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This paper concerns the existence of bounded classical solutions to the attraction-repulsion chemotaxis system with logistic source (⋆) { u t = Δ u − χ ∇ ⋅ ( u ∇ v ) + ξ ∇ ⋅ ( u ∇ w ) + f ( u ) , x ∈ Ω , t > 0 , 0 = Δ v − β v + α u , x ∈ Ω , t > 0 0 = Δ w − δ w + γ u , x ∈ Ω , t > 0 in a smooth bounded domain Ω ⊆ R N ( N ≥ 1 ) , subject to nonnegative initial data and homogeneous Neumann boundary conditions, where f ( u ) ≤ a − b u r for all u ≥ 0 with some a ≥ 0 , b > 0 and r ≥ 1 . Here χ , α , ξ , β as well as γ and δ are positive constants. It is proved that the corresponding system ( ⋆ ) possesses a unique global bounded classical solution in the balance case χ α = ξ γ with r > 2 N − 2 N or, the attraction domination case ξ α > ξ γ with b ≥ ( N − 2 ) + N ( χ α − ξ γ ) and r = 2 , respectively. The study of this paper improves the results in Li-Xiang (2016) [12] , Xu-Zheng (2018) [39] , Wang (2016) [26] as well as Zhao et al. (2017) [42] and Tello-Winkler (2007) [23] , in which, the assumption b > ( N − 2 ) + N ( χ α − ξ γ ) (see Li-Xiang (2016) as well as Wang (2016) and Zhao et al. (2017)) or b > ( N − 2 ) + N χ (see Tello-Winkler (2007)) or r > 2 N + 2 N + 2 (see Xu-Zheng (2018)) or r > N 2 + 4 N − N 2 (see Li-Xiang (2016)) are intrinsically required.

All-inorganic perovskite nanocrystals (NCs) are promising candidates for light-emitting diodes (LEDs) owing to their excellent optoelectronic properties. However, the pure-red perovskite LEDs (PeLEDs) available today made from mixed-halide CsPb(Br/I)

Although tremendous progress has recently been made in quasi-2D perovskite light-emitting diodes (PeLEDs), the performance of red PeLEDs emitting at ≈650-660 nm, which have wide prospects for application in photodynamic therapy, is still limited by an inefficient energy transfer process between the quasi-2D perovskite layers. Herein, a symmetric molecule of 3,3'-(9H-fluorene-9,9-diyl)dipropanamide (FDPA) is designed and developed with two functional acylamino groups and incorporated into the quasi-2D perovskites as the additive for achieving high-performance red PeLEDs. It is demonstrated that the agent can simultaneously diminish the van der Waals gaps between individual perovskite layers and passivate uncoordinated Pb

Pseudo-natural products (pseudo-NPs) are de novo combinations of natural product (NP) fragments that define novel bioactive chemotypes. For their discovery, new design principles are being sought. Previously, pseudo-NPs were synthesized by the combination of fragments originating from biosynthetically unrelated NPs to guarantee structural novelty and novel bioactivity. We report the combination of fragments from biosynthetically related NPs in novel arrangements to yield a novel chemotype with activity not shared by the guiding fragments. We describe the synthesis of the polyketide pseudo-NP grismonone and identify it as a structurally novel and potent inhibitor of Hedgehog signaling. The insight that the de novo combination of fragments derived from biosynthetically related NPs may also yield new biologically relevant compound classes with unexpected bioactivity may be considered a chemical extension or diversion of existing biosynthetic pathways and greatly expands the opportunities for exploration of biologically relevant chemical space by means of the pseudo-NP principle.

This paper proposes a new non-destructive method to reconstruct the distribution of residual stresses around notches from the measured displacements under external loads. For this purpose, a linear...

The possible usage of different carbon nanostructures, including C24 nanocage, carbon nanotube (CNT), and hexa-peri-hexabenzocoronene nanographene (HBC) is studied in the anode of K-ion batteries (KIBs) by DFT calculations. Based on the calculations, both of K and K+ species preferentially adsorb on the center of a hexagon of the studied nanostructures. The results show that the underlying mechanism of the K+ adsorption is the cation-π interaction, and by increasing the curvature of the adsorbents the interaction becomes weaker. When the curvature is reduced, the adsorption energy of the K atom becomes more positive and the adsorption mechanism changes from ionic to nonionic. This study suggests that the mechanism of the strength of K interaction and the structure curvature are the main factors in determining the cell voltage (Ucell) of the KIBs. The C24 cage generates a negative Ucell which is physically meaningless, and it cannot be used as an anode material. The CNT produces a very small Ucell of 0.09 V, while the HBC is suggested to be a proper nanostructure for use in the KIBs because of its large Ucell about 1.45 V.

We study a coupled Navier–Stokes–Nernst–Planck–Poisson system arising from electrohydrodynamics in critical Besov-weak-Herz spaces. When the initial value sufficiently small, we prove the existence and uniqueness of global mild solution to the cauchy problem in this spaces for $n\geq3$. The spaces is larger than some other known critical spaces.

A stereoselective amination/cyclization cascade process has been developed that allows for the preparation of a series of unsaturated and substituted caprolactam derivatives in good yields. This conceptually novel protocol takes advantage of the easy access and modular character of vinyl γ-lactones that can be prepared from simple precursors. Activation of the lactone substrate in the presence of a suitable Pd precursor and newly developed phosphoramidite ligand offers a stereocontrolled ring-opening/allylic amination manifold under ambient conditions. The intermediate (E)-configured ε-amino acid can be cyclized using a suitable dehydrating agent in an efficient one-pot, two-step sequence. This overall highly chemo-, stereo- and regio-selective transformation streamlines the production of a wide variety of modifiable and valuable caprolactam building blocks in an operationally attractive way., A Pd-mediated stereoselective tandem process has been developed towards a large variety of functional caprolactam synthons.

This paper deals with a boundary-value problem in three-dimensional smoothly bounded domains for a coupled chemotaxis-growth system generalizing the prototype \begin{document}$\begin{align} \left\{\begin{array}{ll} u_t = \Delta u-\nabla\cdot(u\nabla v)+\mu u(1-u),\quad x\in \Omega, t>0,\\ { }{ v_t = \Delta v- v +w},\quad x\in \Omega, t>0,\\ { }{\tau w_t+\delta w = u},\quad x\in \Omega, t>0\\ \end{array}\right. \end{align} (*)$ \end{document} in a smoothly bounded domain \begin{document}$ \Omega\subset\mathbb{R}^N(N\geq1) $\end{document} under zero-flux boundary conditions, which describe the spread and aggregative behavior of the Mountain Pine Beetle in forest habitat, where the parameters \begin{document}$ \mu $\end{document} as well as \begin{document}$ \delta $\end{document} and \begin{document}$ \tau $\end{document} are positive. Based on an new energy-type argument combined with maximal Sobolev regularity theory, it is proved that global classical solutions exist whenever \begin{document}$ \mu>\left\{ \begin{array}{ll} {0, \; \; \; {\rm{if}}\; \; N\leq4},\\ {\frac{(N-4)_{+}}{N-2}\max\{1,\lambda_{0}\},\; \; \; {\rm{if}}\; \; N\geq5}\\ \end{array} \right. $\end{document} and the initial data \begin{document}$ (u_0,v_0,w_0) $\end{document} are sufficiently regular. Here \begin{document}$ \lambda_0 $\end{document} is a positive constant which is corresponding to the maximal Sobolev regularity. This extends some recent results by several authors.

The first asymmetric synthesis of important α,α-disubstituted N-alkyl allyl amine scaffolds through allylic substitution is reported. This approach is based on palladium catalysis and features ample scope with respect to both the allylic precursor and amine reagent, and high asymmetric induction with enantiomeric ratios (e.r.) up to 98.5:1.5. The use of less-reactive anilines is also feasible, providing enantioenriched α,α-disubstituted N-aryl allylic amines.

Tertiary allylic alcohols were conveniently converted into either (Z)- or (E)-configured α,β-unsaturated γ-amino acids by treatment with secondary amines under Pd catalysis at ambient conditions. The key to control the stereochemical course of these formal allylic aminations was the presence of a suitable diphosphine ligand, with dppp [1,3-bis(diphenylphosphino)propane, L12] providing high yields and selectivities for the (Z) isomers, whereas the bis[(2-diphenylphosphino)phenyl]ether (DPEPhos) derivative L1' allowed for selective formation of the corresponding (E) isomeric products. This ligand-controlled, stereodivergent protocol thus shows promise for the stereoselective preparation of allylic amine products from a common substrate precursor.

We deal with the boundedness of solutions of a class of quasilinear chemotaxis systems generalizing the prototype (⁎) { u t = ∇ ⋅ ( ϕ ( u ) ∇ u ) − ∇ ⋅ ( u ∇ v ) + μ u ( 1 − u ) , x ∈ Ω , t > 0 , v t = Δ v − v + u , x ∈ Ω , t > 0 , ∂ u ∂ ν = ∂ v ∂ ν = 0 , x ∈ ∂ Ω , t > 0 , u ( x , 0 ) = u 0 ( x ) , v ( x , 0 ) = v 0 ( x ) , x ∈ Ω , where R N ( N ≥ 2 ) is a bounded domain with zero-flux boundary condition, μ > 0 is a positive parameter, and ϕ ( u ) = ( u + 1 ) − α . It is shown that for all reasonably regular initial data, system (⁎) admits a global existence and boundedness of solutions when α α 0 for some α 0 > 2 − N N + 2 , thereby proving that the value α = 2 − N N + 2 is not critical in this regard. This extends previous results that rely on a different energy-type inequality.

Tertiary allylic alcohols equipped with a carboxyl group can be smoothly aminated under ambient conditions by a conceptually new and stereoselective protocol under palladium catalysis. The in situ formed Z-configured γ-amino acid cyclizes to afford an α,β-unsaturated γ-lactam, releasing water as the only byproduct. This practical catalytic transformation highlights the use of a carboxyl group acting as an activating and stereodirecting functional group to provide a wide series of pharma-relevant building blocks. Various control reactions support the crucial role of the carboxyl group in the substrate to mediate these transformations.

Functionalized cyclic organic carbonates and related heterocycles have emerged as highly versatile heterocyclic substrates for ring-opening and decarboxylative catalytic transformations allowing for the development of new stereo- and enantioselective C-N, C-O, C-C, C-S and C-B bond formation reactions. Transition-metal-mediated conversions have only recently been rejuvenated as powerful approaches towards the preparation of more complex molecules. This minireview will highlight the potential of cyclic carbonates and structurally related heterocycles with a focus on their synthetic value and the mechanistic manifolds that are involved upon their conversion.

For the first time, compounds with lanthanum from the main family element Boron (LaBx) were investigated as an active layer for thin-film transistors (TFTs). Detailed studies showed that the room-temperature fabricated LaBx thin film was in the crystalline state with a relatively narrow optical band gap of 2.28 eV. The atom ration of La/B was related to the working pressure during the sputtering process and the atom ration of La/B increased with the increase of the working pressure, which will result in the freer electrons in the LaBx thin film. LaBx-TFT without any intentionally annealing steps exhibited a saturation mobility of 0.44 cm2·V−1·s−1, which is a subthreshold swing (SS) of 0.26 V/decade and a Ion/Ioff ratio larger than 104. The room-temperature process is attractive for its compatibility with almost all kinds of flexible substrates and the LaBx semiconductor may be a new choice for the channel materials in TFTs.

A general methodology for the synthesis of enantioenriched tertiary allylic aryl ethers through Pd-catalyzed decarbox- ylative reactions of vinyl cyclic carbonates and phenols is presented. Switching of the regioselectivity toward the formation of linear products by a judicious choice of the ligand is also reported

The mode competition of the bichromatic laser emission in two-dimensional (2D) random medium was studied. Based on the time-dependent theory, a model for dual-wavelength random laser was established. The Maxwell equations and rate equations were combined and solved by using the finite different time domain (FDTD) method. Results show that the emission intensity of both wavelength ranges increases simultaneously with the increasing of the surface-filling fraction. The mode dominance of the bichromatic emission can be switched by changing the scatterer radius. The emission intensity of the longer wavelength increases when enlarging the excitation area. The controllability of these lasing modes may provide a potential application of optical switches.

We report the existence and stability of defect solitons (DSs) in two-dimensional parity-time-symmetric photonic lattices with self-focusing Kerr nonlinearity. We analyze the effect of different values of the local defect strength parameter on stability properties of DSs. In the case of a positive defect, the DSs only exist in the semi-infinite gap and can propagate stably in their entire existence domain. For the uniform optical lattices (zero-defect lattices), the DSs also exist only in the semi-infinite gap, but they are unstable upon propagation only in a tiny domain of their existence region, near the edge of the first Bloch band. In the case of a negative defect, the DSs can exist in both the semi-infinite gap and in the first gap. In the first gap, they are stable only for moderate powers but are unstable for both high- and low-power regimes, near the edges of the first and the second Bloch bands. All DSs in the semi-infinite gap were found to be unstable. Thus the domains of stability can be effectively controlled by tuning the value and sign of the defect strength parameter.

Recently, thermally activated delayed fluorescence (TADF) organic light-emitting diodes (OLEDs) have attracted both academic and industrial interest due to their extraordinary characteristics, such as high efficiency, low driving voltage, bright luminance, lower power consumption and potentially long lifetime. In this invited review, the fundamental concepts of TADF have been firstly introduced. Then, main approaches to realize WOLEDs based on TADF have been summarized. More specifically, the recent development of WOLEDs based on all TADF emitters, WOLEDs based on TADF and conventional fluorescence emitters, hybrid WOLEDs based on blue TADF and phosphorescence emitters and WOLEDs based on TADF exciplex host and phosphorescence dopants is highlighted. In particular, design strategies, device structures, working mechanisms and electroluminescent processes of the representative WOLEDs based on TADF are reviewed. Finally, challenges and opportunities for further enhancement of the performance of WOLEDs based on TADF are presented. Published version

The cholesteric liquid crystal can be regarded as a multilayer that consists of many layer uniaxial thin films that exhibit optical rotation. For the convenient discussion of the polarization states of the transmitted wave through a cholesteric liquid crystal, a new 2×2 matrix is given, in which the matrix element is changed into the complex exponential. Here we discuss the treatment process of this method in detail and its role in the investigation of the polarization states. Using this method we easily study the polarization states of the transmitted wave. The calculated results show that the polarization states of wave will be changed when it propagates along the cholesteric liquid crystal.

We give an interface between two same media whose orientation of optical axis, however, is rotated, and describe a method in detail to show how to calculate reflectance coefficient in this interface. We also give the theoretical simulation of the reflectance coefficient and discuss the effect of the rotation angle and the direction of electron vector on the reflectance coefficient. For the un-polarized lights the theoretical calculated results show that the reflectance coefficients (rx1 and ry1) are very small when the rotated angle is small, and they arrive at the maximum value as the rotation angle is equal to a decided value. For the polarized light, when the rotation angle is small, the reflectance coefficients (rx1 and ry1) are also small. Only when the rotation angle increases to a certain extent, they can reach the maximum values and be strongly affected by the direction of electronic vector. However, this effect on the reflectance coefficient in the direction of the maximum refraction is different from that in the direction of minimum refraction.

We report the synthesis of Tb(1−x)PO4:xEu3+ (x=0–1) nanophosphors directly by a simple hydrothermal method with citric acid (CA) as the organic additive and without further sintering treatment. The nanocrystals are well-faceted and show a highly symmetrical structure. The energy transfer between Tb3+ and Eu3+ in TbPO4 nanocrystal was investigated, and tunable emission wavelengths were realized in the materials by changing the doping concentration of Eu3+. The increase of Eu3+ concentration can lead to the interaction between neighboring Eu3+, which results in concentration quenching.

We numerically show the generation of robust vortex clusters embedded in a two-dimensional beam propagating in a dissipative medium described by the generic cubic-quintic complex Ginzburg-Landau equation with an inhomogeneous effective diffusion term, which is asymmetrical in the two transverse directions and periodically modulated in the longitudinal direction. We show the generation of stable optical vortex clusters for different values of the winding number (topological charge) of the input optical beam. We have found that the number of individual vortex solitons that form the robust vortex cluster is equal to the winding number of the input beam. We have obtained the relationships between the amplitudes and oscillation periods of the inhomogeneous effective diffusion and the cubic gain and diffusion (viscosity) parameters, which depict the regions of existence and stability of vortex clusters. The obtained results offer a method to form robust vortex clusters embedded in two-dimensional optical beams, and we envisage potential applications in the area of structured light.

The temporal properties of the random laser under ultrashort pulse pumping has been studied in disordered media theoretically. The waveform can be modified by varying the surface-filling fraction and refractive index of the random medium.

Nonlinear optical pulses with sub-picosecond width will exhibit the phenomena of timing jitter and pulse decay induced by the third-order dispersion and Raman self-frequency shift. The optical phase conjugation is proposed to compensate for the high-order dispersion and high-order nonlinear effect. However, the spectral phase conjugation can’t eliminate the time delay induced by Raman self-frequency shift and the temporal phase conjugation can’t avoid the pulse splitting into two pieces induced by the third order dispersion. Thus, the schemes of the combination of the spectral and temporal phase conjugation are supposed to use for recovering the distorted pulse and reducing the time delay induced by the third-order dispersion and Raman self-frequency shift. There exist the optimized schemes to deploy the relative position between the spectral phase conjugator and the temporal phase conjugator to obtain the optimization transmission qualities with the minimum penalty for timing jitter and pulse distortion. In addition, the spectral phase conjugator and temporal phase conjugator should be settled down after the midway and before the midway, respectively, in order to obtain the residual third-order dispersion to enhance the frequency red-shift trend of two polarization components after the temporal phase conjugator for reducing the time delay.

An optical phase conjugator is used to enhance the robustness of optical pulses to polarization dispersion. The polarization components of optical pulses form a breather in birefringent fibers firstly and make a polarization component along fast axis compressed through spectra inversion function of the optical phase conjugator. The two polarization modes are compressed further due to the cross-phase modulation effect and trap each other fully in time domain. The optical phase conjugator is required to settle down before higher birefringent fibers in order to suppress the influence of birefringence effectively. The limit value of δ reaches 7.5 that can be suppressed by enhanced robustness of the optical pulses by using the optical phase conjugator in the case that each polarization component is a fundamental soliton. Moreover, the function of the optical phase conjugator will reduce the delay of optical pulses for a different polarization angle.

We report the existence and stability of nonlocal defect solitons (NDSs) in parity–time-symmetric photonic lattices with spatially modulated nonlocal nonlinearity. We reveal that solitons exist in the semi-infinite gap and a defect in the real part of nonlinear lattices plays a significant role in controlling the extent of the stability domains. We show that the existence and stability of the NDSs can be profoundly affected by the parameters of the nonlinear lattice structures.

We study the solitons in parity-time symmetric potential in the medium with spatially modulated nonlocal nonlinearity. It is found that the coefficient of the spatially modulated nonlinearity and the degree of the uniform nonlocality can profoundly affect the stability of solitons. There exist stable solitons in low-power region, and unstable solitons in high-power region. In the unstable cases, the solitons exhibit jump from the original site to the next one, and they can continue the motion into the other lattices. The region of the stable soliton can be expanded by increasing the coefficient of the modulated nonlocality. Finally, critical amplitude of the imaginary part of the linear PT lattices is obtained, above which solitons are unstable and decay immediately.