Partial differentiation of Europa and implications for the origin of materials in the Jupiter system
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Efficient GPU-computing simulation platform JAX-CPFEM for differentiable crystal plasticity finite element method
We present the formulation and applications of JAX-CPFEM, an open-source, GPU-accelerated, and differentiable 3-D crystal plasticity finite element method (CPFEM) software package. Leveraging the modern computing architecture JAX, JAX-CPFEM features high performance through array programming and GPU acceleration, achieving a 39× speedup in a polycrystal case with ~52,000 degrees of freedom compared to MOOSE with MPI (8 cores). Furthermore, JAX-CPFEM utilizes the automatic differentiation technique, enabling users to handle complex, non-linear constitutive materials laws without manually deriving the case-specific Jacobian matrix. Beyond solving forward problems, JAX-CPFEM demonstrates its potential in an inverse design pipeline, where initial crystallographic orientations of polycrystal copper are optimized to achieve targeted mechanical properties under deformations. The end-to-end differentiability of JAX-CPFEM allows automatic sensitivity calculations and high-dimensional inverse design using gradient-based optimization. The concept of differentiable JAX-CPFEM provides an affordable, flexible, and multi-purpose tool, advancing efficient and accessible computational tools for inverse design in smart manufacturing.
Novel function of TREK-1 in regulating adipocyte differentiation and lipid accumulation
K2P (two-pore domain potassium) channels, a diversified class of K+-selective ion channels, have been found to affect a wide range of physiological processes in the body. Despite their established significance in regulating proliferation and differentiation in multiple cell types, K2P channels’ specific role in adipogenic differentiation (adipogenesis) remains poorly understood. In this study, we investigated the engagement of K2P channels, specifically KCNK2 (also known as TREK-1), in adipogenesis using primary cultured adipocytes and TREK-1 knockout (KO) mice. Our findings showed that TREK-1 expression in adipocytes decreases substantially during adipogenesis. This typically causes an increased Ca2+ influx and alters the electrical potential of the cell membrane in 3T3-L1 cell lines. Furthermore, we observed an increase in differentiation and lipid accumulation in both 3T3-L1 cell lines and primary cultured adipocytes when the TREK-1 activity was blocked with Spadin, the specific inhibitors, and TREK-1 shRNA. Finally, our findings revealed that mice lacking TREK-1 gained more fat mass and had worse glucose tolerance when fed a high-fat diet (HFD) compared to the wild-type controls. The findings demonstrate that increase of the membrane potential at adipocytes through the downregulation of TREK-1 can influence the progression of adipogenesis.
Metabolic control analysis of biogeochemical systems
Many reactive systems involve processes operating at different scales, such as hydrodynamic transport and diffusion, abiotic chemical reactions, microbial metabolism, and population dynamics. Determining the influence of these processes on system dynamics is critical for model design and for prioritizing parameter estimation efforts. Metabolic control analysis is a framework for quantifying the role of enzymes in cellular biochemical networks, but its applicability to biogeochemical and other reactive systems remains unexplored. Here I show how the core concepts of metabolic control analysis can be generalized to much more complex reactive systems, enabling insight into the roles of physical transport, population dynamics, and chemical kinetics at organismal to planetary scales. I demonstrate the power of this framework for two systems of importance to ocean biogeochemistry: A simplified (mostly didactic) model for the sulfate methane transition zone in Black Sea sediments, and a more comprehensive model for the oxygen minimum zone in Saanich Inlet near steady state. I find that physical transport is by far the greatest rate-limiting factor for sulfate-driven methane oxidation in the first system and for fixed nitrogen loss in the second system.
TRPML1 ion channel promotes HepaRG cell differentiation under simulated microgravity conditions
Stem cell differentiation must be regulated by intricate and complex interactions between cells and their surrounding environment, ensuring normal organ and tissue morphology such as the liver1. Though it is well acknowledged that microgravity provides necessary mechanical force signals for cell fate2, how microgravity affects growth, differentiation, and communication is still largely unknown due to the lack of real experimental scenarios and reproducibility tools. Here, Rotating Flat Chamber (RFC) was used to simulate ground-based microgravity effects to study how microgravity effects affect the differentiation of HepaRG (hepatic progenitor cells) cells. Unexpectedly, the results show that RFC conditions could promote HepaRG cell differentiation which exhibited increased expression of Alpha-fetoprotein (AFP), albumin (ALB), and Recombinant Cytokeratin 18 (CK18). Through screening a series of mechanical receptors, the ion channel TRPML1 was critical for promoting the differentiation effect under RFC conditions. Once TRPML1 was activated by stimulated microgravity effects, the concentration of lysosomal calcium ions was increased to activate the Wnt/β-catenin signaling pathway, which finally led to enhanced cell differentiation of HepaRG cells. In addition, the cytoskeleton was remodeled under RFC conditions to influence the expression of PI (3,5) P2, which is the best-known activator of TRPML1. In summary, our findings have established a mechanism by which simulated microgravity promotes the differentiation of HepaRG cells through the TRPML1 signaling pathway, which provides a potential target for the regulation of hepatic stem/progenitor cell differentiation and embryonic liver development under real microgravity conditions.
Metasurface enabled high-order differentiator
Metasurface-enabled optical analog differentiation has garnered significant attention due to its inherent capacity of parallel operation, compactness, and low power consumption. Most previous works focused on the first- and second-order operations, while several significant works have also achieved higher-order differentiation in both real space and k-space. However, how to construct the desired optical transfer function in a practical system to realize scalable and multi-order-parallel high-order differentiation of images in real space, and particularly how to leverage it to tackle practical problems, have not been fully explored. Here, drawing on the basic mathematical feature of the Fourier transform, we theoretically propose universal phase-gradient functions of the Pancharatnam-Berry-phase-based meta-device for performing arbitrary order differentiation. The fifth-order optical differentiations for both intensity and phase images are realized in the experiment. More importantly, by exploring this elaborately designed spatial differentiator, we construct another scheme for optical super-resolution and achieve the estimation of the distance between two incoherent point sources within 0.015 of the Rayleigh distance, which thereby provides a potential toolkit for optical alignment in high-precision semiconductor nano-fabrication. Our findings hold promise for image processing, microscopy imaging, and optical super-resolution imaging.
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