Abstract:The satellite clocks used in the BeiDou-2 satellite navigation System (BDS) are Chinese self-developed Rb atomic clocks, and their performances and stabilities are worse than GPS and Galileo satellite clocks. Due to special periodic noises and nonlinear system errors existing in the BDS clock offset series, the GPS ultra-rapid clock model, which uses a simple quadratic polynomial plus one periodic is not suitable for BDS. Therefore, an improved prediction model for BDS satellite clocks is proposed in order to enhance the precision of ultra-rapid predicted clock offsets. First, a basic quadratic polynomial model which is fit for the rubidium (Rb) clock is constructed for BDS. Second, the main cyclic terms are detected and identified by the Fast Fourier Transform (FFT) method according to every satellite clock offset series. The detected results show that most BDS clocks have special cyclic terms which are different from the orbit periods. Therefore, two main cyclic terms are added to absorb the periodic effects. Third, after the quadratic polynomial plus two periodic fitting, some evident nonlinear system errors also exist in the model residual, and the Back Propagation (BP) neural network model is chosen to compensate for these nonlinear system errors. The simulation results show that the performance and precision using the improved model are better than that of China iGMAS ultra-rapid prediction (ISU-P) products and the Deutsches GeoForschungsZentrum GFZ BDS ultra-rapid prediction (GBU-P) products. Comparing to ISU-P products, the average improvements using the proposed model in 3 h, 6 h, 12 h and 24 h are 23.1%, 21.3%, 20.2%, and 19.8%, respectively. Meanwhile the accuracy improvements of the proposed model are 9.9%, 13.9%, 17.3%, and 21.2% compared to GBU-P products. In addition, the kinematic Precise Point Positioning (PPP) example using 8 Multi-GNSS Experiment MGEX stations shows that the precision based on the proposed clock model has improved about 16%, 14%, and 38% in the North (N), East (E) and Height (H) components.

Morphology- and crystal facet-controlled Cu2O nanocrystals (NCs), including cubic Cu2O (c-Cu2O) NCs with {100} facets, rhombic dodecahedral Cu2O (d-Cu2O) NCs with {110} facets, and concave octahedral Cu2O (o-Cu2O) NCs with high-index facets, are prepared and employed as catalysts for the electrochemical reduction of CO2 to C2+ products (ethylene, ethanol, and n-propanol). In situ Raman characterizations demonstrate that the surfaces of all three Cu2O NCs are rapidly converted to metallic Cu during CO2 reduction and reoxidized to smaller-sized Cu2O NCs after tests. Specifically, the o-Cu2O catalyst reveals the highest Faradaic efficiency (48.3%) and partial current density (17.7 mA cm–2) for C2+ products at −1.1 V versus reversible hydrogen electrode compared to c-Cu2O and d-Cu2O, which is competitive among the reported Cu and Cu2O catalysts. In addition, abundant crystal defects/grain boundaries and high-index facets are observed on the surface of reconstructed o-Cu2O, which may serve as the active sites and benefit the C–C coupling during CO2 reduction. This work provides a new strategy to achieve efficient C2+ production from electrochemical CO2 reduction via crystal facet regulation of Cu2O catalysts.

Late gene transcription in herpesviruses is dependent on viral DNA replication in cis but the mechanistic basis for this linkage remains unknown. DNA replication results in demethylated DNA, topological changes, removal of proteins and recruitment of proteins to promoters. One or more of these effects of DNA replication may facilitate late gene transcription. Using 5-azacytidine to promote demethylation of DNA, we demonstrate that late gene transcription cannot be rescued by DNA demethylation. Late gene transcription precedes significant increases in DNA copy number, indicating that increased template numbers also do not contribute to the linkage between replication and late gene transcription. By using serial, timed blockade of DNA replication and measurement of late gene mRNA accumulation, we demonstrate that late gene transcription requires ongoing DNA replication. Consistent with these findings, blocking DNA replication led to dissolution of DNA replication complexes which also contain RNA polymerase II and BGLF4, an EBV protein required for transcription of several late genes. These data indicate that ongoing DNA replication maintains integrity of a replication-transcription complex which is required for recruitment and retention of factors necessary for late gene transcription.

Genomic DNA replication is a universal and essential process for all herpesvirus including human cytomegalovirus (HCMV). HCMV UL70 protein, which is believed to encode the primase activity of the viral DNA replication machinery and is highly conserved among herpesviruses, needs to be localized in the nucleus, the site of viral DNA synthesis. No host factors that facilitate the nuclear import of UL70 have been reported. In this study, we provided the first direct evidence that UL70 specifically interacts with a highly conserved and ubiquitously expressed member of the heat shock protein Hsp40/DNAJ family, DNAJB6, which is expressed as two isoforms, a and b, as a result of alternative splicing. The interaction of UL70 with a common region of DNAJB6a and b was identified by both a two hybrid screen in yeast and coimmunoprecipitation in human cells. In transfected cells, UL70 was primarily co-localized with DNAJB6a in the nuclei and with DNAJB6b in the cytoplasm, respectively. The nuclear import of UL70 was increased in cells in which DNAJB6a was up-regulated or DNAJB6b was down-regulated, and was reduced in cells in which DNAJB6a was down-regulated or DNAJB6b was up-regulated. Furthermore, the level of viral DNA synthesis and progeny production was increased in cells in which DNAJB6a was up-regulated or DNAJB6b was down-regulated, and was reduced in cells in which DNAJB6a was down-regulated or DNAJB6b was up-regulated. Thus, DNAJB6a and b appear to enhance the nuclear import and cytoplasmic accumulation of UL70, respectively. Our results also suggest that the relative expression levels of DNAJB6 isoforms may play a key role in regulating the cellular localization of UL70, leading to modulation of HCMV DNA synthesis and lytic infection.

SnS 2 nanoplate-like products were fabricated via a facile hydrothermal process of a mixed solution containing SnCl 4 and thiourea (SC(NH 2 ) 2 ) without organic capping agent, and their composition, crystallinity, and morphology can be adjusted by varying the SC(NH 2 ) 2 /SnCl 4 molar ratio. In particular, regular hexagon-shaped SnS 2 nanoplates with an average size of ∼275 nm and thickness of ∼56 nm were attained when the SC(NH 2 ) 2 / (SnCl 4 ) molar ratio is 6:1. The obtained SnS 2 nanoplates exhibit layered structures with exposed {001} facets and a single-crystalline feature, and its growth mechanism was proposed according to the hydrothermal time-dependent experimental results. The regular hexagon-shaped SnS 2 nanoplates achieve high photocatalytic H 2 production activity of 356 μmol h −1 under visible light (λ ≥ 420 nm) irradiation, much better than that of the irregular nanoplate-like products. The higher crystallinity and fewer defects of the regular hexagon-shaped SnS 2 nanoplates compared to the irregular ones can more efficiently retard the photogenerated charge recombination, while the S atoms with higher density in the exposed {001} facets might be beneficial for the formation of H bonds with H 2 O molecules, which then cause good dispersity and photocatalytic activity for H 2 production of the SnS 2 nanoplates. These results demonstrate the potential application of SnS 2 nanoplates in the photocatalytic H 2 production field, and might provide guidance to the controllable syntheses of the family of MS 2 photocatalysts with a highly efficient H 2 production property.

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Although AgInS as one kind of ternary chalcogenides has been extensively investigated due to its band-edge positions meeting the thermodynamic requirement for water photosplitting, very little attention has been focused on the crystallinity and facet effects of AgInS on its photocatalytic activity. Herein, a facile hydrothermal route was developed to fabricate regular single-crystalline AgInS octahedrons with only {111} facets exposed. Also, the effects of the hydrothermal reaction conditions on the composition, crystal phase, crystallinity, and morphology of the obtained AgInS products (hereafter denoted as AIS-x, where x represents the pH value of the reaction solution) were investigated, and it was found that the accurately released S ions from the thermal decomposition of thioacetamide (TAA) is the central factor for the nucleation and growth of the AgInS octahedrons. The experimental results indicate that the resultant regular AgInS octahedrons (AIS-10.6) exhibit the best photocatalytic activity for H production among those AgInS products, and the higher crystallinity and fewer defects of the AgInS octahedrons compared to the other AgInS products can retard the photogenerated charge recombination, while those indium atoms with higher density in the exposed {111} facets might be beneficial for the photocatalytic H production reaction by acting as active sites to promote the charge separation and transfer processes. The results presented here provide new insights into the significance of crystallinity and exposed facets in the visible-light-responsive activity of AgInS, thus paving new ways into the design and synthesis of high-performance, cost-effective AgInS photocatalysts for H production.

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