Highly Robust Reentrant Superconductivity in CsV_3Sb_5 under Pressure

We present the superconducting(SC) property and high-robustness of structural stability of kagome CsV_3Sb_5 under in situ high pressures.For the initial SC-I phase,its T_c is quickly enhanced from 3.5 K to 7.6 K and then totally suppressed at P-10 GPa.With further increasing pressure,an SC-Ⅱ phase emerges at P-15 GPa and persists up to 100 GPa.The T_c rapidly increases to the maximal value of 5.2 K at P=53.6 GPa and slowly decreases to 4.7 K at P=100 GPa.A two-dome-like variation of T_c in CsV_3Sb_5 is concluded here.The Raman measurements demonstrate that weakening of E_(2g) mode and strengthening of E_(1g) mode occur without phase transition in the SC-II phase,which is supported by the results of phonon spectra calculations.Electronic structure calculations reveal that exertion of pressure may bridge the gap of topological surface nontrivial states near E_F,i.e.,disappearance of Z2 invariant.Meanwhile,the Fermi surface enlarges significantly,consistent with the increased carrier density.The findings here suggest that the change of electronic structure and strengthened electron-phonon coupling should be responsible for the pressure-induced reentrant SC.

Novel Superconducting Electrides in Ca–S System under High Pressures

Due to their unique structure properties,most of the electrides that possess extra electrons locating in interstitial regions as anions are insulators.Metallic and superconducting electrides are very rare under ambient conditions.We systematically search possible compounds in Ca-S systems stabilized under various pressures up to 200 GPa,and investigate their crystal structures and properties using first-principles calculations.We predict a series of novel stoichiometries in Ca-S systems as potential superconductors,including P2_(1)/m Ca_(3)S, Pnma Ca_(3)S,Pnma Ca_(2)S,Cmcm Ca_(2)S,Fddd CaS_(2),Immm CaS_(3) and C2/c CaS_(4).The P4mbm Ca_(3)S phase exhibits a maximum Tc value of ~20K.It is interesting to notice that the P2_(1)/m Ca_(3)S and Pnma Ca_(2)S stabilized at 60 and 50 GPa behave as superconducting electrides with critical temperatures Tc of 7.04 K and 0.26 K,respectively.More importantly,our results demonstrate that P2_(1)/m Ca_(3)S and Pnma Ca_(2)S are dynamically stable at 5 GPa and 0 GPa,respectively,indicating a high possibility to be quenched to ambient condition or synthesized using the large volume press.

Stable Compositions, Structures and Electronic Properties in K–Ga Systems Under Pressure

New stable stoichiometries in K-Ga systems are firstly investigated up to 100 GPa by the unbiased structure searching techniques.Six novel compositions as K4Ga,K3Ga,K2Ga,KGa,KGa2 and KGa4 are found to be thermodynamically stable under pressure.Most of the predicted stable phases exhibit metallic character,while the Fd3m KGa phase behaves as a semiconductor with a bandgap ~1.62 eV.Notably,the gallium atoms exhibit different interesting morphologies;e.g.,Ga2 units,zigzag chains,six rings and cage.We further investigate the bonding nature of K-Ga systems with help of electron localization function and Bader charge analyses.Strong covalent bonding characteristics are found between the Ga and Ga atoms,and ionic bonding patterns are observed between the K and Ga atoms.Meanwhile,we notice charge transferring from the K atom to the Ga atom in the K-Ga systems.The present results can be helpful for understanding the diverse structures and properties of K-Ga binary compounds at high pressures.

Correlation of p38MAPK,ERK1/2 and JNK expression in peripheral blood with the cytokines and pain mediators in patients with post-herpetic neuralgia

Objective: To study the correlation of p38MAPK, ERK1/2 and JNK expression in peripheral blood with the cytokines and pain mediators in patients with post-herpetic neuralgia (PHN). Methods: Patients who were diagnosed with herpes zoster for the first time in the Second Hospital of Hanbin District Ankang City between March 2015 and April 2016 were selected and divided into the PHN group who were combined with post-herpetic neuralgia and the pure HZ group who were without neuralgia, and the healthy volunteers who received physical examination in the Second Hospital of Hanbin District Ankang City during the same period were selected as control group. The peripheral blood was collected to determine the expression of MAPK signaling molecules, and serum was collected to determine the contents of cytokines and pain mediators. Results: p38MAPK, ERK1/2 and JNK mRNA expression in peripheral blood as well as 5-HT, CGRP, SP, NSE, S100B, IFN-γ, TNF-α and IL-17 levels in serum of PHN group and HZ group were significantly higher than those of control group while β-EP levels were significantly lower than that of control group;p38MAPK, ERK1/2 and JNK mRNA expression in peripheral blood as well as 5-HT, CGRP, SP, NSE, S100B, IFN-γ, TNF-α and IL-17 levels in serum of PHN group were significantly higher than those of HZ group while β-EP level was significantly lower than that of HZ group. p38MAPK, ERK1/2 and JNK expression in peripheral blood of PHN patients were positively correlated with CGRP, 5-HT, SP, NSE, S100B, IFN-γ, TNF-α and IL-17 levels in serum, and negatively correlated with β-EP level in serum. Conclusion: The high expression of p38MAPK, ERK1/2 and JNK in peripheral blood of PHN patients can increase the secretion of cytokines and algogenic mediators and decrease the secretion of analgesic mediators.

环硅氧烷阴离子开环均聚及共聚研究进展

聚硅氧烷是一类典型的有机/无机杂化聚合物,具有耐高低温、优异的环境适应性等突出性能,在航空航天、国防科技等领域应用广泛.环硅氧烷单体阴离子开环聚合是制备不同链结构及功能化聚硅氧烷的重要途径,也是推动有机硅聚合物发展的重要研究领域之一.本文以阴离子开环聚合制备聚硅氧烷所涉及的环硅氧烷单体为线索,梳理了与不同化学结构环硅氧烷单体均聚及共聚相匹配的引发体系、聚合条件,以及聚合产物状态,并对相关研究工作做了论述介绍.此外,本文基于此线索对代表性研究体系做了简明罗列,便于高效检索及整体对比认知.

Pressure fluctuation characteristics in the pressurization unit of a multiphase pump

The tip clearance induces the tip leakage vortex(TLV),which has a great impact on the pressure fluctuation characteristics of the multiphase pump.To investigate the effect of the tip clearance on the pressure fluctuations,based on the Reynolds time-averaged Navier-Stokes equation and the shear stress transfer(SST)k-ωturbulence model,the three-dimensional turbulent flow in the pump is numerically simulated for different tip clearances in the water and gas-liquid two-phase cases by using the ANSYS CFX software and the results are verified with experimental data.It is shown the greater pressure fluctuation intensity corresponds with the TLV both in the water and gas-liquid two-phase cases.In the meantime,the location of the maximum pressure fluctuation intensity is related to the tip clearance size.In addition,for different tip clearances,the pressure fluctuation intensity with the rotor and stator interaction(RSI)is relatively larger.The difference is that when R_(tc)=1.5 mm,the pressure fluctuation intensity near the impeller middle point is also relatively larger.On the whole,the pressure fluctuation intensity in the gas-liquid two-phase case is larger than that in the water case.Furthermore,the gas causes the frequency of the high-amplitude pressure fluctuation in the impeller and the diffuser to be shifted from 7 f_(n)(f_(n) denotes impeller rotational frequency)and 3 f_(n) to the low-frequency region,respectively.The pressure fluctuations at the blade-passing frequency(BPF)and the multiple BPFs gradually disappear.Meanwhile,the amplitude at the dominant frequency in the gas-liquid two-phase case is at least one order of magnitude smaller than that in the water case,and the peak-to-peak value of the pressure fluctuation is also much smaller.