Three model polyurethane hard segments based on dimethylol butanoic acid (DMBA) and 1,6-hexane diisocyanate (HDI), toluene diisocyanate (TDI) and 4,4'-diphenylmethane diisocyanate (MDI) were prepared by the soluti...Three model polyurethane hard segments based on dimethylol butanoic acid (DMBA) and 1,6-hexane diisocyanate (HDI), toluene diisocyanate (TDI) and 4,4'-diphenylmethane diisocyanate (MDI) were prepared by the solution method. Fourier Infrared (FTIR) spectroscopy was employed to study the H-bonds in these model polyurethanes. The model polyurethane hard segment prepared from HDI and 1,4-butanodiol (BDO) was used for comparison. It was found that the incorporation of the pendent carboxyl through DMBA into the model hard segments weakens the original NH…O = C H-bond but gives more H-bond patterns based on the two H-bond donors, urethane NH and carboxylic OH. The carboxylic dimer is one of the main H-bond types and is stronger than another main H-bond type NH…O=C. In addition, the H-bond in aromatic model hard segments is stronger than that of aliphatic hard segments. The appearance of the free C=O and the fact that almost all N—H is H-bonded suggest that there possibly exist either the third H-bond acceptor or the H-bond formed by one acceptor with two donors.展开更多
The elastic-plastic indentation properties of materials with varying ratio of hardness to Young’s modulus(H/E) were analyzed with the finite element method. And the indentation stress fields of materials with varying...The elastic-plastic indentation properties of materials with varying ratio of hardness to Young’s modulus(H/E) were analyzed with the finite element method. And the indentation stress fields of materials with varying ratio H/E on the surface were studied by the experiment. The results show that the penetration depth, contact radius, plastic pile-up and the degree of elastic recovery depend strongly on the ratio H/E. Moreover, graphs were established to describe the relationship between the elastic-plastic indentation parameters and H/E. The established graphs can be used to predict the H/E of materials when compared with experimental data.展开更多
目的:探讨急性ST段抬高型心肌梗死(STEMI)患者低密度脂蛋白胆固醇(LDL-C)/高密度脂蛋白胆固醇(HDL-C)比值(LHR)与其院内主要不良心血管事件(MACE)的相关性及其在临床中的应用价值。方法:收集发病12h内就诊的481例STEMI住院患者的临床资...目的:探讨急性ST段抬高型心肌梗死(STEMI)患者低密度脂蛋白胆固醇(LDL-C)/高密度脂蛋白胆固醇(HDL-C)比值(LHR)与其院内主要不良心血管事件(MACE)的相关性及其在临床中的应用价值。方法:收集发病12h内就诊的481例STEMI住院患者的临床资料及MACE发生情况,根据LHR的中位数(2.9)将患者分为低LHR组(LHR≤2.9,n=223)和高LHR组(LHR>2.9,n=258)。分析LHR与STEMI患者院内MACE的相关性。结果:高LHR组患者院内MACE比例均高于低LHR组[恶性室性心律失常:29(11.2%) VS 9(4.0%),P=0.004;高度房室传导阻滞:22(8.5%) VS 6(2.7%),P=0.006;心源性休克+死亡:29(11.2%) VS 7(3.1%),P=0.001]。恶性室性心律失常、心源性休克+死亡患者LHR差异有统计学意义(P均<0.05)。Pearson相关分析显示,除高度房室传导阻滞(r=0.060,P>0.05)外,LHR与恶性室性心律失常(r=0.121)、心源性休克和死亡(r=0.115)均显著相关(P<0.05)。多因素Logistic回归分析显示,LHR、空腹血糖是STEMI患者发生院内MACE的独立危险因素(P均<0.05)。ROC曲线显示LHR预测STEMI患者院内MACE的曲线下面积为0.606(95%CI:0.544~0.668),cut-off值为2.854,敏感度为80.6%,特异度为52.1%;LHR>2.854时STEMI住院患者很可能会发生MACE。结论:STEMI患者LHR升高与恶性室性心律失常、心源性休克及死亡发生呈正相关。LHR是STEMI患者发生MACE的独立危险因素,对恶性室性心律失常、心源性休克及死亡发生有一定的预测价值。展开更多
基金This work was supported by the Natural Science Foundation of Henan Province (004030600)
文摘Three model polyurethane hard segments based on dimethylol butanoic acid (DMBA) and 1,6-hexane diisocyanate (HDI), toluene diisocyanate (TDI) and 4,4'-diphenylmethane diisocyanate (MDI) were prepared by the solution method. Fourier Infrared (FTIR) spectroscopy was employed to study the H-bonds in these model polyurethanes. The model polyurethane hard segment prepared from HDI and 1,4-butanodiol (BDO) was used for comparison. It was found that the incorporation of the pendent carboxyl through DMBA into the model hard segments weakens the original NH…O = C H-bond but gives more H-bond patterns based on the two H-bond donors, urethane NH and carboxylic OH. The carboxylic dimer is one of the main H-bond types and is stronger than another main H-bond type NH…O=C. In addition, the H-bond in aromatic model hard segments is stronger than that of aliphatic hard segments. The appearance of the free C=O and the fact that almost all N—H is H-bonded suggest that there possibly exist either the third H-bond acceptor or the H-bond formed by one acceptor with two donors.
基金Science Research Foundation of Shanghai Municipal Education Commission (No.06VZ004)
文摘The elastic-plastic indentation properties of materials with varying ratio of hardness to Young’s modulus(H/E) were analyzed with the finite element method. And the indentation stress fields of materials with varying ratio H/E on the surface were studied by the experiment. The results show that the penetration depth, contact radius, plastic pile-up and the degree of elastic recovery depend strongly on the ratio H/E. Moreover, graphs were established to describe the relationship between the elastic-plastic indentation parameters and H/E. The established graphs can be used to predict the H/E of materials when compared with experimental data.
文摘目的:探讨急性ST段抬高型心肌梗死(STEMI)患者低密度脂蛋白胆固醇(LDL-C)/高密度脂蛋白胆固醇(HDL-C)比值(LHR)与其院内主要不良心血管事件(MACE)的相关性及其在临床中的应用价值。方法:收集发病12h内就诊的481例STEMI住院患者的临床资料及MACE发生情况,根据LHR的中位数(2.9)将患者分为低LHR组(LHR≤2.9,n=223)和高LHR组(LHR>2.9,n=258)。分析LHR与STEMI患者院内MACE的相关性。结果:高LHR组患者院内MACE比例均高于低LHR组[恶性室性心律失常:29(11.2%) VS 9(4.0%),P=0.004;高度房室传导阻滞:22(8.5%) VS 6(2.7%),P=0.006;心源性休克+死亡:29(11.2%) VS 7(3.1%),P=0.001]。恶性室性心律失常、心源性休克+死亡患者LHR差异有统计学意义(P均<0.05)。Pearson相关分析显示,除高度房室传导阻滞(r=0.060,P>0.05)外,LHR与恶性室性心律失常(r=0.121)、心源性休克和死亡(r=0.115)均显著相关(P<0.05)。多因素Logistic回归分析显示,LHR、空腹血糖是STEMI患者发生院内MACE的独立危险因素(P均<0.05)。ROC曲线显示LHR预测STEMI患者院内MACE的曲线下面积为0.606(95%CI:0.544~0.668),cut-off值为2.854,敏感度为80.6%,特异度为52.1%;LHR>2.854时STEMI住院患者很可能会发生MACE。结论:STEMI患者LHR升高与恶性室性心律失常、心源性休克及死亡发生呈正相关。LHR是STEMI患者发生MACE的独立危险因素,对恶性室性心律失常、心源性休克及死亡发生有一定的预测价值。
