[en] In a series of letters, we present teaching videos on topics which are difficult to understand for students, or which are difficult to realize experimentally in school, if at all. These videos can be used for quantitative analysis or visualization of phenomena. Here we present videos on aero and fluid dynamics which deal with the Navier-Stokes equation, the continuity equation and Karman's vortex street. (letters and comments)

[en] A video of the Reynolds transition experiment, developed for physics teaching, shows the continuous transition from laminar to turbulent flow. Additionally, the critical Reynolds number of the experimental set-up is determined approximately. By looking at it, the user of the video can measure all necessary data and then calculate a result

[en] The infrastructure behind home.cern and 1000 other Drupal websites serves more than 15,000 unique visitors daily. To best serve the site owners, a small engineering team needs development speed to adapt to their evolving needs and operational velocity to troubleshoot emerging problems rapidly. We designed a new Web Frameworks platform by extending Kubernetes to replace the ageing physical infrastructure and reduce the dependency on homebrew components. The new platform is modular, built around standard components and thus less complex to operate. Some requirements are covered solely by upstream open source projects, whereas others by components shared across CERN’s web hosting platforms. We leverage the Operator framework and the Kubernetes API to get observability, policy enforcement, access control and auditing, and high availability for free. Thanks to containers and namespaces, websites are isolated. This isolation clarifies security boundaries and minimizes attack surface, while empowering site owners. In this work we present the new system’s open-source design contrasted with the one it replaces, demonstrating how we drastically reduced our technical debt.

[en] In a series of letters we present teaching videos on topics where the learners of physics used to have problems. The first video presents an experimental set-up by which the absorption lines (D₁, D₂) of sodium can be resolved simultaneous with the emission lines. The second video allows us to determine their wavelengths in comparison with calibrated spectral lines of mercury. This type of multimedia should not replace the real demonstration experiment, but is of good support for a long distant learner or for simply reading a textbook. (letters and comments)

No abstract available

[en] For the first time a high-pressure gas target has been investigated at the bremsstrahlung facility at the ELBE accelerator of the Forschungszentrum Dresden-Rossendorf. The experiment was carried out at an electron beam energy of 12 MeV in order to study the energy region up to the neutron separation. GEANT4 simulations were performed to subtract the atomic background from the measured spectrum and deduce the intensity of the resonantly scattered γ-rays. Considering also transitions from states in the quasicontinuum, simulations of γ-ray cascades were carried out with a new code to estimate branching ratios. As a result the photoabsorption cross section obtained from transitions to the ground state is calculated. The data will be presented in the context of further photon-scattering experiments performed in Rossendorf on the stable isotopes at the closed neutron shell N=50.

[en] The NeuLAND detector at the R³B experiment at the future FAIR facility in Darmstadt aims to detect fast neutrons (0.2-1.0 GeV) with high time and spatial resolutions (σ_t<100 ps, σ_x,y,z<1 cm). The multigap resistive plate chamber (MRPC) based prototypes developed so far and a full MRPC-based NeuLAND have been modeled in the R³BRoot simulation framework. The test-beam data obtained with the single-electron mode of the ELBE 40 MeV electron accelerator have been successfully reproduced in the simulation. The predicted response of the full-size NeuLAND for high-energy neutrons is discussed. Namely, the quality of the position and TOF determination important for momentum reconstruction are detailed. Furthermore, a key feature, i.e., the capability for multineutron recognition is also presented.

No abstract available

[en] We examine spinor Bose-Einstein condensates in optical superlattices theoretically using a Bose-Hubbard Hamiltonian that takes spin effects into account. Assuming that a small number of spin-1 bosons is loaded in an optical potential, we study single-particle tunneling that occurs when one lattice site is ramped up relative to a neighboring site. Spin-dependent effects modify the tunneling events in a qualitative and quantitative way. Depending on the asymmetry of the double well, different types of magnetic order occur, making the system of spin-1 bosons in an optical superlattice a model for mesoscopic magnetism. We use a double-well potential as a unit cell for a one-dimensional superlattice. Homogeneous and inhomogeneous magnetic fields are applied, and the effects of the linear and the quadratic Zeeman shifts are examined. We also investigate the bipartite entanglement between the sites and construct states of maximal entanglement. The entanglement in our system is due to both orbital and spin degrees of freedom. We calculate the contribution of orbital and spin entanglements and show that the sum of these two terms gives a lower bound for the total entanglement.

[en] The fast Fourier transformation has been the gold standard for transforming data from time to frequency domain in many spectroscopic methods, including NMR. While reliable, it has as a drawback that it requires a grid of uniformly sampled data points. This needs very long measuring times for sampling in multidimensional experiments in all indirect dimensions uniformly and even does not allow reaching optimal evolution times that would match the resolution power of modern high-field instruments. Thus, many alternative sampling and transformation schemes have been proposed. Their common challenges are the suppression of the artifacts due to the non-uniformity of the sampling schedules, the preservation of the relative signal amplitudes, and the computing time needed for spectra reconstruction. Here we present a fast implementation of the Iterative Soft Thresholding approach (istHMS) that can reconstruct high-resolution non-uniformly sampled NMR data up to four dimensions within a few hours and make routine reconstruction of high-resolution NUS 3D and 4D spectra convenient. We include a graphical user interface for generating sampling schedules with the Poisson-Gap method and an estimation of optimal evolution times based on molecular properties. The performance of the approach is demonstrated with the reconstruction of non-uniformly sampled medium and high-resolution 3D and 4D protein spectra acquired with sampling densities as low as 0.8%. The method presented here facilitates acquisition, reconstruction and use of multidimensional NMR spectra at otherwise unreachable spectral resolution in indirect dimensions.