Effect of bis(tributyltin)oxide on reproduction and population growth rate of calanoid copepod Schmackeria poplesia

A full life-cycle toxicity test,combined with histology,on calanoid copepod Schmackeria poplesia was used to study the effect of bis(tributyltin)oxide(TBTO).The results indicate no sex-specific differences in TBTO toxicity.Long-term mortalities of the copepods exposed to concentrations higher than 20 ng TBTO L-1were significantly elevated compared with that of control,and larval development was inhibited when they were exposed to 40 and 60 ng TBTO L-1.The percentages of ovigerous females were reduced compared with the control(P<0.01)after 24 days exposure to concentrations higher than 10 ng TBTO L-1.Histological examinations suggest that exposure to TBTO might block the posterior end of the diverticula and inhibits the production of egg sacs.A modified Euler-Lotka equation was used to calculate a population-level endpoint,the intrinsic rate of natural increase(rm),from individual life-table endpoints,i.e.mortality rate,time of release of first brood,sex ratio,the fraction of ovigerous females among all females as well as the number of nauplii per ovigerous female.Apart from the highest TBTO concentration(60 ng L-1),where all females aborted their egg sacs,20 ng TBTO L-1was the only concentration that significantly decreased rm compared with that of control(an effect associated with decreased sex ratio).The results show that the S.poplesia is affected by prolonged exposure to low concentrations of TBTO.The full life-cycle toxicity test combined with histology experiments provides more integral understanding of the toxicity of endocrine disrupters.

FINGERNAIL GROWTH RATE IN A NORMAL CHINESE POPULATION

Objective To investigate fingernail growth rate (FNGR) role in the physiological or pathological status of the fingernails in normal Chinese population. Methods The FNGR was measured with vernier caliper. The data of 1 595 fingernails from 208 normal Chinese subjects (including 96 men and 112 women; age ranging from 14 to 78 years) were analyzed. Results The average FNGR was (0.104±0.027) mm per day. Higher growth rates were observed in males than in females, in the young individuals than in the old individuals, in summer than in winter, and in the right hand than in the left hand, respectively. The FNGR differed among fingernails and decreased in order of precedence: middle fingernails, index fingernails or ring fingernails, thumb and little fingernails. Conclusion FNGR was significantly associated with age, gender and temperature. Different fingernail grew at an individual speed.

The Control Efficiency of Plant Alcohol Extracts on the Laboratory Populations of Myzus persicae(Sulzer)and Lipaphis erysimi (Kaltenbach)

The effects of semiochemicals extracted from 63 species of plants, on peach aphid (Myzus per-sicae) and mustard aphid (Lipaphis erysimi), were studied in laboratory. The deterrent rate, reproduction deterrent index and the interferential index of population control (IIPC) was used to evaluate the efficiency of semiochemicals on population control of the two target aphids. The results showed that the extracts of 34 species of common plants have noticeable effect on both aphid populations, especially, Xanthium sibiricum Petr. Et Widd. and Syngonium podophyllum Schott. These plant extracts could be used to construct the plant pro-tectant to protect crops.

Population Characteristics and Future Population Countermeasures for the Studied Counties in Tibet, China

Focusing on the 18 counties along “One River and Two Tributaries” region, and based on the data from China 3nl, 4th and 5th population censuses, this article has analyzed the time and spatial changing patterns of the population in this region. The analyses show that since the 3nl population census, total population, average age and total birth rate have all changed considerably: ① Total population has grown, fast, with most counties' annual average growth rate of more than 10. ② In terms of the region's average age, in 2000 the age in the 18 counties is younger than 30 years old. ③ Compared with the 3nl population census, labor force by the 5th census is much younger. ④ Countermeasures are proposed to control population by controlling birth rate as the result of the local resident's quality improvement by education.

A growing captive population erodes the wild Red-crowned Cranes(Grus japonensis) in China

Background: The Red-crowned Crane(Grus japonensis) is an endangered bird species and while the wild population continues to decrease in China, the captive population has dramatically increased over the last two decades. We hypothesized that some of the captive Red-crowned Cranes originated from the wild and that a growing captive population is eroding the wild population in China.Methods: We surveyed the size of the population and determined the average annual growth rate, reproductive success rate and mortality rate of captive Red-crowned Cranes in 2013 in China. We assessed this erosion effect through mathematical models, in which the size of the captive Red-crowned Crane population was determined from the annual growth rate, the reproductive success rate and the rate of mortality.Results: We found there were a total of 1520 captive Red-crowned Cranes in 2013 in China, with an average annual gro-wth rate of 7.46%, a reproductive success rate of 9.17% and a mortality rate of 3.6%. We found that approximately 1027 supplementary Red-crowned Cranes per year and a total of 244, over the 14 year period from 1999 to 2013, were needed to account for the growing captive population in China.Conclusion: We conclude that the 244 birds probably came from the wild by taking eggs and capturing juveniles or adults and hence accepted the hypothesis. Perhaps more surprisingly, our annual estimate of the number of supplementary Red-crowned Cranes in captive populations is very conservative, with the erosion effect substantially underestimated, because the total number of captive Red-crowned Cranes in 2013 was underestimated, with the annual reproductive success rate in zoos overestimated. The existence of an erosion effect provides a new perspective for the interpretation of why the Red-crowned Crane population in the wild continues to decrease. In our opinion, it is important to understand the consequences of this erosion effect on the management and conservation of this endangered bird species in China.

Intra-specific variations of two Leymus chinensis divergence populations in Songnen Plain, Northeast China

Population demography, seed production, biomass allocation, net photosynthesis and transpiration of two Leymus chinensis divergent populations and between two years in Songnen plain, northeast China were compared. Strong differences between the dry 1997 and moist 1998 occurred in vegetative shoot and sexual shoot densities, sexual differentiation and tiller densities, as well as in the lengths of inflorescence, seed numbers per inflorescence, seed weights and biomass allocation in each population respectively ( P < 0.01). While strong differences between the two populations occurred in vegetative shoot densities, sexual shoot densities, sexual differentiation and seed weights in each year ( P < 0.01). The differences between the two populations in tiller densities and in biomass allocation to sexual shoots were significant ( P <0.05). But there were no significant differences between the two populations in the lengths of inflorescence, seed numbers per inflorescence and biomass allocation to rhizomes and vegetative shoots ( P >0.05). Excepting the transpiration rate in the early June, the differences between the two populations in net photosynthesis and transpiration rate of vegetative shoots and sexual shoots were strongly significant in the early June and July respectively ( P <0.01). Relative stable variations in population demography and physiological traits between the two populations indicated that they are divergently in the Songnen Plain.

ESTIMATION OF ABUNDANCE AND DISTRIBUTION OF MOOSE POPULATION IN CHINA

The geographical distribution and the abundance of Moose(Alces alces)popula-tion were studied in Northeastern China between 1985 and 1987,309 trails on the snow crossingthe 2,446km sampling lines were counted.The Moose range had been shrunked to northwest for100-200 km since 1976,and at present they covered an area about 190,000 km^2.The densitiesvaried from 0.0187 Mooses/km^2 to 0.1226 Mooses/km^2 and the average was 0.0519Mooses/km^2.The Moose population size was 9,955±397 Mooses(α=0.2,P=84.5%),about7000 of them was distributed in Daxinganling Mountains and the others were in XiaoxinganlingMountains.The present population had decreased to 53.4%in 1976,and the annual decreaserate was 6.27%.At present,Moose population is likely rare in China and should be strictly pro-tected.

Comparisons of Growth and Survival Performance Among Selected Families and Wild Populations of Fenneropenaeus chinensis

In this study,families of selected population for growth(SP_BWT),selected population for white spot syndrome virus(WSSV)resistance(SP_RW),Bohai wild population(WP_BH)and Huanghai wild population(WP_HH)of F.chinensis were constructed through artificial insemination and with the standardized procedure of larvae rearing.Growth and survival performance were studied among four populations after a 70 days common test.The results showed that the maximum least square mean of body weight was 17.50 g in SP_BWT while the minimum was 13.03 g in WP_HH.Compared with WP_BH,body weight of SP_BWT increased by 23.41%(P<0.01)and that of SP_RW by 12.20%(P>0.05).Body weights of SP_BWT and SP_RW were significantly higher than that of WP_HH,which increased by 34.31%(P<0.01)and 22.10%(P<0.05),respectively.The mean AGR of four populations was 0.19,0.18,0.17 and 0.16 g d^(-1),respectively.Coefficient of variation of body weight among four populations was high,which ranged from 32.67% to 35.25%.Such a range showed that there was the potentiality for further improvement in selected populations.Coefficient of variation of survival rate among four populations was low,varying between 3.20% and 5.90%.The difference of survival was highly significant(P<0.01)between SP_BWT and WP_BH,and significant(P<0.05)between SP_RW and WP_BH.However,no significant difference among other populations(P>0.05)was observed.Different growth performances were also observed among different families in each population.The body weight of 798F family was the highest.The absolute growth rate(AGR)was 0.25 g d^(-1),150%higher than that of the lowest one,0.1 g d^(-1) in 807F family.Survival rate of families among four populations was different.The highest was 94.74%,and the lowest was 71.88%.

Effects of anthropogenic disturbances on natural regeneration and population structure of gum arabic tree (Acacia senegal)in the woodlands of Lake Baringo ecosystem, Kenya

Despite the ecological and economic importance of Acacia senegal, little is known about the effects of anthropogenic disturbances on its natural regeneration patterns and population structure. We investigated the effects of these factors within the Lake Baringo woodland ecosystem. Data was collected from 60 plots of 20 m × 20 m systematically distributed in four A. senegal-dominated populations within the Lake Baringo woodland. Sample populations spanned a degradation gradient measured by a population disturbance index (PDI). Trees were measured for diameter at breast height (DBH) and categorized by growth stages: seedling, sapling and adult tree. Higher seedling and sapling densities were recorded in lightly than heavily disturbed populations, but only sapling density was significantly different between the two disturbance levels (P = 0.02). Lightly disturbed populations revealed a reversed J-shape size-class distribution (SCD) indicative of stable structure unlike the heavily disturbed populations. The quotient and permutation indices indicated unstable populations with episodic recruitment and mortality. Our study reveals that natural regeneration and population structure of A. senegal were affected majorly by selective harvesting and heavy browsing. Suitable management strategies to control livestock grazing and illegal tree harvesting within the woodland is required to promote conservation of the species genetic resources

An assessment of factors leading to the decline of Beclardia macrostachya (orchidaceae) population in Mauritius

Clearing of forest land for agriculture and urbanization following colonization have reduced the forest cover in Mauritius to 3% of total land cover. Today exotic species such as Psidium cattleianum (wild guava), Araucaria columnaris, and Ravenala madagascarensis dominate at Pigeon Wood, the only site in Mauritius where Beclardia can be found, leaving little space for very few indigenous tree species like Labourdonnaisia glauca, Apholoia theiformis and Foetida mauritiana. Beclardia macrostachya is an orchid endemic to Mauritius, Madagascar andReunion. Though it is abundant in the latter countries, it is one of the rarest orchids in Mauritius. An assessment of the factors associated with the stability of this orchid was carried out in forests of these three countries to understand the drastic decline of this orchid in Mauritius. Morphometric and fertility counts carried out at different forests revealed differences in fitness and fertility rates among forests of the same countries and between different countries. Stability of the different Beclardia populations was carried out based on counts of juveniles and adults. Higher fertility rates and most stable populations were observed in the forests of Reunion Island (Bebours) and Madagascar (Ambohitanteley), whereas very low fruit set were observed in Mauritius, unless manual pollination was carried out. Microscopic analysis revealed the presence of pelotons of endomycorrhiza during the early development of the seedlings, in vivo. Based on comparative studies among the different sites, pollinator limitation and absence of suitable hosts were the primary factors that led to the present decline in Mauritius. The high density of wild guava, Psidium cattleianum, which has slowly taken up most of the forest areas inMauritiushas affected the regenerating capacity of Beclardia macrostachya and the density of putative hosts of this orchid. GC-MS/MS analysis of nectar revealed α-D- glucopyranose to be the primary reward of the pollinators and benzyl alcohol, methoxybenzyl alcohol and methoxy methyl phenol to be components floral fragrance.

Facing the 2013 Gold Rush: A Population Viability Analysis for the Endangered White-Lipped Peccary (<i>Tayassu pecari</i>) in Corcovado National Park, Costa Rica

The white-lipped peccary (Tayassu pecari) is facing range-wide declines throughout the Neotropics. It has been eliminated from about 89% of its historical range in Costa Rica. Corcovado National Park, in the Osa Peninsula of Costa Rica, is the last remaining stronghold for the white-lipped peccary in the country. In 2013, the Park experienced a sudden gold rush that brought with it a wave of 250 miners and vigorous hunting pressures on the population. Given that the species is endangered and is susceptible to hunting due to its herding behavior and tendency to cohere and attack when threatened rather than flee, it is important to assess its probability of extinction under various hunting scenarios. Incorporating data from studies on the life history of the species throughout its range in the Neotropics and in Corcovado, I used the population viability analysis software VORTEX to simulate the population trajectories and probabilities of extinction of the species under current hunting pressures and under various management scenarios. The results of this study revealed that under the 2013 scenario where 250 miners were present in the Park, the population of white-lipped peccaries has a about a 40% chance of extinction within five years and about a 99% chance of extinction within 10 years. Moreover, there is an “extinction threshold” for the population between the presence of 100 and 150 miners hunting in the Park. At this threshold, the population growth rate, r, drops from a positive growth rate (r = 0.09, SD = 0.08) to a negative one (r = -0.07, SD = 0.29). I suggest that anti-mining and anti-poaching laws be enforced immediately, and that the number of miners be reduced to 100 at a minimum, if not completely, in order to ensure that the population of white-lipped peccaries becomes viable and evades a local extinction.

A Study of the Universal Two-child Policy’s Impact on China’s Future Population

The most essential step in adjusting and improving the childbearing policy, the universal two-child policy will produce far-reaching impacts on the future development of China’s population. With its implementation, the country’s total population will peak later, the underage population and its proportion will increase substantially, the working-age population will experience a slower decline, and the aging of China’s population will be eased. However, the drop in the proportion of working-age people over the last 15 years has expedited the reduction of the demographic dividend, the elderly population will remain unaffected over the next 60 years, the aging of the population will continue to deepen, and at the same time, the increased child dependency burden will expand the overall dependency ratio.

Analyzing and Projection of Future Bangladesh Population Using Logistic Growth Model

Bangladesh is a densely populated country than many other countries of the world. The population growth is termed as alarming, however, knowledge of growth in the years to come would be useful in planning for the development of the country. This article is based on the projection of future population growth of the country. The available actual population census data during 1991-2011 of Bangladesh was applied to the application of a non-linear, non-autonomous ordinary differential equation familiar as Verhulst logistic population model with the maximum environmental capability of Bangladesh. Bangladesh will reach its carrying capacity of 245.09 million population in the next 56 years i.e. the year 2067 and then it decreases as S-shaped curve. The article has provided a focus on the changing trends of the growth of the population of Bangladesh.

Fair Plan 9: Engineering Human Population to Help Safeguard Earth’s Climate

Our Fair Plan to Safeguard Earth’s Climate reduces the emission of greenhouse gases to zero over the 80-year time period 2020 to 2100. To accomplish this, humanity must reduce its carbon intensity—the amount of CO2 emitted per unit of energy—and its energy intensity—the amount of energy needed to generate a unit of Gross World Product. As shown in our Fair Plan 8 paper, reducing the future growth of the human population can also contribute to the reduction in greenhouse-gas emissions. Here, we explore this further. We project the historical decrease in Total Fertility Rate (TFR) across the 21st century toward its logistical asymptotic Reference value of 2.04 Births Per Woman (BPW). We then engineer the asymptotic TFR beginning in 2020 to 1.95, 1.85, 1.75, 1.65 & 1.55 BPW. We project the population across the 21st century for the Reference and engineered TFRs. We do so using the results of Basten, Lutz and Scherbov (2013) for the population evolution across the 21st century for 8 constant TFR values (=2.50, 2.25, 2.00, 1.75, 1.50, 1.25, 1.00 & 0.75 BPW). We find that purposefully engineering the asymptotic TFR can significantly contribute to achieving the reduction in greenhouse-gas emissions needed to transition to our Fair Plan to Safeguard Earth’s Climate.

改进群体智能算法的无线传感器网络覆盖优化

为解决无线传感器网络(Wireless Sensor Networks,WSN)节点分布不均和随机部署中的低覆盖率问题,该文提出一种改进群体智能算法的无线传感器网络覆盖优化算法,即改进的黑猩猩优化和哈里斯鹰优化的混合优化算法(Improved Chimp Optimization and Harris Hawk Optimization Algorithm,ICHHO).该算法首先对黑猩猩优化算法(Chimpanzee Optimization Algorithm,ChOA)进行改进,使用Levy Flight来改善其探索阶段,然后设计一个更新的公式来计算猎物逃逸能量,作为开发和探索之间的选择因素.传感器节点随机部署后,将ICHHO在传感器节点上执行,按照改进策略更新个体位置信息,计算相应的适应程度,找到最优传感器位置,并根据传感器概率模型确定网络最优覆盖率.仿真结果验证了ICHHO对于解决WSN覆盖问题的适用性,与其他优化算法的对比结果显示,ICHHO在提高覆盖率方面优于其他算法.

中国人口老龄化的过去、现在和未来

从20世纪70年代初期开始的计划生育,使得中国妇女生育率快速下降,也预示着人口老龄化速度将在一定阶段明显加快。本文回顾了中国人口出生率和死亡率的下降过程,描述了以往不同时间点中国人口年龄结构的变化,利用2020年第七次全国人口普查数据分析了老年人口的状况和特点,并对未来50年中国人口和老龄化进程进行了预测。研究发现:2022—2036年是老年人口增长最快的时期,2037—2051年进入中速增长阶段,2052—2063年老年人口增长速度迅速递减,从2056年开始老年人口出现负增长,老年人口数量有所减少。从2068年开始到未来的一段时间老年人口增长速度会在0附近波动,而且会长期保持下去。尽管老年人口出现负增长,但是老年人口所占比例仍然会持续上升,老龄化进程将大幅度减缓,这会在很大程度上缓解老龄化和老龄问题带来的压力。总之,未来30年是积极应对人口老龄化、解决老龄问题的关键时期。然而,与“30后”“40后”父母相比,“50后”“60后”“70后”父母现有子女数大幅度减少,家庭养老将难以为继,未来社会养老将面临巨大压力。

2016-2021年北京市5岁以下儿童死亡变化趋势及死因研究

目的 分析2016-2021年北京市5岁以下儿童死亡率(U5MR)变化趋势及主要死因,为制定、调整干预策略提供依据。方法 提取北京市妇幼保健网络信息系统中2016-2021年5岁以下儿童死亡监测数据,对北京市U5MR和不同年龄组死亡率变化趋势及主要死因进行回顾性分析。结果 2016-2021年北京市U5MR呈下降趋势,2021年下降至2.24‰,已达到国际领先水平。5岁以下儿童各年龄组中,新生儿死亡率(NMR)下降速度最快,年度变化百分比(APC)为-8.98%(95%CI:-13.14%~-5.59%),是2016-2021年北京市U5MR下降的主要原因;而1~<5岁儿童死亡率呈上升趋势(APC=13.50%,95%CI:1.06%~27.51%)。2016-2021年早产或低出生体重(APC=-14.00%,95%CI:-23.51%~-6.38%)和其他新生儿疾病死亡率(APC=-25.91%,95%CI:-44.69%~-12.43%),呈下降趋势;意外伤害死亡率呈上升趋势(APC=12.34%,95%CI:5.11%~19.72%)。2021年主要死因中,远郊地区先天异常、意外伤害、早产或低出生体重和出生窒息死亡率均高于城市地区。2016-2021年,城市地区和远郊地区早产或低出生体重死亡率均呈下降趋势,城市地区出生窒息和远郊地区其他新生儿病死亡率呈下降趋势;城市地区意外伤害和肺炎死亡率呈上升趋势。结论 北京市在降低NMR以及降低早产或低出生体重和其他新生儿病等疾病死亡率方面成果显著,但同时还应重视意外伤害、先天异常和出生窒息等主要死因防控,并加强对1~<5岁儿童群体的关注。