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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

Logistic Growth The logistic equation is a model of limited population growth. The exponential growth model  

E-print Network

9­28­1998 Logistic Growth The logistic equation is a model of limited population growth and K grow almost exponentially at first. Growth slows as N nears the limiting population K. As t !1, N. The exponential growth model dN dt = aN; a ? 0: is not bad in situations where resources are unlimited

Ikenaga, Bruce

4

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

E-print Network

, as shown by reindeer on Pribilof Islands for 30 years after introduction. Exponential growth occurs when not often occur (for long) in nature. But colonizations like the reindeer example, or recovery

Creel, Scott

5

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

PubMed Central

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.  

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

7

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

8

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

9

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

10

Population Growth  

NSDL National Science Digital Library

These activities explore population growth rates and its consequences with regard to the distribution of natural resources. Population growth is perhaps the most important environmental issue of our time. As population increases and as people seek to raise their standard of living, more stress is put on our earth’s finite resources.One aspect of the population issue is the sheer magnitude of the numbers involved. World population did not reach 1 billion until the year 1800. Since then it has grown exponentially to reach our current 6.7 billion.

2009-01-01

11

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

12

Lesson 29: Exponential Growth and Decay  

NSDL National Science Digital Library

The lesson begins with a discussion about growth factors and percent increase, leading to the presentation of the compound interest formula. Following this focus on growth, exponential decay is introduced. The lesson concludes with a comparison between exponential and linear growth, highlighting the difference in the additive and multiplicative patterns in their growth patterns.

2011-01-01

13

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

14

Black Hole Instabilities and Exponential Growth  

E-print Network

Recently, a general analysis has been given of the stability with respect to axisymmetric perturbations of stationary-axisymmetric black holes and black branes in vacuum general relativity in arbitrary dimensions. It was shown that positivity of canonical energy on an appropriate space of perturbations is necessary and sufficient for stability. However, the notions of both "stability" and "instability" in this result are significantly weaker than one would like to obtain. In this paper, we prove that if a perturbation of the form $\\pounds_t \\delta g$---with $\\delta g$ a solution to the linearized Einstein equation---has negative canonical energy, then that perturbation must, in fact, grow exponentially in time. The key idea is to make use of the $t$- or ($t$-$\\phi$)-reflection isometry, $i$, of the background spacetime and decompose the initial data for perturbations into their odd and even parts under $i$. We then write the canonical energy as $\\mathscr E\\ = \\mathscr K + \\mathscr U$, where $\\mathscr K$ and $\\mathscr U$, respectively, denote the canonical energy of the odd part (kinetic energy) and even part (potential energy). One of the main results of this paper is the proof that $\\mathscr K$ is positive definite for any black hole background. We use $\\mathscr K$ to construct a Hilbert space $\\mathscr H$ on which time evolution is given in terms of a self-adjoint operator $\\tilde {\\mathcal A}$, whose spectrum includes negative values if and only if $\\mathscr U$ fails to be positive. Negative spectrum of $\\tilde{\\mathcal A}$ implies exponential growth of the perturbations in $\\mathscr H$ that have nontrivial projection into the negative spectral subspace. This includes all perturbations of the form $\\pounds_t \\delta g$ with negative canonical energy. A "Rayleigh-Ritz" type of variational principle is derived, which can be used to obtain lower bounds on the rate of exponential growth.

Kartik Prabhu; Robert M. Wald

2015-01-12

15

Mutant number distribution in an exponentially growing population  

NASA Astrophysics Data System (ADS)

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

Keller, Peter; Antal, Tibor

2015-01-01

16

Modeling Population Growth and Extinction  

ERIC Educational Resources Information Center

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

Gordon, Sheldon P.

2009-01-01

17

Exponential growth, energetic Hubbert cycles, and the advancement of technology  

E-print Network

Exponential growth, energetic Hubbert cycles, and the advancement of technology Tad W. Patzek for the existence of energetic Hubbert cycles and their practical equivalence to the logistic growth curves

Patzek, Tadeusz W.

18

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

19

Teaching Exponential Growth and Decay: Examples from Medicine  

ERIC Educational Resources Information Center

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

Hobbie, Russell K.

1973-01-01

20

Exponential order statistic models of software reliability growth  

NASA Technical Reports Server (NTRS)

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

Miller, D. R.

1985-01-01

21

Black Hole Instabilities and Exponential Growth  

E-print Network

Recently, a general analysis has been given of the stability with respect to axisymmetric perturbations of stationary-axisymmetric black holes and black branes in vacuum general relativity in arbitrary dimensions. It was shown that positivity of canonical energy on an appropriate space of perturbations is necessary and sufficient for stability. However, the notions of both "stability" and "instability" in this result are significantly weaker than one would like to obtain. In this paper, we prove that if a perturbation of the form $\\pounds_t \\delta g$---with $\\delta g$ a solution to the linearized Einstein equation---has negative canonical energy, then that perturbation must, in fact, grow exponentially in time. The key idea is to make use of the $t$- or ($t$-$\\phi$)-reflection isometry, $i$, of the background spacetime and decompose the initial data for perturbations into their odd and even parts under $i$. We then write the canonical energy as $\\mathscr E\\ = \\mathscr K + \\mathscr U$, where $\\mathscr K$ and $...

Prabhu, Kartik

2015-01-01

22

World Population Growth  

NSDL National Science Digital Library

Using Maple, Mathmatica, or MatLab, learner should be able 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.

Smith, David; Moore, Lawrence

2001-01-22

23

World Population Growth  

NSDL National Science Digital Library

Using Maple, Mathmatica, or MatLab, learner should be able 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.

Smith, David; Moore, Lawrence

2001-01-23

24

Exponential energy growth in adiabatically changing Hamiltonian systems  

NASA Astrophysics Data System (ADS)

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

Pereira, Tiago; Turaev, Dmitry

2015-01-01

25

Internal Diffusion Limited Aggregation on Discrete Groups Having Exponential Growth  

Microsoft Academic Search

The internal diffusion limited aggregation (DLA) has been introduced by Diaconis and Fulton [Rend. Sem. Mat. Univ. Pol. Torino\\u000a 49, 95–119 (1991)]. It is a growth model defined on an infinite set and associated to a Markov chain on this set. We focus here\\u000a on sets which are finitely generated groups with exponential growth. We prove a shape theorem for

Sébastien Blachère; Sara Brofferio

2007-01-01

26

[Population growth, 1986].  

PubMed

The authors examine recent population growth in the Federal Republic of Germany and present population statistics, the most recent of which are for 1986. A section on natural increase includes information on marriages and marriage age; births, including data on national origin; mothers' age structure; deaths, including stillbirths and infant deaths; births among resident foreigners; and public opinion concerning population size and growth. A section on growth due to migration examines internal migration and the international migration of German citizens and foreigners. Data and estimates are based on a variety of official and nonofficial sources. PMID:12178643

Proebsting, H; Fleischer, H

1987-08-01

27

Population Growth in Yeasts  

NSDL National Science Digital Library

This lesson is the second of two that explore cellular respiration and population growth in yeasts. In the first lesson, students set up a simple way to indirectly observe and quantify the amount of respiration occurring in yeast-molasses cultures. Based on questions that arose during the first lesson and its associated activity, students in this lesson work in small groups to design experiments that determine how environmental factors affect yeast population growth.

Engineering K-Phd Program

28

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

E-print Network

Critical Mutation Rate Has an Exponential Dependence on Population Size in Haploid and Diploid that are both fit and robust. At high mutation rates, individuals with greater mutational robustness can capable of determining the relationship between population size, the critical mutation rate at which

Channon, Alastair

29

Rapid population growth.  

PubMed

At the current rate of population growth, world population by 2000 is expected to reach 7 billion or more, with developing countries accounting for some 5.4 billion, and economically advanced nations accounting for 1.6 billion. 'Population explosion' is the result of falling mortality rates and continuing high birth rates. Many European countries, and Japan, have already completed what is termed as demographic transition, that is, birth rates have fallen to below 20 births per 1000 population, death rates to 10/1000 population, and annual growth rates are 1% or less; annual growth rates for less developed countries ranged from 2 to 3.5%. Less developed countries can be divided into 3 groups: 1) countries with both high birth and death rates; 2) countries with high birth rates and low death rates; and 3) countries with intermediate and declining birth rates and low death rates. Rapid population growth has serious economic consequences. It encourages inequities in income distribution; it limits rate of growth of gross national product by holding down level of savings and capital investments; it exerts pressure on agricultural production and land; and it creates unemployment problems. In addition, the quality of education for increasing number of chidren is adversely affected, as high proportions of children reduce the amount that can be spent for the education of each child out of the educational budget; the cost and adequacy of health and welfare services are affected in a similar way. Other serious consequences of rapid population growth are maternal death and illness, and physical and mental retardation of children of very poor families. It is very urgent that over a billion births be prevented in the next 30 years to reduce annual population growth rate from the current 2% to 1% per year. PMID:12261450

1972-01-01

30

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

31

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

32

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

33

Some Similarities between the Spread of an Infectious Disease and Population Growth  

NSDL National Science Digital Library

A simple simulation demonstrates how spread of an infectious disease can result in exponential increase in the number of infected individuals. Discussion questions and a graphing activity develop an understanding of exponential and logistic population growth.

Doherty, Jennifer; Waldron, Ingrid

34

Control exponential growth of tumor cells with slow spread of oncolytic virus.  

PubMed

Great attention has been paid to cancer therapy by means of oncolytic viruses, but the fast virus-spread, which eliminates all tumor cells, cannot be applied to solid tumors. As slow virus-spread is applied, solid tumors are expected to be controlled but complicated dynamical behaviors appear. In this paper we investigate bifurcations of equilibria in the oncolytic virus dynamics model with exponential growth of tumor cells and slow virus-spread. We find conditions of parameters for saddle-node bifurcation, Hopf bifurcation and Bogdanov-Takens bifurcation. Those conditions give thresholds for slow virus-spread to control the population of tumor cells within an appropriate range. PMID:25435412

Si, Wen; Zhang, Weinian

2015-02-21

35

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.

James J. Rutledge

36

Population growth, poverty and health  

Microsoft Academic Search

One of the most popular explanations for the many problems that face Africa is population growth. Africa's population has doubled since 1960. Africa has the highest fertility rate in the world and the rate of population growth is higher than in any other region. At the same time, Africa faces a social and economic situation that is viewed by many

Joachim S. Kibirige

1997-01-01

37

Effects of Body Size and Temperature on Population Growth  

Microsoft Academic Search

For at least 200 years, since the time of Malthus, pop- ulation growth has been recognized as providing a critical link be- tween the performance of individual organisms and the ecology and evolution of species. We present a theory that shows how the intrinsic rate of exponential population growth, , and the carrying capacity, rmax K, depend on individual metabolic

2004-01-01

38

Pairwise Comparisons of Mitochondrial DNA Sequences in Stable and Exponentially Growing Populations  

Microsoft Academic Search

We consider the distribution of pairwise sequence differences of mitochondrial DNA or of other nonrecombining portions of the genome in a population that has been of constant size and in a population that has been growing in size exponentially for a long time. We show that, in a population of constant size, the sample distribution of pairwise differences will typically

Montgomery Slatkin; Rr Hudson

1991-01-01

39

U.S. Population Growth.  

ERIC Educational Resources Information Center

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

Dillner, Harry

40

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

41

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

42

Population Explosion: Modeling Phage Growth  

NSDL National Science Digital Library

How is the relationship between phages and their bacterial hosts like that of predators and prey? How does this relationship differ? What are the factors that contribute to phage production in the cell? What can the phage concentration in a high titer lysate tell us about both of these populations? We can investigate these questions and more with an Excel spreadsheet model for phage growth. * explore a multiple parameter model of population growth in bacteriophages that demonstrates interdependence with the population of bacterial hosts

Jean Douthwright (Beloit College; Biology)

2006-05-20

43

Population aging and control of population growth.  

PubMed

This article describes China's population structure and the impacts of population control and fertility decline on the increases in elderly population. China's population structure shifted from 40.7% of the population aged 0-14 years in 1964 to 27.6% in 1990. The proportion of elderly increased from 3.6% in 1964 to 5.6% in 1990. By the year 2000 it is expected that the number of elderly will increase to 7%, or 90 million people. The process of aging will be determined by fertility. Mortality is expected to decline steadily and at a slower pace than aging. By 2040 it is expected that 15.4% of total population will be aged 0-14 years and 19.8% of total population will be aged over 65 years. The total dependent population was 33.2% in 1990 and may reach 35.2% in 2040. Although the dependent population in 1982 was 38.5%, the proportion of aged was only 4.9%. If China maintains a fertility rate of 2.0, which was the rate in 1995, the total dependency ratio in 2040 will be 75.9%, and the elderly dependency ratio will be 46.3%. If the total fertility rate had declined to 2.0 children per woman in 1980, population would slowly have risen to 1.5 billion in 2050 and then declined. It is suggested that to achieve a smaller population size and zero growth China must maintain fertility at a lower level. A higher fertility would result in a more balanced age structure but a great pressure on resources. Chinese citizens who adopted the one-child family norm will face the added burden of four elderly parents. It is urged that the one-child family norm be replaced with a two-child family norm. The shift to a two-child family norm would result in some short-term imbalances, but would result in a lighter dependency burden for succeeding generations and less fluctuations in family size and structure. A smooth and gradual transition to a two-child policy would result in a decline in population around 2030. PMID:12347486

Tu, P

1996-04-01

44

Canada's population: growth and dualism.  

PubMed

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

Beaujot, R P

1978-04-01

45

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

46

Making a stand: five centuries of population growth in colonizing populations of Pinus ponderosa.  

PubMed

The processes underlying the development of new populations are important for understanding how species colonize new territory and form viable long-term populations. Life-history-mediated processes such as Allee effects and dispersal capability may interact with climate variability and site-specific factors to govern population success and failure over extended time frames. We studied four disjunct populations of ponderosa pine in the Bighorn Basin of north-central Wyoming to examine population growth spanning more than five centuries. The study populations are separated from continuous ponderosa pine forest by distances ranging from 15 to >100 km. Strong evidence indicates that the initial colonizing individuals are still present, yielding a nearly complete record of population history. All trees in each population were aged using dendroecological techniques. The populations were all founded between 1530 and 1655 cal yr CE. All show logistic growth patterns, with initial exponential growth followed by a slowing during the mid to late 20th century. Initial population growth was slower than expectations from a logistic regression model at all four populations, but increased during the mid-18th century. Initial lags in population growth may have been due to strong Allee effects. A combination of overcoming Allee effects and a transition to favorable climate conditions may have facilitated a mid-18th century pulse in population growth rate. PMID:22764493

Lesser, Mark R; Jackson, Stephen T

2012-05-01

47

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

USGS Publications Warehouse

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

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

1979-01-01

48

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,

49

Answers to WS9 = .4u exponential growth  

E-print Network

= 4V - .06V 2 = 4V 1 - V 66.7 logistic equation with carrying capacity K = 66.7. If V = 0. the value of V at equilibrium is smaller than the carrying capacity of V . this is due to the fact carrying capacity. 4. there is no equilibrium with both populations present. This is due to the fact

Vraciu, Adela

50

Quantitative requirements for exponential growth of Alcaligenes eutrophus.  

PubMed Central

Quantitative nutrient requirements for unrestricted autotrophic growth of Alcaligenes eutrophus were determined. Minimum saturating concentrations of Mg2+, SO42-, PO43-, Fe3+, and Na2+ for an optical density increase of 2 were 10(-4) M 8 X10(-5) M, 5 X 10(-4) to 6 X 10(-4) M, 10(-5) M, and 10(-7) to 2 X 10(-7) M, respectively. Trace metal requirements for cobalt, chromium, and copper were also demonstrated, but minimum concentrations could not be determined because other reagents contributed a high background of these metals. Under certain conditions an apparent response to zinc was observed, although other experiments suggest the zinc salt contained another metal that was required for growth. Poly-beta-hydroxybutyrate biosynthesis was shown to be initiated by a magnesium or sulfate deficiency as well as by a nitrogen or phosphate deficiency. PMID:984831

Repaske, R; Repaske, A C

1976-01-01

51

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.

52

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

53

Political economy of population growth.  

PubMed

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

Mehta, S; Mehta, H S

1987-01-01

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

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

PubMed

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

Alexander, Tal; Natarajan, Priyamvada

2014-09-12

56

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

NASA Astrophysics Data System (ADS)

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

Alexander, Tal; Natarajan, Priyamvada

2014-09-01

57

The Western Africa Ebola Virus Disease Epidemic Exhibits Both Global Exponential and Local Polynomial Growth Rates  

PubMed Central

Background: While many infectious disease epidemics are initially characterized by an exponential growth in time, we show that district-level Ebola virus disease (EVD) outbreaks in West Africa follow slower polynomial-based growth kinetics over several generations of the disease. Methods: We analyzed epidemic growth patterns at three different spatial scales (regional, national, and subnational) of the Ebola virus disease epidemic in Guinea, Sierra Leone and Liberia by compiling publicly available weekly time series of reported EVD case numbers from the patient database available from the World Health Organization website for the period 05-Jan to 17-Dec 2014. Results: We found significant differences in the growth patterns of EVD cases at the scale of the country, district, and other subnational administrative divisions. The national cumulative curves of EVD cases in Guinea, Sierra Leone, and Liberia show periods of approximate exponential growth. In contrast, local epidemics are asynchronous and exhibit slow growth patterns during 3 or more EVD generations, which can be better approximated by a polynomial than an exponential function. Conclusions: The slower than expected growth pattern of local EVD outbreaks could result from a variety of factors, including behavior changes, success of control interventions, or intrinsic features of the disease such as a high level of clustering. Quantifying the contribution of each of these factors could help refine estimates of final epidemic size and the relative impact of different mitigation efforts in current and future EVD outbreaks.

Chowell, Gerardo; Viboud, Cécile; Hyman, James M; Simonsen, Lone

2015-01-01

58

Stretched exponential estimate on growth of the number of periodic points for prevalent diffeomorphisms  

E-print Network

Stretched exponential estimate on growth of the number of periodic points for prevalent we show that, by contrast, for a measure-theoretic notion of genericity we call "prevalence, there is a prevalent set of C1+ (or smoother) diffeomorphisms for which the number of period n points is bounded above

Kaloshin, Vadim

59

Environmental impact of population growth  

NASA Astrophysics Data System (ADS)

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

Naylor, Rosamond; Matson, Pamela

60

Estimation of population growth or decline in genetically monitored populations.  

PubMed

This article introduces a new general method for genealogical inference that samples independent genealogical histories using importance sampling (IS) and then samples other parameters with Markov chain Monte Carlo (MCMC). It is then possible to more easily utilize the advantages of importance sampling in a fully Bayesian framework. The method is applied to the problem of estimating recent changes in effective population size from temporally spaced gene frequency data. The method gives the posterior distribution of effective population size at the time of the oldest sample and at the time of the most recent sample, assuming a model of exponential growth or decline during the interval. The effect of changes in number of alleles, number of loci, and sample size on the accuracy of the method is described using test simulations, and it is concluded that these have an approximately equivalent effect. The method is used on three example data sets and problems in interpreting the posterior densities are highlighted and discussed. PMID:12871921

Beaumont, Mark A

2003-07-01

61

Population growth and global warming.  

PubMed

When I was born in 1930, the human population of the world was a mere 2 billion. Today, it has already reached 6.8?billion, and is projected to reach 9.1 billion by 2050. That is unsustainable. It is slowly beginning to dawn on us that Global Warming is the result of increasing human CO2 emissions, and the more people there are in the world, the worse it will become. Ultimately, it is the sky that will prove to be the limit to our numbers. The developed countries of the world are the most affluent, and also the most effluent, so we must lead by example and contain our own population growth and per capita emissions. We also have a big debt to repay to former colonial territories in Africa, Asia and South America, who desperately need our help to contain their excessive rates of population growth. Belgian and Dutch obstetricians and gynaecologists can play a critical role in this endeavour. After all, we already have a pill that will stop global warming - the oral contraceptive pill. PMID:25478068

Short, R V

2009-01-01

62

Subharmonic Resonances in Plasmas: Exponential and Superexponential Growth of Driven Relativistic Plasma Waves  

NASA Astrophysics Data System (ADS)

Subharmonic resonant beat-wave excitation of nonlinear relativistic plasma waves is studied analytically and in particle-in-cell simulations. We find that if the frequency separation of the lasers, ??, is 2?p or 3?p ( ?p is the plasma frequency), then plasma waves are still excited at ?p but they grow exponentially or superexponentially rather than secularly. Both of these subharmonic resonant instabilities saturate due to relativistic detuning. The analytical growth rates and saturation levels agree with the simulation results.

Ren, C.; Dodd, E. S.; Gordon, D.; Mori, W. B.

2000-10-01

63

Comparing growth patterns among field populations of cereal aphids reveals factors  

E-print Network

Comparing growth patterns among field populations of cereal aphids reveals factors limiting species of aphids that may become serious pests. With increasing abundance, the proportion of a particular species in the total aphid population may remain constant, suggesting a density-independent exponential

Kratochvíl, Lukas

64

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

65

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

66

Future Population Growth Trends in California  

E-print Network

- Migrate the Population Control Total Race/ethnic distribution Age and sex distribution #12;STEP 5Future Population Growth Trends in California Mary Heim Demographic Research Unit California Department of Finance #12;THE METHOD #12;Pn=P0+B-D+NM Pn=projected population Po=beginning population B

Keller, Arturo A.

67

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

68

Subharmonic resonances in plasmas: exponential and superexponential growth of driven relativistic plasma waves  

PubMed

Subharmonic resonant beat-wave excitation of nonlinear relativistic plasma waves is studied analytically and in particle-in-cell simulations. We find that if the frequency separation of the lasers, Deltaomega, is 2omega(p) or 3omega(p) ( omega(p) is the plasma frequency), then plasma waves are still excited at omega(p) but they grow exponentially or superexponentially rather than secularly. Both of these subharmonic resonant instabilities saturate due to relativistic detuning. The analytical growth rates and saturation levels agree with the simulation results. PMID:11030909

Ren; Dodd; Gordon; Mori

2000-10-16

69

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

70

Population Growth and Economic and Social Development.  

ERIC Educational Resources Information Center

Because evidence is clear that in many developing countries development will be postponed indefinitely unless slower population growth can be achieved soon, the international community must work together in a renewed effort to slow population growth. Assistance can be accomplished in three ways: (1) encouraging dialog aimed at forging…

Clausen, A. W.

71

How population growth affects linkage disequilibrium.  

PubMed

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

Rogers, Alan R

2014-08-01

72

Population growth and development: the Kenyan experience.  

PubMed

Rapid population growth in Kenya and high fertility impacts negatively on economic development. The growth and high fertility results in declines in gross national product, per capita food consumption, and land quality; a high dependency ratio; urban crowding; and inadequate health systems. East Africa has the highest crude birth rates in Africa, and Kenya has the highest birth rate of 54/1000 population in East Africa. The African crude death rate is 50% higher than the world average, but Kenya's death rate is the lowest in East Africa and comparable to North American and European death rates. Kenya has the highest rate of natural increase of about 4%. Population growth rates rose over the decades. Kenya's average population density is well above the sub-Saharan African average and much lower than very high density countries. Population is unequally distributed. Regional densities are widely divergent, and the highest densities in Western province are well above densities in Rwanda and Burundi. Urban growth has increased, as has migration to urban areas. Nairobi has 57% of urban population. Improved health and nutrition have contributed to increased life expectancy. The desired family size is large. The impact of demographic factors on economic conditions is evident in the decline in gross national product per capita growth to under 1% during 1972-88. A slight upswing occurred during 1988-93, but other crises are emerging. Food production has not kept pace with population growth. Production has been low due to serious land degradation, short fallow periods, and traditional farming practices. Population pressure has forced families to shift agriculture onto marginal lands, and desertification has increased. A growing proportion of the population is unemployed or underemployed. Population programs should address the underlying conditions for fertility decline. PMID:12291578

Nyamwange, M

1995-01-01

73

A population growth model forced by random, episodic disturbances  

NASA Astrophysics Data System (ADS)

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

Peckham, S. D.

2011-12-01

74

Population Growth and CO2 Emissions  

NSDL National Science Digital Library

Shows the projected growth in CO2 emissions through 2100. Shows the potential levels of atmospheric CO2 with slowing population growth, rapid technological change, both, or neither. Shows that either will substantially lower the carbon footprint of human activity, but that both are needed for sustainable levels of Carbon emissions.

AAAS Atlas of Population and Environment

75

Jawara worried over population growth rate.  

PubMed

Gambian President, Dawda Jawara, in opening parliament, expressed concern about the effect of the country's high rate of population growth on socioeconomic development. The current estimated total population size is 815,000; it will reach 1 million in 7 years at the current annual growth rate of 3%. Population density will rise from 74 to 90 persons per sq. km; this would make Gambia the fourth most densely populated country in Africa. An elaborate program of activities, which included nationwide film shows, mass rallies, population songs, press briefings and special radio panel discussions, was carried out in order to focus the attention of citizens on the consequences of this high rate of growth. The Minister of Economic Planning and Industrial Development, Mr. Mbemba Jatta, made a statement on Radio Gambia concerning the decreased ability of Gambia to provide facilities for a population growing at such a high rate; with its limited resources, Gambia would find it difficult to provide for the needs of 40,000 babies born annually or to create jobs for the 13,000 persons entering the labor force. PMID:12346163

1991-01-01

76

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

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

2013-01-01

77

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

ERIC Educational Resources Information Center

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

Castillo-Garsow, Carlos

2010-01-01

78

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

79

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

80

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

81

Chips, Architectures and Algorithms: Reflections on the Exponential Growth of Digital Signal Processing Capability  

Microsoft Academic Search

The celebrated 1965 prediction by Gordon Moore regarding exponential improvements in integrated circuit density is so widely known, and has proven so accurate, that it has been elevated to the status of a \\

Mark A. Richards; Gary A. Shaw

2003-01-01

82

Design issues for population growth models  

PubMed Central

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

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

2010-01-01

83

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

84

EFFECTS OF EXPONENTIAL AND CONVENTIONAL FERTILIZATION ON GROWTH NUTRIENT UPTAKE BY FIVE MEDITERRANEAN PINES IN GREENHOUSE  

Microsoft Academic Search

Photoperiod, temperature, humidity and fertilization are the main factors which influence active development in the nursery phase. Fertilizers, which usually contain greater amounts of nitrogen than other nutrients, can be applied in two ways; conventionally, by periodically adding of constant doses of nutrients and exponentially increasing the nutrient doses in accordance with the stage of crop development. Previous experiments have

P. Vil; J. De Las Heras; M. Honrubia

85

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 technique that revealed species-specific aphid consump- tion rates with a factorial field experiment on aphid population growth. Only cursorial spiders retarded aphid population growth in our cage experiment

Illinois at Chicago, University of

86

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

Technology Transfer Automated Retrieval System (TEKTRAN)

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

87

Exponential growth for the wave equation with compact time-periodic positive potential  

Microsoft Academic Search

We prove the existence of smooth positive potentials V.t;x\\/; periodic in time and with compact support in x, for which the Cauchy problem for the wave equation utt Åxu CV.t;x\\/u D 0 has solutions with exponentially growing global and local energy. Moreover, we show that there are resonances, ´ 2 C, jj> 1, associated toV.t;x\\/. c 2008 Wiley Periodicals, Inc.

Ferruccio Colombini; VESSELIN PETKOV; JEFFREY RAUCH

2009-01-01

88

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

89

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

90

Effect of benzalkonium chloride on viability and energy metabolism in exponential- and stationary-growth-phase cells of Listeria monocytogenes.  

PubMed

The difference in killing exponential- and stationary-phase cells of Listeria monocytogenes by benzalkonium chloride (BAC) was investigated by plate counting and linked to relevant bioenergetic parameters. At a low concentration of BAC (8 mg liter(-1)), a similar reduction in viable cell numbers was observed for stationary-phase cells and exponential-phase cells (an approximately 0.22-log unit reduction), although their membrane potential and pH gradient were dissipated. However, at higher concentrations of BAC, exponential-phase cells were more susceptible than stationary-phase cells. At 25 mg liter(-1), the difference in survival on plates was more than 3 log units. For both types of cells, killing, i.e., more than 1-log unit reduction in survival on plates, coincided with complete inhibition of acidification and respiration and total depletion of ATP pools. Killing efficiency was not influenced by the presence of glucose, brain heart infusion medium, or oxygen. Our results suggest that growth phase is one of the major factors that determine the susceptibility of L. monocytogenes to BAC. PMID:11307882

Luppens, S B; Abee, T; Oosterom, J

2001-04-01

91

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

SciTech Connect

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., E-mail: cxaplanteris@yahoo.com [Plasma Physics Laboratory, IMS, NCSR “Demokritos”, Athens, Greece and Hellenic Army Academy, Vari Attica (Greece); Xaplanteris, L. C. [School of Physics, National and Kapodistrian University of Athens, Athens (Greece)] [School of Physics, National and Kapodistrian University of Athens, Athens (Greece); Leousis, D. P. [Technical High School of Athens, Athens (Greece)] [Technical High School of Athens, Athens (Greece)

2014-03-15

92

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

93

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

94

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

E-print Network

Surface Growth of a Motile Bacterial Population Resembles Growth in a Chemostat Daniel A. Koster, that is similar to bacterial growth in a chemostat predicts that the fraction of the population lagging behind in space in terms of their gene expression and growth.5,7,8 Bacterial colonies on hard surfaces typically

95

LETTER Contributions of long-distance dispersal to population growth in colonising Pinus ponderosa populations  

E-print Network

LETTER Contributions of long-distance dispersal to population growth in colonising Pinus ponderosa disjunct populations of Pinus ponderosa that were initially established by long-distance dispersal. Keywords Allee effects, intrinsic population growth, long-distance dispersal, parentage, Pinus ponderosa

Hui, Bowen

96

Development of Populations 177 6.6 Growth of Populations with Sexual Reproduction  

E-print Network

Development of Populations 177 6.6 Growth of Populations with Sexual Reproduction G. Alsmeyer In Section 5.9, we studied the effect of sexual reproduction on criticality and ex- tinction risk-negative Alsmeyer G (2005). Growth of Populations with Sexual Reproduction. In: Branching Processes: Variation

Alsmeyer, Gerold

97

Understanding Linear and Exponential Growth: Searching for the Roots in 6- To 9-Year-Olds  

ERIC Educational Resources Information Center

Previous studies have suggested that children as young as 9 years old have developed an understanding of non-linear growth processes prior to formal education. The present experiment aimed at investigating this competency in even younger samples (i.e., in kindergartners, first, and third graders, ages 6, 7 and 9, respectively). Children (N=90)…

Ebersbach, Mirjam; Van Dooren, Wim; Van den Noortgate, Wim; Resing, Wilma C. M.

2008-01-01

98

U.S. Population Growth: Prospects and Policy.  

ERIC Educational Resources Information Center

The Commission on Population Growth and the American Future concluded that zero population growth (ZPG) is in the best interest of the United States. To achieve ZPG in the future, the United States must keep fertility and net immigration relatively low. Practical problems are discussed. (RM)

McFalls, Joseph A., Jr.; And Others

1984-01-01

99

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

100

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

101

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

102

Resources and Population Alan R. Rogers  

E-print Network

that limits the growth of a population is called a "mechanism of population regulation." These mech- 2 #12 Population ecology is concerned with the growth (and decline) of populations of plants and animals, including the fundamental principles of popu- lation growth: the exponential increase of unregulated populations, various

Rogers, Alan R.

103

Between-population variation in pre-adolescent growth.  

PubMed

Between-population differences in rates of physical growth and development and attained body size are well documented, but it is difficult to determine the extent to which these differences can be attributed to genetic and environmental factors. The greatest differences are to be found between populations in industrialised and non-industrialised nations, and between well-off and poorer groups within countries. Although genetic factors cannot be discounted, such differences can largely be attributed to differences in environmental quality experienced, influencing growth largely through differentials in nutritional well-being and exposure to, and treatment of, infectious disease. Growth patterns of well-off populations and groups of high socio-economic status are less heterogeneous, but differences between major global population groupings may still exist, bringing into question the validity of the concept of an international reference for the growth of young children. In this article, information pointing to genetic differences in the growth of children of different populations is summarised, and the acceptability of the NCHS (National Center for Health Statistics, 1977) references for height by age for international use is examined. It is concluded that the growth patterns of all major population groupings are likely to have similar genetic potential, with the exception of Asiatics. However, there are no data on either secular trends or well-off groups from populations that have until recently been genetically isolated, and it is not known whether they share the same potential for growth as the major populations that surround them. In addition, very little is known about the genetic potential for growth of Aboriginal populations in Australia, or in Pacific Islands populations. It is suggested that the growth references for height by age in current international use are at best only imperfect yardsticks for nutritional assessment. PMID:8005091

Ulijaszek, S J

1994-02-01

104

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

105

Extreme natural hazards: population growth, globalization and environmental change  

E-print Network

have global consequences. The hazards of supervolcanic eruptions and asteroid impacts could cause as a consequence of population growth and globalization. It is likely that in the future, we will experience

Huppert, Herbert

106

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

107

Population Blocks.  

ERIC Educational Resources Information Center

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

Smith, Martin H.

1992-01-01

108

[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

109

Population, land, and growth1 Claire Loupias and Bertrand Wigniolle  

E-print Network

Population, land, and growth1 Claire Loupias and Bertrand Wigniolle Université d in economic and pop- ulation growth with a long run perspective, emphasizing the role of land in the development process. Starting from a pre-industrialization state called the "Malthusian regime", land

Paris-Sud XI, Université de

110

reproduction and juvenile growth at a cyclic population peak  

Microsoft Academic Search

Summary 1. Snowshoe hare (Lepus americanus (Erxleben)) populations were provided with supplemental food on two study grids in the south-west Yukon to examine the effects of food on reproduction and juvenile growth. 2. Timing of parturition, pregnancy rates, litter sizes, male breeding condition, and juvenile growth rates were measured on two food grids and on two control grids during two

MARK O'DONOGHUE; CHARLES J. KREBS

111

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

112

Prison population growth and crime reduction  

Microsoft Academic Search

The impact of state prison populations on crime is typically estimated by applying the lambda, the individual crime rate, of prisoners or arrestees. We outline the problems with this approach, attempt to reanalyze the widely divergent lambdas derived in past research, and make adjustments necessary to use lambdas for estimating the incapacitation impact. The result is an uncertain estimate of

Thomas B. Marvell; Carlisle E. Moody

1994-01-01

113

Using Lemna to Study Geometric Population Growth.  

ERIC Educational Resources Information Center

An experiment in which students collect and analyze data on the population size of a real organism rather that on a model is presented. The activity allows for the integration of mathematics, graphing techniques, and the use of computers. The lesson is designed to follow the learning cycle format. (KR)

DeBuhr, Larry E.

1991-01-01

114

Population growth. Its magnitude and implications for development.  

PubMed

A summary of the 1984 World Development Report is provided. The 3 major points stressed in the report were: 1) rapid population growth adversely affects development, 2) governments must adopt policies to reduce fertility, and 3) policies adopted by many countries have effectively reduced fertility. World population growth began accelerating at 0.5%/year in the 18th century, and by 1950 the annual acceleration rate was 2%. Most of the increase in population size is occurring in less developed countries, and this increase is due in part to the recent decline in mortality experienced by these countries. Of the 80 million individuals who will be added to the world's population in 1984, 70 million will be in the developing countries. Since 1965 the population growth rate for developing countries as a group declined from 2.4% to 2%. However, because of the high proportion of younger aged individuals in developing countries, the decline in fertility is expected to level off. According to World Bank population projections, the world population will stabilize at around 11 billion in 2150. During the interium, the population of developing countries will increase from its present level of 3.6 billion to 8.4 billion, and the population of developed countries will increase from 1.2 billion to 1.4 billion. These projections are probably overly optimistic. The adverse impact on development of rapid population growth is due to several factors. 1st, resources which could be used for investment must instead be used to fulfill the consumption needs of an increased number of people. 2nd, increases in the labor force must be absorbed by the agricultural sector, and this reduces agricultural productivity. 3rd, rapid population growth increases management problems. The adaption of policies by governments to reduce fertility is a necessary step in halting population growth. For poor families, children provide economic security. Therefore, governments must act to improve the economic conditions for poor families if they hope to reduce population growth. Education and job opportunities must be expanded and social security provided for the elderly. In the past it was assumed that fertility would only decline when urbanization, industrialization, and income reached a certain level. It is now known that appropriate policies can effectively reduce fertility even in the absence of economic advancement. Fertility declines are more closely related to increases in literacy and life expectancy than to increases in the gross national product. Family planning programs in China, Colombia, Egypt, India, Indonesia, Korea, Sri Lanka, and Tunisia have reduced fertility far below the level normally associated with the income levels prevailing in those countries. PMID:12266357

Birdsall, N

1984-09-01

115

Metropolitan migration and population growth in selected developing countries.  

PubMed

The purpose of this article is to estimate the components of metropolitan population growth in selected developing countries during 1960-1970 period. The study examines population growth in 26 cities: 5 are in Africa, 8 in Asia, and 13 in Latin America, using data from national census publications. These cities in general are the political capitals of their countries, but some additional large cities were selected in Brazil, Mexico, and South Africa. All cities, at the beginning of the 1960-1970 decade had over 500,000 population; Accra, the only exception, reached this population level during the 1960s. Some cities had over 4 million residents in 1970. Net migration contributed about 37% to total metropolitan population growth; the remainder of the growth is attributable to natural increase. Migration has a much stronger impact on metropolitan growth than suggested by the above figure: 1) Several metropolitan areas, for various reasons, are unlikely to receive many migrants; without those cities, the share of metropolitan growth from net migration is 44%. 2) Estimates of the natural increase of migrants after their arrival in the metropolitan areas, when added to migration itself, changes the total contribution of migration to 49% in some metropolitan areas. 3) Even where net migration contributes a smaller proportion to metropolitan growth than natural increase, the rates of net migration are generally high and should be viewed in the context of rapid metropolitan population growth from natural increase alone. Finally, the paper also compares the components of metropolitan growth with the components of growth in the remaining urban areas. The results show that the metropolitan areas, in general, grow faster than the remaining urban areas, and that this more rapid growth is mostly due to a higher rate of net migration. Given the significance of migration for metropolitan growth, further investigations of the effects of these migration streams, particularly with respect to in-migration and out-migration, would greatly benefit understanding of the detailed and interconnected process of population growth, migration, employment and social welfare of city residents. PMID:12265836

1983-01-01

116

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

PubMed Central

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

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

1996-01-01

117

Approximations Exponential  

E-print Network

Schemes and Applications 83 6.1 Monte Carlo methods . . . . . . . . . . . . . . . . . . . . . 83 6 Theory of Filtering Processes . . . . . . . . . . . . 120 A.3 Design of exponential families worker performs an experiment and obtains some data. On the basis of data, certain conclusions are drawn

Bröcker, Jochen

118

[Economic growth and changes in the structure of the population].  

PubMed

A reevaluation of classic works by Simon Kuznets and Wassily Leontief suggests that their conclusions concerning the interrelationships between economic growth and population structure correspond to relatively highly specialized characteristics of present forms of capitalist development or underdevelopment and not necessarily to capitalist development within a new international economic order or to socialist development. Kuznets' work seems to offer conclusive proof of the negative effects of rapid population growth on economic development for 3 reasons: 1) requirements for capital are greater, 2) total production and per capita consumption are greatly reduced with high dependency ratios, and 3) rapid growth in consumption is more difficult when the population is growing more rapidly. However, at least 4 problems are noted when Kuznets' ideas are applied to the 3rd world. Kuznets assumes that growth of physical capital is the only source of growth, so that only increased investment can increase returns. Secondly, assuming the same ratio of capital/output for all cases assumes that no substitution of labor for capital is possible. Third, the assumption that participation rates remain the same regardless of dependency ratios may be incorrect. And finally, the difference in per capita consumption that Kuznets attributes to differences in rates of population growth represents a tiny proportion of the total gap in the standard of living of rich countries with slow population growth and poor countries with rapid growth. Kuznets' argument has considerable validity in Third World countries which relay on traditional patterns of capitalist accumulation, but the problems represent the effects of rapid population growth only under the current modes of capitalist expansion. The negative effect of high fertility on savings has probably been greatly exaggerated, and the problems of providing educational facilities and health care for ever larger numbers of persons have been poorly conceptualized. To the degree that employment security, decent salaries, and social programs for the elderly are provided, as they are at present only in socialist countries of the Third World, the incentives for large families will be reduced. The work of Leontief, based on a computer model with 2625 equations, demonstrates that regardless of the rates of population growth in Third World countries, little change in the gap between rich and poor countries can be expected in the foreseeable future. PMID:12265328

Conroy, M E

1980-01-01

119

Shanghai: a case study of negative population growth.  

PubMed

This article examines the implications of zero population growth (ZPG) in Shanghai. In 1993 the crude birth rate was 6.50%, the crude mortality rate was 7.27%, and the natural rate of population growth was -0.78%. Shanghai achieved negative population growth (NPG) for the first time in 1993. NPG occurs when the number of births is less than the number of deaths. NPG occurs more frequently in developed rather than developing countries such as China. Shanghai had replacement or below replacement fertility since 1971, when the total fertility rate (TFR) was 1.84 children/woman. China's TFR reached 2.31 children/woman in 1990, whereas Shanghai's TFR of 2.36 children/woman occurred in 1969. In order to reach NPG in Shanghai, fertility was low for 20 years. NPG is reached through low fertility, reduced numbers of women of childbearing age, and increased numbers of elderly. China's age pyramid showed 28% of total population aged under 15 years in 1990 compared to Shanghai's 18%. 9% of China's population comprised people older than 60 years, while Shanghai's elderly amounted to 14% of total population. A comparison of demographic and socioeconomic measures among other countries with ZPG or NPG showed that the age structure of population determined this status. ZPG or NPG countries are characterized as having smaller reproductive age populations with low fertility and larger elderly populations with growth in the crude mortality rate. It took Shanghai 20 years to reach a low fertility population and a sufficiently large elderly population for ZPG to occur. Shanghai's fertility declines were largely due to 30 years of family planning: the one child rate, the contraceptive usage rate, the one-child certificate rate, and the sterilization rate. These measures were already low by the 1970s, when family planning became widespread in China. Shanghai was ahead of China in socioeconomic growth. Shanghai's NPG illustrated continuous progress in development and family planning and aging of the population. PMID:12290862

Gu, B

1995-01-01

120

Assessment of fish populations III: fish metrics and growth.  

E-print Network

growth curve 0.0 10.0 20.0 30.0 40.0 50.0 60.0 0 2 4 6 8 10 12 age (years) length(cm) L )1( ))(( 0ttK t e at year (t+1) against the fish's length the previous year (t) Thus, if we know the ages of fish: · constructing age-length keys · computing the age structure of a population · back-calculating growth rates

Limburg, Karin E.

121

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

PubMed

Population strategies to relieve the density pressures on land and resources in Tanzania have not considered the basic causes of population growth. Resettlement results in the same environmental degradation as in the original settlement. There should be a reduction in the population growth and planning of proper land use and resource exploitation before resettlement. Rural development must include a decline in the dependency on subsistence agriculture. Population in Tanzania increased by 213% during 1948-88. An absolute increase in population size during 1978-88 is recorded despite a slight decline in the rate of growth. Death rates declined, but birth rates were relatively stable at around 50 per 1000 population. Regions with the highest growth rates were Dar es Salaam (4.8%), Rukwa (4.3%), Arusha (3.8%), Mbeya (3.1%), and Ruvuma (3.2%). The regions with the lowest rates were Tanga and Kilimanjaro (2.1%), Coast (2.1%), Lindi (2%), and Mtwara (1.4%). Low growth rates are attributed to low fertility and high infertility. Other factors affecting high growth rates are culture, rates of natural increase, intensity of internal and international migration, climatic conditions, and availability of resources. In 1988 46% of the population was under 15 years old. Per capita land availability declined from 11.8 hectares in 1948 to 3.8 hectares in 1988. The number of landless peasants increased. Productivity declined, and distances to farms increased. The total fertility rate was 6.5 children per woman in 1988 and 6.1 during 1991-92. Slight declines were apparent in the crude birth rate also. High fertility was a response to universal marriage, low contraceptive use (7% using modern methods during 1991-92), declining lactation periods, high mortality rates, and old traditions favoring large families. Children were used extensively in time-consuming and labor-intensive activities, such as fetching water. The mean number of children ever born was higher among women with 1-4 years of schooling compared to women with no formal education and women with 5 or more years of education. Population growth contributes to deforestation, soil erosion, desertification, famine, drought, flooding, and demand for firewood. PMID:12179895

Madulu, N F

1995-03-01

122

Optimal management strategies to control local population growth or population spread may not be the same.  

PubMed

The objective of most pest management programs is to "control" the pest species. However, optimal control of local abundance and population growth may require different management strategies than optimal control of spatial spread. We use coupled demographic-dispersal models to address the relative importance of different management approaches to these two main control objectives for the invasive thistle Carduus nutans. The models are parameterized with data from thistle populations in the native (France) and invaded ranges (Australia and New Zealand). We assess a wide range of commonly used management strategies for their absolute and relative impacts on population growth and spread in both invaded-range scenarios. The projected population growth rate in New Zealand is more than twice that in Australia, while the spread rate is more than four times the Australian value. In general, spread and growth are both most strongly affected by the same life cycle transitions; however, in a few cases certain vital rates disproportionately affect either spread or growth. The transition that represents the contribution of large rosettes in one year to the number of large rosettes in the following year (the large rosette-large rosette transition) in Australia is dominated by reproduction (rather than survival) and hence is relatively more important to spread than to population growth. In New Zealand, the small rosette-small rosette transition is also predominantly dispersal-related. However, establishment of small plants from the seed bank contributes more to population growth than spread, as no dispersal is involved. The fine-resolution vital-rate-based modeling approach allows us to identify potentially novel optimal management strategies: approaches that reduce microsite availability show promise for reducing both population growth and spread, while strategies that affect dispersal parameters will affect spread. Additionally, the relative ranking of some biocontrol agents shifts depending on whether control of population growth or population spread is the desired outcome and therefore could alter which of the agents are preferred for release in a new area. The possibility of differences in ranked agent effectiveness has been predicted theoretically, but never before demonstrated using field data. PMID:20597297

Shea, Katriona; Jongejans, Eelke; Skarpaas, Olav; Kelly, Dave; Sheppard, Andy W

2010-06-01

123

The Economic Base of Recent Population Growth in Nonmetropolitan Settings.  

ERIC Educational Resources Information Center

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

Long, Larry; DeAre, Diana

124

Water Quality and Quantity Concerns Population growth, increasing water demands,  

E-print Network

. Water-conservation programs have resulted in a potential savings of 611 million gallons annually, valuedWater Quality and Quantity Concerns Population growth, increasing water demands, contamination issues and drought have placed the state's water supply under tremendous stress. Water demand in Texas

125

Extreme natural hazards: population growth, globalization and environmental change  

Microsoft Academic Search

Mankind is becoming ever more susceptible to natural disasters, largely as a consequence of population growth and globalization. It is likely that in the future, we will experience several disasters per year that kill more than 10000 people. A calamity with a million casualties is just a matter of time. This situation is mainly a consequence of increased vulnerability. Climate

Herbert E. Huppert; R. Stephen J. Sparks

2006-01-01

126

A Long-Range View of World Population Growth  

Microsoft Academic Search

Mankind is undergoing an extraordinary ex pansion of numbers, unparalleled in history, which began in the eighteenth century and which has gathered increasing momentum since the beginning of the present century. The increase of the earth's human population during the last two hundred years has been three times greater than the cumulated growth during all the previous millennia of man's

John D. Durand

1967-01-01

127

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

PubMed

Radiation dose calculation using models of the human anatomy has been a subject of great interest to radiation protection, medical imaging, and radiotherapy. However, early pioneers of this field did not foresee the exponential growth of research activity as observed today. This review article walks the reader through the history of the research and development in this field of study which started some 50 years ago. This review identifies a clear progression of computational phantom complexity which can be denoted by three distinct generations. The first generation of stylized phantoms, representing a grouping of less than dozen models, was initially developed in the 1960s at Oak Ridge National Laboratory to calculate internal doses from nuclear medicine procedures. Despite their anatomical simplicity, these computational phantoms were the best tools available at the time for internal/external dosimetry, image evaluation, and treatment dose evaluations. A second generation of a large number of voxelized phantoms arose rapidly in the late 1980s as a result of the increased availability of tomographic medical imaging and computers. Surprisingly, the last decade saw the emergence of the third generation of phantoms which are based on advanced geometries called boundary representation (BREP) in the form of Non-Uniform Rational B-Splines (NURBS) or polygonal meshes. This new class of phantoms now consists of over 287 models including those used for non-ionizing radiation applications. This review article aims to provide the reader with a general understanding of how the field of computational phantoms came about and the technical challenges it faced at different times. This goal is achieved by defining basic geometry modeling techniques and by analyzing selected phantoms in terms of geometrical features and dosimetric problems to be solved. The rich historical information is summarized in four tables that are aided by highlights in the text on how some of the most well-known phantoms were developed and used in practice. Some of the information covered in this review has not been previously reported, for example, the CAM and CAF phantoms developed in 1970s for space radiation applications. The author also clarifies confusion about 'population-average' prospective dosimetry needed for radiological protection under the current ICRP radiation protection system and 'individualized' retrospective dosimetry often performed for medical physics studies. To illustrate the impact of computational phantoms, a section of this article is devoted to examples from the author's own research group. Finally the author explains an unexpected finding during the course of preparing for this article that the phantoms from the past 50 years followed a pattern of exponential growth. The review ends on a brief discussion of future research needs (a supplementary file '3DPhantoms.pdf' to figure 15 is available for download that will allow a reader to interactively visualize the phantoms in 3D). PMID:25144730

Xu, X George

2014-09-21

128

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

129

Neighbors' problems, our problems: population growth in Central America.  

PubMed

A largely ignored issue, Central America faces its most pressing problem in its soaring population growth, one that is wreaking havoc on its economic and social infrastructures. Rising by a factor of 7, Central America's population -- presently 28.9 million -- is expected to reach 7.7 million by the year 2000, and 62.8 million by 2025. Typical of most of the Third World, Central America's population explosion stems from the fact that while the latter half of the 20th century has seen reductions of mortality rates, brought on by improvements of general health conditions, birth rates have remained excessively high. Despite moderate declines in the birth rate, Central American women still average 3-6 children. These demographic factors pose catastrophic consequences for Central America's natural resources, urban development and labor force. And they also threaten to increase migration to the US. Economic pressures have put great demands on the region's rain forests, exploited both for its resources and cleared away to create farmland. Today, only 40% of the original forest remains, and almost 3% more is destroyed annually. The area's capital cities have seen their populations increase 3-6 fold between 1950 and 1980. This explosion places further demands on already overburdened urban infrastructures, and has led to a mushrooming of squatter settlements. It has also led to a massive increase in the urban labor force which cannot be accommodated by the region's economies, which are in disarray due to falling export commodity earnings, limited natural resources, and scant investment capital. The economic woes could further increase the flow of workers to the US (15-20% of El Salvador's total population has already filed to the US). Historically, the region had attempted to offset population growth through economic development, but such expectations were not met, especially with the economic decline that wiped out gains made during the 1960s and 70s. Only recently have the countries acknowledged the need to halt population growth. PMID:12178972

Fox, R W

1990-06-01

130

Individual growth rates in natural field vole, Microtus agrestis , populations exhibiting cyclic population dynamics  

Microsoft Academic Search

Rodents that have multi-annual cycles of density are known to have flexible growth strategies, and the “Chitty effect”, whereby\\u000a adults in the high-density phase of the cycle exhibit larger average body mass than during the low phase, is a well-documented\\u000a feature of cyclic populations. Despite this, there have been no studies that have repeatedly monitored individual vole growth\\u000a over time

Sarah Janette Burthe; Xavier Lambin; Sandra Telfer; Alex Douglas; Pablo Beldomenico; Andrew Smith; Michael Begon

2010-01-01

131

Population growth in colonial America: A study of Ipswich, Massachusetts.  

PubMed

Abstract During the colonial period, the settlements that subsequently became the United States of America experienced a tremendous growth of population. Although part of this increase was due to emigration from England and other European countries, most of the growth must be laid to the natural increase of the immigrants and their descendants. We are only beginning to probe the mechanisms ofthis increase. By numerous local studies, using the methods of historical demography that have largely been developed with work in French and English sources, we should eventually be able to describe the demographic nature of New World communities, and to understand how their populations were responding to a new physical, social and economic environment. PMID:22070145

Norton, S L

1971-11-01

132

Math 114 Class 23 Fall 2005 Population Models and Qualitative Analysis  

E-print Network

the population? How well do you think this model would work in capturing the bacterial growth over time? What that track the growth of a population over time; the SIR model we examined some weeks ago is such a model of population growth is known as both exponential growth and Malthus growth. Sketch the function dB/dt versus B

Buckmire, Ron

133

Genomic growth curves of an outbred pig population  

PubMed Central

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.

2013-01-01

134

Population growth and the changing ecosystem in Mindanao.  

PubMed

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

Magdalena, F V

1996-04-01

135

Cellular content of ribonucleic acid and protein in Saccharomyces cerevisiae as a function of exponential growth rate: calculation of the apparent peptide chain elongation rate.  

PubMed Central

The average cellular content of ribonucleic acid and protein was determined in cultures of Saccharomyces cerevisiae growing exponentially at different rates in a variety of media. Estimations of the proportion of total cellular ribonucleic acid that is made up of ribosomal ribonucleic acid were used to calculate the average number of ribosomes per cell at the different growth rates. The fraction of ribosomes actively engaged in translation was estimated by sucrose gradient centrifugation of ribosomes and polysomes. These data were used in a calculation of the apparent time taken for the addition of an amino acid to the growing polypeptide chain; this value was found to vary linearly with growth rate over a fivefold range of doubling times. PMID:1089627

Boehlke, K W; Friesen, J D

1975-01-01

136

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

137

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

PubMed

Food demands for staple grains are expected to almost double over the next 25 years in South Asia, due to population growth and increased standards of living. Trends in the mid-1990s suggest that neither pessimism nor optimism prevails in the region. There is wide diversity among and within countries. Trends suggest that population densities are already the highest in the world, and the amount of arable land is declining. Urban growth has moved onto farm land and farmers have been pushed onto more marginal lands or have become landless. Land intensification has produced mixed results. Cereal production per capita has increased since the 1950s in India, with about 75% of the region's population, but Pakistan's increases were not sustained into the 1980s. Average daily caloric intake per person in the region of 2214 is below the level in Sub-Saharan Africa. In Bangladesh, levels are particularly worrisome at 2037. The environmental impact has not been easily quantified, but experts have suggested that pressure on farm land has contributed to loss of soil fertility and water resource loss. Further intensification of farming is feasible, but difficult and more expensive than in the past. Regardless of production problems and solutions, there is also the very real problem of poor food distribution and lack of purchasing power. Farm management skills must be utilized, if environmental degradation is to be avoided. There is the added unknown of what climate changes will occur and how agricultural production will be affected. The policy implications are that increased food production must be made a political priority. Policies must support agricultural research into improved technologies and support distribution of technological advances to a wider number of farmers. Rural infrastructures such as roads, market outlets, and credit agencies must be established. Policies must be removed that disadvantage farmers, such as inappropriate subsidies for irrigation water, inadequate tenure agreements, and price setting. Slowing population growth provides time to adjust to expanding production and saving the environment. PMID:12319284

Greenspan, A

1994-12-01

138

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

139

Population growth and United States politics in the 1970s.  

PubMed

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

Nash, A E

1973-01-01

140

Deer Population  

NSDL National Science Digital Library

The deer population activity allows students to experiment with the factors which influence population dynamics. In their exploration, they encounter both exponential and logistic growth curves. Students should be familiar with the concepts of birth and death rates, emigration and immigration, predation, limiting factors such as food supply and habitat size, and carrying capacity. The activity is self-paced with extensions provided for those who have extra time.

School, Maryland V.

141

Bivariate Generalized Exponential Distribution  

E-print Network

Bivariate Generalized Exponential Distribution Debasis Kundu and Rameshwar D. Gupta Abstract Recently it is observed that the generalized exponential distribution can be used quite effectively exponential distribution so that the marginals have generalized exponential distributions. It is observed

Kundu, Debasis

142

Theoretical Population Biology 69 (2006) 181191 The ideal free distribution and bacterial growth on two substrates  

E-print Network

Theoretical Population Biology 69 (2006) 181­191 The ideal free distribution and bacterial growth population growth rate. For batch bacterial growth, the model predicts that as the concentration is good. For bacterial growth in the chemostat, the model predicts that at low dilution rates bacteria

Krivan, Vlastimil

143

Reproductive health, population growth, economic development and environmental change.  

PubMed

World population will increase by 1000 million, or by 20%, within 10 years. Ninety-five per cent of this increase will occur in the South, in areas that are already economically, environmentally and politically fragile. Morbidity and mortality associated with reproduction will be greater in the current decade than in any period in human history. Annually, 40-60 million pregnancies will be terminated and 5-10 million children will die within one year of birth. AIDS-related infections, e.g. tuberculosis, will undermine health care in Africa (and elsewhere) and in places AIDS-related deaths will decimate the work-force. The growth in population and associated morbidity will inhibit global economic development and spawn new problems. The key issues are migration, the spread of disease, the supply of water and the degradation of land, and fiscal policies with respect to family planning, pharmaceuticals and Third-World debt. Full education, particularly of women, and more effective family planning in the South have the power to unlock the problem. Failure will see the developed countries, with their 800 million population, swamped by the health, economic and environmental problems of the South, with its projected population of 5400 million people for the year 2000. PMID:8222991

Lincoln, D W

1993-01-01

144

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

145

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

USGS Publications Warehouse

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

Gill, V.A.; Hatch, S.A.; Lanctot, R.B.

2004-01-01

146

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

PubMed Central

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

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

2014-01-01

147

Population.  

ERIC Educational Resources Information Center

In an effort to help meet the growing interest and concern about the problems created by the rapid growth of population, The International Planned Parenthood Federation has prepared this booklet with the aim of assisting the study of the history and future trends of population growth and its impact on individual and family welfare, national,…

International Planned Parenthood Federation, London (England).

148

Contributions of long-distance dispersal to population growth in colonising Pinus ponderosa populations.  

PubMed

Long-distance dispersal is an integral part of plant species migration and population development. We aged and genotyped 1125 individuals in four disjunct populations of Pinus ponderosa that were initially established by long-distance dispersal in the 16th and 17th centuries. Parentage analysis was used to determine if individuals were the product of local reproductive events (two parents present), long-distance pollen dispersal (one parent present) or long-distance seed dispersal (no parents present). All individuals established in the first century at each site were the result of long-distance dispersal. Individuals reproduced at younger ages with increasing age of the overall population. These results suggest Allee effects, where populations were initially unable to expand on their own, and were dependent on long-distance dispersal to overcome a minimum-size threshold. Our results demonstrate that long-distance dispersal was not only necessary for initial colonisation but also to sustain subsequent population growth during early phases of expansion. PMID:23279647

Lesser, Mark R; Jackson, Stephen T

2013-03-01

149

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

150

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

151

STA4000 Final Report -Detailed Analysis Investigation on Iceland Population Growth and Climate  

E-print Network

of Iceland Population Growth and Climate Change. 2 Data Source 2.1 Population of Iceland Iceland are therefore common. The climate of Iceland is also influence by the ice flow in the East Greenland CurrentSTA4000 Final Report - Detailed Analysis Investigation on Iceland Population Growth and Climate

Rosenthal, Jeffrey S.

152

21 March 2002 FUTURE WORLD POPULATION GROWTH TO BE CONCENTRATED IN URBAN AREAS OF WORLD  

E-print Network

(more) POP/815 21 March 2002 FUTURE WORLD POPULATION GROWTH TO BE CONCENTRATED IN URBAN AREAS OF WORLD According to New Report Issued by United Nations Population Division NEW YORK, 21 March (DESA) -- Virtually all the population growth expected at the world level during the next 30 years

Huang, Youqin

153

Geographical implications of population and settlement growth in Late Antique Palestine  

Microsoft Academic Search

Late Antiquity (second–seventh centuries C.E.) is considered to be the most populated period in the history of Palestine before. This article deals with the reasons and mechanisms that allowed this population growth. Most scholars believe that the population growth should be attributed to the theological change that took place during the fourth century, when Palestine became the ‘Holy Land’. Based

D. Bar

2004-01-01

154

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

155

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

156

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

157

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

158

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

PubMed Central

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

Polanski, A; Kimmel, M

2003-01-01

159

An assessment of bird habitat quality using population growth rates  

USGS Publications Warehouse

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

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

2006-01-01

160

Population growth and a sustainable environment. The Machakos story.  

PubMed

The view is taken that population density in the Machakos District (boundaries prior to 1992) of Kenya influenced both environmental conservation and productivity through adaptation of new technologies. Changes in resource management in Machakos District are identified as a shift to cash crop production, experimentation with staple food options, faster tillage, use of fertilizers for enhancing soil fertility, and livestock and tree cultivation. These agricultural changes occurred due to subdivision of landholdings among sons, private appropriation of scarce grazing land, and land scarcity. Intensive practices such as intensive livestock feeding systems and the permanent manuring of fields increased the efficiency of nutrient cycling through plants, animals, and soils. The Akamba custom gave land rights to those who tilled the soil first. Formal land registration occurred after 1968 and favored owners and investors. Small farm investment was made possible through work off-farm and remittances. The value of output per square kilometer at constant prices increased during 1930-87. Cultivated land area also increased during this period, but mostly on poorer quality land. Agricultural changes were enhanced by social and institutional factors such as small family units and greater partnerships between husband and wife. Families pooled resources through collectives. Women played leadership roles. Competing interest groups and organizations have evolved and enabled people to articulate their needs and obtain access to resources at all levels. These institutions increased in strength over time and with increased density. The cost of service provision decreased with greater population numbers. Development of roads and schools facilitated formal education. Population density, market growth, and a generally supportive economic environment are viewed as the factors responsible for changes in Machakos District. Technological change is viewed as an endogenous process of adaptation to new technologies. Changes in Machakos District are viewed as driven by a combination of exogenous and endogenous practices and local initiative. PMID:12290153

Mortimore, M; Tiffen, M

1994-10-01

161

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

EPA Science Inventory

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

162

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

163

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

164

Laguerre-type population dynamics models  

E-print Network

, the exponential function ex is transformed into the Tricomi function C0(-x) := n=0 xn (n!)2 , the powers (x + y-exponentials en(t) are increasing convex functions for t 0, but increasing slower with respect to exp t. For this rea- son these functions are useful in order to approximate different behaviors of population growth

Bretti, Gabriella

165

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 ...

166

Population divergence in compensatory growth responses and their costs in sticklebacks  

PubMed Central

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

Ab Ghani, Nurul Izza; Merilä, Juha

2015-01-01

167

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

ERIC Educational Resources Information Center

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

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

168

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

E-print Network

Contributions of vital rates to growth of a protected population of American black bears Michael S have evaluated such contributions of vital rates to l for American black bears (Ursus americanus). We rates to variation in growth rate (l) of a population of black bears inhabiting the Pisgah Bear

Mitchell, Mike

169

Recent Population Growth and Change among Asian-Americans.  

ERIC Educational Resources Information Center

Data from the 1990 Census and recent Current Population Survey reports are used to describe population change among Asian-Americans. Comparisons are made between Asian-Americans and the general non-Asian population and among Asian-Americans, focusing on four subgroups: Chinese, Filipinos, Japanese, and Koreans. Specific features examined in…

Vann, Barbara H.; Ryu, Jai P.

170

A macro analysis of population growth of China's ethnic groups in the 1980s.  

PubMed

8% of China's population is comprised of the 55 identified ethnic groups in 1990. The growth rate of this population between 1982 and 1990 was very high at 38.7/1000, or an increase of 1.43 over the previous 18 years. Natural increase was 18/1000. The total fertility rate was 2.9 in 1990. The causes for such rapid growth are reaffirmation of ethnic identity, a high fertility rate, and intermarriage with Han residents. 59% of the increased population reflected a new classification as an ethnic minority. Intermarriage with Han accounted for 4.4% of the increase. Since the revolution of 1949, there has been a release from the former oppression and population declines. In 1978, preferential policies were mandated for ethnic groups, which encouraged ethnic recognition. Ethnic status was enhanced and national awareness of ethnic groups was increased. The visual display of the ethnic age pyramid is evidence that the shape is quite different from the Han population. There are greater numbers of teenagers and those in reproductive ages. This cluster will affect population growth after the century's end. Ethnic population growth due to reaffirmation of ethnic identity also is different from natural increase in regional migration. A rise in population density within a location is not apparent. Carrying capacity of the local economy, resources, or environment is unaffected by the increase. It is inappropriate to measure the population pressure of high ethnic population growth. Eventually, ethnic growth will affect the growth rate of the national population. In ethnic areas, population growth should be planned in concert with economic development, use of resources, and protection of the ecology. Thus, ethnic area income/capita will be increased, inequality will be erased, and national autonomy achieved. The social stability and prosperity of all China is dependent on respect for happiness among ethnic minorities and economic and social development. PMID:12317818

Yang, S; Liu, W

1992-06-01

171

Testing Biopolitics against World Population growth in the 20th century Paul-Andr ROSENTAL  

E-print Network

of a field of biopolitical action cannot necessarily be reduced to population control if modes of political Connelly's work Fatal #12;2 Misconception: The Struggle to Control World Population (Belknap, Harvard1 Testing Biopolitics against World Population growth in the 20th century Paul-André ROSENTAL

Paris-Sud XI, Université de

172

Neutral genomic regions refine models of recent rapid human population growth  

E-print Network

often on human populations of European descent, estimates of Ne from genetic variation have been tra of recent rapid growth in effective population size, although estimates have varied greatly among studies analyzing the population structure of 9,716 European Americans. We used very high coverage sequencing

Keinan, Alon

173

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 Central

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

174

Stochastic stable population growth in integral projection models: theory and application  

Microsoft Academic Search

Stochastic matrix projection models are widely used to model age- or stage-structured populations with vital rates that fluctuate\\u000a randomly over time. Practical applications of these models rest on qualitative properties such as the existence of a long\\u000a term population growth rate, asymptotic log-normality of total population size, and weak ergodicity of population structure.\\u000a We show here that these properties are

Stephen P. Ellner; Mark Rees

2007-01-01

175

Exponential possibility regression analysis  

Microsoft Academic Search

This paper aims at giving the application of possibility theory based on exponential distributions to regression analysis. A general outline of the possibility theory is illustrated by exponential possibility distributions. It is shown that possibility analysis is well corresponding to statistical analysis. Using exponential possibility analysis, we propose possibility regression analysis which is suitable for rough phenomena arising from social

H. Tanaka; H. Ishibuchi; S. Yoshikawa

1995-01-01

176

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

PubMed

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

Johnson, Christopher N; Brook, Barry W

2011-12-22

177

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.

178

Incoming Population: Where Will the People Live? Coping with Growth.  

ERIC Educational Resources Information Center

The guide describes an assessment procedure that can be used by sparsely populated communities located near a potential development to help predict where the incoming population will choose to live and shop. First, a numerical model, the "gravity model," is presented which utilizes community size and the distance from the community to the…

Siegler, Theodore R.

179

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

180

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

PubMed Central

While the concept of population growth rate has been of central importance in the development of the theory of population dynamics, few empirical studies consider the intrinsic growth rate in detail, let alone how it may vary within and between populations of the same species. In an attempt to link theory with data we take two approaches. First, we address the question 'what growth rate patterns does theory predict we should see in time-series?' The models make a number of predictions, which in general are supported by a comparative study between time-series of harvesting data from 352 red grouse populations. Variations in growth rate between grouse populations were associated with factors that reflected the quality and availability of the main food plant of the grouse. However, while these results support predictions from theory, they provide no clear insight into the mechanisms influencing reductions in population growth rate and regulation. In the second part of the paper, we consider the results of experiments, first at the individual level and then at the population level, to identify the important mechanisms influencing changes in individual productivity and population growth rate. The parasitic nematode Trichostrongylus tenuis is found to have an important influence on productivity, and when incorporated into models with their patterns of distribution between individuals has a destabilizing effect and generates negative growth rates. The hypothesis that negative growth rates at the population level were caused by parasites was demonstrated by a replicated population level experiment. With a sound and tested model framework we then explore the interaction with other natural enemies and show that in general they tend to stabilize variations in growth rate. Interestingly, the models show selective predators that remove heavily infected individuals can release the grouse from parasite-induced regulation and allow equilibrium populations to rise. By contrast, a tick-borne virus that killed chicks simply leads to a reduction in the equilibrium. When humans take grouse they do not appear to stabilize populations and this may be because many of the infective stages are available for infection before harvesting commences. In our opinion, an understanding of growth rates and population dynamics is best achieved through a mechanistic approach that includes a sound experimental approach with the development of models. Models can be tested further to explore how the community of predators and others interact with their prey. PMID:12396517

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

2002-01-01

181

Quantitative analysis of population heterogeneity of the adaptive salt stress response and growth capacity of Bacillus cereus ATCC 14579  

Microsoft Academic Search

Bacterial populations can display heterogeneity with respect to both the adaptive stress response and growth capacity of individual cells. The growth dynamics of Bacillus cereus ATCC 14579 during mild and severe salt stress exposure were investigated for the population as a whole in liquid culture. To quantitatively assess the population heterogeneity of the stress response and growth capacity at a

Besten den H. M. W; Colin J. Ingham; Hylckama Vlieg van J. E. T; M.M. Beerthuyzen; T. Abee

2007-01-01

182

Ramet population ecology of Panicum virgatum in the field – Competitively random growth of ramets and foraging behavior of ramet populations  

Microsoft Academic Search

The authors investigated the heterogeneous size patterns and dynamic growth of the ramet population of Panicum virgatum, a clonal caespitose plant, limited to the space occupied by a ramet bunch and the time of the ramet yearly life cycle, to understand the ecology of clonal caespitose plants in the field, where the ramet bunch generally consisted of more than one

Xinguo Yang; Tianlong Wu; Xu Cheng

2008-01-01

183

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

184

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

185

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

E-print Network

, including the threatened Eastern Indigo Snake (Drymarchon couperi). We used 11 years (1999­2009) of capture-mark-recapture in the highest likelihood of long-term population stability and growth. Keywords AIC Á Capture-mark-recapture

Oli, Madan K.

186

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

187

Assessing plausible rates of population growth in humpback whales from life-history data  

Microsoft Academic Search

The rate of growth of any population is a quantity of interest in conservation and management and is constrained by biological\\u000a factors. In this study, recent data on life-history parameters influencing rates of population growth in humpback whales,\\u000a including survival, age at first parturition and calving rate are reviewed. Monte Carlo simulations are used to compute a\\u000a distribution of rates

Alexandre N. ZerbiniPhillip; Phillip J. Clapham; Paul R. Wade

2010-01-01

188

A heterogeneous population model for the analysis of bacterial growth kinetics  

Microsoft Academic Search

A two-compartment, heterogeneous population model (HPM) was derived using the simulation software SB ModelMaker© to describe the growth of Listeria monocytogenes in bacteriological media at 5–35 °C. The model assumed that, at time t = 0, the inoculum was distributed between two distinct compartments, Non-Growing and Growing, and that growth could be described by four parameters: initial total cell population

R. C. McKellar

1997-01-01

189

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

190

Molecular-Level Variation Affects Population Growth in a Butterfly Metapopulation  

PubMed Central

The dynamics of natural populations are thought to be dominated by demographic and environmental processes with little influence of intraspecific genetic variation and natural selection, apart from inbreeding depression possibly reducing population growth in small populations. Here we analyse hundreds of well-characterised local populations in a large metapopulation of the Glanville fritillary butterfly (Melitaea cinxia), which persists in a balance between stochastic local extinctions and recolonisations in a network of 4,000 discrete habitat patches. We show that the allelic composition of the glycolytic enzyme phosphoglucose isomerase (Pgi) has a significant effect on the growth of local populations, consistent with previously reported effects of allelic variation on flight metabolic performance and fecundity in the Glanville fritillary and Colias butterflies. The strength and the sign of the molecular effect on population growth are sensitive to the ecological context (the area and spatial connectivity of the habitat patches), which affects genotype-specific gene flow and the influence of migration on the dynamics of local populations. The biological significance of the results for Pgi is underscored by lack of any association between population growth and allelic variation at six other loci typed in the same material. In demonstrating, to our knowledge for the first time, that molecular variation in a candidate gene affects population growth, this study challenges the perception that differential performance of individual genotypes, leading to differential fitness, is irrelevant to population dynamics. These results also demonstrate that the spatial configuration of habitat and spatial dynamics of populations contribute to maintenance of Pgi polymorphism in this species. PMID:16620151

Saccheri, Ilik

2006-01-01

191

Smolt Transformation in Two California Steelhead Populations: Effects of Temporal Variability in Growth  

Microsoft Academic Search

We tested the effect of temporal patterns in food supply on life history decisions in coastal steelhead Oncorhynchus mykiss irideus from a Central California coastal (CCC) population (Scott Creek) and a Northern California Central Valley (NCCV) population (upper Sacramento River basin). We manipulated growth through feeding experiments conducted from May to the following March using warm (2006 cohort) and cool

Michael P. Beakes; William H. Satterthwaite; Erin M. Collins; David R. Swank; Joseph E. Merz; Robert G. Titus; Susan M. Sogard; Marc Mangel

2010-01-01

192

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

193

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

Technology Transfer Automated Retrieval System (TEKTRAN)

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

194

Global health action on a crowded Earth: Bay Area perspectives on population growth,  

E-print Network

Global health action on a crowded Earth: Bay Area perspectives on population growth, environment, and political instability--we must continue finding innovative ways to achieve global health goals. Population to booming metropolises, there is a need for transdisciplinary and collaborative global health action

Derisi, Joseph

195

Effect of food waste compost on microbial population, soil enzyme activity and lettuce growth  

Microsoft Academic Search

The effect of food waste (FW) composted with MS® (Miraculous Soil Microorganisms) was compared with commercial compost (CC) and mineral fertilizer (MF) on bacterial and fungal populations, soil enzyme activities and growth of lettuce in a greenhouse. Populations of fungi and bacteria, soil biomass, and soil enzyme activities in the rhizosphere of FW treatments significantly increased compared to control (CON),

Jae-Jung Lee; Ro-Dong Park; Yong-Woong Kim; Jae-Han Shim; Dong-Hyun Chae; Yo-Sup Rim; Bo-Kyoon Sohn; Tae-Hwan Kim; Kil-Yong Kim

2004-01-01

196

Porous materials with two populations of voids under internal pressure: II. Growth and  

E-print Network

Porous materials with two populations of voids under internal pressure: II. Growth and coalescence of voids Pierre-Guy Vincent a,b , Yann Monerie a,c , Pierre Suquet b,1 aInstitut de Radioprotection et de S is devoted to the mechanical behavior of polycrystalline materials with two populations of voids, small

Paris-Sud XI, Université de

197

Economic transformation, population growth and the long-run world income distribution  

Microsoft Academic Search

We present and calibrate a model where trade with advanced economies spurs development, and trade opportunities depend on the relative population in advanced and developing countries. As developing countries become advanced, prospects improve for the remaining developing countries. If population growth differentials between developing and advanced economies are small, economic development accelerates over time. Otherwise, long-run global prosperity requires a

Marcos Chamon; Michael Kremer

2009-01-01

198

Economic Transformation, Population Growth and the Long-Run World Income Distribution  

Microsoft Academic Search

We construct and calibrate a model of the world economy in which countries’ opportunities to develop depend on their trade with advanced economies. Trade opportunities in turn depend on the relative population of the advanced and developing world. As developing countries become advanced, they further improve the trade prospects for the remaining developing countries. As long as the population growth

Marcos Chamon; Michael Kremer

2006-01-01

199

Robustness of cheetah asymptotic growth rate and implications to population models  

E-print Network

Robustness of cheetah asymptotic growth rate and implications to population models Joan Lubben1 cheetah (Acinonyx jubatus) is in decline due to hunting, poaching, loss of habitat, lack of genetic diversity and death of cubs due to natural predators such as lions and hyenas. Previous cheetah population

Logan, David

200

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...

201

High production in a herbaceous perennial plant achieved by continuous growth and synchronized population dynamics  

Microsoft Academic Search

Continuous changes in the population dynamics, above- and belowground biomass, growth rates, and production of the emergent rush Juncus effusus were evaluated over an annual period in a subtemperate riparian wetland. Extant and emerging individual photosynthetic culms (shoots) were labeled individually and their growth dynamics quantified in replicated plots. Lengths of living (chlorophyllous) portions and basal diameters of several thousand

Robert G Wetzel; Michael J Howe

1999-01-01

202

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 that stabilize novel phenotypes. Often, this adaptation involves regulatory changes which modulate gene expression. In the budding yeast, ribosomal-related gene expression correlates with cell growth rate across

Barkai, Naama

203

Modeling circadian clock-cell cycle interaction effects on cell population growth rates  

E-print Network

for autonomous periods of the cell cycle around 24 h and above 48 h. We study the effect of mutation of circadian proliferation. Particularly, we show that Cry1, Cry2 mutations decrease the growth rate of cells, Per2 mutationModeling circadian clock-cell cycle interaction effects on cell population growth rates R. El

Boyer, Edmond

204

Individual and Population Level Variation in Growth Parameters for Steelhead Trout Oncorhynchus mykiss in  

E-print Network

to growth data for juvenile steelhead trout (Oncorhynchus19 mykiss) from California. We grew fish fromIndividual and Population Level Variation in Growth Parameters for Steelhead Trout Oncorhynchus mykiss in Central California Christopher A. Simon(1), William H. Satterthwaite(1,2), Michael P. Beakes (1

205

Effect of Population Density on Growth of Land Snail Helix aspersa maxima  

Microsoft Academic Search

The first few weeks of life are of great importance for the growth of snails. Breeders have to carefully handle this delicate and costly phase. The impact of population density increased with the number of animals and the duration of nursery. The highest tested densities did not have a negative effect on growth up to two weeks, after which a

A. Blanc; J. Attia

1992-01-01

206

CAUSES OF MORTALITY IN CALIFORNIA SEA OTTERS DURING PERIODS OF POPULATION GROWTH AND DECLINE  

Microsoft Academic Search

Elevated mortality appears to be the main reason for both sluggish growth and periods of decline in the threatened California sea otter population. We asses- sed causes of mortality from salvage records of 3,105 beach-cast carcasses recov- ered from 1968 through 1999, contrasting two periods of growth with two periods of decline. Overall, an estimated 409640% of the deaths were

James A. Estes; Brian B. Hatfield; Katherine Ralls; Jack Ames

2003-01-01

207

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

ERIC Educational Resources Information Center

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

Garcia, David

2011-01-01

208

The almost-sure population growth rate in branching Brownian motion with a quadratic breeding potential  

E-print Network

In this note we consider a branching Brownian motion (BBM) on $\\mathbb{R}$ in which a particle at spatial position $y$ splits into two at rate $\\beta y^2$, where $\\beta>0$ is a constant. This is a critical breeding rate for BBM in the sense that the expected population size blows up in finite time while the population size remains finite, almost surely, for all time. We find an asymptotic for the almost sure rate of growth of the population.

Berestycki, J; Harris, J W; Harris, S C

2009-01-01

209

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

210

Circadian rhythm and cell population growth June 17, 2010  

E-print Network

entrainment perturbations, of the central hypothalamic circadian clock in tumor-bearing mice leads proliferation. It has been observed in tumor-bearing laboratory rodents that a severe disruption of these physio- logical rhythms results in accelerated tumor growth. The question of accurately representing the control

211

Flower Power: Sunflowers as a Model for Logistic Growth  

ERIC Educational Resources Information Center

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

Fernandez, Eileen; Geist, Kristi A.

2011-01-01

212

The singularity is not near: slowing growth of Wikipedia  

Microsoft Academic Search

Prior research on Wikipedia has characterized the growth in content and editors as being fundamentally exponential in nature, extrapolating current trends into the future. We show that recent editing activity suggests that Wikipedia growth has slowed, and perhaps plateaued, indicating that it may have come against its limits to growth. We measure growth, population shifts, and patterns of editor and

Bongwon Suh; Gregorio Convertino; Ed H. Chi; Peter Pirolli

2009-01-01

213

Population Change in the Midwest: Nonmetro Population Growth Lags Metro Increase.  

ERIC Educational Resources Information Center

Midwest population gains in the 1990s were eclipsed by other regions, and nonmetro areas fared worse than metro counties. Less populous and more isolated counties were more likely to lose residents and to lose youth. The Midwest gained Hispanic residents in the 1990s, but numerical increases were much larger in metro counties. Implications for…

Goudy, Willis

2002-01-01

214

THE EXPONENTIATED FR¶ ECHET DISTRIBUTION  

Microsoft Academic Search

Gupta et al. (Communication in Statistics|Theory and Methods, 1998, 27, 887{904) in- troduced the exponentiated exponential distribution as a generalization of the standard exponential distribution. In this note we introduce a distribution that generalizes the standard Frechet distribution in the same way the exponentiated exponential distribu- tion generalizes the standard exponential distribution. We refer to this new distribution as the

Saralees Nadarajah; Samuel Kotz

215

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

SciTech Connect

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

Nacci, D.; Gleason, T.; Munns, W.R. Jr. [Environmental Protection Agency, Narragansett, RI (United States). Environmental Research Lab.

1995-12-31

216

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

217

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

218

Comparison of individual-based modeling and population approaches for prediction of foodborne pathogens growth.  

PubMed

Individual-based modeling (IBM) approach combined with the microenvironment modeling of vacuum-packed cold-smoked salmon was more effective to describe the variability of the growth of a few Listeria monocytogenes cells contaminating irradiated salmon slices than the traditional population models. The IBM approach was particularly relevant to predict the absence of growth in 25% (5 among 20) of artificially contaminated cold-smoked salmon samples stored at 8 °C. These results confirmed similar observations obtained with smear soft cheese (Ferrier et al., 2013). These two different food models were used to compare the IBM/microscale and population/macroscale modeling approaches in more global exposure and risk assessment frameworks taking into account the variability and/or the uncertainty of the factors influencing the growth of L. monocytogenes. We observed that the traditional population models significantly overestimate exposure and risk estimates in comparison to IBM approach when contamination of foods occurs with a low number of cells (<100 per serving). Moreover, the exposure estimates obtained with the population model were characterized by a great uncertainty. The overestimation was mainly linked to the ability of IBM to predict no growth situations rather than the consideration of microscale environment. On the other hand, when the aim of quantitative risk assessment studies is only to assess the relative impact of changes in control measures affecting the growth of foodborne bacteria, the two modeling approach gave similar results and the simplest population approach was suitable. PMID:25500386

Augustin, Jean-Christophe; Ferrier, Rachel; Hezard, Bernard; Lintz, Adrienne; Stahl, Valérie

2015-02-01

219

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

NASA Astrophysics Data System (ADS)

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

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

2013-08-01

220

Effects of diet on population growth of psocids Lepinotus reticulatus and Liposcelis entomophila.  

PubMed

We investigated the suitability of 11 diets as culture media for the psocids Lepinotus reticulatus Enderlein (Psocoptera: Trogiidae) and Liposcelis entomophila (Enderlein) (Psocoptera: Liposcelididae). The culture media comprised six diets made of plain cereals, namely, wheat (Triticum aestivum L.), corn (Zea mays L.), milo Sorghum bicolor (L.), barley (Hordeum vulgare L.), oats (Avena sativa L.), and rice (Oryza sativa L.), and five artificial diets. We found that, with the exception of corn, L. reticulatus population increase was greater on plain cereal diets than on artificial diets, and the greatest population growth was on oats. There was an inverse relationship between L. reticulatus population growth and diet compactness. L. entomophila populations grew fastest on wheat, barley, and a mixture of cracked wheat, rice krispies, and brewer's yeast (97:2:1, wt:wt). The proportion of females was greater in diets that were less suitable for L. entomophila population growth compared with that in the more suitable diets. Diet compactness had a weak effect on L. entomophila population growth. This study also has established the relative level of suitability of damaged wheat, corn, milo, barley, oats, and rice to L. reticulatus and L. entomophila. PMID:18459431

Opit, G P; Throne, J E

2008-04-01

221

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

PubMed

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

Westoff, C F

1973-10-01

222

Urban population growth: implications for India and South Asia.  

PubMed

In India more than 1/2 the total urban population is concentrated in the 6 cities with populations of 1 million or more. Densities in some areas of these cities reach 100,000-500,000 people per square mile. In Calcutta an estimated 600,000 people live on the pavement because they are too poor to afford shelter. Large cities in developing areas tend to draw migrants not only from rural areas but also from smaller towns. These people are disproportionately single, better educated, with higher occupational level. The smaller town is the poorer because they have left. Cities also draw the hopeless and the landless and, in addition, have high fertility rates. All Asian countries have a large dependency ratio. A drop in dependency ratio would help offset the high proportion of gross national product (GNP) which has to be reinvested just to keep per capita income at a constant level. In India this largely demographi c investment exceeds 1% of the GNP. Because of the improved infant survival rates combined with high birthrates between 1955-1965, the labor force will increase very rapidly between 1970-1980 in South Asia. This problem of finding employment will be aggravated in urban centers due to migration. As the number of frustrated rural dwellers come to the cities hoping for work and finding none, they become a force threatening stability. Industries must be decentralized to revitalize rural areas. Housing schemes and vigorous birth control projects must be put into force to eliminate slum conditions and squatters. In Asia industrailization and urbanization are in the early stages; if housing is as bad as it is today, what will it be like when industrialization becomes advanced? The money now spent aimlessly on wandering beggars needs to be funneled into health and welfare systems to raise their level. Education and transportation are critically strained by Asia's urbanization. According to Kingsley Davis, even if Asia had 100% effective family planning so that each couple had only the children desired, there would still be a population crisis because of the social structure which motivates couples to have large families. More education for women seems to be the answer. Women with primary education tend to have 6.6 children; with middle school education, 5.0; high school, 4.6; and those with some university, 2.0. PMID:12257938

Murickan, J

1974-01-01

223

Population growth impacts of zero net international migration.  

PubMed

"In a country such as the United States, the contribution of net international migration to overall population change overshadows the contribution of natural increase.... Some analysts have assumed that if the same number of people leave and enter the country each year, then the effect of net international migration will be zero. This article examines that assumption and shows that it is fallacious. Examining the direct, indirect, total, and negative demographic impacts of zero net international migration through simulations with demographic data, we demonstrate that zero net international migration is not the same and therefore does not have the same demographic results and implications as zero international migration. We conclude that zero net international migration should not be confused with zero international migration." PMID:12292873

Bouvier, L F; Poston, D L; Zhai, N B

1997-01-01

224

A MULTI-PATCH MALARIA MODEL WITH LOGISTIC GROWTH POPULATIONS*  

PubMed Central

In this paper, we propose a multi-patch model to study the effects of population dispersal on the spatial spread of malaria between patches. The basic reproduction number R0 is derived and it is shown that the disease-free equilibrium is locally asymptotically stable if R0<1 and unstable if R0>1. Bounds on the disease-free equilibrium and R0 are given. A sufficient condition for the existence of an endemic equilibrium when R0>1 is obtained. For the two-patch submodel, the dependence of R0 on the movement of exposed, infectious, and recovered humans between the two patches is investigated. Numerical simulations indicate that travel can help the disease to become endemic in both patches, even though the disease dies out in each isolated patch. However, if travel rates are continuously increased, the disease may die out again in both patches. PMID:23723531

GAO, DAOZHOU; RUAN, SHIGUI

2013-01-01

225

A MULTI-PATCH MALARIA MODEL WITH LOGISTIC GROWTH POPULATIONS.  

PubMed

In this paper, we propose a multi-patch model to study the effects of population dispersal on the spatial spread of malaria between patches. The basic reproduction number [Formula: see text] is derived and it is shown that the disease-free equilibrium is locally asymptotically stable if [Formula: see text] and unstable if [Formula: see text]. Bounds on the disease-free equilibrium and [Formula: see text] are given. A sufficient condition for the existence of an endemic equilibrium when [Formula: see text] is obtained. For the two-patch submodel, the dependence of [Formula: see text] on the movement of exposed, infectious, and recovered humans between the two patches is investigated. Numerical simulations indicate that travel can help the disease to become endemic in both patches, even though the disease dies out in each isolated patch. However, if travel rates are continuously increased, the disease may die out again in both patches. PMID:23723531

Gao, Daozhou; Ruan, Shigui

2012-01-01

226

India in the Twenty-first Century: The Challenge of Population Growth. Fulbright-Hays Summer Seminars Abroad, 1997 (India).  

ERIC Educational Resources Information Center

This paper contains a course outline for a five-hour graduate class focusing on the issue of population in India. Students examine contributing factors to population growth, along with studying characteristics of, and efforts to, control population growth. The significance of ethnic diversity in India also is addressed. Group discussion and group…

La Fleur, Mary Ann

227

Distinguishing between linear and exponential cell growth during the division cycle: Single-cell studies, cell-culture studies, and the object of cell-cycle research  

Microsoft Academic Search

BACKGROUND: Two approaches to understanding growth during the cell cycle are single-cell studies, where growth during the cell cycle of a single cell is measured, and cell-culture studies, where growth during the cell cycle of a large number of cells as an aggregate is analyzed. Mitchison has proposed that single-cell studies, because they show variations in cell growth patterns, are

Stephen Cooper

2006-01-01

228

Generation time, net reproductive rate, and growth in stage-age-structured populations.  

PubMed

Major insights into the relationship between life-history features and fitness have come from Lotka's proof that population growth rate is determined by the level (expected amount) of reproduction and the average timing of reproduction of an individual. But this classical result is limited to age-structured populations. Here we generalize this result to populations structured by stage and age by providing a new, unique measure of reproductive timing (Tc) that, along with net reproductive rate (R0), has a direct mathematical relationship to and approximates growth rate (r). We use simple examples to show how reproductive timing Tc and level R0 are shaped by stage dynamics (individual trait changes), selection on the trait, and parent-offspring phenotypic correlation. We also show how population structure can affect dispersion in reproduction among ages and stages. These macroscopic features of the life history determine population growth rate r and reveal a complex interplay of trait dynamics, timing, and level of reproduction. Our results contribute to a new framework of population and evolutionary dynamics in stage-and-age-structured populations. PMID:24823821

Steiner, Ulrich K; Tuljapurkar, Shripad; Coulson, Tim

2014-06-01

229

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

230

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

231

How exponential are FREDs?  

NASA Astrophysics Data System (ADS)

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

Schaefer, Bradley E.; Dyson, Samuel E.

1996-08-01

232

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

233

Section 3.1. Population Ch. 3.1. Population Growth  

E-print Network

, with Thomas Malthus's statement that, "The power of population is indefinitely greater than the power in the earth to produce subsistence for man," (Malthus, 1798). Malthus envisioned an impending human doomsday (Malthus 1798). He argued that arable land is finite and agricultural production grows geometrically while

Lopez-Carr, David

234

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

235

Population growth and development of Liposcelis pearmani (Psocoptera: Liposcelididae) at constant temperatures and relative humidities.  

PubMed

Psocids of genus Liposcelis are now considered serious pests of stored products. We investigated the effects of eight temperatures (22.5, 25.0, 27.5, 30.0, 32.5, 35.0, 37.5, and 40.0°C) and four relative humidities (43, 55, 63, and 75%) on population growth and development of the psocid Liposcelis pearmani Lienhard. L. pearmani did not survive at 37.5 and 40.0°C, at all relative humidities tested; at 43% RH, at all temperatures tested; and at 55% RH, at 32.5 and 35°C. The greatest population growth was recorded at 32.5°C and 75% RH (32-fold growth). L. pearmani males have two to four nymphal instars, and the percentages of males with two, three, and four instars were 17, 63, and 20%, respectively. Female L. pearmani have two to five instars, and the percentages of females with two, three, four, and five instars were 5, 39, 55, and 1%, respectively. We developed temperature-dependent development equations for male and female eggs, individual nymphal, combined nymphal, and combined immature stages. Based on 30-d population growth, L. pearmani cannot survive at temperatures >35.0°C; does not thrive at low relative humidities (55%), at temperatures above 25°C; and has a high optimum relative humidity for population growth (75%). Therefore, we expect it to have a more limited distribution compared with other Liposcelis species. These data provide a better understanding of how temperature and RH may influence L. pearmani population dynamics and can be used in population growth models to help develop effective management strategies for this psocid, and to predict its occurrence. PMID:22251679

Aminatou, B A; Gautam, S G; Opit, G P; Talley, J; Shakya, K

2011-08-01

236

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

237

An econometric analysis of the effects of population change on economic growth: a study of Taiwan.  

PubMed

This study used an econometric model, estimated from time series data, to evaluate the effects of demographic factors on the T aiwanese economy. The simulation results suggest that, in the short run, a stationary population produces significantly higher income per capita than rapid population growth; in the long run, however, rapid population growth produces a slightly higher income per capita. Under assumptions of very low fertility trends, the population size, equivalent adult consumers, and labor force can be expected to grow by no more than 50% in a century, whereas under the very high fertility trend assumptions, they would more than double. The reason that lower fertility populations produce a smaller gross domestic product per capita in the long run than the normal fertility population is that the negative effects of a slower growing labor force dominate the positive effects of a faster growing capital formation. In terms of the present values of annual income per capita, the slow growing population shows considerably better economic performance. Given the immediate economic advantages of lower fertility, it is important for developing countries with high birth rates to reduce fertility in order to produce higher per capita income effects and break out of poverty. It is considered of little importance that the slow growing populations eventually produce slightly smaller per capita. PMID:12340242

Tung, S L

1984-08-01

238

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

239

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

USGS Publications Warehouse

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

Hansen, Michael J.; Nate, Nancy A.

2014-01-01

240

Patterns of muscle growth in early and late maturing populations of Atlantic salmon ( Salmo salar L.)  

Microsoft Academic Search

Muscle growth was investigated in two populations of Atlantic salmon (Salmo salar L) derived from an early maturing stock of West Coast Scottish origin (strain X) and a late maturing stock (strain Y) of Norwegian origin. Fish from six families per population were PIT-tagged and reared together in a 5×5×5 m sea cage between April 1997 and September 1998. The

Ian A. Johnston; Richard Alderson; Claire Sandham; David Mitchell; Craig Selkirk; Alistair Dingwall; David Nickell; Remi Baker; Billy Robertson; David Whyte; John Springate

2000-01-01

241

A View of the Future: The Effect of Policy on Prison Population Growth  

Microsoft Academic Search

The prison population in Illinois is projected to increase from over 28,000 to nearly 45,400 by the year 2000. It will cost $1.2 billion for construction just to maintain prison crowding at 68% double and multicelling. This article examines the factors driving this growth, provides a projection of the future prison population levels, and simulates a variety of policy options

Nola M. Joyce

1992-01-01

242

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

243

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

244

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

PubMed Central

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

2014-01-01

245

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

246

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

ERIC Educational Resources Information Center

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

McNicoll, Geoffrey

247

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

248

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

E-print Network

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 individual growth before and after the refuge was established. Our estimates are based on an annual mark-recapture survey conducted at the Gull Island Shoal 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 after the refuge was established. Our results suggest that growth of mature lake trout (particularly wild fish) decreased significantly in the post-refuge 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.

Mary C. Fabrizio; U. S. Geological Survey; Robert M. Dorazio; U. S. Geological Survey; Stephen T. Schram

2001-01-01

249

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

250

vol. 163, no. 3 the american naturalist march 2004 Effects of Body Size and Temperature on Population Growth  

E-print Network

on the Prin- ciple of Population, Thomas Malthus (1798) noted that all populations had the potential the time of Malthus, pop- ulation growth has been recognized as providing a critical link be- tween

Brown, James H.

251

Growth rates and variances of unexploited wolf populations in dynamic equilibria  

USGS Publications Warehouse

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

Mech, L. David; Fieberg, John

2015-01-01

252

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

PubMed

The importance of individuals to the dynamics of populations may depend on reproductive status, especially for species with complex social structure. Loss of reproductive individuals in socially complex species could disproportionately affect population dynamics by destabilizing social structure and reducing population growth. Alternatively, compensatory mechanisms such as rapid replacement of breeders may result in little disruption. The impact of breeder loss on the population dynamics of social species remains poorly understood. We evaluated the effect of breeder loss on social stability, recruitment and population growth of grey wolves (Canis lupus) in Denali National Park and Preserve, Alaska using a 26-year dataset of 387 radiocollared wolves. Harvest of breeding wolves is a highly contentious conservation and management issue worldwide, with unknown population-level consequences. Breeder loss preceded 77% of cases (n = 53) of pack dissolution from 1986 to 2012. Packs were more likely to dissolve if a female or both breeders were lost and pack size was small. Harvest of breeders increased the probability of pack dissolution, likely because the timing of harvest coincided with the breeding season of wolves. Rates of denning and successful recruitment were uniformly high for packs that did not experience breeder loss; however, packs that lost breeders exhibited lower denning and recruitment rates. Breeder mortality and pack dissolution had no significant effects on immediate or longer term population dynamics. Our results indicate the importance of breeding individuals is context dependent. The impact of breeder loss on social group persistence, reproduction and population growth may be greatest when average group sizes are small and mortality occurs during the breeding season. This study highlights the importance of reproductive individuals in maintaining group cohesion in social species, but at the population level socially complex species may be resilient to disruption and harvest through strong compensatory mechanisms. PMID:25041127

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

2014-07-01

253

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...

254

Growth rates of the population in a branching Brownian motion with an inhomogeneous breeding potential  

E-print Network

We consider a branching particle system where each particle moves as an independent Brownian motion and breeds at a rate proportional to its distance from the origin raised to the power $p$, for $p\\in[0,2)$. The asymptotic behaviour of the right-most particle for this system is already known; in this article we give large deviations probabilities for particles following "difficult" paths, growth rates along "easy" paths, the total population growth rate, and we derive the optimal paths which particles must follow to achieve this growth rate.

Berestycki, Julien; Harris, John W; Harris, Simon C; Roberts, Matthew I

2012-01-01

255

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

PubMed Central

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

2003-01-01

256

Nutritional status and growth of children on macrobiotic diets: a population-based study  

Microsoft Academic Search

This thesis reports on the relationship between diet, growth, blood chemistry, psychomotor development, and clinical findings in the Dutch population of children on macrobiotic diets.- The macrobiotic diet mainly consisted of cereals, pulses and vegetables with small additions of seaweeds, fermented foods, nuts and seeds. meat and dairy products were avoided, whereas fish was occasionally being eaten but not by

P. C. Dagnelie

1988-01-01

257

Plant Population Growth and Competition in a Light Gradient A mathematical model of canopy partitioning  

E-print Network

Plant Population Growth and Competition in a Light Gradient A mathematical model of canopy Abstract Can a difference in the heights at which plants place their leaves, a pattern we call canopy-shading. This first of three related papers formulates a prototype single species canopy struc- ture model from

Nevai, Andrew

258

Root Growth and Yield of Differing Alfalfa Rooting Populations under Increasing Salinity and Zero Leaching  

E-print Network

Root Growth and Yield of Differing Alfalfa Rooting Populations under Increasing Salinity and Zero-rootedAccumulation of salinity in the root zone can be detrimental to crops such as alfalfa to exploit the lower average salinitysustained crop production. Irrigation, even with moderately saline water, pushes accumulated salts deeper

Smith, Steven E.

259

Ecosystem Scale Declines in Elk Recruitment and Population Growth with Wolf Colonization: A Before-  

E-print Network

of the effects of wolf predation on their primary prey (elk ­ Cervus elaphus) in a system where top-down, bottom in elk numbers immediately after wolf recolonization, relatively weak additive effects of direct wolfEcosystem Scale Declines in Elk Recruitment and Population Growth with Wolf Colonization: A Before

Creel, Scott

260

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

261

Numerical approximations for population growth model by rational Chebyshev and Hermite functions collocation approach: A comparison  

Microsoft Academic Search

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

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

2010-01-01

262

Effects of resistance genes and insecticidal seed treatments on soybean aphid population growth and development  

E-print Network

1 Effects of resistance genes and insecticidal seed treatments on soybean aphid population growth Lafayette, IN, 47907, USA. Introduction Soybean aphid (Aphis glycines) is an introduced pest first reported. 2004). Heavy infestation of aphids causes distortion of leaves, reduction of seed pods and yield loss

Ginzel, Matthew

263

FORAGE FISH POPULATIONS AND GROWTH OF MUSKELLUNGE IN A SOUTH DAKOTA POWER PLANT COOLING RESERVOIR  

E-print Network

FORAGE FISH POPULATIONS AND GROWTH OF MUSKELLUNGE IN A SOUTH DAKOTA POWER PLANT COOLING RESERVOIR and facilities at the cooling reservoir; D. T. Henley, T. L. Margenau, R. J. Krska, S. C. Johnson, and G. B POWER PLANT COOLING RESERVOIR This thesis is approved as a creditable and independent investigation

264

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

Microsoft Academic Search

The impact of solar heating and infrared cooling on the growth of a population of drops is studied with two numerical modeling frameworks. An eddy-resolving model (ERM) simulation of Arctic stratus clouds is used to generate a dataset of 500 parcel trajectories that follow the mean dynamic motions of the simulated cloud. The 500-parcel dataset is used to drive a

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

2000-01-01

265

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

266

PLANTINSECT INTERACTIONS Inducible Responses in Papaya: Impact on Population Growth Rates of  

E-print Network

PLANTÐINSECT INTERACTIONS Inducible Responses in Papaya: Impact on Population Growth Rates in their shared host plant, papaya. Three key parasites attack papaya foliage in Hawaii: the carmine spider mite, Tetranychus cinnabarinus (Boisduval); the papaya rust mite, Calacarus flagelliseta Fletch- mann

Rosenheim, Jay A.

267

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.

268

Economic Transformation, Population Growth, and the Long-Run World Income Distribution  

Microsoft Academic Search

This paper considers the long-run evolution of the world economy in a model where countries' opportunities to develop depend on their trade with advanced economies. As developing countries become advanced, they further improve trade opportunities for the remaining developing countries. Whether or not the world economy converges to widespread prosperity depends on the population growth differential between developing and advanced

Marcos Chamon; Michael Kremer

2006-01-01

269

Address of the Past President Human Population Growth and the Carrying Capacity Concept  

E-print Network

Address of the Past President Human Population Growth and the Carrying Capacity Concept INTRODUCTION The concept of carrying capacity has a rich history in ecology for the study of plant and animal to the problem of human carrying capacity. In this paper, we briefly review the history of the car rying capacity

Haddad, Nick

270

A stochastic model for population migration and the growth of human settlements during the Neolithic  

E-print Network

advection and spatial variation in diffusivity and carrying capacity, in the framework of the FisherA stochastic model for population migration and the growth of human settlements during of the formation of human settlements along the river valley. The numerical results show that the individual

Moss, David

271

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

Technology Transfer Automated Retrieval System (TEKTRAN)

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

272

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

273

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 ABSTRACT A density manipulation experiment was conducted at Seven Mile Beach, Western Australia. to compare to emigration of tagged individuals to other reefs. The difficulties of conducting manipulation experiments

274

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

275

Uncertainty in Population Growth Rates: Determining Confidence Intervals from Point Estimates of Parameters  

PubMed Central

Background Demographic models are widely used in conservation and management, and their parameterisation often relies on data collected for other purposes. When underlying data lack clear indications of associated uncertainty, modellers often fail to account for that uncertainty in model outputs, such as estimates of population growth. Methodology/Principal Findings We applied a likelihood approach to infer uncertainty retrospectively from point estimates of vital rates. Combining this with resampling techniques and projection modelling, we show that confidence intervals for population growth estimates are easy to derive. We used similar techniques to examine the effects of sample size on uncertainty. Our approach is illustrated using data on the red fox, Vulpes vulpes, a predator of ecological and cultural importance, and the most widespread extant terrestrial mammal. We show that uncertainty surrounding estimated population growth rates can be high, even for relatively well-studied populations. Halving that uncertainty typically requires a quadrupling of sampling effort. Conclusions/Significance Our results compel caution when comparing demographic trends between populations without accounting for uncertainty. Our methods will be widely applicable to demographic studies of many species. PMID:21049049

Devenish Nelson, Eleanor S.; Harris, Stephen; Soulsbury, Carl D.; Richards, Shane A.; Stephens, Philip A.

2010-01-01

276

Timescales of Freshwater Depletion with GRACE, Population Growth, and Land Cover  

NASA Astrophysics Data System (ADS)

Human-induced pressures on global freshwater supplies are ever increasing, especially in arid and semi-arid regions. Freshwater demands are placed on fragile groundwater systems and aging or lacking infrastructure for surface water storage by domestic, agricultural, and industrial uses. Traditional regional water supply sources will likely become less reliable in the future with climate change and population growth. These traditional water systems have the potential to be pushed to the limits of depletion or inaccessibility if sustainable management practices are not implemented. The work presented here analyzes connections between freshwater availability, land cover type, and population. In doing so, we develop an understanding of the dynamics between population growth, freshwater depletion, and agricultural productivity. We gain an improved understanding of dominant water supply sources by region and how these supplies might change with increasing use. A focus is placed on understanding groundwater-dependent systems. Future population growth scenarios analyze the time scales for which freshwater supplies are depleted to meet the demands of agriculture and domestic water use. NASA's Gravity Recovery and Climate Experiment (GRACE) quantifies current rates of freshwater depletion as compared to total freshwater storage. Land cover type and population density is quantified with the best available data by region.

Richey, A. S.; Famiglietti, J. S.

2012-12-01

277

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

278

Cell Growth and Size Homeostasis in Silico  

NASA Astrophysics Data System (ADS)

Cell growth in size is a complex process coordinated by intrinsic and environmental signals. In a recent work [Tzur et al., Science, 2009, 325:167-171], size distributions in an exponentially growing population of mammalian cells were used to infer the growth rate in size. The results suggest that cell growth is neither linear nor exponential, but subject to size-dependent regulation. To explain their data, we build a model in which the cell growth rate is controlled by the relative amount of mRNA and ribosomes in a cell. Plus a stochastic division rule, the evolutionary process of a population of cells can be simulated and the statistics of the in-silico population agree well with the experimental data. To further explore the model space, alternative growth models and division rules are studied. This work may serve as a starting point for us to understand the rational behind cell growth and size regulation using predictive models.

Hu, Yucheng; Zhu, Tianqi

2014-03-01

279

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

280

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

281

Dr. Z's Calc2 Handout for Lecture 22 [ Models involving y = k(y -b); Exponential Growth and Decay] By Doron Zeilberger  

E-print Network

] By Doron Zeilberger Problem Type P22.1: A bacteria culture starts with B0 bacteria and grows at a rate2 hours. (d) When will the population reach B2? Example Problem P22.1: A bacteria culture starts proportional to its size. After T1 hours there are B1 bacteria. (a) Find an expression for the number

Zeilberger, Doron

282

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

PubMed Central

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

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

2000-01-01

283

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

284

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

285

Spatially Directed Guidance of Stem Cell Population Migration by Immobilized Patterns of Growth Factors  

PubMed Central

We investigated how engineered gradients of exogenous growth factors, immobilized to an extracellular matrix material, influence collective guidance of stem cell populations over extended time (>1 day) and length (>1 mm) scales in vitro. Patterns of low-to-high, high-to-low, and uniform concentrations of heparin-binding epidermal growth factor-like growth factor were inkjet printed at precise locations on fibrin substrates. Proliferation and migration responses of mesenchymal stem cells seeded at pattern origins were observed with time-lapse video microscopy and analyzed using both manual and automated computer vision-based cell tracking techniques. Based on results of established chemotaxis studies, we expected that the low-to-high gradient would most effectively direct cell guidance away from the cell source. All printed patterns, however, were found to direct net collective cell guidance with comparable responses. Our analysis revealed that collective “cell diffusion” down a cell-to-cell confinement gradient originating at the cell starting lines and not the net sum of directed individual cell migration up a growth factor concentration gradient is the principal driving force for directing mesenchymal stem cell population outgrowth from a cell source. These results suggest that simple uniform distributions of growth factors immobilized to an extracellular matrix material may be as effective in directing cell migration into a wound site as more complex patterns with concentration gradients. PMID:21272933

Miller, Eric D.; Li, Kang; Kanade, Takeo; Weiss, Lee E.; Walker, Lynn M.; Campbell, Phil G.

2011-01-01

286

The exponential hash function  

Microsoft Academic Search

In this paper an efficient open address hash function called exponential hashing is developed. The motivation for this hash function resulted from our ongoing efforts to apply dynamical systems theory to the study of hashing; however, the analysis conducted in this paper is primarily based on traditional number theory. Proofs of optimal table parameter choices are provided for a number

Bradley J. Smith; Gregory L. Heileman; Chaouki T. Abdallah

1997-01-01

287

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

288

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

289

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

290

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...

291

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

292

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

293

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

294

Nerve growth cone lamellipodia contain two populations of actin filaments that differ in organization and polarity  

PubMed Central

The organization and polarity of actin filaments in neuronal growth cones was studied with negative stain and freeze-etch EM using a permeabilization protocol that caused little detectable change in morphology when cultured nerve growth cones were observed by video- enhanced differential interference contrast microscopy. The lamellipodial actin cytoskeleton was composed of two distinct subpopulations: a population of 40-100-nm-wide filament bundles radiated from the leading edge, and a second population of branching short filaments filled the volume between the dorsal and ventral membrane surfaces. Together, the two populations formed the three- dimensional structural network seen within expanding lamellipodia. Interaction of the actin filaments with the ventral membrane surface occurred along the length of the filaments via membrane associated proteins. The long bundled filament population was primarily involved in these interactions. The filament tips of either population appeared to interact with the membrane only at the leading edge; this interaction was mediated by a globular Triton-insoluble material. Actin filament polarity was determined by decoration with myosin S1 or heavy meromyosin. Previous reports have suggested that the polarity of the actin filaments in motile cells is uniform, with the barbed ends toward the leading edge. We observed that the actin filament polarity within growth cone lamellipodia is not uniform; although the predominant orientation was with the barbed end toward the leading edge (47-56%), 22-25% of the filaments had the opposite orientation with their pointed ends toward the leading edge, and 19-31% ran parallel to the leading edge. The two actin filament populations display distinct polarity profiles: the longer filaments appear to be oriented predominantly with their barbed ends toward the leading edge, whereas the short filaments appear to be randomly oriented. The different length, organization and polarity of the two filament populations suggest that they differ in stability and function. The population of bundled long filaments, which appeared to be more ventrally located and in contact with membrane proteins, may be more stable than the population of short branched filaments. The location, organization, and polarity of the long bundled filaments suggest that they may be necessary for the expansion of lamellipodia and for the production of tension mediated by receptors to substrate adhesion molecules. PMID:1447299

1992-01-01

295

Inhibition of the sodium-translocating NADH-ubiquinone oxidoreductase [Na+-NQR] decreases cholera toxin production in Vibrio cholerae O1 at the late exponential growth phase.  

PubMed

Two virulence factors produced by Vibrio cholerae, cholera toxin (CT) and toxin-corregulated pilus (TCP), are indispensable for cholera infection. ToxT is the central regulatory protein involved in activation of CT and TCP expression. We previously reported that lack of a respiration-linked sodium-translocating NADH-ubiquinone oxidoreductase (Na(+)-NQR) significantly increases toxT transcription. In this study, we further characterized this link and found that Na(+)-NQR affects toxT expression only at the early-log growth phase, whereas lack of Na(+)-NQR decreases CT production after the mid-log growth phase. Such decreased CT production was independent of toxT and ctxB transcription. Supplementing a respiratory substrate, l-lactate, into the growth media restored CT production in the nqrA-F mutant, suggesting that decreased CT production in the Na(+)-NQR mutant is dependent on electron transport chain (ETC) activity. This notion was supported by the observations that two chemical inhibitors, a Na(+)-NQR specific inhibitor 2-n-Heptyl-4-hydroxyquinoline N-oxide (HQNO) and a succinate dehydrogenase (SDH) inhibitor, thenoyltrifluoroacetone (TTFA), strongly inhibited CT production in both classical and El Tor biotype strains of V. cholerae. Accordingly, we propose the main respiratory enzyme of V. cholerae, as a potential drug target to treat cholera because human mitochondria do not contain Na(+)-NQR orthologs. PMID:24361395

Minato, Yusuke; Fassio, Sara R; Reddekopp, Rylan L; Häse, Claudia C

2014-01-01

296

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

297

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

298

Matrix models for size-structured populations: unrealistic fast growth or simply diffusion?  

PubMed

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 i to class i + 1, ? 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

299

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

NASA Astrophysics Data System (ADS)

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

Farooq, M.; Muslim, M.

2014-11-01

300

Local environment and density-dependent feedbacks determine population growth in a forest herb.  

PubMed

Linking spatial variation in environmental factors to variation in demographic rates is essential for a mechanistic understanding of the dynamics of populations. However, we still know relatively little about such links, partly because feedbacks via intraspecific density make them difficult to observe in natural populations. We conducted a detailed field study and investigated simultaneous effects of environmental factors and the intraspecific density of individuals on the demography of the herb Lathyrus vernus. In regression models of vital rates we identified effects associated with spring shade on survival and growth, while density was negatively correlated with these vital rates. Density was also negatively correlated with average individual size in the study plots, which is consistent with self-thinning. In addition, average plant sizes were larger than predicted by density in plots that were less shaded by the tree canopy, indicating an environmentally determined carrying capacity. A size-structured integral projection model based on the vital rate regressions revealed that the identified effects of shade and density were strong enough to produce differences in stable population sizes similar to those observed in the field. The results illustrate how the local environment can determine dynamics of populations and that intraspecific density may have to be more carefully considered in studies of plant demography and population viability analyses of threatened species. We conclude that demographic approaches incorporating information about both density and key environmental factors are powerful tools for understanding the processes that interact to determine population dynamics and abundances. PMID:25224800

Dahlgren, Johan P; Ostergård, Hannah; Ehrlén, Johan

2014-12-01

301

Avoid population growth to reduce water stress and food demand. Prof. Malin Falkenmark on water, food and population.  

PubMed

Global food security is closely linked to the overall availability of water. In some regions of the world, water scarcity will increasingly constrain crop production, forcing a dependency upon food imports. This problem will be particularly acute in dry-climate countries with rapid population growth. Water availability is therefore a fundamental condition for socioeconomic development which requires policymaker attention. Crops depend upon soil moisture and aquifers and rivers. Poor rainfalls and depleted aquifers threaten crop yields. The larger the population, the more water is needed for social and economic needs, including irrigation. However, water for irrigation competes with the water needs of households and industry. Recent research indicates that many dry-climate countries are moving farther away from the possibility of food self-sufficiency. These countries should study their comparative advantages to determine what to export in exchange for food imports from the sub-humid and humid regions of the world. Governments should also promote family planning and the small family norm with the goal of reducing water stress and food demand. PMID:12292040

1996-01-01

302

Spatial analysis of cattle and shoat population in Ethiopia: growth trend, distribution and market access.  

PubMed

The livestock subsector has an enormous contribution to Ethiopia's national economy and livelihoods of many Ethiopians. The subsector contributes about 16.5% of the national Gross Domestic Product (GDP) and 35.6% of the agricultural GDP. It also contributes 15% of export earnings and 30% of agricultural employment. The livestock subsector currently support and sustain livelihoods for 80% of all rural population. The GDP of livestock related activities valued at 59 billion birr. Ethiopian livestock population trends, distribution and marketing vary considerably across space and time due to a variety of reasons. This study was aimed to assess cattle and shoat population growth trend, distribution and their access to market. Regression analysis was used to assess the cattle and shoat population growth trend and Geographic Information Systems (GIS) techniques were used to determine the spatial distribution of cattle and shoats, and their relative access to market. The data sets used are agricultural census (2001/02) and annual CSA agricultural sample survey (1995/96 to 2012/13). In the past eighteen years, the livestock population namely cattle, sheep and goat grew from 54.5 million to over 103.5 million with average annual increment of 3.4 million. The current average national cattle, sheep and goat population per km(2) are estimated to be 71, 33 and 29 respectively (excluding Addis Ababa, Afar and Somali regions). From the total livestock population the country owns about 46% cattle, 43% sheep and 40% goats are reared within 10 km radius from major livestock market centres and all-weather roads. On the other hand, three fourth of the country's land mass which comprises 15% of the cattle, 20% of the sheep and 21% of goat population is not accessible to market (greater than 30 km from major livestock market centres). It is found that the central highland regions account for the largest share of livestock population and also more accessible to market. Defining the spatial and temporal variations of livestock population is crucial in order to develop a sound and geographically targeted livestock development policy. PMID:25019048

Leta, Samson; Mesele, Frehiwot

2014-01-01

303

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

PubMed

A proposed framework, which was introduced at the 1989 meetings of the American Association for the Advancement of Science, included political constraints as well as population growth as a proximate cause with potentially important impacts on the environment in Paul and Ann Ehrlich's well-known PAT equation. PAT limitations are identified as the 1.2 billion people caught in the debt-poverty trap, less developed countries' balance of payments deficits, and "distortionary factors" that undermined economic incentives and contributed to mismanagement of resources. Such factors could be keeping farm prices low and have an impact on deterring use of environmentally sound traditional agricultural practices. Mismanagement of public lands occurs when large commercial enterprises or large scale mechanization displace population onto marginal or less productive lands. Intergroup warfare is a new form impacting on the environment. In Burma loggers are authorized to clear cut large tracts of teak forests in order to ferret out Karen guerrillas. Over 15 million refugees were thus displaced and forced to live in encampments that require trees for shelter, firewood for survival, and overgrazing of livestock. Social and economic environments are also undermined by "dependency" factors such as trade protectionism, brain drain, and limited foreign aid. The Group of 77 Non-Aligned Developing Countries proposed that discussions of the links between population and the environment be omitted from the agenda of the 1994 UN Conference on Population and Development. Basic clarifications are needed to distinguish ultimate versus proximate factors and current versus future concerns. The debate ignores distribution patterns, migration, or changing age structures. The debate blames unjustifiably rapid population growth as the ultimate cause of global environmental degradation and links population growth to a host of other social problems such as famine and refugees, while ignoring civil unrest. The evidence suggests that population limitation will probably prevent environmental degradation in poor, resource constrained countries from getting worse. Resource conservation will remain unaffected. The World Bank proposes National Environmental Action Plans or the Cleaver Schreiber proposal for a "nexus strategy" for balancing food supply and population in Africa. PMID:12290504

Shaw, R P

1992-02-01

304

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

305

Light disappears rapidly (exponentially)  

E-print Network

#12;#12;#12;#12;Light disappears rapidly (exponentially) with depth At the same time, the color of the light shifts #12;#12;#12;#12;· Euphotic zone ­ plentiful light ­ 0-100 m (about) · Dysphotic zone ­ very, very little light ­ 100-1000 m (about) · Aphotic zone ­ no light ­ below 1000 m #12;Sunlight in Water

Kudela, Raphael M.

306

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

PubMed

China's population in 1993 was 1.18 billion, which makes it the most populous nation in the world. The Chinese population policy aims to control growth and improve the quality of human resources. Most Chinese recognize the need for family planning. Replacement level fertility has been achieved, because there are limited resources to support a large population. Scarce resources are limiting economic development. There has been a loss of arable land, and the dream of 2 hectares of land, a cow, a wife and children, and a comfortable bed are not attainable. Water resources are also limited, the ratio of water to arable land is unevenly balanced, and there is overdrawing of groundwater. Energy shortages, environmental pollution, and pressure on employment are other effects of population pressure. The surplus labor force is about 150-190 million farmering laborers. Labor productivity has declined due to excess labor. Projections are that 20-25% of employees are surplus, and unemployed in urban areas will total 10 million. Without a strong family planning program, there will be a rural labor surplus of 200-360 million people by the year 2000. One benefit of lower population growth is the savings in child-rearing expenses. Estimated births averted between 1971 and 1992 was about 250 million, which translates to a savings of $500 billion. About 66% of this sum would be recovered in the same period and 33% would be recovered between 1993-2007. Government and nongovernmental spending on family planning totaled an estimated $10 billion between 1971-92. The ratio of input to output for averted births is 1 to 17. Total spending would have been RMB 2500 billion yuan for child rearing of averted births between 1971-92 and RMB 1828 billion yuan between 1991-2005. The saved money could be invested in economic development. An estimated 10% of national income could be saved. Another benefit from low population growth is the increased consumption evident between 1971-90. There has not been any significant change in the employment pattern in China. Women have benefitted from smaller families and greater involvement in the work force. 689 poor counties were identified as needing assistance, which resulted in increased incomes. PMID:12318709

Jiang, Z; Zhang, L

1994-02-01

307

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

PubMed

The Third International UN Conference on Population and Development took place in Cairo in early September 1994 with the participation of 200 governments and 1000 nongovernmental organizations to discuss ways of stabilizing world population at the possible lowest level and how industrialized countries could contribute to this effort. As a consequence of the advances in reproductive medicine the use of contraceptives skyrocketed: in 1994 more than half of men and women were using contraception compared to only 5% in 1950. However, the demographic momentum would still increase world population for another 100 years, even if fertility would drop to 2.2 children per couple (compared to 4 children in 1990). Nevertheless, the present generation could be instrumental in deciding whether the world's population will remain around 8 billion or reach 12 billion between 2050 and 2150. Poor countries can no longer afford an annual growth rate of 2-4% while also trying to improve living standards; this would require an economic growth rate of 6-8%. For the control of population growth both a sustainable environmental policy in the North, with rapid transition to renewable energy and recycling, and a more effective population policy in the South are needed. Family planning (FP) is the precondition of stabilization. The global FP outlays are envisioned to double from the 1994 figure of $5 billion to over $10 billion in the year 2000, with donor contributions to increase from 20% to 40% of the total. The US contribution is to double from $500 million by 2000, while the European Commission decided to boost expenditures for FP from DM 30 million in 1994 to DM 600 million by 2000. Japan is also expending $3 billion during this period. Recent promising developments have emerged: national pronatalist policies have diminished sharply and the pronatalist influence of religions has also declined. Political commitment at the highest level is central to a successful population policy as demonstrated in Indonesia, Bangladesh, and Egypt, whereas its lack resulted in failures in Pakistan, Turkey, and Algeria. PMID:12290837

Rhein, E

1994-08-25

308

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

Nicolè, Florence; Jacquemyn, Hans; Tuljapurkar, Shripad

2013-01-01

309

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

PubMed

Evidence of inbreeding depression is commonly detected from the fitness traits of animals, yet its effects on population growth rates of endangered species are rarely assessed. We examined whether inbreeding depression was affecting Sierra Nevada bighorn sheep (Ovis canadensis sierrae), a subspecies listed as endangered under the U.S. Endangered Species Act. Our objectives were to characterize genetic variation in this subspecies; test whether inbreeding depression affects bighorn sheep vital rates (adult survival and female fecundity); evaluate whether inbreeding depression may limit subspecies recovery; and examine the potential for genetic management to increase population growth rates. Genetic variation in 4 populations of Sierra Nevada bighorn sheep was among the lowest reported for any wild bighorn sheep population, and our results suggest that inbreeding depression has reduced adult female fecundity. Despite this population sizes and growth rates predicted from matrix-based projection models demonstrated that inbreeding depression would not substantially inhibit the recovery of Sierra Nevada bighorn sheep populations in the next approximately 8 bighorn sheep generations (48 years). Furthermore, simulations of genetic rescue within the subspecies did not suggest that such activities would appreciably increase population sizes or growth rates during the period we modeled (10 bighorn sheep generations, 60 years). Only simulations that augmented the Mono Basin population with genetic variation from other subspecies, which is not currently a management option, predicted significant increases in population size. Although we recommend that recovery activities should minimize future losses of genetic variation, genetic effects within these endangered populations-either negative (inbreeding depression) or positive (within subspecies genetic rescue)-appear unlikely to dramatically compromise or stimulate short-term conservation efforts. The distinction between detecting the effects of inbreeding depression on a component vital rate (e.g., fecundity) and the effects of inbreeding depression on population growth underscores the importance of quantifying inbreeding costs relative to population dynamics to effectively manage endangered populations. PMID:22070275

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

2011-12-01

310

Local population extinction and vitality of an epiphytic lichen in fragmented old-growth forest.  

PubMed

The population dynamics of organisms living in short-lived habitats will largely depend on the turnover of habitat patches. It has been suggested that epiphytes, whose host plants can be regarded as habitat patches, often form such patch-tracking populations. However, very little is known about the long-term fate of epiphyte individuals and populations. We estimated life span and assessed environmental factors influencing changes in vitality, fertility, abundance, and distribution of the epiphytic lichen species Lobaria pulmonaria on two spatial scales, individual trees and forest patches, over a period of approximately 10 years in 66 old-growth forest fragments. The lichen had gone extinct from 7 of the 66 sites (13.0%) where it was found 10 years earlier, even though the sites remained unchanged. The risk of local population extinction increased with decreasing population size. In contrast to the decrease in the number of occupied trees and sites, the mean area of the lichen per tree increased by 43.0%. The number of trees with fertile ramets of L. pulmonaria increased from 7 (approximately 1%) to 61 (approximately 10%) trees, and the number of forest fragments with fertile ramets increased from 4 to 23 fragments. The mean annual rate of L. pulmonaria extinction at the tree level was estimated to be 2.52%, translating into an expected lifetime of 39.7 years. This disappearance rate is higher than estimated mortality rates for potential host trees. The risk of extinction at the tree level was significantly positively related to tree circumference and differed between tree species. The probability of presence of fertile ramets increased significantly with local population size. Our results show a long expected lifetime of Lobaria pulmonaria ramets on individual trees and a recent increase in vitality, probably due to decreasing air pollution. The population is, however, declining slowly even though remaining stands are left uncut, which we interpret as an extinction debt. PMID:20715632

Ockinger, Erik; Nilsson, Sven G

2010-07-01

311

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

PubMed Central

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

Freeland, Mark S.; Schendler, Carol Ellen

1983-01-01

312

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

PubMed Central

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

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

2011-01-01

313

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. PMID:25242830

Taylor, Marylee C.; Schroeder, Matthew B.

2014-01-01

314

Quadratic exponential vectors  

SciTech Connect

We give a necessary and sufficient condition for the existence of a quadratic exponential vector with test function in L{sup 2}(R{sup d}) intersection L{sup {infinity}}(R{sup d}). We prove the linear independence and totality, in the quadratic Fock space, of these vectors. Using a technique different from the one used by Accardi et al. [Quantum Probability and Infinite Dimensional Analysis, Vol. 25, p. 262, (2009)], we also extend, to a more general class of test functions, the explicit form of the scalar product between two such vectors.

Accardi, Luigi; Dhahri, Ameur [Volterra Center, University of Roma Tor Vergata, Via Columbia 2, 00133 Roma (Italy)

2009-12-15

315

Growth and population dynamic model for the non-zooxanthellate temperate solitary coral Leptopsammia pruvoti (Scleractinia, Dendrophylliidae)  

Microsoft Academic Search

In corals where complex life history processes decoupling age from size (e.g., fragmentation, fusion, partial colony mortality)\\u000a are rare or clearly detectable, individual age may be determined from size, and age-based growth and population dynamic models\\u000a may be applied. One example is the solitary Mediterranean coral Leptopsammia pruvoti Lacaze-Duthiers 1897, whose population size and structure, and growth rates were determined

Stefano Goffredo; Erik Caroselli; Guido Mattioli; Francesco Zaccanti

2010-01-01

316

Endogenous fertility, mortality and economic growth: Can a Malthusian framework account for the conflicting historical trends in population?  

Microsoft Academic Search

The 19th century economist Thomas Robert Malthus hypothesized that the long-run supply of labor is completely elastic at a fixed wage-income level because population growth tends to outstrip real output growth. Dynamic equilibrium with constant income and population is achieved through equilibrating adjustments in “positive checks” (mortality, starvation) and “preventive checks” (marriage, fertility). Developing economies since the Industrial Revolution, and

Isaac Ehrlich; Jinyoung Kim

2005-01-01

317

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

PubMed Central

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

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

2014-01-01

318

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

319

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

320

Exponential smoothing weighted correlations  

NASA Astrophysics Data System (ADS)

In many practical applications, correlation matrices might be affected by the "curse of dimensionality" and by an excessive sensitiveness to outliers and remote observations. These shortcomings can cause problems of statistical robustness especially accentuated when a system of dynamic correlations over a running window is concerned. These drawbacks can be partially mitigated by assigning a structure of weights to observational events. In this paper, we discuss Pearson's ? and Kendall's ? correlation matrices, weighted with an exponential smoothing, computed on moving windows using a data-set of daily returns for 300 NYSE highly capitalized companies in the period between 2001 and 2003. Criteria for jointly determining optimal weights together with the optimal length of the running window are proposed. We find that the exponential smoothing can provide more robust and reliable dynamic measures and we discuss that a careful choice of the parameters can reduce the autocorrelation of dynamic correlations whilst keeping significance and robustness of the measure. Weighted correlations are found to be smoother and recovering faster from market turbulence than their unweighted counterparts, helping also to discriminate more effectively genuine from spurious correlations.

Pozzi, F.; Di Matteo, T.; Aste, T.

2012-06-01

321

On Tractable Exponential Sums  

NASA Astrophysics Data System (ADS)

We consider the problem of evaluating certain exponential sums. These sums take the form sum_{x_1,x_2, ldots, x_n in {Z}_N } e^{2 ? i/N {f(x_1,x_2, ldots, x_n)} }, where each x i is summed over a ring ? N , and f(x 1, x 2,..., x n ) is a multivariate polynomial with integer coefficients. We show that the sum can be evaluated in polynomial time in n and logN when f is a quadratic polynomial. This is true even when the factorization of N is unknown. Previously, this was known for a prime modulus N. On the other hand, for very specific families of polynomials of degree ? 3 we show the problem is #P-hard, even for any fixed prime or prime power modulus. This leads to a complexity dichotomy theorem - a complete classification of each problem to be either computable in polynomial time or #P-hard - for a class of exponential sums. These sums arise in the classifications of graph homomorphisms and some other counting CSP type problems, and these results lead to complexity dichotomy theorems. For the polynomial-time algorithm, Gauss sums form the basic building blocks; for the hardness result we prove group-theoretic necessary conditions for tractability.

Cai, Jin-Yi; Chen, Xi; Lipton, Richard; Lu, Pinyan

322

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

323

Beaver-mediated methane emission: The effects of population growth in Eurasia and the Americas.  

PubMed

Globally, greenhouse gas budgets are dominated by natural sources, and aquatic ecosystems are a prominent source of methane (CH4) to the atmosphere. Beaver (Castor canadensis and Castor fiber) populations have experienced human-driven change, and CH4 emissions associated with their habitat remain uncertain. This study reports the effect of near extinction and recovery of beavers globally on aquatic CH4 emissions and habitat. Resurgence of native beaver populations and their introduction in other regions accounts for emission of 0.18-0.80 Tg CH4 year(-1) (year 2000). This flux is approximately 200 times larger than emissions from the same systems (ponds and flowing waters that became ponds) circa 1900. Beaver population recovery was estimated to have led to the creation of 9500-42 000 km(2) of ponded water, and increased riparian interface length of >200 000 km. Continued range expansion and population growth in South America and Europe could further increase CH4 emissions. PMID:25515021

Whitfield, Colin J; Baulch, Helen M; Chun, Kwok P; Westbrook, Cherie J

2015-02-01

324

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.

Parand, K; Taghavi, A; 10.1002/mma.1318

2010-01-01

325

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

2010-08-16

326

Numerical approximations for population growth model by rational Chebyshev and Hermite functions collocation approach: A comparison  

NASA Astrophysics Data System (ADS)

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.

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

2010-11-01

327

Programmable models of growth and mutation of cancer-cell populations  

E-print Network

In this paper we propose a systematic approach to construct mathematical models describing populations of cancer-cells at different stages of disease development. The methodology we propose is based on stochastic Concurrent Constraint Programming, a flexible stochastic modelling language. The methodology is tested on (and partially motivated by) the study of prostate cancer. In particular, we prove how our method is suitable to systematically reconstruct different mathematical models of prostate cancer growth - together with interactions with different kinds of hormone therapy - at different levels of refinement.

Bortolussi, Luca; 10.4204/EPTCS.67.4

2011-01-01

328

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

329

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

USGS Publications Warehouse

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

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

2009-01-01

330

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

331

Behavioural and growth differences between experienced and naive populations of a native crayfish in the presence of invasive rusty crayfish  

Microsoft Academic Search

SUMMARY 1. Species invasions are a leading threat to native species and ecosystems. How populations of native species respond to the presence of invasive species will ultimately determine their long-term persistence. 2. In this study, we capitalise on a unique opportunity to compare the behaviour and growth of naõ ¨ve and experienced virile crayfish (Orconectes virilis Hagen) populations in the

NICOLE M. H AYES; K ATRINA; J. B UTKAS; J ULIAN; D. O LDEN; M. J AKE V ANDER

2009-01-01

332

Population growth rate of a common understory herb decreases non-linearly across a gradient of deer herbivory  

E-print Network

populations of white-tailed deer (henceforth deer) throughout eastern North America (McCabe and McCabe, 1997 interactions Matrix model Tolerance A B S T R A C T Overabundant white-tailed deer (Odocoileus virginianusPopulation growth rate of a common understory herb decreases non-linearly across a gradient of deer

333

Age structure and growth pattern in two populations of the golden-striped salamander Chioglossa lusitanica (Caudata, Salamandridae)  

Microsoft Academic Search

We studied age structure and growth in two populations of the golden-striped salamander, Chioglossa lusitanica, in northern Portugal by cohort analysis and skeletochronology. Lines of Arrested Growth (LAG) deposited during the larval phase could be distinguished from LAG deposited after metamorphosis. One or two LAG were found in larvae, with counts corresponding to age in years as predicted from larval

V. Lima; J. W. Arntzen; N. M. Ferrand

2000-01-01

334

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

335

Modeling the effect of deregulated proliferation and apoptosis on the growth dynamics of epithelial cell populations in vitro.  

PubMed

We present a three-dimensional individual cell-based, biophysical model to study the effect of normal and malfunctioning growth regulation and control on the spatial-temporal organization of growing cell populations in vitro. The model includes explicit representations of typical epithelial cell growth regulation and control mechanisms, namely 1), a cell-cell contact-mediated form of growth inhibition; 2), a cell-substrate contact-dependent cell-cycle arrest; and 3), a cell-substrate contact-dependent programmed cell death (anoikis). The model cells are characterized by experimentally accessible biomechanical and cell-biological parameters. First, we study by variation of these cell-specific parameters which of them affect the macroscopic morphology and growth kinetics of a cell population within the initial expanding phase. Second, we apply selective knockouts of growth regulation and control mechanisms to investigate how the different mechanisms collectively act together. Thereby our simulation studies cover the growth behavior of epithelial cell populations ranging from undifferentiated stem cell populations via transformed variants up to tumor cell lines in vitro. We find that the cell-specific parameters, and in particular the strength of the cell-substrate anchorage, have a significant impact on the population morphology. Furthermore, they control the efficacy of the growth regulation and control mechanisms, and consequently tune the transition from controlled to uncontrolled growth that is induced by the failures of these mechanisms. Interestingly, however, we find the qualitative and quantitative growth kinetics to be remarkably robust against variations of cell-specific parameters. We compare our simulation results with experimental findings on a number of epithelial and tumor cell populations and suggest in vitro experiments to test our model predictions. PMID:15475585

Galle, Jörg; Loeffler, Markus; Drasdo, Dirk

2005-01-01

336

Joint effects of density and a growth inhibitor on the life history and population growth rate of the midge Chironomus riparius.  

PubMed

Results of previous laboratory studies suggest that high population density often buffers the effects of chemical stressors that predominately increase mortality. Mortality stressors act to release more resources for the survivors and, therefore, produce less-than-additive effects. By contrast, growth stressors are expected to have opposite results or more-than-additive effects. We investigated the effects of a growth inhibitor (lufenuron) on larval growth and survival of Chironomus riparius and examined its joint effects with density on population growth rate (PGR). Exposure to 60 microg/kg sediment or greater inhibited larval growth, and exposure to 88 microg/kg or greater often resulted in mortality before reaching emergence. The effects of lufenuron, however, differed with population density. At 88 microg/kg, mortalities and, to a lesser extent, reduced fecundity resulted in a reduction in PGR at low density. Conversely, when populations were initiated at high density, PGR was similar to that of controls, because the few survivors reached maturity sooner and started producing offspring earlier. The effect of density as a growth stressor therefore was stronger than the effect of lufenuron, which had effects similar to those of a mortality stressor and produced less-than-additive effects. Long-term studies under field conditions, however, are needed before less-than-additive effects are considered to be the norm. PMID:16110992

Hooper, Helen L; Sibly, Richard M; Hutchinson, Thomas H; Maund, Stephen J

2005-05-01

337

Water scarcity in the tropical Andes: population growth outweighs climate change  

NASA Astrophysics Data System (ADS)

Globally, water resources for cities are under increasing stress. Two main stressors are climate change and population growth, but evaluating their relative impact is difficult, especially because of the complex topology of water supply. This is especially true in the tropical Andes, which is a region with strong climatic gradients and topographical limits to water resources. In this study we present an evaluation of both stressors on water resources in a geospatial framework to identify gradients in water availability that may lead to conflicts over water use. We focus on 4 major cities in, or receiving water from the tropical Andes. A multi-model dataset of 19 climate models is used as input for a regional water balance model. Per capita water availability is evaluated along topographic gradients for the present, and for future scenarios of population growth and climate change. In all cases, the median projection of climate change suggests a relatively limited impact on water availability but uncertainties are large. Despite these uncertainties, we find that the expected demographic changes are very likely to outpace the impact of climate change on water availability and should therefore be the priority for local policy making. However, distinctive geospatial patterns characterize the supply systems of the studied cities, highlighting the need to analyse the topology of water supply within an ecosystem services context. Our approach is flexible enough to be extended to other regions, stressors and water resources topologies.

Buytaert, W.; De Bièvre, B.

2012-12-01

338

In situ growth rates and biofilm development of Pseudomonas aeruginosa populations in chronic lung infections.  

PubMed

The growth dynamics of bacterial pathogens within infected hosts are a fundamental but poorly understood feature of most infections. We have focused on the in situ distribution and growth characteristics of two prevailing and transmissible Pseudomonas aeruginosa clones that have caused chronic lung infections in cystic fibrosis (CF) patients for more than 20 years. We used fluorescence in situ hybridization (FISH) directly on sputum specimens to examine the spatial distribution of the infecting P. aeruginosa cells. Mucoid variants were present in sputum as cell clusters surrounded by an extracellular matrix, whereas nonmucoid variants were present mainly as dispersed cells. To obtain estimates of the growth rates of P. aeruginosa in CF lungs, we used quantitative FISH to indirectly measure growth rates of bacteria in sputum samples (reflecting the in vivo lung conditions). The concentration of rRNA in bacteria isolated from sputa was measured and correlated with the rRNA contents of the same bacteria growing in vitro at defined rates. The results showed that most cells were actively growing with doubling times of between 100 and 200 min, with some growing even faster. Only a small stationary-phase subpopulation seemed to be present in sputa. This was found for both mucoid and nonmucoid variants despite their different organizations in sputum. The results suggest that the bacterial population may be confronted with selection forces that favor optimized growth activities. This scenario constitutes a new perspective on the adaptation and evolution of P. aeruginosa during chronic infections in CF patients in particular and on long-term infections in general. PMID:18156255

Yang, Lei; Haagensen, Janus A J; Jelsbak, Lars; Johansen, Helle Krogh; Sternberg, Claus; Høiby, Niels; Molin, Søren

2008-04-01

339

Genetic diversity of different populations and improved growth in the F1 hybrids in the swimming crab (Portunus trituberculatus).  

PubMed

The swimming crab, Portunus trituberculatus, is widely distributed throughout the coastal waters of Asian-Pacific nations and is an important economic species in this region. The aquaculture of swimming crabs has been plagued by problems associated with low growth rates, poor flesh quality, and weak disease resistance. To overcome these problems, selective breeding programs have been suggested as a means of genetically improving these traits in stock populations. In this study, we evaluated the genetic differentiation of 3 different geographical populations (Zhoushan: S; Laizhou Bay: L; and Haizhou Bay: H) using 8 polymorphic microsatellite loci. Nine strains of first filial generation were obtained, with 3 geographically populations as parental stock. We assessed the growth and survival rates of the F1 generation to identify new strains or breeds showing improvements in these economically important traits. Our results indicated that pairwise FST among populations was significantly higher than 0 (P = 0.0000) for every population pair, ranging from 0.0810 to 0.1083 for 3 different geographical populations. We observed significant heterosis for the growth and viability (survival) traits, although some strains (crossbred combinations) showed evidence of hybrid weakness in some growth measurements. One particular strain ("SL") outperformed other combinations, displaying the greatest extent of heterosis over the growth and viability (survival) traits. These results indicate that hybridization may be used to increase the performance of P. trituberculatus in aquaculture. PMID:25511029

Gao, B Q; Liu, P; Li, J; Wang, Q Y; Li, X P

2014-01-01

340

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

341

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

342

Population.  

ERIC Educational Resources Information Center

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

King, Pat; Landahl, John

343

Phase Space Interpretation of Exponential Fermi Acceleration  

E-print Network

Recently, the occurrence of exponential Fermi acceleration has been reported in a rectangular billiard with an oscillating bar inside [K. Shah, D. Turaev, and V. Rom-Kedar, Phys. Rev. E {\\bf 81}, 056205 (2010)]. In the present work, we analyze the underlying physical mechanism and show that the phenomenon can be understood as a sequence of highly correlated motions, consisting of alternating phases of free propagation and motion along the invariant spanning curves of the well-known one-dimensional Fermi-Ulam model. The key mechanism for the occurrence of exponential Fermi acceleration can be captured in a random walk model in velocity space with step width proportional to the velocity itself. The model reproduces the occurrence of exponential Fermi acceleration and provides a good ab initio prediction of the value of the growth rate including its full parameter-dependency. Our analysis clearly points out the requirements for exponential Fermi acceleration, thereby opening the perspective of finding other systems exhibiting this unusual behaviour.

Benno Liebchen; Robert Büchner; Christoph Petri; Fotis K. Diakonos; Florian Lenz; Peter Schmelcher

2011-07-18

344

Somatic growth of a school-aged population from Mozambique: trend and biosocial meaning.  

PubMed

A cross-sectional study of children and adolescents from Maputo, Mozambique, was carried out in order to (1) describe the current growth status of children and adolescents from Maputo, (2) evaluate the relative status of the growth and development of youth from Maputo compared to WHO international standards, (3) assess the relationship between socioeconomic status and growth and development, and (4) assess the impact that the civil war (1980-1992) had on the health status of children and adolescents living in Maputo. The sample is composed of 2,271 subjects (1,098 boys and 1,173 girls), age 6 to 17 years. Somatic measures included height, weight, and skinfold thicknesses from which nutritional indicators were calculated and plotted against WHO norms. Subjects were divided into three groups according to their socioeconomic status. Data from a cross-sectional study done in the same areas in 1992 was used to analyze the impact of war. Beginning at 11 years, Maputo students are always shorter and weigh less than the WHO standards. BMI in boys from 11 years and in girls from 12 years is somewhat lower than the WHO norms. A social gradient is evident, favoring those students with higher socioeconomic status. Height, weight, BMI, fat mass, and lean body mass are always higher in the 1999 sample than in the 1992 study. We conclude that (1) there is a substantial difference in height and weight values of Maputo children and adolescents compared to WHO standards; (2) there is a clear advantage of being of higher socioeconomic status; (3) socioeconomic status, hygiene, and sanitation are the main factors responsible for the greater values of the 1999 sample; and (4) differences between the stature of students with higher socioeconomic status and the WHO norms are almost irrelevant. This last aspect reveals the importance of socioeconomic factors in determining the growth process, implying its importance in facilitating the "expression" of the genotypes available in the population. PMID:16485776

Prista, A; Maia, A J R; Saranga, S; Nhantumbo, L; Marques, A T; Beunen, G

2005-08-01

345

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

346

Euler's number II: Complex exponentials  

NSDL National Science Digital Library

We express the exponential function of an imaginary variable in terms of sine and cosine. The "complex exponentials" that result trace out a circle in the complex plane. Pointing to one of the positions in the complex plane, we obtain the identity exp(i pi) = -1.

2013-06-21

347

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

348

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

349

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.

MIT BLOSSOMS

2012-06-03

350

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

351

Effect of Portulaca oleracea extracts on growth performance and microbial populations in ceca of broilers.  

PubMed

The aim of this study was to investigate the effects of Portulaca oleracea extracts on growth performance and microbial populations in the ceca of broilers. A total of 120 one-day-old broilers were randomly divided into 3 groups. Portulaca oleracea extracts were added to diets at 0.2 and 0.4% (wt/wt; POL-0.2, POL-0.4), respectively. The control (CON) group was administered with no P. oleracea extract supplementation. Body weight gain and feed conversion ratio were recorded every 2 wk. On d 28 and 42, the cecal contents were collected and assayed for Escherichia coli, Lactobacillus, and Bifidobacterium populations. Additionally, the pH of the ileum and cecum was measured. The results showed that both on d 28 and 42 BW gain of P. oleracea extract supplementation groups was significantly higher, whereas the feed conversion ratio was lower (P < 0.05) compared with CON. On d 28 and 42, significantly (P < 0.05) fewer E. coli were recovered from ceca of broilers provided with the POL-0.2 diet than from broilers provided with the control diet. The quantities of Lactobacillus and Bifidobacterium of POL-0.2 were significantly (P < 0.05) higher than CON. Results showed P. oleracea extracts have no distinct influence on intestinal pH. These data suggest that P. oleracea extract supplementation significantly altered the cecal bacterial community without affecting the intestinal pH. PMID:23571345

Zhao, X H; He, X; Yang, X F; Zhong, X H

2013-05-01

352

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

PubMed Central

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

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

1982-01-01

353

Involvement of fibroblast growth factor receptor genes in benign prostate hyperplasia in a Korean population.  

PubMed

Fibroblast growth factors (FGFs) and their receptors (FGFRs) have been implicated in prostate growth and are overexpressed in benign prostatic hyperplasia (BPH). In this study, we investigated whether single nucleotide polymorphisms (SNPs) of the FGFR genes (FGFR1 and FGFR2) were associated with BPH and its clinical phenotypes in a population of Korean men. We genotyped four SNPs in the exons of FGFR1 and FGFR2 (rs13317 in FGFR1; rs755793, rs1047100, and rs3135831 in FGFR2) using direct sequencing in 218 BPH patients and 213 control subjects. No SNPs of FGFR1 or FGFR2 genes were associated with BPH. However, analysis according to clinical phenotypes showed that rs1047100 of FGFR2 was associated with prostate volume in BPH in the dominant model (GA/AA versus GG, P = 0.010). In addition, a significant association was observed between rs13317 of FGFR1 and international prostate symptom score (IPSS) in the additive (TC versus CC versus TT, P = 0.0022) and dominant models (TC/CC versus TT, P = 0.005). Allele frequency analysis also showed significant association between rs13317 and IPSS (P = 0.005). These results suggested that FGFR genes could be related to progression of BPH. PMID:24385678

Park, Hae Jeong; Kim, Su Kang; Kim, Jong Woo; Lee, Sang Hyub; Yoo, Koo Han; Chung, Joo-Ho

2013-01-01

354

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

355

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

356

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

SciTech Connect

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

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

2000-03-01

357

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

PubMed Central

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

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

2011-01-01

358

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

PubMed Central

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

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

2015-01-01

359

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

PubMed

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

Suh, S H

1987-01-01

360

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

PubMed Central

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

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

2013-01-01

361

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

362

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

363

Insulin-like Growth Factors and Prostate Cancer: A Population-based Case-Control Study in China  

Microsoft Academic Search

Abstract Insulin-like growth factors (IGFs) have potent mitogenic and antiapoptotic effects on prostate epithelial cells. Through modulation of IGF bioactivity and other mechanisms, IGF-binding proteins (IGFBPs) also have growth-regulatory effects on prostate cells. Recently, IGF-I and IGFBP-3 have been implicated in prostate cancer risk among,Western populations. To assess whether IGF-I, IGF-II, IGFBP-1, or IGFBP-3 are also associated with prostate cancer

Anand P. Chokkalingam; Michael Pollak; Capri-mara Fillmore; Yu-tang Gao; Frank Z. Stanczyk; Jie Deng; Isabell A. Sesterhenn; F. Kash Mostofi; Thomas R. Fears; M. Patricia Madigan; Regina G. Ziegler; Joseph F. Fraumeni; Ann W. Hsing

2001-01-01

364

Long-term climate-related changes in somatic growth and population dynamics of Hokkaido chum salmon  

Microsoft Academic Search

We used multiple regression and path analysis to examine the effects of regional and larger spatial scales of climatic\\/oceanic\\u000a conditions on the growth, survival, and population dynamics of Hokkaido chum salmon (Oncorhynchus keta). Variability in the growth of chum salmon at ages 1 to 4 was estimated from scale analysis and the back-calculation method\\u000a using scales of 4-year-old adults returning

Hyunju Seo; Hideaki Kudo; Masahide Kaeriyama

2011-01-01

365

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

PubMed

We studied the effects of temperature and relative humidity on population growth and development of the psocid Liposcelis brunnea Motschulsky. L. brunnea did not survive at 43% RH, but populations increased from 22.5 to 32.5 degrees C and 55-75% RH. Interestingly, we found population growth was higher at 63% RH than at 75% RH, and the greatest population growth was recorded at 32.5 degrees C and 63% RH. At 35 degrees C, L. brunnea nymphal survivorship was 33%, and populations declined or barely grew. L. brunnea males have two to four nymphal instars, and the percentages of males with two, three, and four instars were 13, 82, and 5%, respectively. Female L. brunnea have three to five instars, and the percentages of females with three, four, and five instars were 18, 78, and 4%, respectively. The life cycle was shorter for males than females. We developed temperature-dependent development equations for male and female eggs, individual nymphal, combined nymphal, and combined immature stages and nymphal survivorship. The ability of L. brunnea to multiply rather rapidly at 55% RH may allow it to thrive under conditions of low relative humidity where other Liposcelis species may not. These data give us a better understanding of L. brunnea population dynamics and can be used to help develop effective management strategies for this psocid. PMID:19610458

Opit, G P; Throne, J E

2009-06-01

366

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

367

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

PubMed Central

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

Sargent, Lindsey W; Lodge, David M

2014-01-01

368

Implications of Unequal Rates of Population Growth for Trade Revisited : Lessons from Closed Form Solutions to an Overlapping Generations General Equilibrium Model under Autarky and Trade Scenarios  

Microsoft Academic Search

We study closed form solutions that we obtained from a two-sector, two-factor overlap- ping generations model under autarky and free trade scenarios for ana la Heckscher-Ohlin exploration of the possible implications of population growth dierentials for the patterns of trade flows between economies that are identical except for population growth rates. Our analysis shows that dierences in population growth rates

Mohamed Mehdi Jelassi; Serdar Sayan

2004-01-01

369

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

USGS Publications Warehouse

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

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

2014-01-01

370

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

371

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

PubMed

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

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

2014-10-01

372

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

NASA Astrophysics Data System (ADS)

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

Prisniakov, Vladimir

2002-01-01

373

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

Technology Transfer Automated Retrieval System (TEKTRAN)

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

374

Fish growth and degree-days I: selecting a base temperature for a within-population study  

E-print Network

ARTICLE Fish growth and degree-days I: selecting a base temperature for a within-population study Kyle A. Chezik, Nigel P. Lester, and Paul A. Venturelli Abstract: Degree-days (DD) are an increasingly energy that an ectotherm has experienced can be quantified using a degree-day approach (also known

Venturelli, Paul

375

Age, Growth, and Mortality of Introduced Flathead Catfish in Atlantic Rivers and a Review of Other Populations  

E-print Network

age ranged from 5 years in the Neosho River, Kansas (Minckley and Deacon 1959), to 28 years populations; the maximum reported length was 1,118 mm from a fish captured in the Kansas River, Kansas (CrossAge, Growth, and Mortality of Introduced Flathead Catfish in Atlantic Rivers and a Review of Other

Kwak, Thomas J.

376

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

377

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

ERIC Educational Resources Information Center

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

Bartlett, Albert A.

1996-01-01

378

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.

379

Is radioactive decay really exponential?  

NASA Astrophysics Data System (ADS)

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 12550 years by comparing radiocarbon dates with dates obtained from dendrochronology. It is well known that this approach shows that radiocarbon dates of over 3000 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.

Aston, P. J.

2012-03-01

380

Using a population growth model to simulate response of Plodia interpunctella Hübner populations to timing and frequency of insecticide treatments  

Technology Transfer Automated Retrieval System (TEKTRAN)

Management strategies for urban and stored-product pests are chosen for a variety of attributes including cost, efficacy and human safety. Low-risk alternatives to traditional neurotoxic insecticides, such as insect growth regulators, may be valuable management options. However, as these products be...

381

Vascular endothelial growth factor gene polymorphisms in age-related macular degeneration in a Turkish population  

PubMed Central

AIM To assess the association between age-related macular degeneration (AMD) and three single nucleotide polymorphisms (SNPs) related to the vascular endothelial growth factor (VEGF) gene. METHODS The patients who were diagnosed with AMD were included in this prospective study. Three SNPs (rs1413711, rs2146323, and rs3025033) of the VEGF gene were genotyped by real-time polymerase chain reaction in the genomic DNA isolated from peripheral blood samples of the 82 patients and 80 controls. RESULTS The genotype frequencies of rs1413711 and rs2146323 were not significantly different between the study group and the control group (P=0.072 and P=0.058). However, there was a significant difference in the genotype frequencies of these SNPs between the wet type AMD and dry type AMD (P=0.005 and P=0.010, respectively). One of the SNPs (rs1413711) was also found to be associated with the severity of AMD (P=0.001) with significant genotype distribution between early, intermediate, and advanced stages of the disease. The ancestral alleles were protective for both SNPs while the polymorphic alleles increased the risk for dry AMD. CONCLUSION VEGF SNPs rs1413711 and rs2146323 polymorphisms are significantly associated with AMD subtypes in our population. PMID:25349791

Bulgu, Yunus; Cetin, Gokhan Ozan; Caner, Vildan; Cetin, Ebru Nevin; Yaylali, Volkan; Yildirim, Cem

2014-01-01

382

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

PubMed Central

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

Fuller, Amy C.; Harhay, Michael O.

2011-01-01

383

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

USGS Publications Warehouse

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

Obedzinski, M.; Letcher, B.H.

2004-01-01

384

People and environment: what is the relationship between exploitation of natural resources and population growth in the South?  

PubMed

This article reviews the nature and scale of the problems between natural resource management (NRM), agricultural productivity, and population growth in developing countries. It suggests a framework for examining the dynamics of land quality change, and reviews the evidence on land management under population pressure in tropical hillside areas and suggests some lessons learned for policy development. The evidence suggests that the effect of population on land quality is unknown; it depends upon economic and institutional factors. Aggregate data obscures the dynamics of change. There are four distinct patterns of land use changes with different market, population, and agro-environmental conditions: irrigated lands, high potential rain-fed lands, long-settled marginal lands, and frontier marginal lands. Sustainable NRM and strategies of agricultural development vary with population and market growth in these four areas. Currently 50% of the poorest people live on marginal lands. When countries and regions are more dependent upon marginal lands for food production, the key environmental issues are devegetation, nutrient depletion, and erosion. The 1997 Templeton and Scheer review examined 150 studies that focused on land use, intensity, and quality under forest, crops, and pastures in hilly-mountainous areas. Studies suggest that many hill and mountain areas could sustain high production levels without excessive resource degradation, depending upon the impact of microeconomic incentives on choice of production systems. Local populations cannot cope with the challenge of sustainable intensification without supportive policy and institutions. PMID:12321782

Scherr, S J

1997-01-01

385

Growth rates in outbreak populations of the corallivorous gastropod Drupella cornus (Röding 1798) at Ningaloo Reef, Western Australia  

NASA Astrophysics Data System (ADS)

Mark and recapture experiments were used to estimate the size-at-age relationship of the coral-eating gastropod Drupella cornus at Ningaloo Reef, Western Australia. Animals 15 mm long increased in length by 5.2 mm in six months at a site in an early stage of an outbreak, but by only 3.8 mm at a site within an established outbreak. Snails larger than 35 mm grew very little. Based on observed growth rates fitted to a Richards function growth equation, snails 28 mm long judged to be reproductively mature would be 2.5 to 3.5 years old, suggesting that local outbreaks represent no more than one or two generations of recruits. Indirect evidence indicates that growth is more rapid in the earlier than in later stages of outbreaking populations. The growth and timing of life-history transitions of D. cornus are not unusual among other muricid species.

Black, R.; Johnson, M. S.

1994-07-01

386

Plasticity in reproduction and growth among 52 range-wide populations of a Mediterranean conifer: adaptive responses to environmental stress.  

PubMed

A plastic response towards enhanced reproduction is expected in stressful environments, but it is assumed to trade off against vegetative growth and efficiency in the use of available resources deployed in reproduction [reproductive efficiency (RE)]. Evidence supporting this expectation is scarce for plants, particularly for long-lived species. Forest trees such as Mediterranean pines provide ideal models to study the adaptive value of allocation to reproduction vs. vegetative growth given their among-population differentiation for adaptive traits and their remarkable capacity to cope with dry and low-fertility environments. We studied 52 range-wide Pinus halepensis populations planted into two environmentally contrasting sites during their initial reproductive stage. We investigated the effect of site, population and their interaction on vegetative growth, threshold size for female reproduction, reproductive-vegetative size relationships and RE. We quantified correlations among traits and environmental variables to identify allocation trade-offs and ecotypic trends. Genetic variation for plasticity was high for vegetative growth, whereas it was nonsignificant for reproduction. Size-corrected reproduction was enhanced in the more stressful site supporting the expectation for adverse conditions to elicit plastic responses in reproductive allometry. However, RE was unrelated with early reproductive investment. Our results followed theoretical predictions and support that phenotypic plasticity for reproduction is adaptive under stressful environments. Considering expectations of increased drought in the Mediterranean, we hypothesize that phenotypic plasticity together with natural selection on reproductive traits will play a relevant role in the future adaptation of forest tree species. PMID:23944274

Santos-Del-Blanco, L; Bonser, S P; Valladares, F; Chambel, M R; Climent, J

2013-09-01

387

Population mixture model for nonlinear telomere dynamics  

NASA Astrophysics Data System (ADS)

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

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

2008-12-01

388

Life cycle and population growth rate of Caenorhabditis elegans studied by a new method  

PubMed Central

Background The free-living nematode Caenorhabditis elegans is the predominant model organism in biological research, being used by a huge number of laboratories worldwide. Many researchers have evaluated life-history traits of C. elegans in investigations covering quite different aspects such as ecotoxicology, inbreeding depression and heterosis, dietary restriction/supplement, mutations, and ageing. Such traits include juvenile growth rates, age at sexual maturity, adult body size, age-specific fecundity/mortality, total reproduction, mean and maximum lifespan, and intrinsic population growth rates. However, we found that in life-cycle experiments care is needed regarding protocol design. Here, we test a recently developed method that overcomes some problems associated with traditional cultivation techniques. In this fast and yet precise approach, single individuals are maintained within hanging drops of semi-fluid culture medium, allowing the simultaneous investigation of various life-history traits at any desired degree of accuracy. Here, the life cycles of wild-type C. elegans strains N2 (Bristol, UK) and MY6 (Münster, Germany) were compared at 20°C with 5 × 109 Escherichia coli ml-1 as food source. Results High-resolution life tables and fecundity schedules of the two strains are presented. Though isolated 700 km and 60 years apart from each other, the two strains barely differed in life-cycle parameters. For strain N2 (n = 69), the intrinsic rate of natural increase (rmd-1), calculated according to the Lotka equation, was 1.375, the net reproductive rate (R0) 291, the mean generation time (T) 90 h, and the minimum generation time (Tmin) 73.0 h. The corresponding values for strain MY6 (n = 72) were rm = 1.460, R0 = 289, T = 84 h, and Tmin = 67.3 h. Peak egg-laying rates in both strains exceeded 140 eggs d-1. Juvenile and early adulthood mortality was negligible. Strain N2 lived, on average, for 16.7 d, while strain MY6 died 2 days earlier; however, differences in survivorship curves were statistically non-significant. Conclusion We found no evidence that adaptation to the laboratory altered the life history traits of C. elegans strain N2. Our results, discussed in the light of earlier studies on C. elegans, demonstrate certain advantages of the hanging drop method in investigations of nematode life cycles. Assuming that its reproducibility is validated in further studies, the method will reduce the inter-laboratory variability of life-history estimates and may ultimately prove to be more convenient than the current standard methods used by C. elegans researchers. PMID:19445697

Muschiol, Daniel; Schroeder, Fabian; Traunspurger, Walter

2009-01-01

389

Non-linearity and heterogeneity in modeling of population dynamics.  

PubMed

The study of population growth reveals that the behaviors that follow the power law appear in numerous biological, demographical, ecological, physical and other contexts. Parabolic models appear to be realistic approximations of real-life replicator systems, while hyperbolic models were successfully applied to problems of global demography and appear relevant in quasispecies and hypercycle modeling. Nevertheless, it is not always clear why non-exponential growth is observed empirically and what possible origins of the non-exponential models are. In this paper the power equation is considered within the frameworks of inhomogeneous population models; it is proven that any power equation describes the total population size of a frequency-dependent model with Gamma-distributed Malthusian parameter. Additionally, any super-exponential equation describes the dynamics of inhomogeneous Malthusian density-dependent population model. All statistical characteristics of the underlying inhomogeneous models are computed explicitly. The results of this analysis show that population heterogeneity can be a reasonable explanation for power law accurately describing total population growth. PMID:25262656

Karev, Georgy P

2014-12-01

390

Population structure, sex ratio and growth of the seabob shrimp Xiphopenaeus kroyeri (Decapoda, Penaeidae) from coastal waters of southern Brazil  

PubMed Central

Abstract This study evaluated the growth and population structure of Xiphopenaeus kroyeri in Babitonga Bay, southern Brazil. Monthly trawls were conducted from July 2010 through June 2011, using a shrimp boat outfitted with double-rig nets, at depths from 5 to 17 m. Differences from the expected 0.5 sex ratio were determined by applying a Binomial test. A von Bertalanffy growth model was used to estimate the individual growth, and longevity was calculated using its inverted formula. A total of 4,007 individuals were measured, including 1,106 juveniles (sexually immature) and 2,901 adults. Females predominated in the larger size classes. Males and females showed asymptotic lengths of 27.7 mm and 31.4 mm, growth constants of 0.0086 and 0.0070 per day, and longevities of 538 and 661 days, respectively. The predominance of females in larger size classes is the general rule in species of Penaeidae. The paradigm of latitudinal-effect does not appear to apply to seabob shrimp on the southern Brazilian coast, perhaps because of the small proportion of larger individuals, the occurrence of cryptic species, or the intense fishing pressure in this region. The longevity values are within the general range for species of Penaeidae. The higher estimates for longevity in populations at lower latitudes may have occurred because of the growth constants observed at these locations, resulting in overestimation of this parameter.

Grabowski, Raphael Cezar; Simões, Sabrina Morilhas; Castilho, Antonio Leão

2014-01-01

391

Analysis of growth rate effects on productivity on recombinant Escherichia coli populations using molecular mechanism models  

Microsoft Academic Search

The influence of growth rate on Escherichia coli plasmid content and expression of a cloned-gene product has been described by a mathematical model based upon the molecular mechanism of lambdadv plasmid replication and known relationships between growth rate and transcription and translation activities of the host cell. The model simulates correctly decreases in plasmid content with increasing growth rate as

Sun Bok Lee; James E. Bailey

1984-01-01

392

Population demographics of catostomids in large river ecosystems: effects of discharge and temperature on recruitment dynamics and growth  

USGS Publications Warehouse

Catostomids are among the most widespread and ecologically important groups of fishes in North America, particularly in large river systems. Despite their importance, little information is available on their population demographics and even less is known about factors influencing their population dynamics. The objectives of this study were to describe annual mortality, recruitment variation, and growth of eight catostomid species, and to evaluate the effects of discharge and temperature on year-class strength and growth in Iowa rivers. Catostomids were sampled from 3-km reaches in four nonwadable rivers during June–August 2009. Northern hogsucker, Hypentelium nigricans, golden redhorse, Moxostoma erythrurum, and shorthead redhorse, M. macrolepidotum, typically lived 6–8 years, had very stable recruitment, and had high total annual mortality (i.e., 40–60%). Golden redhorse exhibited the fastest growth of all species. Growth of northern hogsucker and shorthead redhorse was intermediate to the other catostomids. Highfin carpsucker, Carpiodes velifer, quillback, Carpiodes cyprinus, and white sucker, Catostomus commersonii, had high growth rates, low mortality (i.e., 25–30%), and relatively stable recruitment. River carpsucker, Carpiodes carpio, and silver redhorse, M. anisurum, had higher maximum ages (up to age 11), slower growth, lower total annual mortality (20–25%), and higher recruitment variability than the other species. Neither discharge nor temperature was strongly related to recruitment of catostomids. In contrast, several interesting patterns were observed with regard to growth. Species (e.g., carpsuckers, Carpiodes spp.) that typically consume prey items most common in fine substrates (e.g., chironomids) had higher growth rates in reaches dominated by sand and silt substrate. Species (e.g., northern hogsucker) that consume prey associated with large substrates (e.g., plecopterans) had much faster growth in reaches with a high proportion of rocky substrates. Temperature was weakly related to growth of catostomids; however, discharge explained a substantial amount of the variation in growth of nearly all species. Results of this study provide important information on the autecology of catostomids that can be used for comparison among species and systems. These data also suggest that connection of rivers with their floodplain is an important feature for catostomids in temperate river systems.

Quist, M.C.; Spiegel, J.R.

2011-01-01

393

Effects of salinity on survival, growth, reproductive and life span characteristics of Artemia populations from Urmia Lake and neighboring lagoons.  

PubMed

This study deals with effects of different salinities on the survival, growth, reproductive and lifespan characteristics of three Artemia populations from Urmia Lake and small lagoons at the vicinity of the lake under laboratory conditions. Experimental salinities ranged from 75 to 175 g L(-1). Salinity was proved to have significant impact on the majority of the characters studied in this survey. Growth and survival in bisexual A. urmiana and parthenogenetic Artemia from Lake Urmia were significantly higher with respect to the parthenogenetic Artemia from lagoons at most of the salinities tested. Reproductive characteristics such as total number of broods, total offspring number of offspring in each brood and number of offspring at each day of reproductive period reduced with increasing salinity. Moreover higher salinity prolonged the prereproductive period but shortened the total reproductive period. Higher salinities also affected the percentage of encystment and post-reproductive period, showing significantly higher values in parthenogenetic populations in comparison to bisexual A. urmiana. PMID:18817185

Agh, N; Van Stappen, G; Bossier, P; Sepehri, H; Lotfi, V; Rouhani, S M Razavi; Sorgeloos, P

2008-01-15

394

In a long-term experimental demography study, excluding ungulates reversed invader's explosive population growth rate and restored natives.  

PubMed

A major goal in ecology is to understand mechanisms that increase invasion success of exotic species. A recent hypothesis implicates altered species interactions resulting from ungulate herbivore overabundance as a key cause of exotic plant domination. To test this hypothesis, we maintained an experimental demography deer exclusion study for 6 y in a forest where the native ungulate Odocoileus virginianus (white-tailed deer) is overabundant and Alliaria petiolata (garlic mustard) is aggressively invading. Because population growth is multiplicative across time, we introduce metrics that correctly integrate experimental effects across treatment years, the cumulative population growth rate, ?c, and its geometric mean, ?per-year, the time-averaged annual population growth rate. We determined ?c and ?per-year of the invader and of a common native, Trillium erectum. Our results conclusively demonstrate that deer are required for the success of Alliaria; its projected population trajectory shifted from explosive growth in the presence of deer (?per-year = 1.33) to decline toward extinction where deer are excluded (?per-year = 0.88). In contrast, Trillium's ?per-year was suppressed in the presence of deer relative to deer exclusion (?per-year = 1.04 vs. 1.20, respectively). Retrospective sensitivity analyses revealed that the largest negative effect of deer exclusion on Alliaria came from rosette transitions, whereas the largest positive effect on Trillium came from reproductive transitions. Deer exclusion lowered Alliaria density while increasing Trillium density. Our results provide definitive experimental support that interactions with overabundant ungulates enhance demographic success of invaders and depress natives' success, with broad implications for biodiversity and ecosystem function worldwide. PMID:24616522

Kalisz, Susan; Spigler, Rachel B; Horvitz, Carol C

2014-03-25

395

Annual shoot growth in different populations of Lonicera involucrata collected in North America and grown in Norway  

Microsoft Academic Search

Seeds were collected from shrubs and brushwood of Lonicera involucrata (Rich.) Banks ex K. Spreng. in coastal Oregon (44–45° N) and interior British Columbia (54–55° N). The annual shoot growth of the resulting half-sib families and populations was studied in Ås, Norway (60° N). The move of these locally adapted types to a new environment revealed the great genetic variation

Johanna L. F. Erstad

1991-01-01

396

Changes in Population, Growth, and Physiological Indices of Longnose Dace ( Rhinichthys cataractae ) in the Red Deer River, Alberta, Canada  

Microsoft Academic Search

The Red Deer River, Alberta, Canada is a prairie river that is impacted by the point-source input of Red Deer’s municipal\\u000a wastewater effluent and non-point- source agricultural runoff. We used population, growth, and physiological performance end\\u000a points in longnose dace (Rhinichthys cataractae), an endemic and abundant minnow, to evaluate changes in fish health over a 220 km section of the

Ken M. Jeffries; Leland J. Jackson; Lisa E. Peters; Kelly R. Munkittrick

2008-01-01

397

Somatic and population growth in selected cladoceran and rotifer species offered the cyanobacterium it Microcystis aeruginosa as food  

Microsoft Academic Search

The ability of cladocerans and rotifers to utilise the cyanobacterium Microcystis aeruginosa was tested by comparing the somatic\\u000a and population growth in cultures using Chlorella and Microcystis as food types. Five species of cladocerans (Ceriodaphnia\\u000a cornuta, Scapholeberis kingi, Moina macrocopa, Daphnia carinata, Simocephalus vetulus) and two species of rotifers (Brachionus\\u000a calyciflorus, Hexarthra mira) were used in this study. In order

S. Nandini; T. R. Rao

1997-01-01

398

In a long-term experimental demography study, excluding ungulates reversed invader's explosive population growth rate and restored natives  

PubMed Central

A major goal in ecology is to understand mechanisms that increase invasion success of exotic species. A recent hypothesis implicates altered species interactions resulting from ungulate herbivore overabundance as a key cause of exotic plant domination. To test this hypothesis, we maintained an experimental demography deer exclusion study for 6 y in a forest where the native ungulate Odocoileus virginianus (white-tailed deer) is overabundant and Alliaria petiolata (garlic mustard) is aggressively invading. Because population growth is multiplicative across time, we introduce metrics that correctly integrate experimental effects across treatment years, the cumulative population growth rate, ?c, and its geometric mean, ?per-year, the time-averaged annual population growth rate. We determined ?c and ?per-year of the invader and of a common native, Trillium erectum. Our results conclusively demonstrate that deer are required for the success of Alliaria; its projected population trajectory shifted from explosive growth in the presence of deer (?per-year = 1.33) to decline toward extinction where deer are excluded (?per-year = 0.88). In contrast, Trillium’s ?per-year was suppressed in the presence of deer relative to deer exclusion (?per-year = 1.04 vs. 1.20, respectively). Retrospective sensitivity analyses revealed that the largest negative effect of deer exclusion on Alliaria came from rosette transitions, whereas the largest positive effect on Trillium came from reproductive transitions. Deer exclusion lowered Alliaria density while increasing Trillium density. Our results provide definitive experimental support that interactions with overabundant ungulates enhance demographic success of invaders and depress natives’ success, with broad implications for biodiversity and ecosystem function worldwide. PMID:24616522

Kalisz, Susan; Spigler, Rachel B.; Horvitz, Carol C.

2014-01-01

399

Differential expression of secretion machinery during bacterial growth: SecY and SecF decrease while SecA increases during transition from exponential phase to stationary phase.  

PubMed

Transcription of many house-keeping genes, including secY and some other sec genes, decreases in the transition from the exponential phase to the stationary phase (feast to famine) in Bacillus subtilis. Unexpectedly and in contradiction to earlier reports, enhanced transcription was observed for another group of sec genes, including secA which codes for an essential ATPase for protein secretion. Consistent with the transcription data, the SecA protein of B. subtilis increases significantly in the stationary phase. Immunoblot analyses of Sec proteins during the transition in Escherichia coli also revealed the pronounced decreases of SecY and SecF and the increase of SecA, resulting in drastic increases of SecA/SecY and SecA/SecF ratios from exponential to stationary phases. The differential expression of Sec proteins in the stationary phase suggests the possibility of specific physiological functions. PMID:23852076

Yang, Chun-Kai; Lu, Chung-Dar; Tai, Phang C

2013-12-01

400

[Changes of four common plant populations growth and their anti-oxidative enzymatic system in desertification process].  

PubMed

This paper studied the changes of the growth and anti-oxidative enzymatic system of four common plant populations during the desertification process of sandy grassland. The results showed that in the process of desertification, the individual height and density and the density percentage of the populations all had a decreasing trend. The growth of Melilotoides ruthenica was more vigorous before moderate desertification (MD) stage, but restricted after that. In MD stage, the growth of Leymus chinensis was heavily restricted, and its individual height, density and density percentage accounted for 57.19%, 2.50% and 6.22% of those in original vegetation (OV) stage, respectively. The individual height and density of Cleistogenes squarrosa and Artemisia frigida increased in the stages of potential desertification (PD), light desertification (LD) or MD because of their phase status of dominant species and their stronger stress resistance. The SOD and POD activities of the common plant populations increased in PD and MD stages, but decreased in LD and heavy desertification (HD) stages. The CAT activity of Leymus chinensis was higher, whose response to desertification was not significant (P > 0.05), and that of Melilotoides ruthenica increased significantly in PD and HD stages (P < or = 0.01). The activities of the three anti-oxidative enzymes in the common plant populations, except the CAT activity of Melilotoides ruthenica, decreased in HD stage. The MDA content in the common populations increased firstly, then decreased, and finally increased from OV to MD stage, and had a significant difference in different desertification gradients (P < or = 0.05). Based on the integrated analysis of the ecological and physiological changes, it could be concluded that Leymus chinensis was more sensitive to desertification, while Melilotoides ruthenica had a stronger bioenergy. PMID:15825438

Zhu, Zhimei; Yang, Chi

2004-12-01

401

Understanding the determinate-indeterminate fecundity dichotomy in fish populations using a temperature dependent oocyte growth model  

NASA Astrophysics Data System (ADS)

The fecundity type (determinate vs. indeterminate) is still uncertain for many commercially important fish populations affecting accuracy in fecundity estimations and hindering the selection of appropriate egg production methods for stock assessment purposes. It is broadly considered that boreal fish populations living in colder habitats are determinate spawners whilst populations residing in warmer habitats tend to be indeterminate spawners. In the present study we modelled the determinate-indeterminate fecundity type in batch spawning fishes, i.e. fish that spawn several batches of eggs per spawning season, based on the relationship between oocyte growth period and the duration of the spawning period considering that both variables can be affected by water temperature and latitudinal distributions. Individual based models (IBMs) were developed to explore how the interaction of these variables can result in a series of patterns along the continuum from extreme determinacy, i.e. annual fecundity being recruited long before the onset of the spawning period, to indeterminacy. Model simulations showed that fish stocks with oocyte growth periods longer than the spawning period are predicted to exhibit determinate fecundity which provides a fair justification for why cold water species with slow oocyte growth and limited spawning periods are determinate spawners and vice versa.

Ganias, Kostas; Lowerre-Barbieri, Susan K.; Cooper, Wade

2015-02-01

402

The effects of dietary protein levels on the population growth, performance, and physiology of honey bee workers during early spring.  

PubMed

This study was conducted to investigate the effects of dietary protein levels on honey bee colonies, specifically the population growth, physiology, and longevity of honey bee workers during early spring. Diets containing four different levels of crude protein (25.0, 29.5, 34.0, or 38.5%) and pure pollen (control) were evaluated. Twenty-five colonies of honey bees with sister queens were used in the study. We compared the effects of the different bee diets by measuring population growth, emergent worker weight, midgut proteolytic enzyme activity, hypopharyngeal gland development, and survival. After 48 d, the cumulative number of workers produced by the colonies ranged from 22,420 to 29,519, providing a significant fit to a quadratic equation that predicts the maximum population growth when the diet contains 31.7% crude protein. Significantly greater emergent worker weight, midgut proteolytic enzyme activity, hypopharyngeal gland acini, and survival were observed in the colonies that were fed diets containing 34.0% crude protein compared with the other crude protein levels. Although higher emergent worker weight and survival were observed in the colonies that were fed the control diet, there were no significant differences between the control colonies and the colonies that were fed 34.0% crude protein. Based on these results, we concluded that a dietary crude protein content of 29.5-34.0% is recommended to maximize the reproduction rate of honey bee colonies in early spring. PMID:25368092

Zheng, Benle; Wu, Zaifu; Xu, Baohua

2014-01-01

403

Approximating Functions with Exponential Functions  

ERIC Educational Resources Information Center

The possibility of approximating a function with a linear combination of exponential functions of the form e[superscript x], e[superscript 2x], ... is considered as a parallel development to the notion of Taylor polynomials which approximate a function with a linear combination of power function terms. The sinusoidal functions sin "x" and cos "x"…

Gordon, Sheldon P.

2005-01-01

404

Performance analysis of exponential backoff  

Microsoft Academic Search

New analytical results are given for the performance of the exponential backoff (EB) algorithm. Most available studies on EB focus on the stability of the algorithm and little attention has been paid to the performance analysis of EB. In this paper, we analyze EB and obtain saturation throughput and medium access delay of a packet for a given number of

Byung-Jae Kwak; Nah-Oak Song; Leonard E. Miller

2005-01-01

405

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...

406

F-LE Exponential growth versus polynomial growth  

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 table below shows the values of $2^x$ and $2x^3 + 1$ for some whole number values of $x$: $x2^x2x^3+1$ 123 2417 3855 416129 532251 The numbers in t...

407

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...

408

Potential Effects of Environmental Contamination on Yuma Myotis Demography and Population Growth  

Microsoft Academic Search

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

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

2007-01-01

409

THE INFLUENCE OF MODEL TIME STEP ON THE RELATIVE SENSITIVIY OF POPULATION GROWTH RATE TO REPRODUCTION  

EPA Science Inventory

In recent years there has been an increasing interest in using population models in environmental assessments. Matrix population models represent a valuable tool for extrapolating from life stage-specific stressor effects on survival and reproduction to effects on finite populati...

410

Novel genes continue to enhance population growth in adders ( Vipera berus)  

Microsoft Academic Search

In 1999, we published a report on how an introduction of 20 males into a severely inbred and isolated population of adders (Vipera berus) halted its decline towards extinction, induced a profound change in population genetic variability, resulted in a dramatic increase in offspring viability and thus in a rapid increase in numbers. Since the publication of our paper we

Thomas Madsen; Beata Ujvari; Mats Olsson

2004-01-01

411

EFFECTS OF FOREST MANAGEMENT ON DENSITY, SURVIVAL, AND POPULATION GROWTH OF WOOD THRUSHES  

Microsoft Academic Search

Loss and alteration of breeding habitat have been proposed as causes of declines in several Neo- tropical 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 \\\\Vildlife Refuge (PNWR) in Georgia. We estimated density, adult and juvenile su~val rates,

LARKIN A. POWELL; D. B. Warnell; JASON D. LANG; MICHAELJ. CONROY; DAVID G. KREMENTZ

412

Effects of Conventional and Conservational Tillage Systems on Soybean Growth and Soil Microbial Populations  

Technology Transfer Automated Retrieval System (TEKTRAN)

Tillage systems play an important role in crop growth and soil improvement. To determine the best tillage system for the dark soil area of northeast China with dark clay soil type (Millisol), this study was conducted to examine the influence of different tillage systems on soybean growth and soil mi...

413

Kinetic Behaviors of a Competitive Population and Fitness System in Exchange-Driven Growth  

NASA Astrophysics Data System (ADS)

We proposed an aggregation model of two species aggregates of fitness and population to study the interaction between the two species in their exchange-driven processes of the same species by introducing the monomer birth of fitness catalyzed by the population, where the fitness aggregates perform self-death process and the population aggregates perform self-birth process. The kinetic behaviors of the aggregate size distributions of the fitness and population were analyzed by the rate equation approach with their exchange rate kernel K1(k,j) = K1kj and K2(k,j) = K2kj, the fitness aggregate's self-death rate kernel J1(k) = J1k, population aggregate's self-birth rate kernel J2(k) = J2k and population-catalyzed fitness birth rate kernel I(k,j) = Ikjv. The kinetic behavior of the fitness was found depending crucially on the parameter v, which reflects the dependence of the population-catalyzed fitness birth rate on the size of the catalyst (population) aggregate. (i) In the v <= 0 case, the effect of catalyzed-birth of fitness is rather weak and the exchange-driven aggregation and self-death of the fitness dominate the process, and the fitness aggregate size distribution ak(t) does not have scale form. (ii) When v > 0, the effect of the population-catalyzed birth of fitness gets strong enough, and the catalyzed-birth and self-death of the fitness aggregates, together with the self-birth of the population aggregates dominate the evolution process of the fitness aggregates. The aggregate size distribution ak(t) approaches a generalized scaling form.

Lu, Ke; Lin, Zhen-Quan; Sun, Yun-Fei

2008-07-01

414

Exponential size distribution of von Willebrand factor.  

PubMed

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

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

2013-09-01

415

Effects of chestnut tannins and coconut oil on growth performance, methane emission, ruminal fermentation, and microbial populations in sheep.  

PubMed

This study was conducted to evaluate the effects of chestnut tannins (CT) and coconut oil (CO) on growth performance, methane (CH?) emission, ruminal fermentation, and microbial populations in sheep. A total of 48 Rideau Arcott sheep (average body weight 31.5±1.97 kg, 16 wk old) were randomly assigned into 6 treatment groups in a 3 × 2 factorial design, with CT and CO as the main effects (8 sheep per group). The treatments were control diet (CTR), 10 or 30 g of CT/kg of diet (CT10 and CT30), 25 g of CO/kg of concentrate (CO25), and 10 or 30 g of CT/kg of diet+25 g of CO/kg of concentrate (CT10CO25 and CT30CO25). After the feeding trial (60 d), all sheep were moved to respiratory chambers to measure CH? emission. After CH? emission measurements, all sheep were slaughtered to obtain rumen fluid samples. Results showed that the addition of CT, CO, and CT+CO had no significant effects on growth performance of sheep but reduced CH? emission. Addition of CT reduced the NH?-N concentration in rumen fluid in CT30. Addition of CO decreased the concentration of total volatile fatty acids in rumen fluid. No significant differences were observed in pH and molar proportion of volatile fatty acids among treatments. Addition of CT, CO, and CT+CO significantly decreased methanogen and protozoa populations. Moreover, CO decreased counts of Fibrobacter succinogenes. No significant differences were observed in populations of fungi, Ruminococcus flavefaciens, or Ruminococcus albus among treatments. In conclusion, supplementation of CT and CO seemed to be a feasible means of decreasing emissions of CH? from sheep by reduction of methanogen and protozoa populations with no negative effect on growth performance. PMID:22118094

Liu, H; Vaddella, V; Zhou, D

2011-12-01

416

Identification of Top-Down Forces Regulating Cotton Aphid Population Growth in Transgenic Bt Cotton in Central China  

PubMed Central

The cotton aphid Aphis gossypii Glover is the main aphid pest in cotton fields in the Yangtze River Valley Cotton-planting Zone (YRZ) in central China. Various natural enemies may attack the cotton aphid in Bt cotton fields but no studies have identified potential specific top-down forces that could help manage this pest in the YRZ in China. In order to identify possibilities for managing the cotton aphid, we monitored cotton aphid population dynamics and identified the effect of natural enemies on cotton aphid population growth using various exclusion cages in transgenic Cry1Ac (Bt)+CpTI (Cowpea trypsin inhibitor) cotton field in 2011. The aphid population growth in the open field (control) was significantly lower than those protected or restricted from exposure to natural enemies in the various exclusion cage types tested. The ladybird predator Propylaea japonica Thunberg represented 65% of Coccinellidae predators, and other predators consisted mainly of syrphids (2.1%) and spiders (1.5%). The aphid parasitoids Aphidiines represented 76.7% of the total count of the natural enemy guild (mainly Lysiphlebia japonica Ashmead and Binodoxys indicus Subba Rao & Sharma). Our results showed that P. japonica can effectively delay the establishment and subsequent population growth of aphids during the cotton growing season. Aphidiines could also reduce aphid density although their impact may be shadowed by the presence of coccinellids in the open field (likely both owing to resource competition and intraguild predation). The implications of these results are discussed in a framework of the compatibility of transgenic crops and top-down forces exerted by natural enemy guild. PMID:25170907

Han, Peng; Niu, Chang-ying; Desneux, Nicolas

2014-01-01

417

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

PubMed

We investigated the effects of eight temperatures (22.5, 25.0, 27.5, 30.0, 32.5, 35.0, 37.5, and 40.0 degrees C) and four relative humidities (43, 55, 63, and 75%) on population growth and development of the psocid Liposcelis rufa Broadhead (Psocoptera: Liposcelididae). L. rufa did not survive at 43% RH, at all temperatures tested; at 55% RH, at the highest four temperatures; and at 63% RH and 40.0 degrees C. The greatest population growth was recorded at 35.0 degrees C and 75% RH (73-fold growth). At 40.0 degrees C, L. rufa populations declined or barely grew. L. rufa males have two to four nymphal instars, and the percentages of males with two, three, and four instars were 31, 54, and 15%, respectively. Female L. rufa have two to five instars, and the percentages of females with two, three, four, and five instars were 2, 44, 42, and 12%, respectively. The life cycle was shorter for males than females. We developed temperature-dependent developmental equations for male and female eggs, individual nymphal, combined nymphal, and combined immature stages. The ability of L. rufa to reproduce at a relative humidity of 55% and temperatures of 22.5-30.0 degrees C and at relative humidities of 63-75% and temperatures of 22.5-37.5 degrees C, in addition to being able to survive at 40.0 degrees C, suggests that this species would be expected to have a broader distribution than other Liposcelis species. These data provide a better understanding of L. rufa population dynamics and can be used to help develop effective management strategies for this psocid. PMID:21061997

Gautam, S G; Opit, G P; Giles, K L

2010-10-01

418

Identification of top-down forces regulating cotton aphid population growth in transgenic Bt cotton in central China.  

PubMed

The cotton aphid Aphis gossypii Glover is the main aphid pest in cotton fields in the Yangtze River Valley Cotton-planting Zone (YRZ) in central China. Various natural enemies may attack the cotton aphid in Bt cotton fields but no studies have identified potential specific top-down forces that could help manage this pest in the YRZ in China. In order to identify possibilities for managing the cotton aphid, we monitored cotton aphid population dynamics and identified the effect of natural enemies on cotton aphid population growth using various exclusion cages in transgenic Cry1Ac (Bt)+CpTI (Cowpea trypsin inhibitor) cotton field in 2011. The aphid population growth in the open field (control) was significantly lower than those protected or restricted from exposure to natural enemies in the various exclusion cage types tested. The ladybird predator Propylaea japonica Thunberg represented 65% of Coccinellidae predators, and other predators consisted mainly of syrphids (2.1%) and spiders (1.5%). The aphid parasitoids Aphidiines represented 76.7% of the total count of the natural enemy guild (mainly Lysiphlebia japonica Ashmead and Binodoxys indicus Subba Rao & Sharma). Our results showed that P. japonica can effectively delay the establishment and subsequent population growth of aphids during the cotton growing season. Aphidiines could also reduce aphid density although their impact may be shadowed by the presence of coccinellids in the open field (likely both owing to resource competition and intraguild predation). The implications of these results are discussed in a framework of the compatibility of transgenic crops and top-down forces exerted by natural enemy guild. PMID:25170907

Han, Peng; Niu, Chang-ying; Desneux, Nicolas

2014-01-01

419

Experimental evolution alters the rate and temporal pattern of population growth in Batrachochytrium dendrobatidis, a lethal fungal pathogen of amphibians.  

PubMed

Virulence of infectious pathogens can be unstable and evolve rapidly depending on the evolutionary dynamics of the organism. Experimental evolution can be used to characterize pathogen evolution, often with the underlying objective of understanding evolution of virulence. We used experimental evolution techniques (serial transfer experiments) to investigate differential growth and virulence of Batrachochytrium dendrobatidis (Bd), a fungal pathogen that causes amphibian chytridiomycosis. We tested two lineages of Bd that were derived from a single cryo-archived isolate; one lineage (P10) was passaged 10 times, whereas the second lineage (P50) was passaged 50 times. We quantified time to zoospore release, maximum zoospore densities, and timing of zoospore activity and then modeled population growth rates. We also conducted exposure experiments with a susceptible amphibian species, the common green tree frog (Litoria caerulea) to test the differential pathogenicity. We found that the P50 lineage had shorter time to zoospore production (T min ), faster rate of sporangia death (d s ), and an overall greater intrinsic population growth rate (?). These patterns of population growth in vitro corresponded with higher prevalence and intensities of infection in exposed Litoria caerulea, although the differences were not significant. Our results corroborate studies that suggest that Bd may be able to evolve relatively rapidly. Our findings also challenge the general assumption that pathogens will always attenuate in culture because shifts in Bd virulence may depend on laboratory culturing practices. These findings have practical implications for the laboratory maintenance of Bd isolates and underscore the importance of understanding the evolution of virulence in amphibian chytridiomycosis. PMID:25478154

Voyles, Jamie; Johnson, Leah R; Briggs, Cheryl J; Cashins, Scott D; Alford, Ross A; Berger, Lee; Skerratt, Lee F; Speare, Rick; Rosenblum, Erica Bree

2014-09-01

420

The relationship between flowering time and growth responses to drought in the Arabidopsis Landsberg erecta x Antwerp-1 population  

PubMed Central

Limited water availability is one of the most prominent abiotic constraints to plant survival and reproduction. Thus, plants have evolved different strategies to cope with water deficit, including modification of their growth and timing of developmental events such as flowering. In this work, we explore the link between flowering time and growth responses to moderate drought stress in Arabidopsis thaliana using natural variation for these traits found in the Landsberg erecta x Antwerp-1 recombinant inbred line population. We developed and phenotyped near isogenic lines containing different allelic combinations at three interacting quantitative trait loci (QTL) affecting both flowering time and growth in response to water deficit. We used these lines to confirm additive and epistatic effects of the three QTL and observed a strong association between late flowering and reduced sensitivity to drought. Analyses of growth responses to drought over time revealed that late flowering plants were able to recover their growth in the second half of their vegetative development. In contrast, early flowering, a common drought escape strategy that ensures plant survival under severe water deficit, was associated with strongly impaired plant fitness. The results presented here indicate that late flowering may be advantageous under continuous mild water deficit as it allows stress acclimatization over time. PMID:25426126

Schmalenbach, Inga; Zhang, Lei; Reymond, Matthieu; Jiménez-Gómez, José M.

2014-01-01

421

Spatial variation in population growth rate and community structure affects local and regional dynamics.  

PubMed

1. Theory predicting that populations with high maximum rates of increase (r(max)) will be less stable, and that metapopulations with high average r(max) will be less synchronous, was tested using a small protist, Bodo, that inhabits pitcher plant leaves (Sarracenia purpurea L.). The effects of predators and resources on these relationships were also determined. 2. Abundance data collected for a total of 60 populations of Bodo, over a period of 3 months, at six sites in three bogs in eastern Canada, were used to test these predictions. Mosquitoes were manipulated in half the leaves partway through the season to increase the range of predation rates. 3. Dynamics differed greatly among leaves and sites, but most populations exhibited one or more episodes of rapid increase followed by a population crash. Estimates of r(max) obtained using a linear mixed-effects model, ranged from 1 x 5 to 2 x 7 per day. Resource levels (captured insect) and midge abundances affected r(max). 4. Higher r(max) was associated with greater temporal variability and lower synchrony as predicted. However, in contrast to expectations, populations with higher r(max) also had lower mean abundance and were more suppressed by predators. 5. This study demonstrates that the link between r(max) and temporal variability is key to understanding the dynamics of populations that spend little time near equilibrium, and to predicting and interpreting the effects of community structure on the dynamics of such populations. PMID:18624742

Trzcinski, M Kurtis; Walde, Sandra J; Taylor, Philip D

2008-11-01

422

Population growth in snow geese: a modeling approach integrating demographic and survey information.  

PubMed

There are few analytic tools available to formally integrate information coming from population surveys and demographic studies. The Kalman filter is a procedure that facilitates such integration. Based on a state-space model, we can obtain a likelihood function for the survey data using a Kalman filter, which we may then combine with a likelihood for the demographic data. In this paper, we used this combined approach to analyze the population dynamics of a hunted species, the Greater Snow Goose (Chen caerulescens atlantica), and to examine the extent to which it can improve previous demographic population models. The state equation of the state-space model was a matrix population model with fecundity and regression parameters relating adult survival and harvest rate estimated in a previous capture-recapture study. The observation equation combined the output from this model with estimates from an annual spring photographic survey of the population. The maximum likelihood estimates of the regression parameters from the combined analysis differed little from the values of the original capture-recapture analysis, though their precision improved. The model output was found to be insensitive to a wide range of coefficient of variation (CV) in fecundity parameters. We found a close match between the surveyed and smoothed population size estimates generated by the Kalman filter over an 18-year period, and the estimated CV of the survey (0.078-0.150) was quite compatible with its assumed value (approximately 0.10). When we used the updated parameter values to predict future population size, the model underestimated the surveyed population size by 18% over a three-year period. However, this could be explained by a concurrent change in the survey method. We conclude that the Kalman filter is a promising approach to forecast population change because it incorporates survey information in a formal way compared with ad hoc approaches that either neglect this information or require some parameter or model tuning. PMID:17601135

Gauthier, Gilles; Besbeas, Panagiotis; Lebreton, Jean-Dominique; Morgan, Byron J T

2007-06-01

423

Raindrop Momentum Triggers Growth of Leaf-Associated Populations of Pseudomonas syringae on Field-Grown Snap Bean Plants  

PubMed Central

Observational and microclimate modification experiments were conducted under field conditions to determine the role of the physical environment in effecting large increases in phyllosphere population sizes of Pseudomonas syringae pv. syringae, the causal agent of bacterial brown spot disease of snap bean (Phaseolus vulgaris L.). Comparisons of daily changes in population sizes of P. syringae on three plantings of snap bean cultivar Cascade and one of cultivar Eagle with weather conditions indicated a strong association of rainfalls with periods of 1 to 3 days in duration during which increases in bacterial population sizes were greater than 10-fold and up to 1,000-fold. The effects of rain on populations of P. syringae were explored further by modifying the microclimate of bean plants in the field with polyethylene shelters to shield plants from rain and fine-mesh inert screens to modify the momentum of raindrops. After each of three separate intense rains, the greater-than-10-fold increases in population sizes of P. syringae observed on plants exposed to the rains did not occur on plants in the shelters or under the screens. The screens decreased the velocity and, thus, the momentum of raindrops but not the volume or quality of rainwater that fell on plants under the screens. Thus, the absence of increases in population sizes of P. syringae on plants under the screens suggests that raindrop momentum plays a role in the growth-triggering effect of intense rains on populations of P. syringae on bean plants under field conditions. PMID:16535362

Hirano, S. S.; Baker, L. S.; Upper, C. D.

1996-01-01

424

Recovering Population Parameters from a Single Gene Genealogy: An Unbiased Estimator of the Growth Rate  

E-print Network

to the low variation of the NLFT. We further analyze a set of 63 mtDNA sequences from blue whales (BWs, blue whale population,large-sample theory, mitochondrial DNA. Researcharticle Introduction Because

425

Whooping crane (Grus americana) demography and environmental factors in a population growth simulation model  

E-print Network

The Whooping Crane (Grus americana) is among North AmericaÂ?s most charismatic species. Between 1938 and 2004, the population that migrates between Aransas National Wildlife Refuge (ANWR) and Wood Buffalo National Park (WBNP), grew from 18 to 217...

Gil de Weir, Karine

2006-08-16

426

Yellow-bellied marmot population dynamics: demographic mechanisms of growth and decline  

E-print Network

of individually marked animals, we investigated the demographic mechanisms of the temporal and spatial dynamics of a yellow-bellied marmot (Marmota flaviventris) population. Prospective elasticity analyses indicated juvenile survival (Pj) would have the largest...

Oli, Madan K.; Armitage, Kenneth

2004-09-01

427

Yellow-Bellied Marmot Population Dynamics: Demographic Mechanisms of Growth and Decline  

E-print Network

of individually marked animals, we investigated the demographic mechanisms of the temporal and spatial dynamics of a yellow-bellied marmot (Marmota flaviventris) population. Prospective elasticity analyses indicated juvenile survival (Pj) would have the largest...

Oli, Madan K.; Armitage, Kenneth B.

2004-01-01

428

Adaptation to metal-contaminated soils in populations of the moss, Ceratodon purpureus: Vegetative growth and reproductive expression  

SciTech Connect

Many observations suggest that morphological evolution occurs slowly in bryophytes, and this has been suggested to reflect low genetic diversity within species. Isozyme studies, however, stand in apparent contrast and have shown that bryophytes can contain high levels of genetic variability within and among populations. In light of this conflict, we tested the potential of the moss, Ceratodon purpureus, to undergo adaptive change (i.e., ecotypic differentiation) in response to soils that have been contaminated with high levels of metals for 90 years by measuring gametophytic growth and reproductive expression under experimental conditions. Variation in protonemal growth in sterile culture indicates that plants from one population growing on contaminated soil near a smelter are significantly more tolerant of zinc, cadmium, and lead than plants from uncontaminated sites. Results from a common garden experiment, in which plants were grown on soil from the smelter site, indicate that plants from near the smelter are significantly more tolerant of contaminated soils than plants from uncontaminated sites for vegetative growth. The same experiment suggests that plants from the smelter site are also more tolerant in terms of gametangial production (although we could not test this statistically). Our results demonstrate that C. purpureus has been able to undergo relatively rapid evolution in response to strong selective pressures. 29 refs., 4 figs., 5 tabs.

Jules, E.S.; Shaw, A.J. (Univ. of Michigan, Ann Arbor, MI (United States))

1994-06-01

429

Population Growth of the Cladoceran, Daphnia magna: A Quantitative Analysis of the Effects of Different Algal Food  

PubMed Central

In this study, we examined the effects of two phytoplankton species, Chlorella vulgaris and Stephanodiscus hantzschii, on growth of the zooplankton Daphnia magna. Our experimental approach utilized stable isotopes to determine the contribution of food algae to offspring characteristics and to the size of adult D. magna individuals. When equal amounts of food algae were provided (in terms of carbon content), the size of individuals, adult zooplankton, and their offspring increased significantly following the provision of S. hantzschii, but not after the provision of C. vulgaris or of a combination of the two species. Offspring size was unaffected when C. vulgaris or a mixture of the two algal species was delivered, whereas providing only S. hantzschii increased the production of larger-sized offspring. Stable isotope analysis revealed significant assimilation of diatom-derived materials that was important for the growth of D. magna populations. Our results confirm the applicability of stable isotope approaches for clarifying the contribution of different food algae and elucidate the importance of food quality for growth of D. magna individuals and populations. Furthermore, we expect that stable isotope analysis will help to further precisely examine the contribution of prey to predators or grazers in controlled experiments. PMID:24752042

Choi, Jong-Yun; Kim, Seong-Ki; Chang, Kwang-Hyeon; Kim, Myoung-Chul; La, Geung-Hwan; Joo, Gea-Jae; Jeong, Kwang-Seuk

2014-01-01

430

Leslie/Lefkovitch Matrix Models for Age or Stage-structured Populations  

NSDL National Science Digital Library

This excel workbook uses the Leslie matrix model for population projection of age-class structured populations, and also allows Lefkovitch matrix models for stage-class structured populations. The user enters age or stage specific fecundity and survival rates as well as the populationâÂÂs initial proportions. The workbook calculates the matrix with corresponding eigenvalues for finite growth rate and eigenvectors for stable age/stage distribution and reproductive value. The graphical output included illustrates the stabilization of population structure, reproductive values and the finite rate of increase. It also includes exponential growth curves and semi-log plots of the population growth. The user can view population projections for four actual datasets.

John Jungck (Beloit College;Biology); Jennifer Spangenberg (Beloit College;)

2005-05-21

431

Absolute Continuous Bivariate Generalized Exponential Distribution  

E-print Network

Absolute Continuous Bivariate Generalized Exponential Distribution Debasis Kundu and Rameshwar D. Gupta Abstract Generalized exponential distribution has been used quite effectively to model posi- tively skewed lifetime data as an alternative to the well known Weibull or gamma distributions

Kundu, Debasis

432

Weighted Marshall-Olkin Bivariate Exponential Distribution  

E-print Network

Weighted Marshall-Olkin Bivariate Exponential Distribution Ahad Jamalizadeh§ & Debasis Kundu of weighted Marshall-Olkin bivariate exponential distribu- tions. This new singular distribution has density function; Singular distribution; Maximum likelihood estimators; Fisher information matrix; Asymp

Kundu, Debasis

433

Growth and condition of bluegills in Wisconsin lakes: effects of population density and lake pH  

USGS Publications Warehouse

Growth and condition of bluegills epomis macrochirusfrom five acidic lakes (pH 5.1-6.0) and six circumneutral lakes (pH 6.7-7.5) in northern Wisconsin were compared. Although mean condition factors and mean back-calculated total lengths at ages 1 to 4 varied significantly among lakes, the differences were not related to lake pH. Rather, the ranks of mean condition factors and back-calculated lengths at ages 2, 3, and 4 were negatively correlated with relative density of bluegills among the lakes. Because of the dominating effect of density, growth rates and condition factors are not useful as indicators of chronic, pH-related stress on bluegill populations.

Wiener, J.G.; Hanneman, W.R.

1982-01-01

434

Growth and condition of bluegills in Wisconsin lakes: effects of population density and lake pH  

SciTech Connect

Growth and condition of bluegills (Lepomis macrochirus) from five acidic lakes (pH 5.1-6.0) and six circumneutral lakes (pH 6.7-7.6) in northern Wisconsin were compared. Although mean condition factors and mean back-calculated total lengths at ages 1 to 4 varied significantly among lakes, the differences were not related to lake pH. Rather, the ranks of mean condition factors and back-calculated lengths at ages 2, 3, and 4 were negatively correlated with relative density of bluegills among the lakes. Because of the dominating effect of density, growth rates and condition factors are not useful as indicators of chronic, pH-related stress on bluegill populations.

Wiener, J.G. (Columbia National Fisheries Research Lab., La Crosse, WI); Hanneman, W.R.

1982-11-01

435

Food supplements increase adult tarsus length, but not growth rate, in an island population of house sparrows (Passer domesticus)  

PubMed Central

Background Variation in food supply during early development can influence growth rate and body size in many species. However, whilst the detrimental effects of food restriction have often been studied in natural populations, how young individuals respond to an artificial increase in food supply is rarely investigated. Here, we investigated both the short-term and long-term effects of providing house sparrow chicks with food supplements during a key period of growth and development and assessed whether providing food supplements had any persistent effect upon adult size (measured here as tarsus length). Results Male nestlings tended to reach higher mass asymptotes than females. Furthermore, brood size was negatively associated with a chick's asymptotic mass. However, providing food supplements had no influence upon the growth rate or the asymptotic mass of chicks. Adults that received food supplements as chicks were larger, in terms of their tarsus length, than adults that did not receive extra food as chicks. In addition, the variation in tarsus length amongst adult males that were given food supplements as chicks was significantly less than the variance observed amongst males that did not receive food supplements. Conclusions Our results demonstrate that the food supply chicks experience during a critical developmental period can have a permanent effect upon their adult phenotype. Furthermore, providing extra food to chicks resulted in sex-biased variance in a size-related trait amongst adults, which shows that the degree of sexual size dimorphism can be affected by the environment experienced during growth. PMID:22018144

2011-01-01

436

Simulated Warming Differentially Affects the Growth and Competitive Ability of Centaurea maculosa Populations from Home and Introduced Ranges  

PubMed Central

Climate warming may drive invasions by exotic plants, thereby raising concerns over the risks of invasive plants. However, little is known about how climate warming influences the growth and competitive ability of exotic plants from their home and introduced ranges. We conducted a common garden experiment with an invasive plant Centaurea maculosa and a native plant Poa pratensis, in which a mixture of sand and vermiculite was used as a neutral medium, and contrasted the total biomass, competitive effects, and competitive responses of C. maculosa populations from Europe (home range) and North America (introduced range) under two different temperatures. The warming-induced inhibitory effects on the growth of C. maculosa alone were stronger in Europe than in North America. The competitive ability of C. maculosa plants from North America was greater than that of plants from Europe under the ambient condition whereas this competitive ability followed the opposite direction under the warming condition, suggesting that warming may enable European C. maculosa to be more invasive. Across two continents, warming treatment increased the competitive advantage instead of the growth advantage of C. maculosa, suggesting that climate warming may facilitate C. maculosa invasions through altering competitive outcomes between C. maculosa and its neighbors. Additionally, the growth response of C. maculosa to warming could predict its ability to avoid being suppressed by its neighbors. PMID:22303485

He, Wei-Ming; Li, Jing-Ji; Peng, Pei-Hao

2012-01-01

437

Impacts of population growth and economic development on water quality of a lake: case study of Lake Victoria Kenya water.  

PubMed

Anthropogenic-induced water quality pollution is a major environmental problem in freshwater ecosystems today. As a result of this, eutrophication of lakes occurs. Population and economic development are key drivers of water resource pollution. To evaluate how growth in the riparian population and in the gross domestic product (GDP) with unplanned development affects the water quality of the lake, this paper evaluates Lake Victoria Kenyan waters basin. Waters quality data between 1990 and 2012 were analyzed along with reviews of published literature, papers, and reports. The nitrate-nitrogen (NO3-N), soluble phosphorus (PO4-P), chlorophyll a, and Secchi transparencies were evaluated as they are key water quality indicators. The NO3-N increased from 10 ?g l(-1) in 1990 to 98 ?g 1(-1) in 2008, while PO4-P increased from 4 ?g l(-1) in 1990 to 57 ?g l(-1) in 2008. The population and economic growth of Kenya are increasing with both having minimums in 1990 of 24.143 million people and 12.18 billion US dollars, to maximums in 2010 of 39.742 million people and 32.163 billion US dollars, respectively. A Secchi transparency is reducing with time, indicating an increasing pollution. This was confirmed by an increase in aquatic vegetation using an analysis of moderate resolution imaging spectroradiometer (MODIS) images of 2000 and 2012 of Kenyan waters. This study found that increasing population and GDP increases pollution discharge thus polluting lakes. One of major factors causing lake water pollution is the unplanned or poor waste management policy and service. PMID:24442964

Juma, Dauglas Wafula; Wang, Hongtao; Li, Fengting

2014-04-01