Abstract To investigate the effect of polyurea on the protective performance of a steel target plate under the combination of shock wave and fragments, the failure characteristics, damage process and micro mechanism of the polyurea coated steel plates with different coating methods under the combination of explosion shock waves and fragments were analyzed through experiments and numerical simulations. The results showed that single-sided coatings aggravated the damage of target plate when the coating thickness was 2 mm. While the polyurea thickness greater than 4 mm could significantly reduce the damage degree of the steel plate. When the polyurea was coated on the double sides, it would aggravate the damage, no matter how thick the polyurea was. Through microscopic research, it was found that the front coated polyurea was severely ablated by detonation products, which greatly reduce its energy absorption efficiency. The polyurea coated on the back underwent tensile fracture under the influence of tensile stress wave. The breaking of intramolecular hydrogen bond of polyurea was the key to the energy absorption of polyurea.

Abstract In this paper, LS-dyna software was used to simulate the charging process of cylindrical shell when EFP has different angles, and some interesting phenomena and laws were found. Cylindrical elastic wave σr was generated when the cylindrical shell was impacted by EFP. The cylindrical elastic wave σr was correlated with the time required for the cylindrical shell charge to be successfully detonated. When the EFP warhead penetration Angle θ ranges from 0° to 10°, the σr increases linearly with (cosθ)-1/2. With the increase of θ, the tangential velocity vy had an obvious effect on the impact of EFP on the cylindrical shell, and the linear relationship between the elastic wave σr and (cosθ)-1/2 does not change. When the θ was greater than 45°, EFP could not successfully impact and detonate the cylindrical shell charge. The EFP velocity was measured by velocity measurement method with an error of 1.3%. The experimental results have strong similarity with the simulation results, indicating that the parameters of the numerical simulation model have good reliability.

Abstract The dynamic responses of the high-speed railway bridge under the train passage can greatly affect the safety of the entire high-speed train and bridge system. Traditionally, these responses are obtained using either field measurement or numerical analysis. Both tools have their own limitations. For instance, the coupling dynamic train-bridge analysis is generally complicated and time-consuming. This paper proposes a novel machine learning based approach for efficient safety evaluation of the high speed train and short span bridge system. Artificial neural networks are established to map the complicated train-bridge system and to attain the critical bridge displacements. The proposed approach incorporates a complete numerical train-bridge system model to produce reliable data for the neural network training, considering multiple significant random features in the train-bridge system. Various neural network architectures are investigated and compared to find optimal ones that have considerable potentials in realizing online response prediction and safety evaluation. Although the proposed approach focuses on the high-speed train and short span bridge, the methodology is general and can also be applied to other scenarios associated with the vehicle-bridge systems.

Abstract Background: Tumor microenvironment (TME) plays a vital role in determining the outcomes of radiotherapy. As an important component of TME, vascular endothelial cells are involved in the perivascular resistance niche (PVRN), which is formed by inflammation or cytokine production induced by ionizing radiation (IR). Protein kinase CK2 is a constitutively active serine/threonine kinase which plays a vital role in cell proliferation and inflammation. In this study, we investigated the potential role of CK2 in PVRN after IR exposure. Result: Specific CK2 inhibitors, Quinalizarin and CX-4945, were employed to effectively suppressed the kinase activity of CK2 in human umbilical vein endothelial cells (HUVECs) without affecting their viability. Results showing that conditioned medium from IR-exposed HUVECs increased cell viability of A549 and H460 cells, and the pretreatment of CK2 inhibitors slowed down such increment. The secretion of IL-8 and IL-6 in HUVECs was induced after exposure with IR, but significantly inhibited by the addition of CK2 inhibitors. Furthermore, IR exposure elevated the nuclear phosphorylated factor-κB (NF-κB) p65 expression in HUVECs, which was a master factor regulating cytokine production. But when pretreated with CK2 inhibitors, such elevation was significantly suppressed. Conclusion: This study indicated that protein kinase CK2 is involved in the key process of the IR induced perivascular resistant niche, namely cytokine production, by endothelial cells, which finally led to radioresistance of non-small cell lung cancer cells. Thus, the inhibition of CK2 may be a promising way to improve the outcomes of radiation in nonsmall cell lung cancer cells.

OBJECTIVES: This study investigated whether the serum matrix metalloproteinase-9 level is an independent predictor of recurrence after catheter ablation for persistent atrial fibrillation. METHODS: Fifty-eight consecutive patients with persistent atrial fibrillation were enrolled and underwent catheter ablation. The serum matrix metalloproteinase-9 level was detected before ablation and its relationship with recurrent arrhythmia was analyzed at the end of the follow-up. RESULTS: After a mean follow-up of 12.1±7.2 months, 21 (36.2%) patients had a recurrence of their arrhythmia after catheter ablation. At baseline, the matrix metalloproteinase-9 level was higher in the patients with recurrence than in the non-recurrent group (305.77±88.90 vs 234.41±93.36 ng/ml, respectively, p=0.006). A multivariate analysis showed that the matrix metalloproteinase-9 level was an independent predictor of arrhythmia recurrence, as was a history of atrial fibrillation and the diameter of the left atrium. CONCLUSION: The serum matrix metalloproteinase-9 level is an independent predictor of recurrent arrhythmia after catheter ablation in patients with persistent atrial fibrillation.

A new complex [Cd(btca)0.5(H2O)3] (1) (H4btca: 1,2,4,5-benzenetetracarboxlyic acid) has been synthesized and characterized by single crystal X-ray diffraction studies, elemental analysis and FT-IR. In compound 1, Cd(II) center atoms coordinate to three ligand btca4- anions and three water molecules with a six-coordinated distorted octahedral geometry. Four carboxyl groups of btca4- adopt μ2-η2:η0 and μ1-η1:η0 two different coordination modes. The whole anion btca4- acts as a hexadentate bridge to connect adjacent Cd(II) atoms, resulting in 2D layer structure. Further, these two-dimensional layers are linked together by O-H···O to give rise to three-dimensional structure. Thermal stability and luminescent property of 1 are investigated. CdO micro-crystalline particles are then produced by calcination of compound 1 at 580 ºC. The obtained CdO is characterized by XRD and SEM analyses.