ABSTRACT
:To predict the epidemiological trend of coronavirus disease 2019 (COVID-19) by mathematical modeling based on the population mobility and the epidemic prevention and control measures. : As of February 8，2020，the information of 151 confirmed cases in Yueqing，Zhejiang province were obtained，including patients' infection process，population mobility between Yueqing and Wuhan，etc. To simulate and predict the development trend of COVID-19 in Yueqing, the study established two-stage mathematical models，integrating the population mobility data with the date of symptom appearance of confirmed cases and the transmission dynamics of imported and local cases. : It was found that in the early stage of the pandemic，the number of daily imported cases from Wuhan (using the date of symptom appearance) was positively associated with the number of population travelling from Wuhan to Yueqing on the same day and 6 and 9 days before that. The study predicted that the final outbreak size in Yueqing would be 170 according to the number of imported cases estimated by consulting the population number travelling from Wuhan to Yueqing and the susceptible-exposed-infectious-recovered (SEIR) model; while the number would be 165 if using the reported daily number of imported cases. These estimates were close to the 170，the actual monitoring number of cases in Yueqing as of April 27，2020. : The two-stage modeling approach used in this study can accurately predict COVID-19 epidemiological trend.
Subject(s)
Humans , COVID-19 , China/epidemiology , Disease Outbreaks , Models, Theoretical , Pandemics , SARS-CoV-2ABSTRACT
:To evaluate the impact of socioeconomic status，population mobility，prevention and control measures on the early-stage coronavirus disease 2019 (COVID-19) development in major cities of China. : The rate of daily new confirmed COVID-19 cases in the 51 cities with the largest number of cumulative confirmed cases as of February 19，2020 (except those in Hubei province) were collected and analyzed using the time series cluster analysis. It was then assessed according to three aspects，that is, socioeconomic status，population mobility，and control measures for the pandemic. : According to the analysis on the 51 cities，4 development patterns of COVID-19 were obtained，including a high-incidence pattern (in Xinyu)，a late high-incidence pattern (in Ganzi)，a moderate incidence pattern (in Wenzhou and other 12 cities)，and a low and stable incidence pattern (in Hangzhou and other 35 cities). Cities with different types and within the same type both had different scores on the three aspects. : There were relatively large difference on the COVID-19 development among different cities in China，possibly affected by socioeconomic status，population mobility and prevention and control measures that were taken. Therefore，a timely public health emergency response and travel restriction measures inside the city can interfere the development of the pandemic. Population flow from high risk area can largely affect the number of cumulative confirmed cases.
Subject(s)
Humans , COVID-19 , China/epidemiology , Cities , SARS-CoV-2 , Social ClassABSTRACT
This study aimed to quantitatively assess the effectiveness of the Wuhan lockdown measure on controlling the spread of coronavirus diesase 2019 (COVID-19). : Firstly，estimate the daily new infection rate in Wuhan before January 23，2020 when the city went into lockdown by consulting the data of Wuhan population mobility and the number of cases imported from Wuhan in 217 cities of Mainland China. Then estimate what the daily new infection rate would have been in Wuhan from January 24 to January 30th if the lockdown measure had been delayed for 7 days，assuming that the daily new infection in Wuhan after January 23 increased in a high，moderate and low trend respectively (using exponential, linear and logarithm growth models). Based on that，calculate the number of infection cases imported from Wuhan during this period. Finally，predict the possible impact of 7-day delayed lockdown in Wuhan on the epidemic situation in China using the susceptible-exposed-infectious-removed (SEIR) model. : The daily new infection rate in Wuhan was estimated to be 0.021%，0.026%，0.029%，0.033% and 0.070% respectively from January 19 to January 23. And there were at least 20 066 infection cases in Wuhan by January 23，2020. If Wuhan lockdown measure had been delayed for 7 days，the daily new infection rate on January 30 would have been 0.335% in the exponential growth model，0.129% in the linear growth model，and 0.070% in the logarithm growth model. Correspondingly，there would have been 32 075，24 819 and 20 334 infection cases travelling from Wuhan to other areas of Mainland China，and the number of cumulative confirmed cases as of March 19 in Mainland China would have been 3.3-3.9 times of the officially reported number. Conclusions: Timely taking city-level lockdown measure in Wuhan in the early stage of COVID-19 outbreak is essential in containing the spread of the disease in China.
Subject(s)
Humans , COVID-19 , China/epidemiology , Cities , Communicable Disease Control , SARS-CoV-2ABSTRACT
BACKGROUND:Biomechanical compatibility is the necessary condition to ensure the stable osseointegration with implants that then can function over a long period; therefore, it is especialy important to get knowledge about distribution of stress and strain between the maxilary central incisor and its surrounding bone tissue. OBJECTIVE: Based on five different anatomical types of natural teeth, to study the regularity of stress distribution between the maxilary central incisor root and implant.METHODS: According to the five different anatomical types of natural maxilary central incisors, UGNX and ANSYS were used to set up three-dimensional finite element models (B1, B2, M1, M2, P1) for the implant and surrounding structures, which were under 100 N static load at angles of 0o, 30o, 45o, 60o, 90o with the long axis of teeth. Then, the stress distribution between the five kinds of maxilary central incisor roots and implants was analyzed. RESULTS AND CONCLUSION:Among the five different anatomical types, the equivalent stress for both the natural central incisor and implant were increased with the increasing of angles, and the implant had a higher raising trend. The equivalent stress for the natural tooth concentrated upon B1 for the maximum value and M1 for the minimum value; while the equivalent stress for the implant focused on the maximum value at M1 and the minimum value at M2. There was a gap of 2%-31% between the equivalent stresses for the natural tooth roots and a gap of 4%-21% for the implants. The stress distribution range for the implant was just smaler than that for the natural tooth roots. It implies that the bit force of implant and natural tooth is in positive proportion to the bite angles, and the bite force that implant can burden is smaler than that the central incisor can.
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Objective To evaluate the value of spiral CT and panoramic radiographs in preoperative assessment the jaw condition of patients for dental implantation.Methods 80 patients required dental implant restoration,these patients were Manned by CT and panoramic radiographs in preoperative,then selected suitable patients for dental implant restoration,reconstructed the jaw based on spiral CT data and guided the dental implant design and implanration.Results The spiral CT examination could be more accurate selection criteria for the patients needed dental implant restoration and more accurately showed the situation of edentulous ridge bone.Conclusion The reconstructed of three-dimensional imaging of spiral CT could precisely show the bone situation in the jaw needed dental implant and the important anatomic structures,could effectively assist denture design and the direction and depth of dental implants.was more superiority than panoramic radiographs.
ABSTRACT
Objective To examine the effect of oral external suction on environmental pollution of microorganism in dental clinic.Methods Aerobe was counted na observation index of air contamination and air sample of the area leveal 1m and 2.5 m,hight 1m,which using oral cavity collectors of aspirator or not was collected by the method of sedimentation.Results The datum of the group with oral cavity collectors of aspirator was much lower than the group without it.Conclusion Environmental pollution from tooth treatment in dental clinic can be reduced by using oral extemal suction.