Physikalisch-Technische Bundesanstalt

Selective attention involves prioritising relevant sensory input while suppressing irrelevant stimuli. It has been proposed that oscillatory alpha-band activity (~10 Hz) aids this process by functionally inhibiting early sensory regions. However, recent studies have challenged this notion. Our EEG and MEG studies aimed to investigate whether human alpha oscillations serve as a 'gatekeeper' for downstream signal transmission. We first observed these effects in an EEG study and then replicated them using MEG, which allowed us to localise the sources. We employed a cross-modal paradigm where visual cues indicated whether upcoming targets required visual or auditory discrimination. To assess inhibition, we utilised frequency-tagging, simultaneously flickering the fixation cross at 36 Hz and playing amplitude-modulated white noise at 40 Hz during the cue-to-target interval. Consistent with prior research, we observed an increase in posterior alpha activity following cues signalling auditory targets. However, remarkably, both visual and auditory frequency-tagged responses amplified in anticipation of auditory targets, correlating with alpha activity amplitude. Our findings suggest that when attention shifts to auditory processing, the visual stream remains responsive and is not hindered by occipital alpha activity. This implies that alpha modulation does not solely regulate 'gain control' in early visual areas but rather orchestrates signal transmission to later stages of the processing stream.

Convergence and parallelism are contentious terms in evolutionary biology, but both denote essentially a ubiquitous phenomenon: The occurrence of similar phenotypes, in different evolutionary lineages, in a way that cannot be easily reconducted to descent from a shared ancestor. In this article, we trace the historical definitions of the two terms and the current conceptual frameworks to classify instances of repeated evolution, presenting the limits of these approaches in considering convergence and parallelism as a strict dichotomy rather than as part of a continuum along the spectrum of phenotypic similarity. We then present cases of convergence-broadly defined-from plant domestication and specialized metabolism, with the objective of understanding the intricacies between natural selection, constraints and drift underlying the recurrent appearance of complex traits.

Die Weiterentwicklung der DIN 45680 „Messung und Bewertung tieffrequenter Geräuschimmissionen in der Nachbarschaft“ wird durch das nur sehr begrenzt zur Verfügung stehende Wissen über eine potenzielle Exposition und ihre Auswirkungen auf den Menschen erschwert. Vom Umweltbundesamt [zum vollständigen Text gelangen Sie über die oben angegebene URL]

In radiotherapy and particle therapy, the stability of the beam energy must be checked routinely during quality assurance. This is of particular importance when varying the dose rate via the beam intensity of the accelerator in order to study the FLASH effect when comparing irradiations with conventional and ultra-high doserates. The standard method of energy verification based on the measurement of percent depth-dose curves in a water phantom is time-consuming and in the case of ultra-high dose-rate beams, may also present a non-negligible radiation protection problem. A compact, portable multileaf Faraday cup (MLFC) with 128 channels was developed for energy determination based on the measurement of depth-charge curves. Its design is optimized for clinical electron beams in a range between 3 and 25MeV. The read-out unit of the MLFC displays the beam energy in real time. The device was tested in strongly pulsed electron beams such as those present in irradiations with ultra-high doses per pulse as well as in conventional clinical electron beams. The same detector was used for proof of concept in a single measurement campaign in pulsed beams of therapeutical protons (conventional dose rates) from a synchrotron source using a suitable range shifter. The MLFC was calibrated with monoenergetic electron beams as well as against depth-dose curves. Simulations were carried out forcomparison. The MLFC works well under ultra-high pulse dose rate conditions as well as in conventional electron beams generated by a medical accelerator. Changes in the beam energy of below 20keV (0.1% of 20MeV) can be clearly identified by means of the MLFC. For proton beams, well-defined peaks in the depth-charge curves are observed for each single synchrotron spill with a total charge of only about 1nC. The energy values resulting from MC simulations of the measured MLFC data agree with the actual proton energies within 2 . The MLFC can be used for quick validation of the energy stability when carrying out experiments comparing electron beams of conventional and ultra-high dose rates. The same device can be used in the pulsed ion beams from asynchrotron.

Abstract Accurate neutron capture cross sections are essential for the design and operation of fast reactors using MOX fuels. For $$^{242}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mmultiscripts> <mml:mrow/> <mml:mrow/> <mml:mn>242</mml:mn> </mml:mmultiscripts> </mml:math> Pu, the Nuclear Energy Agency (NEA) recommends 8–12% accuracy in the fast energy region (2–500 keV), compared to the current uncertainty of 35%. Moreover, integral experiments and previous measurements suggest the evaluated $$^{242}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mmultiscripts> <mml:mrow/> <mml:mrow/> <mml:mn>242</mml:mn> </mml:mmultiscripts> </mml:math> Pu(n, $$\gamma $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mi>γ</mml:mi> </mml:math> ) cross section is overestimated, particularly in the JEFF-3.3 library, which shows a 14% overestimation between 1 keV and 1 MeV. Recent measurements from LANSCE reported a 20–30% reduction in the 1–40 keV range relative to evaluations. To solve these discrepancies, the $$^{242}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mmultiscripts> <mml:mrow/> <mml:mrow/> <mml:mn>242</mml:mn> </mml:mmultiscripts> </mml:math> Pu(n, $$\gamma $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mi>γ</mml:mi> </mml:math> ) cross section was measured from 1 to 600 keV at CERN n_TOF-EAR1 facility using a 95(4) mg $$^{242}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mmultiscripts> <mml:mrow/> <mml:mrow/> <mml:mn>242</mml:mn> </mml:mmultiscripts> </mml:math> Pu target, enriched to 99.959%. Gamma rays from neutron capture were detected with an array of $$\hbox {C}_6\hbox {D}_6$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msub> <mml:mtext>C</mml:mtext> <mml:mn>6</mml:mn> </mml:msub> <mml:msub> <mml:mtext>D</mml:mtext> <mml:mn>6</mml:mn> </mml:msub> </mml:mrow> </mml:math> scintillators and a novel application of the Pulse Height Weighting Technique was employed. The resulting cross section presents a systematic uncertainty between 8 and 12%, reducing the current uncertainties of 35% and achieving the accuracy requested by the NEA. Analysis using FITACS produced average resonance parameters, consistent with the analysis of the resolved resonance region. Our data align well with Wisshak and Käeppeler, and are 10–14% lower than JEFF-3.3 in the 1–250 keV range, helping to achieve consistency with integral benchmarks. At higher energies, our results are in reasonable agreement with ENDF/B-VIII.1 and JEFF-3.3. In contrast, DANCE results appear to underestimate the cross section by a factor of 2–3 above a few keV.

We introduce an absorption imaging technique for ultracold gases that suppresses interference fringes and coherence-induced artifacts by reducing the transverse spatial coherence of the imaging light. The method preserves the narrow spectral bandwidth required for resonant absorption imaging and is implemented as a modular extension to standard imaging setups using a rotating diffuser. We demonstrate tunability of the illumination light's coherence without modifying the imaging optics. Using this approach, we achieve reliable imaging of ultracold atomic clouds in micron-scale proximity to complex surfaces, where standing waves, edge diffraction, and speckle severely limit conventional absorption imaging.

This article addresses the use of dielectric tuners in low-loss reconfigurable bandpass filters based on TM<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">010</inf>-mode dielectric resonators. A fully reconfigurable 4th-order L-band filter is presented with adaptable center-frequency and band-width. Based on the tuning requirements, the design is explored in terms of resonator topology, as well as of inter-resonator and input/output coupling levels. The proposed filter is successfully designed, manufactured, and measured, demonstrating a clear agreement between simulated and experimental results. Using dielectric zirconia rods, the implemented prototype successfully exhibited efficient center-frequency tuning between 1.4 – 1.9 GHz with low-loss and high quality-factor larger than 1200. Also, the absolute bandwidth (BW) is reconfigured effectively from 60 MHz to 100 MHz.

Abstract Modern machine learning (ML) systems, particularly deep neural networks, have become increasingly complex and opaque, making reliable uncertainty quantification (UQ) essential. Conventional UQ methods often prove inadequate for black-box model evaluation scenarios, either because model internals are not accessible or because the resulting uncertainty is expressed in terms of a related predictor rather than the model under evaluation. We introduce U-TraCE (Uncertainty Tracking for Complex Estimators), a novel UQ method built on the Conformal Prediction (CP) framework that provides formal and traceable uncertainty bounds for opaque ML systems. Unlike existing CP approaches, which describe uncertainty through confidence intervals or prediction set sizes at a fixed uncertainty level, U-TraCE yields an explicit numerical bound on the error probability of the standalone black-box model. U-TraCE was evaluated on diverse tasks, including MNIST classification and cardiac magnetic resonance imaging (MRI) segmentation, representing both benchmark and real-world domains. Across these settings, it produced conservative yet well-calibrated uncertainty bounds that closely follow empirical uncertainty, even with limited calibration data. By bridging theoretical UQ and operational model validation, U-TraCE establishes a foundation for objective and automated conformity assessment of complex ML systems, supporting trustworthy deployment in safety-critical environments.

Developments in ultrastable lasers have fueled remarkable advances in optical frequency metrology and quantum science. A key ingredient in further improving laser frequency stability is the use of low-noise mirror materials such as AlGaAs crystalline coatings. However, excess noise observed with these coatings limits the performance of cryogenic silicon cavities with AlGaAs mirrors to similar levels achieved with conventional dielectric coatings. With a new pair of crystalline coated mirrors in a 6-cm-long cryogenic silicon cavity operated at 17K, we demonstrate a clear advantage of crystalline coatings over dielectric coatings. The achieved fractional frequency stability of 2.5×10^{-17} at 10s is four times better than expected for dielectric mirrors and corresponds to more than a tenfold reduction in the coating mechanical loss factor. We also combine two silicon cavities to demonstrate optical frequency averaging for enhanced stability. In addition, we present a long-term frequency drift record of four cryogenic silicon cavities measured over several years. These results open up realistic prospects for cavity-stabilized lasers with 10^{-18} fractional stability, as well as an all-optical timescale with continuously operating optical local oscillators.

Historically, the realization of the base unit kelvin was exclusively possible via International Temperature Scales (ITS). The new definition of the kelvin and the accompanying Mise en Pratique of the kelvin (MeP-K) enables the alternative to use primary thermometry for the realization of the kelvin. During the last years, considerable improvements in primary thermometry in the low-temperature range have been achieved. Thereby, above 300 K, still a lot of work is necessary to be competitive with the existing ITS realization. In this contribution, the interplay between primary thermometry, ITS and scale carriers (platinum resistance thermometers, thermocouples) in a historical perspective is sketched. After a short introduction to primary thermometry in general and the established techniques within the MeP-K, the focus will lie on the challenges connected with thermodynamic temperature measurement above 300 K. The advantages and disadvantages of the different techniques will be discussed briefly, and a summary will be given showing that thermodynamic temperature T, TITS and scale carriers are highly connected and improvement in one field relies on improvement in the others. The background of the discussion will be the deficiencies of the existing ITS and thus the requirements for the temperature-measurement community. This article is part of the Theo Murphy meeting issue 'The redefined kelvin: progress and prospects'.