This paper gives a summary of the fossil data from the Sinian Doushantuo' an Lantian Formation in the Xiuning area, Anhui Province, China, and reports the genital butt structure comparable to that of some modern a...This paper gives a summary of the fossil data from the Sinian Doushantuo' an Lantian Formation in the Xiuning area, Anhui Province, China, and reports the genital butt structure comparable to that of some modern advanced algae and the fossil structure comparable to the dehiscence of sporangia as well as the ontogenetic phenomenon occurring possibly from the formation of embryos by zygote germination to the production of sessile benthonic algal adults. This phenomenon furnishes a useful clue to the further study of the life history of alternate generations in advanced algae and provides megafossil evidence for the sex differentiation of metaphytic algae.展开更多
We develop a mathematical model to investigate the effect of contact tracing on containing epidemic outbreaks and slowing down the spread of transmissible diseases.We propose a discrete-time epidemic model structured ...We develop a mathematical model to investigate the effect of contact tracing on containing epidemic outbreaks and slowing down the spread of transmissible diseases.We propose a discrete-time epidemic model structured by disease-age which includes general features of contact tracing.The model is fitted to data reported for the early spread of COVID-19 in South Korea,Brazil,and Venezuela.The calibrated values for the contact tracing parameters reflect the order pattern observed in its performance intensity within the three countries.Using the fitted values,we estimate the effective reproduction number R_(e)and investigate its responses to varied control scenarios of contact tracing.Alongside the positivity of solutions,and a stability analysis of the disease-free equilibrium are provided.展开更多
Objective:To record the reproductive pattern of a natural population of Pterocladiella capillacea from Gáldar(Canary Islands,Spain)from February to August in relation to temperature,irradiance and photoperiod env...Objective:To record the reproductive pattern of a natural population of Pterocladiella capillacea from Gáldar(Canary Islands,Spain)from February to August in relation to temperature,irradiance and photoperiod environmental conditions.Methods:Field observation of reproductive thalli was used at different seasons in the year.Results:Tetrasporophytes and vegetative thalli were observed during all the period of study,while female gametophytes bearing cystocarps have been found from May to August in correspondence with the highest water temperature and irradiance values.Conclusions:Our data suggest that the temperature may be the determining factor which regulates the presence of tetrasporophytes in the field.The constant presence of tetrasporophytes could depend on the low excursion range of water temperature(4-5℃)throughout the period of study,with the highest abundance in February at 20℃.展开更多
基金This study was supported by the National Natural Science Foundation of China Grant No.49472084
文摘This paper gives a summary of the fossil data from the Sinian Doushantuo' an Lantian Formation in the Xiuning area, Anhui Province, China, and reports the genital butt structure comparable to that of some modern advanced algae and the fossil structure comparable to the dehiscence of sporangia as well as the ontogenetic phenomenon occurring possibly from the formation of embryos by zygote germination to the production of sessile benthonic algal adults. This phenomenon furnishes a useful clue to the further study of the life history of alternate generations in advanced algae and provides megafossil evidence for the sex differentiation of metaphytic algae.
文摘We develop a mathematical model to investigate the effect of contact tracing on containing epidemic outbreaks and slowing down the spread of transmissible diseases.We propose a discrete-time epidemic model structured by disease-age which includes general features of contact tracing.The model is fitted to data reported for the early spread of COVID-19 in South Korea,Brazil,and Venezuela.The calibrated values for the contact tracing parameters reflect the order pattern observed in its performance intensity within the three countries.Using the fitted values,we estimate the effective reproduction number R_(e)and investigate its responses to varied control scenarios of contact tracing.Alongside the positivity of solutions,and a stability analysis of the disease-free equilibrium are provided.
文摘Objective:To record the reproductive pattern of a natural population of Pterocladiella capillacea from Gáldar(Canary Islands,Spain)from February to August in relation to temperature,irradiance and photoperiod environmental conditions.Methods:Field observation of reproductive thalli was used at different seasons in the year.Results:Tetrasporophytes and vegetative thalli were observed during all the period of study,while female gametophytes bearing cystocarps have been found from May to August in correspondence with the highest water temperature and irradiance values.Conclusions:Our data suggest that the temperature may be the determining factor which regulates the presence of tetrasporophytes in the field.The constant presence of tetrasporophytes could depend on the low excursion range of water temperature(4-5℃)throughout the period of study,with the highest abundance in February at 20℃.
