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A boron Lewis acid catalyzes trans-carboacyloxylations of ynamides with esters to afford fully substituted acyclic enol esters/carbonates in high yields and with excellent stereocontrol.

We study the topological properties of the one-dimensional p-wave Aubry–André–Harper (AAH) model with periodic incommensurate potential and transition coupling. The calculation results show that due to co-influence of the incommensurate potential and modulation phase, three topological phases arise in different parameter regions: a topologically trivial phase, Su–Schrieffer–Heeger (SSH)-like topological phase, and Kitaev-like topological superconducting phase with Majorana zero modes. By evaluating the Andreev reflection conductance, we see that in the Kitaev-like phase, the quantized conductance plateau comes into being at the zero-bias limit, due to the occurrence of resonant Andreev reflection. In addition, when the disorder effect is incorporated, the SSH-like topology is modified sensitively and the degenerate topological states split, whereas the Kitaev-like topological phase is robust to weak disorder. Finally, we find that disorder can induce topological phase transition, i.e. from the topologically trivial phase to the topological phase. Based on these results, we believe that our findings have significance for studying the topological phase transition in a one-dimensional topological superconducting system. Also, it provides a feasible scheme for clarifying different topological phases.

Aberrant DNA methylation of genes is closely linked to many aspects of tumor development. This study focuses on the effect of DNA hypermethylation of von Willebrand factor C domain containing 2 (VWC2) on colorectal cancer (CRC) progression and the underpinning mechanism. According to data in the bioinformatic systems, VWC2 had the highest degree of DNA methylation in colonic adenocarcinoma, and it showed DNA hypermethylation in rectal adenocarcinoma as well. CRC and the para-tumorous tissues were collected from 86 patients. VWC2 was expressed at low levels in CRC samples and inversely correlated with tumor stage and tumor biomarker expression. DNA hypermethylation and reduced expression of VWC2 were also detected in CRC cell lines HCT-116 and HT29. VWC2 overexpression suppressed the malignant growth of cells in vitro and in vivo. Co-immunoprecipitation and western blot assays showed that small ubiquitin-like modifier 1 (SUMO1) mediated SUMOylation of DNA methyltransferase 1 (DNMT1) and strengthened its protein stability, which promoted DNA methylation and suppression of the VWC2 gene. In summary, this study demonstrates that SUMO1-mediated activation of DNMT1 induces DNA methylation and downregulation of VWC2 in CRC to augment cancer development.

Energy and topological-state properties of the one-dimensional non-Hermitian spin-orbit-coupled Su–Schrieffer–Heeger lattice are theoretically investigated by introducing spin-dependent onsite imaginary potentials with gain and loss. It is found that imaginary potentials lead to the appearance of imaginary energies in the topologically nontrivial phase region, and ${\cal {PT}}$ phase transition occurs in the topologically trivial region. In addition, the imaginary potentials and spin–orbit coupling act together to make the topological phase transition occur in the topologically trivial region, and the topologically nontrivial region becomes wider. The energy spectrum results show that imaginary potentials and spin–orbit coupling have obvious effects on the zero-energy edge states of this system, which mainly lie in the presence of four types of zero-energy states with different localization and numbers. Furthermore, we discuss diagonal disorder and the transport behavior of system, further characterizing the properties of the individual topological states. The above results indicate the special adjustment effect of imaginary potentials and spin–orbit coupling on the band structure of such a system.

Using a three-dimensional classical method, we theoretically explore the frustrated double ionization (FDI) of Ar atoms under few-cycle linearly polarized laser pulses with different carrier-envelope phases (CEPs). Our calculated spectra are similar to the recent experimentally observed two peeks in the electron momentum distribution (Larimian et al 2020 Phys. Rev. Res. 2 013021). The dependence of FDI on laser CEPs is investigated, and the result reveals that the two different pathways of FDI can be controlled by CEPs. The information on which pathway leads to FDI is encoded in the electron-electron energy distribution shortly after recollision and momentum distribution at the ionization time after recollision.

Chromium triiodide (CrI3) monolayers have attracted much attention among the first two-dimensional materials discovered experimentally in both electronics and spintronics due to their potential applications. By means of density functional theory, we perform investigations of the electronic structures and magnetic properties of CrI3 monolayer doped with 3 d transition-metal (TM) atoms, which is also called CrXI6 monolayer with X changed from Sc to Fe. It is shown that the electron properties of the CrXI6 system can be tuned from semiconductor to metal/half-metal, which depend on the types of TM atoms. In addition, the CrXI6 system improves ferromagnetic (FM) stabilities, enhancement of magnetic moments, and FM-to-antiferromagnetic transition. These findings enrich the potential application perspectives of CrI3 monolayer in spintronics.

Using the two-dimensional classical ensemble method, we investigate the nonsequential double-ionization (NSDI) processes of Ar atom by few-cycle linearly polarized laser field. We demonstrate that the recollision-induced excitation with subsequent ionization (RESI) and the recollision-induced ionization (RII) channels can be effectively controlled by laser intensities. Moreover, the carrier-envelope-phases (CEPs) play a key role in controlling RESI and RII mechanism. The correlated electron momentum distribution is demonstrated for the RII and RESI channels at different CEPs and intensities.

The corrosion characteristics of 316SS and 304SS in subcritical and supercritical aqueous systems including chloride of approximate 4600 mg/L at 25 MPa and 250 °C, 350 °C, 425 °C, and 520 °C are comparatively investigated. Some local corrosion areas occurred on the surfaces of SS316, not on that of 304SS, at 250 °C and 425 °C, while at 350 °C, all the sample surfaces were covered by large amounts of corrosion products and clay materials due to the predominant precipitation for the formation of the outer subscale. Whether in reducing subcritical and supercritical industrial sludge suspension or in oxidizing supercritical sludge system, 304SS owns better corrosion resistance than 316SS due to higher chromium concentration of former.

Electron transport through the quantum-dot system with ferromagnetic leads is theoretically investigated, by introducing one Majorana bound state (MBS) to be side-coupled with the dot. It is shown that even for the ferromagnetic leads, the zero-bias conductance is manifested as a peak. However, its magnitude becomes more adjustable, especially when the dot suffers from the external magnetic field and superconducting proximity effect. The other notable result is that the magnetoresistance displays interesting characteristics in this system, which is related to the interplay between the magnetization direction of the MBS and other structural parameters. We believe that this work can be helpful in presenting the MBS-assisted transport behaviors in quantum-dot systems.

Nonsequential double ionization of Ar by a counter-rotating two-color circularly polarized laser field is theoretically investigated. At the combined intensity in the “knee” structure range, the double ionization occurs mainly through recollision induced excitation followed by subsequent ionization of Ar + ∗ . By tracing the history of the recollision trajectories, we explain how the relative intensity ratio of the two colors controls the correlated electron dynamics and optimizes the ionization yields. The major channels contributing to enhancing the double ionization are through the elliptical trajectories with smaller travel time but not through the triangle shape or the other long cycle trajectories. Furthermore, the correlated electron dynamics could be limited to the attosecond time scale by adjusting the relative intensity ratio. Finally, the double ionization from doubly excited complex at low laser intensity is qualitatively discussed.

We theoretically investigate the high-order harmonic generation (HHG) and the spatial distribution in HHG of the H 2 + molecule by introducing a time-delayed two-color laser field which consists of the mid-infrared and near-infrared laser field. For the different time delays of the two-color laser fields, the pulse shapes are changed which result in the variation of the electron recombined with the nuclei along the positive- or negative-z direction. When the time delay is 0 fs (1.34 fs), a smooth harmonic plateau from the electron recombined with the nuclei along the negative (positive)-z direction can be achieved. An isolated attosecond pulse with a duration of about 99 as is generated when the time delay is 1.34 fs. We perform the classical analysis which is consistent with the numerical results from the one-dimensional non-Born-Oppenheimer time dependent Schrodinger equation (TDSE). We also investigate emission time of harmonics in terms of a time-frequency analysis to further understand the underlying physical mechanism.

By using classical ensemble method, we investigate the double ionization of CS 2 molecule in linearly, the bichromatic counterrotating circularly polarized laser fields and the combination of bichromatic counterrotating circularly polarized laser fields and static field, respectively. The numerical results show that the ionization probability in the bichromatic counterrotating circularly polarized laser fields is about 2 order magnitude higher than that in linearly polarized laser field. When a static field is added, the ionization probability is the largest. Besides, the “knee” structure occurs at about 0.05 PW/cm 2 in linearly polarized laser field; whereas “knee” structure is disappeared in the bichromatic counterrotating circularly polarized laser fields and combined laser field. The corresponding momentum distribution of CS 2 molecule presents a “finger-like” structure at about 0.05 PW/cm 2 in linearly polarized field. By analysing the energy distributions of double-ionized electrons versus time and corresponding trajectories, we find that, for linearly polarized case non-sequential double ionization (NSDI) is predominant at about 0.05 PW/cm 2 , for bichromatic counterrotating circularly polarized laser fields, one electron ionizes after another which indicate sequential ionization process (SDI). When the static field is added, the two electrons undergoes a long pre-ionization process first and then ionizes one after another, and the pre-ionization process lasts longer than other two cases.

The Majorana-induced Andreev reflection is theoretically investigated, by considering an additional quantum dot coupled to the normal metallic lead. We find that the quantum dot takes variable effect on the zero-bias conductance induced by the Majorana zero mode. The non-superconducting dot with zero-energy level can suppress the Andreev reflection. Otherwise, the quantum dot only changes the width of the Andreev reflection peak around the zero-bias point with its magnitude equal to 2 e 2 h . Alternatively for the Majorana nonzero mode, the effect of quantum dot becomes dominant, including the zero-bias result. Our findings provide new insights for understanding the Andreev reflection driven by the Majorana modes in experiment.

We theoretically investigate the frustrated double ionization (FDI) of Ar atoms with counter-rotating two-color circular (CRTC) laser fields using the three-dimensional (3D) classical ensemble method. Our results show that the FDI probability depends upon the intensity ratio of the CRTC laser fields. The FDI event accompanied with the recollision excitation with subsequent ionization is prevalent and three pathways exist in FDI processes driven by CRTC laser fields. The momentum distribution of a recaptured electron at the ionization time after recollision indicates that the momentum being close to the vector potential is a necessary condition for FDI events to occur. In addition, the recaptured electron most probably transitions to a Rydberg state of which the quantum number is ten in the CRTC fields.

With the semiclassical ensemble model, we explore the relative phase-dependent nonsequential double ionization (NSDI) of Mg by counter-rotating two-color circularly polarized (TCCP) laser pulses. The yield of Mg2+ sensitively depends on the relative phase Δφ and the intensity of TCCP laser fields. At Δφ = 1.5π, the yield of Mg2+ exhibits a pronounced peak in the 0.05 PW/cm2 laser field. This behavior results from the increase of the initial transverse velocity compensating for the drift velocity with the decreasing angle by analyzing the angular distributions of the electron pairs in four relative phases. By changing the relative phases, we find that the recollision excitation with subsequent ionization and the recollision-impact ionization mechanisms can be controlled with TCCP laser fields.

Glioma is the most lethal type of primary brain tumor characterized by aggressiveness and a poor prognosis. Histone deacetylase 4 (HDAC4) is frequently dysregulated in human malignancies. However, its biological functions in the development of glioma are not fully understood. The present study aimed to evaluate HDAC4 expression in human glioma and to elucidate the mechanistic role of HDAC4 in glioma. The results suggested that HDAC4 was significantly upregulated in glioma tissues and a number of glioma cell lines compared with adjacent non-tumor tissues and the non-cancerous human glial cell line SVG p12, respectively (P

We investigated the nonsequential double ionization (NSDI) in Ar by two-color elliptically polarized laser field with a three-dimensional (3D) classical ensemble method. We study the relative phase effect of NSDI and distinguish two particular recollision channels in NSDI, which are recollision–impact ionization (RII) and recollision-induced excitation with subsequent ionization (RESI), according to the delay-time between the recollision and the final double ionization. The numerical results indicate that the ion momentum distribution is changed and the triangle structure is more obvious with the decrease of the relative phase. We also demonstrate that the RESI process always dominates in the whole double ionization process and the ratio of RESI and RII channels can be influenced by the relative phase.

We theoretically investigate the high-order harmonic generation (HHG) from laser–solid interaction in a doped semiconductor by solving the one-dimensional time-dependent Schrodinger equation within the single active electron model. The results show that the energy band of the valence and the low conduction band can be split into a small band in the doped semiconductor. The splitting band gap can be controlled by changing the depth of the potential well of the doped semiconductor, and the second HHG plateau can be enhanced. We also demonstrate the energy band structures in coordinate space with different numbers of dopant. Time-dependent population imaging is used to illustrate the change of the splitting band gap with different depths of the potential well of the doped semiconductor.

This study examined the impact of corporate governance on environmental information disclosure in the China context. Our data was based on Shanghai A-share companies for the period 2008 to 2011. We examined the effect of corporate governance from different aspects. We found that Outstanding shares rate, State-holding ratio, and CEO/Chairman duality negatively affect environmental disclosure index (EDI) significantly; Proportion of independent directors, supervisory board and board sizes positively affect EDI significantly. Our results indicate that in China, corporate governance does influence the extent of environmental information disclosure significantly.

Using the classical ensemble model, we investigate the nonsequential double ionization (NSDI) of Ar and Mg in the two-color elliptically polarized laser pulse for different elliptical polarizations. Numerical results show that for Ar atoms the NSDI yield increases as the ellipticity increases, which is different from the case of Mg atoms. Moreover, the correlated behavior in the correlated electron momentum along the x direction and ion momentum distributions of Ar atoms are influenced by the ellipticity. By statistical analysis of different times, we can conclude that the ellipticity may be responsible for the NSDI processes. The correlated momenta distributions along the x direction at the recollision time are demonstrated and the results show that the travelling time and ellipticity can affect the emitted directions of both electrons.

We theoretically investigate the high-order harmonic generation (HHG) of the H2 + molecule in an asymmetric nonhomogeneous laser field by solving the one-dimensional time-dependent Schrodinger equation within the non-Born–Oppenheimer approximation. The results show that even harmonics with a small redshift can be observed in an asymmetric nonhomogeneous laser field. We also investigate the spatial distribution of the HHG spectra to explain the appearance of the even harmonics with a small redshift. The HHG was separated into two parts according to the electronic coordinate z (z > 0 and z < 0) to illustrate the contributions to the HHG from the two nuclei. Furthermore, the underlying physical mechanism of the generation of even harmonics with a small redshift is illustrated by the interference term of the HHG spectra.

Hibifolin, the highest-content bioactive flavonoid of the flowers of Abelmoschus manihot, was incubated with human intestinal bacteria, and four metabolites (1-4) were obtained from the incubated solution by chromatographic methods. The structures of the four metabolites were elucidated as gossypetin 8-O-beta-D-4''-deoxy- Delta(4'')-glucuropyranoside (1), gossypetin (2), quercetin (3), and 8-methoxy-quercetin (4), respectively, on the basis of UV, NMR, and MS data. Metabolite 1 was obtained as a new compound with a specific beta-D-4''-deoxy-Delta(4'')-glucuropyranosyl moiety, which was formed through a unique and novel metabolic pathway that has not been reported previously.

Using the three-dimensional classical ensemble method, we investigate the nonsequential double-ionization (NSDI) process of Mg in few-cycle circularly polarized laser fields. We demonstrate the time evolution of the distribution of the electron energy, the repulsion energy between double-ionized electrons, the distance between the nucleus and double-ionized electrons, and the momentum of double-ionized electrons. By analyzing these theoretical results, we find that a few-cycle pulse would allow a single recollision event. In addition, the correlated momentum distribution, the angular distribution between double-ionized electrons, and the ion momentum distribution with different delay time, which is the time interval between final double ionization and recollision, are also demonstrated and the results show that the delay time plays a key role in electron emission processes.

High-order-harmonic generation (HHG) for the ${{\mathrm{H}}_{2}}^{+}$ molecule in a 3-fs, 800-nm few-cycle Gaussian laser pulse combined with a static field is investigated by solving the one-dimensional electronic and one-dimensional nuclear time-dependent Schr\"odinger equation within the non-Born-Oppenheimer approximation. The spatial distribution in HHG is demonstrated and the results present the recombination process of the electron with the two nuclei, respectively. The spatial distribution of the HHG spectra shows that there is little possibility of the recombination of the electron with the nuclei around the origin $z=0$ a.u. and equilibrium internuclear positions $z=\ifmmode\pm\else\textpm\fi{}1.3$ a.u. This characteristic is irrelevant to laser parameters and is only attributed to the molecular structure. Furthermore, we investigate the time-dependent electron-nuclear wave packet and ionization probability to further explain the underlying physical mechanism.

By using classical ensemble method, we investigate the double ionization of C3H6 molecule with different structures (propene and cyclopropane) in intense laser fields. The numerical results show that the non-sequential double ionization occurs in propene molecule rather than cyclopropane molecule in 1200 nm laser field. To further explain this interesting phenomenon, the momentum distribution of double ionized electrons is presented and the result presents the "finger-like" structure at about 30 TW/cm2 of propene molecule, and this structure is more obvious than that in cyclopropane molecule. The above phenomena are also demonstrated by analysing the energy distributions of double-ionized electrons versus time. Moreover, we also investigated the angular distribution at the end of pulse, which is different between propene and cyclopropane.

We investigate the spectral redshift of high-order harmonics of the H2 + (D2 +) molecule by numerically solving the non-Born–Oppenheimer time-dependent Schrodinger equation (TDSE). The results show that the spectral redshift of high-order harmonics can be observed by adding a weak pulse in the falling part of the trapezoidal laser pulses. Comparing with the H2 + molecule, the shift of high-order harmonic generation (HHG) spectrum for the D2 + molecule is more obvious. We employ the spatial distribution in HHG and time-frequency analysis to illustrate the physical mechanism of the spectral redshift of high-order harmonics.

With the three-dimensional (3D) classical ensemble method, we theoretically investigate the recollision dynamics in strong-field nonsequential double ionization (NSDI) of Ar by counter-rotating two-color circularly polarized laser fields. With the analysis of the NSDI trajectories, we find that not only multiple-recollision but also single-recollision processes occur in the double ionization events. Furthermore, the multiple-recollision and single-recollision processes both undergo the recollision-induced excitation with subsequent ionization (RESI) and recollision-induced ionization (RII). The angle between the momentum and the force of the laser field at the recollision moment can affect the times of the recollision.

Molecular high-order harmonic generation of H and its isotopes is investigated by numerical simulations of the non-Born–Oppenheimer time-dependent Schrodinger equations. The general characteristic of the typical high-order harmonic generation (HHG) spectra for the H molecule indicates that only the odd harmonics can be generated. Here we show that how the initial vibrational states and nuclear dynamics break down this standard characteristic, i.e. a redshift or blueshift of the harmonics appears. We investigate the effect of the initial vibrational states on the redshift or blueshift of the HHG spectrum under trapezoidal laser pulses. The ionization probability and time-frequency analysis are used to illustrate the physical mechanism of the shift of the harmonics. We also show the HHG spectra from the different isotopes of H molecule with different initial vibrational states.

With the classical ensemble method, the correlated-electron dynamics of Mg atom from a doubly excited, transition Coulomb complex in few-cycle circularly polarized (CP) laser field at low laser intensity is theoretically investigated. The low energy transfer during the recollision process indicates that the two electrons cannot release directly, but it can pass through a doubly excited state, and then escape with the ionization time difference. The numerical results show that the feature of the sequential double ionization (SDI) can be observed in the nonsequential double ionization (NSDI) process. The SDI-like results demonstrate that the intermediate state has lost any memory of its formation dynamics. The distribution of the angle between the two release directions of the two electrons also depends on the ionization time difference. Finally, the influence of e-e Coulomb repulsion is discussed.

The control of the spatial distribution in the high-order harmonic generation (HHG) of a H2 + molecule is theoretically investigated by the combination of a mid-infrared laser pulse and a terahertz (THz) field. We use a THz pulse to steer the electron motion, and the numerical results show that the cutoff of the harmonic from the recombination of the electron with the nucleus along the negative-z direction is enhanced and the case along the positive-z direction is suppressed when a THz field is added. The underlying physical mechanism is illustrated by the semi-classical three step model and the ionization probability. The time-frequency analysis further demonstrates the asymmetric spatial distribution in a HHG controlled by adding a THz field.

To study the effects and role of leptin pretreatment and ischemic preconditioning (IPC) on the reduction of myocardial ischemia/reperfusion injury (MIRI) in mouse.Thirty-six male C57BL/6 mice were randomized into five groups: (1)sham operation group (n=12); (2) brief ischemia/reperfusion (I/R) treatment group (n=6), in which the mice were subjected to three cycles of a 3-minute regional ischemia followed by a 5-minute reperfusion (I/R cycle); (3) MIRI group (n=6), in which MIRI was established in the mice by blocking anterior descending branch of left coronary artery for 30 minutes, followed by 120 minutes reperfusion; (4) IPC group (n=6), in which three I/R cycles were performed on the mice followed by the MIRI protocol; (5) leptin pretreatment group (leptin group, n=6), in which 50 microg/kg of leptin was injected intraperitoneally to the mice 30 minutes before myocardial ischemia. From 6 mice of the sham operation group and from the mice of brief I/R group, serum samples were collected at different time points (0, 5, 30 and 120 minutes) after reperfusion to measure changes in serum leptin level. From the rest of the mice, blood and heart samples were harvested at 120 minutes after reperfusion to analyze the myocardial function and infarct size, leptin, myeloperoxidase (MPO), tumor necrosis factor-alpha (TNF-alpha), and interleukin-6 (IL-6) levels.IPC procedure resulted in an increase in serum leptin level shortly after reperfusion. The leptin level increased significantly than that of sham operation group [(6.24+/-2.34) microg/L vs. (1.35+/-0.45) microg/L] at 5 minutes after I/R, and reached the peak value of (12.36+/-1.33) microg/L at 30 minutes after I/R. Then it gradually decreased to its original (0 minute after reperfusion) value [(1.96+/-1.33) microg/L] at 120 minutes after I/R. There was no difference compared with sham operation group [(1.16+/-0.25) microg/L, P0.05]. Administration of leptin or IPC before MIRI significantly reduced infarct size [(11.50+/-2.26)%, (9.00+/-1.90)% vs. (37.00+/-2.53)%], the myocardial leptin levels [(8.36+/-3.42) microg/g, (6.71+/-2.03) microg/g vs. (15.51+/-3.92) microg/g], MPO [(17.10+/-3.95) microg/g, (13.33+/-2.88) microg/g vs. (30.83+/-4.06) microg/g], serum leptin levels [(15.03+/-1.87) microg/L, (11.85+/-0.72) microg/L vs. (29.55+/-2.31) microg/L], serum TNF-alpha [(35.10+/-10.12) ng/L, (27.04+/-5.18) ng/L vs. (81.34+/-14.20) ng/L], and IL-6 levels [(167.39+/-72.83) ng/L, (149.13+/-37.69) ng/L vs. (477.30+/-29.09) ng/L, all P0.01].Pretreatment using leptin results in preconditioning-like tolerance against infarction dysfunction. This cardiac protection effect is mediated, in part, via suppression of inflammation in preconditioned myocardium.

The carrier-envelop-phase (CEP) dependence of nonsequential double ionization (NSDI) of atomic Ar with few-cycle elliptically polarized laser pulse is investigated using 2D classical ensemble method. We distinguish two particular recollision channels in NSDI, which are recollision-impact ionization (RII) and recollision-induced excitation with subsequent ionization (RESI). We separate the RII and RESI channels according to the delay time between recollision and final double ionization. By tracing the history of the trajectories, we find the electron correlation spectra as well as the competition between the two channels are sensitively dependent on the laser field CEP. Finally, control can be achieved between the two channels by varying the CEP.