scholarly journals Modeling schistosomiasis transmission: the importance of snail population structure

2021 ◽  
Vol 14 (1) ◽  
Author(s):  
Larissa C. Anderson ◽  
Eric S. Loker ◽  
Helen J. Wearing
Keyword(s):  
Age Structure ◽  
Human Infection ◽  
Infection Prevalence ◽  
Snail Population ◽  
Snail Infection ◽  
Deterministic Models ◽  
Population Age Structure ◽  
Force Of Infection ◽  
The Impact ◽  
The Relationship

Abstract Background Schistosomiasis is a neglected tropical disease endemic in 54 countries. A major Schistosoma species, Schistosoma mansoni, is sustained via a life cycle that includes both human and snail hosts. Mathematical models of S. mansoni transmission, used to elucidate the complexities of the transmission cycle and estimate the impact of intervention efforts, often focus primarily on the human host. However, S. mansoni incurs physiological costs in snails that vary with the age of the snail when first infected. Snail demography and the age of snail infection could thus affect the force of infection experienced by humans, which is frequently used to predict the impact of various control strategies. Methods To address how these snail host and parasite interactions influence model predictions, we developed deterministic models of schistosomiasis transmission that include varying complexity in the snail population age structure. Specifically, we examined how model outputs, such as schistosome prevalence in human and snail populations, respond to the inclusion of snail age structure. Results Our models suggest that snail population age structure modifies the force of infection experienced by humans and the relationship between snail infection prevalence and corresponding human infection prevalence. There are significant differences in estimated snail infection, cercarial density and mean worm burden between models without snail population dynamics and those with snail populations, and between models with a homogeneous snail population and those with age stratification. The variation between finely age-stratified snail populations and those grouped into only juvenile and adult life stages is, however, minimal. Conclusions These results indicate that including snails and snail age structure in a schistosomiasis transmission model alters the relationship between snail and human infection prevalence. This highlights the importance of accounting for a heterogeneous intermediate host population in models of schistosomiasis transmission where the impact of proposed control measures is being considered.

scholarly journals Examining the Role of Population Age Structure upon Residential Electricity Demand: A Case from Korea

2019 ◽  
Vol 11 (14) ◽  
pp. 3914 ◽  
Author(s):  
Jaehyeok Kim ◽  
Minwoo Jang ◽  
Donghyun Shin
Keyword(s):  
Age Structure ◽  
Energy Demand ◽  
Population Group ◽  
Strong Relationship ◽  
Electricity Demand ◽  
Advanced Economy ◽  
Population Age Structure ◽  
Long Run ◽  
Residential Electricity ◽  
The Impact

In this article, we empirically investigate the impact of the population age structure on electricity demand. Our study is motivated by suggestions from existing literature that demographic factors can play an important role in energy demand. Using Korean regional level panel data for 2000 to 2016, we estimate the long-run elasticities through employing cointegration regression and the short-run marginal effects by developing a panel error correction model. It is worth investigating the Korean case, since Korea is aging faster than any other advanced economy, and at the same time is one of the heaviest energy users in the world. To our knowledge, this is the first study analyzing how the population age structure affects residential electricity demand, based on regional data in Korea. Our analysis presents the following results. First, an increase in the youth population raises the residential electricity demand in the short- and long-run. Second, an increase in the population of people aged 65 and over also increases this electricity demand in the short- and long-run. Third, among the group of people aged 65 and over, we further investigate the impact of an older population group, aged 80 and over, but separately, on their residential electricity demand. However, in general there is no strong relationship in the short- and long-run.

On the interpretation of age—prevalence curves for schistosome infections of host snails

Parasitology ◽  
1989 ◽  
Vol 99 (1) ◽  
pp. 47-56 ◽  
Author(s):  
M. E. J. Woolhouse
Keyword(s):  
Survival Rate ◽  
Field Studies ◽  
Significant Loss ◽  
High Rate ◽  
Snail Population ◽  
Infection Rates ◽  
Force Of Infection ◽  
Age Dependent ◽  
The Relationship ◽  
Patent Infection

SUMMARYThe prevalence of schistosome infections in intermediate host snails varies with snail age. The relationship between age and prevalence, the age—prevalence curve, is complex and may vary in space and time, and among parasite—host species. Field studies show that the shape of the age—prevalence curve may be seasonally variable, and that at some times there may be a decline in prevalence among older snails. This paper attempts to explain these observations in terms of the underlying epidemiological processes. A discrete-time version of Muench's catalytic model for age-dependent infection is developed. Model simulations were carried out using life-history and epidemiological parameters derived from studies ofSchistosoma haematobium—Bulinus globususin Zimbabwe. Analysis of model behaviour identifies aspects of the schistosome— snail interaction that affect the shape of the age—prevalence curve. The following features can result in a decline in prevalence among older snails. (1) A decrease in the survival rate of patent infected snails with age. (2) A decrease in the force of infection with age. (3) A high rate of loss of infection. (4) A heterogeneity in the snail population such that the probability of infection is correlated with snail fecundity. (This would occur if there existed a spatial correlation between force of infection and fecundity, or if there were a correlation between fecundity and susceptibility.) The evidence for the occurrence of these features in the field is assessed. Survival rate is related more closely to the duration of patent infection than to ageper se. The evidence for age-dependent force of infection is equivocal. Significant loss-of-infection rates have yet to be demonstrated. Heterogeneities in force of infection and fecundity have been reported and, for the Zimbabwe data, this mechanism can explain seasonally in the age—prevalence curve as a function of known seasonal variation in the force of infection and snail fecundity.

The Population Age Structure of Spotted Knapweed (Centaurea maculosa) in Montana

Weed Science ◽  
1987 ◽  
Vol 35 (2) ◽  
pp. 194-198 ◽  
Author(s):  
Keith W. Boggs ◽  
Jim M. Story
Keyword(s):  
High Mortality ◽  
Age Structure ◽  
Secondary Xylem ◽  
Older Age ◽  
Centaurea Maculosa ◽  
Early Age ◽  
Spotted Knapweed ◽  
Age Classes ◽  
Population Age Structure ◽  
The Relationship

Spotted knapweed (Centaurea maculosa Lam. # CENMA) communities were sampled to determine the relationship between age and the number of root rings, and the population age structure. Spotted knapweed taproots add one ring of secondary xylem annually. In 1984, populations were expanding with high densities of individuals in the early age classes, followed by a steady decline in the older classes. In 1985, the majority of the individuals in knapweed populations were in the older age classes. This change in the population age structure was attributed to high mortality among the young age classes due to a drought in 1985. The maximum age class at the sites ranged from 5 to 9 yr. The percentage of plants with floral stalks increased with age to a peak of 75% in the fifth year in 1984 and in the seventh year in 1985.

scholarly journals Analytical Generalization of the Depreciation Multiplier as a Factor of Extended Reproduction of Fixed Assets Depending on the Age Structure

2020 ◽  
Vol 24 (5) ◽  
pp. 41-61
Author(s):  
L. A. Antonov
Keyword(s):  
Age Structure ◽  
Computer Modelling ◽  
Quantitative Characteristic ◽  
Research Work ◽  
Theoretical Models ◽  
Theoretical Research ◽  
Fixed Assets ◽  
Accelerated Depreciation ◽  
The Impact ◽  
The Relationship

The subject of the study is the expansion multiplier as a quantitative characteristic of the depreciation expansive effect in models of the extended reproduction of fixed assets. The aim of the study is to identify the impact of the age structure of fixed assets on the expansion multiplier value factoring in various methods of calculating depreciation. The research methods include mathematical and computer modelling, as well as deductive logic as a process of reasoning from more general to more specific. The high depreciation of fixed assets of Russian enterprises and the high demand for  depreciation as a source of funds for their renewal and extended reproduction ensure the relevance of the study. The results of the study include the models of extended reproduction of fixed assets due to the expansive depreciation effect using  various  methods  of  accruing  depreciation;  demonstrate  the  relationship  between  the  age  structure of fixed assets and the expansion multiplier. Generalizing the methods of depreciation in terms of their impact on the expansion multiplier values provides the scientific novelty of the research. This paper introduces the expansion multiplier calculation formulas for general and special accelerated depreciation and limits of multiplicative potential of accelerated depreciation. The conclusions of the research work illustrate the possibility of using the expansion multiplier to plan and optimize the depreciation policies of organizations, as well as to evaluate the multiplier of fixed assets in various economies. The authors identified the problems of applying the expansive depreciation effect as a means of extended reproduction of fixed assets in practice, as a result of the limitations of its theoretical models. In overcoming the identified limitations, areas of technical theoretical research are proposed.

scholarly journals Women living with their mothers-in-law

2021 ◽  
Vol 5 ◽  
pp. 170
Author(s):  
Kristin E Bietsch ◽  
Katherine H LaNasa ◽  
Emily Sonneveldt
Keyword(s):  
Age Structure ◽  
Age Groups ◽  
Married Women ◽  
Future Research ◽  
Demographic And Health Surveys ◽  
African Countries ◽  
Head Of Household ◽  
Sub Saharan ◽  
The Impact ◽  
The Relationship

Background Many studies have documented the impacts mothers-in-law have on daughters-in-law living in the same household, but few have quantified the scale of this co-residence.  This study aims to estimate the proportion of married women living with their mothers-in-law across countries and time.  Methods Using household rosters from 250 Demographic and Health Surveys in 75 countries, this paper uses the “relationship to head of household” question to identify households where married women live with their mothers-in-law.  For select countries with large changes, we decompose changes in rates into changes in the age structure of married women and the rate of women living with their mothers-in-law by age. Results This paper finds large variation in family structure around the globe, from 1% of married women in Rwanda to 49% in Tajikistan living with their mother-in-law.  Many countries with high co-residence in the 1990s continue to see high and increasing numbers today, especially in Central and Southern Asia, while some North and sub-Saharan African countries experienced substantial declines.  Decomposing changes by age and rates shows that changes in the age structure of married women is not driving changes in co-residence, but rather the rates are changing across age groups.  Conclusions These findings show the large variation in women living with their mothers-in-law across the globe.  The authors provide publicly available code and future research ideas to encourage others to further our understanding of the impact of living with her mother-in-law on a woman’s life.

Accent Policy and Accent Modification Enterprises as Potential Indicators of Intercultural Power Relations: A Call for an Updated Research Agenda

2013 ◽  
Vol 3 (1) ◽  
pp. 22-33 ◽  
Author(s):  
Brynne D. Ovalle ◽  
Rahul Chakraborty
Keyword(s):  
International Relations ◽  
Identity Construction ◽  
Social Theory ◽  
Power Relations ◽  
Linguistic Diversity ◽  
Cultural Organization ◽  
Using Data ◽  
The Individual ◽  
The Impact ◽  
The Relationship

This article has two purposes: (a) to examine the relationship between intercultural power relations and the widespread practice of accent discrimination and (b) to underscore the ramifications of accent discrimination both for the individual and for global society as a whole. First, authors review social theory regarding language and group identity construction, and then go on to integrate more current studies linking accent bias to sociocultural variables. Authors discuss three examples of intercultural accent discrimination in order to illustrate how this link manifests itself in the broader context of international relations (i.e., how accent discrimination is generated in situations of unequal power) and, using a review of current research, assess the consequences of accent discrimination for the individual. Finally, the article highlights the impact that linguistic discrimination is having on linguistic diversity globally, partially using data from the United Nations Educational, Scientific and Cultural Organization (UNESCO) and partially by offering a potential context for interpreting the emergence of practices that seek to reduce or modify speaker accents.

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