Science.gov

Sample records for exponential population growth

  1. Modeling Exponential Population Growth

    ERIC Educational Resources Information Center

    McCormick, Bonnie

    2009-01-01

    The concept of population growth patterns is a key component of understanding evolution by natural selection and population dynamics in ecosystems. The National Science Education Standards (NSES) include standards related to population growth in sections on biological evolution, interdependence of organisms, and science in personal and social…

  2. Modeling the Pre-Industrial Roots of Modern Super-Exponential Population Growth

    PubMed Central

    Stutz, Aaron Jonas

    2014-01-01

    To Malthus, rapid human population growth—so evident in 18th Century Europe—was obviously unsustainable. In his Essay on the Principle of Population, Malthus cogently argued that environmental and socioeconomic constraints on population rise were inevitable. Yet, he penned his essay on the eve of the global census size reaching one billion, as nearly two centuries of super-exponential increase were taking off. Introducing a novel extension of J. E. Cohen's hallmark coupled difference equation model of human population dynamics and carrying capacity, this article examines just how elastic population growth limits may be in response to demographic change. The revised model involves a simple formalization of how consumption costs influence carrying capacity elasticity over time. Recognizing that complex social resource-extraction networks support ongoing consumption-based investment in family formation and intergenerational resource transfers, it is important to consider how consumption has impacted the human environment and demography—especially as global population has become very large. Sensitivity analysis of the consumption-cost model's fit to historical population estimates, modern census data, and 21st Century demographic projections supports a critical conclusion. The recent population explosion was systemically determined by long-term, distinctly pre-industrial cultural evolution. It is suggested that modern globalizing transitions in technology, susceptibility to infectious disease, information flows and accumulation, and economic complexity were endogenous products of much earlier biocultural evolution of family formation's embeddedness in larger, hierarchically self-organizing cultural systems, which could potentially support high population elasticity of carrying capacity. Modern super-exponential population growth cannot be considered separately from long-term change in the multi-scalar political economy that connects family formation and

  3. Can the Site-Frequency Spectrum Distinguish Exponential Population Growth from Multiple-Merger Coalescents?

    PubMed Central

    Eldon, Bjarki; Birkner, Matthias; Blath, Jochen; Freund, Fabian

    2015-01-01

    The ability of the site-frequency spectrum (SFS) to reflect the particularities of gene genealogies exhibiting multiple mergers of ancestral lines as opposed to those obtained in the presence of population growth is our focus. An excess of singletons is a well-known characteristic of both population growth and multiple mergers. Other aspects of the SFS, in particular, the weight of the right tail, are, however, affected in specific ways by the two model classes. Using an approximate likelihood method and minimum-distance statistics, our estimates of statistical power indicate that exponential and algebraic growth can indeed be distinguished from multiple-merger coalescents, even for moderate sample sizes, if the number of segregating sites is high enough. A normalized version of the SFS (nSFS) is also used as a summary statistic in an approximate Bayesian computation (ABC) approach. The results give further positive evidence as to the general eligibility of the SFS to distinguish between the different histories. PMID:25575536

  4. Universality in stochastic exponential growth.

    PubMed

    Iyer-Biswas, Srividya; Crooks, Gavin E; Scherer, Norbert F; Dinner, Aaron R

    2014-07-11

    Recent imaging data for single bacterial cells reveal that their mean sizes grow exponentially in time and that their size distributions collapse to a single curve when rescaled by their means. An analogous result holds for the division-time distributions. A model is needed to delineate the minimal requirements for these scaling behaviors. We formulate a microscopic theory of stochastic exponential growth as a Master Equation that accounts for these observations, in contrast to existing quantitative models of stochastic exponential growth (e.g., the Black-Scholes equation or geometric Brownian motion). Our model, the stochastic Hinshelwood cycle (SHC), is an autocatalytic reaction cycle in which each molecular species catalyzes the production of the next. By finding exact analytical solutions to the SHC and the corresponding first passage time problem, we uncover universal signatures of fluctuations in exponential growth and division. The model makes minimal assumptions, and we describe how more complex reaction networks can reduce to such a cycle. We thus expect similar scalings to be discovered in stochastic processes resulting in exponential growth that appear in diverse contexts such as cosmology, finance, technology, and population growth. PMID:25062238

  5. Universality in Stochastic Exponential Growth

    NASA Astrophysics Data System (ADS)

    Iyer-Biswas, Srividya; Crooks, Gavin E.; Scherer, Norbert F.; Dinner, Aaron R.

    2014-07-01

    Recent imaging data for single bacterial cells reveal that their mean sizes grow exponentially in time and that their size distributions collapse to a single curve when rescaled by their means. An analogous result holds for the division-time distributions. A model is needed to delineate the minimal requirements for these scaling behaviors. We formulate a microscopic theory of stochastic exponential growth as a Master Equation that accounts for these observations, in contrast to existing quantitative models of stochastic exponential growth (e.g., the Black-Scholes equation or geometric Brownian motion). Our model, the stochastic Hinshelwood cycle (SHC), is an autocatalytic reaction cycle in which each molecular species catalyzes the production of the next. By finding exact analytical solutions to the SHC and the corresponding first passage time problem, we uncover universal signatures of fluctuations in exponential growth and division. The model makes minimal assumptions, and we describe how more complex reaction networks can reduce to such a cycle. We thus expect similar scalings to be discovered in stochastic processes resulting in exponential growth that appear in diverse contexts such as cosmology, finance, technology, and population growth.

  6. Noise in Exponential Growth

    NASA Astrophysics Data System (ADS)

    Iyer-Biswas, Srividya; Wright, Charles; Henry, Jon; Burov, Stas; Lin, Yihan; Crosson, Sean; Dinner, Aaron; Scherer, Norbert

    2013-03-01

    The interplay between growth and division of cells is has been studied in the context of exponential growth of bacterial cells (in suitable conditions) for decades. However, bulk culture studies obscure phenomena that manifest in single cells over many generations. We introduce a unique technology combining microfluidics, single-cell imaging, and quantitative analysis. This enables us to track the growth of single Caulobacter crescentus stalked cells over hundreds of generations. The statistics that we extract indicate a size thresholding mechanism for cell division and a non-trivial scaling collapse of division time distributions at different temperatures. In this talk I shall discuss these observations and a stochastic model of growth and division that captures all our observations with no free parameters.

  7. A Simulation To Model Exponential Growth.

    ERIC Educational Resources Information Center

    Appelbaum, Elizabeth Berman

    2000-01-01

    Describes a simulation using dice-tossing students in a population cluster to model the growth of cancer cells. This growth is recorded in a scatterplot and compared to an exponential function graph. (KHR)

  8. How well can the exponential-growth coalescent approximate constant-rate birth–death population dynamics?

    PubMed Central

    Stadler, Tanja; Vaughan, Timothy G.; Gavryushkin, Alex; Guindon, Stephane; Kühnert, Denise; Leventhal, Gabriel E.; Drummond, Alexei J.

    2015-01-01

    One of the central objectives in the field of phylodynamics is the quantification of population dynamic processes using genetic sequence data or in some cases phenotypic data. Phylodynamics has been successfully applied to many different processes, such as the spread of infectious diseases, within-host evolution of a pathogen, macroevolution and even language evolution. Phylodynamic analysis requires a probability distribution on phylogenetic trees spanned by the genetic data. Because such a probability distribution is not available for many common stochastic population dynamic processes, coalescent-based approximations assuming deterministic population size changes are widely employed. Key to many population dynamic models, in particular epidemiological models, is a period of exponential population growth during the initial phase. Here, we show that the coalescent does not well approximate stochastic exponential population growth, which is typically modelled by a birth–death process. We demonstrate that introducing demographic stochasticity into the population size function of the coalescent improves the approximation for values of R0 close to 1, but substantial differences remain for large R0. In addition, the computational advantage of using an approximation over exact models vanishes when introducing such demographic stochasticity. These results highlight that we need to increase efforts to develop phylodynamic tools that correctly account for the stochasticity of population dynamic models for inference. PMID:25876846

  9. Simulating Population Growth.

    ERIC Educational Resources Information Center

    Byington, Scott

    1997-01-01

    Presents a strategy to help students grasp the important implications of population growth. Involves an interactive demonstration that allows students to experience exponential and logistic population growth followed by a discussion of the implications of population-growth principles. (JRH)

  10. An Exponential Growth Learning Trajectory: Students' Emerging Understanding of Exponential Growth through Covariation

    ERIC Educational Resources Information Center

    Ellis, Amy B.; Ozgur, Zekiye; Kulow, Torrey; Dogan, Muhammed F.; Amidon, Joel

    2016-01-01

    This article presents an Exponential Growth Learning Trajectory (EGLT), a trajectory identifying and characterizing middle grade students' initial and developing understanding of exponential growth as a result of an instructional emphasis on covariation. The EGLT explicates students' thinking and learning over time in relation to a set of tasks…

  11. A Simple Mechanical Experiment on Exponential Growth

    ERIC Educational Resources Information Center

    McGrew, Ralph

    2015-01-01

    With a rod, cord, pulleys, and slotted masses, students can observe and graph exponential growth in the cord tension over a factor of increase as large as several hundred. This experiment is adaptable for use either in algebra-based or calculus-based physics courses, fitting naturally with the study of sliding friction. Significant parts of the…

  12. Exponential Growth of Nonlinear Ballooning Instability

    SciTech Connect

    Zhu, P.; Hegna, C. C.; Sovinec, C. R.

    2009-06-12

    Recent ideal magnetohydrodynamic (MHD) theory predicts that a perturbation evolving from a linear ballooning instability will continue to grow exponentially in the intermediate nonlinear phase at the same linear growth rate. This prediction is confirmed in ideal MHD simulations. When the Lagrangian compression, a measure of the ballooning nonlinearity, becomes of the order of unity, the intermediate nonlinear phase is entered, during which the maximum plasma displacement amplitude as well as the total kinetic energy continues to grow exponentially at the rate of the corresponding linear phase.

  13. Mutant number distribution in an exponentially growing population

    NASA Astrophysics Data System (ADS)

    Keller, Peter; Antal, Tibor

    2015-01-01

    We present an explicit solution to a classic model of cell-population growth introduced by Luria and Delbrück (1943 Genetics 28 491-511) 70 years ago to study the emergence of mutations in bacterial populations. In this model a wild-type population is assumed to grow exponentially in a deterministic fashion. Proportional to the wild-type population size, mutants arrive randomly and initiate new sub-populations of mutants that grow stochastically according to a supercritical birth and death process. We give an exact expression for the generating function of the total number of mutants at a given wild-type population size. We present a simple expression for the probability of finding no mutants, and a recursion formula for the probability of finding a given number of mutants. In the ‘large population-small mutation’ limit we recover recent results of Kessler and Levine (2014 J. Stat. Phys. doi:10.1007/s10955-014-1143-3) for a fully stochastic version of the process.

  14. 101 Ways to Teach About Exponential Growth and Its Consequences.

    ERIC Educational Resources Information Center

    Allen, Rodney F., Ed.

    Exponential growth is a mega-concept which has many applications. It is fundamental to understanding how and why systems work and fail, be they natural or man-made systems. Lessons/activities in this booklet are designed for Florida teachers to help provide their students with an understanding of the nature and implications of exponential growth.…

  15. Population growth and economic growth.

    PubMed

    Narayana, D L

    1984-01-01

    This discussion of the issues relating to the problem posed by population explosion in the developing countries and economic growth in the contemporary world covers the following: predictions of economic and social trends; the Malthusian theory of population; the classical or stationary theory of population; the medical triage model; ecological disaster; the Global 2000 study; the limits to growth; critiques of the Limits to Growth model; nonrenewable resources; food and agriculture; population explosion and stabilization; space and ocean colonization; and the limits perspective. The Limits to Growth model, a general equilibrium anti-growth model, is the gloomiest economic model ever constructed. None of the doomsday models, the Malthusian theory, the classical stationary state, the neo-Malthusian medical triage model, the Global 2000 study, are so far reaching in their consequences. The course of events that followed the publication of the "Limits to Growth" in 1972 in the form of 2 oil shocks, food shock, pollution shock, and price shock seemed to bear out formally the gloomy predictions of the thesis with a remarkable speed. The 12 years of economic experience and the knowledge of resource trends postulate that even if the economic pressures visualized by the model are at work they are neither far reaching nor so drastic. Appropriate action can solve them. There are several limitations to the Limits to Growth model. The central theme of the model, which is overshoot and collapse, is unlikely to be the course of events. The model is too aggregative to be realistic. It exaggerates the ecological disaster arising out of the exponential growth of population and industry. The gross underestimation of renewable resources is a basic flaw of the model. The most critical weakness of the model is its gross underestimation of the historical trend of technological progress and the technological possiblities within industry and agriculture. The model does correctly emphasize

  16. Exponential increases of RNA virus fitness during large population transmissions.

    PubMed Central

    Novella, I S; Duarte, E A; Elena, S F; Moya, A; Domingo, E; Holland, J J

    1995-01-01

    The great adaptability shown by RNA viruses is a consequence of their high mutation rates. Here we investigate the kinetics of virus fitness gains during repeated transfers of large virus populations in cell culture. Results always show that fitness increases exponentially. Low fitness clones exhibit regular increases observed as biphasic periods of exponential evolutionary improvement, while neutral clones show monophasic kinetics. These results are significant for RNA virus epidemiology, optimal handling of attenuated live virus vaccines, and routine laboratory procedures. PMID:7597039

  17. Exponential growth of bacteria: Constant multiplication through division

    NASA Astrophysics Data System (ADS)

    Hagen, Stephen J.

    2010-12-01

    The growth of a bacterial culture is one of the most familiar examples of exponential growth, with important consequences in biology and medicine. Bacterial growth involves more than just a rate constant. To sustain exponential growth, the cell must carefully coordinate the accumulation of mass, constant replication of the chromosome, and physical division. Hence, the growth rate is centrally important in any physical and chemical description of a bacterial cell. These aspects of bacterial growth can be described by empirical laws that suggest simple and intuitive models. Therefore, a quantitative discussion of bacterial growth could be a part of any undergraduate biophysics course. We present a general overview of some classic experimental studies and mathematical models of bacterial growth from a mostly physical perspective.

  18. Exponential order statistic models of software reliability growth

    NASA Technical Reports Server (NTRS)

    Miller, D. R.

    1985-01-01

    Failure times of a software reliabilty growth process are modeled as order statistics of independent, nonidentically distributed exponential random variables. The Jelinsky-Moranda, Goel-Okumoto, Littlewood, Musa-Okumoto Logarithmic, and Power Law models are all special cases of Exponential Order Statistic Models, but there are many additional examples also. Various characterizations, properties and examples of this class of models are developed and presented.

  19. Exponential order statistic models of software reliability growth

    NASA Technical Reports Server (NTRS)

    Miller, D. R.

    1986-01-01

    Failure times of a software reliability growth process are modeled as order statistics of independent, nonidentically distributed exponential random variables. The Jelinsky-Moranda, Goel-Okumoto, Littlewood, Musa-Okumoto Logarithmic, and Power Law models are all special cases of Exponential Order Statistic Models, but there are many additional examples also. Various characterizations, properties and examples of this class of models are developed and presented.

  20. Teaching Exponential Growth and Decay: Examples from Medicine

    ERIC Educational Resources Information Center

    Hobbie, Russell K.

    1973-01-01

    A treatment of exponential growth and decay is sketched which does not require knowledge of calculus, and hence, it can be applied to many cases in the biological and medical sciences. Some examples are bacterial growth, sterilization, clearance, and drug absorption. (DF)

  1. Exponential energy growth in adiabatically changing Hamiltonian systems

    NASA Astrophysics Data System (ADS)

    Pereira, Tiago; Turaev, Dmitry

    2015-01-01

    We show that the mixed phase space dynamics of a typical smooth Hamiltonian system universally leads to a sustained exponential growth of energy at a slow periodic variation of parameters. We build a model for this process in terms of geometric Brownian motion with a positive drift, and relate it to the steady entropy increase after each period of the parameters variation.

  2. Modeling Population Growth and Extinction

    ERIC Educational Resources Information Center

    Gordon, Sheldon P.

    2009-01-01

    The exponential growth model and the logistic model typically introduced in the mathematics curriculum presume that a population grows exclusively. In reality, species can also die out and more sophisticated models that take the possibility of extinction into account are needed. In this article, two extensions of the logistic model are considered,…

  3. Critical Mutation Rate Has an Exponential Dependence on Population Size in Haploid and Diploid Populations

    PubMed Central

    Aston, Elizabeth; Channon, Alastair; Day, Charles; Knight, Christopher G.

    2013-01-01

    Understanding the effect of population size on the key parameters of evolution is particularly important for populations nearing extinction. There are evolutionary pressures to evolve sequences that are both fit and robust. At high mutation rates, individuals with greater mutational robustness can outcompete those with higher fitness. This is survival-of-the-flattest, and has been observed in digital organisms, theoretically, in simulated RNA evolution, and in RNA viruses. We introduce an algorithmic method capable of determining the relationship between population size, the critical mutation rate at which individuals with greater robustness to mutation are favoured over individuals with greater fitness, and the error threshold. Verification for this method is provided against analytical models for the error threshold. We show that the critical mutation rate for increasing haploid population sizes can be approximated by an exponential function, with much lower mutation rates tolerated by small populations. This is in contrast to previous studies which identified that critical mutation rate was independent of population size. The algorithm is extended to diploid populations in a system modelled on the biological process of meiosis. The results confirm that the relationship remains exponential, but show that both the critical mutation rate and error threshold are lower for diploids, rather than higher as might have been expected. Analyzing the transition from critical mutation rate to error threshold provides an improved definition of critical mutation rate. Natural populations with their numbers in decline can be expected to lose genetic material in line with the exponential model, accelerating and potentially irreversibly advancing their decline, and this could potentially affect extinction, recovery and population management strategy. The effect of population size is particularly strong in small populations with 100 individuals or less; the exponential model has

  4. Iterative exponential growth of stereo- and sequence-controlled polymers

    NASA Astrophysics Data System (ADS)

    Barnes, Jonathan C.; Ehrlich, Deborah J. C.; Gao, Angela X.; Leibfarth, Frank A.; Jiang, Yivan; Zhou, Erica; Jamison, Timothy F.; Johnson, Jeremiah A.

    2015-10-01

    Chemists have long sought sequence-controlled synthetic polymers that mimic nature's biopolymers, but a practical synthetic route that enables absolute control over polymer sequence and structure remains a key challenge. Here, we report an iterative exponential growth plus side-chain functionalization (IEG+) strategy that begins with enantiopure epoxides and facilitates the efficient synthesis of a family of uniform >3 kDa macromolecules of varying sequence and stereoconfiguration that are coupled to produce unimolecular polymers (>6 kDa) with sequences and structures that cannot be obtained using traditional polymerization techniques. Selective side-chain deprotection of three hexadecamers is also demonstrated, which imbues each compound with the ability to dissolve in water. We anticipate that these new macromolecules and the general IEG+ strategy will find broad application as a versatile platform for the scalable synthesis of sequence-controlled polymers.

  5. [Population Growth and Development].

    ERIC Educational Resources Information Center

    Clausen, A. W.

    Rapid population growth as a central development problem, the proper domain of government in reducing population growth, and effective measures which can be taken to reduce fertility are examined. Rapid population growth puts a brake on development because it exacerbates the difficult choice between higher consumption now and the investment needed…

  6. Study on Biodegradation Process of Polyethylene Glycol with Exponential Glowth of Microbial Population

    NASA Astrophysics Data System (ADS)

    Watanabe, Masaji; Kawai, Fusako

    Biodegradation of polyethylene glycol is studied mathematically. A mathematical model for depolymerization process of exogenous type is described. When a degradation rate is a product of a time factor and a molecular factor, a time dependent model can be transformed into a time independent model, and techniques developed in previous studies can be applied to the time independent model to determine the molecular factor. The time factor can be determined assuming the exponential growth of the microbial population. Those techniques are described, and numerical results are presented. A comparison between a numerical result and an experimental result shows that the mathematical method is appropriate for practical applications.

  7. Impact of Population Growth

    ERIC Educational Resources Information Center

    Ehrlich, Paul R.; Holdren, John P.

    1971-01-01

    Discusses the interrelated crises in population growth, natural resources, and environmental quality. Major problems include population control, redirection of technology, closed resource cycles, equitable opportunity distribution and prosperity. Population growth is regarded as causing a disportionate world-wide negative environmental impact.…

  8. Exponential growth of codimensions of identities of algebras with unity

    NASA Astrophysics Data System (ADS)

    Zaicev, M. V.; Repovš, D.

    2015-10-01

    The asymptotic behaviour is studied of exponentially bounded sequences of codimensions of identities of algebras with unity. A series of algebras is constructed for which the base of the exponential increases by exactly 1 when an outer unity is adjoined to the original algebra. It is shown that the PI-exponents of unital algebras can take any value greater than 2, and the exponents of finite-dimensional unital algebras form a dense subset in the domain \\lbrack 2,∞). Bibliography: 34 titles.

  9. Teaching about Population Growth.

    ERIC Educational Resources Information Center

    Otero, George G., Jr., Comp.

    This teaching guide contains 20 activities on population growth for students in grades 6-12. The purpose is to help students gain the skills, knowledge, and understanding of population dynamics so that they can make rational decisions and take responsible action regarding population matters and public policy. Activities are organized around the…

  10. Exponential growth of dental schools in Chile: effects on academic, economic and workforce issues.

    PubMed

    Cartes-Velásquez, Ricardo Andrés

    2013-01-01

    In the last 30 years, Chile has undergone noteworthy economic development and an exponential growth in the access of its population to higher education. The aim of this paper was to review the changes in academic, economic and workforce issues that occurred as a consequence of the growth in supply of undergraduate dental vacancies between 1997 and 2011. Data collected from the Consejo de Educación Superior - CES, Comisión Nacional de Acreditación - CNA, and Instituto Nacional de Estadísticas de Chile - INE included these variables: number of dental schools, school type (private or traditional, see explanation below), city where the school is located, entry vacancies, total student enrollment, admission scores, percentile rank of dentistry as a university career, tuition fees, accreditation status, and number of inhabitants. There was an exponential increase in dental schools in Chile (5 to 34) that occurred in association with the rise in tuition fees (US$ 3900 to US$ 9800), a deterioration in the academic level of dental students (650 to 550 points in admission scores) and a predicted 77.5% oversupply of dentists by 2025, according to WHO criteria. The exponential increase in dental schools in Chile brought about negative consequences, such as increasing career costs, deterioration in the academic level of dental students, and an oversupply of dentists, associated with lower incomes and possibly leading to unemployment. Additional research should be conducted to determine whether an increase in the number of dentists can improve the population's access to dental care and reduce the oral disease burden. PMID:24346044

  11. Exponential growth of publications on carbon nanodots by Chinese authors

    PubMed Central

    Wang, Junqing; Choi, Hak Soo

    2015-01-01

    Publication statistics was retrieved on carbon nanodots (C-dots) from 2004 up till 2014 using the web of ScienceTM search engine. The number of publications from Chinese authors increased exponentially during this period. Till 2014 China mainland authors contributed 47% of the total publications. Publications on pharmacology and toxicology lagged far behind the publications on chemistry and material science, indicating that research is not solidly moving toward the direction of application. PMID:26380753

  12. Population growth and consumption.

    PubMed

    Chalkley, K

    1997-04-01

    The relationship between population growth, resource consumption, and environmental degradation is complex. The rise in "greenhouse gases" that will cause climatic change is clearly due to human activity, and pollutants are often concentrated in densely populated areas. However, even an area with a negative population growth, such as Russia, can experience severe environmental degradation due to poor management. Consumption patterns have the most effect on ozone depletion, while population growth threatens biodiversity of and within species through the destruction of ecosystems. Migration joins population growth and social factors, such as land inequality, as major causes of deforestation, and global demand for water is expected to increase faster than the rate of population growth. Coastal development and over-fishing threaten to deplete the oceans, while soil quality is threatened by inappropriate land use. Estimates of the earth's carrying capacity range from less than 3 billion to more than 44 billion people, indicating how difficult it is to assess this figure. Development efforts throughout the world may lead to human gains that will ultimately be negated by environmental losses. These factors have led to growing support for environmentally sustainable development. PMID:12319715

  13. Global population growth.

    PubMed

    Langmore, J

    1992-07-01

    The global population passed 5 billion in 1987. In the year 2000 the world's population will be more than 6 billion, increasing by 90-100 million each year. About 95% of future demographic growth will take place in developing countries. The number of school age children is projected to increase from 940 million in 1980 to 1280 million by the year 2000. Under current labor force growth projections in developing countries, around 1.6 billion new jobs will have to be created between 1980 and 2025, with nearly 1 billion of them in Asia. Population often increases at a more rapid rate than agricultural growth. Food production per capita has declined in 70 developing countries. Much of the projected population increase will take place in environmentally fragile regions of the developing world. Population pressures contribute to deforestation, desertification, and scarcity of clean water. The United Nations Population Fund has estimated that in Asia over 43% of women not using family planning would like to postpone, space, or limit their childbearing. Over half of the world's couples of reproductive age are now using contraception. Family planning to postpone the first birth and to eliminate late child bearing would reduce both child loss and maternal illness and death. Both infant and maternal mortality are greater with higher order births. Reducing average family size is an effective way of reducing infant and maternal mortality. The World Bank has given high priority to population assistance, with large programs in Bangladesh, Egypt, India, Indonesia, the Philippines, and Thailand. Population assistance provided by the Australian International Development Assistance Bureau totaled about $4.5 million during 1989-90 and is expected to be about $8 million during 1991-92. Australia should increase the proportion of its development assistance budget devoted to population, and family planning programs should increase to around $26 million in line with other major donors

  14. Slow Crack Growth of Brittle Materials With Exponential Crack-Velocity Formulation. Part 1; Analysis

    NASA Technical Reports Server (NTRS)

    Choi, Sung R.; Nemeth, Noel N.; Gyekenyesi, John P.

    2002-01-01

    Extensive slow-crack-growth (SCG) analysis was made using a primary exponential crack-velocity formulation under three widely used load configurations: constant stress rate, constant stress, and cyclic stress. Although the use of the exponential formulation in determining SCG parameters of a material requires somewhat inconvenient numerical procedures, the resulting solutions presented gave almost the same degree of simplicity in both data analysis and experiments as did the power-law formulation. However, the fact that the inert strength of a material should be known in advance to determine the corresponding SCG parameters was a major drawback of the exponential formulation as compared with the power-law formulation.

  15. Line transect estimation of population size: the exponential case with grouped data

    USGS Publications Warehouse

    Anderson, D.R.; Burnham, K.P.; Crain, B.R.

    1979-01-01

    Gates, Marshall, and Olson (1968) investigated the line transect method of estimating grouse population densities in the case where sighting probabilities are exponential. This work is followed by a simulation study in Gates (1969). A general overview of line transect analysis is presented by Burnham and Anderson (1976). These articles all deal with the ungrouped data case. In the present article, an analysis of line transect data is formulated under the Gates framework of exponential sighting probabilities and in the context of grouped data.

  16. [Poverty and population growth].

    PubMed

    1983-07-01

    In the mid-1970s, some 120 million Latin Americans were unable to satisfy their most basic material needs. 55 million of them were in extreme indigency, unable to satisfy their minimal food needs even by using their entire incomes for that purpose. The rapid rate of demographic growth in Latin America influences the growth of the poor strata, who in absolute and relative terms show the highest rates of population growth. Despite heterogeneity in the manifestations of poverty, the poor have certain traits in common: employment outside the modern sector, with low productivity and little hope of generating stable incomes, low consumption capability, and lack of political power. 1 of the great problems of economic development in Latin America is the exclusion of the poorest strata from employment in better paid jobs. The high rate of fertility and rapid population growth provoke a negative interaction between population and development, in which the poorest strata reproduce most rapidly, becoming even poorer. A program of family planning within a development effort providing employment and income is needed to mitigate the problem, and no avenue or effort of implementation should be neglected on ideological grounds. Between 1960-70, the share of the poorest 20% of the population declined from 3.1% to 2.5% of the toal income of the region, while that of the poorest 1/2 increased slightly from 13.4% to 13.9%. In 1970 the poorest 20% had a per capita income of about US $70/year. It has been estimated that the proportion of the poor in Latin America declined from 51% in 1960 to 40% in 1970 and 33% at present, but the absolute number of persons affected continues to increase. PMID:12339314

  17. Z-type control of populations for Lotka-Volterra model with exponential convergence.

    PubMed

    Zhang, Yunong; Yan, Xiaogang; Liao, Bolin; Zhang, Yinyan; Ding, Yaqiong

    2016-02-01

    The population control of the Lotka-Volterra model is one of the most important and widely investigated issues in mathematical ecology. In this study, assuming that birth rate is controllable and using the Z-type dynamic method, we develop Z-type control laws to drive the prey population and/or predator population to a desired state to keep species away from extinction and to improve ecosystem stability. A direct controller group is initially designed to control the prey and predator populations simultaneously. Two indirect controllers are then proposed for prey population control and predator population control by exerting exogenous measure on another species. All three control laws possess exponential convergence performances. Finally, the corresponding numerical simulations are performed. Results substantiate the theoretical analysis and effectiveness of such Z-type control laws for the population control of the Lotka-Volterra model. PMID:26644036

  18. Rapid growth of seed black holes in the early universe by supra-exponential accretion.

    PubMed

    Alexander, Tal; Natarajan, Priyamvada

    2014-09-12

    Mass accretion by black holes (BHs) is typically capped at the Eddington rate, when radiation's push balances gravity's pull. However, even exponential growth at the Eddington-limited e-folding time t(E) ~ few × 0.01 billion years is too slow to grow stellar-mass BH seeds into the supermassive luminous quasars that are observed when the universe is 1 billion years old. We propose a dynamical mechanism that can trigger supra-exponential accretion in the early universe, when a BH seed is bound in a star cluster fed by the ubiquitous dense cold gas flows. The high gas opacity traps the accretion radiation, while the low-mass BH's random motions suppress the formation of a slowly draining accretion disk. Supra-exponential growth can thus explain the puzzling emergence of supermassive BHs that power luminous quasars so soon after the Big Bang. PMID:25103410

  19. Rapid growth of seed black holes in the early universe by supra-exponential accretion

    NASA Astrophysics Data System (ADS)

    Alexander, Tal; Natarajan, Priyamvada

    2014-09-01

    Mass accretion by black holes (BHs) is typically capped at the Eddington rate, when radiation's push balances gravity's pull. However, even exponential growth at the Eddington-limited e-folding time tE ~ few × 0.01 billion years is too slow to grow stellar-mass BH seeds into the supermassive luminous quasars that are observed when the universe is 1 billion years old. We propose a dynamical mechanism that can trigger supra-exponential accretion in the early universe, when a BH seed is bound in a star cluster fed by the ubiquitous dense cold gas flows. The high gas opacity traps the accretion radiation, while the low-mass BH's random motions suppress the formation of a slowly draining accretion disk. Supra-exponential growth can thus explain the puzzling emergence of supermassive BHs that power luminous quasars so soon after the Big Bang.

  20. Exponential Growth and the Shifting Global Center of Gravity of Science Production, 1900-2011

    ERIC Educational Resources Information Center

    Zhang, Liang; Powell, Justin J. W.; Baker, David P.

    2015-01-01

    Long historical trends in scientific discovery led mid-20th century scientometricians to mark the advent of "big science"--extensive science production--and predicted that over the next few decades, the exponential growth would slow, resulting in lower rates of increase in production at the upper limit of a logistic curve. They were…

  1. Implicit and Explicit Knowledge of Linear and Exponential Growth in 5- and 9-Year-Olds

    ERIC Educational Resources Information Center

    Ebersbach, Mirjam; Resing, Wilma C. M.

    2008-01-01

    The present study examined children's implicit and explicit knowledge of linear and non-linear processes. Five- and nine-year-olds (N = 60) were asked to forecast linear and exponential growth by providing the corresponding number of beads. Implicit knowledge was assessed via the magnitudes of the forecasts; explicit knowledge was investigated…

  2. Understanding Exponential Growth: As Simple as a Drop in a Bucket.

    ERIC Educational Resources Information Center

    Goldberg, Fred; Shuman, James

    1984-01-01

    Provides procedures for a simple laboratory activity on exponential growth and its characteristic doubling time. The equipment needed consists of a large plastic bucket, an eyedropper, a stopwatch, an assortment of containers and graduated cylinders, and a supply of water. (JN)

  3. The mechanism of double-exponential growth in hyper-inflation

    NASA Astrophysics Data System (ADS)

    Mizuno, T.; Takayasu, M.; Takayasu, H.

    2002-05-01

    Analyzing historical data of price indices, we find an extraordinary growth phenomenon in several examples of hyper-inflation in which, price changes are approximated nicely by double-exponential functions of time. In order to explain such behavior we introduce the general coarse-graining technique in physics, the Monte Carlo renormalization group method, to the price dynamics. Starting from a microscopic stochastic equation describing dealers’ actions in open markets, we obtain a macroscopic noiseless equation of price consistent with the observation. The effect of auto-catalytic shortening of characteristic time caused by mob psychology is shown to be responsible for the double-exponential behavior.

  4. A magnetosome-associated cytochrome MamP is critical for magnetite crystal growth during the exponential growth phase.

    PubMed

    Taoka, Azuma; Eguchi, Yukako; Mise, Shingo; Oestreicher, Zachery; Uno, Fumio; Fukumori, Yoshihiro

    2014-09-01

    Magnetotactic bacteria use a specific set of conserved proteins to biomineralize crystals of magnetite or greigite within their cells in organelles called magnetosomes. Using Magnetospirillum magneticum AMB-1, we examined one of the magnetotactic bacteria-specific conserved proteins named MamP that was recently reported as a new type of cytochrome c that has iron oxidase activity. We found that MamP is a membrane-bound cytochrome, and the MamP content increases during the exponential growth phase compared to two other magnetosome-associated proteins on the same operon, MamA and MamK. To assess the function of MamP, we overproduced MamP from plasmids in wild-type (WT) AMB-1 and found that during the exponential phase of growth, these cells contained more magnetite crystals that were the same size as crystals in WT cells. Conversely, when the heme c-binding motifs within the mamP on the plasmid was mutated, the cells produced the same number of crystals, but smaller crystals than in WT cells during exponential growth. These results strongly suggest that during the exponential phase of growth, MamP is crucial to the normal growth of magnetite crystals during biomineralization. PMID:25048532

  5. Growth potential of exponential- and stationary-phase Salmonella Typhimurium during sausage fermentation.

    PubMed

    Birk, T; Henriksen, S; Müller, K; Hansen, T B; Aabo, S

    2016-11-01

    Raw meat for sausage production can be contaminated with Salmonella. For technical reasons, meat is often frozen prior to mincing but it is unknown how growth of Salmonella in meat prior to freezing affects its growth potential during sausage fermentation. We investigated survival of exponential- and stationary-phase Salmonella Typhimurium (DT12 and DTU292) during freezing at -18°C and their subsequent growth potential during 72h sausage fermentation at 25°C. After 0, 7 and >35d of frozen storage, sausage batters were prepared with NaCl (3%) and NaNO2 (0, 100ppm) and fermented with and without starter culture. With no starter culture, both strains grew in both growth phases. In general, a functional starter culture abolished S. Typhimurium growth independent of growth phase and we concluded that ensuring correct fermentation is important for sausage safety. However, despite efficient fermentation, sporadic growth of exponential-phase cells of S. Typhimurium was observed drawing attention to the handling and storage of sausage meat. PMID:27423056

  6. Improved exponential product cum dual to product type estimator of population mean

    NASA Astrophysics Data System (ADS)

    Singh, B. K.; Choudhury, Sanjib; Kumar, Abhishek

    2013-09-01

    In the present paper, an efficient exponential product cum dual to product type estimator has been proposed to estimate the population mean of the study variable by using simple random sampling scheme. The bias and mean squared error of the proposed estimator have been obtained up to the first order of approximation. A comparison has been made with existing similar estimators. The estimator has shown its efficiency over other estimators in terms of mean squared error (MSE). The numerical demonstrations have been made to show the gain in the estimator under study.

  7. Population growth and environmental degradation in Malawi.

    PubMed

    Kalipeni, E

    1992-01-01

    Malawi has been ranked by the World Bank as one of the poorest countries in Africa. Malawi's only resources are its people and fertile soil, which comprises about 55% of land area. Environmental degradation and population growth conditions in Malawi were used to illustrate the model of environmental degradation linked to population pressure on land resources and government development strategies that favored large-scale agricultural farms. The result has been deforestation, overgrazing, overuse of land for subsistence, and increased population density. The argument was that population growth in some developing countries has been so rapid that environmental collapse is the result. The theoretical framework linking population growth, environment, and resources emphasized processes: 1) the precursor stage of underlying causes; 2) the problem phase with potential ecological and economic decline; and 3) consequences (environmental decline, reduction in food production systems, and reduction in standard of living). The precursors were identified as an agrarian society, lack of a population policy, and emphasis on large families. The problems were rapid population growth and immigration from Mozambique, which led to increased demand for trees for fuel and consequent deforestation, increased demand for arable land and consequent landlessness, increased investment in livestock and consequent overgrazing, and continued population momentum which was a financial burden to government and resulted in increased labor competition. The ecological consequences were soil erosion, degradation of vegetation, and water supply contamination and decline. Eventually, famines will occur and lead to disease, migration, deserted villages, urbanization, unemployment, ethnic conflicts, and political unrest. Population was estimated at 8.75 million in 1990, with exponential growth expected. Completed family size was 6.6 children per woman. Even replacement fertility would mean growth for 50 more

  8. Forecasting Financial Extremes: A Network Degree Measure of Super-Exponential Growth.

    PubMed

    Yan, Wanfeng; van Tuyll van Serooskerken, Edgar

    2015-01-01

    Investors in stock market are usually greedy during bull markets and scared during bear markets. The greed or fear spreads across investors quickly. This is known as the herding effect, and often leads to a fast movement of stock prices. During such market regimes, stock prices change at a super-exponential rate and are normally followed by a trend reversal that corrects the previous overreaction. In this paper, we construct an indicator to measure the magnitude of the super-exponential growth of stock prices, by measuring the degree of the price network, generated from the price time series. Twelve major international stock indices have been investigated. Error diagram tests show that this new indicator has strong predictive power for financial extremes, both peaks and troughs. By varying the parameters used to construct the error diagram, we show the predictive power is very robust. The new indicator has a better performance than the LPPL pattern recognition indicator. PMID:26339793

  9. Forecasting Financial Extremes: A Network Degree Measure of Super-Exponential Growth

    PubMed Central

    Yan, Wanfeng; van Tuyll van Serooskerken, Edgar

    2015-01-01

    Investors in stock market are usually greedy during bull markets and scared during bear markets. The greed or fear spreads across investors quickly. This is known as the herding effect, and often leads to a fast movement of stock prices. During such market regimes, stock prices change at a super-exponential rate and are normally followed by a trend reversal that corrects the previous overreaction. In this paper, we construct an indicator to measure the magnitude of the super-exponential growth of stock prices, by measuring the degree of the price network, generated from the price time series. Twelve major international stock indices have been investigated. Error diagram tests show that this new indicator has strong predictive power for financial extremes, both peaks and troughs. By varying the parameters used to construct the error diagram, we show the predictive power is very robust. The new indicator has a better performance than the LPPL pattern recognition indicator. PMID:26339793

  10. Power Law Versus Exponential Form of Slow Crack Growth of Advanced Structural Ceramics: Dynamic Fatigue

    NASA Technical Reports Server (NTRS)

    Choi, Sung R.; Gyekenyesi, John P.

    2002-01-01

    The life prediction analysis based on an exponential crack velocity formulation was examined using a variety of experimental data on glass and advanced structural ceramics in constant stress-rate ("dynamic fatigue") and preload testing at ambient and elevated temperatures. The data fit to the strength versus In (stress rate) relation was found to be very reasonable for most of the materials. It was also found that preloading technique was equally applicable for the case of slow crack growth (SCG) parameter n > 30. The major limitation in the exponential crack velocity formulation, however, was that an inert strength of a material must be known priori to evaluate the important SCG parameter n, a significant drawback as compared to the conventional power-law crack velocity formulation.

  11. U.S. Population Growth.

    ERIC Educational Resources Information Center

    Dillner, Harry

    This autoinstructional lesson deals with the study of man and his environment. No previous experience or learning in this field is required. Emphasis is placed on analysis of population growth and the impact population growth and trends have on natural resource depletion. The behavioral objectives (five) are listed. The study guide for the…

  12. Population Growth: Crisis and Challenge.

    ERIC Educational Resources Information Center

    Beaton, John R., Ed.; Doberenz, Alexander R., Ed.

    The proceedings of this first annual symposium on population growth considers the consequences of this growth, along with possible means of regulation. Topics of speeches include: Population Outlook in Asia (Irene Taeuber); Malnutrition is a Problem of Ecology (Paul Gyorgy); The Leisure Explosion (E. H. Storey); Effects of Pollution on Population…

  13. Observation of Self-Amplified Spontaneous Emission and Exponential Growth at 530 nm

    NASA Astrophysics Data System (ADS)

    Milton, S. V.; Gluskin, E.; Biedron, S. G.; Dejus, R. J.; den Hartog, P. K.; Galayda, J. N.; Kim, K.-J.; Lewellen, J. W.; Moog, E. R.; Sajaev, V.; Sereno, N. S.; Travish, G.; Vinokurov, N. A.; Arnold, N. D.; Benson, C.; Berg, W.; Biggs, J. A.; Borland, M.; Carwardine, J. A.; Chae, Y.-C.; Decker, G.; Deriy, B. N.; Erdmann, M. J.; Friedsam, H.; Gold, C.; Grelick, A. E.; Hahne, M. W.; Harkay, K. C.; Huang, Z.; Lessner, E. S.; Lill, R. M.; Lumpkin, A. H.; Makarov, O. A.; Markovich, G. M.; Meyer, D.; Nassiri, A.; Noonan, J. R.; Pasky, S. J.; Pile, G.; Smith, T. L.; Soliday, R.; Tieman, B. J.; Trakhtenberg, E. M.; Trento, G. F.; Vasserman, I. B.; Walters, D. R.; Wang, X. J.; Wiemerslage, G.; Xu, S.; Yang, B.-X.

    2000-07-01

    Experimental evidence for self-amplified spontaneous emission (SASE) at 530 nm is reported. The measurements were made at the low-energy undulator test line facility at the Advanced Photon Source, Argonne National Laboratory. The experimental setup and details of the experimental results are presented, as well as preliminary analysis. This experiment extends to shorter wavelengths the operational knowledge of a linac-based SASE free-electron laser and explicitly shows the predicted exponential growth in intensity of the optical pulse as a function of length along the undulator.

  14. Exponential energy growth due to slow parameter oscillations in quantum mechanical systems

    NASA Astrophysics Data System (ADS)

    Turaev, Dmitry

    2016-05-01

    It is shown that a periodic emergence and destruction of an additional quantum number leads to an exponential growth of energy of a quantum mechanical system subjected to a slow periodic variation of parameters. The main example is given by systems (e.g., quantum billiards and quantum graphs) with periodically divided configuration space. In special cases, the process can also lead to a long period of cooling that precedes the acceleration, and to the desertion of the states with a particular value of the quantum number.

  15. Deterministic versus stochastic aspects of superexponential population growth models

    NASA Astrophysics Data System (ADS)

    Grosjean, Nicolas; Huillet, Thierry

    2016-08-01

    Deterministic population growth models with power-law rates can exhibit a large variety of growth behaviors, ranging from algebraic, exponential to hyperexponential (finite time explosion). In this setup, selfsimilarity considerations play a key role, together with two time substitutions. Two stochastic versions of such models are investigated, showing a much richer variety of behaviors. One is the Lamperti construction of selfsimilar positive stochastic processes based on the exponentiation of spectrally positive processes, followed by an appropriate time change. The other one is based on stable continuous-state branching processes, given by another Lamperti time substitution applied to stable spectrally positive processes.

  16. An integrated model for predictive microbiology and simultaneous determination of lag phase duration and exponential growth rate

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A new mechanistic growth model was developed to describe microbial growth under isothermal conditions. The development of the mathematical model was based on the fundamental phenomenon of microbial growth, which is normally a three-stage process that includes lag, exponential, and stationary phases...

  17. Population Growth: Stretching the Limits.

    ERIC Educational Resources Information Center

    Brouse, Deborah E.

    1990-01-01

    Three population education activities that can be used to illustrate the effects of uncontrolled population growth are presented. Included are "Crowding Can Be Seedy," which uses seeds; "Something for Everyone," which illustrates competition for resources; and "More or Less," which illustrates the relationship between humans and the environment.…

  18. Canada's population: growth and dualism.

    PubMed

    Beaujot, R P

    1978-04-01

    In Canada the current 1.3% population growth rate is causing some concern. Those concerned argue that such a rate of growth in combination with high levels of consumption could jeopardize the country's resource base and its comfortable style of living. Many Canadians are questioning high levels of immigration, for now that the fertility level is below replacement level, net immigration contributes substantially to population growth (over 1/3 in 1976). The growing proportion of non-Europeans among recent immigrants is causing resentment, and, in a tight job market, immigrants are regarded as threats to the World War 2 baby boom cohort who are now at working ages. The baby boom generation also puts stress on housing and health services, and it will increase the need for pension checks as it ages. Although French fertility is no longer high and immigration is no longer dominated by the British, the French group's 200-year struggle to preserve its identity continues on in the current effort of the Quebec government to enforce the use of French language by law within that province. Geography and climate dictate another demographic fact that divides the country and pervades its history. In addition to intense regionalism, uneven population distribution is responsible for 2 other concerns: the rapid growth of several already large cities and depopulation of many small communities. Focus in this discussion is on Canada's population growth in the past and as projected for the future, historical and current fertility, mortality and immigration trends, the search for a new immigration policy, the impact of the baby boom generation on the population's age structure and the problems this creates, and recent shifts in population distribution and in the country's ethnic and linguistic makeup. The population policy proposals evolved thus far involve to a great extent the use of immigration as a lever for achieving given population objectives. PMID:12335577

  19. A Minimal Model of the E. Coli Bacterium in Exponential Phase Growth

    NASA Astrophysics Data System (ADS)

    Maitra, Arijit; Dill, Ken

    2013-03-01

    We study the fundamental process of exponential cell growth in the E. Coli bacterium under conditions of extracellular glucose limitations using a minimalistic reaction framework by accounting for energy metabolism and protein synthesis. The cell model has three nodes: ATP, the ribosomal and the non-ribosomal proteins. Their interdependencies and dynamics are wrapped in a system of ordinary differential equations. The formulations of their interactive fluxes capture the essence of cellular physiology under conditions of growth. We solve the model numerically for different glucose concentrations, and, where possible, explore the cell states analytically under steady state conditions. We verify the model predictions with available experimental data. The model lets us quantify the coupling between energy generation and biomass growth. An implication of this model is that it provides a layout to compute the fitness landscape in terms of the parameters of the cells, such as the protein translation rates, to make hypotheses about possible routes for cellular evolution under glucose limitation. Laufer Center for Phys. and Quant. Biology.

  20. Population Growth: Family Planning Programs.

    ERIC Educational Resources Information Center

    Doberenz, Alexander R., Ed.; Taylor, N. Burwell G., Ed.

    These proceedings of the second annual symposium on population growth bring together speeches and panel discussions on family planning programs. Titles of speeches delivered are: Communicating Family Planning (Mrs. Jean Hutchinson); Effects of New York's Abortion Law Change (Dr. Walter Rogers); The Law and Birth Control, Sterilization and Abortion…

  1. Nutrition, Development, and Population Growth

    ERIC Educational Resources Information Center

    Berg, Alan

    1973-01-01

    Focuses on the problem of malnutrition in developing countries through a description of its interrelationships with human development, national economies, economic growth and income, agricultural advances, the crisis in infant feeding practices, new foods, and the population dilemma. Outlines possible future policy directions to significantly…

  2. Entrainability of cell cycle oscillator models with exponential growth of cell mass.

    PubMed

    Nakao, Mitsuyuki; Enkhkhudulmur, Tsog-Erdene; Katayama, Norihiro; Karashima, Akihiro

    2014-01-01

    Among various aspects of cell cycle, understanding synchronization mechanism of cell cycle is important because of the following reasons. (1)Cycles of cell assembly should synchronize to form an organ. (2) Synchronizing cell cycles are required to experimental analysis of regulatory mechanisms of cell cycles. (3) Cell cycle has a distinct phase relationship with the other biological rhythms such as circadian rhythm. However, forced as well as mutual entrainment mechanisms are not clearly known. In this study, we investigated entrainability of cell cycle models of yeast cell under the periodic forcing to both of the cell mass and molecular dynamics. Dynamics of models under study involve the cell mass growing exponentially. In our result, they are shown to allow only a limited frequency range for being entrained by the periodic forcing. In contrast, models with linear growth are shown to be entrained in a wider frequency range. It is concluded that if the cell mass is included in the cell cycle regulation, its entrainability is sensitive to a shape of growth curve assumed in the model. PMID:25571564

  3. Political economy of population growth.

    PubMed

    Mehta, S; Mehta, H S

    1987-01-01

    Tracing the origin of political economy as a class-science, this paper focuses on the political economy of population growth. Exposing the limitations of Malthusian ideas and their invalidity even for the capitalist economies, it discusses the subsequent revival of the Malthusian model during the period of de-colonization and the misinterpretation of the relationship between population growth and development in the developing and developed countries. Taking India, China, and Japan as some case studies, the paper examines the relationship between birth rate levels and some correlates. It elaborates on the Indian experience, emphasizing the association of population growth with poverty and unemployment and lays bare some of the hidden causes of these phenomena. The authors examine some interstate variations in India and identify constraints and prospects of the existing population policy. The paper proposes outlines of a democratic population policy as an integral part of India's development strategy which should recognize human beings not simply as consumers but also as producers of material values. It pleads for 1) restructuring of property relations; 2) bringing down the mortality rates and raising of the literacy levels, especially among females; and 3) improving nutritional levels, as prerequisites for bringing down birth rates. PMID:12179026

  4. Anomalous Growth of Aging Populations

    NASA Astrophysics Data System (ADS)

    Grebenkov, Denis S.

    2016-04-01

    We consider a discrete-time population dynamics with age-dependent structure. At every time step, one of the alive individuals from the population is chosen randomly and removed with probability q_k depending on its age, whereas a new individual of age 1 is born with probability r. The model can also describe a single queue in which the service order is random while the service efficiency depends on a customer's "age" in the queue. We propose a mean field approximation to investigate the long-time asymptotic behavior of the mean population size. The age dependence is shown to lead to anomalous power-law growth of the population at the critical regime. The scaling exponent is determined by the asymptotic behavior of the probabilities q_k at large k. The mean field approximation is validated by Monte Carlo simulations.

  5. Teaching the Verhulst Model: A Teaching Experiment in Covariational Reasoning and Exponential Growth

    ERIC Educational Resources Information Center

    Castillo-Garsow, Carlos

    2010-01-01

    Both Thompson and the duo of Confrey and Smith describe how students might be taught to build "ways of thinking" about exponential behavior by coordinating the covariation of two changing quantities, however, these authors build exponential behavior from different meanings of covariation. Confrey and Smith advocate beginning with discrete additive…

  6. The Cultural Divide: Exponential Growth in Classical 2D and Metabolic Equilibrium in 3D Environments

    PubMed Central

    Kanlaya, Rattiyaporn; Borkowski, Kamil; Schwämmle, Veit; Dai, Jie; Joensen, Kira Eyd; Wojdyla, Katarzyna; Carvalho, Vasco Botelho; Fey, Stephen J.

    2014-01-01

    Introduction Cellular metabolism can be considered to have two extremes: one is characterized by exponential growth (in 2D cultures) and the other by a dynamic equilibrium (in 3D cultures). We have analyzed the proteome and cellular architecture at these two extremes and found that they are dramatically different. Results Structurally, actin organization is changed, microtubules are increased and keratins 8 and 18 decreased. Metabolically, glycolysis, fatty acid metabolism and the pentose phosphate shunt are increased while TCA cycle and oxidative phosphorylation is unchanged. Enzymes involved in cholesterol and urea synthesis are increased consistent with the attainment of cholesterol and urea production rates seen in vivo. DNA repair enzymes are increased even though cells are predominantly in Go. Transport around the cell – along the microtubules, through the nuclear pore and in various types of vesicles has been prioritized. There are numerous coherent changes in transcription, splicing, translation, protein folding and degradation. The amount of individual proteins within complexes is shown to be highly coordinated. Typically subunits which initiate a particular function are present in increased amounts compared to other subunits of the same complex. Summary We have previously demonstrated that cells at dynamic equilibrium can match the physiological performance of cells in tissues in vivo. Here we describe the multitude of protein changes necessary to achieve this performance. PMID:25222612

  7. Metabolic Flux Analysis during the Exponential Growth Phase of Saccharomyces cerevisiae in Wine Fermentations

    PubMed Central

    Quirós, Manuel; Martínez-Moreno, Rubén; Albiol, Joan; Morales, Pilar; Vázquez-Lima, Felícitas; Barreiro-Vázquez, Antonio; Ferrer, Pau; Gonzalez, Ramon

    2013-01-01

    As a consequence of the increase in global average temperature, grapes with the adequate phenolic and aromatic maturity tend to be overripe by the time of harvest, resulting in increased sugar concentrations and imbalanced C/N ratios in fermenting musts. This fact sets obvious additional hurdles in the challenge of obtaining wines with reduced alcohols levels, a new trend in consumer demands. It would therefore be interesting to understand Saccharomyces cerevisiae physiology during the fermentation of must with these altered characteristics. The present study aims to determine the distribution of metabolic fluxes during the yeast exponential growth phase, when both carbon and nitrogen sources are in excess, using continuous cultures. Two different sugar concentrations were studied under two different winemaking temperature conditions. Although consumption and production rates for key metabolites were severely affected by the different experimental conditions studied, the general distribution of fluxes in central carbon metabolism was basically conserved in all cases. It was also observed that temperature and sugar concentration exerted a higher effect on the pentose phosphate pathway and glycerol formation than on glycolysis and ethanol production. Additionally, nitrogen uptake, both quantitatively and qualitatively, was strongly influenced by environmental conditions. This work provides the most complete stoichiometric model used for Metabolic Flux Analysis of S. cerevisiae in wine fermentations employed so far, including the synthesis and release of relevant aroma compounds and could be used in the design of optimal nitrogen supplementation of wine fermentations. PMID:23967264

  8. Long-wave theory for a new convective instability with exponential growth normal to the wall.

    PubMed

    Healey, J J

    2005-05-15

    A linear stability theory is presented for the boundary-layer flow produced by an infinite disc rotating at constant angular velocity in otherwise undisturbed fluid. The theory is developed in the limit of long waves and when the effects of viscosity on the waves can be neglected. This is the parameter regime recently identified by the author in a numerical stability investigation where a curious new type of instability was found in which disturbances propagate and grow exponentially in the direction normal to the disc, (i.e. the growth takes place in a region of zero mean shear). The theory describes the mechanisms controlling the instability, the role and location of critical points, and presents a saddle-point analysis describing the large-time evolution of a wave packet in frames of reference moving normal to the disc. The theory also shows that the previously obtained numerical solutions for numerically large wavelengths do indeed lie in the asymptotic long-wave regime, and so the behaviour and mechanisms described here may apply to a number of cross-flow instability problems. PMID:16105773

  9. Environmental impact of population growth

    NASA Astrophysics Data System (ADS)

    Naylor, Rosamond; Matson, Pamela

    Earth's population currently numbers 5.4 billion; even given optimistic assumptions for reduction in growth rates, the number will double by the middle of the next century with most of the increase in the developing countries. Rapid population growth in the developing world raises the fundamental dilemma of how to alleviate chronic hunger and poverty in the short run while preserving the atmosphere and ecosystem services required for long-term human and biospheric sustenance. This dilemma, and the compromises required to solve it, were discussed by twenty-five researchers from five countries at the Aspen Global Change Institute 1992 Summer Science Session III, Food, Conservation, and Global Environmental Change: Is Compromise Possible?, held from August 16 to 28, in Aspen, Colo.

  10. Population growth can be checked.

    PubMed

    Shukla, J P

    Since independence, India's population size has doubled. The rate of growth was 2.5% during 1971-81, an increase from the rate of 2.15% observed during the 1951-61 period. The increase indicated that efforts to decrease population growth have not succeeded. The implications with respect to food, housing, clothing, education, and health facilities, which are fundamental to improving the physical quality of life, are severe. This demographic trend is a serious impediment to progress. The population growth is due to a constant birthrate and a sharp decline in mortality. Reducing the birthrate is necessary to reduce the rate of growth. An attitudinal change adopting the norm of family limitation should be encouraged through propaganda, socioeconomic programs, and religious and cultural organizations. Other measures to bring about a decline in the birthrate include: increasing the marriage age, and expanding educational and employment opportunities for women and girls. These measures will require substantial effort and time. Incentives may show more immediate effects. Monetary incentives are not desired because of the possibility of misuse. However the government could assume responsibility for the education and guarantee employment of children of couples who have only one child, and provide free education to children of couples with only 2 children. These incentives are not likely to be misused, can be available to all segments of the population, and involve no immediate large financial burden on the government. In addition, scholarships to the Harijan students should be limited to 2 per family. If these measures are accepted, they could quickly reduce the birth rate. PMID:12311944

  11. Human Population: Fundamentals of Growth and Change.

    ERIC Educational Resources Information Center

    Stauffer, Cheryl Lynn, Ed.

    This booklet focuses on eight elements of population dynamics: "Population Growth and Distribution"; "Natural Increase and Future Growth"; "Effect of Migration on Population Growth"; "Three Patterns of Population Change"; "Patterns of World Urbanization"; "The Status of Women"; "World Health"; and "Environmental Relationships." Charts and graphs…

  12. [Population growth and the environment].

    PubMed

    Hogan, D J

    1991-01-01

    The impact of population growth on the enviornment has been extensively researched; it consists of the depletion of resources (agricultural land absorbed by urban expansion, loss of soils, desertification, loss of biodiversity, less availability of minerals, dwindling of petroleum reserves) and the degradation of natural resources (air and water pollution). For politicians, journalists, and environmentalists, population growth is identified as the principal villain, which is a unidirectional and negative opinion. Demography is supposed to examine the negative and positive effects of the environment-population relationship; however, it is postulated that there has not been much produced in the last 2 centuries in this area. Examination of the research literature does not indicate any view that transcends the Malthusian vision, although a few empirical studies exist (Hogan, 1989). Durham (1979) identified the replacement of subsistence agriculture by export-oriented agriculture as the key factor in overpopulation in El Salvador and Honduras that led to migrations and international conflicts. Tudela (1987) related a similar process in the Mexican state of Tabasco, where a period of malnutrition was accompanied by the expansion of export agriculture and nutritional improvements emanated only from recapturing subsistence agriculture. Fearnside (1986) researched the dynamics of the occupation and destruction of Amazonia. However, Kahn and Simon went further and denied the existence of real environmental problems: population is the ultimate resource, and the more minds, the more good ideas and solutions for any problem. However, in all these cases of pure or modified Malthusianism the relation of population/resources is reduced to a unidimensional relationship; and fertility, mortality, migration, marriage, and age structure receive little attention. A prime candidate for the attention of population specialists should be migration and patterns of settlement and their

  13. Slow Crack Growth of Brittle Materials With Exponential Crack-Velocity Formulation. Part 2; Constant Stress Rate Experiments

    NASA Technical Reports Server (NTRS)

    Choi, Sung R.; Nemeth, Noel N.; Gyekenyesi, John P.

    2002-01-01

    The previously determined life prediction analysis based on an exponential crack-velocity formulation was examined using a variety of experimental data on glass and advanced structural ceramics in constant stress rate and preload testing at ambient and elevated temperatures. The data fit to the relation of strength versus the log of the stress rate was very reasonable for most of the materials. Also, the preloading technique was determined equally applicable to the case of slow-crack-growth (SCG) parameter n greater than 30 for both the power-law and exponential formulations. The major limitation in the exponential crack-velocity formulation, however, was that the inert strength of a material must be known a priori to evaluate the important SCG parameter n, a significant drawback as compared with the conventional power-law crack-velocity formulation.

  14. Slow Crack Growth of Brittle Materials With Exponential Crack-Velocity Formulation. Part 3; Constant Stress and Cyclic Stress Experiments

    NASA Technical Reports Server (NTRS)

    Choi, Sung R.; Nemeth, Noel N.; Gyekenyesi, John P.

    2002-01-01

    The previously determined life prediction analysis based on an exponential crack-velocity formulation was examined using a variety of experimental data on advanced structural ceramics tested under constant stress and cyclic stress loading at ambient and elevated temperatures. The data fit to the relation between the time to failure and applied stress (or maximum applied stress in cyclic loading) was very reasonable for most of the materials studied. It was also found that life prediction for cyclic stress loading from data of constant stress loading in the exponential formulation was in good agreement with the experimental data, resulting in a similar degree of accuracy as compared with the power-law formulation. The major limitation in the exponential crack-velocity formulation, however, was that the inert strength of a material must be known a priori to evaluate the important slow-crack-growth (SCG) parameter n, a significant drawback as compared with the conventional power-law crack-velocity formulation.

  15. Novel representation of exponential functions of power series which arise in statistical mechanics and population genetics

    NASA Astrophysics Data System (ADS)

    Ma, W. T.; Sandri, G. vH.; Sarkar, S.

    1991-05-01

    We use the convolution power of infinite sequences to obtain a novel representation of exponential functions of power series which often arise in statistical mechanics. We thus obtain new formulas for the configuration and cluster integrals of pairwise interacting systems of molecules in an imperfect gas. We prove that the asymptotic behaviour of the Luria-Delbrück distribution is pn∼ cn-2. We derive a new, simple and computationally efficient recursion relation for pn.

  16. Finite amplitude folding: transition from exponential to layer length controlled growth

    NASA Astrophysics Data System (ADS)

    Schmalholz, Stefan M.; Podladchikov, Yuri Yu.

    2000-06-01

    A new finite amplitude theory of folding has been developed by the combined application of analytical, asymptotic and numerical methods. The existing linear folding theory has been improved by considering nonlinear weakening of membrane stresses, which is caused by the stretching of the competent layer during folding. The resulting theory is simple and accurate for finite amplitude folding and is not restricted to infinitesimal amplitudes, as is the classical linear theory of folding. Two folding modes relevant to most natural settings were considered: (i) both membrane and fiber stresses are viscous during folding (the 'viscous' mode); (ii) membrane stresses are viscous whereas fiber stresses are elastic (the 'viscoelastic' mode). For these two modes, the new theory provided a nonlinear, ordinary differential equation for fold amplification during shortening and an estimate for crossover amplitude and strain where the linear theory breaks down. A new analytical relationship for amplitude versus strain was derived for strains much larger than the crossover strain. The new relationship agrees well with complete 2D numerical solutions for up to threefold shortening, whereas the exponential solution predicted by the linear theory is inaccurate by orders of magnitude for strains larger than the crossover value. Analysis of the crossover strain and amplitude as a function of the controlling parameters demonstrates that the linear theory is only applicable for a small range of amplitudes and strains. This renders unreliable the large strain prediction of wavelength selection based on the linear theory, especially for folding at high competence contrasts. To resolve this problem, the new finite amplitude theory is used to calculate the evolution of the growth rate spectra during progressive folding. The growth rate spectra exhibited splitting of a single maximum (predicted by the linear theory) into two maxima at large strains. This bifurcation occurred for both

  17. Finite amplitude folding: transition from exponential to layer length controlled growth

    NASA Astrophysics Data System (ADS)

    Schmalholz, Stefan M.; Podladchikov, Yuri Yu.

    2000-09-01

    A new finite amplitude theory of folding has been developed by the combined application of analytical, asymptotic and numerical methods. The existing linear folding theory has been improved by considering nonlinear weakening of membrane stresses, which is caused by the stretching of the competent layer during folding. The resulting theory is simple and accurate for finite amplitude folding and is not restricted to infinitesimal amplitudes, as is the classical linear theory of folding. Two folding modes relevant to most natural settings were considered: (i) both membrane and fiber stresses are viscous during folding (the 'viscous' mode); (ii) membrane stresses are viscous whereas fiber stresses are elastic (the 'viscoelastic' mode). For these two modes, the new theory provided a nonlinear, ordinary differential equation for fold amplification during shortening and an estimate for crossover amplitude and strain where the linear theory breaks down. A new analytical relationship for amplitude versus strain was derived for strains much larger than the crossover strain. The new relationship agrees well with complete 2D numerical solutions for up to threefold shortening, whereas the exponential solution predicted by the linear theory is inaccurate by orders of magnitude for strains larger than the crossover value. Analysis of the crossover strain and amplitude as a function of the controlling parameters demonstrates that the linear theory is only applicable for a small range of amplitudes and strains. This renders unreliable the large strain prediction of wavelength selection based on the linear theory, especially for folding at high competence contrasts. To resolve this problem, the new finite amplitude theory is used to calculate the evolution of the growth rate spectra during progressive folding. The growth rate spectra exhibited splitting of a single maximum (predicted by the linear theory) into two maxima at large strains. This bifurcation occurred for both

  18. Migration, population growth, and development.

    PubMed

    1983-01-01

    In the 30 years between 1950 and 1980, the population of the developing world almost doubled--from 1.7 to 3.3 billion. Among the most conspicuous signs of this increase are the growth of cities and, in some areas, international labor migration. Since 1950 the cities in Africa, Asia, and Latin America have been growing more than twice as fast as those in North America and Europe. Some of the biggest cities are growing fastest--by as much as 8 percent each year. At this rate they will double in less than a decade. About 40 percent of this growth is due to migration and 60 percent to the children born in the cities to natives and the newly arrived migrants. Altogether, about one billion people (1,000 million) now live in developing-country cities, where fewer than 300 million lived in 1950. About 15 to 20 million workers, mostly from developing countries, are now international migrants. About half travel to Europe and the US, the rest to other developing countries. Many of the migrants, especially to the US, Europe, or the Middle East, want to bring their families eventually and settle permanently. Migration to African destinations is more likely to be temporary or seasonal, while Latin American and Asian patterns are mixed. Policy makers in developing countries are voicing concern about the highly visible social, economic, and political problems created by rapid urbanization and by large-scale international labor migration. While governments have tried a variety of policies to influence population distribution, most have been limited in scope and had little success. As long as birth rates remain high in some areas and large differences in wages exist between jobs in different places, most of these policies have little hope of stopping or reversing long-term trends. Family planning programs, although they do not create immediate jobs or higher wages in rural areas, can help to reduce the high birth rates that produce an ever-increasing supply of potential migrants

  19. Deoxyribonucleic Acid Synthesis During Exponential Growth and Microcyst Formation in Myxococcus xanthus

    PubMed Central

    Rosenberg, Eugene; Katarski, Mary; Gottlieb, Peter

    1967-01-01

    Myxococcus xanthus in exponential phase with a generation time of 270 min contained a period of 50 min during which deoxyribonucleic acid (DNA) synthesis did not take place. After induction of microcysts by the glycerol technique, the DNA content increased 19%. Autoradiographic experiments demonstrated that the DNA made after glycerol induction was not evenly distributed among the microcysts. The distribution of grains per microcyst fits the following model of chromosome replication: in exponential phase, each daughter cell receives two chromosomes which are replicated sequentially during 80% of the divison cycle; after microcyst induction, no chromosomes are initiated. Mathematical formulas were derived which predict the kinetics and discrete probability distribution for several chromosome models. PMID:6032514

  20. Human population and atmospheric carbon dioxide growth dynamics: Diagnostics for the future

    NASA Astrophysics Data System (ADS)

    Hüsler, A. D.; Sornette, D.

    2014-10-01

    We analyze the growth rates of human population and of atmospheric carbon dioxide by comparing the relative merits of two benchmark models, the exponential law and the finite-time-singular (FTS) power law. The later results from positive feedbacks, either direct or mediated by other dynamical variables, as shown in our presentation of a simple endogenous macroeconomic dynamical growth model describing the growth dynamics of coupled processes involving human population (labor in economic terms), capital and technology (proxies by CO2 emissions). Human population in the context of our energy intensive economies constitutes arguably the most important underlying driving variable of the content of carbon dioxide in the atmosphere. Using some of the best databases available, we perform empirical analyses confirming that the human population on Earth has been growing super-exponentially until the mid-1960s, followed by a decelerated sub-exponential growth, with a tendency to plateau at just an exponential growth in the last decade with an average growth rate of 1.0% per year. In contrast, we find that the content of carbon dioxide in the atmosphere has continued to accelerate super-exponentially until 1990, with a transition to a progressive deceleration since then, with an average growth rate of approximately 2% per year in the last decade. To go back to CO2 atmosphere contents equal to or smaller than the level of 1990 as has been the broadly advertised goals of international treaties since 1990 requires herculean changes: from a dynamical point of view, the approximately exponential growth must not only turn to negative acceleration but also negative velocity to reverse the trend.

  1. Population growth rates: issues and an application.

    PubMed Central

    Godfray, H Charles J; Rees, Mark

    2002-01-01

    Current issues in population dynamics are discussed in the context of The Royal Society Discussion Meeting 'Population growth rate: determining factors and role in population regulation'. In particular, different views on the centrality of population growth rates to the study of population dynamics and the role of experiments and theory are explored. Major themes emerging include the role of modern statistical techniques in bringing together experimental and theoretical studies, the importance of long-term experimentation and the need for ecology to have model systems, and the value of population growth rate as a means of understanding and predicting population change. The last point is illustrated by the application of a recently introduced technique, integral projection modelling, to study the population growth rate of a monocarpic perennial plant, its elasticities to different life-history components and the evolution of an evolutionarily stable strategy size at flowering. PMID:12396521

  2. Approximate models for the study of exponential changed quantities: Application on the plasma waves growth rate or damping

    SciTech Connect

    Xaplanteris, C. L.; Xaplanteris, L. C.; Leousis, D. P.

    2014-03-15

    Many physical phenomena that concern the research these days are basically complicated because of being multi-parametric. Thus, their study and understanding meets with big if not unsolved obstacles. Such complicated and multi-parametric is the plasmatic state as well, where the plasma and the physical quantities that appear along with it have chaotic behavior. Many of those physical quantities change exponentially and at most times they are stabilized by presenting wavy behavior. Mostly in the transitive state rather than the steady state, the exponentially changing quantities (Growth, Damping etc) depend on each other in most cases. Thus, it is difficult to distinguish the cause from the result. The present paper attempts to help this difficult study and understanding by proposing mathematical exponential models that could relate with the study and understanding of the plasmatic wavy instability behavior. Such instabilities are already detected, understood and presented in previous publications of our laboratory. In other words, our new contribution is the study of the already known plasmatic quantities by using mathematical models (modeling and simulation). These methods are both useful and applicable in the chaotic theory. In addition, our ambition is to also conduct a list of models useful for the study of chaotic problems, such as those that appear into the plasma, starting with this paper's examples.

  3. Hispanic Population Growth and Rural Income Inequality

    ERIC Educational Resources Information Center

    Parrado, Emilio A.; Kandel, William A.

    2010-01-01

    We analyze the relationship between Hispanic population growth and changes in U.S. rural income inequality from 1990 through 2000. Applying comparative approaches used for urban areas we disentangle Hispanic population growth's contribution to inequality by comparing and statistically modeling changes in the family income Gini coefficient across…

  4. Lack of synchronization between iron uptake and cell growth leads to iron overload in Saccharomyces cerevisiae during post-exponential growth modes

    PubMed Central

    Park, Jinkyu; McCormick, Sean P.; Chakrabarti, Mrinmoy; Lindahl, Paul A.

    2014-01-01

    Fermenting cells growing exponentially on rich (YPAD) medium transitioned to a slow-growing state as glucose levels declined and their metabolism shifted to respiration. During exponential growth, Fe import and cell growth rates were matched, affording an approximately invariant cellular Fe concentration. During the transitionary period, the high-affinity Fe import rate declined slower than the cell growth rate declined, causing Fe to accumulate, initially as FeIII oxyhydroxide nanoparticles but eventually as mitochondrial and vacuolar Fe. Once in slow-growth mode, Fe import and cell growth rates were again matched, and the cellular Fe concentration was again approximately invariant. Fermenting cells grown on minimal medium (MM) grew more slowly during exponential phase and transitioned to a true stationary state as glucose levels declined. The Fe concentration of MM cells that just entered stationary state was similar to that of YPAD cells, but MM cells continued to accumulate Fe in stationary state. Fe initially accumulated as nanoparticles and high-spin FeII species, but vacuolar FeIII also eventually accumulated. Surprisingly, Fe-packed 5-day-old MM cells suffered no more ROS damage than younger cells, suggesting that Fe concentration alone does not accurately predict the extent of ROS damage. The mode and rate of growth at the time of harvesting dramatically affected cellular Fe content. A mathematical model of Fe metabolism in a growing cell was developed. The model included Fe import via a regulated high-affinity pathway and an unregulated low-affinity pathway. Fe import from the cytosol into vacuoles and mitochondria, and nanoparticle formation were also included. The model captured essential trafficking behavior, demonstrating that cells regulate Fe import in accordance with their overall growth rate and that they misregulate Fe import when nanoparticles accumulate. The lack of regulation of Fe in yeast is perhaps unique compared to the tight regulation of

  5. The Growth of the Black Metropolitan Population.

    ERIC Educational Resources Information Center

    Taeuber, Conrad; Mosher, William T.

    The urbanization of the black population is a relatively recent phenomenon. Historically, migration has been the major source of the growth of the black population in the large cities of the North, yet the migration from nonmetropolitan to metropolitan areas has been going long enough to have established a substantial black population in the…

  6. A new mechanistic growth model for simultaneous determination of lag phase duration and exponential growth rate and a new Belehdradek-type model for evaluating the effect of temperature on growth rate

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A new mechanistic growth model was developed to describe microbial growth under isothermal conditions. The new mathematical model was derived from the basic observation of bacterial growth that may include lag, exponential, and stationary phases. With this model, the lag phase duration and exponen...

  7. Transition to independence by subadult beavers (Castor canadensis) in an unexploited, exponentially growing population

    USGS Publications Warehouse

    DeStefano, S.; Koenen, Kiana K. G.; Henner, C.M.; Strules, J.

    2006-01-01

    We conducted a 4-year study of beavers Castor canadensis to compare the movements, survival and habitat of adults established in existing colonies to juveniles dispersing to new sites in a region with high beaver densities along a suburban-rural gradient. Estimates of annual survival were high for adult and juvenile beavers. Of nine known mortalities, seven (78%) were juveniles. Mortalities occurred during spring-summer, and none during fall-winter. There was a trend toward higher-to-lower survival along the suburban-rural gradient, respectively. Human-induced mortality (e.g. trapping and shooting) was higher in rural areas, whereas nonhuman-induced mortality (e.g. disease, accidents) was higher in suburban areas. Fifteen (14 subadults and one adult) beavers moved from natal colonies to other areas. The average dispersal distance for subadults was 4.5 km (SE = 1.0) along streams or rivers, or 3.5 km (SE = 0.7) straight-line point-to-point. Most dispersal movements were made in spring (April-June). In two cases, individual subadults made return movements from their dispersal sites back to their natal colonies. Dispersal sites tended to be in smaller, shallower wetlands or streams and in areas with higher overstorey canopy closure compared with natal colonies. Woody vegetation usually preferred by beavers for food tended to be less common at dispersal sites than at natal colonies. In regions with high densities of beaver, dispersing juveniles are likely to attempt to colonize lower quality sites. High densities of beavers also lead to more human-beaver conflicts and, in Massachusetts, the pest control management options in place during the past decade have been ineffectual at controlling population levels. Alternately, in regions with no beavers or very low densities and where reintroductions are being attempted, the landscape matrix surrounding release sites should include suitable sites for dispersing young to establish colonies.

  8. Production of Thiol Species From An Exponential Growth Diatom Under Copper Exposure

    NASA Astrophysics Data System (ADS)

    Tang, D.; Shafer, M. M.; Karner, D. A.; Armstrong, D. E.; Schauer, J.

    2003-12-01

    The intracellar induction of phytochelatins is a well documented response of eukaryotic microorganisms to aqueous metal exposure. The extracellular release of thiolic compounds from algal species has been observed; and in some cases, this release can contribute a significant fraction of the uncharacterized metal-complexing ligands. Glutathione (GSH) or cysteine is among the detectable thiols excreted. A quantitative assessment of the excretion of thiols from algae cells into growth media is needed to assess the significance of biogenic-thiols as a source of strong ligands in natural waters and as a "forgotten" route in sulfur biogeochemical cycle. Unbuffered growth media (e.g., without adding complexing ligand such as EDTA) have only rarely been used to study the possible release of metal-complexing ligands from algal species, and the ligand titration techniques used varied considerably. The majority of culture studies have applied metal-buffered media. A direct comparison of released ligands under buffered and unbuffered conditions is lacking, partially due to the inherent difficulties of the titration methods applied. Using HPLC with fluorescence detection of thiol-monobromobimane derivatives, we were able to follow the dynamic change of GSH released in both media types during algal growth: (1) the cell quotas for thiols and pigments varied (mostly decreases) with growth time. Therefore, pigment-normalized cellular thiol concentrations were more or less conservative. (2) GSH was released into both the EDTA-buffered and -unbuffered growth media at similar concentrations. (3) at similar available Cu concentrations, EDTA possibly enhanced, rather than hindered, the release of GSH.

  9. A population growth model forced by random, episodic disturbances

    NASA Astrophysics Data System (ADS)

    Peckham, S. D.

    2011-12-01

    As a first step to quantify and better understand the nature of thresholds in ecosystems, a prototype population dynamics model has been developed and analyzed for the case where a population is subjected to random, episodic disturbances. This model assumes that disturbances occur at random times (following a Poisson event process) and have random magnitudes that determine the fraction of the population that survives the disturbance. Disturbances may be events such as fire, drought, disease or infestation. Between disturbances, the model assumes that population growth is deterministic and can be modeled by an exponential or logistic equation. The model is characterized by time, t, and four other parameters: the initial population size, N0, the per capita growth rate, r, the expected number of disturbance events per unit time, λ , and μ = E(X), where X is the random fraction (between 0 and 1) of the population that survives a given disturbance. What is nice about this simple, stochastic model is that it is mathematically tractable and clearly exhibits threshold behavior that can be computed explicitly in terms of the model parameters. In particular, the long-term behavior of the model is characterized by an easily-computed indicator that is a function of the model parameters. Whenever the model parameters are such that this indicator is less than zero, the expected value of the random population size declines over time and is unsustainable. But whenever it is greater than zero, the expected population size grows, despite the random disturbances. The case where the indicator is zero therefore represents a type of critical threshold for this problem that determines whether or not the population is likely to survive the disturbances. A number of analytic results will be presented along with numerical results from a large number of simulations.

  10. Population priorities: the challenge of continued rapid population growth

    PubMed Central

    Turner, Adair

    2009-01-01

    Rapid population growth continues in the least developed countries. The revisionist case that rapid population could be overcome by technology, that population density was advantageous, that capital shallowing is not a vital concern and that empirical investigations had not proved a correlation between high population growth and low per capita income was both empirically and theoretically flawed. In the modern world, population density does not play the role it did in nineteenth-century Europe and rates of growth in some of today's least developed nations are four times than those in nineteenth-century Europe, and without major accumulation of capital per capita, no major economy has or is likely to make the low- to middle-income transition. Though not sufficient, capital accumulation for growth is absolutely essential to economic growth. While there are good reasons for objecting to the enforced nature of the Chinese one-child policy, we should not underestimate the positive impact which that policy has almost certainly had and will have over the next several decades on Chinese economic performance. And a valid reticence about telling developing countries that they must contain fertility should not lead us to underestimate the severely adverse impact of high fertility rates on the economic performance and prospects of many countries in Africa and the Middle East. PMID:19770149

  11. Population priorities: the challenge of continued rapid population growth.

    PubMed

    Turner, Adair

    2009-10-27

    Rapid population growth continues in the least developed countries. The revisionist case that rapid population could be overcome by technology, that population density was advantageous, that capital shallowing is not a vital concern and that empirical investigations had not proved a correlation between high population growth and low per capita income was both empirically and theoretically flawed. In the modern world, population density does not play the role it did in nineteenth-century Europe and rates of growth in some of today's least developed nations are four times than those in nineteenth-century Europe, and without major accumulation of capital per capita, no major economy has or is likely to make the low- to middle-income transition. Though not sufficient, capital accumulation for growth is absolutely essential to economic growth. While there are good reasons for objecting to the enforced nature of the Chinese one-child policy, we should not underestimate the positive impact which that policy has almost certainly had and will have over the next several decades on Chinese economic performance. And a valid reticence about telling developing countries that they must contain fertility should not lead us to underestimate the severely adverse impact of high fertility rates on the economic performance and prospects of many countries in Africa and the Middle East. PMID:19770149

  12. Population Growth Types in India, 1961-71

    ERIC Educational Resources Information Center

    Chakravarti, A. K.

    1976-01-01

    An effective means of cartographic representation of India's population growth and its spatial characteristics is the focus of this paper. A population growth index and population growth types are discussed. (Author/ND)

  13. Five proposals re China's population growth control.

    PubMed

    Liu, Z; Wu, C; Lin, F

    1983-01-01

    China's population was 540 million in 1949. By the end of 1978 the population will reach 960 million, representing a 2% average annual growth rate. High population growth 1) is costly, 2) makes finding employment difficult, since there is little still land still to be reclaimed and agricultural productivity cannot be upgraded if backward farming techniques are used simply to employ more people, and 3) reduces the quality of material and cutural life. Nearly half of consumer funds accumulated in 1949-1977 was spent to provide basic needs for China's 600 million people. Housing has especially suffered: average per capita living space is only 2 square meters in some cities. With over 100 million primary school children and tens of millions in secondary schools, education funds must be allocated to the lower grades, to higher education's detriment. Each generation's age structure determines the next generation's reproduction scale and speed. This historical principle leads to the following: 1) population growth will continue to be vigorous given growth at a 2% rate, or if a percentage of rural (30%) and urban (10%) couples continue to have more than 2 children, or if every couple only has 2 children; 2) population stagnation requires continuous, persistent efforts, abolishing 2 or more children and encouraging one child per couple. Stagnation can be reached by 2008, with 1,200 million people. Political and ideological education combined with effective economic measures must solve the population problem. 5 strong measures must be taken: 1) economic policies and incentives should assist couples with one or no child, 2) every means should be used to communicate the population problem to the people, 3) population control should be part of the national economy program, 4) 3 births should be prohibited and one child per couple advocated, and 5) a permanent "population committee" should be established to insure ongoing population programs, policies, study, and evaluation

  14. Vietnam's campaign to reduce population growth.

    PubMed

    Haub, C

    1999-10-01

    This paper reports campaigns to reduce the population growth in Vietnam. In July, red banners flew above the broad boulevard in Hanoi proclaiming World Population Day. This widespread public attention to population issues is not surprising, given the country's sharp reduction in fertility and widespread citizen support for smaller families. Since 1961, Vietnam has been trying to formulate a policy to reduce the population rate growth. The policy was a reaction to the results of the 1960 Census of the Democratic Republic of Vietnam and reflected long-standing concerns over food shortages, as well as a desire to improve women's health and welfare. After the reunification in 1975, the policy was extended to the entire country. Since then, Vietnam's growth rate has been declining, suggesting that the national campaign for smaller families is succeeding in changing deeply held attitudes and perceptions, in addition to current practices. While the fertility decline in Vietnam may not be the world's fastest, the success of the national population policy has forever altered the country's prospect for population growth. PMID:12295331

  15. How Population Growth Affects Linkage Disequilibrium

    PubMed Central

    Rogers, Alan R.

    2014-01-01

    The “LD curve” relates the linkage disequilibrium (LD) between pairs of nucleotide sites to the distance that separates them along the chromosome. The shape of this curve reflects natural selection, admixture between populations, and the history of population size. This article derives new results about the last of these effects. When a population expands in size, the LD curve grows steeper, and this effect is especially pronounced following a bottleneck in population size. When a population shrinks, the LD curve rises but remains relatively flat. As LD converges toward a new equilibrium, its time path may not be monotonic. Following an episode of growth, for example, it declines to a low value before rising toward the new equilibrium. These changes happen at different rates for different LD statistics. They are especially slow for estimates of σd2, which therefore allow inferences about ancient population history. For the human population of Europe, these results suggest a history of population growth. PMID:24907258

  16. Population growth and sustainable development in China.

    PubMed

    Gui, S

    1998-12-01

    This article identifies the adverse impacts of population growth in China and offers suggestions for attaining sustainable development. Although China has below replacement level fertility, population will continue to increase. Chinese demographers project that the total fertility rate will average 2.1 each year until 2010, 2.1 until 2050, or 1.88 until 2010 and 1.6 during 2010-2050 under high, medium, and low variants, respectively. Total population would number 1.69 billion, 1.50 billion, or 1.46 billion under various projections, respectively, by 2050. Continued growth is expected to seriously slow economic development, to hinder improvements in the quality of and full use of human resources, to depress increases in per-capita economic development levels, and to impact on reasonable use of resources and environmental protection. The averting of 5 million births would save 35.5 billion yuan. Population growth has reduced the per-capita share of cultivated land from 0.19 to 0.08 hectares during 1952-95. There are about 150-190 million surplus rural laborers. Registered unemployment in cities was 3.1% in 1997. 11.5 million were laid-off workers. The working-age population will exceed 900 million during 2007-26. China's gross national product (GNP) was the 8th highest in the world in 1990, but its per-capita GNP was in 100th place. China's abundant natural resources are seriously reduced when population is considered. Environmental damage is already evident. Population growth needs to be controlled through family planning, an old-age social security program, and long-term population policies. Society needs healthier births and childbearing and better educated children. PMID:12321930

  17. Lag Phase Is a Distinct Growth Phase That Prepares Bacteria for Exponential Growth and Involves Transient Metal Accumulation

    PubMed Central

    Rolfe, Matthew D.; Rice, Christopher J.; Lucchini, Sacha; Pin, Carmen; Thompson, Arthur; Cameron, Andrew D. S.; Alston, Mark; Stringer, Michael F.; Betts, Roy P.; Baranyi, József; Peck, Michael W.

    2012-01-01

    Lag phase represents the earliest and most poorly understood stage of the bacterial growth cycle. We developed a reproducible experimental system and conducted functional genomic and physiological analyses of a 2-h lag phase in Salmonella enterica serovar Typhimurium. Adaptation began within 4 min of inoculation into fresh LB medium with the transient expression of genes involved in phosphate uptake. The main lag-phase transcriptional program initiated at 20 min with the upregulation of 945 genes encoding processes such as transcription, translation, iron-sulfur protein assembly, nucleotide metabolism, LPS biosynthesis, and aerobic respiration. ChIP-chip revealed that RNA polymerase was not “poised” upstream of the bacterial genes that are rapidly induced at the beginning of lag phase, suggesting a mechanism that involves de novo partitioning of RNA polymerase to transcribe 522 bacterial genes within 4 min of leaving stationary phase. We used inductively coupled plasma mass spectrometry (ICP-MS) to discover that iron, calcium, and manganese are accumulated by S. Typhimurium during lag phase, while levels of cobalt, nickel, and sodium showed distinct growth-phase-specific patterns. The high concentration of iron during lag phase was associated with transient sensitivity to oxidative stress. The study of lag phase promises to identify the physiological and regulatory processes responsible for adaptation to new environments. PMID:22139505

  18. Comparison of logistic equations for population growth.

    PubMed

    Jensen, A L

    1975-12-01

    Two different forms of the logistic equation for population growth appear in the ecological literature. In the form of the logistic equation that appears in recent ecology textbooks the parameters are the instantaneous rate of natural increase per individual and the carrying capacity of the environment. In the form of the logistic equation that appears in some older literature the parameters are the instantaneous birth rate per individual and the carrying capacity. The decision whether to use one form or the other depends on which form of the equation is biologically more realistic. In this study the form of the logistic equation in which the instantaneous birth rate per individual is a parameter is shown to be more realistic in terms of the birth and death processes of population growth. Application of the logistic equation to calculate yield from an exploited fish population also shows that the parameters must be the instantaneous birth rate per individual and the carrying capacity. PMID:1203427

  19. On the theory of global population growth

    NASA Astrophysics Data System (ADS)

    Kapitza, Sergei P.

    2010-12-01

    Ours is an epoch of global demographic revolution, a time of a rapid transition from explosive population growth to a low reproduction level. This, possibly the most momentous change ever witnessed by humankind has, first and foremost, important implications for the dynamics of population. But it also affects billions of people in all aspects of their lives, and it is for this reason that demographic processes have grown into a vast problem, both globally and in Russia. Their fundamental understanding will to a large extent impact the present, the short-term future following the current critical epoch, the stable and uniform global development and its priorities, and indeed global security. Quantitative treatment of historical processes is reached using the phenomenological theory of mankind's population growth. This theory relies on the concepts and methods of physics and its conclusions should take into account the ideas of economics and genetics.

  20. Impact of demographic policy on population growth.

    PubMed

    Podyashchikh, P

    1968-01-01

    Various bourgeois theories, including the reactionary Malthusianism and its variants, challenge the Marxist-Leninist revolutionary theory on the growth of population. Bourgeois science maintains that unchanging biological laws of proliferation form the foundation of social life. Malthus, in his "An Essay on the Principle of Population," contends that population increases in a geometric rate, while means of subsistence tend to increase only in an arithmetic rate: neither the way of production nor social conditions but this law of nature in control of proliferation had been the cause of overpopulation, which again leads to misery, hunger, and unemployment. From this follows the possible conclusion that the working classes should be concerned not about how to change the social order but how to reduce the number of childbirths. Progressive science views the laws of social life in a totally different way. Marxism-Leninism teaches that population size, despite the markedly important role played by it in historical progress, fails to represent that main force of social progress which determines the mode of production and of the distribution of material goods, but just the reverse: the mode of production determines the growth of population, the changes in its density and composition. Marxism-Leninism teaches that each historical stage of production (slavery, feudalism, capitalism) has its own special, historically valid demographic law. Bourgeois science maintains that humankind faces an absolute overpopulation caused by the means of production lagging behind the growth of population. Actually this is only a relative overpopulation due to the fact that capitalistic production is subjected to the interests of increasing capitalistic profit and not to those of meeting the demands of population. In socialist countries, production is incessantly developing and expanding, and employment of the entire productive population is ensured. Consequently, the problem of relative

  1. Simulation of population growth and structure of the population

    NASA Astrophysics Data System (ADS)

    Maksymowicz, A. Z.

    2002-08-01

    A computer study of population growth and biological ageing in the Penna model is presented. The stress is put on the analysis of the age structure and the distribution of 'bad' mutations m in the population. Results of computer simulation are compared with the simplest logistic model approach which ignores genetic contribution to the life game and accounts only for death due to limited environmental capacity, the Verhulst factor. The Penna model accounts also for genetic load and results of the simulation show that the final population essentially consists of the fittest individuals, as is expected. A more detailed analysis of the genome structure Δ( m) discloses significant marks of the history. The main conclusions are: (a) there is a clear correlation between population n, age a and the number m of bad mutations and (b) there is no correlation between particular configurations Δ( m) of genomes of the same m and the fraction of the population of this characteristics Δ( m). A typical run takes a couple of hours on an HP EXEMPLAR machine, and for a population of about n=10 6.

  2. Stochastic dynamics and logistic population growth

    NASA Astrophysics Data System (ADS)

    Méndez, Vicenç; Assaf, Michael; Campos, Daniel; Horsthemke, Werner

    2015-06-01

    The Verhulst model is probably the best known macroscopic rate equation in population ecology. It depends on two parameters, the intrinsic growth rate and the carrying capacity. These parameters can be estimated for different populations and are related to the reproductive fitness and the competition for limited resources, respectively. We investigate analytically and numerically the simplest possible microscopic scenarios that give rise to the logistic equation in the deterministic mean-field limit. We provide a definition of the two parameters of the Verhulst equation in terms of microscopic parameters. In addition, we derive the conditions for extinction or persistence of the population by employing either the momentum-space spectral theory or the real-space Wentzel-Kramers-Brillouin approximation to determine the probability distribution function and the mean time to extinction of the population. Our analytical results agree well with numerical simulations.

  3. Stochastic dynamics and logistic population growth.

    PubMed

    Méndez, Vicenç; Assaf, Michael; Campos, Daniel; Horsthemke, Werner

    2015-06-01

    The Verhulst model is probably the best known macroscopic rate equation in population ecology. It depends on two parameters, the intrinsic growth rate and the carrying capacity. These parameters can be estimated for different populations and are related to the reproductive fitness and the competition for limited resources, respectively. We investigate analytically and numerically the simplest possible microscopic scenarios that give rise to the logistic equation in the deterministic mean-field limit. We provide a definition of the two parameters of the Verhulst equation in terms of microscopic parameters. In addition, we derive the conditions for extinction or persistence of the population by employing either the momentum-space spectral theory or the real-space Wentzel-Kramers-Brillouin approximation to determine the probability distribution function and the mean time to extinction of the population. Our analytical results agree well with numerical simulations. PMID:26172687

  4. Segregated growth kinetics of Escherichia coli DH5α-NH36 in exponential-fed perfusion culture for pDNA vaccine production.

    PubMed

    Munguía-Soto, Rodolfo; García-Rendón, Aurora; Garibay-Escobar, Adriana; Guerrero-Germán, Patricia; Tejeda-Mansir, Armando

    2015-01-01

    The clinical demand of plasmid DNA (pDNA) has been increasing constantly. An exponential-fed perfusion (EFP) culture is a new mode for plasmid production for clinical trials and commercialization. However, the culture conditions may lead to cell filamentation and growth cessation. In this study, the variation of the physiological state and the plasmid contents of Escherichia coli DH5α hosting pVAX1-NH36 in an EFP culture for application as a Leishmaniasis vaccine was investigated. The culture performance was monitored using flow cytometry (FC) and real-time quantitative PCR. The FC studies showed a high viability of cell population and a constant distribution of complexity and size. A high homogeneity of pDNA (>95 % of supercoiled) was obtained, which might be attributed to a better culture environment. The obtained plasmid specific and volumetric yields of 1.8 mg/g dcw and 36.5 mg/L represent typical values for laboratory-scale plasmid production in a defined medium. A segregated kinetic model of the perfusion system was developed and fitted to the experimental data (R(2) > 0.96). A practical conclusion of this work is that a space-time yield analysis of a bioprocess requires a viability evaluation. This new strategy of culture operation might help in the efficient production of pDNA for therapeutic use. PMID:25556882

  5. Design issues for population growth models

    PubMed Central

    López Fidalgo, J.; Ortiz Rodríguez, I.M.

    2010-01-01

    We briefly review and discuss design issues for population growth and decline models. We then use a flexible growth and decline model as an illustrative example and apply optimal design theory to find optimal sampling times for estimating model parameters, specific parameters and interesting functions of the model parameters for the model with two real applications. Robustness properties of the optimal designs are investigated when nominal values or the model is mis-specified, and also under a different optimality criterion. To facilitate use of optimal design ideas in practice, we also introduce a website for generating a variety of optimal designs for popular models from different disciplines. PMID:21647244

  6. Maximum likelihood estimation of population growth rates based on the coalescent.

    PubMed Central

    Kuhner, M K; Yamato, J; Felsenstein, J

    1998-01-01

    We describe a method for co-estimating 4Nemu (four times the product of effective population size and neutral mutation rate) and population growth rate from sequence samples using Metropolis-Hastings sampling. Population growth (or decline) is assumed to be exponential. The estimates of growth rate are biased upwards, especially when 4Nemu is low; there is also a slight upwards bias in the estimate of 4Nemu itself due to correlation between the parameters. This bias cannot be attributed solely to Metropolis-Hastings sampling but appears to be an inherent property of the estimator and is expected to appear in any approach which estimates growth rate from genealogy structure. Sampling additional unlinked loci is much more effective in reducing the bias than increasing the number or length of sequences from the same locus. PMID:9584114

  7. The small RNA, DsrA, is essential for the low temperature expression of RpoS during exponential growth in Escherichia coli.

    PubMed Central

    Sledjeski, D D; Gupta, A; Gottesman, S

    1996-01-01

    dsrA encodes a small, untranslated RNA. When over-expressed, DsrA antagonizes the H-NS-mediated silencing of numerous promoters. Cells devoid of DsrA grow normally and show little change in the expression of a number of H-NS-silenced genes. Expression of a transcriptional fusion of lacZ to dsrB, the gene next to dsrA, is significantly lower in cells carrying mutations in dsrA. All expression of beta-galactosidase from the dsrB::lacZ fusion is also dependent on the stationary phase sigma factor, RpoS. DsrA RNA was found to regulate dsrB::lacZ indirectly, by modulating RpoS synthesis. Levels of RpoS protein are substantially lower in a dsrA mutant, both in stationary and exponential phase cells. Mutations in dsrA decrease the expression of an RpoS::LacZ translational fusion, but not a transcriptional fusion, suggesting that DsrA is acting after transcription initiation. While RpoS expression is very low in exponential phase at temperatures of 30 degrees C and above, at 20 degrees C there is substantial synthesis of RpoS during exponential growth, all dependent on DsrA RNA. dsrA expression is also increased at low temperatures. These results suggest a new role for RpoS during exponential growth at low temperatures, mediated by DsrA. Images PMID:8670904

  8. Rural population growth and living conditions.

    PubMed

    Li, N; Zhu, C

    1991-01-01

    The problem of the effect of population growth on subsistence conditions is addressed by developing generalized premises, principles, and methods for quantifying standards or conditions for growth. This method is applied to 1989 data for Nanzheng Country, China. Background information is provided on an experiment made public in 1985 and implemented in 1986 by the Family Planning (FP) Department of Nanzheng County of Shaanxi Province in Hongmiao District in which the following conditions were placed on bearing a second child: 1) income must be 20% higher than the average village income level, and breeders must have an average income of not 400 yuan/year, crop planters not 300 yuan/year, textile weavers not 200 yuan/year, and industrial and subsidiary production workers not 400 yuan/year (generally 4 pigs or 100 chickens or ducks) or 2) 100 income-producing trees must be planted around he residential area/family plot or stony fields must be transformed into arable land under the contract responsibility system, or groves, orchards, or tea plantations must be planted. These conditions must be met one year prior to proposing to have a second child. The approval rate in 1986-88 was 88.7%, and the second parity rate was 78.4%. Deteriorated conditions had not yet occurred in this country when this proposal was made. The premises considered important in preparing assistance conditions were determined. 1) Conditions for population growth should be resolved within the area. 2) Subsistence conditions should be taken care of by the family. 3) There should be a centralized standard, not a family standard, such that living conditions/capita should not decrease because of population growth. Quantification is made expressing the relationship between subsistence and growth. The application of these conditions for households in Hongmiao District is that the average subsistence conditions need to be higher than other households by 12.3% for new population growth. The assumption is

  9. Correlation between PLD repair capacity and the survival curve of human fibroblasts in exponential growth phase: analysis in terms of several parameters

    SciTech Connect

    Fertil, B.; Deschavanne, P.J.; Debieu, D.; Malaise, E.P.

    1988-10-01

    Published data on the in vitro radiosensitivity of 46 nontransformed fibroblasts of different genetic origins studied in plateau phase with immediate or delayed plating were used to investigate to what extent potentially lethal damage repair capacity is related to intrinsic radiosensitivity (i.e., irradiated in exponential growth phase). While most of the survival curve analysis is conducted in terms of D0, Dq, and the mean inactivation dose D, some of the data are also discussed in terms of the linear-quadratic model parameter alpha. Using D it is shown that: (i) the radiosensitivity of human fibroblasts in exponential growth phase does not significantly differ from that of plateau-phase fibroblasts with immediate plating; (ii) the radiosensitivity of plateau-phase cells with delayed plating is correlated to the radiosensitivity of cells with immediate plating: the more radioresistant the cell strain in exponential growth phase, the higher its repair capacity; (iii) the repair capacity of the cell strains is related to their genetic origin. In conclusion, we suggest that the survival curve of growing cells depends on the repair capacity of the cells.

  10. Population growth, demographic change, and cultural landscapes.

    PubMed

    Woodgate, G; Sage, C

    1994-01-01

    The inclusion of both ecological and socioeconomic components within landscapes makes possible the perception of the hierarchical character of landscape organization. A research approach is needed to conceptualize cultural landscapes as the product of interaction between society and nature. Richard Norgaard's 1984 paper on coevolutionary agricultural development attempts to meet this challenge. Coevolution is the interactive synthesis of natural and social mechanisms of change that characterize the relationship between social systems and ecosystems. The relationship between population, consumption, and environmental changes is complex. Currently industrialized countries present the biggest threat to global environmental resources. The issue of carrying capacity is the corollary of population and the environment. It is primarily the technological factor rather than population that needs to be controlled. The relationship between rich and poor countries is determined by superior economic power. An analysis of landscape change is made, tracing the coevolution of society and environment from the end of the feudal era and making comparisons with continental Europe. Over the years since 1945 the need to realize potential economies of scale has resulted in a wholesale loss of woodlands, hedgerows, and small ponds in the UK. In a global context the likely impacts of population growth and demographic change on landscapes will be influenced by such socioeconomic factors as technology and affluence; policies that ignore cause and effect; and the traditional tendency to treat the environment as a waste repository and a supply depot. PMID:12290867

  11. Living bacteria rheology: Population growth, aggregation patterns, and collective behavior under different shear flows

    NASA Astrophysics Data System (ADS)

    Patrício, P.; Almeida, P. L.; Portela, R.; Sobral, R. G.; Grilo, I. R.; Cidade, T.; Leal, C. R.

    2014-08-01

    The activity of growing living bacteria was investigated using real-time and in situ rheology—in stationary and oscillatory shear. Two different strains of the human pathogen Staphylococcus aureus—strain COL and its isogenic cell wall autolysis mutant, RUSAL9—were considered in this work. For low bacteria density, strain COL forms small clusters, while the mutant, presenting deficient cell separation, forms irregular larger aggregates. In the early stages of growth, when subjected to a stationary shear, the viscosity of the cultures of both strains increases with the population of cells. As the bacteria reach the exponential phase of growth, the viscosity of the cultures of the two strains follows different and rich behaviors, with no counterpart in the optical density or in the population's colony-forming units measurements. While the viscosity of strain COL culture keeps increasing during the exponential phase and returns close to its initial value for the late phase of growth, where the population stabilizes, the viscosity of the mutant strain culture decreases steeply, still in the exponential phase, remains constant for some time, and increases again, reaching a constant plateau at a maximum value for the late phase of growth. These complex viscoelastic behaviors, which were observed to be shear-stress-dependent, are a consequence of two coupled effects: the cell density continuous increase and its changing interacting properties. The viscous and elastic moduli of strain COL culture, obtained with oscillatory shear, exhibit power-law behaviors whose exponents are dependent on the bacteria growth stage. The viscous and elastic moduli of the mutant culture have complex behaviors, emerging from the different relaxation times that are associated with the large molecules of the medium and the self-organized structures of bacteria. Nevertheless, these behaviors reflect the bacteria growth stage.

  12. World Population: Fundamentals of Growth. Student Chartbook. Third Edition.

    ERIC Educational Resources Information Center

    Kent, Mary Mederios

    This booklet is designed for K-12 students and educators to learn about world population growth factors. Data are shown through charts and graphs with brief explanations. The booklet contains: (1) "World Population Growth and Regional Distribution through History"; (2) "Population Growth through Natural Increase"; (3) "Effect of Migration on…

  13. Modeling the growth of individuals in plant populations: local density variation in a strand population of Xanthium strumarium (Asteraceae).

    PubMed

    Weiner, J; Kinsman, S; Williams, S

    1998-11-01

    We studied the growth of individual Xanthium strumarium plants growing at four naturally occurring local densities on a beach in Maine: (1) isolated plants, (2) pairs of plants ≤1 cm apart, (3) four plants within 4 cm of each other, and (4) discrete dense clumps of 10-39 plants. A combination of nondestructive measurements every 2 wk and parallel calibration harvests provided very good estimates of the growth in aboveground biomass of over 400 individual plants over 8 wk and afforded the opportunity to fit explicit growth models to 293 of them. There was large individual variation in growth and resultant size within the population and within all densities. Local crowding played a role in determining plant size within the population: there were significant differences in final size between all densities except pairs and quadruples, which were almost identical. Overall, plants growing at higher densities were more variable in growth and final size than plants growing at lower densities, but this was due to increased variation among groups (greater variation in local density and/or greater environmental heterogeneity), not to increased variation within groups. Thus, there was no evidence of size asymmetric competition in this population. The growth of most plants was close to exponential over the study period, but half the plants were slightly better fit by a sigmoidal (logistic) model. The proportion of plants better fit by the logistic model increased with density and with initial plant size. The use of explicit growth models over several growth intervals to describe stand development can provide more biological content and more statistical power than "growth-size" methods that analyze growth intervals separately. PMID:21680325

  14. Fitness and density-dependent population growth in Drosophila melanogaster

    SciTech Connect

    Mueller, L.D.; Ayala, F.J.

    1981-03-01

    The density-dependent rates of population growth were determined for 26 populations of Drosophila melanogaster maintained in the serial transfer system. Twenty-five populations were homozygous for an entire chromosome 2 sampled from nature; the other was a random heterozygous population. Rates of population growth around the carrying capacity cannot explain the large fitness depression of these lines. However, the homozygous lines show large differences in rates of population growth at low densities relative to the random heterozygous standard. The average relative fitness of the homozygous lines, as determined from the growth rates at the lowest density, is 0.51.

  15. An exponential growth of computational phantom research in radiation protection, imaging, and radiotherapy: A review of the fifty-year history

    PubMed Central

    Xu, X. George

    2014-01-01

    -known phantoms were developed and used in practice. Some of the information covered in this review has not been previously reported, for example, the CAM and CAF phantoms developed in 1970s for space radiation applications. The author also clarifies confusion about “population-average” prospective dosimetry needed for radiological protection under the current ICRP radiation protection system and “individualized” retrospective dosimetry often performed for medical physics studies. To illustrate the impact of computational phantoms, a section of this article is devoted to examples from the author’s own research group. Finally the author explains an unexpected finding during the course of preparing for this article that the phantoms from the past 50 years followed a pattern of exponential growth. The review ends on a brief discussion of future research needs (A supplementary file “3DPhantoms.pdf” to Figure 15 is available for download that will allow a reader to interactively visualize the phantoms in 3D). PMID:25144730

  16. An exponential growth of computational phantom research in radiation protection, imaging, and radiotherapy: a review of the fifty-year history.

    PubMed

    Xu, X George

    2014-09-21

    well-known phantoms were developed and used in practice. Some of the information covered in this review has not been previously reported, for example, the CAM and CAF phantoms developed in 1970s for space radiation applications. The author also clarifies confusion about 'population-average' prospective dosimetry needed for radiological protection under the current ICRP radiation protection system and 'individualized' retrospective dosimetry often performed for medical physics studies. To illustrate the impact of computational phantoms, a section of this article is devoted to examples from the author's own research group. Finally the author explains an unexpected finding during the course of preparing for this article that the phantoms from the past 50 years followed a pattern of exponential growth. The review ends on a brief discussion of future research needs (a supplementary file '3DPhantoms.pdf' to figure 15 is available for download that will allow a reader to interactively visualize the phantoms in 3D). PMID:25144730

  17. Shanghai: a study on the spatial growth of population and economy in a Chinese metropolitan area.

    PubMed

    Zhu, J

    1995-01-01

    In this study of the growth in population and industry in Shanghai, China, between the 1982 and 1990 censuses, data on administrative divisions was normalized through digitization and spatial analysis. Analysis focused on spatial units, intensity of growth, time period, distance, rate of growth, and direction of spatial growth. The trisection method divided the city into city proper, outskirts, and suburbs. The distance function method considered the distance from center city as a function: exponential, power, trigonometric, logarithmic, and polynomial. Population growth and employment in all sectors increased in the outskirts and suburbs and decreased in the city proper except tertiary sectors. Primary sector employment decreased in all three sections. Employment in the secondary increased faster in the outskirts and suburbs than the total rate of growth of population and employment. In the city secondary sector employment rates decreased faster than total population and employment rates. The tertiary sector had the highest rate of growth in all sections, and employment grew faster than secondary sector rates. Tertiary growth was highest in real estate, finance, and insurance. Industrial growth in the secondary sector was 160.2% in the suburbs, 156.6% in the outskirts, and 80.9% in the city. In the distance function analysis, industry expanded further out than the entire secondary sector. Commerce grew the fastest in areas 15.4 km from center city. Economic growth was faster after economic reforms in 1978. Growth was led by industry and followed by the secondary sector, the tertiary sector, and population. Industrial expansion resulted from inner pressure, political factors controlling size, the social and economic system, and the housing construction and distribution system. Initially sociopsychological factors affected urban concentration. PMID:12288964

  18. Population growth rate and its determinants: an overview.

    PubMed Central

    Sibly, Richard M; Hone, Jim

    2002-01-01

    We argue that population growth rate is the key unifying variable linking the various facets of population ecology. The importance of population growth rate lies partly in its central role in forecasting future population trends; indeed if the form of density dependence were constant and known, then the future population dynamics could to some degree be predicted. We argue that population growth rate is also central to our understanding of environmental stress: environmental stressors should be defined as factors which when first applied to a population reduce population growth rate. The joint action of such stressors determines an organism's ecological niche, which should be defined as the set of environmental conditions where population growth rate is greater than zero (where population growth rate = r = log(e)(N(t+1)/N(t))). While environmental stressors have negative effects on population growth rate, the same is true of population density, the case of negative linear effects corresponding to the well-known logistic equation. Following Sinclair, we recognize population regulation as occurring when population growth rate is negatively density dependent. Surprisingly, given its fundamental importance in population ecology, only 25 studies were discovered in the literature in which population growth rate has been plotted against population density. In 12 of these the effects of density were linear; in all but two of the remainder the relationship was concave viewed from above. Alternative approaches to establishing the determinants of population growth rate are reviewed, paying special attention to the demographic and mechanistic approaches. The effects of population density on population growth rate may act through their effects on food availability and associated effects on somatic growth, fecundity and survival, according to a 'numerical response', the evidence for which is briefly reviewed. Alternatively, there may be effects on population growth rate of

  19. Different isotope and chemical patterns of pyrite oxidation related to lag and exponential growth phases of Acidithiobacillus ferrooxidans reveal a microbial growth strategy

    NASA Astrophysics Data System (ADS)

    Brunner, Benjamin; Yu, Jae-Young; Mielke, Randall E.; MacAskill, John A.; Madzunkov, Stojan; McGenity, Terry J.; Coleman, Max

    2008-06-01

    The solution chemistry during the initial (slow increase of dissolved iron and sulfate) and main stage (rapid increase of dissolved iron and sulfate) of pyrite leaching by Acidithiobacillus ferrooxidans (Af) at a starting pH of 2.05 shows significant differences. During the initial stage, ferrous iron (Fe2+) is the dominant iron species in solution and the molar ratio of produced sulfate (SO42-) and total iron (Fetot) is 1.1, thus does not reflect the stoichiometry of pyrite (FeS2). During the main stage, ferric iron (Fe3+) is the dominant iron species in solution and the SO42-:Fetot ratio is with 1.9, close to the stoichiometry of FeS2. Another difference between initial and main stage is an initial trend to slightly higher pH values followed by a drop during the main stage to pH 1.84. These observations raise the question if there are different modes of bioleaching of pyrite, and if there are, what those modes imply in terms of leaching mechanisms. Different oxygen and sulfur isotope trends of sulfate during the initial and main stages of pyrite oxidation confirm that there are two pyrite bioleaching modes. The biochemical reactions during initial stage are best explained by the net reaction FeS2 + 3O2 ⇒ Fe2+ + SO42- + SO2(g). The degassing of sulfur dioxide (SO2) acts as sink for sulfur depleted in 34S compared to pyrite, and is the cause of the SO42-:Fetot ratio of 1.1 and the near constant pH. During the exponential phase, pyrite sulfur is almost quantitatively converted to sulfate, according to the net reaction FeS2 + 15/4O2 + 1/2H2O ⇒ Fe3+ + 2SO42- + H+. We hypothesize that the transition between the modes of bioleaching of pyrite is due to the impact of the accumulation of ferrous iron, which induces changes in the metabolic activity of Af and may act as an inhibitor for the oxidation of sulfur species. This transition defines a fundamental change in the growth strategy of Af. A mode, where bacteria gain energy by oxidation of elemental sulfur to

  20. Population Growth and Poverty in the Developing World.

    ERIC Educational Resources Information Center

    Birdsall, Nancy

    1980-01-01

    The link between rapid population growth and the absolute poverty which currently afflicts 780 million people in developing countries (excluding China and other centrally planned economies) is examined. As a result of rapid population growth, many countries suffer slow per capita income growth, a lack of progress in reducing income inequality, and…

  1. Energy and fluxes of thermal runaway electrons produced by exponential growth of streamers during the stepping of lightning leaders and in transient luminous events

    NASA Astrophysics Data System (ADS)

    Celestin, Sebastien; Pasko, Victor P.

    2011-03-01

    In the present paper, we demonstrate that the exponential expansion of streamers propagating in fields higher than the critical fields for stable propagation of streamers of a given polarity leads to the exponential growth of electric potential differences in streamer heads. These electric potential differences are directly related to the energy that thermal runaway electrons can gain once created. Using full energy range relativistic Monte Carlo simulations, we show that the exponential growth of potential differences in streamers gives rise to the production of runaway electrons with energies as high as ˜100 keV, with most of electrons residing in energy range around several tens of keVs. We apply these concepts in the case of lightning stepped leaders during the stage of negative corona flash. The computation of electric field produced by stepped leaders demonstrates for the first time that those energetic electrons are capable of further acceleration up to the MeV energies. Moreover, the flux of runaway electrons produced by streamers suggests that stepped leaders produce a considerable number of energetic electrons, which is in agreement with the number of energetic photons observed from satellites in terrestrial gamma ray flashes (TGFs). The results suggest that previously proposed process of relativistic runaway electron avalanche is difficult to sustain in the low-electric fields observed in thunderclouds and is generally not needed for explanation of TGFs. The present work also gives insights on relations between physical properties of energetic electrons produced in streamers and the internal electrical properties of streamer discharges, which can further help development and interpretation of X-ray diagnostics of these discharges.

  2. Population Growth and a Sustainable Environment.

    ERIC Educational Resources Information Center

    Mortimore, Michael; Tiffen, Mary

    1994-01-01

    Provides a history of farming practices in a densely populated area of Kenya where a recent study of the resource management practices showed positive, not negative, influences of increasing population density on both environmental conservation and productivity. (LZ)

  3. Recovering population parameters from a single gene genealogy: an unbiased estimator of the growth rate.

    PubMed

    Maruvka, Yosef E; Shnerb, Nadav M; Bar-Yam, Yaneer; Wakeley, John

    2011-05-01

    We show that the number of lineages ancestral to a sample, as a function of time back into the past, which we call the number of lineages as a function of time (NLFT), is a nearly deterministic property of large-sample gene genealogies. We obtain analytic expressions for the NLFT for both constant-sized and exponentially growing populations. The low level of stochastic variation associated with the NLFT of a large sample suggests using the NLFT to make estimates of population parameters. Based on this, we develop a new computational method of inferring the size and growth rate of a population from a large sample of DNA sequences at a single locus. We apply our method first to a sample of 1,212 mitochondrial DNA (mtDNA) sequences from China, confirming a pattern of recent population growth previously identified using other techniques, but with much smaller confidence intervals for past population sizes due to the low variation of the NLFT. We further analyze a set of 63 mtDNA sequences from blue whales (BWs), concluding that the population grew in the past. This calls for reevaluation of previous studies that were based on the assumption that the BW population was fixed. PMID:21172828

  4. Integrated kinetic and probabilistic modeling of the growth potential of bacterial populations.

    PubMed

    George, S M; Métris, A; Baranyi, J

    2015-05-01

    When bacteria are exposed to osmotic stress, some cells recover and grow, while others die or are unculturable. This leads to a viable count growth curve where the cell number decreases before the onset of the exponential growth phase. From such curves, it is impossible to estimate what proportion of the initial cells generates the growth because it leads to an ill-conditioned numerical problem. Here, we applied a combination of experimental and statistical methods, based on optical density measurements, to infer both the probability of growth and the maximum specific growth rate of the culture. We quantified the growth potential of a bacterial population as a quantity composed from the probability of growth and the "suitability" of the growing subpopulation to the new environment. We found that, for all three laboratory media studied, the probability of growth decreased while the "work to be done" by the growing subpopulation (defined as the negative logarithm of their suitability parameter) increased with NaCl concentration. The results suggest that the effect of medium on the probability of growth could be described by a simple shift parameter, a differential NaCl concentration that can be accounted for by the change in the medium composition. Finally, we highlighted the need for further understanding of the effect of the osmoprotectant glycine betaine on metabolism. PMID:25747002

  5. Volatility and Growth in Populations of Rural Associations

    ERIC Educational Resources Information Center

    Wollebaek, Dag

    2010-01-01

    This article uses unique community-level data aggregated from censuses of associations to analyze growth and volatility in rural populations of grassroots associations. A qualitative comparative analysis (QCA) shows that the two main paths to growth were (1) centralization in polycephalous (multicentered) municipalities and (2) population growth…

  6. Population growth and atmospheric emissions in California. Final report

    SciTech Connect

    Cramer, J.C.

    1998-03-01

    The objectives of this research are to better understand and estimate the net effects of population growth on emissions in California and to estimate the net benefits of air quality programs, which have offset the negative effects of population growth and achieved actual reductions in emissions.

  7. Population growth and development: the case of Bangladesh.

    PubMed

    Nakibullah, A

    1998-04-01

    In a poor, overly populated country such as Bangladesh, some believe that a high rate of population growth is a cause of poverty which impedes economic development. Population growth would therefore be exogenous to economic development. However, others believe that rapid population growth is a consequence rather than a cause of poverty. Population growth is therefore endogenous to economic development. Findings are presented from an investigation of whether population growth has been exogenous or endogenous with respect to Bangladesh's development process during the past 3 decades. The increase in per capita real gross domestic product (GDP) is used as a measure of development. Data on population, real GDP per capita, and real investment share of GDP are drawn from the Penn World Table prepared by Summers and Heston in 1991. The data are annual and cover the period 1959-90. Analysis of the data indicate that population growth is endogenous to Bangladesh's development process. These findings are reflected both in the Granger causality tests and the decompositions of variances of detrended real GDP per capita and population growth. PMID:12294506

  8. Pattern of variation in avian population growth rates.

    PubMed Central

    Saether, Bernt-Erik; Engen, Steinar

    2002-01-01

    A central question in population ecology is to understand why population growth rates differ over time. Here, we describe how the long-term growth of populations is not only influenced by parameters affecting the expected dynamics, for example form of density dependence and specific population growth rate, but is also affected by environmental and demographic stochasticity. Using long-term studies of fluctuations of bird populations, we show an interaction between the stochastic and the deterministic components of the population dynamics: high specific growth rates at small densities r(1) are typically positively correlated with the environmental variance sigma(e)(2). Furthermore, theta, a single parameter describing the form of the density regulation in the theta-logistic density-regulation model, is negatively correlated with r(1). These patterns are in turn correlated with interspecific differences in life-history characteristics. Higher specific growth rates, larger stochastic effects on the population dynamics and stronger density regulation at small densities are found in species with large clutch sizes or high adult mortality rates than in long-lived species. Unfortunately, large uncertainties in parameter estimates, as well as strong stochastic effects on the population dynamics, will often make even short-term population projections unreliable. We illustrate that the concept of population prediction interval can be useful in evaluating the consequences of these uncertainties in the population projections for the choice of management actions. PMID:12396511

  9. Menaquinone Synthesis is Critical for Maintaining Mycobacterial Viability During Exponential Growth and Recovery from Non-Replicating Persistence

    PubMed Central

    Dhiman, Rakesh K.; Mahapatra, Sebabrata; Slayden, Richard A.; Boyne, Melissa E.; Lenaerts, Anne; Hinshaw, Jerald C.; Angala, Shiva K.; Chatterjee, Delphi; Biswas, Kallolmay; Narayanasamy, Prabagaran; Kurosu, Michio; Crick, Dean C.

    2016-01-01

    Summary Understanding the basis of bacterial persistence in latent infections is critical for eradication of tuberculosis. Analysis of Mycobacterium tuberculosis mRNA expression in an in vitro model of non-replicating persistence indicated that the bacilli require electron transport chain components and ATP synthesis for survival. Additionally, low μM concentrations of aminoalkoxydiphenylmethane derivatives inhibited both the aerobic growth and survival of non-replicating, persistent M. tuberculosis. Metabolic labeling studies and quantitation of cellular menaquinone levels suggested that menaquinone synthesis, and consequently electron transport, is the target of the aminoalkoxydiphenylmethane derivatives. This hypothesis is strongly supported by the observations that treatment with these compounds inhibits oxygen consumption and that supplementation of growth medium with exogenous menaquinone rescued both growth and oxygen consumption of treated bacilli. In vitro assays indicate that the aminoalkoxydiphenylmethane derivatives specifically inhibit MenA, an enzyme involved in the synthesis of menaquinone. Thus, the results provide insight into the physiology of mycobacterial persistence and a basis for the development of novel drugs that enhance eradication of persistent bacilli and latent tuberculosis. PMID:19220750

  10. Bounded Population Growth: A Curve Fitting Lesson.

    ERIC Educational Resources Information Center

    Mathews, John H.

    1992-01-01

    Presents two mathematical methods for fitting the logistic curve to population data supplied by the U.S. Census Bureau utilizing computer algebra software to carry out the computations and plot graphs. (JKK)

  11. [Five recommendations for controlling population growth in China].

    PubMed

    Lui, Z; Wu, C P; Lin, F D

    1980-10-01

    The rapid population growth rate (2% annually from 1949 to 1978) caused great difficulties for China's national economy because it increased the burden of families, communities, and government. It caused employment problems and slowed increases in living standards and educational levels. The best way to control population growth is based on a combination of political education and effective economic measures. The recommendations are: 1) coordinate employment, food rationing, salaries, bonuses, health treatment, age and condition of retirement, preschool care and education with family planning programs, maintain the elderly's living standard, and give preference to childless and single child families; 2) educate people about family planning and incorporate population growth and family planning into political and economics courses in high school and college; 3) incorporate population control into national economic plans; 4) prohibit families with 3 children and advocate 1 child per couple; and 5) establish a permanent population committee to plan, develop, and implement population policies and related research. PMID:12264235

  12. Food Production, Population Growth, and Environmental Quality. Caltech Population Program Occasional Papers, Series 1, Number 7.

    ERIC Educational Resources Information Center

    Groth, Edward, III

    This paper, one in a series of occasional publications, discusses trends in food production and population growth, emphasizing how environmental quality will be affected. The series is intended to increase understanding of the interrelationships between population growth and socioeconomic and cultural patterns throughout the world, and to…

  13. [The fear of numbers or the challenge of population growth?].

    PubMed

    Loriaux, M

    1991-12-01

    Africa, currently one of the least densely populated continents, is growing so rapidly that its population will comprise some 1.5 billion inhabitants around 2020, and Africans will be more numerous than the population of the developed world. Attitudes about Africa's population size vary widely; many educated Africans believe that low density is a greater disadvantage than overpopulation, but most specialists believe the population of the developing world, and of Africa especially, to be too large, the prospects of significant voluntary reduction are dim. The rate of population growth has thus attracted attention as a factor amenable to modification. Africa's demographic transition remains largely in the future. Its case is unique because of the rate of demographic growth and because the phase of rapid growth will apparently continue far longer in Africa than in any other continent. The widening gap between population growth rates and rates of economic development in Africa inspires great pessimism about the future wellbeing of the population. Population officials urge that demographic growth be slowed in order to reduce pressure on economic and ecological resources and to gain time for social and economic development. But despite the consensus of international organizations, such as the UN Fund for Population, on the desirability of slowing population growth to encourage and permit economic growth, there has actually been relatively little progress since the time of Malthus in understanding the relationship between population, development, and the environment. Some recent works suggest that demographic growth has benefits as well as disadvantages, and the net impact on development is uncertain. Demographic pressure is in this view a far more potent force for innovation than is usually recognized. Population is not just an exogenous variable in development, but it is at the heart of the process. There can be no true integration of population into development until

  14. Population Blocks.

    ERIC Educational Resources Information Center

    Smith, Martin H.

    1992-01-01

    Describes an educational game called "Population Blocks" that is designed to illustrate the concept of exponential growth of the human population and some potential effects of overpopulation. The game material consists of wooden blocks; 18 blocks are painted green (representing land), 7 are painted blue (representing water); and the remaining…

  15. Agriculture, population growth, and statistical analysis of the radiocarbon record

    PubMed Central

    Zahid, H. Jabran; Robinson, Erick; Kelly, Robert L.

    2016-01-01

    The human population has grown significantly since the onset of the Holocene about 12,000 y ago. Despite decades of research, the factors determining prehistoric population growth remain uncertain. Here, we examine measurements of the rate of growth of the prehistoric human population based on statistical analysis of the radiocarbon record. We find that, during most of the Holocene, human populations worldwide grew at a long-term annual rate of 0.04%. Statistical analysis of the radiocarbon record shows that transitioning farming societies experienced the same rate of growth as contemporaneous foraging societies. The same rate of growth measured for populations dwelling in a range of environments and practicing a variety of subsistence strategies suggests that the global climate and/or endogenous biological factors, not adaptability to local environment or subsistence practices, regulated the long-term growth of the human population during most of the Holocene. Our results demonstrate that statistical analyses of large ensembles of radiocarbon dates are robust and valuable for quantitatively investigating the demography of prehistoric human populations worldwide. PMID:26699457

  16. Agriculture, population growth, and statistical analysis of the radiocarbon record.

    PubMed

    Zahid, H Jabran; Robinson, Erick; Kelly, Robert L

    2016-01-26

    The human population has grown significantly since the onset of the Holocene about 12,000 y ago. Despite decades of research, the factors determining prehistoric population growth remain uncertain. Here, we examine measurements of the rate of growth of the prehistoric human population based on statistical analysis of the radiocarbon record. We find that, during most of the Holocene, human populations worldwide grew at a long-term annual rate of 0.04%. Statistical analysis of the radiocarbon record shows that transitioning farming societies experienced the same rate of growth as contemporaneous foraging societies. The same rate of growth measured for populations dwelling in a range of environments and practicing a variety of subsistence strategies suggests that the global climate and/or endogenous biological factors, not adaptability to local environment or subsistence practices, regulated the long-term growth of the human population during most of the Holocene. Our results demonstrate that statistical analyses of large ensembles of radiocarbon dates are robust and valuable for quantitatively investigating the demography of prehistoric human populations worldwide. PMID:26699457

  17. Parameter Estimates in Differential Equation Models for Population Growth

    ERIC Educational Resources Information Center

    Winkel, Brian J.

    2011-01-01

    We estimate the parameters present in several differential equation models of population growth, specifically logistic growth models and two-species competition models. We discuss student-evolved strategies and offer "Mathematica" code for a gradient search approach. We use historical (1930s) data from microbial studies of the Russian biologist,…

  18. The New Population Debate: Two Views on Population Growth and Economic Development. Population Trends and Public Policy, Number 7.

    ERIC Educational Resources Information Center

    King, Timothy; Kelley, Allen C.

    Articles representing two views on the issue of rapid population growth and economic development are presented. Although the authors present different perspectives, they agree on many of the fundamentals. For example, both reject alarmism about impending "population explosions" and the use of population as a scapegoat for all Third World ills.…

  19. A Role for M-Matrices in Modelling Population Growth

    ERIC Educational Resources Information Center

    James, Glyn; Rumchev, Ventsi

    2006-01-01

    Adopting a discrete-time cohort-type model to represent the dynamics of a population, the problem of achieving a desired total size of the population under a balanced growth (contraction) and the problem of maintaining the desired size, once achieved, are studied. Properties of positive-time systems and M-matrices are used to develop the results,…

  20. Correlated responses in body composition to divergent selection for exponential growth rate to 14 or 42 days of age in chickens.

    PubMed

    Sizemore, F G; Barbato, G F

    2002-07-01

    Chicks divergently selected for 14-d (14H and 14L) or 42-d (42H and 42L) exponential growth rate (EGR) over five generations were used to determine correlated responses between growth at different ages and body composition. Regression coefficient estimates across five generations of selection were not significant for any line at either age for percentage total body water or protein. Genetic correlations between EGR from hatching to 14 d of age (EGR14) and 42-d percentage carcass fat were -0.18, -0.57, 0.63, and -0.79 among the 14H, 14L, 42H, and 42L lines, respectively. Genetic correlations between EGR from hatching to 42 d of age (EGR42) and 42-d percentage carcass fat were 0.09, -0.67,0.50, and -0.75 among the 14H, 14L, 42H, and 42L lines, respectively. During the short-term selection experiment, selection for fast EGR14 or EGR42 increased fat at the age of selection. However, selection for fast EGR42 increased body weight and percentage fat at 42 d of age (DOA), whereas selection for fast EGR14 increased body weight but not fat at 42 DOA. Therefore, it is possible to simultaneously select for high body weight at, or near, the inflection point of the growth curve without increasing fat deposition or obesity by taking advantage of the lack of a genetic correlation between EGR14 and body fat percentage at later ages. PMID:12162352

  1. Population growth. Its magnitude and implications for development.

    PubMed

    Birdsall, N

    1984-09-01

    A summary of the 1984 World Development Report is provided. The 3 major points stressed in the report were: 1) rapid population growth adversely affects development, 2) governments must adopt policies to reduce fertility, and 3) policies adopted by many countries have effectively reduced fertility. World population growth began accelerating at 0.5%/year in the 18th century, and by 1950 the annual acceleration rate was 2%. Most of the increase in population size is occurring in less developed countries, and this increase is due in part to the recent decline in mortality experienced by these countries. Of the 80 million individuals who will be added to the world's population in 1984, 70 million will be in the developing countries. Since 1965 the population growth rate for developing countries as a group declined from 2.4% to 2%. However, because of the high proportion of younger aged individuals in developing countries, the decline in fertility is expected to level off. According to World Bank population projections, the world population will stabilize at around 11 billion in 2150. During the interium, the population of developing countries will increase from its present level of 3.6 billion to 8.4 billion, and the population of developed countries will increase from 1.2 billion to 1.4 billion. These projections are probably overly optimistic. The adverse impact on development of rapid population growth is due to several factors. 1st, resources which could be used for investment must instead be used to fulfill the consumption needs of an increased number of people. 2nd, increases in the labor force must be absorbed by the agricultural sector, and this reduces agricultural productivity. 3rd, rapid population growth increases management problems. The adaption of policies by governments to reduce fertility is a necessary step in halting population growth. For poor families, children provide economic security. Therefore, governments must act to improve the economic

  2. Exponential Growth through Pattern Exploration

    ERIC Educational Resources Information Center

    Brown, Betty

    2005-01-01

    Participants at the Summer Institute Pattern Exploration: Integration Math and Science in the Middle Grades used and developed a method treat arithmetic, algebra and geometry as one entity. The use of iterative geometric constructions is seen to reinforce the concepts of exponents, ratios and algebraic expressions for the nth stage of the…

  3. Recognizing Exponential Growth. Classroom Notes

    ERIC Educational Resources Information Center

    Dobbs, David E.

    2004-01-01

    Two heuristic and three rigorous arguments are given for the fact that functions of the form Ce[kx], with C an arbitrary constant, are the only solutions of the equation dy/dx=ky where k is constant. Various of the proofs in this self-contained note could find classroom use in a first-year calculus course, an introductory course on differential…

  4. Growth dynamics and the evolution of cooperation in microbial populations

    NASA Astrophysics Data System (ADS)

    Cremer, Jonas; Melbinger, Anna; Frey, Erwin

    2012-02-01

    Microbes providing public goods are widespread in nature despite running the risk of being exploited by free-riders. However, the precise ecological factors supporting cooperation are still puzzling. Following recent experiments, we consider the role of population growth and the repetitive fragmentation of populations into new colonies mimicking simple microbial life-cycles. Individual-based modeling reveals that demographic fluctuations, which lead to a large variance in the composition of colonies, promote cooperation. Biased by population dynamics these fluctuations result in two qualitatively distinct regimes of robust cooperation under repetitive fragmentation into groups. First, if the level of cooperation exceeds a threshold, cooperators will take over the whole population. Second, cooperators can also emerge from a single mutant leading to a robust coexistence between cooperators and free-riders. We find frequency and size of population bottlenecks, and growth dynamics to be the major ecological factors determining the regimes and thereby the evolutionary pathway towards cooperation.

  5. The Escherichia coli FIS protein is not required for the activation of tyrT transcription on entry into exponential growth.

    PubMed Central

    Lazarus, L R; Travers, A A

    1993-01-01

    The Escherichia coli DNA bending protein factor for inversion stimulation (FIS), is neither necessary nor responsible for the stimulation of transcription from the wild type promoter for the tyrT operon (encoding a species of tyrosine tRNA) that occurs upon resumption of exponential growth. This conclusion is unexpected given that the regulatory element required for optimal transcription of tyrT contains three binding sites for FIS protein. In addition, it is in apparent conflict with reports from other laboratories which have described FIS-dependent activation of the stable RNA promoters rrnB P1 and thrU(tufB) in vivo. However, tyrT transcription is stimulated in a FIS-dependent manner both in vivo and in vitro when promoter function is impaired by mutation of the promoter itself or by the addition of the polymerase effector guanosine 5'-diphosphate 3'-diphosphate. These conditions, which expose a requirement for activation of stable RNA synthesis by FIS, suggest that FIS serves an adaptive role permitting high levels of stable RNA transcription on nutritional shift-up when RNA polymerase levels are depleted. In principle such a mechanism could confer a significant selective advantage thus accounting for the conservation of FIS binding sites in the regulatory regions of stable RNA promoters. Images PMID:7685276

  6. Growth Kinetics of Listeria monocytogenes in Broth and Beef Frankfurters– Determination of Lag Phase Duration and Exponential Growth Rate under Isothermal Conditions

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The objective of this research was to develop a new kinetic model to describe the isothermal growth of microorganisms. The new model was tested with Listeria monocytogenes in broth and frankfurters, and compared with two commonly used models - Baranyi and modified Gompertz models. Bias factor (BF)...

  7. Giving Exponential Functions a Fair Shake

    ERIC Educational Resources Information Center

    Wanko, Jeffrey J.

    2005-01-01

    This article details an exploration of exponential decay and growth relationships using M&M's and dice. Students collect data for mathematical models and use graphing calculators to make sense of the general form of the exponential functions. (Contains 10 figures and 2 tables.)

  8. A model of northern pintail productivity and population growth rate

    USGS Publications Warehouse

    Flint, P.L.; Grand, J.B.; Rockwell, R.F.

    1998-01-01

    Our objective was to synthesize individual components of reproductive ecology into a single estimate of productivity and to assess the relative effects of survival and productivity on population dynamics. We used information on nesting ecology, renesting potential, and duckling survival of northern pintails (Anas acuta) collected on the Yukon-Kuskokvim Delta (Y-K Delta), Alaska, 1991-95, to model the number of ducklings produced under a range of nest success and duckling survival probabilities. Using average values of 25% nest success, 11% duckling survival, and 56% renesting probability from our study population, we calculated that all young in our population were produced by 13% of the breeding females, and that early-nesting females produced more young than later-nesting females. Further, we calculated, on average, that each female produced only 0.16 young females/nesting season. We combined these results with estimates of first-year and adult survival to examine the growth rate (??) of the population and the relative contributions of these demographic parameters to that growth rate. Contrary to aerial survey data, the population projection model suggests our study population is declining rapidly (?? = 0.6969). The relative effects on population growth rate were 0.1175 for reproductive success, 0.1175 for first-year survival, and 0.8825 for adult survival. Adult survival had the greatest influence on ?? for our population, and this conclusion was robust over a range of survival and productivity estimates. Given published estimates of annual survival for adult females (61%), our model suggested nest success and duckling survival need to increase to approximately 40% to achieve population stability. We discuss reasons for the apparent discrepancy in population trends between our model and aerial surveys in terms of bias in productivity and survival estimates.

  9. Understanding the size growth of massive galaxies through stellar populations

    NASA Astrophysics Data System (ADS)

    Ferreras, Ignacio

    2015-08-01

    The growth of massive galaxies remains an open problem. The observational evidence seems to converge on a two-stage scenario, where a compact massive core is formed during an early, intense burst, followed by a more extended process of mass and size growth at intermediate redshift (z<2). This talk focuses on the latter, exploring the growth of massive galaxies through a detailed analysis of the stellar populations in close pairs, to study their formation history. Two surveys are explored (SHARDS and GAMA), probing the stellar populations of pre-merging systems out to z~1.3, and down to a mass ratio ~1:100. We will compare the results between medium band spectral fitting (SHARDS) and those from a more targeted analysis of line strengths in the GAMA data. The combination of the two datasets provide a unique insight of the growth channel of massive galaxies via mergers.

  10. Latino Population Growth and Hospital Uncompensated Care in California

    PubMed Central

    O’Brien, Matthew J.; Mennis, Jeremy; Alos, Victor A.; Grande, David T.; Roby, Dylan H.; Ortega, Alexander N.

    2015-01-01

    Objectives. We examined the association between the size and growth of Latino populations and hospitals’ uncompensated care in California. Methods. Our sample consisted of general acute care hospitals in California operating during 2000 and 2010 (n = 251). We merged California hospital data with US Census data for each hospital service area. We used spatial analysis, multivariate regression, and fixed-effect models. Results. We found a significant association between the growth of California’s Latino population and hospitals’ uncompensated care in the unadjusted regression. This association was still significant after we controlled for hospital and community population characteristics. After we added market characteristics into the final model, this relationship became nonsignificant. Conclusions. Our findings suggest that systematic support is needed in areas with rapid Latino population growth to control hospitals’ uncompensated care, especially if Latinos are excluded from or do not respond to the insurance options made available through the Affordable Care Act. Improving availability of resources for hospitals and providers in areas with high Latino population growth could help alleviate financial pressures. PMID:26066960

  11. Populational Growth Models Proportional to Beta Densities with Allee Effect

    NASA Astrophysics Data System (ADS)

    Aleixo, Sandra M.; Rocha, J. Leonel; Pestana, Dinis D.

    2009-05-01

    We consider populations growth models with Allee effect, proportional to beta densities with shape parameters p and 2, where the dynamical complexity is related with the Malthusian parameter r. For p>2, these models exhibit a population dynamics with natural Allee effect. However, in the case of 1

  12. Relationships between growth, population structure and sea surface temperature in the temperate solitary coral Balanophyllia europaea (Scleractinia, Dendrophylliidae)

    NASA Astrophysics Data System (ADS)

    Goffredo, S.; Caroselli, E.; Mattioli, G.; Pignotti, E.; Zaccanti, F.

    2008-09-01

    The demographic characteristics of the solitary zooxanthellate scleractinian Balanophyllia europaea, endemic to the Mediterranean, were determined in six populations, on a latitudinal gradient along the Italian coast, and compared with the mean annual sea surface temperature (SST). Growth rate correlated negatively, and asymptotic length of the individuals positively with SST. With increasing SST, the distributions of age frequencies moved away from a typical steady state structure (i.e., exponential decrease in the frequency of individuals with age), indicating less stable populations and showed a deficiency of individuals in the younger-age classes. These observations suggest that high temperatures are an adverse factor to the B. europaea symbiosis. Using projected increases in seawater temperature, most of the B. europaea populations in the Mediterranean are expected to be close to their thermal limits by 2100 and the populations at that time may support few young individuals.

  13. In Bacillus subtilis LutR is part of the global complex regulatory network governing the adaptation to the transition from exponential growth to stationary phase.

    PubMed

    Irigül-Sönmez, Öykü; Köroğlu, Türkan E; Öztürk, Büşra; Kovács, Ákos T; Kuipers, Oscar P; Yazgan-Karataş, Ayten

    2014-02-01

    The lutR gene, encoding a product resembling a GntR-family transcriptional regulator, has previously been identified as a gene required for the production of the dipeptide antibiotic bacilysin in Bacillus subtilis. To understand the broader regulatory roles of LutR in B. subtilis, we studied the genome-wide effects of a lutR null mutation by combining transcriptional profiling studies using DNA microarrays, reverse transcription quantitative PCR, lacZ fusion analyses and gel mobility shift assays. We report that 65 transcriptional units corresponding to 23 mono-cistronic units and 42 operons show altered expression levels in lutR mutant cells, as compared with lutR(+) wild-type cells in early stationary phase. Among these, 11 single genes and 25 operons are likely to be under direct control of LutR. The products of these genes are involved in a variety of physiological processes associated with the onset of stationary phase in B. subtilis, including degradative enzyme production, antibiotic production and resistance, carbohydrate utilization and transport, nitrogen metabolism, phosphate uptake, fatty acid and phospholipid biosynthesis, protein synthesis and translocation, cell-wall metabolism, energy production, transfer of mobile genetic elements, induction of phage-related genes, sporulation, delay of sporulation and cannibalism, and biofilm formation. Furthermore, an electrophoretic mobility shift assay performed in the presence of both SinR and LutR revealed a close overlap between the LutR and SinR targets. Our data also revealed a significant overlap with the AbrB regulon. Together, these findings reveal that LutR is part of the global complex, interconnected regulatory systems governing adaptation of bacteria to the transition from exponential growth to stationary phase. PMID:24196425

  14. Population and prehistory I: Food-dependent population growth in constant environments.

    PubMed

    Lee, Charlotte T; Tuljapurkar, Shripad

    2008-06-01

    We present a demographic model that describes the feedbacks between food supply, human mortality and fertility rates, and labor availability in expanding populations, where arable land area is not limiting. This model provides a quantitative framework to describe how environment, technology, and culture interact to influence the fates of preindustrial agricultural populations. We present equilibrium conditions and derive approximations for the equilibrium population growth rate, food availability, and other food-dependent measures of population well-being. We examine how the approximations respond to environmental changes and to human choices, and find that the impact of environmental quality depends upon whether it manifests through agricultural yield or maximum (food-independent) survival rates. Human choices can complement or offset environmental effects: greater labor investments increase both population growth and well-being, and therefore can counteract lower agricultural yield, while fertility control decreases the growth rate but can increase or decrease well-being. Finally we establish equilibrium stability criteria, and argue that the potential for loss of local stability at low population growth rates could have important consequences for populations that suffer significant environmental or demographic shocks. PMID:18439637

  15. Population growth, agrarian peasant economy and environmental degradation in Tanzania.

    PubMed

    Madulu, N F

    1995-03-01

    Population strategies to relieve the density pressures on land and resources in Tanzania have not considered the basic causes of population growth. Resettlement results in the same environmental degradation as in the original settlement. There should be a reduction in the population growth and planning of proper land use and resource exploitation before resettlement. Rural development must include a decline in the dependency on subsistence agriculture. Population in Tanzania increased by 213% during 1948-88. An absolute increase in population size during 1978-88 is recorded despite a slight decline in the rate of growth. Death rates declined, but birth rates were relatively stable at around 50 per 1000 population. Regions with the highest growth rates were Dar es Salaam (4.8%), Rukwa (4.3%), Arusha (3.8%), Mbeya (3.1%), and Ruvuma (3.2%). The regions with the lowest rates were Tanga and Kilimanjaro (2.1%), Coast (2.1%), Lindi (2%), and Mtwara (1.4%). Low growth rates are attributed to low fertility and high infertility. Other factors affecting high growth rates are culture, rates of natural increase, intensity of internal and international migration, climatic conditions, and availability of resources. In 1988 46% of the population was under 15 years old. Per capita land availability declined from 11.8 hectares in 1948 to 3.8 hectares in 1988. The number of landless peasants increased. Productivity declined, and distances to farms increased. The total fertility rate was 6.5 children per woman in 1988 and 6.1 during 1991-92. Slight declines were apparent in the crude birth rate also. High fertility was a response to universal marriage, low contraceptive use (7% using modern methods during 1991-92), declining lactation periods, high mortality rates, and old traditions favoring large families. Children were used extensively in time-consuming and labor-intensive activities, such as fetching water. The mean number of children ever born was higher among women with 1

  16. Meteorological limits on the growth and development of screwworm populations

    NASA Technical Reports Server (NTRS)

    Phinney, D. E.; Arp, G. K.

    1978-01-01

    A program to evaluate the use of remotely sensed data as an additional tool in existing and projected efforts to eradicate the screwworm began in 1973. Estimating weather conditions by use of remotely sensed data was part of the study. Next, the effect of weather on screwworm populations was modeled. A significant portion of the variation in screwworm population growth and development has been traced to weather-related parameters. This report deals with the salient points of the weather and the screwworm population interaction.

  17. Economic consequences of population size, structure and growth.

    PubMed

    Lee, R

    1983-01-01

    There seems to be 4 major approaches to conceptualizing and modeling demographic influences on economic and social welfare. These approaches are combined in various ways to construct richer and more comprehensive models. The basic approaches are: demographic influences on household or family behavior; population growth and reproducible capital; population size and fixed factors; and population and advantages of scale. These 4 models emphasize the supply side effects of population. A few of the ways in which these theories have been combined are sketched. Neoclassical growth models often have been combined with age distributed populations of individuals (or households), assumed to pursue optimal life cycle consumption and saving. In some well known development models, neoclassical growth models for the modern sector are linked by labor markets and migration to fixed factor (land) models of the traditional (agricultural) sector. A whole series of macro simulation models for developed and developing countries was based on single sector neoclassical growth models with age distributed populations. Yet, typically the household level foundations of assumed age distribution effects were not worked out. Simon's (1977) simulation models are in a class by themselves, for they are the only models that attempt to incorporate all the kinds of effects discussed. The economic demography of the individual and family cycle, as it is affected by regimes of fertility, mortality, and nuptiality, taken as given, are considered. The examination touches on many of the purported consequences of aggregate population growth and age composition, since so many of these are based implicitly or explicitly on assertions about micro level behavior. Demographic influences on saving and consumption, on general labor supply and female labor supply, and on problems of youth and old age dependency frequently fall in this category. Finally, attention is focused specifically on macro economic issues in

  18. Women and Population Growth: Choice beyond Childbearing. Worldwatch Paper 16.

    ERIC Educational Resources Information Center

    Newland, Kathleen

    The paper explores the relationship of women's childbearing attitudes to educational and work opportunities. Program administrators for family planning, educational programs, and national development efforts in developing countries must realize the importance of the social and cultural environment in designing programs to reduce population growth.…

  19. Is There Hidden Potential for Rural Population Growth in Sweden?

    ERIC Educational Resources Information Center

    Niedomysl, Thomas; Amcoff, Jan

    2011-01-01

    Rural depopulation is a concern in many countries, and various policy initiatives have been taken to combat such trends. This article examines whether hidden potential for rural population growth can be found in Sweden. If such potential exists, it implies that the development prospects for many rural areas are not as unpromising as they may seem…

  20. The Economic Base of Recent Population Growth in Nonmetropolitan Settings.

    ERIC Educational Resources Information Center

    Long, Larry; DeAre, Diana

    In the late 1970s both jobs and population were growing more rapidly outside metropolitan areas. As a group, nonmetropolitan counties not adjacent to a metropolitan area experienced a faster rate of employment growth than metropolitan areas between 1975-79. Even in rural counties (no urban place of 2,500 or more) not adjacent to a metropolitan…

  1. Computer Simulation of the Population Growth (Schizosaccharomyces Pombe) Experiment.

    ERIC Educational Resources Information Center

    Daley, Michael; Hillier, Douglas

    1981-01-01

    Describes a computer program (available from authors) developed to simulate "Growth of a Population (Yeast) Experiment." Students actively revise the counting techniques with realistically simulated haemocytometer or eye-piece grid and are reminded of the necessary dilution technique. Program can be modified to introduce such variables as…

  2. An Exceptional Exponential Function

    ERIC Educational Resources Information Center

    Curgus, Branko

    2006-01-01

    We show that there is a link between a standard calculus problem of finding the best view of a painting and special tangent lines to the graphs of exponential functions. Surprisingly, the exponential function with the "best view" is not the one with the base "e." A similar link is established for families of functions obtained by composing…

  3. Immigration enhances fast growth of a newly established source population.

    PubMed

    Santoro, Simone; Green, Andy J; Figuerola, Jordi

    2016-04-01

    Abstract. Immigration and local recruitment play a central role in determining the growth rate of breeding populations. Unraveling these processes in newly established pop- ulations is of great importance to increase our understanding of how species change their distributions in response to global change. We studied the largest colony of glossy ibis (Plegadis falcinellus) in Western Europe (established in 1996 in Doñana, SW-Spain) by using capture-recapture methods, count estimates, and projection matrix modeling to: (1) test the effect of resource availability and competition on local recruitment dynamics, (2) investigate the contribution of local recruitment vs. immigration on population growth, and (3) assess the role of this population in source/sink dynamics. We found different dynamics before and after the establishment of satellite colonies in Doñana in 2004. Between 1996 and 2003, the population increased rapidly, fueled by immigrants (≈ 58 breeding females/ yr). Between 2003 and 2007, however, both colony size increase and immigration were negligible. Immigration played a major role in colony growth, but simultaneously this colony was a source population driving expansion of the species range as suggested by (1) absolute and relative estimates of the observed growth rate relative to that predicted by self-recruitment, and (2) numerous observations of Doñana-born individuals breeding elsewhere. Local recruitment, which was particularly high for first-year individuals (probability > 0.8 for the early study years), was not directly related to resource availability or previous-year breeding success. Local recruitment decreased rapidly at a threshold population size, however, when other satellite colonies became established at Dofiana. Our study suggests that even when recruitment at an early age and high productivity are observed, immigration can still play a pivotal role in promoting the fast growth of new populations at the edge of a species range, at

  4. Habitat-Specific Population Growth of a Farmland Bird

    PubMed Central

    Arlt, Debora; Forslund, Pär; Jeppsson, Tobias; Pärt, Tomas

    2008-01-01

    Background To assess population persistence of species living in heterogeneous landscapes, the effects of habitat on reproduction and survival have to be investigated. Methodology/Principal Findings We used a matrix population model to estimate habitat-specific population growth rates for a population of northern wheatears Oenanthe oenanthe breeding in farmland consisting of a mosaic of distinct habitat (land use) types. Based on extensive long-term data on reproduction and survival, habitats characterised by tall field layers (spring- and autumn-sown crop fields, ungrazed grasslands) displayed negative stochastic population growth rates (log λs: −0.332, −0.429, −0.168, respectively), that were markedly lower than growth rates of habitats characterised by permanently short field layers (pastures grazed by cattle or horses, and farmyards, log λs: −0.056, +0.081, −0.059). Although habitats differed with respect to reproductive performance, differences in habitat-specific population growth were largely due to differences in adult and first-year survival rates, as shown by a life table response experiment (LTRE). Conclusions/Significance Our results show that estimation of survival rates is important for realistic assessments of habitat quality. Results also indicate that grazed grasslands and farmyards may act as source habitats, whereas crop fields and ungrazed grasslands with tall field layers may act as sink habitats. We suggest that the strong decline of northern wheatears in Swedish farmland may be linked to the corresponding observed loss of high quality breeding habitat, i.e. grazed semi-natural grasslands. PMID:18714351

  5. [Rapid population growth is unfavorable to prosperity of minority areas].

    PubMed

    Zhang, T

    1991-04-01

    According to China's 1990 census, the ethnic minority population increased by 35.5% from the 1982 census, 23 percentage points higher than the Han nationality. Among 55 ethnic minorities, 16 had growth rates of over 50% between 1982 and 1990. The Korean ethnic minority had the lowest growth rate, which was only 8.73%. The high growth rate of the ethnic minority population was due to the high level of natural increase and policy factors. With the changing policies toward ethnic minorities, preferential treatment has been give to the them in education, employment, career promotion, and childbearing quota. These policies stimulated switching from the Han nationality to the minority status. 50-60% of growth in the minority population between the 2 censuses has been attributed to the status switching. The per capita GNP in the minority administrative areas was 54.9% lower than in Han areas in 1980. It became 69% lower in 1988. Excessive growth of the ethnic minority population hindered education attainment and economic and resources development. Some ethnic minorities have an illiteracy rate of over 90% and an infant mortality rate of 171/1000. The ecological environment in certain minority areas is deteriorating due to extensive tree-felling and primitive farming methods. In contrast, the Korean minority developed its education program earlier on. Its total fertility rate has been around 1.4 since 1974 and it is gradually changing into a stationary population. Currently, no Korean National counties or townships are below the poverty line. The prevalence of disability is 3.5% in the Korean population, the lowest of all the ethnic groups. It is important to focus population programs among the ethnic minorities to increase their health and educational status. Promoting family planning programs, strictly enforcing the criteria for switching to minority status or setting deadlines to preference treatment eligibility for those who switched status could be possible policies

  6. How exponential are FREDs?

    NASA Astrophysics Data System (ADS)

    Schaefer, Bradley E.; Dyson, Samuel E.

    1996-08-01

    A common Gamma-Ray Burst-light curve shape is the ``FRED'' or ``fast-rise exponential-decay.'' But how exponential is the tail? Are they merely decaying with some smoothly decreasing decline rate, or is the functional form an exponential to within the uncertainties? If the shape really is an exponential, then it would be reasonable to assign some physically significant time scale to the burst. That is, there would have to be some specific mechanism that produces the characteristic decay profile. So if an exponential is found, then we will know that the decay light curve profile is governed by one mechanism (at least for simple FREDs) instead of by complex/multiple mechanisms. As such, a specific number amenable to theory can be derived for each FRED. We report on the fitting of exponentials (and two other shapes) to the tails of ten bright BATSE bursts. The BATSE trigger numbers are 105, 257, 451, 907, 1406, 1578, 1883, 1885, 1989, and 2193. Our technique was to perform a least square fit to the tail from some time after peak until the light curve approaches background. We find that most FREDs are not exponentials, although a few come close. But since the other candidate shapes come close just as often, we conclude that the FREDs are misnamed.

  7. Understanding the size growth of massive galaxies through stellar populations

    NASA Astrophysics Data System (ADS)

    Ferreras, I.; Trujillo, I.; Mármol-Queraltó, E.; Pérez-González, P.

    Massive early-type galaxies undergo a significant process of evolution with redshift on the stellar mass vs size plane. Furthermore, this trend does not depend on the age of their stellar populations. Therefore, such an evolution should involve processes that do not include a significant amount of star formation, leaving (mostly) dry mergers as the main growth channel. By studying close pairs involving a massive galaxy, one can quantify the role of mergers on the growth of massive galaxies. A recent study based on the SHARDS dataset reveals that minor mergers cannot be the dominant mechanism to explain the bulk of size growth in these systems. Merging is found to provide a constant fractional growth rate of ~10% per Gyr from redshift z=1, corresponding to an overall stellar mass increase of 2× between z=1 and z=0.

  8. Islamic Republic of Iran population growth rate declines.

    PubMed

    1996-01-01

    In April 1996, at the 52nd Session of the UN Economic and Social Commission for Asia and the Pacific (ESCAP), the delegate from the Islamic Republic of Iran announced that social indicators indicate acceptable improvement. The average population growth rate fell from 3.9% (1981-1991) to less than 2% (1995). High birth rates and an influx of refugees during 1981-1991 accounted for the high population growth rate. The marked decline in the birth rate, brought about mainly by effective family planning and health programs, has contributed greatly to the reduced population growth rate. The government has focused on rural areas. 86% of rural households now have access to piped water. More than 60% have electricity. The overall literacy rate in Iran has reached 79%. The entire population has access to free or subsidized primary health care services. The Second Development Plan of Iran centers on the significance of the role that mothers have in shaping society and individuals by their child raising abilities, particularly in the early years. The Iranian delegate endorsed the secretariat's plan for helping members and associate members to reach their development goals and objectives. PMID:12291139

  9. Wirth: Key to slowing population growth -- education of girls.

    PubMed

    Fuller, J

    1998-09-01

    The president of the UN Foundation, Tim Wirth, cites education programs for girls as a key to slowing the pace of population growth. Wirth suggests stabilizing the world's population in order to be sure, particularly in the poorest countries, that people have opportunities. The security of the nation and the world hinges upon a sustainable, equitable balance between human numbers and the planet's capacity to support life. Disregarding the issue of population and consumption will destroy the habitat of the world and destroy the very systems that allow life to exist on Earth. The education of girls is a critical area for stabilizing population. Hence, inadequate education is a powerful determinant of high fertility and ensures that individuals do not live up to their potential. The Program of Action adopted at the 1994 ICPD held in Cairo showed that when women have control over their lives, they are better able to contribute to a society that presents them with choices. Conversely, the lack of decision-making power negatively affects a woman's productive role in the family. Wirth also emphasizes the importance of family planning as part of a comprehensive approach to slow population growth. Wirth believes that the Cairo Plus Five Conference to be held in the Hague on February 8-12, 1999, will be very important in making the Program of Action more visible and effective. PMID:12322266

  10. An Unusual Exponential Graph

    ERIC Educational Resources Information Center

    Syed, M. Qasim; Lovatt, Ian

    2014-01-01

    This paper is an addition to the series of papers on the exponential function begun by Albert Bartlett. In particular, we ask how the graph of the exponential function y = e[superscript -t/t] would appear if y were plotted versus ln t rather than the normal practice of plotting ln y versus t. In answering this question, we find a new way to…

  11. [The decline in population growth, income distribution, and economic recession].

    PubMed

    Banguero, H

    1983-05-01

    This work uses Keynesian principles and an analysis of the Colombian population in the 1970s to argue that the Colombian policy of slowing population growth, which was adopted with the aim of improving the general welfare of the population, has had shortterm negative effects on effective demand and thus on the level of employment and welfare. These negative effects were caused by the inflexibility of income distribution, which prevented expansion of the internal market, complicated by the stagnant condition of the external sector and the budget deficit. The results of the Colombian case study demonstrate how the deceleration of population growth beginning in the 1960s had a significant impact on the levels of consumption and savings and on the patterns of consumption, leading to low levels of investment and little dynamism. Although the current Colombian economic recession is aggravated by contextual factors such as the world economic recession, the high cost of capital, the industrial recession, and declining food production among others, at the core of the crisis are longer term structural determinants such as the decline in the rate of population growth and the highly unequal distribution of income and wealth, which have contributed to a shrinking of the internal market for some types of goods. Given the unlikelihood of renewed rapid population growth, the Keynesian model suggests that the only alternative for increasing aggregate demand is state intervention through public spending and investment and reorientation of the financial system to achieve a dynamic redistribution of income. Based on these findings and on proposals of other analysts, a stragegy for revitalization is proposed which would imply a gradual income redistribution to allow increased consumption of mass produced goods by the low income groups. Direct consumption subsidies would be avoided because of their inflationary and import-expanding tendencies; rather, incentives and support would be

  12. Rapid population growth and environmental degradation: ultimate versus proximate factors.

    PubMed

    Shaw, R P

    1989-01-01

    This philosophical review of 2 arguments about responsibility for and solutions to environmental degradation concludes that both sides are correct: the ultimate and the proximal causes. Ultimate causes of pollution are defined as the technology responsible for a given type of pollution, such as burning fossil fuel; proximate causes are defined as situation-specific factors confounding the problem, such as population density or rate of growth. Commoner and others argue that developed countries with low or negative population growth rates are responsible for 80% of world pollution, primarily in polluting technologies such as automobiles, power generation, plastics, pesticides, toxic wastes, garbage, warfaring, and nuclear weapons wastes. Distortionary policies also contribute; examples are agricultural trade protection, land mismanagement, urban bias in expenditures, and institutional rigidity., Poor nations are responsible for very little pollution because poverty allows little waste or expenditures for polluting, synthetic technologies. The proximal causes of pollution include numbers and rate of growth of populations responsible for the pollution. Since change in the ultimate cause of pollution remains out of reach, altering the numbers of polluters can make a difference. Predictions are made for proportions of the world's total waste production, assuming current 1.6 tons/capita for developed countries and 0.17 tons/capita for developing countries. If developing countries grow at current rates and become more wealthy, they will be emitting half the world's waste by 2025. ON the other hand, unsustainable population growth goes along with inadequate investment in human capital: education, health, employment, infrastructure. The solution is to improve farming technologies in the 117 non-self-sufficient countries, fund development in the most unsustainable enclaves of growing countries, break institutionalized socio-political rigidity in these enclaves, and focus on

  13. Population growth and the changing ecosystem in Mindanao.

    PubMed

    Magdalena, F V

    1996-04-01

    Mindanao is the second largest island in the Philippines. Once considered the greenest spot on earth, it has since been highly exploited. This paper discusses the changing ecosystem of the island as a result of rapid population growth since the early 1900s. Not much is known about Mindanao before 1900. From 1913, however, population grew on Mindanao as the American colonial government established agricultural colonies to open up the south for trade and development. Colonial settlement together with migration and natural population increase led to environmental resource degradation and the displacement of indigenous communities such as the Moros and Lumads. Legal and illegal logging and rampant kaingin agriculture have also stressed the environment. The opening of the Mindanao frontier, Philippine development, the Great Migration, incursion of the Mindanao upland, deforestation, the displacement of indigenous communities, and the possible maintenance and rehabilitation of the ecosystem are discussed. PMID:12292068

  14. Stochastic resonance in a generalized Von Foerster population growth model

    NASA Astrophysics Data System (ADS)

    Lumi, N.; Mankin, R.

    2014-11-01

    The stochastic dynamics of a population growth model, similar to the Von Foerster model for human population, is studied. The influence of fluctuating environment on the carrying capacity is modeled as a multiplicative dichotomous noise. It is established that an interplay between nonlinearity and environmental fluctuations can cause single unidirectional discontinuous transitions of the mean population size versus the noise amplitude, i.e., an increase of noise amplitude can induce a jump from a state with a moderate number of individuals to that with a very large number, while by decreasing the noise amplitude an opposite transition cannot be effected. An analytical expression of the mean escape time for such transitions is found. Particularly, it is shown that the mean transition time exhibits a strong minimum at intermediate values of noise correlation time, i.e., the phenomenon of stochastic resonance occurs. Applications of the results in ecology are also discussed.

  15. Stochastic resonance in a generalized Von Foerster population growth model

    SciTech Connect

    Lumi, N.; Mankin, R.

    2014-11-12

    The stochastic dynamics of a population growth model, similar to the Von Foerster model for human population, is studied. The influence of fluctuating environment on the carrying capacity is modeled as a multiplicative dichotomous noise. It is established that an interplay between nonlinearity and environmental fluctuations can cause single unidirectional discontinuous transitions of the mean population size versus the noise amplitude, i.e., an increase of noise amplitude can induce a jump from a state with a moderate number of individuals to that with a very large number, while by decreasing the noise amplitude an opposite transition cannot be effected. An analytical expression of the mean escape time for such transitions is found. Particularly, it is shown that the mean transition time exhibits a strong minimum at intermediate values of noise correlation time, i.e., the phenomenon of stochastic resonance occurs. Applications of the results in ecology are also discussed.

  16. What is Growth? Concurrent determination of a bacterial population's many shades of growth

    NASA Astrophysics Data System (ADS)

    Lambert, Guillaume; Kussell, Edo

    2013-03-01

    One of the most exciting developments in the study of the physics of microbial life is the ability to precisely monitor stochastic variations of gene expression in individual cells. A fundamental question is whether these variations improve the long-term ability of a population to adapt to new environments. While variations in gene expression in bacteria are easily measured through the use of reporter systems such as green fluorescent proteins and its variants, precise determination of a cell's growth rate, and how it is influenced by its immediate environment, remains challenging. Here, we show that many conflicting and ambiguous definitions of bacterial growth can actually be used interchangeably in E. coli. Indeed, by monitoring small populations of E. coli bacteria inside a microfluidic device, we show that seemingly independent measurements of growth (elongation rate and the average division time, for instance) agree very precisely with one another. We combine these definitions with the population's length and age distribution to very precisely quantify the influence of temperature variations on a population's growth rate. We conclude by using coalescence theory to describe the evolution of a population's genetic structure over time.

  17. Apocalypse when? Population growth and food supply in South Asia.

    PubMed

    Greenspan, A

    1994-12-01

    Food demands for staple grains are expected to almost double over the next 25 years in South Asia, due to population growth and increased standards of living. Trends in the mid-1990s suggest that neither pessimism nor optimism prevails in the region. There is wide diversity among and within countries. Trends suggest that population densities are already the highest in the world, and the amount of arable land is declining. Urban growth has moved onto farm land and farmers have been pushed onto more marginal lands or have become landless. Land intensification has produced mixed results. Cereal production per capita has increased since the 1950s in India, with about 75% of the region's population, but Pakistan's increases were not sustained into the 1980s. Average daily caloric intake per person in the region of 2214 is below the level in Sub-Saharan Africa. In Bangladesh, levels are particularly worrisome at 2037. The environmental impact has not been easily quantified, but experts have suggested that pressure on farm land has contributed to loss of soil fertility and water resource loss. Further intensification of farming is feasible, but difficult and more expensive than in the past. Regardless of production problems and solutions, there is also the very real problem of poor food distribution and lack of purchasing power. Farm management skills must be utilized, if environmental degradation is to be avoided. There is the added unknown of what climate changes will occur and how agricultural production will be affected. The policy implications are that increased food production must be made a political priority. Policies must support agricultural research into improved technologies and support distribution of technological advances to a wider number of farmers. Rural infrastructures such as roads, market outlets, and credit agencies must be established. Policies must be removed that disadvantage farmers, such as inappropriate subsidies for irrigation water

  18. Age-related changes in the distributions of depressive symptom items in the general population: a cross-sectional study using the exponential distribution model

    PubMed Central

    Kawasaki, Yohei; Ide, Kazuki; Yamada, Hiroshi; Furukawa, Toshiaki A.; Ono, Yutaka

    2016-01-01

    Background. Previous research has reported inconsistent evidence of the trajectory of depressive symptoms across the adult lifespan. We investigated how the distributions of each item score change with age and determined whether the trajectory of depressive symptoms varied with the scoring methods of the questionnaire. Methods. We analyzed data collected from 21,040 subjects who participated in the national survey in Japan. Depressive symptoms were assessed using the Center for Epidemiologic Studies Depression Scale (CES-D). The CES-D has 20 items, each of which is scored in four grades of “rarely,” “some,” “much,” and “most of the time.” We used the exponential distribution model which fits the distributions of 16 negative symptom items of CES-D, with the probabilities of “some,” “much,” “most,” and “rarely” expressed as P, Pr, Pr2, and 1 − P × (r2 + r + 1). Results. The distributions of the responses to 16 negative symptom items followed the common exponential model across all age groups. The mean of the estimated parameter r of 16 negative items showed a U-shape pattern, being high during 12–29 years, remaining low during 30–50 years, and then increasing again over 60 years. The trajectory of depressive symptom scores simulating the binary method was different from that of the empirical scores using the Likert method. Conclusions. Our findings show that the increase in the depressive symptoms score during older age is based on the increase of the parameter r. The differences in the scoring method may contribute to the different age-related patterns across the adult lifespan. PMID:26788427

  19. Age-related changes in the distributions of depressive symptom items in the general population: a cross-sectional study using the exponential distribution model.

    PubMed

    Tomitaka, Shinichiro; Kawasaki, Yohei; Ide, Kazuki; Yamada, Hiroshi; Furukawa, Toshiaki A; Ono, Yutaka

    2016-01-01

    Background. Previous research has reported inconsistent evidence of the trajectory of depressive symptoms across the adult lifespan. We investigated how the distributions of each item score change with age and determined whether the trajectory of depressive symptoms varied with the scoring methods of the questionnaire. Methods. We analyzed data collected from 21,040 subjects who participated in the national survey in Japan. Depressive symptoms were assessed using the Center for Epidemiologic Studies Depression Scale (CES-D). The CES-D has 20 items, each of which is scored in four grades of "rarely," "some," "much," and "most of the time." We used the exponential distribution model which fits the distributions of 16 negative symptom items of CES-D, with the probabilities of "some," "much," "most," and "rarely" expressed as P, Pr, Pr (2), and 1 - P × (r (2) + r + 1). Results. The distributions of the responses to 16 negative symptom items followed the common exponential model across all age groups. The mean of the estimated parameter r of 16 negative items showed a U-shape pattern, being high during 12-29 years, remaining low during 30-50 years, and then increasing again over 60 years. The trajectory of depressive symptom scores simulating the binary method was different from that of the empirical scores using the Likert method. Conclusions. Our findings show that the increase in the depressive symptoms score during older age is based on the increase of the parameter r. The differences in the scoring method may contribute to the different age-related patterns across the adult lifespan. PMID:26788427

  20. Review of "Going Exponential: Growing the Charter School Sector's Best"

    ERIC Educational Resources Information Center

    Garcia, David

    2011-01-01

    This Progressive Policy Institute report argues that charter schools should be expanded rapidly and exponentially. Citing exponential growth organizations, such as Starbucks and Apple, as well as the rapid growth of molds, viruses and cancers, the report advocates for similar growth models for charter schools. However, there is no explanation of…

  1. Population growth and food supply in sub-Saharan Africa.

    PubMed

    Meerman, J; Cochrane, S H

    1982-09-01

    It is argued in this article that sub-Saharan Africa, given its present institutions and endowments of capital and technology, is already dangerously close to overpopulation. The rapid growth of its population projected for the next decades will greatly increase human misery and depress economic development. Specifically, rapid population growth will have disastrous effects on the region's ability to increase exports and provide people with food. There must be a search for new ways in which these effects could be mitigated. In sub-Saharan Africa fertility either continues to be very high or is increasing, in part due to some decline in traditional practices that reduce fertility, such as prolonged breastfeeding. This situation and the expectation of declining mortality imply that African population growth may increase further. Currently, population in sub-Saharan Africa is about half that of India and a third of China. There are 2 main reasons why reduced fertility in the next few decades is unlikely in sub-Saharan Africa as a whole: Africa has low literacy, high infant and child mortality, and low urbanization; and average African fertility rates may even increase for the next 20 years or so. The question that arises is what are the implications of continuing and rapid population growth for the African food supply. The region's cereal production is largely restricted to 4 grains, i.e., millet, sorghum, maize, and rice. The volume of grain production is less, by weight, than 60% of the production of roots and tubers. There are 2 main differences between the output of these crops in sub-Saharan Africa and the rest of the world: yields/hectare are lower in Africa than in elsewhere; and yields have generally been decreasing or largely constant in Africa. The low productivity has several causes. Today, population pressure has brought diminishing returns to traditional agriculture in much of the Sahel and the savanna, in parts of East Africa, Southern Africa, and parts

  2. Population growth and poverty in the developing world.

    PubMed

    Birdsall, N

    1980-12-01

    The links between rapid population growth and the absolute poverty currently affecting 780 million people in the developing countries (excluding China and other centrally planned economies) were examined. Absolute poverty is defined as having less than the income necessary to ensure a daily diet of 2150 calories per person ($200 per person a year in 1970 United States dollars). Focus is on poverty and demography in the developing world (defining poverty; income, fertility and life expectancy; demographic change and poverty), effect of poverty on fertility, family planning programs and the poor, and the outlook for the future. Rapid population growth stretches both national and family budgets thin with the increasing numbers of children to be fed and educated and workers to be provided with jobs. Slower per capita income growth, lack of progress in reducing income inequality, and more poverty are the probable consequences. Many characteristics of poverty can cause high fertility -- high infant mortality, lack of education for women in particular, too little family income to invest in children, inequitable shares in national income, and the inaccessibility of family planning. Experience in China, Indonesia, Taiwan, Colombia, Korea, Sri Lanka, Cuba and Costa Rica demonstrate that birthrates can decline rapidly in low income groups and countries when basic health care, education, and low-cost or free family planning services are made widely available. PMID:12262264

  3. Interspecific synchrony of seabird population growth rate and breeding success

    PubMed Central

    Robinson, James P W; Dornelas, Maria; Ojanguren, Alfredo F

    2013-01-01

    Environmental variability can destabilize communities by causing correlated interspecific fluctuations that weaken the portfolio effect, yet evidence of such a mechanism is rare in natural systems. Here, we ask whether the population dynamics of similar sympatric species of a seabird breeding community are synchronized, and if these species have similar exceptional responses to environmental variation. We used a 24-year time series of the breeding success and population growth rate of a marine top predator species group to assess the degree of synchrony between species demography. We then developed a novel method to examine the species group – all species combined – response to environmental variability, in particular, whether multiple species experience similar, pronounced fluctuations in their demography. Multiple species were positively correlated in breeding success and growth rate. Evidence of “exceptional” years was found, where the species group experienced pronounced fluctuations in their demography. The synchronous response of the species group was negatively correlated with winter sea surface temperature of the preceding year for both growth rate and breeding success. We present evidence for synchronous, exceptional responses of a species group that are driven by environmental variation. Such species covariation destabilizes communities by reducing the portfolio effect, and such exceptional responses may increase the risk of a state change in this community. Our understanding of the future responses to environmental change requires an increased focus on the short-term fluctuations in demography that are driven by extreme environmental variability. PMID:23919147

  4. Population growth and United States politics in the 1970s.

    PubMed

    Nash, A E

    1973-01-01

    The 2 themes of this century, increasing environmental fragility and increasing human demands on government, are underlined by the failure of government to effectively govern, and the complex technology and modern communication systems which further divide the developing nations from the developed ones. Population stabilization may help relieve the tension between increasing expectation from government and the fiscal bind in 3 ways: 1)a higher per capita income would increase per capita government revenue which would have a better chance of meeting citizen expectations, 2)a moderately redistributive effect on personal income might occur by decreasing unwanted fertility through the dynamics of economics and increasing the role of government in elevating living standards, and 3)with reduction of government expenditure per capita, the cost of providing any given level of service would decrease. The nuclear age has altered the concept of what constitutes national security. Rapid population growth in the developing countries is also significant, and the United States economy depends on overseas investment. A constructive foreign policy, as opposed to neoimperialism or isolationism, is recommended to help influence world population growth. PMID:4788263

  5. Colonization, population growth, and nesting success of Black Oystercatchers following a seismic uplift

    USGS Publications Warehouse

    Gill, V.A.; Hatch, Shyla A.; Lanctot, Richard B.

    2004-01-01

    We present data on the colonization of Middleton Island, Alaska, by Black Oystercatchers (Haematopus bachmani) following the creation of an extensive rocky intertidal zone after the Alaskan earthquake of 1964. The first pair of oystercatchers was detected in 1976, and it was another 5 years before the population increased to three pairs. Oystercatcher numbers increased steadily thereafter, with a population explosion occurring in the 1990s. By 2002, there were 171 territorial pairs on the island. The total number of birds increased from two in 1976 to 718 in 2002. Breeding-pair densities on Middleton Island are the highest recorded for any portion of Alaska, averaging more than 5 pairs per km of shoreline in 2002. Nesting success in 2001 and 2002 was greater (83% or more of the eggs laid hatched) than that reported for any other population of oystercatchers in Alaska or along the Pacific Coast. We attribute this exponential growth rate and exceptionally high reproductive success to the large area of available and suitable habitat, the low number of avian predators and the complete lack of mammalian predators, low rate of nest loss to high tides and storm surges, and a low level of human disturbance. We propose nominating Middleton Island as a regional Western Hemisphere Shorebird Reserve Network site because a high percentage of the world's and region's population of Black Oystercatchers resides there during the breeding season. Further, since Middleton Island may be the single most important site in Alaska for Black Oystercatchers, we suggest it be protected from future development.

  6. Growth in an English population from the Industrial Revolution.

    PubMed

    Mays, S; Brickley, M; Ives, R

    2008-05-01

    The rapid urbanization of the Industrial Revolution in 18th-19th century England presented new health challenges. Our aim is to investigate using English skeletal remains whether the living conditions for an urban working class group in the Industrial Revolution negatively impacted upon their skeletal growth compared with a population from a rural agrarian parish. The Industrial Revolution skeletal material is from St Martin's Churchyard, Birmingham (SMB), West Midlands. It dates primarily from the first half of the nineteenth century when Birmingham was a major manufacturing center. The rural group is from Wharram Percy (WP), North Yorkshire, and dates from 10th-19th century AD. The methodology involves plotting diaphyseal bone lengths versus dental age for subadults. No overall difference was found between the two populations in bone length-for-age among the 2- to 18-year cohort. However the younger parts of the SMB cohort were smaller than at WP; the opposite was true of the older parts of the cohort. Growth rate, as inferred from crosssectional data, appeared greater at SMB than at WP. The only result consistent with expectations is the larger bone dimensions in young children from WP, but this likely reflects prolonged breastfeeding at WP not differences in urban and rural environments. That the deleterious health effects that we know accompanied the major transition in human society from a rural agrarian to an urban industrialized living environment should be little manifest in skeletal endochondral growth data is discouraging for those who would use such methodology to monitor health in earlier populations. PMID:18186509

  7. Population growth of Yellowstone grizzly bears: Uncertainty and future monitoring

    USGS Publications Warehouse

    Harris, R.B.; White, Gary C.; Schwartz, C.C.; Haroldson, M.A.

    2007-01-01

    Grizzly bears (Ursus arctos) in the Greater Yellowstone Ecosystem of the US Rocky Mountains have recently increased in numbers, but remain vulnerable due to isolation from other populations and predicted reductions in favored food resources. Harris et al. (2006) projected how this population might fare in the future under alternative survival rates, and in doing so estimated the rate of population growth, 1983–2002. We address issues that remain from that earlier work: (1) the degree of uncertainty surrounding our estimates of the rate of population change (λ); (2) the effect of correlation among demographic parameters on these estimates; and (3) how a future monitoring system using counts of females accompanied by cubs might usefully differentiate between short-term, expected, and inconsequential fluctuations versus a true change in system state. We used Monte Carlo re-sampling of beta distributions derived from the demographic parameters used by Harris et al. (2006) to derive distributions of λ during 1983–2002 given our sampling uncertainty. Approximate 95% confidence intervals were 0.972–1.096 (assuming females with unresolved fates died) and 1.008–1.115 (with unresolved females censored at last contact). We used well-supported models of Haroldson et al. (2006) and Schwartz et al. (2006a,b,c) to assess the strength of correlations among demographic processes and the effect of omitting them in projection models. Incorporating correlations among demographic parameters yielded point estimates of λ that were nearly identical to those from the earlier model that omitted correlations, but yielded wider confidence intervals surrounding λ. Finally, we suggest that fitting linear and quadratic curves to the trend suggested by the estimated number of females with cubs in the ecosystem, and using AICc model weights to infer population sizes and λ provides an objective means to monitoring approximate population trajectories in addition to demographic

  8. Herbivory: effects on plant abundance, distribution and population growth

    PubMed Central

    Maron, John L; Crone, Elizabeth

    2006-01-01

    Plants are attacked by many different consumers. A critical question is how often, and under what conditions, common reductions in growth, fecundity or even survival that occur due to herbivory translate to meaningful impacts on abundance, distribution or dynamics of plant populations. Here, we review population-level studies of the effects of consumers on plant dynamics and evaluate: (i) whether particular consumers have predictably more or less influence on plant abundance, (ii) whether particular plant life-history types are predictably more vulnerable to herbivory at the population level, (iii) whether the strength of plant–consumer interactions shifts predictably across environmental gradients and (iv) the role of consumers in influencing plant distributional limits. Existing studies demonstrate numerous examples of consumers limiting local plant abundance and distribution. We found larger effects of consumers on grassland than woodland forbs, stronger effects of herbivory in areas with high versus low disturbance, but no systematic or unambiguous differences in the impact of consumers based on plant life-history or herbivore feeding mode. However, our ability to evaluate these and other patterns is limited by the small (but growing) number of studies in this area. As an impetus for further study, we review strengths and challenges of population-level studies, such as interpreting net impacts of consumers in the presence of density dependence and seed bank dynamics. PMID:17002942

  9. Social policy and population growth in South-East Asia.

    PubMed

    You Poh Seng Rao, B; Shantakumar, G

    1974-01-01

    Social and population policies are considered for the 10 countries comprising Southeast Asia--Burma, Indonesia, the Khmer Republic, Laos, Malaysia, the Philippines, Singapore, Thailand, North Vietnam, and South Vietnam. All but Singapore have high fertility rates and Burma, Indonesia, the Khmer Republic, Laos and the two Vietnams have high mortality rates also. Government expenditures for education and social security systems is expanding throughout the region and it is hoped that their continued growth will contribute substantially to the effective implementation of population policies. Population policies in the 5 countries which have them are discussed. These are Indonesia, Malaysia, the Philippines, Singapore, and Thailand. It is noted, however, that declaration of policy is but the first step. Strategies and programs differ from one country to the next and depend very much on the stage of development, level of literacy, degree of urbanization, and other factors. Family planning activities generally are endogenous to urban social systems but exogenous to rural social systems. Thus, the rural elite has a large role to play in making population policies an integral part of rural life. The possibility is considered of developing workable incentive packages integrating health, education, and social security benefits with suitable emphasis on fertility reduction. PMID:12307191

  10. Population growth and land use in Nepal: "the great turnabout".

    PubMed

    Hrabovszky, J P; Miyan, K

    1987-08-01

    Historically, Nepal has demonstrated a "great turnabout" trend, in which initial immigration from the lowland areas to the mountains has been replaced by accelerating migration from the hills to the plains. The reason for this reversal has been a rapid growth in population within the confines of limited availability of potentially cultivable land. Given Nepal's slow economic development, the overwhelming majority of increases in population have to be accommodated within the agricultural sector, on which 83% of Nepal's households are dependent. Fundamental land use issues in Nepal include rapid achievement of the final limit of land suitability for cultivation and the speed at which land can be brought into cultivation. The Government of Nepal has developed the objectives of increased food production to provide a satisfactory diet for the population, increased per capita income, improved regional balance in income and development, conservation of natural resources such as land and forests, and overall development of the economy through income generation, export earnings, and release of agricultural labor to other sectors. 3 perspective studies have identified a number of policies and programs that could bring Nepal closer to these goals. These studies analyzed potential land use development, agricultural production, and food availability by the year 2005. Most essential is the need to intensify land use not only in crop agriculture, but also grasslands and forest use. Land must be allocated to uses that represent the most productive use of that land without being degrading. Technologies are available for land use in each of the main types of uses--crop agriculture, livestock, and forests--that can provide protection against land degradation. Finally, irrigation is a key element in raising agricultural output. Close cooperation between the government and the people is crucial for the success of the task of finding a balance between population growth and its demand

  11. Defining and explaining tropical deforestation: shifting cultivation and population growth in colonial Madagascar (1896-1940).

    PubMed

    Jarosz, L

    1993-10-01

    The case study of deforestation in Madagascar demonstrated how deforestation is a complex phenomenon that reflects interconnections between land-based resources, human groups, and global political economy; specifically, there is a link between changing land use practices affecting shifting cultivation and tropical deforestation. The general development model of exponential population growth and shifting cultivation causing deforestation and environmental degradation is too simplified, places undue blame on the victims, and isolates shifting cultivation practices from the reality of land use patterns in specific places at specific times. Problematic also is the way definition, delimitation, and discussion of environmental problems shapes possible solutions. This analysis suggests a theoretical view that links reconstructed regional geography with political ecology. The assertion is that deforestation is historically based on multiple social processes within Madagascar. Land use practices and resource access decisions during the colonial period affected land management and degradation. The colonial state policy played a role in the destruction of tropical flora by fire, shifting cultivation, and grazing, and the responses of Europeans and Malagasys. Context and multiplicity of motivations and practices were key. A review was presented of reconstructed regional geography and political ecology and global tropical deforestation. The description of the political economy of deforestation during colonial times focused on the movement of population into the forests after 1896 and French annexation. Famine resulted. Shifting cultivation laws were passed between 1881 and 1913, due to the desire for rational forest resource management. Ecologically and socially these rules were difficult to enforce; there were resistance due to the threat of the elimination of subsistence living for wage work. Destructive logging practices and forest product extraction after 1921 are described

  12. Development Planning and Population Growth and Redistribution in the Republic of Iraq.

    ERIC Educational Resources Information Center

    El Attar, M. E.; Salman, A. D.

    Utilizing the 1947, 1957, and l965 census data and the 1970 preliminary population count, the relationship between population growth and redistribution and development planning in Iraq was examined. Trends in rural-urban population growth, migration, and population redistribution were examined as they pertained to the socioeconomic development…

  13. Estimated impact of global population growth on future wilderness extent

    NASA Astrophysics Data System (ADS)

    Dumont, E.

    2012-06-01

    Wilderness areas in the world are threatened by the environmental impacts of the growing global human population. This study estimates the impact of birth rate on the future surface area of biodiverse wilderness and on the proportion of this area without major extinctions. The following four drivers are considered: human population growth (1), agricultural efficiency (2), groundwater drawdown by irrigation (3), and non-agricultural space used by humans (buildings, gardens, roads, etc.) (4). This study indicates that the surface area of biodiverse unmanaged land will reduce with about 5.4% between 2012 and 2050. Further, it indicates that the biodiverse land without major extinctions will reduce with about 10.5%. These percentages are based on a commonly used population trajectory which assumes that birth rates across the globe will reduce in a similar way as has occurred in the past in many developed countries. Future birth rate is however very uncertain. Plausible future birth rates lower than the expected rates lead to much smaller reductions in surface area of biodiverse unmanaged land (0.7% as opposed to 5.4%), and a reduction in the biodiverse land without major extinctions of about 5.6% (as opposed to 10.5%). This indicates that birth rate is an important factor influencing the quality and quantity of wilderness remaining in the future.

  14. World population growth, family planning, and American foreign policy.

    PubMed

    Sharpless, J

    1995-01-01

    The US decision since the 1960s to link foreign policy with family planning and population control is noteworthy for its intention to change the demographic structure of foreign countries and the magnitude of the initiative. The current population ideologies are part of the legacy of 19th century views on science, morality, and political economy. Strong constraints were placed on US foreign policy since World War II, particularly due to presumptions about the role of developing countries in Cold War ideology. Domestic debates revolved around issues of feminism, birth control, abortion, and family political issues. Since the 1960s, environmental degradation and resource depletion were an added global dimension of US population issues. Between 1935 and 1958 birth control movements evolved from the ideologies of utopian socialists, Malthusians, women's rights activists, civil libertarians, and advocates of sexual freedom. There was a shift from acceptance of birth control to questions about the role of national government in supporting distribution of birth control. Immediately postwar the debates over birth control were outside political circles. The concept of family planning as a middle class family issue shifted the focus from freeing women from the burdens of housework to making women more efficient housewives. Family planning could not be taken as a national policy concern without justification as a major issue, a link to national security, belief in the success of intervention, and a justifiable means of inclusion in public policy. US government involvement began with agricultural education, technological assistance, and economic development that would satisfy the world's growing population. Cold War politics forced population growth as an issue to be considered within the realm of foreign policy and diplomacy. US government sponsored family planning was enthusiastic during 1967-74 but restrained during the 1980s. The 1990s has been an era of redefinition of

  15. Deletion of the Escherichia coli pseudouridine synthase gene truB blocks formation of pseudouridine 55 in tRNA in vivo, does not affect exponential growth, but confers a strong selective disadvantage in competition with wild-type cells.

    PubMed Central

    Gutgsell, N; Englund, N; Niu, L; Kaya, Y; Lane, B G; Ofengand, J

    2000-01-01

    Previous work from this laboratory (Nurse et al., RNA, 1995, 1:102-112) established that TruB, a pseudouridine (psi) synthase from Escherichia coli, was able to make psi55 in tRNA transcripts but not in transcripts of full-length or fragmented 16S or 23S ribosomal RNAs. By deletion of the truB gene, we now show that TruB is the only protein in E. coli able to make psi55 in vivo. Lack of TruB and psi55 did not affect the exponential growth rate but did confer a strong selective disadvantage on the mutant when it was competed against wild-type. The negative selection did not appear to be acting at either the exponential or stationary phase. Transformation with a plasmid vector conferring carbenicillin resistance and growth in carbenicillin markedly increased the selective disadvantage, as did growth at 42 degrees C, and both together were approximately additive such that three cycles of competitive growth sufficed to reduce the mutant strain to approximately 0.2% of its original value. The most striking finding was that all growth effects could be reversed by transformation with a plasmid carrying a truB gene coding for a D48C mutation in TruB. Direct analysis showed that this mutant did not make psi55 under the conditions of the competition experiment. Therefore, the growth defect due to the lack of TruB must be due to the lack of some other function of the protein, possibly an RNA chaperone activity, but not to the absence of psi55. PMID:11142385

  16. Density but not climate affects the population growth rate of guanacos ( Lama guanicoe) (Artiodactyla, Camelidae).

    PubMed

    Zubillaga, María; Skewes, Oscar; Soto, Nicolás; Rabinovich, Jorge E

    2013-01-01

    We analyzed the effects of population density and climatic variables on the rate of population growth in the guanaco ( Lama guanicoe), a wild camelid species in South America. We used a time series of 36 years (1977-2012) of population sampling in Tierra del Fuego, Chile. Individuals were grouped in three age-classes: newborns, juveniles, and adults; for each year a female population transition matrix was constructed, and the population growth rate (λ) was estimated for each year as the matrix highest positive eigenvalue. We applied a regression analysis with finite population growth rate (λ) as dependent variable, and total guanaco population, sheep population, annual mean precipitation, and winter mean temperature as independent variables, with and without time lags. The effect of guanaco population size was statistically significant, but the effects of the sheep population and the climatic variables on guanaco population growth rate were not statistically significant. PMID:25187878

  17. Density but not climate affects the population growth rate of guanacos ( Lama guanicoe) (Artiodactyla, Camelidae)

    PubMed Central

    Zubillaga, María; Skewes, Oscar; Soto, Nicolás; Rabinovich, Jorge E

    2014-01-01

    We analyzed the effects of population density and climatic variables on the rate of population growth in the guanaco ( Lama guanicoe), a wild camelid species in South America. We used a time series of 36 years (1977-2012) of population sampling in Tierra del Fuego, Chile. Individuals were grouped in three age-classes: newborns, juveniles, and adults; for each year a female population transition matrix was constructed, and the population growth rate (λ) was estimated for each year as the matrix highest positive eigenvalue. We applied a regression analysis with finite population growth rate (λ) as dependent variable, and total guanaco population, sheep population, annual mean precipitation, and winter mean temperature as independent variables, with and without time lags. The effect of guanaco population size was statistically significant, but the effects of the sheep population and the climatic variables on guanaco population growth rate were not statistically significant. PMID:25187878

  18. Population growth: U.S. and Latin American views.

    PubMed

    Hall, M F

    1973-11-01

    Abstract This article is an attempt at interpretation. As one who has worked professionally both in the United States and in Latin America, I would like to interpret how I see the United States and Latin America responding to the high Latin American population growth rate. This is a personal interpretation and as such, of course, is biassed. It is also a very broad subject to which a few pages of interpretation can hardly do justice. The very generalizations 'the United States' and 'Latin America' lend themselves to misunderstanding. These are not homogeneous areas but contain a variety of forces pulling in many directions. And yet, just because this is such a difficult subject as well as such an important one in the world of to-day, it is perhaps worth while to try to distil some common components which may help us gain a better understanding of the actions of others as well as our own. PMID:22091763

  19. Global warming, population growth, and natural resources for food production.

    PubMed

    Pimentel, D

    1991-01-01

    Destruction of forests and the considerable burning of fossil fuels is directly causing the level of carbon dioxide and other greenhouse gases including methane, carbon monoxide, and nitrous oxide in the atmosphere to rise. Population growth in the US and the world indirectly contributes to this global warming. This has led the majority of scientists interested in weather and climate to predict that the planet's temperature will increase from 1.5 to 4.5 degrees Celsius by 2050. These forecasted climactic changes will most likely strongly affect crop production. Specifically these scientists expect the potential changes in temperature, moisture, carbon dioxide, and pests to decrease food production in North America. The degree of changes hinges on each crop and its environmental needs. If farmers begin using improved agricultural technology, the fall in crop yields can be somewhat counterbalanced. Even without global warming, however, agriculture in North America must embrace sensible ecological resource management practices such as conserving soil, water, energy, and biological resources. These sustainable agricultural practices would serve agriculture, farmers, the environment, and society. Agriculturalists, farmers, and society are already interested in sustainable agriculture. Still scientists must conduct more research on the multiple effects of potential global climate change on many different crops under various environmental conditions and on new technologies that farmers might use in agricultural production. We must cut down our consumption of fossil fuel, reduce deforestation, erase poverty, and protect our soil, water, and biological resources. The most important action we need to take, however, is to check population growth. PMID:12344889

  20. New explicit expressions for relative frequencies of single-nucleotide polymorphisms with application to statistical inference on population growth.

    PubMed Central

    Polanski, A; Kimmel, M

    2003-01-01

    We present new methodology for calculating sampling distributions of single-nucleotide polymorphism (SNP) frequencies in populations with time-varying size. Our approach is based on deriving analytical expressions for frequencies of SNPs. Analytical expressions allow for computations that are faster and more accurate than Monte Carlo simulations. In contrast to other articles showing analytical formulas for frequencies of SNPs, we derive expressions that contain coefficients that do not explode when the genealogy size increases. We also provide analytical formulas to describe the way in which the ascertainment procedure modifies SNP distributions. Using our methods, we study the power to test the hypothesis of exponential population expansion vs. the hypothesis of evolution with constant population size. We also analyze some of the available SNP data and we compare our results of demographic parameters estimation to those obtained in previous studies in population genetics. The analyzed data seem consistent with the hypothesis of past population growth of modern humans. The analysis of the data also shows a very strong sensitivity of estimated demographic parameters to changes of the model of the ascertainment procedure. PMID:14504247

  1. An assessment of bird habitat quality using population growth rates

    USGS Publications Warehouse

    Knutson, M.G.; Powell, L.A.; Hines, R.K.; Friberg, M.A.; Niemi, G.J.

    2006-01-01

    Survival and reproduction directly affect population growth rate (lambda) making lambda a fundamental parameter for assessing habitat quality. We used field data, literature review, and a computer simulation to predict annual productivity and lambda for several species of landbirds breeding in floodplain and upland forests in the Midwestern United States. We monitored 1735 nests of 27 species; 760 nests were in the uplands and 975 were in the floodplain. Each type of forest habitat (upland and floodplain) was a source habitat for some species. Despite a relatively low proportion of regional forest cover, the majority of species had stable or increasing populations in all or some habitats, including six species of conservation concern. In our search for a simple analog for lambda, we found that only adult apparent survival, juvenile survival, and annual productivity were correlated with lambda; daily nest survival and relative abundance estimated from point counts were not. Survival and annual productivity are among the most costly demographic parameters to measure and there does not seem to be a low-cost alternative. In addition, our literature search revealed that the demographic parameters needed to model annual productivity and lambda were unavailable for several species. More collective effort across North America is needed to fill the gaps in our knowledge of demographic parameters necessary to model both annual productivity and lambda. Managers can use habitat-specific predictions of annual productivity to compare habitat quality among species and habitats for purposes of evaluating management plans.

  2. Grassland ecology and population growth: striking a balance.

    PubMed

    Hou, D; Duan, C; Zhang, D

    2000-06-01

    Degradation of forest and grasslands in western China attributes to the soil erosion and desertification in the country. Researchers have established that the primary reason for the degradation of grasslands is overgrazing, which in turn is caused by a number of factors, including over-population and over-reliance on animal husbandry. In addition, the existing administrative system has also proved ineffective in ensuring sustainable development. On contrary, many local governments even encourage exploitative development of grassland; thus, localities opened up grassland for growing crops in an effort to increase income. According to estimates, degraded grassland accounts for more than one-third of utilizable acreage and another one-third suffers from a profusion of rats and pests. To redress the situation, central government should implement strategies in achieving sustainable development, such as providing banking and tax incentives for the development of the secondary and tertiary industries, and supporting education and training of youths from herding areas. Moreover, government should increase spending on infrastructural construction and ecological preservation. Finally, the family planning program needs to be enforced to control population growth and improve the quality of peoples¿ lives. PMID:12322589

  3. Contribution of population growth to per capita income and sectoral output growth in Japan, 1880-1970.

    PubMed

    Yamaguchi, M; Kennedy, G

    1984-09-01

    The authors measured the positive and negative contributions of population and labor force growth to the growth of per capita income and sectoral output in Japan in the 1880-1970 period. A 2-sector growth accounting model that treats population and labor growth as separate variables was used. 3 alternative methods were used: the Residual method, the Verdoorn method, and the factor augmenting rate method. The total contribution of population cum labor growth to per capita income growth tended to be negative in the 1880-1930 period and positive in the 1930-40 and 1950-70. Over the 1880-1970 period as a whole, population cum labor growth made a positive contribution to per capita income growth under the Residual method (0.35%/year), the factor augmenting rate method (0.29%/year), and the Verdoorn method (0.01%/year). In addition, population cum labor growth contributed positively to sectoral output growth. The average contribution to agricultural output growth ranged from 1.03% (Verdoorn) - 1.46%/year (factor augmenting rate), while the average contribution to nonagricultural output growth ranged from 1.22% (Verdoorn) - 1.60%/year (Residual). Although these results are dependent on the model used, the fact that all 3 methods yielded consistent results suggests that population cum labor growth did make a positive contribution to per capita income and sectoral output growth in Japan. These findings imply that in economies where the rate of technical change in agricultural and nonagricultural sectors exceeds population growth, policies that reduce agricultural elasticities may be preferable; on the other hand, policies that reduce agricultural elasticities are to be avoided in economies with low rates of technical change. Moreover, in the early stages of economic development, policies that increase agricultural income and price elasticities should be considered. PMID:12340109

  4. Population growth and a sustainable environment. The Machakos story.

    PubMed

    Mortimore, M; Tiffen, M

    1994-10-01

    The view is taken that population density in the Machakos District (boundaries prior to 1992) of Kenya influenced both environmental conservation and productivity through adaptation of new technologies. Changes in resource management in Machakos District are identified as a shift to cash crop production, experimentation with staple food options, faster tillage, use of fertilizers for enhancing soil fertility, and livestock and tree cultivation. These agricultural changes occurred due to subdivision of landholdings among sons, private appropriation of scarce grazing land, and land scarcity. Intensive practices such as intensive livestock feeding systems and the permanent manuring of fields increased the efficiency of nutrient cycling through plants, animals, and soils. The Akamba custom gave land rights to those who tilled the soil first. Formal land registration occurred after 1968 and favored owners and investors. Small farm investment was made possible through work off-farm and remittances. The value of output per square kilometer at constant prices increased during 1930-87. Cultivated land area also increased during this period, but mostly on poorer quality land. Agricultural changes were enhanced by social and institutional factors such as small family units and greater partnerships between husband and wife. Families pooled resources through collectives. Women played leadership roles. Competing interest groups and organizations have evolved and enabled people to articulate their needs and obtain access to resources at all levels. These institutions increased in strength over time and with increased density. The cost of service provision decreased with greater population numbers. Development of roads and schools facilitated formal education. Population density, market growth, and a generally supportive economic environment are viewed as the factors responsible for changes in Machakos District. Technological change is viewed as an endogenous process of adaptation

  5. A Population Growth Trend Analysis for Neotricula aperta, the Snail Intermediate Host of Schistosoma mekongi, after Construction of the Pak-Mun Dam

    PubMed Central

    Attwood, Stephen W.; Upatham, E. Suchart

    2013-01-01

    Background The Pak-Mun dam is a controversial hydro-power project on the Mun River in Northeast Thailand. The dam is sited in a habitat of the freshwater snail Neotricula aperta, which is the intermediate host for the parasitic blood-fluke Schistosoma mekongi causing Mekong schistosomiasis in humans in Cambodia and Laos. Few data are available which can be used to assess the effects of water resource development on N. aperta. The aim of this study was to obtain data and to analyze the possible impact of the dam on N. aperta population growth. Methodology/Principal Findings Estimated population densities were recorded for an N. aperta population in the Mun River 27 km upstream of Pak-Mun, from 1990 to 2011. The Pak-Mul dam began to operate in 1994. Population growth was modeled using a linear mixed model expression of a modified Gompertz stochastic state-space exponential growth model. The N. aperta population was found to be quite stable, with the estimated growth parameter not significantly different from zero. Nevertheless, some marked changes in snail population density were observed which were coincident with changes in dam operation policy. Conclusions/Significance The study found that there has been no marked increase in N. aperta population growth following operation of the Pak-Mun dam. The analysis did indicate a large and statistically significant increase in population density immediately after the dam came into operation; however, this increase was not persistent. The study has provided the first vital baseline data on N. aperta population behavior near to the Pak-Mun dam and suggests that the operation policy of the dam may have an impact on snail population density. Nevertheless, additional studies are required for other N. aperta populations in the Mun River and for an extended time series, to confirm or refine the findings of this work. PMID:24244775

  6. Exponentiated power Lindley distribution

    PubMed Central

    Ashour, Samir K.; Eltehiwy, Mahmoud A.

    2014-01-01

    A new generalization of the Lindley distribution is recently proposed by Ghitany et al. [1], called as the power Lindley distribution. Another generalization of the Lindley distribution was introduced by Nadarajah et al. [2], named as the generalized Lindley distribution. This paper proposes a more generalization of the Lindley distribution which generalizes the two. We refer to this new generalization as the exponentiated power Lindley distribution. The new distribution is important since it contains as special sub-models some widely well-known distributions in addition to the above two models, such as the Lindley distribution among many others. It also provides more flexibility to analyze complex real data sets. We study some statistical properties for the new distribution. We discuss maximum likelihood estimation of the distribution parameters. Least square estimation is used to evaluate the parameters. Three algorithms are proposed for generating random data from the proposed distribution. An application of the model to a real data set is analyzed using the new distribution, which shows that the exponentiated power Lindley distribution can be used quite effectively in analyzing real lifetime data. PMID:26644927

  7. Exponentiated power Lindley distribution.

    PubMed

    Ashour, Samir K; Eltehiwy, Mahmoud A

    2015-11-01

    A new generalization of the Lindley distribution is recently proposed by Ghitany et al. [1], called as the power Lindley distribution. Another generalization of the Lindley distribution was introduced by Nadarajah et al. [2], named as the generalized Lindley distribution. This paper proposes a more generalization of the Lindley distribution which generalizes the two. We refer to this new generalization as the exponentiated power Lindley distribution. The new distribution is important since it contains as special sub-models some widely well-known distributions in addition to the above two models, such as the Lindley distribution among many others. It also provides more flexibility to analyze complex real data sets. We study some statistical properties for the new distribution. We discuss maximum likelihood estimation of the distribution parameters. Least square estimation is used to evaluate the parameters. Three algorithms are proposed for generating random data from the proposed distribution. An application of the model to a real data set is analyzed using the new distribution, which shows that the exponentiated power Lindley distribution can be used quite effectively in analyzing real lifetime data. PMID:26644927

  8. Population Growth in the 1990s: Patterns within the United States.

    ERIC Educational Resources Information Center

    Perry, Marc

    2002-01-01

    Examines population growth during the 1990s for a variety of geographic levels including regions, divisions, states, metropolitan areas, counties, and large cities. Compares growth rates for the 1990s with earlier decades to provide an historical context for present-day trends in population growth and decline. Discusses how differential population…

  9. People of New Mexico: Size, Growth and Hispanic Population from the 1980 Census. Research Report 482.

    ERIC Educational Resources Information Center

    Williams, James D.

    New Mexico, while small, is a state of great diversity in terms of size, growth, and Hispanic concentration of population. Data from the 1980 census indicate New Mexico is the 37th largest state with slightly more than 1.3 million persons and is ninth among the states in percentage of population growth. Growth comes from two demographic sources:…

  10. THE INFLUENCE OF MODEL TIME STEP ON THE RELATIVE SENSITIVITY OF POPULATION GROWTH TO SURVIVAL, GROWTH AND REPRODUCTION

    EPA Science Inventory

    Matrix population models are often used to extrapolate from life stage-specific stressor effects on survival and reproduction to population-level effects. Demographic elasticity analysis of a matrix model allows an evaluation of the relative sensitivity of population growth rate ...

  11. MECHANISMS OF FLUID SHEAR-INDUCED INHIBITION OF POPULATION GROWTH IN A RED-TIDE DINOFLAGELLATE

    EPA Science Inventory

    Net population growth of some dinoflagellates is inhibited by fluid shear at shear stresses comparable with those generated during oceanic turbulence. Decreased net growth may occur through lowered cell division, increased mortality, or both. The dominant mechanism under various ...

  12. Using Spreadsheets To Model Population Growth, Competition and Predation in Nature.

    ERIC Educational Resources Information Center

    Carter, Ashley J. R.

    1999-01-01

    Describes how to place mathematical equations modeling population growth into a spreadsheet that performs calculations quickly and easily. Suggests experiments that can be performed with the spreadsheets. (WRM)

  13. Why does human culture increase exponentially?

    PubMed

    Enquist, M; Ghirlanda, S; Jarrick, A; Wachtmeister, C-A

    2008-08-01

    Historical records show that culture can increase exponentially in time, e.g., in number of poems, musical works, scientific discoveries. We model how human capacities for creativity and cultural transmission may make such an increase possible, suggesting that: (1) creativity played a major role at the origin of human culture and for its accumulation throughout history, because cultural transmission cannot, on its own, generate exponentially increasing amounts of culture; (2) exponential increase in amount of culture can only occur if creativity is positively influenced by culture. The evolution of cultural transmission is often considered the main genetic bottleneck for the origin of culture, because natural selection cannot favor cultural transmission without any culture to transmit. Our models suggest that an increase in individual creativity may have been the first step toward human culture, because in a population of creative individuals there may be enough non-genetic information to favor the evolution of cultural transmission. PMID:18571686

  14. Comparative Study of Population Growth and Agricultural Change: C - Case Study of India. Asian Population Studies Series No. 23.

    ERIC Educational Resources Information Center

    United Nations Economic and Social Commission for Asia and the Pacific, Bangkok (Thailand).

    This report, the third in a series of five reports of the Comparative Study of Population Growth and Agricultural Change, describes a study of the two states of India (Punjaband and Orissa) which attempted to clarify the relationship between population pressure and agricultural change through a time series analysis. This study: (1) outlines trends…

  15. The petroleum exponential (again)

    NASA Astrophysics Data System (ADS)

    Bell, Peter M.

    The U.S. production and reserves of liquid and gaseous petroleum have declined since 1960, at least in the lower 48 states. This decline stems from decreased discovery rates, as predicted by M. King Hubbert in the mid-1950's. Hubbert's once unpopular views were based on statistical analysis of the production history of the petroleum industry, and now, even with inclusion of the statistical perturbation caused by the Prudhoe Bay-North Alaskan Slope discovery (the largest oil field ever found in the United States), it seems clear again that production is following the exponential curve to depletion of the resource—to the end of the ultimate yield of petroleum from wells in the United States.In a recent report, C. Hall and C. Cleveland of Cornell University show that large atypical discoveries, such as the Prudhoe Bay find, are but minor influences on what now appears to be the crucial intersection of two exponentials [Science, 211, 576-579, 1981]: the production-per-drilled-foot curve of Hubbert, which crosses zero production no later than the year 2005; the other, a curve that plots the energy cost of drilling and extraction with time; that is, the cost-time rate of how much oil is used to drill and extract oil from the ground. The intersection, if no other discoveries the size of the Prudhoe Bay field are made, could be as early as 1990, the end of the present decade. The inclusion of each Prudhoe-Bay-size find extends the year of intersection by only about 6 years. Beyond that point, more than one barrel of petroleum would be expended for each barrel extracted from the ground. The oil exploration-extraction and refining industry is currently the second most energy-intensive industry in the U.S., and the message seems clear. Either more efficient drilling and production techniques are discovered, or domestic production will cease well before the end of this century if the Hubbert analysis modified by Hall and Cleveland is correct.

  16. The effects of invertebrate herbivores on plant population growth: a meta-regression analysis.

    PubMed

    Katz, Daniel S W

    2016-09-01

    Over the last two decades, an increasing number of studies have quantified the effects of herbivory on plant populations using stage-structured population models and integral projection models, allowing for the calculation of plant population growth rates (λ) with and without herbivory. In this paper, I assembled 29 studies and conducted a meta-regression to determine the importance of invertebrate herbivores to population growth rates (λ) while accounting for missing data. I found that invertebrate herbivory often induced important reductions in plant population growth rates (with herbivory, λ was 1.08 ± 0.36; without herbivory, λ was 1.28 ± 0.58). This relationship tended to be weaker for seed predation than for other types of herbivory, except when seed predation rates were very high. Even so, the amount by which studies reduced herbivory was a poor predictor of differences in population growth rates-which strongly cautions against using measured herbivory rates as a proxy for the impact of herbivores. Herbivory reduced plant population growth rates significantly more when potential growth rates were high, which helps to explain why there was less variation in actual population growth rates than in potential population growth rates. The synthesis of these studies also shows the need for future studies to report variance in estimates of λ and to quantify how λ varies as a function of plant density. PMID:27017603

  17. Population Growth and Demographic Structure. Proceedings of the United Nations Expert Group Meeting on Population Growth and Demographic Structure (Paris, France, November 16-20, 1992).

    ERIC Educational Resources Information Center

    United Nations, New York, NY. Dept. of Economic and Social Affairs.

    This volume contains the report and recommendations of the United Nations-sponsored meeting on population growth and demographic structure which was held in Paris, November 1992. Materials in the volume can serve as useful tools for future research on the relations between population, environment, and development and further the work of the United…

  18. Population divergence in compensatory growth responses and their costs in sticklebacks

    PubMed Central

    Ab Ghani, Nurul Izza; Merilä, Juha

    2015-01-01

    Compensatory growth (CG) may be an adaptive mechanism that helps to restore an organisms’ growth trajectory and adult size from deviations caused by early life resource limitation. Yet, few studies have investigated the genetic basis of CG potential and existence of genetically based population differentiation in CG potential. We studied population differentiation, genetic basis, and costs of CG potential in nine-spined sticklebacks (Pungitius pungitius) differing in their normal growth patterns. As selection favors large body size in pond and small body size in marine populations, we expected CG to occur in the pond but not in the marine population. By manipulating feeding conditions (viz. high, low and recovery feeding treatments), we found clear evidence for CG in the pond but not in the marine population, as well as evidence for catch-up growth (i.e., size compensation without growth acceleration) in both populations. In the marine population, overcompensation occurred individuals from the recovery treatment grew eventually larger than those from the high feeding treatment. In both populations, the recovery feeding treatment reduced maturation probability. The recovery feeding treatment also reduced survival probability in the marine but not in the pond population. Analysis of interpopulation hybrids further suggested that both genetic and maternal effects contributed to the population differences in CG. Hence, apart from demonstrating intrinsic costs for recovery growth, both genetic and maternal effects were identified to be important modulators of CG responses. The results provide an evidence for adaptive differentiation in recovery growth potential. PMID:25628860

  19. OPINION: Safe exponential manufacturing

    NASA Astrophysics Data System (ADS)

    Phoenix, Chris; Drexler, Eric

    2004-08-01

    In 1959, Richard Feynman pointed out that nanometre-scale machines could be built and operated, and that the precision inherent in molecular construction would make it easy to build multiple identical copies. This raised the possibility of exponential manufacturing, in which production systems could rapidly and cheaply increase their productive capacity, which in turn suggested the possibility of destructive runaway self-replication. Early proposals for artificial nanomachinery focused on small self-replicating machines, discussing their potential productivity and their potential destructiveness if abused. In the light of controversy regarding scenarios based on runaway replication (so-called 'grey goo'), a review of current thinking regarding nanotechnology-based manufacturing is in order. Nanotechnology-based fabrication can be thoroughly non-biological and inherently safe: such systems need have no ability to move about, use natural resources, or undergo incremental mutation. Moreover, self-replication is unnecessary: the development and use of highly productive systems of nanomachinery (nanofactories) need not involve the construction of autonomous self-replicating nanomachines. Accordingly, the construction of anything resembling a dangerous self-replicating nanomachine can and should be prohibited. Although advanced nanotechnologies could (with great difficulty and little incentive) be used to build such devices, other concerns present greater problems. Since weapon systems will be both easier to build and more likely to draw investment, the potential for dangerous systems is best considered in the context of military competition and arms control.

  20. Taking Exception. Reduced mortality leads to population growth: an inconvenient truth.

    PubMed

    Shelton, James D

    2014-05-01

    Reduced mortality has been the predominant cause of the marked global population growth over the last 3/4 of a century. While improved child survival increases motivation to reduce fertility, it comes too little and too late to forestall substantial population growth. And, beyond motivation, couples need effective means to control their fertility. It is an inconvenient truth that reducing child mortality contributes considerably to the population growth destined to compromise the quality of life of many, particularly in sub-Saharan Africa. Vigorous child survival programming is of course imperative. Wide access to voluntary family planning can help mitigate that growth and provide many other benefits. PMID:25276571

  1. Population level consequences of toxicological influences on individual growth and reproduction in Lumbricus rubellus (Lumbricidae, Oligochaeta).

    PubMed

    Klok, C; de Roos, A M

    1996-03-01

    The effects of increased environmental concentrations of copper on the population dynamics of Lumbricus rubellus are investigated. A size-structured matrix model is used to translate sublethal effects on individual growth and reproduction into their population dynamical consequences. Laboratory data on growth and reproduction under different, sublethal conditions of copper stress are used to parameterize the model. An estimate for the critical threshold concentration of copper (critical in a sense that the population growth rate at this concentration equals zero), obtained from the model analysis, agrees well with observations on field populations of L. rubellus. PMID:8723748

  2. Dynamics of single-species population growth: stability or chaos

    SciTech Connect

    Mueller, L.D.; Ayala, F.J.

    1981-01-01

    We have examined stability at the carrying capacity for 25 genetically different populations of Drosophila melanogaster. In spite of their genetic heterogeneity, 20 of the populations yield stable equilibria and none have eigenvalues significantly greater than one. Computer simulations demonstrate how selection at the individual level may account for population stability (and, hence, that group selection is not necessary for the evolution of stability). Recent theoretical studies on density-dependent selection in random environments provide predictions consistent with our empirical findings.

  3. A Photometer for Measuring Population Growth in Yeast.

    ERIC Educational Resources Information Center

    Tatina, Robert; Hartley, Tamela; Thomas, Danita

    1999-01-01

    Describes the construction and use of an inexpensive, portable photometer designed specifically for estimating population sizes in yeast cultures. Suggests activities for use with the photometer. (WRM)

  4. Density estimation and population growth of mosquitofish (Gambusia affinis) in rice fields.

    PubMed

    Stewart, R J; Miura, T

    1985-03-01

    Mark-release-recapture estimation of population density was performed with mosquitofish in a rice field habitat. Regression analysis showed a relationship between absolute density and mean number of fish per trap. Trap counts were converted to density estimates with data from several fields and growth curves were calculated to describe seasonal growth of mosquitofish populations at three different initial stocking rates. The calculated curves showed a good correspondence to field populations of mosquitofish. PMID:2906659

  5. D-Alanylation of Teichoic Acids and Loss of Poly-N-Acetyl Glucosamine in Staphylococcus aureus during Exponential Growth Phase Enhance IL-12 Production in Murine Dendritic Cells

    PubMed Central

    Lund, Lisbeth Drozd; Ingmer, Hanne; Frøkiær, Hanne

    2016-01-01

    Staphylococcus aureus is a major human pathogen that has evolved very efficient immune evading strategies leading to persistent colonization. During different stages of growth, S. aureus express various surface molecules, which may affect the immune stimulating properties, but very little is known about their role in immune stimulation and evasion. Depending on the growth phase, S. aureus may affect antigen presenting cells differently. Here, the impact of growth phases and the surface molecules lipoteichoic acid, peptidoglycan and poly-N-acetyl glucosamine on the induction of IL-12 imperative for an efficient clearance of S. aureus was studied in dendritic cells (DCs). Exponential phase (EP) S. aureus was superior to stationary phase (SP) bacteria in induction of IL-12, which required actin-mediated endocytosis and endosomal acidification. Moreover, addition of staphylococcal cell wall derived peptidoglycan to EP S. aureus stimulated cells increased bacterial uptake but abrogated IL-12 induction, while addition of lipoteichoic acid increased IL-12 production but had no effect on the bacterial uptake. Depletion of the capability to produce poly-N-acetyl glucosamine increased the IL-12 inducing activity of EP bacteria. Furthermore, the mutant dltA unable to produce D-alanylated teichoic acids failed to induce IL-12 but like peptidoglycan and the toll-like receptor (TLR) ligands LPS and Pam3CSK4 the mutant stimulated increased macropinocytosis. In conclusion, the IL-12 response by DCs against S. aureus is highly growth phase dependent, relies on cell wall D-alanylation, endocytosis and subsequent endosomal degradation, and is abrogated by receptor induced macropinocytosis. PMID:26872029

  6. Population Growth and Policies in Mega-Cities. Sao Paulo.

    ERIC Educational Resources Information Center

    United Nations New York, NY. Dept. of Economic and Social Information and Policy Analysis.

    This document is one in a series of studies that focus on the population policies and plans of a number of mega-cities in developing countries. The object of the series is to examine the formulation, implementation, and evaluation of the population policies of mega-cities from a broad perspective, emphasizing the reciprocal links between…

  7. The demographic consequences of mutualism: ants increase host-plant fruit production but not population growth.

    PubMed

    Ford, Kevin R; Ness, Joshua H; Bronstein, Judith L; Morris, William F

    2015-10-01

    The impact of mutualists on a partner's demography depends on how they affect the partner's multiple vital rates and how those vital rates, in turn, affect population growth. However, mutualism studies rarely measure effects on multiple vital rates or integrate them to assess the ultimate impact on population growth. We used vital rate data, population models and simulations of long-term population dynamics to quantify the demographic impact of a guild of ant species on the plant Ferocactus wislizeni. The ants feed at the plant's extrafloral nectaries and attack herbivores attempting to consume reproductive organs. Ant-guarded plants produced significantly more fruit, but ants had no significant effect on individual growth or survival. After integrating ant effects across these vital rates, we found that projected population growth was not significantly different between unguarded and ant-guarded plants because population growth was only weakly influenced by differences in fruit production (though strongly influenced by differences in individual growth and survival). However, simulations showed that ants could positively affect long-term plant population dynamics through services provided during rare but important events (herbivore outbreaks that reduce survival or years of high seedling recruitment associated with abundant precipitation). Thus, in this seemingly clear example of mutualism, the interaction may actually yield no clear benefit to plant population growth, or if it does, may only do so through the actions of the ants during rare events. These insights demonstrate the value of taking a demographic approach to studying the consequences of mutualism. PMID:26003308

  8. On the Matrix Exponential Function

    ERIC Educational Resources Information Center

    Hou, Shui-Hung; Hou, Edwin; Pang, Wan-Kai

    2006-01-01

    A novel and simple formula for computing the matrix exponential function is presented. Specifically, it can be used to derive explicit formulas for the matrix exponential of a general matrix A satisfying p(A) = 0 for a polynomial p(s). It is ready for use in a classroom and suitable for both hand as well as symbolic computation.

  9. THE EFFECT OF RANDOM VARIATIONS OF DIFFERENT TYPES ON POPULATION GROWTH

    PubMed Central

    Levins, R.

    1969-01-01

    The probability distributions of population size are derived for populations living in randomly varying environments for both density-dependent and density-independent population growth. The effects of random variation in the rate of increase, the carrying capacity, and sampling variation in numbers are examined. PMID:5256407

  10. Impacts of Hispanic Population Growth on Rural Wages. Agricultural Economic Report.

    ERIC Educational Resources Information Center

    Newman, Constance

    Although earnings generally increased in rural areas in the 1990s, Hispanic population growth led to lower wages for at least one segment of the rural population--workers with a high school degree (skilled workers), particularly men in this skill group. Using data from the Bureau of Economic Analysis and the Current Population Survey, this report…

  11. Black Population Distribution and Growth in the United States. Geography Curriculum Project.

    ERIC Educational Resources Information Center

    Pelletti, John C.

    The self-study unit for intermediate grades deals with growth and distribution of the black population of the United States. The unit shows how and why the black population started from a rural southern base and became a largely urban population, compares the black people of two cities, one northern and one southern, and discusses how they are…

  12. Life-history and spatial determinants of somatic growth dynamics in Komodo dragon populations.

    PubMed

    Laver, Rebecca J; Purwandana, Deni; Ariefiandy, Achmad; Imansyah, Jeri; Forsyth, David; Ciofi, Claudio; Jessop, Tim S

    2012-01-01

    Somatic growth patterns represent a major component of organismal fitness and may vary among sexes and populations due to genetic and environmental processes leading to profound differences in life-history and demography. This study considered the ontogenic, sex-specific and spatial dynamics of somatic growth patterns in ten populations of the world's largest lizard the Komodo dragon (Varanus komodoensis). The growth of 400 individual Komodo dragons was measured in a capture-mark-recapture study at ten sites on four islands in eastern Indonesia, from 2002 to 2010. Generalized Additive Mixed Models (GAMMs) and information-theoretic methods were used to examine how growth rates varied with size, age and sex, and across and within islands in relation to site-specific prey availability, lizard population density and inbreeding coefficients. Growth trajectories differed significantly with size and between sexes, indicating different energy allocation tactics and overall costs associated with reproduction. This leads to disparities in maximum body sizes and longevity. Spatial variation in growth was strongly supported by a curvilinear density-dependent growth model with highest growth rates occurring at intermediate population densities. Sex-specific trade-offs in growth underpin key differences in Komodo dragon life-history including evidence for high costs of reproduction in females. Further, inverse density-dependent growth may have profound effects on individual and population level processes that influence the demography of this species. PMID:23028983

  13. Life-History and Spatial Determinants of Somatic Growth Dynamics in Komodo Dragon Populations

    PubMed Central

    Laver, Rebecca J.; Purwandana, Deni; Ariefiandy, Achmad; Imansyah, Jeri; Forsyth, David; Ciofi, Claudio; Jessop, Tim S.

    2012-01-01

    Somatic growth patterns represent a major component of organismal fitness and may vary among sexes and populations due to genetic and environmental processes leading to profound differences in life-history and demography. This study considered the ontogenic, sex-specific and spatial dynamics of somatic growth patterns in ten populations of the world’s largest lizard the Komodo dragon (Varanus komodoensis). The growth of 400 individual Komodo dragons was measured in a capture-mark-recapture study at ten sites on four islands in eastern Indonesia, from 2002 to 2010. Generalized Additive Mixed Models (GAMMs) and information-theoretic methods were used to examine how growth rates varied with size, age and sex, and across and within islands in relation to site-specific prey availability, lizard population density and inbreeding coefficients. Growth trajectories differed significantly with size and between sexes, indicating different energy allocation tactics and overall costs associated with reproduction. This leads to disparities in maximum body sizes and longevity. Spatial variation in growth was strongly supported by a curvilinear density-dependent growth model with highest growth rates occurring at intermediate population densities. Sex-specific trade-offs in growth underpin key differences in Komodo dragon life-history including evidence for high costs of reproduction in females. Further, inverse density-dependent growth may have profound effects on individual and population level processes that influence the demography of this species. PMID:23028983

  14. Effects of Climate Change on Plant Population Growth Rate and Community Composition Change

    PubMed Central

    Chang, Xiao-Yu; Chen, Bao-Ming; Liu, Gang; Zhou, Ting; Jia, Xiao-Rong; Peng, Shao-Lin

    2015-01-01

    The impacts of climate change on forest community composition are still not well known. Although directional trends in climate change and community composition change were reported in recent years, further quantitative analyses are urgently needed. Previous studies focused on measuring population growth rates in a single time period, neglecting the development of the populations. Here we aimed to compose a method for calculating the community composition change, and to testify the impacts of climate change on community composition change within a relatively short period (several decades) based on long-term monitoring data from two plots—Dinghushan Biosphere Reserve, China (DBR) and Barro Colorado Island, Panama (BCI)—that are located in tropical and subtropical regions. We proposed a relatively more concise index, Slnλ, which refers to an overall population growth rate based on the dominant species in a community. The results indicated that the population growth rate of a majority of populations has decreased over the past few decades. This decrease was mainly caused by population development. The increasing temperature had a positive effect on population growth rates and community change rates. Our results promote understanding and explaining variations in population growth rates and community composition rates, and are helpful to predict population dynamics and population responses to climate change. PMID:26039073

  15. Future population growth: researchers in three countries quantify causes and propose policies.

    PubMed

    1997-01-01

    This article discusses Population Council analyses conducted by social scientists from India, Kenya, and the Philippines. These scientists agreed that population momentum would continue to increase population size, and that governments must strengthen and create a range of economic, health, and social programs and policies to slow population growth. Multiple approaches will be needed. John Bongaarts is credited with being the first to identify the key role of population momentum and to decompose growth into unwanted fertility, high desired fertility, and population momentum. Unwanted fertility is responsible for about 19% of projected population growth in India, 26% in Kenya, and 16% in the Philippines. High wanted fertility accounts for 20% of future growth in India, 6% in Kenya, and 19% in the Philippines. Population momentum can account for under 50% or over 90% of growth. Unwanted fertility can be addressed by fulfilling unmet need and increasing knowledge of methods, reducing the fear of side effects and disapproval, and eliminating poor service. Family planning programs need to be strengthened and integrated with maternal and child health services. Preferred and actual family sizes can be reduced by lowering infant mortality by means of increasing infant and child health services and girls' educational attainment. Population momentum can be addressed by delaying age at marriage and childbearing through improving social conditions. Investments in human development through education, training, and income generation can create the conditions for slowing population growth. Countries should decompose population growth into its components of unwanted and high wanted fertility and population momentum as a means of distributing resources most effectively. PMID:12292641

  16. Understanding contributions of cohort effects to growth rates of fluctuating populations.

    PubMed

    Wittmer, Heiko U; Powell, Roger A; King, Carolyn M

    2007-09-01

    1. Understanding contributions of cohort effects to variation in population growth of fluctuating populations is of great interest in evolutionary biology and may be critical in contributing towards wildlife and conservation management. Cohort-specific contributions to population growth can be evaluated using age-specific matrix models and associated elasticity analyses. 2. We developed age-specific matrix models for naturally fluctuating populations of stoats Mustela erminea in New Zealand beech forests. Dynamics and productivity of stoat populations in this environment are related to the 3-5 year masting cycle of beech trees and consequent effects on the abundance of rodents. 3. The finite rate of increase (lambda) of stoat populations in New Zealand beech forests varied substantially, from 1.98 during seedfall years to 0.58 during post-seedfall years. Predicted mean growth rates for stoat populations in continuous 3-, 4- or 5-year cycles are 0.85, 1.00 and 1.13. The variation in population growth was a consequence of high reproductive success of females during seedfall years combined with low survival and fertility of females of the post-seedfall cohort. 4. Variation in population growth was consistently more sensitive to changes in survival rates both when each matrix was evaluated in isolation and when matrices were linked into cycles. Relative contributions to variation in population growth from survival and fertility, especially in 0-1-year-old stoats, also depend on the year of the cycle and the number of transitional years before a new cycle is initiated. 5. Consequently, management strategies aimed at reducing stoat populations that may be best during one phase of the beech seedfall cycle may not be the most efficient during other phases of the cycle. We suggest that management strategies based on elasticities of vital rates need to consider how population growth rates vary so as to meet appropriate economic and conservation targets. PMID:17714273

  17. Population growth and economic development in the very long run: a simulation model of three revolutions.

    PubMed

    Steinmann, G; Komlos, J

    1988-08-01

    The authors propose an economic model capable of simulating the 4 main historical stages of civilization: hunting, agricultural, industrial, and postindustrial. An output-maximizing society to respond to changes in factor endowments by switching technologies. Changes in factor proportions arise through population growth and capital accumulation. A slow rate of exogenous technical process is assumed. The model synthesizes Malthusian and Boserupian notions of the effect of population growth on per capita output. Initially the capital-diluting effect of population growth dominates. As population density increases, however, and a threshold is reached, the Boserupian effect becomes crucial, and a technological revolution occurs. The cycle is thereafter repeated. After the second economic revolution, however, the Malthusian constraint dissolves permanently, as population growth can continue without being constrained by diminishing returns to labor. By synthesizing Malthusian and Boserupian notions, the model is able to capture the salient features of economic development in the very long run. PMID:12315554

  18. Reconstructing the dynamics of ancient human populations from radiocarbon dates: 10 000 years of population growth in Australia

    PubMed Central

    Johnson, Christopher N.; Brook, Barry W.

    2011-01-01

    Measuring trends in the size of prehistoric populations is fundamental to our understanding of the demography of ancient people and their responses to environmental change. Archaeologists commonly use the temporal distribution of radiocarbon dates to reconstruct population trends, but this can give a false picture of population growth because of the loss of evidence from older sites. We demonstrate a method for quantifying this bias, and we use it to test for population growth through the Holocene of Australia. We used model simulations to show how turnover of site occupation across an archaeological landscape, interacting with erasure of evidence at abandoned sites, can create an increase in apparent site occupation towards the present when occupation density is actually constant. By estimating the probabilities of abandonment and erasure from archaeological data, we then used the model to show that this effect does not account for the observed increase in occupation through the Holocene in Australia. This is best explained by population growth, which was low for the first part of the Holocene but accelerated about 5000 years ago. Our results provide new evidence for the dynamism of non-agricultural populations through the Holocene. PMID:21561972

  19. Reconstructing the dynamics of ancient human populations from radiocarbon dates: 10 000 years of population growth in Australia.

    PubMed

    Johnson, Christopher N; Brook, Barry W

    2011-12-22

    Measuring trends in the size of prehistoric populations is fundamental to our understanding of the demography of ancient people and their responses to environmental change. Archaeologists commonly use the temporal distribution of radiocarbon dates to reconstruct population trends, but this can give a false picture of population growth because of the loss of evidence from older sites. We demonstrate a method for quantifying this bias, and we use it to test for population growth through the Holocene of Australia. We used model simulations to show how turnover of site occupation across an archaeological landscape, interacting with erasure of evidence at abandoned sites, can create an increase in apparent site occupation towards the present when occupation density is actually constant. By estimating the probabilities of abandonment and erasure from archaeological data, we then used the model to show that this effect does not account for the observed increase in occupation through the Holocene in Australia. This is best explained by population growth, which was low for the first part of the Holocene but accelerated about 5000 years ago. Our results provide new evidence for the dynamism of non-agricultural populations through the Holocene. PMID:21561972

  20. Trophic interactions and population growth rates: describing patterns and identifying mechanisms.

    PubMed Central

    Hudson, Peter J; Dobson, Andy P; Cattadori, Isabella M; Newborn, David; Haydon, Dan T; Shaw, Darren J; Benton, Tim G; Grenfell, Bryan T

    2002-01-01

    While the concept of population growth rate has been of central importance in the development of the theory of population dynamics, few empirical studies consider the intrinsic growth rate in detail, let alone how it may vary within and between populations of the same species. In an attempt to link theory with data we take two approaches. First, we address the question 'what growth rate patterns does theory predict we should see in time-series?' The models make a number of predictions, which in general are supported by a comparative study between time-series of harvesting data from 352 red grouse populations. Variations in growth rate between grouse populations were associated with factors that reflected the quality and availability of the main food plant of the grouse. However, while these results support predictions from theory, they provide no clear insight into the mechanisms influencing reductions in population growth rate and regulation. In the second part of the paper, we consider the results of experiments, first at the individual level and then at the population level, to identify the important mechanisms influencing changes in individual productivity and population growth rate. The parasitic nematode Trichostrongylus tenuis is found to have an important influence on productivity, and when incorporated into models with their patterns of distribution between individuals has a destabilizing effect and generates negative growth rates. The hypothesis that negative growth rates at the population level were caused by parasites was demonstrated by a replicated population level experiment. With a sound and tested model framework we then explore the interaction with other natural enemies and show that in general they tend to stabilize variations in growth rate. Interestingly, the models show selective predators that remove heavily infected individuals can release the grouse from parasite-induced regulation and allow equilibrium populations to rise. By contrast, a

  1. Calculating the Financial Impact of Population Growth on Education.

    ERIC Educational Resources Information Center

    Cline, Daniel H.

    It is particularly difficult to make accurate enrollment projections for areas that are experiencing a rapid expansion in their population. The traditional method of calculating cohort survival ratios must be modified and supplemented with additional information to ensure accuracy; cost projection methods require detailed analyses of current costs…

  2. Student-Teacher Population Growth Model. Working Paper.

    ERIC Educational Resources Information Center

    Zabrowski, Edward K.; And Others

    This mathematical model of the educational system calculates information on population groups by sex, race, age, and educational level. The model can be used to answer questions about what would happen to the flows of students and teachers through the formal educational system if these flows are changed at various stages. The report discusses the…

  3. World Bank Atlas: Population, Per Capita Product and Growth Rates.

    ERIC Educational Resources Information Center

    World Bank, Washington, DC.

    The ninth edition of the World Bank Atlas shows estimates of population, gross national product, and per capita production of 189 countries and territories for 1972. The data presented in the atlas are the result of the work of the World Bank Group whose major purpose is to provide both financial and technical assistance and to improve the living…

  4. Variability in winter climate and winter extremes reduces population growth of an alpine butterfly.

    PubMed

    Roland, Jens; Matter, Stephen F

    2013-01-01

    We examined the long-term, 15-year pattern of population change in a network of 21 Rocky Mountain populations of Parnassius smintheus butterflies in response to climatic variation. We found that winter values of the broadscale climate variable, the Pacific Decadal Oscillation (PDO) index, were a strong predictor of annual population growth, much more so than were endogenous biotic factors related to population density. The relationship between PDO and population growth was nonlinear. Populations declined in years with extreme winter PDO values, when there were either extremely warm or extremely cold sea surface temperatures in the eastern Pacific relative to that in the western Pacific. Results suggest that more variable winters, and more frequent extremely cold or warm winters, will result in more frequent decline of these populations, a pattern exacerbated by the trend for increasingly variable winters seen over the past century. PMID:23600253

  5. Exponential approximations in optimal design

    NASA Technical Reports Server (NTRS)

    Belegundu, A. D.; Rajan, S. D.; Rajgopal, J.

    1990-01-01

    One-point and two-point exponential functions have been developed and proved to be very effective approximations of structural response. The exponential has been compared to the linear, reciprocal and quadratic fit methods. Four test problems in structural analysis have been selected. The use of such approximations is attractive in structural optimization to reduce the numbers of exact analyses which involve computationally expensive finite element analysis.

  6. Flower Power: Sunflowers as a Model for Logistic Growth

    ERIC Educational Resources Information Center

    Fernandez, Eileen; Geist, Kristi A.

    2011-01-01

    Logistic growth displays an interesting pattern: It starts fast, exhibiting the rapid growth characteristic of exponential models. As time passes, it slows in response to constraints such as limited resources or reallocation of energy. The growth continues to slow until it reaches a limit, called capacity. When the growth describes a population,…

  7. Survival, recruitment, and population growth rate of an important mesopredator: the northern raccoon.

    PubMed

    Troyer, Elizabeth M; Cameron Devitt, Susan E; Sunquist, Melvin E; Goswami, Varun R; Oli, Madan K

    2014-01-01

    Populations of mesopredators (mid-sized mammalian carnivores) are expanding in size and range amid declining apex predator populations and ever-growing human presence, leading to significant ecological impacts. Despite their obvious importance, population dynamics have scarcely been studied for most mesopredator species. Information on basic population parameters and processes under a range of conditions is necessary for managing these species. Here we investigate survival, recruitment, and population growth rate of a widely distributed and abundant mesopredator, the northern raccoon (Procyon lotor), using Pradel's temporal symmetry models and >6 years of monthly capture-mark-recapture data collected in a protected area. Monthly apparent survival probability was higher for females (0.949, 95% CI = 0.936-0.960) than for males (0.908, 95% CI = 0.893-0.920), while monthly recruitment rate was higher for males (0.091, 95% CI = 0.078-0.106) than for females (0.054, 95% CI = 0.042-0.067). Finally, monthly realized population growth rate was 1.000 (95% CI = 0.996-1.004), indicating that our study population has reached a stable equilibrium in this relatively undisturbed habitat. There was little evidence for substantial temporal variation in population growth rate or its components. Our study is one of the first to quantify survival, recruitment, and realized population growth rate of raccoons using long-term data and rigorous statistical models. PMID:24901349

  8. Population developmental stage determines the recovery potential of Daphnia magna populations after fenvalerate application.

    PubMed

    Pieters, Barry J; Liess, Matthias

    2006-10-01

    This study investigated the responses of Daphnia magna populations to pulsed exposures of the pyrethroid insecticide Fenvalerate applied during an early and a late stage of population development, and analyzed the dynamics of the subsequent recovery. A novel digital observation technique was used to describe the size and numbers of animals. High Fenvalerate concentrations caused high mortality rates during exponential population growth as well as during the food-limited stationary phase. However, recovery of populations took considerably longer in the stationary phase than in populations growing exponentially. The poor nutritional and reproductive state of food-deprived adults was indicated as the main cause of the slow recovery of populations. It is argued that populations operating at the carrying capacity of their environment are vulnerable to toxicant-induced disturbances to an extent not predictable from observations on exponentially growing populations such as are commonly used in ecotoxicology. PMID:17051815

  9. [The relationships between population growth and environment: from doctrinal to empirical].

    PubMed

    Tabutin, D; Thiltges, E

    1992-01-01

    This work provides a brief review of changing attitudes toward population growth, the environment, and economic development, and summarizes the major theoretical doctrines concerning the interrelations between rapid population growth and environmental damage and results of research on the topic. The general optimism about the prospects for progress in the Southern hemisphere of the 1950s and 1960s gave way to greater skepticism and recognition of problems in the 1970s. The creation of the UN Population Fund in 1969 and the UN Environmental Program in 1972 reflected increasing concern in the international community about demographic growth and environmental degradation in the south. Economic and social conditions appeared to worsen in the 1980s, with the recession and structural adjustment programs having a disproportionate impact on the most destitute. New integrating concepts and paradigms including that of sustainable development arose in this context of profound crisis in many Third World economics and societies. The most widely accepted position on the connection between population growth and environmental degradation since the late 1970s has been a nuanced neo-Malthusian approach which sees demographic pressure not as the direct cause of environmental problems, but as an aggravating factor. The slowing of population growth is viewed as 1 element in an overall strategy that also includes encouragement of development and elimination of poverty. The extreme positions that rapid population growth is the major cause of environmental degeneration or that population growth has little actual effect on the environment have been largely abandoned. The impact of population growth on the environment can be analyzed at the global, regional, or local level. On the global level, there is agreement that 2 major factors responsible for environmental deterioration are the model of economic development followed in the Northern countries and the poverty of much of the population

  10. Modeling tradeoffs in avian life history traits and consequences for population growth

    USGS Publications Warehouse

    Clark, M.E.; Martin, T.E.

    2007-01-01

    Variation in population dynamics is inherently related to life history characteristics of species, which vary markedly even within phylogenetic groups such as passerine birds. We computed the finite rate of population change (??) from a matrix projection model and from mark-recapture observations for 23 bird species breeding in northern Arizona. We used sensitivity analyses and a simulation model to separate contributions of different life history traits to population growth rate. In particular we focused on contrasting effects of components of reproduction (nest success, clutch size, number of clutches, and juvenile survival) versus adult survival on ??. We explored how changes in nest success or adult survival coupled to costs in other life history parameters affected ?? over a life history gradient provided by our 23 Arizona species, as well as a broader sample of 121 North American passerine species. We further examined these effects for more than 200 passeriform and piciform populations breeding across North America. Model simulations indicate nest success and juvenile survival exert the largest effects on population growth in species with moderate to high reproductive output, whereas adult survival contributed more to population growth in long-lived species. Our simulations suggest that monitoring breeding success in populations across a broad geographic area provides an important index for identifying neotropical migratory populations at risk of serious population declines and a potential method for identifying large-scale mechanisms regulating population dynamics. ?? 2007 Elsevier B.V. All rights reserved.