealing concept without screws, utilizing O-rings in combination with precise compression geometry. Uniform electrical contacting minimizing metal content in the NMR-sensitive volume was validated via microelectrode voltage mapping. The inlet water temperature was controlled between 60 and 80 °C using a non-magnetic heat tube.The functionality of the newly developed NMR cell is demonstrated by electrochemical and NMR experiments in the second part of the contribution. The 1H signal-to-noise ratio and resolution allowed chemical shift analysis, while T1/T2 contrast enabled differentiation between MEA and water signals. MRI revealed water and gas bubble distribution during operation. Impedance spectroscopy and cyclic voltammetry results were consistent with labscale PEM electrolysis.This novel in operando NMR cell provides an effective method for investigating degradation phenomena during long-term PEM electrolysis experiments, leveraging the wide variety of experiments available with commercial probes
2025 Open Science Recognition Prize
No full textThe Prithvi-Geospatial AI Foundation Model Team receives the 2025 Open Science Recognition Prize by the American Geophysical Union for pioneering open-access AI foundation models that advance Earth science and exemplify global collaboration, transparency, and education
