内镜下胆总管取石术后胆总管结石复发的危险因素及择期胆囊切除术对复发的影响

目的分析经内镜逆行胰胆管造影术(ERCP)联合内镜下十二指肠乳头括约肌切开术(EST)的胆总管取石术后胆总管结石复发的危险因素,探讨择期行腹腔镜胆囊切除术(LC)对胆总管结石复发的影响。方法选取2008年9月-2012年9月ERCP联合EST胆总管取石术289例患者,其合并胆囊结石,择期行LC。按胆总管结石是否复发分为复发组和无复发组,按是否行LC分为LC组和无LC组。均记录性别、年龄、体质指数(BMI)、胆囊切除史、总胆红素水平、黄疸和壶腹周围憩室情况;使用熊去氧胆酸(UDCA)药物情况;胆道狭窄、胆管成角、胆总管直径;结石的性质、数量和大小;机械碎石、鼻胆管引流情况。跟踪随访5年。结果胆总管结石复发时间(27.1±14.6)个月。复发组与无复发组相比:胆总管直径分别为(17.7±3.7)和(15.5±4.4)mm;胆总管结石直径≥15 mm例数分别占41.3%和16.8%;壶腹周围憩室例数分别占61.9%和13.7%,差异均有统计学意义(P=0.007~0.011)。胆总管直径≥15 mm和存在壶腹周围憩室是胆总管结石复发的危险因素(OR=1.789~1.941,均P <0.05),择期LC不是复发的危险因素(P>0.05)。LC组与无LC组5年累计胆总管结石复发率分别为24.5%和26.1%,差异无统计学意义(P>0.05)。结论胆总管直径≥15 mm,存在壶腹周围憩室是ERCP+EST胆总管取石术后胆总管结石复发的危险因素;择期行LC并不能降低胆总管结石的复发率。

Advances in coatings on biodegradable magnesium alloys

The clinic applications of bioabsorbable magnesium(Mg)and its alloys have been significantly restricted owing to their poor corrosion resistance.Besides elemental alloying,surface modification and functionality is a major approach to increasing corrosion resistance for magnesium alloys.This article reviews the cutting-edge advances and progress of biodegradable surface coatings upon Mg alloys over the last decades,aims to build up a knowledge framework of surface modification on biodegradable Mg alloys.A considerable number of conversion,deposition,mechanical and functional coatings and their preparation methods are discussed.The emphasis has been placed on the composition of chemical conversion and deposited coatings to overcome the disadvantages of adhesion,corrosion resistance and biocompatibility of a single coating for biomedical materials.The issues have been addressed on the integration of the structural and functional factors of the composite coatings.

Advances in bioorganic molecules inspired degradation and surface modifications on Mg and its alloys

Mg alloys possess biodegradability,suitable mechanical properties,and biocompatibility,which make them possible to be used as biodegradable implants.However,the uncontrollable degradation of Mg alloys limits their general applications.In addition to the factors from the metallic materials themselves,like alloy compositions,heat treatment process and microstructure,some external factors,relating to the test/service environment,also affect the degradation rate of Mg alloys,such as inorganic salts,bioorganic small molecules,bioorganic macromolecules.The influence of bioorganic molecules on Mg corrosion and its protection has attracted more and more attentions.In this work,the cutting-edge advances in the influence of bioorganic molecules(i.e.,protein,glucose,amino acids,vitamins and polypeptide)and their coupling effect on Mg degradation and the formation of protection coatings were reviewed.The research orientations of biomedical Mg alloys in exploring degradation mechanisms in vitro were proposed,and the impact of bioorganic molecules on the protective approaches were also explored.

In Vitro Study On Corrosion Behaviors of Novel Zn-ZnO Composites

Currently,the widely investigated Mg,Fe and their alloys are facing the corrosion rate problems,either too fast or too slow.Zn has standard electrode potentials between Mg and Fe,implying a more apposite degradation rate[1].Moreover,Zn is an essen-

Comparison of microstructure,mechanical property,and degradation rate of Mg-1Li-1Ca and Mg-4Li-1Ca alloys

Mg-1 wt.%Li-1 wt.%Ca(LX11)and Mg-4 wt.%Li-1 wt.%Ca(LX41)alloys share the same hexagonal closed-packed crystalline structure.However,the differences in microstructure,mechanical properties,and degradation rates between the two alloys are not well understood.Hereby,the above three aspects of LX11 and LX41 alloys were studied via optical microscopy,tensile tests,and electrochemical polarization and electrochemical impedance spectroscopy,together with hydrogen evolution.The concentration of the released Mg^(2+),Ca^(2+),and Li+ions was analyzed using a flame atomic absorption spectrophotometer.Results demonstrated that the LX11 alloy was composed of finerα-Mg grains,fewer twins,and smaller volume fractions of the intermetallic phases Mg_(2)Ca than the LX41 alloy.The increasing Li concentration generated a weak decrease in the yield strength of the Mg-Li-Ca alloys,a remarkable increase in elongation to failure,and a stable ultimate tensile strength.The LX11 alloy had better corrosion resistance than the LX41 alloy.The release rate of the cations(Mg^(2+),Ca^(2+),and Li+)varied significantly with time.The release rate of metallic ions in Hank’s solution cannot reflect the true corrosion rate of Mg-Li-Ca alloys due to the formation of the precipitated corrosion products and their difference in solubility.The dealloying corrosion mechanism of the Mg_(2)Ca phase in Mg-Li-Ca alloys was proposed.

Advance in Antibacterial Magnesium Alloys and Surface Coatings on Magnesium Alloys:A Review

Magnesium(Mg)alloys as a bioabsorbable light metal have shown great clinical potential as bone replacement implants.In this review,the categories,progress in cutting-edge preparation technologies and antibacterial mechanisms of Mg alloys and considerable numbers of corrosion-resistant and functional coatings are summarized.The relationship among the microstructure(grain size,intermetallic compounds),biocorrosion resistance and biocompatibility for antibacterial Mg alloys is discussed.The challenge and outlooks of biomedical Mg alloys and coatings are proposed from an antibacterial perspective.

Construction of TiO2/silane nanofilm on AZ31 magnesium alloy for controlled degradability and enhanced biocompatibility

A TiO2 nanofilm was prepared on the surface of AZ31 magnesium alloy with controllable thickness through atomic layer deposition(ALD) technique, which can adjust the corrosion behaviors of AZ31 Mg alloy.Compared with the untreated Mg alloys, corrosion current densities(icorr)can decline by 58% in the 200-cycles TiO2-covered Mg alloy and further decline by up to 74% with the thickness of nanofilm up to 63 nm(400 cycles).The subsequent modification with a cross-linked conversion layer of 3-aminopropyltriethoxysilane(APTES) by a dipping method can produce a compact silane coating on TiO2 nanofilm, which can seal pinholes of TiO2 nanofilm and serve as a barrier to further adjust the corrosion behavior of the substrate.The icorrcan decline about two orders of magnitude in the TiO2/silane composite coating.Making the adjustable corrosion rate come true, which can be attributed to the precise control on the thickness of metal oxide nanofilm and additional protection from the compact silane coating.In vitro study discloses that the TiO2/silane hybrid coating shows higher expression of alkaline phosphatase(ALP)and can promote cellular adhesion and proliferation with better cytocompatibility than untreated Mg alloy.

Biodegradation,hemocompatibility and covalent bonding mechanism of electrografting polyethylacrylate coating on Mg alloy for cardiovascular stent

Organic coatings are the most widely employed approach for the promotion of corrosion resistance of magnesium(Mg)alloys.Unfortunately,traditional organic coatings are weakly bonded to Mg substrates due to physical adsorption.Herein,a polyethylacrylate(PEA)coating was fabricated on Mg-Zn-YNd alloy via electro-grafting.The surface structure and chemical composition were characterized by means of scanning electron microscope(SEM),energy dispersive X-ray spectroscopy(EDS),atomic force microscope(AFM)and Fourier transform infrared(FTIR)as well as time of flight-secondary ion mass spectrometer(To F-SIMS).The results showed that the surface roughness of PEA coating was dominated by scan rate;while the coverage and integrity of PEA coating were mainly affected by the monomer concentration and sweep circles.To F-SIMS results indicated that PEA coating was wholly covered on Mg alloy,and the presence of C2H3Mg-fragment confirmed the covalent bond between PEA coating and Mg alloy.In addition,DFT calculation results of the adsorption of EA molecules with Mg substrate agree well with the experimental phenomena and observation,suggesting that the electrons in 3s orbit of Mg atoms and 2pz orbit of C1 atom participated in the formation of covalent bond between PEA coating and Mg substrate.Potentiodynamic polarization curves and immersion test demonstrated that the PEA coatings could effectively enhance the corrosion resistance of Mg alloy.The platelet adhesion results designated that platelets were barely visible on PEA coating,which implied that PEA coating could effectively prevent the thrombosis and coagulation of platelets.PEA coating might be a promising candidate coating of Mg alloy for cardiovascular stent.

Biodegradation behavior of micro-arc oxidation coating on magnesium alloy-from a protein perspective

Protein exerts a critical influence on the degradation behavior of absorbable magnesium(Mg)-based implants.However,the interaction mechanism between protein and a micro-arc oxidation(MAO)coating on Mg alloys remains unclear.Hereby,a MAO coating was fabricated on AZ31 Mg alloy.And its degradation behavior in phosphate buffer saline(PBS)containing bovine serum albumin(BSA)was investigated and compared with that of the uncoated alloy.Surface morphologies and chemical compositions were studied using Field-emission scanning electron microscope(FE-SEM),Fourier transform infrared spectrophotometer(FT-IR)and X-ray diffraction(XRD).The degradation behavior of the bare Mg alloy and its MAO coating was studied through electrochemical and hydrogen evolution tests.Cytotoxicity assay was applied to evaluate the biocompatibility of Mg alloy substrate and MAO coating.Results indicated that the presence of BSA decreased the degradation rate of Mg alloy substrate because BSA(RCH(NH2)COO‾)molecules combined with Mg2+ions to form(RCH(NH2)COO)2Mg and thus inhibited the dissolution of Mg(OH)2 by impeding the attack of Cl‾ions.In the case of MAO coated Mg alloy,the adsorption of BSA on MAO coating and the formation of(RCH(NH2)COO)2Mg exhibited a synergistic effect and enhanced the corrosion resistance of the coated alloy significantly.Furthermore,cell bioactive assay suggested that the MAO coating had good viability for MG63 cells due to its high surface area.

A review on biodegradable materials for cardiovascular stent application

A stent is a medical device designed to serve as a temporary or permanent internal scaffold to maintain or increase the lumen of a body conduit. The researcher;~ and engineers diverted to investigate biodegradable materials due to the limitation of metallic materials in stent application such as stent restenosis which requires prolonged anti platelet therapy, often result in smaller lumen after implantation and obstruct re-stenting treatments. Biomedical implants with temporary function for the vascular intervention are extensively studied in recent years. The rationale for biodegradable stent is to provide the support for the vessel in predicted period of time and then degrading into biocompatible constituent. The degradation of stent makes the re-stenting possible after several months and also ameliorates the vessel wall quality. The present article focuses on the biodegradable materials for the cardiovascular stent. The objective of this review is to describe the possible biodegradable materials for stent and their properties such as design criteria, degradation behavior, drawbacks and advantages with their recent clinical and preclinical trials.

Influence of Zn Content on Microstructure and Tensile Properties of Mg–Zn–Y–Nd Alloy

In the present study,the effect of Zn content on the microstructure and deformation behavior of the as-cast Mg-Zn-Y-Nd alloy has been investigated.The results showed that as Zn content increased,the volume fraction of secondary phases increased.Moreover,the phase transformation from W-phase to W-phase and I-phase occurred.In the as-cast state,W-phase exists as eutectic and large block form.When Zn content increases to 6 and 8%（wt%）,small I-phase could precipitate around W-phase particles.Additionally,the effect of Zn content on the tensile properties and deformation behavior varies with the testing temperature.At room temperature,the tensile strength increases with Zn content,whereas the elongation increases initially and then decreases.At 250℃,as Zn content increases,the tensile strength decreases initially and then increases slightly,whereas the elongation decreases.At 350℃,the elongation increases with Zn content,whereas the tensile strength decreases initially and then increases slightly.

New nitinol endovascular stent-graft system for abdominal aortic aneurysm with finite element analysis and experimental verification

Abdominal aortic aneurysm(AAA) is one of the most common and catastrophic manifestations of the acute aortic syndrome that can be treated with endovascular aneurysm repair(EVAR) which requires a specially designed stent-graft system.In this work, a self-expanding nickel–titanium(nitinol) stent-graft system is aiming at AAA using finite element analysis(FEA) methods to analyze both fatigue behaviors and radial forces.Based on the systematic analysis of the parametric variations, a final stent-graft system was developed by the selection and arrangement of the individual stent components, targeting an optimal performance for the treatment of AAA.Experimental tests, animal tests and clinical trials were carried out to confirm the results.Both animal trials and clinical trials showed comparable curative effects with Medtronic Endurant stent-graft(SG) systems.

Photothermal-controlled sustainable degradation of protective coating modified Mg alloy using near-infrared light

Controlling the corrosion rate is critical for practical applications of Mg-based alloys. In this work, we constructed a protective coating of hybrid polycaprolactone(H-PCL)/indocyanine green(ICG) on AZ31 Mg alloy,whose degradation rate was controlled by 808-nm nearinfrared(NIR) light irradiation. The corrosion behaviors of H-PCL/ICG coated Mg alloys were systematically investigated by potentiodynamic polarization tests, electrochemical impedance spectroscopy(EIS) and hydrogen evolution experiments. The results disclosed that the H-PCL/ICG composite coating could effectively protect Mg alloy from corroding without NIR light irradiation. In contrast, under 808-nm NIR light irradiation, the corrosion resistance of this composite coating was decreased significantly, i.e., the corrosion current density(i_(corr))increasedfrom(8.81 ± 1.068) 9 10^(-8) to(1.22 ± 0.545) 9 10^(-6) A·cm^(-2). This is because the component of ICG in the coating was excited to produce heat locally, which triggered the glass transition temperature(T_(g)) of H-PCL in the coating, resulting in the motion of the molecular chain segment. Consequently, the electrolytes penetrated the coating and corroded the Mg substrate. In vitro biological experiment indicated that the synthesized coating exhibited good cytocompatibility.Hence, these findings will provide a new strategy for designing novel photoresponsive coatings to remotely adjust the degradation rate of biodegradable metals for biomedical applications.

New Formulas of Shear Strain during Equal-channel Angular Pressing Process with Consideration of Influences of Velocity and Motion Trajectory

The influences of die parameters on shear strain were investigated by using two-dimensional finite element simulation.New formulas of shear strain were proposed.According to the results of formulas,the shear strain showed a linear dependence on the difference between internal and external fillet radius and the slope was determined by the intersection angle.The simulation results indicated that the velocities of the points from different zones were different in the specimen and the motion trajectories of different points did not follow geometrical laws.The influences of the average velocity and the motion trajectory on shear strain were incorporated in the formula to calculate the shear strain produced during equalchannel angular pressing process.The reliability of simulation results has been partially validated by experiments.

Martensitic transformation and magnetic properties of Ti-doped NiCoMnSn shape memory alloy

Martensitic transformation, microstructure, and magnetic properties of Ti-doped Ni43-xTixCo7Mn43Sn7（at%）（x = 0, 0.5, 1.0, 2.0, and 4.0） shape memory alloys were investigated. The results show that transformation temperatures of Ni43Co7Mn43Sn7 can be efficiently adjusted by the substitution of Ti for Ni. For example, the martensitic transformation starting temperature（Ms） is reduced by about 278 K with 4 at% addition of Ti. Room temperature microstructure evolves from single tetragonal martensite for the Ti-free alloy to dual phases（tetragonal martensite ＋ second phase） with 0.5 at%, 1.0 at%, and2.0 at% addition of Ti to dual phases（cubic austenite ＋ second phase） for 4.0 at% Ti-doped alloy. The mechanical properties can be obviously improved by adding an appropriate amount of Ti. A noteworthy point is that magnetic-field-induced reverse transformation is observed in Ni39Ti4Co7Mn43Sn7 alloy.

Achieving High Strength and High Electrical Conductivity in a CuCrZr Alloy Using Equal-Channel Angular Pressing

In the present work, a CuCrZr alloy characterized by ultrafine grains and nanoscale particles was prepared by equalchannel angular pressing （ECAP） at 450℃. A desired combination of a tensile strength （580 MPa） and an electrical conductivity （81% International Annealed Copper Standard） is simultaneously obtained in the as-ECAP-processed CuCrZr alloy without additional aging treatment. The improved properties can be mainly attributed to the ultrafine grains and nanoscale precipitates. This processing may pave a way to develop the CuCrZr alloys having high strength and high electrical conductivity for engineering applications.