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Based on the national policies, regulations and documents on residency training, this paper sorts out the historical evolution of the standardized residency training system in China, and divides its development into four stages: preliminary exploration, local pilot, national trials, and implementation. It also puts forward some practical thoughts on its development law and future trend, such aspects as that the system reform follows the top-down administrative order and indicative plan, the system pays attention to the gradual implementation on the basis of summing up practical experience, and the system needs continuous implementation and improvement from the overall perspective.
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Objective To investigate the clinical and pathological features of patients with esophageal neuroendocrine carcinoma (ENEC).Methods From January 2011 to November 2018,107 patients with pathologically confirmed ENEC were enrolled at the First Affiliated Hospital of Zhengzhou University.The clinical manifestation,tumor location,tumor size,clinical pathological classification and immunohistochemical markers were analyzed.Statistical description was used for measurement data analysis,and chi-square test was performed for classification data analysis.Results Among 107 patients with ENEC,feeling obstruction during eating was the most common initial symptom,accounting for 63.6％ (68/107);followed by chest and back pain,accounting for 13.1％ (14/107).About 60.7％ (65/107) patients were diagnosed by biopsy under endoscopy and 39.3％ (42/107) patients were confirmed by pathological diagnosis after surgery.The proportion of tumor located in the upper thoracic esophagus and middle and lower thoracic segments was 13.1％ (14/107),45.8％ (49/107) and 41.1％ (44/107),respectively.The length of tumor was 0.7 cm to 9.0 cm,and the median was 2.5 cm.Among them,57.0％ (61/107) were less than 2.5 cm and 43.0％ (46/107) were over 2.5 cm.Among 107 patients,50 (46.7％) patients were ulcerative type,32 (29.9％) patients were medullary type,16 (15.0％) patients were mushroom type and nine (8.4％) patients were protrude type.Among 107 patients,96 (89.7％) patients were pure neuroendocrine carcinoma (P-NEC;including 95 small cell types,one large cell type);11 (10.3％) patients were mixed neuroendocrine carcinoma (M-NEC;including nine small cell carcinoma mixed with squamous cell carcinoma,two small cell carcinoma mixed with adenocarcinoma).The positive rates of synaptophysin,CD56 and chromogranin A were 99.0％ (104/105),98.0％ (100/102) and 31.5％ (17/54),respectively.Ki-67 proliferation index of 47.7％ tumors (51/107) was between 90％ and 100％.P-NEC with the maximum diameter over 2.5 cm accounting for 42.1％ (45/107),and M-NEC accounting for 0.9％ (1/107).The maximum diameter of P-NEC group was larger than that of M-NEC group,and the difference was statistically significant (x2 =4.311,P =0.038).Conclusions ENEC is a kind of highly aggressive malignant tumor with nonspecific manifestations.The diagnosis mainly depends on histopathology and immunohistochemistry.
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Aim To observate the effect of chemokine receptor(CXCR4) gene transfection on biological behavior of bone marrow mesenchymal stem cells in vitro.Methods Firstly, bone marrow mesenchymal stem cells were divided into three groups:GFP(transfected GFP into MSCs), CXCR4+(transfected CXCR4+ into MSCs) and CXCR4-(transfected CXCR4-into MSCs) group.Then, their capacity of proliferation, differentiation and migration ability (in vitro) was assessed with immunofluorescence cytochemistry method, flow cytometry assay and Transwell cell chemotaxis test.Results The high or low expression of CXCR4 had no effect on their ability of proliferation and differentiation into lung tissue.Compared with GFP group, however, CXCR4+-MSCs group significantly increased the number of migrating cells, while CXCR4——MSCs group showed no change in the number of migrating cells.Conclusions The proliferation and differentiation capacities are not affected by the high or low expression of CXCR4.The high expression of CXCR4 can significantly enhance the migration ability of MSCs to inflammatory lesions, and the low one has no effect on the migration of the cells.After the transplantation of MSCs, CXCR4′s high expression will access to the lesion area to participate in tissue repairing rapidly and largely, significantly enhancing the therapeutic efficacy.
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To improve the performance of the afterburner for the turbofan engine, an innovative type of mixer, namely, the chevron mixer, was considered to enhance the mixture between the core flow and the bypass flow. Computational fluid dynamics (CFD) simulations investigated the aerodynamic performances and combustion characteristics of the chevron mixer inside a typical afterburner. Three types of mixer, namely, CC (chevrons tilted into core flow), CB (chevrons tilted into bypass flow), and CA (chevrons tilted into core flow and bypass flow alternately), respectively, were studied on the aerodynamic performances of mixing process. The chevrons arrangement has significant effect on the mixing characteristics and the CA mode seems to be advantageous for the generation of the stronger streamwise vortices with lower aerodynamic loss. Further investigations on combustion characteristics for CA mode were performed. Calculation results reveal that the local temperature distribution at the leading edge section of flame holder is improved under the action of streamwise vortices shedding from chevron mixers. Consequently, the combustion efficiency increased by 3.5% compared with confluent mixer under the same fuel supply scheme.
