The role of North Pacific bomb cyclones in the onset of January 2021 sudden stratospheric warming (SSW) is examined by conducting a set of numerical model experiments. The control simulation, ...initialized 10 days before the SSW onset, successfully reproduces the SSW. As this event is preceded by the bomb cyclones in the North Pacific, their impact is tested by initializing the model without them. This sensitivity experiment shows much weaker polar‐vortex deceleration than the control simulation, resulting in no distinct SSW onset. This difference is attributable to the dampened constructive linear interference between the climatological wave and the cyclone‐related wavenumber‐one anomaly in the sensitivity experiment. It weakens the vertical propagation of wavenumber‐one wave into the stratosphere, thereby reducing wave breaking in the polar stratosphere. This result suggests that bomb cyclones should be considered for better understanding SSW and improving its predictability.
Plain Language Summary
Sudden stratospheric warming (SSW) is a dramatic event characterized by abrupt warming in the polar stratosphere. During this event, the eastward winds encircling the polar stratosphere change to westward winds, due to the breaking of the upward‐propagating planetary‐scale waves. Since the SSW is often followed by unusual weather events (e.g., cold surges), an accurate prediction of SSW is important for a better weather prediction. Here, we examine the role of the rapidly developing North Pacific cyclones in initiating the 2021 SSW. A set of numerical model experiments show that without cyclones, the 2021 SSW is not initiated due to the reduced breaking of the upward‐propagating planetary‐scale waves. This result suggests that the rapidly developing North Pacific cyclones should be considered for better understanding SSW and improving its predictability.
Key Points
The 2021 SSW is successfully reproduced by a model initialized 10 days before the stratospheric warming (SSW)
The model initialized without the North Pacific bomb cyclone does not simulate the 2021 SSW
Removing the North Pacific bomb cyclone reduces the k = 1 wave propagation into the stratosphere, reducing wave breaking in the stratosphere
Abstract
Herein, we report the divergent synthesis of quinolines and quinolones
via
a transfer hydrogenative condensation of
ortho
‐nitrobenzyl alcohols in one step. The reaction proceeded using the ...cyclopentadienone iron complex without any additional redox reagents. After transfer hydrogenation between
ortho
‐nitrobenzyl alcohols and secondary alcohols, the subsequent Friedländer annulation affords polysubstituted quinoline products in 22–90% (39 examples). The developed method was also applied to synthesize quinolones by using primary alcohols instead of secondary alcohols (12 examples). The obtained quinoline products were converted into several drug candidates to demonstrate its synthetic potential.
With the rapid advances in wearable electronics, the research on carbon-based and/or organic materials and devices has become increasingly important, owing to their advantages in terms of cost, ...weight, and mechanical deformability. Here, we report an effective material and device design for an integrative wearable cardiac monitor based on carbon nanotube (CNT) electronics and voltage-dependent color-tunable organic light-emitting diodes (CTOLEDs). A p-MOS inverter based on four CNT transistors allows high amplification and thereby successful acquisition of the electrocardiogram (ECG) signals. In the CTOLEDs, an ultrathin exciton block layer of bis2-(diphenylphosphino)phenylether oxide is used to manipulate the balance of charges between two adjacent emission layers, bis2-(4,6-difluorophenyl)pyridinato-C 2,N(picolinato)iridium(III) and bis(2-phenylquinolyl-N,C(2′))iridium(acetylacetonate), which thereby produces different colors with respect to applied voltages. The ultrathin nature of the fabricated devices supports extreme wearability and conformal integration of the sensor on human skin. The wearable CTOLEDs integrated with CNT electronics are used to display human ECG changes in real-time using tunable colors. These materials and device strategies provide opportunities for next generation wearable health indicators.
Rhizolutin (1) was discovered as a natural product of ginseng‐rhizospheric Streptomyces sp. WON17. Its structure features an unprecedented 7/10/6‐tricyclic dilactone carbon skeleton composed of ...dimethylcyclodecatriene flanked by a 7‐membered and a 6‐membered lactone ring based on spectroscopic analysis. During an unbiased screening of natural product libraries, this novel compound was found to dissociate amyloid‐β (Aβ) plaques and tau tangles, which are key pathological hallmarks of Alzheimer's disease (AD). Rhizolutin treatment of APP/PS1 double transgenic mice with AD significantly dissociated hippocampal plaques. In vitro, rhizolutin substantially decreased Aβ‐induced apoptosis and inflammation in neuronal and glial cells. Our findings introduce a unique chemical entity that targets Aβ and tau concurrently by mimicking misfolded protein clearance mechanisms of immunotherapy, which is prominently investigated in clinical trials.
Rhizolutin was discovered from a ginseng‐rhizospheric Streptomyces strain and structurally characterized as an unprecedented 7/10/6‐tricyclic dilactone based on spectroscopic analysis and chemical derivatizations. Rhizolutin was found to dissociate Aβ and tau aggregates and reduced Alzheimer's disease (AD)‐like pathology in APP/PS1 transgenic mice.
The iron-catalyzed hydrogen transfer strategy has been applied to the redox condensation of o-hydroxynitrobenzene with alcohol, leading to the formation of benzoxazole derivatives. A wide range of ...2-substituted benzoxazoles were synthesized in good to excellent yields without the addition of an external redox agent. A series of control experiments provided a plausible mechanism. Furthermore, the reaction system was successfully extended to the synthesis of benzothiazoles and benzimidazoles.
Systematic inactivation of nonribosomal peptide synthetase (NRPS) domains and translocation of the thioesterase (TE) domain revealed several unprecedented nonlinear NRPS assembly processes during the ...biosynthesis of the cyclodepsipeptide WS9326A in Streptomyces sp. SNM55. First, two sets of type ΙΙ TE (TEΙΙ)‐like enzymes mediate the shuttling of activated amino acids between two sets of stand‐alone adenylation (A)‐thiolation (T) didomain modules and an “A‐less” condensation (C)‐T module with distinctive specificities and flexibilities. This was confirmed by the elucidation of the affinities of the A‐T didomains for the TEΙΙs and its structure. Second, the C‐T didomain module operates iteratively and independently from other modules in the same protein to catalyze two chain elongation cycles. Third, this biosynthetic pathway includes the first example of module skipping, where the interpolated C and T domains are required for chain transfer.
Systematic manipulation of the nonribosomal peptide synthetase (NRPS) domains in combination with elucidation of the interactions between the unique domains and structure revealed several hitherto unprecedented nonlinear NRPS assembly processes during the biosynthesis of cyclodepsipeptide WS9326A.
Herein, we present the iron-catalyzed oxidative cyclization of alcohol/methyl arene with 2-amino styrene to synthesize polysubstituted quinoline. Low-oxidation level substrates such as alcohols and ...methyl arenes are converted to aldehydes in the presence of an iron catalyst and di-t-butyl peroxide. Then, the quinoline scaffold is synthesized through imine condensation/radical cyclization/oxidative aromatization. Our protocol showed a broad substrate scope, and various functionalization and fluorescence applications of quinoline products demonstrated its synthetic ability.
Herein, we describe novel iron-catalyzed transfer hydrogenation between alcohols and 1-(2-nitrophenyl)pyrroles for the synthesis of pyrrolo1,2-αquinoxalines. The tricarbonyl (η4-cyclopentadienone) ...iron complex catalyzed the oxidation of alcohols and the reduction of nitroarenes, and the corresponding aldehydes and aniline were generated in situ. The resulting Pictet–Spengler-type annulation/oxidation completed the quinoxaline structure formation. The protocol tolerated various kinds of functional groups and provided 29 samples of 4-substituted pyrrolo1,2-αquinoxalines. The developed method was also applied for the synthesis of additional polyheterocycles.
α-Alkyl and α-olefin nitriles are very important for organic synthesis and medicinal chemistry. However, different types of catalysts are employed to achieve either α-alkylation of nitriles by ...borrowing hydrogen or α-olefination by dehydrogenative coupling methods. Designing and developing high-performance earth-abundant catalysts that can procure different products from the same starting materials remain a great challenge. Herein, we report an iron(0) catalyst system that achieves chemoselectivity between borrowing hydrogen and dehydrogenative coupling protocols by simply changing the base. A broad range of nitriles and alcohols, including benzylic, linear aliphatic, cycloaliphatic, heterocyclic, and allylic alcohols, were selectively and efficiently converted to the corresponding products. Mechanistic studies reveal that the reaction mechanism proceeds through a dehydrogenative pathway. This iron catalytic protocol is environmentally benign and atom-efficient with the liberation of H2 and H2O as green byproducts.
