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The Pelona–Orocopia–Rand (POR) schists were emplaced during the Farallon flat subduction in the early Cenozoic and now occupy the root of major strike-slip faults of the San Andreas Fault system. The POR schists are considered frictionally stable at lower temperatures than other basement rocks, limiting the maximum depth of seismicity in Southern California. However, experimental constraints on the composition and frictional properties of POR schists are still missing. Here, we study the frictional behavior of synthetic gouge derived from Pelona, Portal, and Rand Mountain schist wall rocks under hydrothermal, triaxial conditions. We conduct velocity-step experiments from 0.04 to 1 μm/s from room temperature to 500ºC under 200 MPa effective normal stress, including a 30 MPa porefluid pressure. The frictional stability of POR schists in the lower crust is caused by a thermally activated transition from slip-rate- and state-dependent friction to inherently stable, rate-dependent creep between 300ºC and 500ºC, depending on sample composition and slip-rate. The mineralogy of POR schists shows much variability caused by different protoliths and metamorphic grades, featuring various amounts of phyllosilicates, quartz, feldspar, and amphibole. Pelona and Portal schists exhibit a velocity-weakening regime enabling the nucleation and propagation of earthquakes when exhumed in the middle crust, as in the Mojave section of the San Andreas Fault. The contrasted frictional properties of POR schists exemplify the lithological control of seismic processes and associated hazards. 

Online reinforcement learning (RL) enhances policies through direct interactions with the environment, but faces challenges related to sample efficiency. In contrast, offline RL leverages extensive pre-collected data to learn policies, but often produces suboptimal results due to limited data coverage. Recent efforts integrate offline and online RL in order to harness the advantages of both approaches. However, effectively combining online and offline RL remains challenging due to issues that include catastrophic forgetting, lack of robustness to data quality and limited sample efficiency in data utilization. In an effort to address these challenges, we introduce A3RL, which incorporates a novel confidence aware Active Advantage Aligned (A3) sampling strategy that dynamically prioritizes data aligned with the policy's evolving needs from both online and offline sources, optimizing policy improvement. Moreover, we provide theoretical insights into the effectiveness of our active sampling strategy and conduct diverse empirical experiments and ablation studies, demonstrating that our method outperforms competing online RL techniques that leverage offline data. Our code will be publicly available at:this https URL. 

The upstream mechanobiological pathways that regulate the downstream mineralization rates in periodontal tissues are limitedly understood. Herein, we spatially colocalized and correlated compression and tension strain profiles with the expressions of mechanosensory ion channels (MS-ion) TRPV4 and PIEZO1, biometal zinc, mitochondrial function marker (MFN2), cell senescence indicator (p16), and oxygen status marker hypoxia-inducible factor-1α (HIF-1α) in rats fed hard and soft foods. The observed zinc and related cellular homeostasis in vivo were ascertained by TRPV4 and PIEZO1 agonists and antagonists on human periodontal ligament fibroblasts ex vivo. Four-week-old male Sprague-Dawley rats were fed hard (n= 3) or soft (n= 3) foods for 4 wk (in vivo). Significant changes in alveolar socket and root shapes with decreased periodontal ligament space and increased cementum volume fraction were observed in maxillae on reduced loads (soft food). Reduced loads impaired distally localized compression-stimulated PIEZO1 and mesially localized tension-stimulated TRPV4, decreased mitochondrial function (MFN2), and increased cell senescence in mesial and distal periodontal regions. The switch inHIF-1αfrom hard food–distal to soft food–mesial indicated a plausible effect of shear-regulated blood and oxygen flows in the periodontal complex. Blunting or activating TRPV4 or PIEZO1 MS-ion channels by channel-specific antagonists or agonists in human periodontal ligament fibroblast cultures (in vitro) indicated a positive correlation between zinc levels and zinc transporters but not with MS-ion channel expressions. The effects of reduced chewing loads in vivo were analogous to TRPV4 and PIEZO1 antagonists in vitro. Study results collectively illustrated that tension-induced TRPV4 and compression-induced PIEZO1 activations are necessary for cell metabolism. An increased hypoxic state with reduced functional loads can be a conducive environment for cementum growth. From a practical standpoint, dose rate–controlled loads can modulate tension and compression-specific MS-ion channel activation, cellular zinc, andHIF-1αtranscription. These mechanobiochemical events indicate the plausible catalytic role of biometal zinc in mineralization, periodontal maintenance, and dentoalveolar joint function.