Chapter 1: Theoretical Foundations

1973 ◽  
Vol 27 ◽  
pp. 6-10 ◽  
Author(s):  
Kenneth M. Weiss
Keyword(s):  
Age Distribution ◽  
Human Populations ◽  
Stable Form ◽  
Stable Age Distribution ◽  
Theoretical Population ◽  
Stable Population Theory ◽  
Number Of Individuals ◽  
Theoretical Foundations ◽  
Stable Populations

The approach to population structure followed in this work is that of stable population theory as developed by A. J. Lotka and others. An early exposition of this theory is found in Lotka (1956); more recently it has been summarized by Coale (1972), Keyfitz (1968), and Shryock and Siegel(1971).The theory of stable populations requires that a population is infinite in size, has no net immigration or outmigration, and has fixed rates of fertility and mortality at each age. These assumptions are often approximated closely enough by real populations for the theory to be useful. Given the stated conditions, a population is described by its age distribution, or the number of individuals at each age. Since the theoretical population is infinite, the age distribution is defined in terms of relative numbers or percentages rather than finite numbers of individuals at each age.The age structure is determined by the rates of mortality and fertility. It has been proved by Lotka that, no matter what the initial age distribution, a population under these assumptions approaches a certain age distribution which is determined by those rates. The result is the so-called stable age distribution since it will no longer change if mortality and fertility remain fixed. In fact, a temporary perturbation in these rates will only temporarily disturb the age distribution, which will quickly return to the stable form. Human populations approach the stable age distribution in well under 100 yr after the rates become fixed.

Frequency distribution of Wuchereria bancrofti microfilariae in human populations and its relationships with age and sex

Parasitology ◽  
1990 ◽  
Vol 101 (3) ◽  
pp. 429-434 ◽  
Author(s):  
P. K. Das ◽  
A. Manoharan ◽  
A. Srividya ◽  
B. T. Grenfell ◽  
D. A. P. Bundy ◽  
...  
Keyword(s):  
Frequency Distribution ◽  
Negative Binomial ◽  
Age Distribution ◽  
Indirect Evidence ◽  
Wuchereria Bancrofti ◽  
Parameter Estimates ◽  
Human Populations ◽  
Sampling Errors ◽  
Frequency Distributions ◽  
Age And Sex

SUMMARYThis paper examines the effects of host age and sex on the frequency distribution of Wuchereria bancrofti infections in the human host. Microfilarial counts from a large data base on the epidemiology of bancroftian filariasis in Pondicherry, South India are analysed. Frequency distributions of microfilarial counts divided by age are successfully described by zero-truncated negative binomial distributions, fitted by maximum likelihood. Parameter estimates from the fits indicate a significant trend of decreasing overdispersion with age in the distributions above age 10; this pattern provides indirect evidence for the operation of density-dependent constraints on microfilarial intensity. The analysis also provides estimates of the proportion of mf-positive individuals who are identified as negative due to sampling errors (around 5% of the total negatives). This allows the construction of corrected mf age–prevalence curves, which indicate that the observed prevalence may underestimate the true figures by between 25% and 100%. The age distribution of mf-negative individuals in the population is discussed in terms of current hypotheses about the interaction between disease and infection.

scholarly journals STUDI LALAT PENGOROK DAUN LIRIOMYZA SPP. PADA PERTANAMAN BAWANG DAUN, DAN PARASITOID OPIUS CHROMATOMYIAE BELOKOBYLSKIJ & WHARTON (HYMENOPTERA: BRACONIDAE)

2009 ◽  
Vol 9 (1) ◽  
pp. 22-31
Author(s):  
Rusli Rustam ◽  
Aunu Rauf ◽  
Nina Maryana ◽  
Pudjianto Pudjianto ◽  
Dadang Dadang
Keyword(s):  
Age Distribution ◽  
Host Density ◽  
Field Studies ◽  
Reproductive Value ◽  
Laboratory Studies ◽  
Demographic Parameter ◽  
Liriomyza Huidobrensis ◽  
Stable Age Distribution ◽  
Net Reproduction ◽  
Density Results

Studies on Leafminer Liriomyza spp. in Green Onion Fields, and Parasitoid Opius chromatomyiae Belokobylskij & Wharton (Hymenoptera: Braconidae).  Field studies were conducted to determine population abundance of leafminers and their parasitoids in green onion fields in Puncak, West Java. In addition to that, laboratory studies were carried out to determine demographic parameter of Opius chromatomyiae as well as response of parasitoid to increasing host density. Results revealed that green onions were infested by two species of leafminers, Liriomyza huidobrensis and Liriomyza chinensis.  Leafminer flies emerged from Erwor leaves (54.5) were significantly higher than those of RP leaves (18.65) (P = 0.0005). However, number of  leafminer flies caught on sticky traps was not statistically different (P = 0.297).  Two species of parasitoid, Hemiptarsenus varicornis and O. chromatomyiae, were associated with leafminers in green onion fields. Higher number of parasitoids emerged from Erwor leaves (13.68) as compared to RP (6.90) (P =0.0007 ). However, level of parasitization were 24.36% on Erwor and 28.45% on RP, and was not significantly different (P = 0.387). Laboratory studies indicated that net reproduction (Ro) of O. chromatomyiae was 28.55, generation time (T) 15.96 days, intrinsic growth rate 0.21, and total of reproductive value 223.64.  The stable age distribution of parasitoid were 37.93% eggs, 24.92% larvae, 20.36% pupae and 16.78% adults.  The parasitoid showed functional response type II to increasing host density, with a = 0.08 and Th = 2.58.

scholarly journals The long-term effects of the Amoco Cadiz oil spill

1982 ◽  
Vol 297 (1087) ◽  
pp. 323-333 ◽  
Keyword(s):  
Salt Marshes ◽  
Age Distribution ◽  
Life Cycles ◽  
Long Term Effects ◽  
Delayed Effects ◽  
Sea Birds ◽  
Stable Age Distribution ◽  
Rot Disease ◽  
One Year

The supertanker Amoco Cadiz wrecked on the coast of northern Brittany in April 1978. The resulting spill of 223000 t of crude oil polluted some 360 km of rocky or sandy shores, salt marshes and estuaries. An immediate mortality impact was observed. Populations of bivalves, periwinkles, limpets, peracarid crustaceans, heart urchins and sea birds were the most severely affected. Populations of polychaete worms, large crustaceans and coastal fishes were less affected. Three to six generations (5—10 years for bivalves but up to 60 years for birds) may be necessary before populations retrieve their stable age distribution. Delayed effects on mortality, growth and recruitment were still observed up to 3 years after the spill. Estuarine flat fishes and mullets had reduced growth, fecundity and recruitment; they were affected by fin rot disease. Populations of clams and nematodes in the meiofauna declined one year after the spill. Weathered oil is still present in low-energy areas. Species with short life cycles tend to replace long-lived species. A fauna of cirratulid and capitellid polychaete worms now prevails in sandy to m uddy areas. For several clam populations, recruitment remains unstable. Three years after the spill it is still premature to decide how long it will take before populations and ecosystems reach their former or new equilibria.

scholarly journals Surveillance of endemic human coronaviruses (HCoV-NL63, OC43 and 229E) associated with pneumonia in Kilifi, Kenya

2020 ◽  
Vol 5 ◽  
pp. 150
Author(s):  
Grieven P. Otieno ◽  
Nickson Murunga ◽  
Charles N. Agoti ◽  
Katherine E. Gallagher ◽  
Juliet O. Awori ◽  
...  
Keyword(s):  
Respiratory Virus ◽  
Seasonal Pattern ◽  
Severe Disease ◽  
Age Distribution ◽  
Coastal Region ◽  
Severe Pneumonia ◽  
Human Populations ◽  
Surveillance Period ◽  
Human Coronaviruses ◽  
Epidemiological Characteristics

Introduction: Human coronaviruses (HCoVs) circulate endemically in human populations, often with seasonal variation. We describe the long-term patterns of paediatric disease associated with three of these viruses, HCoV-NL63, OC43 and 229E, in coastal Kenya. Methods: Continuous surveillance of pneumonia admissions was conducted at the Kilifi county hospital (KCH) located in the northern coastal region of Kenya. Children aged <5 years admitted to KCH with clinically defined syndromic severe or very severe pneumonia were recruited. Respiratory samples were taken and tested for 15 virus targets, using real-time polymerase chain reaction. Unadjusted odds ratios were used to estimate the association between demographic and clinical characteristics and HCoV positivity. Results: From 2007 to 2019, we observed 11,445 pneumonia admissions, of which 314 (3.9%) tested positive for at least one HCoV type. There were 129 (41.1%) OC43, 99 (31.5%) 229E, 74 (23.6%) NL63 positive cases and 12 (3.8%) cases of HCoV to HCoV coinfection.  Among HCoV positive cases, 47% (n=147) were coinfected with other respiratory virus pathogens. The majority of HCoV cases were among children aged <1 year (66%, n=208), though there was no age-dependence in the proportion testing positive. HCoV-OC43 was predominant of the three HCoV types throughout the surveillance period. Evidence for seasonality was not identified. Conclusions: Overall, 4% of paediatric pneumonia admissions were associated with three endemic HCoVs, with a high proportion of cases co-occurring with another respiratory virus, with no clear seasonal pattern, and with the age-distribution of cases following that of pneumonia admissions (i.e. highest in infants). These observations suggest, at most, a small severe disease contribution of endemic HCoVs in this tropical setting and offer insight into the potential future burden and epidemiological characteristics of SARS-CoV-2.

Mapping the Local

2017 ◽  
Author(s):  
Christopher Ali
Keyword(s):  
The United States ◽  
Critical Geography ◽  
Critical Regionalism ◽  
Holistic Understanding ◽  
Local Media ◽  
Local Space ◽  
The Uk ◽  
Analytical Frameworks ◽  
Theoretical Foundations

Chapter 1 unpacks the theoretical foundations and analytical frameworks of the local by thematically mapping its various interpretations throughout critical political economy, critical theory, and critical geography. The chapter begins with a conversation about the local in everyday life and then moves on to conceptual and critical understandings of the local, space, place, and community, analyzing the themes of “local as place,” “local as community,” “local as market,” “local as resistive,” and “local as fetish.” Throughout these interrelated discussions, examples are drawn from local media in the United States, the UK, and Canada. The ultimate goal of this chapter is to move the reader toward a more holistic understanding of the local as developed in the theory of critical regionalism.

Stage-structured models

2019 ◽  
pp. 145-165
Author(s):  
Louis W. Botsford ◽  
J. Wilson White ◽  
Alan Hastings
Keyword(s):  
Age Distribution ◽  
Projection Matrix ◽  
Leslie Matrix ◽  
Individual State ◽  
State Variable ◽  
Population Variable ◽  
Real Population ◽  
Age Structured ◽  
The Individual

This chapter moves to models in which developmental stage is the individual state variable, and abundance at each stage is the population variable. Stage is a period within an individual life history (e.g. juvenile, adult); organisms may survive within a stage or “grow” to other stages. This movement and survival is represented by a projection matrix that describes the transitions between stages over time. The projection matrix is similar to the Leslie matrix for age-structured models (Chapter 3), except it has entries other than just those in the first row and the sub-diagonal. Stage models are conceptually problematic because real population dynamics ultimately depend on the age distribution within each stage category. Stage-based models obscure that age structure, thus stage is not an adequate expression of state (Chapter 1). This chapter demonstrates how this introduces artifacts in model analysis, particularly of transients, and presents some ways to avoid those artifacts.

Stable Age Distribution

2016 ◽  
Author(s):  
Monica Nordberg ◽  
Douglas M. Templeton ◽  
Ole Andersen ◽  
John H. Duffus
Keyword(s):  
Age Distribution ◽  
Stable Age Distribution
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