Recently, short online videos have been highly recognized by video market users and have developed rapidly. This study aims to explore why users enjoy watching and sharing short online videos by ...applying the theory of flow experience. Previous research has extensively examined traditional video arts such as TV and movies and text or image based, while research on short online videos has increased only in recent years. To improve the precision and comprehensiveness of the research, social influence is also used as a variable. This study takes the short video representative platform DouYin as a case study and the Chinese user market as the background. Through questionnaires, 406 users' data about short online video experiences were collected. After statistical analysis, the study finds that flow experience has a significant impact on participative behaviour and sharing behaviour for short online videos. According to further analyses, the flow experience, social norms, perceived critical mass and participative and sharing behaviour constitute three groups of mediating relationships. Finally, the discussion of the research results provides help to broaden the academic scope of the flow experience and video art, improve the short online video platform environment, and upgrade short online video services.
The classification and lattice model construction of symmetry-protected topological (SPT) phases in interacting fermion systems are very interesting but challenging. In this paper, we give a ...systematic fixed-point wave function construction of fermionic SPT (FSPT) states for generic fermionic symmetry groupGf=Z2f×ω2Gbwhich is a central extension of bosonic symmetry groupGb(may contain time-reversal symmetry) by the fermion parity symmetry groupZ2f={1,Pf}. Our construction is based on the concept of an equivalence class of finite-depth fermionic symmetric local unitary transformations and decorating symmetry domain wall picture, subjected to certain obstructions. We also discuss the systematical construction and classification of boundary anomalous SPT states which leads to a trivialization of the corresponding bulk FSPT states. Thus, we conjecture that the obstruction-free and trivialization-free constructions naturally lead to a classification of FSPT phases. Each fixed-point wave function admits an exactly solvable commuting-projector Hamiltonian. We believe that our classification scheme can be generalized to point and space group symmetry as well as continuum Lie group symmetry.
Dearomatization reactions provide rapid access to structurally complex three-dimensional molecules from simple aromatic compounds. Plenty of reports have demonstrated their utilities in the synthesis ...of natural products, medicinal chemistry, and materials science in the last decades. Recently, visible-light mediated photocatalysis has emerged as a powerful tool to promote many kinds of transformations. The dearomatization reactions induced by visible-light have also made significant progress during the past several years. This review provides an overview of visible-light induced dearomatization reactions classified based on the manner in which aromaticity is disrupted.
This review provides an overview of visible-light induced dearomatization reactions classified based on the manner in which aromaticity is disrupted.
The classification and construction of symmetry-protected topological (SPT) phases in interacting boson and fermion systems have become a fascinating theoretical direction in recent years. It has ...been shown that (generalized) group cohomology theory or cobordism theory gives rise to a complete classification of SPT phases in interacting boson or spin systems. The construction and classification of SPT phases in interacting fermion systems are much more complicated, especially in three dimensions. In this work, we revisit this problem based on an equivalence class of fermionic symmetric local unitary transformations. We construct very general fixed-point SPT wave functions for interacting fermion systems. We naturally reproduce the partial classifications given by special group supercohomology theory, and we show that with an additionalB˜H2(Gb,Z2)structure the so-called obstruction-free subgroup ofH2(Gb,Z2), a complete classification of SPT phases for three-dimensional interacting fermion systems with a total symmetry groupGf=Gb×Z2fcan be obtained for unitary symmetry groupGb. We also discuss the procedure for deriving a general group supercohomology theory in arbitrary dimensions.
Symmetry-protected topological (SPT) phases are bulk-gapped quantum phases with symmetries, which have gapless or degenerate boundary states as long as the symmetries are not broken. The SPT phases ...in free fermion systems, such as topological insulators, can be classified; however, it is not known what SPT phases exist in general interacting systems. We present a systematic way to construct SPT phases in interacting bosonic systems. Just as group theory allows us to construct 230 crystal structures in three-dimensional space, we use group cohomology theory to systematically construct different interacting bosonic SPT phases in any dimension and with any symmetry, leading to the discovery of bosonic topological insulators and superconductors.
To investigate the biomechanical effects of the lumbar posterior complex on the adjacent segments after posterior lumbar interbody fusion (PLIF) surgeries.
A finite element model of the L1-S1 segment ...was modified to simulate PLIF with total laminectomy (PLIF-LAM) and PLIF with hemilaminectomy (PLIF-HEMI) procedures. The models were subjected to a 400N follower load with a 7.5-N.m moment of flexion, extension, torsion, and lateral bending. The range of motion (ROM), intradiscal pressure (IDP), and ligament force were compared.
In Flexion, the ROM, IDP and ligament force of posterior longitudinal ligament, intertransverse ligament, and capsular ligament remarkably increased at the proximal adjacent segment in the PLIF-LAM model, and slightly increased in the PLIF-HEMI model. There was almost no difference for the ROM, IDP and ligament force at L5-S1 level between the two PLIF models although the ligament forces of ligamenta flava remarkably increased compared with the intact lumbar spine (INT) model. For the other loading conditions, these two models almost showed no difference in ROM, IDP and ligament force on the adjacent discs.
Preserved posterior complex acts as the posterior tension band during PLIF surgery and results in less ROM, IDP and ligament forces on the proximal adjacent segment in flexion. Preserving the posterior complex during decompression can be effective on preventing adjacent segment degeneration (ASD) following PLIF surgeries.
Dearomatization of indoles provides efficient synthetic routes for substituted indolines. In most cases, indoles serve as nucleophiles. Reported here is an asymmetric dearomatization reaction of ...indole derivatives that function as electrophiles. The combination of a photocatalyst and chiral phosphoric acid open to air unlocks the umpolung reactivity of indoles, enabling their dearomatization with N‐hydroxycarbamates as nucleophiles. A variety of fused indolines bearing intriguing oxy‐amines were constructed in excellent yields with moderate to high enantioselectivities. Mechanistic studies show that the realization of two sequential single‐electron transfer oxidations of the indole derivatives is key, generating the configurationally biased carbocation species while providing the source of stereochemical induction. These results not only provide an efficient synthesis of enantioenriched indoline derivatives, but also offer a novel strategy for further designing asymmetric dearomatization reactions.
Unlocked: Dearomatization of indoles and their derivatives provides efficient synthetic routes for substituted indolines. For this asymmetric dearomatization reaction the indoles function as electrophiles. The combined utilization of a photocatalyst and chiral phosphoric acid (CPA) open to air unlocks the umpolung reactivity of indoles, enabling enantioselective dearomatization of indoles with N‐hydroxycarbamates as nucleophiles.
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