Platinum‐catalyzed formal 5+2 and 4+2 annulations of isoxazoles with heterosubstituted alkynes enabled the atom‐economical synthesis of valuable 1,3‐oxazepines and 2,5‐dihydropyridines, respectively. ...Importantly, this Pt catalysis not only led to unique reactivity dramatically divergent from that observed under Au catalysis, but also proceeded via unprecedented α‐imino platinum carbene intermediates.
Gold's deviant relative: Platinum‐catalyzed formal 5+2 and 4+2 annulations of isoxazoles and heterosubstituted alkynes provided valuable 1,3‐oxazepines and 2,5‐dihydropyridines (see scheme). This reactivity deviates dramatically from that observed under gold catalysis and involves the generation of an α‐imino platinum carbene. A computational study provided evidence for the proposed mechanism of this unusual tandem sequence.
Organic–inorganic metal halide perovskite solar cells (PSCs) have achieved certified power conversion efficiency (PCE) of 25.2% with complex compositional and bandgap engineering. However, the ...thermal instability of methylammonium (MA) cation can cause the degradation of the perovskite film, remaining a risk for the long‐term stability of the devices. Herein, a unique method is demonstrated to fabricate highly phase‐stable perovskite film without MA by introducing cesium chloride (CsCl) in the double cation (Cs, formamidinium) perovskite precursor. Moreover, due to the suboptimal bandgap of bromide (Br−), the amount of Br− is regulated, leading to high power conversion efficiency. As a result, MA‐free perovskite solar cells achieve remarkable long‐term stability and a PCE of 20.50%, which is one of the best results for MA‐free PSCs. Moreover, the unencapsulated device retains about 80% of the original efficiencies after a 1000 h aging study. These results provide a feasible approach to enhance solar cell stability and performance simultaneously, paving the way for commercializing PSCs.
A highly phase‐stable perovskite film without the methylammonium cation is fabricated by introducing cesium chloride in the double cation Cs, formamidinium perovskite precursor, leading to high power conversion efficiency of 20.5% and remarkable long‐term stability. The unencapsulated perovskite solar cell retains about 80% of its initial efficiency after a 1000 h aging study, demonstrating a feasible approach to enhance solar cell efficiency and stability simultaneously.
As there is a rapid development of robotics in the field of automation engineering, ego-motion estimation has become a most challenging task. In this review, we presented a model to help describe the ...PnP problems, and introduced two most common solutions. The P3P solution is the smallest subset of control points that yields a finite number of solutions. The EPnP solution is to reduce the complexity by expressing the n 3D points as a weighted sum of four virtual control points. The former solution is widely applied while there are 3 pairs of corresponding points in the problem. However, in most real cases, the latter is more used.
AbstractObjectiveTo study the clinical characteristics of patients in Zhejiang province, China, infected with the 2019 severe acute respiratory syndrome coronavirus 2 (SARS-Cov-2) responsible for ...coronavirus disease 2019 (covid-2019).DesignRetrospective case series.SettingSeven hospitals in Zhejiang province, China.Participants62 patients admitted to hospital with laboratory confirmed SARS-Cov-2 infection. Data were collected from 10 January 2020 to 26 January 2020.Main outcome measuresClinical data, collected using a standardised case report form, such as temperature, history of exposure, incubation period. If information was not clear, the working group in Hangzhou contacted the doctor responsible for treating the patient for clarification.ResultsOf the 62 patients studied (median age 41 years), only one was admitted to an intensive care unit, and no patients died during the study. According to research, none of the infected patients in Zhejiang province were ever exposed to the Huanan seafood market, the original source of the virus; all studied cases were infected by human to human transmission. The most common symptoms at onset of illness were fever in 48 (77%) patients, cough in 50 (81%), expectoration in 35 (56%), headache in 21 (34%), myalgia or fatigue in 32 (52%), diarrhoea in 3 (8%), and haemoptysis in 2 (3%). Only two patients (3%) developed shortness of breath on admission. The median time from exposure to onset of illness was 4 days (interquartile range 3-5 days), and from onset of symptoms to first hospital admission was 2 (1-4) days.ConclusionAs of early February 2020, compared with patients initially infected with SARS-Cov-2 in Wuhan, the symptoms of patients in Zhejiang province are relatively mild.
Summary
Spray‐induced gene silencing (SIGS) is an innovative strategy for crop protection. However, the mechanism of SIGS is not known. Here, we first demonstrate that secondary small interfering RNA ...(siRNA) amplification limits the application of SIGS. A myosin5 gene (Myo5) was chosen as the target of SIGS in an agronomically important pathogen—Fusarium asiaticum. Five segments corresponding to the different regions of the Myo5 gene were found to efficiently silence Myo5, resulting in cell wall defects, life cycle disruption and virulence reduction. Myo5‐8 (one of the Myo5 segments) induced sequence‐specific RNA interference (RNAi) activity in F. asiaticum, F. graminearum, F. tricinctum and F. oxysporum, but not in other fungi, in vitro. Remarkably, the silencing of Myo5 lasted for only 9 h unless the double‐stranded RNA (dsRNA) was continuously supplied, because F. asiaticum is unable to maintain siRNA amplification. After spraying on plants, dsRNAs were more efficiently taken up via the wounded surface. The antifungal activity of dsRNAs taken up by plant cells was higher and longer lasting than that dried onto the plant surface. In contrast with dsRNAs in fungi, dsRNAs in plant cells could efficiently turn into substantial siRNAs via secondary amplification machinery. Our findings provide new implications to develop SIGS as a mainstream disease control strategy against Fusarium and other fungi.
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•Proton conductive carboxylate-based MOFs were reviewed.•Aliphatic carboxylate-based and aromatic carboxylate-based MOFs were included.•Proton conductivity and conducting mechanism ...were discussed.•The future development trend of such MOFs is prospected.
As a significant type of crystalline solid proton conducting materials, metal–organic frameworks (MOFs) have been paid great attention and pursued by researchers. In this review, we will mainly summarize the proton conduction explorations of MOFs based on carboxylate ligands (including aliphatic carboxylate-based and aromatic carboxylate-based MOFs) from the aspects of synthetic strategies, stability, proton conductive properties and mechanism, application, etc. Finally, on the basis of summarization of literature and our own research on proton conduction, development prospects and challenges for such conductive materials in the future are highlighted.
Despite the excellent photovoltaic properties achieved by perovskite solar cells at the laboratory scale, hybrid perovskites decompose in the presence of air, especially at high temperatures and in ...humid environments. Consequently, high‐efficiency perovskites are usually prepared in dry/inert environments, which are expensive and less convenient for scale‐up purposes. Here, a new approach based on the inclusion of an in situ polymerizable ionic liquid, 1,3‐bis(4‐vinylbenzyl)imidazolium chloride (bvbimCl), is presented, which allows perovskite films to be manufactured under humid environments, additionally leading to a material with improved quality and long‐term stability. The approach, which is transferrable to several perovskite formulations, allows efficiencies as high as 17% for MAPbI3 processed in air % relative humidity (RH) ≥30 (from an initial 15%), and 19.92% for FAMAPbI3 fabricated in %RH ≥50 (from an initial 17%), providing one of the best performances to date under similar conditions.
The inclusion of a novel in situ polymerizable ionic liquid, 1,3‐bis(4‐vinylbenzyl)imidazolium chloride (bvbimCl), allows perovskite films to be manufactured under humid environments, conferring improved materials quality, higher power conversion efficiency, and long‐term stability.
In this paper, we propose an approach to realize substrate integrated waveguide (SIW)-based leaky-wave antennas (LWAs) supporting continuous beam scanning from backward to forward above the cutoff ...frequency. First, through phase delay analysis, it was found that SIWs with straight transverse slots support backward and forward radiation of the -1-order mode with an open-stopband (OSB) in between. Subsequently, by introducing additional longitudinal slots as parallel components, the OSB can be suppressed, leading to continuous beam scanning at least from -40° through broadside to 35°. The proposed method only requires a planar structure and obtains less dispersive beam scanning compared with a composite right/left-handed (CRLH) LWA. Both simulations and measurements verify the intended beam scanning operation while verifying the underlying theory.
Biochars are increasingly recognized as environmentally friendly and cheap remediation agents for soil pollution. The roles of silicon in biochars and interactions between silicon and carbon have ...been neglected in the literature to date, while the transformation, morphology, and dissolution of silicon in Si-rich biochars remain largely unaddressed. In this study, Si-rich biochars derived from rice straw were prepared under 150–700 °C (named RS150-RS700). The transformation and morphology of carbon and silicon in biochar particles were monitored by FTIR, XRD, and SEM-EDX. With increasing pyrolytic temperature, silicon accumulated, and its speciation changed from amorphous to crystalline matter, while the organic matter evolved from aliphatic to aromatic. For rice straw biomass containing amorphous carbon and amorphous silicon, dehydration (<250 °C) made silicic acid polymerize, resulting in a closer integration of carbon and silicon. At medium pyrolysis temperatures (250–350 °C), an intense cracking of carbon components occurred, and, thus, the silicon located in the inside tissue was exposed. At high pyrolysis temperatures (500–700 °C), the biochar became condensed due to the aromatization of carbon and crystallization of silicon. Correspondingly, the carbon release in water significantly decreased, while the silicon release somewhat decreased and then sharply increased with pyrolytic temperature. Along with SEM-EDX images of biochars before and after water washing, we proposed a structural relationship between carbon and silicon in biochars to explain the mutual protection between carbon and silicon under different pyrolysis temperatures, which contribute to the broader understanding of biochar chemistry and structure. The silicon dissolution kinetics suggests that high Si biochars could serve as a novel slow release source of biologically available Si in low Si agricultural soils.
High hardness (TiZr)C ceramic with dislocation networks Guo, Xiao‐Jie; Xin, Xiao‐Ting; Bao, Weichao ...
Journal of the American Ceramic Society,
September 2022, 2022-09-00, 20220901, Letnik:
105, Številka:
9
Journal Article
Recenzirano
Raising the configurational entropy in a solid solution ceramic is regarded as a promising strategy to improve the mechanical properties of ceramics, especially when five or more elements are mixed ...to form so‐called high‐entropy ceramics. However, in this study, we report that the binary (TiZr)C solid solution ceramics can demonstrate high hardness comparable or even superior to high‐entropy ceramics. Followed by a carbothermal reduction synthesis of carbide powders, the bulk ceramics were synthesized by hot pressing. Via increasing the hot pressing temperature to 2200°C, a full solid solution of equimolar (TiZr)C was obtained in contrast to phase separation at lower sintering temperatures, for example, 2000 and 2100°C. The dislocation networks are observed in the single‐phase (TiZr)C ceramic and should be the product of competition between enthalpy and entropy in a binary full solid solution. These defects finally contribute to the high nano‐hardness of 41.9 ± 1.4 GPa (H) and the Vickers hardness of 22.0 ± 0.6 GPa (HV at 49 N).
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