Partial differentiation of Europa and implications for the origin of materials in the Jupiter system
Related Articles
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.
Unraveling the dynamics of magnetization in topological insulator-ferromagnet heterostructures via spin-orbit torque
Spin–orbit coupling is a relativistic effect coupling the orbital angular momentum with the spin, which determines the physical properties of condensed matter. For instance, the spin–orbit coupling strongly influences spin dynamics, opening the possibility for promising applications. The topological insulator–ferromagnet heterostructure is a typical example exhibiting spin dynamics driven by current-induced spin–orbit torque. Recent observations of the sign flip of Hall conductivity imply that the spin–orbit torque is strong enough to flip magnetization within this heterostructure. Motivated by this, our study elucidates the conditions governing spin flips by studying the magnetization dynamics. We establish that the interplay between spin-anisotropy and spin–orbit torque plays a crucial role in the magnetization dynamics. Furthermore, we categorize various modes of magnetization dynamics, constructing a comprehensive phase diagram across distinct energy scales, damping constants, and applied frequencies. We also consider the effect of a magnetic field on the magnetization dynamics. This research not only offers insights into controlling spin direction but also charts a new pathway to the practical application of spin–orbit coupled systems.
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.
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.
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.
Responses