分类: 生物学 >> 生物物理学 >> 生物物理、生物化学与分子生物学 提交时间: 2016-05-12
摘要: The architecture and structural details of chromatin assembler, chromatin modifier, and chromatin remodeler, and their complexes with nucleosome and chromatin, are critical for revealing the molecular mechanisms for the establishment, maintenance and regulation of epigenetic information. The fast-developing cryo-electron microscopy (cryo-EM) provides an indispensible tool for the structure determiantion of the huge, multi-subunits, and flexible epigenetic regulation related macromolecular assemblies. In this review, we summarized the recent progresses on EM structural studies of macromolecules and complexes relating to epigenetic regulation.
分类: 生物学 >> 动物学 提交时间: 2022-04-16 合作期刊: 《古脊椎动物学报》
摘要: Shanshenmiaozui site in Nihewan Basin in North China is a recently discovered Early Pleistocene site which yields rich and diverse mammalian fossils. In the fauna, the small and medium-sized bovid fossils are well represented and can be referred to the following taxa: Spirocerus wongi, Gazella sinensis, Ovis shantungensis and Megalovis piveteaui respectively, among which G. sinensis is the dominate species. S. wongi and G. sinensis are mainly represented by horn-cores and partial skull bones as well as mandibles; in addition, metacarpal and/or metatarsal bones were also recognized for all of the four species. The horn-cores are easy to be identified to the species level, while the dentitions and the postcranial bones underwent a series of examinations and comparisons before getting properly determined and referred to the most approximate taxa. Among the postcranial bones, the metapodials, especially to the metacarpal bones special attentions were paid, which are crucial not only for taxonomic identification, but also for phylogenetic and paleoecological reconstructions; the previously misidentified metapodial specimens in Nihewan fauna were reconsidered in this paper. In the SSMZ fauna, the bovid guild is dominated by Gazella and Bison, which indicates steppe was the most important biome in Nihewan Basin during Early Pleistocene.
分类: 物理学 >> 地球物理学、天文学和天体物理学 提交时间: 2024-01-09 合作期刊: 《Research in Astronomy and Astrophysics》
摘要: Spectral classification plays a crucial role in the analysis of astronomical data. Currently, stellar spectral classification primarily relies on one-dimensional (1D) spectra and necessitates a sufficient signal-to-noise ratio (S/N). However, in cases where the S/N is low, obtaining valuable information becomes impractical. In this paper, we propose a novel model called DRC-Net (Double-branch celestial spectral classification network based on residual mechanisms) for stellar classification, which operates solely on two-dimensional (2D) spectra. The model consists of two branches that use 1D convolutions to reduce the dimensionality of the 2D spectral composed of both blue and red arms. In the following, the features extracted from both branches are fused, and the fused result undergoes further feature extraction before being fed into the classifier for final output generation. The data set is from the Large Sky Area Multi-Object Fiber Spectroscopic Telescope, comprising 15,680 spectra of F, G, and K types. The preprocessing process includes normalization and the early stopping mechanism. The experimental results demonstrate that the proposed DRC-Net achieved remarkable classification precision of 93.0%, 83.5%, and 86.9% for F, G, and K types, respectively, surpassing the performance of 1D spectral classification methods. Furthermore, different S/N intervals are tested to judge the classification ability of DRC-Net. The results reveal that DRC-Net, as a 2D spectral classification model, can deliver superior classification outcomes for the spectra with low S/Ns. These experimental findings not only validate the efficiency of DRC-Net but also confirm the enhanced noise resistance ability exhibited by 2D spectra.
分类: 核科学技术 >> 辐射物理与技术 提交时间: 2021-12-31
摘要: The muon radiography imaging technique for high-atomic-number objects (Z) and large-volume objects via muon transmission imaging and muon multiple scattering imaging remains a popular topic in the field of radiation detection imaging. However, few imaging studies have been reported on low and medium Z objects at the centimeter scale. This paper presents an imaging system that consists of three layers of a position-sensitive detector and four plastic scintillation detectors. It acquires data by coincidence detection technique of cosmic-ray muon and its secondary particles. A 3D imaging algorithm based on the density of the coinciding muon trajectory was developed, and 4D imaging that takes the atomic number dimension into account by considering the secondary particle ratio information was achieved. The resultant reconstructed 3D images could distinguish between a series of cubes with 5-mm side lengths and 2-mm intervals. If the imaging time is more than 20 days, this method can distinguish intervals with a width of 1 mm. The 4D images can specify target objects with low, medium, and high Z values.
分类: 医学、药学 >> 药学 提交时间: 2022-12-26
摘要: 目的:在非小细胞肺癌患者中,免疫检查点抑制剂联合化疗方案比传统化疗方案为患者提供了更多获益。然而,依然有部分患者无法得到获益,存在着免疫耐受的现象。临床可测量的生物标志物是预测临床结果和优化剂量策略所必需的。本研究旨在通过定量系统药理学(QSP)研究可获得的生物标志物,这些生物标志物可以预测非小细胞肺癌患者的临床结果,并优化atezolizumab和nab紫杉醇联合治疗的给药策略。 方法:使用MATLAB中的SimBiology工具箱,基于已发表的三阴性乳腺癌QSP模型开发该模型。利用该模型,我们生成了一个虚拟患者队列以进行虚拟临床试验模拟,并使用来自真实临床试验(IMpower131)的数据进行模型校准和验证。 结果:最终QSP模型预测与临床报告的疗效终点一致。患者的肿瘤中基线CD8+和CD4+T细胞密度与临床获益显著相关。Roc分析进一步揭示了它们作为联合治疗方案的预测生物标志物的潜力。虚拟临床试验模拟显示,将nab紫杉醇剂量从100 mg/m2降至75 mg/m2将导致ORR降低,但依然高于atezolizumab单药治疗。三种atezolizumab给药策略联合nab紫杉醇显示出相似的疗效。 结论:本研究提供了一个QSP模型,可用于生成虚拟患者队列并进行虚拟临床试验。我们的研究结果证明了它在预测免疫疗法和化疗的疗效、识别预测性生物标志物以及指导未来临床试验设计方面的潜力。