Effects of friction stir processing and nano-hydroxyapatite on the microstructure,hardness,degradation rate and in-vitro bioactivity of WE43 alloy for biomedical applications

Nowadays,magnesium alloys are emerging in biomedical implants for their similar properties to natural bones.However,the rapid degradation of magnesium alloys in biological media hinders successful implantation.Refinement of microstructure,as well as reinforcement particles can significantly improve the degradation rate.In this work,multi-pass friction stir processing(FSP)was proposed to synthesize WE43/nano-hydroxyapatite(n HA)surface composite,the microstructure,reinforced particle distribution,micro-hardness,corrosion behavior and in-vitro bioactivity were studied.The subsequent FSP passes of WE43 alloy and WE43/n HA composite refined the grain size which was reduced by 94.29%and 95.92%(2.63 and 1.88μm,respectively)compared to base metal after three passes.This resulted in increasing the microhardness by 120%(90.86 HV0.1)and 135%(105.59 HV0.1)for the WE43 and WE43-n HA,respectively.It is found that increasing FSP passes improved the uniform distribution of n HA particles within the composite matrix which led to improved corrosion resistance and less degradation rate.The corrosion rate of the FSPed WE43/n HA composite after three passes was reduced by 38.2%(4.13 mm/year)and the degradation rate was reduced by 69.7%(2.87 mm/y).This is attributed to secondary phase(Mg24Y5and Mg41Nd5)particle fragmentation and redistribution,as well as a homogeneous distribution of n HA.Additionally,the growing Ca-P and Mg(OH)2layer formed on the surface represented a protective layer that reduced the degradation rate.The wettability test revealed a relatively hydrophilic surface with water contact angle of 49.1±2.2°compared to 71.2±2.1°for base metal.Also,biomineralization test showed that apatite layer grew after immersion 7d in simulated body fluid with atomic ratio of Ca/P 1.60 approaching the stoichiometric ratio(1.67)indicating superior bioactivity of FSPed WE43/n HA composite after three passes.These results raise that the grain refinement by FSP and introduction of n HA particles significantly improved the degradation rate and in-vitro bioactivity of WE43 alloy for biomedical applications.

A new angiotensin-converting enzyme inhibitor from Peperomia pellucida(L.) Kunth

Objective:To isolate,identify,and evaluate a new angiotensin-converting enzyme inhibitor from Peperomia pellucida(L.)Kunth herbs.Methods:A dried sample of Peperomia pellucida herb was successively macerated with n-hexane and ethyl acetate.The ethyl acetate extract solution was evaporated to obtain the crude extract.Vacuum liquid column chromatography and thin layer chromatography were performed to obtain two pure compounds.Then,both compounds were elucidated and identified using the spectroscopic method.Angiotensin-converting enzyme inhibitory activity studies of both compounds were determined using angiotensin-converting enzyme kit WST-1 with spectrophotometer microplate reader 96-well at 450 nm wavelength.Results:Two bioactive compounds were successfully isolated from Peperomia pellucida herb,including a new compound of 2,3,5-trimethoxy-9-(12,14,15-trimethoxybenzyl)-1 H-indene and pellucidin A.Both compounds demonstrated angiotensin-converting enzyme inhibitory activity,with IC50 values of 72 μM(27.95 μg/mL)and 1 1μM(4.4 μg/mL),respectively.Conclusions:In the present study,two active angiotensin-converting enzyme inhibitors were successfully isolated and purified from Peperomia pellucida which is used as an antihypertensive in traditional medicine,and support its use as an angiotensin-converting enzyme-inhibiting drug.

Effects of Mg^(2+) interstitial ion on the properties of Mg_(0.5+x/2)Si_(2-x)Al_(x)(PO_(4))_(3) ceramic electrolytes

Nasicon type,Mg_(0.5+x/2)Si_(2-x)Al_(x)(PO_(4))_(3) was synthesized using citric acid assisted sol-gel method.The X-ray diffraction was applied to investigate the effect of extra Mg^(2+)interstitial ion on the phase,unit cell parameters and structure of the samples.The Mg_(0.625)Si_(1.75)Al_(0.25)(PO_(4))_(3) sample exhibited highest bulk conductivity value of 1.54×10^(−4)S cm^(−1)at ambient temperature.The frequency dependence of theσac of these ceramic electrolytes follows the universal power law variation,σac(ω)=σo+Aωα.The conductivity parameters such as hopping frequencies,charge carrier concentration and mobile ion concentration proved that the increase in conductivity with x was due to the existence of Mg^(2+) interstitial ions.The experiment results also revealed that the dielectric constant and dielectric loss decreased with frequency.The Mg_(0.625)Si_(1.75)Al_(0.25)(PO_(4))_(3) was found to be electrochemically stable up to 2.51 V at ambient temperature.

A comprehensive review on the chemical constituents,sesquiterpenoid biosynthesis and biological activities of Sarcandra glabra

Sarcandra glabra(Thunb.)Nakai is a perennial evergreen herb categorised within the Sarcandra Gardner genus under the Chloranthaceae family.Indigenous to tropical and subtropical regions of East Asia and India,this species is extensively distributed across China,particularly in the southern regions(Sichuan,Yunnan,and Jiangxi).In addition to its high ornamental value,S.glabra has a rich history of use in traditional Chinese medicine,evident through its empirical prescriptions for various ailments like pneumonia,dysentery,fractures,bruises,numbness,amenorrhea,rheumatism,and other diseases.Besides,modern pharmacological studies have revealed various biological activities,such as antitumour,anti-bacterial,anti-viral anti-inflammatory and immunomodulatory effects.The diverse chemical constituents of S.glabra have fascinated natural product researchers since the 1900s.To date,over 400 compounds including terpenoids,coumarins,lignans,flavonoids,sterols,anthraquinones,organic acids,and organic esters have been isolated and characterised,some featuring unprecedented structures.This review comprehensively examines the current understanding of S.glabra’s phytochemistry and pharmacology,with emphasis on the chemistry and biosynthesis of its unique chemotaxonomic marker,the lindenane-type sesquiterpenoids.

Electrochemical performance of overlithiated Li1＋xNi0.8Co0.2O2： structural and oxidation state studies

Pure, layered compounds of overlithiated Li1＋xNi0.8Co0.2O2（x = 0.05 and 0.1） were successfully prepared by a modified combustion method. XRD studies showed that cell parameters of the material decreased with increasing the lithium content. SEM revealed that the morphology of particles changed from rounded polyhedral-like crystallites to sharp-edged polyhedral crystals with more doped lithium. EDX showed that the stoichiometries of Ni and Co agrees with calculated synthesized values. Electrochemical studies revealed the overlithiated samples have improved capacities as well as cycling behavior. The sample with x = 0.05 shows the best performance with a specific capacity of 113.29 mA.h.g-1 and the best capacity retention of 92.2% over 10 cycles. XPS results showed that the binding energy of Li ls is decreased for the Li doped samples with the smallest value for the x = 0.05 sample, implying that Li＋ ions can be extracted more easily from Li1.05Ni0.8Co0.2O2 than the other stoichiometries accounting for the improved performance of the material. Considerations of core level XPS peaks for transition metals reveal the existence in several oxidation states. However, the percentage of the＋3 oxidation state of transition metals for the when x = 0.1 is the highest and the availability for charge transition from the ＋3 to＋4 state of the transition metal during deintercalation is more readily available.