Next-generation X-ray satellite telescopes such as XRISM, NewAthena and Lynx will enable observations of exotic astrophysical sources at unprecedented spectral and spatial resolution. Proper interpretation of these data demands that the accuracy of the models is at least within the uncertainty of the observations. One set of quantities that might not currently meet this requirement is transition energies of various astrophysically relevant ions. Current databases are populated with many untested theoretical calculations. Accurate laboratory benchmarks are required to better understand the coming data. We obtained laboratory spectra of X-ray lines from a silicon plasma at an average spectral resolving power of $\sim$7500 with a spherically bent crystal spectrometer on the Z facility at Sandia National Laboratories. Many of the lines in the data are measured here for the first time. We report measurements of 53 transitions originating from the K-shells of He-like to B-like silicon in the energy range between $\sim$1795 and 1880 eV (6.6–6.9 Å). The lines were identified by qualitative comparison against a full synthetic spectrum calculated with ATOMIC. The average fractional uncertainty (uncertainty/energy) for all reported lines is ${\sim}5.4 \times 10^{-5}$. We compare the measured quantities against transition energies calculated with RATS and FAC as well as those reported in the NIST ASD and XSTAR’s uaDB. Average absolute differences relative to experimentally measured values are 0.20, 0.32, 0.17 and 0.38 eV, respectively. All calculations/databases show good agreement with the experimental values; NIST ASD shows the closest match overall.

The work presented here revisits the Velikhov-ionisation instability, an instability first discovered in the early 1960s (Velikhov, E. P. 1962 1st International Conference on MHD Electrical Power Generation, Newcastle upon Tyne, England, p. 135). This mode strongly deteriorates the performance of magnetohydrodynamic (MHD) energy convertors in which the seed gas must be at a substantially higher temperature than the high density primary gas, the latter gas carrying almost all the energy. Specifically, a finite temperature difference is necessary for the MHD generator to successfully act as a topping cycle for nuclear (fission and fusion) power plants. The ionisation instability has thus been viewed for many years as a show stopper for MHD nuclear topping cycles. Even so, some experimental observations, never fully exploited, show that nearly full ionisation of the seed gas can stabilise this dangerous instability. One goal of the research presented here is to provide a first-principles theoretical explanation for these experimental observations. The stabilisation can theoretically produce high temperature ratios, of the order of 10, by carefully choosing the density of the unionised seed gas. A second goal of the research is to investigate whether or not the recent development of high-field, high-temperature REBCO (rare-earth barium copper oxide) superconductors can lead to substantially improved power plant efficiency. Here, it is shown that the answer is subtle – no clear conclusions can be drawn, a consequence of the fact that the new stability criterion is a local one. What is needed to assess overall plant efficiency is a global analysis. Additional work has recently been completed on a newly developed global model which answers this question and will be reported on in a future paper.

We use a graph to define a new stability condition for algebraic moduli spaces of rational curves. We characterise when the tropical compactification of the moduli space agrees with the theory of geometric tropicalisation. The characterisation statement occurs only when the graph is complete multipartite.

An action of a group G on a set X is said to be quasi-n-transitive if the diagonal action of G on $X^n$ has only finitely many orbits. We show that branch groups, a special class of groups of automorphisms of rooted trees, cannot act quasi-2-transitively on infinite sets.

The Vlasov–Maxwell equations provide kinetic simulations of collisionless plasmas, but numerically solving them on classical computers is often impractical. This is due to the computational resource constraints imposed by the time evolution in the six-dimensional phase space, which requires broad spatial and temporal scales. The novelty of this study is to implement a quantum–classical hybrid Vlasov–Maxwell solver and the rigorous numerical scheme evaluation by numerical simulations. Specifically, the Vlasov solver implements the Hamiltonian simulation based on quantum singular value transformation, coupled with a classical Maxwell solver. We perform numerical simulation of a one-dimensional advection test and a one-spatial-dimension, one-velocity-dimension two-stream instability test on the Qiskit-Aer-GPU quantum circuit emulator with an A100 GPU. The computational complexity of our quantum algorithm can potentially be reduced from the classical $\mathcal{O}(N^6T^2/\epsilon )$ to $\mathcal{O}\left (\text{poly}(\log {N})\left (NT+T\log \left (T/\epsilon \right )\right )\right )$ for the $N$ grid system, simulation time $T$ and error tolerance $\epsilon$ in the limit where the number of queries is large enough and the error is small enough. Furthermore, the numerical analysis reveals that our quantum algorithm is robust under larger time steps compared with classical algorithms with the constraint of Courant–Friedrichs–Lewy condition.

Two desert cyanobacterial strains, Chroococcidiopsis sp. CCMEE 010 and CCMEE 130, capable far-red light photoacclimation (FaRLiP), were investigated for the stability of biosignatures after six years of desiccation. Biosignature detectability was demonstrated by confocal laser scanning microscopy and Raman spectroscopy thus highlighting that these two FaRLiP cyanobacteria are a novel reservoir of an array of pigments, encompassing canonical chlorophyll a, far-red shifted chlorophylls, phycobilins and carotenoids. The recorded signals were comparable to those of dried cells of Chroococcidiopsis sp. CCMEE 029, CCMEE 057 and CCMEE 064, not capable of FaRLiP acclimation and previously reported for biosignature stability and survivability after exposure to space and Mars-like conditions during the BIOMEX (BIOlogy and Mars EXperiment) and BOSS (Biofilm Organisms Surfing Space) low Earth orbit missions. Since infrared-light driven photosynthesis has implications for the habitability of Mars as well as exoplanets, the stability of far-red shifted chlorophylls in dried Chroococcidiopsis is a prerequisite for future experimentations under simulated planetary conditions in the laboratory or directly into space. It is anticipated that post-flight investigations of FaRLiP cyanobacteria as part of the BioSigN (Bio-Signatures and habitable Niches) space mission will contribute to gather novel insights into biosignature degradation/stability and thus prepare future planetary exploration missions to Mars. In addition, the scored viability of strains CCMEE 010 and CCMEE 130 after prolonged desiccation is relevant to investigate life endurance under deep space conditions, as planned by the BioMoon mission that aims to expose dried and rehydrated extremophiles on the Moon surface after exposure to deep space.

The pulse duration is a critical parameter of picosecond-petawatt laser systems because it directly affects the results of high-energy-density physics experiments. This study systematically investigated the effects of the spectral width, central wavelength and beam-pointing deviations on pulse duration stability at the SG-II facility. A theoretical analysis of the relationship between spectra and pulse duration is conducted to quantify the impact on pulse duration stability, and the results are further validated through experimental measurements. In addition, beam-pointing deviations at the stretcher significantly affect the pulse duration. For example, a 27 μrad deviation can induce a 30% pulse duration variation. In contrast, the compressor exhibits greater robustness. Based on simulation and experimental results, we identify operational tolerance ranges for spectral width and beam-pointing deviation to maintain pulse duration stability within 5% at the SG-II facility. These findings provide critical guidance for optimizing the performance and reliability of chirped-pulse amplification/optical parametric chirped-pulse amplification-based high-power laser systems.

We present a number of measures and techniques to characterise and effectively construct quasi-isodynamic stellarators within the near-axis framework, without the need to resort to the computation of global equilibria. These include measures of the reliability of the model (including aspect-ratio limits and the appearance of ripple wells), quantification of omnigeneity through $\epsilon _{\mathrm{eff}}$, measure and construction of MHD-stabilised fields, and the sensitivity of the field to the pressure gradient. The paper presents, discusses and gives examples of all of these, for which expansions to second order are crucial. This opens the door to the exploration of how key underlying choices of the field design govern the interaction of desired properties (‘trade-offs’) and provides a practical toolkit to perform efficient optimisation directly within the space of near-axis quasi-isodynamic configurations.

Developing reduced-order models for the transport of solid particles in turbulence typically requires a statistical description of the particle–turbulence interactions. In this work, we utilize a statistical framework to derive continuum equations for the moments of the slip velocity of inertial, settling Lagrangian particles in a turbulent boundary layer. Using coupled Eulerian–Lagrangian direct numerical simulations, we then identify the dominant mechanisms controlling the slip velocity variance, and find that for a range of Stokes number ${S{\kern-0.5pt}t}^+$, Settling number ${S{\kern-0.5pt}v}^+$ and Reynolds number $\textit{Re}_\tau$ (based on frictional scales),the slip variance is primarily controlled by local differences between the ‘seen’ variance and the particle velocity variance, while terms appearing due to the inhomogeneity of the turbulence are subleading until ${S{\kern-0.5pt}v}^+$ becomes large. We also consider several comparative metrics to assess the relative magnitudes of the fluctuating slip velocity and the mean slip velocity, and we find that the vertical mean slip increases rapidly with ${S{\kern-0.5pt}v}^+$, rendering the variance relatively small – an effect found to be most substantial for ${S{\kern-0.5pt}v}^+\gt 1$. Finally, we compare the results with a model of the acceleration variance (Berk & Coletti 2021 J. Fluid Mech. 917, A47) based the concept of a response function described in Csanady (1963 J. Atmos. Sci. 20, 201–208), highlighting the role of the crossing trajectories mechanism. We find that while there is good agreement for low ${S{\kern-0.5pt}v}^+$, systematic errors remain, possibly due to implicit non-local effects arising from rapid particle settling and inhomogeneous turbulence. We conclude with a discussion of the implications of this work for modelling the transport of coarse dust grains in the atmospheric surface layer.

Powerful lasers may be used in the future to produce magnetic fields that would allow us to study turbulent magnetohydrodynamic inverse cascade behaviour. This has so far only been seen in numerical simulations. In the laboratory, however, the produced fields may be highly anisotropic. Here, we present corresponding simulations to show that, during the turbulent decay, such a magnetic field undergoes spontaneous isotropisation. As a consequence, we find the decay dynamics to be similar to that in isotropic turbulence. We also find that an initially pointwise non-helical magnetic field is unstable and develops magnetic helicity fluctuations that can be quantified by the Hosking integral. It is a conserved quantity that characterises magnetic helicity fluctuations and governs the turbulent decay when the mean magnetic helicity vanishes. As in earlier work, the ratio of the magnetic decay time to the Alfvén time is found to be approximately $50$ in the helical and non-helical cases. At intermediate times, the ratio can even reach a hundred. This ratio determines the endpoints of cosmological magnetic field evolution.

Understanding microbial adaptations to the extreme conditions of space is crucial for both astronaut health and the integrity of spacecraft materials. This study comparatively analyses the cosmic radiation resistance and growth responses to simulated microgravity (SMG) of a wild-type strain and an International Space Station (ISS) isolate of Penicillium rubens. Resistance to helium- and iron-ion radiation was determined, alongside growth under SMG using clinorotation. The results revealed that the ISS isolate exhibited higher resistance to both helium- and iron-ion radiation than the wild-type strain, suggesting adaptive mechanisms that enhance survival in space environments. Additionally, while the ISS isolate demonstrated significantly increased growth in SMG compared to normal gravity conditions, the wild-type strain showed no difference between the two conditions. These findings indicate that prolonged exposure to the space environment may select for traits that enhance resistance to cosmic radiation and alter growth dynamics under microgravity. Such adaptations could have implications for microbial monitoring in space habitats, planetary protection policies, and potential biotechnological applications in space. Further investigations into the genetic and metabolic differences between both strains may provide deeper insights into fungal adaptation to space environments.

Presented here is a novel formulation of the mean-field dynamo as a modulational instability of magnetohydrodynamic (MHD) turbulence. This formulation, termed mean-field wave kinetics (MFWK), is based on the Weyl symbol calculus and allows describing the interaction between the mean fields (magnetic field and fluid velocity) and turbulence without requiring scale separation that is commonly assumed in the literature. The turbulence is described by the Wigner–Moyal equation for the spectrum of the two-point correlation matrix (Wigner matrix) of magnetic-field and velocity fluctuations and depicts the turbulence as an effective plasma of quantum-like particles that interact via the mean fields. Eddy–eddy interactions, which serve as ‘collisions’ in this effective plasma, are modelled within the standard minimal tau approximation to aid comparison with existing theories. Using MFWK, the non-local electromotive force is calculated for generic turbulence from first principles, modulo the limitations of MFWK. This result is then used to study, both analytically and numerically, the modulational modes of MHD turbulence, which appear as linear instabilities of the said effective quantum-like plasma of fluctuations. The standard $\alpha ^2$-dynamo and other known results are reproduced as special cases. A new dynamo effect is predicted that is driven by correlations between the turbulent flow velocity and the turbulent current.

Non-autonomous self-similar sets are a family of compact sets which are, in some sense, highly homogeneous in space but highly inhomogeneous in scale. The main purpose of this paper is to clarify various regularity properties and separation conditions relevant for the fine local scaling properties of these sets. A simple application of our results is a precise formula for the Assouad dimension of non-autonomous self-similar sets in $\mathbb{R}^d$ satisfying a certain “bounded neighbourhood” condition, which generalises earlier work of Li–Li–Miao–Xi and Olson–Robinson–Sharples. We also see that the bounded neighbourhood assumption is, in few different senses, as general as possible.