Finite Element Analysis of the Mechanical Properties of Axially Compressed Square High-Strength Concrete-Filled Steel Tube Stub Columns Based on a Constitutive Model for High-Strength Materials.

With the development of new concrete technology, high-strength concrete has been used worldwide. In particular, more economic benefits can be achieved by applying high-strength concrete-filled steel tube (HSCFST) columns in the concrete core walls of super high-rise buildings. A constitutive relation with high applicability for high-strength materials with different strength grades is proposed. Based on this constitutive model, a brick element model of 181 sets of axially compressed square HSCFST members is established and experimentally verified. The effects of the concrete strength, diameter-to-thickness ratio, and steel yield strength on the axial compressive capacities of these members were investigated based on finite element calculation results. The results showed that with an increase in the concrete strength, the ultimate bearing capacities of CS-CC, HS-HC, HS-CC, and CS-HC stub column members increased by 60%, 24%, 44%, and 21% at most, respectively. Additionally, as the steel yield strength increased, the ultimate bearing capacities of CS-CC, HS-HC, HS-CC, and CS-HC stub column members increased by 8.8%, 5.1%, 8.5%, and 5.2%, respectively, Hence, material strength has the greatest impact on CS-CC and HS-CC. The confinement effect of the square steel tube on the concrete weakens as the strength grade of steel or concrete increases. Notably, the confinement effect of steel tube on the concrete is strongest in CS-CC and weakest in the CS-HC. In addition, the confinement coefficients of square HSCFST stub columns with different combinations of concrete and steel strengths were analyzed. Based on the superposition principle in the ultimate state, a practical axial compressive capacity calculation formula for three types of square HSCFSTs is established. Compared with existing major design code formulas, the proposed formula is more accurate and concise and has a clear physical meaning.

Value of the platelet-to-lymphocyte ratio in the prediction of left ventricular thrombus in anterior ST-elevation myocardial infarction with left ventricular dysfunction.

BACKGROUND: The predictors of left ventricular thrombus (LVT) formation are not well defined in the contemporary era, especially in those patients at high risk. We aimed to evaluate whether the platelet/lymphocyte ratio (PLR) is valuable in the determination of LVT formation in patients with anterior ST-elevation myocardial infarction (STEMI) and left ventricular (LV) dysfunction. METHODS: The LVT group (n = 46) was identified from anterior STEMI patients with LV dysfunction who were treated with primary percutaneous coronary intervention (PCI) from January 2017 to December 2019 at the China-Japan Union Hospital of Jilin University. The no-LVT group (n = 92) were also selected from the same batch of patients and were age- and sex-matched to the patients with LVT. The PLR was determined at admission and was calculated as the ratio of the platelet count to the lymphocyte count using the complete blood count. The presence of LVT was determined by echocardiography. RESULTS: The PLR were significantly higher in patients with LVT than in no-LVT group (p = 0.001). In a receiver operator characteristic curve (ROC) analysis, using a cut-off value of 118.07 (AUC 0.673, 95% CI: 0.574-0.771, P = 0.001), the PLR could independently predict the occurrence of LVT. Multivariate analysis showed that an increased PLR (OR = 1.011, 95% CI: 1.004-1.018, P = 0.002), the presence of a left ventricular aneurysm (OR = 46.350, 95% CI: 5.659-379.615, P < 0.001) and increased DTBT (OR = 1.005, 95% CI: 1.001-1.009, P = 0.012) were independent predictors of LVT formation. CONCLUSIONS: In acute anterior STEMI patients with LV dysfunction, an increased PLR and DTBT and the presence of an LV aneurysm were independent predictors of LVT formation. A larger prospective study is warranted to evaluate this result. TRIAL REGISTRATION: This study was registered (May 4, 2019) on Chinese Clinical Trial Registry ( ChiCTR-DDD-17011214 ).

[System Amplifying NK Cells Using Mononuclear Cell Culture].

OBJECTIVE: To develop an easy method to amplify natural killer (NK) cells by using mononuclear cells in vitro, so as to lay the basis for NK cell therapy. METHODS: Umbilical cord blood from 3 healthy full-term pregnant women was collected, and the peripheral blood mononuclear cells (PBMNC) were harvested by density gradient centrifugation. Each sample of PBMNC was divided into 3 groups: CD16mAb, CD3 mAb and CD16mAb+CD3mAb- groups. The culture flasks were pre-coated with CD16, CD3 or CD3 plus CD16 mAb. The PBMNCs were cultured in serum-free media containing autologous plasma, recombinant human IL-2, IL-15 and IL-21 for 14 days under the same conditions. The total viable cell count was calculated. Flow cytometry was used to determine the ratio of CD56+CD3- cells, MTT assay was used to measure the killing rate of NK cells under different effector/target ratio, by using the K562 cells as the target cells. RESULTS: After 14 days of culture, the total cell numbers of CD16mAb, CD3mAb and CD16mAb +CD3mAb groups increased by 45.71±5.54, 87.41±19.77 and 4.88±51.84 times, respectively, and those of CD3mAb group were significantly higher than the other 2 groups (P<0.05). The ratio of CD56+CD3- cells before culture was 0.1663±0.0201, which was 0.8167±0.0500, 0.8077±0.0589 and 0.8077±0.0273 after incubation with CD16mAb, CD3mAb and CD16mAb +CD3mAb for 14 days, respectively (P>0.05). MTT test showed that the killing efficiencies were not significantly different among the 3 groups when the effector/target ratios were 1:1, 5:1 and 10:1 (P>0.05). CONCLUSION: By incubation with anti-CD3 monoclonal antibody, IL-2, IL-15 and IL-21, the highly purified NK cells can be obtained from mononucleated cells, thus providing a simple method for NK cell therapy.