Search for: All records

Nanoindentation was performed on individual grains of a polycrystalline Mg sample with c-axis declination angles ranging from parallel (0°) to perpendicular (90°) to the c-axis. Hardness was highest at ∼0°, decreased up to ∼55°, and then increased at ∼90° to an intermediate level. At ∼0°, high-density 〈c + a〉 dislocations extended deep into the crystal, contributing to high hardness. At ∼55°, 〈c + a〉 dislocations were confined near the indent, and occasional extension twinning reoriented the crystal to ∼45°, promoting 〈a〉 slip in both matrix and twin, leading to low hardness. At ∼90°, extension twinning reoriented the crystal to ∼0°, inducing texture hardening and intermediate hardness. Despite the complex stress state in nanoindentation, which fundamentally differs from the uniaxial stress in bulk tensile and compression tests, the combined contributions of dislocation and twinning still give rise to measurable hardness anisotropy, suggesting nanoindentation as a high-throughput technique for probing orientation-dependent mechanical behavior in Mg. 

Organisms use circadian clocks to synchronize physiological processes to anticipate the Earth’s day-night cycles and regulate responses to environmental signals to gain competitive advantage. While divergent genetic clocks have been studied extensively in bacteria, fungi, plants, and animals, an ancient conserved circadian redox rhythm has been recently reported. However, its biological function and physiological outputs remain elusive. Here, we uncovered the coexistence of redox and genetic rhythms with distinct period lengths and transcriptional targets through concurrent metabolic and transcriptional time-course measurements in anArabidopsislong-period clock mutant. Analysis of the target genes indicated regulation of the immune-induced programmed cell death (PCD) by the redox rhythm. Moreover, this time-of-day-sensitive PCD was eliminated by redox perturbations and by blocking the signaling pathway of the plant defense hormones jasmonic acid/ethylene, while remaining intact in genetic clock-defective backgrounds. This study shows that compared to robust genetic clocks, the more sensitive circadian redox rhythm serves as a signaling hub in regulating incidental energy-intensive processes, such as immune-induced PCD involving reprogramming of chloroplast and mitochondria activities, to provide organisms a flexible strategy to mitigate metabolic overload during stress responses. 

This study presents a comprehensive analysis of the etching effects on β-Ga2O3 using two methods: H2_N2 (a mixture of hydrogen and nitrogen) etching and triethylgallium (TEGa) in situ etching performed in a metal-organic chemical vapor deposition system. By employing a mix of H2 and N2 gases at varying chamber pressures and maintaining a constant etching temperature of 750 °C, we investigated the etching dynamics across three different β-Ga2O3 orientations: (010), (001), and (2¯01). Field emission scanning electron microscopy analysis showed that the etching behavior of β-Ga2O3 depends on the crystal orientation, with the (010) orientation showing notably uniform and smooth surfaces, indicating its suitability for vertical device applications. High-aspect-ratio β-Ga2O3 fin arrays were fabricated on (010) substrates using H2_N2 etching, yielding fin structures with widths of 2 μm and depths of 3.1 μm, along with smooth and well-defined sidewalls. The etching process achieved exceptionally high etch rates (>18 μm/h) with a strong dependence on pressure and sidewall orientation, revealing the trade-off between etch depth and surface smoothness. Separately, TEGa in situ etching was investigated as an alternative etching technique for both β-Ga2O3 and β-(AlxGa1−x)2O3 films. The results revealed that the (010) orientation exhibited relatively high etching rates while maintaining smoother sidewalls and top surfaces, making it favorable for device processing. In contrast, the (001) orientation showed strong resistance to TEGa etching. Furthermore, Al-incorporated β-(AlxGa1−x)2O3 films showed substantially lower etch rates compared to pure β-Ga2O3, suggesting their potential use as an effective etch-stop layer in advanced device fabrication.