Background and objectives:Coronavirus disease 2019(COVID-19)is a pandemic that has become a major source of morbidity and mortality worldwide,affecting the physical and mental health of individuals influencing reprodu...Background and objectives:Coronavirus disease 2019(COVID-19)is a pandemic that has become a major source of morbidity and mortality worldwide,affecting the physical and mental health of individuals influencing reproduction.Despite the threat,it poses to maternal health in sub-Saharan Africa and Nigeria,there is little or no data on the impact it has on fertility,conception,gestation and birth.To compare the birth rate between pre-COVID and COVID times using selected months of the year.Materials and methods:This was a secondary analysis of cross-sectional analytical study data from the birth registries of three tertiary hospitals,comparing two years[2019(Pre-COVID)]versus[2020(COVID era)]using three months of the year(October to December).The data relied upon was obtained from birth registries in three busy maternity clinics all within tertiary hospitals in South-East Nigeria and we aimed at discussing the potential impacts of COVID-19 on fertility in Nigeria.The secondary outcome measures were;mode of delivery,booking status of the participants,maternal age and occupation.Results:There was a significant decrease in tertiary-hospital based birth rate by 92 births(P=0.0009;95%CI:-16.0519 to-4.1481)among mothers in all the three hospitals in 2020 during the COVID period(post lockdown months)of October to December.There was a significant difference in the mode of delivery for mothers(P=0.0096)with a 95%confidence interval of 1.0664 to 1.5916,as more gave birth through vaginal delivery during the 2020 COVID-19 period than pre-COVID-19.Conclusion:Tertiary-hospital based birth rates were reduced during the pandemic.Our multi-centre study extrapolated on possible factors that may have played a role in this decline in their birth rate,which includes but is not limited to;decreased access to hospital care due to the total lockdowns/curfews and worsening inflation and economic recession in the country.展开更多
Objective It is well known that a dual trigger treatment can improve clinical outcomes of in vitro fertilization(IVF)in high or normal ovarian responders.However,it is not clear whether dual triggering also benefits p...Objective It is well known that a dual trigger treatment can improve clinical outcomes of in vitro fertilization(IVF)in high or normal ovarian responders.However,it is not clear whether dual triggering also benefits patients with diminished ovarian reserve(DOR).The aim of this study was to investigate whether a dual trigger treatment of gonadotropin-releasing hormone(GnRH)agonist combined with human chorionic gonadotropin(hCG)for final follicular maturation improves the cumulative live birth rate(CLBR)during the GnRH-antagonist cycle in patients with DOR.Methods This retrospective study included patients with DOR who received a GnRH-antagonist protocol during IVF and intracytoplasmic sperm injection(IVF-ICSI)cycles at Peking University People’s Hospital from January 1,2017 through December 31,2017.Oocyte maturation was triggered by GnRH combined with hCG(n=110)or hCG alone(n=71).Embryos were transferred on the third day after oocyte retrieval or during a subsequent freeze-thaw cycle.Patients were followed up for 3 years.Results The dual trigger treatment did not affect CLBR,which is an overall determinant of the success rate of assisted reproductive technology(ART).Women in the dual trigger group had significantly higher rates of fertilization than those in the hCG group(90.1%vs.83.9%,P=0.040).Conclusion Dual trigger with GnRH agonist and hCG did not improve CLBR in patients with DOR,but did slightly improve fertilization rate,oocyte count,and embryo quality.展开更多
There were few studies of cumulative live birth rates(CLBRs) based on multicenter reproductive clinical data from the general Chinese population.Here we report a retrospective cohort study,including 14 311 women with1...There were few studies of cumulative live birth rates(CLBRs) based on multicenter reproductive clinical data from the general Chinese population.Here we report a retrospective cohort study,including 14 311 women with17 315 cycles,in three reproductive centers to evaluate two estimated parameters of CLBRs with multiple transfer cycles of in vitro fertilization(IVF)/intracytoplasmic sperm injection(ICSI) in a Chinese population.We found that CLBRs were related to female age and endometrial thickness.By the fourth transfer cycle,the conservative and optimal estimates of CLBRs were 52.95% and 77.30% in women under 30 years of age,and 18.17% and26.51% in those 37 years of age or older,respectively.The two estimates were 44.70% and 63.15% in women with endometrial thickness more than 7 mm,and 32.05% and 46.18% in those with less than 7 mm,respectively.In addition,body mass index(BMI),duration of infertility,and infertility diagnoses may also be related to CLBRs on certain conditions.The findings from this study on CLBRs after multiple transfer cycles of IVF/ICSI treatment on different conditions in the Chinese population should be beneficial to both infertile couples and clinicians.展开更多
Purpose: Urbanization, obesity and ageing associated with lifestyle changes (Westernized diet patterns, pollution, physical inactivity) have been proposed as the major contributing factors for the global rise in breas...Purpose: Urbanization, obesity and ageing associated with lifestyle changes (Westernized diet patterns, pollution, physical inactivity) have been proposed as the major contributing factors for the global rise in breast cancer (BCa) and have been the variables used to predict the future breast cancer rate. At the same time, socio-economic level, instead of birth rate, has been proposed for explanation of dramatic regional variations of breast cancer incidence. We sought to determine which factor plays the determining role in predicting worldwide breast cancer incidence rates and regional variations. Methods: Bivariate correlation was conducted to examine the relationships between country-specific estimates of birth rate, BCa incidence, urbanization, overweight, ageing and GDP. Partial correlation was performed to identify the correlation between BCa incidence with each independent variable while we controlled the other four variables. Multiple linear regression was used to identify the most significant predictors of BCa incidence. Post hoc Scheff and independent T-Test analysis were performed to compare mean differences in BCa incidence rates and residuals of BCa standardised on birth rate in the WHO regions, and UN developed and developing regions respectively. Results: Worldwide, BCa incidence rate tends to increase while birth rate decreases and urbanization, overweight, ageing and GDP increase. However, birth rate was the only variable that had a significant correlation with BCa incidence when controlled for the other four variables. Birth rate was the only significant predictor of BCa incidence in regression analysis. Multiple mean differences of BCa incidence between regions were significant, but all disappeared when the contributing effect of birth rate on BCa incidence rate was removed. Conclusions: Birth rate plays a determining role in worldwide BCa incidence rate and regional variations. Current BCa projection methods may estimate future rates of BCa poorly if they fail to incorporate the impact of birth rate.展开更多
Background:More and more scholars have called for the cumulative live birth rate(CLBR)of a complete ovarian stimulation cycle as a key indicator for assisted reproductive technology.This research aims to study the CLB...Background:More and more scholars have called for the cumulative live birth rate(CLBR)of a complete ovarian stimulation cycle as a key indicator for assisted reproductive technology.This research aims to study the CLBR of the first ovarian hyperstimulation cycles and analyze the related prognosis factors that might affect the CLBR.Methods:Our retrospective study included first in vitro fertilization or intracytoplasmic sperm injection(IVF/ICSI)cycles performed between January 2013 to December 2014.A total of 17,978 couples of first ovarian hyperstimulation IVF/ICSI cycles were included.The study was followed up for 4 years to observe the CLBR.The multivariable logistic regression model was used to analyze the prognosis factor,P value of<0.05 was considered statistically significant.Results:The cumulative pregnancy rate was 58.14%(10,452/17,978),and the CLBR was 49.66%(8928/17,978).The female age was younger in the live birth group when compared with the non-live birth group(30.81±4.05 vs.33.09±5.13,P<0.001).The average duration of infertility was shorter than the non-live birth cohort(4.22±3.11 vs.5.06±4.08,P<0.001).The preliminary gonadotropin used and the total number of gonadotropin used were lower in the live birth group when compared with the non-live birth group(both P<0.001).Meanwhile,the number of oocytes retrieved and transferrable embryos were both significantly higher in the live birth group(15.35±7.98 vs.11.35±7.60,P<0.001;6.66±5.19 vs.3.62±3.51,P<0.001,respectively).Conclusions:The women's age,body mass index,duration of infertility years,infertility factors,controlled ovarian hyperstimulation protocol,the number of acquired oocytes,and number of transferrable embryos are the prognosis factors that significantly affected the CLBR.展开更多
The present study aimed to evaluate the clinical outcomes of magnetic-activated cell sorting(MACS)in sperm preparation for male subjects with a sperm DNA fragmentation index(DFI)≥30%.A total of 86 patients who had un...The present study aimed to evaluate the clinical outcomes of magnetic-activated cell sorting(MACS)in sperm preparation for male subjects with a sperm DNA fragmentation index(DFI)≥30%.A total of 86 patients who had undergone their first long-term long protocol were selected.The protocol involved in vitro fertilization(IVF)and intracytoplasmic sperm injection(ICSI)cycles,and the patients were divided into the MACS or control groups.The MACS group included sperm samples analyzed with MACS that were combined with density gradient centrifugation(DGC)and the swim-up(SU)technique(n=39),and the control group included sperm samples prepared using standard techniques(DGC and SU;n=41).No differences were noted with regard to basic clinical characteristics,number of oocytes retrieved,normal fertilization rate,cleavage rate,or transplantable embryo rate between the two groups in IVF/ICSI.In addition,the clinical pregnancy and implantation rates of the first embryo transfer cycles indicated no significant differences between the two groups.However,there was a tendency to improve the live birth rate(LBR)of the first embryo transfer cycle(63.2%vs 53.9%)and the cumulative LBR(79.5%vs 70.7%)in the MACS group compared with the control group.Moreover,the number of transferred embryos(mean±standard deviation[s.d.]:1.7±0.7 vs 2.3±1.6)and the transfer number of each retrieved cycle(mean±s.d.:1.2±0.5 vs 1.6±0.8)were significantly lower in the MACS group than those in the control group.Thus,the selection of nonapoptotic spermatozoa by MACS for higher sperm DFI could improve assisted reproductive clinical outcomes.展开更多
Objective:To investigate cumulative live birth rate (cLBR) per oocyte retrieval in infertile patients aged 40 years and over undergoing their first in vitro fertilization/intracytoplasmic sperm injection cycles and to...Objective:To investigate cumulative live birth rate (cLBR) per oocyte retrieval in infertile patients aged 40 years and over undergoing their first in vitro fertilization/intracytoplasmic sperm injection cycles and to identify the possible predictors.Methods:A total of 1,613 patients at a university hospital in China from January 2013 to May 2017 were enrolled in this retrospective study.All data for fresh and subsequent frozen-thawed cycles were analyzed.Multivariate logistic regression analysis with stepwise selection of possible predictors for cLBR was performed,and Loess curve was constructed to determine the association between cLBR and the number of oocytes retrieved.Results:cLBR significantly increased with the number of oocytes retrieved and reached up to 75% when > 20 oocytes were retrieved (P<0.001).Variables of antral follicle count (AFC) and the number of oocytes retrieved were selected using multiple logistic regression analysis with stepwise selection to predict the significance of cLBR.cLBR demonstrated an obvious upward trend as the number of oocytes retrieval increased in the Loess curve.Conclusions:For patients aged 40 years and over,AFC and the number of oocytes retrieved were two key predictors for cLBR and maximization of ovarian reserve exploitation was pivotal to increase the chance of live birth.展开更多
We study global asymptotic stability for an SIS epidemic model with maturation delay proposed by K. Cooke, P. van den Driessche and X. Zou, Interaction of maturation delay and nonlinear birth in population and epidemi...We study global asymptotic stability for an SIS epidemic model with maturation delay proposed by K. Cooke, P. van den Driessche and X. Zou, Interaction of maturation delay and nonlinear birth in population and epidemic models, J. Math. Biol. 39(4) (1999) 332-352. It is assumed that the population has a nonlinear birth term and disease causes death of infective individuals. By using a monotone iterative method, we establish sufficient conditions for the global stability of an endemic equilibrium when it exists dependently on the monotone property of the birth rate function. Based on the analysis, we further study the model with two specific birth rate functions BI(N) = be-aN and B3(N) = A/N + c, where N denotes the total population. For each model, we obtain the disease induced death rate which guarantees the global stability of the endemic equilibrium and this gives a positive answer for an open problem by X. Q. Zhao and X. Zou, Threshold dynamics in a delayed SIS epidemic model, J. Math. Anal. Appl. 257(2) (2001) 282-291.展开更多
CHINA has achieved remarkable results in birth control since adopting a basic state policy of family planning to control the birth rate and increase the population quality. According to the "1997 Statistic Bullet...CHINA has achieved remarkable results in birth control since adopting a basic state policy of family planning to control the birth rate and increase the population quality. According to the "1997 Statistic Bulletin for National Economy and Social Development," a document recently issued by the State Statistics Bureau, China maintained a low birth rate of 16.57 per thousand in 1997—a natural population growth of one percent. Women of child-bearing age now average about two births each, a decrease from six in 1970.展开更多
In this paper, we propose an SIRS epidemic model with pulse vaccination, birth pulse and Logistic death rate. By using the stroboscopic map of a discrete dynamical system, the disease-free periodic solution (DFPS for ...In this paper, we propose an SIRS epidemic model with pulse vaccination, birth pulse and Logistic death rate. By using the stroboscopic map of a discrete dynamical system, the disease-free periodic solution (DFPS for short) of the model under pulse vaccination and birth pulse is obtained. Based on the Floquet theory and comparison theorem of impulsive differential equations, the global asymptotic stability of the DFPS is given, and sufficient conditions for the permanence of the model are obtained. In addition, numerical simulations are done to confirm our theoretical results.展开更多
文摘Background and objectives:Coronavirus disease 2019(COVID-19)is a pandemic that has become a major source of morbidity and mortality worldwide,affecting the physical and mental health of individuals influencing reproduction.Despite the threat,it poses to maternal health in sub-Saharan Africa and Nigeria,there is little or no data on the impact it has on fertility,conception,gestation and birth.To compare the birth rate between pre-COVID and COVID times using selected months of the year.Materials and methods:This was a secondary analysis of cross-sectional analytical study data from the birth registries of three tertiary hospitals,comparing two years[2019(Pre-COVID)]versus[2020(COVID era)]using three months of the year(October to December).The data relied upon was obtained from birth registries in three busy maternity clinics all within tertiary hospitals in South-East Nigeria and we aimed at discussing the potential impacts of COVID-19 on fertility in Nigeria.The secondary outcome measures were;mode of delivery,booking status of the participants,maternal age and occupation.Results:There was a significant decrease in tertiary-hospital based birth rate by 92 births(P=0.0009;95%CI:-16.0519 to-4.1481)among mothers in all the three hospitals in 2020 during the COVID period(post lockdown months)of October to December.There was a significant difference in the mode of delivery for mothers(P=0.0096)with a 95%confidence interval of 1.0664 to 1.5916,as more gave birth through vaginal delivery during the 2020 COVID-19 period than pre-COVID-19.Conclusion:Tertiary-hospital based birth rates were reduced during the pandemic.Our multi-centre study extrapolated on possible factors that may have played a role in this decline in their birth rate,which includes but is not limited to;decreased access to hospital care due to the total lockdowns/curfews and worsening inflation and economic recession in the country.
基金supported by grants from the Scientific Research Development Fund of Peking University People’s Hospital(No.RDY2020-27)Clinical Medicine Plus X-Young Scholars Project,Peking University,and the Fundamental Research Funds for the Central Universities(No.PKU2021LCXQ020).
文摘Objective It is well known that a dual trigger treatment can improve clinical outcomes of in vitro fertilization(IVF)in high or normal ovarian responders.However,it is not clear whether dual triggering also benefits patients with diminished ovarian reserve(DOR).The aim of this study was to investigate whether a dual trigger treatment of gonadotropin-releasing hormone(GnRH)agonist combined with human chorionic gonadotropin(hCG)for final follicular maturation improves the cumulative live birth rate(CLBR)during the GnRH-antagonist cycle in patients with DOR.Methods This retrospective study included patients with DOR who received a GnRH-antagonist protocol during IVF and intracytoplasmic sperm injection(IVF-ICSI)cycles at Peking University People’s Hospital from January 1,2017 through December 31,2017.Oocyte maturation was triggered by GnRH combined with hCG(n=110)or hCG alone(n=71).Embryos were transferred on the third day after oocyte retrieval or during a subsequent freeze-thaw cycle.Patients were followed up for 3 years.Results The dual trigger treatment did not affect CLBR,which is an overall determinant of the success rate of assisted reproductive technology(ART).Women in the dual trigger group had significantly higher rates of fertilization than those in the hCG group(90.1%vs.83.9%,P=0.040).Conclusion Dual trigger with GnRH agonist and hCG did not improve CLBR in patients with DOR,but did slightly improve fertilization rate,oocyte count,and embryo quality.
基金supported by National Key Research&Development Program(Grant No.2016YFC1000200,No.2016YFC1000204,and No.2018YFC1004200)the State Key Program of National Natural Science of China(Grant No.31530047)+2 种基金National Natural Science Foundation of China(Grant No.81602927)Innovation Fund of State Key Laboratory of Reproductive Medicine(Grant No.SKLRMGC201802)Top-notch Academic Programs Project of Jiangsu Higher Education Institutions(Grant No.PPZY2015A067)。
文摘There were few studies of cumulative live birth rates(CLBRs) based on multicenter reproductive clinical data from the general Chinese population.Here we report a retrospective cohort study,including 14 311 women with17 315 cycles,in three reproductive centers to evaluate two estimated parameters of CLBRs with multiple transfer cycles of in vitro fertilization(IVF)/intracytoplasmic sperm injection(ICSI) in a Chinese population.We found that CLBRs were related to female age and endometrial thickness.By the fourth transfer cycle,the conservative and optimal estimates of CLBRs were 52.95% and 77.30% in women under 30 years of age,and 18.17% and26.51% in those 37 years of age or older,respectively.The two estimates were 44.70% and 63.15% in women with endometrial thickness more than 7 mm,and 32.05% and 46.18% in those with less than 7 mm,respectively.In addition,body mass index(BMI),duration of infertility,and infertility diagnoses may also be related to CLBRs on certain conditions.The findings from this study on CLBRs after multiple transfer cycles of IVF/ICSI treatment on different conditions in the Chinese population should be beneficial to both infertile couples and clinicians.
文摘Purpose: Urbanization, obesity and ageing associated with lifestyle changes (Westernized diet patterns, pollution, physical inactivity) have been proposed as the major contributing factors for the global rise in breast cancer (BCa) and have been the variables used to predict the future breast cancer rate. At the same time, socio-economic level, instead of birth rate, has been proposed for explanation of dramatic regional variations of breast cancer incidence. We sought to determine which factor plays the determining role in predicting worldwide breast cancer incidence rates and regional variations. Methods: Bivariate correlation was conducted to examine the relationships between country-specific estimates of birth rate, BCa incidence, urbanization, overweight, ageing and GDP. Partial correlation was performed to identify the correlation between BCa incidence with each independent variable while we controlled the other four variables. Multiple linear regression was used to identify the most significant predictors of BCa incidence. Post hoc Scheff and independent T-Test analysis were performed to compare mean differences in BCa incidence rates and residuals of BCa standardised on birth rate in the WHO regions, and UN developed and developing regions respectively. Results: Worldwide, BCa incidence rate tends to increase while birth rate decreases and urbanization, overweight, ageing and GDP increase. However, birth rate was the only variable that had a significant correlation with BCa incidence when controlled for the other four variables. Birth rate was the only significant predictor of BCa incidence in regression analysis. Multiple mean differences of BCa incidence between regions were significant, but all disappeared when the contributing effect of birth rate on BCa incidence rate was removed. Conclusions: Birth rate plays a determining role in worldwide BCa incidence rate and regional variations. Current BCa projection methods may estimate future rates of BCa poorly if they fail to incorporate the impact of birth rate.
基金supported by grants from the National Key Research and Development Program of China(No.2018YFC1002106)the National Science Foundation for Young Scientists of China(No.81801447).
文摘Background:More and more scholars have called for the cumulative live birth rate(CLBR)of a complete ovarian stimulation cycle as a key indicator for assisted reproductive technology.This research aims to study the CLBR of the first ovarian hyperstimulation cycles and analyze the related prognosis factors that might affect the CLBR.Methods:Our retrospective study included first in vitro fertilization or intracytoplasmic sperm injection(IVF/ICSI)cycles performed between January 2013 to December 2014.A total of 17,978 couples of first ovarian hyperstimulation IVF/ICSI cycles were included.The study was followed up for 4 years to observe the CLBR.The multivariable logistic regression model was used to analyze the prognosis factor,P value of<0.05 was considered statistically significant.Results:The cumulative pregnancy rate was 58.14%(10,452/17,978),and the CLBR was 49.66%(8928/17,978).The female age was younger in the live birth group when compared with the non-live birth group(30.81±4.05 vs.33.09±5.13,P<0.001).The average duration of infertility was shorter than the non-live birth cohort(4.22±3.11 vs.5.06±4.08,P<0.001).The preliminary gonadotropin used and the total number of gonadotropin used were lower in the live birth group when compared with the non-live birth group(both P<0.001).Meanwhile,the number of oocytes retrieved and transferrable embryos were both significantly higher in the live birth group(15.35±7.98 vs.11.35±7.60,P<0.001;6.66±5.19 vs.3.62±3.51,P<0.001,respectively).Conclusions:The women's age,body mass index,duration of infertility years,infertility factors,controlled ovarian hyperstimulation protocol,the number of acquired oocytes,and number of transferrable embryos are the prognosis factors that significantly affected the CLBR.
基金supported by the National Natural Science Foundation of China(No.81801518 and No.82071646).
文摘The present study aimed to evaluate the clinical outcomes of magnetic-activated cell sorting(MACS)in sperm preparation for male subjects with a sperm DNA fragmentation index(DFI)≥30%.A total of 86 patients who had undergone their first long-term long protocol were selected.The protocol involved in vitro fertilization(IVF)and intracytoplasmic sperm injection(ICSI)cycles,and the patients were divided into the MACS or control groups.The MACS group included sperm samples analyzed with MACS that were combined with density gradient centrifugation(DGC)and the swim-up(SU)technique(n=39),and the control group included sperm samples prepared using standard techniques(DGC and SU;n=41).No differences were noted with regard to basic clinical characteristics,number of oocytes retrieved,normal fertilization rate,cleavage rate,or transplantable embryo rate between the two groups in IVF/ICSI.In addition,the clinical pregnancy and implantation rates of the first embryo transfer cycles indicated no significant differences between the two groups.However,there was a tendency to improve the live birth rate(LBR)of the first embryo transfer cycle(63.2%vs 53.9%)and the cumulative LBR(79.5%vs 70.7%)in the MACS group compared with the control group.Moreover,the number of transferred embryos(mean±standard deviation[s.d.]:1.7±0.7 vs 2.3±1.6)and the transfer number of each retrieved cycle(mean±s.d.:1.2±0.5 vs 1.6±0.8)were significantly lower in the MACS group than those in the control group.Thus,the selection of nonapoptotic spermatozoa by MACS for higher sperm DFI could improve assisted reproductive clinical outcomes.
基金This study was supported by the National Natural Science Foundation of China (81871214,81801449)the National Key R&D Program of China (2017YFC1001603)the Medical Scientific Technology Research Foundation of Guangdong Province of China (A20200226)。
文摘Objective:To investigate cumulative live birth rate (cLBR) per oocyte retrieval in infertile patients aged 40 years and over undergoing their first in vitro fertilization/intracytoplasmic sperm injection cycles and to identify the possible predictors.Methods:A total of 1,613 patients at a university hospital in China from January 2013 to May 2017 were enrolled in this retrospective study.All data for fresh and subsequent frozen-thawed cycles were analyzed.Multivariate logistic regression analysis with stepwise selection of possible predictors for cLBR was performed,and Loess curve was constructed to determine the association between cLBR and the number of oocytes retrieved.Results:cLBR significantly increased with the number of oocytes retrieved and reached up to 75% when > 20 oocytes were retrieved (P<0.001).Variables of antral follicle count (AFC) and the number of oocytes retrieved were selected using multiple logistic regression analysis with stepwise selection to predict the significance of cLBR.cLBR demonstrated an obvious upward trend as the number of oocytes retrieval increased in the Loess curve.Conclusions:For patients aged 40 years and over,AFC and the number of oocytes retrieved were two key predictors for cLBR and maximization of ovarian reserve exploitation was pivotal to increase the chance of live birth.
文摘We study global asymptotic stability for an SIS epidemic model with maturation delay proposed by K. Cooke, P. van den Driessche and X. Zou, Interaction of maturation delay and nonlinear birth in population and epidemic models, J. Math. Biol. 39(4) (1999) 332-352. It is assumed that the population has a nonlinear birth term and disease causes death of infective individuals. By using a monotone iterative method, we establish sufficient conditions for the global stability of an endemic equilibrium when it exists dependently on the monotone property of the birth rate function. Based on the analysis, we further study the model with two specific birth rate functions BI(N) = be-aN and B3(N) = A/N + c, where N denotes the total population. For each model, we obtain the disease induced death rate which guarantees the global stability of the endemic equilibrium and this gives a positive answer for an open problem by X. Q. Zhao and X. Zou, Threshold dynamics in a delayed SIS epidemic model, J. Math. Anal. Appl. 257(2) (2001) 282-291.
文摘CHINA has achieved remarkable results in birth control since adopting a basic state policy of family planning to control the birth rate and increase the population quality. According to the "1997 Statistic Bulletin for National Economy and Social Development," a document recently issued by the State Statistics Bureau, China maintained a low birth rate of 16.57 per thousand in 1997—a natural population growth of one percent. Women of child-bearing age now average about two births each, a decrease from six in 1970.
基金The Fundamental Research Funds for the Central Universities,CHD (300102129202)the NSF (11701041) of China+1 种基金the Natural Science Basic Research Plan (2018JM1011) in Shaanxi Province of ChinaScientific Innovation Practice Project (300103002110) of Postgraduates of Chang’an University
文摘In this paper, we propose an SIRS epidemic model with pulse vaccination, birth pulse and Logistic death rate. By using the stroboscopic map of a discrete dynamical system, the disease-free periodic solution (DFPS for short) of the model under pulse vaccination and birth pulse is obtained. Based on the Floquet theory and comparison theorem of impulsive differential equations, the global asymptotic stability of the DFPS is given, and sufficient conditions for the permanence of the model are obtained. In addition, numerical simulations are done to confirm our theoretical results.