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Hustle in the melt Phase transformations such as freezing and melting are familiar phenomena, but the direct observation of the atomic-level structural changes involved has only been possible since the recent development of ultrafast diffraction methods. Sciaini et al . now use electron diffraction to show that the melting of crystalline bismuth upon laser excitation is exceptionally rapid, taking less than half the period of a lattice vibration. The extraordinary fast melting is attributed to profound laser-induced changes in the potential energy surface of the bismuth lattice: in the changed potential, the atoms experience strong driving forces that launch them from their initial equilibrium positions and towards the disorder typical of liquids. Electron diffraction is used to show that the melting of crystalline bismuth after laser excitation occurs exceptionally fast, within half the period of a lattice vibration. The extraordinary fast melting is attributed to profound laser-induced changes in the potential energy surface of the bismuth lattice: in the changed potential, the atoms experience strong driving forces that launch them from their initial equilibrium positions and towards the disorder typical of liquids. The development of X-ray and electron diffraction methods with ultrahigh time resolution has made it possible to map directly, at the atomic level, structural changes in solids induced by laser excitation 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 . This has resulted in unprecedented insights into the lattice dynamics of solids undergoing phase transitions. In aluminium, for example, femtosecond optical excitation hardly affects the potential energy surface of the lattice; instead, melting of the material is governed by the transfer of thermal energy between the excited electrons and the initially cold lattice 1 . In semiconductors, in contrast, exciting ∼10 per cent of the valence electrons results in non-thermal lattice collapse owing to the antibonding character of the conduction band 2 , 3 , 4 , 5 , 9 , 10 . These different material responses raise the intriguing question of how Peierls-distorted systems 11 such as bismuth 12 will respond to strong excitations. The evolution of the atomic configuration of bismuth upon excitation of its A 1g lattice mode, which involves damped oscillations of atoms along the direction of the Peierls distortion of the crystal, has been probed 6 , 7 , 8 , but the actual melting of the material has not yet been investigated. Here we present a femtosecond electron diffraction study of the structural changes in crystalline bismuth as it undergoes laser-induced melting. We find that the dynamics of the phase transition depend strongly on the excitation intensity, with melting occurring within 190 fs (that is, within half a period of the unperturbed A 1g lattice mode 6 , 7 , 8 ) at the highest excitation. We attribute the surprising speed of the melting process to laser-induced changes in the potential energy surface of the lattice, which result in strong acceleration of the atoms along the longitudinal direction of the lattice and efficient coupling of this motion to an unstable transverse vibrational mode. That is, the atomic motions in crystalline bismuth can be electronically accelerated so that the solid-to-liquid 13 phase transition occurs on a sub-vibrational timescale.

We explore how improvisational (improv) theater can be used to illuminate the everyday performance of regional identity. This can help manage reactivity-related and counter-performative effects during qualitative research. By utilizing improv theater as a performative qualitative method, we highlight its analytical potential. We identify methodological gaps in existing qualitative research and human geography studies, and we propose a methodological framework for integrating improvisational theater into research practice. Participants of improv theater-workshops draw on personal and collective experiences rooted in their personal backgrounds to evoke emotions related to their home regions. By engaging in spontaneous and unscripted performances, individuals express nuanced perceptions of regional identity that may elude traditional qualitative approaches. Ultimately, we illuminate the complex interplay between individuals and the transformative potential of improvisational theater.

When an intense light field strongly interacts with the band structure of a solid, the formation of hybrid light-matter quantum states becomes possible. Examples of such Floquet-Bloch states have been reported, but engineering of the band structure using Floquet states can suffer from dissipation and decoherence. Sustaining the necessary quantum coherence of the light-matter interactions requires robust electronic states in combination with strong fields of suitable polarization and frequency. Here, we explore the quantum coherent coupling of nano-focused surface plasmon polaritons (SPP) to distinct electronic states in the band structure of a solid. We observe above-threshold electron emission from the Au(111) Shockley surface state by the absorption of up to seven SPP quanta. Using time-resolved photoelectron spectroscopy the coherence of the interaction of the SPPs with the surface state during electron emission is investigated and the process is shown to be similar to light-driven above threshold electron emission. Ultimately, our work could render SPP-based Floquet engineering in nano-optical systems feasible. Floquet theory describes transient states driven by a light-matter interaction and could potentially be used to engineer the band structure and the topology of solid-state systems. Here, the authors investigate coherent photoemission from a gold surface caused by a strong surface plasmon polariton excitation, which could be used to realize surface plasmon polariton driven Floquet effects in nanostructures.

Large, high-quality layers of hexagonal boron nitride (hBN) are a prerequisite for further advancement in scientific investigation and technological utilization of this exceptional 2D material. Here we address this demand by investigating chemical vapor deposition synthesis of hBN on an Ir(111) substrate, and focus on the substrate morphology, more specifically mono-atomic steps that are always present on all catalytic surfaces of practical use. From low-energy electron microscopy and atomic force microscopy data, we are able to set up an extended Wulff construction scheme and provide a clear elaboration of different interactions governing the equilibrium shapes of the growing hBN islands that deviate from the idealistic triangular form. Most importantly, intrinsic hBN edge energy and interaction with the iridium step edges are examined separately, revealing in such way the importance of substrate step morphology for the island structure and the overall quality of 2D materials.

Quantum path interferences occur whenever multiple equivalent and coherent transitions result in a common final state. Such interferences strongly modify the probability of a particle to be found in that final state, a key concept of quantum coherent control. When multiple nonlinear and energy-degenerate transitions occur in a system, the multitude of possible quantum path interferences is hard to disentangle experimentally. Here, we analyze quantum path interferences during the nonlinear emission of electrons from hybrid plasmonic and photonic fields using time-resolved photoemission electron microscopy. We experimentally distinguish quantum path interferences by exploiting the momentum difference between photons and plasmons and through balancing the relative contributions of their respective fields. Our work provides a fundamental understanding of the nonlinear photon–plasmon–electron interaction. Distinguishing emission processes in momentum space, as introduced here, could allow nano-optical quantum-correlations to be studied without destroying the quantum path interferences.

Background: Staurosporine-dependent single and collective cell migration patterns of breast carcinoma cells MDA-MB-231, MCF-7, and SK-BR-3 were analysed to characterise the presence of drug-dependent migration promoting and inhibiting yin-yang effects. Methods: Migration patterns of various breast cancer cells after staurosporine treatment were investigated using Western blot, cell toxicity assays, single and collective cell migration assays, and video time-lapse. Statistical analyses were performed with Kruskal–Wallis and Fligner–Killeen tests. Results: Application of staurosporine induced the migration of single MCF-7 cells but inhibited collective cell migration. With the exception of low-density SK-BR-3 cells, staurosporine induced the generation of immobile flattened giant cells. Video time-lapse analysis revealed that within the borderline of cell collectives, staurosporine reduced the velocity of individual MDA-MB-231 and SK-BR-3, but not of MCF-7 cells. In individual MCF-7 cells, mainly the directionality of migration became disturbed, which led to an increased migration rate parallel to the borderline, and hereby to an inhibition of the migration of the cell collective as a total. Moreover, the application of staurosporine led to a transient activation of ERK1/2 in all cell lines. Conclusion: Dependent on the context (single versus collective cells), a drug may induce opposite effects in the same cell line.

Purpose Orthorexia nervosa is defined as the fixation on health-conscious eating behaviour and has recently been discussed as a new variant of disordered eating. The aim of the present study was to analyse orthorexic eating behaviour in an inpatient treatment sample of female anorexics to investigate the relation between anorexic and orthorexic eating behaviour. Method Female anorexic patients with low ( n  = 29) and pronounced ( n  = 13) orthorexic eating behaviour as well as a matched control group composed of healthy females ( n  = 30) were compared with regard to several aspects of disordered eating, hypochondriacal traits, food consumption frequency and fulfilment of basic psychological needs in terms of eating. Orthorexic eating behaviour was assessed using the Düsseldorfer Orthorexie Skala. Results Fulfilment of basic psychological needs with respect to autonomy and competence is higher in anorexic individuals with pronounced orthorexic eating behaviour compared to patients with low orthorexic eating behaviour. Furthermore, patients with pronounced orthorexic eating behaviour state eating healthy food regardless of calorie content more often. No difference was found for hypochondriacal traits and eating disordered symptoms in general. Conclusions Orthorexic eating behaviour enhances self-perception of eating behaviour as autonomous and competent, indicating that it might serve as a coping strategy in anorexic individuals. Further research is needed to investigate if this tendency in food selection strategy leads to positive effects in the long term.

Spectroscopic photoemission microscopy is used to detect and quantify a ponderomotive shift in the energy of electrons that are emitted from a surface plasmon polariton focus. The focus is formed on an atomically flat Au(111) surface by an Archimedean spiral and is spatiotemporally separated from the circularly polarized light pulse used to excite the spiral. A spectroscopic analysis of electrons emitted from the focus exhibits a peaked above-threshold electron emission spectrum. From the shift of the peaks as function of laser power the field strength of the surface plasmon polariton was quantitatively determined free parameters. Estimations of the Keldysh parameter = 4.4 and the adiabaticity parameter = 4700 indicate that electron emission occurs in a regime of multiplasmon absorption and nonlocalized surface plasmon fields.

The recent demonstration of single-crystal organic optoelectronic devices has received widespread attention 1 , 2 , 3 , 4 . But practical applications of such devices require the use of inexpensive organic films deposited on a wide variety of substrates. Unfortunately, the physical properties of these organic thin films do not compare favourably to those of single-crystal materials. Moreover, the basic physical principles governing organic thin-film growth and crystallization are not well understood. Here we report an in situ study of the evolution of pentacene thin films, utilizing the real-time imaging capabilities of photoelectron emission microscopy. By a combination of careful substrate preparation and surface energy control, we succeed in growing thin films with single-crystal grain sizes approaching 0.1 millimetre (a factor of 20–100 larger than previously achieved), which are large enough to fully contain a complete device. We find that organic thin-film growth closely mimics epitaxial growth of inorganic materials, and we expect that strategies and concepts developed for these inorganic systems will provide guidance for the further development and optimization of molecular thin-film devices.

Spectroscopic photoemission microscopy is a well-established method to investigate the electronic structure of surfaces. In modern photoemission microscopes, the electron optics allow imaging of the image plane, momentum plane, or dispersive plane, depending on the lens setting. Furthermore, apertures allow filtering of energy-, real-, and momentum space. Here, we describe how a standard spectroscopic and low-energy electron microscope can be equipped with an additional slit at the entrance of the already present hemispherical analyzer to enable an angle- and energy-resolved photoemission mode with micrometer spatial selectivity. We apply a photogrammetric calibration to correct for image distortions of the projective system behind the analyzer and present spectra recorded on Au(111) as a benchmark. Our approach makes data acquisition in energy–momentum space more efficient, which is a necessity for laser-based pump–probe photoemission microscopy with femtosecond time resolution.