The social lockdowns and strict control measures initiated to combat the COVID-19 pandemic have had an impact on human migration.In this study,big data was used to analyze spatial patterns of population migration in 3...The social lockdowns and strict control measures initiated to combat the COVID-19 pandemic have had an impact on human migration.In this study,big data was used to analyze spatial patterns of population migration in 369 Chinese cities during the COVID-19 outbreak and to identify determinants of population migration.We found that the overall migration intensity decreased by 39.87%compared to the same period in 2019 prior to the COVID-19 outbreak.COVID-19 severely affected human migration.The public holidays and weekends have impacted human migration from the perspective of time scale.The spatial pattern of China’s population distribution presents a diamond structure that is dense in the east and sparse in the west,which is bounded by the Hu line and the cities such as Beijing,Shanghai,Guangzhou and Chengdu as nodes to connect.There is a strong consistency between the population distribution center and the level of urban development.The urban human migration network is centered on provincial capitals or municipalities at the regional scale,showing a prominent"center-periphery"structure.COVID-19 dispersed the forces of human migration in time and changed the direction of human migration in space.But it did not change the pattern of national migration.The most critical factors influencing mass migration are income levels and traditional culture.This study reveals the impacts of major public health emergencies on conventional migration patterns and provides a scientific theoretical reference for COVID-19 prevention and control.展开更多
目的:利用锥形束CT(cone-beam computed tomography,CBCT)分析倾斜性内收(retraction adjunct with tip,R&Tp)及控根性内收(retraction adjunct with torque,R&Tq)两种不同上颌前牙内收方式引发法牙槽骨改建差异。方法:收集于2...目的:利用锥形束CT(cone-beam computed tomography,CBCT)分析倾斜性内收(retraction adjunct with tip,R&Tp)及控根性内收(retraction adjunct with torque,R&Tq)两种不同上颌前牙内收方式引发法牙槽骨改建差异。方法:收集于2016年5月~2018年5月厦门医学院附属口腔医院正畸科收治并矫治完成的患者88例(共352颗上颌前牙),依据前牙的实际内收方式分为倾斜性内收组(P组,172颗)和控根性内收组(Q组,180颗)。利用CBCT和三维影像分析比较两组牙齿内收及牙槽骨改建指标。结果:牙齿内收指标的变化,P组患者上颌前牙的ΔIE-VD、ΔLAI/PP明显高于Q组(P<0.05),内收距离及内收角度明显高于Q组。P组患者ΔRA-VD为负值,而Q组患者为正值(P<0.05),根尖移动方向相反。牙槽骨改建指标的变化,P组唇侧厚度由根颈部至根尖部均明显减少,且由根颈部至根尖部的减少量逐渐提高。腭侧厚度S1明显减少,而S2~S3明显增加。总厚度T1明显减少,而T2~T3明显增加。唇侧高度及腭侧高度均明显减少,且腭侧的减少量相对较大。Q组唇侧厚度由根颈部至根尖部均明显增加,但增加量相对较小。腭侧厚度均明显减少,且由根颈部至根尖部的减少量逐渐降低。总厚度T1~T3均明显减少,且由根颈部至根尖部的减少量逐渐降低。唇侧高度及腭侧高度均明显减少,且腭侧的减少量相对较大,且程度大于P组。结论:倾斜性内收时的唇侧根尖部、腭侧根颈部及控根性内收时的腭侧根颈部及中部区域均为牙槽骨吸收的高发部位,上颌前牙过度内收时可导致以上部位的牙槽骨损伤。展开更多
基金This work was sponsored by Natural Science Foundation of Henan(Grant No.202300410076).
文摘The social lockdowns and strict control measures initiated to combat the COVID-19 pandemic have had an impact on human migration.In this study,big data was used to analyze spatial patterns of population migration in 369 Chinese cities during the COVID-19 outbreak and to identify determinants of population migration.We found that the overall migration intensity decreased by 39.87%compared to the same period in 2019 prior to the COVID-19 outbreak.COVID-19 severely affected human migration.The public holidays and weekends have impacted human migration from the perspective of time scale.The spatial pattern of China’s population distribution presents a diamond structure that is dense in the east and sparse in the west,which is bounded by the Hu line and the cities such as Beijing,Shanghai,Guangzhou and Chengdu as nodes to connect.There is a strong consistency between the population distribution center and the level of urban development.The urban human migration network is centered on provincial capitals or municipalities at the regional scale,showing a prominent"center-periphery"structure.COVID-19 dispersed the forces of human migration in time and changed the direction of human migration in space.But it did not change the pattern of national migration.The most critical factors influencing mass migration are income levels and traditional culture.This study reveals the impacts of major public health emergencies on conventional migration patterns and provides a scientific theoretical reference for COVID-19 prevention and control.
文摘目的:利用锥形束CT(cone-beam computed tomography,CBCT)分析倾斜性内收(retraction adjunct with tip,R&Tp)及控根性内收(retraction adjunct with torque,R&Tq)两种不同上颌前牙内收方式引发法牙槽骨改建差异。方法:收集于2016年5月~2018年5月厦门医学院附属口腔医院正畸科收治并矫治完成的患者88例(共352颗上颌前牙),依据前牙的实际内收方式分为倾斜性内收组(P组,172颗)和控根性内收组(Q组,180颗)。利用CBCT和三维影像分析比较两组牙齿内收及牙槽骨改建指标。结果:牙齿内收指标的变化,P组患者上颌前牙的ΔIE-VD、ΔLAI/PP明显高于Q组(P<0.05),内收距离及内收角度明显高于Q组。P组患者ΔRA-VD为负值,而Q组患者为正值(P<0.05),根尖移动方向相反。牙槽骨改建指标的变化,P组唇侧厚度由根颈部至根尖部均明显减少,且由根颈部至根尖部的减少量逐渐提高。腭侧厚度S1明显减少,而S2~S3明显增加。总厚度T1明显减少,而T2~T3明显增加。唇侧高度及腭侧高度均明显减少,且腭侧的减少量相对较大。Q组唇侧厚度由根颈部至根尖部均明显增加,但增加量相对较小。腭侧厚度均明显减少,且由根颈部至根尖部的减少量逐渐降低。总厚度T1~T3均明显减少,且由根颈部至根尖部的减少量逐渐降低。唇侧高度及腭侧高度均明显减少,且腭侧的减少量相对较大,且程度大于P组。结论:倾斜性内收时的唇侧根尖部、腭侧根颈部及控根性内收时的腭侧根颈部及中部区域均为牙槽骨吸收的高发部位,上颌前牙过度内收时可导致以上部位的牙槽骨损伤。
