Nanoporous Copper-Nickel - Macroscopic bodies of a strong and deformable nanoporous base metal by dealloying

Uniform macroscopic samples of nanoporous metal with high deformability have so far been limited to precious metals such as Au, Pd and Pt. Here we propose nanoporous Copper-Nickel (npCN) as a nanoporous base metal that can be made with mm dimensions and exhibits significant deformability. NpCN forms a uniform bicontinous network structure with feature sizes that can be controlled from 13 to 40 nm by thermal annealing. Continuous compression tests confirm ductile deformation behavior accompanied with a high strength compared to macroporous Cu- and Ni-foams with similar solid fraction

A characterization and detection method for x-ray excitation of M\"ossbauer nuclei beyond the low-excitation regime

Up to now, experiments involving M\"ossbauer nuclei have been restricted to the low-excitation regime. The reason for this is the narrow spectral line width of the nuclei. This defining feature enables M\"ossbauer spectroscopy with remarkable resolution and convenient control and measurements in the time domain, but at the same time implies that only a tiny part of the photons delivered by accelerator-based x-ray sources with orders-of-magnitude larger pulse bandwidth are resonant with the nuclei. X-ray free-electron lasers promise a substantial enhancement of the number of nuclear-resonant photons per pulse, such that excitations beyond the low-excitation (LER) regime come within reach. This raises the question, how the onset of non-linear excitations could be experimentally verified. Here, we develop and explore a method to detect an excitation of nuclear ensembles beyond the LER for ensembles of nuclei embedded in x-ray waveguides. It relies on the comparison of the x-rays coherently and incoherently scattered off of the nuclei. As a key result, we show that the ratio of the two observables is constant within the LER, essentially independent of the details of the nuclear system and the characteristics of the exciting x-rays. Conversely, deviations from this equivalence serve as a direct indication of excitations beyond the LER. Building upon this observation, we develop a variety of experimental signatures both, for near-instantaneous impulsive and for temporally-extended non-impulsive x-ray excitation. Correlating coherently and incoherently scattered intensities further allows one to compare theoretical models of nonlinear excitations more rigorously to corresponding experiments.Comment: 21 pages, 6 figure

Unraveling Time- and Frequency-Resolved Nuclear Resonant Scattering Spectra

Owing to their extremely narrow line-widths and exceptional coherence properties, M\"ossbauer nuclei form a promising platform for quantum optics, spectroscopy and dynamics at energies of hard x-rays. A key requirement for further progress is the development of more powerful measurement and data analysis techniques. As one approach, recent experiments have employed time- and frequency-resolved measurements, as compared to the established approaches of measuring time-resolved or frequency-resolved spectra separately. In these experiments, the frequency-dependence is implemented using a tunable single-line nuclear reference absorber. Here, we develop spectroscopy and analysis techniques for such time- and frequency-resolved Nuclear Resonant Scattering spectra in the frequency-frequency domain. Our approach is based on a Fourier-transform of the experimentally accessible intensities along the time axis, which results in complex-valued frequency-frequency correlation (FFC) spectra. We show that these FFC spectra not only exhibit a particularly simple structure, disentangling the different scattering contributions, but also allow one to directly access nuclear target properties and the complex-valued nuclear resonant part of the target response. In a second part, we explore the potential of an additional phase control of the x-rays resonantly scattered off of the reference absorber for our scheme. Such control provides selective access to specific scattering pathways, allowing for their separate analysis without the need to constrain the parameter space to certain frequency or time limits. All results are illustrated with pertinent examples in Nuclear Forward Scattering and in reflection off of thin-film x-ray cavities containing thin layers of M\"ossbauer nuclei.Comment: 26 pages, 13 figure

Fano resonances in scattering: an alternative perspective

In a previous paper it has been shown that the interference of the first and second order pole of the Green's function at an exceptional point, as well as the interference of the first order poles in the vicinity of the exceptional point, gives rise to asymmetric scattering cross section profiles. In the present paper we demonstrate that these line profiles are indeed well described by the Beutler-Fano formula, and thus are genuine Fano resonances. Also further away from the exceptional points excellent agreement can be found by introducing energy dependent Fano parameters.Comment: 4 pages, 3 figures, 3 tables, additional reference

From Monocular SLAM to Autonomous Drone Exploration

Micro aerial vehicles (MAVs) are strongly limited in their payload and power capacity. In order to implement autonomous navigation, algorithms are therefore desirable that use sensory equipment that is as small, low-weight, and low-power consuming as possible. In this paper, we propose a method for autonomous MAV navigation and exploration using a low-cost consumer-grade quadrocopter equipped with a monocular camera. Our vision-based navigation system builds on LSD-SLAM which estimates the MAV trajectory and a semi-dense reconstruction of the environment in real-time. Since LSD-SLAM only determines depth at high gradient pixels, texture-less areas are not directly observed so that previous exploration methods that assume dense map information cannot directly be applied. We propose an obstacle mapping and exploration approach that takes the properties of our semi-dense monocular SLAM system into account. In experiments, we demonstrate our vision-based autonomous navigation and exploration system with a Parrot Bebop MAV

Die postinfektionellen Wirkungen von Kupferhydroxid und Kupfersulfat auf Konidien von Venturia inaequalis

The post-infection activity of copper hydroxide and copper sulfate against conidia of Venturia inaequalis were evaluated using an in vitro test system based on isolated apple leaf cuticles. Experiments were conducted at 20°C and treatments were applied 24 or 48 h after inoculation. Experiments were assessed by counting living primary stromata 72 h after inoculation using fluorescence microscopy and fluorescein diacetate (FDA) as a vital stain. Copper hydroxide and copper sulfate showed post-infection activity and killed primary stromata, provided the surface of the CM was kept wet. Copper hydroxide was more effective than copper sulfate and was able to kill all primary stromata 24 h after inoculation at concentrations of 116 and 231 mg l-1. Results indicate different modes of action for the highly water soluble copper sulfate and the slightly soluble copper hydroxide. Application of copper hydroxide to dry CM did not kill primary stromata. Hence, for copper hydroxide to exert post-infection activity leaves must be wet

The post-infection activity of hydrated lime against conidia of Venturia inaequalis

The post-infection activity of hydrated lime against conidia of Venturia inaequalis was evaluated using an in vitro test system based on isolated apple leaf cuticles. Experiments were conducted at 20°C and treatments were applied 24 or 48 h after inoculation. Experiments were assessed by counting living primary stromata 72 h after inoculation using fluorescence microscopy and fluorescein diacetate (FDA) as a vital stain. At the conditions of the in vitro test system hydrated lime had a post-infection activity. Suspension of 5 g l-1 applied 24 h after inoculation (16 h after infection) killed all primary stromata and stopped their further development. Treatments 48 h after inoculation reduced the number of vital primary stromata to 60% of control. Treatments with saturated solutions of hydrated lime (pH 12.45) and with KOH solutions of different pH showed that a pH higher than 12.4 was needed to be 100% effective. Suspensions of calcium carbonate (6.75 g l-1) had no effect

Die postinfektionelle Wirkung von Calciumhydroxid auf Konidien von Venturia inaequalis

The post-infection activity of hydrated lime against conidia of Venturia inaequalis was evaluated using an in vitro test system based on isolated apple leaf cuticles. Experiments were conducted at 20°C and treatments were applied 24 or 48 h after inoculation. Experiments were assessed by counting living primary stromata 72 h after inoculation using fluorescence microscopy and fluorescein diacetate (FDA) as a vital stain. At the conditions of the in vitro test system hydrated lime had a post-infection activity. Suspension of 5 g l-1 applied 24 h after inoculation (16 h after infection) killed all primary stromata and stopped their further development. Treatments 48 h after inoculation reduced the number of vital primary stromata to 60% of control. Treatments with saturated solutions of hydrated lime (pH 12.45) and with KOH solutions of different pH showed that a pH higher than 12.4 was needed to be 100% effective. Suspensions of calcium carbonate (6.75 g l-1) had no effect