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On the representation of piecewise quadratic functions by neural networks
(2025-09-09) Teichrib, Dieter; Schulze Darup, Moritz
Neural networks (NNs) are commonly used to approximate functions based on data samples, as they are a universal function approximator for a large class of functions. However, choosing a suitable topology in terms of depth, width and activation function for NNs that allow for low error approximations is a non-trivial task. For the approximation of continuous piecewise affine (PWA) functions, this task has been solved by showing that for every PWA function, there exist NNs with rectified linear unit (relu) and maxout activation that allow an exact representation of the PWA function. This connection between PWA functions and NNs has led to some valuable insights into the representation capabilities of NNs. Moreover, the connection was used in control for approximating the PWA optimal control law of model predictive control (MPC) for linear systems. We show that a similar connection exists between NNs and continuous piecewise quadratic (PWQ) functions by deriving topologies for NNs that allow an exact representation of arbitrary PWQ functions with a polyhedral domain partition. Furthermore, we demonstrate that the proposed NNs can efficiently approximate the PWQ optimal value function for linear MPC.
The FIFA 11 + Referees program improves knee proprioception in female futsal referees
(2025-09-17) Khosravi rad, Fatemeh; Zarei, Mostafa; Hosseini, Seyed Mohammad; Asgari, Mojtaba
While the FIFA 11 + Referees program (the 11 + Referees) is the only structured injury prevention program for referees, its effects on injury-related risk factors among referees remain underexplored. This study investigated the effects of the 11 + Referees on knee joint proprioception and dynamic balance. Thirty four female referees from the Tehran Premier Futsal League voluntarily participated and were randomly assigned to either a control group (n = 17) or the 11 + Referees group (n = 17). All participants underwent a baseline assessment including knee joint proprioception at angular velocities of 15°/s, 45°/s, and 60°/s, and position sense, as well as dynamic balance. Subsequently, the intervention group performed the 11 + Referees program three times weekly for 8 weeks, while the control group performed general warm-ups. Post-intervention, the same test battery was administered, and changes were analyzed to identify the program’s effects on the measures understudied. Significant improvements were observed in knee joint proprioception at 15°/s (F = 18.19, p < 0.001, η²=0.44), 45°/s (F = 4.07, p = 0.056, ηp²=0.15), and 60°/s (F = 6.63, p = 0.017, η²=0.22) in the intervention group. However, dynamic balance did not show significant improvement (F = 0.79, p = 0.38, η²=0.033). In conclusion, an eight-week application of the 11 + Referees enhanced knee joint proprioception in female referees with large effect sizes, but had no significant effect on dynamic balance. Improvements in proprioception may be attributed to neuromuscular adaptations resulting from regular program use. The absence of balance improvement could be due to the short intervention period and the hard futsal court surface, which may limit the effectiveness of certain balance exercises. Future studies should explore the program's effects on other injury risk factors and injury rates.
A reliable in vitro rumen culture system and workflow for screening anti-methanogenic compounds
(2025-12-01) Laric, Philip P.; Mortazavi, Armina; Wegrzyn, Ewa; Simon, Kathrin; Rittel, Pauline S.; Trefz, Florian M.; Sabass, Benedikt
Arguably the biggest man-made challenge of the century is halting climate change. Livestock’s methane (CH4) emissions, a greenhouse gas with a higher global warming potential than carbon dioxide (CO2), represent a prime target for reducing anthropogenic impact. While the reduction of enteric methane emissions through feed additives has been demonstrated, potent and affordable compounds inhibiting methanogenesis in ruminants are not yet well established. Reliable methods for reproducible cultivation of the rumen microbiome in the laboratory are an essential tool for the study of methanogenesis. We have developed a versatile setup that allows for the cultivation of the ruminal microbiome in a benchtop configuration and combines, miniaturizes, and improves existing systems. The design is based on standard laboratory equipment, including bottles, serological pipettes, tubing, and Luer-Lock valves. The apparatus enables long-term cultivation of primary cultures extracted from the rumen of slaughtered cattle. We describe rumen content acquisition, preparation, the cultivation procedure, and demonstrate the system’s performance. The efficacy of the system is demonstrated through the administration of various concentrations of state-of-the-art methanogenesis inhibitors. These inhibitors include lyophilized Asparagopsis taxiformis (AT), bromoform (BF), iodoform (IF), 3-nitrooxypropanol (3-NOP), rapeseed oil, and BF dissolved in rapeseed oil, with maximum CH4 reductions of 96.29% (p = 5.00E-05, Cohen’s d = 30.29), 98.22% (p = 2.88E-05, d = 23.07), 96.26% (p = 1.03E-05, d = 30.29), 74.63% (p = 8.88E-05, d = 13.32), 28.96% (p = 0.001, d = 3.99), and 98.51% (p = 4.18E-06, d = 39.94), respectively, in comparison to the negative control. The gas production dynamics in our setup align with previously published results, which supports the validity of the system. Compared to conventional methodologies, the described setup offers enhanced versatility and ease of use. Furthermore, Fourier-transform-infrared-spectroscopy is implemented in a novel and low-cost approach for quantifying CH₄ and CO₂ in the headspace gas. Together, these methodological advances provide an accessible and reproducible platform for long-term in vitro rumen cultivation for the screening of anti-methanogenic additives.
Ultraflat honeycomb stanene nanoribbons on Au(111)
(2025-12-01) Hochhaus, Julian Andreas; Hilgers, Stefanie; Kononov, Alexander; Weinert, Philipp; Berges, Ulf; Hövel, Heinz; Westphal, Carsten
Sn on Au(111) undergoes a structural and chemical evolution depending on the submonolayer coverage. After deposition of ≈ 2∕3 ML Sn, the coverage was controlled by temperature-driven desorption. Annealing to 450K produced the striped phase, which consists of alternating honeycomb and square-like Sn stripes, with periodicities ranging from Rec(13 × 2√3) to Rec(19 × 2√3),most commonly Rec(16 × 2√3). Honeycomb regions are atomically flat, with a Sn–Sn bond length of ≈2.88 Å. Low-energy electron diffraction (LEED), atomically resolved scanning tunneling microscopy (STM), and X-ray photoelectron spectroscopy (XPS) reveal structural and chemical transitions as a function of Sn coverage. Without further annealing, deposition yields a square-like X-phase atop an Au2Sn interface alloy. Annealing induces dealloying and the formation of the striped phase, while further desorption produces a √7 stretched honeycomb phase. Annealing above 480K, and at ≈ 0.35 ML coverage, the Au2Sn alloy reforms. For the striped phase, a model is proposed where square-like stripes grow on Au2Sn regions and honeycomb stripes on Au(111). The alternating regions correspond to zigzag stanene nanoribbons of ≈ 1.5nmto 3.2 nm width. The structural transitions of the Sn/Au(111) system highlight its structural versatility, driven by alloying–dealloying processes at the interface.
High-temporal-resolution dataset of uni-, bidirectional, and dynamic electric vehicle charging profiles
(2025-07-10) Esser, Marcel; Orfanoudakis, Stavros; Homaee, Omid; Vahidinasab, Vahid; Vergara, Pedro P.; Spina, Alfio
The transition to Electric Vehicles (EVs) introduces challenges for power grid integration, particularly due to the growing demand for charging infrastructure. To support research on smart charging strategies and bidirectional charging applications, this study presents an open-access dataset containing 142 EV charging profiles obtained in a laboratory environment. The dataset includes static charging and discharging scenarios alongside dynamic profiles where the charging power is varied over time. These scenarios are applied to eight commercially available EVs, three of which support bidirectional charging. It features tests in alternating current and direct current charging modes and includes high-resolution time series of grid and vehicle parameters at sub-second intervals. The dataset is technically validated by assessing charging efficiency, reactive power injection, harmonics, and its suitability for development of digital EV models. This dataset supports applications like model validation, grid integration simulations in the context of Vehicle-to-Grid (V2G), charging infrastructure planning, and smart charging strategy development.