Rapid progress in nanotechnology allows us to develop a large number of innovative wearables such as activity trackers, advanced textiles, and healthcare devices. However, manufacturing processes for ...desirable nanostructure are usually complex and expensive. Moreover, materials used for these devices are mainly derived from nonrenewable resources. Therefore, it poses growing problems for living environment, and causes incompatible discomfort for human beings with long‐time wearing. Here, a self‐powered cellulose fiber based triboelectric nanogenerator (cf‐TENG) system is presented through developing 1D eco‐friendly cellulose microfibers/nanofibers (CMFs/CNFs) into 2D CMFs/CNFs/Ag hierarchical nanostructure. Silver nanofibers membrane is successfully introduced into the cf‐TENG system by using CMFs/CNFs as template, which shows excellent antibacterial activity. Enabled by its desirable porous nanostructure and unique electricity generation feature, the cf‐TENG system is capable of removing PM2.5 with high efficiency of 98.83% and monitoring breathing status without using an external power supply. This work provides a novel and sustainable strategy for self‐powered wearable electronics in healthcare applications, and furthermore paves a way for next‐generation flexible, biocompatible electronics.
The introduction of 1D eco‐friendly cellulose microfibers/nanofibers (CMFs/CNFs) into 2D CMFs/CNFs/Ag hierarchical nanostructure for a self‐powered triboelectric nanogenerator system enables the device with high efficiency for PM2.5 removal (98.83%), excellent antibacterial activity, and monitoring breathing without an external power supply, due to desirable pores/nanofibers design in the hierarchical nanostructure and a unique electricity generation feature of the device.
We describe a cerium‐catalyzed aerobic oxidative ring expansion for the expedient construction of synthetically challenging macrolactones under visible‐light conditions. Cyanoanthracene has been ...employed as co‐catalyst to accelerate the turnover of the cerium cycle leading to a fast conversion within 20 min of irradiation. Taking advantage of the high efficiency and operationally simple conditions, a collection of over 100 macrolactones equipped with ring systems ranging from 9‐ to 19‐membered macrocycles have been prepared from simple building blocks. Moreover, the enabling potential of this strategy to simplify the generation of molecular complexity has been demonstrated through the concise synthesis of sonnerlactone.
Challenging macrolactones can now be modularly assembled through a photocatalytic aerobic oxidative ring expansion of cyclic ketones. With the assistance of an organophotocatalyst, α‐alkoxyketones can be transformed into macrolactones with 20 min of blue LED irradiation, ultimately enabling the rapid assembly of a large collection of structurally diverse lactones.
Based on the unified creep and plasticity theory, an improved constitutive model is proposed in this study to describe the uniaxial mechanical behaviour of Sn3.0Ag0.5Cu (SAC305) solder alloy ...subjected to a wide range of strain rates. In the usual service condition of electronic devices, the strain rates of solder material are far less than 1.0 s
−1
at which the creep deformation is dominant, especially at higher working temperatures. However, the strain rate could range from 1.0 to 300 s
−1
under drop impact in electronic packaging structures, which is drawing more attention due to lack of experimental data, especially on dynamic mechanical properties of lead-free solder alloys. In extreme impact conditions, the solder material may experience even higher strain rates. As different mechanisms dominate the respective regime of strain rates, the developed constitutive model is calibrated to be applicable to most of the strain rate regimes by properly considering the coupled effect of creep and plasticity. Moreover, the parameters in the proposed model are defined with clear physical meanings and reasonably determined by regression to the published experimental studies. Lastly, the developed model is compared with other constitutive models from the literature, including the power-law equation for creep deformation at low strain rates and the Johnson–Cook model for plastic deformation at high strain rates. It is concluded that the proposed model is more generalized and capable of predicting uniaxial mechanical behaviour of SAC305 solder at low, medium and high strain rates with reasonable accuracy.
mRNA vaccines for COVID-19: what, why and how Park, Jung Woo; Lagniton, Philip N P; Liu, Yu ...
International journal of biological sciences,
01/2021, Letnik:
17, Številka:
6
Journal Article
Recenzirano
Odprti dostop
The Coronavirus disease-19 (COVID-19) pandemic, caused by severe acute respiratory syndrome coronavirus -2 (SARS-CoV-2), has impacted human lives in the most profound ways with millions of infections ...and deaths. Scientists and pharmaceutical companies have been in race to produce vaccines against SARS-CoV-2. Vaccine generation usually demands years of developing and testing for efficacy and safety. However, it only took less than one year to generate two mRNA vaccines from their development to deployment. The rapid production time, cost-effectiveness, versatility in vaccine design, and clinically proven ability to induce cellular and humoral immune response have crowned mRNA vaccines with spotlights as most promising vaccine candidates in the fight against the pandemic. In this review, we discuss the general principles of mRNA vaccine design and working mechanisms of the vaccines, and provide an up-to-date summary of pre-clinical and clinical trials on seven anti-COVID-19 mRNA candidate vaccines, with the focus on the two mRNA vaccines already licensed for vaccination. In addition, we highlight the key strategies in designing mRNA vaccines to maximize the expression of immunogens and avoid intrinsic innate immune response. We also provide some perspective for future vaccine development against COVID-19 and other pathogens.
A Ru-catalyzed direct oxidative cross-coupling reaction of acrylates was developed. It offers a straightforward and atom-economical protocol for the synthesis of functionalized (Z,E)-muconate ...derivatives in moderate to good yields with good stereo- and chemoselectivities. The conjugated muconates bearing differentiable terminal functionality can be selectively transformed into versatile synthetic intermediates widely used in organic synthesis.
Under mild reaction conditions with inexpensive cerium and nickel catalysts, easily accessible free alcohols can now be utilized as operationally simple and robust carbon pronucleophiles in selective ...C(sp3)–C(sp2) cross-couplings. Facilitated by automated high-throughput experimentation, sterically encumbered benzoate ligands have been identified for robust cerium complexes, enabling the synergistic cooperation of cerium catalysis in the emerging metallaphotoredox catalysis. A broad range of free alcohols and aromatic halides can be facilely employed in this transformation, representing a new paradigm for the C(sp3)–C(sp2) bond construction between free alcohols and aryl halides with the extrusion of formaldehyde. Moreover, mechanistic investigations have been conducted, leading to the identification of a tribenzoate cerium(III) complex as a viable intermediate.
Recent realization of high sodium‐ion conductivities (>10−2 S cm−1) in inorganic solid electrolytes (ISEs) at room temperature will certainly trigger a boom in all‐solid‐state sodium batteries ...(ASS‐SBs). However, their electrochemical stable windows and compatibility to high capacity/voltage electrodes are unsatisfactory. Developing ideal ISEs that deliver high Na+ ion conductivities, good electrochemical/chemical stability, and compatible electrode/ISE interface is key for the success of high‐performance ASS‐SBs. In this review, focus is mainly on the fundamentals and strategies to optimize ASS‐SB performances from the aspects of ISE and interface, and note that interfacial issues are also ISE‐related. The latest progress in ISEs, including fundamentals of the sodium‐ion conduction mechanism, key parameters dominating the Na+ ion conduction in terms of crystal structure, lattice dynamics, point defects, and grain boundaries, and prototyping strategies for cell design, are elaborated from the perspectives of material and defect chemistry. The key challenges and future opportunities are discussed, and rational solutions are provided.
This review discusses the fundamentals of sodium ionic conduction in inorganic solid electrolytes (ISEs), identifies the key parameters dominating the sodium ionic conduction, and proposes prototyping strategies for both solid electrolyte and full cell design, from the perspectives of materials and defect chemistry. The key challenges and future opportunities for all‐solid‐state sodium batteries using ISEs are also discussed in detail.
Biocatalytic cascade reactions using isolated stereoselective enzymes or whole cells in one‐pot processes lead to value‐added chiral products in a single workup. The concept has been restricted ...mainly to starting materials and intermediate products that are accepted by the respective wild‐type enzymes. In the present study, we exploited directed evolution as a means to create E. coli whole cells for regio‐ and stereoselective cascade sequences that are not possible using man‐made catalysts. The approach is illustrated using P450‐BM3 in combination with appropriate alcohol dehydrogenases as catalysts in either two‐, three‐, or four‐step cascade reactions starting from cyclohexane, cyclohexanol, or cyclohexanone, respectively, leading to either (R,R)‐, (S,S)‐, or meso‐cyclohexane‐1,2‐diol. The one‐pot conversion of cyclohexane into (R)‐ or (S)‐2‐hydroxycyclohexanone in the absence of ADH is also described.
Four steps in one pot: E. coli cells harboring P450‐BM3 mutants and appropriate alcohol dehydrogenases were obtained by directed evolution. Such cells enable one‐pot cascade reactions of cyclohexane with selective formation of all three stereoisomeric cyclohexane‐1,2‐diols.
Abstract Defects and microstructures have been utilized to effectively modulate electromagnetic (EM) wave absorption for mitigating electromagnetic pollution and stealth issues. However, precisely ...feasibly tailoring them still remains challenging. Here, by using a multilevel hollow cobalt sulfide embedded in a heteroatomic sulfur (S) ‐doped carbon aerogel, a preferential reaction strategy of modulating point defects and hollow microstructures via controllable S atoms migration is proposed to improve the EM wave absorption. S atoms contribute to the creation of hollow structures via Kirkendall effects, as well as inducing point defects in the carbon lattice through doping. More significantly, the mechanisms prioritizing the formation of hollow structures over defects have been discovered, with low‐velocity atomic migration primarily modulating the microstructure for interfacial polarization and impedance matching, and high‐velocity atom migration focused on introducing defects to achieve polarization and conductive loss. The resulting aerogel exhibits an exceptionally maximum reflection loss of −52.82 dB and an effective absorption bandwidth of 8.82 GHz, which far exceeds most of the currently reported materials. Experimental and theoretical approaches, including microwave heating, Tesla interaction, first principles, and far‐field simulation, are comprehensively employed to verify its absorption effect and mechanism. Furthermore, the combination of excellent infrared stealth and self‐cleaning properties opens up its potential applications in complex environments.
PDF
