Visible‐light‐induced radical decarboxylative functionalization of carboxylic acids and their derivatives has recently received considerable attention as a novel and efficient method to create CC ...and CX bonds. Generally, this visible‐light‐promoted decarboxylation process can smoothly occur under mild reaction conditions with a broad range of substrates and an excellent functional‐group tolerance. The radical species formed from the decarboxylation step can participate in not only single photocatalytic transformations, but also dual‐catalytic cross‐coupling reactions by combining photoredox catalysis with other catalytic processes. Recent advances in this research area are discussed herein.
Photo op: A novel functionalization reaction using visible‐light‐induced photoredox catalysis has recently been developed (see title). The formed radical species can participate in not only single photocatalytic transformations, but also dual‐catalytic reactions by combining photoredox catalysis with other catalytic methods. Recent advances in this research area are discussed herein.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
In the last few decades, topological phase.sup.1-11 has emerged as a new classification of matter states beyond the Ginzburg-Landau symmetry-breaking paradigm. The underlying global invariant is ...usually well characterized by integers, such as Chern numbers or winding numbers--the Abelian charges.sup.12-15. Very recently, researchers proposed the notion of non-Abelian topological charges.sup.16-19, which possess non-commutative and fruitful braiding structures with multiple (more than one) bandgaps tangled together. Here we experimentally observe the non-Abelian topological charges in a time-reversal and inversion-symmetric transmission line network. The quaternion-valued non-Abelian topological charges are clearly mapped onto an eigenstate-frame sphere. Moreover, we find a non-Abelian quotient relation that provides a global perspective on the distribution of edge/domain-wall states. Our work opens the door towards characterization and manipulation of non-Abelian topological charges, which may lead to interesting observables such as trajectory-dependent Dirac/Weyl node collisions in two-dimensional systems.sup.16,17,20, admissible nodal line configurations in three dimensions.sup.16,19,20, and may provide insight into certain strongly correlated phases of twisted bilayer graphene.sup.21.
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Molecular solar thermal (MOST) materials, which can efficiently capture solar energy and release it as heat on demand, are promising candidates for future personal thermal management (PTM) ...applications, preferably in the form of fabrics. However, developing MOST fabrics with high energy‐storage capacity and stable working performance remains a significant challenge because of the low energy density of the molecular materials and their leakage from the fabric. Here, an efficient and robust MOST fabric for PTM using azopyrazole‐containing microcapsules with a deep‐UV‐filter shell is reported. The MOST fabric, which can co‐harvest solar and thermal energy, achieves efficient photocharging and photo‐discharging (>90% photoconversion), a high energy density of 2.5 kJ m−2, and long‐term storage sustainability at month scale. Moreover, it can undergo multiple cycles of washing, rubbing, and recharging without significant loss of energy‐storage capacity. This MOST microcapsule strategy is easily used for the scalable production of a MOST fabric for solar thermal moxibustion. This achievement offers a promising route for the application of wearable MOST materials with high energy‐storage performance and robustness in PTM.
A novel MOST fabric with high energy‐storage capacity and robustness is demonstrated for personal thermal management (PTM). Based on a MOST microcapsule with deep‐UV‐filter shell and encapsulated azopyrazole molecules, the MOST fabric displays ideal energy‐storage density up to 2.5 kJ m−2 and high robustness in rechargeability, washing, and rubbing.
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Scale variation is one of the key challenges in object detection. In this work, we first present a controlled experiment to investigate the effect of receptive fields for scale variation in object ...detection. Based on the findings from the exploration experiments, we propose a novel Trident Network (TridentNet) aiming to generate scale-specific feature maps with a uniform representational power. We construct a parallel multi-branch architecture in which each branch shares the same transformation parameters but with different receptive fields. Then, we adopt a scale-aware training scheme to specialize each branch by sampling object instances of proper scales for training. As a bonus, a fast approximation version of TridentNet could achieve significant improvements without any additional parameters and computational cost compared with the vanilla detector. On the COCO dataset, our TridentNet with ResNet-101 backbone achieves state-of-the-art single-model results of 48.4 mAP. Codes are available at https://git.io/fj5vR.
We propose two nuclear- and L2,1-norm regularized 2D neighborhood preserving projection (2DNPP) methods for extracting representative 2D image features. 2DNPP extracts neighborhood preserving ...features by minimizing a Frobenius norm-based reconstruction error that is very sensitive noise and outliers in given data. To make the distance metric more reliable and robust, and encode the neighborhood reconstruction error more accurately, we minimize the nuclear- and L2,1-norm-based reconstruction error, respectively and measure it over each image. Technically, we propose two enhanced variants of 2DNPP, nuclear-norm-based 2DNPP and sparse reconstruction-based 2DNPP. Besides, to optimize the projection for more promising feature extraction, we also add the nuclear- and sparse L2,1-norm constraints on it accordingly, where L2,1-norm ensures the projection to be sparse in rows so that discriminative features are learnt in the latent subspace and the nuclear-norm ensures the low-rank property of features by projecting data into their respective subspaces. By fully considering the neighborhood preserving power, using more reliable and robust distance metric, and imposing the low-rank or sparse constraints on projections at the same time, our methods can outperform related state-of-the-arts in a variety of simulation settings.
Single-quantum emitters are an important resource for photonic quantum technologies, constituting building blocks for single-photon sources, stationary qubits, and deterministic quantum gates. Robust ...implementation of such functions is achieved through systems that provide both strong light-matter interactions and a low-loss interface between emitters and optical fields. Existing platforms providing such functionality at the single-node level present steep scalability challenges. Here, we develop a heterogeneous photonic integration platform that provides such capabilities in a scalable on-chip implementation, allowing direct integration of GaAs waveguides and cavities containing self-assembled InAs/GaAs quantum dots-a mature class of solid-state quantum emitter-with low-loss Si
N
waveguides. We demonstrate a highly efficient optical interface between Si
N
waveguides and single-quantum dots in GaAs geometries, with performance approaching that of devices optimized for each material individually. This includes quantum dot radiative rate enhancement in microcavities, and a path for reaching the non-perturbative strong-coupling regime.Effective use of single emitters in quantum photonics requires coherent emission, strong light-matter coupling, low losses and scalable fabrication. Here, Davanco et al. stride toward this goal by hybrid on-chip integration of Si3N4 waveguides and GaAs nanophotonic geometries with InAs quantum dots.
Spark plasma sintering (SPS), also known as pulsed electric current sintering (PECS) or field-assisted sintering technique (FAST), belongs to a class of powder metallurgy techniques. In SPS, the ...sample is simultaneously subjected to a uniaxial pressure and electrical current in a vacuum or protective atmosphere. Although the fundamental principles of this procedure were first proposed over 50 years ago, SPS acquired major importance only within the last 20 years. Scholars come to realize that SPS technique enables control of the powder surface condition, atomic diffusion behavior, and phase stability and crystal growth behavior, as well as accelerating densification of hard-to-sinter materials. This review summarizes the latest research findings with respect to experimental procedures, densification behaviors, microstructural characteristics, and mechanical properties of various traditional and novel materials synthesized using SPS, mainly highlighting the heating mechanisms in SPS and the effects induced by multi-physical fields on materials. In addition, influences of operating parameters containing current, voltage, and uniaxial pressure on product characteristics are reviewed for a wide range of materialsincluding hard-to-sinter materials, carbon-containing materials, nanocrystalline materials, non-equilibrium materials, gradient materials, interconnect materials, complex shape materials, and advanced functional materials.
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•Effects of current, electric fields and pressure on SPS processing and micro-mechanisms in materials are investigated.•The state-of-the-art concepts of SPS devices for R&D and industrial application are presented.•The common technological superiority and optimization mechanisms of applying SPS in every material system are illustrated.•Overview on the design, experiment and simulation of both structural and functional materials developed by SPS technique.
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Molecular photoswitches (e.g., azobenzenes) can reversibly interconvert between their thermodynamically stable and metastable isomers upon light irradiations. However, it remains challenging to ...integrate both high bidirectional photoconversion and long metastable‐state lifetime into a photoswitchable functionality. Here, we introduce pyrazolylazophenyl ethers (pzAzo ethers) as a class of azo photoswitches that provides quantitative (>98 %) trans–cis photoisomerization (365 nm light), near‐quantitative (95–96 %) reverse isomerization (532 nm light), and a long cis‐isomer half‐life of three months. They can be easily synthesized in high yields and readily functionalized at one or both sides with a broad scope of substituent groups. Molecular systems incorporating pzAzo ethers can be endowed with high responsiveness, robust reversibility, and long persistent metastable states. Such superior yet pragmatic azo switches hold high promise for upgraded photoregulation in many light‐responsive applications.
Great switches: Pyrazolylazophenyl ether‐based photoswitches integrate (near‐)quantitative photoisomerizations and a three‐months thermal half‐life, and they can be easily prepared and functionalized for incorporation into various chemical systems (see figure, PSS=photostationary state).
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We propose a type of elastic metamaterial comprising fluid-solid composite inclusions which can possess a negative shear modulus and negative mass density over a large frequency region. Such a ...material has the unique property that only transverse waves can propagate with a negative dispersion while longitudinal waves are forbidden. This leads to many interesting phenomena such as negative refraction, which is demonstrated by using a wedge sample and a significant amount of mode conversion from transverse waves to longitudinal waves that cannot occur on the interface of two natural solids.
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Following the progress on mono‐heteroaryl azo switches (Het‐N=N‐Ph), a few bis‐heteroaryl azo switches (Het‐N=N‐Het) have been studied recently, whereas the nonsymmetric bis‐heteroaryl ones ...(Het1‐N=N‐Het2) that can combine the respective merits of each heterocycle, have received little attention. Here we report thiazolylazopyrazoles as nonsymmetric bis‐heteroaryl azo switches that combine the visible‐light switching character of the thiazole ring and the ease of o‐substitution of the pyrazole ring. Thiazolylazopyrazoles can achieve (near‐)quantitative visible‐light isomerization in both directions and long Z‐isomer thermal half‐lives of several days. In contrast to the drastically destabilizing effect of o‐methylation, o‐carbonylation of the pyrazole ring can remarkably stabilize Z isomers by inducing attractive intramolecular interactions (dispersion, C−H⋅⋅⋅N bond, and lone‐pair⋅⋅⋅π interaction). Our work highlights the importance of the rational combination of two heterocycles and suitable structural substitution in developing bis‐heteroaryl azo switches.
Thiazolylazopyrazoles are developed as nonsymmetric bis‐heteroaryl azo switches that achieve (near‐)quantitative isomerization in both directions by o‐substitution. The Z‐isomer half‐lives can be prolonged to several days through inducing attractive intramolecular interactions to an o‐carbonyl group on the pyrazole. In contrast, o‐methylation of the pyrazole results in a destabilizing effect.
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