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Introduction Although endodontic infection is caused by multi-bacteria species, Enterococcus faecalis is usually isolated in chronic apical periodontitis. The aim of this study was to evaluate the effectiveness and mechanical safety of cold plasma therapy in disinfecting 3-week E. faecalis biofilms. Methods Teeth with 3-week E. faecalis biofilm were treated with AC argon/oxygen (Ar/O 2 ) cold plasma for various treatment times and compared with those treated with Ca(OH) 2 , 2% chlorhexidine gel, and Ca(OH) 2 /chlorhexidine for a week. Antimicrobial efficacy was assessed by colony-forming unit method. Scanning electron microscopy was used to assess the morphologic changes of E. faecalis biofilm by plasma. Confocal laser scanning microscopy was used to confirm the viability of the biofilm after the plasma treatment. Microhardness and roughness changes of root canal dentin caused by plasma were verified with Vickers Hardness Tester and 3D Profile Measurement Laser Microscope, respectively. Results There were no detectable live bacteria after 12 minutes of cold plasma treatment. This was further confirmed by scanning electron microscopy and confocal laser scanning microscopy results. Microhardness and roughness of root canal dentin showed no significant difference after plasma treatment. Conclusions Atmospheric pressure cold plasma is an effective therapy in endodontics for its strong sterilization effect on fully matured biofilm within a few minutes. Meanwhile, it has an accepted mechanical safety for its low temperature and not affecting the microhardness and roughness of root canal dentin significantly. [ABSTRACT FROM AUTHOR]

Cu–9Ni–6Sn specimens with different Nb contents ranging from 0 to 0.22 wt% were prepared by a vacuum induction furnace, and needle-like NbNi 3 particles were found at the grain boundaries and interior after solution treatment. The results indicated that these NbNi 3 particles suppressed the discontinuous precipitation (DP) growth during aging treatment. By using Johnson-Mehl-Avrami-Kolmogorov (JMAK) equation and Arrhenius equation, the kinetics of DP is also figured out and the activation energy (Q) of the DP in Cu–9Ni–6Sn- x Nb (x = 0, 0.05, 0.22 wt%) alloys are 75.8 kJ/mol, 80.9 kJ/mol and 88.5 kJ/mol, respectively, indicating that the atom diffusion for producing DP is more difficult in Nb-bearing alloys, and the formation of DP is inhibited correspondingly. What's more, the lamellar spacing (S) of DP increased and the growth rate of DP decreased in the with the Nb-bearing Cu–9Ni–6Sn alloy. • Fine grain sizes are appeared in Nb-addition alloy. • The NbNi 3 particles are observed in Nb-addition alloy. • The DP in Cu–9Ni–6Sn alloy can be suppressed by addition of Nb. • Interlamellar spacing of DP increases with increasing Nb content. [ABSTRACT FROM AUTHOR]

A highly regio- and stereoselective trans -hydrofluorination of N -sulfonyl ynamides has been realized with AgF as the fluorination reagent, affording ( Z )-α-fluoroenamides in good to excellent yields. The reaction proceeds under mild reaction conditions and shows good functional group compatibility. [ABSTRACT FROM AUTHOR]

• Twenty-five circular HCFHST stub columns after exposure to the heating and cooling process were tested under axial compression. • The effects of various parameters on the temperature distribution, spalling of the steel-concrete interface, failure modes, mid-height stress and strain, and post-fire mechanical performance were analyzed. • Available design methods for normal strength CFST columns were evaluated for their applicability to the unexposed and exposed HCFHST columns. The high-strength concrete-filled high-strength steel tubular (HCFHST) column is an innovative type of high-performance steel-concrete composite component, which has a broad prospect for engineering applications. To investigate the axial compressive behavior of post-fire HCFHST stub columns with circular cross-sections, twenty-five specimens were heated following ISO 834 standard fire and then loaded to failure under axial compression after being cooled. The effects of various heating durations, concrete and steel strength on the temperature distribution, spalling of the steel-concrete interface, post-fire ultimate bearing capacity and axial stiffness were analyzed. The residual ultimate capacity and axial stiffness of HCFHST stub columns experience a pronounced decrease as the heating duration increases. High strength steel has no significant contribution to the enhancement of the post-fire axial stiffness of HCFHST stub columns, and the effect level of high-strength concrete on the failure load of composite columns subjected to different heating durations is similar. Finally, the applicability of relevant equations for the residual compressive capacity of the ordinary strength CFST column to HCFHST stub columns was evaluated. The evaluation results revealed that available methods of conventional strength CFST stub columns cannot obtain accurate post-fire resistance predictions of circular HCFHST stub columns. [ABSTRACT FROM AUTHOR]

Abstract: A novel copper-catalyzed, base-free direct thiolation of xanthines and related heterocycles is described, featuring the use of inexpensive Cu(OAc)2·H2O as the catalyst, O2 as a clean and cheap oxidant, and easy-to-handle disulfides as the thiolation reagents. It works well for both aryl and alkyl disulfides. Moreover, the resultant products can be converted into 8-(hetero)aryl- or alkenyl-substituted xanthines in good yields via the Liebeskind–Srogl coupling reaction. [Copyright &y& Elsevier]

• Simulate accurately time histories of the piston slap impact forces and the vibratory response of cylinder. • Coupled system between engine block structure and acoustic field of water coolant passage. • Analyze the influences of sound speed and natural modes. Liner cavitation is caused by water pressure fluctuation in water coolant passage. When the negative pressure falls below the saturated vapor pressure, the impulsive pressure following the implosion of cavitation bubbles causes cavitation erosion on wet cylinder liner surface. Prediction of coolant pressure fluctuation is crucial to relieve liner cavitation erosion. Vibration of internal combustion engine especially liner vibration is thought of as the primary cause of liner cavitation. Piston slap is deemed as the major factor of engine vibration. The present work establishes a coupled system between entire engine structure and water coolant passage acoustic field considering their vibration characteristics by finite element method and boundary element method. Mechanism of piston slap is proposed and the resulting slap forces are applied on cylinder to predict water coolant pressure fluctuation. The influence of sound speed variation of acoustic field on pressure fluctuation is discussed. The contributions of natural modes of engine and water acoustic field to largest negative pressure are analyzed. [ABSTRACT FROM AUTHOR]

• We investigated the hydrate formation mechanism using hydrogen-propane gas. • A pressure >2.0 MPa is not conducive to hydrogen-propane hydrate formation. • Pressure range of 0.8–1.8 MPa is optimal for hydrogen-propane hydrate formation. Hydrogen-propane hydrate is a promising practical hydrogen storage medium. However, the optimal conditions for the hydrogen-propane hydrate remain unclear. In this study, the thermodynamic and kinetic characteristics of hydrogen-propane gas (molar ratio 0.67/0.33) hydrate formation were investigated using experiments and molecular dynamics simulation. Moreover, the effect of liquid propane on hydrogen-propane hydrate formation in the pressure range of 0.5–2.8 MPa was investigated. The characteristic peaks of the heat flow curve during the experiment showed that under the pressure range of 2.0–2.8 MPa, propane hydrate and the ice-liquid propane mixture formed but not hydrogen-propane hydrate. Raman spectroscopy verified that when the initial pressure was higher than 2.0 MPa, only propane hydrate formed. Molecular dynamics simulation results showed that if liquefied propane exists, propane molecules will aggregate, preventing water molecules from contacting crystal nuclei and inhibiting hydrogen bonding, further hindering the growth of hydrogen-propane hydrate. Based on the experimental and theoretical analysis, the pressure range of 0.8–1.8 MPa is optimal for hydrogen-propane hydrate formation, specifically corresponding to the initial molar ratio of hydrogen to propane at 0.67/0.33. This study aids in determining the optimal operating conditions for hydrate-based hydrogen storage. [ABSTRACT FROM AUTHOR]

• A new type of impedance model at opening ports has been confirmed. • Impedance model combines a one order sound tube with circular piston sound source. • Pressure under the vibration of all walls was smaller than single cylinder vibration. • Integration of liner and cylinder block might help to eliminate cavitation potential. Liner cavitation erosion results from pressure fluctuation of water coolant around cylinders. The characteristics of acoustic field of water chamber are especially important to estimate the potential of liner cavitation. The specialty of water chamber geometry requires a new impedance model of the opening ports, which was simulated by combining a one dimensional sound pipe with piston sound source at infinite plate. The validity of the proposed impedance model has been confirmed by the comparison of attenuation ratio with experiment of actual cylinder block. By changing the clearance between piston and cylinder liner, the influence of cylinder vibration acceleration on water pressure variation was studied, which revealed that the larger clearance results in stronger pressure fluctuation dominated by certain frequencies components. The pressure fluctuation induced by the vibration of whole walls was compared with that induced by the vibration of one cylinder, it revealed that integration of liner and cylinder block may reduce the amplitude of pressure fluctuation. [ABSTRACT FROM AUTHOR]