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Understanding of dynamical responses and mechanical characteristics of metals and alloys at high strain rates holds significant importance in fundamental physics and optimizing the performance capabilities of materials. During high-speed impact scenarios, materials may be subjected to high pressure and plastic deformation, which have the potential to modulate their mechanical attributes. In this study, high-speed planar impact experiments were conducted to investigate the progressive alterations in the microstructures and mechanical properties in coarse-grain body-centered cubic (bcc) iron subjected to high-strain-rate (approximately 2.60–3.89 × 106 s−1) impact reaching approximately 15 GPa in a one-stage light-gas gun. The nanoindentation tests show that the nano-hardness of the post-shock iron improves 1.5 times from approximately 1.75–2.70 GPa. Microscopic analyses of the post-shock bcc-iron show no significant grain refinement but a noticeable increase in the twin boundaries (TBs) and low angle grain boundaries (LAGBs) proportion with increasing shock pressure. Therefore, the interaction between TBs, LAGBs, and dislocations in post-shock iron grains plays an important role in mediating its mechanical properties. Our findings serve as possible guidance for exploring the mechanical properties of single-crystalline and poly-crystalline iron-based materials, such as steel, with optimized mechanical performance. [ABSTRACT FROM AUTHOR]

We measure the electrical resistivity of hcp iron up to ∼170  GPa and ∼3000  K using a four-probe van der Pauw method coupled with homogeneous flattop laser heating in a DAC, and compute its electrical and thermal conductivity by first-principles molecular dynamics including electron-phonon and electron-electron scattering. We find that the measured resistivity of hcp iron increases almost linearly with temperature, and is consistent with our computations. The results constrain the resistivity and thermal conductivity of hcp iron to ∼80±5  μΩ cm and ∼100±10  W m^{-1} K^{-1}, respectively, at conditions near the core-mantle boundary. Our results indicate an adiabatic heat flow of ∼10±1  TW out of the core, supporting a present-day geodynamo driven by thermal and compositional convection.

Grain rotation caused by the movement of dislocations is a determinant factor for the mechanical behavior of metals. In general, the grain rotation may be mediated by grain boundary dislocations (GB-dis) and intragranular dislocations (In-dis), which are closely associated with grain size. Few works have investigated how grain size depends on grain rotation, and the competitive mechanism between GB-dis and In-dis remains unclear. The present work investigates the structural evolution and deformation of coarse-grained tungsten under high pressure. The results show that under high pressure, the nano-sized grains preferentially rotate with dislocation climbing in GBs. Under high pressure, In-dis migrate faster across coarse grains and are absorbed by GBs on the other side, resulting in grain rotation. Elevated temperature also facilitates the migration of In-dis to arrive GBs where they can be absorbed by GBs, thus promoting grain rotation. The theoretical results show that grain rotation occurs easily under high pressure and high temperature. With increasing grain size, the stress-induced rotation mechanism goes from being dominated by GB-dis to being dominated by In-dis migration. The competitive relationship between GB-dis and In-dis during grain rotation is elaborated, providing a new strategy for designing materials under high pressure. [ABSTRACT FROM AUTHOR]

The investigation of iron under high pressure and temperatures is crucial to understand the Earth's core structure and composition and the generation of magnetic fields. Here, we present new in situ XRD measurements for iron in an off-Hugoniot state by laser-driven ramp compression at pressure of 200–238 GPa. The lattice parameters for the hexagonal (hcp)-Fe phase and the c/a ratios were obtained to compare them with previous static and dynamical data, which provides the direct confirmation of such parameters via the different compression paths and strain rates. This work indicates that laser ramp compression can be utilized to provide crystal structure information and direct key information on the crystal structure of Fe at the ultrahigh pressure–temperature conditions relevant for planetology. [ABSTRACT FROM AUTHOR]

BACKGROUND: Temperature is a primary factor that determines the eco‐geographical distribution and population development of invasive insects. Temperature stress leads to various negative effects, including excess reactive oxygen species (ROS), and catalase (CAT) is a key enzyme against ROS in the antioxidant pathway. The whitefly Bemisia tabaci MED is a typical invasive pest that causes damage worldwide. Our previous studies have shown that CAT promotes whitefly adaptation to high temperature by eliminating ROS. However, the mechanism underlying the low‐temperature adaptation of whiteflies is still unknown. RESULTS: In this study, we investigated the role of CAT in the low‐temperature tolerance of B. tabaci MED by analyzing its survival rate, reproduction, and ROS levels at 25 °C (as a control, suitable temperature), 20 °C (moderately decreased temperature), and 4 °C (severely decreased temperature). Silencing of BtCAT1, BtCAT2, or BtCAT3 reduced the viability of whiteflies under a short‐term severely decreased temperature (4 °C), which manifested as decreases in survival and fecundity accompanied by significant increases in ROS levels. Moreover, even at a moderately decreased temperature (20 °C), silencing of BtCAT1 led to high ROS levels and low survival rates in adults. CONCLUSION: Silencing of BtCATs significantly increased the sensitivity of B. tabaci MED to low temperatures. BtCAT1 is likely more essential than other BtCATs for low‐temperature tolerance in whiteflies. © 2024 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Thioredoxins (TRXs) are central to redox regulation, modulating enzyme activities to adapt metabolism to environmental changes. Previous research emphasized mitochondrial and microsomal TRX o1 and h2 influence on mitochondrial metabolism, including photorespiration and the tricarboxylic acid (TCA) cycle. Our study aimed to compare TRX‐based regulation circuits towards environmental cues mainly affecting photorespiration. Metabolite snapshots, phenotypes and CO2 assimilation were compared among single and multiple TRX mutants in the wild‐type and the glycine decarboxylase T‐protein knockdown (gldt1) background. Our analyses provided evidence for additive negative effects of combined TRX o1 and h2 deficiency on growth and photosynthesis. Especially metabolite accumulation patterns suggest a shared regulation mechanism mainly on mitochondrial dihydrolipoamide dehydrogenase (mtLPD1)‐dependent pathways. Quantification of pyridine nucleotides, in conjunction with 13C‐labelling approaches, and biochemical analysis of recombinant mtLPD1 supported this. It also revealed mtLPD1 inhibition by NADH, pointing at an additional measure to fine‐tune it's activity. Collectively, we propose that lack of TRX o1 and h2 perturbs the mitochondrial redox state, which impacts on other pathways through shifts in the NADH/NAD+ ratio via mtLPD1. This regulation module might represent a node for simultaneous adjustments of photorespiration, the TCA cycle and branched chain amino acid degradation under fluctuating environmental conditions. Summary statement: Thioredoxins o1 and h2 concertedly adapt the performance of mtLPD1‐dependent pathways towards short‐ and long‐term environmental changes. Simultaneous adjustments of mitochondrial pathway fluxes are achieved through fine tuning of mtLPD1 activity via redox regulation and subcellular NADH/NAD+ ratios. [ABSTRACT FROM AUTHOR]