The study of myocardial protective effect of creatine phosphate sodium in liver transplant patients

Objective:To study the cardioprotective effectof creatine phosphate sodium by measuring perioperative myocardial enzymes of allogeneic liver transplant patients.Methods:The 26 cases of orthotopic liver transplant patients were randomly divided into control group and creatine phosphate sodium group,13 cases in each group.The creatine phosphate sodium group were given creatine phosphate sodium 30 mg/kg at the time of induction.The control group were given equal amount of N.S.All patients at six-phase of before surgery,after anesthesia,before anhepatic phase,anhepatic phase,new liver and the 12 hours after surgery extraction radial artery.The CK,CK-MB and cTnI activity was measured.Results:To compared with control group,creatine phosphate sodium group’s plasma CK,CK-MB and cTnI concentrations in before anhepatic phase,anhepatic phase,new liver and the 12 hours after surgery 4 phase are significantly lower(p<0.05).Conclusions:The creatine phosphate sodium has a protective effect on liver transplantation in patients with myocardial damage.

Characterization of the asymmetric evolving yield and flow of 6016-T4 aluminum alloy and DP490 steel

6016-T4 aluminum alloy and DP490 steel were systematically tested under 24 proportional loading paths,including uniaxial tensile tests with a 15°increment,uniaxial compressive and simple shear tests with a 45°increment,and biaxial tensile tests using cruciform specimens.Cruciform specimens in the rolling/transverse and 45°/135°sampling directions were tested with seven and four different stress ra-tios,respectively.The normal and diagonal planes plastic work contours and the yield stresses under uniaxial tension and compression were measured to investigate the anisotropic yield.Meanwhile,the normal and diagonal planes directions of plastic strain rate and the rα-values under uniaxial tension and compression were characterized to confirm the plastic flow.Several existing asymmetric yield crite-ria under the associated and non-associated flow rules were comprehensively evaluated to describe the asymmetric plastic anisotropy of 6016-T4 aluminum alloy and DP490 steel.The results suggest that in the investigated yield criteria,the non-associated models can predict the tension and compression asym-metry of materials more accurately than the associated models,and the function of stress triaxiality can more effectively describe the asymmetric yield behavior than the first stress invariant.In addition,the pure shear stress states are helpful in assessing the validity and applicability of advanced asymmetric yield stress functions,and the inspection of diagonal plane plastic work contours containing more pure shear stress states should prioritized over that of normal plane plastic work contours.The evaluation of plastic potential functions should not only consider the prediction accuracy of the normal plane di-rections of plastic strain rate,but also further check the diagonal plane directions of plastic strain rate.Expressing mechanical properties as a function of equivalent plastic strain to calibrate parameters of the yield criterion allows the continuous capture of anisotropic evolution of the asymmetric yield surface and the changes in the asymmetric plastic potential surface.

A Hot Cracking Initiation Criterion Based on Solidification Liquid Film Characteristic and Microstructure

Herein,a hot cracking initiation criterion based on the characteristics of solidification liquid film and the microstructure was proposed,which integrated both the mechanical and non-mechanical factors during solidification.The criterion also took the effect of the shrinkage volume of the solid-liquid two-phase in the mushy zone,the flow behavior of the liquid film and the microstructure on the feeding behavior into account.Meanwhile,the effect factors of hot cracking initiation such as alloy composition,microstructure,mold design and process condition were included in this criterion,and it could quantitatively calculate whether hot cracks occurred under a certain state or not during solidification.The criterion was utilized to predict whether hot cracks occurred in Al-4.0 wt%Cu alloy in different initial solidification states or not,which was consistent with the experimental results and verified its reliability.According to the criterion expression,Vfeeding*was related with five effect factors includingη,ΔP*,l*,r*and n,in which r*and n were in positive correlation with Vfeeding*whileη,ΔP*and l*were in negative correlation with that,which provided a good instructive significance for mold design,process optimization and composition and microstructure regulation of alloys and simultaneously further enriched the mechanism and influencing factors of hot cracking initiation.Furthermore,a multiscale simulation method for calculating the characteristic parameters of hot tearing behavior during solidification was also provided in this study.

Infuence of Liquid Film Characteristics on Hot Cracking Initiation in Al–Cu Alloys at the End of Solidifcation

In this study,Al–4Cu alloy specimens with spherical grains and liquid flms were obtained by isothermal reheating treatment.The hot cracking of the solidifcation process was determined using a modifed constrained rod casting experimental apparatus,and the efect of liquid flm characteristics at the end of solidifcation on hot cracking initiation of Al–4Cu alloys was systematically investigated by combining molecular dynamics simulations and other methods.With the extension of soaking time,the liquid fraction(liquid flm fraction at the end of solidifcation)and grain shape factor increased with higher isothermal reheating temperatures.Additionally,the widened flling channel decreased the hot cracking initiation temperature and the critical hot cracking shrinkage stress was found to increase,thus reducing the hot cracking severity in Al–4Cu alloys.Molecular dynamics simulations revealed that with the extension of soaking time,the composition of the liquid flm changed at diferent isothermal reheating temperatures,but the short-range structure and atomic ordering of the liquid flm remained the same.The activity of the liquid flm increased in equilibrium,leading to a decrease in viscosity and an increase in fuidity,which contributed to the flling behaviour.After isothermal reheating at 640℃for 60 min,the liquid fraction reached the maximum,and the viscosity of the liquid flm was the minimum.In addition,almost no hot cracks were found.

Manipulating internal flow units toward favorable plasticity in Zr-based bulk-metallic glasses by hydrogenation

This work intends to manipulate the internal flow units in Zr_(55)Cu_(30)Ni_(5)Al_(10)bulk-metallic glasses(BMGs)through plasma-assisted hydrogenation to generate a positive microalloying effect on plasticity.Based on the cooperative shear model theory,serration-flow statistics during nanoindentation loading and creep tests during the holding stage were used to analyze the influence of hydrogen on the behavior of flow units in BMGs.Experimental observations showed that the hydrogen in the Zr_(55)Cu_(30)Ni_(5)Al_(10)BMGs caused mechanical softening,plasticity improvement,and structural relaxation.Analysis also showed that the average volume,size,and activation energy of internal flow units in the BMGs all increased as a result of the increase in the hydrogen content.The hydrogenation in the BMGs was found to lead to a prolifera-tion of shear bands,which promoted plasticity.The aggregation of these internal flow units reduced the stress required for plastic deformation through shear bands,ultimately causing softening and structural relaxation.

Hot Deformation Behaviors in Ti-6Al-4V/(TiB+TiC)Composites

Thermal compression testing was investigated using the Gleeble 3800 thermal simulator,and thermal deformation behavior of particle-reinforced titanium matrix composites(TMCs)was studied under deformation temperatures of 750-900°C,strain rates of 0.001-1 s^(-1),and experimental deformation of 60%.According to obtained flow stress curves,the hot deformation characteristics were analyzed.Based on the Arrhenius hyperbolic sinusoidal model,the constitutive equation at high temperature was established.Based on the theory of dynamic material models,a hot processing map of TMCs at high temperature was established,and the peak region of power dissipation rate and the instability region in the hot processing map were both determined.At the same time,the corresponding microstructures in the peak power dissipation rate and rheological instability regions were observed.The results showed that flow stress decreased with increasing deformation temperature and increased with increasing strain rate.The thermal deformation activation energy of titanium matrix composites was 301.8 kJ/mol.The Ti-6Al-4V/(TiB+TiC)composites possessed only one instability zone under high-temperature compression at a strain of 0.5,with corresponding temperatures at 750-840°C and strain rates at 0.1-1 s^(-1).The optimal thermal deformation parameters included corresponding temperatures of 830-880°C and strain rates of 0.001-0.05 s^(-1).The microstructures corresponding to optimal hot working parameters in processing maps were more homogeneous than the microstructures in the instability zone,including the distribution uniformity of reinforcement and the degree of dynamic recrystallization,and no instability phenomena including abnormal grain growth,microcracks or intensive fracture of reinforcements were found,indicating that the hot processing map had a positive guiding effect on the option of desirable material thermal-working parameters.