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Craniosynostosis is a group of disorders of premature calvarial suture fusion. The identity of the calvarial stem cells (CSCs) that produce fusion-driving osteoblasts in craniosynostosis remains poorly understood. Here we show that both physiologic calvarial mineralization and pathologic calvarial fusion in craniosynostosis reflect the interaction of two separate stem cell lineages; a previously identified cathepsin K (CTSK) lineage CSC1 (CTSK+ CSC) and a separate discoidin domain-containing receptor 2 (DDR2) lineage stem cell (DDR2+ CSC) that we identified in this study. Deletion of Twist1, a gene associated with craniosynostosis in humans2,3, solely in CTSK+ CSCs is sufficient to drive craniosynostosis in mice, but the sites that are destined to fuse exhibit an unexpected depletion of CTSK+ CSCs and a corresponding expansion of DDR2+ CSCs, with DDR2+ CSC expansion being a direct maladaptive response to CTSK+ CSC depletion. DDR2+ CSCs display full stemness features, and our results establish the presence of two distinct stem cell lineages in the sutures, with both populations contributing to physiologic calvarial mineralization. DDR2+ CSCs mediate a distinct form of endochondral ossification without the typical haematopoietic marrow formation. Implantation of DDR2+ CSCs into suture sites is sufficient to induce fusion, and this phenotype was prevented by co-transplantation of CTSK+ CSCs. Finally, the human counterparts of DDR2+ CSCs and CTSK+ CSCs display conserved functional properties in xenograft assays. The interaction between these two stem cell populations provides a new biologic interface for the modulation of calvarial mineralization and suture patency.

Abstract. Marine diazotrophs convert dinitrogen (N2) gas intobioavailable nitrogen (N), supporting life in the global ocean. In 2012, thefirst version of the global oceanic diazotroph database (version 1) waspublished. Here, we present an updated version of the database (version 2),significantly increasing the number of in situ diazotrophic measurements from13 565 to 55 286. Data points for N2 fixation rates, diazotrophic cellabundance, and nifH gene copy abundance have increased by 184 %, 86 %, and809 %, respectively. Version 2 includes two new data sheets for the nifH genecopy abundance of non-cyanobacterial diazotrophs and cell-specific N2fixation rates. The measurements of N2 fixation rates approximatelyfollow a log-normal distribution in both version 1 and version 2. However,version 2 considerably extends both the left and right tails of thedistribution. Consequently, when estimating global oceanic N2 fixationrates using the geometric means of different ocean basins, version 1 andversion 2 yield similar rates (43–57 versus 45–63 Tg N yr−1; rangesbased on one geometric standard error). In contrast, when using arithmeticmeans, version 2 suggests a significantly higher rate of 223±30 Tg N yr−1 (mean ± standard error; same hereafter) compared to version 1(74±7 Tg N yr−1). Specifically, substantial rate increases areestimated for the South Pacific Ocean (88±23 versus 20±2 Tg N yr−1), primarily driven by measurements in the southwestern subtropics,and for the North Atlantic Ocean (40±9 versus 10±2 Tg N yr−1). Moreover, version 2 estimates the N2 fixation rate in theIndian Ocean to be 35±14 Tg N yr−1, which could not be estimatedusing version 1 due to limited data availability. Furthermore, a comparisonof N2 fixation rates obtained through different measurement methods atthe same months, locations, and depths reveals that the conventional15N2 bubble method yields lower rates in 69 % cases compared tothe new 15N2 dissolution method. This updated version of thedatabase can facilitate future studies in marine ecology andbiogeochemistry. The database is stored at the Figshare repository(https://doi.org/10.6084/m9.figshare.21677687; Shao etal., 2022).

Aiming at the problems of unbalanced inter-modal optimization and inadequate fusion of multimodal features in multimodal sentiment analysis, a multimodal sentiment analysis model combining dynamic gradient mechanism and multi-view co-attention mechanism (DG-MCM) is proposed, which can effectively mine single-modal representation and fully integrate multimodal information. Firstly, the model uses pre-trained model BERT (bidirectional encoder representation from transformers) and stacked long short-term memory (SLSTM) to learn the features of text, audio and video, and proposes a dynamic gradient mechanism. By monitoring the contribution difference and learning speed of each mode, the feature learning of each mode is assisted. Secondly, the features of different modes obtained are fused using the multi-view co-attention mechanism. By projecting every two modes into multiple spaces for interaction, more adequate fusion features are obtained. Finally, fusion features and single-modal features are spliced together for sentiment prediction. Experimental results on CMU-MOSI and CMU-MOSEI datasets show that this model can fully learn information between single mode and different modes, and effectively improve the accuracy of multimodal sentiment analysis.

Objective Dual‐plate fixation was thought to be the gold standard for treating complicated bicondylar tibial plateau fractures, yet it was found to be hard to accommodate the posterior column in three‐column fractures. Currently, column‐specific fixation is becoming more and more recognized, but no comprehensive investigation has been performed to back it up. Therefore, the objective of this study was to validate the importance of posterior column fixation in the three‐column tibial fractures by a finite element (FE) analysis and clinical study. Methods In FE analysis, three models were developed: the longitudinal triple‐plate group (LTPG), the oblique triple‐plate group (OTPG), and the dual‐plate group (DPG). Three loading scenarios were simulated. The distribution of the displacement and the equivalent von Mises stress (VMS) in each structure was calculated. The comparative measurements including the maximum posterior column collapse (MPCC), the maximum total displacement of the model (MTD), the maximum VMS of cortical posterior column (MPC‐VMS), and the maximum VMS located on each group of plates and screws (MPS‐VMS). The clinical study evaluated the indicators between the groups with or without the posterior plate, including operation time, blood loss volume, full‐weight bearing period, Hospital for Special Surgery Knee Scoring system (HSS), Rasmussen score, and common postoperative complications. Results In the FE analysis, the MPCC, the MPC‐VMS, and the MTD were detected in much lower amounts in LTPG and OTPG than in DPG. In comparison with DPG, the LTPG and OTPG had larger MPS‐VMS. In the clinical study, 35 cases were included. In the triple‐plate (14) and dual‐plate (21) groups, the operation took 115.6 min and 100.5 min (p

The nuclear thermal propulsion (NTP) boasts advantages such as high specific impulse, substantial thrust, and extended operating time, giving it a clear edge in deep space exploration and orbital maneuvers. To fully harness the potential of NTP, a comprehensive system performance analysis is crucial to ensure reliability and efficiency under various operational conditions. This study provided an overview of the historical development and current status of nuclear thermal propulsion system analysis programs, both nationally and internationally. It also conducted an in-depth analysis of programs utilized in projects such as NERVA and SNTP. Building on an examination of historical international program advancements and current research requirements, system performance analysis is categorized into three primary components:steady-state performance design and optimization, steady-state off-design performance analysis, and transient performance analysis. Based on the independently developed program for analyzing nuclear engine systems (PANES) at Institute of Nuclear and New Energy Technology, Tsinghua University, an integrated NTP system analysis program framework based on "flow network-heat network" was proposed. The one-dimensional flow network model employed a concept similar to the staggered grid commonly used in computational fluid dynamics (CFD). It separately handled the momentum conservation equation in the resistance/inertia segment and the continuity and energy conservation equations in the capacitance segment. The thermal network model was solved based on the solid energy equation considering heat capacity. Coupled calculations of the thermal network and flow network were achieved by considering heat exchange in the capacitance segment of the flow network. Specifically, a point reactor model based on backward Euler (BE) or Crank-Nicolson (CN) time discretization formats was established to facilitate the calculation of power produce processes. To enhance the understanding and optimization of turbine performance, a turbine model was developed, employing iterative methods to determine mass flow based on turbine inlet parameters, pressure ratios, and characteristic curves. Additionally, to accurately simulate centrifugal pump behavior, a centrifugal pump model based on Suter curves was implemented. The integration of these models provides a comprehensive approach for considering and effectively designing and optimizing the performance of turbine and pump components within the NTP system. This work lays a crucial foundation for further research and application of NTP system design methods, paving the way for future advancements in space exploration and offering exciting prospects for upcoming space missions.

The performance of space nuclear reactors and spacecraft is significantly influenced by the size and mass of shield, therefore shielding design and optimization are crucial for the development of space nuclear power systems. In this paper, shielding design and optimization process was proposed, and the effectiveness was verified through an optimized shielding design for the Jupiter Icy Moons Orbiter (JIMO) reactor. Building upon the open lattice reactor concept of the JIMO project, the neutronic design of the JIMO reactor was supplemented. The shielding design and optimization for the reactor employed a layered combination of beryllium (Be), boron carbide (B4C), tungsten (W), and lithium hydride (LiH). Considering the radial distribution of radiation dose, the Monte Carlo method was utilized to compute the neutron flux and the photon dose at the payload. Additionally, the neutron dose at the leading edge of the LiH was taken into account. Given the computational cost associated with the Monte Carlo method, the stepwise optimization approach was proposed after the analysis of the coupled transport characteristics of neutrons and photons and the shielding design principles. The stepwise optimization and analysis revealed several key findings. Firstly, the multi-layer Be-B4C configuration, compared to the single-layer Be plus single-layer B4C arrangement, effectively reduces reflected neutrons, thereby diminishing the mass required for photon shielding material. This reduction results from a decrease in the secondary photons generated within the leading-edge structural materials. Secondly, due to the lower photon doses at the outer edge resulting from the strong penetration ability of photons, the mass of the photon shielding material can be reduced by decreasing the photon shielding radius. Thirdly, a shielding configuration with a Be to B4C thickness ratio of 7:3 demonstrates excellent shielding effectiveness while maintaining a relatively small mass. Finally, placing W at 30 cm from the shielding leading edge not only reduces the photon shielding radius but also decreases the generation of the secondary photons, leading to an optimal shielding mass. The optimized shielding demonstrates equivalent radiation attenuation capabilities to the JIMO shielding, encompassing the attenuation of neutron flux and photon dose at the payload and neutron absorption dose at the leading edge of LiH. Simultaneously, the shielding mass is reduced by 98.41 kg. This underscores the effectiveness of the shielding optimization process. The developed shield and the associated design process have the potential to serve as a valuable reference for future shielding design and optimization for space nuclear reactors.