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Magnetic fields in the upper atmospheres of solar-like stars are believed to provide an enormous amount of energy to power the hot coronae and drive large-scale eruptions that could impact the habitability of planetary systems around these stars. However, these magnetic fields have never been routinely measured on stars beyond the solar system. Through decade-long spectropolarimetric observations, we have now achieved the measurements of magnetic fields in the lower and middle chromospheres of three M-dwarfs. Our results indicate that the line-of-sight component of the chromospheric magnetic fields can reach up to hundreds of Gauss, whose sign frequently opposes that of the photospheric field. The measurements highlight the magnetic field complexity and the variation with height close to the surface of these M-dwarfs. They provide critical constraints on the energy budget responsible for heating and eruptions of stellar upper atmospheres, and enable assessments of how stellar magnetic activity may affect exoplanet environments. Magnetic fields in stellar upper atmospheres are key to understanding stellar activity and its planetary effects. Here, the authors study chromospheric magnetic fields in three M-dwarf stars using spectropolarimetric observations, finding fields reaching hundreds of Gauss with complex height-dependent structures.

In order to solve the problem of the low efficiency of lactose hydrolysis using traditional metal–organic frameworks (MOFs) nanozymes, Brønsted acid active sites (-COOH) were firstly introduced into Fe-MIL-101 nanozymes to enhance the lactose hydrolysis activity of MOFs bearing Lewis acid sites in this study. When compared to Fe-MIL-101, Fe-MIL-101-COOH exhibited improved catalytic performance, showing a lactose conversion rate of up to 78%. Our experiments suggested that this enhancement could be attributed to the synergistic effect between the Brønsted acidic COOH groups and Lewis acidic Fe clusters. Furthermore, Fe-MIL-101-COOH displayed good stability and reusability with no significant loss in catalytic activity observed after at least five consecutive cycles. Our results showed that the activity of Fe-MIL-101-COOH with Brønsted acid active sites was better than that of Fe-MIL-101. Fe-MIL-101-COOH could be applied to the hydrolysis of lactose in milk powder and the conversion rate of lactose was higher than 48%. This study provided support for the application of MOFs nanozymes in lactose catalytic conversion. Graphical Abstract

In this study, we used Fe-MIL-101 nanozyme to convert lactose into lactitol, and it was proved that Fe-MIL-101 nanozyme has lactase-like activity. Due to the potential health effects of nanomaterials, we evaluated the cytotoxicity of Fe-MIL-101 nanozyme. To reduce the potential toxicity of the nanozyme, we applied centrifugation and membrane filtration. When the membrane aperture size was 100 nm, the residual content of Fe-MIL-101 nanozyme was 14.09 μg/mL. The residual content of Fe-MIL-101 nanozyme was reduced by optimizing time, temperature, and Fe-MIL-101 nanozyme-to-substrate ratio. It was showed that the concentration of Fe was 38.47 mg/kg and the concentration of H 2 BDC was 0 mg/kg under optimized conditions (110℃, 2 h of reaction and the ratio of Fe-MIL-101 nanozyme to substrate is 1:20). The result met the national standard of China. Experiments measuring cytotoxicity, oxidative stress, and cell membrane damage revealed that less than 20 μg/mL Fe-MIL-101 nanozyme had no significant cytotoxicity. Our study findings showed that Fe-MIL-101 nanozyme reduced lactose content in milk.

Pulsation frequencies offer a unique opportunity to probe the interior of hot B subdwarf (sdB) stars. In this study, we present the results by analysing the pulsation properties of the sdB star TIC 293165262 using the TESS 21-sector photometry in Cycles 1, 3 and 5. Fifteen significant frequencies were detected within the frequency range of <500  μ Hz, all of which were identified as low-frequency g-mode oscillations. By analysing the two resolved incomplete multiplets with spacings of ∼  0.056 and ∼  0.099  μ Hz, we derived a rotational period of 99.8 ± 1.8 days, indicating that TIC 293165262 is a relatively slow rotating single sdB star. The period spacings of ℓ = 1 and ℓ = 2 sequences were determined as 264 and 154 s, respectively, which resulted in a mode discriminant of seven ℓ = 1 modes, three ℓ = 2 modes and two satisfied the both. During the five observational segments, the frequency and amplitude variations of six significant pulsations were clearly observed, revealing nonlinear weak mode interactions. These linear and nonlinear properties of pulsations in TIC 293165262 highlighted the continuous provision of high-quality photometry for pulsating sdB stars by the TESS mission.

Young, solar-like stars in the pre-main sequence (PMS) stage exhibit vigorous magnetic activity that significantly influences their circumstellar environments and the processes of planetary formation and evolution. In binary systems, tidal forces and magnetic interactions can further shape the magnetic geometry. We report a longitudinal preference of star spots, chromospheric activities, and flares in the active single-lined spectroscopic PMS binary system V2279 Cyg, based on long-term photometric observations from \\textit{Kepler} and \\textit{TESS} alongside spectroscopic data from LAMOST. The system is classified as a weak-line T Tauri binary, with component masses estimated at 0.86 \\(M_\\odot\\) and 0.27 \\(M_\\odot\\). V2279 Cyg's nearly circular orbit is synchronized with its 4.126-day rotational period. Observations reveal large star spot regions clustered near the far-side hemisphere. Spectroscopic data show strong, double-peak H\\(\\alpha\\) emission, the strength of which is highly correlated with star spot distribution, indicating the presence of an active longitude on the primary star. We also mapped the prominence structure co-rotating with the primary star, suggesting a dense structure close to the near-side hemisphere. Furthermore, we identify an inactive longitude of flares during the 4-year \\textit{Kepler} observations, where the frequency of flare activity is significantly reduced after the superior conjunction, marking the first such identification in active binary systems. Additionally, a white light superflare, releasing energy of \\(2.5 \\times 10^{37}\\) erg, was detected in \\textit{TESS} observations. These findings provide valuable insights into the magnetic field geometry and dynamo processes in PMS binaries, underscoring the critical role of tidal interactions in shaping magnetic activities.

Magnetic fields in the upper atmospheres of solar-like stars are believed to provide an enormous amount of energy to power the hot coronae and drive large-scale eruptions that could impact the habitability of planetary systems around these stars. However, these magnetic fields have never been routinely measured on stars beyond the solar system. Through decade-long spectropolarimetric observations, we have now achieved the measurements of magnetic fields in the lower and middle chromospheres of three M-dwarfs. Our results indicate that the line-of-sight component of the chromospheric magnetic fields can reach up to hundreds of Gauss, whose sign frequently opposes that of the photospheric field. The measurements highlight the magnetic field complexity and the variation with height close to the surface of these M-dwarfs. They provide critical constraints on the energy budget responsible for heating and eruptions of stellar upper atmospheres, and enable assessments of how stellar magnetic activity may affect exoplanet environments.

K2 photometry is suitable for the exploitation of mode variability on short timescales in hot B subdwarf stars, which is important to constrain nonlinear quantities addressed by the stellar theory of high-order perturbation in the future. We analyze the \\(\\sim80\\)~d high-quality K2 data collected on PG~0101+039 and extract the frequency content of oscillation. We then determine its rotational and orbital properties, as well as characterize the dynamics of amplitude and frequency. The frequencies are extracted from light curves via a standard prewhitening technique. The binary information is obtained from variations both in brightness and radial velocities. Amplitude and frequency modulation of oscillation modes are measured by piece-wise light curves and characterized by EMCMC method. We have extracted 137 independent frequencies in PG~0101+039 and derived period spacing of ~252s and 144s for the dipole and quadruple modes, respectively. We derive a rotation rate of 8.81+-0.06d and ~8.60+-0.16d based on g- and p-mode multiplets, implying a marginally differential rotation with a probability of ~ 60%. We find that the rotation period is much shorter than the orbital period of ~0.57d, indicating that this system is not synchronized. Amplitude and frequency modulation are measurable for 44 frequencies with high enough amplitude, including 12 rotational components. We characterize their modulating patterns and find a clear correlation between amplitude and frequency variation, which is linked to nonlinear resonant couplings. In general, the modulating scale and timescale are on an order of a few dozen of nano hertz and a few tens of days, respectively, whose values are important constraints to future calculations of nonlinear amplitude equations.

Stellar flares are critical phenomena on stellar surfaces, which are closely tied to stellar magnetism. While extensively studied in main-sequence (MS) stars, their occurrence in evolved compact stars, specifically hot subdwarfs and white dwarfs (WDs), remains scarcely explored. Based on Cycles 1-5 of TESS photometry, we conducted a pioneering survey of flare events in \\(\\sim12,000\\) compact stars, corresponding to \\(\\sim38,000\\) light curves with 2-minute cadence. Through dedicated techniques for detrending light curves, identifying preliminary flare candidates, and validating them via machine learning, we established a catalog of 1016 flares from 193 compact stars, including 182 from 58 sdB/sdO stars and 834 from 135 WDs, respectively. However, all flaring compact stars showed signs of contamination from nearby objects or companion stars, preventing sole attribution of the detected flares. For WDs, it is highly probable that the flares originated from their cool MS companions. In contrast, the higher luminosities of sdB/sdO stars diminish companion contributions, suggesting that detected flares originated from sdB/sdO stars themselves or through close magnetic interactions with companions. Focusing on a refined sample of 23 flares from 13 sdB/sdO stars, we found their flare frequency distributions were slightly divergent from those of cool MS stars; instead, they resemble those of hot B/A-type MS stars having radiative envelopes. This similarity implies the flares on sdB/sdO stars, if these flares did originate from them, may share underlying mechanisms with hot MS stars, which warrants further investigation.

The SiTian project, with its vast field of view, will become an ideal platform for asteroid scientific research. In this study, we develop a pipeline to analyze the photometry of asteroids and derive their periods from the data collected by the SiTian pathfinder project Mini-SiTian (MST). The pipeline is applied to the MST f02 region, a MST test region with a sky area of \\(2.29^{\\circ} \\times 1.53^{\\circ}\\). Rotation periods of 22 asteroids are derived by the obtained light curves analysis. Among them, there are 8 asteroids available in the Asteroid Lightcurve Photometry Database (ALCDEF), and 6 of them with more photometric points (\\(>\\)200) have similar period parameters as the ones in ALCDEF. Additionally, the periods for 14 of these asteroids are newly obtained and are not listed in ALCDEF. This study demonstrates the feasibility of asteroid photometric research by the SiTian project. It shows that future observations from the SiTian project will provide even more photometry of asteroids, significantly increasing the number of available light curves. The potential vast photometric data of asteroids will help us to further understand the physics of asteroids, their material composition, and the formation and evolution of the solar system.

Structure self‐modification of graphitic carbon nitride (g‐C3N4) without the assistance of other species has attracted considerable attention. In this study, the structure vacancy defect modified diatomic‐layered g‐C3N4 nanosheet (VCN) is synthesized by thermal treatment of bulk g‐C3N4 in a quartz tube with vacuum atmosphere that will generate a pressure‐thermal dual driving force to boost the exfoliation and formation of structure vacancy for g‐C3N4. The as‐prepared VCN possesses a large specific surface area with a rich pore structure to provide more active centers for catalytic reactions. Furthermore, the as‐formed special defect level in VCN sample can generate a higher exciton density at photoexcitation stage. Meanwhile, the photogenerated charges will rapidly transfer to VCN surface due to the greatly shortened transfer path resulting from the ultrathin structure (≈1.5 nm), which corresponds to two graphite carbon nitride atomic layers. In addition, the defect level alleviates the drawback of enlarged bandgap caused by the quantum size effect of nano‐scaled g‐C3N4, resulting in a well visible‐light utilization. As a result, the VCN sample exhibits an excellent photocatalytic performance both in hydrogen production and photodegradation of typical antibiotics. The vacancy defect modified diatomic‐layered g‐C3N4 nanosheets are prepared by thermal treatment of bulk g‐C3N4 in a quartz tube with vacuum atmosphere. The prepared photocatalyst exhibits an excellent photocatalytic performance both in hydrogen production and photodegradation of typical antibiotics due to the special role of defect and ultrathin structure in increasing exciton density and carrier transfer.