Conformal Ricei collineations of static spherically symmetric spacetimes are studied. The general form of the vector fields generating eonformal Rieei eollineations is found when the Rieei tensor is non-degenerate, in...Conformal Ricei collineations of static spherically symmetric spacetimes are studied. The general form of the vector fields generating eonformal Rieei eollineations is found when the Rieei tensor is non-degenerate, in which ease the number of independent eonformal Rieei eollineations is 15, the maximum number for four-dimensional manifolds. In the degenerate ease it is found that the static spherically symmetric spaeetimes always have an infinite number of eonformal Rieei eollineations. Some examples are provided which admit non-trivial eonformal Rieei eollineations, and perfect fluid source of the matter.展开更多
A complete classification of static space times with maximal symmetric transverse spaces is provided, according to their Ricci collineations. The classification is made when one component of Ricci collineation vector ...A complete classification of static space times with maximal symmetric transverse spaces is provided, according to their Ricci collineations. The classification is made when one component of Ricci collineation vector field V is non-zero （cases 1 - 4）, two components of V are non-zero （cases 5 - 10）, and three components of V are non-zero （cases 11 - 14）, respectlvily. Both non-degenerate （detRab ≠ 0） as well as the degenerate （det Rab = 0） cases are discussed and some new metrics are found.展开更多
The Imperial Citadel of Thang Long is a crucial case in ancient Vietnam’s planning and design history.Although historical materials indicate that the orientation of the Imperial Citadel of Thang Long has a dialectica...The Imperial Citadel of Thang Long is a crucial case in ancient Vietnam’s planning and design history.Although historical materials indicate that the orientation of the Imperial Citadel of Thang Long has a dialectical unity relationship with the surroundingmountains,current research is only speculative generalization and lacks empirical analysis.Based on existing findings,this paper identifies the collineation measurement as a generalmethod in the Sinosphere countries for determining spatial orientation.Using a mixed-method of historical archives,fieldwork and simulation model,this paper summarizeshistorical cluesandthreedesignperspectives related to spatial orientation by statistical analysis.Further,it analyzes the logic and application of collineation measurement in constructing the Imperial Citadel of Thang Long.The results show that Vietnamese designers used Tàn Viên Mountain as a component of Thang Long city by collineating the twomountain peaks to the west.Tàn Viên Mountain and the highlands extending eastward fromit are used as the key to establishing the position of the Imperial Citadel,setting the spatial structure of human settlements,and the development of city space.The location,layout,and formof important buildings in the Imperial Citadel are also closely related to the surrounding landscape within 50 km.展开更多
Background: Maternal and neonatal mortality remains a public health problem in Benin. Each year, approximately 1500 maternal deaths and more than 12,000 newborn deaths are recorded there. In order to correct the situa...Background: Maternal and neonatal mortality remains a public health problem in Benin. Each year, approximately 1500 maternal deaths and more than 12,000 newborn deaths are recorded there. In order to correct the situation, strategies such as the implementation of Emergency Obstetric and Neonatal Care (EmONC) were initiated. Objective: Determine the rates of maternal deaths in EmONC centers in the Collines department from 2018 to 2022. Framework and Methods: The study took place in Benin precisely in the Collines department. This was a descriptive cross-sectional study. Data collection was carried out during the first two weeks of January 2023 and covered data from the 09 Basic Emergency Obstetric and Neonatal Care centers (BEMONC) and the Obstetric and Neonatal Care centers of Complete Emergency (CEmONC) of the Collines department from 2018 to 2022. An estimate of the ratios of maternal deaths occurring at the level of the EmONC centers of the Collines department from 2018-2022 was carried out followed by constructive suggestions. Results: During the five years (2018 to 2022), the Collines department recorded 42,582 live births with 148 maternal deaths, i.e. a ratio of 348 maternal deaths per 100,000 live births. Between 2018 and 2022, the highest maternal death ratio was recorded in 2019, i.e. 425 maternal deaths per 100,000 live births for all EmONC centers and 607 maternal deaths per 100,000 live births in EmONC centers. The highest maternal death ratio at the BEmONC center level was recorded in 2020, i.e. 129 maternal deaths per 100,000 births. Conclusion: These results suggest that despite the implementation of EmONC in the Collines department, maternal deaths have not decreased. To improve these outcomes for a reduction in maternal deaths, urgent action must be taken.展开更多
Skin depigmentation is a worrying practice that is gaining popularity, particularly among young girls. However, this practice poses health risks. It also reflects a negative view of black skin color. This was a cross-...Skin depigmentation is a worrying practice that is gaining popularity, particularly among young girls. However, this practice poses health risks. It also reflects a negative view of black skin color. This was a cross-sectional study carried out between April and May 2023 which involved 1039 female students from schools and universities in the Collines department selected by stratified sampling. Data was collected during a face-to-face interview using a questionnaire providing information on the demographic, socio-cultural, and economic characteristics of the girls. The depigmentation products used were identified as well as the complications caused by the use of these products. Statistical analysis made it possible to calculate the frequencies and logistic regression made it possible to identify the factors associated with depigmentation. The prevalence of depigmentation among the girls surveyed was 78.2%. The main products used were soaps based on mercurial derivative and hydroquinone (21.6%) and lotions based on hydroquinone and corticosteroids (75.7%). The factors associated with the practice of depigmentation were the ethnicity of the respondents (OR = 2.52;95% CI = [0.47 - 13.33], p = 0.001);the average monthly income of the parents (OR = 3.26;95% CI = [1.71 - 6.09], p = 0.003);the opinion of the respondents on depigmentation (OR = 2.48;95% CI = [0.84 - 7.3], p < 0.001) and the value given to light skin versus black skin (OR = 3.41;95% CI = [2.32 - 5.01], p < 0.001). In conclusion, the prevalence of depigmentation among the girls surveyed is high. Consequently, reinforced awareness measures and stricter control of bleaching products are imperative to address this high prevalence of the phenomenon.展开更多
文摘Conformal Ricei collineations of static spherically symmetric spacetimes are studied. The general form of the vector fields generating eonformal Rieei eollineations is found when the Rieei tensor is non-degenerate, in which ease the number of independent eonformal Rieei eollineations is 15, the maximum number for four-dimensional manifolds. In the degenerate ease it is found that the static spherically symmetric spaeetimes always have an infinite number of eonformal Rieei eollineations. Some examples are provided which admit non-trivial eonformal Rieei eollineations, and perfect fluid source of the matter.
基金The project supported by National Natural Science Foundation of China under Grant Nos. 10325525 and 90403029, and Ministry of Science and Technology of China under Grant No. TG1999075401
文摘A complete classification of static space times with maximal symmetric transverse spaces is provided, according to their Ricci collineations. The classification is made when one component of Ricci collineation vector field V is non-zero （cases 1 - 4）, two components of V are non-zero （cases 5 - 10）, and three components of V are non-zero （cases 11 - 14）, respectlvily. Both non-degenerate （detRab ≠ 0） as well as the degenerate （det Rab = 0） cases are discussed and some new metrics are found.
文摘The Imperial Citadel of Thang Long is a crucial case in ancient Vietnam’s planning and design history.Although historical materials indicate that the orientation of the Imperial Citadel of Thang Long has a dialectical unity relationship with the surroundingmountains,current research is only speculative generalization and lacks empirical analysis.Based on existing findings,this paper identifies the collineation measurement as a generalmethod in the Sinosphere countries for determining spatial orientation.Using a mixed-method of historical archives,fieldwork and simulation model,this paper summarizeshistorical cluesandthreedesignperspectives related to spatial orientation by statistical analysis.Further,it analyzes the logic and application of collineation measurement in constructing the Imperial Citadel of Thang Long.The results show that Vietnamese designers used Tàn Viên Mountain as a component of Thang Long city by collineating the twomountain peaks to the west.Tàn Viên Mountain and the highlands extending eastward fromit are used as the key to establishing the position of the Imperial Citadel,setting the spatial structure of human settlements,and the development of city space.The location,layout,and formof important buildings in the Imperial Citadel are also closely related to the surrounding landscape within 50 km.
文摘Background: Maternal and neonatal mortality remains a public health problem in Benin. Each year, approximately 1500 maternal deaths and more than 12,000 newborn deaths are recorded there. In order to correct the situation, strategies such as the implementation of Emergency Obstetric and Neonatal Care (EmONC) were initiated. Objective: Determine the rates of maternal deaths in EmONC centers in the Collines department from 2018 to 2022. Framework and Methods: The study took place in Benin precisely in the Collines department. This was a descriptive cross-sectional study. Data collection was carried out during the first two weeks of January 2023 and covered data from the 09 Basic Emergency Obstetric and Neonatal Care centers (BEMONC) and the Obstetric and Neonatal Care centers of Complete Emergency (CEmONC) of the Collines department from 2018 to 2022. An estimate of the ratios of maternal deaths occurring at the level of the EmONC centers of the Collines department from 2018-2022 was carried out followed by constructive suggestions. Results: During the five years (2018 to 2022), the Collines department recorded 42,582 live births with 148 maternal deaths, i.e. a ratio of 348 maternal deaths per 100,000 live births. Between 2018 and 2022, the highest maternal death ratio was recorded in 2019, i.e. 425 maternal deaths per 100,000 live births for all EmONC centers and 607 maternal deaths per 100,000 live births in EmONC centers. The highest maternal death ratio at the BEmONC center level was recorded in 2020, i.e. 129 maternal deaths per 100,000 births. Conclusion: These results suggest that despite the implementation of EmONC in the Collines department, maternal deaths have not decreased. To improve these outcomes for a reduction in maternal deaths, urgent action must be taken.
文摘Skin depigmentation is a worrying practice that is gaining popularity, particularly among young girls. However, this practice poses health risks. It also reflects a negative view of black skin color. This was a cross-sectional study carried out between April and May 2023 which involved 1039 female students from schools and universities in the Collines department selected by stratified sampling. Data was collected during a face-to-face interview using a questionnaire providing information on the demographic, socio-cultural, and economic characteristics of the girls. The depigmentation products used were identified as well as the complications caused by the use of these products. Statistical analysis made it possible to calculate the frequencies and logistic regression made it possible to identify the factors associated with depigmentation. The prevalence of depigmentation among the girls surveyed was 78.2%. The main products used were soaps based on mercurial derivative and hydroquinone (21.6%) and lotions based on hydroquinone and corticosteroids (75.7%). The factors associated with the practice of depigmentation were the ethnicity of the respondents (OR = 2.52;95% CI = [0.47 - 13.33], p = 0.001);the average monthly income of the parents (OR = 3.26;95% CI = [1.71 - 6.09], p = 0.003);the opinion of the respondents on depigmentation (OR = 2.48;95% CI = [0.84 - 7.3], p < 0.001) and the value given to light skin versus black skin (OR = 3.41;95% CI = [2.32 - 5.01], p < 0.001). In conclusion, the prevalence of depigmentation among the girls surveyed is high. Consequently, reinforced awareness measures and stricter control of bleaching products are imperative to address this high prevalence of the phenomenon.
