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Magnetic holes (MHs) are localized structures characterized by magnetic field depressions, accompanied by an enhancement in plasma thermal pressure. These pressure‐balanced structures span a broad range of scales in space, from fluid to kinetic regimes. The kinetic‐scale MHs are ubiquitous in the solar wind; however, the exploration is limited due to the lack of high‐resolution particle measurements. Here, we utilize Solar Orbiter observations to explore ion dynamics within an ion‐scale MH. The ion energy spectrum exhibits enhanced and depressed phase‐space densities for ions above and below 10 eV, respectively. The enhancements of perpendicular and parallel temperatures in this deep MH result in a quasi‐isotropic ion pitch angle distribution. The ion diamagnetic drift contributes to the agyrotropy around the boundaries, forming an ion vortex consistent with the magnetic field depression. These results align well with a kinetic equilibrium model, confirming the stability and self‐consistency of ion‐scale MHs in the solar wind.

The generation of kinetic‐scale flux ropes (KSFRs) is closely related to magnetic reconnection. Both flux ropes and reconnection sites are detected in the magnetosheath and can impact the dynamics upstream of the magnetopause. In this study, using the Magnetospheric Multiscale satellite, 12,623 KSFRs with a scale <20 RCi are statistically studied in the Earth's dayside magnetosheath. It is found that they are mostly generated near the bow shock (BS), and propagate downstream in the magnetosheath. Their quantity significantly increases as the scale decreases, consistent with a flux rope coalescence model. Moreover, the solar wind parameters can control the occurrence rate of KSFRs. They are more easily generated at high Mach number, large proton density, and weak magnetic field strength of the solar wind, similar to the conditions that favor BS reconnection. Our study shows a close connection between KSFR generation and BS reconnection. Plain Language Summary Kinetic‐scale flux ropes (KSFRs) exist widely in near‐earth space and play an important role in mass transport, energy conversion, and dissipation during magnetic field reconnection. The KSFR in the magnetosheath can be generated by reconnection in three regions: the magnetopause, the magnetosheath, and the BS. The spatial distribution of KSFRs can indirectly reflect the reconnection situation in the magnetosheath. We use various methods to select the KSFRs and study their spatial distribution and generation in the magnetosheath. Our results show that BS reconnection plays an important role in generating the KSFR in the magnetosheath. Key Points Kinetic‐scale flux ropes observed in the magnetosheath are primarily generated near the bow shock (BS) and travel to downstream magnetosheath The quantity of flux ropes significantly increases as their scale decreases, which is in accordance with the FR coalescence model The occurrence of flux ropes is influenced by solar wind parameters, and could strongly correlate with BS reconnection

Background Pseudomonas putida is a promising candidate for the industrial production of biofuels and biochemicals because of its high tolerance to toxic compounds and its ability to grow on a wide variety of substrates. Engineering this organism for improved performances and predicting metabolic responses upon genetic perturbations requires reliable descriptions of its metabolism in the form of stoichiometric and kinetic models. Results In this work, we developed kinetic models of P. putida to predict the metabolic phenotypes and design metabolic engineering interventions for the production of biochemicals. The developed kinetic models contain 775 reactions and 245 metabolites. Furthermore, we introduce here a novel set of constraints within thermodynamics-based flux analysis that allow for considering concentrations of metabolites that exist in several compartments as separate entities. We started by a gap-filling and thermodynamic curation of iJN1411, the genome-scale model of P. putida KT2440. We then systematically reduced the curated iJN1411 model, and we created three core stoichiometric models of different complexity that describe the central carbon metabolism of P. putida. Using the medium complexity core model as a scaffold, we generated populations of large-scale kinetic models for two studies. In the first study, the developed kinetic models successfully captured the experimentally observed metabolic responses to several single-gene knockouts of a wild-type strain of P. putida KT2440 growing on glucose. In the second study, we used the developed models to propose metabolic engineering interventions for improved robustness of this organism to the stress condition of increased ATP demand. Conclusions The study demonstrates the potential and predictive capabilities of the kinetic models that allow for rational design and optimization of recombinant P. putida strains for improved production of biofuels and biochemicals. The curated genome-scale model of P. putida together with the developed large-scale stoichiometric and kinetic models represents a significant resource for researchers in industry and academia.

Solar wind is probably the best laboratory to study turbulence in astrophysical plasmas. In addition to the presence of magnetic field, the differences with neutral fluid isotropic turbulence are: (i) weakness of collisional dissipation and (ii) presence of several characteristic space and time scales. In this paper we discuss observational properties of solar wind turbulence in a large range from the MHD to the electron scales. At MHD scales, within the inertial range, turbulence cascade of magnetic fluctuations develops mostly in the plane perpendicular to the mean field, with the Kolmogorov scaling for the perpendicular cascade and for the parallel one. Solar wind turbulence is compressible in nature: density fluctuations at MHD scales have the Kolmogorov spectrum. Velocity fluctuations do not follow magnetic field ones: their spectrum is a power-law with a −3/2 spectral index. Probability distribution functions of different plasma parameters are not Gaussian, indicating presence of intermittency. At the moment there is no global model taking into account all these observed properties of the inertial range. At ion scales, turbulent spectra have a break, compressibility increases and the density fluctuation spectrum has a local flattening. Around ion scales, magnetic spectra are variable and ion instabilities occur as a function of the local plasma parameters. Between ion and electron scales, a small scale turbulent cascade seems to be established. It is characterized by a well defined power-law spectrum in magnetic and density fluctuations with a spectral index close to −2.8. Approaching electron scales, the fluctuations are no more self-similar: an exponential cut-off is usually observed (for time intervals without quasi-parallel whistlers) indicating an onset of dissipation. The small scale inertial range between ion and electron scales and the electron dissipation range can be together described by , with α ≃8/3 and the dissipation scale ℓ d close to the electron Larmor radius ℓ d ≃ ρ e . The nature of this small scale cascade and a possible dissipation mechanism are still under debate.

Magnetic holes at the ion-to-electron kinetic scale (KSMHs) are one of the extremely small intermittent structures generated in turbulent magnetized plasmas. In recent years, the explorations of KSMHs have made substantial strides, driven by the ultra-high-precision observational data gathered from the Magnetospheric Multiscale (MMS) mission. This review paper summarizes the up-to-date characteristics of the KSMHs observed in Earth’s turbulent magnetosheath, as well as their potential impacts on space plasma. This review starts by introducing the fundamental properties of the KSMHs, including observational features, particle behaviors, scales, geometries, and distributions in terrestrial space. Researchers have discovered that KSMHs display a quasi-circular electron vortex-like structure attributed to electron diamagnetic drift. These electrons exhibit noticeable non-gyrotropy and undergo acceleration. The occurrence rate of KSMH in the Earth’s magnetosheath is significantly greater than in the solar wind and magnetotail, suggesting the turbulent magnetosheath is a primary source region. Additionally, KSMHs have also been generated in turbulence simulations and successfully reproduced by the kinetic equilibrium models. Furthermore, KSMHs have demonstrated their ability to accelerate electrons by a novel non-adiabatic electron acceleration mechanism, serve as an additional avenue for energy dissipation during magnetic reconnection, and generate diverse wave phenomena, including whistler waves, electrostatic solitary waves, and electron cyclotron waves in space plasma. These results highlight the magnetic hole’s impact such as wave-particle interaction, energy cascade/dissipation, and particle acceleration/heating in space plasma. We end this paper by summarizing these discoveries, discussing the generation mechanism, similar structures, and observations in the Earth’s magnetotail and solar wind, and presenting a future extension perspective in this active field.

The paper presents the latest results of the studies of small-scale fluctuations in a turbulent flow of solar wind (SW) using measurements with extremely high temporal resolution (up to 0.03 s) of the bright monitor of SW (BMSW) plasma spectrometer operating on astrophysical SPECTR-R spacecraft at distances up to 350 000 km from the Earth. The spectra of SW ion flux fluctuations in the range of scales between 0.03 and 100 s are systematically analysed. The difference of slopes in low- and high-frequency parts of spectra and the frequency of the break point between these two characteristic slopes was analysed for different conditions in the SW. The statistical properties of the SW ion flux fluctuations were thoroughly analysed on scales less than 10 s. A high level of intermittency is demonstrated. The extended self-similarity of SW ion flux turbulent flow is constantly observed. The approximation of non-Gaussian probability distribution function of ion flux fluctuations by the Tsallis statistics shows the non-extensive character of SW fluctuations. Statistical characteristics of ion flux fluctuations are compared with the predictions of a log-Poisson model. The log-Poisson parametrization of the structure function scaling has shown that well-defined filament-like plasma structures are, as a rule, observed in the turbulent SW flows.

Solar wind is a highly turbulent medium exhibiting fluctuations ranging from the solar sidereal rotation period to proton and electron gyroperiods. Their amplitudes show remarkable scalings with frequency across more than seven decades, suggesting a self‐similar nature for these fluctuations. However, these fluctuations are not globally scale invariant and require a multifractal approach. Multifractality is closely related to intermittency, a phenomenon that has been studied in the solar wind for more than three decades. We now have a rather complete picture of the nature of the most intermittent events and the radial/latitudinal dependence of this phenomenon in the heliosphere. Parallel shocks, slow mode shocks or tangential discontinuities/current sheets identified as the border between adjacent flux tubes are the most intermittent structures within the low‐frequency turbulence. It is more complicated and fascinating to understand the nature of intermittent events at kinetic scales since they are directly related to dissipative phenomena and might be the key to understanding the dissipation mechanisms in the collisionless solar wind plasma. Unfortunately, we still do not have adequate plasma observations at kinetic scales to work on, but several studies, mostly numeric, have addressed this topic suggesting that discontinuities, small‐scale current sheets, and sites which are candidates for reconnection events might be regions where dissipative phenomena are at work with consequent plasma heating and acceleration. This review is intended to provide the reader with a quick overview on the past and most recent understanding of intermittency phenomenon in the solar wind from fluid to kinetic scales. Plain Language Summary Turbulence in ordinary fluid appears as an irregular and chaotic state of motion, both in space and time. However, there are structures which have a lifetime longer than the surrounding stochastic fluctuations, that is, coherent structures. These structures, which appear like vortices of all sizes, are the sites where the kinetic energy of the fluid is dissipated. While stochastic fluctuations around these structures are described by a Gaussian statistics, vortices represent intense events not obedient to the same statistics. They can be considered regions characterized by intense fluctuations surrounded by regular (“normal”) fluctuations. Coherent structures are not evenly distributed within the fluid, which alternates regions of low activity to regions of intense activity in an intermittent fashion. Similarly to ordinary fluids, a magnetofluid like the solar wind exhibits an intermittent behavior. Numerical experiments devoted to reproducing solar wind turbulence indicate that small‐scale coherent structures, not yet fully accessible to in situ plasma measurements, represent candidate sites where turbulence energy could be dissipated to eventually heat the plasma. Solar wind heating is still an open problem, and understanding the nature of these coherent structures is the key to solving it. This paper aims to summarize past and present efforts in this direction. Key Points The solar wind is a highly turbulent medium, and its fluctuations have a multifractal character The intermittency phenomenon is observed at fluid and kinetic scales Fluid scales intermittency is related to coherent structures; kinetic scales intermittency is directly related to dissipative phenomena

Background Recent advancements in omics measurement technologies have led to an ever-increasing amount of available experimental data that necessitate systems-oriented methodologies for efficient and systematic integration of data into consistent large-scale kinetic models. These models can help us to uncover new insights into cellular physiology and also to assist in the rational design of bioreactor or fermentation processes. Optimization and Risk Analysis of Complex Living Entities (ORACLE) framework for the construction of large-scale kinetic models can be used as guidance for formulating alternative metabolic engineering strategies. Results We used ORACLE in a metabolic engineering problem: improvement of the xylose uptake rate during mixed glucose-xylose consumption in a recombinant Saccharomyces cerevisiae strain. Using the data from bioreactor fermentations, we characterized network flux and concentration profiles representing possible physiological states of the analyzed strain. We then identified enzymes that could lead to improved flux through xylose transporters (XTR). For some of the identified enzymes, including hexokinase (HXK), we could not deduce if their control over XTR was positive or negative. We thus performed a follow-up experiment, and we found out that HXK2 deletion improves xylose uptake rate. The data from the performed experiments were then used to prune the kinetic models, and the predictions of the pruned population of kinetic models were in agreement with the experimental data collected on the HXK2-deficient S. cerevisiae strain. Conclusions We present a design-build-test cycle composed of modeling efforts and experiments with a glucose-xylose co-utilizing recombinant S. cerevisiae and its HXK2-deficient mutant that allowed us to uncover interdependencies between upper glycolysis and xylose uptake pathway. Through this cycle, we also obtained kinetic models with improved prediction capabilities. The present study demonstrates the potential of integrated “modeling and experiments” systems biology approaches that can be applied for diverse applications ranging from biotechnology to drug discovery.

Biohydrogen production from renewable resources using dark fermentation has become an increasingly attractive solution in sustainable global energy supply. So far, there has been no report on the controllability analysis of biohydrogen production using dark fermentation. Process controllability is a crucial factor determining process feasibility. This paper presents a new criterion for assessing biohydrogen process controllability based on PI control. It proposes the critical loop gain derived via Routh stability analysis as a measure of process controllability. Results show that the dark fermentation using the bacteria from anaerobic dairy sludge and substrate source from sugarcane vinasse can lead to a highly controllable process with a critical loop gain value of 4.3. For the two other cases, an increase of substrate concentration from 10 g/L to 40 g/L substantially reduces the controllability. The proposed controllability criterion is easily adopted to assess the process feasibilty based on experimental data.

This study develops a multiscale modeling framework integrating finite element simulation, CALPHAD thermodynamics, and phase-field modeling to investigate microstructural evolution during semi-solid slurry preparation of Al-7Si alloy via the SEED process. The established non-isothermal phase-field model dynamically couples temperature and concentration distributions, updating solute partition coefficients and interfacial equilibrium concentrations in real-time through CALPHAD computation. Adapted to actual process scales, By integrating boundary conditions derived from finite element simulations—including cooling rates and CALPHAD-coupled thermodynamic parameters—we established a thermo-kinetic multiscale modeling framework that bridges macroscopic temperature evolution with mesoscopic phase-field simulations. The model successfully simulates hundreds of seconds of microstructure evolution, encompassing the entire slurry preparation process. Combined with experimental validation, this approach accurately reproduces the dynamic evolution of temperature and concentration distributions during continuous cooling, significantly improving the predictability of competitive growth and spheroidization mechanisms in multi-grain systems.