The discovery of the Van Allen radiation belts marked a prominent milestone in space physics. Recent advances, through the measurements of two CubeSat missions, have shed new light on the dynamics of ...energetic particles in the near‐Earth environment. Measurements from CSSWE, a student‐led mission, revealed that the decay of low‐energy neutrons, associated with cosmic rays impacting the atmosphere, is the primary source of relativistic electrons at the inner edge of the inner belt (Li et al., Nature, 2017, https://doi.org/10.1038/nature2464). Recently CIRBE captured striking details of energetic electron dynamics (Li et al., GRL, 2024, https://doi.org/10.1029/2023gl107521), further demonstrating high‐quality science achievable with CubeSat missions.
Plain Language Summary
CubeSats are small, low‐cost satellites that are becoming increasingly popular for scientific research. In this commentary, the author shares his personal experience of leading students and professionals in developing and operating two CubeSats that measure energetic particles in the near‐Earth environment. The first CubeSat was launched in 2012, operated until the end of 2014, and far exceeded expectations, producing valuable scientific results. The second CubeSat, launched in 2023, has a much more advanced instrument and revealed far more detailed dynamics of energetic particles. We believe such a commentary may be of general interest and provide encouragement to other teams involved in development of a CubeSat mission, which can be an excellent way to do high‐quality scientific research at a relatively low cost.
Key Points
High‐impact science can be accomplished by a student‐led CubeSat mission, with professional mentorship
With continued miniaturization of spacecraft subsystems, high‐resolution and quality‐measurements from a CubeSat are achievable
Synergistic team efforts, early and frequent testing, and a stroke of luck are required to be successful
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Metal–organic frameworks (MOFs) are an emerging class of compositions for electro- and photoelectrocatalytic energy conversion processes. Understanding and improving the charge-transport processes ...within these high surface area molecular redox catalyst assemblies are critical since the charge carrier conductivity is inherently limited in MOFs. Here, we examine a series of four chemically identical but structurally different hydrolytically robust ZrIV-MOFs constructed from tetrakis(4-carboxyphenyl)porphyrinato iron(III), TCPP(FeIII) to understand how their topological construction affects redox hopping conductivity. While a structural variation fixes center-to-center distances to define the hopping rate, we probe that altering the central metal spin-state can further tune the TCPP(FeIII/II) reorganization energy of the self-exchange process. Significant increase in the hopping rate was observed upon axial coordination of 1-methyl imidazole (MIM), which converts a weakly halide bound high-spin (HS) TCPP(FeIII/II) to the six-coordinated low-spin (LS) complex. Our electrochemical and resonance Raman data reveal that pore geometry that defines the Fe–Fe distance in these frameworks dictate the steric demand to accommodate two MIM-molecules, and thus, the population of LS vs HS species is a function of topology in the presence of an excess ligand.
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IJS, KILJ, NUK, PNG, UL, UM
Nowadays, large-scale oriented functional porous materials have been sought after by researchers. However, regulation of the long-range uniform and oriented structures of the material remains a ...challenge. Herein, ultralong anisotropic cellulose nanofibril (CNF) aerogels with uniformly ordered structures of pore walls inspired by lotus petioles were constructed by applying external speeds to counterbalance the growth driving forces of ice crystals. Based on the growth law of ice crystals, the ice crystals grew at a stable rate when the applied external speed was 0.04 mm/s, ensuring the consistent orientation of the large-scale CNF aerogel. The aerogel exhibited a rapid long-range directional transport ability to different liquid solvents, delivering ethanol up to 40 mm from bottom to top within 50 s. Moreover, by introducing rectorites with good cation-exchange properties, the resulting long-range composite possessed an enhanced adsorption capacity for methylene blue. Furthermore, aerogel successfully achieved real-time dye purification at a long distance, such as fast dye adsorption or selective adsorption. This flexible and straightforward strategy of fabricating ultralong oriented CNF aerogel materials is expected to promote the development of functional aerogels in directional liquid transport and sewage treatment.
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IJS, KILJ, NUK, PNG, UL, UM
Anti-icing surface is crucial to the safety of aircraft, power line, mechanical apparatus and other important devices, while the current superhydrophobic surfaces are facing dilemmas of short ...lifespan, poor stability and complex processing, owing to the low-strength of coating or required post-chemical modification. Here, considering the pivotal role of micro-nano textures in enhancing the stability and lifespan of ice-repellent surfaces, grating textures with micro-nano tertiary structures on aluminum alloy surface were directly constructed through picosecond laser processing. These hierarchically textured surfaces exhibit low-temperature-adaptive water repellency, which delays frozen time and drops frozen temperature. The above scenario was fundamentally understood from viewpoint of both wettability and thermodynamics. These results are extremely important for fabricating superhydrophobic metallic surface with long lifespan and delayed frozen performance without any chemical modification.
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•Micro-nano tertiary structures were constructed on aluminium alloy surface through picosecond laser processing.•The laser processed surfaces exhibit superhydrophobicity.•These hierarchically textured surfaces exhibit delayed frozen time and dropped frozen temperature of icing.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
A number of relativistic electron loss processes exist in the inner magnetosphere, and the extent to which MeV electron precipitation into Earth's atmosphere plays a role in radiation belt dynamics ...is a topic of much debate. In this work, we investigate the contribution of electron precipitation to radiation belt losses, looking at what times and locations precipitation is important. Through high‐cadence low‐altitude measurements from the Solar, Anomalous, and Magnetospheric Particle Explorer (SAMPEX) satellite, we examine the distributions of millisecond (microburst) as well as longer‐duration (band‐type) precipitation and the relative contributions of these two precipitation types to radiation belt dynamics during high‐speed stream (HSS)‐driven storms. Different local time and radial distributions between microbursts and precipitation bands suggest different scattering mechanisms as the causes of the two precipitation types. In a superposed epoch study of 42 HSS‐driven storms, enhanced main and recovery phase losses to the atmosphere are observed. Microburst occurrence rates peak in the recovery phase of the storms, while their magnitudes remain fairly constant over storm phase. Precipitation bands show an increase in both occurrence and magnitude at storm onset, particularly at the inner edge of the outer radiation belt. The observations, enabled by the high time resolution and large geometric factor and field of view of the SAMPEX/Heavy Ion Large Telescope (HILT) instrument, reveal when and where microburst and band‐type precipitation are contributing to radiation belt dynamics during HSS‐driven storms.
Key Points
SAMPEX/HILT observes microburst and band‐type rapid precipitation events
Relative role of these loss processes is examined across MLT, L, and storm phase
Significant radiation belt electron precipitation is observed during HSS storms
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Dual-function electrochromic supercapacitors (ECSs) that indicate their real-time charge capacity in color are fabricated using tungsten trioxide (WO3) and Li-doped ion gels containing hydroquinone ...(HQ). The ECSs can simultaneously serve as either electrochromic devices or supercapacitors. The coloration/bleaching and charging/discharging characteristics are investigated between 0 and −1.5 V. At the optimal HQ concentration, large transmittance contrast (∼91%), high coloration efficiency (∼61.9 cm2/C), high areal capacitance (∼13.6 mF/cm2), and good charging/discharging cyclic stability are achieved. Flexible ECSs are fabricated on plastic substrates by exploiting the elastic characteristics of the gel electrolytes, and they exhibit good bending durability. Moreover, practical feasibility is evaluated by demonstrating the use of the ECSs as an energy storage device and a power source.
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IJS, KILJ, NUK, PNG, UL, UM
To achieve a better understanding of the dominant loss mechanisms for the rapid dropouts of radiation belt electrons, three distinct radiation belt dropout events observed by Van Allen Probes are ...comprehensively investigated. For each event, observations of the pitch angle distribution of electron fluxes and electromagnetic ion cyclotron (EMIC) waves are analyzed to determine the effects of atmospheric precipitation loss due to pitch angle scattering induced by EMIC waves. Last closed drift shells (LCDS) and magnetopause standoff position are obtained to evaluate the effects of magnetopause shadowing loss. Evolution of electron phase space density (PSD) versus L* profiles and the μ and K (first and second adiabatic invariants) dependence of the electron PSD drops are calculated to further analyze the dominant loss mechanisms at different L*. Our findings suggest that these radiation belt dropouts can be classified into distinct classes in terms of dominant loss mechanisms: magnetopause shadowing dominant, EMIC wave scattering dominant, and combination of both mechanisms. Different from previous understanding, our results show that magnetopause shadowing can deplete electrons at L* < 4, while EMIC waves can efficiently scatter electrons at L* > 4. Compared to the magnetopause standoff position, it is more reliable to use LCDS to evaluate the impact of magnetopause shadowing. The evolution of electron PSD versus L* profile and the μ, K dependence of electron PSD drops can provide critical and credible clues regarding the mechanisms responsible for electron losses at different L* over the outer radiation belt.
Key Points
Radiation belt dropouts can be classified into three distinct classes in terms of dominant loss mechanisms
Magnetopause shadowing can deplete electrons at L* < 4, while EMIC waves can efficiently scatter electrons at L* > 4
The μ, K dependence of electron PSD drops can provide critical and credible clues regarding the electron loss mechanisms at different L*
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
The microstructure evolution and mechanical properties of as-homogenized Mg-3Al-3Sn-1Zn (ATZ331) alloy with an initial grain size of ∼126.7 µm are studied during multi-pass high-speed rolling (HSR) ...process. The main deformation mechanism governing the microstructure is comprised of twinning and dislocation migration, Firstly, high dislocation density and twinning generated during HSR. Then, the dislocations are rearranged and incorporated as subgrain boundaries (sub-GBs), leading to a reduction of grain size with an increase in rolling pass. Results show that a fine and uniform microstructure (1.1 µm) of HSRed ATZ331 is achieved after the sixth pass, with a yield strength (YS), ultimate tensile strength (UTS), and elongation to failure (FE) of 319 MPa, 360 MPa, and 5.9 %, respectively. After being subject to HSR, low-temperature short-time annealing is carried out in order to improve ductility, which has proven to bring about sufficient static recrystallization (SRX). The SRX mechanism of ATZ331 alloy after HSR processing is found to consist of the classical recovery followed by recrystallization. Subgrains are formed by the realignment and absorption of the accumulated dislocations, which is followed by the migration of low angle grain boundaries (LAGBs) and their transformation into high angle grain boundaries (HAGBs). Finally, the sample with fine average grain size (1.7 µm) is achieved. Furthermore, the YS, the UTS, and the FE of ATZ331 are 253 MPa, 313 MPa, and 9.8 %, respectively.
•The YS, the UTS, and the FE of HSRed ATZ331 are 319 MPa, 360 MPa, and 5.9 %, respectively, and those of the samples annealed at 200 °C for 5 min are 253 MPa, 313 MPa, and 9.8 %, respectively.•The grain size of HSRed and annealed samples are 1.1 µm and 1.6 µm, respectively.•The SRX mechanisms of the ATZ331 alloy after HSR is the classic recovery followed by recrystallization.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Abstract
Metal
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organic frameworks (MOFs) are widely studied molecular assemblies that have demonstrated promise for a range of potential applications. Given the unique and well-established ...photophysical and electrochemical properties of porphyrins, porphyrin-based MOFs are emerging as promising candidates for energy harvesting and conversion applications. Here we discuss the physical properties of porphyrin-based MOFs, highlighting the evolution of various optical and electronic features as a function of their modular framework structures and compositional variations.
Flexible electrochromic devices (ECDs) based on Li-doped ion gels and tungsten trioxide (WO3) are demonstrated. Colored ECDs cannot be produced using conventional ion gels comprised of copolymers and ...room temperature ionic liquids (RTILs) due to a lack of cations that can be inserted into WO3. Based on considerations of the coloration mechanism, we developed Li-doped ion gels and applied these to devices. The effects of Li salt concentration are systematically examined, with respect to device dynamics, coloration efficiency, and transmittance contrast. In addition, the coloration/bleaching switching stability of the ECD produced using optimal Li salt content is investigated. The ECD exhibits distinct colored and bleached states even after 24 h operation in air. Using the described Li-doped ion gel electrolytes, flexible WO3 ECDs were successfully demonstrated with good bending stability and no electrolyte leakage.
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•Non-volatile, Li-doped ion gel electrolytes are designed for flexible WO3-based ECDs.•ECDs exhibit low voltage operation (–0.9 V) and large transmittance contrast (~85%) between colored and bleached states.•Electrolyte leakage is not observed in flexible ECDs containing Li-doped gel electrolyte when bending deformation is applied.•Flexible ECDs maintain ~90.3 and ~84.5% of initial optical transmittance and coloration efficiency after 1000 bending tests.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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