In this letter, a deep learning framework for direction of arrival (DOA) estimation is developed. We first show that the columns of the array covariance matrix can be formulated as under-sampled ...noisy linear measurements of the spatial spectrum. Then, a deep convolution network (DCN) that learns the inverse transformation from large training dataset is introduced. In contrast to traditional sparsity-inducing methods with computationally complex iterations, the proposed DCN-based framework could efficiently obtain DOA estimates in near real time. Moreover, the utilization of the sparsity prior improves DOA estimation performance compared to existing deep learning based methods. Simulation results have demonstrated the superiority of the proposed method in both DOA estimation precision and computation efficiency especially when SNR is low.
Although much effort has been spent on the enantioselective synthesis of tertiary alkyl fluorides, the synthesis of compounds containing such a stereogenic center within an array of stereocenters, ...particularly two vicinal ones, remains a synthetic challenge, and no method to control the configuration of each stereogenic center independently has been reported. We describe a strategy to achieve such a stereodivergent synthesis of vicinal stereogenic centers, one containing a fluorine atom, by forming the connecting carbon–carbon bond with a catalyst system comprising an iridium complex that controls the configuration at the electrophilic carbon and a copper catalyst that controls the configuration at the nucleophilic fluorine-containing carbon. These reactions occur with alkyl- and aryl-substituted allylic esters and the unstabilized enolates of azaaryl ketones, esters, and amides in high yield, diastereoselectivity, and enantioselectivity (generally >90% yield, >20:1 dr, 97−99% ee). Access to all four stereoisomers of products demonstrates the precise control of the two configurations independently. This methodology extends to the stereodivergent construction of vicinal quaternary and tertiary stereocenters in similarly high yield and selectivity. DFT calculations uncover the origin of stereoselectivity of copper enolate in allylic substitution.
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IJS, KILJ, NUK, PNG, UL, UM
Tunable terahertz (THz) functional devices have exhibited superior performances due to the use of active materials, such as liquid crystals, graphene, and semiconductors. However, the tunable range ...of constitutive parameters of materials is still limited, which leads to the low modulation depth of THz devices. Here, we demonstrate a broadband tunable THz absorber based on hybrid vanadium dioxide (VO
) metamaterials. Unlike other phase change materials, VO
exhibits an insulator-to-metal transition characteristic and the conductivity can be increased by 4-5 orders of magnitude under external stimulus including electric fields, optical, and thermal pumps. Based on the unique transition character of VO
, the maximum tunable range of the proposed absorber can be realized from 5% to 100% by an external thermal excitation. Meanwhile, an absorption greater than 80% in a continuous range with a bandwidth about 2.0 THz can be obtained when VO
is in its metal phase at high temperature. Furthermore, the absorber is insensitive to the incident angle up to 50° and such a broadband THz absorber can be used in applications including imaging, modulating, cloaking, and so on.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Herein we describe a mild method for the dual C(sp3)−H bond functionalization of saturated nitrogen‐containing heterocycles through a sequential visible‐light photocatalyzed dehydrogenation/2+2 ...cycloaddition procedure. As a complementary approach to the well‐established use of iminium ion and α‐amino radical intermediates, the elusive cyclic enamine intermediates were effectively generated by photoredox catalysis under mild conditions and efficiently captured by acetylene esters to form a wide array of bicyclic amino acid derivatives, thus enabling the simultaneous functionalization of two vicinal C(sp3)−H bonds.
A great team: A dual C(sp3)−H bond functionalization strategy was developed by merging dehydrogenation under visible‐light photocatalysis with a 2+2 cycloaddition reaction in a sequential process. This method enabled cyclobutene rings to be fused to various saturated nitrogen‐containing heterocycles to produce a series of cyclic amino acid derivatives.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Electronically matched nucleophilic 1,6‐conjugate addition has been well studied and widely applied in synthetic areas. In contrast, nucleophilic 1,5‐conjugate addition represents an electronically ...forbidden process and is considered unfeasible. Here, we describe modular protocols for 1,5‐conjugate addition reactions via palladium hydride catalysis. Both palladium and synergistic Pd/organocatalyst systems are developed to catalyze 1,5‐conjugate reaction, followed by inter‐ or intramolecular 3+2 cyclization. A migratory 1,5‐addition protocol is established to corroborate the feasibility of this umpolung concept. The 1,5‐addition products are conveniently transformed into a series of privileged enantioenriched motifs, including polysubstituted tetrahydrofuran, dihydrofuran, cyclopropane, cyclobutane, azetidine, oxetane, thietane, spirocycle and bridged rings. Preliminary mechanistic studies corroborate the involvement of palladium hydride catalysis.
An unconventional umpolung protocol was demonstrated for novel 1,5‐conjugate additions via palladium hydride catalyst. Three catalytic reaction modes including 1,5‐addition cascade with inter‐ and intramolecular 3+2 cyclization and migratory 1,5‐addition were established via palladium or palladium/organo‐cocatalysis.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Advocacy of the use of facemasks by the public as a measure against the spread of COVID‐19 is controversial, with some healthcare professionals arguing that the use of a face mask may increase the ...rate at which people touch their faces, due to readjusting the mask. We assessed the facial touching behaviour of bus passengers in China before and after the outbreak of COVID‐19 and found that wearing a face mask does not increase the number of hand‐face contacts and is likely, therefore, to have a positive beneficial effect on suppressing the spread of COVID‐19 within populations when used in conjunction with social distancing measures.
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BFBNIB, DOBA, FZAB, GIS, IJS, IZUM, KILJ, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBMB, UILJ, UKNU, UL, UM, UPUK
Chain walking has been an efficient route to realize the functionalization of inert C(sp3)−H bonds, but this strategy is limited to mono‐olefin migration and functionalization. Herein, we demonstrate ...the feasibility of tandem directed simultaneous migrations of remote olefins and stereoselective allylation for the first time. The adoption of palladium hydride catalysis and secondary amine morpholine as solvent is critical for achieving high substrate compatibility and stereochemical control with this method. The protocol is also applicable to the functionalization of three vicinal C(sp3)−H bonds and thus construct three continuous stereocenters along a propylidene moiety via a short synthetic process. Preliminary mechanistic experiments corroborated the design of simultaneous walking of remote dienes.
The enantioselective migratory allylation of remote dienes via palladium‐catalyzed simultaneous/directed chain walking is reported. The transformation provides a potential route to achieving stereoselective functionalization of multiple continuous C(sp3)−H bonds.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Iron homeostasis disturbance has been implicated in Alzheimer's disease (AD), and excess iron exacerbates oxidative damage and cognitive defects. Ferroptosis is a nonapoptotic form of cell death ...dependent upon intracellular iron. However, the involvement of ferroptosis in the pathogenesis of AD remains elusive. Here, we report that ferroportin1 (Fpn), the only identified mammalian nonheme iron exporter, was downregulated in the brains of APPswe/PS1dE9 mice as an Alzheimer's mouse model and Alzheimer's patients. Genetic deletion of Fpn in principal neurons of the neocortex and hippocampus by breeding Fpn
mice with NEX-Cre mice led to AD-like hippocampal atrophy and memory deficits. Interestingly, the canonical morphological and molecular characteristics of ferroptosis were observed in both Fpn
and AD mice. Gene set enrichment analysis (GSEA) of ferroptosis-related RNA-seq data showed that the differentially expressed genes were highly enriched in gene sets associated with AD. Furthermore, administration of specific inhibitors of ferroptosis effectively reduced the neuronal death and memory impairments induced by Aβ aggregation in vitro and in vivo. In addition, restoring Fpn ameliorated ferroptosis and memory impairment in APPswe/PS1dE9 mice. Our study demonstrates the critical role of Fpn and ferroptosis in the progression of AD, thus provides promising therapeutic approaches for this disease.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
In this letter, we propose a coherent support vector regression (SVR) scheme to address the wideband direction of arrival (DOA) estimation problem. This learning-based method deals with wideband DOA ...estimation by treating it as a function approximation issue. The proposed approach first decomposes the wideband array outputs into several narrowband components, then approximates the functional relationship between the decomposed narrowband data and the DOA with coherent SVR scheme through training. The trained function is then capable of estimating the DOA when wideband signal with unknown impinging direction arrives. We prove the effectiveness and superiority of the presented method by simulation experiments. Simulation results show that the new technique has a better performance in terms of estimation errors than the conventional broadband DOA estimation method, especially in demanding scenarios with low SNR and limited snapshots. Moreover, the proposed approach also relaxes the unambiguous array element-spacing restrictions, i.e., it has extended the frequency range of wideband signals where direction finding without angle ambiguity is achievable.
The enantioselective construction of carbon-heteroatom and carbon-carbon bonds that are alpha to ketones leads to the formation of substructures that are ubiquitous in natural products, ...pharmaceuticals and agrochemicals. Traditional methods to form such bonds have relied on combining ketone enolates with electrophiles. Reactions with heteroatom-based electrophiles require special reagents in which the heteroatom, which is typically nucleophilic, has been rendered electrophilic by changes to the oxidation state. The resulting products usually require post-synthetic transformations to unveil the functional group in the final desired products. Moreover, different catalytic systems are typically required for the reaction of different electrophiles. Here, we report a strategy for the formal enantioselective α-functionalization of ketones to form products containing a diverse array of substituents at the alpha position with a single catalyst. This strategy involves an unusual reversal of the role of the nucleophile and electrophile to form C-N, C-O, C-S and C-C bonds from a series of masked ketone electrophiles and a wide range of conventional heteroatom and carbon nucleophiles catalysed by a metallacyclic iridium catalyst.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
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