A Generic Bamboo-Based Carbothermal Method for Preparing Carbide (SiC, B\u3csub\u3e4\u3c/sub\u3eC, TiC, TaC, NbC, Ti\u3csub\u3ex\u3c/sub\u3eNb\u3csub\u3e1-x\u3c/sub\u3eC, and Ta\u3csub\u3ex\u3c/sub\u3e Nb\u3csub\u3e1-x\u3c/sub\u3eC) Nanowires

Finding a general procedure to produce a whole class of materials in a similar way is a desired goal of materials chemistry. In this work, we report a new bamboo-based carbothermal method to prepare nanowires of covalent carbides (SiC and B4C) and interstitial carbides (TiC, TaC, NbC, TixNb1−xC, and TaxNb1−xC). The use of natural nanoporous bamboo as both the renewable carbon source and the template for the formation of catalyst particles greatly simplifies the synthesis process. Based on the structural, morphological and elemental analysis, volatileoxides or halides assisted vapour–liquid–solid growth mechanism was proposed. This bamboo based carbothermal method can be generalized to other carbide systems, providing a general, one-pot, convenient, low-cost, nontoxic, mass production, and innovative strategy for the synthesis of carbide nanostructures

Impact of initial water vapor on the upscale growing process of a squall line in South China

During the spring and summer seasons, in the South China region where abundant water vapor is present, squall lines can rapidly develop into larger scales within a short period of time. In order to explore the influence of water vapor content on the process of squall line scale growth in South China, using the WRF model, a numerical simulation was conducted for a squall line system in South China on 11 May 2020. We investigated the effect of the variation of water vapor at different levels on its intensity and structure, and discussed the growth mechanism of the squall line system. This squall line occurred with the presence of high-level jet and low-level wind shear complementing each other, within an unstable layer of "dry at the high level and wet at the low level". The simulation showed that, in the early stage of the squall line development, a large maximum convective available potential energy (MCAPE) was observed in the southern part of the convection and coastal warm areas, which is beneficial for the accumulation of unstable energy here. Meanwhile, with the high low-level wind shear, the linear structure of the convection was well maintained. Subsequently, the squall line propagated southward and merged with warm region convection, resulting a further scale growth. Water vapor experiments showed that the MCAPE values are primarily influenced by the moisture content in the low-level atmosphere. More low-level moisture content causes stronger thunderstorm high pressure. Additionally, the presence of higher MCAPE values and larger low-level vertical wind shear contribute to the growth of convective cells in the post-convective stage, prolonging their existence. Reducing the mid-level water vapor content results in a decrease in intense surface precipitation, a weakening of convective intensity, and a quick dissipation into individual convective cells. But when the squall line moves into the area with high MCAPE values, it once again develops into a linear structure. Therefore, an increase in low-level moisture or a decrease in mid-level moisture favors the genesis of convection. However, reducing mid-level moisture results in relatively drier air at mid-levels, making it difficult for the linear structure to be sustained. Further investigation into the internal structure of the squall line reveals that vertical motion and rear inflow also influence the scale growth of the squall line. In the convective system analyzed in this study, the strong rearward inflow enhances the upward motion and generates forward outflow, leading to severe surface wind. Strengthening low-level moisture not only increases the size of the stratiform cloud region at the rear of the convection, but also leads to a stronger upward motion sustaining vertically, which promotes prolonged convective activity. On the other hand, reducing mid-level moisture weakens convective intensity and lowers the height of the echo tops. During the development stage, the rearward inflow intensifies, and dry cold air descends rapidly, leading to the strengthening of the surface cold pool, and causing strong winds due to the forward outflow

Prospect for VLBI Network Extension: the First Results of an Ad-hoc S2 Array Experiments

The Canadian S2 system gives a chance for Russian and some other radio telescopes in the world to be involved into international VLBI programs. Brief descriptions of previous S2 experiments and future possibilities are presented

23 MHz widely wavelength-tunable L-band dissipative soliton from an all-fiber Er-doped laser

Via careful choice of Er-doped fiber length in the cavity, a widely wavelength-tunable L-band dissipative soliton all-fiber Er-doped laser incorporating a L-band optimized polarizing fiber grating device is experimentally demonstrated. The laser delivers 15.38 ps dissipative soliton pulses centered at 1597.34 nm with 3 dB bandwidth of 34.6 nm under 622 mW pump power. The pulse repetition rate is 23 MHz. After using single mode fiber at external cavity, the pulse duration is compressed to 772 fs. With nonlinear polarization rotation-based intracavity comb filter, the central wavelength of the generated dissipative soliton can be tuned from 1567 nm to 1606 nm with a spectral tuning range of 39 nm, which, to the best of our knowledge, is the widest tuning range yet reported for a dissipative soliton fiber laser working in communication band

A Study on the Dual Thermo- and pH-Responsive Behaviors of Well-Defined Star-like Block Copolymers Synthesize by Combining of RAFT Polymerization and Thiol-Ene Click Reaction

A series of stimuli-responsive star-like block copolymers are synthesized via the combination of reversible addition, fragmentation chain transfer (RAFT) polymerization, and photo-initiated thiol-ene (PITE) click reaction. The controllable block ratio and block sequence, narrow distribution of molecular weight, and customized arm numbers of the star-shaped copolymers reveal the feasibility and benefits of combination of RAFT polymerization and PITE click reaction for synthesis of well-defined star-like (co)polymers. A clear insight into the relationship among the arm number, block sequence, and block ratio of the star-like block copolymers and their stimuli-responsive aggregation behavior was achieved via dynamic light scattering and UV-vis spectroscopy study. Notably, the star-like poly(acrylic acid)-b-poly(2-(dimethylamino) ethyl methacrylate) (star-PAA-b-PDMAEMA) shows higher lower critical solution temperature (LCST) compared to star-PDMAEMA-b-PAA with the same arm number and block ratio due to the inner charged PAA segments at pH > IEP. In addition, for star-like PAA-b-PDMAEMA, higher PAA content enhances the hydrophilicity of the polymer in basic solution and leads to the LCST increase, except for star-PAA1-b-PDMAEMA4 at pH = 9.0 (≈IEP). For star-PDMAEMA-b-PAA, the PAA content shows minimal effect on their LCSTs, except for the polymer in solution with pH = 9.5, which is far from their IEP. The star-like block copolymers with well-defined structure and tunable composition, especially the facile-controlled block sequence, bring us a challenging opportunity to control the stimuli-responsive properties of star-like block copolymers

FFT-Based Numerical Method for Nonlinear Elastic Contact

Abstract In theoretical research pertaining to sealing, a contact model must be used to obtain the leakage channel. However, for elastoplastic contact, current numerical methods require a long calculation time. Hyperelastic contact is typically simplified to a linear elastic contact problem, which must be improved in terms of calculation accuracy. Based on the fast Fourier transform, a numerical method suitable for elastoplastic and hyperelastic frictionless contact that can be used for solving two-dimensional and three-dimensional (3D) contact problems is proposed herein. The nonlinear elastic contact problem is converted into a linear elastic contact problem considering residual deformation (or the equivalent residual deformation). Results from numerical simulations for elastic, elastoplastic, and hyperelastic contact between a hemisphere and a rigid plane are compared with those obtained using the finite element method to verify the accuracy of the numerical method. Compared with the existing elastoplastic contact numerical methods, the proposed method achieves a higher calculation efficiency while ensuring a certain calculation accuracy (i.e., the pressure error does not exceed 15%, whereas the calculation time does not exceed 10 min in a 64 × 64 grid). For hyperelastic contact, the proposed method reduces the dependence of the approximation result on the load, as in a linear elastic approximation. Finally, using the sealing application as an example, the contact and leakage rates between complicated 3D rough surfaces are calculated. Despite a certain error, the simplified numerical method yields a better approximation result than the linear elastic contact approximation. Additionally, the result can be used as fast solutions in engineering applications

The development of an effective synthetic route of lesinurad (RDEA594)

Abstract Background Lesinurad is a novel selective uric acid salt transport protein 1 (URAT1) inhibitor which is approved in the USA for the treatment of gout. However, there are some shortcomings among the reported synthetic routes, such as expensive materials, environmental pollution and poor yield. Results In this study, an efficient, practical and environmentally-friendly synthetic route of lesinurad is reported. The main advantages of this route include inexpensive starting materials, mild conditions and acceptable overall yield (38.8%). Conclusion Generally, this procedure is reasonable, reliable and suitable for industrial production. Graphical abstract The improved synthetic procedure of lesinurad (I)

First discovery of novel 3-hydroxy-quinazoline-2,4(1H,3H)-diones as specific anti-vaccinia and adenovirus agents via 'privileged scaffold' refining approach

A series of 1,2,3-triazolyl 3-hydroxy-quinazoline-2,4(1H,3H)-diones was constructed utilizing Cu(I)-catalyzed azide-alkyne 1,3-dipolar cycloaddition (CuAAC) method. The biological significance of the novel synthesized quinazolines was highlighted by evaluating them in vitro for antiviral activity, wherein several compounds exhibited excellent activity specifically against vaccinia and adenovirus. Especially, 24b11 displayed the most potent inhibitory activity against vaccinia with an EC50 value of 1.7μM, which was 15 fold than that of the reference drug Cidofovir (EC50=25μM). 24b13 was the most potent compound against adenovirus-2 with an EC50 value of 6.2μM, which proved lower than all the reference drugs. Preliminary structure-activity relationships were also discussed. To the best of our knowledge, no data are present in the literature on antiviral activity of 3-hydroxy-quinazoline-2,4(1H,3H)-diones against DNA-viruses. Thus, these findings warrant further investigations (library expansion and compound refinement) on this novel class of antiviral agents.publisher: Elsevier articletitle: First discovery of novel 3-hydroxy-quinazoline-2,4(1H,3H)-diones as specific anti-vaccinia and adenovirus agents via ‘privileged scaffold’ refining approach journaltitle: Bioorganic & Medicinal Chemistry Letters articlelink: http://dx.doi.org/10.1016/j.bmcl.2016.09.071 content_type: article copyright: © 2016 Elsevier Ltd. All rights reserved.status: publishe

Search, Identification, and Design of Effective Antiviral Drugs Against Pandemic Human Coronaviruses

Recent coronavirus outbreaks of SARS-CoV-1 (2002–2003), MERS-CoV (since 2012), and SARS-CoV-2 (since the end of 2019) are examples of how viruses can damage health care and generate havoc all over the world. Coronavirus can spread quickly from person to person causing high morbidity and mortality. Unfortunately, the antiviral armamentarium is insufficient to fight these infections. In this chapter, we provide a detailed summary of the current situation in the development of drugs directed against pandemic human coronaviruses. Apart from the recently licensed remdesivir, other antiviral agents discussed in this review include molecules targeting viral components (e.g., RNA polymerase inhibitors, entry inhibitors, or protease inhibitors), compounds interfering with virus-host interactions, and drugs identified in large screening assays, effective against coronavirus replication, but with an uncertain mechanism of action.Financial support from the Key Project of NSFC for International Cooperation (No. 81420108027), and the Key Research and Development Project of Shandong Province (No. 2017CXGC1401, 2019JZZY021011, 2020SFXGFY08) are gratefully acknowledged. Work in Madrid was supported by grants of the Ministry of Science and Innovation of Spain (PID2019-104176RB-I00/AEI/10.13039/501100011033) and CSIC (2019AEP001). An institutional grant of the Fundación Ramón Areces to the CBMSO is also acknowledged.Peer reviewe