Imaging Molecular Structure through Femtosecond Photoelectron Diffraction on Aligned and Oriented Gas-Phase Molecules

This paper gives an account of our progress towards performing femtosecond time-resolved photoelectron diffraction on gas-phase molecules in a pump-probe setup combining optical lasers and an X-ray Free-Electron Laser. We present results of two experiments aimed at measuring photoelectron angular distributions of laser-aligned 1-ethynyl-4-fluorobenzene (C8H5F) and dissociating, laseraligned 1,4-dibromobenzene (C6H4Br2) molecules and discuss them in the larger context of photoelectron diffraction on gas-phase molecules. We also show how the strong nanosecond laser pulse used for adiabatically laser-aligning the molecules influences the measured electron and ion spectra and angular distributions, and discuss how this may affect the outcome of future time-resolved photoelectron diffraction experiments.Comment: 24 pages, 10 figures, Faraday Discussions 17

Where have all the petrels gone? Forty years (1978–2020) of Wilson’s Storm Petrel (Oceanites oceanicus) population dynamics at King George Island (Isla 25 de Mayo, Antarctica) in a changing climate

Numerous seabird species are experiencing population declines, and this trend is expected to continue or even accelerate in the future. To understand the effects of environmental change on seabird populations, long-term studies are vital, but rare. Here, we present over four decades (1978–2020) of population dynamic and reproductive performance data of Wilson’s Storm Petrels (Oceanites oceanicus) from King George Island (Isla 25 de Mayo), Antarctica. We determined temporal trends in population size, breeding output, and chick growth rates, and related interannual variation in these variables to various environmental variables. Our study revealed a decline of 90% in population size of Wilson’s Storm Petrels in two colonies, and considerable changes in breeding output and chick growth rates. Temporal changes in breeding demographics were linked to interannual environmental variation, either causing changes in food availability (particularly Antarctic krill, Euphausia superba) or in nest burrow accessibility due to snow blocking the entrance. With the expected rise in air and sea surface temperatures, the predicted increases in precipitation over the Antarctic Peninsula will likely lead to increased snowstorm prevalence. Additionally, the rising temperatures will likely reduce food availability due to reduced sea ice cover in the wintering grounds of Antarctic krill, or by changing phyto- and zooplankton community compositions. The ongoing environmental changes may thus lead to a further population decline, or at the very least will not allow the population to recover. Monitoring the population dynamics of Antarctic seabirds is vital to increase our understanding of climate change-induced changes in polar food webs

Dynamics and inertia of skyrmionic spin structures

Skyrmions are topologically protected winding vector fields characterized by a spherical topology. Magnetic skyrmions can arise as the result of the interplay of various interactions, including exchange, dipolar and anisotropy energy in the case of magnetic bubbles and an additional Dzyaloshinskii-Moriya interaction in the case of chiral skyrmions. Whereas the static and low-frequency dynamics of skyrmions are already well under control, their gigahertz dynamical behaviour has not been directly observed in real space. Here, we image the gigahertz gyrotropic eigenmode dynamics of a single magnetic bubble and use its trajectory to experimentally confirm its skyrmion topology. The particular trajectory points to the presence of strong inertia, with a mass much larger than predicted by existing theories. This mass is endowed by the topological confinement of the skyrmion and the energy associated with its size change. It is thereby expected to be found in all skyrmionic structures in magnetic systems and beyond. Our experiments demonstrate that the mass term plays a key role in describing skyrmion dynamics.

Activation of human alveolar macrophages via P2 receptors: coupling to intracellular Ca2+ increases and cytokine secretion

Alveolar macrophages play a crucial role in the pathogenesis of inflammatory airway diseases. By the generation and release of different inflammatory mediators they contribute to both recruitment of different leukocytes into the lung and to airway remodeling. A potent stimulus for the release of inflammatory cytokines is ATP, which mediates its cellular effects through the interaction with different membrane receptors, belonging to the P2X and P2Y families. The aim of this study was to characterize the biological properties of purinoceptors in human alveolar macrophages obtained from bronchoalveolar lavages in the context of inflammatory airway diseases. The present study is the first showing that human alveolar macrophages express mRNA for different P2 subtypes, namely P2X(1), P2X(4), P2X(5), P2X(7), P2Y(1), P2Y(2), P2Y(4), P2Y(6), P2Y(11), P2Y(13), and P2Y(14). We also showed that extracellular ATP induced Ca(2+) transients and increased IL-1beta secretion via P2X receptors. Furthermore, extracellular nucleotides inhibited production of IL-12p40 and TNF-alpha, whereas IL-6 secretion was up-regulated. In summary, our data further support the hypothesis that purinoceptors are involved in the pathogenesis of inflammatory lung diseases

Correction: Where have all the petrels gone? Forty years (1978–2020) of Wilson’s Storm Petrel (Oceanites oceanicus) population dynamics at King George Island (Isla 25 de Mayo, Antarctica) in a changing climate

Ausems ANMA, Kuepper ND, Archuby D, et al. Correction: Where have all the petrels gone? Forty years (1978–2020) of Wilson’s Storm Petrel (Oceanites oceanicus) population dynamics at King George Island (Isla 25 de Mayo, Antarctica) in a changing climate. Polar Biology . 2024;47(2):187

Post-sample aperture for low background diffraction experiments at X-ray free-electron lasers

The success of diffraction experiments from weakly scattering samples strongly depends on achieving an optimal signal-to-noise ratio. This is particularly important in single-particle imaging experiments where diffraction signals are typically very weak and the experiments are often accompanied by significant background scattering. A simple way to tremendously reduce background scattering by placing an aperture downstream of the sample has been developed and its application in a single-particle X-ray imaging experiment at FLASH is demonstrated. Using the concept of a post-sample aperture it was possible to reduce the background scattering levels by two orders of magnitude