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

    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.

  5. 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

  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.

    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.

  19. 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.

  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. 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)

  2. 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…

  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. 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.

  9. 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

  10. 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

  11. 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…

  12. 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…

  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. 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

  7. 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

  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. 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.

  19. 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

  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.

    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

  3. 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.

  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

    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

  16. 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

  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. 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…

  3. 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…

  4. 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

  5. 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.

  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. 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…

  19. 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.…

  20. 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…

  1. 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…

  2. 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…

  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. 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.

  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. 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

  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. 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

  3. 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

  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. 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

  9. 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

  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. 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

  14. 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.

  15. 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

  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

    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

  7. 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

  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. 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.

  18. 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…

  19. 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

  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. 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

  5. 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

  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. 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.

  8. 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

  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. 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…

  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. 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…

  3. 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

  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.

  11. Temporal association between childhood leukaemia and population growth in Swiss municipalities.

    PubMed

    Lupatsch, Judith E; Kreis, Christian; Zwahlen, Marcel; Niggli, Felix; Ammann, Roland A; Kuehni, Claudia E; Spycher, Ben D

    2016-08-01

    The population mixing hypothesis proposes that childhood leukaemia (CL) might be a rare complication of a yet unidentified subclinical infection. Large population influxes into previously isolated rural areas may foster localised epidemics of the postulated infection causing a subsequent increase of CL. While marked population growth after a period of stability was central to the formulation of the hypothesis and to the early studies on population mixing, there is a lack of objective criteria to define such growth patterns. We aimed to determine whether periods of marked population growth coincided with increases in the risk of CL in Swiss municipalities. We identified incident cases of CL aged 0-15 years for the period 1985-2010 from the Swiss Childhood Cancer Registry. Annual data on population counts in Swiss municipalities were obtained for 1980-2010. As exposures, we defined (1) cumulative population growth during a 5-year moving time window centred on each year (1985-2010) and (2) periods of 'take-off growth' identified by segmented linear regression. We compared CL incidence across exposure categories using Poisson regression and tested for effect modification by degree of urbanisation. Our study included 1500 incident cases and 2561 municipalities. The incident rate ratio (IRR) comparing the highest to the lowest quintile of 5-year population growth was 1.18 (95 % CI 0.96, 1.46) in all municipalities and 1.33 (95 % CI 0.93, 1.92) in rural municipalities (p value interaction 0.36). In municipalities with take-off growth, the IRR comparing the take-off period (>6 % annual population growth) with the initial period of low or negative growth (<2 %) was 2.07 (95 % CI 0.95, 4.51) overall and 2.99 (1.11, 8.05) in rural areas (p interaction 0.52). Our study provides further support for the population mixing hypothesis and underlines the need to distinguish take-off growth from other growth patterns in future research. PMID:27251152

  12. Inverse problem for the Verhulst equation of limited population growth with discrete experiment data

    NASA Astrophysics Data System (ADS)

    Azimov, Anvar; Kasenov, Syrym; Nurseitov, Daniyar; Serovajsky, Simon

    2016-08-01

    Verhulst limited growth model with unknown parameters of growth is considered. These parameters are defined by discrete experiment data. This inverse problem is solved with using gradient method with interpolation of data and without it. Approximation of the delta-function is used for the latter case. As an example the bacteria population E.coli is considered.

  13. Rural Renaissance in America? The Revival of Population Growth in Remote Areas.

    ERIC Educational Resources Information Center

    Morrison, Peter A.; Wheeler, Judith P.

    Presenting narrative and tabular documentation of the revival of population growth in remote, rural areas and the decline of growth in urban areas, this bulletin describes the characteristics of these shifts, considers their possible causes, and suggests some of the problems and potential benefits. Specifically, this report presents the following:…

  14. SUITABILITY OF SELECTED CROPS AND SOIL FOR GARDEN SYMPHYLAN (SYMPHYLA, SCUTIGERELLIDAE: SCUTIGERELLA IMMACULATA NEWPORT) POPULATION GROWTH

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The suitability of selected crops and soil for garden symphylan (Scutigerella immaculata Newport) population growth was studied in the laboratory and field. In the laboratory, we measured the population increase of S. immaculata after 8 w from a starting density of 35 in pots of spinach (Spinacia o...

  15. New Patterns of American Metropolitan Population Growth in the 1970s.

    ERIC Educational Resources Information Center

    Phillips, Phillip D.

    1978-01-01

    Discusses three aspects of post-1970 American metropolitan population trends: the general dimensions of change between pre- and post-1970 population growth patterns are presented; possible causes of these changes are examined; college or high school level classroom exercises that generate awareness of recent trends and their causes are outlined.…

  16. The Future and Population: What Will a No-Growth Society Be Like? A Teaching Module.

    ERIC Educational Resources Information Center

    Population Reference Bureau, Inc., Washington, DC.

    This teaching module for high school students and adults examines the future of zero population growth in 26 countries by the year 2000. The module contains an essay for students to read, followed by exercises, activities, and discussion questions based on the essay. Objectives include understanding the components of population change, identifying…

  17. SUBLETHAL NARCOSIS AND POPULATION PERSISTENCE: A MODELING STUDY ON GROWTH EFFECTS

    EPA Science Inventory

    This study of a Daphnia population model suggests that sublethal effects of nonpolar narcotics on growth of individual organisms can result in ultimate extinction of the population at chronic chemical concentrations near the effect concentration that leads to a 50% reduction in i...

  18. The between-population genetic architecture of growth, maturation, and plasticity in Atlantic salmon.

    PubMed

    Debes, Paul Vincent; Fraser, Dylan John; Yates, Matthew; Hutchings, Jeffrey A

    2014-04-01

    The between-population genetic architecture for growth and maturation has not been examined in detail for many animal species despite its central importance in understanding hybrid fitness. We studied the genetic architecture of population divergence in: (i) maturation probabilities at the same age; (ii) size at age and growth, while accounting for maturity status and sex; and (iii) growth plasticity in response to environmental factors, using divergent wild and domesticated Atlantic salmon (Salmo salar). Our work examined two populations and their multigenerational hybrids in a common experimental arrangement in which salinity and quantity of suspended sediments were manipulated to mimic naturally occurring environmental variation. Average specific growth rates across environments differed among crosses, maturity groups, and cross-by-maturity groups, but a growth-rate reduction in the presence of suspended sediments was equal for all groups. Our results revealed both additive and nonadditive outbreeding effects for size at age and for growth rates that differed with life stage, as well as the presence of different sex- and size-specific maturation probabilities between populations. The major implication of our work is that estimates of the genetic architecture of growth and maturation can be biased if one does not simultaneously account for temporal changes in growth and for different maturation probabilities between populations. Namely, these correlated traits interact differently within each population and between sexes and among generations, due to nonadditive effects and a level of independence in the genetic control for traits. Our results emphasize the challenges to investigating and predicting phenotypic changes resulting from between-population outbreeding. PMID:24473933

  19. Active population growth and immigration hypotheses in Western Europe.

    PubMed

    Feld, S

    2000-03-01

    The paper examines, in respect of 12 Western European countries over a period of 20 years, the widely held view that any decline in their working population should be offset by greater reliance on immigrant labor. This research, based on demographic projections and forecasts regarding labor market participation rates by age and sex for each of the countries concerned, focuses on the two most likely scenarios. It appears that only Italy will be faced with a fall in its working population. All other western countries will either maintain the same level or, more generally, see their workforce grow substantially. Accordingly, the authors may safely assert that there is no risk of a shortage of workers between now and the year 2020, and that an increasing supply of labor will render reliance on a greater influx of immigrant workers unnecessary. The second part analyses changes in the structure of the demand for labor. The authors deal chiefly with the phenomenon of the concentration of foreign manpower in each sector, its flexibility and mobility in a context of unemployment, as well as the impact of new technologies and globalization on the main determinants of international migration of labor. PMID:12158990

  20. A new ODE tumor growth modeling based on tumor population dynamics

    SciTech Connect

    Oroji, Amin; Omar, Mohd bin; Yarahmadian, Shantia

    2015-10-22

    In this paper a new mathematical model for the population of tumor growth treated by radiation is proposed. The cells dynamics population in each state and the dynamics of whole tumor population are studied. Furthermore, a new definition of tumor lifespan is presented. Finally, the effects of two main parameters, treatment parameter (q), and repair mechanism parameter (r) on tumor lifespan are probed, and it is showed that the change in treatment parameter (q) highly affects the tumor lifespan.

  1. A new ODE tumor growth modeling based on tumor population dynamics

    NASA Astrophysics Data System (ADS)

    Oroji, Amin; Omar, Mohd bin; Yarahmadian, Shantia

    2015-10-01

    In this paper a new mathematical model for the population of tumor growth treated by radiation is proposed. The cells dynamics population in each state and the dynamics of whole tumor population are studied. Furthermore, a new definition of tumor lifespan is presented. Finally, the effects of two main parameters, treatment parameter (q), and repair mechanism parameter (r) on tumor lifespan are probed, and it is showed that the change in treatment parameter (q) highly affects the tumor lifespan.

  2. Rapid population growth and fragile environments: the sub-Saharan African and south Asian experience.

    PubMed

    Caldwell, J C; Caldwell, P

    1994-02-18

    Case studies of the world's two poorest regions, sub-Saharan Africa and South Asia, were used to illustrate the compromised standard of living of the poor and environmental damage due to continued rapid population growth. The conclusion was that the livelihoods of the poor should not be endangered for preserving the living standards of richer people. Nations must not ignore the challenges of reducing population growth as fast as can be achieved. The transitional period over the next 50 years is the main concern, because population growth rates will be slowing. Rural population growth is expected to decline from 60% of total population growth in South Asia to 7% between 2000 and 2025; similarly the decline in sub-Saharan Africa would be from 50% to 15%. Over the past 30 years, food production in South Asia has kept pace with population growth. Sub-Saharan Africa has adopted food importation to meet demand. African problems are a low resource base, faster population growth, and the fact that governments and individuals are too poor to maintain soil fertility. Long-term studies of how much soil depletion will occur are not available for these regions, and local area studies are not as pessimistic. Transition policies are needed to put "people first in terms of engineered or directed population and ecological change." The six main issues are the following: 1) the Brundtland Commission appropriately identified poverty as the main cause and effect of environmental degradation because of the threat to survival; 2) the verdict is still out about whether food production will keep pace with population growth through economic growth and investment in agriculture; 3) empirical research is needed to examine local social and regulatory institutions and the possibility of reinforcing these mechanisms rather than instituting central controls; 4) central coercion or modernizing economic policies can destroy local level controls; 5) famine is a complex ecological phenomenon and the

  3. [Fifty years of population growth and absorbing manual labor in Brazil, 1950-2000].

    PubMed

    Paiva, P D

    1986-01-01

    The economically active population has grown rapidly in Brazil, resulting either from population growth or increased female participation in the work force. This rhythm of growth will continue at least until the end of this century. The authors suggest that the impact of the recent decline in fertility will be moderate and will only affect the younger age groups. Despite the rapid growth of employment in the processing industry, the relative size of the so-called informal sector has remained stable since 1950. It is further predicted that, given the economically active population's rate of growth and the decrease in employment in agriculture, there will be a great demand for urban employment in the next 20 years. PMID:12143702

  4. Population growth rate determinants for Arbacia: Evaluating ecological relevance of toxicity test endpoints

    SciTech Connect

    Nacci, D.; Gleason, T.; Munns, W.R. Jr.

    1995-12-31

    A population dynamics model for the sea urchin, Arbacia punctulata, was recently developed incorporating life stage endpoints frequently measured in acute and chronic toxicity studies. Model elasticity analysis was used to demonstrate that population growth rate was influenced most by adult survival and least by early life stage success, calling into question the ecological relevance of results from standardized Arbacia fertilization and larval development toxicity tests. Two approaches were used to continue this evaluation. Actual and hypothetical dose-response curves for toxicant exposures over multiple life stages were used to evaluate contributions to population growth rate of stage-specific toxicant effects. Additionally, relationships between critical life stages were developed from laboratory data for Arbacia. The results of this analysis underscore the importance of understanding both endpoint sensitivity to toxicants and sensitivity of population growth rate to test endpoints in determining the ecological relevance of toxicity tests results.

  5. Adult survival and population growth rate in Colorado big brown bats (Eptesicus fuscus)

    USGS Publications Warehouse

    O'Shea, T.J.; Ellison, L.E.; Stanley, T.R.

    2011-01-01

    We studied adult survival and population growth at multiple maternity colonies of big brown bats (Eptesicus fuscus) in Fort Collins, Colorado. We investigated hypotheses about survival using information-theoretic methods and mark-recapture analyses based on passive detection of adult females tagged with passive integrated transponders. We constructed a 3-stage life-history matrix model to estimate population growth rate (??) and assessed the relative importance of adult survival and other life-history parameters to population growth through elasticity and sensitivity analysis. Annual adult survival at 5 maternity colonies monitored from 2001 to 2005 was estimated at 0.79 (95% confidence interval [95% CI] = 0.77-0.82). Adult survival varied by year and roost, with low survival during an extreme drought year, a finding with negative implications for bat populations because of the likelihood of increasing drought in western North America due to global climate change. Adult survival during winter was higher than in summer, and mean life expectancies calculated from survival estimates were lower than maximum longevity records. We modeled adult survival with recruitment parameter estimates from the same population. The study population was growing (?? = 1.096; 95% CI = 1.057-1.135). Adult survival was the most important demographic parameter for population growth. Growth clearly had the highest elasticity to adult survival, followed by juvenile survival and adult fecundity (approximately equivalent in rank). Elasticity was lowest for fecundity of yearlings. The relative importances of the various life-history parameters for population growth rate are similar to those of large mammals. ?? 2011 American Society of Mammalogists.

  6. A stochastic population model to evaluate Moapa dace (Moapa coriacea) population growth under alternative management scenarios

    USGS Publications Warehouse

    Perry, Russell W.; Jones, Edward; Scoppettone, G. Gary

    2015-01-01

    Increasing or decreasing the total carrying capacity of all stream segments resulted in changes in equilibrium population size that were directly proportional to the change in capacity. However, changes in carrying capacity to some stream segments but not others could result in disproportionate changes in equilibrium population sizes by altering density-dependent movement and survival in the stream network. These simulations show how our IBM can provide a useful management tool for understanding the effect of restoration actions or reintroductions on carrying capacity, and, in turn, how these changes affect Moapa dace abundance. Such tools are critical for devising management strategies to achieve recovery goals.

  7. Sexual Reproduction in a Simple Growth Population Model

    NASA Astrophysics Data System (ADS)

    Lemos, Carlos Gentil Oro; Santos, Marcio

    2012-05-01

    One of the most important characteristics in the survival of a species is related to the kind of reproduction responsible for the offspring generation. However, only in the last years the role played by sexual reproduction has been investigated. Then, for a better understanding of this kind of process we introduce, in this work, a surface reaction model that describes the role of the sexual reproduction. In our model two different elements of the species, representing male and female, can interact to reproduce a new element. The sex of this new element is chosen with a given probability and in order to take into account the mortality rate we introduce another kind of individual. The value of the spatial density of this element remains constant during the time evolution of the system. The model is studied using Monte Carlo simulations and mean field approximation. Depending on the values of the control parameters of the model, the system can attain two stationary states: In one of them the population survives and in the other it can be extinguished. Besides, accordingly to our results, the phase diagram of the model shows a discontinuous transition between these two states.

  8. Coupled dynamics of energy budget and population growth of tilapia in response to pulsed waterborne copper.

    PubMed

    Chen, Wei-Yu; Lin, Chia-Jung; Ju, Yun-Ru; Tsai, Jeng-Wei; Liao, Chung-Min

    2012-11-01

    The impact of environmentally pulsed metal exposure on population dynamics of aquatic organisms remains poorly understood and highly unpredictable. The purpose of our study was to link a dynamic energy budget model to a toxicokinetic/toxicodynamic (TK/TD). We used the model to investigate tilapia population dynamics in response to pulsed waterborne copper (Cu) assessed with available empirical data. We mechanistically linked the acute and chronic bioassays of pulsed waterborne Cu at the scale of individuals to tilapia populations to capture the interaction between environment and population growth and reproduction. A three-stage matrix population model of larva-juvenile-adult was used to project offspring production through two generations. The estimated median population growth rate (λ) decreased from 1.0419 to 0.9991 under pulsed Cu activities ranging from 1.6 to 2.0 μg L(-1). Our results revealed that the influence on λ was predominately due to changes in the adult survival and larval survival and growth functions. We found that pulsed timing has potential impacts on physiological responses and population abundance. Our study indicated that increasing time intervals between first and second pulses decreased mortality and growth inhibition of tilapia populations, indicating that during long pulsed intervals tilapia may have enough time to recover. Our study concluded that the bioenergetics-based matrix population methodology could be employed in a life-cycle toxicity assessment framework to explore the effect of stage-specific mode-of-actions in population response to pulsed contaminants. PMID:22851126

  9. Toxicology across scales: Cell population growth in vitro predicts reduced fish growth.

    PubMed

    Stadnicka-Michalak, Julita; Schirmer, Kristin; Ashauer, Roman

    2015-08-01

    Environmental risk assessment of chemicals is essential but often relies on ethically controversial and expensive methods. We show that tests using cell cultures, combined with modeling of toxicological effects, can replace tests with juvenile fish. Hundreds of thousands of fish at this developmental stage are annually used to assess the influence of chemicals on growth. Juveniles are more sensitive than adult fish, and their growth can affect their chances to survive and reproduce. Thus, to reduce the number of fish used for such tests, we propose a method that can quantitatively predict chemical impact on fish growth based on in vitro data. Our model predicts reduced fish growth in two fish species in excellent agreement with measured in vivo data of two pesticides. This promising step toward alternatives to fish toxicity testing is simple, inexpensive, and fast and only requires in vitro data for model calibration. PMID:26601229

  10. Toxicology across scales: Cell population growth in vitro predicts reduced fish growth

    PubMed Central

    Stadnicka-Michalak, Julita; Schirmer, Kristin; Ashauer, Roman

    2015-01-01

    Environmental risk assessment of chemicals is essential but often relies on ethically controversial and expensive methods. We show that tests using cell cultures, combined with modeling of toxicological effects, can replace tests with juvenile fish. Hundreds of thousands of fish at this developmental stage are annually used to assess the influence of chemicals on growth. Juveniles are more sensitive than adult fish, and their growth can affect their chances to survive and reproduce. Thus, to reduce the number of fish used for such tests, we propose a method that can quantitatively predict chemical impact on fish growth based on in vitro data. Our model predicts reduced fish growth in two fish species in excellent agreement with measured in vivo data of two pesticides. This promising step toward alternatives to fish toxicity testing is simple, inexpensive, and fast and only requires in vitro data for model calibration. PMID:26601229

  11. Population growth and social change: a note on rural society.

    PubMed

    Barnabas, A P

    1974-01-01

    Changing social conditons, particularly in rural areas, often create a feeling of normlessness. For such major changes as family limitation to be accepted in rural India, those involved must understand the total social change which will be necessary. In rural areas today the desire for motherhood is a matter of being accepted. A barren woman suffers social ostracism; folk tales tell of even animals refusing to eat a meal prepared by a barren woman. A women with a large family is particularly respected, especially if they are well provided for. The other reasons given for having large numbers of children are family survival, care in old age, increase in family income, to get more share in the property, to follow the community pattern, and to make the home happier. There is a rationale for most of these. High infant and child mortality account for the family survival, The only security the parents have is the children. More children increase the family share in a joint-family land-holding. Raising the age at marriage for girls has often been suggested as a population control measure, but what is the girl to do until 19? Rural parents do not feel their obligations to their daughter have been discharged until she is married and it is the parents who are blamed if no arrangments have been made. The idea of her becoming educated is not socially acceptable and rural boys are reluctant to marry educated girls. India's values pertaining to divorce, widow remarriage, and abortion are already undergoing change. Migration to the cities is bringing about change. Looking to the cities may bring about modernization, but the fact that the young men are the ones moving away is leading a lack of leadership in the villages. To bring about the social conditions favorable to modernization agriculture should be modernized, reducing the need for labor; factories should be built in rural areas to take up this slack in agricultural employment, and perhaps it would become acceptable for

  12. The Commission on Population Growth and the American Future: its origins, operations, and aftermath.

    PubMed

    Westoff, C F

    1973-10-01

    The origins, organization, and operation of the Commission on Population Growth and the American Future and the response to its report are described. The origins of the Commission are traced to a concern with the consequences of U.S. population growth on the part of such key individuals as John D. Rockefeller 3rd and Paul Ehrlich. Because the Commission was a statutory creation of Congress, its membership included 4 Congressmen in addition to 20 distinguished citizens representing a spectrum of groups and views. The evaluation of the consequences of growth, as opposed to the means of reducing fertility, became the major concern of the research effort. Several issues led to differences within the Commission: 1) A narrow versus a broad definition of the scope of the report; 2) differing perceptions of the population problem as manifested by the ecological view, the "unwanted fertility" school, and the social justice view. The social science work contracted by the Commission had a significant impact on the final report's substance: 1) the demographic work on population projections was crucial to the analysis of the consequences of growth; 2) evaluating the demographic capability of national "growth center strategy" had an influence; and 3) the need to eliminate unwanted fertility was confirmed as a necessary priority. The basic thrust of the Commission's report was to recomment slowing growth in order to maximize the quality of life. PMID:12257905

  13. Age, growth and mortality in four populations of the boring bivalve Lithophaga patagonica from Argentina

    NASA Astrophysics Data System (ADS)

    Bagur, María; Richardson, Christopher A.; Gutiérrez, Jorge L.; Arribas, Lorena P.; Doldan, M. Socorro; Palomo, M. Gabriela

    2013-08-01

    The boring bivalve Lithophaga patagonica (d'Orbigny, 1842) is a locally abundant inhabitant of hard substrata in the coastal waters of the Southwestern Atlantic. In this paper, we describe the growth, age and mortality of three intertidal rock-boring populations of L. patagonica and one subtidal oyster shell (Ostrea puelchana) boring population. An analysis of acetate peel replicas of shell sections showed that L. patagonica slows down its growth during autumn-winter, which leads to changes in the direction and rate of shell deposition and the formation of conspicuous annual (low temperature induced) clefts in the shell margin. Cleft counts and Von Bertalanffy growth analyses indicated that maximum age varies from 4 years in the oyster-boring population to 13 years in a rock-boring one (longevity estimates varied between 6.5 and 15 years, respectively). Maximum asymptotic length (L∞) and Von Bertalanffy growth constant (K) were also variable between populations (L∞ between 14.76 and 36.95 mm and K from 0.20 to 0.90 yr- 1 respectively). Mortality rates were higher at the two southernmost populations. Type (rock vs. oyster), composition and hardness of the substrata are likely the main factors controlling the observed differences between populations.

  14. Exponential Finite-Difference Technique

    NASA Technical Reports Server (NTRS)

    Handschuh, Robert F.

    1989-01-01

    Report discusses use of explicit exponential finite-difference technique to solve various diffusion-type partial differential equations. Study extends technique to transient-heat-transfer problems in one dimensional cylindrical coordinates and two and three dimensional Cartesian coordinates and to some nonlinear problems in one or two Cartesian coordinates.

  15. Linear or Exponential Number Lines

    ERIC Educational Resources Information Center

    Stafford, Pat

    2011-01-01

    Having decided to spend some time looking at one's understanding of numbers, the author was inspired by "Alex's Adventures in Numberland," by Alex Bellos to look at one's innate appreciation of number. Bellos quotes research studies suggesting that an individual's natural appreciation of numbers is more likely to be exponential rather than linear,…

  16. Slow Protein Fluctuations Explain the Emergence of Growth Phenotypes and Persistence in Clonal Bacterial Populations

    PubMed Central

    Rocco, Andrea; Kierzek, Andrzej M.; McFadden, Johnjoe

    2013-01-01

    One of the most challenging problems in microbiology is to understand how a small fraction of microbes that resists killing by antibiotics can emerge in a population of genetically identical cells, the phenomenon known as persistence or drug tolerance. Its characteristic signature is the biphasic kill curve, whereby microbes exposed to a bactericidal agent are initially killed very rapidly but then much more slowly. Here we relate this problem to the more general problem of understanding the emergence of distinct growth phenotypes in clonal populations. We address the problem mathematically by adopting the framework of the phenomenon of so-called weak ergodicity breaking, well known in dynamical physical systems, which we extend to the biological context. We show analytically and by direct stochastic simulations that distinct growth phenotypes can emerge as a consequence of slow-down of stochastic fluctuations in the expression of a gene controlling growth rate. In the regime of fast gene transcription, the system is ergodic, the growth rate distribution is unimodal, and accounts for one phenotype only. In contrast, at slow transcription and fast translation, weakly non-ergodic components emerge, the population distribution of growth rates becomes bimodal, and two distinct growth phenotypes are identified. When coupled to the well-established growth rate dependence of antibiotic killing, this model describes the observed fast and slow killing phases, and reproduces much of the phenomenology of bacterial persistence. The model has major implications for efforts to develop control strategies for persistent infections. PMID:23382887

  17. Survival, Recruitment, and Population Growth Rate of an Important Mesopredator: The Northern Raccoon

    PubMed Central

    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

  18. The presence of Bt-transgenic oilseed rape in wild mustard populations affects plant growth.

    PubMed

    Liu, Yongbo; Stewart, C Neal; Li, Junsheng; Huang, Hai; Zhang, Xitao

    2015-12-01

    The adventitious presence of transgenic plants in wild plant populations is of ecological and regulatory concern, but the consequences of adventitious presence are not well understood. Here, we introduced Bacillus thuringiensis Cry1Ac (Bt)-transgenic oilseed rape (Bt OSR, Brassica napus) with various frequencies into wild mustard (Brassica juncea) populations. We sought to better understand the adventitious presence of this transgenic insecticidal crop in a wild-relative plant population. We assessed the factors of competition, resource availability and diamondback moth (Plutella xylostella) infestation on plant population dynamics. As expected, Bt OSR performed better than wild mustard in mixed populations under herbivore attack in habitats with enough resources, whereas wild mustard had higher fitness when Bt OSR was rarer in habitats with limited resources. Results suggest that the presence of insect-resistant transgenic plants could decrease the growth of wild mustard and Bt OSR plants and their populations, especially under high herbivore pressure. PMID:26338267

  19. On the growth of primary industry and population of China’s counties

    NASA Astrophysics Data System (ADS)

    Xie, Wen-Jie; Gu, Gao-Feng; Zhou, Wei-Xing

    2010-09-01

    The growth dynamics of complex organizations have attracted much interest of econophysicists and sociophysicists in recent years. However, most of the studies are done for developed countries. We investigate the growth dynamics of the primary industry and the population of 2079 counties in mainland China using the data from the China County Statistical Yearbooks from 2000 to 2006. We find that the annual growth rates are distributed according to Student’s t distribution with the tail exponent less than 2. We find power-law relationships between the sample standard deviation of the growth rates and the initial size. The scaling exponent is less than 0.5 for the primary industry and close to 0.5 for the population.

  20. Role of prey and intraspecific density dependence on the population growth of an avian top predator

    NASA Astrophysics Data System (ADS)

    Fernandez-de-Simon, Javier; Díaz-Ruiz, Francisco; Cirilli, Francesca; Tortosa, Francisco S.; Villafuerte, Rafael; Ferreras, Pablo

    2014-10-01

    Exploring predator-prey systems in diverse ecosystems increases our knowledge about ecological processes. Predator population growth may be positive when conspecific density is low but predators also need areas with prey availability, associated with competition, which increases the risk of suffering losses but stabilises populations. We studied relationships between European rabbits Oryctolagus cuniculus (prey) and adult eagle owls Bubo bubo (predators) in south-western Europe. We assessed models explaining the predator population growth and stability. We estimated the abundance of rabbits and adult eagle owls during three years in eight localities of central-southern Spain. We explored models including rabbit and adult eagle owl abundance, accounting for yearly variations and including the locality as a random variable. We found that population growth of adult eagle owls was positive in situations with low conspecific abundance and tended to be negative but approaching equilibrium in situations of higher conspecific abundance. Population growth was also positively related to previous summer rabbit density when taking into account eagle owl conspecific abundance, possibly indicating that rabbits may support recruitment. Furthermore, abundance stability of adult eagle owls was positively related to previous winter-spring rabbit density, which could suggest predator population stabilisation through quick territory occupation in high-quality areas. These results exemplify the trade-off between prey availability and abundance of adult predators related to population growth and abundance stability in the eagle owl-rabbit system in south-western Europe. Despite rabbits have greatly declined during the last decades and eagle owls locally specialise on them, eagle owls currently have a favourable conservation status. As eagle owls are the only nocturnal raptor with such dependence on rabbits, this could point out that predators may overcome prey decreases in areas with

  1. Population growth and development of the psocid Liposcelis brunnea Motschulsky (Psocoptera: Liposcelididae) at constant temperatures and relative humidities

    Technology Transfer Automated Retrieval System (TEKTRAN)

    We investigated the effects of temperature and relative humidity on population growth and development of the psocid Liposcelis brunnea Motschulsky. L. brunnea did not survive at 43% RH, while populations increased from 22.5-32.5°C and 55 -75% RH. Interestingly, we found L. brunnea population growth ...

  2. Isonicotinic acid hydrazide inhibits cell population growth during teratogenesis of chick embryo.

    PubMed

    Joshi, M V; Shah, V B; Modak, S P

    1991-01-01

    In chick embryos treated with a 4 hr pulse of 7.2 X 10(-5) M isonicotinic acid hydrazide (INH) the cell population growth is inhibited with an increased population doubling time. Teratogenised blastoderm cells complete their ongoing cell cycle and arrest in G1 phase. A chase with an equimolar concentration of pyridoxal-5-phosphate restores the growth rate after a lag of 4 hr equivalent to the duration of treatment with INH. Presumptive mesoblast cells invaginated through the primitive streak and neuroectoblast cells induced prior to the application of INH differentiate, while the teratogen inhibits morphogenesis and organization of organ primordia. PMID:1864614

  3. Rapid Population Growth and Human Carrying Capacity: Two Perspectives. World Bank Staff Working Papers No. 690 and Population and Development Series No. 15.

    ERIC Educational Resources Information Center

    Mahar, Dennis J., Ed.; And Others

    Two perspectives on carrying capacity and population growth are examined. The first perspective, "Carrying Capacity and Rapid Population Growth: Definition, Cases, and Consequences" (Robert Muscat), explores the possible meanings of the idea of carrying capacity under developing country conditions, looks at historical and present-day cases of…

  4. Influence of Plant Population and Nitrogen-Fertilizer at Various Levels on Growth and Growth Efficiency of Maize

    PubMed Central

    Tajul, M. I.; Alam, M. M.; Hossain, S. M. M.; Naher, K.; Rafii, M. Y.; Latif, M. A.

    2013-01-01

    Field experiments were conducted to evaluate plant population and N-fertilizer effects on yield and yield components of maize (Zea mays L.). Three levels of plant populations (53000, 66000, and 800000 plants ha−1 corresponding to spacings of 75 × 25, 60 × 25, and 50 × 25 cm) and 4 doses of N (100, 140, 180, and 220 kg ha−1) were the treatment variables. Results revealed that plant growth, light interception (LI), yield attributes, and grain yield varied significantly due to the variations in population density and N-rates. Crop growth rate (CGR) was the highest with the population of 80,000 ha−1 receiving 220 kg N ha−1, while relative growth rate (RGR) showed an opposite trend of CGR. Light absorption was maximum when most of densely populated plant received the highest amount of N (220 kg N ha−1). Response of soil-plant-analysis development (SPAD) value as well as N-content to N-rates was found significant. Plant height was the maximum at the lowest plant density with the highest amount of N. Plants that received 180 kg N ha−1 with 80,000 plants ha−1 had larger foliage, greater SPAD value, and higher amount of grains cob−1 that contributed to the maximum yield (5.03 t ha−1) and the maximum harvest index (HI) compared to the plants in other treatments. PMID:24163615

  5. Causes of mortality in California sea otters during periods of population growth and decline

    USGS Publications Warehouse

    Estes, J.A.; Hatfield, B.B.; Ralls, K.; Ames, J.

    2003-01-01

    Elevated mortality appears to be the main reason for both sluggish growth and periods of decline in the threatened California sea otter population. We assessed causes of mortality from salvage records of 3,105 beach-cast carcasses recovered from 1968 through 1999, contrasting two periods of growth with two periods of decline. Overall, an estimated 40%-60% of the deaths were not recovered and 70% of the recovered carcasses died from unknown causes. Nonetheless, several common patterns were evident in the salvage records during the periods of population decline. These included greater percentages of (1) prime age animals (3-10 yr), (2) carcasses killed by great white shark attacks, (3) carcasses recovered in spring and summer, and (4) carcasses for which the cause of death was unknown. Neither sex composition nor the proportion of carcasses dying of infectious disease varied consistently between periods of population increase and decline. The population decline from 1976 to 1984 was likely due to incidental mortality in a set-net fishery, and the decline from 1995 to 1999 may be related to a developing live-fish fishery. Long-term trends unrelated to periods of growth and decline included a decrease in per capita pup production and mass/length ratios of adult carcasses over the 31-yr study. The generally high proportion of deaths from infectious disease suggests that this factor has contributed to the chronically sluggish growth rate of the California sea otter population.

  6. Effects of recruitment, growth, and exploitation on walleye population size structure in northern Wisconsin lakes

    USGS Publications Warehouse

    Hansen, Michael J.; Nate, Nancy A.

    2014-01-01

    We evaluated the dynamics of walleye Sander vitreus population size structure, as indexed by the proportional size distribution (PSD) of quality-length fish, in Escanaba Lake during 1967–2003 and in 204 other lakes in northern Wisconsin during 1990–2011. We estimated PSD from angler-caught walleyes in Escanaba Lake and from spring electrofishing in 204 other lakes, and then related PSD to annual estimates of recruitment to age-3, length at age 3, and annual angling exploitation rate. In Escanaba Lake during 1967–2003, annual estimates of PSD were highly dynamic, growth (positively) explained 35% of PSD variation, recruitment explained only 3% of PSD variation, and exploitation explained only 7% of PSD variation. In 204 other northern Wisconsin lakes during 1990–2011, PSD varied widely among lakes, recruitment (negatively) explained 29% of PSD variation, growth (positively) explained 21% of PSD variation, and exploitation explained only 4% of PSD variation. We conclude that population size structure was most strongly driven by recruitment and growth, rather than exploitation, in northern Wisconsin walleye populations. Studies of other species over wide spatial and temporal ranges of recruitment, growth, and mortality are needed to determine which dynamic rate most strongly influences population size structure of other species. Our findings indicate a need to be cautious about assuming exploitation is a strong driver of walleye population size structure.

  7. Multigenerational effect of perfluorooctane sulfonate (PFOS) on the individual fitness and population growth of Daphnia magna.

    PubMed

    Jeong, Tae-Yong; Yuk, Min-Su; Jeon, Junho; Kim, Sang Don

    2016-11-01

    We investigated the multigenerational effect of PFOS to individual fitness (e.g., body weight, acetylcholinesterase and glutathione S-transferase) and population growth (e.g., offspring number and time to first brood) of Daphnia magna during continuous and discontinuous exposures. The intrinsic rate of population growth was also calculated. In the continuous exposure, population growth-related adverse effects were detected during all test periods, and the adverse effect tended to be weaker in later generations. On the other hand, individual fitness-related adverse effects were observed from F1 not in F0 and deteriorated as the generation number increased. These results imply that individual fitness worsens although the population growth is restored in later generations. Upon discontinuous exposure, a few but significant adverse effects were observed during the non-exposure period and highest effects were detected during the re-exposure period. This encourages the study of different exposure scenarios, which may result in unexpected and higher PFOS toxicity. Consequently, this study confirms adverse effects of PFOS to Daphnia magna in multigenerational period and supports reasons for studies linking individual fitness changes to population dynamics and covering diverse exposure scenarios to evaluate the risk of PFOS in a water environment. PMID:27396314

  8. Existence of Limit Cycles in the Solow Model with Delayed-Logistic Population Growth

    PubMed Central

    2014-01-01

    This paper is devoted to the existence and stability analysis of limit cycles in a delayed mathematical model for the economy growth. Specifically the Solow model is further improved by inserting the time delay into the logistic population growth rate. Moreover, by choosing the time delay as a bifurcation parameter, we prove that the system loses its stability and a Hopf bifurcation occurs when time delay passes through critical values. Finally, numerical simulations are carried out for supporting the analytical results. PMID:24592147

  9. Dynamics of individual growth in a recovering population of lake trout (Salvelinus namaycush)

    USGS Publications Warehouse

    Fabrizio, Mary C.; Dorazio, Robert M.; Schram, Stephen T.

    2001-01-01

    In 1976, the Wisconsin Department of Natural Resources established a refuge for a nearly depleted population of lake trout (Salvelinus namaycush) at Gull Island Shoal, Lake Superior. The refuge was intended to reduce fishing mortality by protecting adult lake trout. We examined the growth dynamics of these lake trout during the period of recovery by comparing estimates of ndividual growth before and after the refuge was established. Our estimates are based on an annual mark-recapture survey conducted at the spawning area since 1969. We developed a model that allowed mean growth rates to differ among individuals of different sizes and that accommodated variation in growth rates of individuals of the same size. Likelihood ratio tests were used to determine if the mean growth increments of lake trout changed ater the refuge was established. Our results suggest that growth of mature lake trout (particularly wild fish) decreased significantly in the postrefuge period. This decreased growth may have been associated with a reduction in food availability. We also observed reductions in growth as wild fish grew older and larger, which suggests that the growth of these fish may be adequately approximated by a von Bertalanffy growth model if it becomes possible to obtain accurate ages.

  10. Exponential tilting in Bayesian asymptotics

    PubMed Central

    Kharroubi, S. A.; Sweeting, T. J.

    2016-01-01

    We use exponential tilting to obtain versions of asymptotic formulae for Bayesian computation that do not involve conditional maxima of the likelihood function, yielding a more stable computational procedure and significantly reducing computational time. In particular we present an alternative version of the Laplace approximation for a marginal posterior density. Implementation of the asymptotic formulae and a modified signed root based importance sampler are illustrated with an example. PMID:27279661

  11. Comparison of native and introduced flathead catfish populations in Alabama and Georgia: Growth, mortality, and management

    USGS Publications Warehouse

    Sakaris, P.C.; Irwin, E.R.; Jolley, J.C.; Harrison, D.

    2006-01-01

    We compared growth of flathead catfish Pylodictis olivaris from two native populations in Alabama (Coosa and Tallapoosa rivers) and two introduced populations in Georgia (Ocmulgee and Satilla rivers). We also compared mortality rates and potential outcomes of various management regimes (minimum length limits [MLLs]) among the populations. Total length-log10(age) regression slopes for introduced fish were higher than those for native fish, and von Bertalanffy growth coefficients (K) were greater for introduced fish (Ocmulgee: 0.195; Satilla: 0.201) than for native individuals (Coosa: 0.057; Tallapoosa: 0.059). Therefore, introduced flathead catfish grew more rapidly than those in their native range. Mortality (instantaneous mortality rate, Z) was higher in the Satilla River population (Z = -0.602) than in the Ocmulgee River (Z = -0.227) and Coosa River (Z = -0.156) populations. However, fish in the Satilla River population had been introduced for only 10 years and presumably did not reach their theoretical maximum age, potentially biasing the mortality estimate for that population. Simulation of management regimes in Fishery Analyses and Simulation Tools software predicted that maximum biomass of flathead catfish in the Ocmulgee (1,668 kg) and Satilla (1,137 kg) rivers was substantially larger than that in the Coosa (873 kg) and Tallapoosa (768 kg) populations. However, increased exploitation rates in the Ocmulgee and Satilla River populations resulted in dramatic declines in overall biomass, especially at lower MLLs (254 and 356 mm, respectively). Therefore, in systems where introduced flathead catfish represent an important recreational fishery but have dramatically reduced the abundance of native fishes through predation, minimal protection is recommended. We contend that rapid growth of introduced flathead catfish has major implications for their management and the conservation of native fishes. ?? Copyright by the American Fisheries Society 2006.

  12. Impacts of breeder loss on social structure, reproduction and population growth in a social canid.

    PubMed

    Borg, Bridget L; Brainerd, Scott M; Meier, Thomas J; Prugh, Laura R

    2015-01-01

    The importance of individuals to the dynamics of populations may depend on reproductive status, especially for species with complex social structure. Loss of reproductive individuals in socially complex species could disproportionately affect population dynamics by destabilizing social structure and reducing population growth. Alternatively, compensatory mechanisms such as rapid replacement of breeders may result in little disruption. The impact of breeder loss on the population dynamics of social species remains poorly understood. We evaluated the effect of breeder loss on social stability, recruitment and population growth of grey wolves (Canis lupus) in Denali National Park and Preserve, Alaska using a 26-year dataset of 387 radiocollared wolves. Harvest of breeding wolves is a highly contentious conservation and management issue worldwide, with unknown population-level consequences. Breeder loss preceded 77% of cases (n = 53) of pack dissolution from 1986 to 2012. Packs were more likely to dissolve if a female or both breeders were lost and pack size was small. Harvest of breeders increased the probability of pack dissolution, likely because the timing of harvest coincided with the breeding season of wolves. Rates of denning and successful recruitment were uniformly high for packs that did not experience breeder loss; however, packs that lost breeders exhibited lower denning and recruitment rates. Breeder mortality and pack dissolution had no significant effects on immediate or longer term population dynamics. Our results indicate the importance of breeding individuals is context dependent. The impact of breeder loss on social group persistence, reproduction and population growth may be greatest when average group sizes are small and mortality occurs during the breeding season. This study highlights the importance of reproductive individuals in maintaining group cohesion in social species, but at the population level socially complex species may be resilient

  13. Growth rates and variances of unexploited wolf populations in dynamic equilibria

    USGS Publications Warehouse

    Mech, L. David; Fieberg, John

    2015-01-01

    Several states have begun harvesting gray wolves (Canis lupus), and these states and various European countries are closely monitoring their wolf populations. To provide appropriate perspective for determining unusual or extreme fluctuations in their managed wolf populations, we analyzed natural, long-term, wolf-population-density trajectories totaling 130 years of data from 3 areas: Isle Royale National Park in Lake Superior, Michigan, USA; the east-central Superior National Forest in northeastern Minnesota, USA; and Denali National Park, Alaska, USA. Ratios between minimum and maximum annual sizes for 2 mainland populations (n = 28 and 46 yr) varied from 2.5–2.8, whereas for Isle Royale (n = 56 yr), the ratio was 6.3. The interquartile range (25th percentile, 75th percentile) for annual growth rates, Nt+1/Nt, was (0.88, 1.14), (0.92, 1.11), and (0.86, 1.12) for Denali, Superior National Forest, and Isle Royale respectively. We fit a density-independent model and a Ricker model to each time series, and in both cases we considered the potential for observation error. Mean growth rates from the density-independent model were close to 0 for all 3 populations, with 95% credible intervals including 0. We view the estimated model parameters, including those describing annual variability or process variance, as providing useful summaries of the trajectories of these populations. The estimates of these natural wolf population parameters can serve as benchmarks for comparison with those of recovering wolf populations. Because our study populations were all from circumscribed areas, fluctuations in them represent fluctuations in densities (i.e., changes in numbers are not confounded by changes in occupied area as would be the case with populations expanding their range, as are wolf populations in many states).

  14. Population Growth of Small Harmful Rats in Grassland Subjected to Noise

    NASA Astrophysics Data System (ADS)

    Liu, Xue-Mei; Li, Zhi-Bing; Xie, Hui-Zhang; Ai, Bao-Quan; Cheng, Xiao-Bo; Liu, Liang-Gang

    2007-07-01

    The population growth of small harmful rats in grassland subjected to environment fluctuation has been modelled in a logistic equation. Two correlated random variables responsible to the fluctuation of the genetic factor and the suppression factor are used. A two-peak structure of the steady probability distribution of rate population is observed in the large fluctuation regime of the genetic factor. With the increase of correlation constant λ, the steady probability distribution can change from two peaks to a single peak. The suppression factor μ and its fluctuation also affect the steady probability distribution and can push it toward a small population.

  15. Population dynamics of bowfin in a south Georgia reservoir: latitudinal comparisons of population structure, growth, and mortality

    USGS Publications Warehouse

    Porter, Nicholas J.; Bonvechio, Timothy F.; McCormick, Joshua L.; Quist, Michael

    2014-01-01

    The objectives of this study were to evaluate the population dynamics of bowfin (Amia calva) in Lake Lindsay Grace, Georgia, and to compare those dynamics to other bowfin populations. Relative abundance of bowfin sampled in 2010 in Lake Lindsay Grace was low and variable (mean±SD; 2.7±4.7 fish per hour of electrofishing). Total length (TL) of bowfin collected in Lake Lindsay Grace varied from 233–683 mm. Age of bowfin in Lake Lindsay Grace varied from 0–5 yr. Total annual mortality (A) was estimated at 68%. Both sexes appeared to be fully mature by age 2 with gonadosomatic index values above 8 for females and close to 1 for males. The majority of females were older, longer, and heavier than males. Bowfin in Lake Lindsay Grace had fast growth up to age 4 and higher total annual mortality than the other populations examined in this study. A chi-square test indicated that size structure of bowfin from Lake Lindsay Grace was different than those of a Louisiana population and two bowfin populations from the upper Mississippi River. To further assess bowfin size structure, we proposed standard length (i.e., TL) categories: stock (200 mm, 8 inches), quality (350 mm, 14 inches), preferred (460 mm, 18 inches), memorable (560 mm, 22, inches), and trophy (710 mm, 28 inches). Because our knowledge of bowfin ecology is limited, additional understanding of bowfin population dynamics provides important insight that can be used in management of bowfin across their distribution.

  16. The control of population growth is the function of the central government.

    PubMed

    1994-04-01

    This speech of Mr. Jiang Zemin, General Secretary of the Central Committee of the Chinese Communist Party and Chairman of the People's Republic of China, before the National Forum on Family Planning Work refers to the need to strictly and effectively implement the family planning program in 1994. Socioeconomic reforms will be occurring simultaneously. Success of the family planning program is attributed to Party Committees, governments, cadres, and the masses. Even though there have been advances made in slowing population growth, the vast size of the Chinese population still poses problems. China's state policy is to modernize and to maintain strict control of overrapid population growth. The strategy is to move toward a market economy, while continuing to slow population growth but without market regulation of population growth. Family planning serves the state and the people through voluntary action. The public must receive "meticulous" education and help with day to day problems in production, daily life, and human reproduction. Government departments and nongovernmental organizations need to work together. Family planning use is the obligation of every citizen, who should be made aware of relevant national policy and of the need for devotion to country. Benefits will be received by the state and families, when family planning is used. Family planning will be cultivated as an honorable act, and boys and girls will be valued equally. The educational program will train leaders and cadres to take a leadership role in practicing family planning. Party organizations and governments at all levels should take personal responsibility for program implementation. Erratic efforts are not good enough; the task is long and arduous. Serious difficulties still exist in rural areas, and program focus should be directed to rural areas and the floating population. Reports were also made at the Forum on the population status and preparatory meetings of the forthcoming women

  17. Consequences of Rapid Population Growth: An Overview. World Bank Staff Working Papers No. 691 and Population and Development Series No. 16.

    ERIC Educational Resources Information Center

    McNicoll, Geoffrey

    A systematic discussion of the consequences of rapid population growth for economics and social systems examines growth resulting from mortality decline in the absence of comparable fertility decline. Growth resulting from net migration is also considered. The background and rationale for the study are supplied in a brief introduction. Part 2…

  18. Effects of climate change on long-term population growth of pronghorn in an arid environment

    USGS Publications Warehouse

    Gedir, Jay V.; Cain, James W.; Harris, Grant; Turnbull, Trey T.

    2015-01-01

    Climate often drives ungulate population dynamics, and as climates change, some areas may become unsuitable for species persistence. Unraveling the relationships between climate and population dynamics, and projecting them across time, advances ecological understanding that informs and steers sustainable conservation for species. Using pronghorn (Antilocapra americana) as an ecological model, we used a Bayesian approach to analyze long-term population, precipitation, and temperature data from 18 populations in the southwestern United States. We determined which long-term (12 and 24 months) or short-term (gestation trimester and lactation period) climatic conditions best predicted annual rate of population growth (λ). We used these predictions to project population trends through 2090. Projections incorporated downscaled climatic data matched to pronghorn range for each population, given a high and a lower atmospheric CO2 concentration scenario. Since the 1990s, 15 of the pronghorn populations declined in abundance. Sixteen populations demonstrated a significant relationship between precipitation and λ, and in 13 of these, temperature was also significant. Precipitation predictors of λ were highly seasonal, with lactation being the most important period, followed by early and late gestation. The influence of temperature on λ was less seasonal than precipitation, and lacked a clear temporal pattern. The climatic projections indicated that all of these pronghorn populations would experience increased temperatures, while the direction and magnitude of precipitation had high population-specific variation. Models predicted that nine populations would be extirpated or approaching extirpation by 2090. Results were consistent across both atmospheric CO2 concentration scenarios, indicating robustness of trends irrespective of climatic severity. In the southwestern United States, the climate underpinning pronghorn populations is shifting, making conditions increasingly

  19. EFFECT OF FLUID SHEAR AND IRRADIANCE ON POPULATION GROWTH AND CELLULAR TOXIN CONTENT OF THE DINOFLAGELLATE ALEXANDRIUM FUNDYENSE.

    EPA Science Inventory

    The potential for in situ turbulence to inhibit dinoflagellate population growth has been demonstrated by experimentally exposing dinoflagellate cultures to quantified shear flow. However, despite interest in understanding environmental factors that affect the growth of toxic din...

  20. Rapid Population Growth and Rural Community Change: A Focus on Land Use Issues.

    ERIC Educational Resources Information Center

    Garkovich, Lorraine

    Land use controls are often a major point of conflict between recent migrants and long-term residents of rapidly growing communities. Such conflict was noted in a case study of a rural community undergoing rapid population growth. The revision of a comprehensive land use plan for the community provided the opportunity to evaluate citizen…

  1. Population Growth Rates: Connecting Mathematics to Studies of Society and the Environment

    ERIC Educational Resources Information Center

    Ninbet, Steven; Hurley, Gabrielle; Weldon, Elizabeth

    2006-01-01

    This article reports on the teaching of a unit of lessons which integrates mathematics with studies of society and the environment. The unit entitled "Population Growth Rates" was taught to a double class of Year 6 students by a team of three teachers. The objectives of the unit were: (1) to provide students with a real-world context in which to…

  2. Population growth and development of the psocid Lepinotus reticulatus at constant temperatures and relative humidities

    Technology Transfer Automated Retrieval System (TEKTRAN)

    We investigated the effects of temperature and relative humidity on population growth and development of the psocid Lepinotus reticulatus Enderlein. Part of this study assessed the effects of marking psocids using methylene blue, chalk powder, and fluorescent powder to differentiate nymphal stages d...

  3. The Effect of Population Growth upon the Quantity of Education Children Receive.

    ERIC Educational Resources Information Center

    Simon, Julian L.; Pilarski, Adam M.

    1979-01-01

    There is indeed some negative effect of population growth on the amount of education in developing nations, but the effect is less severe than has been thought. This finding is in sharp contrast to previous conclusions drawn from similar cross-national data. Available from Review of Economics and Statistics, M-8 Littauer Center, Cambridge, MA…

  4. Population Growth. Understanding Global Change: Earth Science and Human Impacts. Global Change Instruction Program.

    ERIC Educational Resources Information Center

    Jacobsen, Judith E.

    The Global Change Instruction Program was designed by college professors to fill a need for interdisciplinary materials on the emerging science of global change. This instructional module concentrates on interactions between population growth and human activities that produce global change. The materials are designed for undergraduate students…

  5. Validity of Personal Growth Initiative Scale Scores with a Mexican American College Student Population

    ERIC Educational Resources Information Center

    Robitschek, Christine

    2003-01-01

    This study tested the validity of scores on the Personal Growth Initiative Scale (PGIS; C. Robitschek, 1998, 1999) with a Mexican American college student sample. Results indicated that the PGIS scores appear to be culturally relevant for this population, with scores on the PGIS having many similar relations with other variables that have been…

  6. Teaching Population Growth Using Cultures of Vinegar Eels, "Turbatrix aceti" (Nematoda)

    ERIC Educational Resources Information Center

    Wallace, Robert L.

    2005-01-01

    A simple laboratory exercise is presented that follows the population growth of the common vinegar eel, "Turbatrix aceti" (Nematoda), in a microcosm using a simple culture medium. It lends itself to an exercise in a single semester course. (Contains 4 figures.)

  7. Potential effects of environmental contamination on Yuma Myotis demography and population growth.

    PubMed

    Frick, Winifred F; Rainey, William E; Pierson, Elizabeth D

    2007-06-01

    Unplanned natural and anthropogenic disasters provide unique opportunities for investigating the influence of perturbations on population vital rates and species recovery times. We investigated the potential effects of a major pesticide spill by comparing annual survival rates using mark-recapture techniques on a riparian bat species, Yuma Myotis (Myotis yumanensis). Demography and population dynamics for most bat species remain poorly understood despite advances in mark-recapture estimation and modeling techniques. We compared survival and population growth rates of two roost populations exposed to a large chemical (metam sodium) spill in the upper Sacramento River in Northern California with two roost populations outside the contaminated area from 1992 to 1996. Hypotheses about long-term effects of the spill on female juvenile and adult survival were tested using an information-theoretic approach (AIC). Working hypotheses included effects of age, chemical spill, and time trend on survival. Female adult survival was higher than female juvenile survival across all sites, suggesting stage-specific mortality risks. Model-averaged estimates of female juvenile survival in the contaminated area (0.50-0.74) were lower than in control roosts (0.60-0.78) for each year in the study, suggesting that the spill may have reduced juvenile survival for several years. Female adult survival (0.73-0.89) did not appear to be strongly affected by the spill during the years of the study. There was an increase in survival for both stage-classes across all populations during the study period, which may have been caused by the end of an extended drought in California in the winter of 1993. The spill-affected population was in decline for the first year of the study as indicated by an estimated growth rate (lambda) < 1, but population growth rates increased during the four-year period. PMID:17555229

  8. Why sustainable population growth is a key to climate change and public health equity.

    PubMed

    Howat, Peter; Stoneham, Melissa

    2011-12-01

    Australia's population could reach 42 million by 2050. This rapid population growth, if unabated, will have significant social, public health and environmental implications. On the one hand, it is a major driver of climate change and environmental degradation; on the other it is likely to be a major contributor to growing social and health issues including a decline in quality of life for many residents. Disadvantaged and vulnerable groups will be most affected. The environmental, social and health-related issues include: pressure on the limited arable land in Australia; increased volumes of industrial and domestic waste; inadequate essential services; traffic congestion; lack of affordable housing; declining mental health; increased obesity problems; and inadequate aged care services. Many of these factors are related to the aggravation of climate change and health inequities. It is critical that the Australian Government develops a sustainable population plan with stabilisation of population growth as an option. The plan needs to ensure adequate hospitals and healthcare services, education facilities, road infrastructure, sustainable transport options, water quality and quantity, utilities and other amenities that are already severely overburdened in Australian cities. There is a need for a guarantee that affordable housing will be available and priority be given to training young people and Indigenous people for employment. This paper presents evidence to support the need for the stabilisation of population growth as one of the most significant measures to control climate change as well as to improve public health equity. PMID:22518917

  9. Population growth, internal migration, and environmental degradation in rural areas of developing countries.

    PubMed

    Bilsborrow, R E

    1992-01-01

    Theoretical and empirical issues are explored as related to the extent to which population growth, particularly population redistribution through internal migration, may influence land use patterns and the deterioration of natural resources. Conceptual approaches are presented including a model of the relationships among population growth, migration, and the rural environment. Population growth has direct effects on increased demand for fuelwood and food and land fragmentation. Indirect effects exist through the demand for food which puts pressure on land extensification and intensification which affects soil quality and out migration which affect deforestation and desertification. The prevailing natural resource endowments affect the extent to which extensification of intensification of agriculture takes place in a given time period, the forms in which it occurs, and whether demographic factors play a significant role. Current trends are described for population growth and redistribution, agricultural expansion, and deforestation, desertification, and soil erosion in low-income counties. Data are for 1990 in Asia (23), Latin American (23), and Africa (39) for 85 countries with a population 1 million. Also described are cross-country relationships and the implications. In Africa population growth rates have not changed substantially and the pressure on resources is significant, while dramatic declines have occurred in east and southeast Asia, in Latin America, population growth has changed considerably. Consequences of socioeconomic development are declines in the % of gross domestic product from agriculture and the agricultural labor force. Only Thailand, Nepal, Indonesia, and North Korea out of 23 Asian countries had increases in the % of total land used for agriculture and this resulted in deforestation. Levels were already high in 1965, with 8 countries having 20% of land in agricultural use and 4 countries having 15% in agricultural use. In Bangladesh and

  10. Population growth and natural resource use: do we need to despair of Africa?.

    PubMed

    Tiffen, M; Mortimore, M

    1993-01-01

    The authors make the case that population growth can lead to increases in agricultural output per head on a sustainable basis. This argument, originally developed by E. Boserup, is "illustrated by a study of Machakos District, Kenya during 1930-1960, which shows that, if policies are supportive, agricultural and non-farm incomes grow faster than even the rapid population growth rate experienced in Africa. Land use capability is not fixed, but can be transformed by investment, new technologies and good management. Lack of investment and consequent degradation are most likely at low population densities. While the study cannot foretell the future, Java illustrates a similar theme at even higher densities." PMID:12287204

  11. Population growth of Nassella trichotoma in grasslands in New Zealand slower today than in the past

    NASA Astrophysics Data System (ADS)

    Lamoureaux, Shona L.; Bourdôt, Graeme W.; Saville, David J.

    2011-09-01

    Nassella trichotoma established in modified tussock-grasslands in New Zealand from about 1860. Management programmes since 1946 have reduced populations to levels no longer impacting pastoral production. Optimising future management requires knowledge of the trajectory of population growth and its regulating demographic processes. To that end, four long-term field experiments were conducted. Net reproductive rate varied from 1.021 to 1.237 year -1 and growth in plant basal diameter from 8.1 to 16.6 mm year -1. The probability of flowering increased with basal diameter and was essentially unity above 50 mm diameter. Populations grubbed annually declined abruptly but recruitment was unaffected and extinction did not occur. Of seeds sown into disturbed and intact pastures, 0-51% produced seedlings and more arose on sunny slopes and from disturbed than intact pasture. Death rates were high; 7 years after sowing, surviving plants represented only 0-9% of the seed sown. Seeds buried 25 mm deep in the pasture litter on two occasions declined in viability at rates of 74 and 89% in the first year and first three months respectively and 26 and 0% year -1 thereafter. Seed production plant -1 (square root scale) increased linearly with plant basal diameter; for example, plants of 11 and 100 mm diameter are predicted to produce 0 and 11,092 spikelets (each with one seed) respectively. We estimate that a N. trichotoma population today will, in the absence of management, take 210 years to increase to 90% of its carrying capacity supporting the hypothesis that population growth in this species is slower than occurred historically. We show that the rates of some demographic processes may be much lower than in the past and suggest this is due to more competitive vegetation resulting from improved management. The size-dependence of many processes supports the need for a size-structured model to explain population growth in this weed.

  12. Exponential Size Distribution of von Willebrand Factor

    PubMed Central

    Lippok, Svenja; Obser, Tobias; Müller, Jochen P.; Stierle, Valentin K.; Benoit, Martin; Budde, Ulrich; Schneppenheim, Reinhard; Rädler, Joachim O.

    2013-01-01

    Von Willebrand Factor (VWF) is a multimeric protein crucial for hemostasis. Under shear flow, it acts as a mechanosensor responding with a size-dependent globule-stretch transition to increasing shear rates. Here, we quantify for the first time, to our knowledge, the size distribution of recombinant VWF and VWF-eGFP using a multilateral approach that involves quantitative gel analysis, fluorescence correlation spectroscopy, and total internal reflection fluorescence microscopy. We find an exponentially decaying size distribution of multimers for recombinant VWF as well as for VWF derived from blood samples in accordance with the notion of a step-growth polymerization process during VWF biosynthesis. The distribution is solely described by the extent of polymerization, which was found to be reduced in the case of the pathologically relevant mutant VWF-IIC. The VWF-specific protease ADAMTS13 systematically shifts the VWF size distribution toward smaller sizes. This dynamic evolution is monitored using fluorescence correlation spectroscopy and compared to a computer simulation of a random cleavage process relating ADAMTS13 concentration to the degree of VWF breakdown. Quantitative assessment of VWF size distribution in terms of an exponential might prove to be useful both as a valuable biophysical characterization and as a possible disease indicator for clinical applications. PMID:24010664

  13. Population size, growth and movements of Anguilla australis in a small lake.

    PubMed

    Jellyman, D J; Crow, S K

    2016-06-01

    To study growth rates, movements and estimate population size of shortfin eels Anguilla australis in a small lake (2·5 ha) near Christchurch, New Zealand, 617 A. australis were tagged with PIT tags. Tag retention was high (95%) and over the seven recapture events spread over 2 years, 55% of tagged A. australis were recaptured. Growth of recaptured A. australis averaged 13·1 mm year(-1) and declined slightly with increasing total length. Distance moved from original capture site increased with increasing time at large. Population estimates of A. australis > 400 mm (susceptible to capture by fyke net) from recaptures of individuals averaged 1451 A. australis, with a biomass of 170 kg ha(-1) . An average of 6·6% of the estimated total population matured as male silver A. australis each year. Results from radio-tracking of four A. australis gave an average nightly foraging area of 2780 m(2) , and there was no apparent preference for inshore movement (within 5-6 m of the shoreline) or offshore movement. Fyke-net efficiency (total catch relative to the estimated total population available to each net) measured over four consecutive nights fishing was 88%. The lack of precision of the shoreline triangulation system used, ±10 m, meant that the positional data were considered too coarse to be used in a proposed novel population estimation technique based on determining population size within foraging areas. PMID:27126719

  14. Impacts of invasive fish removal through angling on population characteristics and juvenile growth rate.

    PubMed

    Evangelista, Charlotte; Britton, Robert J; Cucherousset, Julien

    2015-06-01

    Exploitation can modify the characteristics of fish populations through the selective harvesting of individuals, with this potentially leading to rapid ecological and evolutionary changes. Despite the well-known effects of invasive fishes on aquatic ecosystems generally, the potential effects of their selective removal through angling, a strategy commonly used to manage invasive fish, are poorly understood. The aim of this field-based study was to use the North American pumpkinseed Lepomis gibbosus as the model species to investigate the consequences of selective removal on their population characteristics and juvenile growth rates across 10 populations in artificial lakes in southern France. We found that the maximal individual mass in populations decreased as removal pressure through angling increased, whereas we did not observed any changes in the maximal individual length in populations as removal pressure increased. Total population abundance did not decrease as removal pressure increased; instead, here was a U-shaped relationship between removal pressure and the abundance of medium-bodied individuals. In addition, population biomass had a U-shaped curve response to removal pressure, implying that invasive fish populations can modulate their characteristics to compensate for the negative effects of selective removals. In addition, individual lengths at age 2 and juvenile growth rates decreased as removal pressure through angling increased, suggesting a shift toward an earlier size at maturity and an overall slower growing phenotype. Therefore, these outputs challenge the efficiency of selective management methods, suggesting the use of more proactive strategies to control invasive populations, and the need to investigate the potential ecological and evolutionary repercussions of nonrandom removal. PMID:26078856

  15. Impacts of invasive fish removal through angling on population characteristics and juvenile growth rate

    PubMed Central

    Evangelista, Charlotte; Britton, Robert J; Cucherousset, Julien

    2015-01-01

    Exploitation can modify the characteristics of fish populations through the selective harvesting of individuals, with this potentially leading to rapid ecological and evolutionary changes. Despite the well-known effects of invasive fishes on aquatic ecosystems generally, the potential effects of their selective removal through angling, a strategy commonly used to manage invasive fish, are poorly understood. The aim of this field-based study was to use the North American pumpkinseed Lepomis gibbosus as the model species to investigate the consequences of selective removal on their population characteristics and juvenile growth rates across 10 populations in artificial lakes in southern France. We found that the maximal individual mass in populations decreased as removal pressure through angling increased, whereas we did not observed any changes in the maximal individual length in populations as removal pressure increased. Total population abundance did not decrease as removal pressure increased; instead, here was a U-shaped relationship between removal pressure and the abundance of medium-bodied individuals. In addition, population biomass had a U-shaped curve response to removal pressure, implying that invasive fish populations can modulate their characteristics to compensate for the negative effects of selective removals. In addition, individual lengths at age 2 and juvenile growth rates decreased as removal pressure through angling increased, suggesting a shift toward an earlier size at maturity and an overall slower growing phenotype. Therefore, these outputs challenge the efficiency of selective management methods, suggesting the use of more proactive strategies to control invasive populations, and the need to investigate the potential ecological and evolutionary repercussions of nonrandom removal. PMID:26078856

  16. Exponential Formulae and Effective Operations

    NASA Technical Reports Server (NTRS)

    Mielnik, Bogdan; Fernandez, David J. C.

    1996-01-01

    One of standard methods to predict the phenomena of squeezing consists in splitting the unitary evolution operator into the product of simpler operations. The technique, while mathematically general, is not so simple in applications and leaves some pragmatic problems open. We report an extended class of exponential formulae, which yield a quicker insight into the laboratory details for a class of squeezing operations, and moreover, can be alternatively used to programme different type of operations, as: (1) the free evolution inversion; and (2) the soft simulations of the sharp kicks (so that all abstract results involving the kicks of the oscillator potential, become realistic laboratory prescriptions).

  17. Population ecology of the gulf ribbed mussel across a salinity gradient: recruitment, growth and density

    USGS Publications Warehouse

    Honig, Aaron; Supan, John; LaPeyre, Megan K.

    2015-01-01

    Benthic intertidal bivalves play an essential role in estuarine ecosystems by contributing to habitat provision, water filtration, and promoting productivity. As such, changes that impact population distributions and persistence of local bivalve populations may have large ecosystem level consequences. Recruitment, growth, mortality, population size structure and density of the gulf coast ribbed mussel, Geukensia granosissima, were examined across a salinity gradient in southeastern Louisiana. Data were collected along 100-m transects at interior and edge marsh plots located at duplicate sites in upper (salinity ~4 psu), central (salinity ~8 psu) and lower (salinity ~15 psu) Barataria Bay, Louisiana, U.S.A. Growth, mortality and recruitment were measured in established plots from April through November 2012. Mussel densities were greatest within the middle bay (salinity ~8) regardless of flooding regime, but strongly associated with highest stem densities of Juncus roemerianus vegetation. Mussel recruitment, growth, size and survival were significantly higher at mid and high salinity marsh edge sites as compared to all interior marsh and low salinity sites. The observed patterns of density, growth and mortality in Barataria Bay may reflect detrital food resource availability, host vegetation community distribution along the salinity gradient, salinity tolerance of the mussel, and reduced predation at higher salinity edge sites.

  18. The use of intraallelic variability for testing neutrality and estimating population growth rate.

    PubMed Central

    Slatkin, M; Bertorelle, G

    2001-01-01

    To better understand the forces affecting individual alleles, we introduce a method for finding the joint distribution of the frequency of a neutral allele and the extent of variability at closely linked marker loci (the intraallelic variability). We model three types of intraallelic variability: (a) the number of nonrecombinants at a linked biallelic marker locus, (b) the length of a conserved haplotype, and (c) the number of mutations at a linked marker locus. If the population growth rate is known, the joint distribution provides the basis for a test of neutrality by testing whether the observed level of intraallelic variability is consistent with the observed allele frequency. If the population growth rate is unknown but neutrality can be assumed, the joint distribution provides the likelihood of the growth rate and leads to a maximum-likelihood estimate. We apply the method to data from published data sets for four loci in humans. We conclude that the Delta32 allele at CCR5 and a disease-associated allele at MLH1 arose recently and have been subject to strong selection. Alleles at PAH appear to be neutral and we estimate the recent growth rate of the European population to be approximately 0.027 per generation with a support interval of (0.017-0.037). Four of the relatively common alleles at CFTR also appear to be neutral but DeltaF508 appears to be significantly advantageous to heterozygous carriers. PMID:11404347

  19. Trends in the growth of population and labour force in Pakistan.

    PubMed

    Hashmi, S S

    1990-01-01

    Trends in the growth of the population and labor force in Pakistan are examined and future prospects for growth of population and labor, particularly agriculture, are estimated. The definition of labor force as employed or seeking work after a short period of employment has led to a great disparity in results for women in the labor force. Past trends in population growth reflected a growth rate of 1.6% for the 1950's, and 2.4% in 1960. The population rose to 84.3 million in 1981 from 42.6 million in 1961, which intercensally was an increase of 3.6% per annum for 1961-72 and 3.1% per annum for 1972-81. The estimated rate for 1981-86 was 2.9%/year. The rural population doubled and the urban tripled. There was a net migration of 2.123 million to urban areas reported in the 1981 census. There is also evidence of a high sex ratio. Balochistan (7.1%) and Sindh (3.6%) provinces have the highest growth rates. Although the largest population is in the Punjab, the growth is the lowest at 2.7%. The population is primarily young -- 44.5% 15 years in 1981, which is the highest in the world. Under high, medium, and low levels of fertility, prospective trends are estimated for 2006 and 2031, and by sex every 5 years from 1981. Population under high fertility is expected to reach 270 million by 2031, which is 3.39 persons/hectare. The population/hectare of land under cultivation was 4.25 in 1981 and is expected to rise to 13.49 persons/hectare in 2031. 11 million acres could be brought under cultivation to reduce the ratio. However, there are ecological considerations as well as an employment problem. The dependency ratio under the high variant will decline from 76.8 persons 0-14 and 65 years/100 persons 15-64 years in 1986 to 70.3 in 2006 which is still considerably higher than other developing countries. It is suggested that replacement level fertility be attained as soon as possible. Under low fertility, replacement level can be reached by 2011 with strong political commitment

  20. Toxicity of chlorinated phenoxyacetic acid herbicides in the experimental eukaryotic model Saccharomyces cerevisiae: role of pH and of growth phase and size of the yeast cell population.

    PubMed

    Cabral, M G; Viegas, C A; Teixeira, M C; Sá-Correia, I

    2003-04-01

    The inhibitory effect of the herbicides 2-methyl-4-chlorophenoxyacetic acid (MCPA) and 2,4-dichlorophenoxyacetic acid (2,4-D) in Saccharomyces cerevisiae growth is strongly dependent on medium pH (range 2.5-6.5). Consistent with the concept that the toxic form is the liposoluble undissociated form, at values close to their pK(a) (3.07 and 2.73, respectively) the toxicity is high, decreasing with the increase of external pH. In addition, the toxicity of identical concentrations of the undissociated acid form is pH independent, as observed with 2,4-dichlorophenol (2,4-DCP), an intermediate of 2,4-D degradation. Consequently, at pH values above 3.5 (approximately one unit higher than 2,4-D pK(a)), 2,4-DCP becomes more toxic than the original herbicide. A dose-dependent inhibition of growth kinetics and increased duration of growth latency is observed following sudden exposure of an unadapted yeast cell population to the presence of the herbicides. This contrasts with the effect of 2,4-DCP, which essentially affects growth kinetics. Experimental evidences suggest that the acid herbicides toxicity is not exclusively dependent on the liposolubility of the toxic form, as may essentially be the case of 2,4-DCP. An unadapted yeast cell population at the early stationary-phase of growth under nutrient limitation is significantly more resistant to short-term herbicide induced death than an exponential-phase population. Consequently, the duration of growth latency is reduced, as observed with the increase of the size of the herbicide stressed population. However, these physiological parameters have no significant effect either on growth kinetics, following growth resumption under herbicide stress, or on the growth curve of yeast cells previously adapted to the herbicides, indicating that their role is exerted at the level of cell adaptation. PMID:12586155

  1. Trans-theta logistics: a new family of population growth sigmoid functions.

    PubMed

    Kozusko, F; Bourdeau, M

    2011-12-01

    Sigmoid functions have been applied in many areas to model self limited population growth. The most popular functions; General Logistic (GL), General von Bertalanffy (GV), and Gompertz (G), comprise a family of functions called Theta Logistic ([Formula: see text] L). Previously, we introduced a simple model of tumor cell population dynamics which provided a unifying foundation for these functions. In the model the total population (N) is divided into reproducing (P) and non-reproducing/quiescent (Q) sub-populations. The modes of the rate of change of ratio P/N was shown to produce GL, GV or G growth. We now generalize the population dynamics model and extend the possible modes of the P/N rate of change. We produce a new family of sigmoid growth functions, Trans-General Logistic (TGL), Trans-General von Bertalanffy (TGV) and Trans-Gompertz (TG)), which as a group we have named Trans-Theta Logistic (T [Formula: see text] L) since they exist when the [Formula: see text] L are translated from a two parameter into a three parameter phase space. Additionally, the model produces a new trigonometric based sigmoid (TS). The [Formula: see text] L sigmoids have an inflection point size fixed by a single parameter and an inflection age fixed by both of the defining parameters. T [Formula: see text] L and TS sigmoids have an inflection point size defined by two parameters in bounding relationships and inflection point age defined by three parameters (two bounded). While the Theta Logistic sigmoids provided flexibility in defining the inflection point size, the Trans-Theta Logistic sigmoids provide flexibility in defining the inflection point size and age. By matching the slopes at the inflection points we compare the range of values of inflection point age for T [Formula: see text] L versus [Formula: see text] L for model growth curves. PMID:21528359

  2. Increasing Dengue Incidence in Singapore over the Past 40 Years: Population Growth, Climate and Mobility.

    PubMed

    Struchiner, Claudio Jose; Rocklöv, Joacim; Wilder-Smith, Annelies; Massad, Eduardo

    2015-01-01

    In Singapore, the frequency and magnitude of dengue epidemics have increased significantly over the past 40 years. It is important to understand the main drivers for the rapid increase in dengue incidence. We studied the relative contributions of putative drivers for the rise of dengue in Singapore: population growth, climate parameters and international air passenger arrivals from dengue endemic countries, for the time period of 1974 until 2011. We used multivariable Poisson regression models with the following predictors: Annual Population Size; Aedes Premises Index; Mean Annual Temperature; Minimum and Maximum Temperature Recorded in each year; Annual Precipitation and Annual Number of Air Passengers arriving from dengue-endemic South-East Asia to Singapore. The relative risk (RR) of the increase in dengue incidence due to population growth over the study period was 42.7, while the climate variables (mean and minimum temperature) together explained an RR of 7.1 (RR defined as risk at the end of the time period relative to the beginning and goodness of fit associated with the model leading to these estimates assessed by pseudo-R2 equal to 0.83). Estimating the extent of the contribution of these individual factors on the increasing dengue incidence, we found that population growth contributed to 86% while the residual 14% was explained by increase in temperature. We found no correlation with incoming air passenger arrivals into Singapore from dengue endemic countries. Our findings have significant implications for predicting future trends of the dengue epidemics given the rapid urbanization with population growth in many dengue endemic countries. It is time for policy-makers and the scientific community alike to pay more attention to the negative impact of urbanization and urban climate on diseases such as dengue. PMID:26322517

  3. Increasing Dengue Incidence in Singapore over the Past 40 Years: Population Growth, Climate and Mobility

    PubMed Central

    Struchiner, Claudio Jose; Rocklöv, Joacim; Wilder-Smith, Annelies; Massad, Eduardo

    2015-01-01

    In Singapore, the frequency and magnitude of dengue epidemics have increased significantly over the past 40 years. It is important to understand the main drivers for the rapid increase in dengue incidence. We studied the relative contributions of putative drivers for the rise of dengue in Singapore: population growth, climate parameters and international air passenger arrivals from dengue endemic countries, for the time period of 1974 until 2011. We used multivariable Poisson regression models with the following predictors: Annual Population Size; Aedes Premises Index; Mean Annual Temperature; Minimum and Maximum Temperature Recorded in each year; Annual Precipitation and Annual Number of Air Passengers arriving from dengue-endemic South-East Asia to Singapore. The relative risk (RR) of the increase in dengue incidence due to population growth over the study period was 42.7, while the climate variables (mean and minimum temperature) together explained an RR of 7.1 (RR defined as risk at the end of the time period relative to the beginning and goodness of fit associated with the model leading to these estimates assessed by pseudo-R2 equal to 0.83). Estimating the extent of the contribution of these individual factors on the increasing dengue incidence, we found that population growth contributed to 86% while the residual 14% was explained by increase in temperature. We found no correlation with incoming air passenger arrivals into Singapore from dengue endemic countries. Our findings have significant implications for predicting future trends of the dengue epidemics given the rapid urbanization with population growth in many dengue endemic countries. It is time for policy-makers and the scientific community alike to pay more attention to the negative impact of urbanization and urban climate on diseases such as dengue. PMID:26322517

  4. Loss of foundation species increases population growth of exotic forbs in sagebrush steppe.

    PubMed

    Prevéy, Janet S; Germino, Matthew J; Huntly, Nancy J

    2010-10-01

    The invasion and spread of exotic plants following land disturbance threatens semiarid ecosystems. In sagebrush steppe, soil water is scarce and is partitioned between deep-rooted perennial shrubs and shallower-rooted native forbs and grasses. Disturbances commonly remove shrubs, leaving grass-dominated communities, and may allow for the exploitation of water resources by the many species of invasive, tap-rooted forbs that are increasingly successful in this habitat. We hypothesized that exotic forb populations would benefit from increased soil water made available by removal of sagebrush, a foundation species capable of deep-rooting, in semiarid shrub-steppe ecosystems. To test this hypothesis, we used periodic matrix models to examine effects of experimental manipulations of soil water on population growth of two exotic forb species, Tragopogon dubius and Lactuca serriola, in sagebrush steppe of southern Idaho, USA. We used elasticity analyses to examine which stages in the life cycle of T. dubius and L. serriola had the largest relative influence on population growth. We studied the demography of T. dubius and L. serriola in three treatments: (1) control, in which vegetation was not disturbed, (2) shrubs removed, or (3) shrubs removed but winter-spring recharge of deep-soil water blocked by rainout shelters. The short-term population growth rate (Lambda) of T. dubius in the shrub-removal treatment was more than double that of T. dubius in either sheltered or control treatments, both of which had limited soil water. All L. serriola individuals that emerged in undisturbed sagebrush plots died, whereas Lambda of L. serriola was high (Lambda > 2.5) in all shrub-removal plots, whether they had rainout shelters or not. Population growth of both forbs in all treatments was most responsive to flowering and seed production, which are life stages that should be particularly reliant on deep-soil water, as well as seedling establishment, which is important to most plant

  5. Mammalian Herbivores Alter the Population Growth and Spatial Establishment of an Early-Establishing Grassland Species.

    PubMed

    Sullivan, Lauren L; Danielson, Brent J; Harpole, W Stanley

    2016-01-01

    Plant-herbivore interactions influence the establishment context of plant species, as herbivores alter the community context in which individual species establish, and the spatial relationship between individuals and their source population as plants invade. This relationship can be described using an establishment kernel, which takes into account movement through seed dispersal, and subsequent establishment of adults. Mammalian herbivores are hypothesized to influence plant population growth and establishment through a combination of consumption of seeds and seedlings, and movement of seeds. While the movement abilities of plants are well known, we have very few empirical mechanistic tests of how biotic factors like mammalian herbivores influence this spread potential. As herbivores of all sizes are abundant on the landscape, we asked the question, how do mammalian herbivores influence the population growth, spatial establishment, and the community establishment context of an early-recruiting native prairie legume, Chamaecrista fasciculata? We planted C. fasciculata in source populations within a four-acre tallgrass prairie restoration in plots with and without herbivores, and monitored its establishment with respect to distance from the source populations. We found that herbivores decreased population growth, and decreased the mean and range establishment distance. Additionally, C. fasciculata established more often without herbivores, and when surrounded by weedy, annual species. Our results provide insight into how the interactions between plants and herbivores can alter the spatial dynamics of developing plant communities, which is vital for colonization and range spread with fragmentation and climate change. Mammalian herbivores have the potential to both slow rates of establishment, but also determine the types of plant communities that surround invading species. Therefore, it is essential to consider the herbivore community when attempting to restore

  6. Mammalian Herbivores Alter the Population Growth and Spatial Establishment of an Early-Establishing Grassland Species

    PubMed Central

    Sullivan, Lauren L.; Danielson, Brent J.; Harpole, W. Stanley

    2016-01-01

    Plant-herbivore interactions influence the establishment context of plant species, as herbivores alter the community context in which individual species establish, and the spatial relationship between individuals and their source population as plants invade. This relationship can be described using an establishment kernel, which takes into account movement through seed dispersal, and subsequent establishment of adults. Mammalian herbivores are hypothesized to influence plant population growth and establishment through a combination of consumption of seeds and seedlings, and movement of seeds. While the movement abilities of plants are well known, we have very few empirical mechanistic tests of how biotic factors like mammalian herbivores influence this spread potential. As herbivores of all sizes are abundant on the landscape, we asked the question, how do mammalian herbivores influence the population growth, spatial establishment, and the community establishment context of an early-recruiting native prairie legume, Chamaecrista fasciculata? We planted C. fasciculata in source populations within a four-acre tallgrass prairie restoration in plots with and without herbivores, and monitored its establishment with respect to distance from the source populations. We found that herbivores decreased population growth, and decreased the mean and range establishment distance. Additionally, C. fasciculata established more often without herbivores, and when surrounded by weedy, annual species. Our results provide insight into how the interactions between plants and herbivores can alter the spatial dynamics of developing plant communities, which is vital for colonization and range spread with fragmentation and climate change. Mammalian herbivores have the potential to both slow rates of establishment, but also determine the types of plant communities that surround invading species. Therefore, it is essential to consider the herbivore community when attempting to restore

  7. The effects of population density on juvenile growth rate in white-tailed deer.

    PubMed

    Barr, Brannon; Wolverton, Steve

    2014-10-01

    Animal body size is driven by habitat quality, food availability, and nutrition. Adult size can relate to birth weight, to length of the ontogenetic growth period, and/or to the rate of growth. Data requirements are high for studying these growth mechanisms, but large datasets exist for some game species. In North America, large harvest datasets exist for white-tailed deer (Odocoileus virginianus), but such data are collected under a variety of conditions and are generally dismissed for ecological research beyond local population and habitat management. We contend that such data are useful for studying the ecology of white-tailed deer growth and body size when analyzed at ordinal scale. In this paper, we test the response of growth rate to food availability by fitting a logarithmic equation that estimates growth rate only to harvest data from Fort Hood, Texas, and track changes in growth rate over time. Results of this ordinal scale model are compared to previously published models that include additional parameters, such as birth weight and adult weight. It is shown that body size responds to food availability by variation in growth rate. Models that estimate multiple parameters may not work with harvest data because they are prone to error, which renders estimates from complex models too variable to detect interannual changes in growth rate that this ordinal scale model captures. This model can be applied to harvest data, from which inferences about factors that influence animal growth and body size (e.g., habitat quality and nutritional availability) can be drawn. PMID:25148782

  8. The Effects of Population Density on Juvenile Growth Rate in White-Tailed Deer

    NASA Astrophysics Data System (ADS)

    Barr, Brannon; Wolverton, Steve

    2014-10-01

    Animal body size is driven by habitat quality, food availability, and nutrition. Adult size can relate to birth weight, to length of the ontogenetic growth period, and/or to the rate of growth. Data requirements are high for studying these growth mechanisms, but large datasets exist for some game species. In North America, large harvest datasets exist for white-tailed deer ( Odocoileus virginianus), but such data are collected under a variety of conditions and are generally dismissed for ecological research beyond local population and habitat management. We contend that such data are useful for studying the ecology of white-tailed deer growth and body size when analyzed at ordinal scale. In this paper, we test the response of growth rate to food availability by fitting a logarithmic equation that estimates growth rate only to harvest data from Fort Hood, Texas, and track changes in growth rate over time. Results of this ordinal scale model are compared to previously published models that include additional parameters, such as birth weight and adult weight. It is shown that body size responds to food availability by variation in growth rate. Models that estimate multiple parameters may not work with harvest data because they are prone to error, which renders estimates from complex models too variable to detect interannual changes in growth rate that this ordinal scale model captures. This model can be applied to harvest data, from which inferences about factors that influence animal growth and body size (e.g., habitat quality and nutritional availability) can be drawn.

  9. The evolution of paternal care can lead to population growth in artificial societies.

    PubMed

    Salgado, Mauricio

    2015-09-01

    Evolutionary models of paternal care predict that when female reproductive effort is higher than male reproductive effort, selection might favour the emergence of unconditional male cooperation towards females, even when the latter group does not reciprocate. However, previous models have assumed constant population sizes, so the ecology of interacting individuals and its effects on population dynamics have been neglected. This paper reports an agent-based model that incorporates ecological dynamics into evolutionary game dynamics by allowing populations to vary. As previous models demonstrate, paternal care only evolves when female reproductive effort is higher than that of males, and the optimal strategy for females is to exploit male unconditional cooperation. The model also shows that evolution of this behaviour drives some simulations towards regimes of population growth. Thanks to the evolution of paternal care, females׳ inter-birth intervals are shortened and causing them to reproduce faster. Thus, it is suggested that the evolution of paternal care in species with differential reproductive effort between sexes could be associated to population growth. Nevertheless, the modelled evolutionary dynamics are stochastic, so differences in reproductive effort are necessary but not sufficient conditions for the evolution of paternal care. PMID:26051195

  10. Effects of population increase on cui-ui growth and maturation

    USGS Publications Warehouse

    Scoppettone, G.G.; Rissler, P.H.

    2007-01-01

    Cui-ui Chasmistes cujus is endemic to Pyramid Lake, Nevada. The cui-ui population declined during much of the 20th century as a result of water diversion and the formation of a shallow and virtually impassable delta at the mouth of the Truckee River, its spawning habitat. The population increased more than 10-fold to more than 1 million adults after access to the river was restored, creating a period of relatively higher density. This change presented the opportunity to test intraspecific density effects on cui-ui age and length at maturity and on growth. We also compared the year-class structure of the adult population before and after improved access. At low density, cui-ui mean age at maturation was 9.2 years for males and 9.6 for females; at high density, it was significantly higher: 11.8 years for males and 12.0 for females. There was no significant change in mean fork length at maturity related to population increase. Growth patterns differed between high and low density, the low-density fish growing faster than high-density fish before their respective mean age of maturity; past their mean age at maturity, high-density fish grew significantly faster than low-density fish. Fish in both density periods reached similar lengths by about 19-20 years of age. Year-class structure for both density periods consisted of strong year-classes, which predominated the adult population for several years.

  11. Rapid population growth. Effects on the social infrastructures of southern Africa.

    PubMed

    Smith, J D

    1995-01-01

    Southern Africa's high rate of population growth and widespread poverty have serious implications for the region's social infrastructure. Large increases in the school-age population have undermined efforts to improve the quality of education since all resources are directed toward expansion of availability. To achieve a teacher-pupil ratio of 1:40 at the primary level and 1:35 at the secondary level, an estimated additional 50,000 classrooms would be required. Also jeopardized by high fertility is access to health services, safe water, and sanitation. In Mozambique, for example, where only 30% of the population has access to health services, the under-five years mortality rate is 297/1000 live births and the physician-population ratio is 1:37,970. Substandard housing, homelessness, congestion, deteriorating public services, pollution, and crime dominate urban areas. The single most effective intervention to reduce population growth in Southern Africa is female education. Women without a secondary education bear an average of seven children; if 40% of women attend secondary school, this drops to three children. Thus, governments must make gender equality a central focus of development planning and ensure that women are participants in this process. Property and inheritance laws that serve to increase the economic need for early marriage should be eliminated. Public health programs, including family planning, must be expanded. Finally, women's organizations should be strengthened and urged to foster female empowerment. PMID:12346213

  12. Population Growth of Pratylenchus penetrans on Winter Cover Crops Grown in the Pacific Northwest

    PubMed Central

    Forge, T. A.; Ingham, R. E.; Kaufman, D.; Pinkerton, J. N.

    2000-01-01

    Population growth of Pratylenchus penetrans on 13 fall and winter cover crops was studied in the greenhouse and field. All crops except oat cv. Saia supported population growth of P. penetrans in greenhouse experiments, although the response of P. penetrans to oat cv. Saia varied considerably between experiments. The mean ratio of the final population density/initial population density (Pf/Pi) after 16 weeks for P. penetrans added to a greenhouse soil mix was 0.09, whereas Pf/Pi values after 10 weeks for two experiments with naturally infested soil were 0.95 and 2.3. Although P. penetrans increased on sudangrass cv. Trudan 8 and sudangrass × sorghum hybrid cv. SS 222, subsequent incorporation of sudangrass vegetation into soil reduced P. penetrans populations to preplant levels. Field experiments were inconclusive but suggested that oat cv. Saia or rye cv. Wheeler may be better choices for winter cover than weed-contaminated fallow or other crops on P. penetrans-infested sites in the Pacific Northwest. PMID:19270948

  13. Socio-Economic Instability and the Scaling of Energy Use with Population Size

    PubMed Central

    DeLong, John P.; Burger, Oskar

    2015-01-01

    The size of the human population is relevant to the development of a sustainable world, yet the forces setting growth or declines in the human population are poorly understood. Generally, population growth rates depend on whether new individuals compete for the same energy (leading to Malthusian or density-dependent growth) or help to generate new energy (leading to exponential and super-exponential growth). It has been hypothesized that exponential and super-exponential growth in humans has resulted from carrying capacity, which is in part determined by energy availability, keeping pace with or exceeding the rate of population growth. We evaluated the relationship between energy use and population size for countries with long records of both and the world as a whole to assess whether energy yields are consistent with the idea of an increasing carrying capacity. We find that on average energy use has indeed kept pace with population size over long time periods. We also show, however, that the energy-population scaling exponent plummets during, and its temporal variability increases preceding, periods of social, political, technological, and environmental change. We suggest that efforts to increase the reliability of future energy yields may be essential for stabilizing both population growth and the global socio-economic system. PMID:26091499

  14. The Contribution of Population Health and Demographic Change to Economic Growth in China and India.

    PubMed

    Bloom, David E; Canning, David; Hu, Linlin; Liu, Yuanli; Mahal, Ajay; Yip, Winnie

    2010-03-01

    We find that a cross-country model of economic growth successfully tracks the growth takeoffs in China and India. The major drivers of the predicted takeoffs are improved health, increased openness to trade, and a rising labor force-to-population ratio due to fertility decline. We also explore the effect of the reallocation of labor from low-productivity agriculture to the higher-productivity industry and service sectors. Including the money value of longevity improvements in a measure of full income reduces the gap between the magnitude of China's takeoff relative to India's due to the relative stagnation in life expectancy in China since 1980. PMID:20419074

  15. The Contribution of Population Health and Demographic Change to Economic Growth in China and India

    PubMed Central

    Bloom, David E.; Canning, David; Hu, Linlin; Liu, Yuanli; Mahal, Ajay; Yip, Winnie

    2010-01-01

    We find that a cross-country model of economic growth successfully tracks the growth takeoffs in China and India. The major drivers of the predicted takeoffs are improved health, increased openness to trade, and a rising labor force-to-population ratio due to fertility decline. We also explore the effect of the reallocation of labor from low-productivity agriculture to the higher-productivity industry and service sectors. Including the money value of longevity improvements in a measure of full income reduces the gap between the magnitude of China's takeoff relative to India's due to the relative stagnation in life expectancy in China since 1980. PMID:20419074

  16. The Association between Natural Amenities, Rural Population Growth, and Long-Term Residents' Economic Well-Being

    ERIC Educational Resources Information Center

    Hunter, Lori M; Boardman, Jason D.; Saint Onge, Jarron M.

    2005-01-01

    Population growth in rural areas characterized by high levels of natural amenities has recently received substantial research attention. A noted concern with amenity-driven rural population growth is its potential to raise local costs-of-living while yielding only low-wage service sector employment for long-term residents. The work presented here…

  17. On the bubble? With healthcare job growth outstripping population in aging Rust Belt cities, some question the trend's durability.

    PubMed

    Carlson, Joe; Kutscher, Beth

    2013-03-01

    Aging Rust Belt cities are some of the leaders in healthcare job growth despite stagnant or decreasing populations, even amid mounting pressure to cut healthcare costs. Areas seeing rapid population growth aren't as dependent on healthcare. "Cities that are growing quickly are most likely adding diversified industries," says Dr. Sheldon Retchin, of the Virginia Commonwealth University Health System. PMID:23516730

  18. Population Growth in New Hampshire during the Nineteenth and Twentieth Centuries. Studies in New England Geography, Number 1.

    ERIC Educational Resources Information Center

    Hobart, Christine L.

    This paper traces the shifts in New Hampshire's state and county population during the nineteenth and twentieth centuries, focusing on the growth of urban centers and industry. From 1790 to 1840 most of New Hampshire's population growth was agricultural despite the beginnings of industrialization and urbanization. These processes greatly…

  19. Age, growth, and mortality of introduced flathead catfish in Atlantic rivers and a review of other populations

    USGS Publications Warehouse

    Kwak, T.J.; Pine, William E., III; Waters, D.S.

    2006-01-01

    Knowledge of individual growth and mortality rates of an introduced fish population is required to determine the success and degree of establishment as well as to predict the fish's impact on native fauna. The age and growth of flathead catfish Pylodictis olivaris have been studied extensively in the species' native and introduced ranges, and estimates have varied widely. We quantified individual growth rates and age structure of three introduced flathead catfish populations in North Carolina's Atlantic slope rivers using sagittal otoliths, determined trends in growth rates over time, compared these estimates among rivers in native and introduced ranges, and determined total mortality rates for each population. Growth was significantly faster in the Northeast Cape Fear River (NECFR) than in the Lumber and Neuse rivers. Fish in the NECFR grew to a total length of 700 mm by age 7, whereas fish in the Neuse and Lumber river populations reached this length by 8 and 10 years, respectively. The growth rates of fish in all three rivers were consistently higher than those of native riverine populations, similar to those of native reservoir populations, and slower than those of other introduced riverine populations. In general, recent cohorts (1998-2001 year-classes) in these three rivers exhibited slower growth among all ages than did cohorts previous to the 1998 year-class. The annual total mortality rate was similar among the three rivers, ranging from 0.16 to 0.20. These mortality estimates are considerably lower than those from the Missouri and Mississippi rivers, suggesting relatively low fishing mortality for these introduced populations. Overall, flathead catfish populations in reservoirs grow faster than those in rivers, the growth rates of introduced populations exceed those of native populations, and eastern United States populations grow faster than those in western states. Such trends constitute critical information for understanding and managing local

  20. The Exponential Function, XI: The New Flat Earth Society.

    ERIC Educational Resources Information Center

    Bartlett, Albert A.

    1996-01-01

    Discusses issues related to perpetual population growth. Argues that if we believe that there are no limits to growth, we will have to abandon the concept of a spherical Earth which puts limits to growth. (JRH)

  1. Enhanced (hydrodynamic) transport induced by population growth in reaction–diffusion systems with application to population genetics

    PubMed Central

    Vlad, Marcel Ovidiu; Cavalli-Sforza, L. Luca; Ross, John

    2004-01-01

    We consider a system made up of different physical, chemical, or biological species undergoing replication, transformation, and disappearance processes, as well as slow diffusive motion. We show that for systems with net growth the balance between kinetics and the diffusion process may lead to fast, enhanced hydrodynamic transport. Solitary waves in the system, if they exist, stabilize the enhanced transport, leading to constant transport speeds. We apply our theory to the problem of determining the original mutation position from the current geographic distribution of a given mutation. We show that our theory is in good agreement with a simulation study of the mutation problem presented in the literature. It is possible to evaluate migratory trajectories from measured data related to the current distribution of mutations in human populations. PMID:15231998

  2. Models for optimal harvest with convex function of growth rate of a population

    SciTech Connect

    Lyashenko, O.I.

    1995-12-10

    Two models for growth of a population, which are described by a Cauchy problem for an ordinary differential equation with right-hand side depending on the population size and time, are investigated. The first model is time-discrete, i.e., the moments of harvest are fixed and discrete. The second model is time-continuous, i.e., a crop is harvested continuously in time. For autonomous systems, the second model is a particular case of the variational model for optimal control with constraints investigated in. However, the prerequisites and the method of investigation are somewhat different, for they are based on Lemma 1 presented below. In this paper, the existence and uniqueness theorem for the solution of the discrete and continuous problems of optimal harvest is proved, and the corresponding algorithms are presented. The results obtained are illustrated by a model for growth of the light-requiring green alga Chlorella.

  3. Real-Time Exponential Curve Fits Using Discrete Calculus

    NASA Technical Reports Server (NTRS)

    Rowe, Geoffrey

    2010-01-01

    An improved solution for curve fitting data to an exponential equation (y = Ae(exp Bt) + C) has been developed. This improvement is in four areas -- speed, stability, determinant processing time, and the removal of limits. The solution presented avoids iterative techniques and their stability errors by using three mathematical ideas: discrete calculus, a special relationship (be tween exponential curves and the Mean Value Theorem for Derivatives), and a simple linear curve fit algorithm. This method can also be applied to fitting data to the general power law equation y = Ax(exp B) + C and the general geometric growth equation y = Ak(exp Bt) + C.

  4. Fully exponentially correlated wavefunctions for small atoms

    SciTech Connect

    Harris, Frank E.

    2015-01-22

    Fully exponentially correlated atomic wavefunctions are constructed from exponentials in all the interparticle coordinates, in contrast to correlated wavefunctions of the Hylleraas form, in which only the electron-nuclear distances occur exponentially, with electron-electron distances entering only as integer powers. The full exponential correlation causes many-configuration wavefunctions to converge with expansion length more rapidly than either orbital formulations or correlated wavefunctions of the Hylleraas type. The present contribution surveys the effectiveness of fully exponentially correlated functions for the three-body system (the He isoelectronic series) and reports their application to a four-body system (the Li atom)

  5. Effects of density and fire on the vital rates and population growth of a perennial goldenaster

    PubMed Central

    Gornish, Elise S.

    2013-01-01

    Intraspecific density effects are generally associated with other factors, like disturbance. Therefore, the ways in which density effects might interact with disturbance to modify the relationships between vital rates and population growth must be understood. I quantified the effects of density on the life-history stages of the perennial composite Pityopsis aspera over 3 years, the span of which included years in which fire did and did not occur. In an experimental study, I estimated the survival, growth and reproduction for shoots in plots established across a natural range of densities in Florida, USA. In a novel analysis, a regression-design life-table response experiment was used to determine which transitions were associated with density, how they contributed to differences in estimated population growth rates and how this relationship differed as a result of fire. The shape of the relationship between population growth rate (λ) and density was modified by fire, primarily as a result of contributions from adult flowering stasis and survival, and first-year survival probabilities. Fire modified and even reversed the effect of extreme densities on adult flowering stasis and survival and of first-year survival, resulting in more positive contributions from these transitions to λ at the lowest and highest density values. These results demonstrate the first application of a regression-design life-table response experiment to elucidating the interactive effects of density and fire. They highlight the utility of this approach for both capturing the complex dynamics of populations and establishing a means of determining how vital rates might contribute to differences in demography across densities.

  6. Effect of microstructure on population growth parameters of Escherichia coli in gelatin-dextran systems.

    PubMed

    Boons, Kathleen; Noriega, Estefanía; Van den Broeck, Rob; David, Charlotte C; Hofkens, Johan; Van Impe, Jan F

    2014-09-01

    Current literature acknowledges the effect of food structure on bacterial dynamics. Most studies introduce this "structure" factor using a single gelling agent, resulting in a homogeneous environment, whereas in practice most food products are heterogeneous. Therefore, this study focuses on heterogeneous protein-polysaccharide mixtures, based on gelatin and dextran. These mixtures show phase separation, leading to a range of heterogeneous microstructures by adjusting relative concentrations of both gelling agents. Based on confocal microscope observations, the growth of Escherichia coli in gelatin-dextran systems was observed to occur in the dextran phase. To find a relation between microscopic and population behavior, growth experiments were performed in binary and singular gelatin-dextran systems and culture broth at 23.5°C, with or without adding 2.9% (wt/vol) NaCl. The Baranyi and Roberts growth model was fitted to the experimental data and parameter estimates were statistically compared. For salted binary mixtures, a decrease in the population maximum cell density was observed with increasing gelatin concentration. In this series, for one type of microstructure, i.e., a gelatin matrix phase with a disperse dextran phase, the maximum cell density decreased with decreasing percentage of dextran phase. However, this relation no longer held when other types of microstructure were observed. Compared to singular systems, adding a second gelling agent in the presence of NaCl had an effect on population lag phases and maximum cell densities. For unsalted media, the growth parameters of singular and binary mixtures were comparable. Introducing this information into mathematical models leads to more reliable growth predictions and enhanced food safety. PMID:24951795

  7. Dynamics and forecasting of population growth and urban expansion in Srinagar City - A Geospatial Approach

    NASA Astrophysics Data System (ADS)

    Farooq, M.; Muslim, M.

    2014-11-01

    The urban areas of developing countries are densely populated and need the use of sophisticated monitoring systems, such as remote sensing and geographical information systems (GIS). The urban sprawl of a city is best understood by studying the dynamics of LULC change which can be easily generated by using sequential satellite images, required for the prediction of urban growth. Multivariate statistical techniques and regression models have been used to establish the relationship between the urban growth and its causative factors and for forecast of the population growth and urban expansion. In Srinagar city, one of the fastest growing metropolitan cities situated in Jammu and Kashmir State of India, sprawl is taking its toll on the natural resources at an alarming pace. The present study was carried over a period of 40 years (1971-2011), to understand the dynamics of spatial and temporal variability of urban sprawl. The results reveal that built-up area has increased by 585.08 % while as the population has increased by 214.75 %. The forecast showed an increase of 246.84 km2 in built-up area which exceeds the overall carrying capacity of the city. The most common conversions were also evaluated.

  8. The relationship between population growth and real assessed market values: note.

    PubMed

    Gamble, H B; Downing, R H

    1985-07-01

    Various indices are commonly used to measure growth or decline in communities and regions, but this article suggests another measure which is fairly easy to obtain--the change over time in real assessed market values. Computer storage and analysis of real estate assessment and sales data make it possible to determine accurate true assessment ratios which can be used to calculate reasonable estimates of market values. This article shows the relationship between population growth from 1970 to 1980 and the changes in real assessed market values of various property classes for over 400 Pennsylvania townships. This can provide insight into the kind and nature of community change. The most noteworthy aspect of these data, not apparent in conventional growth measures, is the magnitude of increases of residential property values in all growth categories, but particularly in the high growth townships. This kind of data could be calculated by countries or by regions; this might be more informative and useful to planners and researchers in such form. Comparing local data to regional, community, or state landmark data can help identify strengths and weaknesses or the particular nature of a community's growth. PMID:12314193

  9. Estimation of contributions to population growth: a reverse-time capture-recapture approach

    USGS Publications Warehouse

    Nichols, J.D.; Hines, J.E.; Lebreton, J.D.; Pradel, R.

    2000-01-01

    We consider methods for estimating the relative contributions of different demographic components, and their associated vital rates, to population growth. We identify components of the population at time i (including a component for animals not in the population at i). For each such component we ask the following question: 'What is the probability that an individual randomly selected from the population at time i + 1 was a member of this component at i?' The estimation methods for these probabilities ((i) are based on capture-recapture studies of marked animal populations and use reverse-time modeling. We consider several different sampling situations and present example analyses for meadow voles, Microtus pennsylvanicus. The relationship between these (i parameters and elasticities (and other parameters based on projection matrix asymptotics) is noted and discussed. We conclude by suggesting that model-based asymptotics be viewed as demographic theory and that direct estimation approaches be used to test this theory with data from sampled populations with marked animals.

  10. Life-history correlates of maximum population growth rates in marine fishes.

    PubMed Central

    Denney, Nicola H; Jennings, Simon; Reynolds, John D

    2002-01-01

    Theory predicts that populations of animals with late maturity, low fecundity, large body size and low body growth rates will have low potential rates of population increase at low abundance. If this is true, then these traits may be used to predict the intrinsic rate of increase for species or populations, as well as extinction risks. We used life-history and population data for 63 stocks of commercially exploited fish species from the northeast Atlantic to test relationships between life-history parameters and the rate of population increase at low abundance. We used cross-taxonomic analyses among stocks and among species, and analyses that accounted for phylogenetic relationships. These analyses confirmed that large-bodied, slow-growing stocks and species had significantly lower rates of recruitment and adult production per spawning adult at low abundance. Furthermore, high ages at maturity were significantly correlated with low maximum recruit production. Contrary to expectation, fecundity was significantly negatively related to recruit production, due to its positive relationship with maximum body size. Our results support theoretical predictions, and suggest that a simply measured life-history parameter can provide a useful tool for predicting rates of recovery from low population abundance. PMID:12427316

  11. Vulnerability of Korean water resources to climate change and population growth.

    PubMed

    Chang, H; Franczyk, J; Im, E-S; Kwon, W-T; Bae, D-H; Jung, I-W

    2007-01-01

    Freshwater availability is affected by changes in climate and growth. We assessed the freshwater vulnerability for five major Korean river basins for 2015 and 2030. We used a regional climate model based on the IPCC SRES A2 scenario, US Geological Survey's Precipitation Rainfall Simulation Model, and population and industrial growth scenarios for impact assessment. The model simulation results suggest increasing spatial and temporal variations of water stress for the basins that are already developed. While freshwater is more vulnerable to growth scenarios than the climate change scenario, climate change alone could decrease mean annual runoff by 10% in four major river basins by 2030. As the first national assessment of climate change, we suggest possible adaptive water resource management and policy strategies for reducing climate related risks in Korea. PMID:17851205

  12. Verification of SNPs Associated with Growth Traits in Two Populations of Farmed Atlantic Salmon

    PubMed Central

    Tsai, Hsin Y.; Hamilton, Alastair; Guy, Derrick R.; Tinch, Alan E.; Bishop, Steve C.; Houston, Ross D.

    2015-01-01

    Understanding the relationship between genetic variants and traits of economic importance in aquaculture species is pertinent to selective breeding programmes. High-throughput sequencing technologies have enabled the discovery of large numbers of SNPs in Atlantic salmon, and high density SNP arrays now exist. A previous genome-wide association study (GWAS) using a high density SNP array (132K SNPs) has revealed the polygenic nature of early growth traits in salmon, but has also identified candidate SNPs showing suggestive associations with these traits. The aim of this study was to test the association of the candidate growth-associated SNPs in a separate population of farmed Atlantic salmon to verify their effects. Identifying SNP-trait associations in two populations provides evidence that the associations are true and robust. Using a large cohort (N = 1152), we successfully genotyped eight candidate SNPs from the previous GWAS, two of which were significantly associated with several growth and fillet traits measured at harvest. The genes proximal to these SNPs were identified by alignment to the salmon reference genome and are discussed in the context of their potential role in underpinning genetic variation in salmon growth. PMID:26703584

  13. The impact of population growth on environment: the debate heats up.

    PubMed

    Shaw, R P

    1992-02-01

    A proposed framework, which was introduced at the 1989 meetings of the American Association for the Advancement of Science, included political constraints as well as population growth as a proximate cause with potentially important impacts on the environment in Paul and Ann Ehrlich's well-known PAT equation. PAT limitations are identified as the 1.2 billion people caught in the debt-poverty trap, less developed countries' balance of payments deficits, and "distortionary factors" that undermined economic incentives and contributed to mismanagement of resources. Such factors could be keeping farm prices low and have an impact on deterring use of environmentally sound traditional agricultural practices. Mismanagement of public lands occurs when large commercial enterprises or large scale mechanization displace population onto marginal or less productive lands. Intergroup warfare is a new form impacting on the environment. In Burma loggers are authorized to clear cut large tracts of teak forests in order to ferret out Karen guerrillas. Over 15 million refugees were thus displaced and forced to live in encampments that require trees for shelter, firewood for survival, and overgrazing of livestock. Social and economic environments are also undermined by "dependency" factors such as trade protectionism, brain drain, and limited foreign aid. The Group of 77 Non-Aligned Developing Countries proposed that discussions of the links between population and the environment be omitted from the agenda of the 1994 UN Conference on Population and Development. Basic clarifications are needed to distinguish ultimate versus proximate factors and current versus future concerns. The debate ignores distribution patterns, migration, or changing age structures. The debate blames unjustifiably rapid population growth as the ultimate cause of global environmental degradation and links population growth to a host of other social problems such as famine and refugees, while ignoring civil unrest

  14. APPLICATION OF ELASTICITY ANALYSES AND PERTURBATION SIMULATIONS IN DETERMINING STRESSOR IMPACTS ON POPULATION GROWTH RATE AND EXTINCTION RISK

    EPA Science Inventory

    Population structure and life history strategies are determinants of how populations respond to stressor-induced impairments in individual-level responses, but a consistent and holistic analysis has not been reported. Effects on population growth rate were modeled using five theo...

  15. Determining Individual Variation in Growth and Its Implication for Life-History and Population Processes Using the Empirical Bayes Method

    PubMed Central

    Vincenzi, Simone; Mangel, Marc; Crivelli, Alain J.; Munch, Stephan; Skaug, Hans J.

    2014-01-01

    The differences in demographic and life-history processes between organisms living in the same population have important consequences for ecological and evolutionary dynamics. Modern statistical and computational methods allow the investigation of individual and shared (among homogeneous groups) determinants of the observed variation in growth. We use an Empirical Bayes approach to estimate individual and shared variation in somatic growth using a von Bertalanffy growth model with random effects. To illustrate the power and generality of the method, we consider two populations of marble trout Salmo marmoratus living in Slovenian streams, where individually tagged fish have been sampled for more than 15 years. We use year-of-birth cohort, population density during the first year of life, and individual random effects as potential predictors of the von Bertalanffy growth function's parameters k (rate of growth) and (asymptotic size). Our results showed that size ranks were largely maintained throughout marble trout lifetime in both populations. According to the Akaike Information Criterion (AIC), the best models showed different growth patterns for year-of-birth cohorts as well as the existence of substantial individual variation in growth trajectories after accounting for the cohort effect. For both populations, models including density during the first year of life showed that growth tended to decrease with increasing population density early in life. Model validation showed that predictions of individual growth trajectories using the random-effects model were more accurate than predictions based on mean size-at-age of fish. PMID:25211603

  16. Population growth study of the rotifer Brachionus sp. fed with triazine-exposed microalgae.

    PubMed

    Rioboo, C; Prado, R; Herrero, C; Cid, A

    2007-08-01

    Few data exist on potential toxic effects that pollutants may have on zooplankton fed microalgae exposed to pesticides. For that reason, microalgal cultures were exposed to different concentrations of the triazine herbicide terbutryn, and used as exclusive food source to Brachionus sp. females, with the aim to evaluate potential deleterious effects upon population growth, survival, reproduction and feeding of the rotifer. Chlorella vulgaris cells were able to accumulate terbutryn, removing more than 90% of the total amount of herbicide in all the exposed cultures. Growth curves of Brachionus sp. showed that population density decreased as terbutryn concentration increased in the microalgal cells. In fact, this species of rotifer did not survive beyond four days when fed with microalgae exposed to 500 nM terbutryn. Percentage of reproductive females in rotifer populations fed with terbutryn-exposed microalgae decreased significantly as herbicide concentration increased. In control cultures, reproductive females laid a maximum of three eggs per individual; whereas in 100 nM cultures, reproductive females laid only one egg per individual throughout the treatment period. Terbutryn accumulated in C. vulgaris provoked a decrease in the feeding rate of Brachionus sp. cultures fed with these microalgae with respect to control cultures. After this treatment period, all the rotifer populations, except those fed with 500 nM terbutryn-exposed microalgae, showed recovery patterns when they were returned to fresh medium containing herbicide-free microalga. Taking into account the results obtained, uptake of pesticides by phytoplankton can directly affect higher trophic levels. PMID:17553575

  17. Anatomy of a bottleneck: diagnosing factors limiting population growth in the Puerto Rican parrot

    USGS Publications Warehouse

    Beissenger, S.R.; Wunderle, J.M., Jr.; Meyers, J.M.; Saether, B.-E.; Engen, S.

    2008-01-01

    The relative importance of genetic, demographic, environmental, and catastrophic processes that maintain population bottlenecks has received little consideration. We evaluate the role of these factors in maintaining the Puerto Rican Parrot (Amazona vittata) in a prolonged bottleneck from 1973 through 2000 despite intensive conservation efforts. We first conduct a risk analysis, then examine evidence for the importance of specific processes maintaining the bottleneck using the multiple competing hypotheses approach, and finally integrate these results through a sensitivity analysis of a demographic model using life-stage simulation analysis (LSA) to determine the relative importance of genetic, demographic, environmental, and catastrophic processes on population growth. Annual population growth has been slow and variable (1.0 6 5.2 parrots per year, or an average k?1.05 6 0.19) from 16 parrots (1973) to a high of 40-42 birds (1997-1998). A risk analysis based on population prediction intervals (PPI) indicates great risk and large uncertainty, with a range of 22?83 birds in the 90% PPI only five years into the future. Four primary factors (reduced hatching success due to inbreeding, failure of adults to nest, nest failure due to nongenetic causes, and reduced survival of adults and juveniles) were responsible for maintaining the bottleneck. Egghatchability rates were low (70.6% per egg and 76.8% per pair), and hatchability increased after mate changes, suggesting inbreeding effects. Only an average of 34% of the population nested annually, which was well below the percentage of adults that should have reached an age of first breeding (41-56%). This chronic failure to nest appears to have been caused primarily by environmental and/or behavioral factors, and not by nest-site scarcity or a skewed sex ratio. Nest failure rates from nongenetic causes (i.e., predation, parasitism, and wet cavities) were low (29%) due to active management (protecting nests and fostering

  18. Effects of Sample Size on Estimates of Population Growth Rates Calculated with Matrix Models

    PubMed Central

    Fiske, Ian J.; Bruna, Emilio M.; Bolker, Benjamin M.

    2008-01-01

    Background Matrix models are widely used to study the dynamics and demography of populations. An important but overlooked issue is how the number of individuals sampled influences estimates of the population growth rate (λ) calculated with matrix models. Even unbiased estimates of vital rates do not ensure unbiased estimates of λ–Jensen's Inequality implies that even when the estimates of the vital rates are accurate, small sample sizes lead to biased estimates of λ due to increased sampling variance. We investigated if sampling variability and the distribution of sampling effort among size classes lead to biases in estimates of λ. Methodology/Principal Findings Using data from a long-term field study of plant demography, we simulated the effects of sampling variance by drawing vital rates and calculating λ for increasingly larger populations drawn from a total population of 3842 plants. We then compared these estimates of λ with those based on the entire population and calculated the resulting bias. Finally, we conducted a review of the literature to determine the sample sizes typically used when parameterizing matrix models used to study plant demography. Conclusions/Significance We found significant bias at small sample sizes when survival was low (survival = 0.5), and that sampling with a more-realistic inverse J-shaped population structure exacerbated this bias. However our simulations also demonstrate that these biases rapidly become negligible with increasing sample sizes or as survival increases. For many of the sample sizes used in demographic studies, matrix models are probably robust to the biases resulting from sampling variance of vital rates. However, this conclusion may depend on the structure of populations or the distribution of sampling effort in ways that are unexplored. We suggest more intensive sampling of populations when individual survival is low and greater sampling of stages with high elasticities. PMID:18769483

  19. Grid cells analysis of urban growth using remote sensing and population census data

    NASA Astrophysics Data System (ADS)

    Bagan, H.; Yamagata, Y.

    2012-12-01

    Urban growth and sprawl have drastically altered the ecosystems and ecosystem services. Urban areas are an increasingly important component of the global environment, yet they remain one of the most challenging areas for conducting research. Remote sensing based information is one of the most important resources to support urban planning and administration in megacities. It is possible to provide the up-to-date information regarding the extent, growth, and physical characteristics of urban land. Remote sensing provides spatially consistent image information that covers broad areas with both high spatial resolution and high temporal frequency. Therefore, remote sensing is an important tool for providing information on urban land-cover characteristics and their changes over time at various spatial and temporal scales. Urban land-use and land-cover changes are linked to socio-economic activities. Urbanization includes both the physical growth of a city and the movement of people to urban areas. As a consequence, it is essential to combine remote sensing derived parameters with socio-economic parameter to analyze the spatial-temporal changes and interaction of both factors. The aim of the research was to use1-km2 grid cells to investigate the spatial and temporal dynamics of urban growth in the world mega cities. The research was conducted in the 50 global cities using Landsat ETM/TM remote sensing imagery from 1985 - 2011, and time series population census data (1-km2 resolution gridded population census data of Japan and 2.5 arc-minute resolutions Gridded Population of the World). First, maximum likelihood classification (MLC) method were used to produce land cover maps by using Landsat images. Then intersect the land cover maps with 1-km2 grid cell maps to represents the proportion of each land cover category within each 1-km2 grid cell. Finally, we combined the proportional land cover maps with gridded population census data on 1-km2 resolution grid cells to

  20. Survival and growth of Cronobacter sakazakii on fresh-cut fruit and the effect of UV-C illumination and electrolyzed water in the reduction of its population.

    PubMed

    Santo, David; Graça, Ana; Nunes, Carla; Quintas, Célia

    2016-08-16

    Cronobacter sakazakii, found in foods such as powdered infant formula and plant origin ready-to-eat food, is an opportunistic pathogen to infants, neonates and vulnerable adults. The objective of this study was to monitor the growth of C. sakazakii in fresh-cut 'Royal gala' apple, 'Rocha' pear, and 'Piel de sapo' melon, and the effect of UV-C illumination, acidic electrolyzed water (AEW) and neutral electrolyzed water (NEW) in the reduction of its population. Fresh-cut fruits were inoculated and incubated at different temperatures during 10days while monitoring C. sakazakii. The inhibitory activity of different doses of UV-C (0-10kJ.m(2)), electrolyzed water and sodium hypochlorite (SH) (100ppm chlorine) was evaluated on the fruits inoculated with C. sakazakii. The bacterium showed a significant growth in the fruits at 12 and 20°C, but did not grow at 4°C, despite having survived for 10days. At 8°C, adaptation phases of 0.6-3.9days were estimated in the fruits before exponential growth. The UV-C 7.5 and 10kJ/m(2) produced greater C. sakazakii population decreases (2-2.4logcfu/g) than AEW (1.3-1.8logcfu/g), NEW (1-1.2logcfu/g) and SH (0.8-1.4logcfu/g). The UV-C decontamination system and refrigeration at 4°C, may contribute to the product's safety and quality. The results help better understand the behavior of C. sakazakii on fresh-cut fruit alerting producers of the necessity to respect the high hygienic practices, adequate refrigerating temperature maintenance and caution with the tendency to prolong the validity of this kind of ready-to-eat food. PMID:27163653

  1. The impacts of lower population growth on the quality of life and economic development: China's experience.

    PubMed

    Jiang, Z; Zhang, L

    1994-02-01

    China's population in 1993 was 1.18 billion, which makes it the most populous nation in the world. The Chinese population policy aims to control growth and improve the quality of human resources. Most Chinese recognize the need for family planning. Replacement level fertility has been achieved, because there are limited resources to support a large population. Scarce resources are limiting economic development. There has been a loss of arable land, and the dream of 2 hectares of land, a cow, a wife and children, and a comfortable bed are not attainable. Water resources are also limited, the ratio of water to arable land is unevenly balanced, and there is overdrawing of groundwater. Energy shortages, environmental pollution, and pressure on employment are other effects of population pressure. The surplus labor force is about 150-190 million farmering laborers. Labor productivity has declined due to excess labor. Projections are that 20-25% of employees are surplus, and unemployed in urban areas will total 10 million. Without a strong family planning program, there will be a rural labor surplus of 200-360 million people by the year 2000. One benefit of lower population growth is the savings in child-rearing expenses. Estimated births averted between 1971 and 1992 was about 250 million, which translates to a savings of $500 billion. About 66% of this sum would be recovered in the same period and 33% would be recovered between 1993-2007. Government and nongovernmental spending on family planning totaled an estimated $10 billion between 1971-92. The ratio of input to output for averted births is 1 to 17. Total spending would have been RMB 2500 billion yuan for child rearing of averted births between 1971-92 and RMB 1828 billion yuan between 1991-2005. The saved money could be invested in economic development. An estimated 10% of national income could be saved. Another benefit from low population growth is the increased consumption evident between 1971-90. There has not

  2. The future fertility of mankind: effects on world population growth and migration.

    PubMed

    Short, R V

    2001-01-01

    The world's population, currently just over 6 billion, is projected to increase to 9-10 billion by the year 2050. Most of this growth will occur in the developing countries of Asia, where there is an enormous unmet demand for contraception, while an increasing number of developed countries will have declining populations. The human immunodeficiency virus (HIV) pandemic will target developing countries, with India destined to become its new epicenter. By 2050, there may be 1 billion HIV-infected people in the world. The significant protective effect of male circumcision may spare Islamic countries, such as Pakistan, Bangladesh, Iran and Indonesia, from the worst effects of the pandemic. Australia will be increasingly threatened by the high rates of population growth of her Asian neighbours. This, coupled with political instability and sea-level rises as a consequence of global warming, will turn the present trickle of refugees from a variety of Asian countries seeking safe haven on our sparsely populated northern coastline into a veritable flood. There will come a time when we have neither the manpower, nor the means, nor even the moral right to intercept, detain or repatriate the thousands who will come in peace, in search of a better life. However, if Australia is to stabilize its future population at around 23 million, which seems highly desirable on ecological grounds, then the net immigration rate must be limited to approximately 50000 people per year. Because the final point of departure for all these refugees is Indonesia, it is essential that Australia maintains good relations with Indonesia, so that together we can attempt to manage the refugee problem. However, Indonesia's own population is destined to increase by 100 million in the next 50 years, which will only exacerbate the situation. Australia would be well advised to make a major increase in its paltry financial assistance to Indonesia's excellent family planning programmes, which are currently

  3. [The decline in the population growth rate--a priority issue in international politics].

    PubMed

    Rhein, E

    1994-08-25

    The Third International UN Conference on Population and Development took place in Cairo in early September 1994 with the participation of 200 governments and 1000 nongovernmental organizations to discuss ways of stabilizing world population at the possible lowest level and how industrialized countries could contribute to this effort. As a consequence of the advances in reproductive medicine the use of contraceptives skyrocketed: in 1994 more than half of men and women were using contraception compared to only 5% in 1950. However, the demographic momentum would still increase world population for another 100 years, even if fertility would drop to 2.2 children per couple (compared to 4 children in 1990). Nevertheless, the present generation could be instrumental in deciding whether the world's population will remain around 8 billion or reach 12 billion between 2050 and 2150. Poor countries can no longer afford an annual growth rate of 2-4% while also trying to improve living standards; this would require an economic growth rate of 6-8%. For the control of population growth both a sustainable environmental policy in the North, with rapid transition to renewable energy and recycling, and a more effective population policy in the South are needed. Family planning (FP) is the precondition of stabilization. The global FP outlays are envisioned to double from the 1994 figure of $5 billion to over $10 billion in the year 2000, with donor contributions to increase from 20% to 40% of the total. The US contribution is to double from $500 million by 2000, while the European Commission decided to boost expenditures for FP from DM 30 million in 1994 to DM 600 million by 2000. Japan is also expending $3 billion during this period. Recent promising developments have emerged: national pronatalist policies have diminished sharply and the pronatalist influence of religions has also declined. Political commitment at the highest level is central to a successful population policy as

  4. Field population abundance of leafhopper (Homoptera: Cicadelidae) and planthopper (Homoptera: Delphacidae) as affected by rice growth stages

    NASA Astrophysics Data System (ADS)

    Hafizal, M. M.; Idris, A. B.

    2013-11-01

    The leafhopper (Homoptera: Delphacidae) and planthopper (Homoptera: Cicadelidae) are considered as important rice pest in Asia including Malaysia. As phloem-feeders, they can cause loss to rice growth development and their population abundance is thought to be influenced by rice growth stages. This study was conducted to examine the population of Delphacidae and Cicadelidae between different rice growth stages, i.e. before and after rice planting periods. Monthly sampling was conducted in three sites in Kuala Selangor at before planting, vegetative, reproductive, maturing stages and post-harvest period using sweeping net and light traps. Population abundance of Delphacidae and Cicadelidae were found to be significantly different and positively correlated with different rice growth stages (p<0.05). Delphacidae was most abundance during maturing stages, while the abundance of Cicadelidae peaked during reproductive stage of rice growth. Differences in temporal abundance of the population of these two homopterans indicated adaptive feeding strategy to reduce food competition.

  5. Genetic analysis of leg problems and growth in a random mating broiler population.

    PubMed

    González-Cerón, F; Rekaya, R; Anthony, N B; Aggrey, S E

    2015-02-01

    Improvement in growth has been widely reported as the cause of increased incidence of leg problems in broiler chickens. We report herein the genetic relationship between growth and leg problems in a random mating broiler control population. The traits studied were valgus (VL), varus (VR), and tibial dyschondroplasia (TD), which were expressed on a binary scale of 0 (normal) and 1 (abnormal); growth rates from 0 to 4 wk (BWG 0-4) and from 0 to 6 wk of age (BWG 0-6); and residual feed intake from 5 to 6 wk of age (RFI 5-6). A threshold-linear mixed model was employed for the joint analysis of the categorical and linear traits. Incidences of VL, VR, and TD were 26, 4, and 2%, respectively. Heritability of leg problems ranged from 0.11 to 0.13. Phenotypic correlations alluded to an unfavorable relationship between growth and leg problems; however, the genetic relationship between growth and leg problems was extremely weak, ranging from 0.01 to 0.08. There is, therefore, a basis for genetic improvement in leg problems. However, improved management practices would also be important to reduce incidence of leg problems in broiler chickens. PMID:25589079

  6. Using a laboratory-based growth model to estimate mass- and temperature-dependent growth parameters across populations of juvenile Chinook Salmon

    USGS Publications Warehouse

    Perry, Russell W.; Plumb, John M.; Huntington, Charles

    2015-01-01

    To estimate the parameters that govern mass- and temperature-dependent growth, we conducted a meta-analysis of existing growth data from juvenile Chinook Salmon Oncorhynchus tshawytscha that were fed an ad libitum ration of a pelleted diet. Although the growth of juvenile Chinook Salmon has been well studied, research has focused on a single population, a narrow range of fish sizes, or a narrow range of temperatures. Therefore, we incorporated the Ratkowsky model for temperature-dependent growth into an allometric growth model; this model was then fitted to growth data from 11 data sources representing nine populations of juvenile Chinook Salmon. The model fit the growth data well, explaining 98% of the variation in final mass. The estimated allometric mass exponent (b) was 0.338 (SE = 0.025), similar to estimates reported for other salmonids. This estimate of b will be particularly useful for estimating mass-standardized growth rates of juvenile Chinook Salmon. In addition, the lower thermal limit, optimal temperature, and upper thermal limit for growth were estimated to be 1.8°C (SE = 0.63°C), 19.0°C (SE = 0.27°C), and 24.9°C (SE = 0.02°C), respectively. By taking a meta-analytical approach, we were able to provide a growth model that is applicable across populations of juvenile Chinook Salmon receiving an ad libitum ration of a pelleted diet.

  7. Examining Perceptions of Rapid Population Growth in North and South Gondar Zones, Northwest Ethiopia

    PubMed Central

    Worku, Alemayehu

    2009-01-01

    Ethiopia is one of the most populous countries in Africa and ranks second only to Nigeria. Rapid population growth has hampered the country's development, making the eradication of extreme poverty and hunger difficult. This study which had two components—quantitative and qualitative—was aimed at exploring the perceptions of women and other social groups on the prevailing population pressures. The quantitative study involved 3,512 women aged 15–49 years. The qualitative study consisted of five focus-group discussions and six key-informant interviews. Over 90% of women (n=3,512) who participated in the quantitative study and nearly all the focus-group discussants and interviewees (n=39) felt that something should be done to keep the population from growing too fast. Most (over 90%) participants approved of the Government passing a law regarding the maximum number of children that a couple should have. It is, therefore, timely for the responsible bodies to exert maximum effort and commitment in responding to the emerging attitudes of the people by making the population problem a priority. PMID:20099762

  8. Biomass, growth, and development of populations of herbivorous zooplankton in the southeastern Bering Sea during spring

    SciTech Connect

    Vidal, J.; Smith, S.L.

    1985-09-01

    Two distinct communities of herbivorous zooplankton, separated by an oceanographic front, inhabit the continental shelf and slope of the southeastern Bering Sea during spring. The community over the outer shelf and slope is dominated by populations of large-sized oceanic copepods (mainly Neocalanus ssp.) that develop early in spring and attain maximum biomass and growth rates by mid- to late spring. Total biomass and growth rates of herbivores follow the spring outburst of phytoplankton; during April and May biomass increases from less than or equal to1 to approx.14 g C m/sup -2/ on the slope and to approx.10 g C m/sup -2/ on the outer shelf, and maximum growth rates >500 and approx.300 mg C m/sup -2/ day/sup -1/ occure on the slope and outer shelf, respectively in May. The dominant species, N. plumchrus, grows from copepodid I and V between late March and early May, and after attaining maximum body weight in late May and early June it begins its downward migration. The inshore community on the middle shelf is dominated by the euphausiid Thysanoessa raschi in April and May and by the copepod Calanus marshallae in late May and early June. Total biomass (less than or equal to g C m/sup -2/) and growth rates (less than or equal to50 mg C m/sup -2/) of the inshore community are substantially lower than those of the offshore community and show a delayed response to the spring bloom of phytoplankton; both biomass and growth rates increase about one month after the bloom. Small herbivorous copepods contributed little to the total biomass and growth rates of either community and the cumulative community growth rates during April and May decreases from 18.3 g C m/sup -2/ on the slope to 2.5 g C m/sup -2/ on the middle shelf. 79 refs., 15 figs., 7 tabs.

  9. National Health Expenditure Growth in the 1980's: An Aging Population, New Technologies, and Increasing Competition

    PubMed Central

    Freeland, Mark S.; Schendler, Carol Ellen

    1983-01-01

    Health care spending in the United States more than tripled between 1971 and 1981, increasing from $83 billion to $287 billion. This growth in health sector spending substantially outpaced overall growth in the economy, averaging 13.2 percent per year compared to 10.5 percent for the gross national product (GNP). By 1981, one out of every ten dollars of GNP was spent on health care, compared to one out of every thirteen dollars of GNP in 1971. If current trends continue and if present health care financing arrangements remain basically unchanged, national health expenditures are projected to reach approximately $756 billion in 1990 and consume roughly 12 percent of GNP. The focal issue in health care today is cost and cost Increases. The outlook for the 1980's is for continued rapid growth but at a diminished rate. The primary force behind this moderating growth is projected lower inflation. However, real growth rates are also expected to moderate slightly. The chief factors influencing the growth of health expenditures in the eighties are expected to be aging of the population, new medical technologies, increasing competition, restrained public funding, growth in real income, increased health manpower, and a deceleration in economy-wide inflation. Managers, policy makers and providers in the health sector, as in all sectors, must include in today's decisions probable future trends. Inflation, economic shocks, and unanticipated outcomes of policies over the last decade have intensified the need for periodic assessments of individual industries and their relationship to the macro economy. This article provides such an assessment for the health care industry. Baseline current-law projections of national health expenditures are made to 1990. PMID:10309852

  10. Agricultural adjuvants: acute mortality and effects on population growth rate of Daphnia pulex after chronic exposure.

    PubMed

    Stark, John D; Walthall, William K

    2003-12-01

    Acute and chronic toxicity of eight agricultural adjuvants (Bond, Kinetic, Plyac, R-11, Silwet L-77, Sylgard 309, X-77, and WaterMaxx) to Daphnia pulex were evaluated with 48-h acute lethal concentration estimates (LC50) and a 10-d population growth-rate measurement, the instantaneous rate of increase (r1). Based on LC50, the order of toxicity was R-11 > X-77 = Sylgard 309 = Silwet L-77 > Kinetic > Bond > Plyac > WaterMaxx; all LC50 estimates were higher than the expected environmental concentration (EEC) of 0.79 mg/L, indicating that none of these adjuvants should cause high levels of mortality in wild D. pulex populations. Extinction, defined as negative population growth rate, occurred after exposure to 0.9 mg/L R-11, 13 mg/L X-77, 25 mg/L Kinetic, 28 mg/L Silwet, 18 mg/L Sylgard, 450 mg/L Bond, 610 mg/L Plyac, and 1,600 mg/L WaterMaxx. Concentrations that caused extinction were substantially below the acute LC50 for R-11, Kinetic, Plyac, X-77, and Bond. The no-observable-effects concentration (NOEC) and lowest-observable-effects concentration (LOEC) for the number of offspring per surviving female after exposure to R-11 were 0.5 and 0.75 mg/L, respectively. The NOEC and LOEC for population size after exposure to R-11 were (1.25 and 0.5 mg/L, respectively. Both of these values were lower than the EEC, indicating that R-11 does have the potential to cause damage to D. pulex populations after application at recommended field rates. The wide range of concentrations causing extinction makes it difficult to generalize about the potential impacts that agricultural adjuvants might have on aquatic ecosystems. Therefore, additional studies that examine effects on other nontarget organisms and determine residues in aquatic ecosystems may be warranted. PMID:14713050

  11. Theory, computation, and application of exponential splines

    NASA Technical Reports Server (NTRS)

    Mccartin, B. J.

    1981-01-01

    A generalization of the semiclassical cubic spline known in the literature as the exponential spline is discussed. In actuality, the exponential spline represents a continuum of interpolants ranging from the cubic spline to the linear spline. A particular member of this family is uniquely specified by the choice of certain tension parameters. The theoretical underpinnings of the exponential spline are outlined. This development roughly parallels the existing theory for cubic splines. The primary extension lies in the ability of the exponential spline to preserve convexity and monotonicity present in the data. Next, the numerical computation of the exponential spline is discussed. A variety of numerical devices are employed to produce a stable and robust algorithm. An algorithm for the selection of tension parameters that will produce a shape preserving approximant is developed. A sequence of selected curve-fitting examples are presented which clearly demonstrate the advantages of exponential splines over cubic splines.

  12. EXPONENTIAL GALAXY DISKS FROM STELLAR SCATTERING

    SciTech Connect

    Elmegreen, Bruce G.; Struck, Curtis E-mail: curt@iastate.edu

    2013-10-01

    Stellar scattering off of orbiting or transient clumps is shown to lead to the formation of exponential profiles in both surface density and velocity dispersion in a two-dimensional non-self gravitating stellar disk with a fixed halo potential. The exponential forms for both nearly flat rotation curves and near-solid-body rotation curves. The exponential does not depend on initial conditions, spiral arms, bars, viscosity, star formation, or strong shear. After a rapid initial development, the exponential saturates to an approximately fixed scale length. The inner exponential in a two-component profile has a break radius comparable to the initial disk radius; the outer exponential is primarily scattered stars.

  13. Crowded growth leads to the spontaneous evolution of semistable coexistence in laboratory yeast populations

    PubMed Central

    Frenkel, Evgeni M.; McDonald, Michael J.; Van Dyken, J. David; Kosheleva, Katya; Lang, Gregory I.; Desai, Michael M.

    2015-01-01

    Identifying the mechanisms that create and maintain biodiversity is a central challenge in biology. Stable diversification of microbial populations often requires the evolution of differences in resource utilization. Alternatively, coexistence can be maintained by specialization to exploit spatial heterogeneity in the environment. Here, we report spontaneous diversification maintained by a related but distinct mechanism: crowding avoidance. During experimental evolution of laboratory Saccharomyces cerevisiae populations, we observed the repeated appearance of “adherent” (A) lineages able to grow as a dispersed film, in contrast to their crowded “bottom-dweller” (B) ancestors. These two types stably coexist because dispersal reduces interference competition for nutrients among kin, at the cost of a slower maximum growth rate. This tradeoff causes the frequencies of the two types to oscillate around equilibrium over the course of repeated cycles of growth, crowding, and dispersal. However, further coevolution of the A and B types can perturb and eventually destroy their coexistence over longer time scales. We introduce a simple mathematical model of this “semistable” coexistence, which explains the interplay between ecological and evolutionary dynamics. Because crowded growth generally limits nutrient access in biofilms, the mechanism we report here may be broadly important in maintaining diversity in these natural environments. PMID:26240355

  14. Dynamical consequences of adaptation of the growth rates in a system of three competing populations

    NASA Astrophysics Data System (ADS)

    Dimitrova, Zlatinka I.; Vitanov, Nikolay K.

    2001-09-01

    We investigate the nonlinear dynamics of a system of populations competing for the same limited resource for the case where each of the populations adapts its growth rate to the total number of individuals in all populations. We consider regions of parameter space where chaotic motion of the Shilnikov kind exists and present results for two characteristic values of the growth ratio adaptation factor r*: r* = -0.15 and 5. Negative r* can lead to vanishing of regions of chaotic motion and to a stabilization of a fixed point of the studied model system of differential equations. Positive r* lead to changes of the shape of the bifurcation diagrams in comparison with the bifurcation diagrams for the case without adaptation. For the case r* = 5 we observe transition to chaos by period-doubling bifurcations, windows of periodic motion between the regions of chaotic motion and a region of transient chaos after the last window of periodic motion. The Lyapunov dimension for the chaotic attractors is close to two and the Lyapunov spectrum has a structure which allows a topological analysis of the attractors of the investigated system.

  15. THE IMPACT OF HISPANIC POPULATION GROWTH ON THE OUTLOOK OF AFRICAN AMERICANS

    PubMed Central

    Taylor, Marylee C.; Schroeder, Matthew B.

    2014-01-01

    We know too little about the effects of immigration on black Americans. If prior research yields mixed evidence about immigration’s consequences for the objective well-being of African Americans, it is silent about effects of immigration on blacks’ subjective well-being. To fill that void, this paper assesses the impact of the expanding Hispanic population on black Americans from a social psychological perspective. We ask whether blacks’ self-reported distress, social distrust, or attitudes toward Hispanics and immigrants are affected by the size of the local Hispanic population or by the percentage growth in local Hispanic residents. Answers come from responses of non-Hispanic black participants in the 1998–2002 General Social Surveys, linked to 1990 and 2000 census data. Contrary to pessimistic claims, most social psychological outcomes, including measures of economic distress, manifest no impact of local Hispanic numbers. The four exceptions, significant effects of local Hispanic population share or percentage growth evenly split in valence, underscore the complexity of recent immigration’s effects on African Americans. PMID:25242830

  16. Deforestation driven by urban population growth and agricultural trade in the twenty-first century

    NASA Astrophysics Data System (ADS)

    Defries, Ruth S.; Rudel, Thomas; Uriarte, Maria; Hansen, Matthew

    2010-03-01

    Reducing atmospheric carbon emissions from tropical deforestation is at present considered a cost-effective option for mitigating climate change. However, the forces associated with tropical forest loss are uncertain. Here we use satellite-based estimates of forest loss for 2000 to 2005 (ref. 2) to assess economic, agricultural and demographic correlates across 41 countries in the humid tropics. Two methods of analysis-linear regression and regression tree-show that forest loss is positively correlated with urban population growth and exports of agricultural products for this time period. Rural population growth is not associated with forest loss, indicating the importance of urban-based and international demands for agricultural products as drivers of deforestation. The strong trend in movement of people to cities in the tropics is, counter-intuitively, likely to be associated with greater pressures for clearing tropical forests. We therefore suggest that policies to reduce deforestation among local, rural populations will not address the main cause of deforestation in the future. Rather, efforts need to focus on reducing deforestation for industrial-scale, export-oriented agricultural production, concomitant with efforts to increase yields in non-forested lands to satisfy demands for agricultural products.

  17. [Does population ecology have general laws?].

    PubMed

    Turchin, P V

    2002-01-01

    There is a widespread opinion among ecologists that ecology lacks general laws. In this paper the author argues that this opinion is mistaken. Taking the case of population dynamics, the author points out that there are several very general law-like propositions that provide the theoretical basis for most population dynamics models that were developed to address specific issues. Some of these foundational principles, like the law of exponential growth, are logically very similar to certain law of physics (Newton's law of intertia, for example, is almost a direct analogue of exponential growth). The author discusses two other principles (population self-limitation and resource-consumer oscillations), as well as the more elementary postulates that underlie them. None of the "laws" that the author proposes for population ecology are new. Collectively ecologists have been using these general principles in guiding development of their models and experiments since the days of Lotka, Volterra, and Gause. PMID:11881213

  18. Translating effects of inbreeding depression on component vital rates to overall population growth in endangered bighorn sheep.

    PubMed

    Johnson, Heather E; Mills, L Scott; Wehausen, John D; Stephenson, Thomas R; Luikart, Gordon

    2011-12-01

    Evidence of inbreeding depression is commonly detected from the fitness traits of animals, yet its effects on population growth rates of endangered species are rarely assessed. We examined whether inbreeding depression was affecting Sierra Nevada bighorn sheep (Ovis canadensis sierrae), a subspecies listed as endangered under the U.S. Endangered Species Act. Our objectives were to characterize genetic variation in this subspecies; test whether inbreeding depression affects bighorn sheep vital rates (adult survival and female fecundity); evaluate whether inbreeding depression may limit subspecies recovery; and examine the potential for genetic management to increase population growth rates. Genetic variation in 4 populations of Sierra Nevada bighorn sheep was among the lowest reported for any wild bighorn sheep population, and our results suggest that inbreeding depression has reduced adult female fecundity. Despite this population sizes and growth rates predicted from matrix-based projection models demonstrated that inbreeding depression would not substantially inhibit the recovery of Sierra Nevada bighorn sheep populations in the next approximately 8 bighorn sheep generations (48 years). Furthermore, simulations of genetic rescue within the subspecies did not suggest that such activities would appreciably increase population sizes or growth rates during the period we modeled (10 bighorn sheep generations, 60 years). Only simulations that augmented the Mono Basin population with genetic variation from other subspecies, which is not currently a management option, predicted significant increases in population size. Although we recommend that recovery activities should minimize future losses of genetic variation, genetic effects within these endangered populations-either negative (inbreeding depression) or positive (within subspecies genetic rescue)-appear unlikely to dramatically compromise or stimulate short-term conservation efforts. The distinction between

  19. IKVAV regulates ERK1/2 and Akt signalling pathways in BMMSC population growth and proliferation

    PubMed Central

    Li, B; Qiu, T; Zhang, P; Wang, X; Yin, Y; Li, S

    2014-01-01

    Objectives The molecular mechanism of bone marrow mesenchymal stem cell (BMMSC) population growth and proliferation, induced by Isoleucyl-lysyl-valyl-alanyl-valine (IKVAV), was explored in this study. Materials and methods IKVAV peptides were synthesized by the solid-phase method. Influence of IKVAV on BMMSC population growth and proliferation were investigated by assays of CCK-8, flow cytometry, real-time PCR and western blotting. Results IKVAV peptide was found to induce proliferation and proliferating cell nuclear antigen (PCNA) synthesis of BMMSC in a dose- and time-dependent manner. Cell cycle analysis showed that the proportion of IKVAV-treated BMMSC in S phase in was higher than controls. Western blot results suggested that mitogen-activated protein kinase/extracellular signal-regulated kinase (MAPK/ERK) and phosphatidylinositol 3-kinase/protein kinase B (PI3K/Akt) signalling pathways were activated by IKVAV by enhancing phosphorylation levels of ERK1/2 and Akt in the BMMSCs. Meanwhile, phosphorylation levels of ERK1/2 and Akt were partially blocked by ERK1/2 inhibitor (PD98059) and Akt inhibitor (wortmannin), respectively. Conclusions Our results demonstrated that IKVAV stimulated BMMSC population growth and proliferation by activating MAPK/ERK1/2 and PI3K/Akt signalling pathways. This study is the first to reveal an enhancement effect of IKVAV peptide on BMMSC at the signal transduction level, and the outcome could provide experimental evidence for application of IKVAV-grafted scaffolds in the field of BMMSC-based tissue engineering. PMID:24617901

  20. Linking individual phenotype to density-dependent population growth: the influence of body size on the population dynamics of malaria vectors

    PubMed Central

    Russell, Tanya L.; Lwetoijera, Dickson W.; Knols, Bart G. J.; Takken, Willem; Killeen, Gerry F.; Ferguson, Heather M.

    2011-01-01

    Understanding the endogenous factors that drive the population dynamics of malaria mosquitoes will facilitate more accurate predictions about vector control effectiveness and our ability to destabilize the growth of either low- or high-density insect populations. We assessed whether variation in phenotypic traits predict the dynamics of Anopheles gambiae sensu lato mosquitoes, the most important vectors of human malaria. Anopheles gambiae dynamics were monitored over a six-month period of seasonal growth and decline. The population exhibited density-dependent feedback, with the carrying capacity being modified by rainfall (97% wAICc support). The individual phenotypic expression of the maternal (p = 0.0001) and current (p = 0.040) body size positively influenced population growth. Our field-based evidence uniquely demonstrates that individual fitness can have population-level impacts and, furthermore, can mitigate the impact of exogenous drivers (e.g. rainfall) in species whose reproduction depends upon it. Once frontline interventions have suppressed mosquito densities, attempts to eliminate malaria with supplementary vector control tools may be attenuated by increased population growth and individual fitness. PMID:21389034

  1. Genetic analysis of bone quality traits and growth in a random mating broiler population.

    PubMed

    González-Cerón, F; Rekaya, R; Aggrey, S E

    2015-05-01

    We report the genetic relationship between growth and bone quality traits in a random mating broiler control population. Traits studied were growth rates from week 0 to 4 [body weight gain (BWG) 0 to 4], from week 0 to 6 (BWG 0 to 6), and residual feed intake (RFI) from week 5 to 6 (RFI 5 to 6). Bone quality traits were obtained at 6 weeks of age. These traits were shank weight (SW), shank length (SL), shank diameter (SDIAM), tibia weight (TW), tibia length (TL), and tibia diameter (TDIAM). Likewise, tibia was used to obtain the tibia density (TDEN), tibia breaking strength (TBS), tibia mineral density (TMD), tibia mineral content (TMC), and tibia ash content (TAC). At the phenotypic level, growth traits were positively correlated with most of the bone quality traits except with TDEN and TAC which tended to show unfavorable associations (-0.04 to -0.31). Heritability of bone quality traits ranged from 0.08 to 0.54. The additive genetic associations of growth traits with weight, length, and diameter of shank and tibia were positive (0.37 to 0.80). A similar pattern was observed with TMD and TMC (0.06 to 0.65). In contrast, growth traits showed unfavorable genetic associations with TDEN, TBS, and TAC (-0.03 to -0.18). It was concluded that bone quality traits have an additive genetic background and they can be improved by means of genetic tools. It appears that selection for growth is negatively correlated with some traits involved in the integrity, health, and maturity of leg bones. PMID:25784765

  2. Optimal policies aimed at stabilization of populations with logistic growth under human intervention.

    PubMed

    Cruz-Rivera, Erica; Vasilieva, Olga

    2013-02-01

    This work examines both positive and negative impacts that economic growth may have on the ecological dynamics and stability of a single biological species. Local extinction of the species may force the social planner to implement defensive expenditures aimed at conservation of the species population by means of habitat protection. The latter may lead to an ecological equilibrium that will be different from the natural equilibrium that would have arisen in the absence of human intervention. Moreover, the existence of such equilibrium is formally demonstrated and its stability properties are revised. Additionally, optimal-choice decision policies are constructed on the basis of Pontryagin's maximum principle. Under such policies together with initial abundance of the species, the growth trajectories will move the system towards the fixed point of maximum species abundance. PMID:22960017

  3. A single dividing cell population with imbalanced fate drives oesophageal tumour growth.

    PubMed

    Frede, Julia; Greulich, Philip; Nagy, Tibor; Simons, Benjamin D; Jones, Philip H

    2016-09-01

    Understanding the cellular mechanisms of tumour growth is key for designing rational anticancer treatment. Here we used genetic lineage tracing to quantify cell behaviour during neoplastic transformation in a model of oesophageal carcinogenesis. We found that cell behaviour was convergent across premalignant tumours, which contained a single proliferating cell population. The rate of cell division was not significantly different in the lesions and the surrounding epithelium. However, dividing tumour cells had a uniform, small bias in cell fate so that, on average, slightly more dividing than non-dividing daughter cells were generated at each round of cell division. In invasive cancers induced by Kras(G12D) expression, dividing cell fate became more strongly biased towards producing dividing over non-dividing cells in a subset of clones. These observations argue that agents that restore the balance of cell fate may prove effective in checking tumour growth, whereas those targeting cycling cells may show little selectivity. PMID:27548914

  4. Phylogenetic prediction of the maximum per capita rate of population growth

    PubMed Central

    Fagan, William F.; Pearson, Yanthe E.; Larsen, Elise A.; Lynch, Heather J.; Turner, Jessica B.; Staver, Hilary; Noble, Andrew E.; Bewick, Sharon; Goldberg, Emma E.

    2013-01-01

    The maximum per capita rate of population growth, r, is a central measure of population biology. However, researchers can only directly calculate r when adequate time series, life tables and similar datasets are available. We instead view r as an evolvable, synthetic life-history trait and use comparative phylogenetic approaches to predict r for poorly known species. Combining molecular phylogenies, life-history trait data and stochastic macroevolutionary models, we predicted r for mammals of the Caniformia and Cervidae. Cross-validation analyses demonstrated that, even with sparse life-history data, comparative methods estimated r well and outperformed models based on body mass. Values of r predicted via comparative methods were in strong rank agreement with observed values and reduced mean prediction errors by approximately 68 per cent compared with two null models. We demonstrate the utility of our method by estimating r for 102 extant species in these mammal groups with unknown life-history traits. PMID:23720545

  5. Long-term growth of desert tortoises (Gopherus agassizii) in a southern Nevada population

    USGS Publications Warehouse

    Medica, Philip A.; Nussear, Kenneth E.; Esque, Todd C.; Saethre, Mary B.

    2012-01-01

    Knowledge of growth rates, age at maturity, and longevity are important aspects of a species life history and are directly applicable to life table creation and population viability analyses. We measured the growth of a cohort of 17 semi-wild Desert Tortoises (Gopherus agassizii) located in Rock Valley, Nevada over a 47-yr period beginning in 1963. The tortoises were initially marked as hatchling and juvenile animals between the years 1963 and 1965 and ranged in size from 47 to 77 mm in plastron length. We assigned ages of 1--4 yr to the tortoises at initial capture based on their body size. These tortoises were recaptured, measured, and weighed approximately annually since their initial capture. Growth of male and female tortoises did not differ significantly until animals reached the age of 23--25 yr. Annual tortoise growth was correlated with the production of ephemeral vegetation, while accounting for size, sex, and repeated measurements of the animals as well as the interval between measurements. However, the production of ephemeral plants was likewise highly correlated (non-linearly) with winter rainfall. Stochastic predation events between 2003 and 2007 decimated this cohort of tortoises. The average age of the long-term surviving tortoises from this cohort was 43 yr with a range of 39--47 yr. Twelve of the tortoises survived to the age of 39 yr and 11 of the 12 reached 40 yr.

  6. Comparison of diaphyseal growth between the Libben Population and the Hamann-Todd chimpanzee sample.

    PubMed

    Simpson, S W; Russell, K F; Lovejoy, C O

    1996-01-01

    The differences in limb lengths and proportions between humans and chimpanzees are widely known. Humans have relatively shorter forelimbs and longer hind limbs than chimpanzees. Humans have a longer period of long bone formation than chimpanzees. Recent advances in estimating age-at-death in chimpanzees from their dentition have allowed us to reexamine long bone growth in chimpanzees using their skeletal remains and compare it with similar data for humans. A chronological normalization procedure allowing direct interspecific comparison of long bone growth is presented. The preadult chimpanzee sample (n = 43) is from the Hamann-Todd Osteological Collection from the Cleveland Museum of Natural History. All human specimens (n = 202) are from the late Woodland Libben Population currently housed at Kent State University. Relying on these cross-sectional data, we conclude that both species elongate their femora at similar absolute (length per unit time) but different relative (length relative to normalized dental age) rates. The species differ in the absolute growth rate of the humerus but share a common normalized rate of growth. Forelimb segment proportion differences between species are due to differential elongation rates of the segments. Hind limb diaphyseal proportions are the same in both species, which suggests that changes in segment length are proportional. Therefore, alternative developmental mechanisms exist in these closely related species which can produce changes in limb length. PMID:8928724

  7. Effect of vitamin B12-enriched thraustochytrids on the population growth of rotifers.

    PubMed

    Hayashi, Masahiro; Yukino, Tsugiyo; Watanabe, Fumio; Miyamoto, Emi; Nakano, Yoshihisa

    2007-01-01

    Newly isolated thraustochytrids showed uptake of vitamin B12 from the culture into the cells. Cultivation of thraustochytrids in a medium containing 1 microg/ml of vitamin B12 greatly increased the contents of vitamin B12 in the cells. Similarly to Schizochytrium limacinum, odd numbered fatty acids decreased in the cells of new isolates cultivated with vitamin B12. Vitamin B12-enriched thraustochytrids, strain mh0186, enhanced the population growth of rotifers fed on the cells as sole feed. PMID:17213643

  8. Patterns of dynamic urban population growth in Russia, 1989-1996: a research report.

    PubMed

    Rowland, R H

    1997-01-01

    "The purpose of this paper is to investigate locations in which rapid urban growth occurred in Russia over the period 1989 to 1996....Particular emphasis will be given to the geographical patterns, economic functions, and population size of rapidly growing towns. In addition, the discussion of trends for 1989-1996 also will be briefly preceded by and compared to those of 1979-1989, although the paper will emphasize trends during the 1990s. Furthermore, the topic of ¿new towns', which themselves often are rapidly growing centers, will be addressed as well." PMID:12292848

  9. The uncertainty of future water supply adequacy in megacities: Effects of population growth and climate change

    NASA Astrophysics Data System (ADS)

    Alarcon, T.; Garcia, M. E.; Small, D. L.; Portney, K.; Islam, S.

    2013-12-01

    Providing water to the expanding population of megacities, which have over 10 million people, with a stressed and aging water infrastructure creates unprecedented challenges. These challenges are exacerbated by dwindling supply and competing demands, altered precipitation and runoff patterns in a changing climate, fragmented water utility business models, and changing consumer behavior. While there is an extensive literature on the effects of climate change on water resources, the uncertainty of climate change predictions continues to be high. This hinders the value of these predictions for municipal water supply planning. The ability of water utilities to meet future water needs will largely depend on their capacity to make decisions under uncertainty. Water stressors, like changes in demographics, climate, and socioeconomic patterns, have varying degrees of uncertainty. Identifying which stressors will have a greater impact on water resources, may reduce the level of future uncertainty for planning and managing water utilities. Within this context, we analyze historical and projected changes of population and climate to quantify the relative impacts of these two stressors on water resources. We focus on megacities that rely primarily on surface water resources to evaluate (a) population growth pattern from 1950-2010 and projected population for 2010-2060; (b) climate change impact on projected climate change scenarios for 2010-2060; and (c) water access for 1950-2010; projected needs for 2010-2060.

  10. Behavioural models of population growth rates: implications for conservation and prediction.

    PubMed Central

    Sutherland, William J; Norris, Ken

    2002-01-01

    Conservation biologists often wish to predict how vertebrate populations will respond to local or global changes in conditions such as those resulting from sea-level rise, deforestation, exploitation, genetically modified crops, global warming, human disturbance or from conservation activities. Predicting the consequences of such changes almost always requires understanding the population growth rate and the density dependence. Traditional means of directly measuring density dependence are often extremely difficult and have the problem that if the environment changes then it is necessary to remeasure the density dependence. We describe an alternative approach that does not require such long datasets and can be used to predict the density dependence under novel conditions. Game theory can be used to describe behavioural decisions that individuals make in response to interference, prey depletion, territorial behaviour or social dominance, and the resultant fitness consequences. It is then possible to predict how survival or reproductive output changes with population size. From this we can then make predictions about the responses of populations to environmental changes. We will illustrate how this can be applied to a range of species and a range of applied problems. PMID:12396518

  11. Growth of bone marrow and skeletal muscle side population stem cells in suspension culture.

    PubMed

    Pacak, Christina A; Cowan, Douglas B

    2014-01-01

    The ability to efficiently isolate and expand various stem cell populations in vitro is crucial for successful translation of cell-based therapies to the clinical setting. One such heterogeneous population that possesses a remarkable potential for the development of cell-based treatments for a variety of degenerative diseases and disorders is called the Side Population (SP). For many years, investigators have isolated these primitive cells based upon their ability to efflux the fluorophore Hoechst 33342. This attribute enabled separation of SP cells derived from multiple tissue sources from other endogenous cell populations using fluorescence-activated cell sorting (FACS). While all tissue-specific SP fractions appear to contain cells with multi-potent stem cell activity, the therapeutic utility of these cells has yet to be fully realized because of the scarcity of this fraction in vivo. In view of that, we developed a method to expand adult murine bone marrow and skeletal muscle-derived SP cells in vitro. Here, we describe a spinner-flask culture system that supports the growth of SP cells in suspension when they are combined with feeder cells cultured on spherical microcarriers. In this way, their distinguishing biological characteristics can be maintained, attachment-stimulated differentiation is avoided, and therapeutically relevant quantities of SP cells are generated. Modification of the described procedure may permit expansion of the SP from other relevant tissue sources and our method is amenable to establishing compliance with current good manufacturing practices. PMID:25173160

  12. Bait stations, hard mast, and black bear population growth in Great Smoky Mountains National Park

    USGS Publications Warehouse

    Clark, Joseph D.; van Manen, Frank T.; Pelton, Michael R.

    2005-01-01

    Bait-station surveys are used by wildlife managers as an index to American black bear (Ursus americanus) population abundance, but the relationship is not well established. Hard mast surveys are similarly used to assess annual black bear food availability which may affect mortality and natality rates. We used data collected in Great Smoky Mountains National Park (GSMNP) from 1989 to 2003 to determine whether changes in the bait-station index (ΔBSI) were associated with estimated rates of bear population growth (λ) and whether hard mast production was related to bear visitation to baits. We also evaluated whether hard mast production from previous years was related to λ. Estimates of λ were based on analysis of capture-recapture data with the Pradel temporal symmetry estimator. Using the Akaike's Information Criterion (AIC), our analysis revealed no direct relationship between ΔBSI and λ. A simulation analysis indicated that our data were adequate to detect a relationship had one existed. Model fit was marginally improved when we added total oak mast production of the previous year as an interaction term suggesting that the BSI was confounded with environmental variables. Consequently the utility of the bait-station survey as a population monitoring technique is questionable at the spatial and temporal scales we studied. Mast survey data, however, were valuable covariates of λ. Population growth for a given year was negatively related to oak mast production 4 and 5 years prior. That finding supported our hypothesis that mast failures can trigger reproductive synchrony, which may not be evident from the trapped sample until years later.

  13. Contributions of vital rates to growth of a protected population of American black bears

    USGS Publications Warehouse

    Mitchell, M.S.; Pacifici, L.B.; Grand, J.B.; Powell, R.A.

    2009-01-01

    Analyses of large, long-lived animals suggest that adult survival generally has the potential to contribute more than reproduction to population growth rate (??), but because survival varies little, high variability in reproduction can have a greater influence. This pattern has been documented for several species of large mammals, but few studies have evaluated such contributions of vital rates to ?? for American black bears (Ursus americanus). We used variance-based perturbation analyses (life table response experiments, LTRE) and analytical sensitivity and elasticity analyses to examine the actual and potential contributions of variation of vital rates to variation in growth rate (??) of a population of black bears inhabiting the Pisgah Bear Sanctuary in the southern Appalachian Mountains of North Carolina, using a 22-year dataset. We found that recruitment varied more than other vital rates; LTRE analyses conducted over several time intervals thus indicated that recruitment generally contributed at least as much as juvenile and adult survival to observed variation in ??, even though the latter 2 vital rates had the greater potential to affect ??. Our findings are consistent with predictions from studies on polar bears (U. maritimus) and grizzly bears (U. arctos), but contrast with the few existing studies on black bears in ways that suggest levels of protection from human-caused mortality might explain whether adult survival or recruitment contribute most to variation in ?? for this species. We hypothesize that ?? is most strongly influenced by recruitment in protected populations where adult survival is relatively high and constant, whereas adult survival will most influence ?? for unprotected populations. ?? 2009 International Association for Bear Research and Management.

  14. Effects of forest management on density, survival, and population growth of wood thrushes

    USGS Publications Warehouse

    Powell, L.A.; Lang, J.D.; Conroy, M.J.; Krementz, D.G.

    2000-01-01

    Loss and alteration of breeding habitat have been proposed as causes of declines in several Neotropical migrant bird populations. We conducted a 4-year study to determine the effects of winter prescribed burning and forest thinning on breeding wood thrush (Hylocichla mustelina) populations at the Piedmont National Wildlife Refuge (PNWR) in Georgia. We estimated density, adult and juvenile survival rates, and apparent annual survival using transect surveys, radiotelemetry, and mist netting. Burning and thinning did not cause lower densities (P = 0.25); wood thrush density ranged from 0.15 to 1.30 pairs/10 ha. No radiomarked male wood thrushes (n = 68) died during the 4 years, but female (n = 63) weekly survival was 0.981 ? 0.014 (SE) for females (n = 63) and 0.976 ? 0.010 for juveniles (n = 38). Apparent annual adult survival was 0.579 (SE = 0.173). Thinning and prescribed burning did not reduce adult or juvenile survival during the breeding season or apparent annual adult survival. Annual population growth (lambda) at PNWR was 1.00 (95% confidence interval = 0.32--1.63), and the considerable uncertainty in this prediction underscores the need for long term monitoring to effectively manage Neotropical migrants. Population growth increased on experimental compartments after the burn and thin (95% CI before = 0.91--0.97, after = 0.98--1.05), while control compartment declined (before = 0.98--1.05, after = 0.87--0.92). We found no evidence that the current management regime at PNWR, designed to improve red-cockaded woodpecker (Picoides borealis) habitat, negatively affected wood thrushes.

  15. Population growth and development in the Third World: the neocolonial context.

    PubMed

    Patterson, J G; Shrestha, N R

    1988-01-01

    Less developed countries (LDCs) that were colonies of other nations continued operating under the same social and political structures set up by the former ruling nations. The small minority of elites in the LDCs held on to the power acquired during colonial times. In order to preserve their political and financial status after independence, they maintained their close linkages to the capitalist nations and their multinational corporations (MNCs). The elites did not generally have popular support, however. These capitalist nations and their commercial interests continue to dictate most LDCs development process which supports the financial interests of the MNCs and the local elites and not those of the majority, the poor. The poor realize that they are trapped and unable to break away from the economic and political structures, therefore, to assure some form of security, they have many children which exacerbates their poverty. Yet population control policies based on Malthusian theory and those that rely on such undimensional, technical approaches as family planning alone cannot cure the multidimensional social problems of high population growth and poverty. Neither the Malthusian nor Marxist theories totally explain the situation in the LDCs or even provide workable solutions. Research on population and development in LDCs needs to address both the Malthusian concern for the problems posed by high growth rates and the Marxist critique of class struggle in development trends. To eliminate the trap of poverty and dependent economies, each country must design its own remedies based on its history, culture, and geography and alter the prevailing social, economic, and political power structures in favor of the poor. 6 propositions that must be modified to each nation's particular problems and needs are presented to guide LDCs in formulating or reformulating policies to alleviate the problems of population and poverty. PMID:12342352

  16. Epidemics, Exponential Functions, and Modeling

    ERIC Educational Resources Information Center

    Bush, Sarah B.; Gibbons, Katie; Karp, Karen S.; Dillon, Fred

    2015-01-01

    The phenomenon of outbreaks of dangerous diseases is both intriguing to students and of mathematical significance, which is exactly why the authors engaged eighth graders in an introductory activity on the growth that occurs as an epidemic spreads. Various contexts can set the stage for such an exploration. Reading adolescent literature like…

  17. Jensen's Inequality and the Impact of Short-Term Environmental Variability on Long-Term Population Growth Rates.

    PubMed

    Pickett, Evan J; Thomson, David L; Li, Teng A; Xing, Shuang

    2015-01-01

    It is well established in theory that short-term environmental fluctuations could affect the long-term growth rates of wildlife populations, but this theory has rarely been tested and there remains little empirical evidence that the effect is actually important in practice. Here we develop models to quantify the effects of daily, seasonal, and yearly temperature fluctuations on the average population growth rates, and we apply them to long-term data on the endangered Black-faced Spoonbill (Platalea minor); an endothermic species whose population growth rates follow a concave relationship with temperature. We demonstrate for the first time that the current levels of temperature variability, particularly seasonal variability, are already large enough to substantially reduce long-term population growth rates. As the climate changes, our results highlight the importance of considering the ecological effects of climate variability and not just average conditions. PMID:26352857

  18. Some socio-economic aspects of population growth in the USSR.

    PubMed

    Simchera, V

    1974-01-01

    This summarizes population trends in the U.S.S.R. since the early 19 00's. On August 9, 1973, the population topped 250 million, almost precisely double that of Russia at the time of the 1st general census in 1897. Since 1922 it had increased by more than 84%. Russia has suffered more population loss in wars than any other country in modern times. The First World War, the Civil War, and the Second World War took a toll of more than 30 million, more than 20 million during the Second World War alone. The extent of these loses can be judged from the following: between 1897 and 1913 the population of Russia increased at the rate of 1.55% per annum or 34.6 million; if this had continued the population would have been at least 182.8 million by the end of 1922. As it was, the population was 136.1 million by 1922 and the hypothetical 182.8 million was not reached until 1952. More than 4/5 of today's population have been born since the October Revolution. Only 43 million were born before the revolution and only 7.5 were born in the last century. The economic base has grown much more rapidly than the population. For the period 1940-1972 the population increased 1.27 times, national income 9.51 times, fixed assets, 8.76 times, industrial production, 13.65 times, agricultural output, 2.14 times, and capital investment 14.52 times. The birthrate has been falling since World War 1 but total population growth has increased steadily. Birthrates have declined from 45.5/1000 in 1913 to 17.8/1000 in 1972 and a slight upturn is seen. It is expected that the birthrate will continue to increase slightly, then stabilize. Much of the population increase has come from significantly reduced mortality rates. 1st and 2nd children now account for 71% of all births. Family allowances, child care, free health care, and other social benefits encourage births while high employment levels for women, a shortage of men in the marriageable age ranges, and late marriages tend to depress the birthrate

  19. Population growth of Varroa destructor (Acari: Varroidae) in honey bee colonies is affected by the number of foragers with mites.

    PubMed

    DeGrandi-Hoffman, Gloria; Ahumada, Fabiana; Zazueta, Victor; Chambers, Mona; Hidalgo, Geoffrey; deJong, Emily Watkins

    2016-05-01

    Varroa mites are a serious pest of honey bees and the leading cause of colony losses. Varroa have relatively low reproductive rates, so populations should not increase rapidly, but often they do. Other factors might contribute to the growth of varroa populations including mite migration into colonies on foragers from other hives. We measured the proportion of foragers carrying mites on their bodies while entering and leaving hives, and determined its relationship to the growth of varroa populations in those hives at two apiary sites. We also compared the estimates of mite population growth with predictions from a varroa population dynamics model that generates estimates of mite population growth based on mite reproduction. Samples of capped brood and adult bees indicated that the proportion of brood cells infested with mites and adult bees with phoretic mites was low through the summer but increased sharply in the fall especially at site 1. The frequency of capturing foragers with mites on their bodies while entering or leaving hives also increased in the fall. The growth of varroa populations at both sites was not significantly related to our colony estimates of successful mite reproduction, but instead to the total number of foragers with mites (entering and leaving the colony). There were more foragers with mites at site 1 than site 2, and mite populations at site 1 were larger especially in the fall. The model accurately estimated phoretic mite populations and infested brood cells until November when predictions were much lower than those measured in colonies. The rapid growth of mite populations particularly in the fall being a product of mite migration rather than mite reproduction only is discussed. PMID:26910522

  20. Stretched Exponential relaxation in pure Se glass

    NASA Astrophysics Data System (ADS)

    Dash, S.; Ravindren, S.; Boolchand, P.

    A universal feature of glasses is the stretched exponential relaxation, f (t) = exp[ - t / τ ] β . The model of diffusion of excitations to randomly distributed traps in a glass by Phillips1 yields the stretched exponent β = d[d +2] where d, the effective dimensionality. We have measured the enthalpy of relaxation ΔHnr (tw) at Tg of Se glass in modulated DSC experiments as glasses age at 300K and find β = 0.43(2) for tw in the 0 growth of interchain structural correlations mediated by both long range (van der Waals forces) and short-range (covalent) interactions. A striking consequence of this relaxation is a narrowing of the glass transition width from 7.1°C to 1.4°C, and the ΔHnr term increasing from 0.21 cal/gm to 0.92 cal/gm. In bulk GexSe100-x glasses as x increases to 20%, the length of the polymeric Sen chains between the Ge-crosslinks decreases to n = 2. and the striking relaxation effects nearly vanish. J.C. Phillips, Rep.Prog.Phys. 59 , 1133 (1996). Supported by NSF Grant DMR 08-53957.

  1. Effect of Population Growths on Water Resources in Dubai Emirate, United Arab Emirates

    NASA Astrophysics Data System (ADS)

    Al-Nuaimi, Hind S.; Murad, Ahmed A.

    The Emirate of Dubai is situated to the north of the United Arab Emirates on the Arabian Gulf. Due to its political stability and strong economy, people are continuing to immigrate to Dubai and this will enhance the stress on water resources. Therefore, demands for water will increase significantly in Dubai. The scarcity of water resources in Dubai is evident. The total production of water in the Dubai has increased to 61,478 million gallons in 2004. About 58,808 million gallons has been produced from the desalination plants in 2004. The production of freshwater from the main aquifers is about 2763 and 2655 million gallons for the years 2003 and 2004, respectively. The reduction of groundwater in 2004 may be ascribed to the low amount of rainfall and to the decreasing capacity of the aquifers. Treated wastewater is another source for water whose quantity was increased from 72 m3 to about 107 m3 in 2000 and 2004, respectively. The increase in water production in Dubai to meet the demand corresponds to population growth and this might be attributed to the political stability and strong economy. Moreover, major problems related to the water resources have appeared and affected the availability of freshwater in Dubai. These problems include: lowering water level and groundwater deterioration. This paper is aimed to assess the impacts of population growth on water resources in Dubai.

  2. Growth, reproduction & population structure of the freshwater crab Sinopotamon yangtsekiense bott, 1967, from Zhejiang, China

    NASA Astrophysics Data System (ADS)

    Chen, Tao; Lai, Wei; Du, Nan-Shan

    1994-03-01

    Monthly investigations were mae on the population of Chinese freshwater crab, Sinopotamon yangtsekiense Bott, 1967 from April, 1984 to March, 1985. The data on 4413 specimens show that the growth was affected mainly by temperature. During the April to November growth period, the crabs' major development occurred from June through October. One year was required for a fine white oocyte to develop into a mature egg. The reproduction period was June October. Females bearing eggs were taken from June August, and crabs with young were found from July October. The females reproduced once a year but could for more than one year. The number of eggs carried by a female varied greatly according to the size of the crab, ranging from 30 to 100 eggs. New-born crabs become mature after 1 2 years. The sex ratio was approximately 1∶1 in the overall population. However, the larger crabs are predominantly male. The age distribution of S. yangtsekinese was estimated from size frequency histograms. There were more adult crabs (over 70%) from June to October and more immature crabs (over 50%) from November to May.

  3. America's Water Supply Challenge: Adaptation to Future Population Growth and Climate Change

    NASA Astrophysics Data System (ADS)

    Mahat, V.; Brown, T. C.; Ramirez, J. A.

    2014-12-01

    Water shortages, and the prospect of such shortages, have been repeatedly faced and addressed as population and economic growth placed increasing demands on available water over the past century. Such challenges have been most common in arid areas, but also have been encountered in some more humid portions of the US during times of drought. The challenges have been met using a wide range of adaptation measures, from large infrastructure projects (e.g., major trans-basin diversions) to alterations in local water prices (e.g., increasing block pricing). The future may bring even greater adaptation challenges as, in addition to continued growth in population, climate change will reduce water supplies in many locations. In this study we report on the relative importance of changes in demand versus changes in supply in causing projected future shortages in basins throughout the contiguous U.S. under different sets of socioeconomic and climatic conditions. We then examine the degree to which projected shortages can be avoided through adaptation. The adaptations examined include reductions in demand of major water use sectors, alterations in water management infrastructure, and inter-basin water transfers.

  4. Influence of packaging conditions on natural microbial population growth of endive.

    PubMed

    Charles, Florence; Rugani, Nathalie; Gontard, Nathalie

    2005-05-01

    The influence of three packaging conditions, i.e., unmodified atmosphere packaging (UAP), passive modified atmosphere packaging (MAP), and active MAP, on the natural microbial population growth of endive was investigated at 20 degrees C. For UAP, endive was placed in macroperforated oriented polypropylene pouches that maintained gas composition close to that of air (21 kPa O2 and 0 kPa CO2) but also limited superficial product dehydration. For MAP, endive was placed in low-density polyethylene pouches that induced a 3 kPa O2 and 5 kPa CO2 equilibrium atmosphere composition. Steady state was reached after 25 h of storage with an oxygen absorbing packet (active MAP) compared with 100 h without the packet (passive MAP) and was maintained for 200 h. After 312 h of storage, both active and passive MAP reduced total aerobic mesophile, yeast, and mold population growth compared with endive in UAP. Active MAP accelerated and improved the inhibition of Pseudomonas spp. and Enterobacteriaceae, respectively, probably because of the rapid O2 depletion during the transition period. A shift in the Enterobacteriaceae subpopulation from Rhanella aquatilis to Enterobacter agglomerans was observed for both passive and active MAP. PMID:15895736

  5. The matrix exponential in transient structural analysis

    NASA Technical Reports Server (NTRS)

    Minnetyan, Levon

    1987-01-01

    The primary usefulness of the presented theory is in the ability to represent the effects of high frequency linear response with accuracy, without requiring very small time steps in the analysis of dynamic response. The matrix exponential contains a series approximation to the dynamic model. However, unlike the usual analysis procedure which truncates the high frequency response, the approximation in the exponential matrix solution is in the time domain. By truncating the series solution to the matrix exponential short, the solution is made inaccurate after a certain time. Yet, up to that time the solution is extremely accurate, including all high frequency effects. By taking finite time increments, the exponential matrix solution can compute the response very accurately. Use of the exponential matrix in structural dynamics is demonstrated by simulating the free vibration response of multi degree of freedom models of cantilever beams.

  6. Estimating the effects of 17α-ethinylestradiol on stochastic population growth rate of fathead minnows: a population synthesis of empirically derived vital rates.

    PubMed

    Schwindt, Adam R; Winkelman, Dana L

    2016-09-01

    Urban freshwater streams in arid climates are wastewater effluent dominated ecosystems particularly impacted by bioactive chemicals including steroid estrogens that disrupt vertebrate reproduction. However, more understanding of the population and ecological consequences of exposure to wastewater effluent is needed. We used empirically derived vital rate estimates from a mesocosm study to develop a stochastic stage-structured population model and evaluated the effect of 17α-ethinylestradiol (EE2), the estrogen in human contraceptive pills, on fathead minnow Pimephales promelas stochastic population growth rate. Tested EE2 concentrations ranged from 3.2 to 10.9 ng L(-1) and produced stochastic population growth rates (λ S ) below 1 at the lowest concentration, indicating potential for population decline. Declines in λ S compared to controls were evident in treatments that were lethal to adult males despite statistically insignificant effects on egg production and juvenile recruitment. In fact, results indicated that λ S was most sensitive to the survival of juveniles and female egg production. More broadly, our results document that population model results may differ even when empirically derived estimates of vital rates are similar among experimental treatments, and demonstrate how population models integrate and project the effects of stressors throughout the life cycle. Thus, stochastic population models can more effectively evaluate the ecological consequences of experimentally derived vital rates. PMID:27372448

  7. Employment problems under declining population growth rates and structural change: the case of Yugoslavia.

    PubMed

    Macura, M

    1974-01-01

    The case of Yugoslavia since World War 2 generally confirms the find ings of Coale and Hoover some 15 years ago that a declining population gives a developing society a chance to grow at a more rapid rate because less of the gross national product is devoted to merely maintaining the status quo. However, until recently insufficient attention was paid to the long-term effects of rapid population growth plus underdevelopment, namely, surplus labor and unemployment. Yugoslavia is currently suffereing the aftereffects of a history of labor surplus caused by high birthrates, especially in the southern Moslem regions. The birthrate was as high as 35/1000 until 1927, took a downward turn during the depression, falling to 26/1000 in 1939, became even more depressed during World War 2, then reached 26-30/1000 in the postwar years. After 1957 a steady decline set in. The rate was around 18/1000 in the early 1970s. Because of the underdeveloped, highly agrarian economy, Yugoslavia has traditionally been a source of abundant labor and emigration. Statistical data has been either nonexistent or unreliable, but there have been self-evident differences in the size of individual cohorts which have had definite bearing on the working-age population. Following World War 2 the country changed from a predominantly peasant, subsistence economy to an industrial socialist society. There has been a steady decline in the participation rate in the work force, from an estimated 46.5% in 1948 to 43.3% in 1971, primarily due to increased education, declining child labor, and greater retirement among older workers. However, the growth of the working-age group was faster than that of the total population because of the high postwar birthrates. Th ere was significant increase in employment from 1,517,000 in 1948 to 4,034,000 in 1971. At the same time the agricultural labor force decrea sed from 70% of total employment to 48%. Despite the industrial growth, in 1971 there were over 290

  8. Association of STAT2 SNP genotypes and growth phenotypes in heifers from an Angus, Brahman and Romosinuano diallel population

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Components of the growth endocrine axis regulate growth and reproduction traits in cattle. A SNP in the promoter of the signal transducer and activator of transcription 2 (STAT2) has been previously reported to be associated with postpartum rebreeding in a diallel beef population composed of 650 hei...

  9. Population growth of Varroa destructor (Acari: Varroidae) in honey bee colonies is affected by the number of foragers with mites

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Varroa mites are a serious pest of honey bees and the leading cause of colony losses. Varroa have relatively low reproductive rates, so populations should not increase rapidly, but often they do. Other factors might contribute to the growth of Varroa populations including mite migration into colonie...

  10. Population trends, growth, and movement of bigmouth buffalo, Ictiobus cyprinellus, in Lake Oahe, 1963-70

    USGS Publications Warehouse

    Moen, Thomas E.

    1974-01-01

    The bigmouth buffalo, Ictiobus cyprinellus, is the most important commercial species in Lake Oahe, a reservoir in the upper Missouri River. The population was dominated by three strong year classes (1959, 1960, and 1962). Estimated population in the fall of 1964 was 540,000 fish of the combined 1959-60 year classes and 5 million of the 1962 year class (equivalent to 81 kg per hectare). Abundance declined irregularly during 1964-70. Annual landings of these two dominant groups during 1965-70 ranged from 149 to 271 metric tons. The total landings during the period amounted to about 151,800 fish of the 1959-60 year classes and 313,000 fish of the 1962 year class. Growth rate was high during the first few years of impoundment and then declined. Males and females grew at about the same rate for the first 4 yr of life, but females were longer and heavier than males at ages V-VIII. At these ages, fish of the 1962 year class were about 10% shorter and 36% lighter than those of the 1959 year class. Growth of tagged and untagged fish was similar. The number of females per male increased with age. Age at maturity increased slightly as growth rate declined. Movement of marked fish was extensive and the recapture of marked fish was directly related to size of fish, location of release, and subsequent fishing pressure; 44% were recaptured downstream from the point of release, and 38% upstream. Females showed a stronger tendency to move downstream than males. Maximum distance traveled was 380 km and maximum rate of travel was 6.4 km per day. Successful reproduction appeared to be associated with flooding of shoreline vegetation during spring and early summer. Inasmuch as little such flooding is expected in the future, annual landings of bigmouth buffalo will probably continue to decline sharply.

  11. Population dynamics and growth of the bivalve Choromytilus meridionalis (Kr.) at different tidal levels

    NASA Astrophysics Data System (ADS)

    Griffiths, Roberta J.

    1981-01-01

    Settlement, growth and reproductive output of a population of Choromytilus meridionalis have been monitored at different shore levels at Bailey's Cottage, False Bay, South Africa. Settlement was irregular, occurring at 4- to 6-year intervals, and confined to the sublittoral and lower littoral of rocky areas. Spat settled on the existing mussel bed and adjacent clean rock surfaces. Continual migration of young mussels up the shore took place during the first 1 to 1·5 years of growth until an even distribution up to 0·5 m above L.W.S. was achieved. Juveniles displaced older individuals by moving between them and forcing them off the rocks so that the majority of the adult population were eliminated from the bed within the first year after spat settlement. Mortality in individual cohorts was largely caused by strong wave action and competition for space. The density of individuals within the mussel bed was closely related to mean shell length. Growth rates varied with habitat and declined markedly with increasing height above L.W.S. Sexual maturity was attained at approximately 20 mm and reproductive output rose from 5 kJ year -1 at this length to 80 kJ year -1 at 100 mm shell length. Since packing densities were much higher in smaller individuals the annual gamete output assessed on an area basis, remained fairly constant as the mussels grew, and averaged 1392 g m -2 year -1 dry weight (31 320 kJ m -2 year -1). Energy expended as gonad output exceeded that due to mortality by a factor of 10.

  12. Seawater chemistry, coccolithophore population growth, and the origin of Cretaceous chalk

    NASA Astrophysics Data System (ADS)

    Stanley, Steven M.; Ries, Justin B.; Hardie, Lawrence A.

    2005-07-01

    The magnesium/calcium ratio (Mg/Ca) and calcium (Ca) concentration of seawater have oscillated throughout geologic time; our experiments indicate that these variables have strongly influenced biomineralization and chalk production by coccolithophores. The high Mg/Ca ratio of modern seawater favors precipitation of high-Mg calcite and/or aragonite. In contrast, the low Mg/Ca ratio of imputed Cretaceous seawater favored precipitation of low-Mg calcite. We have discovered that some coccolithophore species today secrete skeletal elements of high-Mg calcite, rather than low-Mg calcite, as conventionally believed. These species incorporated less Mg when the ambient Mg/Ca ratio was lowered, secreting low-Mg calcite in imputed Cretaceous seawater. Calcification stimulates cocco lithophore population growth by contributing CO2 to photosynthesis. Three extant coc co lithophore species multiplied much faster as the composition of ambient seawater was shifted toward that estimated for Cretaceous seas. Two of these species secreted high-Mg calcite in ambient seawater having Mg/Ca > 1, and incorporation of Mg in a calcite crystal inhibits growth. Calcification of the third species, which secreted low-Mg calcite at all ambient Mg/Ca ratios, is hindered by the high Mg/Ca ratio and low absolute concentration of Ca of modern seawater. We conclude that the ionic composition of Cretaceous seawater enabled cocco lithophores to produce massive chalk deposits, and conversely, that the ionic composition of modern seawater inhibits population growth for most extant coccolitho phore species, which occupy nutrient-poor waters and fail to respond to fertilization by nitrate, phosphate, or iron.

  13. Growth and Reproduction of Glyphosate-Resistant and Susceptible Populations of Kochia scoparia.

    PubMed

    Kumar, Vipan; Jha, Prashant

    2015-01-01

    Evolution of glyphosate-resistant kochia is a threat to no-till wheat-fallow and glyphosate-resistant (GR) cropping systems of the US Great Plains. The EPSPS (5-enol-pyruvylshikimate-3-phosphate synthase) gene amplification confers glyphosate resistance in the tested Kochia scoparia (L.) Schrad populations from Montana. Experiments were conducted in spring to fall 2014 (run 1) and summer 2014 to spring 2015 (run 2) to investigate the growth and reproductive traits of the GR vs. glyphosate-susceptible (SUS) populations of K. scoparia and to determine the relationship of EPSPS gene amplification with the level of glyphosate resistance. GR K. scoparia inbred lines (CHES01 and JOP01) exhibited 2 to 14 relative copies of the EPSPS gene compared with the SUS inbred line with only one copy. In the absence of glyphosate, no differences in growth and reproductive parameters were evident between the tested GR and SUS inbred lines, across an intraspecific competition gradient (1 to 170 plants m-2). GR K. scoparia plants with 2 to 4 copies of the EPSPS gene survived the field-use rate (870 g ha-1) of glyphosate, but failed to survive the 4,350 g ha-1 rate of glyphosate (five-times the field-use rate). In contrast, GR plants with 5 to 14 EPSPS gene copies survived the 4,350 g ha-1 of glyphosate. The results from this research indicate that GR K. scoparia with 5 or more EPSPS gene copies will most likely persist in field populations, irrespective of glyphosate selection pressure. PMID:26580558

  14. Growth and Reproduction of Glyphosate-Resistant and Susceptible Populations of Kochia scoparia

    PubMed Central

    Kumar, Vipan; Jha, Prashant

    2015-01-01

    Evolution of glyphosate-resistant kochia is a threat to no-till wheat-fallow and glyphosate-resistant (GR) cropping systems of the US Great Plains. The EPSPS (5-enol-pyruvylshikimate-3-phosphate synthase) gene amplification confers glyphosate resistance in the tested Kochia scoparia (L.) Schrad populations from Montana. Experiments were conducted in spring to fall 2014 (run 1) and summer 2014 to spring 2015 (run 2) to investigate the growth and reproductive traits of the GR vs. glyphosate-susceptible (SUS) populations of K. scoparia and to determine the relationship of EPSPS gene amplification with the level of glyphosate resistance. GR K. scoparia inbred lines (CHES01 and JOP01) exhibited 2 to 14 relative copies of the EPSPS gene compared with the SUS inbred line with only one copy. In the absence of glyphosate, no differences in growth and reproductive parameters were evident between the tested GR and SUS inbred lines, across an intraspecific competition gradient (1 to 170 plants m-2). GR K. scoparia plants with 2 to 4 copies of the EPSPS gene survived the field-use rate (870 g ha-1) of glyphosate, but failed to survive the 4,350 g ha-1 rate of glyphosate (five-times the field-use rate). In contrast, GR plants with 5 to 14 EPSPS gene copies survived the 4,350 g ha-1 of glyphosate. The results from this research indicate that GR K. scoparia with 5 or more EPSPS gene copies will most likely persist in field populations, irrespective of glyphosate selection pressure. PMID:26580558

  15. Cell Differentiation in a Bacillus thuringiensis Population during Planktonic Growth, Biofilm Formation, and Host Infection

    PubMed Central

    Verplaetse, Emilie; Slamti, Leyla; Gohar, Michel

    2015-01-01

    ABSTRACT Bacillus thuringiensis (Bt) is armed to complete a full cycle in its insect host. During infection, virulence factors are expressed under the control of the quorum sensor PlcR to kill the host. After the host’s death, the quorum sensor NprR controls a necrotrophic lifestyle, allowing the vegetative cells to use the insect cadaver as a bioincubator and to survive. Only a part of the Bt population sporulates in the insect cadaver, and the precise composition of the whole population and its evolution over time are unknown. Using fluorescent reporters to record gene expression at the single-cell level, we have determined the differentiation course of a Bt population and explored the lineage existing among virulent, necrotrophic, and sporulating cells. The dynamics of cell differentiation were monitored during growth in homogenized medium, biofilm formation, and colonization of insect larvae. We demonstrated that in the insect host and in planktonic culture in rich medium, the virulence, necrotrophism, and sporulation regulators are successively activated in the same cell. In contrast, in biofilms, activation of PlcR is dispensable for NprR activation and we observed a greater heterogeneity than under the other two growth conditions. We also showed that sporulating cells arise almost exclusively from necrotrophic cells. In biofilm and in the insect cadaver, we identified an as-yet-uncharacterized category of cells that do not express any of the reporters used. Overall, we showed that PlcR, NprR, and Spo0A act as interconnected integrators to allow finely tuned adaptation of the pathogen to its environment. PMID:25922389

  16. Effect of crop development on biogenic emissions from plant populations grown in closed plant growth chambers

    NASA Technical Reports Server (NTRS)

    Batten, J. H.; Stutte, G. W.; Wheeler, R. M.

    1995-01-01

    The Biomass Production Chamber at John F. Kennedy Space Center is a closed plant growth chamber facility that can be used to monitor the level of biogenic emissions from large populations of plants throughout their entire growth cycle. The head space atmosphere of a 26-day-old lettuce (Lactuca sativa cv. Waldmann's Green) stand was repeatedly sampled and emissions identified and quantified using GC-mass spectrometry. Concentrations of dimethyl sulphide, carbon disulphide, alpha-pinene, furan and 2-methylfuran were not significantly different throughout the day; whereas, isoprene showed significant differences in concentration between samples collected in light and dark periods. Volatile organic compounds from the atmosphere of wheat (Triticum aestivum cv. Yecora Rojo) were analysed and quantified from planting to maturity. Volatile plant-derived compounds included 1-butanol, 2-ethyl-1-hexanol, nonanal, benzaldehyde, tetramethylurea, tetramethylthiourea, 2-methylfuran and 3-methylfuran. Concentrations of volatiles were determined during seedling establishment, vegetative growth, anthesis, grain fill and senescence and found to vary depending on the developmental stage. Atmospheric concentrations of benzaldehyde and nonanal were highest during anthesis, 2-methylfuran and 3-methylfuran concentrations were greatest during grain fill, and the concentration of the tetramethylurea peaked during senescence.

  17. Fracture and Growth Are Competing Forces Determining the Fate of Conformers in Tau Fibril Populations.

    PubMed

    Meyer, Virginia; Holden, Michael R; Weismiller, Hilary A; Eaton, Gareth R; Eaton, Sandra S; Margittai, Martin

    2016-06-01

    Tau fibrils are pathological aggregates that can transfer between neurons and then recruit soluble Tau monomers by template-assisted conversion. The propagation of different fibril polymorphs is thought to be a contributing factor to phenotypic diversity in Alzheimer disease and other Tauopathies. We found that a homogeneous population of Tau fibrils composed of the truncated version K18 (residues 244-372) gradually converted to a new set of fibril conformers when subjected to multiple cycles of seeding and growth. Using double electron-electron resonance (DEER) spectroscopy, we observed that the distances between spin labels at positions 311 and 328 in the fibril core progressively decreased. The findings were corroborated by changes in turbidity, morphology, and protease sensitivity. Fibrils that were initially formed under stirring conditions exhibited an increased fragility compared with fibrils formed quiescently after multiple cycles of seeding. The quiescently formed fibrils were marked by accelerated growth. The difference in fragility and growth between the different conformers explains how the change in incubation condition could lead to the amplification of a minor subpopulation of fibrils. Under quiescent conditions where fibril breakage is minimal, faster growing fibrils have a selective advantage. The findings are of general importance as they suggest that changes in selective pressures during fibril propagation in the human brain could result in the emergence of new fibril conformers with varied clinicopathological consequences. PMID:27080260

  18. Fracture and Growth Are Competing Forces Determining the Fate of Conformers in Tau Fibril Populations*

    PubMed Central

    Meyer, Virginia; Holden, Michael R.; Weismiller, Hilary A.; Eaton, Gareth R.; Eaton, Sandra S.; Margittai, Martin

    2016-01-01

    Tau fibrils are pathological aggregates that can transfer between neurons and then recruit soluble Tau monomers by template-assisted conversion. The propagation of different fibril polymorphs is thought to be a contributing factor to phenotypic diversity in Alzheimer disease and other Tauopathies. We found that a homogeneous population of Tau fibrils composed of the truncated version K18 (residues 244–372) gradually converted to a new set of fibril conformers when subjected to multiple cycles of seeding and growth. Using double electron-electron resonance (DEER) spectroscopy, we observed that the distances between spin labels at positions 311 and 328 in the fibril core progressively decreased. The findings were corroborated by changes in turbidity, morphology, and protease sensitivity. Fibrils that were initially formed under stirring conditions exhibited an increased fragility compared with fibrils formed quiescently after multiple cycles of seeding. The quiescently formed fibrils were marked by accelerated growth. The difference in fragility and growth between the different conformers explains how the change in incubation condition could lead to the amplification of a minor subpopulation of fibrils. Under quiescent conditions where fibril breakage is minimal, faster growing fibrils have a selective advantage. The findings are of general importance as they suggest that changes in selective pressures during fibril propagation in the human brain could result in the emergence of new fibril conformers with varied clinicopathological consequences. PMID:27080260

  19. Solids Retention Time Dependent Phototrophic Growth and Population Changes in Chemostat Cultivation Using Wastewater.

    PubMed

    Shen, Qi; Wall, Judy D; Hu, Zhiqiang

    2016-01-01

    There has been renewed interest in using algae for wastewater polishing and treatment in recent years. Because solids retention time (SRT) is a key design and operating parameter in bioreactor operation, this research determined the effect of SRT on phototrophic growth and microbial population dynamics in continuous-flow chemostat systems. There was a unique feature of phototrophic growth that differed from chemotrophic growth in chemostat. It was found that the phototrophic biomass concentration increased proportionally as SRT increased from 3 to 9 days. Regardless of the change in SRT, a step function model was successfully applied with the predicted phototrophic production rate of 4.5 ± 0.9 g/m(2)·d at the light intensity of 68.5 μmol/m(2)·s. Even though the continuous-flow systems were initially seeded with a 1:1 mixture of green algae and cyanobacteria, Chlorella vulgaris always dominated (98%) in the continuous-flow chemostat systems under steady-state conditions. PMID:26803021

  20. World population and energy growth: Impact on the Caribbean and the roles of energy efficiency improvements and renewable energies

    SciTech Connect

    Sheffield, J.

    1997-06-01

    This paper briefly describes population and energy use trends and their consequences, particularly to the Caribbean region. Historical trends for transitional countries show a decrease in population growth rate as annual per capita commercial energy use increases. If trends continue, an increase in per capita energy will be important to stabilizing populations of transitional countries. Energy efficiency improvements, the role of fossil energy, and the use of alternative energy sources in Caribbean nations are briefly discussed. 6 refs., 3 figs.

  1. Growth performance and intestinal microbial populations of growing pigs fed diets containing sucrose thermal oligosaccharide caramel.

    PubMed

    Orban, J I; Patterson, J A; Adeola, O; Sutton, A L; Richards, G N

    1997-01-01

    Four experiments were conducted to determine growth performance and changes in intestinal microbial populations of growing pigs fed diets containing sucrose thermal oligosaccharide caramel (STOC). Ninety-six barrows and 96 gilts were group-fed experimental nursery diets for 32 d after weaning in both Exp. 1 and 2. For each experiment, pigs were divided into four groups of 48 pigs and were fed either control, antibiotic (Apramycin sulfate, 34 mg/kg), 1% STOC, or 2% STOC diets for 32 d after weaning. Each diet was replicated six times with eight pigs per replication. Pigs were either orally gavaged (Exp 1) with water of STOC (2 g per pig) or pigs were creep-fed (Exp 2) either a control diet or a 2% STOC diet for 5 d before weaning (33 d). At the end of Exp 1 and 2, cecal material was collected for enumeration of total aerobes, total anaerobes, coliforms, lactobacilli, and bifidobacteria. Gilts (96 per experiment) used in Exp. 3 and 4 were weaned at 26 d and fed experimental nursery diets for 32 d. They were fed either a control or 1% STOC diet and were otherwise treated as previously described. There were no significant effects of STOC or antibiotic on ADG, ADFI, feed efficiency, or cecal microbial populations in pigs in this study. Feeding diets containing either antibiotic of STOC did not improve animal performance or change intestinal bacterial populations in the present study. PMID:9027562

  2. Histopathology of growth anomaly affecting the coral, Montipora capitata: implications on biological functions and population viability.

    PubMed

    Burns, John H R; Takabayashi, Misaki

    2011-01-01

    Growth anomalies (GAs) affect the coral, Montipora capitata, at Wai'ōpae, southeast Hawai'i Island. Our histopathological analysis of this disease revealed that the GA tissue undergoes changes which compromise anatomical machinery for biological functions such as defense, feeding, digestion, and reproduction. GA tissue exhibited significant reductions in density of ova (66.1-93.7%), symbiotic dinoflagellates (38.8-67.5%), mesenterial filaments (11.2-29.0%), and nematocytes (28.8-46.0%). Hyperplasia of the basal body wall but no abnormal levels of necrosis and algal or fungal invasion was found in GA tissue. Skeletal density along the basal body wall was significantly reduced in GAs compared to healthy or unaffected sections. The reductions in density of the above histological features in GA tissue were collated with disease severity data to quantify the impact of this disease at the colony and population level. Resulting calculations showed this disease reduces the fecundity of M. capitata colonies at Wai'ōpae by 0.7-49.6%, depending on GA severity, and the overall population fecundity by 2.41±0.29%. In sum, GA in this M. capitata population reduces the coral's critical biological functions and increases susceptibility to erosion, clearly defining itself as a disease and an ecological threat. PMID:22205976

  3. Effects of tag loss on direct estimates of population growth rate

    USGS Publications Warehouse

    Rotella, J.J.; Hines, J.E.

    2005-01-01

    The temporal symmetry approach of R. Pradel can be used with capture-recapture data to produce retrospective estimates of a population's growth rate, lambda(i), and the relative contributions to lambda(i) from different components of the population. Direct estimation of lambda(i) provides an alternative to using population projection matrices to estimate asymptotic lambda and is seeing increased use. However, the robustness of direct estimates of lambda(1) to violations of several key assumptions has not yet been investigated. Here, we consider tag loss as a possible source of bias for scenarios in which the rate of tag loss is (1) the same for all marked animals in the population and (2) a function of tag age. We computed analytic approximations of the expected values for each of the parameter estimators involved in direct estimation and used those values to calculate bias and precision for each parameter estimator. Estimates of lambda(i) were robust to homogeneous rates of tag loss. When tag loss rates varied by tag age, bias occurred for some of the sampling situations evaluated, especially those with low capture probability, a high rate of tag loss, or both. For situations with low rates of tag loss and high capture probability, bias was low and often negligible. Estimates of contributions of demographic components to lambda(i) were not robust to tag loss. Tag loss reduced the precision of all estimates because tag loss results in fewer marked animals remaining available for estimation. Clearly tag loss should be prevented if possible, and should be considered in analyses of lambda(i), but tag loss does not necessarily preclude unbiased estimation of lambda(i).

  4. Growth of Streptococcus mutans in Biofilms Alters Peptide Signaling at the Sub-population Level

    PubMed Central

    Shields, Robert C.; Burne, Robert A.

    2016-01-01

    Streptococcus mutans activates multiple cellular processes in response to the formation of a complex between comX-inducing peptide (XIP) and the ComR transcriptional regulator. Bulk phase and microfluidic experiments previously revealed that ComR-dependent activation of comX is altered by pH and by carbohydrate source. Biofilm formation is a major factor in bacterial survival and virulence in the oral cavity. Here, we sought to determine the response of S. mutans biofilm cells to XIP during different stages of biofilm maturation. Using flow cytometry and confocal microscopy, we showed that exogenous addition of XIP to early biofilms resulted in robust comX activation. However, as the biofilms matured, increasing amounts of XIP were required to activate comX expression. Single-cell analysis demonstrated that the entire population was responding to XIP with activation of comX in early biofilms, but only a sub-population was responding in mature biofilms. The sub-population response of mature biofilms was retained when the cells were dispersed and then treated with XIP. The proportion and intensity of the bi-modal response of mature biofilm cells was altered in mutants lacking the Type II toxins MazF and RelE, or in a strain lacking the (p)ppGpp synthase/hydrolase RelA. Thus, competence signaling is markedly altered in cells growing in mature biofilms, and pathways that control cell death and growth/survival decisions modulate activation of comX expression in these sessile populations. PMID:27471495

  5. Rate and Time Trend of Perinatal, Infant, Maternal Mortality, Natality and Natural Population Growth in Kosovo

    PubMed Central

    Azemi, Mehmedali; Gashi, Sanije; Berisha, Majlinda; Kolgeci, Selim; Ismaili-Jaha, Vlora

    2012-01-01

    Aim: The aim of work has been the presentation of the rate and time trends of some indicators of the heath condition of mothers and children in Kosovo: fetal mortality, early neonatal mortality, perinatal mortality, infant mortality, natality, natural growth of population etc. The treated patients were the newborn and infants in the post neonatal period, women during their pregnancy and those 42 days before and after the delivery. Methods: The data were taken from: register of the patients treated in the Pediatric Clinic of Prishtina, World Health Organization, Mother and Child Health Care, Reproductive Health Care, Ministry of Health of the Republic of Kosovo, Statistical Department of Kosovo, the National Institute of Public Health and several academic texts in the field of pediatrics. Some indicators were analyzed in a period between year 1945-2010 and 1950-2010, whereas some others were analyzed in a time period between year 2000 and 2011. Results: The perinatal mortality rate in 2000 was 29.1‰, whereas in 2011 it was 18.7‰. The fetal mortality rate was 14.5‰ during the year 2000, whereas in 2011 it was 11.0‰, in 2000 the early neonatal mortality was 14.8‰, in 2011 it was 7.5‰. The infant mortality in Kosovo was 164‰ in 1950, whereas in 2010 it was 20.5‰. The most frequent causes of infant mortality have been: lower respiratory tract infections, acute infective diarrhea, perinatal causes, congenital malformations and unclassified conditions. Maternal death rate varied during this time period. Maternal death in 2000 was 23 whereas in 2010 only two cases were reported. Regarding the natality, in 1950 it reached 46.1 ‰, whereas in 2010 it reached 14‰, natural growth of population rate in Kosovo was 29.1‰ in 1950, whereas in 2011 it was 11.0‰. Conclusion: Perinatal mortality rate in Kosovo is still high in comparison with other European countries (Turkey and Kyrgyzstan have the highest perinatal mortality rate), even though it is in a

  6. Effects of wind energy production on growth, demography, and survivorship of a Desert Tortoise (Gopherus agassizii) population in Southern California with comparisons to natural populations

    USGS Publications Warehouse

    Lovich, J.E.; Ennen, J.R.; Madrak, S.; Meyer, K.; Loughran, C.; Bjurlin, C.; Arundel, T.; Turner, W.; Jones, C.; Groenendaal, G.M.

    2011-01-01

    We studied a Desert Tortoise (Gopherus agassizii) population at a large wind energy generation facility near Palm Springs, California over six field seasons from 1997 to 2010. We compared growth and demographic parameters to populations living in less disturbed areas; as well as populations of the closely-related and newly-described G. morafkai elsewhere in the Sonoran Desert of Arizona. We marked 69 individuals of all size classes and estimated a population size of 96 tortoises, or about 15.4/km2. Growth rates for males were lower than reported elsewhere, although maximum body size was larger. The smallest female with shelled eggs was 221 mm and males mature at over 200 mm. Mean male size was greater than that of females. The adult sex ratio was not significantly different from unity. Size frequency histograms were similar over time and when compared to most, but not all, G. morafkai populations in the Sonoran Desert. For a cohort of adult females, we estimated mortality at 8.4% annually due, in part, to site operations. This value was low in comparison to many other populations during the same time period. Other than possible differences in growth rate of males and the high survivorship of females, there appear to be few differences between this population and those in more natural areas. The high productivity of food plants at the site and its limited public access may contribute to the overall stability of the population. However, the effects of utility-scale renewable energy development on tortoises in other, less productive, areas are unknown. Additional research (especially controlled and replicated before and after studies) is urgently needed to address this deficiency because of forecasted expansion of utility-scale renewable energy development in the future.

  7. Population.

    ERIC Educational Resources Information Center

    King, Pat; Landahl, John

    This pamphlet has been prepared in response to a new problem, a rapidly increasing population, and a new need, population education. It is designed to help teachers provide their students with some basic population concepts with stress placed on the elements of decision making. In the first section of the pamphlet, some of the basic concepts of…

  8. Long-term analysis of survival, fertility, and population growth rate of black bears in North Carolina

    USGS Publications Warehouse

    Brongo, L.L.; Mitchell, M.S.; Grand, J.B.

    2005-01-01

    We estimated survival, fertility, and realized and asymptotic population growth rates from 1981 to 2002 for a protected population of black bears (Ursus americanus) in the southern Appalachian Mountains. We used Akaike's information criterion to assess the time interval for averaging observations that was best for estimating vital rates for our study, given our yearly sample sizes. The temporal symmetry approach allowed us to directly assess population growth and to address all losses and gains to the population by using only capture data, offering an alternative to the logistically intensive collection of reproductive data. Models that averaged survival and fertility across 5- and 7-year time intervals were best supported by our data. Studies of black bear populations with annual sample sizes similar to ours should be of at least 5 years in duration to estimate vital rates reliably, and at least 10 years in duration to evaluate changes in population growth rate (??). We also hypothesized that survival would not track changes in ?? because ?? is influenced by both survival and fertility. The 5-year model supported our hypothesis, but the 7-year model did not. Where long-term dynamics of large, relatively stable bear populations are of interest, monitoring survival is likely to be sufficient for evaluating trends in ??. For rapidly changing, small populations, however, failure to incorporate fertility into assessments of ?? could be misleading. ?? 2005 American Society of Mammalogists.

  9. The 'Natural Laboratory', a tool for deciphering growth, lifetime and population dynamics in larger benthic foraminifera

    NASA Astrophysics Data System (ADS)

    Hohenegger, Johann

    2015-04-01

    The shells of symbiont-bearing larger benthic Foraminifera (LBF) represent the response to physiological requirements in dependence of environmental conditions. All compartments of the shell such as chambers and chamberlets accommodate the growth of the cell protoplasm and are adaptations for housing photosymbiotic algae. Investigations on the biology of LBF were predominantly based on laboratory studies. The lifetime of LBF under natural conditions is still unclear. LBF, which can build >100 chambers during their lifetime, are thought to live at least one year under natural conditions. This is supported by studies on population dynamics of eulittoral foraminifera. In species characterized by a time-restricted single reproduction period the mean size of specimens increases from small to large during lifetime simultaneously reducing individual number. This becomes more complex when two or more reproduction times are present within a one-year cycle leading to a mixture of abundant small individuals with few large specimens during the year, while keeping mean size more or less constant. This mixture is typical for most sublittoral megalospheric (gamonts or schizonts) LBF. Nothing is known on the lifetime of agamonts, the diploid asexually reproducing generation. In all hyaline LBF it is thought to be significantly longer than 1 year based on the large size and considering the mean chamber building rate of the gamont/schizonts. Observations on LBF under natural conditions have not been performed yet in the deeper sublittoral. This reflects the difficulties due to intense hydrodynamics that hinder deploying technical equipment for studies in the natural environment. Therefore, studying growth, lifetime and reproduction of sublittoral LBF under natural conditions can be performed using the so-called 'natural laboratory' in comparison with laboratory investigations. The best sampling method in the upper sublittoral from 5 to 70 m depth is by SCUBA diving. Irregular

  10. The protective function of personal growth initiative among a genocide-affected population in Rwanda.

    PubMed

    Blackie, Laura E R; Jayawickreme, Eranda; Forgeard, Marie J C; Jayawickreme, Nuwan

    2015-07-01

    The aim of the current study was to investigate the extent to which individual differences in personal growth initiative (PGI) were associated with lower reports of functional impairment of daily activities among a genocide-affected population in Rwanda. PGI measures an individual's motivation to develop as a person and the extent to which he or she is active in setting goals that work toward achieving self-improvement. We found that PGI was negatively associated with functional impairment when controlling for depression, posttraumatic stress disorder, and other demographic factors. Our results suggest that PGI may constitute an important mindset for facilitating adaptive functioning in the aftermath of adversity and in the midst of psychological distress, and as such they might have practical applications for the development of intervention programs. PMID:26147518

  11. World population growth, soil erosion, and food security. [Adapted from book

    SciTech Connect

    Brown, L.R.

    1981-11-27

    Since 1950, world food output has more than doubled, but in many cases this impressive gain has been achieved by the adoption of agricultural practices that lead to an excessive rate of soil erosion. At least one-fifth, and perhaps as much as one-third, of the global cropland base is losing soil at a rate that is undermining its long-term productivity. World food production per person will eventually begin to decrease if the loss of topsoil continues at current rates. In view of this, there is an urgent need to realign national priorities everywhere in order to get the brakes on world population growth and to finance the adoption of agricultural practices that will preserve the cropland base. (Ed. note: this article was adapted from Mr. Brown's recent book, Building a Sustainable Society (Norton, New York, 1981)). 46 references, 5 tables.

  12. Effects of habitat characteristics on the growth of carrier population leading to increased spread of typhoid fever: a model.

    PubMed

    Shukla, J B; Goyal, Ashish; Singh, Shikha; Chandra, Peeyush

    2014-06-01

    In this paper, a non-linear model is proposed and analyzed to study the effects of habitat characteristics favoring logistically growing carrier population leading to increased spread of typhoid fever. It is assumed that the cumulative density of habitat characteristics and the density of carrier population are governed by logistic models; the growth rate of the former increases as the density of human population increases. The model is analyzed by stability theory of differential equations and computer simulation. The analysis shows that as the density of the infective carrier population increases due to habitat characteristics, the spread of typhoid fever increases in comparison with the case without such factors. PMID:24857178

  13. Growing pains: How risk perception and risk communication research can help to manage the challenges of global population growth.

    PubMed

    Dawson, Ian G J; Johnson, Johnnie E V

    2014-08-01

    In 2011, the global human population reached 7 billion and medium variant projections indicate that it will exceed 9 billion before 2045. Theoretical and empirical perspectives suggest that this growth could lead to an increase in the likelihood of adverse events (e.g., food shortages, climate change, etc.) and/or the severity of adverse events (e.g., famines, natural disasters, etc.). Several scholars have posited that the size to which the global population grows and the extent to which this growth increases the likelihood of adverse outcomes will largely be shaped by individuals' decisions (in households, organizations, governments, etc.). In light of the strong relationship between perceived risk and decision behaviors, it is surprising that there remains a dearth of empirical research that specifically examines the perceived risks of population growth and how these perceptions might influence related decisions. In an attempt to motivate this important strand of research, this article examines the major risks that may be exacerbated by global population growth and draws upon empirical work concerning the perception and communication of risk to identify potential directions for future research. The article also considers how individuals might perceive both the risks and benefits of population growth and be helped to better understand and address the related issues. The answers to these questions could help humanity better manage the emerging consequences of its continuing success in increasing infant survival and adult longevity. PMID:24593179

  14. Exponential fitting quadrature rule for functional equations

    NASA Astrophysics Data System (ADS)

    Cardone, A.; Paternoster, B.; Santomauro, G.

    2012-09-01

    A Gaussian quadrature rule for periodic integrand function is presented. The weights and nodes depend on the frequency of the problem and they are constructed by following the exponential fitting theory. The composite rule based on this formula is derived. The analysis of the error is carried out and it proves that the exponentially fitted Gaussian rule is more accurate than the classical Gauss-Legendre rule when oscillatory functions are treated. Some numerical tests are presented.

  15. Spatial variation in demography and population growth rate: the importance of natal location.

    PubMed

    Reid, J M; Bignal, E M; Bignal, S; McCracken, D I; Monaghan, P

    2006-09-01

    1. Understanding the pattern and magnitude of spatial variation in demography and population growth rate (lambda) is key to understanding the structure and dynamics of natural populations. However, such spatial variation is challenging to quantify. We use>20 years of individual life-history data to quantify small- and large-scale spatial variation in demography and lambda within a single population of red-billed choughs Pyrrhocorax pyrrhocorax on Islay, Scotland. Critically, we demonstrate a major importance of an individual's natal rather than current location in driving observed spatial variation. 2. Breeding success (the number of offspring fledged per breeding attempt) varied among individual chough nest sites but did not vary on a larger spatial scale across Islay. 3. The proportion of fledglings observed to survive to recruiting age varied markedly among individual nest sites and also varied more widely across Islay. Spatial capture-mark-recapture models defined two discrete geographical regions where fledgling survival differed significantly: choughs fledged in region 'BGE' were more likely to survive than choughs fledged in region 'CNSW' as both subadults and adults. 4. The asymptotic lambda attributable to breeding attempts in region BGE exceeded unity, and exceeded that attributable to breeding attempts in region CNSW. Relatively productive and unproductive regions therefore exist within this population. 5. Spatial variation in adult survival was better explained by an individual's natal region than the region where that individual settled to breed. Spatial variation in lambda would consequently have remained undetected had survival been measured across resident breeders rather than across individuals fledged in each region. Furthermore, breeding success was a weak predictor of a nest site's estimated productivity of recruits. 6. We therefore describe marked spatial variation in demography and lambda within a single population of a territorial vertebrate

  16. Control of mushroom sciarid fly Lycoriella ingenua populations with insect growth regulators applied by soil drench.

    PubMed

    Erler, F; Polat, E; Demir, H; Catal, M; Tuna, G

    2011-06-01

    Mushroom sciarid fly Lycoriella ingenua (Dufour, 1839) comb. nov., is one of the most common fly pests affecting the cultivation of Agaricus bisporus (Lange) Imbach in Turkey. In this study, eight insect growth regulators (IGRs)--diflubenzuron, flufenoxuron, lufenuron, methoprene, novaluron, pyriproxyfen, teflubenzuron, and triflumuron-were tested for their potential to control L. ingenua populations in two successive growing periods. Treatments were targeted at larvae as soil drenches; treatment efficacy was evaluated by assessing adult emergence and larval damage. These products were compared with a control treated with water (negative control) and a conventional chemical insecticide (chlorpyrifos ethyl) (positive control). Treatments with the IGRs caused significant reductions in emerging adult numbers and sporophore damage rates compared with the water-treated control over the two growing periods. Of the IGRs tested, novaluron, diflubenzuron, and teflubenzuron had significantly lower numbers of emerging adults than the rest of the IGRs and chlorpyrifos ethyl-treated control in both periods. Treatments with teflubenzuron, pyriproxyfen, novaluron, and diflubenzuron resulted in significantly lower sporophore damage rates than all other treatments. Compared with negative control, there were no significant yield reductions due to applications of selected IGRs. The results suggest that all the IGRs tested can be used as alternatives to conventional pesticides in controlling L. ingenua populations on mushroom. PMID:21735902

  17. Controlling the Growth of Future LEO Debris Populations with Active Debris Removal

    NASA Technical Reports Server (NTRS)

    Liou, J.-C.; Johnson, N. L.; Hill, N. M.

    2008-01-01

    Active debris removal (ADR) was suggested as a potential means to remediate the low Earth orbit (LEO) debris environment as early as the 1980s. The reasons ADR has not become practical are due to its technical difficulties and the high cost associated with the approach. However, as the LEO debris populations continue to increase, ADR may be the only option to preserve the near-Earth environment for future generations. An initial study was completed in 2007 to demonstrate that a simple ADR target selection criterion could be developed to reduce the future debris population growth. The present paper summarizes a comprehensive study based on more realistic simulation scenarios, including fragments generated from the 2007 Fengyun-1C event, mitigation measures, and other target selection options. The simulations were based on the NASA long-term orbital debris projection model, LEGEND. A scenario, where at the end of mission lifetimes, spacecraft and upper stages were moved to 25-year decay orbits, was adopted as the baseline environment for comparison. Different annual removal rates and different ADR target selection criteria were tested, and the resulting 200-year future environment projections were compared with the baseline scenario. Results of this parametric study indicate that (1) an effective removal strategy can be developed based on the mass and collision probability of each object as the selection criterion, and (2) the LEO environment can be stabilized in the next 200 years with an ADR removal rate of five objects per year.

  18. Association of insulin-like growth factor-1 polymorphisms with high myopia in the Chinese population

    PubMed Central

    Zhuang, Wenjuan; Li, Zili; Sheng, Xunlun; Zhao, Jingjing; Li, Shanshan; Yang, Xueqiu; Xiang, Wei; Rong, Weining; Liu, Yani; Zhang, Fangxia

    2012-01-01

    Purpose The purpose of this study was to determine whether genetic variants in the insulin-like growth factor-1 (IGF-1) gene were associated with high myopia in the Chinese population. Methods A case-control association study of 421 unrelated Chinese patients with high myopia and 401 control subjects matched in ethnicity and gender was undertaken. Genomic DNA was prepared from peripheral blood. All individuals were genotyped for 7 tag single nucleotide polymorphisms (tSNPs) across the IGF-1 gene region. Genotypic distribution was tested for Hardy–Weinberg equilibrium. The genotype and allele frequencies were evaluated using the χ2 tests. Bonferroni corrections for multiple comparisons were performed. Results The polymorphism of rs12423791 showed positive association with extreme myopia (pallel=0.006 and pallel1 recessive model=0.004, respectively) after Bonferroni correction for multiple testing and the haplotype GC of rs5742629-rs12423791 was also associated with extreme myopia (p=0.033) after 50,000 permutations for multiple comparisons. Conclusions The polymorphism of rs12423791 in IGF-1 may be associated with extreme myopia in the Chinese population and should be investigated further. PMID:22509095

  19. Activity and growth of microbial populations in pressurized deep-sea sediment and animal gut samples.

    PubMed

    Tabor, P S; Deming, J W; Ohwada, K; Colwell, R R

    1982-08-01

    Benthic animals and sediment samples were collected at deep-sea stations in the northwest (3,600-m depth) and southeast (4,300- and 5200-m depths) Atlantic Ocean. Utilization rates of [14C]glutamate (0.67 to 0.74 nmol) in sediment suspensions incubated at in situ temperatures and pressures (3 to 5 degrees C and 360, 430, or 520 atmospheres) were relatively slow, ranging from 0.09 to 0.39 nmol g-1 day-1, whereas rates for pressurized samples of gut suspensions varied widely, ranging from no detectable activity to a rapid rate of 986 nmol g-1 day-1. Gut flora from a holothurian specimen and a fish demonstrated rapid, barophilic substrate utilization, based on relative rates calculated for pressurized samples and samples held at 1 atm (101.325 kPa). Substrate utilization by microbial populations in several sediment samples was not inhibited by in situ pressure. Deep-sea pressures did not restrict growth, measured as doubling time, of culturable bacteria present in a northwest Atlantic sediment sample and in a gut suspension prepared from an abyssal scavenging amphipod. From the results of this study, it was concluded that microbial populations in benthic environments can demonstrate significant metabolic activity under deep-ocean conditions of temperature and pressure. Furthermore, rates of microbial activity in the guts of benthic macrofauna are potentially more rapid than in surrounding deep-sea sediments. PMID:6127054

  20. Association of Transforming Growth Factor Alpha Polymorphisms with Nonsyndromic Cleft Lip and Palate in Iranian Population

    PubMed Central

    Ebadifar, Asghar; Hamedi, Roya; Khorram Khorshid, Hamid Reza; Saliminejad, Kioomars; Kamali, Koorosh; Aghakhani Moghadam, Fatemeh; Esmaeili Anvar, Nazanin; Ameli, Nazilla

    2015-01-01

    Background: Cleft lip with or without cleft palate (CL/P) is one of the most common congenital anomalies and the etiology of orofacial clefts is multifactorial. Transforming growth factor alpha (TGFA) is expressed at the medial edge epithelium of fusing palatal shelves during craniofacial development. In this study, the association of two important TGFA gene polymorphisms, BamHI (rs11466297) and RsaI (rs3732248), with CL/P was evaluated in an Iranian population. Methods: The frequencies of BamHI and RsaI variations were determined in 105 unrelated Iranian subjects with nonsyndromic CL/P and 218 control subjects using PCR and RFLP methods, and the results were compared with healthy controls. A p-value of <0.05 was considered statistically significant. Results: The BamHI AC genotype was significantly higher (p=0.016) in the patients (12.4%) than the control group (5.0%). The BamHI C allele was significantly higher (p=0.001; OR=3.4, 95% CI: 1.6–7.4) in the cases (8.0%) compared with the control group (2.5%). Conclusion: Our study showed that there was an association between the TGFA BamHI variation and nonsyndromic CL/P in Iranian population. PMID:26605011

  1. Activity and growth of microbial populations in pressurized deep-sea sediment and animal gut samples.

    PubMed Central

    Tabor, P S; Deming, J W; Ohwada, K; Colwell, R R

    1982-01-01

    Benthic animals and sediment samples were collected at deep-sea stations in the northwest (3,600-m depth) and southeast (4,300- and 5200-m depths) Atlantic Ocean. Utilization rates of [14C]glutamate (0.67 to 0.74 nmol) in sediment suspensions incubated at in situ temperatures and pressures (3 to 5 degrees C and 360, 430, or 520 atmospheres) were relatively slow, ranging from 0.09 to 0.39 nmol g-1 day-1, whereas rates for pressurized samples of gut suspensions varied widely, ranging from no detectable activity to a rapid rate of 986 nmol g-1 day-1. Gut flora from a holothurian specimen and a fish demonstrated rapid, barophilic substrate utilization, based on relative rates calculated for pressurized samples and samples held at 1 atm (101.325 kPa). Substrate utilization by microbial populations in several sediment samples was not inhibited by in situ pressure. Deep-sea pressures did not restrict growth, measured as doubling time, of culturable bacteria present in a northwest Atlantic sediment sample and in a gut suspension prepared from an abyssal scavenging amphipod. From the results of this study, it was concluded that microbial populations in benthic environments can demonstrate significant metabolic activity under deep-ocean conditions of temperature and pressure. Furthermore, rates of microbial activity in the guts of benthic macrofauna are potentially more rapid than in surrounding deep-sea sediments. PMID:6127054

  2. Radiative Impacts on the Growth of a Population of Drops within Simulated Summertime Arctic Stratus.

    NASA Astrophysics Data System (ADS)

    Harrington, Jerry Y.; Feingold, Graham; Cotton, William R.

    2000-03-01

    The impact of solar heating and infrared cooling on the growth of a population of drops is studied with two numerical modeling frameworks. An eddy-resolving model (ERM) simulation of Arctic stratus clouds is used to generate a dataset of 500 parcel trajectories that follow the mean dynamic motions of the simulated cloud. The 500-parcel dataset is used to drive a trajectory ensemble model (TEM) coupled to an explicit microphysical model that includes the radiative term in the vapor growth equation. The second framework is that of the ERM itself.Results from the TEM show that the production of drizzle-sized drops is strongly dependent upon parcel cloud-top residence time for both radiative- and nonradiative-influenced growth. Drizzle-sized drops can be produced between 20 and 50 min earlier through the inclusion of the radiative term, which corroborates earlier results. The radiative effect may also cause drops with r < 10 m to evaporate, producing a bimodal size spectrum. Parcel cloud-top residence times as short as 12 min can initiate this bimodal spectrum. TEM results show that the radiative effect increases drizzle drop mass predominately in parcels that tend to contribute to drizzle even in the absence of the radiative term. Activation of large cloud condensation nuclei appears to have a larger effect on drizzle production than does the radiative term. ERM simulations show a weak overall influence of the radiative term. Drizzle onset occurs earlier when the radiative term is included (about 20 min), but there is no strong change in the overall structure or evolution of the cloud.

  3. Radiative impacts on the growth of a population of drops within simulated summertime Arctic stratus

    SciTech Connect

    Harrington, J.Y.; Feingold, G.; Cotton, W.R.

    2000-03-01

    The impact of solar heating and infrared cooling on the growth of a population of drops is studied with two numerical modeling frameworks. An eddy-resolving model (ERM) simulation of Arctic stratus clouds is used to generate a dataset of 500 parcel trajectories that follow the mean dynamic motions of the simulated cloud. The 500-parcel dataset is used to drive a trajectory ensemble model (TEM) coupled to an explicit microphysical model that includes the radiative term in the vapor growth equation. The second framework is that of the ERM itself. Results from the TEM show that the production of drizzle-sized drops is strongly dependent upon parcel cloud-top resistance time for both radiative- and nonradiative-influenced growth. drizzle-sized drops can be produced between 20 and 50 min earlier through the inclusion of the radiative terms, which corroborates earlier results. The radiative effect may also cause drops with r < 10 {mu}m to evaporate, producing a bimodal size spectrum. Parcel cloud-top residence times as short as 12 min can initiate this bimodal spectrum. TEM results show that the radiative effect increases drizzle drop mass predominantly in parcels that tend to contribute to drizzle even in the absence of the radiative term. Activation of large cloud condensation nuclei appears to have a larger effect on drizzle production than does the radiative term. ERM simulations show a weak overall influence of the radiative term. Drizzle onset occurs earlier when the radiative term is included (about 20 min), but there is no strong change in the overall structure or evolution of the cloud.

  4. Mating system, population growth, and management scenario for Kalanchoe pinnata in an invaded seasonally dry tropical forest.

    PubMed

    González de León, Salvador; Herrera, Ileana; Guevara, Roger

    2016-07-01

    Ecological invasions are a major issue worldwide, where successful invasion depends on traits that facilitate dispersion, establishment, and population growth. The nonnative succulent plant Kalanchoe pinnata, reported as invasive in some countries, is widespread in remnants of seasonally dry tropical forest on a volcanic outcrop with high conservation value in east-central Mexico where we assessed its mating system and demographic growth and identified management strategies. To understand its local mating system, we conducted hand-pollination treatments, germination, and survival experiments. Based on the experimental data, we constructed a life-stage population matrix, identified the key traits for population growth, weighted the contributions of vegetative and sexual reproduction, and evaluated management scenarios. Hand-pollination treatments had slight effects on fruit and seed setting, as well as on germination. With natural pollination treatment, the successful germination of seeds from only 2/39 fruit suggests occasional effective natural cross-pollination. The ratios of the metrics for self- and cross-pollinated flowers suggest that K. pinnata is partially self-compatible. Most of the pollinated flowers developed into fruit, but the seed germination and seedling survival rates were low. Thus, vegetative propagation and juvenile survival are the main drivers of population growth. Simulations of a virtual K. pinnata population suggest that an intense and sustained weeding campaign will reduce the population within at least 10 years. Synthesis and applications. The study population is partially self-compatible, but sexual reproduction by K. pinnata is limited at the study site, and population growth is supported by vegetative propagation and juvenile survival. Demographic modeling provides key insights and realistic forecasts on invasion process and therefore is useful to design management strategies. PMID:27386095

  5. Development and population dynamics of Steinernema yirgalemense (Rhabditida: Steinernematidae) and growth characteristics of its associated Xenorhabdus indica symbiont in liquid culture.

    PubMed

    Ferreira, T; Addison, M F; Malan, A P

    2016-05-01

    Entomopathogenic nematodes have become a valuable addition to the range of biological control agents available for insect control. An endemic nematode, Steinernema yirgalemense, has been found to be effective against a wide range of key insect pests. The next step would be the mass production this nematode for commercial application. This requires the establishment of monoxenic cultures of both the nematode and the symbiotic bacterium Xenorhabdus indica. First-stage juveniles of S. yirgalemense were obtained from eggs, while X. indica was isolated from nematode-infected wax moth larvae. The population density of the various life stages of S. yirgalemense during the developmental phase in liquid culture was determined. The recovery of infective juveniles (IJs) to the third-stage feeding juveniles, was 67 ± 10%, reaching a maximum population density of 75,000 IJs ml- 1 on day 13 after inoculation. Adult density increased after 8 days, with the maximum female density being 4600 ml- 1 on day 15, whereas the maximum male density was 4300 ml- 1 on day 12. Growth curves for X. indica showed that the exponential phase was reached 15 h after inoculation to the liquid medium. The stationary phase was reached after 42 h, with an average of 51 × 107 colony-forming units ml- 1. Virulence tests showed a significant difference in insect mortality between in vitro- and in vivo-produced nematodes. The success obtained with the production of S. yirgalemense in liquid culture can serve as the first step in the optimizing and upscaling of the commercial production of nematodes in fermenters. PMID:26156314

  6. The Existence of Weak D-Pullback Exponential Attractor for Nonautonomous Dynamical System.

    PubMed

    Li, Yongjun; Wei, Xiaona; Zhang, Yanhong

    2016-01-01

    First, for a process {U(t, τ)∣t ≥ τ}, we introduce a new concept, called the weak D-pullback exponential attractor, which is a family of sets {ℳ(t)∣t ≤ T}, for any T ∈ ℝ, satisfying the following: (i) ℳ(t) is compact, (ii) ℳ(t) is positively invariant, that is, U(t, τ)ℳ(τ) ⊂ ℳ(t), and (iii) there exist k, l > 0 such that dist(U(t, τ)B(τ), ℳ(t)) ≤ ke (-(t-τ)); that is, ℳ(t) pullback exponential attracts B(τ). Then we give a method to obtain the existence of weak D-pullback exponential attractors for a process. As an application, we obtain the existence of weak D-pullback exponential attractor for reaction diffusion equation in H 0 (1) with exponential growth of the external force. PMID:27119090

  7. Effects of five insect growth regulators on laboratory populations of the North American house-dust mite, Dermatophagoides farinae.

    PubMed

    Downing, A S; Wright, C G; Farrier, M H

    1990-08-01

    The potential of insect growth regulators (methoprene, hydroprene, fenoxycarb, diflubenzuron and triflumuron) to control populations of the North American house-dust mite Dermatophagoides farinae (Hughes) was assessed in laboratory bioassays. Methoprene was most effective at suppressing population growth, especially at concentrations of 1.0% (10,000 ppm) and 5.0% (5000 ppm) active ingredient. Hydroprene, structurally related to methoprene, also suppressed house-dust mite populations but not as consistently as methoprene. Fenoxycarb may be effective at controlling house-dust mites but at greater concentrations than were tested. Diflubenzuron and triflumuron, two chitin-synthesis inhibitors, failed to suppress mite numbers and may, in fact, stimulate reproduction in some cases. Almost all concentration of the insect growth regulators were shown to be ineffective when assayed 90 days after treatment. PMID:2226070

  8. Scaling in the growth of geographically subdivided populations: invariant patterns from a continent-wide biological survey.

    PubMed

    Keitt, Timothy H; Amaral, Luis A N; Buldyrev, Sergey V; Stanley, H Eugene

    2002-05-29

    We consider statistical patterns of variation in growth rates for over 400 species of breeding birds across North America surveyed from 1966 to 1998. We report two results. First, the standard deviation of population growth rates decays as a power-law function of total population size with an exponent beta = 0.36 +/- 0.02. Second, the number of subpopulations, measured as the number of survey locations with non-zero counts, scales to the 3/4 power of total number of birds counted in a given species. We show how these patterns may be related, and discuss a simple stochastic growth model for a geographically subdivided population that formalizes the relationship. We also examine reasons that may explain why some species deviate from these scaling laws. PMID:12079524

  9. Bioconvective patterns, synchrony, and survival. [in light-limited growth model of motile algae culture

    NASA Technical Reports Server (NTRS)

    Noever, David A.

    1990-01-01

    With and without bioconvective pattern formation, a theoretical model predicts growth in light-limited cultures of motile algae. At the critical density for pattern formation, the resulting doubly exponential population curves show an inflection. Such growth corresponds quantitatively to experiments in mechanically unstirred cultures. This attaches survival value to synchronized pattern formation.

  10. The Association Between Natural Amenities, Rural Population Growth, and Long-Term Residents’ Economic Well-Being*

    PubMed Central

    Hunter, Lori M.; Boardman, Jason D.; Saint Onge, Jarron M.

    2011-01-01

    Population growth in rural areas characterized by high levels of natural amenities has recently received substantial research attention. A noted concern with amenity-driven rural population growth is its potential to raise local costs-of-living while yielding only low-wage service sector employment for long-term residents. The work presented here empirically models long-term rural residents’ economic well-being, making use of longitudinal data from the Panel Study of Income Dynamics. In general, the results suggest that long-term rural families residing in high-growth amenity and recreation areas tend to have higher annual incomes than do their counterparts in non-growth amenity/recreation areas, regardless of the sex, race, or age of the family head. However, higher costs-of-living in these areas supplant any relative gains in income. As such, these analyses provide empirical evidence of patterns inferred by earlier anecdotal evidence and case studies. PMID:21874070

  11. The long run effect of green belt amenities upon the population growth: the case of almost linear demand function.

    PubMed

    Suh, S H

    1987-01-01

    "The purpose of this paper is to suggest that, in evaluating the relevance of sustaining the green belt, we must pay more attention to the fact that the green belt amenities can accelerate rather than decelerate the population growth of a city. For this, this paper analyzes the case where there exist green belt amenities and the demand for land function is almost linear. In this case, it can be shown that the green belt is ineffective in restricting the population growth in the long run." PMID:12283599

  12. Geographic Distribution of Habitat, Development, and Population Growth Rates of the Asian Citrus Psyllid, Diaphorina citri, in Mexico

    PubMed Central

    López-Collado, José; Isabel López-Arroyo, J.; Robles-García, Pedro L.; Márquez-Santos, Magdalena

    2013-01-01

    The Asian citrus psyllid, Diaphorina citri Kuwayama (Hemiptera: Psyllidae), is an introduced pest in Mexico and a vector of huanglongbing, a lethal citrus disease. Estimations of the habitat distribution and population growth rates of D. citri are required to establish regional and areawide management strategies and can be used as a pest risk analysis tools. In this study, the habitat distribution of D. citri in Mexico was computed with MaxEnt, an inductive, machine-learning program that uses bioclimatic layers and point location data. Geographic distributions of development and population growth rates were determined by fitting a temperature-dependent, nonlinear model and projecting the rates over the target area, using the annual mean temperature as the predictor variable. The results showed that the most suitable regions for habitat of D. citri comprise the Gulf of Mexico states, Yucatán Peninsula, and areas scattered throughout the Pacific coastal states. Less suitable areas occurred in northern and central states. The most important predictor variables were related to temperature. Development and growth rates had a distribution wider than habitat, reaching some of the northern states of México. Habitat, development, and population growth rates were correlated to each other and with the citrus producing area. These relationships indicated that citrus producing states are within the most suitable regions for the occurrence, development, and population growth of D. citri, therefore increasing the risk of huanglongbing dispersion. PMID:24735280

  13. Phenotypic plasticity in growth and fecundity induced by strong population fluctuations affects reproductive traits of female fish.

    PubMed

    Karjalainen, Juha; Urpanen, Olli; Keskinen, Tapio; Huuskonen, Hannu; Sarvala, Jouko; Valkeajärvi, Pentti; Marjomäki, Timo J

    2016-02-01

    Fish are known for their high phenotypic plasticity in life-history traits in relation to environmental variability, and this is particularly pronounced among salmonids in the Northern Hemisphere. Resource limitation leads to trade-offs in phenotypic plasticity between life-history traits related to the reproduction, growth, and survival of individual fish, which have consequences for the age and size distributions of populations, as well as their dynamics and productivity. We studied the effect of plasticity in growth and fecundity of vendace females on their reproductive traits using a series of long-term incubation experiments. The wild parental fish originated from four separate populations with markedly different densities, and hence naturally induced differences in their growth and fecundity. The energy allocation to somatic tissues and eggs prior to spawning served as a proxy for total resource availability to individual females, and its effects on offspring survival and growth were analyzed. Vendace females allocated a rather constant proportion of available energy to eggs (per body mass) despite different growth patterns depending on the total resources in the different lakes; investment into eggs thus dictated the share remaining for growth. The energy allocation to eggs per mass was higher in young than in old spawners and the egg size and the relative fecundity differed between them: Young females produced more and smaller eggs and larvae than old spawners. In contrast to earlier observations of salmonids, a shortage of maternal food resources did not increase offspring size and survival. Vendace females in sparse populations with ample resources and high growth produced larger eggs and larvae. Vendace accommodate strong population fluctuations by their high plasticity in growth and fecundity, which affect their offspring size and consequently their recruitment and productivity, and account for their persistence and resilience in the face of high

  14. Endless Urban Growth? On the Mismatch of Population, Household and Urban Land Area Growth and Its Effects on the Urban Debate

    PubMed Central

    Haase, Dagmar; Kabisch, Nadja; Haase, Annegret

    2013-01-01

    In European cities, the rate of population growth has declined significantly, while the number of households has increased. This increase in the number of households is associated with an increase in space for housing. To date, the effects of both a declining population and decreasing household numbers remain unclear. In this paper, we analyse the relationship between population and household number development in 188 European cities from 1990–2000 and 2000–2006 to the growth of urban land area and per capita living space. Our results support a trend toward decreasing population with simultaneously increasing household number. However, we also found cites facing both a declining population and a decreasing household number. Nevertheless, the urban land area of these “double-declining” cities has continued to spread because the increasing per capita living space counteracts a reduction in land consumption. We conclude that neither a decline in population nor in household number “automatically” solve the global problem of land consumption. PMID:23840501

  15. Population Growth Rates of Reef Sharks with and without Fishing on the Great Barrier Reef: Robust Estimation with Multiple Models

    PubMed Central

    Hisano, Mizue; Connolly, Sean R.; Robbins, William D.

    2011-01-01

    Overfishing of sharks is a global concern, with increasing numbers of species threatened by overfishing. For many sharks, both catch rates and underwater visual surveys have been criticized as indices of abundance. In this context, estimation of population trends using individual demographic rates provides an important alternative means of assessing population status. However, such estimates involve uncertainties that must be appropriately characterized to credibly and effectively inform conservation efforts and management. Incorporating uncertainties into population assessment is especially important when key demographic rates are obtained via indirect methods, as is often the case for mortality rates of marine organisms subject to fishing. Here, focusing on two reef shark species on the Great Barrier Reef, Australia, we estimated natural and total mortality rates using several indirect methods, and determined the population growth rates resulting from each. We used bootstrapping to quantify the uncertainty associated with each estimate, and to evaluate the extent of agreement between estimates. Multiple models produced highly concordant natural and total mortality rates, and associated population growth rates, once the uncertainties associated with the individual estimates were taken into account. Consensus estimates of natural and total population growth across multiple models support the hypothesis that these species are declining rapidly due to fishing, in contrast to conclusions previously drawn from catch rate trends. Moreover, quantitative projections of abundance differences on fished versus unfished reefs, based on the population growth rate estimates, are comparable to those found in previous studies using underwater visual surveys. These findings appear to justify management actions to substantially reduce the fishing mortality of reef sharks. They also highlight the potential utility of rigorously characterizing uncertainty, and applying multiple

  16. Population growth rates of reef sharks with and without fishing on the great barrier reef: robust estimation with multiple models.

    PubMed

    Hisano, Mizue; Connolly, Sean R; Robbins, William D

    2011-01-01

    Overfishing of sharks is a global concern, with increasing numbers of species threatened by overfishing. For many sharks, both catch rates and underwater visual surveys have been criticized as indices of abundance. In this context, estimation of population trends using individual demographic rates provides an important alternative means of assessing population status. However, such estimates involve uncertainties that must be appropriately characterized to credibly and effectively inform conservation efforts and management. Incorporating uncertainties into population assessment is especially important when key demographic rates are obtained via indirect methods, as is often the case for mortality rates of marine organisms subject to fishing. Here, focusing on two reef shark species on the Great Barrier Reef, Australia, we estimated natural and total mortality rates using several indirect methods, and determined the population growth rates resulting from each. We used bootstrapping to quantify the uncertainty associated with each estimate, and to evaluate the extent of agreement between estimates. Multiple models produced highly concordant natural and total mortality rates, and associated population growth rates, once the uncertainties associated with the individual estimates were taken into account. Consensus estimates of natural and total population growth across multiple models support the hypothesis that these species are declining rapidly due to fishing, in contrast to conclusions previously drawn from catch rate trends. Moreover, quantitative projections of abundance differences on fished versus unfished reefs, based on the population growth rate estimates, are comparable to those found in previous studies using underwater visual surveys. These findings appear to justify management actions to substantially reduce the fishing mortality of reef sharks. They also highlight the potential utility of rigorously characterizing uncertainty, and applying multiple

  17. Temperature effect on the build-up of exponentially growing polyelectrolyte multilayers. An exponential-to-linear transition point.

    PubMed

    Vikulina, Anna S; Anissimov, Yuri G; Singh, Prateek; Prokopović, Vladimir Z; Uhlig, Katja; Jaeger, Magnus S; von Klitzing, Regine; Duschl, Claus; Volodkin, Dmitry

    2016-03-21

    In this study, the effect of temperature on the build-up of exponentially growing polyelectrolyte multilayer films was investigated. It aims at understanding the multilayer growth mechanism as crucially important for the fabrication of tailor-made multilayer films. Model poly(L-lysine)/hyaluronic acid (PLL/HA) multilayers were assembled in the temperature range of 25-85 °C by layer-by-layer deposition using a dipping method. The film growth switches from the exponential to the linear regime at the transition point as a result of limited polymer diffusion into the film. With the increase of the build-up temperature the film growth rate is enhanced in both regimes; the position of the transition point shifts to a higher number of deposition steps confirming the diffusion-mediated growth mechanism. Not only the faster polymer diffusion into the film but also more porous/permeable film structure are responsible for faster film growth at higher preparation temperature. The latter mechanism is assumed from analysis of the film growth rate upon switching of the preparation temperature during the film growth. Interestingly, the as-prepared films are equilibrated and remain intact (no swelling or shrinking) during temperature variation in the range of 25-45 °C. The average activation energy for complexation between PLL and HA in the multilayers calculated from the Arrhenius plot has been found to be about 0.3 kJ mol(-1) for monomers of PLL. Finally, the following processes known to be dependent on temperature are discussed with respect to the multilayer growth: (i) polymer diffusion, (ii) polymer conformational changes, and (iii) inter-polymer interactions. PMID:26911320

  18. Population growth and rural-urban migration, with special reference to Ghana.

    PubMed

    De Graft-johnson, K T

    1974-01-01

    but that once people decide to migrate, they base their choice of destination primarily on economic opportunities available at that end. Distance bears little relationship to choice of destination. To stem this tide efforts need to be made to increase rural income, provide employment opportunities for those displaced as agriculture becomes more efficient, and to provide for greater amenities in rural areas. Urban unemployment is an ever-increasing problem, accentuated by population growth and migration. Intensive rural development is needed to reverse this trend. PMID:12307192

  19. Evolution of invasive traits in nonindigenous species: increased survival and faster growth in invasive populations of rusty crayfish (Orconectes rusticus)

    PubMed Central

    Sargent, Lindsey W; Lodge, David M

    2014-01-01

    The importance of evolution in enhancing the invasiveness of species is not well understood, especially in animals. To evaluate evolution in crayfish invasions, we tested for differences in growth rate, survival, and response to predators between native and invaded range populations of rusty crayfish (Orconectes rusticus). We hypothesized that low conspecific densities during introductions into lakes would select for increased investment in growth and reproduction in invasive populations. We reared crayfish from both ranges in common garden experiments in lakes and mesocosms, the latter in which we also included treatments of predatory fish presence and food quality. In both lake and mesocosm experiments, O. rusticus from invasive populations had significantly faster growth rates and higher survival than individuals from the native range, especially in mesocosms where fish were present. There was no influence of within-range collection location on growth rate. Egg size was similar between ranges and did not affect crayfish growth. Our results, therefore, suggest that growth rate, which previous work has shown contributes to strong community-level impacts of this invasive species, has diverged since O. rusticus was introduced to the invaded range. This result highlights the need to consider evolutionary dynamics in invasive species mitigation strategies. PMID:25469173

  20. Phylogenetic Stochastic Mapping Without Matrix Exponentiation

    PubMed Central

    Irvahn, Jan; Minin, Vladimir N.

    2014-01-01

    Abstract Phylogenetic stochastic mapping is a method for reconstructing the history of trait changes on a phylogenetic tree relating species/organism carrying the trait. State-of-the-art methods assume that the trait evolves according to a continuous-time Markov chain (CTMC) and works well for small state spaces. The computations slow down considerably for larger state spaces (e.g., space of codons), because current methodology relies on exponentiating CTMC infinitesimal rate matrices—an operation whose computational complexity grows as the size of the CTMC state space cubed. In this work, we introduce a new approach, based on a CTMC technique called uniformization, which does not use matrix exponentiation for phylogenetic stochastic mapping. Our method is based on a new Markov chain Monte Carlo (MCMC) algorithm that targets the distribution of trait histories conditional on the trait data observed at the tips of the tree. The computational complexity of our MCMC method grows as the size of the CTMC state space squared. Moreover, in contrast to competing matrix exponentiation methods, if the rate matrix is sparse, we can leverage this sparsity and increase the computational efficiency of our algorithm further. Using simulated data, we illustrate advantages of our MCMC algorithm and investigate how large the state space needs to be for our method to outperform matrix exponentiation approaches. We show that even on the moderately large state space of codons our MCMC method can be significantly faster than currently used matrix exponentiation methods. PMID:24918812

  1. Finite Higher Spin Transformations from Exponentiation

    NASA Astrophysics Data System (ADS)

    Monnier, Samuel

    2015-05-01

    We study the exponentiation of elements of the gauge Lie algebras hs(λ) of three-dimensional higher spin theories. Exponentiable elements generate one-parameter groups of finite higher spin symmetries. We show that elements of hs(λ) in a dense set are exponentiable, when pictured in certain representations of hs(λ), induced from representations of in the complementary series. We also provide a geometric picture of higher spin gauge transformations clarifying the physical origin of these representations. This allows us to construct an infinite-dimensional topological group HS(λ) of finite higher spin symmetries. Interestingly, this construction is possible only for 0 ≤ λ ≤ 1, which are the values for which the higher spin theory is believed to be unitary and for which the Gaberdiel-Gopakumar duality holds. We exponentiate explicitly various commutative subalgebras of hs(λ). Among those, we identify families of elements of hs(λ) exponentiating to the unit of HS(λ), generalizing the logarithms of the holonomies of BTZ black hole connections. Our techniques are generalizable to the Lie algebras relevant to higher spin theories in dimensions above three.

  2. Genetic parameters for growth, reproductive and maternal traits in a multibreed meat sheep population

    PubMed Central

    2009-01-01

    The genetic parameters for growth, reproductive and maternal traits in a multibreed meat sheep population were estimated by applying the Average Information Restricted Maximum Likelihood method to an animal model. Data from a flock supported by the Programa de Melhoramento Genético de Caprinos e Ovinos de Corte (GENECOC) were used. The traits studied included birth weight (BW), weaning weight (WW), slaughter weight (SW), yearling weight (YW), weight gain from birth to weaning (GBW), weight gain from weaning to slaughter (GWS), weight gain from weaning to yearling (GWY), age at first lambing (AFL), lambing interval (LI), gestation length (GL), lambing date (LD - number of days between the start of breeding season and lambing), litter weight at birth (LWB) and litter weight at weaning (LWW). The direct heritabilities were 0.35, 0.81, 0.65, 0.49, 0.20, 0.15 and 0.39 for BW, WW, SW, YW, GBW, GWS and GWY, respectively, and 0.04, 0.06, 0.10, 0.05, 0.15 and 0.11 for AFL, LI, GL, LD, LWB and LWW, respectively. Positive genetic correlations were observed among body weights. In contrast, there was a negative genetic correlation between GBW and GWS (-0.49) and GBW and GWY (-0.56). Positive genetic correlations were observed between AFL and LI, LI and GL, and LWB and LWW. These results indicate a strong maternal influence in this herd and the presence of sufficient genetic variation to allow mass selection for growth traits. Additive effects were of little importance for reproductive traits, and other strategies are necessary to improve the performance of these animals. PMID:21637451

  3. Association Between Vascular Endothelial Growth Factor Gene Polymorphisms with Breast Cancer Risk in an Iranian Population

    PubMed Central

    Rezaei, Maryam; Hashemi, Mohammad; Sanaei, Sara; Mashhadi, Mohammad Ali; Taheri, Mohsen

    2016-01-01

    Breast cancer (BC) is one of the most causes of death in women worldwide. It affects Iranian female population approximately a decade earlier than those in other parts of the world. Previous studies have shown that vascular endothelial growth factor (VEGF) gene variants were associated with BC risk. The current study aimed to evaluate the impact of VEGF rs3025039 (+936C>T), rs2010963 (+405C>G), rs833061 (-460T>C), rs699947 (-2578C>A), and rs35569394 (18-bp I/D) polymorphisms on BC risk in an Iranian population in southeast of Iran. This case–control study was done on 250 BC patients and 215 healthy women. Polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) or PCR was used to genotype the polymorphisms. Our findings showed that VEGF rs699947 variant increased the risk of BC (OR = 1.71, 95% CI = 1.15–2.54, P = 0.009, CA vs CC; OR = 2.12, 95% CI = 1.14–3.93, P = 0.021, AA vs CC; OR = 1.78, 95% CI = 1.22–2.60, P = 0.004, CA+AA vs CC; OR = 1.47, 95% CI = 1.12–1.92, P = 0.005, A vs C). The VEGF rs3025039, rs2010963, rs833061, and rs35569394 variants were not associated with risk/protection of BC. In conclusion, our results proposed that VEGF rs699947 polymorphism may increase the risk of BC development. Furthers studies with larger sample sizes and different ethnicities are necessary to confirm our findings. PMID:27398026

  4. Power Policy 21 Century: Growth of the Population, Economics, Ecology and Entropy

    NASA Astrophysics Data System (ADS)

    Prisniakov, Vladimir

    2002-01-01

    but energy consumed by a man will be a limiting factor. Obtained values of changing in the quantity of population as well as of the consumed fuel quantity in the 21 century have been analysed. The period was defined (2005-2085) when energy hungry is possible due to a higher rate of a human reproduction comparing to the rates of energy consumption. From new position, the laws of the Earth population growth are analysed, based on the equality of the quantity of dying people to the quantity of those bornyears ago, whereis life expectancy. investigated on the base of Second law of thermodynamics. The equation of money exchange dY = (V/p)dM in going from quantity real GNP Y to consumption fuel equivalent E=pd Y takes the form: dE =VdM. General correlation between S and M is proposed: dS = (HV/T)dM, where H is enthalpy; V is velocity of money; T is temperature; p is total prices,is capacity of manufacture resources. This equation shows direction of the spontaneity development of economical processes as part of general law Universe. The original equation of removing from information to matter equation enables to control output natural resources by economic laws, and to control of activities for the restoration wrecked nature.This equation shows the direction of the spontaneity development of economical processes as part of a general Universal law. into account value of expenditure on ecology as part of price and overstated price indexes. The criterions allow to discover numerical values of a stock of money, ecology part of price, velocity of money, value of the taxes, which ensure sustainable development. These equations enable to control output natural resources by economic laws, and to control activities for the restoration of wrecked nature.

  5. Decoherence and Exponential Law: A Solvable Model

    NASA Technical Reports Server (NTRS)

    Pascazio, Saverio; Namiki, Mikio

    1996-01-01

    We analyze a modified version of the 'AgBr' Hamiltonian, solve exactly the equations of motion in terms of SU(2) coherent states, and study the weak-coupling, macroscopic limit of the model, obtaining an exponential behavior at all times. The asymptotic dominance of the exponential behavior is representative of a purely stochastic evolution and can be derived quantum mechanically in the so-called van Hove's limit (which is a weak-coupling, macroscopic limit). At the same time, a temporal behavior of the exponential type, yielding a 'probability dissipation' is closely related to dephasing ('decoherence') effects and one can expect a close connection with a dissipative and irreversible behavior. We stress the central relevance of the problem of dissipation to the quantum measurement theory and to the general topic of decoherence.

  6. Modeling aftershocks as a stretched exponential relaxation

    NASA Astrophysics Data System (ADS)

    Mignan, A.

    2015-11-01

    The decay rate of aftershocks has been modeled as a power law since the pioneering work of Omori in the late nineteenth century. Although other expressions have been proposed in recent decades to describe the temporal behavior of aftershocks, the number of model comparisons remains limited. After reviewing the aftershock models published from the late nineteenth century until today, I solely compare the power law, pure exponential and stretched exponential expressions defined in their simplest forms. By applying statistical methods recommended recently in applied mathematics, I show that all aftershock sequences tested in three regional earthquake catalogs (Southern and Northern California, Taiwan) and with three declustering techniques (nearest-neighbor, second-order moment, window methods) follow a stretched exponential instead of a power law. These results infer that aftershocks are due to a simple relaxation process, in accordance with most other relaxation processes observed in Nature.

  7. Method for exponentiating in cryptographic systems

    DOEpatents

    Brickell, Ernest F.; Gordon, Daniel M.; McCurley, Kevin S.

    1994-01-01

    An improved cryptographic method utilizing exponentiation is provided which has the advantage of reducing the number of multiplications required to determine the legitimacy of a message or user. The basic method comprises the steps of selecting a key from a preapproved group of integer keys g; exponentiating the key by an integer value e, where e represents a digital signature, to generate a value g.sup.e ; transmitting the value g.sup.e to a remote facility by a communications network; receiving the value g.sup.e at the remote facility; and verifying the digital signature as originating from the legitimate user. The exponentiating step comprises the steps of initializing a plurality of memory locations with a plurality of values g.sup.xi ; computi The United States Government has rights in this invention pursuant to Contract No. DE-AC04-76DP00789 between the Department of Energy and AT&T Company.

  8. Long-term data reveal a population decline of the tropical lizard Anolis apletophallus, and a negative affect of el nino years on population growth rate.

    PubMed

    Stapley, Jessica; Garcia, Milton; Andrews, Robin M

    2015-01-01

    Climate change threatens biodiversity worldwide, however predicting how particular species will respond is difficult because climate varies spatially, complex factors regulate population abundance, and species vary in their susceptibility to climate change. Studies need to incorporate these factors with long-term data in order to link climate change to population abundance. We used 40 years of lizard abundance data and local climate data from Barro Colorado Island to ask how climate, total lizard abundance and cohort-specific abundance have changed over time, and how total and cohort-specific abundance relate to climate variables including those predicted to make the species vulnerable to climate change (i.e. temperatures exceeding preferred body temperature). We documented a decrease in lizard abundance over the last 40 years, and changes in the local climate. Population growth rate was related to the previous years' southern oscillation index; increasing following cooler-wetter, la niña years, decreasing following warmer-drier, el nino years. Within-year recruitment was negatively related to rainfall and minimum temperature. This study simultaneously identified climatic factors driving long-term population fluctuations and climate variables influencing short-term annual recruitment, both of which may be contributing to the population decline and influence the population's future persistence. PMID:25671423

  9. Estimates of annual survival, growth, and recruitment of a white-tailed ptarmigan population in Colorado over 43 years

    USGS Publications Warehouse

    Wann, Greg; Aldridge, Cameron L.; Braun, Clait E.

    2014-01-01

    Long-term datasets for high-elevation species are rare, and considerable uncertainty exists in understanding how high-elevation populations have responded to recent climate warming. We present estimates of demographic vital rates from a 43-year population study of white-tailed ptarmigan (Lagopus leucura), a species endemic to alpine habitats in western North America. We used capture-recapture models to estimate annual rates of apparent survival, population growth, and recruitment for breeding-age ptarmigan, and we fit winter weather covariates to models in an attempt to explain annual variation. There were no trends in survival over the study period but there was strong support for age and sex effects. The average rate of annual growth suggests a relatively stable breeding-age population ( λ ¯ = 1.036), but there was considerable variation between years for both population growth and recruitment rates. Winter weather covariates only explained a small amount of variation in female survival and were not an important predictor of male survival. Cumulative winter precipitation was found to have a quadratic effect on female survival, with survival being highest during years of average precipitation. Cumulative winter precipitation was positively correlated with population growth and recruitment rates, although this covariate only explained a small amount of annual variation in these rates and there was considerable uncertainty among the models tested. Our results provide evidence for an alpine-endemic population that has not experienced extirpation or drastic declines. However, more information is needed to understand risks and vulnerabilities of warming effects on juveniles as our analysis was confined to determination of vital rates for breeding-age birds.

  10. Population Growth, Climate Change and Water Scarcity in the Southwestern United States.

    PubMed

    Fuller, Amy C; Harhay, Michael O

    2010-06-30

    PROBLEM STATEMENT: In a simple economic model, water scarcity arises as a result of an imbalance between the supply of and demand for water sources. Distribution in this setting is the source of numerous conflicts globally. APPROACH: Already, the Southwestern United States (US) suffers from annual drought and long-standing feud over natural water resources. RESULTS: Population growth in the Southwestern United States along with the continued effects of climate change (natural and anthropogenic) predicts a perpetual decline in natural water sources, such as smaller snowpacks, in the coming years. As the increasing number of communities across multiple US states that subsist off of natural water supplies face water shortages with increasing severity, further water conflict will emerge. Such conflicts become especially protracted when the diversion of water from a source of benefit to one community negatively impacts nearby communities of humans and economically vital ecosystems (e.g., marshlands or tributaries). CONCLUSION/RECOMMENDATIONS: The ensuing politics and health effects of these diversions can be complicated and future water policies both domestically and internationally are lacking. To draw attention to and stimulate discussion around the lacking policy discussion domestically, herein we document existing and emerging consequences of watery scarcity in the Southwestern United States and briefly outline past and potential future policy responses. PMID:21479150

  11. Carbon isotope fractionation by thermophilic phototrophic sulfur bacteria: evidence for autotrophic growth in natural populations

    NASA Technical Reports Server (NTRS)

    Madigan, M. T.; Takigiku, R.; Lee, R. G.; Gest, H.; Hayes, J. M.

    1989-01-01

    Purple phototrophic bacteria of the genus Chromatium can grow as either photoautotrophs or photoheterotrophs. To determine the growth mode of the thermophilic Chromatium species, Chromatium tepidum, under in situ conditions, we have examined the carbon isotope fractionation patterns in laboratory cultures of this organism and in mats of C. tepidum which develop in sulfide thermal springs in Yellowstone National Park. Isotopic analysis (13C/12C) of total carbon, carotenoid pigments, and bacteriochlorophyll from photoautotrophically grown cultures of C. tepidum yielded 13C fractionation factors near -20%. Cells of C. tepidum grown on excess acetate, wherein synthesis of the Calvin cycle enzyme ribulose-1,5-bisphosphate carboxylase/oxygenase ribulose bisphosphate carboxylase) was greatly repressed, were isotopically heavier, fractionation factors of ca. -7% being observed. Fractionation factors determined by isotopic analyses of cells and pigment fractions of natural populations of C. tepidum growing in three different sulfide thermal springs in Yellowstone National Park were approximately -20%, indicating that this purple sulfur bacterium grows as a photoautotroph in nature.

  12. Population Growth and Characterization of Plant Injuries of Steneotarsonemus spinki Smiley (Acari: Tarsonemidae) on Rice.

    PubMed

    Jaimez-Ruiz, I A; Otero-Colina, G; Valdovinos-Ponce, G; Villanueva-Jiménez, J A; Vera-Graziano, J

    2015-06-01

    Rice is attacked by Steneotarsonemus spinki Smiley, a mite that has dispersed throughout many countries causing important loss on rice production. Rice plants of the variety Morelos A-92 were infested with S. spinki, and its population growth was estimated along plant development. Further, the morphological and histological injuries associated to the mite attack were characterized. The highest infestation level was obtained 13 weeks after plant infestation, with an average of 58.5 mites per plant, predominantly females. Morphological injuries were categorized from level 0 (no injuries from uninfested plants) to level 3, characterized by the highest injuries represented by blotches on the adaxial epidermis of the leaf sheath and on panicles and grains. Plants ranked within levels 0, 1, and 2 for morphological injury did not exhibit clear histological injuries, while those at level 3 exhibited histological injury characterized by destruction of cells of the adaxial epidermis, disorder, color change, and hypertrophy in the mesophyll cells, as well as color change in the abaxial epidermis. Thus, it presented a significant correlation between morphological injuries and mite density level, which can be further adopted to help the control decision-making process for this mite on rice. PMID:26013275

  13. Population Growth, Climate Change and Water Scarcity in the Southwestern United States

    PubMed Central

    Fuller, Amy C.; Harhay, Michael O.

    2011-01-01

    Problem statement In a simple economic model, water scarcity arises as a result of an imbalance between the supply of and demand for water sources. Distribution in this setting is the source of numerous conflicts globally. Approach Already, the Southwestern United States (US) suffers from annual drought and long-standing feud over natural water resources. Results Population growth in the Southwestern United States along with the continued effects of climate change (natural and anthropogenic) predicts a perpetual decline in natural water sources, such as smaller snowpacks, in the coming years. As the increasing number of communities across multiple US states that subsist off of natural water supplies face water shortages with increasing severity, further water conflict will emerge. Such conflicts become especially protracted when the diversion of water from a source of benefit to one community negatively impacts nearby communities of humans and economically vital ecosystems (e.g., marshlands or tributaries). Conclusion/Recommendations The ensuing politics and health effects of these diversions can be complicated and future water policies both domestically and internationally are lacking. To draw attention to and stimulate discussion around the lacking policy discussion domestically, herein we document existing and emerging consequences of watery scarcity in the Southwestern United States and briefly outline past and potential future policy responses. PMID:21479150

  14. The Importance of Population Growth and Regulation in Human Life History Evolution

    PubMed Central

    Baldini, Ryan

    2015-01-01

    Explaining the evolution of human life history traits remains an important challenge for evolutionary anthropologists. Progress is hindered by a poor appreciation of how demographic factors affect the action of natural selection. I review life history theory showing that the quantity maximized by selection depends on whether and how population growth is regulated. I show that the common use of R, a strategy’s expected lifetime number of offspring, as a fitness maximand is only appropriate under a strict set of conditions, which are apparently unappreciated by anthropologists. To concretely show how demography-free life history theory can lead to errors, I reanalyze an influential model of human life history evolution, which investigated the coevolution of a long lifespan and late age of maturity. I show that the model’s conclusions do not hold under simple changes to the implicitly assumed mechanism of density dependence, even when stated assumptions remain unchanged. This analysis suggests that progress in human life history theory requires better understanding of the demography of our ancestors. PMID:25830310

  15. Carbon isotope fractionation by thermophilic phototrophic sulfur bacteria: evidence for autotrophic growth in natural populations.

    PubMed Central

    Madigan, M T; Takigiku, R; Lee, R G; Gest, H; Hayes, J M

    1989-01-01

    Purple phototrophic bacteria of the genus Chromatium can grow as either photoautotrophs or photoheterotrophs. To determine the growth mode of the thermophilic Chromatium species, Chromatium tepidum, under in situ conditions, we have examined the carbon isotope fractionation patterns in laboratory cultures of this organism and in mats of C. tepidum which develop in sulfide thermal springs in Yellowstone National Park. Isotopic analysis (13C/12C) of total carbon, carotenoid pigments, and bacteriochlorophyll from photoautotrophically grown cultures of C. tepidum yielded 13C fractionation factors near -20%. Cells of C. tepidum grown on excess acetate, wherein synthesis of the Calvin cycle enzyme ribulose-1,5-bisphosphate carboxylase/oxygenase ribulose bisphosphate carboxylase) was greatly repressed, were isotopically heavier, fractionation factors of ca. -7% being observed. Fractionation factors determined by isotopic analyses of cells and pigment fractions of natural populations of C. tepidum growing in three different sulfide thermal springs in Yellowstone National Park were approximately -20%, indicating that this purple sulfur bacterium grows as a photoautotroph in nature. PMID:11536609

  16. A method for nonlinear exponential regression analysis

    NASA Technical Reports Server (NTRS)

    Junkin, B. G.

    1971-01-01

    A computer-oriented technique is presented for performing a nonlinear exponential regression analysis on decay-type experimental data. The technique involves the least squares procedure wherein the nonlinear problem is linearized by expansion in a Taylor series. A linear curve fitting procedure for determining the initial nominal estimates for the unknown exponential model parameters is included as an integral part of the technique. A correction matrix was derived and then applied to the nominal estimate to produce an improved set of model parameters. The solution cycle is repeated until some predetermined criterion is satisfied.

  17. Associations of DNA polymorphisms in growth hormone and its transcriptional regulators with growth and carcass traits in two populations of Brangus bulls.

    PubMed

    Thomas, M G; Enns, R M; Shirley, K L; Garcia, M D; Garrett, A J; Silver, G A

    2007-01-01

    Sequence polymorphisms in the growth hormone (GH) gene and its transcriptional regulators, Pit-1 and Prop-1, were evaluated for associations with growth and carcass traits in two populations of Brangus bulls Chihuahuan Desert Rangeland Research Center (CDRRC, N = 248 from 14 sires) and a cooperating breeding program (COOP, N = 186 from 34 sires). Polymorphisms were SNP mutations in intron 4 (C/T) and exon V (C/G) in GH, A/G in exon VI in Pit-1, and A/G in exon III in Prop-1. In the COOP population, bulls of Pit-1 GG genotype had a significantly greater percentage of intramuscular fat than bulls of the AA or AG genotype, and bulls of the Prop-1 AA genotype had significantly greater scrotal circumference than bulls of AG or GG genotypes at ~365 days of age. Also, heterozygous genotypes for the two GH polymorphisms appeared advantageous for traits of muscularity and adiposity in the COOP population. The heterozygous genotype of GH intron 4 SNP was associated with advantages in weight gain, scrotal circumference, and fat thickness in the CDRRC population. The two GH polymorphisms accounted for >/=27.7% of the variation in these traits in the CDRRC population; however, R(2) was <5% in the COOP population. Based on haplotype analyses the two GH SNPs appeared to be in phase; the haplotype analyses also paralleled with the genotype analyses. Polymorphisms in GH and its transcriptional regulators appear to be predictors of growth and carcass traits in Brangus bulls, particularly those with heterozygous GH genotypes. PMID:17469072

  18. Latino Population Growth, Characteristics, and Settlement Trends: Implications for Social Work Education in a Dynamic Political Climate

    ERIC Educational Resources Information Center

    Vidal de Haymes, Maria; Kilty, Keith M.

    2007-01-01

    This paper identifies a number of significant contemporary trends in the Latino population, including the striking growth of the community, new points of entry and settlement for recent immigrants, the mixed-status nature of families, and the increase in the proportion of U.S. households that speak Spanish. The implications of these trends for…

  19. Potential for population growth of the small hive beetle Aethina Tumida (Coleoptera: Nitidulidae) on diets of pollen dough and oranges

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The small hive beetle Aethina tumida Murray, is an African native that has become a serious pest of honey bees in North America and Australia. The beetle is capable of rapid population growth on pollen, honey, and bee brood. It is also capable of feeding and reproducing on various kinds of fruit, ...

  20. Mark-recapture estimates of recruitment, survivorship and population growth rates for the screwworm fly, Cochliomyia hominivorax

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Pradel model mark, release, recapture estimates of survivorship, recruitment, and the rate of density-independent population growth, are presented for eight mark-recapture studies of the screwworm Cochliomyia hominivorax from Costa Rica, totaling 19,714 released and 4,504 recaptured flies. Corrobor...

  1. Population growth of Varroa destructor (Acari: Varroidae) in commercial honey bee colonies treated with beta plant acids.

    PubMed

    DeGrandi-Hoffman, Gloria; Ahumada, Fabiana; Curry, Robert; Probasco, Gene; Schantz, Lloyd

    2014-10-01

    Varroa (Varroa destuctor Anderson and Trueman) populations in honey bee (Apis mellifera L.) colonies might be kept at low levels by well-timed miticide applications. HopGuard(®) (HG) that contains beta plant acids as the active ingredient was used to reduce mite populations. Schedules for applications of the miticide that could maintain low mite levels were tested in hives started from either package bees or splits of larger colonies. The schedules were developed based on defined parameters for efficacy of the miticide and predictions of varroa population growth generated from a mathematical model of honey bee colony-varroa population dynamics. Colonies started from package bees and treated with HG in the package only or with subsequent HG treatments in the summer had 1.2-2.1 mites per 100 bees in August. Untreated controls averaged significantly more mites than treated colonies (3.3 mites per 100 bees). By October, mite populations ranged from 6.3 to 15.0 mites per 100 bees with the lowest mite numbers in colonies treated with HG in August. HG applications in colonies started from splits in April reduced mite populations to 0.12 mites per 100 bees. In September, the treated colonies had significantly fewer mites than the untreated controls. Subsequent HG applications in September that lasted for 3 weeks reduced mite populations to levels in November that were significantly lower than in colonies that were untreated or had an HG treatment that lasted for 1 week. The model accurately predicted colony population growth and varroa levels until the fall when varroa populations measured in colonies established from package bees or splits were much greater than predicted. Possible explanations for the differences between actual and predicted mite populations are discussed. PMID:24828399

  2. The Importance of Human Ecology at the Threshold of the Next Millennium: How Can Population Growth Be Stopped?

    NASA Astrophysics Data System (ADS)

    Nentwig, W.

    Ecology is defined as the set of complex interactions between the biotic and abiotic environments. Human ecology concerns principally the population ecology "only" of Homo sapiens, but it also includes all aspects of global ecology because humans are the most important species. Human demography is characterized by a recent decline in mortality and fertility rates. These demographic transitions have largely been completed in industrialized countries, but not in the 140 developing countries. Approximately 100 countries are following the same demographic pattern as industrialized countries, however with a time delay of several generations. China has effectively reduced its population increase by means that would be unacceptable in Western democracies. Some 44 developing countries still show increasing population growth and no detectable demographic transition in birth rate. Thus one part of the world shows limited (and, in the long run, shrinking) population growth, and another continues with a strong increase. All populations are limited in their development by their sustainability by their environment, for example, food and energy resources, and the extent of pollution which the use of these resources produces. It is argued that in the case of human population the limits of sustainability have already been reached with the 6 billion humans alive today, since at least 20% of these suffer from hunger, natural resources are overexploited, and biodiversity is threatened. In the coming 200years it is more likely that the total population will substantially oscillate rather than approach the predicted 12 billion. The most important goal of human ecology should therefore be to slow population growth as far as possible.

  3. The importance of human ecology at the threshold of the next millennium: how can population growth be stopped?

    PubMed

    Nentwig, W

    1999-09-01

    Ecology is defined as the set of complex interactions between the biotic and abiotic environments. Human ecology concerns principally the population ecology "only" of Homo sapiens, but it also includes all aspects of global ecology because humans are the most important species. Human demography is characterized by a recent decline in mortality and fertility rates. These demographic transitions have largely been completed in industrialized countries, but not in the 140 developing countries. Approximately 100 countries are following the same demographic pattern as industrialized countries, however with a time delay of several generations. China has effectively reduced its population increase by means that would be unacceptable in Western democracies. Some 44 developing countries still show increasing population growth and no detectable demographic transition in birth rate. Thus one part of the world shows limited (and, in the long run, shrinking) population growth, and another continues with a strong increase. All populations are limited in their development by their sustainability by their environment, for example, food and energy resources, and the extent of pollution which the use of these resources produces. It is argued that in the case of human population the limits of sustainability have already been reached with the 6 billion humans alive today, since at least 20% of these suffer from hunger, natural resources are overexploited, and biodiversity is threatened. In the coming 200 years it is more likely that the total population will substantially oscillate rather than approach the predicted 12 billion. The most important goal of human ecology should therefore be to slow population growth as far as possible. PMID:10501689

  4. Range expansions transition from pulled to pushed waves as growth becomes more cooperative in an experimental microbial population.

    PubMed

    Gandhi, Saurabh R; Yurtsev, Eugene Anatoly; Korolev, Kirill S; Gore, Jeff

    2016-06-21

    Range expansions are becoming more frequent due to environmental changes and rare long-distance dispersal, often facilitated by anthropogenic activities. Simple models in theoretical ecology explain many emergent properties of range expansions, such as a constant expansion velocity, in terms of organism-level properties such as growth and dispersal rates. Testing these quantitative predictions in natural populations is difficult because of large environmental variability. Here, we used a controlled microbial model system to study range expansions of populations with and without intraspecific cooperativity. For noncooperative growth, the expansion dynamics were dominated by population growth at the low-density front, which pulled the expansion forward. We found these expansions to be in close quantitative agreement with the classical theory of pulled waves by Fisher [Fisher RA (1937) Ann Eugen 7(4):355-369] and Skellam [Skellam JG (1951) Biometrika 38(1-2):196-218], suitably adapted to our experimental system. However, as cooperativity increased, the expansions transitioned to being pushed, that is, controlled by growth and dispersal in the bulk as well as in the front. Given the prevalence of cooperative growth in nature, understanding the effects of cooperativity is essential to managing invading species and understanding their evolution. PMID:27185918

  5. Range expansions transition from pulled to pushed waves as growth becomes more cooperative in an experimental microbial population

    PubMed Central

    Yurtsev, Eugene Anatoly; Korolev, Kirill S.; Gore, Jeff

    2016-01-01

    Range expansions are becoming more frequent due to environmental changes and rare long-distance dispersal, often facilitated by anthropogenic activities. Simple models in theoretical ecology explain many emergent properties of range expansions, such as a constant expansion velocity, in terms of organism-level properties such as growth and dispersal rates. Testing these quantitative predictions in natural populations is difficult because of large environmental variability. Here, we used a controlled microbial model system to study range expansions of populations with and without intraspecific cooperativity. For noncooperative growth, the expansion dynamics were dominated by population growth at the low-density front, which pulled the expansion forward. We found these expansions to be in close quantitative agreement with the classical theory of pulled waves by Fisher [Fisher RA (1937) Ann Eugen 7(4):355–369] and Skellam [Skellam JG (1951) Biometrika 38(1-2):196–218], suitably adapted to our experimental system. However, as cooperativity increased, the expansions transitioned to being pushed, that is, controlled by growth and dispersal in the bulk as well as in the front. Given the prevalence of cooperative growth in nature, understanding the effects of cooperativity is essential to managing invading species and understanding their evolution. PMID:27185918

  6. Population mixture model for nonlinear telomere dynamics

    NASA Astrophysics Data System (ADS)

    Itzkovitz, Shalev; Shlush, Liran I.; Gluck, Dan; Skorecki, Karl

    2008-12-01

    Telomeres are DNA repeats protecting chromosomal ends which shorten with each cell division, eventually leading to cessation of cell growth. We present a population mixture model that predicts an exponential decrease in telomere length with time. We analytically solve the dynamics of the telomere length distribution. The model provides an excellent fit to available telomere data and accounts for the previously unexplained observation of telomere elongation following stress and bone marrow transplantation, thereby providing insight into the nature of the telomere clock.

  7. Intersection of the Exponential and Logarithmic Curves

    ERIC Educational Resources Information Center

    Boukas, Andreas; Valahas, Theodoros

    2009-01-01

    The study of the number of intersection points of y = a[superscript x] and y = log[subscript a]x can be an interesting topic to present in a single-variable calculus class. In this article, the authors present a classroom presentation outline involving the basic algebra and the elementary calculus of the exponential and logarithmic functions. The…

  8. Graphical Models via Univariate Exponential Family Distributions

    PubMed Central

    Yang, Eunho; Ravikumar, Pradeep; Allen, Genevera I.; Liu, Zhandong

    2016-01-01

    Undirected graphical models, or Markov networks, are a popular class of statistical models, used in a wide variety of applications. Popular instances of this class include Gaussian graphical models and Ising models. In many settings, however, it might not be clear which subclass of graphical models to use, particularly for non-Gaussian and non-categorical data. In this paper, we consider a general sub-class of graphical models where the node-wise conditional distributions arise from exponential families. This allows us to derive multivariate graphical model distributions from univariate exponential family distributions, such as the Poisson, negative binomial, and exponential distributions. Our key contributions include a class of M-estimators to fit these graphical model distributions; and rigorous statistical analysis showing that these M-estimators recover the true graphical model structure exactly, with high probability. We provide examples of genomic and proteomic networks learned via instances of our class of graphical models derived from Poisson and exponential distributions. PMID:27570498

  9. Exponential asymptotics of the Voigt functions

    NASA Astrophysics Data System (ADS)

    Paris, R. B.

    2015-06-01

    We obtain the asymptotic expansion of the Voigt functionss K( x, y) and L( x, y) for large (real) values of the variables x and y, paying particular attention to the exponentially small contributions. A Stokes phenomenon is encountered as with x > 0 fixed. Numerical examples are presented to demonstrate the accuracy of these new expansions.

  10. Kovalevskaya exponents of systems with exponential interaction

    SciTech Connect

    Emel'yanov, K V; Tsygvintsev, A V

    2000-10-31

    The Kovalevskaya exponents are calculated for a class of systems generalizing Toda chains: systems with exponential interaction. It is shown that the known cases of algebraic integrability have no direct analogues in the case of spaces with pseudo-Euclidean metrics because the full-parameter expansions of the general solution contain complex powers of the independent variable.

  11. Kovalevskaya exponents of systems with exponential interaction

    NASA Astrophysics Data System (ADS)

    Emel'yanov, K. V.; Tsygvintsev, A. V.

    2000-10-01

    The Kovalevskaya exponents are calculated for a class of systems generalizing Toda chains: systems with exponential interaction. It is shown that the known cases of algebraic integrability have no direct analogues in the case of spaces with pseudo-Euclidean metrics because the full-parameter expansions of the general solution contain complex powers of the independent variable.

  12. An evaluation of density-dependent and density-independent influences on population growth rates in Weddell seals.

    PubMed

    Rotella, Jay J; Link, William A; Nichols, James D; Hadley, Gillian L; Garrott, Robert A; Proffitt, Kelly M

    2009-04-01

    Much of the existing literature that evaluates the roles of density-dependent and density-independent factors on population dynamics has been called into question in recent years because measurement errors were not properly dealt with in analyses. Using state-space models to account for measurement errors, we evaluated a set of competing models for a 22-year time series of mark-resight estimates of abundance for a breeding population of female Weddell seals (Leptonychotes weddellii) studied in Erebus Bay, Antarctica. We tested for evidence of direct density dependence in growth rates and evaluated whether equilibrium population size was related to seasonal sea-ice extent and the Southern Oscillation Index (SOI). We found strong evidence of negative density dependence in annual growth rates for a population whose estimated size ranged from 438 to 623 females during the study. Based on Bayes factors, a density-dependence-only model was favored over models that also included environmental covariates. According to the favored model, the population had a stationary distribution with a mean of 497 females (SD = 60.5), an expected growth rate of 1.10 (95% credible interval = 1.08-1.15) when population size was 441 females, and a rate of 0.90 (95% credible interval = 0.87-.93) for a population of 553 females. A model including effects of SOI did receive some support and indicated a positive relationship between SOI and population size. However, effects of SOI were not large, and including the effect did not greatly reduce our estimate of process variation. We speculate that direct density dependence occurred because rates of adult survival, breeding, and temporary emigration were affected by limitations on per capita food resources and space for parturition and pup-rearing. To improve understanding of the relative roles of various demographic components and their associated vital rates to population growth rate, mark-recapture methods can be applied that incorporate both

  13. An evaluation of density-dependent and density-independent influences on population growth rates in Weddell seals

    USGS Publications Warehouse

    Rotella, J.J.; Link, W.A.; Nichols, J.D.; Hadley, G.L.; Garrott, R.A.; Proffitt, K.M.

    2009-01-01

    Much of the existing literature that evaluates the roles of density-dependent and density-independent factors on population dynamics has been called into question in recent years because measurement errors were not properly dealt with in analyses. Using state-space models to account for measurement errors, we evaluated a set of competing models for a 22-year time series of mark-resight estimates of abundance for a breeding population of female Weddell seals (Leptonychotes weddellii) studied in Erebus Bay, Antarctica. We tested for evidence of direct density dependence in growth rates and evaluated whether equilibrium population size was related to seasonal sea-ice extent and the Southern Oscillation Index (SOI). We found strong evidence of negative density dependence in annual growth rates for a population whose estimated size ranged from 438 to 623 females during the study. Based on Bayes factors, a density-dependence-only model was favored over models that also included en! vironmental covariates. According to the favored model, the population had a stationary distribution with a mean of 497 females (SD = 60.5), an expected growth rate of 1.10 (95% credible interval 1.08-1.15) when population size was 441 females, and a rate of 0.90 (95% credible interval 0.87-0.93) for a population of 553 females. A model including effects of SOI did receive some support and indicated a positive relationship between SOI and population size. However, effects of SOI were not large, and including the effect did not greatly reduce our estimate of process variation. We speculate that direct density dependence occurred because rates of adult survival, breeding, and temporary emigration were affected by limitations on per capita food resources and space for parturition and pup-rearing. To improve understanding of the relative roles of various demographic components and their associated vital rates to population growth rate, mark-recapture methods can be applied that incorporate both

  14. Variation in freshwater growth and development among five New England Atlantic salmon (Salmo salar) populations reared in a common environment

    USGS Publications Warehouse

    Obedzinski, M.; Letcher, B.H.

    2004-01-01

    We examined phenotypic variation in growth and development from the eyed-egg stage to the age-1+ smolt stage among five New England populations of Atlantic salmon (Salmo salar: East Machias, Narraguagus, Sheepscot, Penobscot, Connecticut) reared in a common laboratory environment. Study populations originated from rivers varying in size, latitude, and level of hatchery supplementation and included one reintroduced population (Connecticut was a recipient of Penobscot origin stock). Phenotypic trait differences were found among populations, and the degree of stock variation depended on ontogeny. Eggs were smaller and hatched sooner in the Penobscot (a northern, intensively managed population), but no stock differences were detected in size or growth efficiency from the onset of exogenous feeding to age 0+ summer. Differences again emerged in age 0+ autumn, with the degree of bimodality in length-frequency distributions differing among stocks; the Connecticut had the highest proportion of upper-mode fish and, ultimately, age-1+ smolts. Although genetic effects could not be entirely separated from maternal effects for egg size variation, it is likely that differences in hatch timing and smolt age had a genetic basis. Early emphasis on age-1+ hatchery-reared smolts in the Connecticut may have led to divergence in smolt age between the Penobscot and Connecticut populations in less than eight generations. ?? 2004 NRC Canada.

  15. Long-Term Data Reveal a Population Decline of the Tropical Lizard Anolis apletophallus, and a Negative Affect of El Nino Years on Population Growth Rate

    PubMed Central

    Stapley, Jessica; Garcia, Milton; Andrews, Robin M.

    2015-01-01

    Climate change threatens biodiversity worldwide, however predicting how particular species will respond is difficult because climate varies spatially, complex factors regulate population abundance, and species vary in their susceptibility to climate change. Studies need to incorporate these factors with long-term data in order to link climate change to population abundance. We used 40 years of lizard abundance data and local climate data from Barro Colorado Island to ask how climate, total lizard abundance and cohort-specific abundance have changed over time, and how total and cohort-specific abundance relate to climate variables including those predicted to make the species vulnerable to climate change (i.e. temperatures exceeding preferred body temperature). We documented a decrease in lizard abundance over the last 40 years, and changes in the local climate. Population growth rate was related to the previous years’ southern oscillation index; increasing following cooler-wetter, la niña years, decreasing following warmer-drier, el nino years. Within-year recruitment was negatively related to rainfall and minimum temperature. This study simultaneously identified climatic factors driving long-term population fluctuations and climate variables influencing short-term annual recruitment, both of which may be contributing to the population decline and influence the population’s future persistence. PMID:25671423

  16. Influence of volcanic activity on the population genetic structure of Hawaiian Tetragnatha spiders: Fragmentation, rapid population growth and the potential for accelerated evolution

    USGS Publications Warehouse

    Vandergast, A.G.; Gillespie, R.G.; Roderick, G.K.

    2004-01-01

    Volcanic activity on the island of Hawaii results in a cyclical pattern of habitat destruction and fragmentation by lava, followed by habitat regeneration on newly formed substrates. While this pattern has been hypothesized to promote the diversification of Hawaiian lineages, there have been few attempts to link geological processes to measurable changes in population structure. We investigated the genetic structure of three species of Hawaiian spiders in forests fragmented by a 150-year-old lava flow on Mauna Loa Volcano, island of Hawaii: Tetragnatha quasimodo (forest and lava flow generalist), T. anuenue and T. brevignatha (forest specialists). To estimate fragmentation effects on population subdivision in each species, we examined variation in mitochondrial and nuclear genomes (DNA sequences and allozymes, respectively). Population subdivision was higher for forest specialists than for the generalist in fragments separated by lava. Patterns of mtDNA sequence evolution also revealed that forest specialists have undergone rapid expansion, while the generalist has experienced more gradual population growth. Results confirm that patterns of neutral genetic variation reflect patterns of volcanic activity in some Tetragnatha species. Our study further suggests that population subdivision and expansion can occur across small spatial and temporal scales, which may facilitate the rapid spread of new character states, leading to speciation as hypothesized by H. L. Carson 30 years ago.

  17. Influence of volcanic activity on the population genetic structure of Hawaiian Tetragnatha spiders: fragmentation, rapid population growth and the potential for accelerated evolution.

    PubMed

    Vandergast, Amy G; Gillespie, Rosemary G; Roderick, George K

    2004-07-01

    Volcanic activity on the island of Hawaii results in a cyclical pattern of habitat destruction and fragmentation by lava, followed by habitat regeneration on newly formed substrates. While this pattern has been hypothesized to promote the diversification of Hawaiian lineages, there have been few attempts to link geological processes to measurable changes in population structure. We investigated the genetic structure of three species of Hawaiian spiders in forests fragmented by a 150-year-old lava flow on Mauna Loa Volcano, island of Hawaii: Tetragnatha quasimodo (forest and lava flow generalist), T. anuenue and T. brevignatha (forest specialists). To estimate fragmentation effects on population subdivision in each species, we examined variation in mitochondrial and nuclear genomes (DNA sequences and allozymes, respectively). Population subdivision was higher for forest specialists than for the generalist in fragments separated by lava. Patterns of mtDNA sequence evolution also revealed that forest specialists have undergone rapid expansion, while the generalist has experienced more gradual population growth. Results confirm that patterns of neutral genetic variation reflect patterns of volcanic activity in some Tetragnatha species. Our study further suggests that population subdivision and expansion can occur across small spatial and temporal scales, which may facilitate the rapid spread of new character states, leading to speciation as hypothesized by H. L. Carson 30 years ago. PMID:15189199

  18. Towards lag phase of microbial populations at growth-limiting conditions: The role of the variability in the growth limits of individual cells.

    PubMed

    Aguirre, Juan S; Koutsoumanis, Konstantinos P

    2016-05-01

    The water activity (aw) growth limits of unheated and heat stressed Listeria monocytogenes individual cells were studied. The aw limits varied from 0.940 to 0.997 and 0.951 to 0.997 for unheated and heat stressed cells, respectively. Due to the above variability a decrease in aw results in the presence of a non-growing fraction in the population leading to an additional pseudo-lag in population growth. In this case the total apparent lag of the population is the sum of the physiological lag of the growing cells (time required to adjust to the new environment) and the pseudo-lag. To investigate the effect of aw on the above lag components, the growth kinetics of L. monocytogenes on tryptone soy agar with aw adjusted to values ranging from 0.997 to 0.940 was monitored. The model of B&R was fitted to the data for the estimation of the apparent lag. In order to estimate the physiological lag of the growing fraction of the inoculum, the model was refitted to the growth data using as initial population level the number of cells that were able to grow (estimated from the number of colonies formed on the agar at the end of storage) and excluding the rest data during the lag. The results showed that for the unheated cells the apparent lag was almost identical to the physiological lag for aw values ranging from 0.997 to 0.970, as the majority of the cells in the initial population was able to grow in these conditions. As the aw decreased from 0.970 to 0.940 however, the number of cells in the population which were able to grow, decreased resulting to an increase in the pseudo-lag. The maximum value of pseudo-lag was 13.1h and it was observed at aw=0.940 where 10% of the total inoculated cells were able to grow. For heat stressed populations a pseudo-lag started to increase at higher aw conditions (0.982) compared to unheated cells. In contrast to the apparent lag, a linear relation between physiological lag and aw was observed for both unheated and heat stressed cells. PMID

  19. Linking temporal changes in the demographic structure and individual growth to the decline in the population of a tropical fish

    NASA Astrophysics Data System (ADS)

    Sirot, Charlotte; Darnaude, Audrey M.; Guilhaumon, François; Ramos-Miranda, Julia; Flores-Hernandez, Domingo; Panfili, Jacques

    2015-11-01

    The exceptional biodiversity and productivity of tropical coastal lagoons can only be preserved by identifying the causes for the decline in the populations living in these vulnerable ecosystems. The Terminos lagoon in Mexico provided an opportunity for studying this issue as some of its fish populations, in particular the Silver Perch (Bairdiella chrysoura), have declined significantly since the 1980s. Fish sampling campaigns carried out over the whole lagoon area in 1979-81 and again in 2006-2011 revealed the mechanisms which may have been responsible for this decline. Based on biometrical data for 295 juveniles and adults from the two periods and on somatic growth derived from 173 otoliths, a study of the temporal changes in the demographic structure and life history traits (individual growth and body condition) made it possible to distinguish the causes of the decline in the B. chrysoura population. Growth models for the lagoon in 1980-1981 and 2006-2011 showed no significant change in the growth parameters of the population over the last 30 years with a logistic model giving an accurate estimate (R2 = 0.66) of the size-at-age for both periods. The decline in the B. chrysoura population could not be explained by an overall decrease in individual size and condition in the lagoon, the average standard length (SL) and Fulton index (FI) having increased slightly since 1980-1981 (4.6 mm and 0.02 for juveniles and 5.42 mm and 0.07 for adults). However, the size structure of the population in the lagoon has changed, with a significant shift in the size distribution of juveniles with a marked reduction in the proportion of juveniles ≤ 60 mm in the captures (90.9% fewer than in 1980-1981). As the otolith growth rate of fish during the first 4 months also decreased significantly between the two sampling periods (-15%), it is suggested that the main reason for the decline in the abundance and biomass of B. chrysoura within this system may be that its habitats are less

  20. The interaction between the spatial distribution of resource patches and population density: consequences for intraspecific growth and morphology.

    PubMed

    Jacobson, Bailey; Grant, James W A; Peres-Neto, Pedro R

    2015-07-01

    How individuals within a population distribute themselves across resource patches of varying quality has been an important focus of ecological theory. The ideal free distribution predicts equal fitness amongst individuals in a 1 : 1 ratio with resources, whereas resource defence theory predicts different degrees of monopolization (fitness variance) as a function of temporal and spatial resource clumping and population density. One overlooked landscape characteristic is the spatial distribution of resource patches, altering the equitability of resource accessibility and thereby the effective number of competitors. While much work has investigated the influence of morphology on competitive ability for different resource types, less is known regarding the phenotypic characteristics conferring relative ability for a single resource type, particularly when exploitative competition predominates. Here we used young-of-the-year rainbow trout (Oncorhynchus mykiss) to test whether and how the spatial distribution of resource patches and population density interact to influence the level and variance of individual growth, as well as if functional morphology relates to competitive ability. Feeding trials were conducted within stream channels under three spatial distributions of nine resource patches (distributed, semi-clumped and clumped) at two density levels (9 and 27 individuals). Average trial growth was greater in high-density treatments with no effect of resource distribution. Within-trial growth variance had opposite patterns across resource distributions. Here, variance decreased at low-population, but increased at high-population densities as patches became increasingly clumped as the result of changes in the levels of interference vs. exploitative competition. Within-trial growth was related to both pre- and post-trial morphology where competitive individuals were those with traits associated with swimming capacity and efficiency: larger heads/bodies/caudal fins