Memristive switching in the surface of a charge-density-wave topological semimetal

Owing to the outstanding properties provided by nontrivial band topology,topological phases of matter are considered as a promising platform towards low-dissipation electronics,efficient spin-charge conversion,and topological quantum computation.Achieving ferroelectricity in topological materials enables the non-volatile control of the quantum states,which could greatly facilitate topological electronic research.However,ferroelectricity is generally incompatible with systems featuring metallicity due to the screening effect of free carriers.In this study,we report the observation of memristive switching based on the ferroelectric surface state of a topological semimetal(TaSe_(4))2I.We find that the surface state of(TaSe_(4))2I presents out-of-plane ferroelectric polarization due to surface reconstruction.With the combination of ferroelectric surface and charge-density-wave-gapped bulk states,an electric-switchable barrier height can be achieved in(TaSe_(4))2I-metal contact.By employing a multi-terminal-grounding design,we manage to construct a prototype ferroelectric memristor based on(TaSe_(4))2I with on/off ratio up to 103,endurance over 103 cycles,and good retention characteristics.The origin of the ferroelectric surface state is further investigated by first-principles calculations,which reveal an interplay between ferroelectricity and band topology.The emergence of ferroelectricity in(TaSe_(4))2I not only demonstrates it as a rare but essential case of ferroelectric topological materials,but also opens new routes towards the implementation of topological materials in functional electronic devices.

The effect of tensile and fluid shear stress on the in vitro degradation of magnesium alloy for stent applications

Magnesium alloys have gained great attention as biodegradable materials for stent applications.Cardiovascular stents are continuously exposed to different types of mechanical loadings simultaneously during service,including tensile,compressive and fluid shear stress.In this study,the in vitro degradation of WE43 wires was investigated under combined effect of tensile loading and fluid shear stress and compared with that experienced an individual loading condition.For the individual mechanical loading treatment,the degradation of magnesium wires was more severely affected by tensile loading than fluid shear stress.Under tensile loading,magnesium wires showed faster increment of corrosion rates,loss of mechanical properties and localized corrosion morphology with the increasing tensile loadings.With the combined stress,smaller variation of the corrosion rates as well as the slower strength degeneration was shown with increasing stress levels,in comparison with the individual treatment of tensile loading.This study could help to understand the effect of complex stress condition on the corrosion of magnesium for the optimization of biodegradable magnesium stents.

Bio-remediation of acephate–Pb(Ⅱ) compound contaminants by Bacillus subtilis FZUL-33

Removal of Pb^（2＋）and biodegradation of organophosphorus have been both widely investigated respectively. However, bio-remediation of both Pb^（2＋）and organophosphorus still remains largely unexplored. Bacillus subtilis FZUL-33, which was isolated from the sediment of a lake, possesses the capability for both biomineralization of Pb^（2＋）and biodegradation of acephate. In the present study, both Pb^（2＋）and acephate were simultaneously removed via biodegradation and biomineralization in aqueous solutions.Batch experiments were conducted to study the influence of p H, interaction time and Pb^（2＋）concentration on the process of removal of Pb2＋. At the temperature of 25°C, the maximum removal of Pb^（2＋）by B. subtilis FZUL-33 was 381.31 ± 11.46 mg/g under the conditions of p H 5.5, initial Pb^（2＋）concentration of 1300 mg/L, and contact time of 10 min. Batch experiments were conducted to study the influence of acephate on removal of Pb^（2＋）and the influence of Pb2＋on biodegradation of acephate by B. subtilis FZUL-33. In the mixed system of acephate–Pb2＋, the results show that biodegradation of acephate by B. subtilis FZUL-33 released PO43＋, which promotes mineralization of Pb2＋. The process of biodegradation of acephate was affected slightly when the concentration of Pb2＋was below 100 mg/L. Based on the results, it can be inferred that the B. subtilis FZUL-33 plays a significant role in bio-remediation of organophosphorus-heavy metal compound contamination.