Spring in EJHG
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A miniaturized MEMS accelerometer with anti-spring mechanism for enhancing sensitivity
Anti-spring mechanisms are widely used for improving the noise performance of MEMS accelerometers due to their stiffness softening effect. However, the existing mechanisms typically require large bias force and displacement for achieving stiffness softening, leading to large device dimensions. Here, we propose a novel anti-spring mechanism composed of two pre-shaped curved beams connected in a parallel configuration, which can achieve stiffness softening without requiring large bias force and displacement. The stiffness softening effect of the mechanism is verified through theoretical modeling and finite element method (FEM) simulation. After that, the mechanism is implemented in a 4.2 mm × 4.9 mm MEMS capacitive accelerometer prototype. The experimental results reveal that the sensitivity of the accelerometer increases by 10.4% compared to the initial sensitivity; at the same time, the noise floor and bias instability decrease by 10.5% and 4.2%. The sensitivity, nonlinearity, bias instability, and noise floor after biasing are 51.1 mV/g, 0.99%, 0.24 mg, and 21.3 ({rm{mu }}{rm{g}}/sqrt{{rm{Hz}}}), respectively. Thus, the proposed mechanism can enhance the performance of the accelerometer. This work provides an innovative approach for improving the performance of MEMS accelerometers while enabling miniaturization.
Contractility of striated muscle tissue increases with environmental stiffness according to a power-law relationship
The interplay between contractility and mechanosensing in striated muscle is important for tissue morphogenesis, load adaptation, and disease progression, but remains poorly understood. Here, we investigate how contractile force generation in neonatal rat cardiac and C2C12 mouse skeletal muscle micro-tissues depends on environmental stiffness. Micro-tissues self-assemble and mature over one week between flexible elastic pillars with adjustable stiffness that we vary over three orders of magnitude. Contractile forces are measured from pillar deflections and are decomposed into static baseline and transient active forces in response to electrical stimulation. After 3–5 days of maturation, we find that the active, but not static, force of both cardiac and skeletal micro-tissues increases with environmental stiffness according to a strong power-law relationship, indicating a pronounced mechanoresponsiveness. Depleting the focal adhesion protein β-parvin in skeletal muscle miscro-tissues reduces absolute contractile force but does not affect mechanoresponsiveness. Our findings highlight the influence of external stiffness in striated muscle during development.
Drivers of mesoscale convective aggregation and spatial humidity variability in the tropical western Pacific
We examine mesoscale convective organisation in the tropical western Pacific using a multivariate analysis of column humidity, precipitation and sea surface temperature (SST) observations. We demonstrate that in boreal summer and autumn, convection remains spatially random despite radiative-feedbacks acting to aggregate convection, which we attribute to the high density of convective moisture sources and the role of wind shear. Instead, in winter and spring, a weak meridional SST gradient exists and convection is usually clustered over the regions of warmer SSTs, with significant meridional humidity gradients. However, this is sporadically interrupted by episodes of convection migration to the coldest SSTs and limited spatial humidity variance. These episodes are the result of westward propagating equatorial waves, which remove meridional humidity gradients. It appears that the drivers of mesoscale convective clustering and humidity variability in the Pacific warm pool are the SST gradients, shear, and equatorial wave dynamics.
Edge states with hidden topology in spinner lattices
Symmetries – whether explicit, latent, or hidden – are fundamental to understanding topological materials. This work introduces a prototypical spring-mass model that extends beyond established canonical models, revealing topological edge states with distinct profiles at opposite edges. These edge states originate from hidden symmetries that become apparent only in deformation coordinates, as opposed to the conventional displacement coordinates used for bulk-boundary correspondence. Our model, realized through the intricate connectivity of a spinner chain, demonstrates experimentally distinct edge states at opposite ends. By extending this framework to two dimensions, we explore the conditions required for such edge waves and their hidden symmetry in deformation coordinates. We also show that these edge states are robust against disorders that respect the hidden symmetry. This research paves the way for advanced material designs with tailored boundary conditions and edge state profiles, offering potential applications in fields such as photonics, acoustics, and mechanical metamaterials.
Cenozoic evolution of spring persistent rainfall in East Asia and North America driven by paleogeography
Spring persistent rainfall is a unique climate phenomenon that prevails in East Asia today, providing precious water resources to this densely populated region. However, its Cenozoic history and underlying mechanisms remain poorly understood. Here we show that the spring persistent rainfall in East Asia has emerged since the Miocene, whereas it previously flourished in North America during the Eocene, as revealed by climate models integrated with climate proxies. The contrasting evolution of spring persistent rainfall in East Asia and North America is determined by paleogeography and further influenced by CO2-induced warming. The uplift of the Tibetan Plateau and the westward drift of the Rocky Mountains have triggered a mid-latitude Rossby wave train since the Miocene, altering the position and intensity of the subtropical highs and thus rainfall patterns. Our results illuminate the Cenozoic evolution of spring persistent rainfall, with implications for the spring climate under the extreme future warming.
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