Enhancing corrosion resistance of plasma electrolytic oxidation coatings on AM50 Mg alloy by inhibitor containing Ba(NO_(3))_(2) solutions

To enhance the long-term corrosion resistance of the plasma electrolytic oxidation(PEO)coating on the magnesium(Mg)alloy,an inorganic salt combined with corrosion inhibitors was used for posttreatment of the coating.In this study,the corrosion performance of PEO-coated AM50 Mg was significantly improved by loading sodium lauryl sulfonate(SDS)and sodium dodecyl benzene sulf-onate into Ba(NO_(3))_(2) post-sealing solutions.Scanning electron microscopy,X-ray photoelectron spectroscopy,X-ray diffraction,Fourier transform infrared spectrometer,and ultraviolet-visible analyses showed that the inhibitors enhanced the incorporation of BaO_(2) into PEO coatings.Electrochemical impedance showed that post-sealing in Ba(NO_(3))_(2)/SDS treatment enhanced corrosion resistance by three orders of magnitude.The total impedance value remained at 926Ω·cm^(2)after immersing in a 0.5wt%NaCl solution for 768 h.A salt spray test for 40 days did not show any obvious region of corrosion,proving excellent post-sealing by Ba(NO_(3))_(2)/SDS treatment.The corrosion resistance of the coating was enhanced through the synergistic effect of BaO2 pore sealing and SDS adsorption.

CsABF3-activated CsSUT1 pathway is implicated in pre-harvest water deficit inducing sucrose accumulation in citrus fruit

Pre-harvest water deficit(PHWD)plays an important role in sugar accumulation of citrus fruit.However,the mechanism is not known well.Here,it was confirmed that PHWD promoted sucrose accumulation of citrus fruit,but had limited effect on fructose,glucose and total acid.A sucrose transporter,Cs SUT1,which localizes to the plasma membrane,was demonstrated to function in sucrose transport induced by PHWD.Compared to wild-type,Cs SUT1 overexpression in citrus calli stimulated sucrose,fructose and glucose accumulation,while its silencing in juice sacs reduced sucrose accumulation.Increased sugar accumulation in transgenic lines enhanced plant drought tolerance,and resulted in decreased electrolyte leakage,malondialdehyde and hydrogen peroxide contents,as well as increased superoxide dismutase activity and proline contents.An abscisic acid(ABA)-responsive transcription factor,Cs ABF3,was found with a same expression pattern with Cs SUT1 under PHWD.Yeast one-hybrid,electrophoretic mobility shift assay and dual-luciferase assays all revealed that Cs ABF3 directly bound with the Cs SUT1 promoter by ABA responsive elements.When Cs ABF3 was overexpressed in citrus calli,the sucrose,fructose and glucose concentration increased correspondingly.Further,transgenic studies demonstrated that Cs ABF3 could affect sucrose accumulation by regulating Cs SUT1.Overall,this study revealed a regulation of Cs ABF3 promoting Cs SUT1 expression and sucrose accumulation in response to PHWD.Our results provide a detail insight into the quality formation of citrus fruit.

Influence of incorporating Si_(3)N_(4) particles into the oxide layer produced by plasma electrolytic oxidation on AM50 Mg alloy on coating morphology and corrosion properties

The influence of incorporating different sizes of Si_(3)N_(4) particles on the microstructure and corrosion properties of a phosphate-based plasma electrolytic oxidation (PEO) coating on AM50 magnesium alloy was investigated. The experiments for this study were performed in alkaline electrolytes containing 1 g/L KOH, 10 g/L Na_(3)PO_(4) with and without three different sized of Si_(3)N_(4) particles. The corrosion properties of PEO coatings were investigated by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) in 0.5 wt.% NaCl solution. Microstructure observations by SEM showed that the surface morphology and composition of the PEO coating were affected greatly by particle addition. Si_(3)N_(4) particles can still be found without decomposition in the final coating due to their high melting point.

Experimental and quantum chemical studies of carboxylates as corrosion inhibitors for AM50 alloy in pH neutral NaCl solution

Sodium salts of mono-and di-carboxylic acids(glycolic,fumaric and benzoic acid)were studied as corrosion inhibitors for AM50 alloy in pH neutral aqueous NaCl environment.Hydrogen evolution,electrochemical and surface characterization techniques were employed to reveal their corrosion inhibition mechanism,whilst the molecular features of inhibitors were investigated by quantum chemical calculation.All inhibitors reduced anodic dissolution of AM50 and their efficiency generally increased with time and concentration from 5 mM to 100 mM.The inhibition mechanism can be described as physisorption of inhibitive molecules on the surface of the intrinsic oxide layer followed by chemisorption with Mg^(2+)and Al^(3+),and the difference in inhibition action among these inhibitors was explained on the molecular scale.

Incorporation of LDH nanocontainers into plasma electrolytic oxidation coatings on Mg alloy

In-situ incorporation of layered double hydroxides(LDH)nanocontainers into plasma electrolytic oxidation(PEO)coatings on AZ91 Mg alloy has been achieved in the present study.Fumarate was selected as Mg corrosion inhibitor for exchange and intercalation into the nanocontainers,which were subsequently incorporated into the coating.It was found that the thickness and compactness of the coatings were increased in the presence of LDH nanocontainers.The corrosion protection performance of the blank PEO,LDH containing PEO and inhibitor loaded coatings was evaluated by means of polarization test and electrochemical impedance spectroscopy(EIS).The degradation process and corrosion resistance of PEO coating were found to be greatly affected by the loaded inhibitor and nanocontainers by means of ion-exchange when corrosion occurs,leading to enhanced and stable corrosion resistance of the substrate.

Fatigue and Corrosion Fatigue Properties of Mg-Zn-Zr-Nd Alloys in Glucose-Containing Simulated Body Fluids

Medical bone implant magnesium(Mg)alloys are subjected to both corrosive environments and complex loads in the human body.The increasing number of hyperglycemic and diabetic patients in recent years has brought new challenges to the fatigue performance of Mg alloys.Therefore,it is significant to study the corrosion fatigue(CF)behavior of medical Mg alloys in glucose-containing simulated body fluids for their clinical applications.Herein,the corrosion and fatigue properties of extruded Mg-Zn-Zr-Nd alloy in Hank’s balanced salt solution(HBSS)containing different concentrations(1 g/L and 3 g/L)of glucose were investigated.The average grain size of the alloy is about 5μm,which provides excellent overall mechanical properties.The conditional fatigue strength of the alloy was 127 MPa in air and 88 MPa and 70 MPa in HBSS containing 1 g/L glucose and 3 g/L glucose,respectively.Fatigue crack initiation points for alloys in air are oxide inclusions and in solution are corrosion pits.The corrosion rate of the alloy is high at the beginning,and decreases as the surface corrosion product layer thickens with the increase of immersion time.The corrosion products of the alloy are mainly Mg(OH)_(2),MgO and a small amount of Ca-P compounds.The electrochemical results indicated that the corrosion rate of the alloys gradually decreased with increasing immersion time,but the corrosion tendency of the alloy was greater in HBSS containing 3 g/L glucose.On the one hand,glucose accelerates the corrosion process by adsorbing large amounts of aggressive Cl^(-)ions.On the other hand,glucose will be oxidized to form gluconic acid,and then reacts with Mg(OH)_(2) and MgO to form Mg gluconate,which destroys the corrosion product film and leads to the aggravation of corrosion and the accumulation of fatigue damage.

Mechanism of Mn on inhibiting Fe-caused magnesium corrosion

In the present study,to understand the mechanism of Mn on inhibiting Fe-caused Mg corrosion,the corrosion behaviour of commercial pure Mg and Mg-6 Mn alloy in 0.6 M NaCl solution is investigated.It is found that in Mg-6 Mn alloy,Fe impurity is incorporated into Mn to form Mn(Fe)phase with Fe as solid solute.The initial galvanic corrosion cannot be reduced through converting Fe-rich phase to Mn(Fe)phase,since Mn(Fe)phase also has relatively strong cathodic activity and has much larger volume fraction than Fe-rich phase.However,the cathodic activation behaviour of pure Mg is inhibited.The cathodic activity even decreases for Mg-Mn alloy with increased exposure time,due to the reduced cathodic HER at the Mn(Fe)particles.Mn can be oxidized at the OCP of Mg-6 Mn alloy,resulting in relatively dense Mn-rich corrosion film on particle surface,which separates the particle from the electrolyte and,consequently,inhibits HER.

Effect of phosphate-based sealing treatment on the corrosion performance of a PEO coated AZ91D mg alloy

This study investigated the effect of sealing treatment on the corrosion performance of plasma electrolytic oxidation(PEO)coated AZ91D Mg alloy with and without addition of corrosion inhibitor.The microstructure,phase composition and corrosion property of the sealed and unsealed coatings were evaluated by using scanning electron microscopy(SEM),energy dispersion spectroscopy(EDS),x-ray diffraction(XRD),x-ray photoelectron spectroscopy(XPS),polarization,and electrochemical impedance spectroscopy(EIS)tests.Electrochemical experiments and salt spray tests showed that,after sealing in phosphate solution containing corrosion inhibitor,the corrosion current density of PEO-coated AZ91D decreased more than 10-fold and the anti-corrosion time in a salt spray environment increased more than three-fold.The corrosion rate of the PEO coating slowed down due to the releasing and adsorbing of the corrosion inhibitors in the pores and cracks of the coating during the corrosion process.

New design principles for the bath towards chromate-and crack-free conversion coatings on magnesium alloys

Cracking and low thickness are major obstacles to the high corrosion performance of conversion coating on magnesium alloy.In this work,the ratio of total acidity to p H(TA/p H)was applied as an indicator,and new principles regarding the design of conversion bath were proposed.The treatment bath should be composed of species that can be categorized into two groups:the first group of species that react with Mg substrate to increase the local p H at the interface;the second group that precipitate and contributes to the growth of coating.The species belong to second group exists in a supersaturated state and its precipitation process is almost independent on the reactions of the species in first group.By this way,a thick and crack-free two-layered conversion coating is obtained.Moreover,the nature of the adjustment of TA/p H and the roles of the oxidizing agent and catalyst were discussed.

In vivo degradability and biocompatibility of a rheo-formed Mg–Zn–Sr alloy for ureteral implantation

The introduction of biodegradable implant materials has significantly improved the postoperative subjective feelings of patients within the past few decades,among which magnesium alloy is widely considered a favorable choice as its appropriate biodegradability and evident antibacterial activity.Here,we reveal a semisolid rheo-formed Mg–Zn–Sr alloy ureteral implant that displayed suitable degradability and biocompatibility in a pig model.Refined non-dendritic microstructure was observed in the rheo-formed alloy,which led to ca.47%increase in ultimate tensile strength(from 195.0 MPa to 288.1 MPa)and more homogeneous degradation process compared with the untreated alloy.No post-interventional inflammation or pathological changes of the test animals were observed during the implantation period,and the corrosion rate(0.22±0.04 mm·y^(-1))perfectly fitted the clinical ureteral stent indwelling time.The urine bacteria numbers decreased from 88±13 CFU·mL^(-1)at 7 weeks post operation to 59±8 CFU·mL^(-1)at 14 weeks post operation,which confirmed the evident antibacterial activity of the alloy.Our study demonstrates that the Mg–Zn–Sr alloy is clinically safe for urinary system,enabling its efficacious use as ureteral implant materials.

Valproic acid therapy decreases serum 25-hydroxyvitamin D level in female infants and toddlers with epilepsy-a pilot longitudinal study

To evaluate if valproic acid(VPA)therapy is associated with vitamin D deficiency among infants and toddlers with epilepsy,a cross-sectional clinical study was conducted in 25 children with epilepsy taking VPA.Blood levels of calcium,phosphorus,alkaline phosphatase,and 25-hydroxy vitamin D[25(OH)D]and plasma VPA level were measured at 1-to 3-month intervals.At the initial and final measurements,vitamin D deficiency or insufficiency was recognized in 8(32%)and 12(42%),respectively.In girls,a decreasing trend in serum25(OH)D levels(P<0.05)was observed.Polytherapy had a significant negative effect on the longitudinal change of 25(OH)D(P<0.05)in girls.In conclusion,our study indicates that a high proportion of girls after VPA therapy had hypovitaminosis D.

Passivation of corrosion product layer on AM50 Mg by corrosion inhibitor

The influence of sodium dodecyl sulfate(SDS)on morphology and chemical composition of corrosion product layer formed onα-Mg matrix and cathodic Al-Mn intermetallic was systematically investigated by using FIB and TEM analysis for the first time to disclose the underlying inhibition mechanism.A porous corrosion bi-layer composed of crystalline MgO and Mg(OH)_(2)was observed on both ofα-Mg and Al-Mn intermetallic.It was found that a passive inner layer was deposited onα-Mg after immersion in SDS-containing NaCl solution,which can be ascribed to steady-state growth of magnesium and aluminum oxide under the protection of hydrophobic group of SDS.The inhibition mechanism of the inhibitor was mainly associated with formation of dense oxide layer onα-Mg matrix and preferential adsorption of SDS on the corrosion layer deposited on Al-Mn intermetallic.

Difference in formation of plasma electrolytic oxidation coatings on MgLi alloy in comparison with pure Mg

In order to study the substrate lattice structure(Li addition)on the growth of plasma electrolytic oxidation(PEO)coatings,Mg Li alloy(11.36 wt.%of Li,cubic)and pure Mg(hexagonal)were treated under a pulsed direct PEO mode in a phosphate electrolyte for different periods of time.The results revealed that the presence of Li and Li-rich phases in the cubic Mg alloy seems to be essential for the treatment result rather than the original lattice structure.A modified discharge behavior of Mg Li alloy finally led to a different microstructure of the coating.The unstable coatings of Mg Li alloy tended to dissolve rapidly though shared the similar composition to that of pure Mg.Li was incorporated only in the primary conversion products at the interface of coating/Mg Li.In spite of the advanced efficiency of energy input during processing,the more porous and thinner PEO coatings on the Mg Li alloy were less resistant to abrasion and corrosion.

Localization of epileptic foci in Children with childhood absence epilepsy by magnetoencephalography combined with synthetic aperture magnetometry

This present study was aimed to investigate the localizable diagnostic value of magnetoencephalography （MEG） combined with synthetic aperture magnetometry （SAM） in childhood absence epilepsy （CAE）. Thirteen CAE patients underwent MEG detection at resting state and after hyperventilation, and then the epileptic loci were located by SAM. In the thirteen CAE patients, epileptic foci were found in five cases （38.5%）, and they were all located in the bilateral frontal lobe, suggesting that the frontal lobe in some CAE patients may serve as the epileptic foci. Our findings indicate that MEG combined with SAM could be of diagnostic value in localizing the epileptic foci in certain CAE patients.

Mechanical properties, biodegradability and cytocompatibility of biodegradable Mg-Zn-Zr-Nd/Y alloys

Biodegradable magnesium alloys have been turned out to be a promising candidate for orthopedic applications.In this study,the mechanical properties,degradation behaviorand cytocompatibility of MgZn-Zr-Nd and Mg-Zn-Zr-Y alloys were studied in comparison with pure Mg.Mechanical tests showed that the strength and ductility of Mg-Zn-Zr-Nd and Mg-Zn-Zr-Y alloys were excellent.The corrosion resistance analyzed by electrochemical test and immersion test in alpha modified eagle(α-MEM) medium with 10% fetal bovine serum(FBS) revealed the degradation of Mg-Zn-Zr-Nd and Mg-Zn-Zr-Y alloys were faster than pure Mg at an early stage but slowed down after long time immersion.The metal ion concentrations were consistent with the corrosion rate.Mg-Zn-Zr-Nd alloy shows better mechanical properties than pure Mg and better corrosion resistance than Mg-Zn-Zr-Y alloy.The direct and indirect in vitro tests with MC3 T3-E1 cells demonstrate that Mg-Zn-Zr-Nd shows the best cytocompatibility and osteogenesis.The results suggest that Mg-Zn-Zr-Nd alloy shows an ideal combination of mechanical,corrosive and biological properties.In summary,these results implying the Mg-Zn-Zr-Nd alloy has great potential to benefit the future development of orthopedic applications.

Antibacterial activities against Porphyromonas gingivalis and biological characteristics of copper-bearing PEO coatings on magnesium

Unlike other parts of the body, jaw defection often involves dental and periodontal tissues, which colonized a great many oral anaerobic bacteria. As a remarkable degradable material, magnesium has become an excellent candidate for orthopedic appliances recently. But the high degradation rate is still a big problem. Making a biodegradable coating with good biocompatibility to slow down the degeneration rate of magnesium is one of the best methods. However, protective coatings will impair the antibacterial effects of magnesium which is caused by the rise of p H value throughout its degradation. To solve this problem, a series of composite coatings with different amounts of Cu O particles(3, 5 and 7 wt.%) were fabricated on pure magnesium through plasma electrolytic oxidation(PEO) to investigate in vitro biocompatibility and the antibacterial abilities against Porphyromonas gingivalis(P. gingivalis). Surface characterization and degradation behavior of the copper-bearing PEO coatings were also systematically studied. Furthermore,the most optimum coating was also systematically studied by X-ray photoelectron spectroscopy(XPS)and electrochemical corrosion test. Results of the present research revealed that adding proper amount of Cu O into PEO coatings could greatly improve the antibacterial abilities of the PEO coatings. The antibacterial activities of copper-bearing PEO coatings were excellent and revealed concentration-dependent and time-dependent. Biocompatibility of copper-bearing PEO coatings showed that proper amount of Cu could promote cell proliferation. Compared with other PEO coatings in this study, PEO-7 Cu showed some inhibition effects on cell proliferation and adhesion for long-term use. Electrochemical corrosion tests and immersion tests showed that PEO-5 Cu and PEO-7 Cu copper-bearing PEO coatings would provide satisfying corrosion resistance effects, while PEO-3 Cu was poorer than PEO coatings without Cu. However, compared with uncoated pure magnesium, the corrosion resistance of the PEO coating was much better. Based on the results of antibacterial ability, biocompatibility, and corrosion resistance of the above copper-bearing PEO coatings, PEO-5 Cu in this research was recommended to be used in patients with jaw defects.

G9a/GLP catalyzes H3K14me1 and H3K14me2 in vivo and in vitro

Dear Editor,Chromatin modifications regulate multiple cellular progressions(Bannister and Kouzarides,2011;Zhang et al.,2021).Numerous histone modifications and their correspondent enzymes have been identified in the past decades(Huang et al.,2014)and more histone modification sites and types have been gradually identified in recent years(Kim et al.,2019;Lu et al.,2019).

A specific assay for JmjC domain-containing lysine demethylase and its application to inhibitor screening

Dear Editor, Chromatin is the macromolecular complex of DNA and histone proteins, which provides the scaffold for the packaging of our entire genome. In the basic unit of chromatin, the nucleosomes contain 147 base pairs of DNA, which is wrapped around a histone octamer, with two each of histones H2A, H2B, H3, and H4. Several types of post-translational modifications, including acetylation, phosphorylation, ubiquitination, and methylation, are possible on the tails of histones (Zhang et al., 2015). Combinations of these modifications determine the chromatin structure and transcriptional regulation of genes. Histone methylation is highlighted because of the specific dynamics related to gene regulation. Aberrant histone methylation has been observed in many types of tumors (Albert and Helin, 2010) and may contribute to the neoplastic transformation of cells (Chi et al., 2010). Histone lysine methylation is regulated by two classes of enzymes that have opposing activities: histone lysine methyltransferases (KMTs) and histone lysine demethylases (KDMs). To date, a number of mammalian KDMs have been discovered (Kooistra and Helin, 2012), and they have been separated into two classes: flavin adenine dinucleotide dependent oxidases, which were first discovered in 2004 (Shi et al., 2004), and Jumonji-C (JmjC) domain-containing enzymes, first identified in 2006 (Tsukada et al., 2006).