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Ophiopogon japonicus (OJ) is a traditional Chinese herbal medicine that has been used for thousands of years. Recently, the anticancer effects of OJ have been reported in multiple types of cancer, particularly in lung cancer. However, the underlying mechanisms remain unclear. In present study, the effects of OJ against NCI-H1299 human lung cancer cells were investigated, and the underlying mechanisms were explored using ultra-high-performance liquid chromatography-quadrupole time-of-flight mass spectrometry (UHPLC/Q-TOF-MS)-based cell metabolomics. As a result, OJ inhibited the proliferation, induced the apoptosis and suppressed the migration of NCIH1299 cells. A total of 22 differential metabolites responsible for the effects of OJ were screened and annotated based on the LC-MS-based cell metabolomics approach. The altered metabolites were involved in three metabolic pathways, including glycerophospholipid metabolism, ether lipid metabolism and glutathione metabolism. These results showed that cell metabolomics-based strategies are promising tools to discover the action mechanisms of OJ against lung cancer cells. [ABSTRACT FROM AUTHOR]

The electronic structure near the Fermi surface determines the electrical properties of the materials, which can be effectively tuned by external pressure. Bi0.5Sb1.5Te3 is a p-type thermoelectric material which holds the record high figure of merit at room temperature. Here it is examined whether the figure of merit of this model system can be further enhanced through some external parameter. With the application of pressure, it is surprisingly found that the power factor of this material exhibits λ behavior with a high value of 4.8 mW m-1 K-2 at pressure of 1.8 GPa. Such an enhancement is found to be driven by pressure-induced electronic topological transition, which is revealed by multiple techniques. Together with a low thermal conductivity of about 0.89 W m-1 K-1 at the same pressure, a figure of merit of 1.6 is achieved at room temperature. The results and findings highlight the electronic topological transition as a new route for improving the thermoelectric properties. [ABSTRACT FROM AUTHOR]

Objective: To analyze the prevalence of hand, foot and mouth disease (HFMD) in China during 2008-2018 and to provide reference for the prevention and control of HFMD. Methods: Literature eligible for selection was retrieved from the China's national knowledge infrastructure project (CNKI), and data from 2008-2018 Chinese HFMD reports were systematically analyzed. Excel and SPSS 20.00 were used for statistical analysis, and GraphPad Prism 6 was used for mapping. Results: The analysis showed that the average incidence rate of HFMD in China from 2008 to 2018 was 123.37±93.14 cases per 100,000 people, with a male-to-female ratio of (1.50±0.15):1, and the vast majority of cases were concentrated in the under-5 age group, mainly in scattered children. The time of onset of HFMD showed obvious seasonal characteristics, in which single-peak provinces were higher than double-peak provinces, with double-peak trends in April-July and October-November, respectively, and single-peak trends mainly in May-July. Based on the spatial distribution study, the incidence pattern showed obvious regional differences (P<0.05), with high incidence concentrated in the southeastern part of the country, and a gradual increase in incidence from west to east and north to south of China. EV71, CA16 and other enteric viruses were the main pathogens of HFMD, with EV71 accounting for 53.5%, CA16 is accounting for 14.3% and other enteric viruses accounting for 32.2% of the pathogens. Conclusions: The incidence of HFMD in China is high, with obvious geographical, seasonal, gender and age distribution characteristics. According to the pattern of HFMD incidence in the region, early prevention and control of key areas and groups is an effective way to cut off the spread of the disease. [ABSTRACT FROM AUTHOR]

Vibrational properties of isoviolanthrone are investigated by Raman scattering at pressures up to 30.5 GPa and room temperature. A complete characterization of phonon spectra under pressure is given for this material. The onset of a phase transition at 11.0 GPa and the formation of a new phase above 13.8 GPa are identified from both the frequency shifts and the changes in the full width half maxima of the intra- and internal modes. The transition is proposed to result from the changes of intra- and intermolecular bonding. The tendencies of the intensity ratios with pressure are in good agreement with the pressure dependence of the resistance at room temperature, indicating that the phase transition may be an electronic origin. The absence of the changes in the lattice modes indicates that the observed phase transition is probably a result of the structural distortions or reorganizations. The reversible character of the transition upon compression and decompression is determined in the entire pressure region studied. [ABSTRACT FROM AUTHOR]

We report high-pressure powder synchrotron X-ray diffraction measurements of overdoped BaFe1.8Co0.2As2 under quasi-hydrostatic pressure up to 40.1 GPa. Our results indicate that a tetragonal (T) to collapsed tetragonal (CT) phase transition occurs at 16.8 GPa and the two phase coexist until 30 GPa, which has not been previously observed in iron arsenide compounds. Both the lattice parameters a and c show discontinuous change for the T and CT phases. The decrease of the c lattice parameter is as large as 12.2% owing to the uniaxial pressure effect. The axial ratio c/a of the T phase exhibits similar features to the other 122-type compounds below 16.8 GPa, whereas there is a very small increase with increasing pressure in the two phase coexistence region. Because of the relationship between the axial ratio and superconductivity, the abnormal expansion may be related to the sudden increase of the strength of antiferromagnetic spin fluctuations. [ABSTRACT FROM AUTHOR]

Raman-scattering measurements were performed on Kxphenanthrene (0 ⩽ x ⩽ 6.0) at room temperature. Three phases (x = 3.0, 3.5, and 4.0) are identified based on the obtained Raman spectra. Only the K3phenanthrene phase is found to exhibit the superconducting transition at 5 K. The C-C stretching modes are observed to broaden and become disordered in Kxphenanthrene with x = 2.0, 2.5, 6.0, indicating some molecular disorder in the metal intercalation process. This disorder is expected to influence the nonmetallic nature of these materials. The absence of metallic character in these nonsuperconducting phases is found from the calculated electronic structures based on the local density approximation. [ABSTRACT FROM AUTHOR]

Superconductivity can be induced with the application of pressure but it disappears eventually upon heavy compression in the iron-based parent compound BaFe2As2. Structural evolution with pressure is used to understand this behavior. By performing synchrotron X-ray powder diffraction measurements with diamond anvil cells up to 26.1 GPa, we find an anomalous behavior of the lattice parameter with a S shape along the a axis but a monotonic decrease in the c-axis lattice parameter with increasing pressure. The close relationship between the axial ratio c/a and the superconducting transition temperature Tc is established for this parent compound. The c/a ratio is suggested to be a measure of the spin fluctuation strength. The reduction of Tc with the further increase of pressure is a result of the pressure-driven weakness of the spin-fluctuation strength in this material. [ABSTRACT FROM AUTHOR]

The experimental discovery of superconductivity was reported in Sm-doped chrysene with Tc ~ 5 K, which provides vital material for exploring unique superconducting mechanism of rare-earth metal doped polycyclic aromatic hydrocarbons. Here the crystal, electronic structures and magnetic characteristics of Sm-doped chrysene have been investigated by the first-principles calculation using the generalized gradient approximation (GGA) plus U method, also including van der Waals correction. We find that Sm-doped chrysene with C2/c space group is the most stable where doped Sm atoms stay on the relative middle of chrysene molecules. This material is stabilized at antiferromagnetic ground-state with the metallic feature. The calculated spin magnetic moment of Sm atom indicates that there are two electrons transferring from Sm to chrysene molecule. Within the framework of GGA+U, the C-2p electronic states mainly contribute to the Fermi surface. Electronic correlation effects are significant to understand the superconductivity in Sm-doped chrysene. [ABSTRACT FROM AUTHOR]

Based on the density functional theory plus the effective Coulomb repulsion U, we have investigated the crystal structure, electronic properties and magnetic characteristics in Sm-doped phenanthrene, recently characterized as a superconductor with Tc ~ 5 - 6 Kelvin. Calculated total energies of different magnetic states indicate that Sm-doped phenanthrene is stable at the ferromagnetic ground-state. Considered the strong electronic correlations effect due to the intercalation of Sm-4f electrons, we found that the Sm-4f contributes to the Fermi surface together with C-2p, which is different from K-doped phenanthrene. Compared with alkali-metaldoped phenanthrene, Sm atom has larger local magnetic moment, which suppresses the superconductivity in conventional superconductors. Our results indicate that the electron-electron correlations play an important role in superconductivity of Sm-doped phenanthrene. [ABSTRACT FROM AUTHOR]

The mechanism of high-temperature superconductivity of copper oxides (cuprates) remains unsolved puzzle in condensed matter physics. The cuprates represent extremely complicated system, showing fascinating variety of quantum phenomena and rich phase diagram as a function of doping. In the suggested "superconducting glue" mechanisms, phonon and spin excitations are invoked most frequently, and it appears that only spin excitations cover the energy scale required to justify very high transition temperature Tc∼165K (as in mercury-based triple layer cuprates compressed to 30 GPa). It appears that pressure is quite important variable helping to boost the Tc record by almost 30°. Pressure may be also considered as a clean tuning parameter, helping to understand the underlying balance of various energy scales and ordered states in cuprates. In this paper, a review of mostly our work on cuprates under pressure will be given, with the emphasis on the interactions between phonon and spin excitations. It appears that there is a strong coupling between superexchange interaction and stretching in-plane oxygen vibrations, which may give rise to a variety of complex phenomena, including the charge-density wave state intertwined with superconductivity and attracting a lot of interest recently. [ABSTRACT FROM AUTHOR]

Saponins are glycosides with triterpenoid or spirostane aglycones that demonstrate various pharmacological effects against mammalian diseases. To promote the research and development of anticancer agents from saponins, this review focuses on the anticancer properties of several typical naturally derived triterpenoid saponins (ginsenosides and saikosaponins) and steroid saponins (dioscin, polyphyllin, and timosaponin) isolated from Chinese medicines. These saponins exhibit in vitro and in vivo anticancer effects, such as anti-proliferation, anti-metastasis, anti-angiogenesis, anti-multidrug resistance, and autophagy regulation actions. In addition, related signaling pathways and target proteins involved in the anticancer effects of saponins are also summarized in this work. [ABSTRACT FROM AUTHOR]

At room environment, all materials can be classified as insulators or metals or in-between semiconductors, by judging whether they are capable of conducting the flow of electrons. One can expect an insulator to convert into a metal and to remain in this state upon further compression, i.e., pressure-induced metallization. Some exceptions were reported recently in elementary metals such as all of the alkali metals and heavy alkaline earth metals (Ca, Sr, and Ba). Here we show that a compound of CLi4 becomes progressively less conductive and eventually insulating upon compression based on ab initio density-functional theory calculations. An unusual path with pressure is found for the phase transition from metal to semimetal, to semiconductor, and eventually to insulator. The Fermi surface filling parameter is used to describe such an antimetallization process. [ABSTRACT FROM AUTHOR]

The structural, vibrational, and electronic properties of GaAs nanowires have been studied in the metastable wurtzite phase via Resonant Raman spectroscopy and synchrotron X-ray diffraction measurements in diamond anvil cells under hydrostatic conditions between 0 and 23 GPa. The direct band gap E0 and the crystal field split-off gap E0 + Δ of wurtzite GaAs increase with pressure and their values become close to those of zinc-blende GaAs at 5 GPa, while being reported slightly larger at lower pressures. Above 21 GPa, a complete structural transition from the wurtzite to an orthorhombic phase is observed in both Raman and X-ray diffraction experiments. [ABSTRACT FROM AUTHOR]

The self-interstitial atoms (SIAs) mediate the evolution of micro-structures which is crucial in understanding the instabilities of hexagonal close packed (HCP) structures. Taking zirconium as a prototype, we investigate the pressure effect on the stabilities of SIAs using first-principles calculations based on density-functional theory. We found that the pressure greatly affects the stability of the SIAs. The SIAs in basal planes are more stable under pressure. The SIA configuration of the lowest formation energy changes from basal octahedral (BO) to octahedral (O) at a pressure of 21 GPa. The lowest formation enthalpy configuration switches from BO to S (split-dumbbell) at the pressure of 30 GPa. The formation volumes of SIAs decrease monotonically in response to an increase in pressure. Our results reveal that it is important to take pressure effects into account when predicting the micro-structural evolution of HCP structures. [ABSTRACT FROM AUTHOR]

We report an anomalous phase transition in compressed In2Se3. The high-pressure studies indicate that In2Se3 transforms to a new isosymmetric R-3m structure at 0.8GPa whilst the volume collapses by ~7%. This phase transition involves a pressure-induced interlayer shear glide with respect to one another. Consequently, the outer Se atoms of one sheet locate into the interstitial sites of three Se atoms in the neighboring sheets that are weakly connected by van der Waals interaction. Interestingly, this interlayer shear glide changes the stacking sequence significantly but leaves crystal symmetry unaffected. This study provides an insight to the mechanisms of the intriguing isosymmetric phase transition. [ABSTRACT FROM AUTHOR]

Pressure can tune material's electronic properties and control its quantum state, making some systems present disconnected superconducting region as observed in iron chalcogenides and heavy fermion CeCu2Si2. For CaC6 superconductor (Tc of 11.5 K), applying pressure first Tc increases and then suppresses and the superconductivity of this compound is eventually disappeared at about 18 GPa. Here, we report a theoretical finding of the re-emergence of superconductivity in heavily compressed CaC6. The predicted phase III (space group Pmmn) with formation of carbon nanofoam is found to be stable at wide pressure range with a Tc up to 14.7 K at 78 GPa. Diamond-like carbon structure is adhered to the phase IV (Cmcm) for compressed CaC6 after 126 GPa, which has bad metallic behavior, indicating again departure from superconductivity. Re-emerged superconductivity in compressed CaC6 paves a new way to design new-type superconductor by inserting metal into nanoporous host lattice. [ABSTRACT FROM AUTHOR]

Finding ways to achieve higher values of the transition temperature, Tc, in superconductors remains a great challenge. The superconducting phase is often one of several competing types of electronic order, including antiferromagnetism and charge density waves. An emerging trend documented in heavy-fermion and organic conductors is that the maximum Tc for superconductivity occurs under external conditions that cause the critical temperature for a competing order to go to zero. Recently, such competition has been found in multilayer copper oxide high-temperature superconductors (HTSCs) that possess two crystallographically inequivalent CuO2 planes in the unit cell. However, whether the competing electronic state can be suppressed to enhance Tc in HTSCs remains an open question. Here we show that pressure-driven phase competition leads to an unusual two-step enhancement of Tc in optimally doped trilayer Bi2Sr2Ca2Cu3O10+δ (Bi2223). We find that Tc first increases with pressure and then decreases after passing through a maximum. Unexpectedly, Tc increases again when the pressure is further raised above a critical value of around 24 GPa, surpassing the first maximum. The presence of this critical pressure is a manifestation of the crossover from the competing order to superconductivity in the inner of the three CuO2 planes. We suggest that the increase at higher pressures occurs as a result of competition between pairing and phase ordering in different CuO2 planes. [ABSTRACT FROM AUTHOR]

Understanding the behavior of hydrogen-rich systems at extreme conditions has significance to both condensed matter physics, where it may provide insight into the metallization and superconductivity of element one, and also to applied research areas, where it can provide guidance for designing improved hydrogen storage materials for transportation applications. Here we report the high-pressure study of the SiH4-H2 binary system up to 6.5 GPa at 300 K in a diamond anvil cell. Raman measurements indicate significant intermolecular interactions between H2 and SiH4. We found that the H2 vibron frequency is softened by the presence of SiH4 by as much as 40cm-1 for the fluid with 50 mol% H2 compared with pure H2 fluid at the same pressures. In contrast, the Si-H stretching modes of SiH4 shift to higher frequency in the mixed fluid compared with pure SiH4. Pressure-induced solidification of the H2-SiH4 fluid shows a binary eutectic point at 72(±2) mol% H2 and 6.1(±0.1) GPa, above which the fluid crystallizes into a mixture of two nearly end-member solids. Neither solid has a pure end-member composition, with the silane-rich solid containing 0.5-1.5 mol% H2 and the hydrogen-rich solid containing 0.5-1 mol% SiH4. These two crystalline phases can be regarded as doped hydrogen-dominant compounds. We were able to superpressurize the sample by 0.2-0.4 GPa above the eutectic before complete crystallization, indicating extended metastability. [ABSTRACT FROM AUTHOR]

There is a great interest in electronic transitions in hydrogen-rich materials under extreme conditions. It has been recently suggested that the group IVa hydrides such as methane (CH4), silane (SiH4), and germane (GeH4) become metallic at far lower pressures than pure hydrogen at equivalent densities because the hydrogen is chemically compressed in group IVa hydride compounds. Here we report measurements of Raman and infrared spectra of silane under pressure. We find that Sill4 undergoes three phase transitions before becoming opaque at 27-30 GPa. The vibrational spectra indicate the material transforms to a polymeric (frame-work) structure in this higher pressure range. Room-temperature infrared reflectivity data reveal that the material exhibits Drude-like metallic behavior above 60 GPa, indicating the onset of pressure-induced metallization. [ABSTRACT FROM AUTHOR]

High-temperature superconductivity in cuprates was discovered almost exactly 20 years ago, but a satisfactory theoretical explanation for this phenomenon is still lacking. The isotope effect has played an important role in establishing electron-phonon interaction as the dominant interaction in conventional superconductors. Here we present a unified picture of the oxygen isotope effect in cuprate superconductors based on a phonon-mediated d-wave pairing model within the Bardeen-Cooper-Schrieffer theory. We show that this model accounts for the magnitude of the isotope exponent as functions of the doping level as well as the variation between different cuprate superconductors. The isotope effect on the superconducting transition is also found to resemble the effect of pressure on the transition. These results indicate that the role of phonons should not be overlooked for explaining the superconductivity in cuprates. [ABSTRACT FROM AUTHOR]

The electronic properties, lattice dynamics, and electron–phonon coupling of the Cmmm phase of GeH4 have been studied by first-principle calculations using density functional perturbation theory. The electronic band structure shows the Cmmm phase metallic nature. It is found strong electron phonon interaction, and the superconducting critical temperature, predicted by Allen–Dynes modified McMillan equation, is about 40 K at 20 GPa. [ABSTRACT FROM AUTHOR]

High-pressure structural properties of tetramethylsilane are investigated by synchrotron powder x-ray diffraction at pressures up to 31.1 GPa and room temperature. A phase with the space group of Pnma is found to appear at 4.2 GPa. Upon compression, the compound transforms to two following phases: the phase with space groups of P21/c at 9.9 GPa and the phase with P2/m at 18.2 GPa successively via a transitional phase. The unique structural character of P21/c supports the phase stability of tetramethylsilane without possible decomposition upon heavy compression. The appearance of the P2/m phase suggests the possible realization of metallization for this material at higher pressure. [ABSTRACT FROM AUTHOR]