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Twisted string actuators (TSAs) have shown strong promise in emerging applications, such as soft robotics and assistive robotics. To construct compact and lightweight TSAs, it is often inevitable to use low-torque and low-speed motors. An accurate TSA model can facilitate the appropriate design of motor-string components and enable TSA’s reliable operation. However, existing models often neglect the twisted strings’ friction and the exerted opposing torque on the motor, which would result in significant discrepancies in predicting the dynamic behaviors of TSAs with low-torque and low-speed motors. This work presents an enhanced model to accurately capture TSA’s dynamics by accounting for the aforementioned phenomena. The theory of torsional closed-wrapped helical springs is used to capture the friction between the twisted strings. The total elastic potential energy of the strings considering string curvature is used to derive the total opposing torque exerted by the twisted strings. The proposed model is experimentally identified, validated, and compared with an existing TSA model to confirm its superior accuracy. 

Abstract Amyloid‐beta (Aβ) peptides, primarily Aβ40 and Aβ42, are central to the formation of amyloid plaques, a pathological hallmark of Alzheimer's disease (AD). These peptides, derived from the amyloid precursor protein (APP), are aggregation prone and neurotoxic. Experimental studies aimed at understanding Aβ aggregation and interaction require pure, monomeric peptides with the native sequences, including the absence of an N‐terminal methionine. We present an optimized protocol for producing recombinant human Aβ40 and Aβ42 using a SUMO fusion system inEscherichia coli. Cleavage of the SUMO tag enables recovery of native‐sequence peptides, producing physiologically relevant monomers with high yield and purity. This method eliminates the need for chemical synthesis and offers a reliable and cost‐effective approach to producing recombinant Aβ suitable for aggregation studies, structural analyses, and interaction assays. The resulting peptides closely mimic endogenous Aβ, facilitating accurate models of Alzheimer's disease pathogenesis and supporting future therapeutics development. © 2025 The Author(s). Current Protocols published by Wiley Periodicals LLC. Basic Protocol: Expression and purification of Aβ40 and Aβ42 fromEscherichia coli 

Abstract Accurate prediction of tropical cyclone (TC) intensity remains a significant challenge partially due to physics deficiencies in forecast models. Improvement of boundary layer physics in the turbulent “gray zone” requires a better understanding of spatiotemporal variations of turbulent properties in low-level high-wind regions. To fill the gap, this study utilizes Anduril’s Altius 600, a small uncrewed aircraft system (sUAS), that collected data in the eye and eyewall regions of category 5 Hurricane Ian (2022) at altitudes below 1.4 km. The highest observed wind speed (WSPD) exceeded 105 m s⁻¹at 650-m altitude. The Altius measured turbulent kinetic energy (TKE) and momentum fluxes that were in good agreement with previous crewed aircraft observations. This study explores the scale-awareness turbulent structure by quantifying turbulence-scale (100 m–2 km) and mesoscale (2–10 km) contributions to the total flux and TKE. The results show that mesoscale eddies dominate the horizontal wind variances compared to turbulent eddies. The horizontal wind variances contribute 70%–90% of the total TKE, while the vertical wind variances contribute 10%–30% of the total TKE. Spectral and wavelet analyses demonstrate eddy scales from a few hundred meters up to 10 km, with unique distributions depending on where observations were taken (e.g., eye vs eyewall). These findings underscore the complex and multiscale nature of TKE and momentum fluxes in intense hurricanes and highlight the critical need for advanced observational tools within the high-wind hurricane boundary layer environment. Significance StatementIt is crucial to improve the understanding of turbulent processes in the low-level high-wind regions of tropical cyclones (TCs) for accurate intensity forecasts. Traditional data collection methods involving crewed aircraft are too risky to access these critical regions. This study demonstrates the use of a small uncrewed aircraft system (sUAS) to collect data at low levels within an intense Hurricane Ian (2022). The wind speed measured by the sUAS exceeded 105 m s⁻¹. Important turbulence parameters are estimated and presented as a function of wind speed, height, and radial locations. We found that mesoscale (2–10 km) eddies contributed to a significant portion of the total momentum transfer relative to turbulence-scale (100 m–2 km) eddies. This work demonstrates the usefulness of sUASs for improving the basic understanding of key physical processes in the high-wind hurricane boundary layer. 

Abstract Chaidez and Edtmair have recently found the first examples of dynamically convex domains in $$\mathbb{R}^{4}$$ that are not symplectomorphic to convex domains, answering a long-standing open question. In this paper, we discover new examples of such domains without referring to Chaidez–Edtmair’s methods. We show a stronger result: that these domains are arbitrarily far from the set of convex domains in $$\mathbb{R}^{4}$$ with respect to the coarse symplectic Banach–Mazur distance. 

Abstract Convective cold pools (CPs) are inherent to mesoscale convective systems and have been identified in tropical cyclone (TC) eyewalls and rainbands. However, their distribution within TCs and their impacts on the TC enthalpy balance are not well understood. This gap is due to the scarcity of high-frequency observations over the ocean. By comparing 1-min data from Saildrone uncrewed surface vehicles to 10-min ocean moored buoy data, we demonstrate that the latter can detect CPs effectively. The analysis of the combined mooring-Saildrone dataset, associated with 241 TCs in the North Atlantic over the period 1998–2023, reveals that the frequencies of occurrence of CPs in the motion-right and shear-left quadrants are 50% and 30% higher than in the motion-left and shear-right quadrants, respectively. This indicates that there is enhanced convection in the motion-right and shear-left quadrants, and TC motion is more important than vertical wind shear in organizing CPs. Although, on average, CPs occur only about 6% of the time in TCs, their contribution to tropospheric latent heat release from their uplifting effect could be comparable to the total surface enthalpy flux in TCs under non-CP conditions. In addition, we found that CP gust fronts can boost surface sensible and latent heat fluxes by 65% and 11%, respectively, which can help low-enthalpy downdraft boundary air recover more quickly, increasing the readiness of the boundary layer for new convection under TC conditions. These findings suggest that properly resolving CP dynamics in TC models could improve the accuracy of TC intensity forecasts. Significance StatementConvective cold pools are bursts of cool, dry air near the surface, often originating from thunderstorms. As they travel, they uplift surface moist air to higher altitudes, which helps form new thunderstorms. As thunderstorms are an integral part of tropical cyclones, the purpose of this study is to investigate the distribution of cold pools inside tropical cyclones and how much they impact tropical cyclone energy. We found that cold pools are more common on the right side of tropical cyclone paths, suggesting stronger thunderstorms in that part of the storm. Despite a low frequency of occurrence of 6%, the amount of energy contributed by cold pools’ uplifting effect in a hurricane can match the total energy released by that hurricane. 

Abstract In the marine boundary layer, the exchange of momentum, heat, and moisture occurs between the atmosphere and ocean. Since it is too dangerous for a crewed aircraft to fly close to the ocean surface to directly obtain these measurements, a sUAS (small Uncrewed Aircraft System) is one of the only viable options. On 24 March 2023 a Black Swift Technologies S0 sUAS was deployed from the NOAA P‐3 on a calm clear day off the west coast of Florida. For 23 min at the end of the mission, the sUAS flew 8 straight line legs with an average length of 2.15 km, at roughly 10 m above the ocean surface, with wind speeds between 3.0 and 4.5 m s⁻¹. For the first time over the open ocean using a sUAS, the 4‐Hz wind and thermodynamic data was used to calculate surface momentum flux, sensible heat flux, and latent flux using both direct covariance methods and the bulk aerodynamic formulas. Since all the flux quantities can be found using both direct and indirect methods, we are able to calculate the exchange coefficients of momentum flux (C_D), latent heat flux (C_E), and sensible heat flux (C_H) with results that are generally in good agreement with previous studies over the same wind speed range. This study demonstrates the ability of sUAS to measure air‐sea interactions. Future intention is to use sUAS to obtain similar measurements in high wind events such as hurricanes which could better help understand hurricane intensification and improve model physics.