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1

Modeling Exponential Population Growth  

ERIC Educational Resources Information Center

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…

McCormick, Bonnie

2009-01-01

2

Population Growth - Exponential and Logistic Models vs. Complex Reality  

NSDL National Science Digital Library

This analysis and discussion activity is designed to help students develop an intuitive understanding of the exponential and logistic models of population growth, including the biological processes that result in exponential or logistic population growth. Students learn about the simplifying assumptions built into the exponential and logistic models and explore how deviations from these assumptions can result in discrepancies between the predictions of these models and actual trends in population size for natural populations. This activity is designed to help high school students meet the Next Generation Science Standards and the Common Core State Standards.

Waldron, Ingrid

3

Necessary and Sufficient Conditions for Asynchronous Exponential Growth in Age Structured Cell Populations with Quiescence  

Microsoft Academic Search

A linear model on age structured cell population is analyzed. The population is divided into proliferating and quiescent compartments. Necessary and sufficient conditions are established for the population to exhibit the asymptotic behavior of asynchronous exponential growth. The model is analyzed as a semigroup of linear operators which is shown to be eventually compact and irreducible.

O. Arino; E. Sánchez; G. F. Webb

1997-01-01

4

A Precalculus Project on Exponential Population Growth and Linear Food Production.  

ERIC Educational Resources Information Center

Discusses a precalculus project in which students create a model United Nations to present and discuss the long-term prognosis for individual countries given data on population growth and food production. Students compare exponential and linear functions to determine whether starvation will occur and prepare oral and written presentations of their…

McDonald, Michael A.; And Others

1996-01-01

5

Modeling the pre-industrial roots of modern super-exponential population growth.  

PubMed

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 intergenerational resource transfers to wider institutions and social networks. PMID:25141019

Stutz, Aaron Jonas

2014-01-01

6

Universality in Stochastic Exponential Growth  

NASA Astrophysics Data System (ADS)

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.

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

2014-07-01

7

Universality in stochastic exponential growth.  

PubMed

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

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

2014-07-11

8

Universality in stochastic exponential growth  

E-print Network

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.

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

2014-07-10

9

An exponential growth model with decreasing r captures bottom-up effects on the population growth of Aphis glycines Matsumura (Hemiptera: Aphididae)  

Microsoft Academic Search

1 There is ample evidence that the life history and population dynamics of aphids are closely linked to plant phenology. Based on life table studies, it has been proposed that the growth of aphid populations could be modeled with an exponential growth model, with r decreasing linearly with time. This model has never been tested under field conditions. 2 The

A. C. Costamagna; W. van der Werf; F. J. J. A. Bianchi; D. A. Landis

2007-01-01

10

A Simulation To Model Exponential Growth.  

ERIC Educational Resources Information Center

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)

Appelbaum, Elizabeth Berman

2000-01-01

11

A PRECALCULUS PROJECT ON EXPONENTIAL POPULATION GROWTH AND LINEAR FOOD PRODUCTION  

Microsoft Academic Search

We present a precalculus project based on a quote by Thomas Malthus—that population increases in a geometric ratio while sustenance increases only in an arithmetic ratio. A model United Nations is created to present and discuss the long term prognosis for individual countries given data on population growth and food production. Student groups, representing various nations, are asked to use

Michael A. McDonald; Emily Puckette; Charles Vuono

1996-01-01

12

Population Explosion Using an Exponential Function  

NSDL National Science Digital Library

This intermediate algebra lesson has students use data from the U.S. Census Bureau's website to explore population growth and exponential functions. The learning object demonstrates how these mathematical functions can be used in a real world situation. Student materials, which include a continuous change model worksheet and a constant rate growth model worksheet, can be found here (the fourth row, second column of the table).

2011-01-05

13

Simulating Population Growth.  

ERIC Educational Resources Information Center

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)

Byington, Scott

1997-01-01

14

Population Growth  

NSDL National Science Digital Library

This series of activities explores the mathematical and environmental aspects of population growth. Using archived census and demographic data as well as up-to-the-minute population estimates from the U.S. Census Bureau, students learn how to model population growth and study the implications of a changing population. The project provides instructions, activities, back-up information, data links, reference materials, on-line help, and an instructor guide. Although intended for high school students, activities 1 through 5 and 9 avoid higher mathematics and offer students work on statistical and historical aspects of population growth appropriate for the middle school level. This on-line project is part of the Center for Improved Engineering and Science Education (CIESE) program, which has developed internet activities for the elementary, middle, and high school level student.

2007-12-12

15

A Learning Cycle on Exponential Growth and the Energy Crises.  

ERIC Educational Resources Information Center

Describes nature and logistics of a learning cycle approach to teaching exponential growth and the energy crisis. Used with both science and nonscience majors, the cycle uses no algebra, never mentions the terms exponential or logarithmic, and requires a calculator. Instructions for obtaining student and instructor materials are provided.…

Dykstra, D. I., Jr.

1982-01-01

16

POPULATION GENETICS OF NEUTRAL MUTATIONS IN EXPONENTIALLY GROWING CANCER CELL POPULATIONS  

PubMed Central

In order to analyze data from cancer genome sequencing projects, we need to be able to distinguish causative, or “driver,” mutations from “passenger” mutations that have no selective effect. Toward this end, we prove results concerning the frequency of neutural mutations in exponentially growing multitype branching processes that have been widely used in cancer modeling. Our results yield a simple new population genetics result for the site frequency spectrum of a sample from an exponentially growing population. PMID:23471293

DURRETT, RICK

2013-01-01

17

Prion Disease: Exponential Growth Requires Membrane Binding Daniel L. Cox,*y  

E-print Network

Prion Disease: Exponential Growth Requires Membrane Binding Daniel L. Cox,*y Rajiv R. P. Sing A hallmark feature of prions, whether in mammals or yeast and fungi, is exponential growth associated that the membrane is necessary for exponential growth of prion aggregates; without it, the kinetics is simply

Yang, Sichun

18

Exponential energy growth in adiabatically changing Hamiltonian Systems  

E-print Network

Fermi acceleration is the process of energy transfer from massive objects in slow motion to light objects that move fast. The model for such process is a time-dependent Hamiltonian system. As the parameters of the system change with time, the energy is no longer conserved, which makes the acceleration possible. One of the main problems is how to generate a sustained and robust energy growth. We show that the non-ergodicity of any chaotic Hamiltonian system must universally lead to the exponential growth of energy at a slow periodic variation of parameters. We build a model for this process in terms of a Geometric Brownian Motion with a positive drift, and relate it to the entropy increase.

Tiago Pereira; Dmitry Turaev

2014-10-07

19

Population growth (annual %)  

NSDL National Science Digital Library

Data set and map pertaining to population growth for all countries as an annual percentage. The World Bank specifies population growth as a World Development Indicator (WDI) -- the statistical benchmark that helps measure the progress of development.

Bank, World

20

[Population Growth and Development].  

ERIC Educational Resources Information Center

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…

Clausen, A. W.

21

Impact of Population Growth  

ERIC Educational Resources Information Center

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.…

Ehrlich, Paul R.; Holdren, John P.

1971-01-01

22

World Population Growth  

NSDL National Science Digital Library

Created by Lang Moore and David Smith for the Connected Curriculum Project, this is a module to study the historical data on human population growth, and to compare the "natural" and "coalition" differential equation models as possible descriptions of the growth pattern. This is one within a much larger set of learning modules hosted by Duke University.

Moore, Lang; Smith, David

2010-05-21

23

World Population Growth  

NSDL National Science Digital Library

Created by Lang Moore and David Smith for the Connected Curriculum Project, the purpose of this module is to study the historical data on human population growth, and to compare the "natural" and "coalition" differential equation models as possible descriptions of the growth pattern. This is one within a much larger set of learning modules hosted by Duke University.

Moore, Lang; Smith, David

2010-05-26

24

Population growth and consumption.  

PubMed

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

Chalkley, K

1997-04-01

25

The role of multiple modeling perspectives in students' learning of exponential growth.  

PubMed

The exponential is among the most important family functions in mathematics; the foundation for the solution of linear differential equations, linear difference equations, and stochastic processes. However there is little research and superficial agreement on how the concepts of exponential growth are learned and/or should be taught initially. In order to investigate these issues, I preformed a teaching experiment with two high school students, which focused on building understandings of exponential growth leading up to the (nonlinear) logistic differential equation model. In this paper, I highlight some of the ways of thinking used by participants in this teaching experiment. From these results I discuss how mathematicians using exponential growth routinely make use of multiple--sometimes contradictory--ways of thinking, as well as the danger that these multiple ways of thinking are not being made distinct to students. PMID:24245624

Castillo-Garsow, Carlos

2013-01-01

26

Global population growth.  

PubMed

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. PMID:12179437

Langmore, J

1992-07-01

27

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

NASA Technical Reports Server (NTRS)

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.

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

2002-01-01

28

Exponential growth rates in a typed branching diffusion  

Microsoft Academic Search

We study the high temperature phase of a family of typed branching diffusions initially studied in [Astérisque 236 (1996) 133–154] and [Lecture Notes in Math. 1729 (2000) 239–256 Springer, Berlin]. The primary aim is to establish some almost-sure limit results for the long-term behavior of this particle system, namely the speed at which the population of particles colonizes both space

J. W. Harris; S. C. Harris

2007-01-01

29

Weak extinction versus global exponential growth of total mass for superdiffusions  

E-print Network

Weak extinction versus global exponential growth of total mass for superdiffusions J´anos Engl of local growth when it is positive, and implies local extinction otherwise. It is easy to show that 2 a sufficient and necessary condition for the superdiffusion X to exhibit weak extinction. We show

Song, Renming

30

Reduced Heme Levels Underlie the Exponential Growth Defect of the Shewanella oneidensis hfq Mutant  

PubMed Central

The RNA chaperone Hfq fulfills important roles in small regulatory RNA (sRNA) function in many bacteria. Loss of Hfq in the dissimilatory metal reducing bacterium Shewanella oneidensis strain MR-1 results in slow exponential phase growth and a reduced terminal cell density at stationary phase. We have found that the exponential phase growth defect of the hfq mutant in LB is the result of reduced heme levels. Both heme levels and exponential phase growth of the hfq mutant can be completely restored by supplementing LB medium with 5-aminolevulinic acid (5-ALA), the first committed intermediate synthesized during heme synthesis. Increasing expression of gtrA, which encodes the enzyme that catalyzes the first step in heme biosynthesis, also restores heme levels and exponential phase growth of the hfq mutant. Taken together, our data indicate that reduced heme levels are responsible for the exponential growth defect of the S. oneidensis hfq mutant in LB medium and suggest that the S. oneidensis hfq mutant is deficient in heme production at the 5-ALA synthesis step. PMID:25356668

Mezoian, Taylor; Hunt, Taylor M.; Keane, Meaghan L.; Leonard, Jessica N.; Scola, Shelby E.; Beer, Emma N.; Perdue, Sarah; Pellock, Brett J.

2014-01-01

31

Laws of population growth  

PubMed Central

An important issue in the study of cities is defining a metropolitan area, because different definitions affect conclusions regarding the statistical distribution of urban activity. A commonly employed method of defining a metropolitan area is the Metropolitan Statistical Areas (MSAs), based on rules attempting to capture the notion of city as a functional economic region, and it is performed by using experience. The construction of MSAs is a time-consuming process and is typically done only for a subset (a few hundreds) of the most highly populated cities. Here, we introduce a method to designate metropolitan areas, denoted “City Clustering Algorithm” (CCA). The CCA is based on spatial distributions of the population at a fine geographic scale, defining a city beyond the scope of its administrative boundaries. We use the CCA to examine Gibrat's law of proportional growth, which postulates that the mean and standard deviation of the growth rate of cities are constant, independent of city size. We find that the mean growth rate of a cluster by utilizing the CCA exhibits deviations from Gibrat's law, and that the standard deviation decreases as a power law with respect to the city size. The CCA allows for the study of the underlying process leading to these deviations, which are shown to arise from the existence of long-range spatial correlations in population growth. These results have sociopolitical implications, for example, for the location of new economic development in cities of varied size. PMID:19033186

Rozenfeld, Hernán D.; Rybski, Diego; Andrade, José S.; Batty, Michael; Stanley, H. Eugene; Makse, Hernán A.

2008-01-01

32

Laws of population growth.  

PubMed

An important issue in the study of cities is defining a metropolitan area, because different definitions affect conclusions regarding the statistical distribution of urban activity. A commonly employed method of defining a metropolitan area is the Metropolitan Statistical Areas (MSAs), based on rules attempting to capture the notion of city as a functional economic region, and it is performed by using experience. The construction of MSAs is a time-consuming process and is typically done only for a subset (a few hundreds) of the most highly populated cities. Here, we introduce a method to designate metropolitan areas, denoted "City Clustering Algorithm" (CCA). The CCA is based on spatial distributions of the population at a fine geographic scale, defining a city beyond the scope of its administrative boundaries. We use the CCA to examine Gibrat's law of proportional growth, which postulates that the mean and standard deviation of the growth rate of cities are constant, independent of city size. We find that the mean growth rate of a cluster by utilizing the CCA exhibits deviations from Gibrat's law, and that the standard deviation decreases as a power law with respect to the city size. The CCA allows for the study of the underlying process leading to these deviations, which are shown to arise from the existence of long-range spatial correlations in population growth. These results have sociopolitical implications, for example, for the location of new economic development in cities of varied size. PMID:19033186

Rozenfeld, Hernán D; Rybski, Diego; Andrade, José S; Batty, Michael; Stanley, H Eugene; Makse, Hernán A

2008-12-01

33

Population Growth: Experimental Models Using Duckweed (Lemna spp.)  

NSDL National Science Digital Library

Experiment 1, "Dynamics of population growth: exponential and logistic growth" examines continuous population growth by growing duckweeds (Lemna spp.) Experiment 2, "Resource limitation and population growth" examines the conditions that result in maximum population growth of Lemna by manipulating the resources that limit growth including nutrients, light, and surface area. Experiment 3, "Population growth and resource competition in Lemna minor and Spirodela polyrhiza", studies the population growth and competition of two species of floating aquatic plants. In Part A the growth of lab populations of Lemna minor and Sprirodela polyrhiza grown alone and in mixed cultures are monitored. In Part B the magnitude of interaction is explored by growing monocultures and mixed cultures under conditions of two nutrient concentrations and two levels of light intensity.

Jefferies, R. L.

2010-02-16

34

The Population Genetic Structure of Clonal Organisms Generated by Exponentially Bounded and Fat-Tailed Dispersal  

PubMed Central

Long-distance dispersal (LDD) plays an important role in many population processes like colonization, range expansion, and epidemics. LDD of small particles like fungal spores is often a result of turbulent wind dispersal and is best described by functions with power-law behavior in the tails (“fat tailed”). The influence of fat-tailed LDD on population genetic structure is reported in this article. In computer simulations, the population structure generated by power-law dispersal with exponents in the range of ?2 to ?1, in distinct contrast to that generated by exponential dispersal, has a fractal structure. As the power-law exponent becomes smaller, the distribution of individual genotypes becomes more self-similar at different scales. Common statistics like GST are not well suited to summarizing differences between the population genetic structures. Instead, fractal and self-similarity statistics demonstrated differences in structure arising from fat-tailed and exponential dispersal. When dispersal is fat tailed, a log–log plot of the Simpson index against distance between subpopulations has an approximately constant gradient over a large range of spatial scales. The fractal dimension D2 is linearly inversely related to the power-law exponent, with a slope of ? ?2. In a large simulation arena, fat-tailed LDD allows colonization of the entire space by all genotypes whereas exponentially bounded dispersal eventually confines all descendants of a single clonal lineage to a relatively small area. PMID:17660543

Wingen, Luzie U.; Brown, James K. M.; Shaw, Michael W.

2007-01-01

35

Abstract Despite the exponential growth in heart rate variability (HRV) research, the reproducibility  

E-print Network

Abstract Despite the exponential growth in heart rate variability (HRV) research. The mean heart rate was more reproducible and could be more accu- rately estimated from very short segments be estimated accurately from short segments (Heart rate variability (HRV) Ã? Interbeat

36

U.S. Population Growth: What Does the Future Hold?  

NSDL National Science Digital Library

College Algebra or Liberal Arts math students are presented with a ConcepTest, a Question of the Day and a write-pair-share activity involving U.S. population growth. The results are quite revealing and show that while students may have learned how to perform the necessary calculations, their conceptual understanding concerning exponential growth may remain faulty. Student knowledge (or lack thereof) of the size of our population and its annual growth rate may also be surprising.

Rutledge, James J.

37

Population Growth, Technology, and the Environment  

NSDL National Science Digital Library

Overview: This Science Object is the second of four Science Objects in the Resources and Human Impact SciPack. It explores how technology can solve problems, but at the same time, can also create new strains on the environment. Improved technology used for harvesting food, coupled with the technology of improved sanitation, has accelerated the growth of the human population. A larger human population increases the impact on the environment and its resources, many of which are limited and non renewable. Due to the rapid growth of the human population and their use of technology in many parts of the world, humans have exceeded the carrying capacity of their environment, compromising human health. Learning Outcomes: Identify, compare, and contrast principles of population growth in humans and other organisms. Explain the limiting factors on the exponential growth of a population (for example: disease, competition for resources). Analyze how technology (antibiotics, harvesting food) has impacted human population growth in an ecosystem (for example: agriculture, aquaculture).

National Science Teachers Association (NSTA)

2008-09-30

38

Differential Expression of Virulence Genes and Motility in Ralstonia (Pseudomonas) solanacearum during Exponential Growth  

PubMed Central

A complex network regulates virulence in Ralstonia solanacearum (formerly Pseudomonas solanacearum); central to this system is PhcA, a LysR-type transcriptional regulator. We report here that two PhcA-regulated virulence factors, endoglucanase (Egl) and acidic exopolysaccharide I (EPS I), and motility are expressed differentially during exponential growth in batch cultures. Tests with strains carrying lacZ fusions in a wild-type genetic background revealed that expression (on a per-cell basis) of phcA was constant but expression of egl and epsB increased 20- to 50-fold during multiplication from 1 x 10(sup7) to 5 x 10(sup8) CFU/ml. Expression of xpsR, an intermediate regulator downstream of PhcA in the regulatory cascade for eps expression, was similar to that of epsB and egl. Motility track photography revealed that all strains were essentially nonmotile at 10(sup6) CFU/ml. As cell density increased, 30 to 50% of wild-type cells were motile between 10(sup7) and 10(sup8) CFU/ml, but this population was again nonmotile at 10(sup9) CFU/ml. In contrast, about 60% of the cells of phcB and phcA mutants remained motile at 10(sup9) CFU/ml. Expression of phcB, which is not positively regulated by PhcA, was the inverse of epsB, egl, and xpsR (i.e., it decreased 20-fold at high cell density). PhcB is essential for production of an extracellular factor, tentatively identified as 3-hydroxypalmitic acid methyl ester (3-OH PAME), that might act as an exponential-phase signal to activate motility or expression of virulence genes. However, growth of the lacZ fusion strains in medium containing excess 3-OH PAME did not result in motility or expression of virulence genes at dramatically lower cell densities, suggesting that 3-OH PAME is not the only factor controlling these traits. PMID:16535550

Clough, S. J.; Flavier, A. B.; Schell, M. A.; Denny, T. P.

1997-01-01

39

Population growth and global security  

Microsoft Academic Search

A new threat to international and domestic security has emerged in the past three decades: uncontrolled world population growth. Current world population growth control efforts are ineffective. Unchecked growth will threaten global security by depleting food, energy, and other resources. Immigration is another complicating factor that is straining the carrying capacity of some overpopulated regions. Barriers to effective action include

Mumford

2009-01-01

40

Population Growth: Crisis and Challenge.  

ERIC Educational Resources Information Center

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…

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

41

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

NASA Astrophysics Data System (ADS)

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.

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

2013-09-01

42

11CR 9/2/2007 1 1.1 Exponential growth and decay.  

E-print Network

11CR 9/2/2007 1 1.1 Exponential growth and decay. Example 1. A year ago I bought a mint condition 100 200 300 400 500 0 1 2 3 4 5 6 7 8 time t valuez z t #12;11CR 9/2/2007 2 Example 2. Your car?­­an interesting example we will look at is the decreasing pressure as the air escapes from a hole in your tire

Taylor, Peter

43

Differential Expression of Virulence Genes and Motility in Ralstonia(Pseudomonas)solanacearumduring Exponential Growth  

Microsoft Academic Search

A complex network regulates virulence in Ralstonia solanacearum (formerly Pseudomonas solanacearum); central to this system is PhcA, a LysR-type transcriptional regulator. We report here that two PhcA-regulated virulence factors, endoglucanase (Egl) and acidic exopolysaccharide I (EPS I), and motility are expressed differentially during exponential growth in batch cultures. Tests with strains carrying lacZ fusions in a wild-typegeneticbackgroundrevealedthatexpression(onaper-cellbasis)ofphcAwasconstantbutexpression ofeglandepsBincreased 20- to

STEVEN J. CLOUGH; ALBERT B. FLAVIER; MARK A. SCHELL; ANDTIMOTHY P. DENNY

1997-01-01

44

Determinants of human population growth.  

PubMed Central

The 20th century has seen unprecedented growth of the human population on this planet. While at the beginning of the century the Earth had an estimated 1.6 billion inhabitants, this number grew to 6.1 billion by the end of the century, and further significant growth is a near certainty. This paper tries to summarize what factors lie behind this extraordinary expansion of the human population and what population growth we can expect for the future. It discusses the concept of demographic transition and the preconditions for a lasting secular fertility decline. Recent fertility declines in all parts of the world now make it likely that human population growth will come to an end over the course of this century, but in parts of the developing world significant population growth is still to be expected over the coming decades. The slowing of population growth through declining birth rates, together with still increasing life expectancy, will result in a strong ageing of population age structure. Finally, this paper presents a global level systematic analysis of the relationship between population density on the one hand, and growth and fertility rates on the other. This analysis indicates that in addition to the well-studied social and economic determinants, population density also presents a significant factor for the levels and trends of human birth rates. PMID:12396512

Lutz, Wolfgang; Qiang, Ren

2002-01-01

45

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

NASA Technical Reports Server (NTRS)

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.

Choi, Sung R.; Gyekenyesi, John P.

2002-01-01

46

Limited Population Growth  

NSDL National Science Digital Library

Using Maple, Mathmatica, or MatLab, the learner should be able to model population as a function of time in a setting where there is a maximum population M that the environment will support. More specifically, to see that we can develop a graphical model from assumptions about the rate of change -- without any knowledge of an algebraic form for the model function

Moore, Lawrence; Smith, David

2001-01-22

47

Dynamic proteome changes of Shigella flexneri 2a during transition from exponential growth to stationary phase.  

PubMed

Shigella flexneri is an infectious pathogen that causes dysentery to human, which remains a serious threat to public health, particularly in developing countries. In this study, the global protein expression patterns of S. flexneri during transition from exponential growth to stationary phase in vitro were analyzed by using 2-D PAGE combined with MALDI-TOF MS. In a time-course experiment with five time points, the relative abundance of 49 protein spots varied significantly. Interestingly, a putative outer membrane protein YciD (OmpW) was almost not detected in the exponential growth phase but became one of the most abundant proteins in the whole stationary-phase proteome. Some proteins regulated by the global regulator FNR were also significantly induced (such as AnsB, AspA, FrdAB, and KatG) or repressed (such as AceEF, OmpX, SodA, and SucAB) during the growth phase transition. These proteins may be the key effectors of the bacterial cell cycle or play important roles in the cellular maintenance and stress responses. Our expression profile data provide valuable information for the study of bacterial physiology and form the basis for future proteomic analyses of this pathogen. PMID:17893076

Zhu, Li; Liu, Xian-Kai; Zhao, Ge; Zhi, Yi-Dan; Bu, Xin; Ying, Tian-Yi; Feng, Er-Ling; Wang, Jie; Zhang, Xue-Min; Huang, Pei-Tang; Wang, Heng-Liang

2007-05-01

48

Limited Population Growth  

NSDL National Science Digital Library

Created for the Connected Curriculum Project, this module models population as a function of time in a setting where there is a maximum population M that the environment will support. More specifically, to see that we can develop a graphical model from assumptions about the rate of change -- without any knowledge of an algebraic form for the model function. This is one within a much larger set of learning modules hosted by Duke University.

Barker, William; Moore, Lang; Schori, Richard; Smith, David

2010-06-07

49

[Population ethics and growth].  

PubMed

In order to formulate and implement a national demographic policy, various areas of science are called upon; however, since human lives are involved, ethical aspects play an important role not only in broad ideological terms, e.g, concerning overpopulation, but whenever practical decisions affecting technology and human resources are made. The article describes how the Catholic Church proposes certain "utopian" views or interpretations as part of an ethical "dynamism" and plurality needed when addressing the problem of overpopulation. 3 main starting point are defined for the determination of a population ethic: 1) ethics defined in terms of "nature," 2) in terms of the "human person," and 3) in terms of social "dialectic" involvement. The first point stresses the natural order of things as prescribed by God and impugns any birth control method; however, so-called natural birth control methods are allowed. The second point suggests that the human person is ethically center stage, a modernized position taken by the Church in tune with social realities and man's inherent intelligence. The primacy of live and responsibility is stressed as opposed to mere biological processes. Following this view, use of contraceptive, and even sterilization is allowed; however, abortion is excluded, since it means the elimination of a human life. The problem of overpopulation should be solved within the individual or micro-social context. The third point holds that it would be extremely myopic to reduce the position of the Church to advocating exclusively natural birth control methods while excluding social involvement. A "cosmic" view of faith would end putting material well-being before individual personal lives, would alert against egoism disguised as quality of life enhancement, and ultimately result in socially responsible fertility. In conclusion, the Church acknowledges that its contribution to the question of population ethics occurs in a pluralistic society that does not necessarily accept its opinions and proposals; however, the Church understands its contribution as a defense and not an imposition of its convictions. It considers it an obligation to accuse, criticize, and propose. PMID:12286718

Boim, D

1988-01-01

50

Fundamentals of Populations and Population Growth  

NSDL National Science Digital Library

This activity reinforces the concepts covered in the lecture presented during LESSON 3 of this unit. It takes the student through the definition of a population. Graphing skills are tested and the difference between the independent and dependent variables is explained. The S-shaped and Boom and Bust growth rate curves are next compared and contrasted. The activity then asks the student to analyze a data table and to plot its points. Students gain personal application of the lesson material. And relate the material to the grand challenge of this unit.

Vu Bioengineering Ret Program

51

Multiple factors underlying the maximum motility of Escherichia coli as cultures enter post-exponential growth.  

PubMed Central

Motility and chemotaxis allow cells to move away from stressful microenvironments. Motility of Escherichia coli in batch cultures, as measured by cell swimming speed, was low in early-exponential-phase cells, peaked as the cells entered post-exponential phase, and declined into early stationary phase. Transcription from the flhB operon and synthesis of flagellin protein similarly peaked in late exponential and early post-exponential phases, respectively. The increase in swimming speed between early-exponential and post-exponential phases was correlated with twofold increases in both flagellar length and flagellar density per cell volume. This increased investment in flagella probably reflects the increased adaptive value of motility in less favorable environments. The decrease in speed between post-exponential and stationary phases was correlated with a threefold decrease in torque produced by the flagellar motors and presumably reflects decreased proton motive force available to stationary-phase cells. Images PMID:8407796

Amsler, C D; Cho, M; Matsumura, P

1993-01-01

52

Population Growth: Family Planning Programs.  

ERIC Educational Resources Information Center

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…

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

53

Cellular Respiration and Population Growth  

NSDL National Science Digital Library

Through two lessons and their associated activities, students explore cellular respiration and population growth in yeasts. Yeast cells are readily obtained and behave predictably, so they are very suitable for use in middle school classrooms. Students are presented with information that enables them to recognize that yeasts are unicellular organisms that are useful to humans.

Engineering K-Phd Program

54

Human Population: Fundamentals of Growth and Change.  

ERIC Educational Resources Information Center

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…

Stauffer, Cheryl Lynn, Ed.

55

Population growth can be checked.  

PubMed

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

Shukla, J P

56

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

PubMed Central

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

Quiros, Manuel; Martinez-Moreno, Ruben; Albiol, Joan; Morales, Pilar; Vazquez-Lima, Felicitas; Barreiro-Vazquez, Antonio; Ferrer, Pau; Gonzalez, Ramon

2013-01-01

57

Metabolic flux analysis during the exponential growth phase of Saccharomyces cerevisiae in wine fermentations.  

PubMed

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

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

2013-01-01

58

Transient Transfection of Suspension Cells by Electroporation 1. Count cells. The cells should be in the exponential phase of growth.  

E-print Network

Transient Transfection of Suspension Cells by Electroporation 1. Count cells. The cells should be in the exponential phase of growth. 2. Collect 4 x 106 cells per transfection. Wash cells twice with Opti-MEM media. NOTE: Omit Penicillin-Streptomycin from the Opti-MEM transfection media, as electroporated cells

Gauthier, Eric

59

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

NASA Technical Reports Server (NTRS)

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.

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

2002-01-01

60

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

NASA Technical Reports Server (NTRS)

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.

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

2002-01-01

61

Lesson 30: Exponential Functions  

NSDL National Science Digital Library

Beginning with a formal definition of an exponential function, the lesson then compares the graphs of increasing and decreasing exponential functions. A comparison between exponential and power functions follows, which leads to methods for determining the h value in the power function h(x) = kx^p and the value of the base b in the exponential function f(x) = ab^x. A procedure for solving exponential equations is presented before a population application problem is solved. The lesson concludes with a discussion about using graphs to find approximate solutions to exponential equations.

2011-01-01

62

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

NASA Astrophysics Data System (ADS)

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 deformation modes. In contrast, the spectra of the cumulative amplification ratio (current over initial amplitude) maintained a single maximum value throughout. The wavelength selectivity is found to decrease at large strains, which helps explain the aperiodic forms of folds commonly observed in nature and the absence of long dominant wavelengths for high competence contrast folding. Calculation of the cumulative amplification spectra for different initial amplitude distributions, ranging from white to red noise, showed that the initial noise has a strong influence on the amplitude spectra for small strains. For larger strains, however, the cumulative amplification spectra were similar despite the strong difference in the initial noise.

Schmalholz, Stefan M.; Podladchikov, Yuri Yu.

2000-09-01

63

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

NASA Astrophysics Data System (ADS)

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 deformation modes. In contrast, the spectra of the cumulative amplification ratio (current over initial amplitude) maintained a single maximum value throughout. The wavelength selectivity is found to decrease at large strains, which helps explain the aperiodic forms of folds commonly observed in nature and the absence of long dominant wavelengths for high competence contrast folding. Calculation of the cumulative amplification spectra for different initial amplitude distributions, ranging from white to red noise, showed that the initial noise has a strong influence on the amplitude spectra for small strains. For larger strains, however, the cumulative amplification spectra were similar despite the strong difference in the initial noise.

Schmalholz, Stefan M.; Podladchikov, Yuri Yu.

2000-06-01

64

Population Growth in Planaria Dugesia tigrina (Gerard) Regulation by the absolute number in the population  

E-print Network

ABSTRACT Planaria reproduce by transverse fission. Isolated worms increase in number exponentially, while social animals at the same density are inhibited in terms of numerical increase, but over a 25 day period undergo a larger increase in mass. Isolated posterior fission products reproduce faster than isolated anterior fission products. Regulation of population growth is independent of density over a 16-fold range and regulatory factors cannot be demonstrated in the medium. Regulation of population growth depends on direct contact between animals. Fission period varies from individual to individual and from period to period for a given individual. Doubling time is related to the absolute number of individuals comprising the population as follows: PN = (PM.N)/(K + N), where PN is the doubling period of a population of N individuals, PM is the doubling time of an infinitely large population, N is the number of individuals in the population, and K is the number of individuals in a population the period of which is one-half PM. At 22 0-24 0 C PM is estimated to be 43.3 days and K is 1.87 individuals. A model system assumes that inhibitor flows through the population from animal to animal from the slowest to the fastest animal in the population thus acting to synchronize population increase as well as to determine the rate of population growth. A possible source of the inhibitor is discussed.

John Davison

65

Population Dynamics of Metastable Growth-Rate Phenotypes  

PubMed Central

Neo-Darwinian evolution has presented a paradigm for population dynamics built on random mutations and selection with a clear separation of time-scales between single-cell mutation rates and the rate of reproduction. Laboratory experiments on evolving populations until now have concentrated on the fixation of beneficial mutations. Following the Darwinian paradigm, these experiments probed populations at low temporal resolution dictated by the rate of rare mutations, ignoring the intermediate evolving phenotypes. Selection however, works on phenotypes rather than genotypes. Research in recent years has uncovered the complexity of genotype-to-phenotype transformation and a wealth of intracellular processes including epigenetic inheritance, which operate on a wide range of time-scales. Here, by studying the adaptation dynamics of genetically rewired yeast cells, we show a novel type of population dynamics in which the intracellular processes intervene in shaping the population structure. Under constant environmental conditions, we measure a wide distribution of growth rates that coexist in the population for very long durations (>100 generations). Remarkably, the fastest growing cells do not take over the population on the time-scale dictated by the width of the growth-rate distributions and simple selection. Additionally, we measure significant fluctuations in the population distribution of various phenotypes: the fraction of exponentially-growing cells, the distributions of single-cell growth-rates and protein content. The observed fluctuations relax on time-scales of many generations and thus do not reflect noisy processes. Rather, our data show that the phenotypic state of the cells, including the growth-rate, for large populations in a constant environment is metastable and varies on time-scales that reflect the importance of long-term intracellular processes in shaping the population structure. This lack of time-scale separation between the intracellular and population processes calls for a new framework for population dynamics which is likely to be significant in a wide range of biological contexts, from evolution to cancer. PMID:24312571

Braun, Erez

2013-01-01

66

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

NASA Astrophysics Data System (ADS)

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.

Hüsler, A. D.; Sornette, D.

2014-10-01

67

Population growth rates: issues and an application.  

PubMed Central

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

Godfray, H Charles J; Rees, Mark

2002-01-01

68

Critical Mutation Rate Has an Exponential Dependence on Population Size Alastair Channon1  

E-print Network

for the Environment, Physical Sciences and Applied Mathematics, Keele University, ST5 5BG, UK 2 School of Engineering by those that have a greater mutational robustness. However, using a genetic algorithm with a simple two animal species may exist in populations consisting of only hundreds or even fewer than ten individuals

Channon, Alastair

69

Population and pavement: population growth and land development in Israel  

Microsoft Academic Search

This research examines land use change in Israel––an intriguing but understudied setting with regard to population–environment\\u000a dynamics. While Israel is fairly unique with regard to its combined high levels of economic prosperity and high population growth, this case study has relevance for developed countries and regions (like the south and southwest regions\\u000a of the USA) which must balance population growth

Daniel E. OrensteinSteven; Steven P. Hamburg

2010-01-01

70

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

NASA Astrophysics Data System (ADS)

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.

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

2014-03-01

71

Hispanic Population Growth and Rural Income Inequality  

ERIC Educational Resources Information Center

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…

Parrado, Emilio A.; Kandel, William A.

2010-01-01

72

Lecture 14: Population growth. Exponential growth described by R0, and r  

E-print Network

mature, fight like mad, mate like mad, and all die (due to a huge pulse of the stress hormone mammalian life history is shown by African wild dogs, which breed one a year (in the dry season, when prey

Creel, Scott

73

On Population Growth Near Protected Areas  

PubMed Central

Background Protected areas are the first, and often only, line of defense in efforts to conserve biodiversity. They might be detrimental or beneficial to rural communities depending on how they alter economic opportunities and access to natural resources. As such, protected areas may attract or repel human settlement. Disproportionate increases in population growth near protected area boundaries may threaten their ability to conserve biodiversity. Methodology/Principal Findings Using decadal population datasets, we analyze population growth across 45 countries and 304 protected areas. We find no evidence for population growth near protected areas to be greater than growth of rural areas in the same country. Furthermore, we argue that what growth does occur near protected areas likely results from a general expansion of nearby population centers. Conclusions/Significance Our results contradict those from a recent study by Wittemyer et al., who claim overwhelming evidence for increased human population growth near protected areas. To understand the disagreement, we re-analyzed the protected areas in Wittemyer et al.'s paper. Their results are simply artifacts of mixing two incompatible datasets. Protected areas may experience unusual population pressures near their edges; indeed, individual case studies provide examples. There is no evidence, however, of a general pattern of disproportionate population growth near protected areas. PMID:19169358

Joppa, Lucas N.; Loarie, Scott R.; Pimm, Stuart L.

2009-01-01

74

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

USGS Publications Warehouse

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.

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

2006-01-01

75

Population growth and development planning in Africa.  

PubMed

Some of the consequences of rapid population growth and their implications for the economic development of the Africa region in the 1980s are outlined. The total population of Africa was estimated to be 412 million in 1976, or 10.2% of the total world population of 4044 million. Population density of the region is comparatively low, but the crude density measure of 14 persons per square kilometer in 1977 obscures the very high percentage of Africa's land which is desert or otherwise not arable. Continued high fertility rates in the region coupled with substantial decline in mortality rates especially for infants and children has resulted in Africa having a youthful population. The growth of cities due primarily to rural-urban migration is 1 of the most pressing problems of the region. Some countries in the region maintain pronatalist policies because they have a small population and regard population growth as a stimulus to the socioeconomic development effort. Few countries such as Kenya, Mauritius, Egypt, and Morocco consider rapid population growth a constraint on their development efforts and are now implementing national policies which aim at reducing the rate of growth of their populations. Population problems in Africa arise mainly from the fact that additions to the population needing education, housing, employment and to be fed adequately are increasing at a rate far more than most African countries can cope with. To illustrate the potential impact of population factors on development, the potential relationships between population and health, education, food supply, labor force supply and employment are analyzed. PMID:12263333

1980-12-01

76

Living bacteria rheology: population growth, aggregation patterns and cooperative behaviour under different shear flows  

E-print Network

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 -- 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 both strains increases with the population of cells. As the bacteria reach the exponential phase of growth, the viscosity of the two strains follow different and rich behaviours, with no counterpart in the optical density or in the population's colony forming units measurements. While the viscosity of strain COL 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 ...

Patricio, P; Portela, R; Sobral, R G; Grilo, I R; Cidade, T; Leal, C R

2014-01-01

77

Simulating Population Growth and Regulation  

ERIC Educational Resources Information Center

Describes a simple manual simulation exercise used in a college sophomore course in environmental biology. Demonstrates ways in which biotic potential and other physiological and behavioral characteristics of living organisms may interact with environmental factors to produce the kind of population behavior actually observed in the real world. (JR)

Moore, Paul J.; Holt, Elvis J.

1973-01-01

78

Population priorities: the challenge of continued rapid population growth  

PubMed Central

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

Turner, Adair

2009-01-01

79

Population priorities: the challenge of continued rapid population growth.  

PubMed

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

Turner, Adair

2009-10-27

80

On growth and dispersal of populations  

Microsoft Academic Search

In his unpublished MA thesis of 1921, the young Hotelling invented an ingenious model of population growth and diffusion. The contribution remained widely unknown until Waldo Tobler and Alan Wilson edited it as an article in 1978. Not even then did it trigger off any outburst of contributions. Meanwhile, in 1951, Skellam invented exactly the same model for non-human populations.

Tönu Puu

1989-01-01

81

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

PubMed

Fermenting cells growing exponentially on rich (YPAD) medium underwent a transition 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 transition period, the high-affinity Fe import rate declined slower than the cell-growth rate declined, causing Fe to accumulate, initially as Fe(III) oxyhydroxide nanoparticles but eventually as mitochondrial and vacuolar Fe. Once the cells had reached 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 the exponential phase and underwent a transition to a true stationary state as glucose levels declined. The Fe concentration of MM cells that just entered the stationary state was similar to that of YPAD cells, but MM cells continued to accumulate Fe in the stationary state. Fe initially accumulated as nanoparticles and high-spin Fe(II) species, but vacuolar Fe(III) also eventually accumulated. Surprisingly, Fe-packed 5-day-old MM cells suffered no more reactive oxygen species (ROS) damage than younger cells, suggesting that the 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 the import of Fe via a regulated high-affinity pathway and an unregulated low-affinity pathway. The import of Fe from the cytosol to 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 other cellular metabolites. This phenomenon likely derives from the unique chemistry associated with Fe nanoparticle formation. PMID:24344915

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

2013-12-31

82

Modeling Microbial Growth  

NSDL National Science Digital Library

Is bacterial growth always exponential? Do bacteria with the fastest rate of growth always have the largest populations? Biota models offer extended opportunities to observe population growth over time. What are the factors that affect growth? Explore continuous, chaotic, and cyclic growth models. * examine the dynamics of growth for populations of virtual bacteria with differing growth rates and carrying capacities

Ethel D. Stanley (Beloit College;Biology)

2006-05-20

83

[For controlling population growth more scientifically].  

PubMed

The February 4, 1982 edition of the People's Daily published a directive of the State Council of the Central Committee of the Chinese Communist Party regarding going a step further in the work of birth control. The spirit of the directive is to adapt to new situations and to push forward the work of birth control. Since the late 1970s, the success of birth control has been seen in the decline of the rate of natural population growth. Birth control work is affected by the new circumstances that rose with the effort to raise economic standards. For instance, the system of fixed responsibility in production that is being implemented in the villages benefits population control. That is, a developing agarian economy can alleviate the problem of supporting the aged, dispel the anxieties of future care of the elderly, and build up a dependable material basis. The spirit of the directive is based on objective truths, as is the control of population growth and the implementation of birth control work. If birth control can succeed in the countryside where 800 million peasants reside, then there is hope for attaining the goals of population control; but, there are differences between urban and rural settings, and the methods for population control cannot be the same for both situations. Nor can it be the same for China's minorities, whose population control programs must be tailored to their particular needs. Meeting the population needs of varying situations with different solutions is more scientific and realistic. The task of controlling population growth is formidable, but the following favorable conditions will facilitate the work: 1) party and governmental support is great, and population planning is an integral part of economic and social planning; 2) birth control organizations exist at all levels; 3) there exists high social and political consciousness among disciplined masses; and 4) there is a body of accumulated experience from which to draw. PMID:12265438

Liu, Y

1982-07-29

84

A Revisionist Look at Population and Growth.  

ERIC Educational Resources Information Center

Presents highlights from a National Research Council report titled "Population Growth and Economic Questions: Policy Questions." Includes brief comments on the report's conclusions related to exhaustible resources, renewable resources, pollution, work productivity, economics of scale and technological innovation, schooling, income distribution,…

Holden, Constance

1986-01-01

85

The phenomenological theory of world population growth  

Microsoft Academic Search

Of all global problems world population growth is the most significant. Demographic data describe this process in a concise and quantitative way in its past and present. Analysing this development it is possible by applying the concepts of systems analysis and synergetics, to work out a mathematical model for a phenomenological description of the global demographic process and to project

Sergei P Kapitza

1996-01-01

86

On the theory of global population growth  

NASA Astrophysics Data System (ADS)

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.

Kapitza, Sergei P.

2010-12-01

87

Lag phase is a distinct growth phase that prepares bacteria for exponential growth and involves transient metal accumulation.  

PubMed

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

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; Hinton, Jay C D

2012-02-01

88

Simulation of population growth and structure of the population  

NASA Astrophysics Data System (ADS)

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 ?( 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 ?( m) of genomes of the same m and the fraction of the population of this characteristics ?( m). A typical run takes a couple of hours on an HP EXEMPLAR machine, and for a population of about n=10 6.

Maksymowicz, A. Z.

2002-08-01

89

Exponential Probabilities  

NSDL National Science Digital Library

The applet, created by Virginia Tech's Department of Statistics, allows you see how probabilities are determined from the exponential distribution. The user determines the mean of the distribution and the limits of probability. Three different probability expressions are available. Click "Calculate" to see the pdf and the cdf. The probability is highlighted in green on the pdf. This is a nice reference tool for anyone studying statistics.

Anderson-Cook, C.; Dorai-Raj, S.; Robinson, T.

2009-01-21

90

Population growth rate and its determinants: an overview  

Microsoft Academic Search

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

Richard M. Sibly; Jim Hone

2002-01-01

91

Alanine transport in plasma membrane vesicles from Yoshida ascites hepatoma cells (AH 130) in the exponential and stationary phase of growth.  

PubMed

The Na(+)-dependent transport of L-alanine into plasma membrane vesicles from Yoshida ascites hepatoma (AH-130) cells in the exponential and stationary phase of growth has been studied. A transient accumulation of the amino acid occurred in the presence of an inwardly directed sodium gradient, in both conditions. However, the height and the shape of the overshoot curve differed noticeably in the two preparations. The accumulation ratio increased three-fold and the maximal uptake value occurred at an earlier time in plasma membrane vesicles from exponential growing rather than stationary phase cells. This might suggest that one of the two systems, A or ASC, serving hepatocytes, is fully expressed only in the exponential phase of growth or, alternatively, that the kinetic parameters of a possibly unique transport system are modified. Inhibition, countertransport as well as adaptive stimulation experiments and kinetic studies suggested the presence of a unique carrier-mediated transport of alanine in both phases of growth. The Vmax value was drastically reduced in the stationary phase of growth whereas the Km value was almost the same in both preparations. Therefore, the differences in time courses observed could be related to changes of the Vmax of a single transport agency rather than to the appearance/disappearance of an additional transport system (e.g. system A) in the conditions studied. PMID:2081337

Leonardi, M G; Comolli, R; Giordana, B

1990-11-01

92

On growth and dispersal of population.  

PubMed

In his unpublished Master's thesis of 1921, the young Hotelling invented an ingenious model of population growth and diffusion. The contribution remained widely unknown until Waldo Tobler and Alan Wilson edited it as an article in 1978. Not even then did it trigger any outburst of contributions. Meanwhile, in 1951, Skellam invented the same model for non-human populations. Unlike in economics, it was a great success in ecology. In a recent contribution, Skellam is named Father of Ecological Diffusion and more than 1000 articles on the subject are listed. There were many attempts at solving the equation, but none were quite successful. The Hotelling and Skellam models both assumed a given saturation population that nature could support. In 1985 the present author suggested that an explicit production function be introduced in the Hotelling model, as a man produces his own means of subsistence. Moreover, it was proposed that diffusion be related to spatial differences in per capita productivity, rather than to those in population density. The present contribution is a rejoinder. It is shown that the stationary solutions to the original Hotelling model are periodic and dip into negative populations, whereas this is avoided by the modified model suggested. It can thus be used to show how agglomerative structures may evolve. PMID:12282360

Puu, T

1989-10-01

93

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

NASA Astrophysics Data System (ADS)

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.

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

2014-08-01

94

Living bacteria rheology: population growth, aggregation patterns and cooperative behaviour under different shear flows  

E-print Network

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 -- 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 both strains increases with the population of cells. As the bacteria reach the exponential phase of growth, the viscosity of the two strains follow different and rich behaviours, with no counterpart in the optical density or in the population's colony forming units measurements. While the viscosity of strain COL 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 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 behaviours, 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, obtained with oscillatory shear, exhibit power-law behaviours whose exponent are dependent on the bacteria growth stage. The viscous and elastic moduli of the mutant have complex behaviours, emerging from the different relaxation times that are associated with the large molecules of the medium and the self-organized structures of bacteria. These behaviours reflect nevertheless the bacteria growth stage.

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

2014-03-06

95

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

PubMed

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

Weiner, J; Kinsman, S; Williams, S

1998-11-01

96

Human population growth and the demographic transition  

PubMed Central

The world and most regions and countries are experiencing unprecedentedly rapid demographic change. The most obvious example of this change is the huge expansion of human numbers: four billion have been added since 1950. Projections for the next half century expect a highly divergent world, with stagnation or potential decline in parts of the developed world and continued rapid growth in the least developed regions. Other demographic processes are also undergoing extraordinary change: women's fertility has dropped rapidly and life expectancy has risen to new highs. Past trends in fertility and mortality have led to very young populations in high fertility countries in the developing world and to increasingly older populations in the developed world. Contemporary societies are now at very different stages of their demographic transitions. This paper summarizes key trends in population size, fertility and mortality, and age structures during these transitions. The focus is on the century from 1950 to 2050, which covers the period of most rapid global demographic transformation. PMID:19770150

Bongaarts, John

2009-01-01

97

Fitness and density-dependent population growth in Drosophila melanogaster  

SciTech Connect

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.

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

1981-03-01

98

Some History Zilber's exponential field  

E-print Network

Some History Zilber's exponential field Blurred exponentiation Blurred Complex Exponentiation or Jonathan Kirby Blurred Complex Exponentiation #12;Some History Zilber's exponential field Blurred exponentiation Outline 1 Some History 2 Zilber's exponential field 3 Blurred exponentiation Blurring Zilber

Kirby, Jonathan

99

Population growth rate and its determinants: an overview.  

PubMed Central

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 population density in addition to those that arise through the partitioning of food between competitors; this is 'interference competition'. The distinction is illustrated using a replicated laboratory experiment on a marine copepod, Tisbe battagliae. Application of these approaches in conservation biology, ecotoxicology and human demography is briefly considered. We conclude that population regulation, density dependence, resource and interference competition, the effects of environmental stress and the form of the ecological niche, are all best defined and analysed in terms of population growth rate. PMID:12396508

Sibly, Richard M; Hone, Jim

2002-01-01

100

Circadian rhythm and cell population growth  

E-print Network

Molecular circadian clocks, that are found in all nucleated cells of mammals, are known to dictate rhythms of approximately 24 hours (circa diem) to many physiological processes. This includes metabolism (e.g., temperature, hormonal blood levels) and cell proliferation. It has been observed in tumor-bearing laboratory rodents that a severe disruption of these physiological rhythms results in accelerated tumor growth. The question of accurately representing the control exerted by circadian clocks on healthy and tumour tissue proliferation to explain this phenomenon has given rise to mathematical developments, which we review. The main goal of these previous works was to examine the influence of a periodic control on the cell division cycle in physiologically structured cell populations, comparing the effects of periodic control with no control, and of different periodic controls between them. We state here a general convexity result that may give a theoretical justification to the concept of cancer chronothera...

Clairambault, Jean; Lepoutre, Thomas

2010-01-01

101

Rapid Population Growth-Cause or Result of Global Problems?  

ERIC Educational Resources Information Center

Explosive population growth is a symptom of the world's unjust and inequitable social, political, and economic conditions. The current rate of growth is staggering, particularly in the cities of the underdeveloped countries. While some progress has been made in slowing population growth, several factors still contribute to its momentum. One of…

Schwartz, Richard H.

102

Volatility and Growth in Populations of Rural Associations  

ERIC Educational Resources Information Center

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…

Wollebaek, Dag

2010-01-01

103

FITNESS AND DENSITY-DEPENDENT POPULATION GROWTH IN DROSOPHILA MELANOGASTER  

E-print Network

FITNESS AND DENSITY-DEPENDENT POPULATION GROWTH IN DROSOPHILA MELANOGASTER LAURENCE D. MUELLER of population growth were determined for 26 populations of Drosophila melanogaster maintained in the serial for genotypesof Drosophila melanogaster homo- zygous for whole second chromosomes sampled from nature. The net

Rose, Michael R.

104

Population growth in U.S. counties, 1840–1990  

Microsoft Academic Search

We examine the location and growth of the U.S. population using county-level census data from 1840 and 1990. Natural characteristics (e.g., access to water transportation) heavily influenced where populations located in 1840, and produced characteristics in existence in 1840 (e.g., educational infrastructure) had a significant influence on subsequent growth. Evidence of population convergence appears only when the most-heavily-populated counties in

Patricia E. Beeson; David N. DeJong; Werner Troesken

2001-01-01

105

2-DE based proteomic analysis of Saccharomyces cerevisiae wild and K+ transport-affected mutant (trk1,2) strains at the growth exponential and stationary phases.  

PubMed

By using a 2-DE based workflow, the proteome of wild and potassium transport mutant trk1,2 under optimal growth potassium concentration (50mM) has been analyzed. At the exponential and stationary phases, both strains showed similar growth, morphology potassium content, and Vmax of rubidium transport, the only difference found being the Km values for this potassium analogue transport, higher for the mutant (20mM) than for the wild (3-6mM) cells. Proteins were buffer-extracted, precipitated, solubilized, quantified, and subjected to 2-DE analysis in the 5-8 pH range. More differences in protein content (37-64mgg(-1) cell dry weight) and number of resolved spots (178-307) were found between growth phases than between strains. In all, 164 spots showed no differences between samples and a total of 105 were considered to be differential after ANOVA test. 171 proteins, corresponding to 71 unique gene products have been identified, this set being dominated by cytosolic species and glycolitic enzymes. The ranking of the more abundant spots revealed no differences between samples and indicated fermentative metabolism, and active cell wall biosynthesis, redox homeostasis, biosynthesis of amino acids, coenzymes, nucleotides, and RNA, and protein turnover, apart from cell division and growth. PCA analysis allowed the separation of growth phases (PC1 and 2) and strains at the stationary phase (PC3 and 4), but not at the exponential one. These results are also supported by clustering analysis. As a general tendency, a number of spots newly appeared at the stationary phase in wild type, and to a lesser extent, in the mutant. These up-accumulated spots corresponded to glycolitic enzymes, indicating a more active glucose catabolism, accompanied by an accumulation of methylglyoxal detoxification, and redox-homeostasis enzymes. Also, more extensive proteolysis was observed at the stationary phase with this resulting in an accumulation of low Mr protein species. PMID:20638488

Curto, Miguel; Valledor, Luis; Navarrete, Clara; Gutiérrez, Dolores; Sychrova, Hana; Ramos, José; Jorrin, Jesús

2010-11-10

106

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

PubMed

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

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

2011-05-01

107

Population Growth and a Sustainable Environment.  

ERIC Educational Resources Information Center

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)

Mortimore, Michael; Tiffen, Mary

1994-01-01

108

Population growth and atmospheric emissions in California. Final report  

SciTech Connect

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.

Cramer, J.C.

1998-03-01

109

[Toward the realization of the goal of zero population growth].  

PubMed

This paper is concerned with the difficulties associated with achieving zero population growth in China. It is noted that although the current rate of natural increase is 1.2 percent, further consideration of population policy goals is necessary. Criticisms of the one-child family policy are examined, and steps needed to achieve zero growth are considered. PMID:12178288

Liu, C

1980-03-01

110

[Population: evolution of Rwandan attitudes or the adaptation of the Rwanda population to population growth].  

PubMed

A consequence of the increasing pressure on Rwanda's ecosystem resulting from population growth has been that demographic factors have played a significant role in modifying attitudes and beliefs of the population. The history of Rwanda demonstrates a constant struggle for survival in the face of increasing population pressure. Migration, colonization of new agricultural lands, adoption of new crops and new forms of animal husbandry have been responses to population pressures. Recent unprecedented population growth has exceeded the capacity of older systems of cultivation and combinations of agricultural and animal husbandry to support the population. Smaller animals have largely replaced the cattle that once roamed freely in extensive pastures, and new techniques of stabling animals, use of organic or chemical fertilizers, and new tools adapted to the shrinking size of farm plots have represented responses to the new demographic realities. The concept of the family is likewise undergoing modification in the face of population growth and modernization. Children, who once were valued as a source of labor and constrained to conform to the wishes of the parents in return for the eventual inheritance of the goods and livelihood, now increasingly look beyond the household for education and employment. Family land holdings have become too small to support all the members with a claim on them. The greater distances between family members inevitably mean that relations between them lose closeness. The choice of a marriage partner is increasingly assumed by the young people themselves and not by their families. Old traditions of food sharing and hospitality have been curtailed because of the increasing scarcity of food. Despite the changes engendered by increasing population pressure, pronatalist sentiments are still widespread. But the desire to assure the future of each child rather than to await his services, a new conception of women less dependent on their reproductive functions, the promotion of small families of 4 or fewer children by the government, and the existence of some fertile-aged women who do not wish to have more children all testify to the appearance of a new attitude toward family planning. A goal of the 4th 5-year plan is to increase the proportion of contraceptive users from 2% to 15%. PMID:12315403

Ngendakumana, M

1988-04-01

111

Pattern of variation in avian population growth rates.  

PubMed Central

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

Saether, Bernt-Erik; Engen, Steinar

2002-01-01

112

Soil science, population growth and food production: some historical developments  

Microsoft Academic Search

The world’s population has doubled since 1960. Currently, the developing world accounts for about 95% of the population growth\\u000a with Africa as the world’s fastest growing continent. The growing population has many implications but most of all it requires\\u000a an increase in agricultural production to meet food demand. Soil science has a long tradition of considering the growth in\\u000a food

Alfred E. Hartemink

2007-01-01

113

Circadian rhythm and cell population growth June 17, 2010  

E-print Network

Circadian rhythm and cell population growth June 17, 2010 Jean Clairambault 1 , 2 , St effect of disruption of circadian rhythms on tumor growth enhancement is indirect, that, growth processes, eigenvalues , circadian rhythms, cancer 1 INRIA, projet BANG, Domaine de Voluceau, BP

114

Surface Growth of a Motile Bacterial Population Resembles Growth in a Chemostat  

E-print Network

, and we observe these parameters in populations of Escherichia coli swimming in galactose soft agar plates;observe a population of Escherichia coli that grows and performs chemotaxis through soft agar plates10Surface Growth of a Motile Bacterial Population Resembles Growth in a Chemostat Daniel A. Koster

115

BIOTIC INFLUENCES AFFECTING POPULATION GROWTH OF  

E-print Network

of Chlorella and Nitz8chia _ Growth curve and division rate of Chlorella _ Growth curve and division rate in conditioned media _ Inhibitory effect o~ Chlorella of Nitz8chia-conditioned medium _ Inhibitory effect on Nitz8chia of Chlorella-condit,ioned medium _ Inhibitory effects of filtrate from conditioned media

116

Laws of population growth Hernn D. Rozenfelda  

E-print Network

College of New York, New York, NY 10031; b Departamento de Física, Universidade Federal do Ceará, 60451-consuming process and is typically done only for a subset (a few hundreds) of the most highly populated cities. Here). The CCA is based on spatial distributions of the population at a fine geographic scale, defining a city

Stanley, H. Eugene

117

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

ERIC Educational Resources Information Center

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…

Groth, Edward, III

118

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

PubMed

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 the value of human resources everywhere is reaffirmed. The recognition by international organizations that per capita income or other economic indicators alone are not adequate measures of progress is a favorable sign. The failure of structural adjustment programs to attain their stated goals and the new resolve to lessen their effects on the most vulnerable population sectors are also promising. New orientations toward development in which human resources are given greater prominence may be as ideologically inspired as those they replaced, but they have the merit of greater neutrality concerning the content and form of development and they do not accept the process of development in the West as their sole reference. PMID:12317452

Loriaux, M

1991-12-01

119

Lesson 33: Applications of Exponential Functions  

NSDL National Science Digital Library

The lesson begins with population application problems looking at doubling time, the constant time that it takes for an exponentially modeled population to double. Application problems concerning half life are then discussed.

2011-01-01

120

ORIGINAL PAPER Overestimates of maternity and population growth rates  

E-print Network

and assessments of population viability. Keywords Maternity rate . Bias . Grizzly bear . Ursus arctos . Growth. Three methods that were described in the study of McLellan (1989) for grizzly bears (Ursus arctos

Richner, Heinz

121

Diet Quality Limits Summer Growth of Field Vole Populations  

PubMed Central

Marked variation occurs in both seasonal and multiannual population density peaks of northern European small mammal species, including voles. The availability of dietary proteins is a key factor limiting the population growth of herbivore species. The objective of this study is to investigate the degree to which protein availability influences the growth of increasing vole populations. We hypothesise that the summer growth of folivorous vole populations is positively associated with dietary protein availability. A field experiment was conducted over a summer reproductive period in 18 vegetated enclosures. Populations of field voles (Microtus agrestis) were randomised amongst three treatment groups: 1) food supplementation with ad libitum high protein (30% dry weight) pellets, 2) food supplementation with ad libitum low protein (1% dry weight; both supplemented foods had equivalent energy content) pellets, and 3) control (no food supplementation), n?=?6 per treatment. Vole density, survival, demographic attributes and condition indicators were monitored with live-trapping and blood sampling. Highest final vole densities were attained in populations that received high protein supplementation and lowest in low protein populations. Control populations displayed intermediate densities. The survival rate of voles was similar in all treatment groups. The proportion of females, and of those that were pregnant or lactating, was highest in the high protein supplemented populations. This suggests that variation in reproductive, rather than survival rates of voles, accounted for density differences between the treatment groups. We found no clear association between population demography and individual physiological condition. Our results demonstrate that dietary protein availability limits vole population growth during the summer growing season. This suggests that the nutritional quality of forage may be an underestimated source of interannual variation in the density and growth rates of widely fluctuating populations of herbivorous small mammals. PMID:24621513

Forbes, Kristian M.; Stuart, Peter; Mappes, Tapio; Hoset, Katrine S.; Henttonen, Heikki; Huitu, Otso

2014-01-01

122

Contrasting Signatures of Population Growth for Mitochondrial DNA and Y Chromosomes among Human Populations in Africa  

E-print Network

Contrasting Signatures of Population Growth for Mitochondrial DNA and Y Chromosomes among Human of their different effective population sizes. This hypothesis predicts thatmitochondrial and Y chromosomal DNA in effective population size. We test this hypothesis by resequencing 6.6 kb of noncoding Y chromosomal DNA

Watkins, Joseph C.

123

Population growth in European cities: Weather matters – but only nationally  

Microsoft Academic Search

CHESHIRE P. C. and MAGRINI S. (2006) Population growth in European cities: weather matters – but only nationally, Regional Studies40, 23–37. This paper investigates differences in the rate of growth of population across the large city-regions of the European Union (EU)-12 between 1980 and 2000. The US model, which assumes perfect factor mobility, does not seem well adapted to European

Paul C. Cheshire; Stefano Magrini

2006-01-01

124

POPULATION GROWTH AND URBAN AGRICULTURE IN YAOUNDE  

Microsoft Academic Search

Summary In less than two decades, Yaounde, the capital of C ameroon has grown into a millionaire city. Much of this growth is attributed to a rapid rate o f rural exodus from the mid 1980s due mainly to declining agricultural fortunes in rural areas. A significant proportion of these new urban dwellers is illiterate or semi-literate and cannot easily

Paul Mukwaya

125

Social structural consequences of population growth.  

PubMed

Estimates from archaeological data of the numbers in the elite classes, nonelite occupational specialists, density of population, city size, and size of political units in the ancient Maya civilization suggest that there was a quantum shift in rate of development in the Early Classic period, associated with intensification of agriculture, and that the social structure approximated to a generalized feudal pattern. PMID:7007390

Adams, R E

1981-01-01

126

[Age structure and growth characteristic of Castanopsis fargesii population].  

PubMed

In this paper, the age structure and growth characteristics of Castanopsis fargesii population in a shade-tolerant broadleaved evergreen forest were studied, aimed to understand more about the regeneration patterns and dynamics of this population. The results showed that the age structure of C. fargesii population was of sporadic type, with two death peaks of a 30-year gap. This population had a good plasticity in growth to light condition. Because there were no significant differences in light condition under the canopy in vertical, the saplings came into their first suppression period when they were 5-8 years old, with a height growth rate less than 0. 1 m x a(-1) lasting for 10 years. The beginning time of the first growth suppression period was by the end of the first death peak of the population, and the ending time of the first growth suppression period was at the beginning of the second death peak of the population, demonstrating that growth characteristic was the key factor affecting the age structure of C. fargesii. PMID:17450723

Song, Kun; Da, Liang-jun; Yang, Tong-hui; Yang, Xu-feng

2007-02-01

127

Metabolic Profiling and Flux Analysis of MEL-2 Human Embryonic Stem Cells during Exponential Growth at Physiological and Atmospheric Oxygen Concentrations.  

PubMed

As human embryonic stem cells (hESCs) steadily progress towards regenerative medicine applications there is an increasing emphasis on the development of bioreactor platforms that enable expansion of these cells to clinically relevant numbers. Surprisingly little is known about the metabolic requirements of hESCs, precluding the rational design and optimisation of such platforms. In this study, we undertook an in-depth characterisation of MEL-2 hESC metabolic behaviour during the exponential growth phase, combining metabolic profiling and flux analysis tools at physiological (hypoxic) and atmospheric (normoxic) oxygen concentrations. To overcome variability in growth profiles and the problem of closing mass balances in a complex environment, we developed protocols to accurately measure uptake and production rates of metabolites, cell density, growth rate and biomass composition, and designed a metabolic flux analysis model for estimating internal rates. hESCs are commonly considered to be highly glycolytic with inactive or immature mitochondria, however, whilst the results of this study confirmed that glycolysis is indeed highly active, we show that at least in MEL-2 hESC, it is supported by the use of oxidative phosphorylation within the mitochondria utilising carbon sources, such as glutamine to maximise ATP production. Under both conditions, glycolysis was disconnected from the mitochondria with all of the glucose being converted to lactate. No difference in the growth rates of cells cultured under physiological or atmospheric oxygen concentrations was observed nor did this cause differences in fluxes through the majority of the internal metabolic pathways associated with biogenesis. These results suggest that hESCs display the conventional Warburg effect, with high aerobic activity despite high lactate production, challenging the idea of an anaerobic metabolism with low mitochondrial activity. The results of this study provide new insight that can be used in rational bioreactor design and in the development of novel culture media for hESC maintenance and expansion. PMID:25412279

Turner, Jennifer; Quek, Lake-Ee; Titmarsh, Drew; Krömer, Jens O; Kao, Li-Pin; Nielsen, Lars; Wolvetang, Ernst; Cooper-White, Justin

2014-01-01

128

Metabolic Profiling and Flux Analysis of MEL-2 Human Embryonic Stem Cells during Exponential Growth at Physiological and Atmospheric Oxygen Concentrations  

PubMed Central

As human embryonic stem cells (hESCs) steadily progress towards regenerative medicine applications there is an increasing emphasis on the development of bioreactor platforms that enable expansion of these cells to clinically relevant numbers. Surprisingly little is known about the metabolic requirements of hESCs, precluding the rational design and optimisation of such platforms. In this study, we undertook an in-depth characterisation of MEL-2 hESC metabolic behaviour during the exponential growth phase, combining metabolic profiling and flux analysis tools at physiological (hypoxic) and atmospheric (normoxic) oxygen concentrations. To overcome variability in growth profiles and the problem of closing mass balances in a complex environment, we developed protocols to accurately measure uptake and production rates of metabolites, cell density, growth rate and biomass composition, and designed a metabolic flux analysis model for estimating internal rates. hESCs are commonly considered to be highly glycolytic with inactive or immature mitochondria, however, whilst the results of this study confirmed that glycolysis is indeed highly active, we show that at least in MEL-2 hESC, it is supported by the use of oxidative phosphorylation within the mitochondria utilising carbon sources, such as glutamine to maximise ATP production. Under both conditions, glycolysis was disconnected from the mitochondria with all of the glucose being converted to lactate. No difference in the growth rates of cells cultured under physiological or atmospheric oxygen concentrations was observed nor did this cause differences in fluxes through the majority of the internal metabolic pathways associated with biogenesis. These results suggest that hESCs display the conventional Warburg effect, with high aerobic activity despite high lactate production, challenging the idea of an anaerobic metabolism with low mitochondrial activity. The results of this study provide new insight that can be used in rational bioreactor design and in the development of novel culture media for hESC maintenance and expansion. PMID:25412279

Titmarsh, Drew; Krömer, Jens O.; Kao, Li-Pin; Nielsen, Lars; Wolvetang, Ernst; Cooper-White, Justin

2014-01-01

129

Parameter Estimates in Differential Equation Models for Population Growth  

ERIC Educational Resources Information Center

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,…

Winkel, Brian J.

2011-01-01

130

Population Growth and Global Security: Toward an American Strategic Commitment.  

ERIC Educational Resources Information Center

Addresses the world population problem by highlighting three crucial areas: the relationship between population growth control and national security issues, the role of American leadership in resolving the problem, and the barriers to effective action. One barrier discussed in detail is the Roman Catholic Church's stand on abortion and…

Mumford, Steven

1981-01-01

131

Herbivory: effects on plant abundance, distribution and population growth  

Microsoft Academic Search

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

John L. Maron; Elizabeth Crone

2006-01-01

132

[Growth comparison among Psammosilene tunicoides populations in tissue culture].  

PubMed

The comparison between the growth of eight populations from Psammosilene tunicoides at Yunnan Province was made by the tissue culture. The initial results showed out two populations from Yunshanping (Lijiang) and Xiaomoyu (Kunming) was dominant than orthers. It would be regard as one of fine germplasm resources for the culture of Psammosilence tunicoides. PMID:16617774

Yang, Yao-wen; Qian, Zi-gang; Wang, Xiao-jia; Wang, Shi-hui

2006-02-01

133

A Role for M-Matrices in Modelling Population Growth  

ERIC Educational Resources Information Center

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,…

James, Glyn; Rumchev, Ventsi

2006-01-01

134

Hunger in Africa: problems of population growth and agricultural productivity.  

PubMed

The problem of hunger in Africa is examined using data from the U.N. Food and Agricultural Organization for the period 1960-1988. The author discusses the relationship between the continent's population growth, agricultural productivity, and environmental damage that have combined to decrease the average daily food intake per capita. He states that "in Africa...the population not only faces problems of uneven food distribution and suffers from the lack of purchasing power; the continent also is confronted by a widening gap between the capacity of its agriculture and the growth of its population. Put very bluntly, Africa is rapidly losing its ability to feed itself." PMID:12284156

Heilig, G

1991-01-01

135

Regulatory Design Governing Progression of Population Growth Phases in Bacteria  

PubMed Central

It has long been noted that batch cultures inoculated with resting bacteria exhibit a progression of growth phases traditionally labeled lag, exponential, pre-stationary and stationary. However, a detailed molecular description of the mechanisms controlling the transitions between these phases is lacking. A core circuit, formed by a subset of regulatory interactions involving five global transcription factors (FIS, HNS, IHF, RpoS and GadX), has been identified by correlating information from the well- established transcriptional regulatory network of Escherichia coli and genome-wide expression data from cultures in these different growth phases. We propose a functional role for this circuit in controlling progression through these phases. Two alternative hypotheses for controlling the transition between the growth phases are first, a continuous graded adjustment to changing environmental conditions, and second, a discontinuous hysteretic switch at critical thresholds between growth phases. We formulate a simple mathematical model of the core circuit, consisting of differential equations based on the power-law formalism, and show by mathematical and computer-assisted analysis that there are critical conditions among the parameters of the model that can lead to hysteretic switch behavior, which – if validated experimentally – would suggest that the transitions between different growth phases might be analogous to cellular differentiation. Based on these provocative results, we propose experiments to test the alternative hypotheses. PMID:22363461

Sandoval, Santiago; Aldana, Maximino; Savageau, Michael A.

2012-01-01

136

Put an end to population growth and improve productivity.  

PubMed

The representative from Korea at the 15th Asian Parliamentarians' Meeting discussed issues concerning the environment, food security, and population growth. The implementation of population control programs is an issue that warrants continuous attention and efforts. The imbalance in the sexes, the decrease in the labor force, the rapid increase in number of senior citizens, insufficient food, unbalanced population distribution due to urbanization, and pollution are some of the new threats humanity faces. Like other developing countries, Korea put environmental protection on the back burner and its economic development took precedence over environmental concerns. As a result, Korea fostered industries that consume massive amounts of energy and resources, polluting the environment. Not only environmental hazards, but also social ills such as population concentration in urban areas, security problems, deteriorating living conditions, and crimes, developed due to industrialization and urbanization. The main priority should be the revival of the earth and the study of the effects of population growth on the environment. The root causes of environmental destruction consist of explosive population growth, industrial pollution, and development; the best way to restrain these destructive forces is to put an end to population growth. To improve food security, humanity needs to make specific action plans to implement the Hague Declaration urging the establishment of the World Food Bank. PMID:12349204

Chung, U W

1999-01-01

137

TOPICAL PROBLEMS: The phenomenological theory of world population growth  

NASA Astrophysics Data System (ADS)

Of all global problems world population growth is the most significant. Demographic data describe this process in a concise and quantitative way in its past and present. Analysing this development it is possible by applying the concepts of systems analysis and synergetics, to work out a mathematical model for a phenomenological description of the global demographic process and to project its trends into the future. Assuming self-similarity as the dynamic principle of development, growth can be described practically over the whole of human history, assuming the growth rate to be proportional to the square of the number of people. The large parameter of the theory and the effective size of a coherent population group is of the order of 105 and the microscopic parameter of the phenomenology is the human lifespan. The demographic transition — a transition to a stabilised world population of some 14 billion in a foreseeable future — is a systemic singularity and is determined by the inherent pattern of growth of an open system, rather than by the lack of resources. The development of a quantitative nonlinear theory of the world population is of interest for interdisciplinary research in anthropology and demography, history and sociology, for population genetics and epidemiology, for studies in evolution of humankind and the origin of man. The model also provides insight into the stability of growth and the present predicament of humankind, and provides a setting for discussing the main global problems.

Kapitza, Sergei P.

1996-01-01

138

Giving Exponential Functions a Fair Shake  

ERIC Educational Resources Information Center

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.)

Wanko, Jeffrey J.

2005-01-01

139

A model of northern pintail productivity and population growth rate  

USGS Publications Warehouse

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.

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

1998-01-01

140

Modeling bacterial population growth from stochastic single-cell dynamics.  

PubMed

A few bacterial cells may be sufficient to produce a food-borne illness outbreak, provided that they are capable of adapting and proliferating on a food matrix. This is why any quantitative health risk assessment policy must incorporate methods to accurately predict the growth of bacterial populations from a small number of pathogens. In this aim, mathematical models have become a powerful tool. Unfortunately, at low cell concentrations, standard deterministic models fail to predict the fate of the population, essentially because the heterogeneity between individuals becomes relevant. In this work, a stochastic differential equation (SDE) model is proposed to describe variability within single-cell growth and division and to simulate population growth from a given initial number of individuals. We provide evidence of the model ability to explain the observed distributions of times to division, including the lag time produced by the adaptation to the environment, by comparing model predictions with experiments from the literature for Escherichia coli, Listeria innocua, and Salmonella enterica. The model is shown to accurately predict experimental growth population dynamics for both small and large microbial populations. The use of stochastic models for the estimation of parameters to successfully fit experimental data is a particularly challenging problem. For instance, if Monte Carlo methods are employed to model the required distributions of times to division, the parameter estimation problem can become numerically intractable. We overcame this limitation by converting the stochastic description to a partial differential equation (backward Kolmogorov) instead, which relates to the distribution of division times. Contrary to previous stochastic formulations based on random parameters, the present model is capable of explaining the variability observed in populations that result from the growth of a small number of initial cells as well as the lack of it compared to populations initiated by a larger number of individuals, where the random effects become negligible. PMID:24928885

Alonso, Antonio A; Molina, Ignacio; Theodoropoulos, Constantinos

2014-09-01

141

The Population Growth Consequences of Variation in Individual Heterozygosity  

PubMed Central

Heterozygosity has been associated with components of fitness in numerous studies across a wide range of taxa. Because heterozygosity is associated with individual performance it is also expected to be associated with population dynamics. However, investigations into the association between heterozygosity and population dynamics have been rare because of difficulties in linking evolutionary and ecological processes. The choice of heterozygosity measure is a further issue confounding such studies as it can be biased by individual differences in the frequencies of the alleles studied, the number of alleles at each locus as well as the total number of loci typed. In this study, we first examine the differences between the principal metrics used to calculate heterozygosity using long-term data from a marked population of Soay sheep (Ovis aries). Next, by means of statistical transformation of the homozygosity weighted by loci index, we determine how heterozygosity contributes to population growth in Soay sheep by modelling individual contributions to population growth (pt(i)) as a function of several covariates, including sex, weight and faecal egg count – a surrogate of parasitic nematode burden in the gut. We demonstrate that although heterozygosity is associated with some components of fitness, most notably adult male reproductive success, in general it is only weakly associated with population growth. PMID:21611172

Di Fonzo, Martina M. I.; Pelletier, Fanie; Clutton-Brock, T.H.; Pemberton, Josephine M.; Coulson, Tim

2011-01-01

142

Meteorological limits on the growth and development of screwworm populations  

NASA Technical Reports Server (NTRS)

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.

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

1978-01-01

143

Demographic Processes Underlying Population Growth and Decline in Salamandra salamandra  

Microsoft Academic Search

Human activity commonly has negative impacts on wildlife. Often, however, only a single element of the life cycle is affected, and it is unclear whether such effects translate into effects on population growth. This is particularly true for research into the causes of global amphibian declines, where experimental research focuses primarily on the aquatic larval stages but theory suggests these

BENEDIKT R. SCHMIDT; REINER FELDMANN; MICHAEL SCHAUB

2005-01-01

144

An American Laboratory: Population Growth and Environmental Quality in California.  

ERIC Educational Resources Information Center

Describes the cumulative impact of rapid population growth, industrial and military activity, agriculture, and motor vehicles on California's environmental and social fabric. Discusses these problems in California as a forecast for the nation and test to consensus-based U.S. representative government. (Author/ MCO)

McConnell, Robert

1993-01-01

145

The Educational Effects of Rapid Rural Population Growth.  

ERIC Educational Resources Information Center

Rapid population growth in rural areas has confronted rural communities and particularly rural educational systems with a number of problems. Sudden, large increases in students crowd school facilities and strain budgets. The different values, attitudes, and orientations toward education of the newcomers act as a catalyst for changes and can cause…

Ross, Peggy J.; Green, Bernal L.

146

Population Growth: The Human Dilemma. An NSTA Environmental Materials Guide.  

ERIC Educational Resources Information Center

This annotated bibliography lists more than 100 books about population growth. The books are intended for students in kindergarten through grade 12 and their teachers. The books were selected on the basis of their appropriateness to the interests of classroom teachers and students, and on the basis of readability and accuracy. Most were published…

Fowler, Kathryn Mervine

147

Is There Hidden Potential for Rural Population Growth in Sweden?  

ERIC Educational Resources Information Center

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…

Niedomysl, Thomas; Amcoff, Jan

2011-01-01

148

Keywords: Deforestation, development, fragmentation, land-use change, population growth.  

E-print Network

1 Keywords: Deforestation, development, fragmentation, land-use change, population growth. Forest; help to cleanse the air and water; supply timber, fuelwood, and other harvested products; serve as places for recreation; help to mitigate the effects of global climate change; and provide other essential

Fried, Jeremy S.

149

Cursorial spiders retard initial aphid population growth at low densities  

E-print Network

Cursorial spiders retard initial aphid population growth at low densities in winter wheat K Generalist predators contribute to pest suppression in agroecosystems. Spider communities, which form that analyzed the impact, separately and together, of equal densities of these two spider functional groups

Illinois at Chicago, University of

150

TOPICAL PROBLEMS: The phenomenological theory of world population growth  

Microsoft Academic Search

Of all global problems world population growth is the most significant. Demographic data describe this process in a concise and quantitative way in its past and present. Analysing this development it is possible by applying the concepts of systems analysis and synergetics, to work out a mathematical model for a phenomenological description of the global demographic process and to project

Sergei P. Kapitza

1996-01-01

151

American Public Opinion on Population Size and Growth  

Microsoft Academic Search

American Public Opinion on Population Size and Growth J. Mayone Stycos Context. A wide variety of recent public opinion surveys have described knowledge of and attitudes toward national demographic trends. Such studies have provided little information on causal factors, and have usually ignored attitudes toward sub-national areas. A recent survey of about 1,000 New York State households has filled in

J. Mayone Stycos

152

Accelerated human population growth at protected area edges.  

PubMed

Protected areas (PAs) have long been criticized as creations of and for an elite few, where associated costs, but few benefits, are borne by marginalized rural communities. Contrary to predictions of this argument, we found that average human population growth rates on the borders of 306 PAs in 45 countries in Africa and Latin America were nearly double average rural growth, suggesting that PAs attract, rather than repel, human settlement. Higher population growth on PA edges is evident across ecoregions, countries, and continents and is correlated positively with international donor investment in national conservation programs and an index of park-related funding. These findings provide insight on the value of PAs for local people, but also highlight a looming threat to PA effectiveness and biodiversity conservation. PMID:18599788

Wittemyer, George; Elsen, Paul; Bean, William T; Burton, A Coleman O; Brashares, Justin S

2008-07-01

153

Determinants of Population Growth in Rajasthan: An Analysis  

E-print Network

Rajasthan is the biggest State of India and is currently in the second phase of demographic transition and is moving towards the third phase of demographic transition with very slow pace. However, state's population will continue to grow for a time period. Rajasthan's performance in the social and economic sector has been poor in past. The poor performance is the outcome of poverty, illiteracy and poor development, which co-exist and reinforce each other. There are many demographic and socio-economic factors responsible for population growth. This paper attempts to identify the demographic and socio-economic variables, which are responsible for population growth in Rajasthan with the help of multivariate analysis.

V. V. Singh; Alka Mittal; Neetish Sharma; Florentin Smarandache

2010-12-01

154

An Exceptional Exponential Function  

ERIC Educational Resources Information Center

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…

Curgus, Branko

2006-01-01

155

The Exponential Distribution  

E-print Network

The Exponential Distribution 38.3 Introduction If an engineer is responsible for the quality of service. If the fan is redesigned so that its lifetime may be modelled by an exponential distribution%ofthefansmaybeexpectedtogiveatleast10000hoursservice.Afterthe redesign,thecalculationbecomes P(T>10000)= 10000 f(t)dt= 10000 0

Vickers, James

156

Exponential distributions on semigroups  

Microsoft Academic Search

Three fundamental characterizations of the standard exponential distribution on [0, ?) are the remaining life, memoryless and constant failure properties. Analogs of these properties are studied for distributions on a class of semigroups in which the semigroup operation replaces addition, a compatible partial order replaces the ordinary order, and a left-invariant measure replaces Lebesgue measure. Partial characterizations of exponential distributions

Kyle Siegrist

1994-01-01

157

Habitat-Specific Population Growth of a Farmland Bird  

PubMed Central

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 ?s: ?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 ?s: ?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

Arlt, Debora; Forslund, Par; Jeppsson, Tobias; Part, Tomas

2008-01-01

158

Health, nutrition, and the roots of world population growth.  

PubMed

The identification of the introduction of modern medicine and public health techniques in developing countries as the cause of the population explosion is questioned; and it is postulated that the roots of the present population crisis can be traced to a worldwide improvement in nutrition that is based less on the total amount of food produced than on a greatly enlarged capacity to distribute it. It is shown how the ev idence is equivocal for malaria eradication, immunization programs, improved sanitation, and the use of antibiotics as the kinds of medical intervention that sent death rates downward on a global basis. Although each of these measures is medically effective, none have been universally applied-a condition that must be attained before the potential value of each can be measured. Therefore sustained population growth has preceded the development of medicine and public health as effective weapons against mortality, both in Europe's population expansion beginning in the 17th century, and in the case of the population growth in the developing nations. The underlying cause of the contemporary population crisis can be traced to the worldwide improvement in nutrition that is based primarily on a greatly enhanced capacity to distribute food. Better food distribution followed the Industrial Revolution and reached the developing countries in the late 19th century at the same time the Third World came under the political control of the West. PMID:4463173

Marshall, C L

1974-01-01

159

Islamic Republic of Iran population growth rate declines.  

PubMed

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

1996-01-01

160

Population growth to put pressure on some food supplies.  

PubMed

Continued high population growth in developing countries is likely to lead to intense pressure to produce more rice, according to estimates from the Manila-based International Rice Research Institute (IRRI). Ms. Mercedita Sombilla, a research scientist with IRRI, said that the projected increase in Asia's population will be the major force in accelerating demand for rice. According to various issues of the ESCAP Population Data Sheet, the population of the region will have increased from 3.3 billion in 1995 to almost 4.6 billion in 2020. The greatest growth in demand is expected to come from the lower-income countries of Asia, such as Bangladesh, India, Myanmar, Philippines, and Viet Nam, she said. However, in terms of overall food supplies, the Organization for Economic Cooperation and Development (OECD) estimates that food supplies will be sufficient. "Expecting reasonably strong productivity growth to be sustainable, no global food crisis seems likely to occur" between now and 2020, the organization stated in its report entitled "The World in 2020: Towards a New Global Age". PMID:12321308

1997-01-01

161

Demographic modeling of transient amplifying cell population growth.  

PubMed

Quantitative measurement for the timings of cell division and death with the application of mathematical models is a standard way to estimate kinetic parameters of cellular proliferation. On the basis of label-based measurement data, several quantitative mathematical models describing short-term dynamics of transient cellular proliferation have been proposed and extensively studied. In the present paper, we show that existing mathematical models for cell population growth can be reformulated as a specific case of generation progression models, a variant of parity progression models developed in mathematical demography. Generation progression ratio (GPR) is defined for a generation progression model as an expected ratio of population increase or decrease via cell division. We also apply a stochastic simulation algorithm which is capable of representing the population growth dynamics of transient amplifying cells for various inter-event time distributions of cell division and death. Demographic modeling and the application of stochastic simulation algorithm presented here can be used as a unified platform to systematically investigate the short term dynamics of cell population growth. PMID:24245725

Nakaoka, Shinji; Inaba, Hisashi

2014-04-01

162

Exponential Graphing Using Technology  

NSDL National Science Digital Library

This lesson is teacher/student directed for discovering and translating exponential functions using a graphing app. The lesson focuses on the translations from a parent graph and how changing the coefficient, base and exponent values relate to the transformation.

Gaynr, Cheryl

2012-07-27

163

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

PubMed

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 provided to 3 productive sectors: traditional agriculture, small factories producing mass consumption goods, and construction of low income housing. The strategy would promote economic growth and expansion without further deterioration of income distribution, employment, and price stability. A simulation study demonstrated the advantages of such a strategy in relation to alternative strategies. PMID:12266019

Banguero, H

1983-05-01

164

A nonlinear structured population model of tumor growth with quiescence  

Microsoft Academic Search

A nonlinear structured cell population model of tumor growth is considered. The model distinguishes between two types of cells\\u000a within the tumor: proliferating and quiescent. Within each class the behavior of individual cells depends on cell size, whereas\\u000a the probabilities of becoming quiescent and returning to the proliferative cycle are in addition controlled by total tumor\\u000a size. The asymptotic behavior

M. Gyllenberg; G. F. Webb

1990-01-01

165

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

PubMed

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 educating and empowering women in these enclaves. Women are in charge of birth spacing and all aspects of management of energy, food, water and the local environment, more so than men, in most countries. PMID:12284190

Shaw, R P

1989-01-01

166

POPULATION GROWTH IN U.S. COUNTIES, 1840-1990  

Microsoft Academic Search

We examine the location and growth of the U.S. population using county-level census data from 1840 and 1990. Counties are described by natural and produced characteristics they possessed in 1840. Natural characteristics include climate, mineral resources and access to natural transportation networks. Produced characteristics include industry mix, educational infrastructure, literacy rates, and access to man-made transportation systems. We investigate how

Patricia E. Beeson; David N. DeJong; Werner Troesken

1999-01-01

167

An Unusual Exponential Graph  

ERIC Educational Resources Information Center

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…

Syed, M. Qasim; Lovatt, Ian

2014-01-01

168

Genomic growth curves of an outbred pig population.  

PubMed

In the current post-genomic era, the genetic basis of pig growth can be understood by assessing SNP marker effects and genomic breeding values (GEBV) based on estimates of these growth curve parameters as phenotypes. Although various statistical methods, such as random regression (RR-BLUP) and Bayesian LASSO (BL), have been applied to genomic selection (GS), none of these has yet been used in a growth curve approach. In this work, we compared the accuracies of RR-BLUP and BL using empirical weight-age data from an outbred F2 (Brazilian Piau X commercial) population. The phenotypes were determined by parameter estimates using a nonlinear logistic regression model and the halothane gene was considered as a marker for evaluating the assumptions of the GS methods in relation to the genetic variation explained by each locus. BL yielded more accurate values for all of the phenotypes evaluated and was used to estimate SNP effects and GEBV vectors. The latter allowed the construction of genomic growth curves, which showed substantial genetic discrimination among animals in the final growth phase. The SNP effect estimates allowed identification of the most relevant markers for each phenotype, the positions of which were coincident with reported QTL regions for growth traits. PMID:24385855

Silva, Fabyano Fonseca E; de Resende, Marcos Deon V; Rocha, Gilson Silvério; Duarte, Darlene Ana S; Lopes, Paulo Sávio; Brustolini, Otávio J B; Thus, Sander; Viana, José Marcelo S; Guimarães, Simone E F

2013-12-01

169

Cross-population analysis of the growth of long bones and the os coxae of three Early Medieval Austrian populations.  

PubMed

Inter-population variability in long-bone and pelvic-bone growth during the Early Medieval period is examined. The materials comprise four archaeological populations: two Slavonic (Gars-Thunau, Zwentendorf, Austria, 10th-century AD), one Avar (Zwölfaxing, Austria, 8th-century AD), and one Anglo-Saxon (Raunds, England, 10th-century AD). Bone measurements are analyzed against dental age estimates in order to assess inter-population differences in growth rates for long-bone and os coxae bone dimensions. Growth curves of the upper and lower extremities of additional archaeological populations and a modern North-American population are also assessed. The expectation was that the greatest differences in growth patterns would be found between the Anglo-Saxon and the Austrian samples, due to their distinct genetic and biocultural background. Minimal differences were expected between the two Slavonic populations, as these were approximately contemporaneous, recovered from geographically close locations, and shared relatively similar archaeological contexts. Growth curves were estimated for each bone dimension by fitting least-squares fourth-order polynomials (which allowed testing of population differences by analysis of covariance), and iteratively estimating Gompertz growth curves. The results showed differences between bones in the extent of inter-population variability, with diaphyseal long-bone growth showing equivalent patterns across the four populations, but significant differences between populations in the growth patterns of distal diaphyseal dimensions of the femur and humerus and the dimensions of the ilium. Varying growth patterns are therefore associated with inter-population differences in absolute dimensions in relation to age as well as variations in growth velocities. Inter-population variability in growth curves in the case of femoral and humeral dimensions were most pronounced during infancy (0-2 years). The most consistent differences in bone growth and related dimensions are between Zwölfaxing and the other samples. No significant differences in growth were detected between the Anglo-Saxon and the Austrian populations. PMID:15981184

Pinhasi, R; Teschler-Nicola, M; Knaus, A; Shaw, P

2005-01-01

170

Acetate Availability and Utilization Supports the Growth of Mutant Sub-Populations on Aging Bacterial Colonies  

PubMed Central

When bacterial colonies age most cells enter a stationary phase, but sub-populations of mutant bacteria can continue to grow and accumulate. These sub-populations include bacteria with mutations in rpoB (RNA polymerase ?-subunit) or rpoS (RNA polymerase stress-response sigma factor). Here we have identified acetate as a nutrient present in the aging colonies that is utilized by these mutant subpopulations to support their continued growth. Proteome analysis of aging colonies showed that several proteins involved in acetate conversion and utilization were upregulated during aging. Acetate is known to be excreted during the exponential growth phase but can be imported later during the transition to stationary phase and converted to acetyl-CoA. Acetyl-CoA is used in multiple processes, including feeding into the TCA cycle, generating ATP via the glyoxylate shunt, as a source of acetyl groups for protein modification, and to support fatty acid biosynthesis. We showed that deletion of acs (encodes acetyl-CoA synthetase; converts acetate into acetyl-CoA) significantly reduced the accumulation of rpoB and rpoS mutant subpopulations on aging colonies. Measurement of radioactive acetate uptake showed that the rate of conversion decreased in aging wild-type colonies, was maintained at a constant level in the rpoB mutant, and significantly increased in the aging rpoS mutant. Finally, we showed that the growth of subpopulations on aging colonies was greatly enhanced if the aging colony itself was unable to utilize acetate, leaving more acetate available for mutant subpopulations to use. Accordingly, the data show that the accumulation of subpopulations of rpoB and rpoS mutants on aging colonies is supported by the availability in the aging colony of acetate, and by the ability of the subpopulation cells to convert the acetate to acetyl-CoA. PMID:25275605

Bergman, Jessica M.; Wrande, Marie; Hughes, Diarmaid

2014-01-01

171

Acetate availability and utilization supports the growth of mutant sub-populations on aging bacterial colonies.  

PubMed

When bacterial colonies age most cells enter a stationary phase, but sub-populations of mutant bacteria can continue to grow and accumulate. These sub-populations include bacteria with mutations in rpoB (RNA polymerase ?-subunit) or rpoS (RNA polymerase stress-response sigma factor). Here we have identified acetate as a nutrient present in the aging colonies that is utilized by these mutant subpopulations to support their continued growth. Proteome analysis of aging colonies showed that several proteins involved in acetate conversion and utilization were upregulated during aging. Acetate is known to be excreted during the exponential growth phase but can be imported later during the transition to stationary phase and converted to acetyl-CoA. Acetyl-CoA is used in multiple processes, including feeding into the TCA cycle, generating ATP via the glyoxylate shunt, as a source of acetyl groups for protein modification, and to support fatty acid biosynthesis. We showed that deletion of acs (encodes acetyl-CoA synthetase; converts acetate into acetyl-CoA) significantly reduced the accumulation of rpoB and rpoS mutant subpopulations on aging colonies. Measurement of radioactive acetate uptake showed that the rate of conversion decreased in aging wild-type colonies, was maintained at a constant level in the rpoB mutant, and significantly increased in the aging rpoS mutant. Finally, we showed that the growth of subpopulations on aging colonies was greatly enhanced if the aging colony itself was unable to utilize acetate, leaving more acetate available for mutant subpopulations to use. Accordingly, the data show that the accumulation of subpopulations of rpoB and rpoS mutants on aging colonies is supported by the availability in the aging colony of acetate, and by the ability of the subpopulation cells to convert the acetate to acetyl-CoA. PMID:25275605

Bergman, Jessica M; Wrande, Marie; Hughes, Diarmaid

2014-01-01

172

Population, internal migration, and economic growth: an empirical analysis.  

PubMed

The role of population growth in the development process has received increasing attention during the last 15 years, as manifested in the literature in 3 broad categories. In the 1st category, the effects of rapid population growth on the growth of income have been studied with the use of simulation models, which sometimes include endogenous population growth. The 2nd category of the literature is concerned with theoretical and empirical studies of the economic determinants of various demographic rates--most usually fertility. Internal migration and dualism is the 3rd population development category to recieve attention. An attempt is made to synthesize developments in these 3 categories by estimating from a consistent set of data a 2 sector economic demographic model in which the major demographic rates are endogenous. Due to the fact that the interactions between economic and demographic variables are nonlinear and complex, the indirect effects of changes in a particular variable may depend upon the balance of numerical coefficients. For this reason it was felt that the model should be empirically grounded. A brief overview of the model is provided, and the model is compared to some similar existing models. Estimation of the model's 9 behavior equations is discussed, followed by a "base run" simulation of a developing country "stereotype" and a report of a number of policy experiments. The relatively new field of economic determinants of demographic variables was drawn upon in estimating equations to endogenize demographic phenomena that are frequently left exogenous in simulation models. The fertility and labor force participation rate functions are fairly standard, but a step beyong existing literature was taken in the life expectancy and intersectorial migration equations. On the economic side, sectoral savings functions were estimated, and it was found that the marginal propensity to save is lower in agriculture than in nonagriculture. Testing to see the effect of a population's age structure on savings rather than assuming a particular direction as Coale-Hoover and Simon do in their models, it was found that a higher proportion of children compete with savings in agriculture but complement savings in industrial areas. This was consistent with the economic value of children in agricultural and nonagricultural regions of less developed countries. The estimated production functions showed that marginal products of labor were considerably higher in agriculture than in nonagriculture. As with other simulation models, the effect of reducing fertility was to accelerate income growth. Reductions in rural fertility were more equitable and raised the overall level of per capita income more than similar efforts directed to urban areas only. PMID:12264901

Moreland, R S

1982-01-01

173

Population growth and food supply in sub-Saharan Africa.  

PubMed

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 of the West African forest belt. There is also the absence of the Green Revolution, i.e., the use of new high yielding seeds and new technologies in agriculture that has led to marked increases in yields in most other parts of the world. A totally different and more productive agriculture might evolve if African governments were to fundamentally change their vision. Existing production technology could allow substantial increases in the yields of many crops if some basic changes were made in the policies affecting agriculture. A way to achieve such change would be to make farming profitable. The effect of population growth in diminishing returns to agriculture also lends urgency to the need for family planning. Generally, population policy in Africa badly needs strengthening. PMID:12264271

Meerman, J; Cochrane, S H

1982-09-01

174

Interspecific synchrony of seabird population growth rate and breeding success.  

PubMed

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

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

2013-07-01

175

Interspecific synchrony of seabird population growth rate and breeding success  

PubMed Central

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

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

2013-01-01

176

Analysis of the impact of population growth in Henan Province on its environment and ecosystem.  

PubMed

"This paper analyzes the effects of population growth on the...environment and ecosystem [of China's Henan Province]. This paper also proposes a key countermeasure to deal with the population growth and environmental improvement of Henan Province." PMID:12294146

Zhao, J

1997-01-01

177

Population growth of Yellowstone grizzly bears: Uncertainty and future monitoring  

USGS Publications Warehouse

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 (??); (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 ?? 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 ?? that were nearly identical to those from the earlier model that omitted correlations, but yielded wider confidence intervals surrounding ??. 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 ?? provides an objective means to monitoring approximate population trajectories in addition to demographic analysis.

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

2007-01-01

178

Herbivory: effects on plant abundance, distribution and population growth  

PubMed Central

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

Maron, John L; Crone, Elizabeth

2006-01-01

179

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

ERIC Educational Resources Information Center

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…

Perry, Marc

2002-01-01

180

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

PubMed

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. During 1900-1941, population was below or at replacement level, but the government still blamed Malagasys. Shifting cultivation meant different things to the subsistence farmers, the state, and international agencies. Denial of context promotes an ideology of repression, fuels fear and prejudice, and promotes the wrong solutions. PMID:12318844

Jarosz, L

1993-10-01

181

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

PubMed

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

Yamaguchi, M; Kennedy, G

1984-09-01

182

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

PubMed

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

Pimentel, D

1991-01-01

183

[The interrelationships among population growth, underdevelopment, and the preservation of peace].  

PubMed

The interrelationships among population growth, underdevelopment, and the preservation of peace are considered. The author first argues that the dilemma of developing countries is not simply population growth but population growth in the absence of the regulating and stabilizing forces need to employ and nourish its numbers. Among the topics discussed are the global history and current trends of population growth, natural resources, demographic transitions, social change and its consequences in third world countries, malnutrition, and the growth of slums in the nuclear age. He also discusses the increased involvement of developing countries in the arms race. PMID:12268736

Khalatbari, P

1986-07-01

184

Bluegill Recruitment, Growth, Population Size Structure, and Associated Factors in Minnesota Lakes  

Microsoft Academic Search

To better understand the differences among populations of bluegill Lepomis macrochirus, we analyzed the relationships between bluegill recruitment, growth, population size structure, and associated factors from approximately 2,600 Minnesota lakes. Potential explanatory variables for our models included bluegill year-class strength, growth, population size structure, the relative abundance and mean weight of predator species, physical and chemical characteristics of lakes, summer

Cynthia M. Tomcko; Rodney B. Pierce

2005-01-01

185

Population, Technology, and Growth: From the Malthusian Regime to the Demographic Transition  

Microsoft Academic Search

This paper develops a unified model of growth, population, and technological progress that is consistent with long-term historical evidence. The economy endoge- nously evolves through three phases. In the Malthusian regime, population growth is positively related to the level of income per capita. Technological progress is slow and is matched by proportional increases in population, so that output per capita

Oded Galor; David N. Weill

2000-01-01

186

Population, Technology, and Growth: From the Malthusian Regime to the Demographic Transition  

Microsoft Academic Search

This paper develops a unified model of growth, population, and technological progress that is consistent with long-term historical evidence. The economy endogenously evolves through three phases. In the Malthusian regime, population growth is positively related to the level of income per capita. Technological progress is slow and is matched by proportional increases in population, so that output per capita is

Oded Galor; David N. Weil

1998-01-01

187

Evolution of thermal physiology and growth rate between populations of the western fence lizard ( Sceloporus occidentalis )  

Microsoft Academic Search

Hatchling Sceloporus occidentalis from northern populations (central Oregon) grow more slowly than hatchlings from southern populations (southern California) in nature. In this study, I determine whether this difference in growth rate results from differences in thermal environment and\\/or in thermoregulatory behavior. To determine the degree to which the thermal environment affects growth rate among populations, I reared hatchings from the

Barry Sinervo

1990-01-01

188

Populations  

NSDL National Science Digital Library

This chapter introduces population as a group of the same kind of organisms in a given space at a given time. The activities in this section will provide students with the opportunity to define population, estimate populations in a community, and count and compare populations within a community. Students will gain the knowledge in describing plant and animal populations living in a community. They will also experiment with plant populations to control growth and development, not to mention discuss the effects of abiotic conditions on a community.

Galle, Janet R.; Warren, Patricia A.

2005-01-01

189

Decomposing variation in population growth into contributions from environment and phenotypes in an age-structured population  

PubMed Central

Evaluating the relative importance of ecological drivers responsible for natural population fluctuations in size is challenging. Longitudinal studies where most individuals are monitored from birth to death and where environmental conditions are known provide a valuable resource to characterize complex ecological interactions. We used a recently developed approach to decompose the observed fluctuation in population growth of the red deer population on the Isle of Rum into contributions from climate, density and their interaction and to quantify their relative importance. We also quantified the contribution of individual covariates, including phenotypic and life-history traits, to population growth. Fluctuations in composition in age and sex classes ((st)age structure) of the population contributed substantially to the population dynamics. Density, climate, birth weight and reproductive status contributed less and approximately equally to the population growth. Our results support the contention that fluctuations in the population's (st)age structure have important consequences for population dynamics and underline the importance of including information on population composition to understand the effect of human-driven changes on population performance of long-lived species. PMID:21715404

Pelletier, Fanie; Moyes, Kelly; Clutton-Brock, Tim H.; Coulson, Tim

2012-01-01

190

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 ...

191

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

ERIC Educational Resources Information Center

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)

Carter, Ashley J. R.

1999-01-01

192

Estimating effects of adult male mortality on grizzly bear population growth and persistence using matrix models  

Microsoft Academic Search

We radio monitored a hunted, sexually segregated grizzly bear (Ursus arctos) population and an unhunted, unsegregated population for demographics and constructed a stage- and age-classified matrix model to test for the effects of adult male mortality and resulting sexual segregation on population growth and persistence. Population parameters in the model were adult female survival, subadult female survival, offspring survival, probability

Robert B. Wielgus; Francois Sarrazin; Regis Ferriere; Jean Clobert

2001-01-01

193

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

ERIC Educational Resources Information Center

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…

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

194

Periodic Exponential Shear of Complex Fluids  

E-print Network

We define a class of flows with exponential kinematics termed Periodic Exponential Shear (PES) flow which involve periodic exponential stretching of fluid elements along with their rotation. We exhibit analytical and numerical results for PES flow by using the Oldroyd-B model for viscoelastic fluids. We calculate the growth in the shear and the normal stresses analytically as well as demonstrate that repeated application of the flow leads to stable oscillatory shear and normal stresses. We define a material function applicable to a periodic, unsteady shear flow and show numerically that this material function exhibits deformation-rate thickening behavior for viscoelastic fluids subject to PES flow. We demonstrate the feasibility of PES flow by presenting preliminary experimental results from a controlled-strain rate rheometer, using a Newtonian mineral oil.

Chirag Kalelkar; Gareth McKinley

2012-05-31

195

Why does human culture increase exponentially?  

PubMed

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

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

2008-08-01

196

Effects of growth phase and temperature on ?B activity within a Listeria monocytogenes population: evidence for RsbV-independent activation of ?B at refrigeration temperatures.  

PubMed

The alternative sigma factor ?B of Listeria monocytogenes is responsible for regulating the transcription of many of the genes necessary for adaptation to both food-related stresses and to conditions found within the gastrointestinal tract of the host. The present study sought to investigate the influence of growth phase and temperature on the activation of ?B within populations of L. monocytogenes EGD-e wild-type, ?sigB, and ?rsbV throughout growth at both 4°C and 37°C, using a reporter fusion that couples expression of EGFP to the strongly ?B-dependent promoter of lmo2230. A similar ?B activation pattern within the population was observed in wt-egfp at both temperatures, with the highest induction of ?B occurring in the early exponential phase of growth when the fluorescent population rapidly increased, eventually reaching the maximum in early stationary phase. Interestingly, induction of ?B activity was heterogeneous, with only a proportion of the cells in the wt-egfp population being fluorescent above the background autofluorescence level. Moreover, significant RsbV-independent activation of ?B was observed during growth at 4°C. This result suggests that an alternative route to ?B activation exists in the absence of RsbV, a finding that is not explained by the current model for ?B regulation. PMID:24734238

Utratna, Marta; Cosgrave, Eoin; Baustian, Claas; Ceredig, Rhodri H; O'Byrne, Conor P

2014-01-01

197

Predicting the growth of a small introduced muskox population using population prediction intervals  

Microsoft Academic Search

Summary 1. A key issue in ecology is the prediction of future population fluctuations. Such population predictions are fundamental for population-viability analysis and are essential for assessing the implications of various management actions. Development of reliable population predictions is however, difficult because it requires estimation and modelling of the separate effects of the deterministic components of the population dynamics as

EINAR J. ASBJORNSEN; BERNT-ERIK SAETHER; JOHN D. C. LINNELL; STEINAR ENGEN; REIDAR ANDERSEN; TORD BRETTEN

2005-01-01

198

Habitat heterogeneity affects population growth in goshawk Accipiter gentilis  

Microsoft Academic Search

Summary 1. The concept of site-dependent population regulation combines the ideas of Ideal Free Distribution-type of habitat settlement and density dependence in a vital rate mediated by habitat heterogeneity. The latter is also known as habitat heterogeneity hypothesis. Site-dependent population regulation hypothesis predicts that increasing population density should lead to inhabitation of increasingly poor territories and decreasing per capita population

Oliver Kruger; Jan Lindstrom

2001-01-01

199

Variation in juvenile growth rates among and within latitudinal populations of the medaka  

Microsoft Academic Search

In ectotherms, lower temperatures at high latitudes would theoretically reduce annual growth rates of individuals. If slower\\u000a growth and resulting smaller body size reduce fitness, individuals at high latitudes may evolve compensatory growth. This\\u000a study compares individual growth rates among and within 12 latitudinal populations of the medaka (Oryzias latipes). Growth rates during juvenile stage were measured in a common,

Kazunori Yamahira; Kenichi Takeshi

2008-01-01

200

INSECTSYMBIONT INTERACTIONS Population Growth of Aphis gossypii and Myzus persicae (Hemiptera  

E-print Network

INSECTÐSYMBIONT INTERACTIONS Population Growth of Aphis gossypii and Myzus persicae (Hemiptera the population growth of an aphid mutualist, Aphis gossypii, and a nonmutualist, Myzus persicae, exposed to two encounters with L. humile. L. humile ignored M. persicae when A. gossypii was absent, whereas T. sessile

Buckel, Jeffrey A.

201

Population Growth Rate: Teaching Guide. Measures of Progress Poster Kit Number 2.  

ERIC Educational Resources Information Center

This teaching guide accompanies the Population Growth Rate poster kit which is designed to teach students about population growth differences between rich and poor nations and about what people in developing countries are doing to help improve their quality of life. The guide is designed for use with: (1) a poster map of the world providing social…

World Bank, Washington, DC.

202

Population, Technology, and Growth: From Malthusian Stagnation to the Demographic Transition and Beyond  

Microsoft Academic Search

This paper develops a unified growth model that captures the historical evolution of population, technology, and output. It encompasses the endogenous transition between three regimes that have characterized economic development. The economy evolves from a Malthusian regime, where technological progress is slow and population growth prevents any sustained rise in income per capita, into a Post-Malthusian regime, where technological progress

Oded Galor; David N. Weil

2000-01-01

203

Growth of geologic fractures into large-strain populations: review of nomenclature, subcritical crack growth, and some implications  

E-print Network

Growth of geologic fractures into large-strain populations: review of nomenclature, subcritical crack growth, and some implications for rock engineering R.A. Schultz* Geomechanics-Rock Fracture Group of Nevada, Reno, NV 89557, USA Accepted 7 October 1999 Abstract Several aspects of fracture arrays

204

Population Growth, (Per Capita) Economic Growth, and Poverty Reduction in Uganda: A brief Summary of Theory and Evidence  

E-print Network

significantly contribute to improvements in poverty, inequality, education, and health outcomes. The notePopulation Growth, (Per Capita) Economic Growth, and Poverty Reduction in Uganda: A brief Summary prospects in Uganda. Moreover, it contributes significantly to low achievements in education, health

Krivobokova, Tatyana

205

Climate, Growth and Population Dynamics of Yukon River Chinook Salmon  

E-print Network

in response to fewer returning salmon. We examined annual growth of age-1.3 and age-1.4 Yukon Chinook salmon scales, 1965–2004, and tested the hypothesis that shifts in Chinook salmon abundance were related to annual growth at sea. Annual scale growth trends were not significantly correlated with salmon abundance indices, sea surface temperature, or climate indices, although growth during the first year at sea appeared to have been affected by the 1977 and 1989 ocean regime shifts. Chinook salmon scale growth was dependent on growth during the previous year, a factor that may have confounded detection of relationships among growth, environmental conditions, and abundance. Scale growth during the second year at sea was greater in oddnumbered years compared with even-numbered years, leading to greater adult length of age-1.3 salmon in oddnumbered years. The alternating-year pattern in Chinook salmon growth was opposite that observed in Bristol Bay sockeye salmon, and it may be related to the higher trophic level of Chinook salmon and indirect competition with pink salmon. This finding highlights the need to investigate alternating-year patterns in salmon growth, prey abundance, and factors that influence these patterns, such as pink salmon.

unknown authors

206

EXPERIMENTAL MANIPULATION OF POPULATION DENSITY AND ITS EFFECTS ON GROWTH AND MORTALITY OF JUVENILE  

E-print Network

EXPERIMENTAL MANIPULATION OF POPULATION DENSITY AND ITS EFFECTS ON GROWTH AND MORTALITY OF JUVENILE growth and mortality for different density groups of juvenile western rock (spiny) lobsters, PanUU'I"l18 of juveniles on a reef may lead to a corresponding reduction in mortality, but no effect on growth was evident

207

Coordination of Gene Expression and Growth-Rate in Natural Populations of Budding Yeast  

E-print Network

Coordination of Gene Expression and Growth-Rate in Natural Populations of Budding Yeast Zvi Tamari expression. In the budding yeast, ribosomal-related gene expression correlates with cell growth rate across different environments. To examine whether the same relationship between gene expression and growth rate

Barkai, Naama

208

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

Microsoft Academic Search

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 quantita- tive

Getu Degu Alene; Alemayehu Worku

2009-01-01

209

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

ERIC Educational Resources Information Center

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…

Newman, Constance

210

MathHelp Notebook on Exponential Functions  

NSDL National Science Digital Library

This site from MathHelp provides an explanation of exponential functions that includes some information on radioactive decay. Other topics include exponential functions, exponential decay, and exploring graphs of exponential functions.

Mathhelp; London, University C.

211

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

PubMed

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

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

2012-01-01

212

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

PubMed Central

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

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

2012-01-01

213

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

ERIC Educational Resources Information Center

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…

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

214

Name:_____________________________ Age Structure and Population Growth. Due March 29.  

E-print Network

:_____________________________ COUNTRY 1 COUNTRY 2 Country Name Where is this country? What type of country is this? (Rich, poor, at war Crude Birth Rate (Births/1000 population/year) Crude Death Rate (Deaths/1000 population/year) Life:_____________________________ 3) 6 points Comment on the birth rates, death rates, and r's for these countries--for example

Mitchell, Randall J.

215

On the Matrix Exponential Function  

ERIC Educational Resources Information Center

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.

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

2006-01-01

216

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

PubMed

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

Steinmann, G; Komlos, J

1988-08-01

217

Four centuries of British economic growth: the roles of technology and population  

Microsoft Academic Search

Using long historical data for Britain over the period 1620–2006, this paper seeks to explain the importance of innovative\\u000a activity, population growth and other factors in inducing the transition from the Malthusian trap to the post-Malthusian growth\\u000a regime. Furthermore, the paper tests the ability of two competing second-generation endogenous growth models to account for\\u000a the British growth experience. The results

Jakob B. Madsen; James B. Ang; Rajabrata Banerjee

2010-01-01

218

POPULATION ECOLOGY Divergent compensatory growth responses within species  

E-print Network

; Atlantic salmon (Salmo salar) Nicieza and Metcalfe 1997; brown trout (Salmo trutta) Johnnson and Bohlin growth following food restriction between groups (control, treatment) of two Atlantic salmon (Salmo salar

Hutchings, Jeffrey A.

219

Population growth of Yellowstone grizzly bears: uncertainty and future monitoring  

E-print Network

(Ursus arctos) in the Greater Yellowstone Ecosystem of the US Rocky Mountains have recently increased, uncertainty, Ursus arctos, Yellowstone Ursus 18(2):168­178 (2007) The grizzly bear (Ursus arctos) population

Harris, Richard B.

220

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

PubMed

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 (?) decreased from 1.0419 to 0.9991 under pulsed Cu activities ranging from 1.6 to 2.0 ?g L(-1). Our results revealed that the influence on ? 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

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

2012-11-01

221

A question of dignity. Impact of rapid population growth on developing countries.  

PubMed

Rapid population growth is one of the major contributing factors to the poverty and under-development of Third World countries--especially African countries, which boast the highest population growth rates in the world. Several factors are responsible for the rapid growth: a drop in mortality rates, a young population, improved standards of living, and attitudes and practices which favor high fertility. Africans view large families as an economic asset and as a symbol of worth and honor, and parents see it as security during old age. The ideal family size in Africa is 5 to 7 children. Because of its complex causes, curbing the rapid growth is not easy. In addition to strategic difficulties, population policies usually meet opposition, often from religious groups. So in order to gain acceptance, population programs need to be integrated with ongoing community development programs. Even though it often engenders opposition, family planning is more crucial then ever, as the rapid population growth continues to create an explosive situation. Rapid growth has led to uncontrolled urbanization, which has produced overcrowding, destitution, crime, pollution, and political turmoil. Rapid growth has outstripped increases in food production, and population pressure has led to the overuse of arable land and its destruction. Rapid growth has also hampered economic development and caused massive unemployment. 45% of Kenya's labor force is unemployed. Ultimately, rapid growth has undermined the quality of life of people. Society's responsibility extends beyond simply ensuring the survival of the population. Society must strive to provide people with a good life--one with dignity. PMID:1960918

Osoro, A A

1991-06-01

222

Cell growth and size homeostasis in silico.  

PubMed

Cell growth in size is a complex process coordinated by intrinsic and environmental signals. In a research work performed by a different group, size distributions of an exponentially growing population of mammalian cells were used to infer cell-growth rate in size. The results suggested that cell growth was neither linear nor exponential, but subject to size-dependent regulation. To explain the observed growth pattern, we built a mathematical model in which growth rate was regulated by the relative amount of mRNA and ribosomes in a cell. Under the growth model and a stochastic division rule, we simulated the evolution of a population of cells. Both the sampled growth rate and size distribution from this in silico population agreed well with experimental data. To explore the model space, alternative growth models and division rules were studied. This work may serve as a starting point to understand the mechanisms behind cell growth and size regulation using predictive models. PMID:24606924

Hu, Yucheng; Zhu, Tianqi

2014-03-01

223

Population Growth and Affluence: The Fissioning of Human Society. Caltech Population Program Occasional Papers, Series 1, Number 9.  

ERIC Educational Resources Information Center

This paper compares population growth and affluence in developed nations in which per capita income and consumption have been relatively high, and in developing nations in which per capita income and consumption have been relatively low. The paper is one in a series of occasional publications intended to increase understanding of the…

Brown, Harrison

224

Linking the Population Growth Rate and the Age-at-Death Distribution  

PubMed Central

The population growth rate is linked to the distribution of age at death. We demonstrate that this link arises because both the birth and death rates depend on the variance of age-at-death. This bears the prospect to separate the influences of the age patterns of fertility and mortality on population growth rate. Here, we show how the age pattern of death affects population growth. Using this insight we derive a new approximation of the population growth rate that uses the first and second moments of the age-at-death distribution. We apply our new approximation to 46 mammalian life tables (including humans) and show that it is on par with the most prominent other approximations. PMID:23103877

Schindler, Susanne; Tuljapurkar, Shripad; Gaillard, Jean-Michel; Coulson, Tim

2013-01-01

225

Genetic variability in a population of arbuscular mycorrhizal fungi causes variation in plant growth  

E-print Network

LETTER Genetic variability in a population of arbuscular mycorrhizal fungi causes variation species of arbuscular mycorrhizal fungi (AMF) alter plant growth and affect plant coexistence these important soil organisms. Keywords Arbuscular mycorrhizal fungi, benefits, costs, functional variability

Alvarez, Nadir

226

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

PubMed Central

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

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

2014-01-01

227

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

PubMed

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

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

2014-01-01

228

ORIGINAL PAPER Potential for successful population establishment  

E-print Network

in the Arthur R. Marshall Loxahatchee National Wildlife Refuge. Prior to this, sacred ibises were seen, thus adding to the potential to increase their breeding population. Exponential population growth rates is eradication of the few pio- neering individuals that are nesting in the Everglades as well as the urban source

Gawlik, Dale E.

229

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

PubMed

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 in the Southern countries. Quantitative studies have been unable to demonstrate at the global level that demographic growth has a primordial effect on the environment. The ecological consequences of poverty cannot be reduced without attacking poverty itself, of which high fertility is but 1 aspect. A growing but still insufficient number of smaller scale studies suggest that demographic growth is not always the major element in environmental damage or in preventable exhaustion of resources. Specific studies are needed on well-defined populations in order to unravel the effects of population growth and other factors. The approach should be systemic and transdisciplinary, depending on a less fragmented vision of reality than that reflected in traditional disciplinary boundaries. PMID:12343873

Tabutin, D; Thiltges, E

1992-01-01

230

Age-specific growth rates: The legacy of past population dynamics  

Microsoft Academic Search

Recent developments in population mathematics have focused attention on a function that is widely available but rarely examined:\\u000a the set of age-specific growth rates in a population. In particular, this set of rates is sufficient for translating the current\\u000a birth rate and age-specific mortality rates into the current age distribution. This growth-rate function contains all of the\\u000a pertinent features of

Shiro Horiuchi; Samuel H. Preston

1988-01-01

231

Constant savings rates and quasi-arithmetic population growth under exhaustible resource constraints  

Microsoft Academic Search

In the Dasgupta–Heal–Solow–Stiglitz (DHSS) model of capital accumulation and resource depletion we show the following equivalence: if an efficient path has constant (gross and net of population growth) savings rates, then population growth must be quasi-arithmetic and the path is a maximin or a classical utilitarian optimum. Conversely, if a path is optimal according to maximin or classical utilitarianism (with

Geir B. Asheim; Wolfgang Buchholz; John M. Hartwick; Tapan Mitra; Cees Withagene

2007-01-01

232

Population Growth & Issues Can we feed the growing world  

E-print Network

-- Environmental and ecological problems Soil erosion, soil degradation Water pollution Health hazards: Rachel) Redistribute food E) Change life style Production vs. distribution Can we feed world population? Overshoot the carrying capacity? Production vs. distribution How to increase food production? Extensification: put

Huang, Youqin

233

Damage segregation in fissioning organisms increases population growth rates  

E-print Network

that this is not so. Early descendants become steadily wearier and less sprightly. Each rod-shaped E. coli has two organisms it seems unlikely." Damage segregation in E. coli experiments in the lab of Francois Taddei track all the individ- uals in a population of E. coli through several generations and measure the amount

Durrett, Richard

234

Polyandry and population growth in a historical Tibetan society  

Microsoft Academic Search

Despite considerable speculation virtually nothing is known about the empirical relationship between traditional Tibetan administrative systems, household processes, and demographic trends in historical Tibetan populations because indigenous data sources have never been systematically analyzed. This article examines a 1958 tax register from Kyirong, formerly a district-level political division in southern Tibet, and demonstrates the significance of such archival sources for

Geoff Childs

2003-01-01

235

Calculating the Financial Impact of Population Growth on Education.  

ERIC Educational Resources Information Center

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…

Cline, Daniel H.

236

Structured Populations, Cell Growth and Measure Valued Balance Laws  

E-print Network

of individuals [13, 21] with a specific structural variable x, for instance the age for the age-structured equation [22] or a phenotypic trait for the selection-mutation equations [5]. The typical functional space the McKendrick age structured population model [18] as well as the nonlinear age structured model [21, 22

237

Exponential Moving Average Stock Model  

NSDL National Science Digital Library

A primary application of econophysics is using digital signal processing techniques to filter and predict market data, which is theorized to exhibit random walk motion. An exponential moving average is one tool that physicists use to smooth data from an input signal to identify its trends. The Exponential Moving Average Stock Model implements three types of exponential moving averages and allows the user to change the parameters of each. The model allows the user to view the results of exponential moving averages computed on the New York Stock Exchange daily closing price of six familiar companies. It demonstrates one way that traders use causal filters to smooth market data and forecast the next day's price.

Mohorn, Matthew

2013-02-14

238

The Poisson and Exponential Models  

ERIC Educational Resources Information Center

The students in a basic course on probability and statistics in Trinidad demonstrated that the number of fatal highway accidents appeared to follow a Poisson distribution while the length of time between deaths followed exponential distribution. (MN)

Richards, Winston A.

1978-01-01

239

Exponential approximations in optimal design  

NASA Technical Reports Server (NTRS)

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.

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

1990-01-01

240

The beta exponentiated Weibull distribution  

Microsoft Academic Search

The Weibull distribution is one of the most important distributions in reliability. For the first time, we introduce the beta exponentiated Weibull distribution which extends recent models by Lee et al. [Beta-Weibull distribution: some properties and applications to censored data, J. Mod. Appl. Statist. Meth. 6 (2007), pp. 173–186] and Barreto-Souza et al. [The beta generalized exponential distribution, J. Statist.

Gauss M. Cordeiro; Antonio Eduardo Gomes; Cibele Queiroz da-Silva; Edwin M. M. Ortega

2011-01-01

241

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

USGS Publications Warehouse

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.

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

2007-01-01

242

Is Radioactive Decay Really Exponential?  

E-print Network

Radioactive decay of an unstable isotope is widely believed to be exponential. This view is supported by experiments on rapidly decaying isotopes but is more difficult to verify for slowly decaying isotopes. The decay of 14C can be calibrated over a period of 12,550 years by comparing radiocarbon dates with dates obtained from dendrochronology. It is well known that this approach shows that radiocarbon dates of over 3,000 years are in error, which is generally attributed to past variation in atmospheric levels of 14C. We note that predicted atmospheric variation (assuming exponential decay) does not agree with results from modelling, and that theoretical quantum mechanics does not predict exact exponential decay. We give mathematical arguments that non-exponential decay should be expected for slowly decaying isotopes and explore the consequences of non-exponential decay. We propose an experimental test of this prediction of non-exponential decay for 14C. If confirmed, a foundation stone of current dating methods will have been removed, requiring a radical reappraisal both of radioisotope dating methods and of currently predicted dates obtained using these methods.

Philip J. Aston

2012-04-26

243

The potential impact of AIDS on population and economic growth rates  

Microsoft Academic Search

AIDS is a human tragedy and a major health problem. The scale of the disease is so large that it now raises questions about the impact of AIDS on the future development path of many of the world's poorest developing countries. Through its effects on population levels and growth rates and on macroeconomic growth, AIDS may influence the prospects for

Lynn R. Brown

1997-01-01

244

Population Growth Makes Waves in the Distribution of Pairwise Genetic Differences  

Microsoft Academic Search

Episodes of population growth and decline leave characteristic signatures in the distribution of nucleotide (or restriction) site differences between pairs of individuals. These signatures appear in histograms showing the relative frequencies of pairs of individuals who differ by i sites, where i = 0, 1, . . . . In this distribution an episode of growth generates a wave that

Alan R. Rogers; Henry Harpending

245

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

E-print Network

have evaluated such contributions of vital rates to l for American black bears (Ursus americanus). We are consistent with predictions from studies on polar bears (U. maritimus) and grizzly bears (U. arctos Carolina, population growth rate, population modeling, sensitivity, Southern Appalachians, Ursus americanus

Mitchell, Mike

246

LARGE NONLETHAL EFFECTS OF AN INVASIVE INVERTEBRATE PREDATOR ON ZOOPLANKTON POPULATION GROWTH RATE  

Microsoft Academic Search

We conducted a study to determine the contribution of lethal and nonlethal effects to a predator's net effect on a prey's population growth rate in a natural setting. We focused on the effects of an invasive invertebrate predator, Bythotrephes longimanus ,o n zooplankton prey populations in Lakes Michigan and Erie. Field data taken at multiple dates and locations in both

Kevin L. Pangle; Scott D. Peacor; Ora E. Johannsson

2007-01-01

247

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...

248

Temporal stability in size distributions and growth rates of three Esox lucius L. populations.  

E-print Network

. A result of cannibalism? L. PERSSON*, A. BERTOLO* AND A. M. DE ROOS§ *Department of Ecology-history characteristics such as minimum and maximum victim:cannibal size ratios and (2) the cannibal-driven population: cannibalism; growth rates; pike; population length structure; predation window. INTRODUCTION The ability

Roos, André M. de

249

Voodoo forecasting: Technical, political and ethical issues regarding the projection of local population growth  

Microsoft Academic Search

The case of an energy production community in Colorado is used to illustrate a) the great need for reliable subnational population forecasts, especially in communities expecting rapid population growth, and b) why such projections, as currently performed, cannot be reliable. Explanations for failure in forecasting are found in the methods themselves, the unavailability and unreliability of key data, politics, and

Elizabeth W. Moen

1984-01-01

250

Stochastic model for population migration and the growth of human settlements during the Neolithic transition  

E-print Network

Stochastic model for population migration and the growth of human settlements during the Neolithic; published 12 August 2008 We present a stochastic two-population model that describes the migration transition. The main idea is that random migration and transition from a sedentary to a foraging way of life

Fedotov, Sergei

251

How Do Non-Reproductive Groups Affect Population Growth? Fabio Augusto Milner  

E-print Network

How Do Non-Reproductive Groups Affect Population Growth? Fabio Augusto Milner Abstract We describe of individuals who do not reproduce. We analyze the effect that the non- reproductive group may have on the dynamics of the whole population in terms of the vital rates and the proportion of non-reproductive

Milner, Fabio Augusto

252

Increasing population growth by asymmetric segregation of a limiting resource during cell division  

E-print Network

Increasing population growth by asymmetric segregation of a limiting resource during cell division times following the shift, generating at each division a single daughter cell, which arrests in G1 alleviates daughter cell division arrest in low-zinc conditions, it results in a lower final population size

Barkai, Naama

253

Age, Growth, and Population Dynamics of Common Bottlenose Dolphins (Tursiops truncatus) Along Coastal Texas  

E-print Network

1 Developmental Field Criteria .................................................................30 2 Length-at-Age Model Parameters..........................................................39 3 Sex-Specific Postnatal Growth..., particularly for populations for which few distribution data are available. The advantage to creating life tables is that they are easy to construct, only require age information, and yield much population information such as age specific mortality rates...

Neuenhoff, Rachel Dawn

2010-10-12

254

Consistent patterns of maturity and density-dependent growth among populations of walleye  

E-print Network

of walleye (Sander vitreus) from Ontario and Quebec, Canada (mean annual GDD = 1200 to 2300 8CÁdays´ provenant de 416 populations de dore´s jaunes (Sander vitreus) de l'Ontario et du Que´bec, Canada (moyenneConsistent patterns of maturity and density- dependent growth among populations of walleye (Sander

Venturelli, Paul

255

The environment and population growth: decade for action  

SciTech Connect

The signs of environmental stress grow as the world's population increases: worn-out farmlands, eroded hillsides, polluted water, parched grasslands, smoke-laden air, depleted ozone, and treeless ranges. Each year about 17 million hectares of tropical forest vanish--an area the size of Tunisia or Uruguay. Fish catches are leveling off. Cities are clogged with refuse. Water and air, instead of sustaining life, cause disease.

Not Available

1992-05-01

256

County wide employment and population growth: an analysis of the 1980s.  

PubMed

"Regional scientists remain interested in studying interregional differences in the growth rates of population and employment. Following the earlier work of Carlino and Mills, this paper examines growth trends at the county level in the U.S. during the period 1981-1989. Five major sectors of employment are examined. A partial adjustment model is developed that captures intercounty differences in amenities, business and fiscal conditions, demography, employment structure, and relative location. Some evidence is given that population and employment growth was simultaneous, although feedback effects apparently were not strong." PMID:12291905

Clark, D E; Murphy, C A

1996-05-01

257

The growth in the US uninsured population: trends in Hispanic subgroups, 1977 to 1992.  

PubMed Central

This paper presents trends in the growth in the US uninsured population, using cross-sectional national estimates from 1977, 1987, 1989, and 1992 and focusing specifically on coverage problems experienced by Hispanic Americans. An examination of the composition of uninsured persons added between 1977 and 1992 shows that almost 40% of the difference is accounted for by persons of Hispanic origin, with those of Mexican origin alone constituting 27%. In addition, the annual average rate of growth in the uninsured Hispanic population between 1977 and 1992 was 9.7%, compared with only 2.3% for the uninsured non-Hispanic population. Images FIGURE 1 PMID:8604794

Berk, M L; Albers, L A; Schur, C L

1996-01-01

258

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

USGS Publications Warehouse

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.

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

2011-01-01

259

The Power of Exponentials, Big and Small - MIT Blossoms  

NSDL National Science Digital Library

Exponential growth is keenly applicable to a variety of different fields ranging from cell growth in biology, nuclear chain reactions in physics to computational complexity in computer science. In this video-based lesson, through various examples and activities, we have tried to compare exponential growth to polynomial growth and to develop an insight about how quickly the number can grow or decay in exponentials. A basic knowledge of scientific notation, plotting graphs and finding intersection of two functions is assumed. It would be better if the students have done pre-calculus, though this is not a requirement. The lesson is about 20 minutes, interspersed with simple activities that can require up to half an hour. The webpage for this video also includes tabs where additional resources and information can be found. These include a Teacher's Guide, a Powers of 2 table, links to other helpful lessons and resources, a transcript of the video, and even an option to download the video.

Blossoms, Mit

2012-06-03

260

On the relationship between population growth and social and economic development.  

PubMed

China's population has grown rapidly since 1949, reaching a size of 1,008,170,000 by 1982. Rapid population growth has been encouraged by a high birth rate coupled with low mortality, traditional preference for sons, and the incorrect assumption that man is only a producer and not a consumer. Rapid population growth directly decreases economic development while producing a rapidly increasing labor force requiring an increase in the number of jobs available. Population growth has already reduced arable land from 3 MN in 1949 to 1.5 MN at present and can also cause sanitation and pollution problems. Only by adopting family plnning and the 1 child family can China gradually slow population growth to correspond with economic development; then the state will be able to improve health care and education and, therefore, population quality. China's population policy is not one of NeoMalthusianism, which advocates birth control and late marriage, and assumes the existence of a capitalist system and does not apply to communist systems. Malthus may have attempted to absolve the nourgeoisie from all blame by aiming his preaching against blind reproduction at the poor; he thought that overpopulation would be reduced by pestilence, war, and famine. Protecting capitalism motivated Malthus and other capitalists, but the Chinese want to promote economic development. Marx has refuted Malthus' views on population. While Chinese population policy and NeoMalthusianism agree on advocating birth control and late marriage, their underlying philosophies are different. The author supports laws and policies on fertility and family planning, and feels that population scientists must be involved in all aspects--study, propaganda, and education--relating to family planning. PMID:12313980

Xu, D

1983-01-01

261

Exponential expansion: galactic destiny or technological hubris?  

NASA Astrophysics Data System (ADS)

Is it our destiny to expand exponentially to populate the galaxy, or is such a vision but an extreme example of technological hubris? The overall record of human evolution and dispersion over the Earth can be cited to support the view that we are a uniquely expansionary and technological animal bound for the stars, yet an examination of the fate of individual migrations and exploratory initiatives raises doubts. Although it may be in keeping with our hubristic nature to predict ultimate galactic expansion, there is no way to specify how far expansionary urges may drive our spacefaring descendants.

Finney, B. R.

262

The ocean blues. Navigating the course of population growth.  

PubMed

Oceans and their role in environmental balance are discussed in this article. Coastal waters within 200 miles from land are identified as providing over half the ocean's total biological productivity and supply of nearly all of the world's fish catch. Almost 3.6 billion people live in coastal areas or within 90 miles of coastal waters, which accounts for about 66% of world population. Coastal land areas account for about 8% of the earth's total land area. 8.3 billion people are expected by 2025 to live in coastal areas. 9 of the 10 largest cities in the world are located on coasts. 7 of the 10 largest cities in the US are coastal cities (54% of the US population or 142 million people). Almost all of the marine pollution is derived from land-based sources, such as sewage, nutrients, sediments, litter, and plastics. Mangroves in coastal waters have been reduced by about 50% to about 90,000 sq. miles worldwide. Global consumption of fish is responsible for depleting fish supplies and the loss of mangroves due to aquaculture of shrimp or other seafood. The US National Fisheries Service is cited for its report that 67 of the 156 fish stocks are overexploited. About 1 billion people, mostly in developing countries, rely on fish as their main food source. If imbalances in demand and supply continue, the rising price of fish and seafood will threaten the lives of about 1 billion or more people. Numerous international and national actions have been taken in order to protect supplies and reduce pollution. Sound resource management practices need to be instituted. Small and large fisheries can begin by reducing the 27 million tons of unintentional fish captures and by converting 29 million tons of fish used for animal feed into food for human consumption. Management of US coastal lands in most coastal states, with the exception of California and Rhode Island, is weak. Maryland has adopted a community-level approach for management of the Chesapeake Bay. Other environmental impacts on oceans are attributed to a weakened ozone layer, which reduces phytoplankton, and to greenhouse effects on sea levels. Phytoplankton is key to supplying oxygen, converting excess carbon dioxide into simple sugars for sustaining life, and supporting aquatic life. Overpopulation has a negative impact on oceans and their life. PMID:12290701

Sarkar, D

1996-01-01

263

Growth analysis of a reestablished population versus a natural population of Bidens cernua L  

Microsoft Academic Search

A reintroduction experiment of Bidens cernua L., a species included in the Red List of Italian Flora, was carried out at Lake Posta Fibreno (Lazio, central Italy). There were no significant differences in the length of the phenological phases between the reestablished population (Pr) and the natural one (Pn). The length of the phenological cycle, from seedling emergence to the

L. Gratani; M. F. Crescente; G. Fabrini; A. Bonito; L. Varone

2009-01-01

264

Sexual Reproduction in a Simple Growth Population Model  

NASA Astrophysics Data System (ADS)

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.

Lemos, Carlos Gentil Oro; Santos, Marcio

2012-05-01

265

An agent-based modelling approach to estimate error in gyrodactylid population growth.  

PubMed

Comparative studies of gyrodactylid monogeneans on different host species or strains rely upon the observation of growth on individual fish maintained within a common environment, summarised using maximum likelihood statistical approaches. Here we describe an agent-based model of gyrodactylid population growth, which we use to evaluate errors due to stochastic reproductive variation in such experimental studies. Parameters for the model use available fecundity and mortality data derived from previously published life tables of Gyrodactylus salaris, and use a new data set of fecundity and mortality statistics for this species on the Neva stock of Atlantic salmon, Salmo salar. Mortality data were analysed using a mark-recapture analysis software package, allowing maximum-likelihood estimation of daily survivorship and mortality. We consistently found that a constant age-specific mortality schedule was most appropriate for G. salaris in experimental datasets, with a daily survivorship of 0.84 at 13°C. This, however, gave unrealistically low population growth rates when used as parameters in the model, and a schedule of constantly increasing mortality was chosen as the best compromise for the model. The model also predicted a realistic age structure for the simulated populations, with 0.32 of the population not yet having given birth for the first time (pre-first birth). The model demonstrated that the population growth rate can be a useful parameter for comparing gyrodactylid populations when these are larger than 20-30 individuals, but that stochastic error rendered the parameter unusable in smaller populations. It also showed that the declining parasite population growth rate typically observed during the course of G. salaris infections cannot be explained through stochastic error and must therefore have a biological basis. Finally, the study showed that most gyrodactylid-host studies of this type are too small to detect subtle differences in local adaptation of gyrodactylid monogeneans between fish stocks. PMID:22771983

Ramírez, Raúl; Harris, Philip D; Bakke, Tor A

2012-08-01

266

Cell Growth and Division  

PubMed Central

In a previous paper, we proposed a model in which the volume growth rate and probability of division of a cell were assumed to be determined by the cell's age and volume. Some further mathematical implications of the model are here explored. In particular we seek properties of the growth and division functions which are required for the balanced exponential growth of a cell population. Integral equations are derived which relate the distribution of birth volumes in successive generations and in which the existence of balanced exponential growth can be treated as an eigenvalue problem. The special case in which all cells divide at the same age is treated in some detail and conditions are derived for the existence of a balanced exponential solution and for its stability or instability. The special case of growth rate proportional to cell volume is seen to have neutral stability. More generally when the division probability depends on age only and growth rate is proportional to cell volume, there is no possibility of balanced exponential growth. Some comparisons are made with experimental results. It is noted that the model permits the appearance of differentiated cells. A generalization of the model is formulated in which cells may be described by many state variables instead of just age and volume. PMID:5643273

Bell, George I.

1968-01-01

267

Slow protein fluctuations explain the emergence of growth phenotypes and persistence in clonal bacterial populations  

E-print Network

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.

Andrea Rocco; Andrzej M. Kierzek; Johnjoe McFadden

2013-10-31

268

The contributions of age and sex to variation in common tern population growth rate.  

PubMed

1. The decomposition of population growth rate into contributions from different demographic rates has many applications, ranging from evolutionary biology to conservation and management. Demographic rates with low variance may be pivotal for population persistence, but variable rates can have a dramatic influence on population growth rate. 2. In this study, the mean and variance in population growth rate (lambda) is decomposed into contributions from different ages and demographic rates using prospective and retrospective matrix analyses for male and female components of an increasing common tern (Sterna hirundo) population. 3. Three main results emerged: (1) subadult return was highly influential in prospective and retrospective analyses; (2) different age-classes made different contributions to variation in lambda: older age classes consistently produced offspring whereas young adults performed well only in high quality years; and (3) demographic rate covariation explained a significant proportion of variation in both sexes. A large contribution to lambda did not imply a large contribution to its variation. 4. This decomposition strengthens the argument that the relationship between variation in demographic rates and variation in lambda is complex. Understanding this relationship and its consequences for population persistence and evolutionary change demands closer examination of the lives, and deaths, of the individuals within populations within species. PMID:17032370

Ezard, T H G; Becker, P H; Coulson, T

2006-11-01

269

Linear or Exponential Number Lines  

ERIC Educational Resources Information Center

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,…

Stafford, Pat

2011-01-01

270

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

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…

Mahar, Dennis J., Ed.; And Others

271

On the growth of primary industry and population of China's counties  

E-print Network

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.

Xie, Wen-Jie; Zhou, Wei-Xing

2010-01-01

272

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

NASA Astrophysics Data System (ADS)

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 favourable climate and prey in the absence of superior competitors with similar foraging mode.

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

2014-10-01

273

Growth and development of three Yugoslav populations in different ecological settings.  

PubMed

The role of genetical and ecological factors in the physical growth and development was studied in three Yugoslav populations living in different ecological settings. Anthropometric measurements of 6,908 children and young adolescents ages 1 to 18 years were taken and the results were compared in regard to ethnic and ecological characteristics. The evidence is presented that significant improvement in physical characteristics follows the improvement in environmental factors including nutrition. In addition to an increase in body height, changes were also noted in the build of the bony frame of the population living under improved environmental conditions. There was a change in the shape of the skeleton from the squatty appearance of the short population to the more lanky shape of the tall population. It is concluded that systematic periodic collection of the information on child growth could serve as a useful monitoring system for the surveillance of ecological and nutritional trends of a country. PMID:961619

Buzina, R

1976-09-01

274

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

USGS Publications Warehouse

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.

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

2003-01-01

275

Growth rates in a wild primate population: ecological influences and maternal effects  

Microsoft Academic Search

Growth rate is a life-history trait often linked to various fitness components, including survival, age of first reproduction, and fecundity. Here we present an analysis of growth-rate variability in a wild population of savannah baboons ( Papio cynocephalus). We found that relative juvenile size was a stable individual trait during the juvenile period: individuals generally remained consistently large-for-age or small-for-age

Jeanne Altmann; Susan C. Alberts

2005-01-01

276

Age structure and spatial patterning of Trillium populations in old-growth forests  

Microsoft Academic Search

We investigated the spatial cohort structure of Trillium populations in old-growth cove forests in Great Smoky Mountains National Park (TN, USA). We mapped the locations of all Trillium\\u000a erectum L., Trillium grandiflorum (Michaux) Salisbury, and Trillium vaseyi Harbison occurring within two 10 × 10 m sample plots at each of three old-growth sites—Anthony Creek, Cove Mountain, and\\u000a Kalanu Prong. The height and life

Christopher R. Webster; Michael A. Jenkins

2008-01-01

277

Population Growth and Land Use Intensification in a Subsistence-based Indigenous Community in the Amazon  

Microsoft Academic Search

Shifting cultivation practiced by indigenous peoples living at low population densities in tropical forests has often been\\u000a described as sustainable and compatible with conservation. However, shifting cultivation at increasing population densities\\u000a has historically been, and still is, a main cause of deforestation worldwide. As many indigenous peoples in tropical forests\\u000a currently experience rapid demographic growth, this raises the question to

Anders Henrik Sirén

2007-01-01

278

ESTIMATES OF POPULATION DENSITY AND GROWTH OF BLACK BEARS IN THE SMOKY MOUNTAINS  

Microsoft Academic Search

To estimate population abundance, data were collected from 1,239 black bears (Ursus americanus) trapped in 3 areas of the Smoky Mountains (SM), 1972-89. Bears were tagged, tattooed, and released, and using the Jolly-Seber open population model, density estimates ranged from 0.09 to 0.35 bears\\/km2. Year-to-year density estimates and the observed rate of growth (0-2%) indicated a stable to slightly increasing

PETER K. MCLEAN; MICHAEL R. PELTON

279

Application of population growth models based on cumulative size to pecan aphids  

Microsoft Academic Search

Models for aphid population growth based on cumulative (past) population size have been developed with both a deterministic\\u000a formulation and a stochastic formulation. This article applies these mechanistic models to analyze a large dataset on pecan\\u000a aphid. The models yield symmetric and right-skewed curves, which differ qualitatively from the observed data which tend to\\u000a be left-skewed. Nevertheless this model-based analysis

James H. Matis; Thomas R. Kiffe; Timothy I. Matis; Douglass E. Stevenson

2006-01-01

280

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

USGS Publications Warehouse

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.

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

2001-01-01

281

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...

282

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

PubMed

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's conference. Views of family planning were presented by the Party Secretary from Sichuan Province and the Governor of Hunan Province. PMID:12346839

1994-04-01

283

El Niño drives timing of breeding but not population growth in the song sparrow (Melospiza melodia).  

PubMed

Increasing evidence suggests that climate change affects the timing of breeding in birds, but there is less evidence to show how such changes affect the population dynamics of birds overall. Over the past 43 years, song sparrows (Melospiza melodia) on Mandarte Island, British Columbia, Canada have not shown an advance in breeding date in response to global warming. However, this population did show considerable annual variation in timing of breeding correlated with the El Niño Southern Oscillation. Birds bred earlier in warmer El Niño years and later in colder La Niña years. Early breeding strongly increased reproductive output. However, annual variation in timing of breeding had little effect on population growth, perhaps because the population is strongly regulated by the rate of recruitment by juveniles. The juvenile recruitment rate declined with increasing population density but showed little response to climate. These findings suggest that populations will vary in response to climate change depending on how climate affects the demographic parameters that contribute most to population growth. PMID:12960365

Wilson, Scott; Arcese, Peter

2003-09-16

284

Dynamic exponential utility indifference valuation  

Microsoft Academic Search

We study the dynamics of the exponential utility indifference value process C(B;\\\\alpha) for a contingent claim B in a semimartingale model with a general continuous filtration. We prove that C(B;\\\\alpha) is (the first component of) the unique solution of a backward stochastic differential equation with a quadratic generator and obtain BMO estimates for the components of this solution. This allows

Michael Mania; Martin Schweizer

2005-01-01

285

Age, growth and population structure of the jumbo flying squid Dosidicus gigas in Peruvian waters  

Microsoft Academic Search

Age, growth and population structure of the jumbo flying squid, Dosidicus gigas, from the jig fishery in Peruvian waters in 1992 were determined by reading daily increments in ground and polished sections of statoliths. The squid ranged in size from 192 to 965mm dorsal mantle length (ML) and no squid were older than 1 year. Two size groups were present

J. Argüelles; P. G. Rodhouse; P. Villegas; G. Castillo

2001-01-01

286

Validity of Personal Growth Initiative Scale Scores With a Mexican American College Student Population  

Microsoft Academic Search

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 found in prior research with mostly

Christine Robitschek

2003-01-01

287

SYNTHESIS Causes and consequences of variation in plant population growth rate: a synthesis of matrix  

E-print Network

-Baptiste Pichancourt,8 Helen Quested6 and Glenda M. Wardle9 Abstract Explaining variation in population growth rates Carmody Rd, St Lucia, Queensland 4067, Australia 3 Section of Ecology, Department of Biology, University, University of Montana, Missoula, MT 59812, USA 6 Department of Botany, Stockholm University, Stockholm 10691

288

ORIGINAL ARTICLE Survival and population growth of a long-lived threatened snake  

E-print Network

1987). Snakes, however, may constitute impor- tant components of ecosystems, in terms of local biomassORIGINAL ARTICLE Survival and population growth of a long-lived threatened snake species, Drymarchon couperi (Eastern Indigo Snake) Natalie L. Hyslop · Dirk J. Stevenson · John N. Macey · Lawrence D

Oli, Madan K.

289

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

E-print Network

Effects of Sample Size on Estimates of Population Growth Rates Calculated with Matrix Models Ian J the estimates of the vital rates are accurate, small sample sizes lead to biased estimates of l due to increased. Finally, we conducted a review of the literature to determine the sample sizes typically used when

Bruna, Emilio M.

290

Population growth and development in the third world: The neocolonial context  

Microsoft Academic Search

and development by emphasizing certain general themes. This renewed discussion is expected to provide a framework for lively and constructive debates on some specific issues which can consequently lead to the formulation of viable approaches to reduce the rates of population growth. While we do not provide a rigorous case-specific empirical analysis, we do argue that the Malthusian premises and

John G. Patterson; Nanda R. Shrestha

1988-01-01

291

Reproductive cycle, larval development, juvenile growth and population dynamics of Patiriella pseudoexigua (Echinodermata: Asteroidea) in Taiwan  

Microsoft Academic Search

A field study was conducted at Wanlitung, southern Taiwan, in 1986–1089, to determine the reproductive cycle, development mode, growth rate and population dynamics of the small seastar Patiriella pseudoexigua (Dartnall), which occurs in highly stressful and disturbed intertidal pools in this area. An inverse relationship between gonad index and pyloric-caccum index was only recorded immediately prior to spawning. A short,

B.-Y. Chen; C.-P. Chen

1992-01-01

292

Water relations and root growth of two populations of Gutierrezia sarothrae  

Microsoft Academic Search

We hypothesise that genotypic differences in transpiration and root growth in the southern and northern populations of Gutierrezia sarothrae are driven by growing season vapour pressure deficit (VPD) and that ecotypic differentiations are linked to corresponding variations in tissue and leaf water relations. Seedlings from an Idaho (ID) and a Texas (TX) seed source were grown either in an open

Changgui Wan; Ronald E Sosebee; Bobby L McMichael

1998-01-01

293

Global Population Growth: 21st Century Challenges. Headline Series No. 302.  

ERIC Educational Resources Information Center

This booklet examines the highly complex and highly nuanced subject of population growth and its consequences. The subject is controversial because it lies at the intersection of so many different disciplines. The primary purpose of the book is to define the large measure of common ground that exists among experts with respect to two critical…

Moffett, George D.

294

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

ERIC Educational Resources Information Center

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…

Garkovich, Lorraine

295

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

ERIC Educational Resources Information Center

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.)

Wallace, Robert L.

2005-01-01

296

GROWTH RATES AND PREVALENCE OF PERKINSUS MARINUS PREVALENCE IN RESTORED OYSTER POPULATIONS IN MARYLAND  

E-print Network

GROWTH RATES AND PREVALENCE OF PERKINSUS MARINUS PREVALENCE IN RESTORED OYSTER POPULATIONS, Solomons, MD 20688; 2 Department of Biology, University of Maryland, College Park, MD 20742; 3 Oyster-produced juvenile oysters have been planted on numerous natural oyster bars in Maryland in an effort to restore

Paynter, Kennedy T.

297

Impacts of Climate Change and Population Growth on Water Stress Becky Witte  

E-print Network

Impacts of Climate Change and Population Growth on Water Stress by Becky Witte Master's Student Department of Hydrology and Water Resources College of Science Advised by: Dr. Larry Winter Department of Hydrology and Water Resources College of Science This project was made possible by the University of Arizona

Fay, Noah

298

Population growth, sustainable development, energy resources and environmental protection: the nuclear option  

Microsoft Academic Search

This paper deals with the satisfaction of the future global energy demand. The gravity of the situation the world is going to face in the coming years is due to many and conflicting problems (world population growth, sustainable development, energy resources, environmental protection). Probably some Countries like Italy live these gravity much more then others, may be because they renounced

Daniele Menniti; Alessandro Burgio; Nadia Scordino

2007-01-01

299

Population growth in those rural areas which are characterised by high levels of natural amenities  

E-print Network

amenities, climate, authentical rural culture, recreation and affordable housing. The concept of "amenityPopulation growth in those rural areas which are characterised by high levels of natural amenities, downshifters, economic migrants and retirees is transforming rural mountain areas. With the new trend

Borsdorf, Axel

300

Growth patterns of Juncus gerardi clonal populations in a coastal habitat  

Microsoft Academic Search

Juncus gerardi populations demonstrated a logistic growth curve during the colonization stage. Shoot production by vegetative multiplication was virtually continuous from December to June. Experiments suggested that the stabilisation stage of the demographic curve reflected water deficit. Taller, fertile, winter and early spring cohorts could be distinguished from shorter, infertile end of spring and beginning of summer cohorts. Shoot emergence

J. B. Bouzillé; A. Bonis; B. Clément; M. Godeau

1997-01-01

301

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

ERIC Educational Resources Information Center

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…

Ninbet, Steven; Hurley, Gabrielle; Weldon, Elizabeth

2006-01-01

302

Biomedical Social Science, Unit VI: Population Growth and Genetic Engineering. Student Text. Revised Version, 1977.  

ERIC Educational Resources Information Center

This collection of lessons and class activities covers two major concepts: (1) population growth and (2) genetic engineering. Lessons consist of readings, questions and answers, and problems of projects where appropriate. Issues are posed in as much as possible in a manner intended to cause the student to reach conclusions and values without being…

Biomedical Interdisciplinary Curriculum Project, Berkeley, CA.

303

Hydrocarbon Leaching, Microbial Population, and Plant Growth in Soil Amended with Petroleum  

Microsoft Academic Search

Two samples of oily waste organics (OWO) from petroleum wells were added to heath soils from Tierra del Fuego, Argentina, and the effects on hydrocarbon leaching, microbial population, and plant growth were studied. These mixtures and a control soil were subjected to four deionized water leachates. For each leachate, total petroleum hydrocarbons (TPH), aliphatic hydrocarbons (ALH), aromatic hydrocarbons (ARH) with

Rodolfo E. Mendoza

1998-01-01

304

Food Security in the Face of Climate Change, Population Growth, and Resource Constraints: Implications for Bangladesh  

Microsoft Academic Search

Ensuring food security has been one of the major national priorities of Bangladesh since its independence in 1971. Now, this national priority is facing new challenges from the possible impacts of climate change in addition to the already existing threats from rapid population growth, declining availability of cultivable land, and inadequate access to water in the dry season. In this

Islam M. Faisal; Saila Parveen

2004-01-01

305

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

ERIC Educational Resources Information Center

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…

Robitschek, Christine

2003-01-01

306

Demographic, mechanistic and density-dependent determinants of population growth rate: a case study in an avian predator.  

PubMed Central

Identifying the determinants of population growth rate is a central topic in population ecology. Three approaches (demographic, mechanistic and density-dependent) used historically to describe the determinants of population growth rate are here compared and combined for an avian predator, the barn owl (Tyto alba). The owl population remained approximately stable (r approximately 0) throughout the period from 1979 to 1991. There was no evidence of density dependence as assessed by goodness of fit to logistic population growth. The finite (lambda) and instantaneous (r) population growth rates were significantly positively related to food (field vole) availability. The demographic rates, annual adult mortality, juvenile mortality and annual fecundity were reported to be correlated with vole abundance. The best fit (R(2) = 0.82) numerical response of the owl population described a positive effect of food (field voles) and a negative additive effect of owl abundance on r. The numerical response of the barn owl population to food availability was estimated from both census and demographic data, with very similar results. Our analysis shows how the demographic and mechanistic determinants of population growth rate are linked; food availability determines demographic rates, and demographic rates determine population growth rate. The effects of food availability on population growth rate are modified by predator abundance. PMID:12396509

Hone, Jim; Sibly, Richard M

2002-01-01

307

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

PubMed

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

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

2007-06-01

308

Growth and Competitive Effects of Centaurea stoebe Populations in Response to Simulated Nitrogen Deposition  

PubMed Central

Increased resource availability can promote invasion by exotic plants, raising concerns over the potential effects of global increases in the deposition of nitrogen (N). It is poorly understood why increased N favors exotics over natives. Fast growth may be a general trait of good invaders and these species may have exceptional abilities to increase growth rates in response to N deposition. Additionally, invaders commonly displace locals, and thus may have inherently greater competitive abilities. The mean growth response of Centaurea stoebe to two N levels was significantly greater than that of North American (NA) species. Growth responses to N did not vary among C. stoebe populations or NA species. Without supplemental N, NA species were better competitors than C. stoebe, and C. stoebe populations varied in competitive effects. The competitive effects of C. stoebe populations increased with N whereas the competitive effects of NA species decreased, eliminating the overall competitive advantage demonstrated by NA species in soil without N added. These results suggest that simulated N deposition may enhance C. stoebe invasion through increasing its growth and relative competitive advantage, and also indicate the possibility of local adaptation in competitive effects across the introduced range of an invader. PMID:22563451

He, Wei-Ming; Montesinos, Daniel; Thelen, Giles C.; Callaway, Ragan M.

2012-01-01

309

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

PubMed

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

Howat, Peter; Stoneham, Melissa

2011-12-01

310

The Evolution of Stellar Exponential Discs  

E-print Network

Models of disc galaxies which invoke viscosity-driven radial flows have long been known to provide a natural explanation for the origin of stellar exponential discs, under the assumption that the star formation and viscous timescales are comparable. We present models which invoke simultaneous star formation, viscous redistribution of gas and cosmologically-motivated gaseous infall and explore the predictions such models make for the scale length evolution and radial star formation history of galactic stellar discs. While the inclusion of viscous flows is essential for ensuring that the stellar disc is always exponential over a significant range in radius, we find that such flows play essentially no role in determining the evolution of the disc scale length. In models in which the main infall phase precedes the onset of star formation and viscous evolution, we find the exponential scale length to be rather invariant with time. On the other hand, models in which star formation/viscous evolution and infall occur concurrently result in a smoothly increasing scale length with time, reflecting the mean angular momentum of material which has fallen in at any given epoch. The disc stellar populations in these models are predominantly young (ie. ages < 5 Gyr) beyond a few scale lengths. In both cases, viscous flows are entirely responsible for transporting material to very large radii. We discuss existing observational constraints on these models from studies of both local and moderate redshift disc galaxies. In particular, a good agreement is found between the solar neighbourhood star formation history predicted by our infall model and the recent observational determination of this quantity by Rocha-Pinto et al (2000).

Annette Ferguson; Cathie Clarke

2001-03-14

311

Frequency-dependent population dynamics: Effect of sex ratio and mating system on the elasticity of population growth rate.  

PubMed

When vital rates depend on population structure (e.g., relative frequencies of males or females), an important question is how the long-term population growth rate ? responds to changes in rates. For instance, availability of mates may depend on the sex ratio of the population and hence reproductive rates could be frequency-dependent. In such cases change in any vital rate alters the structure, which in turn, affect frequency-dependent rates. We show that the elasticity of ? to a rate is the sum of (i) the effect of the linear change in the rate and (ii) the effect of nonlinear changes in frequency-dependent rates. The first component is always positive and is the classical elasticity in density-independent models obtained directly from the population projection matrix. The second component can be positive or negative and is absent in density-independent models. We explicitly express each component of the elasticity as a function of vital rates, eigenvalues and eigenvectors of the population projection matrix. We apply this result to a two-sex model, where male and female fertilities depend on adult sex ratio ? (ratio of females to males) and the mating system (e.g., polygyny) through a harmonic mating function. We show that the nonlinear component of elasticity to a survival rate is negligible only when the average number of mates (per male) is close to ?. In a strictly monogamous species, elasticity to female survival is larger than elasticity to male survival when ?<1 (less females). In a polygynous species, elasticity to female survival can be larger than that of male survival even when sex ratio is female biased. Our results show how demography and mating system together determine the response to selection on sex-specific vital rates. PMID:25174884

Haridas, C V; Eager, Eric Alan; Rebarber, Richard; Tenhumberg, Brigitte

2014-11-01

312

Rapid depletion of genotypes with fast growth and bold personality traits from harvested fish populations  

PubMed Central

The possibility for fishery-induced evolution of life history traits is an important but unresolved issue for exploited fish populations. Because fisheries tend to select and remove the largest individuals, there is the evolutionary potential for lasting effects on fish production and productivity. Size selection represents an indirect mechanism of selection against rapid growth rate, because individual fish may be large because of rapid growth or because of slow growth but old age. The possibility for direct selection on growth rate, whereby fast-growing genotypes are more vulnerable to fishing irrespective of their size, is unexplored. In this scenario, faster-growing genotypes may be more vulnerable to fishing because of greater appetite and correspondingly greater feeding-related activity rates and boldness that could increase encounter with fishing gear and vulnerability to it. In a realistic whole-lake experiment, we show that fast-growing fish genotypes are harvested at three times the rate of the slow-growing genotypes within two replicate lake populations. Overall, 50% of fast-growing individuals were harvested compared with 30% of slow-growing individuals, independent of body size. Greater harvest of fast-growing genotypes was attributable to their greater behavioral vulnerability, being more active and bold. Given that growth is heritable in fishes, we speculate that evolution of slower growth rates attributable to behavioral vulnerability may be widespread in harvested fish populations. Our results indicate that commonly used minimum size-limits will not prevent overexploitation of fast-growing genotypes and individuals because of size-independent growth-rate selection by fishing. PMID:18299567

Biro, Peter A.; Post, John R.

2008-01-01

313

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

PubMed Central

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

Slatkin, M; Bertorelle, G

2001-01-01

314

Endogenous growth of population and income depending on resource and knowledge.  

PubMed

This study focuses on the dynamic, endogenous, nonlinear interactions between the economy, population growth and the environment. Literature on endogenous growth theory was reviewed and the 3-sector demoeconomic model was provided as the analytical framework for the study of sustainable development through the integration of population growth, resource use and economic growth. The model is described in such a way that the labor force is considered as a free migrating variable among three different kinds of employment: the primary sector, which harvests a renewable resource, the secondary or industrial sector, and the tertiary sector, which is responsible for the accumulation of the stock that represents a public good for all three sectors. Presented in this paper is a nontechnical outline of the model that describes the economic, demographic, and environmental interactions considered. Also given are dynamics, market equilibrium and dynamic feedback rules. Furthermore, numerical analysis of the model quantifying the resulting time paths of the variables involved is included. The dynamics are simply the outcome of the nonlinear interactions of the demographic, economic and environmental modules. Numerical studies have also shown that the system variables move with different velocity. Technology and population can generally be regarded as slow moving variables by comparison with resources. PMID:12158986

Prskawetz, A; Feichtinger, G; Luptacik, M; Milik, A; Wirl, F; Hof, F; Lutz, W

1999-01-01

315

Growth in otter (Lutra lutra) populations in the UK as shown by long-term monitoring.  

PubMed

European otters declined dramatically from the 1950s, disappearing from many rivers. We report here on longterm monitoring (from 1977) in 3 catchments in western Britain that were recolonized naturally and in 2 catchments in eastern England that were reinforced by captive-bred otters. A minimum of 16-years data was collected on each river until 2002. At a series of sites in each study river, the percentages which were positive for otters and the number of spraints per sprainting site were recorded and combined to produce an annual index of population. One western river, naturally recolonized, showed rapid early population growth for 5 years, followed by slower growth, while growth was steadier in 2 catchments which already held some otters at the beginning of the study. Colonization on the eastern rivers was slower, with greater fluctuations over time. Annual population growth rates were estimated at 1-7%, higher in the earlier years. A strategy for annual monitoring of otters is recommended. PMID:15151385

Mason, Christopher F; Macdonald, Sheila M

2004-05-01

316

Native insect herbivory limits population growth rate of a non-native thistle.  

PubMed

The influence of native fauna on non-native plant population growth, size, and distribution is not well documented. Previous studies have shown that native insects associated with tall thistle (Cirsium altissimum) also feed on the leaves, stems, and flower heads of the Eurasian congener C. vulgare, thus limiting individual plant performance. In this study, we tested the effects of insect herbivores on the population growth rate of C. vulgare. We experimentally initiated invasions by adding seeds at four unoccupied grassland sites in eastern Nebraska, USA, and recorded plant establishment, survival, and reproduction. Cumulative foliage and floral herbivory reduced C. vulgare seedling density, and prevented almost any reproduction by C. vulgare in half the sites. The matrix model we constructed showed that this herbivory resulted in a reduction of the asymptotic population growth rate (?), from an 88% annual increase to a 54% annual decline. These results provide strong support for the hypothesis that indigenous herbivores limit population invasion of this non-native plant species into otherwise suitable grassland habitat. PMID:24402131

Eckberg, James O; Tenhumberg, Brigitte; Louda, Svata M

2014-05-01

317

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

PubMed

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. Past trends in the labor force, employment and unemployment, and employment by major industry are reported. The labor force participation rate of 29.6% in 1985 is among the lowest in the world. The age structure of the population, inadequate human resource development, and underreporting of females in the labor force account for the low rates. Population grew by 96.5% between 1961 and 81, but labor force increased 77.3% and employment 74.4%. The greatest growth was in the nonagricultural sector. Prospective trends show agricultural labor force growing from 15.1 million in 1981 to 20.2 million in 2006, which is expected to put pressure on agricultural land. Female nonagricultural sector labor force is expected to grow due to increased literacy and fertility declines. PMID:12317085

Hashmi, S S

1990-01-01

318

F-LE Exponential Functions  

NSDL National Science Digital Library

This is a task from the Illustrative Mathematics website that is one part of a complete illustration of the standard to which it is aligned. Each task has at least one solution and some commentary that addresses important asects of the task and its potential use. Here are the first few lines of the commentary for this task: The figure below shows the graphs of the exponential functions $f(x)=c\\cdot 3^x$ and $g(x)=d\\cdot 2^x$, for some numbers $c\\gt 0$ and $d\\gt 0$. They in...

319

Growth in Percutaneous Coronary Intervention Capacity Relative to Population and Disease Prevalence  

PubMed Central

Background The access to and growth of percutaneous coronary intervention (PCI) has not been fully explored with regard to geographic equity and need. Economic factors and timely access to primary PCI provide the impetus for growth in PCI centers, and this is balanced by volume standards and the benefits of regionalized care. Methods and Results Geospatial and statistical analyses were used to model capacity, growth, and access of PCI hospitals relative to population density and myocardial infarction (MI) prevalence at the state level. Longitudinal data were obtained for 2003–2011 from the American Hospital Association, the U.S. Census, and the Centers for Disease Control and Prevention (CDC) with geographical modeling to map PCI locations. The number of PCI centers has grown 21.2% over the last 8 years, with 39% of all hospitals having interventional cardiology capabilities. During the same time, the US population has grown 8.3%, from 217 million to 235 million, and MI prevalence rates have decreased from 4.0% to 3.7%. The most densely concentrated states have a ratio of 8.1 to 12.1 PCI facilities per million of population with significant variability in both MI prevalence and average distance between PCI facilities. Conclusions Over the last decade, the growth rate for PCI centers is 1.5× that of the population growth, while MI prevalence is decreasing. This has created geographic imbalances and access barriers with excess PCI centers relative to need in some regions and inadequate access in others. PMID:24166491

Langabeer, James R.; Henry, Timothy D.; Kereiakes, Dean J.; DelliFraine, Jami; Emert, Jamie; Wang, Zheng; Stuart, Leilani; King, Richard; Segrest, Wendy; Moyer, Peter; Jollis, James G.

2013-01-01

320

Interval type-2 fuzzy logic system to simulate the environment resources stochasticity affecting the growth of a population  

Microsoft Academic Search

There exist several ways to model population growth at present time, which are mainly based on mathematics. However we present a new model based on fuzzy cellular theory. An interval type-2 fuzzy logic system (IT2-FLS) is designed to evaluate the population growth parameters based on the environment resources stochasticity, in time and space. Interval type-2 fuzzy sets are used to

Cecilia Leal-Ramírez; Oscar Castillo; Antonio Rodríguez-Díaz

2009-01-01

321

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

ERIC Educational Resources Information Center

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…

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

2005-01-01

322

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

ERIC Educational Resources Information Center

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…

Hobart, Christine L.

323

The Exponential Phase of HIV/AIDS Epidemic in Japan  

E-print Network

The Exponential Phase of HIV/AIDS Epidemic in Japan Hisashi INABA Institute of Population Problems between the reported HIV/AIDS incidence and the hidden prevalence of HIV could be so large. 1 #12;In the charac- teristics of HIV/AIDS in Japan based on the surveillance data. Next we develop the estimation

Inaba, Hisashi

324

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

PubMed

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 populations, especially during invasion. These data indicate the importance of native species, in this case the dominant shrub, in influencing soil resources and restricting population growth of exotic plants. These results argue that management of invasive plants should focus not only on removal of nonnatives, but also on reestablishment of important native species. PMID:21049877

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

2010-10-01

325

Association between mandibular posterior alveolar morphology and growth pattern in a Chinese population with normal occlusion*  

PubMed Central

Objective: To investigate the relationship between growth patterns and mandibular posterior tooth-alveolar bone complex morphology in a Chinese population with normal occlusion. Methods: Forty-five patients with normal occlusion (23 males, 22 females) were included in this study. Among these patients, 20 displayed the vertical growth pattern, and 20 had the horizontal growth pattern, while the remaining patients displayed the average growth pattern. All of the patients underwent dental cone beam computed tomography (CBCT), which included the region of the mandibular posterior teeth and the alveolar. A linear regression analysis and a correlation analysis between the facial height index (FHI) and the alveolar bone morphology were performed. Results: The inclination of the molars, the thickness of the cortical bone, and the height of the mandibular bone differed significantly between patients with the horizontal growth pattern and those with the vertical growth pattern (P<0.05). Significant positive correlations were found between: the FHI and the inclination of the molars; the FHI and the thickness of the cortical bone; and the FHI and the height of the mandibular bone. Conclusions: The mandibular posterior tooth-alveolar bone complex morphology may be affected by growth patterns. PMID:23303628

Han, Min; Wang, Rong-yang; Liu, Hong; Zhu, Xiu-juan; Wei, Fu-lan; Lv, Tao; Wang, Na-na; Hu, Li-hua; Li, Guo-ju; Liu, Dong-xu; Wang, Chun-ling

2013-01-01

326

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

USGS Publications Warehouse

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 populations.

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

2006-01-01

327

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

NASA Astrophysics Data System (ADS)

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.

Barr, Brannon; Wolverton, Steve

2014-10-01

328

Body downsizing caused by non-consumptive social stress severely depresses population growth rate.  

PubMed

Chronic social stress diverts energy away from growth, reproduction and immunity, and is thus a potential driver of population dynamics. However, the effects of social stress on demographic density dependence remain largely overlooked in ecological theory. Here we combine behavioural experiments, physiology and population modelling to show in a top predator (pike Esox lucius) that social stress alone may be a primary driver of demographic density dependence. Doubling pike density in experimental ponds under controlled prey availability did not significantly change prey intake by pike (i.e. did not significantly change interference or exploitative competition), but induced a neuroendocrine stress response reflecting a size-dependent dominance hierarchy, depressed pike energetic status and lowered pike body growth rate by 23 per cent. Assuming fixed size-dependent survival and fecundity functions parameterized for the Windermere (UK) pike population, stress-induced smaller body size shifts age-specific survival rates and lowers age-specific fecundity, which in Leslie matrices projects into reduced population rate of increase (lambda) by 37-56%. Our models also predict that social stress flattens elasticity profiles of lambda to age-specific survival and fecundity, thus making population persistence more dependent on old individuals. Our results suggest that accounting for non-consumptive social stress from competitors and predators is necessary to accurately understand, predict and manage food-web dynamics. PMID:19923130

Edeline, Eric; Haugen, Thrond O; Weltzien, Finn-Arne; Claessen, David; Winfield, Ian J; Stenseth, Nils Chr; Vøllestad, L Asbjørn

2010-03-22

329

Population Growth of Soybean Aphid, Aphis glycines, Under Varying Levels of Predator Exclusion  

PubMed Central

Although soybean aphid, Aphis glycines Matsumura (Hemiptera: Aphididae), has caused economic damage in several Midwestern states, growers in Missouri have experienced relatively minor damage. To evaluate whether existing predatory insect populations are capable of suppressing or preventing soybean aphid population growth or establishment in Missouri, a predator exclusion study was conducted to gauge the efficacy of predator populations. Three levels of predator exclusion were used; one that excluded all insects (small mesh), one that excluded insects larger than thrips (medium mesh), and one that excluded insects larger than Orius insidiosus (Say) (Hemiptera: Anthocoridae), a principal predator (large mesh). Along with manipulating predator exposure, timing of aphid arrival (infestation) was manipulated. Three infestation times were studied; vegetative (V5), beginning bloom (R1), and beginning pod set (R3). Timing of aphid and predator arrival in a soybean field may affect the soybean aphid's ability to establish and begin reproducing. Cages infested at V5 and with complete predator exclusion reached economic threshold within two weeks, while cages with predators reached economic threshold in four and a half weeks. Cages infested at R1 with complete predator exclusion reached economic threshold within five weeks; cages with predators reached economic threshold within six weeks. Cages infested at R3 never reached threshold (with or without predators). The predator population in Missouri seems robust, capable of depressing the growth of soybean aphid populations once established, and even preventing establishment when the aphid arrived late in the field. PMID:21073344

Meihls, Lisa N.; Clark, Thomas L.; Bailey, Wayne C.; Ellersieck, Mark R.

2010-01-01

330

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

PubMed

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 x 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

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

2000-03-01

331

Effects of population increase on cui-ui growth and maturation  

USGS Publications Warehouse

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.

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

2007-01-01

332

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

PubMed Central

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

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

2010-01-01

333

Soft Gluon Exponentiation and Resummation  

E-print Network

In calculations of (semi-) inclusive events within perturbative Quantum Chromodynamics, large logarithmic corrections arise from certain kinematic regions of interest which need to be resummed. When resumming soft gluon effects one encounters quantities built out of eikonal or Wilson lines (path ordered exponentials). In this thesis we develop a simplified method to calculate higher orders of the singular coefficients of parton distribution functions which is based on the exponentiation of cross sections built out of eikonal lines. As an illustration of the method we determine the previously uncalculated fermionic contribution to the three-loop coefficient A^(3). The knowledge of these coefficients is not only important for the study of the parton distribution functions themselves, but also for the resummation of large logarithmic effects due to soft radiation in a variety of cross sections. In the second part of this thesis we study the energy flow pattern of this soft radiation in jet events. We develop the concept of event shape-energy flow correlations that suppress radiation from unobserved "minijets" outside the region of interest and are sensitive primarily to radiation from the highest-energy jets. We give analytical and numerical results at next-to-leading logarithmic order for shape/flow correlations in e+e- dijet events. We conclude by illustrating the application of our formalism to events with hadrons in the initial state, where the shape/flow correlations can be described via matrices in the space of color exchanges.

Carola F. Berger

2003-05-07

334

Bot fly parasitism of the red-backed vole: host survival, infection risk, and population growth.  

PubMed

Parasites can play an important role in the dynamics of host populations, but empirical evidence remains sparse. We investigated the role of bot fly (Cuterebra spp.) parasitism in red-backed voles (Myodes gapperi) by first assessing the impacts of the parasite on the probability of vole survival under stressful conditions as well as on the reproductive activity of females. We then identified the main factors driving both the individual risk of infection and the abundance of bot flies inside red-backed voles. Finally, we evaluated the impacts of bot fly prevalence on the growth rate of vole populations between mid-July and mid-August. Thirty-six populations of red-backed voles were sampled in the boreal forest of Québec, Canada. The presence and the abundance of parasites in voles, two host life history traits (sex and body condition), three indices of habitat complexity (tree basal area, sapling basal area, coarse woody debris volume), and vole abundance were considered in models evaluating the effects of bot flies on host populations. We found that the probability of survival of red-backed voles in live traps decreased with bot fly infection. Both the individual risk of infection and the abundance of bot flies in red-backed voles were driven mainly by vole abundance rather than by the two host life history traits or the three variables of habitat complexity. Parasitism had population consequences: bot fly prevalence was linked to a decrease in short-term growth rate of vole populations over the summer. We found that bot flies have the potential to reduce survival of red-backed voles, an effect that may apply to large portions of populations. PMID:19011904

Lemaître, Jérôme; Fortin, Daniel; Montiglio, Pierre-Olivier; Darveau, Marcel

2009-03-01

335

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

SciTech Connect

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.

Lyashenko, O.I.

1995-12-10

336

Population differences in the onset of cranial ossification in pumpkinseed ( Lepomis gibbosus ), a potential cost of rapid growth  

Microsoft Academic Search

Interspecific comparisons suggest that a trade-off exists between development and somatic growth rate. We provide evidence for a trade-off between cranial ossification and growth rate within a single species, the pumpkinseed sunfish (Lepomis gibbosus). We compare fish derived from two populations known to differ in their somatic growth rates. Fish were hatched from eggs and maintained under common conditions. Juveniles

Jeffrey D. Arendt; David S. Wilson

2000-01-01

337

Utilization of Capture-Mark-Recapture for the Study of Recruitment and Population Growth Rate  

Microsoft Academic Search

Captorc-mark-recapture data has been cxtensively used fur the study of survival. However, re- cruitment and population growth rat,c can be investigated a? well. The study of recruitment is shown to hr equivalent to the study of survival in reverse and can he carried out by inverting capture histories. The natural parameter in this approach here called seniority probability- is, at

R. Pradel

338

Comparisons of Sex-Specific Growth and Weight–Length Relationships in Minnesota Black Crappie Populations  

Microsoft Academic Search

We examined differences in sex-specific growth and weight–length relationships for five Minnesota populations of black crappies Pomoxis nigromaculatus. Male black crappies typically grew slightly faster than females, but observed differences in mean total lengths (TLs) at age were always 15 mm or less and were typically less than 10 mm. We detected few differences in log10(weight)–log10(TL) regressions between sexes, and

Daniel A. Isermann; Andrew L. Thompson; Philip J. Talmage

2010-01-01

339

Population growth kinetics of the nematode, Steinernema feltiae, in submerged monoxenic culture  

Microsoft Academic Search

Monoxenic cultures of the nematode, Steinernema feltiae, were carried out on two complex liquid media: P1, mainly soybean flour\\/egg yolk\\/yeast extract, and P2, mainly egg yolk\\/yeast extract. Up to 140 000–200 000 nematodes ml-1 were produced within 7 days, and more than 95% of the final population was in the infective juvenile stage. The total nematode concentration growth curve had

Norberto Chavarría-Hernández; Mayra de la Torre

2001-01-01

340

Relationship among placenta previa, fetal growth restriction, and preterm delivery: a population-based study  

Microsoft Academic Search

Objective:To examine the independent contributions of prematurity and fetal growth restriction to low birth weight among women with placenta previa.Methods:A population-based, retrospective cohort study of singleton live births in New Jersey (1989–93) was performed. Mother-infant pairs (n = 544,734) were identified from linked birth certificate and maternal and infant hospital discharge summary data. Women diagnosed with previa were included only

Cande V Ananth; Kitaw Demissie; John C Smulian; Anthony M Vintzileos

2001-01-01

341

AGRICULTURAL ADJUVANTS: ACUTE MORTALITY AND EFFECTS ON POPULATION GROWTH RATE OF DAPHNIA PULEXAFTER CHRONIC EXPOSURE  

Microsoft Academic Search

Abstract—Acute and chronic toxicity of eight agricultural adjuvants (Bond t, Kinetict, Plyact, R-11t, Silwet L-77t, Sylgard 309t, X-77t, and WaterMaxxt )t oDaphnia pulex were evaluated with 48-h acute lethal concentration estimates (LC50) and a 10-d population growth-rate measurement, the instantaneous rate of increase (ri). Based on LC50, the order of toxicity was R-11 . X- 77 5 Sylgard 309 5

JOHN D. STARK; W ILLIAM K. WALTHALL

2003-01-01

342

Effects of human population growth on the Fraser and Okanagan River systems, Canada: a comparative inquiry.  

PubMed

The author compares the impact of human population growth on the Fraser and Okanagan river systems in Canada. The effects "on water, fisheries and other aquatic resources of the two basins are explored along with possibilities and suggestions for their sustainable development. The latter, despite some glimmers of hope, will not be tenable without major changes in public attitude, in government policy at all levels, and in other measures which to many may seem impossible." PMID:12293932

Northcote, T G

1996-10-01

343

Real-Time Exponential Curve Fits Using Discrete Calculus  

NASA Technical Reports Server (NTRS)

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.

Rowe, Geoffrey

2010-01-01

344

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...

345

Comparison of Growth, Condition and Population Structure of White Crappie in Lake Carl Blackwell, 1984-1985 to 1998  

Microsoft Academic Search

White crappie, Pomoxis annularis, is an important sport fish in Oklahoma, but some populations grow slowly or have undesirable population structure. The management of the species is not a settled issue and requires data bases for temporal and\\/or lake to lake comparisons. This paper reports decadal changes in growth, condition and population structure for white crappie in Lake Carl Blackwell,

Wyatt J. Doyle; Dale W. Toetz; Mark E. Payton

346

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

PubMed Central

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

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

2014-01-01

347

Matrix Models for Size-Structured Populations: Unrealistic Fast Growth or Simply Diffusion?  

PubMed Central

Matrix population models are widely used to study population dynamics but have been criticized because their outputs are sensitive to the dimension of the matrix (or, equivalently, to the class width). This sensitivity is concerning for the population growth rate () because this is an intrinsic characteristic of the population that should not depend on the model specification. It has been suggested that the sensitivity of to matrix dimension was linked to the existence of fast pathways (i.e. the fraction of individuals that systematically move up a class), whose proportion increases when class width increases. We showed that for matrix population models with growth transition only from class to class , was independent of the class width when the mortality and the recruitment rates were constant, irrespective of the growth rate. We also showed that if there were indeed fast pathways, there were also in about the same proportion slow pathways (i.e. the fraction of individuals that systematically remained in the same class), and that they jointly act as a diffusion process (where diffusion here is the movement in size of an individual whose size increments are random according to a normal distribution with mean zero). For 53 tree species from a tropical rain forest in the Central African Republic, the diffusion resulting from common matrix dimensions was much stronger than would be realistic. Yet, the sensitivity of to matrix dimension for a class width in the range 1–10 cm was small, much smaller than the sampling uncertainty on the value of . Moreover, could either increase or decrease when class width increased depending on the species. Overall, even if the class width should be kept small enough to limit diffusion, it had little impact on the estimate of for tree species. PMID:24905941

Picard, Nicolas; Liang, Jingjing

2014-01-01

348

Large nonlethal effects of an invasive invertebrate predator on zooplankton population growth rate.  

PubMed

We conducted a study to determine the contribution of lethal and nonlethal effects to a predator's net effect on a prey's population growth rate in a natural setting. We focused on the effects of an invasive invertebrate predator, Bythotrephes longimanus, on zooplankton prey populations in Lakes Michigan and Erie. Field data taken at multiple dates and locations in both systems indicated that the prey species Daphnia mendotae, Daphnia retrocurva, and Bosmina longirostris inhabited deeper portions of the water column as Bythotrephes biomass increased, possibly as an avoidance response to predation. This induced migration reduces predation risk but also can reduce birth rate due to exposure to cooler temperatures. We estimated the nonlethal (i.e., resulting from reduced birth rate) and lethal (i.e., consumptive) effects of Bythotrephes on D. mendotae and Bosmina longirostris. These estimates used diel field survey data of the vertical gradient of zooplankton prey density, Bythotrephes density, light intensity, and temperature with growth and predation rate models derived from laboratory studies. Results indicate that nonlethal effects played a substantial role in the net effect of Bythotrephes on several prey population growth rates in the field, with nonlethal effects on the same order of magnitude as or greater (up to 10-fold) than lethal effects. Our results further indicate that invasive species can have strong nonlethal, behaviorally based effects, despite short evolutionary coexistence with prey species. PMID:17479758

Pangle, Kevin L; Peacor, Scott D; Johannsson, Ora E

2007-02-01

349

Child abuse registration, fetal growth, and preterm birth: a population based study  

PubMed Central

Objectives To study the relation of intra?uterine growth and gestational age with child protection registration in a 20 year whole population birth cohort. Setting West Sussex area of England. Study design Retrospective whole population birth cohort. Outcomes Child protection registration; individual categories of registration—sexual abuse, physical abuse, emotional abuse, and neglect. Population and participants 119?771 infants born in West Sussex between January 1983 and December 2001 with complete data including birth weight, gestational age, maternal age, and postcode. Results In all categories of registration a linear trend was noted such that the lower the birth weight z score the higher the likelihood of child protection registration. Similar trends were noted for gestational age. All these trends were robust to adjustment for maternal age and socioeconomic status. Conclusions The results of this study suggest that lower levels of fetal growth and shorter gestational duration are associated with increased likelihood of child protection registration in all categories including sexual abuse independent of maternal age or socioeconomic status. This study does not permit comment on whether poor fetal growth or preterm birth predispose to child abuse and neglect or the association arises because they share a common pathway. PMID:16537351

Spencer, Nick; Wallace, Ann; Sundrum, Ratna; Bacchus, Claire; Logan, Stuart

2006-01-01

350

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

PubMed Central

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

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

2002-01-01

351

F-LE Exponential growth versus linear growth I  

NSDL National Science Digital Library

This is a task from the Illustrative Mathematics website that is one part of a complete illustration of the standard to which it is aligned. Each task has at least one solution and some commentary that addresses important asects of the task and its potential use. Here are the first few lines of the commentary for this task: Mr. Wiggins gives his daughter Celia two choices of payment for raking leaves: Two dollars for each bag of leaves filled, She will be paid for the numb...

352

F-LE Exponential growth versus linear growth II  

NSDL National Science Digital Library

This is a task from the Illustrative Mathematics website that is one part of a complete illustration of the standard to which it is aligned. Each task has at least one solution and some commentary that addresses important asects of the task and its potential use. Here are the first few lines of the commentary for this task: Using a scientific calculator, Alex makes the following table listing values of $(1.001)^x$ and $2x$ for a few inputs: $x(1.001)^x2x$ 11.0012 101.01004...

353

Impact of the population of spoilage microflora on the growth of Listeria monocytogenes on frankfurters.  

PubMed

Approximately 100 CFU/cm2 of a five-strain mixture of Listeria monocytogenes was coinoculated onto frankfurters with three different concentrations (10(2), 10(4), and 106 CFU/cm2) of an undefined spoilage microflora derived from commercial frankfurters. The frankfurters were vacuum packaged and stored at 10 degrees C for up to 48 days. The populations of L. monocytogenes, aerobic mesophilic bacteria, lactic acid bacteria, and Enterobacteriaceae were determined at various time intervals during storage. After 14 days, the population of L. monocytogenes was highest when grown with a spoilage microflora population of 10(2) CFU/cm2, and this trend continued until 48 days. Throughout the entire storage period, the populations of L. monocytogenes at any concentration of inoculated spoilage microflora rarely differed by more than 0.5 log CFU/cm2, and the maximum observed difference as 1.1 log CFU/cm2 at 40 days. The growth rate of L. monocytogenes was approximately the same at all concentrations of the inoculated spoilage microflora. These results suggest that the concentration of spoilage microflora present on the original processed meat may have a slight impact on the growth of L. monocytogenes in the package. PMID:16541704

Radin, Dragoslava; Niebuhr, Steven E; Dickson, James S

2006-03-01

354

Age, growth, and population structure of the smooth clam Callista chione in the eastern Adriatic Sea  

NASA Astrophysics Data System (ADS)

The age, growth, and population structure of the smooth clam Callista chione were determined from samples collected by hydraulic dredge and SCUBA at four locations in the eastern Adriatic during 2007 and 2008. The age of 436 clam shells was determined from internal growth lines present in shell sections, and the timing of growth line formation was ascertained from monthly collections of clams to occur between August and September when sea water temperatures were maximal. In addition, age of 30 older individuals was verified with acetate peels of polished and etched shell sections. Differences were apparent in the age structure and growth rates of clams collected from the four locations studied. Von Bertalanffy growth (VBG) curves obtained for clams from these locations were L t = 72.4 (1-e-0.25(t - 2.68)) (Rab Island), L t = 74.5 (1-e-0.15(t + 0.57)) (Pag Bay), L t = 79.3 (1-e-0.34(t - 0.97)) (Cetina estuary), and L t = 82.5 (1-e-0.11(t + 2.88)) (Kaštela Bay). The age of the clams ranged between 3 and 44 years; median clam ages were similar at three of the four locations (14, 12, and 12 years, respectively), but was significantly lower in the Cetina estuary (4 years). The VBG growth constants recorded from clams were within the range of values obtained for this species by previous authors. The observed local differences in population structure indicate different levels of exploitation and illustrate the need to establish long-term strategies for a sustainable exploitation of smooth clams in the Croatian Adriatic.

Ezgeta-Bali?, Daria; Peharda, Melita; Richardson, Christopher A.; Kuzmani?, Marina; Vrgo?, Nedo; Isajlovi?, Igor

2011-12-01

355

Limits to Growth--A Role Playing Activity.  

ERIC Educational Resources Information Center

In this lesson, junior high students consider two instances of exponential population growth--one at the local community level and one at the world level--as a way of illuminating some of the problems posed by growth and the limits that may curtail it. (RM)

Intercom, 1985

1985-01-01

356

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

USGS Publications Warehouse

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 captive young into wild nests), diminishing the importance of nest failure as a limiting factor. Annual survival has been periodically reduced by catastrophes (hurricanes), which have greatly constrained population growth, but survival rates were high under non-catastrophic conditions. Although the importance of factors maintaining the Puerto Rican Parrot bottleneck varied throughout the 30-year period of study, we determined their long-term influence using LSA simulations to correlate variation in demographic rates with variation in population growth (k). The bottleneck appears to have been maintained primarily by periodic catastrophes (hurricanes) that reduced adult survival, and secondarily by environmental and/or behavioral factors that resulted in a failure of many adults to nest. The influence of inbreeding through reduced hatching success played a much less significant role, even when additional effects of inbreeding on the production and mortality of young were incorporated into the LSA. Management actions needed to speed recovery include (1) continued nest guarding to minimize the effects of nest failure due to nongenetic causes; (2) creating a second population at another location on the island --a process that was recently initiated--to reduce the chance that hurricane strikes will cause extinction; and (3) determining the causes of the low percentage of breeders in the population and ameliorating them, which would have a large impact on population growth.

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

2008-01-01

357

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

NASA Astrophysics Data System (ADS)

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.

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

2013-11-01

358

Tropomyosin localization reveals distinct populations of microfilaments in neurites and growth cones.  

PubMed

The functional and structural differences between neurites and growth cones suggests the possibility that distinct microfilament populations may exist in each domain. Tropomyosins are integral components of the actin-based microfilament system. Using antibodies which detect three different sets of tropomyosin isoforms, we found that the vast majority of tropomyosin was found in a microfilament-enriched fraction of cultured cortical neurons, therefore enabling us to use the antisera to evaluate compositional differences in neuritic and growth cone microfilaments. An antibody which reacts with all known nonmuscle isoforms of the alpha Tms gene (Tm5NM1-4) stains both neurites and growth cones, whereas a second antibody against the isoform subset, Tm5NM1-2, reacts only with the neurite. A third antibody which reacts with the Tm5a/5b isoforms encoded by a separate gene from alpha Tms was strongly reactive with both neurites and growth cones in 16-h cultures but only with the neurite shaft in 40-h cultures. Treatment of neurons with cytochalasin B allowed neuritic Tm5NM1-2 to spread into growth cones. Removal of the drug resulted in the disappearance of Tm5NM1-2 from the growth cone, indicating that isoform segregation is an active process dependent on intact microfilaments. Treatment of 40-h cultures with nocodazole resulted in the removal of Tm5NM1-2 from the neurite whereas Tm5a/5b now spread back into the growth cone. We conclude that the organization of Tm5NM1-2 and Tm5a/5b in the neurite is at least partially dependent on microtubule integrity. These results indicate that tropomyosin isoforms Tm5NM1-2, Tm5NM3-4, and Tm5a/5b mark three distinct populations of actin filaments in neurites and growth cones. Further, the composition of microfilaments differs between neurites and growth cones and is subject to temporal regulation. PMID:9143561

Schevzov, G; Gunning, P; Jeffrey, P L; Temm-Grove, C; Helfman, D M; Lin, J J; Weinberger, R P

1997-01-01

359

Relative effects of environment and direct species interactions on the population growth rate of an exotic ascidian.  

PubMed

The success of exotic species can be influenced by both the abiotic environment and species interactions. Many studies have demonstrated significant effects of either type of factor on aspects of exotic success, but few have considered their relative effects on population growth rate, a more holistic measure of success. To quantify the relative effects of environment and direct competition on an exotic ascidian, Botrylloides violaceus, I manipulated direct contact interactions at four sites with different abiotic environments and tracked individual colonies over 3 years. I tested site and contact treatment effects on survival, growth and fecundity, and then conducted a life table response experiment on a periodic, size-structured population matrix model to test their effects on population growth rate. Both site and contact interaction were important to explaining variation in survival and growth. Contact interactions decreased the survival and growth of larger colonies but unexpectedly increased the survival of small colonies at some sites, which led to relatively weaker and spatially variable effects on overall population growth rates. Site effects on population growth rates were an order of magnitude larger than contact effects, and site variation in winter vital rates made the largest contributions to changes in population growth rate. The results of this study suggest that the abiotic environment plays a larger role in the success of B. violaceus. Thus, environmental variables, such as temperature and salinity, could be used to predict this exotic species' success under different environmental scenarios, including global climate change. PMID:21344258

Grey, Erin K

2011-08-01

360

[Some problems about the policy of controlling population growth in China].  

PubMed

This discussion of some problems regarding the policy of controlling population growth in China focuses on the formation and the development of the policies of planned population growth control, how demands of modernization require a policy of only 1 child for each couple, and the need for ideological education as well as essential economical and administrative measures. The process of forming and developing the population control policies of China can be divided into 3 phases: the mid-50s to the early 1970s; the early 1970s to March 5, 1978 -- the date the new constitution became effective; and March 5, 1978 to the present. The 1st formal policy on planned popultion control emerged in 1956 at the 8th national meeting of the Communist party. The necessity for propagating planned birth control and advocating planned birth was recognized at this time. During the 2nd phase, the planned birth program was almost stopped by interference from an anti-revolutionary group. The maladjustment between population development and economic development were getting worse during the 1966-1971 period. Health services in both rural and urban areas were developed, and maternal and child health care services were reinforced in order to lower the death rate and to increase the practice of birth planning. The objective was to adjust the birth rate by improving production development and the living coinditions of the people. The new constitution indicated that the country should advocate and practice planned birth. The special committee on planned birth of the State Council, meeting in June 1978, established guidelines for the national planned birth program. The population policy of only 1 child for each couple was proposed for the longterm benefit of China and its people and because of the urgent demand of the 4 modernizations. The indication of the achievement of the 4 modernizations by the end of the 20th century is a per capita income of 1000 United States dollars. To reach the $1000 figure, the per capita income needs to be increased 3-fold. This is a difficult task, and to realize it effort must be placed on both material production and population control. Problems that may result from the advocation of only 1 child for each couple are reviewed. The way to promote the exeuction of the policy of planned control of population growth is to apply ideological education as the major method and to integrate it with economical and administrative measures. PMID:12311034

Wang, N J

1981-04-01

361

Predators select against high growth rates and risk-taking behaviour in domestic trout populations.  

PubMed Central

Domesticated (farm) salmonid fishes display an increased willingness to accept risk while foraging, and achieve high growth rates not observed in nature. Theory predicts that elevated growth rates in domestic salmonids will result in greater risk-taking to access abundant food, but low survival in the presence of predators. In replicated whole-lake experiments, we observed that domestic trout (selected for high growth rates) took greater risks while foraging and grew faster than a wild strain. However, survival consequences for greater growth rates depended upon the predation environment. Domestic trout experienced greater survival when risk was low, but lower survival when risk was high. This suggests that animals with high intrinsic growth rates are selected against in populations with abundant predators, explaining the absence of such phenotypes in nature. This is, to our knowledge, the first large-scale field experiment to directly test this theory and simultaneously quantify the initial invasibility of domestic salmonid strains that escape into the wild from aquaculture operations, and the ecological conditions affecting their survival. PMID:15539348

Biro, Peter A.; Abrahams, Mark V.; Post, John R.; Parkinson, Eric A.

2004-01-01

362

Analysis of cell size and DNA content in exponentially growing and stationary-phase batch cultures of Escherichia coli.  

PubMed Central

Escherichia coli strains were grown in batch cultures in different media, and cell size and DNA content were analyzed by flow cytometry. Steady-state growth required large dilutions and incubation for many generations at low cell concentrations. In rich media, both cell size and DNA content started to decrease at low cell concentrations, long before the cultures left the exponential growth phase. Stationary-phase cultures contained cells with several chromosomes, even after many days, and stationary-phase populations exclusively composed of cells with a single chromosome were never observed, regardless of growth medium. The cells usually contained only one nucleoid, as visualized by phase and fluorescence microscopy. The results have implications for the use of batch cultures to study steady-state and balanced growth and to determine mutation and recombination frequencies in stationary phase. PMID:7592469

Akerlund, T; Nordstrom, K; Bernander, R

1995-01-01

363

Contributions of Covariance: Decomposing the components of stochastic population growth in Cypripedium calceolus  

PubMed Central

Although correlations between vital rates can have important effects on evolution and demography, few studies have investigated their effects on population dynamics. Here, we extend Life Table Response Experiments (LTREs) to variable environments, showing how to quantify contributions made by: (1) mean vital rates, (2) variability driven by environmental fluctuations, (3) correlations implying demographic tradeoffs and reflecting stage transition synchrony and (4) elasticities reflecting local selection pressures. Applying our methods to the Lady’s Slipper orchid Cypripedium calceolus, we found that mean rates accounted for 77.1% of all effects on the stochastic growth rate, variability accounted for 12.6%, elasticities 6.6% and correlations 3.7%. Stochastic effects accounted for 17.6%, 15.3% and 35.9% of the total in our three populations. Larger elasticities to transitions between dormancy states and stronger correlations between emergence and survival suggest that one population was under greater pressure to remain active while the other two showed survival payoffs for dormancy in poor years. Strong negative correlations between dormancy, emergence and stasis balanced opposing contributions, resulting in near-stationarity in two populations. These new methods provide an additional tool for researchers investigating stochastic population dynamics and should be useful for a broad range of applications in basic ecology and conservation biology. PMID:23448889

Nicole, Florence; Jacquemyn, Hans; Tuljapurkar, Shripad

2013-01-01

364

Computer-Guided, Population-Based Screening System for Growth Disorders (CrescNet®) and On-Line Generation of Normative Data for Growth and Development  

Microsoft Academic Search

The mean age at which the diagnosis of growth disorders such as Turner’s syndrome, growth hormone (GH) deficiency or true GH-dependent gigantism is established is still rather late in many countries around the world. In addition, the question of secular trends in a given population and the rate at which childhood obesity is increasing in industrialized countries make it mandatory

W. Kiess; R. Gausche; A. Keller; J. Burmeister; H. Willgerodt; E. Keller

2001-01-01

365

Temperature-dependent population growth of three species of stored product mites (Acari: Acaridida).  

PubMed

The pest potential of stored product mites depends on the reproduction rate that is affected by the environmental conditions. In this study we investigated the effect of temperature, ranging from 5 to 35 degrees C, on the population growth of three important mite species, Acarus siro, Tyrophagus putrescentiae and Auleroglyphus ovatus at 85% r.h. Starting with 10 individuals the population increase of mites was observed after 3 weeks of cultivation, or after 6 weeks for those kept at low temperatures (5, 10, 12.5, and 15 degrees C). The rate of increase was calculated for each temperature and species. The obtained data were fitted with polynomial models. The mite population growth rates increased with increasing moderate temperatures until 25 degrees C, when r ( m )-values were 0.179, 0.177 and 0.190 for A. siro, A. ovatus and T. putrescentiae, respectively. The lower development threshold was 10.2 degrees C in all three species. Estimated upper temperature threshold was higher in T. putrescentiae (49 degrees C) than in A. siro and A. ovatus (38 degrees C). Simulation of the rate of population increase under ideal conditions, using real temperature records obtained from Czech grain stores, showed that the pest mite populations increase only during 3.5 months within a typical 9-month storage season in Central Europe. These results indicate that control of mites, be it chemical, physical or biological, is recommended during the months when allergens and pests are produced, i.e. from September to mid November and in May. PMID:17479350

Aspaly, Gamila; Stejskal, Vaclav; Pekár, Stano; Hubert, Jan

2007-01-01

366

Effects of Meloidogyne spp. and Verticillium dahliae on the growth of two Ixodia achillaeoides populationson the growth of two Ixodia achillaeoides populations  

Microsoft Academic Search

Two populations of Ixodia achillaeoides established from wild plants collected in the Adelaide Hills and the South East areas of South Australia were inoculated\\u000a with Meloidogyne hapla, M. incognita and M. javanica, alone or in combination with Verticillium dahliae in greenhouse experiments. Both V. dahliae and Meloidogyne spp. infected these two I. achillaeoides populations and suppressed growth. However, symptoms of

G. E. Walker

2000-01-01

367

Is wide availability of abortion essential to national population growth control programs? Experiences of 116 countries.  

PubMed

No nation wanting to reduce its growth rate to less than or equal to 1% can expect to do so without the widespread use of abortion. This study, based on the experience of 116 of the world's largest countries, supports the contention that abortion is essential to any national population growth control effort. Existing circumstances in developed countries have facilitated reduction of growth rates to less than 1%, with abortion rates generally in the range of 200 to 500 per 1000 live births. However, developing countries are faced with a different and more difficult set of circumstances that require even greater reliance on abortion. These obstacles include a young population with resultant rapidly growing numbers of young fertile women, poor contraceptive use-effectiveness, low prevalence of contraception, and poor or nonexistent systems for providing contraceptives. By virtue of their profession, physicians play a critical role in family planning and carry a special responsibility in ensuring that abortion services are available to all women who need them. PMID:6742046

Mumford, S D; Kessel, E

1984-07-15

368

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

PubMed Central

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.

Taylor, Marylee C.; Schroeder, Matthew B.

2014-01-01

369

Climate change and population growth in Timor Leste: implications for food security.  

PubMed

The climate in Timor Leste (East Timor) is predicted to become about 1.5 °C warmer and about 10 % wetter on average by 2050. By the same year, the population is expected to triple from 1 to 2.5-3 million. This article maps the predicted changes in temperature and rainfall and reviews the implications of climate change and population growth on agricultural systems. Improved cultivars of maize, rice, cassava, sweet potato and peanuts with high yield performance have been introduced, but these will need to be augmented in the future with better adapted cultivars and new crops, such as food and fodder legumes and new management practices. The requirements for fertilizers to boost yields and terracing and/or contour hedgerows to prevent soil erosion of steeply sloping terrain are discussed. Contour hedges can also be used for fodder for improved animal production to provide protein to reduce malnutrition. PMID:22569843

Molyneux, Nicholas; da Cruz, Gil Rangel; Williams, Robert L; Andersen, Rebecca; Turner, Neil C

2012-12-01

370

Increasing population growth by asymmetric segregation of a limiting resource during cell division  

PubMed Central

We report that when budding yeast are transferred to low-metal environment, they adopt a proliferation pattern in which division is restricted to the subpopulation of mother cells which were born in rich conditions, before the shift. Mother cells continue to divide multiple times following the shift, generating at each division a single daughter cell, which arrests in G1. The transition to a mother-restricted proliferation pattern is characterized by asymmetric segregation of the vacuole to the mother cell and requires the transcription repressor Whi5. Notably, while deletion of WHI5 alleviates daughter cell division arrest in low-zinc conditions, it results in a lower final population size, as cell division rate becomes progressively slower. Our data suggest a new stress-response strategy, in which the dilution of a limiting cellular resource is prevented by maintaining it within a subset of dividing cells, thereby increasing population growth. PMID:23591772

Avraham, Nurit; Soifer, Ilya; Carmi, Miri; Barkai, Naama

2013-01-01

371

Stochastic model for population migration and the growth of human settlements during the Neolithic transition  

NASA Astrophysics Data System (ADS)

We present a stochastic two-population model that describes the migration and growth of semisedentary foragers and sedentary farmers along a river valley during the Neolithic transition. The main idea is that random migration and transition from a sedentary to a foraging way of life, and backwards, is strongly coupled with the local crop production and associated degradation of land. We derive a nonlinear integral equation for the population density coupled with the equations for the density of soil nutrients and crop production. Our model provides a description of the formation of human settlements along the river valley. The numerical results show that the individual farmers have a tendency for aggregation and clustering. We show that the large-scale pattern is a transient phenomenon which eventually disappears due to land degradation.

Fedotov, Sergei; Moss, David; Campos, Daniel

2008-08-01

372

Numerical approximations for population growth model by Rational Chebyshev and Hermite Functions collocation approach: A comparison  

E-print Network

This paper aims to compare rational Chebyshev (RC) and Hermite functions (HF) collocation approach to solve the Volterra's model for population growth of a species within a closed system. This model is a nonlinear integro-differential equation where the integral term represents the effect of toxin. This approach is based on orthogonal functions which will be defined. The collocation method reduces the solution of this problem to the solution of a system of algebraic equations. We also compare these methods with some other numerical results and show that the present approach is applicable for solving nonlinear integro-differential equations.

K. Parand; A. R. Rezaei; A. Taghavi

2010-08-13

373

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

NASA Astrophysics Data System (ADS)

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.

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

2013-12-01

374

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

PubMed

Pradel model mark-release-recapture estimates of survivorship, phi, recruitment, f, and the rate of density-independent population growth, lambda, are presented for eight mark-recapture studies of the screwworm Cochliomyia hominivorax (Coquerel) (Diptera: Calliphoridae) from Costa Rica, totalling 19 573 released and 4476 recaptured flies. Corroborative estimates of survivorship and the rate of population growth based on an extensive review of the literature are also reported. Weighted-mean +/- standard error of the mean (SEM) mark-release-recapture estimates of survivorship, recruitment and the rate of population growth were phi = 0.798 +/- 0.008, f = 0.193 +/- 0.008 and lambda = 1.005 +/- 0.002, respectively. Population doubling time was estimated from lambda at 139 days. Estimates of phi and lambda from the literature both exceeded those calculated by mark-recapture methods and estimates of population doubling times were consequently shorter. PMID:19335838

Matlock, R B; Skoda, S R

2009-06-01

375

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

PubMed

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

Patterson, J G; Shrestha, N R

1988-01-01

376

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

USGS Publications Warehouse

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.

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

2000-01-01

377

Population extinction risks of three Neotropical small mammal species  

Microsoft Academic Search

The population persistence and extinction probabilities of three small mammal species were analyzed by estimating growth\\u000a and extinction properties obtained from 10 years of live-trapping data at two different habitat types in semiarid Chile. We\\u000a used a stochastic formulation with an exponential growth model known as a Wiener-drift process, out of which growth and extinction\\u000a quantities were estimated. The rodent

Mauricio Lima; Pablo A. Marquet; Fabian M. Jaksic

1998-01-01

378

Efficient implementation of the basic state policy of family planning for the control of population growth.  

PubMed

The speeches of Chinese Communist Party General Secretary Jiang Zemin and Premier Li Peng are summarized. The speeches were presented at the National Forum on Family Planning on March 21, 1993. Central Committee Party members, governors, and provincial party secretaries were in attendance. Minister Peng Peiyun of the State Family Planning Commission provided introductory remarks. The highlights of Jiang's and Li's speeches emphasized controlling population growth and achieving the second and third stage targets of the modernization drive. The goal was to develop the country economically while reducing the birth rate. Importance was placed on party officials and organizations taking responsibility for family planning implementation and being firm, yet reasonable and practical. Jiang Zemin mentioned that economic development needed to be speeded up along with effective control of population. Economic development surged during 1992 and many achievements were attained in family planning. Leadership in family planning improved. The sobering reality was that although the population growth rate declined, the absolute numbers of the population were still very hugh: 20 million newborns annually and an annual net increase of population of 13-15 million. Closing the gap between demands of and supply to society will be great. Low fertility was not stabilized; the birth rate was very uneven throughout the country and unplanned births had not been lowered. Because provinces and autonomous regions will be experiencing new problems with the economic reform, and there is a need to devote attention to these situations. The economic goal was gross national strength and per capita share. Family planning regulations should be followed and family planning practice should be included in the socioeconomic plan. Minorities have improved in family planning, but rural areas are still problematic. Premier Li Peng said that lessons learned from past family planning experiences should be applied to the future; rural family planning should be stressed and unevenness smoothed out. Problems have arisen between the public and the party, which need to be worked out to the interest of each. An integrated program of population, economy, society, resources, and the environment needs to occur, and family planning needs to be strengthened so that Chinese characteristics can be taken advantage of in family planning. PMID:12286984

1993-04-01

379

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

PubMed

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. The shortage of men is directly the result of the losses during World War 2. Employment opportunities have changed dramatically. The country has gone from a primarily agricultural nation to one in which 80% of the people are working class wage or salary earners. The current problem is closing the urban-rural gap and equalizing population density. 3/5 of the people are town-dwellers. To fight declining population in the villages and in the areas of Siberia and the Far East, new towns and new industrial and cultural centers are being established such as Bratsk, Ust-Ilim, Norilsk, and others. PMID:12307196

Simchera, V

1974-01-01

380

[Relationships among population growth, capital formation and employment opportunities in developing countries].  

PubMed

The assimilation of technical progress and transfer of active employed population in primary production and other activities of low productivity in industry and services were analyzed as essential factors of the process of economic development in Latin America in relation to the increase of population. The rapid absorption of growing population and the low productivity of the work force are the principal aspects of the problem of sustained development. In 1953 the region's population reached 170 million people and the recent population growth rate was 2.2% a year, equivalent to 3.7 million people, of whom only 1.5 million have been incorporated into the work force. Between 1940 and 1953 the industrial work force of the region increased by 3.7% annually, while the agricultural work force increased only by 1.4%. The per capita gross product in agriculture was $300 in 1953, and $1100 in industry and construction. The gross per capita product increased by 2.6% annually between 1940 and 1953, while the population increased by 2.2% per annum. The participation of foreign capital in the economy during this period amounted to 14% of the gross national product. The development process was prolonged and brought about important changes in the distribution of the work force. In 1953 the agricultural work force made up 58.1% of the total; however, by 1978 its share had dropped to 35.9%, while during the same period the proportion of the industrial work force increased to 26.3% and services to 36.8%. This meant that in absolute numbers about 23 million people in the active population were transferred from agriculture to industry and services. Mainly, the population from rural areas migrated to urban centers, while these countries also had to absorb European immigrants during this period. In 1953, in Latin America, the capital requirement per worker increased to $1550 and rose to $3835 in 1978 because of surging immigration. This figure was still dwarfed by the sum of $13,200 in the US towards the end of this period. PMID:12291424

Prebisch, R

1991-08-01

381

Reversible crystal growth–dissolution and aggregation–breakage: numerical and moment solutions for population balance equations  

Microsoft Academic Search

A general population balance equation (PBE) is proposed to describe combined monomer addition and dissociation (growth and dissolution) and aggregation and fragmentation. The reversible distribution kinetics has applications to a range of natural and manufacturing phenomena, including crystal growth or dissolution with agglomeration and\\/or breakage. A numerical solution to the PBE shows the evolution to a steady-state crystal size. The

Giridhar Madras; Benjamin J McCoy

2004-01-01

382

Life-time growth patterns of pumpkinseed Lepomis gibbosus introduced to Europe, relative to native North American populations  

Microsoft Academic Search

A b s t r a c t . The pumpkinseed Lepomis gibbosus, an omnivorous, nest guarding North American sunfish, was introduced into European waters about 100 years ago. To assess growth performance following introduction, we reviewed the available data for North American and European populations of pumpkinseed and compared the back-calculated age-specific growth for juveniles (standard length, SL, at

Gordon H. COPP; Michael G. FOX; Francisco N. GODINHO; Anna VILA-GISPERT

2004-01-01

383

Growth and Maturity of Hatchery and Wild Lean Lake Trout during Population Recovery in Michigan Waters of Lake Superior  

Microsoft Academic Search

The recovery of populations of wild lake trout Salvelinus namaycush in Lake Superior was the first success among Great Lakes—wide rehabilitation efforts for this species. Knowledge of changes in major demographic factors (e.g., growth and maturity schedules) is very important for enhancing our understanding of stock status during the recovery process, particularly for a fish population with a relatively long

Shawn P. Sitar; Ji X. He

2006-01-01

384

Human Capital and Population Growth in Nonmetropolitan U.S. Counties: The Importance of College Student Migration  

Microsoft Academic Search

Researchers have consistently shown that the stock of human capital in an area, measured as the share of the adult population with a college degree, is a strong predictor of future population growth. This article examines this relationship for U.S. nonmetropolitan counties and posits that student migration for higher education may play an important role. Students often move to an

John V. Winters

2011-01-01

385

Unraveling the origin of exponential law in intra-urban human mobility  

PubMed Central

The vast majority of travel takes place within cities. Recently, new data has become available which allows for the discovery of urban mobility patterns which differ from established results about long distance travel. Specifically, the latest evidence increasingly points to exponential trip length distributions, contrary to the scaling laws observed on larger scales. In this paper, in order to explore the origin of the exponential law, we propose a new model which can predict individual flows in urban areas better. Based on the model, we explain the exponential law of intra-urban mobility as a result of the exponential decrease in average population density in urban areas. Indeed, both empirical and analytical results indicate that the trip length and the population density share the same exponential decaying rate. PMID:24136012

Liang, Xiao; Zhao, Jichang; Dong, Li; Xu, Ke

2013-01-01

386

Fetal growth and psychiatric and socioeconomic problems: population-based sibling comparison.  

PubMed

Background It is unclear whether associations between fetal growth and psychiatric and socioeconomic problems are consistent with causal mechanisms. Aims To estimate the extent to which associations are a result of unmeasured confounding factors using a sibling-comparison approach. Method We predicted outcomes from continuously measured birth weight in a Swedish population cohort (n = 3 291 773), while controlling for measured and unmeasured confounding. Results In the population, lower birth weight (?2500 g) increased the risk of all outcomes. Sibling-comparison models indicated that lower birth weight independently predicted increased risk for autism spectrum disorder (hazard ratio for low birth weight = 2.44, 95% CI 1.99-2.97) and attention-deficit hyperactivity disorder. Although attenuated, associations remained for psychotic or bipolar disorder and educational problems. Associations with suicide attempt, substance use problems and social welfare receipt, however, were fully attenuated in sibling comparisons. Conclusions Results suggest that fetal growth, and factors that influence it, contribute to psychiatric and socioeconomic problems. PMID:25257067

Class, Quetzal A; Rickert, Martin E; Larsson, Henrik; Lichtenstein, Paul; D'Onofrio, Brian M

2014-11-01

387

An exponential decay model for mediation.  

PubMed

Mediation analysis is often used to investigate mechanisms of change in prevention research. Results finding mediation are strengthened when longitudinal data are used because of the need for temporal precedence. Current longitudinal mediation models have focused mainly on linear change, but many variables in prevention change nonlinearly across time. The most common solution to nonlinearity is to add a quadratic term to the linear model, but this can lead to the use of the quadratic function to explain all nonlinearity, regardless of theory and the characteristics of the variables in the model. The current study describes the problems that arise when quadratic functions are used to describe all nonlinearity and how the use of nonlinear functions, such as exponential decay, address many of these problems. In addition, nonlinear models provide several advantages over polynomial models including usefulness of parameters, parsimony, and generalizability. The effects of using nonlinear functions for mediation analysis are then discussed and a nonlinear growth curve model for mediation is presented. An empirical example using data from a randomized intervention study is then provided to illustrate the estimation and interpretation of the model. Implications, limitations, and future directions are also discussed. PMID:23625557

Fritz, Matthew S

2014-10-01

388

ALGEBRAIC PARAMETER ESTIMATION OF DAMPED EXPONENTIALS  

Microsoft Academic Search

The parameter estimation of a sum of exponentials or the exponential fitting of data is a well known problem with a rich history. It is a nonlinear problem which presents sev- eral difficulties as the ill-conditioning when roots have close values and the order of the estimated parameters, among oth- ers. One of the best existing methods is the modified

Aline Neves; Maria D. Miranda; Mamadou Mboup

389

Parameter estimation for multivariate exponential sums  

E-print Network

reconstruct the parameters of an exponential sum h by a novel algorithm, the sparse approximate Prony methodParameter estimation for multivariate exponential sums Daniel Potts Manfred Tasche The recovery of signal parameters from noisy sampled data is an essential problem in digital signal processing

390

Golden-Thompson's inequality for deformed exponentials  

E-print Network

Deformed logarithms and their inverse functions, the deformed exponentials, are important tools in the theory of non-additive entropies and non-extensive statistical mechanics. We formulate and prove counterparts of Golden-Thompson's trace inequality for q-exponentials with parameter q in the interval [1,3].

Frank Hansen

2014-09-03

391

Exponential Separation of Information and Communication  

E-print Network

Exponential Separation of Information and Communication Anat Ganor Gillat Kol Ran Raz Abstract We show an exponential gap between communication complexity and information complexity, by giving an explicit example for a communication task (relation), with information complexity O(k), and distributional

Raz, Ran

392

Get the Lead Out (exponential, logarithmic functions)  

NSDL National Science Digital Library

"Get the Lead Out" extends the study of exponential functions (from the intro, Reading this could help you sleep, caffeine and the body) and can be used to introduce the use of logarithms to "un-do" exponential expressions in solving equations.

2011-01-01

393

Spacevariant Fourier Analysis: the Exponential Chirp Transform  

E-print Network

of the fast exponential chirp algorithm on a data­base of images in a template matching task, and also­Variant Image Processing, Fourier Analysis, Non­Uniform Sampling, Real­Time Imaging, Warped Template Matching to the Mellin­ Transform) provides a fast exponential chirp transform. This provides size and rotation

Schwartz, Eric L.

394

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

SciTech Connect

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.

Sheffield, J.

1997-06-01

395

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

USGS Publications Warehouse

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.

Moen, Thomas E.

1974-01-01

396

Non-occupational exposure to paint fumes during pregnancy and fetal growth in a general population.  

PubMed

Occupational exposure to organic solvents during pregnancy has been associated with reduced fetal growth. Though organic solvents in the form of paint fumes are also found in the home environment, no studies have investigated the effect of such exposure in a general population. We studied associations between residential exposure to paint fumes during pregnancy and fetal growth within the Danish National Birth Cohort which consecutively recruited pregnant women from 1996 to 2002 from all over Denmark. Around the 30th pregnancy week, 19,000 mothers were interviewed about use of paint in their residence during pregnancy. The mothers were also asked about smoking habits and alcohol consumption during pregnancy, pre-pregnancy weight, height, parity and occupation. Information on birth weight and gestational age was obtained from national registers. We found that 45% of the mothers had been exposed to paint fumes in their residence during pregnancy. We found a statistically significant inverse relationship between exposure to paint fumes and the risk of being small for gestational age. There were no statistically significant associations between exposure to paint fumes and birth weight and risk of preterm birth after adjustment for potential confounders. Our results suggest that there are no causal relationship between non-occupational exposure to paint fumes in the residence during pregnancy and fetal growth. PMID:20219188

Sørensen, Mette; Andersen, Anne-Marie N; Raaschou-Nielsen, Ole

2010-05-01

397

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

NASA Technical Reports Server (NTRS)

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.

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

1995-01-01

398

Socially informed random walks: incorporating group dynamics into models of population spread and growth.  

PubMed

Simple correlated random walk (CRW) models are rarely sufficient to describe movement of animals over more than the shortest time scales. However, CRW approaches can be used to model more complex animal movement trajectories by assuming individuals move in one of several different behavioural or movement states, each characterized by a different CRW. The spatial and social context an individual experiences may influence the proportion of time spent in different movement states, with subsequent effects on its spatial distribution, survival and fecundity. While methods to study habitat influences on animal movement have been previously developed, social influences have been largely neglected. Here, we fit a 'socially informed' movement model to data from a population of over 100 elk (Cervus canadensis) reintroduced into a new environment, radio-collared and subsequently tracked over a 4-year period. The analysis shows how elk move further when they are solitary than when they are grouped and incur a higher rate of mortality the further they move away from the release area. We use the model to show how the spatial distribution and growth rate of the population depend on the balance of fission and fusion processes governing the group structure of the population. The results are briefly discussed with respect to the design of species reintroduction programmes. PMID:18270158

Haydon, Daniel T; Morales, Juan M; Yott, Adelle; Jenkins, Deborah A; Rosatte, Rick; Fryxell, John M

2008-05-01

399

Correlations between age, phenotype, and individual contribution to population growth in common terns.  

PubMed

There have been numerous reports of changes in phenology, which are frequently attributed to environmental change. Age-dependent change in phenotypic traits, fledgling production, and the timing of events in the life cycle is also widespread. This means that changes in the age structure of a population could generate changes in phenology, which may be incorrectly attributed to environmental change or microevolution. Here, estimates of selection for arrival date, arrival mass, and laying date are compared when age is and is not corrected for. This is achieved using long-term individual-based data collected from a breeding colony of Common Terns (Sterna hirundo) and a novel fitness measure: individual contributions to population growth. The failure to correct for age generated deceptive estimates of selection in eight out of nine comparisons. In six out of nine comparisons, the direction of selection differed between age-corrected and uncorrected estimates. Persistent individual differences were detected: individuals remained within the same part of the phenotype distribution throughout life. The age-corrected estimates of selection were weak and explained little variation in fitness, suggesting that arrival date, arrival mass, and laying date are not under intense selection in this population. These results also demonstrate the importance of correcting for age when identifying factors associated with changes in seabird phenology. PMID:18027753

Ezard, Thomas H G; Becker, Peter H; Coulson, Tim

2007-10-01

400

Histopathology of Growth Anomaly Affecting the Coral, Montipora capitata: Implications on Biological Functions and Population Viability  

PubMed Central

Growth anomalies (GAs) affect the coral, Montipora capitata, at Wai'?pae, 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'?pae 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

Burns, John H. R.; Takabayashi, Misaki

2011-01-01

401

Ultraviolet radiation increases sensitivity to pesticides: synergistic effects on population growth rate of Daphnia magna at low concentrations.  

PubMed

In the present study we aimed to investigate whether UV-B radiation can exacerbate effects of pesticides fenoxycarb, pirimicarb, and tebufenpyrad on the survival, reproduction, and population growth rate of the standard test species Daphnia magna. We applied sublethal pesticides' concentrations and UV doses and observed no effects on survival. However, we observed synergistic effects of UV and pesticides on both cumulative reproduction and population growth rate (21 days) for fenoxycarb (100 ?g/L) and pirimicarb (10 ?g/L), but a less-than-additive effect for tebufenpyrad (5-10 ?g/L). In the series exposed to UV and fenoxycarb or pirimicarb, the population growth rate dropped down to 0.1, while in the control series it was around 0.3. The results indicate that concentrations of some toxicants that are nontoxic in standard tests can cause harmful population-level effects when combined with UV. PMID:21681397

Beketov, Mikhail A; Speranza, Antonio; Liess, Matthias

2011-09-01

402

Population growth rate responses of Ceriodaphnia dubia to ternary mixtures of specific acting chemicals: pharmacological versus ecotoxicological modes of action.  

PubMed

When considering joint toxic apical effects at higher levels of biological organization, such as the growth of populations, the so-called pharmacological mode of action that relies on toxicological mechanistic effects on molecular target sites may not be relevant. Such effects on population growth rate will depend on the extent to which juvenile and adult survival rates and production rates (juvenile developmental rates and reproduction) are affected by toxic exposure and also by the sensitivity of population growth rates to life-history changes. In such cases, the ecotoxicological mode of action, defined as the crucial life-history trait processes and/or xenobiotic-life-history trait interactions underlying a toxicological effect on population growth rate, should be considered. Life-table response experiments with the crustacean Ceriodaphnia dubia exposed to single and ternary mixtures of nine compounds were conducted to test the hypothesis that joint effects on population growth rates could be predicted from the mixture constituent ecotoxicological mode of action. Joint effects of mixtures containing pharmacologically dissimilar compounds (cadmium, ?-cyhalothrin, and chlorpyrifos) that differentially affected life-history traits contributing to population growth rates were accurately predicted by the independent-action concept. Conversely, the concentration-addition concept accurately predicted joint effects of two different mixtures: one containing pharmacologically similar acting pyrethroids that also affected similarly life-history traits, the other one that included pharmacologically dissimilar compounds (3,4-dichloroaniline, sodium bromide, and fenoxycarb) acting mainly on reproduction rates. These results indicate that when assessing combined effects on population growth rate responses, selection of mixture toxicity conceptual models based on the ecotoxicological mode of action of mixture constituents provided more accurate predictions than those based on the pharmacological mode of action. PMID:22827446

Barata, Carlos; Fernández-San Juan, María; Feo, Maria Luisa; Eljarrrat, Ethel; Soares, Amadeu M V M; Barceló, Damià; Baird, Donald J

2012-09-01

403

Effects of tag loss on direct estimates of population growth rate  

USGS Publications Warehouse

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).

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

2005-01-01

404

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

PubMed Central

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 continuous decrease. Infant mortality considerably decreased (from 164‰ in 1950 to 20.5‰ in 2010). The causes of infant mortality have still been tightly related with the causes of the developing countries. Next to this, natality and the natural population growth have experienced a considerably decrease in Kosovo. Even though there have been some improvements within the health care in Kosovo, there is still a lot to be done with the aim of constant improvement of health care in order to promote the health care for mothers and children. PMID:23678327

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

2012-01-01

405

Stretched exponential survival statistics for microorganisms in radiation field  

NASA Astrophysics Data System (ADS)

The so-called concave or tailed survival curves are reported both for multi and single species bacterial populations. Taking as an example Bacillus pumilus, frequently encountered in decontamination studies, it is shown that the tailed survival curves are adequately described by stretched (0< ?<1) exponential SF=exp[-( D/ D0) ?], where SF denotes the fraction of species surviving the irradiation dose D, D0 is the effective dose, and ? is the dispersion parameter interpreted phenomenologically in terms of radiation sensivity distribution for single species population under the given experimental conditions.

Plonka, Andrzej; Bogus, Wlodzimierz

1999-11-01

406

Exponential Decay of Correlations Implies Area Law  

NASA Astrophysics Data System (ADS)

We prove that a finite correlation length, i.e., exponential decay of correlations, implies an area law for the entanglement entropy of quantum states defined on a line. The entropy bound is exponential in the correlation length of the state, thus reproducing as a particular case Hastings's proof of an area law for groundstates of 1D gapped Hamiltonians. As a consequence, we show that 1D quantum states with exponential decay of correlations have an efficient classical approximate description as a matrix product state of polynomial bond dimension, thus giving an equivalence between injective matrix product states and states with a finite correlation length.

Brandão, Fernando G. S. L.; Horodecki, Micha?

2014-11-01

407

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

PubMed

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

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

2014-06-01

408

Estimating chronic wasting disease effects on mule deer recruitment and population growth.  

PubMed

Chronic wasting disease (CWD), a prion disease of mule deer (Odocoileus hemionus), accelerates mortality and in so doing has the potential to influence population dynamics. Although effects on mule deer survival are clear, how CWD affects recruitment is less certain. We studied how prion infection influenced the number of offspring raised to weaning per adult (?2 yr old) female mule deer and subsequently the estimated growth rate (?) of an infected deer herd. Infected and presumably uninfected radio-collared female deer were observed with their fawns in late summer (August-September) during three consecutive years (2006-2008) in the Table Mesa area of Boulder, Colorado, USA. We counted the number of fawns accompanying each female, then used a fully Bayesian model to estimate recruitment by infected and uninfected females and the effect of the disease on ?. On average, infected females weaned 0.95 fawns (95% credible interval=0.56-1.43) whereas uninfected females weaned 1.34 fawns (95% credible interval=1.09-1.61); the probability that uninfected females weaned more fawns than infected females was 0.93). We used estimates of prevalence to weight recruitment and survival parameters in the transition matrix of a three-age, single-sex matrix model and then used the matrix to calculate effects of CWD on ?. When effects of CWD on both survival and recruitment were included, the modeled ? was 0.97 (95% credible interval = 0.82-1.09). Effects of disease on ? were mediated almost entirely by elevated mortality of infected animals. We conclude that although CWD may affect mule deer recruitment, these effects seem to be sufficiently small that they can be omitted in estimating the influences of CWD on population growth rate. PMID:20966260

Dulberger, Jessie; Hobbs, N Thompson; Swanson, Heather M; Bishop, Chad J; Miller, Michael W

2010-10-01

409

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

NASA Technical Reports Server (NTRS)

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.

Noever, David A.

1990-01-01

410

An analysis of the population growth in the Seventh Five-Year Plan period.  

PubMed

The analysis of the 7th 5-Year, Plan in China indicates 30 million more people than the 1.113 billion targeted for 1990, i.e., total population is 1.143 billion. An average increase of 13.75 million annually between 1980-85 occurred; the average annual births were 20.47 million and deaths were 6.73 million. Between 1985-90, the average increase grew to 17.45 million, with births at 24.95 million and deaths at 7.50 million. There were 4.48 million more births annually in the recent past, attributed to women born during the baby boom in the 1960s. The actual average number of children per couple dropped. 256.47 million women averaged annually were of childbearing ages of 15-49 from 1980-85, and 291.43 million from 1985 to 1990. In the most fecund ages, 20-29 years, the number of women increased by 16.65%, from 86.01 to 100.33 million in 1985-90. The actual 1985 population was 1.05579, and the difference between the expected and the actual in 1985 and the fertility estimates account for the 30 million difference is the 1990 expected and actual population. 10.5 million are due to the estimating error in population and 8 million to the estimating error in fertility. The other 12 million are a result of unanticipated fertility increase. in developing the 7th 5 Year Plan, expectations were too high for the decline in fertility, and unplanned births were not brought under control. The trends in the 1980s were ones of an initial sharp reduction and then narrow ranged fluctuations. The transition was not apparent. There was great eagerness to have a sharp decline because of the overpaid population growth, which was an aspiration not a reality. The 1986-87 period produced millions of unplanned births. Contributing factors were also adjustments made in the family planning policy and ineffective family planning programs. PMID:12343637

Yang, S

1991-06-01

411

Genome-wide association analysis identifies quantitative trait loci for growth in a Landrace purebred population.  

PubMed

Growth-related traits are complex and economically important in the livestock industry. The aim of this study was to identify quantitative trait loci (QTL) and the associated positional candidate genes affecting growth in pigs. A genome-wide association study (GWAS) was performed using the porcine single-nucleotide polymorphism (SNP) 60K bead chip. A mixed-effects model and linear regression approach were used for the GWAS. The data used in the study included 490 purebred Landrace pigs. All experimental animals were genotyped with 39 438 SNPs located throughout the pig autosomes. We identified a strong association between a SNP marker on chromosome 16 and body weight at 71 days of age (ALGA0092396, P = 5.35 × 10(-9) , Bonferroni adjusted P < 0.05). The SNP marker was located near the genomic region containing IRX4, which encodes iroquois homeobox 4. This SNP marker could be useful in the selective breeding program after validating its effect on other populations. PMID:24506094

Jung, E J; Park, H B; Lee, J B; Yoo, C K; Kim, B M; Kim, H I; Kim, B W; Lim, H T

2014-06-01

412

Intrauterine Growth Standards: A Cross-Sectional Study in a Population of Nigerian Newborns  

PubMed Central

The aim of the study was to define an intrauterine growth curve for a population of Nigerian newborn babies. A cross-sectional observational study design was adopted. Weight, length and head circumference were all measured in consecutive singleton deliveries at the University of Ilorin Teaching Hospital over a 3-year period. Gestational age (GA) of the babies was estimated from the last menstrual period or first trimester ultrasound. The estimates obtained were clinically validated using the Ballard score. Mean birth weights and percentiles of the weight, length and head circumferences for the respective GA were estimated using the SPSS 15 software package. A total of 5273 babies were recruited for the study with GA ranging from 25-44 weeks. Comparison of the mean birth weights of the various GA with the data from Denver, Colorado, showed that Nigerian babes tended to weigh less at the early GA, although these differences were not statistically significant. Between 26-36 weeks, the average weights of both sexes were similar; however, beyond this time point there was a consistent increase in the average weight of the males over the female babies. Growth curves for Nigerian newborn babies were generated and showed that the mean birth weight of Nigerian preterm babies was lighter than that of babies in Colorado. The impact of these differences on the classification of newborns will require further evaluation. PMID:25396034

Mokuolu, Olugbenga A.; Adesiyun, Omotayo O.; Suleiman, Mohammed B.; Bello, Mustapha

2012-01-01

413

Differential effects of growth and loss processes in controlling natural phytoplankton populations  

SciTech Connect

An investigation was made of factors controlling algal succession in a small, oligotrophic lake during summer stratification. Weekly measurements were made of growth rate, sedimentation rate, and population density for each of the dominant phytoplankton species. Weekly diel measurements were made of zooplankton grazing rates using /sup 14/C labeled algae. Cyclotella michiganiana was the dominant algae through the end of June at which time Cyclotella comensis began to increase, becoming the dominant by August. In August, high grazing pressure caused the rapid declines of both C. michiganiana and C. comensis which were followed by an increase of Sphaerocystis Schroeteri. The combined effect of greater growth rates and lower loss rates of C. comensis resulted in its dominance over of C. michiganiana. In contrast, the C. comensis - S. Schroeteri succession clearly resulted from differential mortality alone. It is likely that the importance of losses due to sedimentation and/or grazing is large in many lakes and that interspecific competition may be less important in actually controlling seasonal succession.

Crumpton, W.G.

1980-01-01

414

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

NASA Technical Reports Server (NTRS)

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.

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

2008-01-01

415

Bacterial Population in Intestines of the Black Tiger Shrimp (Penaeus monodon) under Different Growth Stages  

PubMed Central

Intestinal bacterial communities in aquaculture have been drawn to attention due to potential benefit to their hosts. To identify core intestinal bacteria in the black tiger shrimp (Penaeus monodon), bacterial populations of disease-free shrimp were characterized from intestines of four developmental stages (15-day-old post larvae (PL15), 1- (J1), 2- (J2), and 3-month-old (J3) juveniles) using pyrosequencing, real-time PCR and denaturing gradient gel electrophoresis (DGGE) approaches. A total of 25,121 pyrosequencing reads (reading length?=?442±24 bases) were obtained, which were categorized by barcode for PL15 (7,045 sequences), J1 (3,055 sequences), J2 (13,130 sequences) and J3 (1,890 sequences). Bacteria in the phyla Bacteroides, Firmicutes and Proteobacteria were found in intestines at all four growth stages. There were 88, 14, 27, and 20 bacterial genera associated with the intestinal tract of PL15, J1, J2 and J3, respectively. Pyrosequencing analysis revealed that Proteobacteria (class Gammaproteobacteria) was a dominant bacteria group with a relative abundance of 89% for PL15 and 99% for J1, J2 and J3. Real-time PCR assay also confirmed that Gammaproteobacteria had the highest relative abundance in intestines from all growth stages. Intestinal bacterial communities from the three juvenile stages were more similar to each other than that of the PL shrimp based on PCA analyses of pyrosequencing results and their DGGE profiles. This study provides descriptive bacterial communities associated to the black tiger shrimp intestines during these growth development stages in rearing facilities. PMID:23577162

Rungrassamee, Wanilada; Klanchui, Amornpan; Chaiyapechara, Sage; Maibunkaew, Sawarot; Tangphatsornruang, Sithichoke; Jiravanichpaisal, Pikul; Karoonuthaisiri, Nitsara

2013-01-01

416

RANDOM FINITE SUBSETS WITH EXPONENTIAL DISTRIBUTIONS  

Microsoft Academic Search

Let S denote the collection of all ?nite subsets of N+. We de?ne an operation on S that makes S into a positive semigroup with set inclu-sion as the associated partial order. Positive semigroups are the natural home for probability distributions with exponential properties, such as the memoryless and constant rate properties. We show that there are no exponential distributions

Kyle Siegrist

2007-01-01

417

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

PubMed Central

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

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

2002-01-01

418

Variation Amongst Survivor Populations of White Clover Collected from Sites Across Europe: Growth Attributes and Physiological Responses to Low Temperature  

PubMed Central

Experiments were carried out at IGER, Aberystwyth, UK to investigate traits of direct relevance to the processes of overwintering and spring growth in white clover (Trifolium repens L.). The plant material used was derived from baseline populations of the cultivar AberHerald and survivor populations generated after 2–3 years’ growth in Germany (Kiel), Sweden (Uppsala) and Switzerland (Zürich). The aims of the experiments were to measure the level of genetic shift that had occurred in certain traits due to selection in the survivor populations by comparing these with the baseline population. The adaptive significance of traits was assessed by determining the extent to which stabilizing selection had operated to reduce levels of intra?population variation. Significant differences were found in the responses of leaf production to two temperature treatments in the survivor populations from Germany and Sweden compared with the Swiss and baseline material. Plants of the former two populations produced much more leaf than the others at the higher temperature, but leaf production rates at the lower temperature did not differ. As this experiment used cloned genotypes in the two treatments, the result suggests that a higher degree of phenotypic plasticity for this trait had been selected for in the German and Swedish populations. These populations also showed greater rates of regrowth of leaves from terminal buds exposed to sub?zero temperatures, but there were no differences between populations in levels of freezing tolerance, or in stolon carbohydrate content. Genetic shift occurred in the degree of unsaturation of stolon lipids, with all three survivor populations possessing higher proportions of unsaturated fatty acids than the baseline. Stabilizing selection also operated on this trait in the survivor populations, suggesting that it is of adaptive significance in cool climates. PMID:12096740

COLLINS, ROSEMARY P.; HELGADÓTTIR, ÁSLAUG; FOTHERGILL, MICK; RHODES, IAN

2002-01-01

419

Ecological studies on the population of isaza, Chaenogobius Isaza Tanaka, in Lake Biwa, with special reference to the effects of population density upon its growth  

Microsoft Academic Search

Summary  \\u000a \\u000a \\u000a \\u000a 1. \\u000a \\u000a In order to get the knowledge on the age composition of “isaza” population in Lake Biwa and the effect of population density\\u000a on growth, monthly distribution of mean body length and mean body weight has been analyzed on the basis of monthly haul by\\u000a “isazabiki” trawl during 1949 to 1953 and also 1960 to 1965.\\u000a \\u000a \\u000a \\u000a \\u000a 2. \\u000a \\u000a There is

Makoto Nagoshi

1966-01-01

420

Population effects of growth hormone transgenic coho salmon depend on food availability and genotype by environment interactions.  

PubMed

Environmental risk assessment of genetically modified organisms requires determination of their fitness and invasiveness relative to conspecifics and other ecosystem members. Cultured growth hormone transgenic coho salmon (Oncorhynchus kisutch) have enhanced feeding capacity and growth, which can result in large enhancements in body size (>7-fold) relative to nontransgenic salmon, but in nature, the ability to compete for available food is a key factor determining survival fitness and invasiveness of a genotype. When transgenic and nontransgenic salmon were cohabitated and competed for different levels of food, transgenic salmon consistently outgrew nontransgenic fish and could affect the growth of nontransgenic cohorts except when food availability was high. When food abundance was low, dominant individuals emerged, invariably transgenic, that directed strong agonistic and cannibalistic behavior to cohorts and dominated the acquisition of limited food resources. When food availability was low, all groups containing transgenic salmon experienced population crashes or complete extinctions, whereas groups containing only nontransgenic salmon had good (72.0 +/- 4.3% SE) survival, and their population biomass continued to increase. Thus, effects of growth hormone transgenic salmon on experimental populations were primarily mediated by an interaction between food availability and population structure. These data, while indicative of forces which may act on natural populations, also underscore the importance of genotype by environment interactions in influencing risk assessment data for genetically modified organisms and suggest that, for species such as salmon which are derived from large complex ecosystems, considerable caution is warranted in applying data from individual studies. PMID:15192145

Devlin, Robert H; D'Andrade, Mark; Uh, Mitchell; Biagi, Carlo A

2004-06-22

421

Sources of variability in spotted owl population growth rate: testing predictions using long-term mark–recapture data  

Microsoft Academic Search

For long-lived iteroparous vertebrates that annually produce few young, life history theory predicts that reproductive output\\u000a (R) and juvenile survival should influence temporal variation in population growth rate (?) more than adult survival does. We\\u000a examined this general prediction using 15 years of mark–recapture data from a population of California spotted owls (Strix occidentalis occidentalis). We found that survival of individuals

Mark E. Seamans; R. J. Gutiérrez

2007-01-01

422

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

PubMed Central

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 assessment methods, to obtain robust estimates of population trends in species threatened by overfishing. PMID:21966402

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

2011-01-01

423

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

PubMed Central

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

Haase, Dagmar; Kabisch, Nadja; Haase, Annegret

2013-01-01