The structural and electronic properties of TiC（110） surfaces are calculated using the first-principles total-energy plane-wave pseudopotential method based on density functional theory. The calculated results of st...The structural and electronic properties of TiC（110） surfaces are calculated using the first-principles total-energy plane-wave pseudopotential method based on density functional theory. The calculated results of structural relaxation and surface energy for TiC（110） slab indicate that slab with 7 layers shows bulk-like characteristic interiors, and the changes of slab occur on the outmost three layers, which shows that the relaxation only influences the top three layers. Meanwhile, the strong Ti—C covalent bonding can be found in the distribution of charge density on the （100） plane. The interlayer Ti—C chemical bonds are reinforced and the outermost interlayer distance is reduced as a result of the charge depletion in the vacuum and the charge accumulations in the interlayer region between the first and second layers. The surface energy of TiC（110） is calculated to be 3.53 J/m2.展开更多
目的调查一起学校肺结核聚集性疫情,探讨密切接触者筛查和预防性服药的重要性。方法对指示病例发生学校开展流行病学调查,采用结核菌素纯化蛋白衍生物(Tuberculin Purified Protein Derivative,TB-PPD)试验、X线胸片检查和症状监测对指...目的调查一起学校肺结核聚集性疫情,探讨密切接触者筛查和预防性服药的重要性。方法对指示病例发生学校开展流行病学调查,采用结核菌素纯化蛋白衍生物(Tuberculin Purified Protein Derivative,TB-PPD)试验、X线胸片检查和症状监测对指示病例的密切接触者进行3次筛查,对TB-PPD强阳性密切接触者实施预防性服药。结果三次密切接触者TB-PPD筛查共筛查417人,TB-PPD强阳性率、阳性率分别为8.39%、32.13%,其中首次筛查的强阳性率(χ^(2)=20.24,P<0.01)、中度阳性率(χ^(2)=14.10,P=0.001)显著高于第二次、第三次筛查。X线胸片共筛查462人,胸片异常率为2.38%,首次筛查、第三次筛查的胸片异常率明显高于第二次筛查(χ^(2)=8.65,P=0.013)。指示病例班级学生TB-PPD筛查强阳性率(χ^(2)=67.89,P<0.01)、阳性率(χ^(2)=91.03,P<0.01)、胸片异常率(χ^(2)=4.73,P<0.05)均高于其他班级学生;指示病例所在寝室学生的胸片异常率高于其他寝室学生(χ^(2)=4.18,P<0.05)。结论指示病例延误诊断、同班同寝室持续密切接触可能是导致疫情发展的主要因素。通过及时、高效开展密切接触者TB-PPD、X线胸片筛查和高覆盖率的预防性服药干预,能有效降低疫情的发生发展。展开更多
基金Project (200902554) supported by National Post-doctor Foundation, ChinaProject (200802015) supported by the Post-Doctor Foundation of Shandong Province, China
文摘The structural and electronic properties of TiC（110） surfaces are calculated using the first-principles total-energy plane-wave pseudopotential method based on density functional theory. The calculated results of structural relaxation and surface energy for TiC（110） slab indicate that slab with 7 layers shows bulk-like characteristic interiors, and the changes of slab occur on the outmost three layers, which shows that the relaxation only influences the top three layers. Meanwhile, the strong Ti—C covalent bonding can be found in the distribution of charge density on the （100） plane. The interlayer Ti—C chemical bonds are reinforced and the outermost interlayer distance is reduced as a result of the charge depletion in the vacuum and the charge accumulations in the interlayer region between the first and second layers. The surface energy of TiC（110） is calculated to be 3.53 J/m2.
文摘目的调查一起学校肺结核聚集性疫情,探讨密切接触者筛查和预防性服药的重要性。方法对指示病例发生学校开展流行病学调查,采用结核菌素纯化蛋白衍生物(Tuberculin Purified Protein Derivative,TB-PPD)试验、X线胸片检查和症状监测对指示病例的密切接触者进行3次筛查,对TB-PPD强阳性密切接触者实施预防性服药。结果三次密切接触者TB-PPD筛查共筛查417人,TB-PPD强阳性率、阳性率分别为8.39%、32.13%,其中首次筛查的强阳性率(χ^(2)=20.24,P<0.01)、中度阳性率(χ^(2)=14.10,P=0.001)显著高于第二次、第三次筛查。X线胸片共筛查462人,胸片异常率为2.38%,首次筛查、第三次筛查的胸片异常率明显高于第二次筛查(χ^(2)=8.65,P=0.013)。指示病例班级学生TB-PPD筛查强阳性率(χ^(2)=67.89,P<0.01)、阳性率(χ^(2)=91.03,P<0.01)、胸片异常率(χ^(2)=4.73,P<0.05)均高于其他班级学生;指示病例所在寝室学生的胸片异常率高于其他寝室学生(χ^(2)=4.18,P<0.05)。结论指示病例延误诊断、同班同寝室持续密切接触可能是导致疫情发展的主要因素。通过及时、高效开展密切接触者TB-PPD、X线胸片筛查和高覆盖率的预防性服药干预,能有效降低疫情的发生发展。
