In eukaryotes, the genome does not exist as a linear molecule but instead is hierarchically packaged inside the nucleus. This complex genome organization includes multiscale structural units of ...chromosome territories, compartments, topologically associating domains, which are often demarcated by architectural proteins such as CTCF and cohesin, and chromatin loops. The 3D organization of chromatin modulates biological processes such as transcription, DNA replication, cell division and meiosis, which are crucial for cell differentiation and animal development. In this Review, we discuss recent progress in our understanding of the general principles of chromatin folding, its regulation and its functions in mammalian development. Specifically, we discuss the dynamics of 3D chromatin and genome organization during gametogenesis, embryonic development, lineage commitment and stem cell differentiation, and focus on the functions of chromatin architecture in transcription regulation. Finally, we discuss the role of 3D genome alterations in the aetiology of developmental disorders and human diseases.
Thermoplastic composites exhibit high toughness and damage tolerance, as well as good impact resistance. Additive manufacturing offers an effective way for making high-performance complex ...thermoplastic composite components without molds,which has a broad application prospect in aerospace and other fields. This article introduces the research progress of additive manufacturing process of short-cut fibers/continuous fibers reinforced thermoplastic composites. The processes and mechanical properties of different resins and fibers are compared. For the additive manufactured PEEK reinforced with 10%（volume fraction, the same below） of shortcut carbon fibers, the tensile strength and modulus can reach 109 MPa and 7.4 GPa, respectively, which is 85% higher than the pure PEEK. For the additive manufactured ABS reinforced with 10% continuous carbon fibers, the tensile strength and modulus can reach 147 MPa and 4.185 GPa, respectively, which is 5 times and 2 times of pure ABS. According to different processing routes a
Drastic epigenetic reprogramming takes place during preimplantation development, leading to the conversion of terminally differentiated gametes to a totipotent embryo. Deficiencies in remodeling of ...the epigenomes can cause severe developmental defects, including embryonic lethality. However, how chromatin modifications and chromatin organization are reprogrammed upon fertilization in mammals has long remained elusive. Here, we review recent progress in understanding how the epigenome is dynamically regulated during early mammalian development. The latest studies, including many from genome-wide perspectives, have revealed unusual principles of reprogramming for histone modifications, chromatin accessibility, and 3D chromatin architecture. These advances have shed light on the regulatory network controlling the earliest development and maternal-zygotic transition.
Fertilization triggers drastic epigenomic reprogramming that converts fully differentiated gametes to totipotent embryos.
Early embryos show noncanonical epigenomes compared with somatic cells and embryonic stem cells.
Allele- and locus-specific inheritance and erasure of parental epigenetic information ensure a successful transition from the parents to the early embryos.
Subsequent establishment of proper zygotic epigenome is essential for embryogenesis.
Chromatin reprogramming during early development includes multilevel reorganization of chromatin accessibility, chromatin modifications, and higher-order chromatin architecture.
•To the best of our knowledge, Mask-CNN is the first end-to-end model that selects deep convolutional descriptors for object recognition, especially for fine-grained image recognition.•We present a ...novel and efficient part-based three-stream model for fine-grained recognition. By discarding the fully connected layers, the proposed M-CNN is computationally efficient (cf. Table 1 and Table 4 in experiments). Additionally, comparing with state-of-the-art methods, M-CNN has smaller feature dimensionality. Beyond those, it achieves the highest classification accuracy on CUB200-2011 and Birdsnap among published methods.•The part localization performance of the proposed model outperforms other part-based finegrained approaches which requires additional bounding boxes. In particular, M-CNN is 12.76% higher than state-of-the-art for head localization on CUB200-2011.
Fine-grained image recognition is a challenging computer vision problem, due to the small inter-class variations caused by highly similar subordinate categories, and the large intra-class variations in poses, scales and rotations. In this paper, we prove that selecting useful deep descriptors contributes well to fine-grained image recognition. Specifically, a novel Mask-CNN model without the fully connected layers is proposed. Based on the part annotations, the proposed model consists of a fully convolutional network to both locate the discriminative parts (e.g., head and torso), and more importantly generate weighted object/part masks for selecting useful and meaningful convolutional descriptors. After that, a three-stream Mask-CNN model is built for aggregating the selected object- and part-level descriptors simultaneously. Thanks to discarding the parameter redundant fully connected layers, our Mask-CNN has a small feature dimensionality and efficient inference speed by comparing with other fine-grained approaches. Furthermore, we obtain a new state-of-the-art accuracy on two challenging fine-grained bird species categorization datasets, which validates the effectiveness of both the descriptor selection scheme and the proposed Mask-CNN model.
Noble metals are important photocatalysts due to their ability to convert light into chemical energy. Hot electrons, generated via the non-radiative decay of localized surface plasmons, can be ...transferred to reactants on the metal surface. Unfortunately, the number of hot electrons per molecule is limited due to charge-carrier recombination. In addition to the reduction half-reaction with hot electrons, also the corresponding oxidation counter-half-reaction must take place since otherwise the overall redox reaction cannot proceed. Here we report on the conceptual importance of promoting the oxidation counter-half-reaction in plasmon-mediated catalysis by photorecycling in order to overcome this general limitation. A six-electron photocatalytic reaction occurs even in the absence of conventional chemical reducing agents due to the photoinduced recycling of Ag atoms from hot holes in the oxidation half-reaction. This concept of multi-electron, counter-half-reaction-promoted photocatalysis provides exciting new opportunities for driving efficient light-to-energy conversion processes.
The
in situ
detection of reactions catalyzed by metal NPs is challenging because the underlying chemical transformations occur at interfaces. Surface-enhanced Raman scattering (SERS), a ...surface-selective, sensitive and label-free vibrational spectroscopic technique, is ideally suited for monitoring of heterogeneous catalysis with high chemical specificity. A major limitation in the past, however, was that small, catalytically active metal NPs do not exhibit the high plasmonic activity required for SERS. This feature article focuses on the design, synthesis and use of bifunctional NPs with both catalytic and plasmonic activity for
in situ
SERS detection of reactions catalyzed by metal NPs. We focus on model reactions induced by chemical reducing agents such as hydride or molecular hydrogen as well as on plasmon-induced photo-catalysis including both photo-oxidation and photo-reduction. Finally, we highlight the concept of photo-recycling on halide-containing silver surfaces for unprecedented multi-electron reduction chemistry.
The
in situ
detection of reactions catalyzed by metal NPs is challenging because the underlying chemical transformations occur at interfaces.
This paper investigates the exponential synchronization of reaction-diffusion neural networks with time-varying delays subject to Dirichlet boundary conditions. A novel type of pinning impulsive ...controllers is proposed to synchronize the reaction-diffusion neural networks with time-varying delays. By applying the Lyapunov functional method, sufficient verifiable conditions are constructed for the exponential synchronization of delayed reaction-diffusion neural networks with large and small delay sizes. It is shown that synchronization can be realized by pinning impulsive control of a small portion of neurons of the network; the technique used in this paper is also applicable to reaction-diffusion networks with Neumann boundary conditions. Numerical examples are presented to demonstrate the effectiveness of the theoretical results.
With the advancement of modern society, information exchange is convenient and fast, and the increase in data volume makes data more convincing. Therefore, in the context of big data, the evaluation ...of college physical education quality is more scientific and objective. In the context of the development of the era of big data, college physical education teaching models mainly involve three micro-classes, MOOCs, and flipped courses. Some colleges and universities use the Internet to innovate physical education teaching methods or introduce innovative teaching software to effectively improve college physical education. The individualized level of class teaching makes it more in line with the physical learning needs of students in the era of big data. Based on this, starting from the big data era and the development of college physical education, combined with specific teaching cases, several college physical education teaching models are introduced, in order to provide help for college physical education teachers to carry out class teaching.
Anatase TiO2 is a typical photocatalyst, and its excellent performance is limited in ultraviolet light range due to its wide band gap of 3.2 eV. A series of Se-doped TiO2 nanoparticles in anatase ...structure with various Se concentrations up to 17.1 at.% were prepared using sol-gel method. The doped Se ions are confirmed to be mainly in the valence state of + 4, which provides extra electronic states in the band gap of TiO2. The band gap is effectively narrowed with the smallest gap energy of 2.17 eV, and the photocatalytic activity is effectively improved due to the extended absorption range. The photocatalytic activity was evaluated by the degradation of Rhodamine B (RhB) in aqueous solution under visible light irradiation. The results show that Se doping significantly improves the photocatalytic activity of TiO2 and 13.63 at.% Se-doped TiO2 has the best performance.
PDF
