Formal [4 + 1] cycloaddition strategy for the synthesis of dihydrobenzofurans via Michael addition of 2-(2-nitrovinyl)-phenols and malonate esters (C1 synthon) and subsequent iodine-catalyzed oxidative annulation

A novel [4 + 1] cycloaddition protocol for the synthesis of dihydrobenzo(naphtho)furan skeletons from readily available 2-(2-nitrovinyl)-phen(naphth)ols and malonate esters via a tandem Michael addition/iodine-catalyzed oxidative annulation has been developed. This method provides a new and facile application of malonate esters as 1,1-nucleophilic/electrophilic type C1 synthons without a pre-functionalization step and the plausible reaction mechanism is proposed.     

Thermosensitive acetylated carboxymethyl chitosan gel depot systems sustained release caffeic acid phenethyl ester for periodontitis treatment

Periodontitis is a chronic inflammatory disease of tooth support tissues leading to progressive destruction of periodontal soft tissues as well as alveolar bone, and can be treated with anti-inflammatory and bone-protective agents to prevent disease progression. Caffeic acid phenethyl ester (CAPE) is a natural polyphenolic compound with anti-inflammation, anti-oxidation and bone tissue repair efficacy. In this work, we synthesized a thermosensitive hydrogel matrix of acetylated carboxymethyl chitosan (A-CC), and firstly applied for periodontal local drug delivery. The biocompatible CAPE-loaded A-CC hydrogel (CAPE-A-CC) has the advantages of forming a drug depot in situ, sustained release and precisely improving the drug concentration in the lesion sites compared with traditional systemic administration. In addition, CAPE-A-CC could significantly inhibit the expression of inflammatory cytokines of TNF-α, IL-1β, IL-6, and IL-17 in macrophages, and increased the expression of alkaline phosphatase (ALP) in human periodontal ligament stem cells (hPDLSC) related to osteogenesis. This study develops a novel in situ thermosensitive hydrogel delivery system to improve the therapeutic potential of natural active ingredient for periodontitis therapy.     

Rigidity of closed submanifolds in a locally symmetric Riemannian manifold

Let M~n(n ≥ 4) be an oriented closed submanifold with parallel mean curvature in an(n + p)-dimensional locally symmetric Riemannian manifold N~(n+p). We prove that if the sectional curvature of N is positively pinched in [δ, 1], and the Ricci curvature of M satisfies a pinching condition, then M is either a totally umbilical submanifold, or δ = 1, and N is of constant curvature. This result generalizes the geometric rigidity theorem due to Xu and Gu[15].     

Synthetic and X-ray structural and reactivity studies of Cp*RuIV complexes containing bidentate dithiocarbonate, xanthate, carbonate, and phosphinate ligands (Cp* = eta5-C5Me5)

The reaction of [Cp*RuCl2]2 (1; Cp* = eta5-C5Me5) with tetraalkyldithiuram disulfides (R2NC(S)SS(S)CNR2, R = Me, Et), isopropylxanthic disulfide ([iPrOC(S)S]2), and bis(thiophosphoryl) disulfide ([(iPrO)2P(S)S]2) led to the isolation of dark-red crystalline solids of Cp*RuIVCl2(eta2-dithiolate) complexes [dithiolate = S2CNR2, DTCR (2a, R = Me; 2b, R = Et), S2COiPr (3), and S2P(iPrO)2 (4)]. Dichlorido substitution in 2 and 3 with DTCEt and S2COiPr anions yielded RuIV derivatives containing bis(DTC) and mixed DTC-dithiocarbonate ligands. These are the first organoruthenium complexes of such ligands. The reaction of monophosphines with 2a resulted in monochlorido substitution, whereas the analogous reaction with 3 resulted in displacement of both chlorido ligands and reduction of the metal center to RuII. Reduction at Ru was also observed in the reaction of 2a with [CpCr(CO)3]2. Of these complexes, only 2 and 3 are air-stable in the solid state for an extended period. All of the complexes have been spectrally characterized, and selected compounds are also crystallographically characterized.     

Molecular dynamics simulations of stretched gold nanowires: the relative utility of different semiempirical potentials

The mechanical elongation of a finite gold nanowire has been studied by molecular dynamics simulations using different semiempirical potentials for transition metals. These potentials have been widely used to study the mechanical properties of finite metal clusters. Combining with density functional theory calculations along several atomic-configuration trajectories predicted by different semiempirical potentials, the authors conclude that the second-moment approximation of the tight-binding scheme (TB-SMA) potential is the most suitable one to describe the energetics of finite Au clusters. They find that for the selected geometries of Au wires studied in this work, the ductile elongation of Au nanowires along the [001] direction predicted by the TB-SMA potential is largely independent of temperature in the range of 0.01-298 K. The elongation leads to the formation of monatomic chains, as has been observed experimentally. The calculated force-versus-elongation curve is remarkably consistent with available experimental results.     

Hyper-Rayleigh and hyper-Raman scatterings with intermediate and two-photon resonances

The normally weak process of hyper-Raman scattering can be greatly enhanced when the excitation is two photon resonant with an electronic transition that is both one and two photon allowed. It might be expected to be further enhanced when a one-photon allowed transition provides an intermediate state resonance in the two-photon excitation step. The theory of this triply resonant process is developed for organic nonlinear chromophores. Experimental results are obtained for one donor-acceptor substituted push-pull chromophore in which the energy of the strongly allowed lowest-lying one-photon state may be tuned by varying the solvent without substantially affecting the two-photon resonant transition. Surprisingly, bringing the one-photon allowed state into resonance does not significantly increase the hyper-Rayleigh or hyper-Raman hyperpolarizabilities. Analysis of the resonance Raman, hyper-Rayleigh, and hyper-Raman profiles suggests that the triply resonant path does not make the dominant contribution to the hyperpolarizability in this system.     

Excited state absorption dynamics in metal cluster polymer [WS4Cu3I(4-bpy)3]n solution

The nonlinear absorptive property of a novel metal cluster [WS(4)Cu(3)I(4-bpy)3]n in DMF solution is studied by using an open-aperture Z-scan technique with picosecond and nanosecond laser pulses at the wavelength of 532 nm. The experimental results show that the cluster has strong nonlinear absorption under the 8 ns pulse excitation and a relatively weak nonlinear absorptive property under the picosecond pulse excitation. The picosecond pump-probe response of the metal cluster is similar to that of C60 solution, which implies that the nonlinear mechanisms are the same for the two materials. By using the rate-equation model, the experimental data are theoretically simulated; several optical parameters of the cluster, especially the lifetime of the higher excited singlet state of the cluster, are obtained.     

Cross -sections of star bodies and dual mixed volumes

In this paper, we establish an extension of Funk's section theorem. Our result has the following corollary: If is a star body in whose central -slices have the same volume (with appropriate dimension) as the central -slices of a centered body , then the dual quermassintegrals satisfy , for any , with equality if and only if . The case that is a centered body implies Funk's section theorem.

     

反饱和吸收激发态非线性材料的Z扫描分析

本文用速率方程理论分析了激发志光学非线性材料非线性吸收和折射,通过数值模拟讨论了激发态和基态吸收截面、折射度相互关系等参数对非线性吸收和折射性质的影响。并从理论上分析了C₆₀甲苯溶液的Z扫描实验曲线,它具有强非线性吸收和弱非线性折射。