Study of metal-ceramic WC/Cu nano-wear behavior and strengthening mechanism

In view of the inherent poor tribological properties of copper,the reinforcement of copper matrix composites with WC particles presents a promising research area with significant industrial influence.Therefore,in the present study,a molecular dynamics approach is used to simulate the process of repeated friction of diamond grinding balls on WC/Cu composites,and the friction force,friction coefficient,abrasion depth,wear rate,abrasion morphology,von-Mises stress,internal defects,workpiece energy,and performance comparison of different layer thicknesses are systematically investigated in the multiple friction process.It is found that the fluctuation amplitude of friction force,friction coefficient,and abrasion depth are smaller and the fluctuation frequency is larger during the initial friction,whereas near the WC phase,there appears extreme values of the above parameters and the von-Mises stress is highly concentrated while the workpiece energy contonues to increase.In the case of the repeated friction,with the increase of friction times,the friction force,friction coefficient,and abrasion depth fluctuation amplitude increase,the fluctuation frequency decreases,the workpiece energy reaches an extreme value near the WC phase,and a large number of dislocations plug,therefore,the region is strengthened.As the distance between the grinding ball and the WC phase decreases,the more obvious the strengthening effect,the stronger the ability of workpiece to resist the wear will be.

Observation of the effect of angiojet to treat acute lower extremity arterial embolization

BACKGROUND Through significant advances in the treatment of peripheral arterial occlusive disease,acute ischemia of the lower extremity is still associated with significant morbidity,limb threat and mortality.The two main causes of acute ischemia in lower extremities are arterial embolism and atherosclerotic arteries.Timely recognition and treatment of acute limb ischemia in emergency situations is essential in order to minimize the duration of ischemia.AIM To investigate the application effect of angiojet thrombolysis in the treatment of acute lower extremity arterial embolization.METHODS Sixty-two patients with acute lower extremity arterial embolization admitted to our hospital from May 2018 to May 2020 were selected.Among them,the observation group(twenty-eight cases)had received angiojet thrombolysis,and the control group(thirty-four cases)had received femoral artery incision and thrombectomy.After thrombus clearance,significant residual stenosis of the lumen was combined with balloon dilation and/or stent implantation.When the thrombus removal was not satisfactory,catheter-directed thrombolysis was performed.The incidence of postoperative complications,recurrence rate and recovery of the two groups were compared.RESULTS There were no significant differences in postoperative recurrence(target vessel reconstruction rate),anklebrachial index and the incidence of postoperative complications between the two groups(P>0.05);there were statistically significant differences in postoperative pain score and postoperative rehabilitation between the two groups(P<0.05).CONCLUSION The application of angiojet in the treatment of acute lower limb artery thromboembolism disease is safe and effective,minimally invasive,quicker recovery after operation,less postoperative complications,which is more suitable for the treatment of femoral popliteal arterial thromboembolism lesions.If the thrombus removal is not satisfactory,the combination of coronary artery aspiration catheter and catheterized directed thrombolysis can be used.Balloon dilation and stent implantation can be considered for obvious lumen stenosis.

Prognostic value of preoperative immune-nutritional scoring systems in remnant gastric cancer patients undergoing surgery

BACKGROUND Remnant gastric cancer(GC)is defined as GC that occurs five years or more after gastrectomy.Systematically evaluating the preoperative immune and nutritional status of patients and analyzing its prognostic impact on postoperative remnant gastric cancer(RGC)patients are crucial.A simple scoring system that combines multiple immune or nutritional indicators to identify nutritional or immune status before surgery is necessary.AIM To evaluate the value of preoperative immune-nutritional scoring systems in predicting the prognosis of patients with RGC.METHODS The clinical data of 54 patients with RGC were collected and analyzed retrospectively.Prognostic nutritional index(PNI),controlled nutritional status(CONUT),and Naples prognostic score(NPS)were calculated by preoperative blood indicators,including absolute lymphocyte count,lymphocyte to monocyte ratio,neutrophil to lymphocyte ratio,serum albumin,and serum total cholesterol.Patients with RGC were divided into groups according to the immune-nutritional risk.The relationship between the three preoperative immune-nutritional scores and clinical characteristics was analyzed.Cox regression and Kaplan–Meier analysis was performed to analyze the difference in overall survival(OS)rate between various immune-nutritional score groups.RESULTS The median age of this cohort was 70.5 years(ranging from 39 to 87 years).No significant correlation was found between most pathological features and immune-nutritional status(P>0.05).Patients with a PNI score<45,CONUT score or NPS score≥3 were considered to be at high immune-nutritional risk.The areas under the receiver operating characteristic curves of PNI,CONUT,and NPS systems for predicting postoperative survival were 0.611[95%confidence interval(CI):0.460–0.763;P=0.161],0.635(95%CI:0.485–0.784;P=0.090),and 0.707(95%CI:0.566–0.848;P=0.009),respectively.Cox regression analysis showed that the three immunenutritional scoring systems were significantly correlated with OS(PNI:P=0.002;CONUT:P=0.039;NPS:P<0.001).Survival analysis revealed a significant difference in OS between different immune-nutritional groups(PNI:75 mo vs 42 mo,P=0.001;CONUT:69 mo vs 48 mo,P=0.033;NPS:77 mo vs 40 mo,P<0.001).CONCLUSION These preoperative immune-nutritional scores are reliable multidimensional prognostic scoring systems for predicting the prognosis of patients with RGC,in which the NPS system has relatively effective predictive performance.

Effect of Substrate Temperature on the Selective Deposition of Diamond Films

Selective deposition of diamond film on patterned Si (100) substrates has been achieved by using microwave plasma chemical vapor deposition (MPCVD) method. The films have been characterized by scanning electron microscope (SEM) and Raman spectrum. The influence of substrate temperature on the nucleation behavior of diamond was discussed in detail and the optimized deposition condition has been obtained.

Cardiac myxoma shedding leads to lower extremity arterial embolism:A case report

BACKGROUND Left cardiac myxoma(CM)is the most common benign tumor of primary cardiac tumors,but because of its special position caused by pathological physiology change,caused by the complications of the heavier,the surface is often accompanied by blood clots,once fall out,it causes peripheral vascular embolization,such as acute lower limb artery embo-lization,harmfulness is large,high morbidity,and easy to occur repeatedly.CASE SUMMARY A 67-year-old male patient suddenly appeared numbness and weakness of the left lower limb and could not walk without obvious incentive.The patient was finally diagnosed as left CM complicated with acute lower limb arterial embolism after completing cardiac ultrasound,computer tomography angiography,and histopathological analysis,such as hematoxylin-eosin stain staining,immunohistochemistry and special staining including alcian blue staining and periodic acid schiff staining.Arterial thrombosis was removed successfully by femoral artery thrombectomy,postoperative numbness and weakness of the patient’s left lower limb disappeared,skin temperature became warm,and dorsal foot artery pulsation was accessible.The patient was readmitted to the hospital 8 mo after discharge for left atrial mass resection,and was diagnosed as CM by postoperative histopathological examination.CONCLUSION Although CM is rare,it may be considered as the source of embolism in patients with acute limb ischemia.Repeated loss of thrombus on the tumor and its surface may lead to repeated embolism of peripheral vessels.Cardiac ultrasound is helpful for early diagnosis.Here,we use this case report to highlight left CM as an important cause of acute limb ischemia and to report our experience in the diagnosis and treatment of lower limb arterial embolism caused by CM detachment.