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This study aims at exploring a general and adaptive control strategy to confront the rapid evolution of an emerging infectious disease ('Disease X'), drawing lessons from the management of COVID-19 in China. We employ a dynamic model incorporating age structures and vaccination statuses, which is calibrated using epidemic data. We therefore estimate the cumulative infection rate (CIR) during the first epidemic wave of Omicron variant after China relaxed its zero-COVID policy to be 82.9% (95% CI: 82.3%, 83.5%), with a case fatality rate (CFR) of 0.25% (95% CI: 0.248%, 0.253%). We further show that if the zero-COVID policy had been eased in January 2022, the CIR and CFR would have decreased to 81.64% and 0.205%, respectively, due to a higher level of immunity from vaccination. However, if we ease the zero-COVID policy during the circulation of Delta variant from June 2021, the CIR would decrease to 74.06% while the CFR would significantly increase to 1.065%. Therefore, in the face of a 'Disease X', the adaptive strategies should be guided by multiple factors, the 'zero-COVID-like' policy could be a feasible and effective way for the control of a variant with relative low transmissibility. However, we should ease the strategy as the virus matures into a new variant with much higher transmissibility, particularly when the population is at a high level of immunity. [ABSTRACT FROM AUTHOR]

HIV/AIDS is among the major viral infectious diseases that are major traits with high human morbidity and mortality impacts and it has detrimental effects on the economies and health of nations worldwide. In the current study, we formulated and analyzed an HIV/AIDS compartmental epidemic model by dividing the entire susceptible human population into two groups, such as the sexually mature and sexually immature stage structure groups with optimal control strategies, since HIV/AIDS has been a cause of death for individuals in different age groups. Qualitatively, we computed the model's unique disease-free and endemic equilibrium points, using the next-generation matrix operator approach we calculated the model basic reproduction number, and we proved the local stabilities of both the model disease-free and endemic equilibrium points using by applying the Routh-Hurwitz stability criteria, we also proved the global stabilities of the model's disease-free and endemic equilibrium points by building the suitable representative Lyapunov function. Using Pontryagin's Maximum Principle, the HIV/AIDS model's optimality system which determines the necessary circumstances to improve the control over the spread of the HIV/AIDS disease is built and examined. We performed numerical simulations to validate the qualitative analysis of the optimal control and explore the effects of the suggested optimal control techniques using the model measure, and the ART treatment measure concurrently, i.e., putting Strategy F into practice is essential to reducing and controlling the spread of HIV/AIDS in the community. Therefore, we urge possible policymakers and public health stakeholders to prioritize the implementation of Strategy F, which aims to reduce and control the prevalence of HIV/AIDS in the population. [ABSTRACT FROM AUTHOR]

Age structure is one of the key characteristics of modeling population dynamics and infectious diseases. In this paper, we consider the existence of traveling wave solutions for a physiological age-structured SIR epidemic model with diffusion. Due to the consideration of physiological age of an individual, the wave profile equation of the age-structured model is a nonmonotone parabolic system. To overcome this difficulty, we first study the existence of solutions for our problem in a bounded interval. This proof is mainly based on the comparison principle which allows us to construct suitable sub and super-solutions, and the Schauder’s fixed point theorem. Then, by letting the length of the bounded interval tend to infinity, we establish the existence of traveling wave solutions if the basic reproduction number R 0 > 1 and the wave speed is greater than the minimal wave speed c ∗ . [ABSTRACT FROM AUTHOR]

Queen parrotfish Scarus vetula and stoplight parrotfish Sparisoma viride are widely distributed throughout the subtropical/tropical regions of the northwestern Atlantic, play important ecological roles in reef ecosystems, and contribute to small-scale commercial landings within several Caribbean management jurisdictions. Prior to this work, no comprehensive life history information existed for either species that combined otolith analysis and gonad histology. Queen parrotfish (n = 390) and stoplight parrotfish (n = 1801) were sampled throughout the U.S. Caribbean from 2013 to 2023. Queen parrotfish range in size from 82 to 402 mm FL and age from 0 to 16 years; stoplight parrotfish ranged from 73 to 433 mm FL and 0 to 20 years. Growth parameter estimates for queen parrotfish were L∞ = 347 mm FL and K = 0.42, when t0 was fixed to −0.06; for stoplight parrotfish, L∞ = 332 mm FL and K = 0.39, with a fixed t0 of −0.06. All female queen parrotfish transitioned to males by a maximum length and age of 322 mm FL and 14 years. In contrast, not all female stoplight parrotfish transitioned to males since the largest and oldest individuals sampled were females. Spawning capable queen parrotfish females were collected from November to August indicating a protracted spawning season of 10 months. Stoplight parrotfish exhibited year-round spawning with >50% of mature females in the spawning capable phase during all months of the year. Based on our overall findings related to life history, queen parrotfish and stoplight parrotfish in the U.S. Caribbean did not appear to exhibit signs of overexploitation which may in part relate to U.S. Caribbean management efforts currently in place that limit the minimum mesh size for traps (which ensures that smaller fish can escape from the traps), a ban on using gillnets to target parrotfish species, and the market driven targeting of "plate-size" fish by commercial spearfishers. The life history information documented in the current study will provide essential information for stock assessments and informed management in the U.S. Caribbean for these two important parrotfish species. [ABSTRACT FROM AUTHOR]

The flat-headed frog, Barbourula busuangensis, is a poorly known, riverine species, endemic to the province of Palawan in the Philippines. We applied capture-mark-recapture (CMR) methods to follow individuals at two sites (Malbato and San Rafael) in the island of Busuanga over 10 months in 2022–2023. We used passive internal transponders (PITs) to mark adult and subadults and single-colored visual internal elastomers (VIEs) for cohorts of juveniles. From a total of 196 frogs PIT-tagged in Malbato and 144 in San Rafael, we obtained overall recapture rates of 49% and 60% respectively. We used the POPAN formulation in MARK software to estimate abundance, survival, movement, and age-class demographics. Our best model estimated an average population size of 268 frogs at Malbato and 232 at San Rafael, and constant survival probabilities (mean ≥ 0.97) at both sites. When adding age classes to the model, abundance of adults was always higher than that of subadults producing an age structure dominated by adults at both sites. Growth rates decreased significantly with body size, being higher in juveniles (1.51 mm/month) and subadults (1.56 mm/month) than in adult frogs (0.60 mm/month). At these growth rates frogs may reach adulthood at 2.5 years, with the oldest individuals likely being over 11 years old. CMR data confirmed site fidelity, and translocation experiments revealed that frogs have the ability to home when displaced 10–50 m upstream and downstream from their original capture site. This is the first long-term study of B. busuangensis using robust field and analysis methods. Our data suggest that B. busuangensis is stable at present in Busuanga, with long-lived adults and dispersing subadults. We expect that these data may serve as baseline of current population abundance, age structure and growth rates which are factors that tend to be affected when species are threatened. In this way it may help researchers and conservation practitioners detect potential changes that may occur as this species confronts the challenges of the Anthropocene. [ABSTRACT FROM AUTHOR]

The demographic potential of the settlements in the Visok micro-region has been significantly disrupted since 1948. The latest census (2022) shows that the Visok micro-region now consists of very small settlements, all with fewer than 100 inhabitants. In all 22 villages of the Visok micro-region, there are only 504 inhabitants, with unfavorable age structures. The region’s average age has remained above 65 for the last 30 years, significantly older than the surrounding areas. Low salaries, bad infrastructure, and the industrialization of Pirot City represent the main reasons for depopulation. The Zavoj Lake catastrophe caused three villages to be submerged, which accelerated depopulation even more. Most of the remaining inhabitants are engaged in farming or work in the construction, stone, and forestry industries, with sheep farming being a notable tradition. The local population shows strong ecological awareness, advocating for industries that align with nature, creating an ideal environment for nature enthusiasts and scientists. The only way for revitalization is to have organized seasonal migrations based on the summer tourist season. The main aim for revitalization would be a national-level plan for creating a brand of untouched nature, with traditional agricultural products for the complete experience.

• We built a whole-phase emission inventory based on flight information. • In many areas with a high flight route density, the emissions were high. • CO 2 could be reduced by 38% under four feasible abatement measures. • Switching travel modes is most the effective measure in reducing emissions. Civil aviation is one of the industries facing the greatest challenge in reaching carbon neutrality by the middle of this century, and this sector also contributes to adverse impacts on the regional air quality and human health. China exhibits the second highest air passenger turnover worldwide. Our understanding of civil aviation emissions must be urgently enhanced, and the mitigation potential should be explored. In this study, on the basis of real domestic flight information for 2019, we built a greenhouse gas and air pollution emission inventory for the civil aviation sector in China with the fuel flow method based on the cruise and other phases. We thoroughly analyzed emissions by region, aircraft and engine types, and aircraft age, based on which we designed four measures to evaluate the abatement potential. We found that the hydrocarbon (HC), CO, NO x , SO 2 , particulate matter (PM) and CO 2 emissions in 2019 reached 79.9 kt (95% CI [51.6–114.5]), 176.3 kt (95% CI [114.5–248.2]), 304.2 kt (95% CI [203.4–420.7]), 23.2 kt (95% CI [14.2–33.7]), 1.0 kt (95% CI [0.61–1.44]) and 87.0 Mt (95% CI [57.4–119.6]), respectively. The cruise phase was the major emission phase, accounting for 67%-87% of the total pollutant emissions. If four measures were jointly implemented, the HC, CO, NO x , SO 2 , PM and CO 2 emissions could be reduced by 61%, 54%, 55%, 45%, 32% and 38%, respectively. Utilizing lower-emission aircraft and switching travel modes could substantially reduce civil aviation emissions in China. [ABSTRACT FROM AUTHOR]

Based on the diversity of transmission routes and host heterogeneity of some infectious diseases, a dynamical model with multi-age-structured, asymptomatic infections, as well as horizontal and vectorial transmission, is proposed. First, the existence and uniqueness of the global positive solution of this model is discussed and the exact expression of the basic reproduction number $ \mathcal{R}_0 $ is obtained using the linear approximation method. Further, we deduce that the disease-free steady state $ \mathcal{E}^0 $ is globally asymptotically stable for $ \mathcal{R}_0 < 1 $, the endemic steady state $ \mathcal{E}^* $ exists and the disease is persistent for $ \mathcal{R}_0 > 1 $. In addition, the locally asymptotically stability of $ \mathcal{E}^* $ is also obtained under some certain conditions. Next, our model is extended to a control problem and the existence and uniqueness of the optimal control by using the Gateaux derivative. Finally, numerical simulations are used to explain the main theoretical results and discuss the impact of age-structured parameters and control strategies on the prevention and control of vector-borne infectious diseases.

Currently, tapping is the only method of obtaining natural rubber, an essential industrial raw material. The stability of the labor force supply for tapping is crucial for the sustainable development of the natural rubber industry. As China's second-largest rubber planting area, Hainan Island had a planting area of 585,800 hectares in 2020, accounting for 45% of the country's total, with over 2 million workers. Labor force shortages and the aging phenomenon in tapping have become increasingly severe and have attracted significant attention. However, the related research lacks detailed spatial information for conversion estimation, which hinders macroeconomic regulation. This study is based on the 2020 Hainan Island natural rubber distribution map, Dynamic World land use classification products, and the WorldPop population distribution dataset. It employs multiple technical operations such as temporal and spatial filtering, removal of small patches, buffer parameter settings, and masking to obtain the 2020 potential tapping labor density map for Hainan's rubber planting areas. Spatial statistical methods are used to analyze the spatial distribution and age structure characteristics of potential tapping labor force in Hainan's rubber planting areas as well as the spatial distribution of labor force shortage degrees after conversion to actual tapping labor force, including the labor force shortage levels and areas for each city and county, revealing the spatial pattern. The results reveal the following: 1) The total number of potential tapping laborers in Hainan's rubber planting areas is 1.567 4 million, with a spatial distribution pattern of high in the north and low in the south. The proportion of the population aged 45~59 years is 34%, indicating a significant aging trend. 2) There are significant spatial differences in the degree of labor shortage. The primary shortage areas are mainly concentrated in the junction areas of the central-western and central-eastern counties, with a belt-like distribution. In contrast, the secondary and tertiary shortage areas are widely distributed in the central-western, central, and some central-eastern county junctions, with shortage in the central area being particularly severe, showing a contiguous distribution. 3) The primary shortage areas in Danzhou City, Baisha County, and Qiongzhong County rank in the top three, with a cumulative area of 50,500 hectares. Baisha, Qiongzhong, Chengmai, and Ledong Counties are also prominent in the secondary and tertiary shortage areas, covering a total area of 23,300 hectares. In total, the area of labor shortage regions in Hainan Island is 141,700 hectares, necessitating a future focus. To address the labor force shortage issue in tapping, it is recommended to strengthen infrastructure construction in the rubber plantations within the shortage areas and actively promote new tapping methods (e.g., low-frequency tapping) or tools (e.g., electric tapping knives) to reduce the labor intensity of tapping and increase the number of trees tapped per capita. This will provide favorable support for the sustainable and healthy development of Hainan's natural rubber industry. By revealing the spatial distribution characteristics and degree of tapping labor shortage, this study aims to provide robust decision-making support for the Hainan provincial government in addressing employment issues of tapping labor, optimizing human resource management strategies, and promoting the sustainable development of the natural rubber industry.

In this paper, we investigate an age-structured model of Hand–Foot–Mouth Disease (HFMD) in a contaminated environment. This paper characterizes both age structure and contaminated environment in the HFMD model and discusses their effects on the time delay in the conversion from exposed to infected individuals. By transforming the original model to an abstract nondensely defined Cauchy problem and utilizing the integrated semi-group theory, we establish the well-posedness of solutions. Then the existence and stability of equilibria are obtained on the basis of the basic reproduction number ℛ 0 . It is proved that the disease-free equilibrium is globally asymptotically stable if ℛ 0 < 1. Meanwhile, the endemic equilibrium is locally asymptotically stable with time delay τ = 0. Furthermore, Hopf bifurcation occurs at endemic equilibrium when τ > 0. Finally, numerical simulations are performed to validate our theoretical results. [ABSTRACT FROM AUTHOR]

The age of individuals has consequences not only for their fitness and behaviour but also for the functioning of the groups they form. Because social behaviour often changes with age, population age structure is expected to shape the social organization, the social environments individuals experience and the operation of social processes within populations. Although research has explored changes in individual social behaviour with age, particularly in controlled settings, there is limited understanding of how age structure governs sociality in wild populations. Here, we synthesize previous research into age-related effects on social processes in natural populations, and discuss the links between age structure, sociality and ecology, specifically focusing on how population age structure might influence social structure and functioning. We highlight the potential for using empirical data from natural populations in combination with social network approaches to uncover pathways linking individual social ageing, population age structure and societal functioning. We discuss the broader implications of these insights for understanding the social impacts of anthropogenic effects on animal population demography and for building a deeper understanding of societal ageing in general. This article is part of the discussion meeting issue 'Understanding age and society using natural populations'. [ABSTRACT FROM AUTHOR]

Since the stochastic age-structured multigroup susceptible-infected-recovering (SIR) epidemic model is nonlinear, the solution of this model is hard to be explicitly represented. It is necessary to construct effective numerical methods so as to predict the number of infections. In addition, the stochastic age-structured multigroup SIR model has features of positivity and boundedness of the solution. Therefore, in this article, in order to ensure that the numerical and analytical solutions must have the same properties, by modifying the classical Euler–Maruyama (EM) scheme, we generate a positivity and boundedness preserving EM (PBPEM) method on temporal space for stochastic age-structured multigroup SIR model, which is proved to have a strong convergence to the true solution over finite time intervals. Moreover, by combining the standard finite element method and the PBPEM method, we propose a full-discrete scheme to show the numerical solutions, as well as analyze the error estimations. Finally, the full-discrete scheme is applied to a general stochastic two-group SIR model and the Chlamydia epidemic model, which shows the superiority of the numerical method. [ABSTRACT FROM AUTHOR]

Copyright of Kufa Studies Center Journal is the property of Republic of Iraq Ministry of Higher Education & Scientific Research (MOHESR) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Based on the diversity of transmission routes and host heterogeneity of some infectious diseases, a dynamical model with multi-age-structured, asymptomatic infections, as well as horizontal and vectorial transmission, is proposed. First, the existence and uniqueness of the global positive solution of this model is discussed and the exact expression of the basic reproduction number is obtained using the linear approximation method. Further, we deduce that the disease-free steady state is globally asymptotically stable for , the endemic steady state exists and the disease is persistent for . In addition, the locally asymptotically stability of is also obtained under some certain conditions. Next, our model is extended to a control problem and the existence and uniqueness of the optimal control by using the Gateaux derivative. Finally, numerical simulations are used to explain the main theoretical results and discuss the impact of age-structured parameters and control strategies on the prevention and control of vector-borne infectious diseases. [ABSTRACT FROM AUTHOR]

To preserve biodiversity, conservation efforts, particularly for endangered species, such as Myristica teysmannii, should be implemented. Myristica teysmannii is native to the Java and Sempu Islands, Indonesia. The aim of the present study was to elucidate the spatial distribution, age structure, and habitat characteristics of M. teysmannii on the Sempu Island and in the Banyu Meneng, Malang protected forest, Indonesia. This exploratory study was conducted through visual encounter survey and plotting methods. We explored 41 and 26 plots in the Sempu Island and nature reserves of Malang, respectively. Myristica teysmannii was found in selected geographical locations, i.e. slopes and near the shorelines of the sea. The nature reserves of Malang contained 73 adult trees, 16 young trees, 45 saplings, and 99 seedlings, and the Sempu Island contained 146 adult trees, 25 young trees, 59 saplings, and 99 seedlings. The distribution and growth of M. teysmannii were influenced by biotic and abiotic factors. Myristica teysmannii was found in association with the detritivore population, which feeds on plant detritus. The results of the present study suggest that the M. teysmannii populations on the Sempu Island and in the nature reserves of Malang, Indonesia, remain uncritical. Nevertheless, the endangered status of M. teysmannii should be considered to maintain and conserve its biodiversity, particularly given the lack of reports on the population structure in other areas on the Java Island or the possibility of environmental destruction. [ABSTRACT FROM AUTHOR]

This paper studies how much the age structure dynamics contributed to China's economic growth between 1991 and 2019. We first propose a theoretical model to describe the impacts of age structure transitions on household consumption, savings, and economic growth. Then, we use China's country-level data between 1991 and 2019 to measure the economic growth rate driven by demographic dividends. Empirical results indicate that before the year 2011, age structure transitions in China led to the increase in both labour supply and the household savings rate, and positively contributed to the country's economic growth in most of the years starting from 1991. In specific, the average annual contribution rate was around 0.25%, with the highest rate being 1.25% in the year 2000. However, the demographic dividends vanished in 2012, since when the country has entered the period of demographic debt. [ABSTRACT FROM AUTHOR]

The Hyrcanian forests have a diverse fauna and flora with many endemic species of plants and animals. The Iranian long-legged wood frog, Rana pseudodalmatina, is one of the endemic species in this forest. The phylogenetic and morphologic analysis indicates the existence of the western and the eastern clades in R. pseudodalmatina. Differences in the life history of the same species can attributed to different habitat quality or climate. The probability of encountering an Iranian long-legged wood frog, R. pseudodalmatina in the western half of the Hyrcanian forests of the southern shores of the Caspian Sea is much higher than in the forests of the eastern sea. This increase in the detection probability can be attributed to higher precipitation levels in the West of the Hyrcanian forests compared to the East. I observed that the Eastern populations tend to have larger sizes. In addition, the individuals of the western branch have a lower mean age (5.29 ± 0.74 years) than the eastern ones (8.36 ± 0.08 years). According to our results, females were larger (54.64 ± 0.53 mm) and older (7.68 ± 0.24 years) than males (48.13 ± 0.39 mm; 5.89 ± 0.39 years) in both eastern and western clades. So, the difference has been attributed to the variation in precipitation between the East and West of the sea, leading to different environmental conditions for R. pseudodalmatina. Hence, any conservation planning to protect this native species of the Hyrcanian forests must consider inter and intra-population differences in the East and West of the Hyrcanian forests. [ABSTRACT FROM AUTHOR]

This paper aims to facilitate a more nuanced understanding of regional disparities in the population age structure at a local scale by applying a recent method for visualizing these disparities. Utilizing data from the three most recent population censuses in Greece, this method applies advanced data visualization techniques to map age distributions, highlighting significant variations in aging patterns across municipalities, towns, and districts. Traditional demographic analysis often overlooks local heterogeneities, leading to broad policies that often fail to address the unique needs of specific regions. Detailed maps are created by integrating geographic data with census data (using R and GIS), enabling policymakers to pinpoint areas with specific demographic challenges and opportunities. This localized approach reveals critical insights, such as regions experiencing rapid population aging, areas with younger population profiles, and zones undergoing demographic transitions. The visualization tool significantly improves the formulation of targeted strategies, enhancing the effectiveness of policies related to healthcare, workforce planning, and social services distribution. Through case studies and comparative analysis, we demonstrate the practical applications and advantages of this method in shaping public policy and strategic planning. This paper contributes to the field of geodemography by introducing and demonstrating a visualization method that enhances the accuracy of demographic analysis, providing policy makers with useful information to better address local demographic challenges and tailor strategies to specific regional needs. [ABSTRACT FROM AUTHOR]

Understanding factors that influence population‐level responses to emerging threats in declining species is crucial for informed conservation action. In amphibian species impacted by the chytrid fungus (Batrachochytrium dendrobatidis), a pathogen that has caused amphibian declines globally, a commonly reported pattern is that more severe population declines tend to occur at higher elevations. Previous research has suggested that this pattern could be driven by reduced environmental suitability for chytrid fungus at lower elevations. However, delayed amphibian maturation, which is common in cold, high elevation populations, could also increase vulnerability to population decline. Here, we tackle this key knowledge gap, focusing on the critically endangered corroboree frogs (Pseudophryne corroboree and P. pengilleyi), which have experienced a pattern of extirpation at higher elevations, with remnant populations persisting at lower elevations. First, we quantify the age structure of two extant low elevation P. pengilleyi populations and museum specimens (both species) collected before the emergence of chytrid fungus in Australia. Male age to maturation varied from 1 to 3 years, with the extant population with higher chytrid prevalence displaying severe age structure truncation. Second, we use population simulations to calculate elasticity values under a range of scenarios with varying ages to maturation and chytrid‐associated mortality. When the population growth rate was fixed at 1, adult survival became increasingly important as age to maturation increases, particularly under a scenario of high chytrid‐associated mortality. Our simulation results indicate that delayed maturation could be a previously underappreciated factor associated with an increased risk of amphibian population decline and that earlier maturation could contribute to population persistence. Our study highlights the importance of examining variation in life history traits to better understand population‐level responses to novel threats and guide the development of appropriate conservation actions. [ABSTRACT FROM AUTHOR]

The survival of relict Taxus wallichiana var. wallichiana (Yunnan yew) is threatened by overexploitation for its quality wood and medicinal properties, particularly for taxol extraction. Understanding the current status of its communities and populations is crucial for protecting existing natural forest resources. We established 53 vegetation plots in Yunnan, southwestern China, where T. wallichiana var. wallichiana is the primary dominant species. These plots were classified into four forest types. The forests were multi-stratified, with T. wallichiana var. wallichiana frequently dominating the subcanopy and shrub layer. Species diversity indices did not significantly differ among the four forest types. The age structure of T. wallichiana var. wallichiana exhibited a multi-modal pattern, with a maximum age of 1165 years. Growth was slow, with an average radial growth rate of 0.78 mm/year. Despite its strong sprouting ability, the species had a poor seedling/sapling bank and suffered from inadequate regeneration. Its seedlings/saplings are shade-intolerant. This study provides a scientific basis for effective conservation strategies, emphasizing the need for in situ regeneration to ensure the survival of T. wallichiana var. wallichiana and its contributions to biodiversity and ecosystem services. [ABSTRACT FROM AUTHOR]

For organisms in temperate environments, seasonal variation in resource availability and weather conditions exert fluctuating selection pressures on survival and fitness, resulting in diverse adaptive responses. By manipulating resource availability on a local spatial scale, we studied seasonal patterns of resource use within natural populations of burying beetles Nicrophorus vespilloides in a Norfolk woodland. Burying beetles are necrophagous insects that breed on vertebrate carcasses. They are active in Europe between April and October, after which they burrow into the soil and overwinter. Using breeding and chemical analyses, we compared the fecundity and physiological state of beetles that differed in their seasonal resource use. We found seasonal variation in carrion use by wild burying beetles and correlated differences in their reproductive success and cuticular hydrocarbon profiles. Our results provide novel insight into the seasonal correlates of behaviour, physiology and life history in burying beetles. [ABSTRACT FROM AUTHOR]

Myctophids are one of the most diverse and abundant fish families in the mesopelagic zone, making them a key component in the marine pelagic community. In the North Atlantic, Benthosema glaciale (glacier lantern fish) is considered the most abundant myctophid north of 35° N, yet some regions within its extensive range lack information on its basic biological parameters. We investigated the growth and described the distribution of B. glaciale in Icelandic waters, including the southern continental shelf, Iceland Basin, and Irminger Sea. Length distribution, growth, relative body condition, age, and otolith‐fish size relationships were analyzed from samples collected opportunistically with pelagic trawls during the International Ecosystem Summer Survey in the Nordic Seas (IESSNS) in July 2020. In total, 1374 individuals were caught, and only a subset of 225 were measured fresh at sea and 89 were frozen and dissected on land. Total lengths of fresh fish ranged from 38 to 85 mm, while dissected individuals ranged from 40 to 74 mm and were 2 to 6 years old. Located over the Reykjanes Ridge in the Iceland Basin region, individuals had a significantly higher mean standard length and mean age, and a lower mean body condition. We reported length–weight relationships for both fresh and frozen samples, indicating evidence that preserving of the specimens through freezing affected relationships. The von Bertalanffy growth curve was calculated along with significant otolith‐fish size relationships where r2 values ranged between 0.87 and 0.92. Our research highlights the importance of cross‐regional studies and provides baseline biology for B. glaciale in Icelandic waters, specifically in the southern continental slope and Reykjanes Ridge. [ABSTRACT FROM AUTHOR]

The proportions of individuals in various age classes in a population of wild animals affect population trends, behaviors, learning, and social structures. Knowledge of age structure is needed for effective conservation and management of populations. However, it is not always possible to determine the age or age class of individual animals, and hence the age structure of the population. Penguins, like most birds, cannot be aged once they molt into adult plumage. Spheniscus penguins attain adult plumage at 6 to 24 months of age, and individuals can live more than 30 years. We studied foot darkening in the four species of Spheniscus penguins to determine if age class can be determined from foot color. We compared how foot color changes with age among the four species to investigate potential functions of the darkening. We found that Spheniscus penguins have pale feet at hatching and the feet become darker with age throughout the lives of individuals. We showed that we can accurately predict the age structure of a colony of Magellanic penguins Spheniscus magellanicus, but not the ages of individual penguins, based on a sample of foot colors. The timing of foot darkening within species was consistent with foot color functioning in protection from UV radiation, and not with foot color functioning in thermoregulation. The species that breeds at the lowest latitudes and experiences the highest UV radiation (Galápagos penguins Spheniscus mendiculus) had feet that darkened at the earliest ages, and the species that breed at higher latitudes and experience less intense insolation (African S. demersus and Magellanic penguins) had feet that darkened latest. Humboldt penguins S. humboldti breed mostly at low latitudes and foot darkening was intermediate between Galápagos and Magellanic penguins. We also found that males' feet darken somewhat earlier than females' feet, likely because females spend more time in their nests (burrows or under vegetation) than males and have less sun exposure. We found that feet darkened in an individual over years, but not within a breeding season. The color change is a life-long process, likely an evolutionary adaptation within species, not a seasonal, temporary response to UV radiation. We propose foot darkening as a way to assess age structure in Spheniscus penguins. Foot color in a colony of Magellanic penguins can provide a rapid, noninvasive method to estimate the age structure of the colony. [ABSTRACT FROM AUTHOR]

We use a panel data set of Japanese firms from 2005 to 2019 to examine how a firm's employee age structure affects its productivity and wages. The pooled ordinary-least-squares (OLS) results indicate a negative relationship between the proportion of older employees and labor productivity. However, the effects disappear after applying a fixed effects (FE) model and the generalized method of moments to consider the unobserved heterogeneity among firms. Moreover, the proportion of older employees does not significantly affect firms' wages. We further examine firm heterogeneity as a factor that contributes to the difference between the pooled OLS and FE estimates. The results suggest that differences in corporate stakeholder characteristics and corporate governance, such as the presence of labor unions and proportion of foreign ownership, may be related to the ratio of older workers and corporate performance. [ABSTRACT FROM AUTHOR]

Copyright of Tropical Geography is the property of Tropical Geography Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

ABSTRACT The introduction of aquatic non‐native species into novel systems may have negative impacts on native biodiversity. Introduced species can predate native species, compete for resources, transmit diseases, hybridise and degrade habitat. To minimise impacts on aquatic biota, management efforts are needed to reduce invasive species abundance. However, eradication or reduction efforts require information about the source of introductions and the biology and ecology of the organism. Therefore, the objective of this study was to quantify population dynamics, natal origins and dispersal characteristics of the introduced Weather Loach Misgurnus anguillicaudatus, which was recently discovered in Georgia, USA waters. Sagittal otoliths were extracted and aged to determine dynamic rate functions, and we performed microchemical analysis on a subset of otoliths to quantify dispersal and introduction events. Sampled Weather Loach consisted of a wide range of ages and lengths, indicating that natural reproduction and recruitment have been occurring for multiple years. The change in otolith microchemistry seen in some fish reveals that they have dispersed from their introduction or reproduction sites into different areas, while others have likely remained in the same system since hatching. Overall, our findings indicate that the Weather Loach populations in Georgia are disjunct, likely stemming from multiple introductions. These results will be used to develop management strategies as well as aid in the effort to continue and enhance outreach regarding the release of unwanted aquarium fish.

The flat-headed frog, Barbourula busuangensis, is a poorly known, riverine species, endemic to the province of Palawan in the Philippines. We applied capture-mark-recapture (CMR) methods to follow individuals at two sites (Malbato and San Rafael) in the island of Busuanga over 10 months in 2022–2023. We used passive internal transponders (PITs) to mark adult and subadults and single-colored visual internal elastomers (VIEs) for cohorts of juveniles. From a total of 196 frogs PIT-tagged in Malbato and 144 in San Rafael, we obtained overall recapture rates of 49% and 60% respectively. We used the POPAN formulation in MARK software to estimate abundance, survival, movement, and age-class demographics. Our best model estimated an average population size of 268 frogs at Malbato and 232 at San Rafael, and constant survival probabilities (mean ≥ 0.97) at both sites. When adding age classes to the model, abundance of adults was always higher than that of subadults producing an age structure dominated by adults at both sites. Growth rates decreased significantly with body size, being higher in juveniles (1.51 mm/month) and subadults (1.56 mm/month) than in adult frogs (0.60 mm/month). At these growth rates frogs may reach adulthood at 2.5 years, with the oldest individuals likely being over 11 years old. CMR data confirmed site fidelity, and translocation experiments revealed that frogs have the ability to home when displaced 10–50 m upstream and downstream from their original capture site. This is the first long-term study of B. busuangensis using robust field and analysis methods. Our data suggest that B. busuangensis is stable at present in Busuanga, with long-lived adults and dispersing subadults. We expect that these data may serve as baseline of current population abundance, age structure and growth rates which are factors that tend to be affected when species are threatened. In this way it may help researchers and conservation practitioners detect potential changes that may occur as this species confronts the challenges of the Anthropocene.

Relict subtropical coniferous forests in China face severe fragmentation, resulting in declining populations, and some are under significant threat from invasive alien species. Despite the crucial importance of understanding forest dynamics, knowledge gaps persist, particularly regarding the impact of invasive plants on vulnerable natives like Keteleeria evelyniana. In this study, we investigated the impact of invasive plants on the regeneration of forests dominated by K. evelyniana, a subtropical relict species in southwestern China. For this purpose, we characterized forest dynamics of 160 forest plots featuring K. evelyniana as the primary dominant species and determined whether the presence of invasive plants was correlated with regeneration of K. evelyniana. We identified four distinct forest types in which K. evelyniana was dominant. We found that radial growth of K. evelyniana trees is faster in younger age-classes today than it was for older trees at the same age. The population structure of K. evelyniana in each forest type exhibited a multimodal age-class distribution. However, three forest types lacked established saplings younger than 10 years old, a situation attributed to the dense coverage of the invasive alien Ageratina adenophora. This invasive species resulted in a reduction of understory species diversity. Additionally, our analysis uncovered a significant negative correlation in phylogenetic relatedness (net relatedness index) between native and invasive alien plant species in eastern Yunnan. This suggests closely related invasive species face heightened competition, hindering successful invasion. Taken together, our findings indicate that successful establishment and habitat restoration of K. evelyniana seedling/saplings require effective measures to control invasive plants.

Amphibians are not only an alternative source of vital protein for humans, but also one of the best bioindicators for ecological studies. In this study, we studied the age structure, body size, and mass of an amphibian species (Pelophylax ridibundus) by sampling from two different frog farms in Türkiye. The age ranged from 4 to 13 (mean: 7.1) years in the Adana site while the age varied from 1 to 12 (mean: 5.2) years in the İstanbul site. Body size ranged between 88.21 and 103.72 mm (mean: 94.99 ± 1.15 mm) in the Adana site and 45.96 and 103.25 mm (mean: 75.90 ± 3.01 mm) in the İstanbul site. The t-test confirmed that the average age, SVL, and weight of the Adana site were higher than those of İstanbul. Body size markedly increased with age and weight (SVL-age: r = 0.659, p < 0.01; SVL-weight: r = 0.877, p < 0.001) in the İstanbul site, while in the Adana site, body size correlated only with weight. In conclusion, our research uses skeletochronology to provide demographic characteristics of marsh frogs from two unexplored frog farms located in the west and south of Türkiye. [ABSTRACT FROM AUTHOR]

Introduction: As a central figure in modern healthcare systems, the family doctor faces a number of challenges, duties and responsibilities. The functioning of a practice for primary medical care is carried out in accordance with constantly emerging and periodically changing regulations and requirements for the economic efficiency of the diagnostic and treatment process on the part of the contractual partner and the institutions to which the doctor is responsible. Objective: To analyze the structure and staffing of the medical staff in primary care in the Plovdiv region during an observed period of time (2017-2022 inclusive). Material and Methods: The object of observation was the Plovdiv Region. A logical unit was the general practitioner (GP, personal physician). Technical units were the established outpatient clinics for primary care. The study was retrospective, for a 6-year period from 2017 to 2022 inclusive. Quantitative and qualitative indicators were used for the analysis. The statistical package SPSS version 27 and Microsoft Excel were used in the computer processing of the collected database. Results: Human resources in primary outpatient medical care are facing the following challenges: an aging population with a negative natural increase, with a deepening imbalance in the territorial distribution and an aging workforce in the health sector, insufficient attractiveness of young generations to some medical specialties. Discussion: A wide range of risk factors related to the conditions, style and lifestyle of people negatively transform the health status and unlock a number of health, social and psychological problems that worsen the quality of life and accelerate the aging process. The results obtained from the analysis of the age structure of the medical staff working in primary care show startling data on the aging of GPs and the lowest percentage of working young doctors. The general practitioner offers their services on the quasi-market of medical services. GPs must have medical, accounting, commercial knowledge and skills as they are practically medical service traders registered under the commercial law. Conclusion: Human resources are not subject to mechanical or mandatory territorial redistribution. A favorable environment, providing opportunities and incentives, activates in the medical specialists themselves (physicians and nurses) a desire to change the workplace and the place of residence. [ABSTRACT FROM AUTHOR]

This paper is concerned with the sustained periodic oscillation phenomenon in a three-species delayed predation system with Holling type II functional response and age structure in top predator. The top predator fertility function is regarded as a piecewise continuous smooth function with regard to their maturation period τ 2 . The complicated dynamic behavior is proved by integrated semigroup theory and Hopf bifurcation theorem for semilinear equations with non-dense domain. Through qualitative analysis and bifurcation study of the system, we yield that this system has a nontrivial periodic solution that bifurcates from the positive equilibrium age distribution when bifurcation parameter τ passes through some critical values. Numerical simulations are also provided to illustrate theoretically analytical results. [ABSTRACT FROM AUTHOR]

For the first time, for the territory of the nature reserve "Gorgany" on the example of the permanent trial area No. 1, a complex characteristic of a typical post-forest meadow was compiled: based on the results of the ecomorphic analysis of the partial flora, its ecological specificity was revealed; according to the data of the weight analysis and the indicators of the projective cover, information was obtained about the features of the spatial organization of the vegetation cover; on the basis of phytoindication, the indicators of the ecological regimes of the edaphotope and climatope were calculated; the structure of the cenopopulation of Gymnadenia conopsea (L.) R.Br., was investigated and the degree of compliance of the growing conditions with the tolerance zone of this species was revealed. The phytosozological value of the trial area is due to the presence of seven species from the Red Book of Ukraine: Gymnadenia conopsea, Dactylorhiza majalis (Rchb.) P.F.Hunt Summerh., Platanthera bifolia (L.) Rich., Neottia ovata (L.) Hartm.., Epipactis helleborine (L.) Crantz, Traunsteinera globosa (L.) Rchb., Galanthus nivalis L.. It was found that the spatial organization of the plant cover is heterogeneous, the indicators of the weight analysis fluctuate in a significant range. The studied area corresponds to fresh forest-meadow ecotopes with complete wetting of the root layer of the soil by precipitation and meltwater. The soils are moderately aerated, weakly acidic, quite rich in mineral salts, but with an insignificant content of carbonates and relatively poor in terms of mineral nitrogen. Such conditions of the edaphotope are favorable for the existence of mesophytes, hemihydrocontrastophobes, subacidophiles, heminitrophiles, hemiaerophobes, subombrophytes, hemioceanists, submicrotherms, hemicryophytes. It was established that the indicators of the ecological regimes of the edaphotope and climatotope are, in general, within the tolerance zone of G. conopsea, but for the regimes of lighting, variability of moisture, aeration and acidity, they approach the limit of the ecological amplitude of the species. A positive factor for its existence is the presence of a formed litter layer (450-500 g per 1 m² of air-dry weight); absence of dense turf (less than 180 g per 1 m²), absence (or insignificant development) of layers of semishrubs and mosses. The number of generative individuals has remained relatively stable for several years, although we can talk about a certain tendency to decrease. [ABSTRACT FROM AUTHOR]

The authors propose and analyze a viral infection model with defectively infected cells and age of the latently infected cells. The existence of steady states is determined by the basic reproduction number of virus. With the Lyapunov's direct method, they establish a threshold dynamics of the model with the basic reproduction number of virus as the threshold parameter. To achieve it, a novel procedure is proposed. Its novelties are two-folded. On one hand, the coefficients involved in the specific forms of the used Lyapunov functionals for the two feasible steady states are determined by the same set of inequalities. On the other hand, for the infection steady state, a new approach is proposed to check whether the derivative of the Lyapunov functional candidate along solutions is negative (semi-)definite or not. This procedure not only simplifies the analysis but also exhibits the relationship between the two Lyapunov functionals for the two feasible steady states. Moreover, the procedure is expected to be applicable for other similar models. [ABSTRACT FROM AUTHOR]

This article surveys the growing field of political demography, which explores the political consequences of structural population change. It underscores the importance of integrating demography and political sociology research to better understand the complex and nuanced relationship between demography and political dynamics. The existing research demonstrates profound and multifaceted impacts of demographic shifts on the political landscape, with different demographic factors having distinct political consequences. Notably, population composition and distribution tend to hold greater political significance than sheer population size and growth. Furthermore, while more research is needed, the existing work suggests that the effect of structural demographic factors is neither inevitable nor without limit; rather, the political consequences of demographic change often exhibit nonlinear patterns and interact with prevailing socioeconomic and institutional contexts. As demographic shifts continue to unfold globally, political demography stands as a promising and enlightening area of research that merits further inquiry. [ABSTRACT FROM AUTHOR]

Copyright of Acta Prataculturae Sinica is the property of Acta Prataculturae Sinica Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The proportions of individuals in various age classes in a population of wild animals affect population trends, behaviors, learning, and social structures. Knowledge of age structure is needed for effective conservation and management of populations. However, it is not always possible to determine the age or age class of individual animals, and hence the age structure of the population. Penguins, like most birds, cannot be aged once they molt into adult plumage. Spheniscus penguins attain adult plumage at 6 to 24 months of age, and individuals can live more than 30 years. We studied foot darkening in the four species of Spheniscus penguins to determine if age class can be determined from foot color. We compared how foot color changes with age among the four species to investigate potential functions of the darkening. We found that Spheniscus penguins have pale feet at hatching and the feet become darker with age throughout the lives of individuals. We showed that we can accurately predict the age structure of a colony of Magellanic penguins Spheniscus magellanicus, but not the ages of individual penguins, based on a sample of foot colors. The timing of foot darkening within species was consistent with foot color functioning in protection from UV radiation, and not with foot color functioning in thermoregulation. The species that breeds at the lowest latitudes and experiences the highest UV radiation (Galápagos penguins Spheniscus mendiculus) had feet that darkened at the earliest ages, and the species that breed at higher latitudes and experience less intense insolation (African S. demersus and Magellanic penguins) had feet that darkened latest. Humboldt penguins S. humboldti breed mostly at low latitudes and foot darkening was intermediate between Galápagos and Magellanic penguins. We also found that males’ feet darken somewhat earlier than females’ feet, likely because females spend more time in their nests (burrows or under vegetation) than males and have less sun exposure. We found that feet darkened in an individual over years, but not within a breeding season. The color change is a life-long process, likely an evolutionary adaptation within species, not a seasonal, temporary response to UV radiation. We propose foot darkening as a way to assess age structure in Spheniscus penguins. Foot color in a colony of Magellanic penguins can provide a rapid, noninvasive method to estimate the age structure of the colony.

The portfolio effect plays a critical role in population productivity and stability. Age structure of spawning salmon represents an example of portfolio effects such that the risks of experiencing unfavorable conditions are spread across time. However, the distribution ofmaturation ages for Pacific salmon (Oncorhynchus spp.) is increasingly concentrated into fewer and younger ages, whichmay impact population resilience to climate change.We explored the population dynamics of Sacramento River fall-run Chinook salmon (O. tshawytscha) under different age structure scenarios using a life-cycle model and compared twomechanisms that can underlie these changes--mortality and maturation. In addition, we tested whether age structure promotes resilience to drought.We found that high age structure diversity increased the stability of population size and harvest compared with low diversity. However, mean population size responded differently depending on the underlying mechanism. Reduced mortality of adult fish ages 4-5 increased escapement, whereas delayed maturation decreased escapement. Overall, high age structure diversity was able to buffer against the adverse effects of droughts by reducing the variability of population size and harvest compared with low diversity. Our results suggest that age structure promotes stability of salmon in an increasingly variable climate.

The study of indigenous pine forests of evolutionary formation as endangered virgin forests is the basic for fundamental research into the processes of formation of sustainable forest communities. The aim of the study presented in the article is a comparative assessment of the structures of tree fractions of phytocenoses according to the parameters of the age series of stands and the successional position, dynamic indicators of woody waste, the influence of the pyrogenic factor, and the presence of rot damage to the stands. Age structures, numerical and linear parameters of pyrogenic factors, their impact on the infestation of trees with rot, volumetric indicators of wood waste and characteristics of natural regeneration, the mass of wood xylolysis products during its decomposition by wood-destroying fungi have been studied in pine biogeocenoses with various dynamic characteristics in the taiga zone of European Russia. Pine biogeocenoses under these conditions have structures of different ages, altered by fires of different types. Using the example of an indigenous pine forest in the Pechora-Ilychskiy Nature Reserve (middle taiga), the influence of pyrogenic effects on the formation of various types of rot and damage to trunks is shown. The volumes of woody waste are distributed according to the stages of decomposition in pine forests with different structural and dynamic characteristics; pine undergrowth – according to height gradations. An example is given of calculating the mass of wood components deposited in the stands and released during the decomposition of woody waste by wood-destroying fungi for the biogeocenosis of the Pechora-Ilychskiy Nature Reserve. The majority of indigenous pine forests in the northern territories have been affected by fires of varying intensity and types, sometimes several times during a development cycle. Pyrogenic effects have a significant on changes in the age structures of pine forests, damage to their trunks, the general infestation of forest stands by wood-destroying fungi of the biotrophic complex, the volumes of woody waste, and the formation of natural regeneration structures.

In this paper, we construct an age-structured epidemic model to analyze the optimal vaccine allocation strategy in an epidemic. We focus on two topics: the first one is the optimal vaccination interval between the first and second doses, and the second one is the optimal vaccine allocation ratio between young and elderly people. On the first topic, we show that the optimal interval tends to become longer as the relative efficacy of the first dose to the second dose (RE) increases. On the second topic, we show that the heterogeneity in the age-dependent susceptibility (HS) affects the optimal allocation ratio between young and elderly people, whereas the heterogeneity in the contact frequency among different age groups (HC) tends to affect the effectiveness of the vaccination campaign. A counterfactual simulation suggests that the epidemic wave in the summer of 2021 in Japan could have been greatly mitigated if the optimal vaccine allocation strategy had been taken.