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Gradient refractive index (GRIN) lenses have recently become a hot topic in compact imaging and achromaticity. Current research focuses on exploiting GRIN materials and upgrading the preparation technology. In this study, infrared (IR) GRIN materials were successfully prepared by spark plasma sintering of multilayer chalcogenide glass (ChGs) powders. ChGs powders were derived from the Ge20Se80‐xTex series glasses (x = 0–28 mol%) with a maximum refractive index difference (Δn) of 0.25. The similar glass transition temperatures (ΔTg < 10°C) promote efficient sintering of multilayer powders. Six‐, eight‐, and ten‐layer powders of different compositions were rapidly sintered with a thickness of 600, 300, and 200 µm per layer, respectively. Such tiny layer thickness enables the GRIN materials to exhibit nearly linear refractive index variation. Energy dispersive spectroscopy line scans well characterized the gradient variation of GRIN. The maximum deviation of the refractive index gradient from the fitted target line was only ± 0.016 for the 10‐layer GRIN. The sintered GRIN shows excellent IR transparency, which is of great interest for mid‐wave and long‐wave infrared imaging. [ABSTRACT FROM AUTHOR]

Cap RNA methylations play important roles in the replication, evasion of host RNA sensor recognition, and pathogenesis. Coronaviruses possess both guanine N7‐ and 2′‐O‐ribose methyltransferases (N7‐MTase and 2′‐O‐MTase) encoded by nonstructural protein (nsp) 14 and nsp16/10 complex, respectively. In this study, we reconstituted the two‐step RNA methylations of N7‐MTase and 2′‐O‐MTase of severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) in vitro and demonstrated its common and different features in comparison with that of SARS‐CoV. We revealed that the nsp16/10 2′‐O‐MTase of SARS‐CoV‐2 has a broader substrate selectivity than the counterpart of SARS‐CoV and can accommodate both unmethylated and uncapped RNA substrates in a sequence‐independent manner. Most intriguingly, the substrate selectivity of nsp16/10 complex is not determined by the apoenzyme of nsp16 MTase but by its cofactor nsp10. These results provide insight into the unique features of SARS‐CoV‐2 MTases and may help develop strategies to precisely intervene in the methylation pathway and pathogenesis of SARS‐CoV‐2. [ABSTRACT FROM AUTHOR]

Chalcogenide solid‐state electrolytes (SSEs) have been receiving growing attentions due to their high ionic conductivity and suitable mechanic properties, especially the Li2S–P2S5 systems incorporated with a second glass network formers (Si, Ge, Sn, and so on) besides P. Although the ionic conductivities are generally enhanced with the second glass network formers, the comprehensive effects of different glass formers on other properties, including electrochemical, cycling, and air stability, remain elusive. To acquire deeper understanding, herein, three common but representative glass network formers (SiS2, GeS2, and SnS2) were introduced into Li2S–P2S5, and their individual effects were investigated systematically. The results of multiscale characterizations before and after lithium stripping/plating cycling confirmed that the introduction of metal cations (Ge, Sn) generally leads to worse electrochemical stability and shorter cycle life of these SSEs toward lithium metal compared with SSEs with nonmetal cation (Si) modification. However, the air stability is related to the binding energy of M–S (M = Si, Ge, Sn), which is consistent with the hard base soft acid theory. This work provides valuable understanding for designing pragmatic Li2S–P2S5–MS2‐based SSEs with high electrochemistry, cycling, and air stability. [ABSTRACT FROM AUTHOR]

A novel coronavirus, severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2), has been identified as the causative agent of the current coronavirus disease 2019 pandemic. Development of animal models that parallel the clinical and pathologic features of disease are highly essential to understanding the pathogenesis of SARS‐CoV‐2 infection and the development of therapeutics and prophylactics. Several mouse models that express the human angiotensin converting enzyme 2 (hACE2) have been created, including transgenic and knock‐in strains, and viral vector‐mediated delivery of hACE2. However, the comparative pathology of these mouse models infected with SARS‐CoV‐2 are unknown. Here, we perform systematic comparisons of the mouse models including K18‐hACE2 mice, KI‐hACE2 mice, Ad5‐hACE2 mice and CAG‐hACE2 mice, which revealed differences in the distribution of lesions and the characteristics of pneumonia induced. Based on these observations, the hACE2 mouse models meet different needs of SARS‐CoV‐2 researches. The similarities or differences among the model‐specific pathologies may help in better understanding the pathogenic process of SARS‐CoV‐2 infection and aiding in the development of effective medications and prophylactic treatments for SARS‐CoV‐2. Highlights: We systematically describe and compare the histopathological changes at acute stage of the four types of SARS‐CoV‐2 infection hACE2 mouse models, which provides a framework that may help in better understanding the pathogenic process of SARS‐CoV‐2 infection. [ABSTRACT FROM AUTHOR]

High ionic conductivity, low grain boundary impedance, and stable electrochemical property have become the focus for all‐solid‐state lithium–sulfur batteries (ASSLSB). One of the approaches is to promote the rapid diffusion of lithium ions by regulating the chemical bond interactions within the framework. The structure control of P5+ substitution for Sn4+ on lithium‐ion transport was explored for a series of Li3PS4–Li4SnS4 glass–ceramic electrolytes. Results showed that the grain boundary impedance of the glass electrolyte was reduced after heat treatments. The formation of LiSnPS microcrystals, a good superionic conductor, was detected by X‐ray diffraction tests. Electrochemical experiments obtained the highest conductivity of 29.5 S cm−1 at 100°C and stable electrochemical window from –0.1 to 5 V at 25°C. In addition, the cell battery was assembled with prepared electrolyte, which is promoted as a candidate solid electrolyte material with improved performance for ASSLSB. [ABSTRACT FROM AUTHOR]

Nonlinear Raman–Nath diffraction is an effective method for frequency conversion in the presence of phase mismatch. In a structure featuring periodically modulated quadratic nonlinearity, the available frequency‐doubled patterns generated from nonlinear Raman–Nath diffraction constitute uniformly spaced points due to the one parametric decided reciprocal lattice vectors. Herein, nonlinear Raman–Nath second‐harmonic generation from the optical Fibonacci superlattice is theoretically investigated, and a propagation equation that describes the properties of frequency‐doubled waves is presented. Abundant diffraction peaks that are substantially more varied than the traditional Raman–Nath regime are observed. The dependence of the generated second‐harmonic signals on the structural parameters and fundamental laser performance is also comprehensively discussed. [ABSTRACT FROM AUTHOR]

A palladium supported on graphitic carbon nitride (Pd/g‐C3N4) catalyzed carbonylative reaction of aryl bromides and arylboronic acids by has been developed for the construction of diaryl ketones. Using benzene‐1,3,5‐triyl triformate (TFBen) as the CO source, the reaction proceeded well to give various diaryl ketones in moderate to good yields. [ABSTRACT FROM AUTHOR]

Alkynones represent one class of interesting building block which are frequently founded in a variety of biologically active compounds.[1] They have been emerged as key intermediates in the synthesis of various natural products and heterocycles.[2] Therefore, a considerable interest has been attracted and numerous strategies have been explored for the synthesis of alkynones. The traditional methods mainly rely on the reactions of acid chlorides with terminal alkynes.>[3–4] However, some drawbacks remain existing, including high reaction temperature, unstable acid chlorides, and poor functional group tolerance. [ABSTRACT FROM AUTHOR]

The glass‐ceramics of AgI‐based electroconductive chalcogenide system was realized using an appropriate heat treatment at a fairly high temperature (Tg + 40°C) and different times ranging from 4 to 20 hours. The crystallization behavior and electroconductive properties of the heat‐treated samples were studied in detail. Transmission study was performed, and the results show that the cut‐off edge of the short wavelength is red‐shifted at prolonged annealing time but remains an excellent transmittance in the mid‐infrared (IR) region. XRD and scanning electron microscopy results indicated that the precipitated crystalline phases are mainly β‐/γ‐AgI. Moreover, a small amount of α‐AgI, which rarely existed at room temperature, is precipitated in the AgI‐rich chalcogenide glass‐ceramics. The ionic conductivity of all glass‐ceramics was enhanced by heat treatment in contrast to that of base glass. Raman analysis exhibited the structure variation in the glass sample after heat treatments. This study provided an observation of crystallization in chalcogenide glass containing large amounts of AgI and be of good guidance to fabricate novel AgI‐based chalcogenide glass‐ceramics that can be candidates in infrared optics and solid electrolyte applications. [ABSTRACT FROM AUTHOR]

A novel family of Ga2S3-Sb2S3-XI (XI = PbI2, CsI, AgI) was investigated to understand the role of metal halides and exploit new chalco-halide glasses for infrared optics. The dependence of the thermal properties, infrared optical properties, and structural information of the novel family on different metal-iodines was investigated. Results showed that metal halides increase the glass stability but decrease the glass network connectivity. The compositional dependence of the short-wave cut-off edge is associated with the electronegativity difference between the cations and anions of the metal halides. Raman study showed that the metal- iodine modified the glass structure mainly through the iodide content, and the cations dissolved in the glass network mostly as charge compensators for the aperiodic network. For the glasses in the series Ga2S3-Sb2S3-XI-Dy3+, Dy3+ emission increased in the PbI2- and CsI-doped glasses but decreased in the AgI-doped glass due to the combined effect of dysprosium and oxygen. For all that, these novel glasses are highly promised for use in infrared optics. [ABSTRACT FROM AUTHOR]

Materials containing rare-earth ions and Ag nanoparticles ( NPs) have been widely applied due to prior demonstration of increase in their luminescence properties. Here, Tm3+ ions-doped bismuth germanate glasses were synthesized by a chemical reduction method based on the conventional melting-quenching technique. The Ag NPs were facilely precipitated in the glass matrix by the chemical reduction method during the annealing process. TEM image shows that the Ag NPs are closely dispersed in the glass matrix. The luminescence properties and energy-transfer mechanism were systematically investigated by means of absorption, emission, and excitation spectra. Significant enhancements of Tm3+ ions emission and a broad emission band centered at 568 nm caused by Ag NPs are observed upon 474-nm excitation. Our research may illustrate the interactions between Tm3+ ions and Ag NPs and provide a simplified way to synthesize the high-efficiency luminescent materials for the blue light-excited W- LEDs. [ABSTRACT FROM AUTHOR]

A series of (1 − x) GeS2.5 - x Sb chalcogenide glasses were prepared using the conventional melt-quenching method. Their microstructure and thermal response were systematically studied. We observe a compositional threshold of x = 0.25 which corresponds to chemical stoichiometric composition in the calorimetric experiments. It is in good accordance with the Raman scattering results and laser-induced phase transformation behavior. They also indicate that phase separation of Sb-rich phase exists in the S-poor samples. Moreover, we got a structural modeling of this phase separation: (1) at x = 0.25, which is chemical stoichiometric composition, the structural motifs are only SbS3 pyramid and GeS4 tetrahedra, and the three-coordinated SbS3 pyramid is isolated by GeS4 tetrahedra; (2) at x < 0.25, the S- S bonds exist in the glass network due to the excess of S; and (3) at x > 0.25, the excess of Sb break the Ge- S and Sb- S bonds to form Sb( Ge)- Sb Bonds, and the Sb atoms segregate from the backbone to nucleate a separate Sb-rich phase. This work provides a new way to investigate the phase separation of glass networks and helps us to better understand their related physical properties. [ABSTRACT FROM AUTHOR]

Diagram of the phase transformation behavior of GeS2- Ga2 S3- CsI glasses is realized in this article and the structure-property dependence of the chalcogenide glasses is elucidated using differential scanning calorimetry and Raman spectroscopy. We observe the compositional threshold of crystallization behavior locates at x = 6-7 mol% in (100− x)(0.8 GeS2-0.2 Ga2 S3)- x CsI glasses, which is confirmed by the thermodynamic studies. Structural motifs are derived from the Raman result that [ Ge( Ga) S4], [ S2 GeI2], [ S3 GaI], and [ S3 Ga- GaS3] were identified to exist in this glass network. Combined with the information of structural threshold, local arrangement of these structural motifs is proposed to explain all the experimental observations, which provides a new way to understand the correlation between crystallization behavior and network structure in chalcogenide glasses. [ABSTRACT FROM AUTHOR]

In nature, valuable and essential multilevel hierarchy structures are common in microstructures and macrostructures. Researchers try to emulate these unique structures or obtain inspiration from them. In general, materials with a single structure are easy to prepare but it is difficult to achieve multiple functions or performances simultaneously. Here, a facile method with general applicability and a high yield for preparing interpenetrating‐syncretic micro‐nanocomposite fibers with a multilevel hierarchy structure via bicomponent electrostatic‐centrifugal spinning is introduced. This 3D structure is distinctive and differs from previous micro‐nanocomposite structure, in which nanofibers are embedded through microfibers. The formation of a longer, more complex and diversified path is close to undulating surface, mainly because of microfiber introduction. Those characteristics in favor of improving the capture rate of particle on the surface. Two different preparation routes are designed. By controlling the spinning parameters, samples with an outstanding filtering efficiency, a low pressure drop, a high quality factor, an optical transparency, and an excellent impact resistant are constructed. Because the different fiber diameters assume different functions, this work could be used to construct diverse materials by using suitable polymers in other fields that require different fiber sizes and a solid multilevel hierarchy structure to improve the mechanical properties and corresponding performance. [ABSTRACT FROM AUTHOR]

Hairy roots were induced from both cotyledon and hypocotyl explants of Isatis indigotica Fort. (indigo woad) through transformation with Agrobaterium rhizogenes strain A4, R1601 and ATCC15834. The results showed that the cotyledons were the preferred explants to hypocotyls and A4 was the most suitable A. rhizogenes strain for the transformation and induction of hairy roots of I. indigotica. High-voltage paper electrophoresis (HVPE) analysis demonstrated the production of mannopine in hairy roots and confirmed the successful transfer of Ri T-DNA (root-inducing transferred DNA) of A. rhizogenes into the I. indigotica genome. Five organic acids, namely CPQ [3-(2-carboxyphenol)-4(3 H )-quinazolinone], syringic acid, salicylic acid, benzoic acid and 2-aminobenzoic acid, which were considered as main antiviral components of I. indigotica, were detected in natural roots, hairy roots and liquid media with high-performance capillary electrophoresis. The results showed CPQ production in hairy roots was significantly higher than that in natural roots. Our results also revealed that all the five organic acids could be excreted from hairy roots into liquid media, and the concentrations of organic acids in the liquid media paralleled those in hairy roots. The hairy roots of I. indigotica grew fast and showed an S-shaped growth curve that reached its apex on the day 24 of culture with a 20-fold increase in fresh weight compared with the starting inoculums. The accumulation of the two organic acids CPQ and syringic acid in liquid media paralleled the growth of hairy roots. MS [Murashige, T. and Skoog, F. (1962) Physiol. Plant. 15, 473-497] medium or half-strength MS medium supplemented with 30 g/l maltose was found to be best for hairy-root culture and accumulation of CPQ.